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Theoretical Study of Sodium-Water Surface Reaction Mechanism
NASA Astrophysics Data System (ADS)
Kikuchi, Shin; Kurihara, Akikazu; Ohshima, Hiroyuki; Hashimoto, Kenro
Computational study of the sodium-water reaction at the gas (water) - liquid (sodium) interface has been carried out using the ab initio (first-principle) method. A possible reaction channel has been identified for the stepwise OH bond dissociations of a single water molecule. The energetics including the binding energy of a water molecule on the sodium surface, the activation energies of the bond cleavages, and the reaction energies, have been evaluated, and the rate constants of the first and second OH bond-breakings have been compared. It was found that the estimated rate constant of the former was much larger than the latter. The results are the basis for constructing the chemical reaction model used in a multi-dimensional sodium-water reaction code, SERAPHIM, being developed by Japan Atomic Energy Agency (JAEA) toward the safety assessment of the steam generator (SG) in a sodium-cooled fast reactor (SFR).
Dynamic effect of sodium-water reaction in fast flux test facility power addition sodium pipes
Huang, S.N.; Anderson, M.J.
The Fast Flux Facility (FFTF) is a demonstration and test facility of the sodium-cooled fast breeder reactor. A power addition'' to the facility is being considered to convert some of the dumped, unused heat into electricity generation. Components and piping systems to be added are sodium-water steam generators, sodium loop extensions from existing dump heat exchangers to sodium-water steam generators, and conventional water/steam loops. The sodium loops can be subjected to the dynamic loadings of pressure pulses that are caused by postulated sodium leaks and subsequent sodium-water reaction in the steam generator. The existing FFTF secondary pipes and the new power addition sodium loops were evaluated for exposure to the dynamic effect of the sodium-water reaction. Elastic and simplified inelastic dynamic analyses were used in this feasibility study. The results indicate that both the maximum strain and strain range are within the allowable limits. Several cycles of the sodium-water reaction can be sustained by the sodium pipes that are supported by ordinary pipe supports and seismic restraints. Expensive axial pipe restraints to withstand the sodium-water reaction loads are not needed, because the pressure-pulse-induced alternating bending stresses act as secondary stresses and the pressure pulse dynamic effect is a deformation-controlled quantity and is self-limiting. 14 refs., 7 figs., 3 tabs.
SWAAM-LT: The long-term, sodium/water reaction analysis method computer code
Shin, Y.W.; Chung, H.H.; Wiedermann, A.H.; Tanabe, H.
The SWAAM-LT Code, developed for analysis of long-term effects of sodium/water reactions, is discussed. The theoretical formulation of the code is described, including the introduction of system matrices for ease of computer programming as a general system code. Also, some typical results of the code predictions for available large scale tests are presented. Test data for the steam generator design with the cover-gas feature and without the cover-gas feature are available and analyzed. The capabilities and limitations of the code are then discussed in light of the comparison between the code prediction and the test data.
Microstructure and deformation mode of a stainless steel rupture disc exposed to sodium-water reaction
Sudha, C.; Parameswaran, P. Kishore, S.; Murthy, C. Meikanda; Rajan, M.; Vijayalakshmi, M.; Raghunathan, V.S.
This paper deals with microstructural studies carried out on an austenitic stainless steel rupture disc which was exposed to sodium-water reaction. The rupture disc was part of a leak simulator put in a micro leak test section which was used to study the 'self wastage' of steam generator tubes. During micro leak testing, the rupture disc failed exhibiting a linear crack at a much lower pressure of 10 MPa rather than bursting open at the higher designed pressure of 15 MPa. The failed rupture disc revealed different microstructural features on the inner (steam exposed) and outer (sodium exposed) surfaces. Using microstructure as the signature, the temperature experienced by the rupture disc was predicted as {>=} 1273 K. Evidence for the exposure of the rupture disc to highly exothermic sodium-water reaction was obtained in the form of sodium rich debris, microcracks and deformation bands. Detailed transmission electron microscopy revealed the nature of deformation bands as deformation twins which is not a preferred failure mode for austenitic stainless steels.
Response of rupture discs to sodium-water reaction pulses. Final report
Cagliostro, D.J.; Desmond, T.P.; Florence, A.L.
A 1/7-scale model of a double rupture disc pressure relief device, designed for the intermediate heat transfer system of a liquid metal fast breeder reactor, was subjected to incident pressure pulses that simulated various sodium-water reaction pulses. General features of the pulses generated were an initial rise in pressure that lasted from 1 to 2 ms followed by a slow decrease in pressure that lasted for more than 50 ms. Pulses with nominal maximum pressures of 50, 100, 150, 200, 400, 600, and 800 psi were generated and transmitted along the pipe to load the rupture discs. The hydrostatic collapse pressure of the spherical cap of the rupture disc, determined by test in the same apparatus, was 250 psi. It is concluded that: (1) incident pressures must exceed half the static collapse pressure to cause rupture and so activate the relief system; and (2) incident pressures above the static collapse pressure result in reflected pressures that are less than the incident pressures.
Sodium-water reaction acoustic noise for liquid phase injections. [LMFBR
Callis, K.R.; Greene, D.A.; Malovrh, J.W.
Data on liquid and steam injections into sodium were recorded during a series of wastage experiments. These data are analyzed for acoustic power and spectral characteristics, expanding the data base up to 10 gm/sec injection rates from the earlier 0.5 gms/sec. No significant difference in acoustic power was measured between low temperature steam and liquid injections for the same mass flowrates. The bandwidth for steam injections is broader than for liquid injections. Reaction product deposition during water injections appears to cause a decrease in signal strength with test duration.
Development of a multiphysics analysis system for sodium-water reaction phenomena in steam generators of sodium-cooled fast reactors
NASA Astrophysics Data System (ADS)
Uchibori, Akihiro; Kurihara, Akikazu; Ohshima, Hiroyuki
A multiphysics analysis system for sodium-water reaction phenomena in a steam generator of sodium-cooled fast reactors was newly developed. The analysis system consists of the mechanistic numerical analysis codes, SERAPHIM, TACT, and RELAP5. The SERAPHIM code calculates the multicomponent multiphase flow and sodium-water chemical reaction caused by discharging of pressurized water vapor. Applicability of the SERAPHIM code was confirmed through the analyses of the experiment on water vapor discharging in liquid sodium. The TACT code was developed to calculate heat transfer from the reacting jet to the adjacent tube and to predict the tube failure occurrence. The numerical models integrated into the TACT code were verified through some related experiments. The RELAP5 code evaluates thermal hydraulic behavior of water inside the tube. The original heat transfer correlations were corrected for the tube rapidly heated by the reacting jet. The developed system enables evaluation of the wastage environment and the possibility of the failure propagation.
Development of a multiphysics analysis system for sodium-water reaction phenomena in steam generators of sodium-cooled fast reactors
Uchibori, Akihiro; Kurihara, Akikazu; Ohshima, Hiroyuki
A multiphysics analysis system for sodium-water reaction phenomena in a steam generator of sodium-cooled fast reactors was newly developed. The analysis system consists of the mechanistic numerical analysis codes, SERAPHIM, TACT, and RELAP5. The SERAPHIM code calculates the multicomponent multiphase flow and sodium-water chemical reaction caused by discharging of pressurized water vapor. Applicability of the SERAPHIM code was confirmed through the analyses of the experiment on water vapor discharging in liquid sodium. The TACT code was developed to calculate heat transfer from the reacting jet to the adjacent tube and to predict the tube failure occurrence. The numerical models integrated into the TACT code were verified through some related experiments. The RELAP5 code evaluates thermal hydraulic behavior of water inside the tube. The original heat transfer correlations were corrected for the tube rapidly heated by the reacting jet. The developed system enables evaluation of the wastage environment and the possibility of the failure propagation.
Analysis of the dynamic response of a double rupture disc assembly to simulated sodium-water reaction pressure pulses
Leonard, J.R.
A series of double rupture disc experiments were conducted in 1979 to evaluate the dynamic response characteristics of this pressure relief apparatus. The tests were performed in a facility with water simulating sodium and rising pressure pulses representative of the pressure increase resulting from a water/steam leak from a steam generator into sodium in the intermediate heat transport system of a breeder reactor power plant. Maximum source pressures ranged in magnitude from 50 psi to 800 psi. Dynamic response characteristics of each of the two rupture discs were similar to those observed in larger scale sodium-water experiments conducted in the Series I and Series II Large Leak Test Program at the Energy Technology Engineering Center. The SRI double rupture disc dynamic behavior was found to be consistent and amendable to modelling in the TRANSWRAP II computer code. A series of correlations which represent rupture disc buckling parameters were developed for use in the TRANSWRAP II code. The semi-empirical modeling of the rupture discs in the TRANSWRAP II code showed very good agreement with the experimental results.
Analysis of large-leak test SWAT-3 Run-6 data by use of sodium-water-reaction analysis code SWAAM-I
Shin, Y.W.; Lin, H.C.
The Sodium Water Advanced Analysis Method computer code (SWAAM-I) is used to analyze the large-leak test data SWAT-3 Run-6. The SWAT-3 is the mockup of the secondary system of the Japanese breeder-reactor demonstration plant Monju. The steam-generator design for the Monju reactor was a helical-coil-tube type with a cover-gas space, and the SWAT-3 Run-6 Test vessel simulates this design of the steam generator. The objectives of this work are: (1) to examine the adequacy of the SWAAM-I code for the helical-coil-tube steam-generator system, (2) to understand and confirm the understanding of phenomena that have major design implications, and (3) to define needs for additional development of SWAAM-I code capabilities.
Signaling reactions on membrane surfaces: breaking the law of averages
NASA Astrophysics Data System (ADS)
Groves, Jay T.
Most intracellular signal transduction reactions take place on the membrane surface. The membrane provides much more than just a surface environment on which signaling molecules are concentrated. There is a growing realization that multiple physical and chemical mechanisms allow the membrane to actively participate in the signaling reactions. Using a combination of single molecule imaging and spectroscopic techniques, my research seeks to directly resolve the actual mechanics of signaling reactions on membrane surfaces both in reconstituted systems and in living cells. These observations are revealing new insights into cellular signaling processes as well as some unexpected functional behaviors of proteins on the membrane surface.
Photosynthetic light reactions: integral to chloroplast retrograde signalling.
Gollan, Peter J; Tikkanen, Mikko; Aro, Eva-Mari
Chloroplast retrograde signalling is ultimately dependent on the function of the photosynthetic light reactions and not only guides the acclimation of the photosynthetic apparatus to changing environmental and metabolic cues, but has a much wider influence on the growth and development of plants. New information generated during the past few years about regulation of photosynthetic light reactions and identification of the underlying regulatory proteins has paved the way towards better understanding of the signalling molecules produced in chloroplasts upon changes in the environment. Likewise, the availability of various mutants lacking regulatory functions has made it possible to address the role of excitation energy distribution and electron flow in the thylakoid membrane in inducing the retrograde signals from chloroplasts to the nucleus. Such signalling molecules also induce and interact with hormonal signalling cascades to provide comprehensive information from chloroplasts to the nucleus. PMID:26318477
Hierarchical Feedback Modules and Reaction Hubs in Cell Signaling Networks
Xu, Jianfeng; Lan, Yueheng
Despite much effort, identification of modular structures and study of their organizing and functional roles remain a formidable challenge in molecular systems biology, which, however, is essential in reaching a systematic understanding of large-scale cell regulation networks and hence gaining capacity of exerting effective interference to cell activity. Combining graph theoretic methods with available dynamics information, we successfully retrieved multiple feedback modules of three important signaling networks. These feedbacks are structurally arranged in a hierarchical way and dynamically produce layered temporal profiles of output signals. We found that global and local feedbacks act in very different ways and on distinct features of the information flow conveyed by signal transduction but work highly coordinately to implement specific biological functions. The redundancy embodied with multiple signal-relaying channels and feedback controls bestow great robustness and the reaction hubs seated at junctions of different paths announce their paramount importance through exquisite parameter management. The current investigation reveals intriguing general features of the organization of cell signaling networks and their relevance to biological function, which may find interesting applications in analysis, design and control of bio-networks. PMID:25951347
Simulation studies in biochemical signaling and enzyme reactions
NASA Astrophysics Data System (ADS)
Nelatury, Sudarshan R.; Vagula, Mary C.
Biochemical pathways characterize various biochemical reaction schemes that involve a set of species and the manner in which they are connected. Determination of schematics that represent these pathways is an important task in understanding metabolism and signal transduction. Examples of these Pathways are: DNA and protein synthesis, and production of several macro-molecules essential for cell survival. A sustained feedback mechanism arises in gene expression and production of mRNA that lead to protein synthesis if the protein so synthesized serves as a transcription factor and becomes a repressor of the gene expression. The cellular regulations are carried out through biochemical networks consisting of reactions and regulatory proteins. Systems biology is a relatively new area that attempts to describe the biochemical pathways analytically and develop reliable mathematical models for the pathways. A complete understanding of chemical reaction kinetics is prohibitively hard thanks to the nonlinear and highly complex mechanisms that regulate protein formation, but attempting to numerically solve some of the governing differential equations seems to offer significant insight about their biochemical picture. To validate these models, one can perform simple experiments in the lab. This paper introduces fundamental ideas in biochemical signaling and attempts to take first steps into the understanding of biochemical oscillations. Initially, the two-pool model of calcium is used to describe the dynamics behind the oscillations. Later we present some elementary results showing biochemical oscillations arising from solving differential equations of Elowitz and Leibler using MATLAB software.
Bayesian parametric estimation of stop-signal reaction time distributions.
Matzke, Dora; Dolan, Conor V; Logan, Gordon D; Brown, Scott D; Wagenmakers, Eric-Jan
The cognitive concept of response inhibition can be measured with the stop-signal paradigm. In this paradigm, participants perform a 2-choice response time (RT) task where, on some of the trials, the primary task is interrupted by a stop signal that prompts participants to withhold their response. The dependent variable of interest is the latency of the unobservable stop response (stop-signal reaction time, or SSRT). Based on the horse race model (Logan & Cowan, 1984), several methods have been developed to estimate SSRTs. None of these approaches allow for the accurate estimation of the entire distribution of SSRTs. Here we introduce a Bayesian parametric approach that addresses this limitation. Our method is based on the assumptions of the horse race model and rests on the concept of censored distributions. We treat response inhibition as a censoring mechanism, where the distribution of RTs on the primary task (go RTs) is censored by the distribution of SSRTs. The method assumes that go RTs and SSRTs are ex-Gaussian distributed and uses Markov chain Monte Carlo sampling to obtain posterior distributions for the model parameters. The method can be applied to individual as well as hierarchical data structures. We present the results of a number of parameter recovery and robustness studies and apply our approach to published data from a stop-signal experiment. PMID:23163766
Transduction of Redox Signaling by Electrophile-Protein Reactions
Rudolph, Tanja K.; Freeman, Bruce A.
Over the last 50 years, the posttranslational modification (PTM) of proteins has emerged as a central mechanism for cells to regulate metabolism, growth, differentiation, cell-cell interactions, and immune responses. By influencing protein structure and function, PTM leads to a multiplication of proteome diversity. Redox-dependent PTMs, mediated by environmental and endogenously generated reactive species, induce cell signaling responses and can have toxic effects in organisms. PTMs induced by the electrophilic by-products of redox reactions most frequently occur at protein thiols; other nucleophilic amino acids serve as less favorable targets. Advances in mass spectrometry and affinity-chemistry strategies have improved the detection of electrophile-induced protein modifications both in vitro and in vivo and have revealed a high degree of amino acid and protein selectivity of electrophilic PTM. The identification of biological targets of electrophiles has motivated further study of the functional impact of various PTM reactions on specific signaling pathways and how this might affect organisms. PMID:19797270
Functional mapping of reaction norms to multiple environmental signals.
Wu, Jiasheng; Zeng, Yanru; Huang, Jianqing; Hou, Wei; Zhu, Jun; Wu, Rongling
Whether there are different genes involved in response to different environmental signals and how these genes interact to determine the final expression of the trait are of fundamental importance in agricultural and biological research. We present a statistical framework for mapping environment-induced genes (or quantitative trait loci, QTLs) of major effects on the expression of a trait that respond to changing environments. This framework is constructed with a maximum-likelihood-based mixture model, in which the mean and covariance structure of environment-induced responses is modelled. The means for responses to continuous environmental states, referred to as reaction norms, are approximated for different QTL genotypes by mathematical equations that were derived from fundamental biological principles or based on statistical goodness-of-fit to observational data. The residual covariance between different environmental states was modelled by autoregressive processes. Such an approach to studying the genetic control of reaction norms can be expected to be advantageous over traditional mapping approaches in which no biological principles and statistical structures are considered. We demonstrate the analytical procedure and power of this approach by modelling the photosynthetic rate process as a function of temperature and light irradiance. Our approach allows for testing how a QTL affects the reaction norm of photosynthetic rate to a specific environment and whether there exist different QTLs to mediate photosynthetic responses to temperature and light irradiance, respectively. PMID:17517157
A Strategy for Minimizing Background Signal in Autoinductive Signal Amplification Reactions for Point-of-Need Assays
Brooks, Adam D.; Yeung, Kimy; Lewis, Gregory G.
Rapid point-of-need assays are used to detect abundant biomarkers. The development of in situ signal amplification reactions could extend these assays to screening and triaging of patients for trace levels of biomarkers, even in resource-limited settings. We, and others, have developed small molecule-based in situ signal amplification reactions that eventually may be useful in this context. Herein we describe a design strategy for minimizing background signal that may occur in the absence of the target analyte, thus moving this in situ signal amplification approach one step closer to practical applications. Specifically, we describe allylic ethers as privileged connectors for linking detection and propagating functionality in a small molecule signal amplification reagent. Allylic ethers minimize background reactions while still enabling controlled release of a propagating signal in order to continue the signal amplification reaction. This paper characterizes the ability of allylic ethers to provide an amplified response, and offers insight into additional design considerations that are needed before in situ small molecule-based signal amplification becomes a viable strategy for point-of-need diagnostics. PMID:26604988
Dependecy of the reaction time from the overlap of signal lights with different colors
NASA Astrophysics Data System (ADS)
Klinger, Karsten D.
The rearward signal aspect consists of lights with different colors. With standard technics these signal lights are located at different places. With new technics it is possible to build signal lights with different colors together in one place. The signals overlap. In experiments at the University of Karlsruhe we studied the dependency between reaction time and overlap of signal lights. We can see, that the total overlap from a yellow turn signal and a red brake signal will increase the reaction time. The increase depends of the ratio between the luminance of the turn indicator signal and the luminance of the brake signal. With a ratio from one to one (best case with minimal increase) we found an increase of 300 milli seconds.
Egg signals for triggering the acrosome reaction in starfish spermatozoa.
Hoshi, M; Amano, T; Okita, Y; Okinaga, T; Matsui, T
Upon encountering the jelly coat of an egg, starfish spermatozoa undergo the acrosome reaction. To induce the acrosome reaction, 3 jelly components act in concert on the spermatozoa: a sulphated glycoprotein named acrosome reaction-inducing substance (ARIS), a group of steroidal saponins named Co-ARIS, and an oligopeptide presumably having an ability to increase the intracellular pH of the spermatozoon. All three are required to mimic the full ability of jelly coat to induce the acrosome reaction instantaneously. A combination of ARIS and Co-ARIS is enough for induction in normal sea water, although its action is almost 2 min slower than the jelly. ARIS can induce the acrosome reaction by itself in high Ca2+ or high pH sea water. When spermatozoa meet the jelly coat, the acrosome reaction is eventually induced because ARIS and Co-ARIS co-operatively increase the intracellular Ca2+ by stimulating verapamil- and maitotoxin-sensitive Ca2+ channels and the oligopeptide increases the intracellular pH by stimulating Na+/H+ exchange systems. PMID:2077126
Prefrontal D1 dopamine signaling is necessary for temporal expectation during reaction time performance
Parker, Krystal L.; Alberico, Stephanie L.; Miller, Adam D.; Narayanan, Nandakumar S.
Responses during a simple reaction time task are influenced by temporal expectation, or the ability to anticipate when a stimulus occurs in time. Here, we test the hypothesis that prefrontal D1 dopamine signaling is necessary for temporal expectation during simple reaction time task performance. We depleted dopamine projections to the medial prefrontal circuits by infusing 6-hydroxidopamine, a selective neurotoxin, into the ventral tegmental area (VTA) of rats, and studied their performance on a simple reaction time task with two delays. VTA dopamine depletion did not change movements or learning of the reaction time task. However, VTA dopamine-depleted animals did not develop delay-dependent speeding of reaction times, suggesting that mesocortical dopamine signaling is required for temporal expectation. Next, we manipulated dopamine signaling within the medial prefrontal cortex using local pharmacology. We found that SCH23390, a D1-type dopamine receptor antagonist, specifically attenuated delay-dependent speeding, while sulpiride, a D2-type receptor antagonist, did not. These data suggest that prefrontal D1 dopamine signaling is necessary for temporal expectation during performance of a simple reaction time task. Our findings provide insight into temporal processing of the prefrontal cortex, and how dopamine signaling influences prefrontal circuits that guide goal-directed behavior. PMID:24120554
Prefrontal D1 dopamine signaling is necessary for temporal expectation during reaction time performance.
Parker, K L; Alberico, S L; Miller, A D; Narayanan, N S
Responses during a simple reaction time task are influenced by temporal expectation, or the ability to anticipate when a stimulus occurs in time. Here, we test the hypothesis that prefrontal D1 dopamine signaling is necessary for temporal expectation during simple reaction time task performance. We depleted dopamine projections to the medial prefrontal circuits by infusing 6-hydroxidopamine, a selective neurotoxin, into the ventral tegmental area (VTA) of rats, and studied their performance on a simple reaction time task with two delays. VTA dopamine depletion did not change movements or learning of the reaction time task. However, VTA dopamine-depleted animals did not develop delay-dependent speeding of reaction times, suggesting that mesocortical dopamine signaling is required for temporal expectation. Next, we manipulated dopamine signaling within the medial prefrontal cortex using local pharmacology. We found that SCH23390, a D1-type dopamine receptor antagonist, specifically attenuated delay-dependent speeding, while sulpiride, a D2-type receptor antagonist, did not. These data suggest that prefrontal D1 dopamine signaling is necessary for temporal expectation during performance of a simple reaction time task. Our findings provide insight into temporal processing of the prefrontal cortex, and how dopamine signaling influences prefrontal circuits that guide goal-directed behavior. PMID:24120554
The cost and capacity of signaling in the Escherichia coli protein reaction network
NASA Astrophysics Data System (ADS)
Axelsen, Jacob Bock; Krishna, Sandeep; Sneppen, Kim
In systems biology new ways are required to analyze the large amount of existing data on regulation of cellular processes. Recent work can be roughly classified into either dynamical models of well-described subsystems, or coarse-grained descriptions of the topology of the molecular networks at the scale of the whole organism. In order to bridge these two disparate approaches one needs to develop simplified descriptions of dynamics and topological measures which address the propagation of signals in molecular networks. Transmission of a signal across a reaction node depends on the presence of other reactants. It will typically be more demanding to transmit a signal across a reaction node with more input links. Sending signals along a path with several subsequent reaction nodes also increases the constraints on the presence of other proteins in the overall network. Therefore counting in and out links along reactions of a potential pathway can give insight into the signaling properties of a particular molecular network. Here, we consider the directed network of protein regulation in E. coli, characterizing its modularity in terms of its potential to transmit signals. We demonstrate that the simplest measure based on identifying subnetworks of strong components, within which each node could send a signal to every other node, does indeed partition the network into functional modules. We suggest that the total number of reactants needed to send a signal between two nodes in the network can be considered as the cost associated with transmitting this signal. Similarly we define spread as the number of reaction products that could be influenced by transmission of a successful signal. Our considerations open for a new class of network measures that implicitly utilize the constrained repertoire of chemical modifications of any biological molecule. The counting of cost and spread connects the topology of networks to the specificity of signaling across the network. Thereby, we
Amplified-response-spectrum analysis of sodium-water reaction pressure waves. [LMFBR
Knittle, D.E.
This report deals with a frequency spectrum evaluation of the SWAAM I predicted double rupture disc assembly operation pressure wave generated in the LLTR Series II A-2 test. It also evaluates the same wave predicted by the TRANSWRAP II code and the pressure wave actually measured upstream of the rupture disc assembly by the test instrumentation in Test A-2. The SWAAM I and TRANSWRAP II codes currently use the same analytical model to characterize the rupture disc until the disc strikes the knife edges. Thereafter, the SWAAM I code relies on analytical techniques to characterize the phenomena, whereas the TRANSWRAP II code uses empirical parameters based on A-2 test data to represent the disc behavior. Any differences in the predicted dynamic pipe loads caused by double rupture disc assembly operation, using the forcing functions predicted by the codes can, therefore, be traced to this difference.
Immobilized Metal Affinity Chromatography Coupled to Multiple Reaction Monitoring Enables Reproducible Quantification of Phospho-signaling.
Kennedy, Jacob J; Yan, Ping; Zhao, Lei; Ivey, Richard G; Voytovich, Uliana J; Moore, Heather D; Lin, Chenwei; Pogosova-Agadjanyan, Era L; Stirewalt, Derek L; Reding, Kerryn W; Whiteaker, Jeffrey R; Paulovich, Amanda G
A major goal in cell signaling research is the quantification of phosphorylation pharmacodynamics following perturbations. Traditional methods of studying cellular phospho-signaling measure one analyte at a time with poor standardization, rendering them inadequate for interrogating network biology and contributing to the irreproducibility of preclinical research. In this study, we test the feasibility of circumventing these issues by coupling immobilized metal affinity chromatography (IMAC)-based enrichment of phosphopeptides with targeted, multiple reaction monitoring (MRM) mass spectrometry to achieve precise, specific, standardized, multiplex quantification of phospho-signaling responses. A multiplex immobilized metal affinity chromatography- multiple reaction monitoring assay targeting phospho-analytes responsive to DNA damage was configured, analytically characterized, and deployed to generate phospho-pharmacodynamic curves from primary and immortalized human cells experiencing genotoxic stress. The multiplexed assays demonstrated linear ranges of ≥3 orders of magnitude, median lower limit of quantification of 0.64 fmol on column, median intra-assay variability of 9.3%, median inter-assay variability of 12.7%, and median total CV of 16.0%. The multiplex immobilized metal affinity chromatography- multiple reaction monitoring assay enabled robust quantification of 107 DNA damage-responsive phosphosites from human cells following DNA damage. The assays have been made publicly available as a resource to the community. The approach is generally applicable, enabling wide interrogation of signaling networks. PMID:26621847
Building an ontology of adverse drug reactions for automated signal generation in pharmacovigilance.
Henegar, Corneliu; Bousquet, Cédric; Lillo-Le Louët, Agnès; Degoulet, Patrice; Jaulent, Marie-Christine
Automated signal generation in pharmacovigilance implements unsupervised statistical machine learning techniques in order to discover unknown adverse drug reactions (ADR) in spontaneous reporting systems. The impact of the terminology used for coding ADRs has not been addressed previously. The Medical Dictionary for Regulatory Activities (MedDRA) used worldwide in pharmacovigilance cases does not provide formal definitions of terms. We have built an ontology of ADRs to describe semantics of MedDRA terms. Ontological subsumption and approximate matching inferences allow a better grouping of medically related conditions. Signal generation performances are significantly improved but time consumption related to modelization remains very important. PMID:16185681
Factors Affecting the Timing of Signal Detection of Adverse Drug Reactions.
Hashiguchi, Masayuki; Imai, Shungo; Uehara, Keiko; Maruyama, Junya; Shimizu, Mikiko; Mochizuki, Mayumi
We investigated factors affecting the timing of signal detection by comparing variations in reporting time of known and unknown ADRs after initial drug release in the USA. Data on adverse event reactions (AERs) submitted to U.S. FDA was used. Six ADRs associated with 6 drugs (rosuvastatin, aripiprazole, teriparatide, telithromycin, exenatide, varenicline) were investigated: Changes in the proportional reporting ratio, reporting odds ratio, and information component as indexes of signal detection were followed every 3 months after each drugs release, and the time for detection of signals was investigated. The time for the detection of signal to be detected after drug release in the USA was 2-10 months for known ADRs and 19-44 months for unknown ones. The median lag time for known and unknown ADRs was 99.0-122.5 days and 185.5-306.0 days, respectively. When the FDA released advisory information on rare but potentially serious health risks of an unknown ADR, the time lag to report from the onset of ADRs to the FDA was shorter. This study suggested that one factor affecting signal detection time is whether an ADR was known or unknown at release. PMID:26641634
Disruption of insulin signalling affects the neuroendocrine stress reaction in Drosophila females.
Rauschenbach, Inga Y; Karpova, Evgenia K; Adonyeva, Natalya V; Andreenkova, Olga V; Faddeeva, Natalya V; Burdina, Elena V; Alekseev, Alexander A; Menshanov, Petr N; Gruntenko, Nataly E
Juvenile hormone (JH) and dopamine are involved in the stress response in insects. The insulin/insulin-like growth factor signalling pathway has also recently been found to be involved in the regulation of various processes, including stress tolerance. However, the relationships between the JH, dopamine and insulin signalling pathways remain unclear. Here, we study the role of insulin signalling in the regulation of JH and dopamine metabolism under normal and heat stress conditions in Drosophila melanogaster females. We show that suppression of the insulin-like receptor (InR) in the corpus allatum, a specialised endocrine gland that synthesises JH, causes an increase in dopamine level and JH-hydrolysing activity and alters the activities of enzymes that produce as well as those that degrade dopamine [alkaline phosphatase (ALP), tyrosine hydroxylase (TH) and dopamine-dependent arylalkylamine N-acetyltransferase (DAT)]. We also found that InR suppression in the corpus allatum modulates dopamine, ALP, TH and JH-hydrolysing activity in response to heat stress and that it decreases the fecundity of the flies. JH application restores dopamine metabolism and fecundity in females with decreased InR expression in the corpus allatum. Our data provide evidence that the insulin/insulin-like growth factor signalling pathway regulates dopamine metabolism in females of D. melanogaster via the system of JH metabolism and that it affects the development of the neuroendocrine stress reaction and interacts with JH in the control of reproduction in this species. PMID:25214494
Leverage principle of retardation signal in titration of double protein via chip moving reaction boundary electrophoresis.
Zhang, Liu-Xia; Cao, Yi-Ren; Xiao, Hua; Liu, Xiao-Ping; Liu, Shao-Rong; Meng, Qing-Hua; Fan, Liu-Yin; Cao, Cheng-Xi
In the present work we address a simple, rapid and quantitative analytical method for detection of different proteins present in biological samples. For this, we proposed the model of titration of double protein (TDP) and its relevant leverage theory relied on the retardation signal of chip moving reaction boundary electrophoresis (MRBE). The leverage principle showed that the product of the first protein content and its absolute retardation signal is equal to that of the second protein content and its absolute one. To manifest the model, we achieved theoretical self-evidence for the demonstration of the leverage principle at first. Then relevant experiments were conducted on the TDP-MRBE chip. The results revealed that (i) there was a leverage principle of retardation signal within the TDP of two pure proteins, and (ii) a lever also existed within these two complex protein samples, evidently demonstrating the validity of TDP model and leverage theory in MRBE chip. It was also showed that the proposed technique could provide a rapid and simple quantitative analysis of two protein samples in a mixture. Finally, we successfully applied the developed technique for the quantification of soymilk in adulterated infant formula. The TDP-MRBE opens up a new window for the detection of adulteration ratio of the poor food (milk) in blended high quality one. PMID:26414025
Receptor clustering affects signal transduction at the membrane level in the reaction-limited regime
NASA Astrophysics Data System (ADS)
Caré, Bertrand R.; Soula, Hédi A.
Many types of membrane receptors are found to be organized as clusters on the cell surface. We investigate the potential effect of such receptor clustering on the intracellular signal transduction stage. We consider a canonical pathway with a membrane receptor (R) activating a membrane-bound intracellular relay protein (G). We use Monte Carlo simulations to recreate biochemical reactions using different receptor spatial distributions and explore the dynamics of the signal transduction. Results show that activation of G by R is severely impaired by R clustering, leading to an apparent blunted biological effect compared to control. Paradoxically, this clustering decreases the half maximal effective dose (ED50) of the transduction stage, increasing the apparent affinity. We study an example of inter-receptor interaction in order to account for possible compensatory effects of clustering and observe the parameter range in which such interactions slightly counterbalance the loss of activation of G. The membrane receptors' spatial distribution affects the internal stages of signal amplification, suggesting a functional role for membrane domains and receptor clustering independently of proximity-induced receptor-receptor interactions.
Ultrasensitive Multiplexed Immunoassay for Tumor Biomarkers Based on DNA Hybridization Chain Reaction Amplifying Signal.
Guo, Jinjin; Wang, Junchun; Zhao, Junqing; Guo, Zilin; Zhang, Yuzhong
In this work, a novel electrochemical immunoassay protocol has been reported for simultaneous determination of multiple tumor biomarkers based on DNA hybridization chain reaction (HCR) for signal amplification. Alpha-fetoprotein (AFP) and prostate specific antigen (PSA) were selected as model biomarkers. The immunoassay protocol contained primary antibodies immobilized on gold nanoparticles (Au NPs), secondary antibodies conjugated with DNA concatemer from HCR of primer, auxiliary probe, and signal probe labeled with signal molecules (methyleneblue (MB) and ferrocene (Fc)). In the presence of target biomarkers, the sandwich immunocomplex was formed between the primary antibodies and secondary antibodies bioconjugates carrying numerous signal molecules. As a result, two well-resolved reduction peaks, one was at -0.35 V (corresponding to MB) and other was at 0.33 V (corresponding to Fc; both vs SCE), were obtained in differential pulse voltammetry, and peak currents changed were related to the level of biomarkers. Under optimal conditions, the electrochemical immunoassay exhibited a wide linear response range (0.5 pg mL(-1) to 50 ng mL(-1)) and low detection limits (PSA, 0.17 pg mL(-1); AFP, 0.25 pg mL(-1)) (at S/N = 3). In addition, the immunoassay was evaluated by analyzing simulate human serum sample, and the recoveries obtained were within 99.4-107.6% for PSA and 97.9-108.2% for AFP, indicating the immnuoassay could be applied to the simultaneous detection of AFP and PSA in human serum samples. PMID:26937717
A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification.
Ma, Cuiping; Wang, Wenshuo; Mulchandani, Ashok; Shi, Chao
A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5 nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs. PMID:24780220
Symmetry breaking in a bulk-surface reaction-diffusion model for signalling networks
NASA Astrophysics Data System (ADS)
Rätz, Andreas; Röger, Matthias
Signalling molecules play an important role for many cellular functions. We investigate here a general system of two membrane reaction-diffusion equations coupled to a diffusion equation inside the cell by a Robin-type boundary condition and a flux term in the membrane equations. A specific model of this form was recently proposed by the authors for the GTPase cycle in cells. We investigate here a putative role of diffusive instabilities in cell polarization. By a linearized stability analysis, we identify two different mechanisms. The first resembles a classical Turing instability for the membrane subsystem and requires (unrealistically) large differences in the lateral diffusion of activator and substrate. On the other hand, the second possibility is induced by the difference in cytosolic and lateral diffusion and appears much more realistic. We complement our theoretical analysis by numerical simulations that confirm the new stability mechanism and allow us to investigate the evolution beyond the regime where the linearization applies.
Designing Driver Assistance Systems with Crossmodal Signals: Multisensory Integration Rules for Saccadic Reaction Times Apply
Steenken, Rike; Weber, Lars; Colonius, Hans; Diederich, Adele
Modern driver assistance systems make increasing use of auditory and tactile signals in order to reduce the driver's visual information load. This entails potential crossmodal interaction effects that need to be taken into account in designing an optimal system. Here we show that saccadic reaction times to visual targets (cockpit or outside mirror), presented in a driving simulator environment and accompanied by auditory or tactile accessories, follow some well-known spatiotemporal rules of multisensory integration, usually found under confined laboratory conditions. Auditory nontargets speed up reaction time by about 80 ms. The effect tends to be maximal when the nontarget is presented 50 ms before the target and when target and nontarget are spatially coincident. The effect of a tactile nontarget (vibrating steering wheel) was less pronounced and not spatially specific. It is shown that the average reaction times are well-described by the stochastic "time window of integration" model for multisensory integration developed by the authors. This two-stage model postulates that crossmodal interaction occurs only if the peripheral processes from the different sensory modalities terminate within a fixed temporal interval, and that the amount of crossmodal interaction manifests itself in an increase or decrease of second stage processing time. A qualitative test is consistent with the model prediction that the probability of interaction, but not the amount of crossmodal interaction, depends on target–nontarget onset asynchrony. A quantitative model fit yields estimates of individual participants' parameters, including the size of the time window. Some consequences for the design of driver assistance systems are discussed. PMID:24800823
Human TLR1 deficiency is associated with impaired mycobacterial signaling and protection from leprosy reversal reaction.
Misch, Elizabeth A; Macdonald, Murdo; Ranjit, Chaman; Sapkota, Bishwa R; Wells, Richard D; Siddiqui, M Ruby; Kaplan, Gilla; Hawn, Thomas R
Toll-like receptors (TLRs) are important regulators of the innate immune response to pathogens, including Mycobacterium leprae, which is recognized by TLR1/2 heterodimers. We previously identified a transmembrane domain polymorphism, TLR1_T1805G, that encodes an isoleucine to serine substitution and is associated with impaired signaling. We hypothesized that this TLR1 SNP regulates the innate immune response and susceptibility to leprosy. In HEK293 cells transfected with the 1805T or 1805G variant and stimulated with extracts of M. leprae, NF-kappaB activity was impaired in cells with the 1805G polymorphism. We next stimulated PBMCs from individuals with different genotypes for this SNP and found that 1805GG individuals had significantly reduced cytokine responses to both whole irradiated M. leprae and cell wall extracts. To investigate whether TLR1 variation is associated with clinical presentations of leprosy or leprosy immune reactions, we examined 933 Nepalese leprosy patients, including 238 with reversal reaction (RR), an immune reaction characterized by a Th1 T cell cytokine response. We found that the 1805G allele was associated with protection from RR with an odds ratio (OR) of 0.51 (95% CI 0.29-0.87, p = 0.01). Individuals with 1805 genotypes GG or TG also had a reduced risk of RR in comparison to genotype TT with an OR of 0.55 (95% CI 0.31-0.97, p = 0.04). To our knowledge, this is the first association of TLR1 with a Th1-mediated immune response. Our findings suggest that TLR1 deficiency influences adaptive immunity during leprosy infection to affect clinical manifestations such as nerve damage and disability. PMID:18461142
Electrochemical sensor for glutathione detection based on mercury ion triggered hybridization chain reaction signal amplification.
Wang, Yonghong; Jiang, Lun; Leng, Qinggang; Wu, Yaohui; He, Xiaoxiao; Wang, Kemin
In this work, we design a new simple and highly sensitive strategy for electrochemical detection of glutathione (GSH) via mercury ion (Hg(2+)) triggered hybridization chain reaction (HCR) signal amplification. It is observed that in the absence of GSH, a specific thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination can fold into hairpin structures. While in the presence of GSH, it thus can be chelated with Hg(2+), resulting in Hg(2+) released from the T-Hg(2+)-T hairpin complex which then forms into ssDNA structure to further hybridize with the surface-immobilized capture DNA probe on the gold electrode with a sticky tail left. The presence of two hairpin helper probes through HCR leads to the formation of extended dsDNA superstructure on the electrode surface, which therefore causes the intercalation of numerous electroactive species ([Ru(NH3)6](3+)) into the dsDNA grooves, followed by a significantly amplified signal output whose intensity is related to the concentration of the GSH. Taking advantage of merits of enzyme-free amplification power of the HCR, the inherent high sensitivity of the electrochemical technique, and label-free detection which utilizes an electroactive species as a signaling molecule that binds to the anionic phosphate backbone of DNA strands via electrostatic force, not only does the proposed strategy enable sensitive detection of GSH, but show high selectivity against other amino acid, making our method a simple and sensitive addition to the amplified GSH detection. PMID:26528805
[Research on early warning signals of adverse drug reactions to parenterally administered xiyanping based on spontaneous reporting system (SRS) data].
Wang, Zhi-Fei; Xiang, Yong-Yang; Xie, Yan-Ming
This article focused on early warning signals regarding the safety of parenterally administered Xiyanping. The study data was obtained from reports made between 2005-2012 from the national spontaneous reporting system (SRS). Proportion reporting ratio (PRR) and Bayesian confidence propagation neural network (BCPNN) algorithms were used to analyse: erythra, pruritus, anaphylactoid reactions and shiver with cold, these 4 adverse drug reactions had a total count of more than 500 events. The article found that Xiyanping's incidence rate of erythra was higher than for background-drugs in every year and in every season. Pruritus was an early warning signal in the second season of 2009, and anaphylactoid reaction was an early warning signal in the fourth season of 2011 and in the second season of 2012. There was however no early warning signal indicated by shiver with cold. This data indicates that erythra maybe an adverse drug reactions to parenterally administered Xiyanping, and if the incidence rate of pruritus and anaphylactoid reaction rises attention should be paid to its safety. PMID:24471321
Photosynthetic light reactions--an adjustable hub in basic production and plant immunity signaling.
Kangasjärvi, Saijaliisa; Tikkanen, Mikko; Durian, Guido; Aro, Eva-Mari
Photosynthetic efficiency is a key trait that influences the sustainable utilization of plants for energy and nutrition. By now, extensive research on photosynthetic processes has underscored important structural and functional relationships among photosynthetic thylakoid membrane protein complexes, and their roles in determining the productivity and stress resistance of plants. Photosystem II photoinhibition-repair cycle, for example, has arisen vital in protecting also Photosystem I against light-induced damage. Availability of highly sophisticated genetic, biochemical and biophysical tools has greatly expanded the catalog of components that carry out photoprotective functions in plants. On thylakoid membranes, these components encompass a network of overlapping systems that allow delicate regulation of linear and cyclic electron transfer pathways, balancing of excitation energy distribution between the two photosystems and dissipation of excess light energy in the antenna system as heat. An increasing number of reports indicate that the above mentioned mechanisms also mediate important functions in the regulation of biotic stress responses in plants. Particularly the handling of excitation energy in the light harvesting II antenna complexes appears central to plant immunity signaling. Comprehensive understanding of the underlying mechanisms and regulatory cross-talk, however, still remain elusive. This review highlights the current understanding of components that regulate the function of photosynthetic light reactions and directly or indirectly also modulate disease resistance in higher plants. PMID:24361390
Controlling the rates of biochemical reactions and signaling networks by shape and volume changes.
Lizana, L; Bauer, B; Orwar, O
In biological systems, chemical activity takes place in micrometer- and nanometer-sized compartments that constantly change in shape and volume. These ever-changing cellular compartments embed chemical reactions, and we demonstrate that the rates of such incorporated reactions are directly affected by the ongoing shape reconfigurations. First, we show that the rate of product formation in an enzymatic reaction can be regulated by simple volume contraction-dilation transitions. The results suggest that mitochondria may regulate the dynamics of interior reaction pathways (e.g., the Krebs cycle) by volume changes. We then show the effect of shape changes on reactions occurring in more complex and structured systems by using biomimetic networks composed of micrometer-sized compartments joined together by nanotubes. Chemical activity was measured by implementing an enzymatic reaction-diffusion system. During ongoing reactions, the network connectivity is changed suddenly (similar to the dynamic tube formations found inside Golgi stacks, for example), and the effect on the reaction is registered. We show that spatiotemporal properties of the reaction-diffusion system are extremely sensitive to sudden changes in network topology and that chemical reactions can be initiated, or boosted, in certain nodes as a function of connectivity. PMID:18337513
Modulation of lead-induced performance deficit in children by varying signal rate in a serial choice reaction task
Winneke, G.; Brockhaus, A.; Collet, W.; Kraemer, U. )
Evidence is presented showing that serial choice reaction performance is disrupted at low blood lead levels (PbB), and that parametric variation of task characteristics modulates the degree of disruption. This evidence is based on two independent studies in 6- to 9-year-old children living in two lead smelter areas in the cities of Nordenham (N = 114) and Stolberg (N = 109) in West Germany. Average PbB was 8.2 micrograms/100 ml (4.4-23.8 micrograms/100 ml) in the Nordenham sample and 7.4 micrograms/100 ml (4.2-18.0 micrograms/100 ml) in the Stolberg sample. Serial choice reaction performance was assessed by means of the Vienna reaction device in which a random sequence of light and tone signals has to be answered by pressing appropriate response buttons. Correct (hits) and false responses (errors) were evaluated as performance measures, and signal rate was varied in order to achieve easy and difficult task conditions. Exposure-related performance deficit was more pronounced for errors than for hits, more clearcut for high than for low signal rates, and proved significant in both studies after correction for confounding using confounder models of different complexities. Some features of the observed deficit resemble clinical observations in children presenting with attention deficit disorder.
Mass Spectrometric-Based Selected Reaction Monitoring of Protein Phosphorylation during Symbiotic Signaling in the Model Legume, Medicago truncatula
Maeda, Junko; Barrett-Wilt, Gregory A.; Sussman, Michael R.
Unlike the major cereal crops corn, rice, and wheat, leguminous plants such as soybean and alfalfa can meet their nitrogen requirement via endosymbiotic associations with soil bacteria. The establishment of this symbiosis is a complex process playing out over several weeks and is facilitated by the exchange of chemical signals between these partners from different kingdoms. Several plant components that are involved in this signaling pathway have been identified, but there is still a great deal of uncertainty regarding the early events in symbiotic signaling, i.e., within the first minutes and hours after the rhizobial signals (Nod factors) are perceived at the plant plasma membrane. The presence of several protein kinases in this pathway suggests a mechanism of signal transduction via posttranslational modification of proteins in which phosphate is added to the hydroxyl groups of serine, threonine and tyrosine amino acid side chains. To monitor the phosphorylation dynamics and complement our previous untargeted 'discovery' approach, we report here the results of experiments using a targeted mass spectrometric technique, Selected Reaction Monitoring (SRM) that enables the quantification of phosphorylation targets with great sensitivity and precision. Using this approach, we confirm a rapid change in the level of phosphorylation in 4 phosphosites of at least 4 plant phosphoproteins that have not been previously characterized. This detailed analysis reveals aspects of the symbiotic signaling mechanism in legumes that, in the long term, will inform efforts to engineer this nitrogen-fixing symbiosis in important non-legume crops such as rice, wheat and corn. PMID:27203723
Mass Spectrometric-Based Selected Reaction Monitoring of Protein Phosphorylation during Symbiotic Signaling in the Model Legume, Medicago truncatula.
Van Ness, Lori K; Jayaraman, Dhileepkumar; Maeda, Junko; Barrett-Wilt, Gregory A; Sussman, Michael R; Ané, Jean-Michel
Unlike the major cereal crops corn, rice, and wheat, leguminous plants such as soybean and alfalfa can meet their nitrogen requirement via endosymbiotic associations with soil bacteria. The establishment of this symbiosis is a complex process playing out over several weeks and is facilitated by the exchange of chemical signals between these partners from different kingdoms. Several plant components that are involved in this signaling pathway have been identified, but there is still a great deal of uncertainty regarding the early events in symbiotic signaling, i.e., within the first minutes and hours after the rhizobial signals (Nod factors) are perceived at the plant plasma membrane. The presence of several protein kinases in this pathway suggests a mechanism of signal transduction via posttranslational modification of proteins in which phosphate is added to the hydroxyl groups of serine, threonine and tyrosine amino acid side chains. To monitor the phosphorylation dynamics and complement our previous untargeted 'discovery' approach, we report here the results of experiments using a targeted mass spectrometric technique, Selected Reaction Monitoring (SRM) that enables the quantification of phosphorylation targets with great sensitivity and precision. Using this approach, we confirm a rapid change in the level of phosphorylation in 4 phosphosites of at least 4 plant phosphoproteins that have not been previously characterized. This detailed analysis reveals aspects of the symbiotic signaling mechanism in legumes that, in the long term, will inform efforts to engineer this nitrogen-fixing symbiosis in important non-legume crops such as rice, wheat and corn. PMID:27203723
Egg-jelly signal molecules for triggering the acrosome reaction in starfish spermatozoa.
Hoshi, M; Nishigaki, T; Ushiyama, A; Okinaga, T; Chiba, K; Matsumoto, M
It was in the early 1950s that J.C. Dan discovered the acrosome reaction in sea urchins, starfishes and several other marine invertebrates at Misaki Marine Biological Station on the Pacific coast of Japan. We now know that in many animals including mammals the acrosome reaction is an essential, and probably the most central, change in spermatozoa for fertilization. Starfish spermatozoa undergo the acrosome reaction upon encountering the jelly coat consisting of glycoproteins, steroid saponins, oligopeptides and inorganic components. To induce the acrosome reaction, three egg jelly components act in concert on the spermatozoa: a highly sulfated glycoprotein named acrosome reaction-inducing substance (ARIS), a group of sulfated steroidal saponins named Co-ARIS, and a group of glutamine-rich tetratriacontapeptides named sperm activating peptide (SAP). The action of ARIS is quite species-specific due to the specificity of ARIS-receptors in a restricted domain of the sperm surface and depends very much on sulfated saccharide chains. Co-ARIS is not much species-specific and its action depends on the sulfate group and steroid side chain. SAPs have a ring of 25 residues and increase the intracellular pH of spermatozoa. None of them can induce the acrosome reaction by itself in normal sea water, but ARIS does induce it in high Ca2+ or high pH sea water. Although a combination of ARIS and either Co-ARIS or SAP induces the acrosome reaction in normal sea water, all three are required to mimic the full activity of dissolved jelly coat. PMID:7981026
Signal Detection of Adverse Drug Reaction of Amoxicillin Using the Korea Adverse Event Reporting System Database.
Soukavong, Mick; Kim, Jungmee; Park, Kyounghoon; Yang, Bo Ram; Lee, Joongyub; Jin, Xue Mei; Park, Byung Joo
We conducted pharmacovigilance data mining for a β-lactam antibiotics, amoxicillin, and compare the adverse events (AEs) with the drug labels of 9 countries including Korea, USA, UK, Japan, Germany, Swiss, Italy, France, and Laos. We used the Korea Adverse Event Reporting System (KAERS) database, a nationwide database of AE reports, between December 1988 and June 2014. Frequentist and Bayesian methods were used to calculate disproportionality distribution of drug-AE pairs. The AE which was detected by all the three indices of proportional reporting ratio (PRR), reporting odds ratio (ROR), and information component (IC) was defined as a signal. The KAERS database contained a total of 807,582 AE reports, among which 1,722 reports were attributed to amoxicillin. Among the 192,510 antibiotics-AE pairs, the number of amoxicillin-AE pairs was 2,913. Among 241 AEs, 52 adverse events were detected as amoxicillin signals. Comparing the drug labels of 9 countries, 12 adverse events including ineffective medicine, bronchitis, rhinitis, sinusitis, dry mouth, gastroesophageal reflux, hypercholesterolemia, gastric carcinoma, abnormal crying, induration, pulmonary carcinoma, and influenza-like symptoms were not listed on any of the labels of nine countries. In conclusion, we detected 12 new signals of amoxicillin which were not listed on the labels of 9 countries. Therefore, it should be followed by signal evaluation including causal association, clinical significance, and preventability. PMID:27510377
Signal Detection of Adverse Drug Reaction of Amoxicillin Using the Korea Adverse Event Reporting System Database
We conducted pharmacovigilance data mining for a β-lactam antibiotics, amoxicillin, and compare the adverse events (AEs) with the drug labels of 9 countries including Korea, USA, UK, Japan, Germany, Swiss, Italy, France, and Laos. We used the Korea Adverse Event Reporting System (KAERS) database, a nationwide database of AE reports, between December 1988 and June 2014. Frequentist and Bayesian methods were used to calculate disproportionality distribution of drug-AE pairs. The AE which was detected by all the three indices of proportional reporting ratio (PRR), reporting odds ratio (ROR), and information component (IC) was defined as a signal. The KAERS database contained a total of 807,582 AE reports, among which 1,722 reports were attributed to amoxicillin. Among the 192,510 antibiotics-AE pairs, the number of amoxicillin-AE pairs was 2,913. Among 241 AEs, 52 adverse events were detected as amoxicillin signals. Comparing the drug labels of 9 countries, 12 adverse events including ineffective medicine, bronchitis, rhinitis, sinusitis, dry mouth, gastroesophageal reflux, hypercholesterolemia, gastric carcinoma, abnormal crying, induration, pulmonary carcinoma, and influenza-like symptoms were not listed on any of the labels of nine countries. In conclusion, we detected 12 new signals of amoxicillin which were not listed on the labels of 9 countries. Therefore, it should be followed by signal evaluation including causal association, clinical significance, and preventability. PMID:27510377
Independent Component Analysis of Functional Networks for Response Inhibition: Inter-Subject Variation in Stop Signal Reaction Time
Zhang, Sheng; Tsai, Shang-Jui; Hu, Sien; Xu, Jiansong; Chao, Herta H.; Calhoun, Vince D.; Li, Chiang-Shan R.
Cognitive control is a critical executive function. Many studies have combined general linear modeling and the stop signal task (SST) to delineate the component processes of cognitive control. For instance, by contrasting stop success (SS) and stop error (SE) trials in the SST, investigators examined regional responses to stop signal inhibition. In contrast to this parameterized approach, independent component analysis (ICA) elucidates brain networks subserving cognitive control. In our earlier work of 59 adults performing the SST during fMRI, we characterized six independent components (ICs). However, none of these ICs correlated with stop signal performance, raising questions about their behavioral validity. Here, in a larger sample (n=100), we identified and explored 23 ICs for correlation with the stop signal reaction time (SSRT), a measure of the efficiency of response inhibition. At a corrected threshold (P < 0.0005), a paracentral lobule-midcingulate network and a left inferior parietal-supplementary motor-somatomotor network showed a positive correlation between SE beta weight and SSRT. In contrast, a midline cerebellum–thalamus–pallidum network showed a negative correlation between SE beta weight and SSRT. These findings suggest that motor preparation and execution prolongs the SSRT, likely via an interaction between the go and stop processes as suggested by the race model. Behaviorally, consistent with this hypothesis, the difference in G and SE reaction times is positively correlated with SSRT across subjects. These new results highlight the importance of cognitive motor regions in response inhibition and support the utility of ICA in uncovering functional networks for cognitive control in the SST. PMID:26089095
Independent component analysis of functional networks for response inhibition: Inter-subject variation in stop signal reaction time.
Zhang, Sheng; Tsai, Shang-Jui; Hu, Sien; Xu, Jiansong; Chao, Herta H; Calhoun, Vince D; Li, Chiang-Shan R
Cognitive control is a critical executive function. Many studies have combined general linear modeling and the stop signal task (SST) to delineate the component processes of cognitive control. For instance, by contrasting stop success (SS) and stop error (SE) trials in the SST, investigators examined regional responses to stop signal inhibition. In contrast to this parameterized approach, independent component analysis (ICA) elucidates brain networks subserving cognitive control. In our earlier work of 59 adults performing the SST during fMRI, we characterized six independent components (ICs). However, none of these ICs correlated with stop signal performance, raising questions about their behavioral validity. Here, in a larger sample (n = 100), we identified and explored 23 ICs for correlation with the stop signal reaction time (SSRT), a measure of the efficiency of response inhibition. At a corrected threshold (P < 0.0005), a paracentral lobule-midcingulate network and a left inferior parietal-supplementary motor-somatomotor network showed a positive correlation between SE beta weight and SSRT. In contrast, a midline cerebellum-thalamus-pallidum network showed a negative correlation between SE beta weight and SSRT. These findings suggest that motor preparation and execution prolongs the SSRT, likely via an interaction between the go and stop processes as suggested by the race model. Behaviorally, consistent with this hypothesis, the difference in G and SE reaction times is positively correlated with SSRT across subjects. These new results highlight the importance of cognitive motor regions in response inhibition and support the utility of ICA in uncovering functional networks for cognitive control in the SST. PMID:26089095
A sensitive electrochemiluminescent aptasensor based on perylene derivatives as a novel co-reaction accelerator for signal amplification.
Yu, Yan-Qing; Zhang, Hai-Yu; Chai, Ya-Qin; Yuan, Ruo; Zhuo, Ying
Herein, a novel signal amplification strategy was designed using the perylene derivative as the co-reaction accelerator toward graphene-CdTe quantum dots (G-CdTe)/S2O8(2-) system to construct a highly sensitive electrochemiluminescent (ECL) aptasensor for thrombin (TB) detection. Firstly, the G-CdTe nanocomposites were prepared by one-step method of in situ generating CdTe quantum dots onto the surface of the graphene oxide by using 3-mercaptopropionic acid as the CdTe QDs stabilizer. Then, a kind of perylene derivative (PTC-Lys), was synthesized by covalently binding L-lysine to 3,4,9,10-perylenetetracarboxylic acid, which was further immobilized onto the G-CdTe by the π-π* stacking and cross-linked the detection thrombin aptamer (TBA II) to obtain the TBA II/PTC-Lys/G-CdTe signal probes. It is worth pointing out that PTC-Lys acting as an efficient co-reaction accelerator interacted with the co-reactant of S2O8(2-) rather than G-CdTe to promote the more oxidant mediators of SO4(•-), which could further react with G-CdTe to produce excited state species G-CdTe* for emitting light. Compared with the G-CdTe/S2O8(2-) ECL system, our proposed strategy with the introduction of co-reaction accelerator of PTC-Lys exhibited ultra-high sensitivity to quantify the concentration of TB from 1.0×10(-7)nM to 10nM with a detection limit of 34aM. PMID:27148827
NMR signal enhancement for hyperpolarized fluids continuously generated in hydrogenation reactions with parahydrogen.
Barskiy, Danila A; Salnikov, Oleg G; Kovtunov, Kirill V; Koptyug, Igor V
In the present study we analyze the factors which can lower hyperpolarization of fluids produced in a continuous flow regime by the parahydrogen-induced polarization technique. We use the findings of this analysis to examine the flow rate dependence of propane hyperpolarization produced in the heterogeneous propylene hydrogenation by parahydrogen over Rh/TiO2 catalyst. We have estimated the maximum attainable propane (1)H hyperpolarization yield and the corrected percentage of pairwise hydrogen addition in heterogeneous hydrogenation, which was found to be ∼7%. The approach developed for polarization analysis is useful for the optimization of experimental setup and reaction conditions to obtain maximum hyperpolarization for parahydrogen-based catalyst-free continuously generated fluids applicable in biomedical magnetic resonance imaging. PMID:25587942
Signaling gradients in cascades of two-state reaction-diffusion systems.
Berezhkovskii, Alexander M; Coppey, Mathieu; Shvartsman, Stanislav Y
Biological networks frequently use cascades, generally defined as chain-like arrangements of similar modules. Spatially lumped cascades can serve as noise filters, time-delay, or thresholding elements. The operation and functional capabilities of spatially distributed cascades are much less understood. Motivated by studies of pattern formation in the early Drosophila embryo, we analyze cascades of 2-state reaction-diffusion systems. At each stage within such as a cascade, a diffusible particle is reversibly bound by immobile traps and can be annihilated in both mobile and immobile states. When trapped, these particles drive the next stage by converting mobile particles of a different type from a passive to active form. The cascade initiated by injection of mobile particles into the first stage. We derive analytical expressions for the steady-state concentration profiles of mobile and immobile particles and analyze how the output of a cascade is controlled by properties of the constituent stages. PMID:19147842
Hyperbranched Hybridization Chain Reaction for Triggered Signal Amplification and Concatenated Logic Circuits.
Bi, Sai; Chen, Min; Jia, Xiaoqiang; Dong, Ying; Wang, Zonghua
A hyper-branched hybridization chain reaction (HB-HCR) is presented herein, which consists of only six species that can metastably coexist until the introduction of an initiator DNA to trigger a cascade of hybridization events, leading to the self-sustained assembly of hyper-branched and nicked double-stranded DNA structures. The system can readily achieve ultrasensitive detection of target DNA. Moreover, the HB-HCR principle is successfully applied to construct three-input concatenated logic circuits with excellent specificity and extended to design a security-mimicking keypad lock system. Significantly, the HB-HCR-based keypad lock can alarm immediately if the "password" is incorrect. Overall, the proposed HB-HCR with high amplification efficiency is simple, homogeneous, fast, robust, and low-cost, and holds great promise in the development of biosensing, in the programmable assembly of DNA architectures, and in molecular logic operations. PMID:26012841
Measuring Attention in Rodents: Comparison of a Modified Signal Detection Task and the 5-Choice Serial Reaction Time Task
Turner, Karly M.; Peak, James; Burne, Thomas H. J.
Neuropsychiatric research has utilized cognitive testing in rodents to improve our understanding of cognitive deficits and for preclinical drug development. However, more sophisticated cognitive tasks have not been as widely exploited due to low throughput and the extensive training time required. We developed a modified signal detection task (SDT) based on the growing body of literature aimed at improving cognitive testing in rodents. This study directly compares performance on the modified SDT with a traditional test for measuring attention, the 5-choice serial reaction time task (5CSRTT). Adult male Sprague-Dawley rats were trained on either the 5CSRTT or the SDT. Briefly, the 5CSRTT required rodents to pay attention to a spatial array of five apertures and respond with a nose poke when an aperture was illuminated. The SDT required the rat to attend to a light panel and respond either left or right to indicate the presence of a signal. In addition, modifications were made to the reward delivery, timing, control of body positioning, and the self-initiation of trials. It was found that less training time was required for the SDT, with both sessions to criteria and daily session duration significantly reduced. Rats performed with a high level of accuracy (>87%) on both tasks, however omissions were far more frequent on the 5CSRTT. The signal duration was reduced on both tasks as a manipulation of task difficulty relevant to attention and a similar pattern of decreasing accuracy was observed on both tasks. These results demonstrate some of the advantages of the SDT over the traditional 5CSRTT as being higher throughput with reduced training time, fewer omission responses and their body position was controlled at stimulus onset. In addition, rats performing the SDT had comparable high levels of accuracy. These results highlight the differences and similarities between the 5CSRTT and a modified SDT as tools for assessing attention in preclinical animal models. PMID
Determination of knockdown resistance allele frequencies in global human head louse populations using the serial invasive signal amplification reaction
Hodgdon, Hilliary E.; Yoon, Kyong Sup; Previte, Domenic J.; Kim, Hyo Jeong; Aboelghar, Gamal E.; Lee, Si Hyeock; Clark, J. Marshall
BACKGROUND Pediculosis is the most prevalent parasitic infestation of humans. Resistance to pyrethrin- and pyrethroid-based pediculicides is due to knockdown (kdr)-type point mutations in the voltage-sensitive sodium channel α-subunit gene. Early detection of resistance is crucial for the selection of effective management strategies. RESULTS Kdr allele frequencies of lice from 14 countries were determined using serial invasive signal amplification reaction. Lice collected from Uruguay, UK and Australia had kdr allele frequencies of 100% while lice from Ecuador, Papua New Guinea, South Korea and Thailand had kdr allele frequencies of 0%. The remaining 7 countries investigated, including seven US populations, two Argentina, Brazil, Denmark, Czech Republic, Egypt and Israel, displayed variable kdr allele frequencies, ranging from 11% to 97%. CONCLUSION The newly developed and validated SISAR method is suitable for accurate monitoring of kdr allele frequencies in head lice. Proactive management is needed where kdr-type resistance is not yet saturated. Based on sodium channel insensitivity and its occurrence in louse populations resistant to pyrethrin- and pyrethroid-based pediculicides, the T917I mutation appears a key marker for resistance. Results from the Egyptian population, however, indicate that phenotypic resistance of lice with single or double mutations (M815I and/or L920F) should also be determined. PMID:20564731
Herbivore-Triggered Electrophysiological Reactions: Candidates for Systemic Signals in Higher Plants and the Challenge of Their Identification.
Zimmermann, Matthias R; Mithöfer, Axel; Will, Torsten; Felle, Hubert H; Furch, Alexandra C U
In stressed plants, electrophysiological reactions (elRs) are presumed to contribute to long-distance intercellular communication between distant plant parts. Because of the focus on abiotic stress-induced elRs in recent decades, biotic stress-triggered elRs have been widely ignored. It is likely that the challenge to identify the particular elR types (action potential [AP], variation potential, and system potential [SP]) was responsible for this course of action. Thus, this survey focused on insect larva feeding (Spodoptera littoralis and Manduca sexta) that triggers distant APs, variation potentials, and SPs in monocotyledonous and dicotyledonous plant species (Hordeum vulgare, Vicia faba, and Nicotiana tabacum). APs were detected only after feeding on the stem/culm, whereas SPs were observed systemically following damage to both stem/culm and leaves. This was attributed to the unequal vascular innervation of the plant and a selective electrophysiological connectivity of the plant tissue. However, striking variations in voltage patterns were detected for each elR type. Further analyses (also in Brassica napus and Cucurbita maxima) employing complementary electrophysiological approaches in response to different stimuli revealed various reasons for these voltage pattern variations: an intrinsic plasticity of elRs, a plant-specific signature of elRs, a specific influence of the applied (a)biotic trigger, the impact of the technical approach, and/or the experimental setup. As a consequence, voltage pattern variations, which are not irregular but rather common, need to be included in electrophysiological signaling analysis. Due to their widespread occurrence, systemic propagation, and respective triggers, elRs should be considered as candidates for long-distance communication in higher plants. PMID:26872949
Direct RNA detection without nucleic acid purification and PCR: Combining sandwich hybridization with signal amplification based on branched hybridization chain reaction.
Xu, Yao; Zheng, Zhi
We have developed a convenient, robust and low-cost RNA detection system suitable for high-throughput applications. This system uses a highly specific sandwich hybridization to capture target RNA directly onto solid support, followed by on-site signal amplification via 2-dimensional, branched hybridizing chain polymerization through toehold-mediated strand displacement reaction. The assay uses SYBR Green to detect targets at concentrations as low as 1pM, without involving nucleic acid purification or any enzymatic reaction, using ordinary oligonucleotides without modification or labeling. The system was demonstrated in the detection of malaria RNA in blood and GAPDH gene expression in cell lysate. PMID:26761615
Assessing the Performance Characteristics of Signals Used by a Clinical Event Monitor to Detect Adverse Drug Reactions in the Nursing Home
Handler, Steven M.; Hanlon, Joseph T.; Perera, Subashan; Saul, Melissa I.; Fridsma, Douglas B.; Visweswaran, Shyam; Studenski, Stephanie A.; Roumani, Yazan F.; Castle, Nicholas G.; Nace, David A.; Becich, Michael J.
Adverse drug reactions (ADRs) are a common cause of morbidity and mortality in the nursing home (NH) setting. Traditional non-automated mechanisms for ADR detection are time-consuming, costly, and fail to detect the majority of ADRs. We describe the implementation and pharmacist evaluation of a clinical event monitor using signals previously developed by our research team to detect potential ADRs in the NH. The overall positive predictive value (PPV) for all signals combined was 81% (54/67), with individual signal PPVs ranging from 0-100%. The PPVs were 53% (10/19) for the antidote signals category and 96% (44/46) for the laboratory/medication combination signals category. The majority 75% (12/16) of the preventable ADRs were laboratory/medication combination signals. The results suggest that ADRs can be detected in the NH setting with a high degree of accuracy using a clinical event monitor that employs a set of signals derived by expert consensus. PMID:18998853
A Reaction Time Advantage for Calculating Beliefs over Public Representations Signals Domain Specificity for "Theory of Mind"
ERIC Educational Resources Information Center
Cohen, Adam S.; German, Tamsin C.
In a task where participants' overt task was to track the location of an object across a sequence of events, reaction times to unpredictable probes requiring an inference about a social agent's beliefs about the location of that object were obtained. Reaction times to false belief situations were faster than responses about the (false) contents of…
Chip-based ingroove microplasma with orthogonal signal collection: new approach for carbon-containing species detection through open air reaction for performance enhancement
Meng, Fanying; Li, Xuemei; Duan, Yixiang
A novel microplasma generator based on ceramic chips has been developed and coupled with optical emission spectrometry through orthogonal detection. Stable microplasma was generated between two electrodes in the ingroove discharge chamber and the optical fiber was set in perpendicular to the gas outlet to collect emitted light. The emission signal of CN is surprisingly enhanced by reacting carbon-containing species with back-diffusion nitrogen from open air, and the enhanced CN signal is successfully applied to sensitively detect organic compounds for the first time. This article focuses to study the structural characteristic and the signal enhancement mechanism through back-diffusion reaction. Several organic compounds were detected directly with the limits of detection down to ppb level. Besides, the advantages of low energy consumption and the chip-based discharge chamber show great potential to be applied in portable devices. This development may lead to a new way for the sensitive detection of organic compounds. PMID:24763181
Detection of adverse drug reactions by medication antidote signals and comparison of their sensitivity with common methods of ADR detection
Khan, Lateef M.; Al-Harthi, Sameer E.; Alkreathy, Huda M.; Osman, Abdel-Moneim M.; Ali, Ahmed S.
Objective To determine the PPVs of selected ten medication antidote signals in recognizing potential ADRs and comparison of their sensitivity with manual chart analysis, and voluntary reporting recognizing the same ADRs. Method The inpatient EMR database of internal medicine department was utilized for a period of one year, adult patients prescribed at least one of the ten signals, were included in the study, recipient patients of antidote signals were assessed for the occurrence of an ADR by Naranjo's tool of ADR evaluation. PPVs of each antidote signal were verified. Result PPV of Methylprednisolone and Phytonadione was 0.28, Metoclopramide and Potassium Chloride – 0.29, Dextrose 50%, Promethazine, Sodium Polystyrene and Loperamide – 0.30, Protamine and Acetylcysteine – 0.33. In comparison of confirmed ADRs of antidote signals with other methods, Dextrose 50%, Metoclopramide, Sodium Polystyrene, Potassium Chloride, Methylprednisolone and Promethazine seem to be extremely significant (P value > 0.0001), while ADRs of Phytonadione, Protamine, Acetylcysteine and Loperamide were insignificant. Conclusion Antidote medication signals have definitive discerning evaluation value of ADRs over routine methods of ADR detection with a high detection rate with a minimum cost; Their integration with hospital EMR database and routine patient safety surveillance enhances transparency, time-saving and facilitates ADR detection. PMID:26594117
Reaction-based colorimetric signaling of Cu(2+) ions by oxidative coupling of phenols with 4-aminoantipyrine.
Kim, Hong Yeong; Lee, Hyo Jin; Chang, Suk-Kyu
A new Cu(2+)-selective chromogenic probe system based on the oxidative coupling of phenols with 4-aminoantipyrine was developed. Cu(2+) ions promoted facile coupling of phenols with 4-aminoantipyrine to yield quinoneimine dyes. Signaling with a number of phenols having no para-substituent, such as o-cresol and m-cresol, as well as p-chlorophenol having para substituent that could be expelled during the oxidation process was possible. The signaling of Cu(2+) ions was not interfered by the presence of representative metal ions except for Al(3+) ions. The possible interference from Al(3+) ions was successfully removed by using fluoride ions as a masking agent. The phenol-4-aminoantipyrine probe system showed chromogenic Cu(2+) signaling by prominent color change from colorless to pink with a detection limit of 8.5×10(-7) M. The signaling of Cu(2+) ions in practical samples using tap water and simulated semiconductor wastewater was also tested. PMID:25476354
Amplification and modulation of fluorescent signals by using hybridization chain reactions for multiplexed sensing of biomolecules in a one-pot
NASA Astrophysics Data System (ADS)
Nishimura, Takahiro; Ogura, Yusuke; Yamada, Kenji; Ohno, Yuko; Tanida, Jun
Fluorescence readout of molecular information is a promising approach for biomolecular sensing. For detection of enormous biomolecules via uorescence, biomolecular information should be converted to codes that can be readout easily and simultaneously. For the purpose, we study a biomolecule uorescence color (B/F) encoders that modulate uorescence signals by control of uorescence resonance energy transfer (FRET). The B/F encoder converts biomolecular signals into uorescent color codes represented with uorescent wavelengths and intensity levels. The combination offers a great number of codes for representing the biomolecular information. In this study, we discuss multiplexed detection of target biomolecules using B/F encoders. Use of the B/F encoders would offer a multiplexed biomolecular sensing in a one-pot without micro-fabrication like DNA microarray. In the experiments, we prepared B/F encoders based on two kinds of hybridization chain reactions (HCR) that make long double-stranded DNA polymers to control positions of uorescence and quencher molecules. In the B/F encoders, target molecules trigger to start assembling the polymer structures. The uorescent molecules in the absence of the targets are near the quenchers and the output uorescence is suppressed by FRET. The polymerization process separates the uorescent and quencher dyes and the uorescent signal increase. The experimental results show that the B/F encoders based on HCRs have linear and independent response to each target, and temporal signals during the encoding reactions are usable for multiplexed readout. This result leads to the multiplexed sensing in a one-pot by uorescent ampli cation and multiple uorescent color-coding.
Activation of the pre-supplementary motor area but not inferior prefrontal cortex in association with short stop signal reaction time – an intra-subject analysis
Chao, Herta HA; Luo, Xi; Chang, Jeremy LK; Li, Chiang-shan R
Background Our previous work described the neural processes of motor response inhibition during a stop signal task (SST). Employing the race model, we computed the stop signal reaction time (SSRT) to index individuals' ability in inhibitory control. The pre-supplementary motor area (preSMA), which shows greater activity in individuals with short as compared to those with long SSRT, plays a role in mediating response inhibition. In contrast, the right inferior prefrontal cortex (rIFC) showed greater activity during stop success as compared to stop error. Here we further pursued this functional differentiation of preSMA and rIFC on the basis of an intra-subject approach. Results Of 65 subjects who participated in four sessions of the SST, we identified 30 individuals who showed a difference in SSRT but were identical in other aspects of stop signal performance between the first ("early") and last two ("late") sessions. By comparing regional brain activation between the two sessions, we confirmed greater preSMA but not rIFC activity during short as compared to long SSRT session within individuals. Furthermore, putamen, anterior cerebellum and middle/posterior cingulate cortex also showed greater activity in association with short SSRT. Conclusion These results are consistent with a role of medial prefrontal cortex in controlled action and inferior frontal cortex in orienting attention. We discussed these findings with respect to the process of attentional monitoring and inhibitory motor control during stop signal inhibition. PMID:19602259
[Signal function of cytokinin 6-benzylaminopurine in the reaction of Triticum aestivum L. mesophyll cells to hyperthermia].
Musiienko, M M; Zhuk, V V; Batsmanova, L M
The signaling effect of 6-benzylaminopurine (BAP) on leaf mesophyll cells of Triticum aestivum L. under hyperthermic conditions was studied. It was found that BAP regulated photosynthetic pigment, hydrogen peroxide content and activity of antioxidant enzymes, namely superoxide dismutase, ascorbate peroxidase and catalase under high-temperature conditions. The additive effect of BAP and high temperature on the activation of cell antioxidant systems was demonstrated. BAP regulated reducing processes in mesophyll leaf cells under high-temperature conditions. PMID:25816607
Polymerase chain reaction coupling with magnetic nanoparticles-based biotin-avidin system for amplification of chemiluminescent detection signals of nucleic acid.
Li, Zhiyang; He, Lei; He, Nongyue; Deng, Yan; Shi, Zhiyang; Wang, Hua; Li, Song; Liu, Hongna; Wang, Zhifei; Wang, Daxin
A novel method was established through the detection of chemiluminescent signals of nucleic acid hybridization based on magnetic nanoparticles (MNPs) and PCR. 5' amino- modified specific probes were immobilized on the surface of silanized MNPs by Schiff reaction between amino and aldehyde group. The probes were used to capture the synthetic biotin-dUTP-labeled DNA fragments which were obtained by polymerase chain reaction (PCR). Then these complexes were bonded with streptavidin-modified alkaline phosphatase (SA-AP). Finally the chemiluminescent signals were detected by adding 3-(2'-spiroadamantane)- 4-methoxy -4-(3"-phosphoryloxy) phenyl-1, 2-dioxetane (AMPPD) which was the substrate reagent of AP. The concentration of probes which were immobilized on the surface of MNPs was studied, how to reduce the adsorption of SA-AP on the surface of MNPs was also researched. It was shown that 12.5 pmol of probes were immobilized on 1 mg of MNPs. Aldehyde-MNPs modified with probes could adsorb SA-AP, affecting the sensitivity of chemiluminescene consequently. Reduction of aldehyde group by sodium borohydride and blocking the bare position of MNPs with bovine serum albumin (BSA) could decrease the background of chemiluminescence, and this method has good specificity in detection of chloramphenicol acetyltransferase (CAT) gene. PMID:21456141
Mixed Quantum-Classical Simulations of Transient Absorption Pump-Probe Signals for a Photo-Induced Electron Transfer Reaction Coupled to an Inner-Sphere Vibrational Mode.
Martinez, Franz; Hanna, Gabriel
In a previous study (Martinez, F.; Hanna, G. Chem. Phys. Lett. 2013, 573, 77-83), we demonstrated the ability of two approximate solutions of the quantum-classical Liouville equation (QCLE) for qualitatively capturing the electronic dynamics in the pump-probe transient absorption (TA) signal of a model of a condensed phase photoinduced electron transfer reaction whose ground and excited donor states have the same equilibrium geometry. However, the question remained as to the ability of these solutions to treat the more complex situation in which the electronic states are coupled to a low-frequency inner-sphere harmonic vibrational mode (representing an intramolecular mode of the donor-acceptor complex) that shifts their equilibrium geometries with respect to each other and thereby gives rise to signatures of vibrational dynamics in the TA signal. Thus, in this study, we investigated this situation by treating the vibrational mode both quantum mechanically and classically within the context of the approximate Poisson bracket mapping equation (PBME) and forward-backward trajectory solutions (FBTS) of the QCLE. Depending on the definition of the quantum subsystem, both PBME and FBTS are capable of qualitatively capturing several of the main features in the exact TA signal and quantitatively capturing the characteristic time scale of the vibrational dynamics, despite the moderately strong subsystem-bath coupling in this model. Particularly, we found that treating the vibrational mode quantum mechanically using either PBME or FBTS better captures the signatures of the vibrational dynamics, while treating it classically using FBTS better captures the decay in the signal. These findings underscore the utility of the PBME and FBTS approaches for efficiently modeling and interpreting TA signals. PMID:26766568
Target-catalyzed hairpin assembly and intramolecular/intermolecular co-reaction for signal amplified electrochemiluminescent detection of microRNA.
Yu, Yan-Qing; Wang, Ji-Peng; Zhao, Min; Hong, Lin-Ru; Chai, Ya-Qin; Yuan, Ruo; Zhuo, Ying
Herein, a new electrochemiluminescence (ECL) strategy for enzyme-free microRNA-21 (miR-21) amplified detection was designed based on target-catalyzed hairpin assembly by combining the signal-amplification capability of both intramolecular and intermolecular ECL co-reaction. In this strategy, two hairpin DNA probes of H1 and H2 were designed as capture probes and detection probes, respectively. To be specific, the capture probes of H1 were immobilized on the multilayer interface of AuNPs and thiosemicarbazide (TSC) assembly on the single-walled carbon nanohorns decorated electrode, while the detection probes of H2 was anchored on the nanocarriers of gold nanoparticals functionalized reduced graphene oxide (Au-rGO) which were tagged with the self-enhanced ruthenium complex (PEI-Ru(ΙΙ)) in advance. Based on the target-catalyzed hairpin assembly, target miR-21 could trigger the hybridization of H1 and H2 to further be released for initiating the next hybridization process to capture a large number of H2 bioconjugates on the sensing surface. Herein, the TSC was used not only as a coupling reagent to attach the AuNPs via Au-S and Au-N bonds but also as a novel intermolecular coreactant to enhance the ECL intensity, and the PEI-Ru(ΙΙ) as emitters exhibited enhanced ECL efficiency. Therefore, a strong ECL signal was achieved by the dual amplification strategies of target recycle and the intramolecular/intermolecular co-reaction of PEI-Ru(ΙΙ) and TSC. The designed protocol provided an ultrasensitive ECL detection of miR-21 down to the sub-femtomolar level with a linear response about 6 orders of magnitude (from 1.0 × 10(-16)M to 1.0 × 10(-11)M) with a relatively low detection limit of 0.03 fM (S/N=3). PMID:26453905
A simple and rapid detection assay for peptides based on the specific recognition of aptamer and signal amplification of hybridization chain reaction.
Ma, Chao; Liu, Haiyun; Tian, Tian; Song, Xianrang; Yu, Jinghua; Yan, Mei
A simple and rapid assay for the detection of peptides is designed based on the specific recognition of aptamer, the quenching effect of graphene oxide (GO) and the efficient signal amplification of hybrid chain reaction (HCR). In this assay, the hairpin structure of aptamer is opened after binding with targets, and the initiation sequence could be exposed to hairpin probe 1 (H1) to open its hairpin structure. Then the opened H1 will open the hairpin structure of hairpin probe 2 (H2), and in turn, the opened initiation sequence of H2 continues to open H1. As a result, the specific recognition of target and fluorescent signals are accumulated through the process in short 1h. Attentively, the aptamer can not only identify target peptides, but also initiate the HCR between H1 and H2. More importantly, the HCR is initiated only after the target recognition of aptamer. After HCR, the excess hairpin probes will be anchored on the GO surface, and the background is greatly reduced due to the quenching effect of GO. By using Mucin-1(MUC1) as a model peptide, the assay has a wide linear range as two orders of magnitude and the detection range is from 0.01 to 5nM with low detection limit of 3.33pM. Therefore, the simple and rapid detection of the target can be realized, and the novel assay has great potential in detecting various peptides and even cancer cells. PMID:27093485
Involvement of mitogen-activated protein kinase and NF-κB signaling pathways in perfluorooctane sulfonic acid-induced inflammatory reaction in BV2 microglial cells.
Zhu, Jingying; Qian, Wenyi; Wang, Yixin; Gao, Rong; Wang, Jun; Xiao, Hang
Microglial activation is closely related to the pathogenesis of neurodegenerative diseases by producing proinflammatory cytokines. Perfluorooctane sulfonic acid (PFOS), known as an emerging persistent organic pollutant, is reported to disturb human immune homeostasis; however, whether it affects cytokine production or the immune response in the central nervous system remains unclear. The present study was aimed to explore whether PFOS contributed to inflammatory action and to investigate the corresponding mechanisms in BV2 microglia. PFOS-mediated morphologic changes, cytokine responses and signaling events were examined by light microscopy, real-time polymerase chain reaction, enzyme-linked immunosorbent assay and Western blot assays. Our results indicated that PFOS increased BV2 cells activation and simultaneously increased tumor necrosis factor alpha and interleukin-6 expression. In addition, the c-Jun N-terminal protein kinase inhibitor (SP600125), as well as ERK1/2 blocker (PD98059), transcriptionally at least, displayed anti-inflammatory properties on PFOS-elicited cytokine responses. Moreover, the inflammatory transcription factor NF-κB was specifically activated by PFOS as well. These results, taken together, suggested that PFOS exerts its functional effects on the response of microglial cell activation via, in part, the c-Jun N-terminal protein kinase, ERK and NF-κB signaling pathways with its subsequent influence on proinflammatory action. PMID:25677194
Silver Nanolabels-Assisted Ion-Exchange Reaction with CdTe Quantum Dots Mediated Exciton Trapping for Signal-On Photoelectrochemical Immunoassay of Mycotoxins.
Lin, Youxiu; Zhou, Qian; Tang, Dianping; Niessner, Reinhard; Yang, Huanghao; Knopp, Dietmar
Mycotoxins, highly toxic secondary metabolites produced by many invading species of filamentous fungi, contaminate different agricultural commodities under favorable temperature and humidity conditions. Herein, we successfully devised a novel signal-on photoelectrochemical immunosensing platform for the quantitative monitoring of mycotoxins (aflatoxin B1, AFB1, used as a model) in foodstuffs on the basis of silver nanolabels-assisted ion-exchange reaction with CdTe quantum dots (QDs) mediated hole-trapping. Initially, a competitive-type immunoreaction was carried out on a high-binding microplate by using silver nanoparticle (AgNP)-labeled AFB1-bovine serum albumin (AFB1-BSA) conjugates as the tags. Then, the carried AgNPs with AFB1-BSA were dissolved by acid to release numerous silver ions, which could induce ion-exchange reaction with the CdTe QDs immobilized on the electrode, thus resulting in formation of surface exciton trapping. Relative to pure CdTe QDs, the formed exciton trapping decreased the photocurrent of the modified electrode. In contrast, the detectable photocurrent increased with the increase of target AFB1 in a dynamic working range from 10 pg mL(-1) to 15 ng mL(-1) at a low limit of detection (LOD) of 3.0 pg mL(-1) under optimal conditions. In addition, the as-prepared photoelectrochemical immunosensing platform also displayed high specificity, good reproducibility, and acceptable method accuracy for detecting naturally contaminated/spiked blank peanut samples with consistent results obtained from the referenced enzyme-linked immunosorbent assay (ELISA) method. PMID:27348353
Simmons, W.R.; Koch, L.J.
A heat exchanger comprising a tank for hot liquid and a plurality of concentric, double tubes for cool liquid extending vertically through the tank is described. These tubes are bonded throughout most of their length but have an unbonded portion at both ends. The inner tubes extend between headers located above and below the tanmk and the outer tubes are welded into tube sheets forming the top and bottom of the tank at locations in the unbonded portions of the tubes. (AEC)
A new paradigm and computational framework to estimate stop-signal reaction time distributions from the inhibition of complex motor sequences
Teichert, Tobias; Ferrera, Vincent P.
Inhibitory control is an important component of executive function that allows organisms to abort emerging behavioral plans or ongoing actions on the fly as new sensory information becomes available. Current models treat inhibitory control as a race between a Go- and a Stop process that may be mediated by partially distinct neural substrates, i.e., the direct and the hyper-direct pathway of the basal ganglia. The fact that finishing times of the Stop process (Stop-Signal Reaction Time, SSRT) cannot be observed directly has precluded a precise comparison of the functional properties that govern the initiation (GoRT) and inhibition (SSRT) of a motor response. To solve this problem, we modified an existing inhibitory paradigm and developed a non-parametric framework to measure the trial-by-trial variability of SSRT. A series of simulations verified that the non-parametric approach is on par with a parametric approach and yields accurate estimates of the entire SSRT distribution from as few as ~750 trials. Our results show that in identical settings, the distribution of SSRT is very similar to the distribution of GoRT albeit somewhat shorter, wider and significantly less right-skewed. The ability to measure the precise shapes of SSRT distributions opens new avenues for research into the functional properties of the hyper-direct pathway that is believed to mediate inhibitory control. PMID:26236226
Theory of energy gain in a laser-amplifier based on a photon-branched chain reaction: Auto-wave amplification mode under the condition of input signal focusing
NASA Astrophysics Data System (ADS)
Letfullin, Renat R.; George, Thomas F.
Huge energy gain is detected theoretically in a pulsed chemical laser amplifier based on a photon-branched chain reaction initiating in a gaseous disperse medium composed of H2-F2-O2-He and Al particles by focused external infrared radiation. It is shown that this effect is observed due to the possibility of the ignition of the laser-chemical reaction into an initial small focal volume of an active medium. It then spreads out of this minimal volume spontaneously in the auto-wave regime without external power sources and subsequently fills the whole volume of the laser cavity with a high intensive electromagnetic field as self-supporting cylindrical photon-branching zones formed by the paths of the rays inside the unstable telescopic cavity. Calculations show that the ignition of an auto-wave photon-branched chain reaction under the condition of external signal focusing strongly reduces the input pulse energy necessary for initiation up to ˜10-8 J, and thereby allows a huge value of the energy gain of ˜1011. The observed effect of this huge laser energy gain makes it possible to construct a self-contained laser with kilojoule output energy, which can be initiated by a very weak source signal.
Signal Transduction Reaction Monitoring Deciphers Site-Specific PI3K-mTOR/MAPK Pathway Dynamics in Oncogene-Induced Senescence.
de Graaf, Erik L; Kaplon, Joanna; Mohammed, Shabaz; Vereijken, Lisette A M; Duarte, Daniel P; Redondo Gallego, Laura; Heck, Albert J R; Peeper, Daniel S; Altelaar, A F Maarten
We report a straightforward strategy to comprehensively monitor signal transduction pathway dynamics in mammalian systems. Combining targeted quantitative proteomics with highly selective phosphopeptide enrichment, we monitor, with great sensitivity, phosphorylation dynamics of the PI3K-mTOR and MAPK signaling networks. Our approach consists of a single enrichment step followed by a single targeted proteomics experiment, circumventing the need for labeling and immune purification while enabling analysis of selected phosphorylation nodes throughout signaling pathways. The need for such a comprehensive pathway analysis is illustrated by highlighting previously uncharacterized phosphorylation changes in oncogene-induced senescence, associated with diverse biological phenotypes and pharmacological intervention of the PI3K-mTOR pathway. PMID:26011226
Do cytokinins function as two-way signals between plants and animals? Cytokinins may not only mediate defence reactions via secondary compounds, but may directly interfere with developmental signals in insects.
Robischon, Marcel
Cytokinins are plant hormones that have, among many other functions, senescence-modulatory effects in plant tissue. This is evident not only from biochemical data, but is vividly illustrated in the "green island" phenotype in plant leaves caused by cytokinins released for example by leaf mining insects or microbial pathogens. It is beyond doubt that, in addition to their roles in plants, cytokinins also provoke physiological and developmental effects in animals. It is hypothesized that the recently much discussed modification of plant metabolism by insects and associated microbes via cytokinin signals has a counterpart in direct cytokinin signalling that interferes with the animals' hormonal systems and impacts their population dynamics. PMID:25652659
Multiplexing oscillatory biochemical signals.
de Ronde, Wiet; ten Wolde, Pieter Rein
In recent years it has been increasingly recognized that biochemical signals are not necessarily constant in time and that the temporal dynamics of a signal can be the information carrier. Moreover, it is now well established that the protein signaling network of living cells has a bow-tie structure and that components are often shared between different signaling pathways. Here we show by mathematical modeling that living cells can multiplex a constant and an oscillatory signal: they can transmit these two signals simultaneously through a common signaling pathway, and yet respond to them specifically and reliably. We find that information transmission is reduced not only by noise arising from the intrinsic stochasticity of biochemical reactions, but also by crosstalk between the different channels. Yet, under biologically relevant conditions more than 2 bits of information can be transmitted per channel, even when the two signals are transmitted simultaneously. These observations suggest that oscillatory signals are ideal for multiplexing signals. PMID:24685537
Theories about misperception of sexual intent, cognitive distortions among rapists, and alcohol's effects on cognition describe processes that may contribute to acquaintance sexual assault. Drawing on these literatures, an experiment was conducted to examine hypotheses about the effects of past sexual assault perpetration and alcohol consumption on 153 college men's reactions to a female confederate. As compared to nonperpetrators, self–acknowledged rapists and verbal coercers reported being more sexually attracted to the confederate. Trained coders were least certain that rapists noticed specific positive and negative cues that the confederate used and most certain that verbal coercers did. Intoxicated participants perceived themselves and their partner as acting more sexually than did sober or placebo participants. Suggestions are discussed for research and treatment programs with college sexual assault perpetrators. PMID:26500390
[Signal systems of plant immunity].
Dmitriev, A P
Plants can recognise the penetrating pathogen and respond to the attack with an array of defense reactions. Signal transduction from receptor in plasma membrane to genome is necessary to activate these reactions. Plant cell signaling systems which take part in signal transduction were discovered and identified recently. The obtained results suggest that plant cells have complex and well coordinated signal network which regulates their immune potential. PMID:12187855
Microfluidic paper-based analytical device for photoelectrochemical immunoassay with multiplex signal amplification using multibranched hybridization chain reaction and PdAu enzyme mimetics.
Lan, Feifei; Sun, Guoqiang; Liang, Linlin; Ge, Shenguang; Yan, Mei; Yu, Jinghua
Combining multibranched hybridization chain reaction (mHCR), the photoelectrochemical (PEC) immunosensor was fabricated with a microfluidic paper-based analytical devices using different sizes of CdTe quantum dots (QDs) sensitized flower-like 3D ZnO superstructures as photoactive materials. Firstly, 4-aminothiophenol (PATP) functioned ZnO was anchored on gold-paper working electrode. With the aid of PATP, large-sized CdTe-COOH QDs (QDs1) were conjugated onto the ZnO surface because of the formation of a strong bond (Zn-S) between the thiol of PATP molecule and the ZnO, and the remaining amino group formed an amide bond with carboxylic acid group capping CdTe. Then the small-sized CdTe-NH2 QDs (QDs2) were modified on the QDs1 by forming amide bond, which leaded to a very strong photocurrent response because of the formation of cosensitized structure. The designed mHCR produced long products with multiple branched arms, which could attached multiple PdAu nanoparticles and catalyze the oxidation of hydroquinone (HQ) using H2O2 as anoxidant. Double strands DNA with multiple branched arms (mdsDNA) was formed by mHCR. In the presence of carcinoembryonic antigen (CEA), PdAu-mdsDNA conjugates-labeled CEA antibody was captured. The concentrations of CEA were measured through the decrease in photocurrent intensity resulting from the increase in steric hindrance of the immunocomplex and the polymeric oxidation product of HQ. In addition, the oxidation product of HQ deposited on the as-obtained electrode, which could efficiently inhibit the photoinduced electron transfer. Under optimal conditions, the PEC immunosensor exhibited excellent analytical performance: the detection range of CEA was from 0.001 to 90 ng mL(-1) with low detection limit of 0.33 pg mL(-1). The as-obtained immunosensor exhibited excellent precision, prominent specificity, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed assay opens a
NASA Astrophysics Data System (ADS)
Wollman, Roy
Stochasticity inherent to biochemical reactions (intrinsic noise) and variability in cellular states (extrinsic noise) degrade information transmitted through signaling networks. We analyzed the ability of temporal signal modulation - that is dynamics - to reduce noise-induced information loss. In the extracellular signal-regulated kinase (ERK), calcium (Ca(2 +)) , and nuclear factor kappa-B (NF- κB) pathways, response dynamics resulted in significantly greater information transmission capacities compared to nondynamic responses. Theoretical analysis demonstrated that signaling dynamics has a key role in overcoming extrinsic noise. Experimental measurements of information transmission in the ERK network under varying signal-to-noise levels confirmed our predictions and showed that signaling dynamics mitigate, and can potentially eliminate, extrinsic noise-induced information loss. By curbing the information-degrading effects of cell-to-cell variability, dynamic responses substantially increase the accuracy of biochemical signaling networks.
Mitochondria and cell signalling
Tait, Stephen W. G.; Green, Douglas R.
Mitochondria have long been considered as crucial organelles, primarily for their roles in biosynthetic reactions such as ATP synthesis. However, it is becoming increasingly apparent that mitochondria are intimately involved in cell signalling pathways. Mitochondria perform various signalling functions, serving as platforms to initiate cell signalling, as well as acting as transducers and effectors in multiple processes. Here, we discuss the active roles that mitochondria have in cell death signalling, innate immunity and autophagy. Common themes of mitochondrial regulation emerge from these diverse but interconnected processes. These include: the outer mitochondrial membrane serving as a major signalling platform, and regulation of cell signalling through mitochondrial dynamics and by mitochondrial metabolites, including ATP and reactive oxygen species. Importantly, defects in mitochondrial control of cell signalling and in the regulation of mitochondrial homeostasis might underpin many diseases, in particular age-related pathologies. PMID:22448037
Goodwin, Roy L.
A voter for providing a single accurate output signal that is derived from the closest two signal levels of three input signals, each of which signals represents a measurement of the same phenomena. By means of the voting circuit, the signals are first sorted by level of amplitude and then ranked as highest, middle or lowest. The highest or lowest signal that is furthest from the middle signal is rejected, while the other highest or lowest signal is selected for processing. The selected high or low signal is then averaged with the middle signal to provide the output signal.
Large-scale sodium-basalt concrete reaction test LSC-1
McCormick, M.W.; Muhlestein, L.D.; Colburn, R.P.; Winkel, B.V.
The energy and hydrogen released from sodium-concrete reactions must be considered the analysis of beyond-design basis accidents for breeder reactors. Consequently, a large-scale sodium-basalt concrete reaction test was completed in the Large Sodium Fire Facility (LSFF) at the Hanford Engineering Development Laboratory (HEDL). 454 kg of sodium at 593{sup 0}C was spilled onto 0.84 m{sup 2} of basalt concrete 0.61 m deep containing two layers of reinforcing steel bar. From the data obtained, it was possible to complete a mass and energy balance for this test. The hydrogen generation and generation rate as functions of time for the duration of the test were determined. The major contribution to the chemical energy was energy associated with the formation of hydrogen (sodium-water reactions).
[Disorders in sodium-water balance].
Petitclerc, Thierry
Water balance control is aimed at normalizing cellular hydration, and sodium balance control at normalizing extracellular volume. Water balance control is based on the regulation of body fluid tonicity, while the control of sodium balance is based on the regulation of effective arterial volume. Disorders of water balance act on cellular hydration: primary disorders induce a proportional change in tonicity; secondary disorders are induced by a change in tonicity or effective arterial volume. Disorders of sodium balance act on extracellular volume: primary disorders of sodium balance induce a change in effective arterial volume; secondary disorders are induced by a change in effective arterial volume. Physical examination of the patient allows assessing the extracellular volume and the severity of the sodium balance disorder. Natremia - that generally reflects tonicity - allows to assess cellular hydration and to determine the type of water balance disorder. In the case of natremia disturbance, the assessment of both the tonicity and the extracellular volume allows the determination of the type of water and/or sodium balance disorder that is necessary for prescribing the adequate therapy. PMID:23177272
Catalysis in reaction networks.
Gopalkrishnan, Manoj
We define catalytic networks as chemical reaction networks with an essentially catalytic reaction pathway: one which is "on" in the presence of certain catalysts and "off" in their absence. We show that examples of catalytic networks include synthetic DNA molecular circuits that have been shown to perform signal amplification and molecular logic. Recall that a critical siphon is a subset of the species in a chemical reaction network whose absence is forward invariant and stoichiometrically compatible with a positive point. Our main theorem is that all weakly-reversible networks with critical siphons are catalytic. Consequently, we obtain new proofs for the persistence of atomic event-systems of Adleman et al., and normal networks of Gnacadja. We define autocatalytic networks, and conjecture that a weakly-reversible reaction network has critical siphons if and only if it is autocatalytic. PMID:21503834
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...
... Signal Words? Signal words are found on pesticide product labels, and they describe the acute (short-term) toxicity ... red letters on the front panel of the product label. 2,4 Acute Oral LD 50 Inhalation LC ...
Quantifying Ubiquitin Signaling
Ordureau, Alban; Münch, Christian; Harper, J. Wade
Ubiquitin (UB)-driven signaling systems permeate biology, and are often integrated with other types of post-translational modifications (PTMs), most notably phosphorylation. Flux through such pathways is typically dictated by the fractional stoichiometry of distinct regulatory modifications and protein assemblies as well as the spatial organization of pathway components. Yet, we rarely understand the dynamics and stoichiometry of rate-limiting intermediates along a reaction trajectory. Here, we review how quantitative proteomic tools and enrichment strategies are being used to quantify UB-dependent signaling systems, and to integrate UB signaling with regulatory phosphorylation events. A key regulatory feature of ubiquitylation is that the identity of UB chain linkage types can control downstream processes. We also describe how proteomic and enzymological tools can be used to identify and quantify UB chain synthesis and linkage preferences. The emergence of sophisticated quantitative proteomic approaches will set a new standard for elucidating biochemical mechanisms of UB-driven signaling systems. PMID:26000850
... using any of these products. Some types of food may also cause adverse drug reactions. For example, grapefruit and grapefruit juice, as well as alcohol and caffeine, may affect how drugs work. Every time your doctor ... interactions with any foods or beverages. What about medicines I've used ...
Boss, Wendy F; Im, Yang Ju
"All things flow and change…even in the stillest matter there is unseen flux and movement." Attributed to Heraclitus (530-470 BC), from The Story of Philosophy by Will Durant. Heraclitus, a Greek philosopher, was thinking on a much larger scale than molecular signaling; however, his visionary comments are an important reminder for those studying signaling today. Even in unstimulated cells, signaling pathways are in constant metabolic flux and provide basal signals that travel throughout the organism. In addition, negatively charged phospholipids, such as the polyphosphorylated inositol phospholipids, provide a circuit board of on/off switches for attracting or repelling proteins that define the membranes of the cell. This template of charged phospholipids is sensitive to discrete changes and metabolic fluxes-e.g., in pH and cations-which contribute to the oscillating signals in the cell. The inherent complexities of a constantly fluctuating system make understanding how plants integrate and process signals challenging. In this review we discuss one aspect of lipid signaling: the inositol family of negatively charged phospholipids and their functions as molecular sensors and regulators of metabolic flux in plants. PMID:22404474
Lee, Raymond Teck Ho; Zhao, Zhonghua; Ingham, Philip W
The Hedgehog (Hh) signalling pathway is one of the key regulators of metazoan development. Hh proteins have been shown to play roles in many developmental processes and have become paradigms for classical morphogens. Dysfunction of the Hh pathway underlies a number of human developmental abnormalities and diseases, making it an important therapeutic target. Interest in Hh signalling thus extends across many fields, from evo-devo to cancer research and regenerative medicine. Here, and in the accompanying poster, we provide an outline of the current understanding of Hh signalling mechanisms, highlighting the similarities and differences between species. PMID:26839340
Effective reaction rates for diffusion-limited reaction cycles
NASA Astrophysics Data System (ADS)
Nałecz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miekisz, Jacek; Lipniacki, Tomasz
Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.
Hartweck, Lynn M
This review covers recent advances in gibberellin (GA) signaling. GA signaling is now understood to hinge on DELLA proteins. DELLAs negatively regulate GA response by activating the promoters of several genes including Xerico, which upregulates the abscisic acid pathway which is antagonistic to GA. DELLAs also promote transcription of the GA receptor, GIBBERELLIN INSENSITIVE DWARF 1 (GID1) and indirectly regulate GA biosynthesis genes enhancing GA responsiveness and feedback control. A structural analysis of GID1 provides a model for understanding GA signaling. GA binds within a pocket of GID1, changes GID1 conformation and increases the affinity of GID1 for DELLA proteins. GA/GID1/DELLA has increased affinity for an F-Box protein and DELLAs are subsequently degraded via the proteasome. Therefore, GA induces growth through degradation of the DELLAs. The binding of DELLA proteins to three of the PHYTOCHROME INTERACTING FACTOR (PIF) proteins integrates light and GA signaling pathways. This binding prevents PIFs 3, 4, and 5 from functioning as positive transcriptional regulators of growth in the dark. Since PIFs are degraded in light, these PIFs can only function in the combined absence of light and presence of GA. New analyses suggest that GA signaling evolved at the same time or just after the plant vascular system and before plants acquired the capacity for seed reproduction. An analysis of sequences cloned from Physcomitrella suggests that GID1 and DELLAs were the first to evolve but did not initially interact. The more recently diverging spike moss Selaginella has all the genes required for GA biosynthesis and signaling, but the role of GA response in Selaginella physiology remains a mystery. PMID:18936962
Adverse local tissue reaction (ALTR) associated with corrosion products in metal-on-metal and dual modular neck total hip replacements is associated with upregulation of interferon gamma-mediated chemokine signaling.
Kolatat, Kritti; Perino, Giorgio; Wilner, Gabrielle; Kaplowitz, Elianna; Ricciardi, Benjamin F; Boettner, Friedrich; Westrich, Geoffrey H; Jerabek, Seth A; Goldring, Steven R; Purdue, P Edward
Adverse local tissue reactions (ALTR) associated with tribocorrosion following total hip arthroplasty (THA) have become a significant clinical concern in recent years. In particular, implants featuring metal-on-metal bearing surfaces and modular femoral stems have been reported to result in elevated rates of ALTR. These tribocorrosion-related tissue reactions are characterized by marked necrosis and lymphocytic infiltration, which contrasts sharply with the macrophagic and foreign body giant cell inflammation associated with polyethylene wear particle induced peri-implant osteolysis. In this study, we characterize tribocorrosion-associated ALTR at a molecular level. Gene expression profiling of peri-implant tissue around failing implants identifies upregulation of numerous inflammatory mediators in ALTR, including several interferon gamma inducible factors, most notably the chemokines MIG/CXCL9 and IP-10/CXCL10. This expression profile is distinct from that associated with polyethylene wear induced osteolysis, which is characterized by induction of markers of alternative macrophage activation, such as chitotriosidase (CHIT-1). Importantly, MIG/CXCL9 and IP-10/CXCL10 are also elevated at the protein level in the synovial fluid and, albeit more moderately, the serum, of ALTR patients, raising the possibility that these factors may serve as circulating biomarkers for the early detection of ALTR in at-risk patients. PMID:25940887
Effects of Stop-Signal Probability in the Stop-Signal Paradigm: The N2/p3 Complex Further Validated
ERIC Educational Resources Information Center
Ramautar, J.R.; Kok, A.; Ridderinkhof, K.R.
The aim of this study was to examine the effects of frequency of occurrence of stop signals in the stop-signal paradigm. Presenting stop signals less frequently resulted in faster reaction times to the go stimulus and a lower probability of inhibition. Also, go stimuli elicited larger and somewhat earlier P3 responses when stop signals occurred…
An overview of mechanisms of redox signaling
Forman, Henry Jay; Ursini, Fulvio; Maiorino, Matilde
A principal characteristic of redox signaling is that it involves an oxidation-reduction reaction or covalent adduct formation between the sensor signaling protein and second messenger. Non-redox signaling may involve alteration of the second messenger as in hydrolysis of GTP by G proteins, modification of the signaling protein as in farnesylation, or simple non-covalent binding of an agonist or second messenger. The chemistry of redox signaling is reviewed here. Specifically we have described how among the so-called reactive oxygen species, only hydroperoxides clearly fit the role of a second messenger. Consideration of reaction kinetics and cellular location strongly suggests that for hydroperoxides, particular protein cysteines are the targets and that the requirements for redox signaling is that these cysteines are in microenvironments in which the cysteine is ionized to the thiolate, and a proton can be donated to form a leaving group. The chemistry described here is the same as occurs in the cysteine and selenocysteine peroxidases that are generally considered the primary defense against oxidative stress. But, these same enzymes can also act as the sensors and transducer for signaling. Conditions that would allow specific signaling by peroxynitrite and superoxide are also defined. Signaling by other electrophiles, which includes lipid peroxidation products, quinones formed from polyphenols and other metabolites also involves reaction with specific protein thiolates. Again, kinetics and location are the primary determinants that provide specificity required for physiological signaling although enzymatic catalysis is not likely involved. PMID:24512843
A label-free and enzyme-free ultra-sensitive transcription factors biosensor using DNA-templated copper nanoparticles as fluorescent indicator and hairpin DNA cascade reaction as signal amplifier.
Sha, Liang; Zhang, Xiaojun; Wang, Guangfeng
Detection and quantification of specific protein with ultralow concentration play a crucial role in biotechnological applications and biomedical diagnostics. In this paper, a label-free and enzyme-free amplified fluorescent biosensor has been developed for transcription factors detection based on AT-rich double-stranded DNA-templated copper nanoparticles (ds DNA/Cu NPs) and hairpin DNA cascade reaction. This strategy was demonstrated by using nuclear factor-kappa B p50 (NF-κB p50) and specific recognition sequences as a model case. In this assay, a triplex consists of double-stranded DNA containing NF-κB p50 specifically binding sequences and a special design single-stranded DNA (Trigger) which is able to activate the hairpin DNA cascade amplifier (HDCA). In the presence of NF-κB p50, the triplex became unstable since the target bound to the recognition sequences with strong affinity. The selective binding event confirmed that the Trigger was successfully released from the triplex and initiated HDCA to yield the product which could effectively template the formation of fluorescent Cu NPs. The experimental results revealed that the advanced strategy was ultra-sensitive for detecting NF-κB p50 in the concentration range from 0.1 to 1000 pM with a detection limit of 0.096 pM. In addition, the relative standard deviation was 4.08% in 3 repetitive assays of 500 pM NF-κB p50, which indicated that the reproducibility of this strategy was acceptable. Besides desirable sensitivity, the developed biosensor also showed high selectivity, cost-effective, and simplified operations. In addition, the proposed biosensing platform is versatile. By conjugating with various specific recognition units, it could hold considerable potential to sensitive and selective detect various DNA-binding proteins and might find wide applications in biomedical fields. PMID:27045526
Fagard, M; Vaucheret, H
Grafting experiments have revealed that transgenic plants that undergo co-suppression of homologous transgenes and endogenous genes or PTGS of exogenous transgenes produce a sequence-specific systemic silencing signal that is able to propagate from cell to cell and at long distance. Similarly, infection of transgenic plants by viruses that carry (part of) a transgene sequence results in global silencing (VIGS) of the integrated transgenes although viral infection is localized. Systemic PTGS and VIGS strongly resemble recovery from virus infection in non-transgenic plants, leading to protection against secondary infection in newly emerging leaves and PTGS of transiently expressed homologous transgenes. The sequence-specific PTGS signal is probably a transgene product (for example, aberrant RNA) or a secondary product (for example, RNA molecules produced by an RNA-dependent RNA polymerase with transgene RNA as a matrix) that mimics the type of viral RNA that is targeted for degradation by cellular defence. Whether some particular cases of transgene TGS could also rely on the production of such a mobile molecule is discussed. PMID:10999411
Ubiquitin signaling in immune responses
Hu, Hongbo; Sun, Shao-Cong
Ubiquitination has emerged as a crucial mechanism that regulates signal transduction in diverse biological processes, including different aspects of immune functions. Ubiquitination regulates pattern-recognition receptor signaling that mediates both innate immune responses and dendritic cell maturation required for initiation of adaptive immune responses. Ubiquitination also regulates the development, activation, and differentiation of T cells, thereby maintaining efficient adaptive immune responses to pathogens and immunological tolerance to self-tissues. Like phosphorylation, ubiquitination is a reversible reaction tightly controlled by the opposing actions of ubiquitin ligases and deubiquitinases. Deregulated ubiquitination events are associated with immunological disorders, including autoimmune and inflammatory diseases. PMID:27012466
ERIC Educational Resources Information Center
Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.
Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…
Practice Gaps: Drug Reactions.
Wolverton, Stephen E
The term "drug reactions" is relevant to dermatology in three categories of reactions: cutaneous drug reactions without systemic features, cutaneous drug reactions with systemic features, and systemic drugs prescribed by the dermatologist with systematic adverse effects. This article uses examples from each of these categories to illustrate several important principles central to drug reaction diagnosis and management. The information presented will help clinicians attain the highest possible level of certainty before making clinical decisions. PMID:27363888
Receptor signaling clusters in the immune synapse
Dustin, Michael L.; Groves, Jay T.
Signaling processes between various immune cells involve large scale spatial reorganization of receptors and signaling molecules within the cell-cell junction. These structures, now collectively referred to as immune synapses, interleave physical and mechanical processes with the cascades of chemical reactions that constitute signal transduction systems. Molecular level clustering, spatial exclusion, and long range directed transport are all emerging as key regulatory mechanisms. The study of these processes is drawing researchers from physical sciences to join the effort and represents a rapidly growing branch of biophysical chemistry. Recent advances in the physical and quantitative analysis of signaling within the immune synapses will be reviewed here. PMID:22404679
Acquisition signal transmitter
NASA Technical Reports Server (NTRS)
Friedman, Morton L. (Inventor)
An encoded information transmitter which transmits a radio frequency carrier that is amplitude modulated by a constant frequency waveform and thereafter amplitude modulated by a predetermined encoded waveform, the constant frequency waveform modulated carrier constituting an acquisition signal and the encoded waveform modulated carrier constituting an information bearing signal, the acquisition signal providing enhanced signal acquisition and interference rejection favoring the information bearing signal. One specific application for this transmitter is as a distress transmitter where a conventional, legislated audio tone modulated signal is transmitted followed first by the acquisition signal and then the information bearing signal, the information bearing signal being encoded with, among other things, vehicle identification data. The acquistion signal enables a receiver to acquire the information bearing signal where the received signal is low and/or where the received signal has a low signal-to-noise ratio in an environment where there are multiple signals in the same frequency band as the information bearing signal.
Reaction-diffusion in the NEURON simulator
McDougal, Robert A.; Hines, Michael L.; Lytton, William W.
In order to support research on the role of cell biological principles (genomics, proteomics, signaling cascades and reaction dynamics) on the dynamics of neuronal response in health and disease, NEURON's Reaction-Diffusion (rxd) module in Python provides specification and simulation for these dynamics, coupled with the electrophysiological dynamics of the cell membrane. Arithmetic operations on species and parameters are overloaded, allowing arbitrary reaction formulas to be specified using Python syntax. These expressions are then transparently compiled into bytecode that uses NumPy for fast vectorized calculations. At each time step, rxd combines NEURON's integrators with SciPy's sparse linear algebra library. PMID:24298253
Reaction-diffusion in the NEURON simulator.
McDougal, Robert A; Hines, Michael L; Lytton, William W
In order to support research on the role of cell biological principles (genomics, proteomics, signaling cascades and reaction dynamics) on the dynamics of neuronal response in health and disease, NEURON's Reaction-Diffusion (rxd) module in Python provides specification and simulation for these dynamics, coupled with the electrophysiological dynamics of the cell membrane. Arithmetic operations on species and parameters are overloaded, allowing arbitrary reaction formulas to be specified using Python syntax. These expressions are then transparently compiled into bytecode that uses NumPy for fast vectorized calculations. At each time step, rxd combines NEURON's integrators with SciPy's sparse linear algebra library. PMID:24298253
Microfluidic chemical reaction circuits
Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C.; Huang, Jiang; Heath, James R.; Phelps, Michael E.; Quake, Stephen R.; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine
New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.
Continuous detonation reaction engine
NASA Technical Reports Server (NTRS)
Lange, O. H.; Stein, R. J.; Tubbs, H. E.
Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity.
Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...
Allergic reaction can be provoked by skin contact with poison plants, chemicals and animal scratches, as well as by ... dust, nuts and shellfish, may also cause allergic reaction. Medications such as penicillin and other antibiotics are ...
Microscale Thermite Reactions.
ERIC Educational Resources Information Center
Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana
Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)
Signal processing by the endosomal system.
Villaseñor, Roberto; Kalaidzidis, Yannis; Zerial, Marino
Cells need to decode chemical or physical signals from their environment in order to make decisions on their fate. In the case of signalling receptors, ligand binding triggers a cascade of chemical reactions but also the internalization of the activated receptors in the endocytic pathway. Here, we highlight recent studies revealing a new role of the endosomal network in signal processing. The diversity of entry pathways and endosomal compartments is exploited to regulate the kinetics of receptor trafficking, and interactions with specific signalling adaptors and effectors. By governing the spatio-temporal distribution of signalling molecules, the endosomal system functions analogously to a digital-analogue computer that regulates the specificity and robustness of the signalling response. PMID:26921695
Reaction coordinates for electron transfer reactions
Rasaiah, Jayendran C.; Zhu Jianjun
The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.
Catalytic diastereoselective petasis reactions.
Muncipinto, Giovanni; Moquist, Philip N; Schreiber, Stuart L; Schaus, Scott E
Multicomponent Petasis reactions: the first diastereoselective Petasis reaction catalyzed by chiral biphenols that enables the synthesis of syn and anti β-amino alcohols in pure form has been developed. The reaction exploits a multicomponent approach that involves boronates, α-hydroxy aldehydes, and amines. PMID:21751322
Reaction efficiency effects on binary chemical reactions
NASA Astrophysics Data System (ADS)
Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos
We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B → 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability γ, where γ is in the range 0 < γ < 1. Our results show that at small γ values the system is reaction limited, but as γ increases it crosses over to a diffusion limited behavior. At early times, for small γ values, the particle density falls slower than for larger γ values. This fall-off goes over a crossover point, around the value of γ = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all γ values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work.
Anaphylactic reactions to cinoxacin.
Stricker, B. H.; Slagboom, G.; Demaeseneer, R.; Slootmaekers, V.; Thijs, I.; Olsson, S.
During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were available the reaction began shortly after taking a single capsule of a second or next course of treatment. Cinoxacin is related to nalidixic acid, and one patient previously treated with that agent subsequently had an anaphylactoid reaction to cinoxacin and later developed a skin reaction to nalidixic acid. There were no deaths, and patients treated as an emergency with plasma expanders or with adrenaline and corticosteroids generally recovered promptly and uneventfully. In view of the potentially fatal consequences of anaphylactic reactions to cinoxacin and other quinolones doctors should take care when prescribing these drugs. PMID:3147004
Reactions to radiocontrast media.
Hong, Sandra J; Wong, Johnson T; Bloch, Kurt J
Adverse reactions to radiocontrast media (RCM) occur unexpectedly and may be life-threatening. This article describes an anaphylactoid reaction (AR) in one patient. The term AR refers to a syndrome clinically similar to anaphylaxis, but these reactions are independent of immunoglobulin E antibody-mediated mast cell or basophil degranulation. This article briefly reviews the literature regarding RCMs and types of reactions to RCM. The risk factors for AR to RCM infusions will be discussed along with current concepts of the pathogenesis of RCM-induced ARs. This article also describes the therapeutic management of patients who have had a previous adverse reaction to RCM and provides an approach to patients who have breakthrough reactions despite adequate premedication, but require additional radiographic studies. PMID:12476546
Noncanonical Reactions of Flavoenzymes
Sobrado, Pablo
Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a "molecular scaffold" in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates. PMID:23203060
Mechanisms in Knockout Reactions
NASA Astrophysics Data System (ADS)
Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.
We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions Be9(C9,B8+X)Y and Be9(B8,Be7+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.
Information processing in multi-step signaling pathways
NASA Astrophysics Data System (ADS)
Ganesan, Ambhi; Hamidzadeh, Archer; Zhang, Jin; Levchenko, Andre
Information processing in complex signaling networks is limited by a high degree of variability in the abundance and activity of biochemical reactions (biological noise) operating in living cells. In this context, it is particularly surprising that many signaling pathways found in eukaryotic cells are composed of long chains of biochemical reactions, which are expected to be subject to accumulating noise and delayed signal processing. Here, we challenge the notion that signaling pathways are insulated chains, and rather view them as parts of extensively branched networks, which can benefit from a low degree of interference between signaling components. We further establish conditions under which this pathway organization would limit noise accumulation, and provide evidence for this type of signal processing in an experimental model of a calcium-activated MAPK cascade. These results address the long-standing problem of diverse organization and structure of signaling networks in live cells.
SENTRA, a database of signal transduction proteins.
D'Souza, M.; Romine, M. F.; Maltsev, N.; Mathematics and Computer Science; PNNL
SENTRA, available via URL http://wit.mcs.anl.gov/WIT2/Sentra/, is a database of proteins associated with microbial signal transduction. The database currently includes the classical two-component signal transduction pathway proteins and methyl-accepting chemotaxis proteins, but will be expanded to also include other classes of signal transduction systems that are modulated by phosphorylation or methylation reactions. Although the majority of database entries are from prokaryotic systems, eukaroytic proteins with bacterial-like signal transduction domains are also included. Currently SENTRA contains signal transduction proteins in 34 complete and almost completely sequenced prokaryotic genomes, as well as sequences from 243 organisms available in public databases (SWISS-PROT and EMBL). The analysis was carried out within the framework of the WIT2 system, which is designed and implemented to support genetic sequence analysis and comparative analysis of sequenced genomes.
Sentra, a database of signal transduction proteins.
Maltsev, N.; Marland, E.; Yu, G. X.; Bhatnagar, S.; Lusk, R.; Mathematics and Computer Science
Sentra (http://www-wit.mcs.anl.gov/sentra) is a database of signal transduction proteins with the emphasis on microbial signal transduction. The database was updated to include classes of signal transduction systems modulated by either phosphorylation or methylation reactions such as PAS proteins and serine/threonine kinases, as well as the classical two-component histidine kinases and methyl-accepting chemotaxis proteins. Currently, Sentra contains signal transduction proteins from 43 completely sequenced prokaryotic genomes as well as sequences from SWISS-PROT and TrEMBL. Signal transduction proteins are annotated with information describing conserved domains, paralogous and orthologous sequences, and conserved chromosomal gene clusters. The newly developed user interface supports flexible search capabilities and extensive visualization of the data.
Signal processor for processing ultrasonic receiver signals
Fasching, George E.
A signal processor is provided which uses an analog integrating circuit in conjunction with a set of digital counters controlled by a precision clock for sampling timing to provide an improved presentation of an ultrasonic transmitter/receiver signal. The signal is sampled relative to the transmitter trigger signal timing at precise times, the selected number of samples are integrated and the integrated samples are transferred and held for recording on a strip chart recorder or converted to digital form for storage. By integrating multiple samples taken at precisely the same time with respect to the trigger for the ultrasonic transmitter, random noise, which is contained in the ultrasonic receiver signal, is reduced relative to the desired useful signal.
Sleeve reaction chamber system
Northrup, M. Allen; Beeman, Barton V.; Benett, William J.; Hadley, Dean R.; Landre, Phoebe; Lehew, Stacy L.; Krulevitch, Peter A.
A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.
Loehman, R.E.; Tomsia, A.P.
Mullite was reacted with pure Al and with Ti or Zr dissolved in Ag-Cu eutectic alloys at 1100 C in Ar. Analysis of the Ti and Zr-containing specimens showed reaction zones with compositions of Ti{sub 50}Cu{sub 3O}O{sub 20} and ZrO{sub 2}, respectively. The Al-mullite specimen showed much more extensive penetration into the ceramic and a more diffuse reaction zone than the other two systems. Al{sub 2}O{sub 3} and Si were the main reaction products for Al-mullite reaction.
Signal verification can promote reliable signalling.
Broom, Mark; Ruxton, Graeme D; Schaefer, H Martin
The central question in communication theory is whether communication is reliable, and if so, which mechanisms select for reliability. The primary approach in the past has been to attribute reliability to strategic costs associated with signalling as predicted by the handicap principle. Yet, reliability can arise through other mechanisms, such as signal verification; but the theoretical understanding of such mechanisms has received relatively little attention. Here, we model whether verification can lead to reliability in repeated interactions that typically characterize mutualisms. Specifically, we model whether fruit consumers that discriminate among poor- and good-quality fruits within a population can select for reliable fruit signals. In our model, plants either signal or they do not; costs associated with signalling are fixed and independent of plant quality. We find parameter combinations where discriminating fruit consumers can select for signal reliability by abandoning unprofitable plants more quickly. This self-serving behaviour imposes costs upon plants as a by-product, rendering it unprofitable for unrewarding plants to signal. Thus, strategic costs to signalling are not a prerequisite for reliable communication. We expect verification to more generally explain signal reliability in repeated consumer-resource interactions that typify mutualisms but also in antagonistic interactions such as mimicry and aposematism. PMID:24068354
Signal verification can promote reliable signalling
Broom, Mark; Ruxton, Graeme D.; Schaefer, H. Martin
The central question in communication theory is whether communication is reliable, and if so, which mechanisms select for reliability. The primary approach in the past has been to attribute reliability to strategic costs associated with signalling as predicted by the handicap principle. Yet, reliability can arise through other mechanisms, such as signal verification; but the theoretical understanding of such mechanisms has received relatively little attention. Here, we model whether verification can lead to reliability in repeated interactions that typically characterize mutualisms. Specifically, we model whether fruit consumers that discriminate among poor- and good-quality fruits within a population can select for reliable fruit signals. In our model, plants either signal or they do not; costs associated with signalling are fixed and independent of plant quality. We find parameter combinations where discriminating fruit consumers can select for signal reliability by abandoning unprofitable plants more quickly. This self-serving behaviour imposes costs upon plants as a by-product, rendering it unprofitable for unrewarding plants to signal. Thus, strategic costs to signalling are not a prerequisite for reliable communication. We expect verification to more generally explain signal reliability in repeated consumer–resource interactions that typify mutualisms but also in antagonistic interactions such as mimicry and aposematism. PMID:24068354
Retroactive Signaling in Short Signaling Pathways
Sepulchre, Jacques-Alexandre; Merajver, Sofía D.; Ventura, Alejandra C.
In biochemical signaling pathways without explicit feedback connections, the core signal transduction is usually described as a one-way communication, going from upstream to downstream in a feedforward chain or network of covalent modification cycles. In this paper we explore the possibility of a new type of signaling called retroactive signaling, offered by the recently demonstrated property of retroactivity in signaling cascades. The possibility of retroactive signaling is analysed in the simplest case of the stationary states of a bicyclic cascade of signaling cycles. In this case, we work out the conditions for which variables of the upstream cycle are affected by a change of the total amount of protein in the downstream cycle, or by a variation of the phosphatase deactivating the same protein. Particularly, we predict the characteristic ranges of the downstream protein, or of the downstream phosphatase, for which a retroactive effect can be observed on the upstream cycle variables. Next, we extend the possibility of retroactive signaling in short but nonlinear signaling pathways involving a few covalent modification cycles. PMID:22848403
Charged-current neutrino-208Pb reactions
NASA Astrophysics Data System (ADS)
Volpe, C.; Auerbach, N.; Colò, G.; van Giai, N.
We present theoretical results on the non-flux-averaged 208Pb(νe,e-)208Bi and 208Pb(νμ,μ-)208Bi reaction cross sections, obtained within the charge-exchange random-phase-approximation. A detailed knowledge of these cross sections is important in different contexts. In particular, it is necessary to assess the possibility of using lead as a detector in future experiments on supernova neutrinos, such as OMNIS and LAND, and eventually detect neutrino oscillation signals by exploiting the spectroscopic properties of 208Bi. We discuss the present status on the theoretical predictions of the reaction cross sections.
Automatic NMR-based identification of chemical reaction types in mixtures of co-occurring reactions.
Latino, Diogo A R S; Aires-de-Sousa, João
The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the (1)H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the (1)H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of
Automatic NMR-Based Identification of Chemical Reaction Types in Mixtures of Co-Occurring Reactions
Latino, Diogo A. R. S.; Aires-de-Sousa, João
The combination of chemoinformatics approaches with NMR techniques and the increasing availability of data allow the resolution of problems far beyond the original application of NMR in structure elucidation/verification. The diversity of applications can range from process monitoring, metabolic profiling, authentication of products, to quality control. An application related to the automatic analysis of complex mixtures concerns mixtures of chemical reactions. We encoded mixtures of chemical reactions with the difference between the 1H NMR spectra of the products and the reactants. All the signals arising from all the reactants of the co-occurring reactions were taken together (a simulated spectrum of the mixture of reactants) and the same was done for products. The difference spectrum is taken as the representation of the mixture of chemical reactions. A data set of 181 chemical reactions was used, each reaction manually assigned to one of 6 types. From this dataset, we simulated mixtures where two reactions of different types would occur simultaneously. Automatic learning methods were trained to classify the reactions occurring in a mixture from the 1H NMR-based descriptor of the mixture. Unsupervised learning methods (self-organizing maps) produced a reasonable clustering of the mixtures by reaction type, and allowed the correct classification of 80% and 63% of the mixtures in two independent test sets of different similarity to the training set. With random forests (RF), the percentage of correct classifications was increased to 99% and 80% for the same test sets. The RF probability associated to the predictions yielded a robust indication of their reliability. This study demonstrates the possibility of applying machine learning methods to automatically identify types of co-occurring chemical reactions from NMR data. Using no explicit structural information about the reactions participants, reaction elucidation is performed without structure elucidation of the
Memory Switches in Chemical Reaction Space
Ramakrishnan, Naren; Bhalla, Upinder S.
Just as complex electronic circuits are built from simple Boolean gates, diverse biological functions, including signal transduction, differentiation, and stress response, frequently use biochemical switches as a functional module. A relatively small number of such switches have been described in the literature, and these exhibit considerable diversity in chemical topology. We asked if biochemical switches are indeed rare and if there are common chemical motifs and family relationships among such switches. We performed a systematic exploration of chemical reaction space by generating all possible stoichiometrically valid chemical configurations up to 3 molecules and 6 reactions and up to 4 molecules and 3 reactions. We used Monte Carlo sampling of parameter space for each such configuration to generate specific models and checked each model for switching properties. We found nearly 4,500 reaction topologies, or about 10% of our tested configurations, that demonstrate switching behavior. Commonly accepted topological features such as feedback were poor predictors of bistability, and we identified new reaction motifs that were likely to be found in switches. Furthermore, the discovered switches were related in that most of the larger configurations were derived from smaller ones by addition of one or more reactions. To explore even larger configurations, we developed two tools: the "bistabilizer," which converts almost-bistable systems into bistable ones, and frequent motif mining, which helps rank untested configurations. Both of these tools increased the coverage of our library of bistable systems. Thus, our systematic exploration of chemical reaction space has produced a valuable resource for investigating the key signaling motif of bistability. PMID:18636099
Hydrogen evolution reaction catalyst
Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan
Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.
Chemical Reaction Problem Solving.
ERIC Educational Resources Information Center
Veal, William
Discusses the role of chemical-equation problem solving in helping students predict reaction products. Methods for helping students learn this process must be taught to students and future teachers by using pedagogical skills within the content of chemistry. Emphasizes that solving chemical reactions should involve creative cognition where…
ERIC Educational Resources Information Center
Cunningham, Kevin
This article presents an assignment in which students are to research and report on a chemical reaction whose increased or decreased rate is of practical importance. Specifically, students are asked to represent the reaction they have chosen with an acceptable chemical equation, identify a factor that influences its rate and explain how and why it…
Soine, T.S.
This patent shows a reusable reaction vessel for such high temperature reactions as the reduction of actinide metal chlorides by calcium metal. The vessel consists of an outer metal shell, an inner container of refractory material such as sintered magnesia, and between these, a bed of loose refractory material impregnated with thermally conductive inorganic salts. (AEC)
McLane, V.; Nordborg, C.; Lemmel, H.D.; Manokhin, V.N.
The cooperating Nuclear Reaction Data Centers are involved in the compilation and exchange of nuclear reaction data for incident neutrons, charged particles and photons. Individual centers may also have services in other areas, e.g., evaluated data, nuclear structure and decay data, reactor physics, nuclear safety; some of this information may also be exchanged between interested centers. 20 refs., 1 tab.
Degradations and Rearrangement Reactions
NASA Astrophysics Data System (ADS)
Zhang, Jianbo
This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.
Oscillating Reactions: Two Analogies
ERIC Educational Resources Information Center
Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.
Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…
Clock Reaction: Outreach Attraction
ERIC Educational Resources Information Center
Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.
Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…
Lipases in lipophilization reactions.
Villeneuve, Pierre
Lipases are used in various sectors, as pharmaceutical, food or detergency industry. Their advantage versus classical chemical catalysts is that they exhibit a better selectivity and operate in milder reaction conditions. Theses enzymes can also be used in lipophilization reactions corresponding to the grafting of a lipophilic moiety to a hydrophilic one such as sugar, amino acids and proteins, or phenolic compounds. The major difficulty to overcome in such enzyme-catalyzed reaction resides in the fact that the two involved substrates greatly differ in term of polarity and solvent affinity. Therefore, several key parameters are to be considered in order to achieve the reaction in satisfactory kinetics and yields. The present review discusses the nature of such parameters (eg solvent nature, water activity, chemical modification of substrates) and illustrates their effect with examples of lipase-catalyzed lipophilization reactions of various sugar, amino acids or phenolic derivatives. PMID:17681737
ERK Signals: Scaffolding Scaffolds?
Casar, Berta; Crespo, Piero
ERK1/2 MAP Kinases become activated in response to multiple intra- and extra-cellular stimuli through a signaling module composed of sequential tiers of cytoplasmic kinases. Scaffold proteins regulate ERK signals by connecting the different components of the module into a multi-enzymatic complex by which signal amplitude and duration are fine-tuned, and also provide signal fidelity by isolating this complex from external interferences. In addition, scaffold proteins play a central role as spatial regulators of ERKs signals. In this respect, depending on the subcellular localization from which the activating signals emanate, defined scaffolds specify which substrates are amenable to be phosphorylated. Recent evidence has unveiled direct interactions among different scaffold protein species. These scaffold-scaffold macro-complexes could constitute an additional level of regulation for ERK signals and may serve as nodes for the integration of incoming signals and the subsequent diversification of the outgoing signals with respect to substrate engagement. PMID:27303664
Smock, Robert G.; Gierasch, Lila M.
Proteins mediate transmission of signals along intercellular and intracellular pathways and between the exterior and the interior of a cell. The dynamic properties of signaling proteins are crucial to their functions. We discuss emerging paradigms for the role of protein dynamics in signaling. A central tenet is that proteins fluctuate among many states on evolutionarily selected energy landscapes. Upstream signals remodel this landscape, causing signaling proteins to transmit information to downstream partners. New methods provide insight into the dynamic properties of signaling proteins at the atomic scale. The next stages in the signaling hierarchy—how multiple signals are integrated and how cellular signaling pathways are organized in space and time—present exciting challenges for the future, requiring bold multidisciplinary approaches. PMID:19359576
Morrey, John R.
Methods of enhancing selected chemical reactions. The population of a selected high vibrational energy state of a reactant molecule is increased substantially above its population at thermal equilibrium by directing onto the molecule a beam of radiant energy from a laser having a combination of frequency and intensity selected to pump the selected energy state, and the reaction is carried out with the temperature, pressure, and concentrations of reactants maintained at a combination of values selected to optimize the reaction in preference to thermal degradation by transforming the absorbed energy into translational motion. The reaction temperature is selected to optimize the reaction. Typically a laser and a frequency doubler emit radiant energy at frequencies of .nu. and 2.nu. into an optical dye within an optical cavity capable of being tuned to a wanted frequency .delta. or a parametric oscillator comprising a non-centrosymmetric crystal having two indices of refraction, to emit radiant energy at the frequencies of .nu., 2.nu., and .delta. (and, with a parametric oscillator, also at 2.nu.-.delta.). Each unwanted frequency is filtered out, and each desired frequency is focused to the desired radiation flux within a reaction chamber and is reflected repeatedly through the chamber while reactants are fed into the chamber and reaction products are removed therefrom.
Reactions of oriented molecules.
Brooks, P R
Beams of oriented molecules have been used to directly study geometrical requirements in chemical reactions. These studies have shown that reactivity is much greater in some orientations than others and demonstrated the existence of steric effects. For some reactions portions of the orientation results are in good accord with traditional views of steric hindrance, but for others it is clear that our chemical intuition needs recalibrating. Indeed, the information gained from simultaneously orienting the reactants and observing the scattering angle of the products may lead to new insights about the detailed mechanism of certain reactions. Further work must be done to extend the scope and detail of the studies described here. More detailed information is needed on the CH(3)I reaction and the CF(3)I reaction. The effects of alkyl groups of various sizes and alkali metals of various sizes are of interest. In addition, reactions where a long-lived complex is formed should be studied to see if orientation is important. Finally, it would be of interest to apply the technique to the sort of reactions that led to our interest in the first place: the S(N)2 displacements in alkyl halides where the fascinating Walden inversion occurs. PMID:17793988
Mechanisms in knockout reactions
NASA Astrophysics Data System (ADS)
Bazin, D.; Charity, R. J.; de Souza, R. T.; Famiano, M. A.; Gade, A.; Henzl, V.; Henzlova, D.; Hudan, S.; Lee, J.; Lukyanov, S.; Lynch, W. G.; McDaniel, S.; Mocko, M.; Obertelli, A.; Rogers, A. M.; Sobotka, L. G.; Terry, J. R.; Tostevin, J. A.; Tsang, M. B.; Wallace, M. S.
We report on the first detailed study of the mechanisms involved in knockout reactions, via a coincidence measurement of the residue and fast proton in one-proton knockout reactions, using the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results on the reactions ^9Be(^9C,^8B+X)Y and ^9Be(^8B,^7Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction (elastic breakup) and stripping (inelastic breakup) reaction mechanisms, as calculated in the eikonal model. The data shows a clear distinction between the two reaction mechanisms, and the observed respective proportions are very well reproduced by the reaction theory. This agreement supports the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes. In particular, this add considerable support to the use of the eikonal model as a quantitative tool, able, for example, to determine single-particle spectroscopic strengths in rare isotopes.
Hypersensitivity reactions to corticosteroids.
Vatti, Rani R; Ali, Fatima; Teuber, Suzanne; Chang, Christopher; Gershwin, M Eric
Hypersensitivity reactions to corticosteroids (CS) are rare in the general population, but they are not uncommon in high-risk groups such as patients who receive repeated doses of CS. Hypersensitivity reactions to steroids are broadly divided into two categories: immediate reactions, typically occurring within 1 h of drug administration, and non-immediate reactions, which manifest more than an hour after drug administration. The latter group is more common. We reviewed the literature using the search terms "hypersensitivity to steroids, adverse effects of steroids, steroid allergy, allergic contact dermatitis, corticosteroid side effects, and type I hypersensitivity" to identify studies or clinical reports of steroid hypersensitivity. We discuss the prevalence, mechanism, presentation, evaluation, and therapeutic options in corticosteroid hypersensitivity reactions. There is a paucity of literature on corticosteroid allergy, with most reports being case reports. Most reports involve non-systemic application of corticosteroids. Steroid hypersensitivity has been associated with type I IgE-mediated allergy including anaphylaxis. The overall prevalence of type I steroid hypersensitivity is estimated to be 0.3-0.5%. Allergic contact dermatitis (ACD) is the most commonly reported non-immediate hypersensitivity reaction and usually follows topical CS application. Atopic dermatitis and stasis dermatitis of the lower extremities are risk factors for the development of ACD from topical CS. Patients can also develop hypersensitivity reactions to nasal, inhaled, oral, and parenteral CS. A close and detailed evaluation is required for the clinician to confirm the presence of a true hypersensitivity reaction to the suspected drug and choose the safest alternative. Choosing an alternative CS is not only paramount to the patient's safety but also ameliorates the worry of developing an allergic, and potentially fatal, steroid hypersensitivity reaction. This evaluation becomes
Abnormal reaction of 2,5-Dimethylfuran
Pevzner, L.M.; Ignat'ev, V.M.
The authors have shown that the expected hydroxymethylation at position 3 of the furan ring does not occur in the reaction of 2,5-dimethylfuran with paraform in acetic acid at 70-80/sup 0/C with the dimethylfuran and paraform in molar ratios of 2:1-1:2, but the products from substitution in the side chain are formed. By vacuum distillation of the reaction mass the authors isolated 2-(5-methyl-2-furyl)- ethanol and a hygroscopic viscous product melting at 136/sup 0/C (5 mm Hg). The yield of the reaction products depends on the molar ratio of the dimethylfuran and paraform. The PMR spectrum of the product contains signals for the ..beta..-protons of the furan ring with chemical shifts of 5.81 and 5.90 ppm, a signal for the methyl group in the furan ring at 2.22 ppm, a doublet at 3.72 ppm with spin-spin coupling constant of 6 Hz, a weak quintet at 3.20 ppm with the same constant, and a broadened signal in the region of 4.66 ppm for the proton of the hydroxyl group.
Wigner, E.P.
A nuclear reactor system is described for breeding fissionable material, including a heat-exchange tank, a high- and a low-pressure chamber therein, heat- exchange tubes connecting these chambers, a solution of U/sup 233/ in heavy water in a reaction container within the tank, a slurry of thorium dioxide in heavy water in a second container surrounding the first container, an inlet conduit including a pump connecting the low pressure chamber to the reaction container, an outlet conduit connecting the high pressure chamber to the reaction container, and means of removing gaseous fission products released in both chambers. (AEC)
Cell Simulation Package for Reactions and Diffusion
Plimpton, Steve; Slepoy, Alex
ChemCell is a simulation package designed for modeling signalling, regulatory, and metabolic pathways in biological cells. It reads input flies that describe the geomeby of the cell and positions of particles that represent proteins, protein complexes, and other bio-molecules. It also reads in lists of reactions and associated rates and other boundary condition information. ChemCell then models the reaction and diffusion of these particles within the cellular geometry as they interact overtime. It produces statistical information about the state of the cell, as well as snapshots of the reaction network. We anticipate ChemCell will be useful to researchers who wish to perform spatio-temporal modeling of cellular processes and who wish to develop new models or algorithms to add to the code. Thus ChemCell is also designed to be easy to modify and extend. The ChemCell package includes auxiliary codes for setting up problems and analyzing output.
Signal sciences workshop proceedings
Candy, J.V.
This meeting is aimed primarily at signal processing and controls. The technical program for the 1997 Workshop includes a variety of efforts in the Signal Sciences with applications in the Microtechnology Area a new program at LLNL and a future area of application for both Signal/Image Sciences. Special sessions organized by various individuals in Seismic and Optical Signal Processing as well as Micro-Impulse Radar Processing highlight the program, while the speakers at the Signal Processing Applications session discuss various applications of signal processing/control to real world problems. For the more theoretical, a session on Signal Processing Algorithms was organized as well as for the more pragmatic, featuring a session on Real-Time Signal Processing.
Chemisorption And Precipitation Reactions
The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...
ERIC Educational Resources Information Center
Matthews, Catherine E.
Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)
Reactor for exothermic reactions
Smith, L.A. Jr.; Hearn, D.; Jones, E.M. Jr.
A liquid phase process is described for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.
ERIC Educational Resources Information Center
Mitchell, Richard S.
Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)
Guthe, T.; Idsöe, O.; Willcox, R. R.
The literature on untoward reactions following the administration of penicillin is reviewed. These reactions, including a certain number of deaths which have been reported, are of particular interest to health administrations and to WHO in view of the large-scale programmes for controlling the treponematoses which are now under way—programmes affecting millions of people in many parts of the world. The most serious problems are anaphylactic sensitivity phenomena and superinfection or cross-infection with penicillin-resistant organisms, and the reactions involved range in intensity from the mildest to the fatal; the incidence of the latter is estimated at 0.1-0.3 per million injections. The authors point out that with increasing use of penicillin, more persons are likely to become sensitized and the number of reactions can therefore be expected to rise. The best prevention against such an increase is the restriction of the unnecessary use of penicillin. PMID:13596877
Yang, William H.; Purchase, Emerson C.R.
Sulfites are widely used as preservatives in the food and pharmaceutical industries. In the United States more than 250 cases of sulfite-related adverse reactions, including anaphylactic shock, asthmatic attacks, urticaria and angioedema, nausea, abdominal pain and diarrhea, seizures and death, have been reported, including 6 deaths allegedly associated with restaurant food containing sulfites. In Canada 10 sulfite-related adverse reactions have been documented, and 1 death suspected to be sulfite-related has occurred. The exact mechanism of sulfite-induced reactions is unknown. Practising physicians should be aware of the clinical manifestations of sulfite-related adverse reactions as well as which foods and pharmaceuticals contain sulfites. Cases should be reported to health officials and proper advice given to the victims to prevent further exposure to sulfites. The food industry, including beer and wine manufacturers, and the pharmaceutical industry should consider using alternative preservatives. In the interim, they should list any sulfites in their products. PMID:4052897
Reactor for exothermic reactions
Smith, Jr., Lawrence A.; Hearn, Dennis; Jones, Jr., Edward M.
A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. Wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.
Autocatalysis in reaction networks.
Deshpande, Abhishek; Gopalkrishnan, Manoj
The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view toward the persistence conjecture. We introduce the notions of "drainable" and "self-replicable" (or autocatalytic) siphons. We show that: Every minimal critical siphon is either drainable or self-replicable; reaction networks without drainable siphons are persistent; and nonautocatalytic weakly reversible networks are persistent. Our results clarify that the difficulties in proving the persistence conjecture are essentially due to competition between drainable and self-replicable siphons. PMID:25245394
Oxygen evolution reaction catalysis
Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.
An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.
Paige, F.E.
Recent experimental data on the properties of jets in hadronic reactions are reviewed and compared with theoretical expectations. Jets are clearly established as the dominant process for high E/sub T/ events in hadronic reactions. The cross section and the other properties of these events are in qualitative and even semiquantitative agreement with expectations based on perturbative QCD. However, we can not yet make precise tests of QCD, primarily because there are substantial uncertainties in the theoretical calculations. 45 references. (WHK)
Signal Processing, Analysis, & Display
Lager, Darrell; Azevado, Stephen
SIG is a general-purpose signal processing, analysis, and display program. Its main purpose is to perform manipulations on time- and frequency-domain signals. However, it has been designed to ultimately accommodate other representations for data such as multiplexed signals and complex matrices. Two user interfaces are provided in SIG - a menu mode for the unfamiliar user and a command mode for more experienced users. In both modes errors are detected as early as possible and are indicated by friendly, meaningful messages. An on-line HELP package is also included. A variety of operations can be performed on time- and frequency-domain signals including operations on the samples of a signal, operations on the entire signal, and operations on two or more signals. Signal processing operations that can be performed are digital filtering (median, Bessel, Butterworth, and Chebychev), ensemble average, resample, auto and cross spectral density, transfer function and impulse response, trend removal, convolution, Fourier transform and inverse window functions (Hamming, Kaiser-Bessel), simulation (ramp, sine, pulsetrain, random), and read/write signals. User definable signal processing algorithms are also featured. SIG has many options including multiple commands per line, command files with arguments,commenting lines, defining commands, and automatic execution for each item in a repeat sequence. Graphical operations on signals and spectra include: x-y plots of time signals; real, imaginary, magnitude, and phase plots of spectra; scaling of spectra for continuous or discrete domain; cursor zoom; families of curves; and multiple viewports.
Exploring Listeners' Real-Time Reactions to Regional Accents
ERIC Educational Resources Information Center
Watson, Kevin; Clark, Lynn
Evaluative reactions to language stimuli are presumably dynamic events, constantly changing through time as the signal unfolds, yet the tools we usually use to capture these reactions provide us with only a snapshot of this process by recording reactions at a single point in time. This paper outlines and evaluates a new methodology which employs…
[Cutaneous adverse drug reactions].
Lebrun-Vignes, B; Valeyrie-Allanore, L
Cutaneous adverse drug reactions (CADR) represent a heterogeneous field including various clinical patterns without specific features suggesting drug causality. Exanthematous eruptions, urticaria and vasculitis are the most common forms of CADR. Fixed eruption is uncommon in western countries. Serious reactions (fatal outcome, sequelae) represent 2% of CADR: bullous reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), DRESS (drug reaction with eosinophilia and systemic symptoms or drug-induced hypersensitivity syndrome) and acute generalized exanthematous pustulosis (AGEP). These forms must be quickly diagnosed to guide their management. The main risk factors are immunosuppression, autoimmunity and some HLA alleles in bullous reactions and DRESS. Most systemic drugs may induce cutaneous adverse reactions, especially antibiotics, anticonvulsivants, antineoplastic drugs, non-steroidal anti-inflammatory drugs, allopurinol and contrast media. Pathogenesis includes immediate or delayed immunologic mechanism, usually not related to dose, and pharmacologic/toxic mechanism, commonly dose-dependent or time-dependent. In case of immunologic mechanism, allergologic exploration is possible to clarify drug causality, with a variable sensitivity according to the drug and to the CADR type. It includes epicutaneous patch testing, prick test and intradermal test. However, no in vivo or in vitro test can confirm the drug causality. To determine the cause of the eruption, a logical approach based on clinical characteristics, chronologic factors and elimination of differential diagnosis is required, completed with a literature search. A reporting to pharmacovigilance network is essential in case of a serious CADR whatever the suspected drug and in any case if the involved drug is a newly marketed one or unusually related to cutaneous reactions. PMID:25458866
TSLP signaling pathway map: a platform for analysis of TSLP-mediated signaling
Zhong, Jun; Sharma, Jyoti; Raju, Rajesh; Palapetta, Shyam Mohan; Prasad, T. S. Keshava; Huang, Tai-Chung; Yoda, Akinori; Tyner, Jeffrey W.; van Bodegom, Diederik; Weinstock, David M.; Ziegler, Steven F.; Pandey, Akhilesh
Thymic stromal lymphopoietin (TSLP) is a four-helix bundle cytokine that plays a critical role in the regulation of immune responses and in the differentiation of hematopoietic cells. TSLP signals through a heterodimeric receptor complex consisting of an interleukin-7 receptor α chain and a unique TSLP receptor (TSLPR) [also known as cytokine receptor-like factor 2 (CRLF2)]. Cellular targets of TSLP include dendritic cells, B cells, mast cells, regulatory T (Treg) cells and CD4+ and CD8+ T cells. The TSLP/TSLPR axis can activate multiple signaling transduction pathways including the JAK/STAT pathway and the PI-3 kinase pathway. Aberrant TSLP/TSLPR signaling has been associated with a variety of human diseases including asthma, atopic dermatitis, nasal polyposis, inflammatory bowel disease, eosinophilic eosophagitis and, most recently, acute lymphoblastic leukemia. A centralized resource of the TSLP signaling pathway cataloging signaling events is not yet available. In this study, we present a literature-annotated resource of reactions in the TSLP signaling pathway. This pathway map is publicly available through NetPath (http://www.netpath.org/), an open access signal transduction pathway resource developed previously by our group. This map includes 236 molecules and 252 reactions that are involved in TSLP/TSLPR signaling pathway. We expect that the TSLP signaling pathway map will provide a rich resource to study the biology of this important cytokine as well as to identify novel therapeutic targets for diseases associated with dysregulated TSLP/TSLPR signaling. Database URL: http://www.netpath.org/pathways?path_id=NetPath_24 PMID:24573880
TSLP signaling pathway map: a platform for analysis of TSLP-mediated signaling.
Zhong, Jun; Sharma, Jyoti; Raju, Rajesh; Palapetta, Shyam Mohan; Prasad, T S Keshava; Huang, Tai-Chung; Yoda, Akinori; Tyner, Jeffrey W; van Bodegom, Diederik; Weinstock, David M; Ziegler, Steven F; Pandey, Akhilesh
Thymic stromal lymphopoietin (TSLP) is a four-helix bundle cytokine that plays a critical role in the regulation of immune responses and in the differentiation of hematopoietic cells. TSLP signals through a heterodimeric receptor complex consisting of an interleukin-7 receptor α chain and a unique TSLP receptor (TSLPR) [also known as cytokine receptor-like factor 2 (CRLF2)]. Cellular targets of TSLP include dendritic cells, B cells, mast cells, regulatory T (Treg) cells and CD4+ and CD8+ T cells. The TSLP/TSLPR axis can activate multiple signaling transduction pathways including the JAK/STAT pathway and the PI-3 kinase pathway. Aberrant TSLP/TSLPR signaling has been associated with a variety of human diseases including asthma, atopic dermatitis, nasal polyposis, inflammatory bowel disease, eosinophilic eosophagitis and, most recently, acute lymphoblastic leukemia. A centralized resource of the TSLP signaling pathway cataloging signaling events is not yet available. In this study, we present a literature-annotated resource of reactions in the TSLP signaling pathway. This pathway map is publicly available through NetPath (http://www.netpath.org/), an open access signal transduction pathway resource developed previously by our group. This map includes 236 molecules and 252 reactions that are involved in TSLP/TSLPR signaling pathway. We expect that the TSLP signaling pathway map will provide a rich resource to study the biology of this important cytokine as well as to identify novel therapeutic targets for diseases associated with dysregulated TSLP/TSLPR signaling. Database URL: http://www.netpath.org/pathways?path_id=NetPath_24. PMID:24573880
Integration of cellular signals in chattering environments.
Rué, P; Domedel-Puig, N; Garcia-Ojalvo, J; Pons, A J
Cells are constantly exposed to fluctuating environmental conditions. External signals are sensed, processed and integrated by cellular signal transduction networks, which translate input signals into specific cellular responses by means of biochemical reactions. These networks have a complex nature, and we are still far from having a complete characterization of the process through which they integrate information, specially given the noisy environment in which that information is embedded. Guided by the many instances of constructive influences of noise that have been reported in the physical sciences in the last decades, here we explore how multiple signals are integrated in an eukaryotic cell in the presence of background noise, or chatter. To that end, we use a Boolean model of a typical human signal transduction network. Despite its complexity, we find that the network is able to display simple patterns of signal integration. Furthermore, our computational analysis shows that these integration patterns depend on the levels of fluctuating background activity carried by other cell inputs. Taken together, our results indicate that signal integration is sensitive to environmental fluctuations, and that this background noise effectively determines the information integration capabilities of the cell. PMID:22584015
Immediate reaction to clarithromycin.
Gangemi, S; Ricciardi, L; Fedele, R; Isola, S; Purello-D'Ambrosio, F
We present the case of bronchospastic reaction to clarithromycin had during a drug challenge test. Personal allergic history was negative for respiratory allergies and positive for adverse drug reactions to general and regional anesthesia and to ceftriaxone. After the administration of 1/4 of therapeutic dose of clarithromycin the patient showed dyspnea, cough and bronchospasm in all the lung fields. The positivity of the test was confirmed by the negativity to the administration of placebo. The quickness and the clinical characteristic of the adverse reaction suggest a pathogenic mechanism of immediate-type hypersensitivity. On reviewing the literature we have found no reports of bronchospastic reaction to clarithromycin. Macrolides are a class of antibiotics mainly used in the last years in place of beta-lactams because of a broad spectrum of action and a low allergic power. In fact, there are few reports on allergic reactions to these molecules. Clarithromycin is one of the latest macrolides, characterised by the presence of a 14-carbon-atom lactone ring as erythromycin, active on a wide spectrum of pathogens. PMID:11449533
Find favorable reactions faster
Yaws, C.L.; Chiang, P.Y. )
Now, equations are given to identify whether the reactions are thermodynamically favorable. The method uses Gibbs free energy of formation for the reactants and products. The equation for any 700 major organic compounds is given as temperature coefficients. Then the reaction can be tested at various temperature levels beyond the standard 298/sup 0/K conditions imposed by many other data tabulations. Data for the water and hydrogen chloride are also included. Gibbs free energy of formation of ideal gas (..delta..G/sub f/, jkoule/g-mol) is calculated from the tabulated coefficients (A, B, C) and the temperature (T, /sup 0/K) using the following equation: (1) ..delta..G/sub f/ = A + BT + CT/sup 2/. Chemical equilibrium for a reaction is associated with the change in Gibbs free energy (..delta..G/sub r/) calculated as follows: (2) ..delta..G/sub r/ = ..delta..G/sub f/, products - ..delta..G/sub f/, reactants. If the change in Gibbs free energy is negative, the thermodynamics for the reaction are favorable. On the other hand, if the change in Gibbs free energy is highly positive, the thermodynamics for the reaction are not favorable and may be feasible only under special circumstances.
Telephone multiline signaling using common signal pair
NASA Technical Reports Server (NTRS)
Goodloe, R. R.; Toole, P. C.; Belt, J. L.; Leininger, D. B. (Inventor)
An operator can rapidly and automatically produce coded electrical signals by manipulating mechanical thumb wheel switches so as to instruct a service center to connect any number of telephone lines to the console thus enabling the operator to listen and/or talk over several lines simultaneously. The system includes an on-site console having several mechanically operated thumb wheel switches to which the desired lines to be connected can be dialed in. Electrical coded signals are fed to a number of banks of line AND gates representing units, tens and hundreds, a group of channel gates, and a command gate. These signals are gated out in a controlled manner to an encoder which generates tones that are transmitted over a single line to a communication service center.
Nanoparticle Reactions on Chip
NASA Astrophysics Data System (ADS)
Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.
The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.
Hipersensitivity Reactions to Corticosteroids.
Berbegal, L; DeLeon, F J; Silvestre, J F
Corticosteroids are widely used drugs in the clinical practice, especially by topic application in dermatology. These substances may act as allergens and produce immediate and delayed hypersensitivity reactions. Allergic contact dermatitis is the most frequent presentation of corticosteroid allergy and it should be studied by patch testing in specific units. The corticosteroids included in the Spanish standard battery are good markers but not ideal. Therefore, if those makers are positive, it is useful to apply a specific battery of corticosteroids and the drugs provided by patients. Immediate reactions are relatively rare but potentially severe, and it is important to confirm the sensitization profile and to guide the use of alternative corticosteroids, because they are often necessary in several diseases. In this article we review the main concepts regarding these two types of hypersensitivity reactions in corticosteroid allergy, as well as their approach in the clinical practice. PMID:26621334
Measurand transient signal suppressor
NASA Technical Reports Server (NTRS)
Bozeman, Richard J., Jr. (Inventor)
A transient signal suppressor for use in a controls system which is adapted to respond to a change in a physical parameter whenever it crosses a predetermined threshold value in a selected direction of increasing or decreasing values with respect to the threshold value and is sustained for a selected discrete time interval is presented. The suppressor includes a sensor transducer for sensing the physical parameter and generating an electrical input signal whenever the sensed physical parameter crosses the threshold level in the selected direction. A manually operated switch is provided for adapting the suppressor to produce an output drive signal whenever the physical parameter crosses the threshold value in the selected direction of increasing or decreasing values. A time delay circuit is selectively adjustable for suppressing the transducer input signal for a preselected one of a plurality of available discrete suppression time and producing an output signal only if the input signal is sustained for a time greater than the selected suppression time. An electronic gate is coupled to receive the transducer input signal and the timer output signal and produce an output drive signal for energizing a control relay whenever the transducer input is a non-transient signal which is sustained beyond the selected time interval.
Cutaneous reactions to vaccinations.
Rosenblatt, Adena E; Stein, Sarah L
Vaccinations are important for infectious disease prevention; however, there are adverse effects of vaccines, many of which are cutaneous. Some of these reactions are due to nonspecific inflammation and irritation at the injection site, whereas other reactions are directly related to the live attenuated virus. Rarely, vaccinations have been associated with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. The onset of certain inflammatory dermatologic conditions, such as lichen planus, granuloma annulare, and pemphigoid, were reported to occur shortly after vaccine administration. Allergic contact dermatitis can develop at the injection site, typically due to adjuvant ingredients in the vaccine, such as thimerosal and aluminum. Vaccinations are important to promote development of both individual and herd immunity. Although most vaccinations are considered relatively safe, there may be adverse effects associated with any vaccine. Cutaneous manifestations make up a large portion of the types of reactions associated with vaccines. There are many different reasons for the development of a cutaneous reaction to a vaccination. Some are directly related to the injection of a live attenuated virus, such as varicella or vaccinia (for immunity to smallpox), whereas others cause more nonspecific erythema and swelling at the injection site, as a result of local inflammation or irritation. Vaccinations have also been associated in rare reports with generalized hypersensitivity reactions, such as erythema multiforme, Stevens-Johnson syndrome, urticaria, acute generalized exanthematous pustulosis, and drug hypersensitivity syndrome. There have been case reports associating the administration of a vaccine with the new onset of a dermatologic condition, such as lichen planus, granuloma annulare, and Sweet syndrome. Finally, allergic contact
Velocity pump reaction turbine
House, P.A.
An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.
Velocity pump reaction turbine
House, Palmer A.
An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.
Velocity pump reaction turbine
House, Palmer A.
An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.
Synthesising periodic triggering signals with genetic oscillators.
Lin, Chun-Liang; Chen, Po-Kuei
The potential of the clock lies in its role of triggering logic reaction for sequential biological circuits. This research introduces an idea of designing a genetic clock generator by Fourier series based on the genetic oscillators. The authors generalise the design idea using a combination of fundamental sinusoidal signals. Since biochemical reaction of the biological system is extremely slow, however, transition between minimal and maximal levels is instantaneous for an ideal clock signal; it is thus not directly realisable in biological systems. That means it would be hard to directly synthesize a square wave generator for use as a genetic clock. They apply Fourier series to represent a square wave as a finite summation of sinusoidal waves generated by some genetic oscillators with different harmonic oscillating frequencies, in which the amplitude alternates at a constant frequency between the fixed minimal and maximal levels with the same duration of time. PMID:24451394
Requirements for security signalling
Pierson, L.G.; Tarman, T.D.
There has been some interest lately in the need for ``authenticated signalling``, and the development of signalling specifications by the ATM Forum that support this need. The purpose of this contribution is to show that if authenticated signalling is required, then supporting signalling facilities for directory services (i.e. key management) are also required. Furthermore, this contribution identifies other security related mechanisms that may also benefit from ATM-level signalling accommodations. For each of these mechanisms outlined here, an overview of the signalling issues and a rough cut at the required fields for supporting Information Elements are provided. Finally, since each of these security mechanisms are specified by a number of different standards, issues pertaining to the selection of a particular security mechanism at connection setup time (i.e. specification of a required ``Security Quality of Service``) are also discussed.
Inflammatory reaction - communication of cells.
Terheyden, Hendrik; Stadlinger, Bernd; Sanz, Mariano; Garbe, Annette I; Meyle, Jörg
This article presents scientific background information on the animated 3D film "Inflammatory Reactions - Communication of Cells" (Quintessence Publications, ISBN 978-1-85097-231-0). Gingivitis and periodontitis are understood as the result of a coordinated action of a few clearly identified cellular players who communicate with each other via cytokines. For didactic reasons, the course of a periodontal infection is described here in four phases: (1) bacterial biofilm formation and development of a host response in the marginal periodontium, (2) innate immune response leading to gingivitis, (3) role of the adaptive immune system in attachment loss and pocket formation, and (4) down-regulation of inflammation and periodontal regeneration and repair following biofilm removal. The control of the cells is discussed as a cytokine network, which can be modulated in pro- or anti-inflammatory direction depending on the control of the bacterial infection. Degradation of soft tissue structural proteins like collagen and proteoglycans by matrix metalloproteinases and degradation of hard tissue matrix by osteoclasts are explained as an interference of the immune system with the natural equilibrium of tissue remodeling. Five mechanisms of promotion of bone loss through the influence of the immune system are described. One example is bone resorption as a consequence of the shift of the RANKL/osteoprotegerin balance by soluble RANKL synthesized by CD4(+) Th 1 cells as well as the interference with the coupling of osteoclasts and osteoblasts through dedifferentiation of osteoblasts by TNFα. Finally, the signaling required for down-regulation of inflammatory reactions and the reasons for the incomplete regeneration after periodontal bone loss are discussed. PMID:23600659
Method and apparatus for controlling gas evolution from chemical reactions
Skorpik, J.R.; Dodson, M.G.
The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846. 8 figs.
Method and apparatus for controlling gas evolution from chemical reactions
Skorpik, James R.; Dodson, Michael G.
The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.
Signal Processing, Analysis, & Display
SIG is a general-purpose signal processing, analysis, and display program. Its main purpose is to perform manipulations on time- and frequency-domain signals. However, it has been designed to ultimately accommodate other representations for data such as multiplexed signals and complex matrices. Two user interfaces are provided in SIG - a menu mode for the unfamiliar user and a command mode for more experienced users. In both modes errors are detected as early as possible andmore » are indicated by friendly, meaningful messages. An on-line HELP package is also included. A variety of operations can be performed on time- and frequency-domain signals including operations on the samples of a signal, operations on the entire signal, and operations on two or more signals. Signal processing operations that can be performed are digital filtering (median, Bessel, Butterworth, and Chebychev), ensemble average, resample, auto and cross spectral density, transfer function and impulse response, trend removal, convolution, Fourier transform and inverse window functions (Hamming, Kaiser-Bessel), simulation (ramp, sine, pulsetrain, random), and read/write signals. User definable signal processing algorithms are also featured. SIG has many options including multiple commands per line, command files with arguments,commenting lines, defining commands, and automatic execution for each item in a repeat sequence. Graphical operations on signals and spectra include: x-y plots of time signals; real, imaginary, magnitude, and phase plots of spectra; scaling of spectra for continuous or discrete domain; cursor zoom; families of curves; and multiple viewports.« less
Digital signal processing the Tevatron BPM signals
Cancelo, G.; James, E.; Wolbers, S.; /Fermilab
The Beam Position Monitor (TeV BPM) readout system at Fermilab's Tevatron has been updated and is currently being commissioned. The new BPMs use new analog and digital hardware to achieve better beam position measurement resolution. The new system reads signals from both ends of the existing directional stripline pickups to provide simultaneous proton and antiproton measurements. The signals provided by the two ends of the BPM pickups are processed by analog band-pass filters and sampled by 14-bit ADCs at 74.3MHz. A crucial part of this work has been the design of digital filters that process the signal. This paper describes the digital processing and estimation techniques used to optimize the beam position measurement. The BPM electronics must operate in narrow-band and wide-band modes to enable measurements of closed-orbit and turn-by-turn positions. The filtering and timing conditions of the signals are tuned accordingly for the operational modes. The analysis and the optimized result for each mode are presented.
Precision signal power measurement
NASA Technical Reports Server (NTRS)
Winkelstein, R.
Accurate estimation of signal power is an important Deep Space Network (DSN) consideration. Ultimately, spacecraft power and weight is saved if no reserve transmitter power is needed to compensate for inaccurate measurements. Spectral measurement of the received signal has proved to be an effective method of estimating signal power over a wide dynamic range. Furthermore, on-line spectral measurements provide an important diagnostic tool for examining spacecraft anomalies. Prototype equipment installed at a 64-m-diameter antenna site has been successfully used to make measurements of carrier power and sideband symmetry of telemetry signals received from the Mariner Mars 1971 spacecraft.
Blockus, Heike; Chédotal, Alain
Slits are secreted proteins that bind to Roundabout (Robo) receptors. Slit-Robo signaling is best known for mediating axon repulsion in the developing nervous system. However, in recent years the functional repertoire of Slits and Robo has expanded tremendously and Slit-Robo signaling has been linked to roles in neurogenesis, angiogenesis and cancer progression among other processes. Likewise, our mechanistic understanding of Slit-Robo signaling has progressed enormously. Here, we summarize new insights into Slit-Robo evolutionary and system-dependent diversity, receptor-ligand interactions, signaling crosstalk and receptor activation. PMID:27578174
Quinoprotein-catalysed reactions.
Anthony, C
This review is concerned with the structure and function of the quinoprotein enzymes, sometimes called quinoenzymes. These have prosthetic groups containing quinones, the name thus being analogous to the flavoproteins containing flavin prosthetic groups. Pyrrolo-quinoline quinone (PQQ) is non-covalently attached, whereas tryptophan tryptophylquinone (TTQ), topaquinone (TPQ) and lysine tyrosylquinone (LTQ) are derived from amino acid residues in the backbone of the enzymes. The mechanisms of the quinoproteins are reviewed and related to their recently determined three-dimensional structures. As expected, the quinone structures in the prosthetic groups play important roles in the mechanisms. A second common feature is the presence of a catalytic base (aspartate) at the active site which initiates the reactions by abstracting a proton from the substrate, and it is likely to be involved in multiple reactions in the mechanism. A third common feature of these enzymes is that the first part of the reaction produces a reduced prosthetic group; this part of the mechanism is fairly well understood. This is followed by an oxidative phase involving electron transfer reactions which remain poorly understood. In both types of dehydrogenase (containing PQQ and TTQ), electrons must pass from the reduced prosthetic group to redox centres in a second recipient protein (or protein domain), whereas in amine oxidases (containing TPQ or LTQ), electrons must be transferred to molecular oxygen by way of a redox-active copper ion in the protein. PMID:9003352
Chain Reaction Polymerization.
ERIC Educational Resources Information Center
McGrath, James E.
The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)
ERIC Educational Resources Information Center
Ramette, R. W.
The exocharmic reactions that can be observed microscopically are discussed. The students can discover the optimal concentration of an acidic lead nitrate solution, so that a crystal of potassium iodide, nudged to the edge of a drop, results in glinting golden hexagons of lead iodide.
Chemical Reactions at Surfaces
Michael Henderson and Nancy Ryan Gray
Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The program this year will cover a broad range of topics, including heterogeneous catalysis and surface chemistry, surfaces in environmental chemistry and energy conversion, reactions at the liquid-solid and liquid-gas interface, electronic materials growth and surface modification, biological interfaces, and electrons and photons at surfaces. An exciting program is planned, with contributions from outstanding speakers and discussion leaders from the international scientific community. The conference provides a dynamic environment with ample time for discussion and interaction. Attendees are encouraged to present posters; the poster sessions are historically well attended and stimulate additional discussions. The conference provides an excellent opportunity for junior researchers (e.g. graduate students or postdocs) to present their work and interact with established leaders in the field.
Radiobiology of tissue reactions.
Dörr, W
Tissue effects of radiation exposure are observed in virtually all normal tissues, with interactions when several organs are involved. Early reactions occur in turnover tissues, where proliferative impairment results in hypoplasia; late reactions, based on combined parenchymal, vascular, and connective tissue changes, result in loss of function within the exposed volume; consequential late effects develop through interactions between early and late effects in the same organ; and very late effects are dominated by vascular sequelae. Invariably, involvement of the immune system is observed. Importantly, latent times of late effects are inversely dependent on the biologically equieffective dose. Each tissue component and--importantly--each individual symptom/endpoint displays a specific dose-effect relationship. Equieffective doses are modulated by exposure conditions: in particular, dose-rate reduction--down to chronic levels--and dose fractionation impact on late responding tissues, while overall exposure time predominantly affects early (and consequential late) reactions. Consequences of partial organ exposure are related to tissue architecture. In 'tubular' organs (gastrointestinal tract, but also vasculature), punctual exposure affects function in downstream compartments. In 'parallel' organs, such as liver or lungs, only exposure of a significant (organ-dependent) fraction of the total volume results in clinical consequences. Forthcoming studies must address biomarkers of the individual risk for tissue reactions, and strategies to prevent/mitigate tissue effects after exposure. PMID:25816259
ERIC Educational Resources Information Center
Armento, Beverly J.; And Others
Provides a reaction by three economic educators to an article by Raymond C. Miller calling for the elimination of economics. Contends that traditional economics does not necessarily lead to the degradation of the environment. Argues that economics should not promote any set of social values. (CFR)
ERIC Educational Resources Information Center
Zaretsky, Lindy
This article presents a principal's reaction to Catherine Marshall and Michael Ward's article on research on social justice and training for leadership. The author applauds Marshall and Ward's efforts to address what is undoubtedly among the most fundamentally important issues facing principals today. Marshall and Ward illuminate the importance of…
Chandler, D.W.
Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.
Reactions to Others' Intimacy.
ERIC Educational Resources Information Center
Neufeldt, David E.; Olinger, Evanelle J.
Research using behavioral measures has indicated that men react less positively to the touch of a same sex individual than women, that both men and women react more positively to the touch of an opposite sex individual than to the touch of a same sex individual, and that men and women do not differ in their reactions to opposite sex touch. This…
Polymerase chain reaction system
Benett, William J.; Richards, James B.; Stratton, Paul L.; Hadley, Dean R.; Milanovich, Fred P.; Belgrader, Phil; Meyer, Peter L.
A portable polymerase chain reaction DNA amplification and detection system includes one or more chamber modules. Each module supports a duplex assay of a biological sample. Each module has two parallel interrogation ports with a linear optical system. The system is capable of being handheld.
ERIC Educational Resources Information Center
Lytle, James H.
This article presents a superintendent's reaction to Catherine Marshall and Michael Ward's article on research on social justice and training for leadership. The author states that there is a problem with Marshall and Ward's article which begins with the title, particularly with the word "training." The author contends that there is a significant…
Enantioselective Vinylogous Organocascade Reactions.
Hepburn, Hamish B; Dell'Amico, Luca; Melchiorre, Paolo
Cascade reactions are powerful tools for rapidly assembling complex molecular architectures from readily available starting materials in a single synthetic operation. Their marriage with asymmetric organocatalysis has led to the development of novel techniques, which are now recognized as reliable strategies for the one-pot enantioselective synthesis of stereochemically dense molecules. In recent years, even more complex synthetic challenges have been addressed by applying the principle of vinylogy to the realm of organocascade catalysis. The key to the success of vinylogous organocascade reactions is the unique ability of the chiral organocatalyst to transfer reactivity to a distal position without losing control on the stereo-determining events. This approach has greatly expanded the synthetic horizons of the field by providing the possibility of forging multiple stereocenters in remote positions from the catalyst's point of action with high selectivity, while simultaneously constructing multiple new bonds. This article critically describes the developments achieved in the field of enantioselective vinylogous organocascade reactions, charting the ideas, the conceptual advances, and the milestone reactions that have been essential for reaching highly practical levels of synthetic efficiency. PMID:27256039
Reaction Formulation: A Bibliography.
ERIC Educational Resources Information Center
Pedrini, D. T.; Pedrini, Bonnie C.
Reaction formation was studied by Sigmund Freud. This defense mechanism may be related to repression, substitution, reversal, and compensation (or over-compensation). Alfred Adler considered compensation a basic process in his individual psychology. Anna Freud discussed some defense mechanisms, and Bibring, Dwyer, Huntington, and Valenstein…
Azlactone Reaction Developments.
de Castro, Pedro P; Carpanez, Arthur G; Amarante, Giovanni W
Azlactones (also known as oxazolones) are heterocycles usually employed in the stereoselective synthesis of α,α-amino acids, heterocycles and natural products. The versatility of the azlactone scaffold arises from the numerous reactive sites, allowing its application in a diversity of transformations. This review aims to cover classical and recent applications of oxazolones, especially those involving stereoselective processes. After a short introduction on their structures and intrinsic reactivities, dynamic kinetic resolution (DKR) processes as well as reactions involving stereoselective formation of a new σ C-C bond, such as alkylation/allylation/arylation, aldol, ene, Michael and Mannich reactions will be exposed. Additionally, cycloadditions, Steglich rearrangement and sulfenylation reactions will also be discussed. Recent developments of the well-known Erlenmeyer azlactones will be described. For the most examples, the proposed mechanism, activation modes and/or key reaction intermediates will be exposed to rationalize both the final product and the observed stereochemistry. Finally, this review gives an overview of the synthetic utility of oxazolones. PMID:27245128
Photoneutron reactions in astrophysics
Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stopani, K. A.
Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing β{sup −}-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between {sup 74}Se and {sup 196}Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (γ, n), (γ, p), or (γ, α) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.
Newsome, D.S.
A review covers the industrial applications of the water-gas shift reaction in hydrogen manufacturing, removing CO from ammonia synthesis feeds, and detoxifying town gas; and the catalyst characteristics, reaction kinetics, and reaction mechanisms of the water-gas shift reactions catalyzed by iron-based, copper-based, or sulfided cobalt-molybdenum catalysts.
Inorganic Reaction Mechanisms. Part I
ERIC Educational Resources Information Center
Cooke, D. O.
Provides a collection of data on the mechanistic aspects of inorganic chemical reactions. Wherever possible includes procedures for classroom demonstration or student project work. The material covered includes gas phase reactions, reactions in solution, mechanisms of electron transfer, the reaction between iron III and iodine, and hydrolysis. (GS)
ERIC Educational Resources Information Center
Schmitz, Guy
The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.
Mustafa, Asif K.; Gadalla, Moataz M.; Snyder, Solomon H.
Nitric oxide is well established as a major signaling molecule. Evidence is accumulating that carbon monoxide and hydrogen sulfide also are physiologic mediators in the cardiovascular, immune, and nervous systems. This Review focuses on mechanisms whereby they signal by binding to metal centers in metalloproteins, such as in guanylyl cyclase, or modifying sulfhydryl groups in protein targets. PMID:19401594
STIM proteins: dynamic calcium signal transducers
Soboloff, Jonathan; Rothberg, Brad S.; Madesh, Muniswamy; Gill, Donald L.
Stromal interaction molecule (STIM) proteins function in cells as dynamic coordinators of cellular calcium (Ca2+) signals. Spanning the endoplasmic reticulum (ER) membrane, they sense tiny changes in the levels of Ca2+ stored within the ER lumen. As ER Ca2+ is released to generate primary Ca2+ signals, STIM proteins undergo an intricate activation reaction and rapidly translocate into junctions formed between the ER and the plasma membrane. There, STIM proteins tether and activate the highly Ca2+-selective Orai channels to mediate finely controlled Ca2+ signals and to homeostatically balance cellular Ca2+. Details are emerging on the remarkable organization within these STIM-induced junctional microdomains and the identification of new regulators and alternative target proteins for STIM. PMID:22914293
Pulsed ion beam investigation of the kinetics of surface reactions
NASA Technical Reports Server (NTRS)
Horton, C. C.; Eck, T. G.; Hoffman, R. W.
Pulsed ion beam measurements of the kinetics of surface reactions are discussed for the case where the width of the ion pulse is comparable to the measured reaction time, but short compared to the time between successive pulses. Theoretical expressions are derived for the time dependence of the ion-induced signals for linear surface reactions. Results are presented for CO emission from surface carbon and CF emission from Teflon induced by oxygen ion bombardment. The strengths and limitations of this technique are described.
NASA Astrophysics Data System (ADS)
Pesaresi, Damiano; Ravanat, Xavier; Thibert, Emmanuel
The characterization of avalanches with seismic signals is an important task. For risk mitigation, estimating remotely avalanche activity by means of seismic signals is a good alternative to direct observations that are often limited by visual conditions and observer's availability. In seismology, the main challenge is to discriminate avalanche signals within the natural earth seismic activity and background noise. Some anthropogenic low frequency (infra-sound) sources like helicopters also generate seismic signals. In order to characterize an avalanche seismic signal, a 3-axis broad band seismometer (Guralp 3T) has been set-up on a real scale avalanche test site in Lautaret (France). The sensor is located in proximity of 2 avalanche paths where avalanches can be artificially released. Preliminary results of seismic records are presented, correlated with avalanche physical parameters (volume released, velocity, energy).
Bioelectric Signal Measuring System
NASA Astrophysics Data System (ADS)
Guadarrama-Santana, A.; Pólo-Parada, L.; García-Valenzuela, A.
We describe a low noise measuring system based on interdigitated electrodes for sensing bioelectrical signals. The system registers differential voltage measurements in order of microvolts. The base noise during measurements was in nanovolts and thus, the sensing signals presented a very good signal to noise ratio. An excitation voltage of 1Vrms with 10 KHz frequency was applied to an interdigitated capacitive sensor without a material under test and to a mirror device simultaneously. The output signals of both devices was then subtracted in order to obtain an initial reference value near cero volts and reduce parasitic capacitances due to the electronics, wiring and system hardware as well. The response of the measuring system was characterized by monitoring temporal bioelectrical signals in real time of biological materials such as embryo chicken heart cells and bovine suprarenal gland cells.
Exosomes in developmental signalling.
McGough, Ian John; Vincent, Jean-Paul
In order to achieve coordinated growth and patterning during development, cells must communicate with one another, sending and receiving signals that regulate their activities. Such developmental signals can be soluble, bound to the extracellular matrix, or tethered to the surface of adjacent cells. Cells can also signal by releasing exosomes - extracellular vesicles containing bioactive molecules such as RNA, DNA and enzymes. Recent work has suggested that exosomes can also carry signalling proteins, including ligands of the Notch receptor and secreted proteins of the Hedgehog and WNT families. Here, we describe the various types of exosomes and their biogenesis. We then survey the experimental strategies used so far to interfere with exosome formation and critically assess the role of exosomes in developmental signalling. PMID:27436038
Biological signals as handicaps.
Grafen, A
An ESS model of Zahavi's handicap principle is constructed. This allows a formal exposition of how the handicap principle works, and shows that its essential elements are strategic. The handicap model is about signalling, and it is proved under fairly general conditions that if the handicap principle's conditions are met, then an evolutionarily stable signalling equilibrium exists in a biological signalling system, and that any signalling equilibrium satisfies the conditions of the handicap principle. Zahavi's major claims for the handicap principle are thus vindicated. The place of cheating is discussed in view of the honesty that follows from the handicap principle. Parallel signalling models in economics are discussed. Interpretations of the handicap principle are compared. The models are not fully explicit about how females use information about male quality, and, less seriously, have no genetics. A companion paper remedies both defects in a model of the handicap principle at work in sexual selection. PMID:2402153
Mitochondrial emitted electromagnetic signals mediate retrograde signaling.
Bagkos, Georgios; Koufopoulos, Kostas; Piperi, Christina
Recent evidence shows that mitochondria regulate nuclear transcriptional activity both in normal and cell stress conditions, known as retrograde signaling. Under normal mitochondrial function, retrograde signaling is associated with mitochondrial biogenesis, normal cell phenotype and metabolic profile. In contrast, mitochondrial dysfunction leads to abnormal (oncogenic) cell phenotype and altered bio-energetic profile (nucleus reprogramming). Despite intense research efforts, a concrete mechanism through which mitochondria determine the group of genes expressed by the nucleus is still missing. The present paper proposes a novel hypothesis regarding retrograde signaling. More specifically, it reveals the mitochondrial membrane potential (MMP) and the accompanied strong electromagnetic field (EF) as key regulatory factors of nuclear activity. Mitochondrial emitted EFs extend in long distance and affect the function of nuclear membrane receptors. Depending on their frequencies, EFs can directly activate or deactivate different groups of nuclear receptors and so determine nuclear gene expression. One of the key features of the above hypothesis is that nuclear membrane receptors, besides their own endogenous or chemical ligands (hormones, lipids, etc.), can also be activated by electromagnetic signals. Moreover, normal MMP values (about -140 mV) are associated with the production of high ATP quantities and small levels of reactive oxygen species (ROS) while the hyperpolarization observed in all cancer cell types leads to a dramatic fall in ATP production and an analogous increase in ROS. The diminished ATP and increased ROS production negatively affect the function of all cellular systems including nucleus. Restoration of mitochondrial function, which is characterized by the fluctuation of MMP and EF values within a certain (normal) range, is proposed as a necessary condition for normal nuclear function and cancer therapy. PMID:26474928
Dearomatization through Halofunctionalization Reactions.
Liang, Xiao-Wei; Zheng, Chao; You, Shu-Li
Recent advances in dearomatization through halofunctionalization reactions are summarized in this Minireview. Two general categories of strategies are currently employed in this field. On one hand, the reaction can be initiated with electrophilic halogenation at an alkyne or alkene moiety. The resulting halonium ion intermediate is then captured by a pendant aromatic ring at the ipso position, affording the dearomatization product. On the other hand, electrophilic halogenation can directly take place at a substituted arene, and the final dearomatization product is furnished by deprotonation or intramolecular nucleophilic trap. Highly enantioselective variants have been realized in the latter case by organocatalysis or transition metal catalysis. By applying these methods, various valuable halogenated polycyclic molecular architectures have been obtained from readily available starting materials. PMID:27377184
It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.
Magnetically suspended reaction wheels
NASA Technical Reports Server (NTRS)
Sabnis, A. V.; Stocking, G. L.; Dendy, J. B.
Magnetic suspensions offer several advantages over conventional bearings, arising because of the contactless nature of the load support. In application to spacecraft reaction wheels, the advantages are low drag torque, wearfree, unlubricated, vacuum-compatible operation, and unlimited life. By the provision of redundancy in the control electronics, single-point failures are eliminated. The rational for selection of a passive radial, active axial, dc magnetic suspension is presented, and the relative merits of 3-loop and single-loop magnetic suspensions are discussed. The design of a .678 N-m-sec (.5 ft-lb-sec) reaction wheel using the single loop magnetic suspension was developed; the design compares favorably with current ball bearing wheels in terms of weight and power.
Polymerase chain displacement reaction.
Harris, Claire L; Sanchez-Vargas, Irma J; Olson, Ken E; Alphey, Luke; Fu, Guoliang
Quantitative PCR assays are now the standard method for viral diagnostics. These assays must be specific, as well as sensitive, to detect the potentially low starting copy number of viral genomic material. We describe a new technique, polymerase chain displacement reaction (PCDR), which uses multiple nested primers in a rapid, capped, one-tube reaction that increases the sensitivity of normal quantitative PCR (qPCR) assays. Sensitivity was increased by approximately 10-fold in a proof-of-principle test on dengue virus sequence. In PCDR, when extension occurs from the outer primer, it displaces the extension strand produced from the inner primer by utilizing a polymerase that has strand displacement activity. This allows a greater than 2-fold increase of amplification product for each amplification cycle and therefore increased sensitivity and speed over conventional PCR. Increased sensitivity in PCDR would be useful in nucleic acid detection for viral diagnostics. PMID:23384180
Chemical computing with reaction-diffusion processes.
Gorecki, J; Gizynski, K; Guzowski, J; Gorecka, J N; Garstecki, P; Gruenert, G; Dittrich, P
Chemical reactions are responsible for information processing in living organisms. It is believed that the basic features of biological computing activity are reflected by a reaction-diffusion medium. We illustrate the ideas of chemical information processing considering the Belousov-Zhabotinsky (BZ) reaction and its photosensitive variant. The computational universality of information processing is demonstrated. For different methods of information coding constructions of the simplest signal processing devices are described. The function performed by a particular device is determined by the geometrical structure of oscillatory (or of excitable) and non-excitable regions of the medium. In a living organism, the brain is created as a self-grown structure of interacting nonlinear elements and reaches its functionality as the result of learning. We discuss whether such a strategy can be adopted for generation of chemical information processing devices. Recent studies have shown that lipid-covered droplets containing solution of reagents of BZ reaction can be transported by a flowing oil. Therefore, structures of droplets can be spontaneously formed at specific non-equilibrium conditions, for example forced by flows in a microfluidic reactor. We describe how to introduce information to a droplet structure, track the information flow inside it and optimize medium evolution to achieve the maximum reliability. Applications of droplet structures for classification tasks are discussed. PMID:26078345
Photochemical reaction dynamics
Moore, B.C.
The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.
Nonhemolytic, noninfectious transfusion reactions.
Barton, J C
The delivery of optimal transfusion therapy requires that the physician first have a thorough understanding of his patient's disease and prior transfusion history. Sometimes the need for blood product administration is more apparent than real. In the selection of necessary therapy, particular blood components, their volumes, and the timing of their administration should be carefully planned. The transfusion of whole blood, particularly as single-unit transfusions, is rarely indicated. Often forgotten, autotransfusion represents a means whereby many subjects who have repeated, unusual, or severe reactions may receive safe treatment. An appreciation of the frequency and manifestations of transfusion-related problems permits effective treatment of ongoing reactions. The prophylactic measures which should be taken against future reactions in most patients are specific, and are the responsibility of the clinician, based upon his bedside observations and laboratory studies. Problems should be discussed with either a hematologist, pathologist, or blood banking expert without hesitation. These guidelines help conserve a precious resource and assure that safe, effective, and economical transfusion therapy is available for all patients in need. PMID:6164098
Lindner, Robert; Kühnle, Angelika
On-surface synthesis constitutes a rapidly growing field of research due to its promising application for creating stable molecular structures on surfaces. While self-assembled structures rely on reversible interactions, on-surface synthesis provides the potential for creating long-term stable structures with well-controlled properties, for example superior electron transport for future molecular electronic devices. On-surface synthesis holds the promise for preparing insoluble compounds that cannot be produced in solution. Another highly exciting aspect of on-surface synthesis is the chance to discover new reaction pathways due to the two-dimensional confinement of the reaction educts. In this review, we discuss the current state-of-the-art and classify the reactions that have been successfully performed so far. Special emphasis is put on electrically insulating surfaces, as these substrates pose particular challenges for on-surface synthesis while at the same time bearing high potential for future use, for example, in molecular electronics. PMID:25965579
Nayak, Surajit; Acharjya, Basanti
In everyday clinical practice, almost all physicians come across many instances of suspected adverse cutaneous drug reactions (ACDR) in different forms. Although such cutaneous reactions are common, comprehensive information regarding their incidence, severity and ultimate health effects are often not available as many cases go unreported. It is also a fact that in the present world, almost everyday a new drug enters market; therefore, a chance of a new drug reaction manifesting somewhere in some form in any corner of world is unknown or unreported. Although many a times, presentation is too trivial and benign, the early identification of the condition and identifying the culprit drug and omit it at earliest holds the keystone in management and prevention of a more severe drug rash. Therefore, not only the dermatologists, but all practicing physicians should be familiar with these conditions to diagnose them early and to be prepared to handle them adequately. However, we all know it is most challenging and practically difficult when patient is on multiple medicines because of myriad clinical symptoms, poorly understood multiple mechanisms of drug-host interaction, relative paucity of laboratory testing that is available for any definitive and confirmatory drug-specific testing. Therefore, in practice, the diagnosis of ACDR is purely based on clinical judgment. In this discussion, we will be primarily focusing on pathomechanism and approach to reach a diagnosis, which is the vital pillar to manage any case of ACDR. PMID:19967009
Bird, G. A.
DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.
NASA Astrophysics Data System (ADS)
Bird, G. A.
DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.
Hedgehog signaling and steroidogenesis.
Finco, Isabella; LaPensee, Christopher R; Krill, Kenneth T; Hammer, Gary D
Since its discovery nearly 30 years ago, the Hedgehog (Hh) signaling pathway has been shown to be pivotal in many developmental and pathophysiological processes in several steroidogenic tissues, including the testis, ovary, adrenal cortex, and placenta. New evidence links the evolutionarily conserved Hh pathway to the steroidogenic organs, demonstrating how Hh signaling can influence their development and homeostasis and can act in concert with steroids to mediate physiological functions. In this review, we highlight the role of the components of the Hh signaling pathway in steroidogenesis of endocrine tissues. PMID:25668018
Plant Cyclic Nucleotide Signalling
Martinez-Atienza, Juliana; Van Ingelgem, Carl; Roef, Luc
The presence of the cyclic nucleotides 3′,5′-cyclic adenyl monophosphate (cAMP) and 3′,5′-cyclic guanyl monophosphate (cGMP) in plants is now generally accepted. In addition, cAMP and cGMP have been implicated in the regulation of important plant processes such as stomatal functioning, monovalent and divalent cation fluxes, chloroplast development, gibberellic acid signalling, pathogen response and gene transcription. However, very little is known regarding the components of cyclic nucleotide signalling in plants. In this addendum, the evidence for specific mechanisms of plant cyclic nucleotide signalling is evaluated and discussed. PMID:19704553
Signal processing for microcalorimeters
NASA Astrophysics Data System (ADS)
Szymkowiak, A. E.; Kelley, R. L.; Moseley, S. H.; Stahle, C. K.
Most of the power in the signals from microcalorimeters occurs at relatively low frequencies. At these frequencies, typical amplifiers will have significant amounts of 1/f noise. Our laboratory systems can also suffer from pickup at several harmonics of the AC power line, and from microphonic pickup at frequencies that vary with the configuration of the apparatus. We have developed some optimal signal processing techniques in order to construct the best possible estimates of our pulse heights in the presence of these non-ideal effects. In addition to a discussion of our laboratory systems, we present our plans for providing this kind of signal processing in flight experiments.
Signalling Network Construction for Modelling Plant Defence Response
Miljkovic, Dragana; Stare, Tjaša; Mozetič, Igor; Podpečan, Vid; Petek, Marko; Witek, Kamil; Dermastia, Marina; Lavrač, Nada; Gruden, Kristina
Plant defence signalling response against various pathogens, including viruses, is a complex phenomenon. In resistant interaction a plant cell perceives the pathogen signal, transduces it within the cell and performs a reprogramming of the cell metabolism leading to the pathogen replication arrest. This work focuses on signalling pathways crucial for the plant defence response, i.e., the salicylic acid, jasmonic acid and ethylene signal transduction pathways, in the Arabidopsis thaliana model plant. The initial signalling network topology was constructed manually by defining the representation formalism, encoding the information from public databases and literature, and composing a pathway diagram. The manually constructed network structure consists of 175 components and 387 reactions. In order to complement the network topology with possibly missing relations, a new approach to automated information extraction from biological literature was developed. This approach, named Bio3graph, allows for automated extraction of biological relations from the literature, resulting in a set of (component1, reaction, component2) triplets and composing a graph structure which can be visualised, compared to the manually constructed topology and examined by the experts. Using a plant defence response vocabulary of components and reaction types, Bio3graph was applied to a set of 9,586 relevant full text articles, resulting in 137 newly detected reactions between the components. Finally, the manually constructed topology and the new reactions were merged to form a network structure consisting of 175 components and 524 reactions. The resulting pathway diagram of plant defence signalling represents a valuable source for further computational modelling and interpretation of omics data. The developed Bio3graph approach, implemented as an executable language processing and graph visualisation workflow, is publically available at http://ropot.ijs.si/bio3graph/and can be utilised for
Timescale analysis of rule-based biochemical reaction networks
Klinke, David J.; Finley, Stacey D.
The flow of information within a cell is governed by a series of protein-protein interactions that can be described as a reaction network. Mathematical models of biochemical reaction networks can be constructed by repetitively applying specific rules that define how reactants interact and what new species are formed upon reaction. To aid in understanding the underlying biochemistry, timescale analysis is one method developed to prune the size of the reaction network. In this work, we extend the methods associated with timescale analysis to reaction rules instead of the species contained within the network. To illustrate this approach, we applied timescale analysis to a simple receptor-ligand binding model and a rule-based model of Interleukin-12 (IL-12) signaling in näive CD4+ T cells. The IL-12 signaling pathway includes multiple protein-protein interactions that collectively transmit information; however, the level of mechanistic detail sufficient to capture the observed dynamics has not been justified based upon the available data. The analysis correctly predicted that reactions associated with JAK2 and TYK2 binding to their corresponding receptor exist at a pseudo-equilibrium. In contrast, reactions associated with ligand binding and receptor turnover regulate cellular response to IL-12. An empirical Bayesian approach was used to estimate the uncertainty in the timescales. This approach complements existing rank- and flux-based methods that can be used to interrogate complex reaction networks. Ultimately, timescale analysis of rule-based models is a computational tool that can be used to reveal the biochemical steps that regulate signaling dynamics. PMID:21954150
The Hyperon {Lambda}(1405) in p+p reactions
Siebenson, Johannes
We present an analysis of the hyperon {Lambda}(1405) for p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the High Acceptance Di-Electron Spectrometer (HADES). A {Lambda}(1405) signal could be reconstructed in both charged decay channels ({Lambda}(1405){yields}{Sigma}{sup {+-}}{pi}{sup {+-}}).
Procedures for Decomposing a Redox Reaction into Half-Reaction
ERIC Educational Resources Information Center
Fishtik, Ilie; Berka, Ladislav H.
A simple algorithm for a complete enumeration of the possible ways a redox reaction (RR) might be uniquely decomposed into half-reactions (HRs) using the response reactions (RERs) formalism is presented. A complete enumeration of the possible ways a RR may be decomposed into HRs is equivalent to a complete enumeration of stoichiometrically…
Reaction Extrema: Extent of Reaction in General Chemistry
ERIC Educational Resources Information Center
Vandezande, Jonathon E.; Vander Griend, Douglas A.; DeKock, Roger L.
Nearly 100 years ago de Donder introduced the term "extent of reaction", ?. We build on that work by defining the concept of reagent extrema for an arbitrary chemical reaction, aA + bB [reversible reaction] yY + zZ. The central equation is ?^[subscript i] = -n[subscript i,0]/?[subscript i]. The symbol ?^[subscript i] represents the…
Strychalski, Wanda; Adalsteinsson, David; Elston, Timothy C
Signaling networks regulate cellular responses to environmental stimuli through cascades of protein interactions. External signals can trigger cells to polarize and move in a specific direction. During migration, spatially localized activity of proteins is maintained. To investigate the effects of morphological changes on intracellular signaling, we developed a numerical scheme consisting of a cut cell finite volume spatial discretization coupled with level set methods to simulate the resulting advection-reaction-diffusion system. We then apply the method to several biochemical reaction networks in changing geometries. We found that a Turing instability can develop exclusively by cell deformations that maintain constant area. For a Turing system with a geometry-dependent single or double peak solution, simulations in a dynamically changing geometry suggest that a single peak solution is the only stable one, independent of the oscillation frequency. The method is also applied to a model of a signaling network in a migrating fibroblast. PMID:24086102
NASA Technical Reports Server (NTRS)
Cullers, D. K.; Linscott, I. R.; Oliver, B. M.
It is believed that the Galaxy might contain ten billion potential life sites. In view of the physical inaccessibility of extraterrestrial life on account of the vast distances involved, a logical first step in a search for extraterrestrial intelligence (SETI) appears to be an attempt to detect signals already being radiated. The characteristics of the signals to be expected are discussed together with the search strategy of a NASA program. It is pointed out that all presently planned searches will use existing radio-astronomy antennas. If no extraterrestrial intelligence signals are discovered, society will have to decide whether SETI justifies a dedicated facility of much greater collecting area. Attention is given to a multichannel spectrum analyzer, CW signal detection, pulse detection, the pattern detector, and details of SETI system operation.
NASA Astrophysics Data System (ADS)
Hoeg, P.
Ocean reflected signals from the GNSS satellites (received at low-Earth orbiting satellites, airplanes and fixed mountain locations) describe the ocean surface mean height, waves, roughness, spectral reflectivity and emissivity. The estimated accuracy of the average surface height is of the order of 10 cm for smooth conditions. Thus global observations could be an important new contribution to long-term variations of the ocean mean height as well as the monitoring of ocean mesoscale eddies, which result in sea-height changes much larger than the accuracy of the GNSS technique for reflected signals. The ocean reflected signals can be divided into two set of measurements, 1) high elevation measurements (equal to low incidence angles) and 2) low elevation grazing angle measurements. For the first type the ocean reflection cross-section has a limited extent. The reflected signal is coherent with smaller errors due to ocean waves, sampling rate and the internal processing method of the receiver. For low elevations, the signal reveals the incoherent scatter process at the reflection zone. To quantify the potential of the GNSS signals for determining spectral reflectivity at low elevations, we present ocean reflection GPS measurements from the Haleakala Summit on Maui, Hawaii, revealing the spectral characteristics of both the direct satellite signal and the ocean reflected signal for low elevation angles. The characteristics of the reflected signal depend on the scattering properties of the sea surface and the footprint of the reflection zone. While the footprint size and shape in turn depends on the signal incidence angle, the ocean mean tilt, and the relative velocities of transmitter and receiver to the reflection point. Thus the scattering properties of the sea surface are related to the sea surface roughness. We present the spectral properties of the signals as received by a high precision GPS instrument, simultaneously in both phase-locked mode and open-loop raw
Heldin, Carl-Henrik; Lu, Benson; Evans, Ron; Gutkind, J Silvio
Communication between cells in a multicellular organism occurs by the production of ligands (proteins, peptides, fatty acids, steroids, gases, and other low-molecular-weight compounds) that are either secreted by cells or presented on their surface, and act on receptors on, or in, other target cells. Such signals control cell growth, migration, survival, and differentiation. Signaling receptors can be single-span plasma membrane receptors associated with tyrosine or serine/threonine kinase activities, proteins with seven transmembrane domains, or intracellular receptors. Ligand-activated receptors convey signals into the cell by activating signaling pathways that ultimately affect cytosolic machineries or nuclear transcriptional programs or by directly translocating to the nucleus to regulate transcription. PMID:27037414
NASA Technical Reports Server (NTRS)
Hymer, R. L.
System provides automatic volume control for an audio amplifier or a voice communication system without introducing noise surges during pauses in the input, and without losing the initial signal when the input resumes.
ERIC Educational Resources Information Center
Lichtman, Jeffrey M.
Introduces the basics of radio astronomy and describes how to assemble several simple systems for receiving radio signals from the cosmos. Includes schematics, parts lists, working drawings, and contact information for radio astronomy suppliers. (11 references) (Author/JJK)
Rhyasen, G W; Starczynowski, D T
Innate immune signalling has an essential role in inflammation, and the dysregulation of signalling components of this pathway is increasingly being recognised as an important mediator in cancer initiation and progression. In some malignancies, dysregulation of inflammatory toll-like receptor (TLR) and interleukin-1 receptor (IL1R) signalling is typified by increased NF-κB activity, and it occurs through somatic mutations, chromosomal deletions, and/or transcriptional deregulation. Interleukin-1 receptor-associated kinase (IRAK) family members are mediators of TLR/IL1R superfamily signalling, and mounting evidence implicates these kinases as viable cancer targets. Although there have been previous efforts aimed at the development of IRAK kinase inhibitors, this is currently an area of renewed interest for cancer drug development. PMID:25290089
NASA Astrophysics Data System (ADS)
Creasey, D. J.
A collection of papers on advanced signal processing in radar, sonar, and communications is presented. The topics addressed include: transmitter aerials, high-power amplifier design for active sonar, radar transmitters, receiver array technology for sonar, new underwater acoustic detectors, diversity techniques in communications receivers, GaAs IC amplifiers for radar and communication receivers, integrated optical techniques for acoustooptic receivers, logarithmic receivers, CCD processors for sonar, acoustooptic correlators, designing in silicon, very high performance integrated circuits, and digital filters. Also discussed are: display types, scan converters in sonar, display ergonomics, simulators, high throughput sonar processors, optical fiber systems for signal processing, satellite communications, VLSI array processor for image and signal processing, ADA, future of cryogenic devices for signal processing applications, advanced image understanding, and VLSI architectures for real-time image processing.
Modularity in signaling systems
NASA Astrophysics Data System (ADS)
Del Vecchio, Domitilla
Modularity is a property by which the behavior of a system does not change upon interconnection. It is crucial for understanding the behavior of a complex system from the behavior of the composing subsystems. Whether modularity holds in biology is an intriguing and largely debated question. In this paper, we discuss this question taking a control system theory view and focusing on signaling systems. In particular, we argue that, despite signaling systems being constituted of structural modules, such as covalent modification cycles, modularity does not hold in general. As in any engineering system, impedance-like effects, called retroactivity, appear at interconnections and alter the behavior of connected modules. We further argue that while signaling systems have evolved sophisticated ways to counter-act retroactivity and enforce modularity, retroactivity may also be exploited to finely control the information processing of signaling pathways. Testable predictions and experimental evidence are discussed with their implications.
Johnstone, R A; Grafen, A
The handicap principle of Zahavi is potentially of great importance to the study of biological communication. Existing models of the handicap principle, however, make the unrealistic assumption that communication is error free. It seems possible, therefore, that Zahavi's arguments do not apply to real signalling systems, in which some degree of error is inevitable. Here, we present a general evolutionarily stable strategy (ESS) model of the handicap principle which incorporates perceptual error. We show that, for a wide range of error functions, error-prone signalling systems must be honest at equilibrium. Perceptual error is thus unlikely to threaten the validity of the handicap principle. Our model represents a step towards greater realism, and also opens up new possibilities for biological signalling theory. Concurrent displays, direct perception of quality, and the evolution of 'amplifiers' and 'attenuators' are all probable features of real signalling systems, yet handicap models based on the assumption of error-free communication cannot accommodate these possibilities. PMID:1354361
Automatic Filtering and Substantiation of Drug Safety Signals
Bauer-Mehren, Anna; van Mullingen, Erik M.; Avillach, Paul; Carrascosa, María del Carmen; Garcia-Serna, Ricard; Piñero, Janet; Singh, Bharat; Lopes, Pedro; Oliveira, José L.; Diallo, Gayo; Ahlberg Helgee, Ernst; Boyer, Scott; Mestres, Jordi; Sanz, Ferran; Kors, Jan A.; Furlong, Laura I.
Drug safety issues pose serious health threats to the population and constitute a major cause of mortality worldwide. Due to the prominent implications to both public health and the pharmaceutical industry, it is of great importance to unravel the molecular mechanisms by which an adverse drug reaction can be potentially elicited. These mechanisms can be investigated by placing the pharmaco-epidemiologically detected adverse drug reaction in an information-rich context and by exploiting all currently available biomedical knowledge to substantiate it. We present a computational framework for the biological annotation of potential adverse drug reactions. First, the proposed framework investigates previous evidences on the drug-event association in the context of biomedical literature (signal filtering). Then, it seeks to provide a biological explanation (signal substantiation) by exploring mechanistic connections that might explain why a drug produces a specific adverse reaction. The mechanistic connections include the activity of the drug, related compounds and drug metabolites on protein targets, the association of protein targets to clinical events, and the annotation of proteins (both protein targets and proteins associated with clinical events) to biological pathways. Hence, the workflows for signal filtering and substantiation integrate modules for literature and database mining, in silico drug-target profiling, and analyses based on gene-disease networks and biological pathways. Application examples of these workflows carried out on selected cases of drug safety signals are discussed. The methodology and workflows presented offer a novel approach to explore the molecular mechanisms underlying adverse drug reactions. PMID:22496632
Singh, Sanjay; Mann, Baldeep Kaur
Insects are a class of living creatures within the arthropods. Insect bite reactions are commonly seen in clinical practice. The present review touches upon the medically important insects and their places in the classification, the sparse literature on the epidemiology of insect bites in India, and different variables influencing the susceptibility of an individual to insect bites. Clinical features of mosquito bites, hypersensitivity to mosquito bites Epstein-Barr virus NK (HMB-EBV-NK) disease, eruptive pseudoangiomatosis, Skeeter syndrome, papular pruritic eruption of HIV/AIDS, and clinical features produced by bed bugs, Mexican chicken bugs, assassin bugs, kissing bugs, fleas, black flies, Blandford flies, louse flies, tsetse flies, midges, and thrips are discussed. Brief account is presented of the immunogenic components of mosquito and bed bug saliva. Papular urticaria is discussed including its epidemiology, the 5 stages of skin reaction, the SCRATCH principle as an aid in diagnosis, and the recent evidence supporting participation of types I, III, and IV hypersensitivity reactions in its causation is summarized. Recent developments in the treatment of pediculosis capitis including spinosad 0.9% suspension, benzyl alcohol 5% lotion, dimethicone 4% lotion, isopropyl myristate 50% rinse, and other suffocants are discussed within the context of evidence derived from randomized controlled trials and key findings of a recent systematic review. We also touch upon a non-chemical treatment of head lice and the ineffectiveness of egg-loosening products. Knockdown resistance (kdr) as the genetic mechanism making the lice nerves insensitive to permethrin is discussed along with the surprising contrary clinical evidence from Europe about efficacy of permethrin in children with head lice carrying kdr-like gene. The review also presents a brief account of insects as vectors of diseases and ends with discussion of prevention of insect bites and some serious adverse effects
NASA Technical Reports Server (NTRS)
Gordon, J. I.; Edgerton, C. F.; Duntley, S. Q.
A nomogram is presented for predicting the sighting range for white, steady-burning signal lights. The theoretical and experimental bases are explained and instructions are provided for its use for a variety of practical problems concerning the visibility of signal lights. The nomogram is appropriate for slant path as well as horizontal sightings, and the gain of range achieved by utilizing binoculars can be predicted by use of it.
Copper mediated carbometalation reactions.
Müller, D S; Marek, I
Since the first discovery of carbocupration of alkynes in the 1970s a tremendous amount of research has been carried out in this field. The exceptionally high selectivities obtained attribute to the great synthetic value of carbocupration reactions. This tutorial review will present the most important features of carbocupration of alkynes and highlight the most relevant reviews. Then a comprehensive review of copper mediated carbometalation of cyclopropenes will follow. The latter method has received much attention over the last decade as it allows the highly selective construction of poly-substituted cyclopropanes which can be transformed into acyclic derivatives bearing one or multiple tertiary or quaternary carbon stereocenters. PMID:26808300
Electronegativity and redox reactions.
Miranda-Quintana, Ramón Alain; Martínez González, Marco; Ayers, Paul W
Using the maximum hardness principle, we show that the oxidation potential of a molecule increases as its electronegativity increases and also increases as its electronegativity in its oxidized state increases. This insight can be used to construct a linear free energy relation for the oxidation potential, which we train on a set of 31 organic redox couples and test on a set of 10 different redox reactions. Better results are obtained when the electronegativity of the oxidized/reduced reagents are adjusted to account for the reagents' interaction with their chemical environment. PMID:27451962
Kubota, Takuo; Michigami, Toshimi; Ozono, Keiichi
Wnt signaling is involved not only in embryonic development but also in maintenance of homeostasis in postnatal tissues. Multiple lines of evidence have increased understanding of the roles of Wnt signaling in bone since mutations in the LRP5 gene were identified in human bone diseases. Canonical Wnt signaling promotes mesenchymal progenitor cells to differentiate into osteoblasts. The canonical Wnt/β-catenin pathway possibly through Lrp6, a co-receptor for Wnts as well as Lrp5, in osteoblasts regulates bone resorption by increasing the OPG/RANKL ratio. However, endogenous inhibitors of Wnt signaling including sclerostin block bone formation. Regulation of sclerostin appears to be one of the mechanisms of PTH anabolic actions on bone. Since sclerostin is almost exclusively expressed in osteocytes, inhibition of sclerostin is the most promising design. Surprisingly, Lrp5 controls bone formation by inhibiting serotonin synthesis in the duodenum, but not by directly promoting bone formation. Pharmacological intervention may be considered in many components of the canonical Wnt signaling pathway, although adverse effects and tumorigenicity to other tissues are important. More studies will be needed to fully understand how the Wnt signaling pathway actually influences bone metabolism and to assure the safety of new interventions. PMID:23926379
Tognetti, Jorge A.; Pontis, Horacio G.; Martínez-Noël, Giselle M.A.
The role of sucrose as a signaling molecule in plants was originally proposed several decades ago. However, recognition of sucrose as a true signal has been largely debated and only recently this role has been fully accepted. The best-studied cases of sucrose signaling involve metabolic processes, such as the induction of fructan or anthocyanin synthesis, but a large volume of scattered information suggests that sucrose signals may control a vast array of developmental processes along the whole life cycle of the plant. Also, wide gaps exist in our current understanding of the intracellular steps that mediate sucrose action. Sucrose concentration in plant tissues tends to be directly related to light intensity, and inversely related to temperature, and accordingly, exogenous sucrose supply often mimics the effect of high light and cold. However, many exceptions to this rule seem to occur due to interactions with other signaling pathways. In conclusion, the sucrose role as a signal molecule in plants is starting to be unveiled and much research is still needed to have a complete map of its significance in plant function. PMID:23333971
Verlinden, Lieve; Vanderschueren, Dirk; Verstuyf, Annemieke
Semaphorin molecules regulate cell adhesion and motility in a wide variety of cell types and are therefore involved in numerous processes including axon guidance, angiogenesis, cardiogenesis, tumor growth, and immune response. Increasing evidence points to a role of transmembrane, membrane-associated and soluble semaphorins during bone development as well as in the control of normal bone homeostasis. Within bone, semaphorins are implicated in the communication between different cell types by relaying signals in an autocrine or paracrine way. Semaphorins are not only involved in bone resorption but also in bone formation. Therefore, targeting semaphorin-induced signaling in bone may constitute an interesting new therapeutic strategy in osteoporosis. However, all the pioneering research on semaphorins is performed in mice and it remains to be established to what extent semaphorin signaling pathways are conserved between mice and men. In addition, knowledge of semaphorin signaling in bone mostly arises from loss/gain of function studies of one single semaphorin and/or receptor. However, different semaphorin molecules are co-expressed in bone and their signaling pathways are likely to interact in a complex and coherent way that needs proper understanding before targeting semaphorin signaling can be therapeutically exploited. PMID:26365296
Organic chemistry: Reactions triggered electrically
NASA Astrophysics Data System (ADS)
Xiang, Limin; Tao, N. J.
Single-molecule experiments have revealed that chemical reactions can be controlled using electric fields -- and that the reaction rate is sensitive to both the direction and the strength of the applied field. See Letter p.88
Positive reaction to allergen (image)
Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...
Hydrazine decomposition and other reactions
NASA Technical Reports Server (NTRS)
Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)
This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.
Demonstration of the Fenton Reaction
ERIC Educational Resources Information Center
Luehrs, Dean C.; Roher, Alex E.
The study demonstrates the Fenton reaction, which is carried out using the Fenton reagent that is used for groundwater and soil remediation. The Fenton reaction can be implicated in DNA damage, Alzheimer's disease, cardiovascular disease and ageing in general.
Allergic reactions to medication (image)
A true allergy to a medication is different than a simple adverse reaction to the drug. The allergic reaction occurs when the immune system, having been exposed to the drug before, creates antibodies to ...
Pulse code modulated signal synchronizer
NASA Technical Reports Server (NTRS)
Kobayashi, H. S. (Inventor)
A bit synchronizer for a split phase PCM transmission is reported that includes three loop circuits which receive incoming phase coded PCM signals. In the first loop, called a Q-loop, a generated, phase coded, PCM signal is multiplied with the incoming signals, and the frequency and phase of the generated signal are nulled to that of the incoming subcarrier signal. In the second loop, called a B-loop, a circuit multiplies a generated signal with incoming signals to null the phase of the generated signal in a bit phase locked relationship to the incoming signal. In a third loop, called the I-loop, a phase coded PCM signal is multiplied with the incoming signals for decoding the bit information from the PCM signal. A counter means is used for timing of the generated signals and timing of sample intervals for each bit period.
''Subthreshold'' reactions involving nuclear fission
Goldhaber, M.; Shrock, R.
We analyze reactions of several types that are naively below threshold but can proceed because of the release of binding energy from nuclear fission and occasionally the formation of Coulombic bound states. These reactions include (i) photofission with pion production and (ii) charged current neutrino-nucleus reactions that lead to fission and/or formation of a Coulomb bound state of a {mu}{sup -} with the nucleus of a fission fragment. We comment on the possible experimental observation of these reactions.
NASA Astrophysics Data System (ADS)
Wright, Stephen W.
An iodine clock reaction that gives a colorless to black result similar to that of the familiar Landolt iodate-bisulfite clock reaction is described. The vitamin C clock reaction uses chemicals that are readily available on the retail market: vitamin C, tincture of iodine, 3% hydrogen peroxide, and laundry starch. Orange juice may be used as the vitamin C source to give an orange to black reaction.
More on Chemical Reaction Balancing.
ERIC Educational Resources Information Center
Swinehart, D. F.
A previous article stated that only the matrix method was powerful enough to balance a particular chemical equation. Shows how this equation can be balanced without using the matrix method. The approach taken involves writing partial mathematical reactions and redox half-reactions, and combining them to yield the final balanced reaction. (JN)
ERIC Educational Resources Information Center
Wright, Stephen W.
Describes an iodine clock reaction that produces an effect similar to the Landolt clock reaction. This reaction uses supermarket chemicals and avoids iodate, bisulfite, and mercury compounds. Ascorbic acid and tincture of iodine are the main reactants with alternate procedures provided for vitamin C tablets and orange juice. (DDR)
Development of detonation reaction engine
NASA Technical Reports Server (NTRS)
Lange, O. H.; Stein, R. J.; Tubbs, H. E.
Reaction engine operates on the principle of a controlled condensed detonation. In this engine the gas products that are expelled from the engine to produce thrust are generated by the condensed detonation reaction. The engine is constructed of two basic sections consisting of a detonation wave generator section and a condensed detonation reaction section.
Mass Transfer with Chemical Reaction.
ERIC Educational Resources Information Center
DeCoursey, W. J.
Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)
Calcium signaling and cytotoxicity.
Kass, G E; Orrenius, S
The divalent calcium cation Ca(2+) is used as a major signaling molecule during cell signal transduction to regulate energy output, cellular metabolism, and phenotype. The basis to the signaling role of Ca(2+) is an intricate network of cellular channels and transporters that allow a low resting concentration of Ca(2+) in the cytosol of the cell ([Ca(2+)]i) but that are also coupled to major dynamic and rapidly exchanging stores. This enables extracellular signals from hormones and growth factors to be transduced as [Ca(2+)]i spikes that are amplitude and frequency encoded. There is considerable evidence that a number of toxic environmental chemicals target these Ca(2+) signaling processes, alter them, and induce cell death by apoptosis. Two major pathways for apoptosis will be considered. The first one involves Ca(2+)-mediated expression of ligands that bind to and activate death receptors such as CD95 (Fas, APO-1). In the second pathway, Ca(2+) has a direct toxic effect and its primary targets include the mitochondria and the endoplasmic reticulum (ER). Mitochondria may respond to an apoptotic Ca(2+) signal by the selective release of cytochrome c or through enhanced production of reactive oxygen species and opening of an inner mitochondrial membrane pore. Toxic agents such as the environmental pollutant tributyltin or the natural plant product thapsigargin, which deplete the ER Ca(2+) stores, will induce as a direct result of this effect the opening of plasma membrane Ca(2+) channels and an ER stress response. In contrast, under some conditions, Ca(2+) signals may be cytoprotective and antagonize the apoptotic machinery. Images Figure 1 Figure 2 Figure 3 PMID:10229704
Signal transduction and chemotaxis in mast cells.
Draber, Petr; Halova, Ivana; Polakovicova, Iva; Kawakami, Toshiaki
Mast cells play crucial roles in both innate and adaptive arms of the immune system. Along with basophils, mast cells are essential effector cells for allergic inflammation that causes asthma, allergic rhinitis, food allergy and atopic dermatitis. Mast cells are usually increased in inflammatory sites of allergy and, upon activation, release various chemical, lipid, peptide and protein mediators of allergic reactions. Since antigen/immunoglobulin E (IgE)-mediated activation of these cells is a central event to trigger allergic reactions, innumerable studies have been conducted on how these cells are activated through cross-linking of the high-affinity IgE receptor (FcεRI). Development of mature mast cells from their progenitor cells is under the influence of several growth factors, of which the stem cell factor (SCF) seems to be the most important. Therefore, how SCF induces mast cell development and activation via its receptor, KIT, has been studied extensively, including a cross-talk between KIT and FcεRI signaling pathways. Although our understanding of the signaling mechanisms of the FcεRI and KIT pathways is far from complete, pharmaceutical applications of the knowledge about these pathways are underway. This review will focus on recent progresses in FcεRI and KIT signaling and chemotaxis. PMID:25941081
Respiration signals from photoplethysmography.
Nilsson, Lena M
Pulse oximetry is based on the technique of photoplethysmography (PPG) wherein light transmitted through tissues is modulated by the pulse. In addition to variations in light modulation by the cardiac cycle, the PPG signal contains a respiratory modulation and variations associated with changing tissue blood volume of other origins. Cardiovascular, respiratory, and neural fluctuations in the PPG signal are of different frequencies and can all be characterized according to their sinusoidal components. PPG was described in 1937 to measure blood volume changes. The technique is today increasingly used, in part because of developments in semiconductor technology during recent decades that have resulted in considerable advances in PPG probe design. Artificial neural networks help to detect complex nonlinear relationships and are extensively used in electronic signal analysis, including PPG. Patient and/or probe-tissue movement artifacts are sources of signal interference. Physiologic variations such as vasoconstriction, a deep gasp, or yawn also affect the signal. Monitoring respiratory rates from PPG are often based on respiratory-induced intensity variations (RIIVs) contained in the baseline of the PPG signal. Qualitative RIIV signals may be used for monitoring purposes regardless of age, gender, anesthesia, and mode of ventilation. Detection of breaths in adult volunteers had a maximal error of 8%, and in infants the rates of overdetected and missed breaths using PPG were 1.5% and 2.7%, respectively. During central apnea, the rhythmic RIIV signals caused by variations in intrathoracic pressure disappear. PPG has been evaluated for detecting airway obstruction with a sensitivity of 75% and a specificity of 85%. The RIIV and the pulse synchronous PPG waveform are sensitive for detecting hypovolemia. The respiratory synchronous variation of the PPG pulse amplitude is an accurate predictor of fluid responsiveness. Pleth variability index is a continuous measure of the
Hydrocracking reactions and catalysis
Dolbear, G.E.
Hydrocracking processes convert aromatic gas oils into high quality gasoline, diesel, and turbine stocks. In doing this, they saturate aromatic rings, crack naphthenes and paraffins, and saturate olefins formed during cracking. The organic chemistry of these steps is well known. Catalysts for hydrocracking contain components for both the hydrogenation and cracking reactions. Hydrogenation activity is provided by Pd or promoted molybdenum or tungsten sulfides. Cracking takes place on strong acid sites in zeolites or amorphous silica aluminas. Specialty catalysts including narrow pore zeolites are used in dewaxing tube oil stocks. Basic nitrogen compounds such as quinoline can poison the acid sites. They are usually removed in a pretreating step, typically with a nickel/molybdenum sulfide catalyst that also removes sulfur.
Laser induced nuclear reactions
Ledingham, Ken; McCanny, Tom; Graham, Paul; Fang Xiao; Singhal, Ravi; Magill, Joe; Creswell, Alan; Sanderson, David; Allott, Ric; Neely, David; Norreys, Peter; Santala, Marko; Zepf, Matthew; Watts, Ian; Clark, Eugene; Krushelnick, Karl; Tatarakis, Michael; Dangor, Bucker; Machecek, Antonin; Wark, Justin
Dramatic improvements in laser technology since 1984 have revolutionised high power laser technology. Application of chirped-pulse amplification techniques has resulted in laser intensities in excess of 10{sup 19} W/cm{sup 2}. In the mid to late eighties, C. K. Rhodes and K. Boyer discussed the possibility of shining laser light of this intensity onto solid surfaces and to cause nuclear transitions. In particular, irradiation of a uranium target could induce electro- and photofission in the focal region of the laser. In this paper it is shown that {mu}Ci of {sup 62}Cu can be generated via the ({gamma},n) reaction by a laser with an intensity of about 10{sup 19} Wcm{sup -2}.
The purpose of this feature is to heighten awareness of specific adverse drug reactions (ADRs), discuss methods of prevention, and promote reporting of ADRs to the US Food and Drug Administration's (FDA's) MedWatch program (800-FDA-1088). If you have reported an interesting, preventable ADR to MedWatch, please consider sharing the account with our readers. Write to Dr. Mancano at ISMP, 200 Lakeside Drive, Suite 200, Horsham, PA 19044 (phone: 215-707-4936; e-mail: email@example.com). Your report will be published anonymously unless otherwise requested. This feature is provided by the Institute for Safe Medication Practices (ISMP) in cooperation with the FDA's MedWatch program and Temple University School of Pharmacy. ISMP is an FDA MedWatch partner. PMID:24421544
Prebiotic photosynthetic reactions.
Chittenden, G J; Schwartz, A W
Historically, numerous attempts have been made to mimic - by means of inorganic model reactions - the photosynthetic fixation of CO2 by green plants. The literature in this field is strewn with claims and counter-claims. Two factors have led us to reexamine this subject: firstly; doubts concerning the highly reducing model for the atmosphere of the primitive Earth and secondly; recent results which demonstrate that photoreductive fixation is feasable on a suitable catalytic surface, for both CO2 and N2. The latter observation is of particular interest due to the well-known susceptibility of NH3 to photolytic destruction. Our review of the literature leads us to suggest that similar processes would have been plausible for the primitive Earth and could have been prebiotic precursors to an early development of CO2-fixing autotrophs. PMID:6791723
Sphingosine 1-phosphate signalling.
Mendelson, Karen; Evans, Todd; Hla, Timothy
Sphingosine 1-phosphate (S1P) is a lipid mediator formed by the metabolism of sphingomyelin. In vertebrates, S1P is secreted into the extracellular environment and signals via G protein-coupled S1P receptors to regulate cell-cell and cell-matrix adhesion, and thereby influence cell migration, differentiation and survival. The expression and localization of S1P receptors is dynamically regulated and controls vascular development, vessel stability and immune cell trafficking. In addition, crucial events during embryogenesis, such as angiogenesis, cardiogenesis, limb development and neurogenesis, are regulated by S1P signalling. Here, and in the accompanying poster, we provide an overview of S1P signalling in development and in disease. PMID:24346695
Yan, Shaomin; Wu, Guang
Cellulase is an enzyme playing a crucial role in biotechnology industries ranging from textile to biofuel because of tremendous amount of cellulose produced in plant. In order to improve cellulase productivity, huge resource has been spent in search for good cellulases from microorganism in remote areas and in creation of ideal cellulase by engineering. However, not much attention is given to the secretion of cellulases from cell into extracellular space, where a cellulase plays its enzymatic role. In this minireview, the signal peptides, which lead secreted proteins to specific secretion systems and scatter in literature, are reviewed. The patterns of signal peptides are checked against 4,101 cellulases documented in UniProtKB, the largest protein database in the world, to determine how these cellulases are secreted. Simultaneous review on both literature and cellulases from the database not only provides updated knowledge on signal peptides but also indicates the gap in our research. PMID:24743986
Telemetry Ranging: Signal Processing
NASA Astrophysics Data System (ADS)
Hamkins, J.; Kinman, P.; Xie, H.; Vilnrotter, V.; Dolinar, S.
This article describes the details of the signal processing used in a telemetry ranging system in which timing information is extracted from the downlink telemetry signal in order to compute spacecraft range. A previous article describes telemetry ranging concepts and architecture, which are a slight variation of a scheme published earlier. As in that earlier work, the telemetry ranging concept eliminates the need for a dedicated downlink ranging signal to communicate the necessary timing information. The present article describes the operation and performance of the major receiver functions on the spacecraft and the ground --- many of which are standard tracking loops already in use in JPL's flight and ground radios --- and how they can be used to provide the relevant information for making a range measurement. It also describes the implementation of these functions in software, and performance of an end-to-end software simulation of the telemetry ranging system.
Endocytosis, Signaling, and Beyond
Di Fiore, Pier Paolo; von Zastrow, Mark
The endocytic network comprises a vast and intricate system of membrane-delimited cell entry and cargo sorting routes running between biochemically and functionally distinct intracellular compartments. The endocytic network caters to the organization and redistribution of diverse subcellular components, and mediates appropriate shuttling and processing of materials acquired from neighboring cells or the extracellular milieu. Such trafficking logistics, despite their importance, represent only one facet of endocytic function. The endocytic network also plays a key role in organizing, mediating, and regulating cellular signal transduction events. Conversely, cellular signaling processes tightly control the endocytic pathway at different steps. The present article provides a perspective on the intimate relationships that exist between particular endocytic and cellular signaling processes in mammalian cells, within the context of understanding the impact of this nexus on integrated physiology. PMID:25085911
Kamath, C; Fodor, I
Understanding changes in global climate is a challenging scientific problem. Simulated and observed data include signals from many sources, and untangling their respective effects is difficult. In order to make meaningful comparisons between different models, and to understand human effects on global climate, we need to isolate the effects of different sources. Recent eruptions of the El Chichon and Mt. Pinatubo volcanoes coincided with large El Nino and Southern Oscillation (ENSO) events, which complicates the separation of their contributions on global temperatures. Current approaches for separating volcano and ENSO signals in global mean data involve parametric models and iterative techniques [3]. We investigate alternative methods based on principal component analysis (PCA) [2] and independent component analysis (ICA) [1]. Our goal is to determine if such techniques can automatically identify the signals corresponding to the different sources, without relying on parametric models.
Exploring Interstellar Chemistry with Broadband Reaction Screening
NASA Astrophysics Data System (ADS)
Zaleski, Daniel Paul
Chirped pulse Fourier transform microwave (CP-FTMW) spectroscopy is a powerful technique for molecular detection and characterization. One of the strengths of this technique is the ability to analyze complex mixtures quickly and unambiguously. This capability is exploited utilizing a method called broadband reaction screening. Discussed in this thesis, chemical reactions in an electric discharge are monitored with broadband rotational spectroscopy, and the products are studied in the context of astrochemistry. Because of advancements in high-speed digital signal processing with increased data throughput, astrochemistry, as a field, is currently experiencing an emerging synergy between broadband laboratory spectra and broadband radio astronomical survey spectra. The availability of high quality radio astronomy survey spectra is expected to dramatically increase in the coming years, which in turn should provide the impetus for moving beyond the traditional "targeted search" model and instead focus on "reaction product screening". Since the two techniques characterize molecules in the same fashion, by their rotational spectra, directly comparing both types of broadband spectra may lead to a better understanding of the complex chemistry that occurs in the interstellar medium. Also discussed in this thesis is the development of two new CP-FTMW spectrometers operating in frequency ranges that are compatible with molecules of astronomical interest.
Cell Simulation Package for Reactions and Diffusion
ChemCell is a simulation package designed for modeling signalling, regulatory, and metabolic pathways in biological cells. It reads input flies that describe the geomeby of the cell and positions of particles that represent proteins, protein complexes, and other bio-molecules. It also reads in lists of reactions and associated rates and other boundary condition information. ChemCell then models the reaction and diffusion of these particles within the cellular geometry as they interact overtime. It produces statisticalmore » information about the state of the cell, as well as snapshots of the reaction network. We anticipate ChemCell will be useful to researchers who wish to perform spatio-temporal modeling of cellular processes and who wish to develop new models or algorithms to add to the code. Thus ChemCell is also designed to be easy to modify and extend. The ChemCell package includes auxiliary codes for setting up problems and analyzing output.« less
Honest signalling with costly gambles
Meacham, Frazer; Perlmutter, Aaron; Bergstrom, Carl T.
Costly signalling theory is commonly invoked as an explanation for how honest communication can be stable when interests conflict. However, the signal costs predicted by costly signalling models often turn out to be unrealistically high. These models generally assume that signal cost is determinate. Here, we consider the case where signal cost is instead stochastic. We examine both discrete and continuous signalling games and show that, under reasonable assumptions, stochasticity in signal costs can decrease the average cost at equilibrium for all individuals. This effect of stochasticity for decreasing signal costs is a fundamental mechanism that probably acts in a wide variety of circumstances. PMID:23904587
Subdiffusion-reaction processes with A→B reactions versus subdiffusion-reaction processes with A+B→B reactions.
Kosztołowicz, Tadeusz; Lewandowska, Katarzyna D
We consider the subdiffusion-reaction process with reactions of a type A+B→B (in which particles A are assumed to be mobile, whereas B are assumed to be static) in comparison to the subdiffusion-reaction process with A→B reactions which was studied by Sokolov, Schmidt, and Sagués [Phys. Rev. E 73, 031102 (2006)]. In both processes a rule that reactions can only occur between particles which continue to exist is taken into account. Although in both processes a probability of the vanishing of particle A due to a reaction is independent of both time and space variables (assuming that in the system with the A+B→B reactions, particles B are distributed homogeneously), we show that subdiffusion-reaction equations describing these processes as well as their Green's functions are qualitatively different. The reason for this difference is as follows. In the case of the former reaction, particles A and B have to meet with some probability before the reaction occurs in contradiction with the case of the latter reaction. For the subdiffusion process with the A+B→B reactions we consider three models which differ in some details concerning a description of the reactions. We base the method considered in this paper on a random walk model in a system with both discrete time and discrete space variables. Then the system with discrete variables is transformed into a system with both continuous time and continuous space variables. Such a method seems to be convenient in analyzing subdiffusion-reaction processes with partially absorbing or partially reflecting walls. The reason is that within this method we can determine Green's functions without a necessity of solving a fractional differential subdiffusion-reaction equation with boundary conditions at the walls. As an example, we use the model to find the Green's functions for a subdiffusive reaction system (with the reactions mentioned above), which is bounded by a partially absorbing wall. This example shows how the model
PKD signaling and pancreatitis
Yuan, Jingzhen; Pandol, Stephen J.
Background Acute pancreatitis is a serious medical disorder with no current therapies directed to the molecular pathogenesis of the disorder. Inflammation, inappropriate intracellular activation of digestive enzymes, and parenchymal acinar cell death by necrosis are the critical pathophysiologic processes of acute pancreatitis. Thus, it is necessary to elucidate the key molecular signals that mediate these pathobiologic processes and develop new therapeutic strategies to attenuate the appropriate signaling pathways in order to improve outcomes for this disease. A novel serine/threonine protein kinase D (PKD) family has emerged as key participants in signal transduction, and this family is increasingly being implicated in the regulation of multiple cellular functions and diseases. Methods This review summarizes recent findings of our group and others regarding the signaling pathway and the biological roles of the PKD family in pancreatic acinar cells. In particular, we highlight our studies of the functions of PKD in several key pathobiologic processes associated with acute pancreatitis in experimental models. Results Our findings reveal that PKD signaling is required for NF-κB activation/inflammation, intracellular zymogen activation, and acinar cell necrosis in rodent experimental pancreatitis. Novel small-molecule PKD inhibitors attenuate the severity of pancreatitis in both in vitro and in vivo experimental models. Further, this review emphasizes our latest advances in the therapeutic application of PKD inhibitors to experimental pancreatitis after the initiation of pancreatitis. Conclusions These novel findings suggest that PKD signaling is a necessary modulator in key initiating pathobiologic processes of pancreatitis, and that it constitutes a novel therapeutic target for treatments of this disorder. PMID:26879861
Packaging signals in alphaviruses.
Frolova, E; Frolov, I; Schlesinger, S
Alphaviruses synthesize large amounts of both genomic and subgenomic RNA in infected cells, but usually only the genomic RNA is packaged. This implies the existence of an encapsidation or packaging signal which would be responsible for selectivity. Previously, we had identified a region of the Sindbis virus genome that interacts specifically with the viral capsid protein. This 132-nucleotide (nt) fragment lies within the coding region of the nsP1 gene (nt 945 to 1076). We proposed that the 132-mer is important for capsid recognition and initiates the formation of the viral nucleocapsid. To study the encapsidation of Sindbis virus RNAs in infected cells, we designed a new assay that uses the self-replicating Sindbis virus genomes (replicons) which lack the viral structural protein genes and contain heterologous sequences under the control of the subgenomic RNA promoter. These replicons can be packaged into viral particles by using defective helper RNAs that contain the structural protein genes (P. Bredenbeek, I. Frolov, C. M. Rice, and S. Schlesinger, J. Virol. 67:6439-6446, 1993). Insertion of the 132-mer into the subgenomic RNA significantly increased the packaging of this RNA into viral particles. We have used this assay and defective helpers that contain the structural protein genes of Ross River virus (RRV) to investigate the location of the encapsidation signal in the RRV genome. Our results show that there are several fragments that could act as packaging signals. They are all located in a different region of the genome than the signal for the Sindbis virus genome. For RRV, the strongest packaging signal lies between nt 2761 and 3062 in the nsP2 gene. This is the same region that was proposed to contain the packaging signal for Semliki Forest virus genomic RNA. PMID:8985344
A Temporal Window for Signal Activation Dictates the Dimensions of a Nodal Signaling Domain
van Boxtel, Antonius L.; Chesebro, John E.; Heliot, Claire; Ramel, Marie-Christine; Stone, Richard K.; Hill, Caroline S.
Summary Morphogen signaling is critical for the growth and patterning of tissues in embryos and adults, but how morphogen signaling gradients are generated in tissues remains controversial. The morphogen Nodal was proposed to form a long-range signaling gradient via a reaction-diffusion system, on the basis of differential diffusion rates of Nodal and its antagonist Lefty. Here we use a specific zebrafish Nodal biosensor combined with immunofluorescence for phosphorylated Smad2 to demonstrate that endogenous Nodal is unlikely to diffuse over a long range. Instead, short-range Nodal signaling activation in a temporal window is sufficient to determine the dimensions of the Nodal signaling domain. The size of this temporal window is set by the differentially timed production of Nodal and Lefty, which arises mainly from repression of Lefty translation by the microRNA miR-430. Thus, temporal information is transformed into spatial information to define the dimensions of the Nodal signaling domain and, consequently, to specify mesendoderm. PMID:26506307
A Temporal Window for Signal Activation Dictates the Dimensions of a Nodal Signaling Domain.
van Boxtel, Antonius L; Chesebro, John E; Heliot, Claire; Ramel, Marie-Christine; Stone, Richard K; Hill, Caroline S
Morphogen signaling is critical for the growth and patterning of tissues in embryos and adults, but how morphogen signaling gradients are generated in tissues remains controversial. The morphogen Nodal was proposed to form a long-range signaling gradient via a reaction-diffusion system, on the basis of differential diffusion rates of Nodal and its antagonist Lefty. Here we use a specific zebrafish Nodal biosensor combined with immunofluorescence for phosphorylated Smad2 to demonstrate that endogenous Nodal is unlikely to diffuse over a long range. Instead, short-range Nodal signaling activation in a temporal window is sufficient to determine the dimensions of the Nodal signaling domain. The size of this temporal window is set by the differentially timed production of Nodal and Lefty, which arises mainly from repression of Lefty translation by the microRNA miR-430. Thus, temporal information is transformed into spatial information to define the dimensions of the Nodal signaling domain and, consequently, to specify mesendoderm. PMID:26506307
Reactive oxygen species generation and signaling in plants
Tripathy, Baishnab Charan; Oelmüller, Ralf
The introduction of molecular oxygen into the atmosphere was accompanied by the generation of reactive oxygen species (ROS) as side products of many biochemical reactions. ROS are permanently generated in plastids, peroxisomes, mitochiondria, the cytosol and the apoplast. Imbalance between ROS generation and safe detoxification generates oxidative stress and the accumulating ROS are harmful for the plants. On the other hand, specific ROS function as signaling molecules and activate signal transduction processes in response to various stresses. Here, we summarize the generation of ROS in the different cellular compartments and the signaling processes which are induced by ROS. PMID:23072988
Multichannel signal enhancement
Lewis, Paul S.
A mixed adaptive filter is formulated for the signal processing problem where desired a priori signal information is not available. The formulation generates a least squares problem which enables the filter output to be calculated directly from an input data matrix. In one embodiment, a folded processor array enables bidirectional data flow to solve the recursive problem by back substitution without global communications. In another embodiment, a balanced processor array solves the recursive problem by forward elimination through the array. In a particular application to magnetoencephalography, the mixed adaptive filter enables an evoked response to an auditory stimulus to be identified from only a single trial.
Mechanisms of auxin signaling.
Lavy, Meirav; Estelle, Mark
The plant hormone auxin triggers complex growth and developmental processes. Its underlying molecular mechanism of action facilitates rapid switching between transcriptional repression and gene activation through the auxin-dependent degradation of transcriptional repressors. The nuclear auxin signaling pathway consists of a small number of core components. However, in most plants each component is represented by a large gene family. The modular construction of the pathway can thus produce diverse transcriptional outputs depending on the cellular and environmental context. Here, and in the accompanying poster, we outline the current model for TIR1/AFB-dependent auxin signaling with an emphasis on recent studies. PMID:27624827
Haykin, S.; Justice, J.H.; Owsley, N.L.; Yen, J.L.; Kak, A.C.
This is the first book to be devoted completely to array signal processing, a subject that has become increasingly important in recent years. The book consists of six chapters. Chapter 1, which is introductory, reviews some basic concepts in wave propagation. The remaining five chapters deal with the theory and applications of array signal processing in (a) exploration seismology, (b) passive sonar, (c) radar, (d) radio astronomy, and (e) tomographic imaging. The various chapters of the book are self-contained. The book is written by a team of five active researchers, who are specialists in the individual fields covered by the pertinent chapters.
Dhanasekaran, Danny N.; Reddy, E. Premkumar
Jun N-terminal kinases or JNKs play a critical role in death receptor-initiated extrinsic as well as mitochondrial intrinsic apoptotic pathways. JNKs activate apoptotic signaling by the upregulation pro-apoptotic genes via the transactivation of specific transcription factors or by directly modulating the activities of mitochondrial pro- and anti-apoptotic proteins through distinct phosphorylation events. This review analyzes our present understanding of the role of JNK in apoptotic signaling and the various mechanisms by which JNK promotes apoptosis PMID:18931691
Noninvasive vital signal monitoring
NASA Astrophysics Data System (ADS)
Wang, Zenan; Chee, Jonny; Chua, Kok Poo; Chen, ZhouDe
Vital signals of patients, such as heart rate, temperature and movement are crucial to monitor patients in hospital. Current heart rate measurement is obtained by using Electrocardiograph, which normally applies electrodes to the patient's body. As electrodes are extremely uncomfortable to ware and hinder patient's movement, a non-invasive vital signal-monitoring device will be a better solution. Similar to Electrocardiograph, the device detects the voltage difference across the heart by using concept of capacitance, which can be obtained by two conductive fiber sewing on the bed sheet. Simultaneous temperature reading can also be detected by using surface mounted temperature sensor. This paper will mainly focus on the heart rate monitoring.
Universal signal conditioning amplifier
NASA Technical Reports Server (NTRS)
Larson, William E.; Hallberg, Carl; Medelius, Pedro J.
Engineers at NASA's Kennedy Space Center have designed a signal conditioning amplifier which automatically matches itself to almost any kind of transducer. The product, called Universal Signal Conditioning Amplifier (USCA), uses state-of-the-art technologies to deliver high accuracy measurements. USCA's features which can be either programmable or automated include: voltage, current, or pulsed excitation, unlimited resolution gain, digital filtering and both analog and digital output. USCA will be used at Kennedy Space Center's launch pads for environmental measurements such as vibrations, strains, temperatures and overpressures. USCA is presently being commercialized through a co-funded agreement between NASA, the State of Florida, and Loral Test and Information Systems, Inc.
29 CFR 1926.1422 - Signals-hand signal chart.
Code of Federal Regulations, 2011 CFR
... 29 Labor 8 2011-07-01 2011-07-01 false Signals-hand signal chart. 1926.1422 Section 1926.1422 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Construction § 1926.1422 Signals—hand signal chart. Hand signal charts must be either posted on the...
29 CFR 1926.1422 - Signals-hand signal chart.
Code of Federal Regulations, 2013 CFR
... 29 Labor 8 2013-07-01 2013-07-01 false Signals-hand signal chart. 1926.1422 Section 1926.1422 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Construction § 1926.1422 Signals—hand signal chart. Hand signal charts must be either posted on the...
29 CFR 1926.1422 - Signals-hand signal chart.
Code of Federal Regulations, 2012 CFR
... 29 Labor 8 2012-07-01 2012-07-01 false Signals-hand signal chart. 1926.1422 Section 1926.1422 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Construction § 1926.1422 Signals—hand signal chart. Hand signal charts must be either posted on the...
29 CFR 1926.1422 - Signals-hand signal chart.
Code of Federal Regulations, 2014 CFR
... 29 Labor 8 2014-07-01 2014-07-01 false Signals-hand signal chart. 1926.1422 Section 1926.1422 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION... Construction § 1926.1422 Signals—hand signal chart. Hand signal charts must be either posted on the...
Nuclear Reactions on Unstable Nuclei and the Surrogate Reaction Technique
Escher, J
Determining reaction cross sections on short-lived nuclear species is a major challenge for nuclear physics and nuclear astrophysics. Many of these nuclei are too difficult to produce with currently available experimental techniques or too short-lived to serve as targets in present-day set-ups. Some nuclear reactions will remain immeasurable even at upcoming and planned radioactive beam facilities. It is therefore important to explore alternative methods for determining reaction cross sections on unstable nuclei.
Cardiolipin asymmetry, oxidation and signaling
Kagan, Valerian E.; Chu, Charleen T.; Tyurina, Yulia Y.; Cheikhi, Amin; Bayir, Hülya
Cardiolipins (CLs) are ancient and unusual dimeric phospholipids localized in the plasma membrane of bacteria and in the inner mitochondrial membrane of eukaryotes. In mitochondria, two types of asymmetries – trans-membrane and molecular - are essential determinants of CL functions. In this review, we describe CL-based signaling mitochondrial pathways realized via modulation of trans-membrane asymmetry and leading to externalization and peroxidation of CLs in mitophagy and apoptosis, respectively. We discuss possible mechanisms of CL translocations from the inner leaflet of the inner to the outer leaflet of the outer mitochondrial membranes. We present redox reaction mechanisms of cytochrome c-catalyzed CL peroxidation as a required stage in the execution of apoptosis as well as a possible source of lipid mediators. We also emphasize the significance of CL-related metabolic pathways as new targets for drug discovery. Finally, a remarkable diversity of polyunsaturated CL species and their oxidation products have evolved in eukaryotes vs. prokaryotes. This diversity - associated with CL molecular asymmetry - is presented as the basis for mitochondrial communications language. PMID:24300280
Stepwise Signal Extraction via Marginal Likelihood
Du, Chao; Kao, Chu-Lan Michael
This paper studies the estimation of stepwise signal. To determine the number and locations of change-points of the stepwise signal, we formulate a maximum marginal likelihood estimator, which can be computed with a quadratic cost using dynamic programming. We carry out extensive investigation on the choice of the prior distribution and study the asymptotic properties of the maximum marginal likelihood estimator. We propose to treat each possible set of change-points equally and adopt an empirical Bayes approach to specify the prior distribution of segment parameters. Detailed simulation study is performed to compare the effectiveness of this method with other existing methods. We demonstrate our method on single-molecule enzyme reaction data and on DNA array CGH data. Our study shows that this method is applicable to a wide range of models and offers appealing results in practice. PMID:27212739
Communication: Resonance reaction in diffusion-influenced bimolecular reactions.
Kolb, Jakob J; Angioletti-Uberti, Stefano; Dzubiella, Joachim
We investigate the influence of a stochastically fluctuating step-barrier potential on bimolecular reaction rates by exact analytical theory and stochastic simulations. We demonstrate that the system exhibits a new "resonant reaction" behavior with rate enhancement if an appropriately defined fluctuation decay length is of the order of the system size. Importantly, we find that in the proximity of resonance, the standard reciprocal additivity law for diffusion and surface reaction rates is violated due to the dynamical coupling of multiple kinetic processes. Together, these findings may have important repercussions on the correct interpretation of various kinetic reaction problems in complex systems, as, e.g., in biomolecular association or catalysis. PMID:26931674
Communication: Resonance reaction in diffusion-influenced bimolecular reactions
NASA Astrophysics Data System (ADS)
Kolb, Jakob J.; Angioletti-Uberti, Stefano; Dzubiella, Joachim
We investigate the influence of a stochastically fluctuating step-barrier potential on bimolecular reaction rates by exact analytical theory and stochastic simulations. We demonstrate that the system exhibits a new "resonant reaction" behavior with rate enhancement if an appropriately defined fluctuation decay length is of the order of the system size. Importantly, we find that in the proximity of resonance, the standard reciprocal additivity law for diffusion and surface reaction rates is violated due to the dynamical coupling of multiple kinetic processes. Together, these findings may have important repercussions on the correct interpretation of various kinetic reaction problems in complex systems, as, e.g., in biomolecular association or catalysis.
NASA Technical Reports Server (NTRS)
Rinard, G. A.; Steffen, D. A.; Sturm, R. E.
Circuit with high common-mode rejection has ability to filter and amplify accepted analog electrocardiogram (ECG) signals of varying amplitude, shape, and polarity. In addition, low power circuit develops standardized pulses that can be counted and averaged by heart/breath rate processor.
Pulsed Terahertz Signal Reconstruction
NASA Astrophysics Data System (ADS)
Fletcher, J. R.; Swift, G. P.; Dai, DeChang; Chamberlain, J. M.; Upadhya, P. C.
A procedure is outlined which can be used to determine the response of an experimental sample to a single, simple broadband frequency pulse in terahertz frequency time domain spectroscopy (TDS). The advantage that accrues from this approach is that oscillations and spurious signals (arising from a variety of sources in the TDS system or from ambient water vapor) can be suppressed. In consequence, small signals (arising from the interaction of the radiation with the sample) can be more readily observed in the presence of noise. Procedures for choosing key parameters and methods for eliminating further artifacts are described. In particular, the use of input functions which are based on the binomial distribution is described. These binomial functions are used to unscramble the sample response to a simple pulse: they have sufficient flexibility to allow for variations in the spectra of different terahertz sources, some of which have low frequency as well as high frequency cutoffs. The signal processing procedure is validated by simple reflection and transmission experiments using a gap between polytetrafluoroethylene (PTFE) plates to mimic a void within a larger material. It is shown that a resolution of 100μm is easily achievable in reflection geometry after signal processing.
Signaling by Sensory Receptors
Julius, David; Nathans, Jeremy
Sensory systems detect small molecules, mechanical perturbations, or radiation via the activation of receptor proteins and downstream signaling cascades in specialized sensory cells. In vertebrates, the two principal categories of sensory receptors are ion channels, which mediate mechanosensation, thermosensation, and acid and salt taste; and G-protein-coupled receptors (GPCRs), which mediate vision, olfaction, and sweet, bitter, and umami tastes. GPCR-based signaling in rods and cones illustrates the fundamental principles of rapid activation and inactivation, signal amplification, and gain control. Channel-based sensory systems illustrate the integration of diverse modulatory signals at the receptor, as seen in the thermosensory/pain system, and the rapid response kinetics that are possible with direct mechanical gating of a channel. Comparisons of sensory receptor gene sequences reveal numerous examples in which gene duplication and sequence divergence have created novel sensory specificities. This is the evolutionary basis for the observed diversity in temperature- and ligand-dependent gating among thermosensory channels, spectral tuning among visual pigments, and odorant binding among olfactory receptors. The coding of complex external stimuli by a limited number of sensory receptor types has led to the evolution of modality-specific and species-specific patterns of retention or loss of sensory information, a filtering operation that selectively emphasizes features in the stimulus that enhance survival in a particular ecological niche. The many specialized anatomic structures, such as the eye and ear, that house primary sensory neurons further enhance the detection of relevant stimuli. PMID:22110046
Intersection auxiliary signal system
NASA Astrophysics Data System (ADS)
Zhang, Jian
Many intersection accidents are related to drivers' inappropriate responses to an amber signal light, due to their misjudgment on the traffic situation and/or their aggressive behavior. To reduce intersection accidents of this nature, this paper proposes the Intersection Auxiliary Signal System (IAS). IAS can be installed at selected intersections, where information regarding signal phasing, intersection geometry and speed limit is transmitted from an ultrasonic/infra-red transmitter. An on-vehicle device receivers and processes the information, the provides the driver with explicit suggestions on the correct action to take (continue to pass or decelerate to stop), or warnings against on-going incorrect actions. IAS is expected to be more effective in suburban intersections, which are usually characterized by greater dimension, longer amber phases, and higher vehicle speeds. Both the intersection transmitters and the on-vehicle processors are expected to have simple structures and low costs. Simulation results show that IAS has a significant effect on reducing red signal violation, especially when there is no significant dilemma zones.
Communication Signals in Lizards.
ERIC Educational Resources Information Center
Carpenter, Charles C.
Discusses mechanisms and functional intent of visual communication signals in iguanid/agamid lizards. Demonstrated that lizards communicate with each other by using pushups and head nods and that each species does this in its own way, conveying different types of information. (JN)
Cullers, D K; Linscott, I R; Oliver, B M
The development of a multi-channel spectrum analyzer (MCSA) for the SETI program is described. The spectrum analyzer is designed for both all-sky surveys and targeted searches. The mechanisms of the MCSA are explained and a diagram is provided. Detection of continuous wave signals, pulses, and patterns is examined. PMID:11542023
Cohen, M Michael
In vertebrate hedgehog signaling, hedgehog ligands are processed to become bilipidated and then multimerize, which allows them to leave the signaling cell via Dispatched 1 and become transported via glypicans and megalin to the responding cells. Hedgehog then interacts with a complex of Patched 1 and Cdo/Boc, which activates endocytic Smoothened to the cilium. Patched 1 regulates the activity of Smoothened (1) via Vitamin D3, which inhibits Smoothened in the absence of hedgehog ligand or (2) via oxysterols, which activate Smoothened in the presence of hedgehog ligand. Hedgehog ligands also interact with Hip1, Patched 2, and Gas1, which regulate the range as well as the level of hedgehog signaling. In vertebrates, Smoothened is shortened at its C-terminal end and lacks most of the phosphorylation sites of importance in Drosophila. Cos2, also of importance in Drosophila, plays no role in mammalian transduction, nor do its homologs Kif7 and Kif27. The cilium may provide a function analogous to that of Cos2 by linking Smoothened to the modulation of Gli transcription factors. Disorders associated with the hedgehog signaling network follow, including nevoid basal cell carcinoma syndrome, holoprosencephaly, Smith-Lemli-Opitz syndrome, Greig cephalopolysyndactyly syndrome, Pallister-Hall syndrome, Carpenter syndrome, and Rubinstein-Taybi syndrome. PMID:20635334
Signals: Applying Academic Analytics
ERIC Educational Resources Information Center
Arnold, Kimberly E.
Academic analytics helps address the public's desire for institutional accountability with regard to student success, given the widespread concern over the cost of higher education and the difficult economic and budgetary conditions prevailing worldwide. Purdue University's Signals project applies the principles of analytics widely used in…
PSFC: a Pathway Signal Flow Calculator App for Cytoscape
Nersisyan, Lilit; Johnson, Graham; Riel-Mehan, Megan; Pico, Alexander; Arakelyan, Arsen
Cell signaling pathways are sequences of biochemical reactions that propagate an input signal, such as a hormone binding to a cell-surface receptor, into the cell to trigger a reactive process. Assessment of pathway activities is crucial for determining which pathways play roles in disease versus normal conditions. To date various pathway flow/perturbation assessment tools are available, however they are constrained to specific algorithms and specific data types. There are no accepted standards for evaluation of pathway activities or simulation of flow propagation events in pathways, and the results of different software are difficult to compare. Here we present Pathway Signal Flow Calculator (PSFC), a Cytoscape app for calculation of a pathway signal flow based on the pathway topology and node input data. The app provides a rich framework for customization of different signal flow algorithms to allow users to apply various approaches within a single computational framework. PMID:26834984
Wnt signaling in osteosarcoma.
Lin, Carol H; Ji, Tao; Chen, Cheng-Fong; Hoang, Bang H
Osteosarcoma (OS) is the most common primary bone malignancy diagnosed in children and adolescents with a high propensity for local invasion and distant metastasis. Despite current multidisciplinary treatments, there has not been a drastic change in overall prognosis within the last two decades. With current treatments, 60-70 % of patients with localized disease survive. Given a propensity of Wnt signaling to control multiple cellular processes, including proliferation, cell fate determination, and differentiation, it is a critical pathway in OS disease progression. At the same time, this pathway is extremely complex with vast arrays of cross-talk. Even though decades of research have linked the role of Wnt to tumorigenesis, there are still outstanding areas that remain poorly understood and even controversial. The canonical Wnt pathway functions to regulate the levels of the transcriptional co-activator β-catenin, which ultimately controls key developmental gene expressions. Given the central role of this mediator, inhibition of Wnt/β-catenin signaling has been investigated as a potential strategy for cancer control. In OS, several secreted protein families modulate the Wnt/β-catenin signaling, including secreted Frizzled-related proteins (sFRPs), Wnt inhibitory protein (WIF), Dickkopf proteins (DKK-1,2,3), sclerostin, and small molecules. This chapter focuses on our current understanding of Wnt/β-catenin signaling in OS, based on recent in vitro and in vivo data. Wnt activates noncanonical signaling pathways as well that are independent of β-catenin which will be discussed. In addition, stem cells and their association with Wnt/β-catenin are important factors to consider. Ultimately, the multiple canonical and noncanonical Wnt/β-catenin agonists and antagonists need to be further explored for potential targeted therapies. PMID:24924167
Cell signaling pathways elicited by asbestos.
Mossman, B T; Faux, S; Janssen, Y; Jimenez, L A; Timblin, C; Zanella, C; Goldberg, J; Walsh, E; Barchowsky, A; Driscoll, K
In recent years, it has become apparent that minerals can trigger alterations in gene expression by initiating signaling events upstream of gene transactivation. These cascades may be initiated at the cell surface after interaction of minerals with the plasma membrane either through receptorlike mechanisms or integrins. Alternatively, signaling pathways may be stimulated by active oxygen species generated both during phagocytosis of minerals and by redox reactions on the mineral surface. At least two signaling cascades linked to activation of transcription factors, i.e., DNA-binding proteins involved in modulating gene expression and DNA replication, are stimulated after exposure of lung cells to asbestos fibers in vitro. These include nuclear factor kappa B (NF kappa B) and the mitogen-activated protein kinase (MAPK) cascade important in regulation of the transcription factor, activator protein-1 (AP-1). Both NF kappa B and AP-1 bind to specific DNA sequences within the regulatory or promoter regions of genes that are critical to cell proliferation and inflammation. Unraveling the cell signaling cascades initiated by mineral dusts and pharmacologic inhibition of these events may be important for the control and treatment of mineral-associated occupational diseases. Images Figure 2. B Figure 3. A Figure 3. B PMID:9400710
Stacking nonenzymatic circuits for high signal gain
Chen, Xi; Briggs, Neima; McLain, Jeremy R.; Ellington, Andrew D.
Signal amplification schemes that do not rely on protein enzymes show great potential in areas as abstruse as DNA computation and as applied as point-of-care molecular diagnostics. Toehold-mediated strand displacement, a programmable form of dynamic DNA hybridization, can be used to design powerful amplification cascades that can achieve polynomial or exponential amplification of input signals. However, experimental implementation of such amplification cascades has been severely hindered by circuit leakage due to catalyst-independent side reactions. In this study, we systematically analyzed the origins, characteristics, and outcomes of circuit leakage in amplification cascades and devised unique methods to obtain high-quality DNA circuits that exhibit minimal leakage. We successfully implemented a two-layer cascade that yielded 7,000-fold signal amplification and a two-stage, four-layer cascade that yielded upward of 600,000-fold signal amplification. Implementation of these unique methods and design principles should greatly empower molecular programming in general and DNA-based molecular diagnostics in particular. PMID:23509255
Stochastic models of intracellular calcium signals
NASA Astrophysics Data System (ADS)
Rüdiger, Sten
Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels-one of the most important cellular signaling mechanisms-feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction-diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker-Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed.
Blaugher, R.D.
A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.
Blaugher, Richard D.
A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.
NASA Astrophysics Data System (ADS)
Gómez, Ana M.
Synthetic protocols based on carbohydrates require the differentiation of their abundant hydroxyl groups, by and large, in order to expose just one single hydroxyl group to the selected reagent. This differentiation is usually carried out with the assistance of protecting groups that block the rest of the hydroxyl groups while being compatible with the given reaction conditions. By corollary, the knowledge and apt choice of the appropriate protecting groups is a key factor in successful synthetic endeavors. In this chapter, an overview of the most commonly employed protecting groups in carbohydrate chemistry is given. Alkyl ethers, being robust protecting groups, have a long history in synthetic carbohydrate chemistry and in related structural studies of polysaccharides. Acetals and ketals, which are of fundamental importance in carbohydrate chemistry, are then discussed. Acyl and silyl protecting groups, which also play an important role in modern monosaccharide transformations, are also presented. Finally, recent blocking strategies are described, including orthogonal strategies, by which the protecting groups are harmoniously combined in modern carbohydrate chemistry.
Formaldehyde reactions in dark clouds
NASA Technical Reports Server (NTRS)
Sen, A. D.; Anicich, V. G.; Federman, S. R.
The low-pressure reactions of formaldehyde (H2CO) with D(+), D2(+), D3(+), and He(+) are studied by the ion-cyclotron resonance technique. These reactions are potential loss processes for formaldehyde in cores of dark interstellar clouds. The deuterated reactants represent direct analogs for protons. Rate coefficients and branching ratios of product channels have been measured. Charge transfer is observed to be the dominant reaction of H2CO with D(+), D2(+), and He(+) ions. Only the D3(+) reaction exhibits a proton-transfer channel. All reactions proceed at rate coefficients near the collision limit. Proton-deuteron exchange reactions are found to be inefficient processes in the formaldehyde system.
Characterising Complex Enzyme Reaction Data.
Dönertaş, Handan Melike; Martínez Cuesta, Sergio; Rahman, Syed Asad; Thornton, Janet M
The relationship between enzyme-catalysed reactions and the Enzyme Commission (EC) number, the widely accepted classification scheme used to characterise enzyme activity, is complex and with the rapid increase in our knowledge of the reactions catalysed by enzymes needs revisiting. We present a manual and computational analysis to investigate this complexity and found that almost one-third of all known EC numbers are linked to more than one reaction in the secondary reaction databases (e.g., KEGG). Although this complexity is often resolved by defining generic, alternative and partial reactions, we have also found individual EC numbers with more than one reaction catalysing different types of bond changes. This analysis adds a new dimension to our understanding of enzyme function and might be useful for the accurate annotation of the function of enzymes and to study the changes in enzyme function during evolution. PMID:26840640
Characterising Complex Enzyme Reaction Data
Rahman, Syed Asad; Thornton, Janet M.
The relationship between enzyme-catalysed reactions and the Enzyme Commission (EC) number, the widely accepted classification scheme used to characterise enzyme activity, is complex and with the rapid increase in our knowledge of the reactions catalysed by enzymes needs revisiting. We present a manual and computational analysis to investigate this complexity and found that almost one-third of all known EC numbers are linked to more than one reaction in the secondary reaction databases (e.g., KEGG). Although this complexity is often resolved by defining generic, alternative and partial reactions, we have also found individual EC numbers with more than one reaction catalysing different types of bond changes. This analysis adds a new dimension to our understanding of enzyme function and might be useful for the accurate annotation of the function of enzymes and to study the changes in enzyme function during evolution. PMID:26840640
Electronic signal generators: A compilation
NASA Technical Reports Server (NTRS)
Electronic signal generator data based on solid state concepts were simplified or refined to meet requirements, such as reliability, simplicity, fail-safe characteristics, and the capability of withstanding environmental extremes. Pulse generators, high voltage pulse generators, oscillators, analog signal generators, square wave signal generators, and special function signal generators are described.
An integrated signal transduction network of macrophage migration inhibitory factor.
Subbannayya, Tejaswini; Variar, Prathyaksha; Advani, Jayshree; Nair, Bipin; Shankar, Subramanian; Gowda, Harsha; Saussez, Sven; Chatterjee, Aditi; Prasad, T S Keshava
Macrophage migration inhibitory factor (MIF) is a glycosylated multi-functional protein that acts as an enzyme as well as a cytokine. MIF mediates its actions through a cell surface class II major histocompatibility chaperone, CD74 and co-receptors such as CD44, CXCR2, CXCR4 or CXCR7. MIF has been implicated in the pathogenesis of several acute and chronic inflammatory diseases. Although MIF is a molecule of biomedical importance, a public resource of MIF signaling pathway is currently lacking. In view of this, we carried out detailed data mining and documentation of the signaling events pertaining to MIF from published literature and developed an integrated reaction map of MIF signaling. This resulted in the cataloguing of 68 molecules belonging to MIF signaling pathway, which includes 24 protein-protein interactions, 44 post-translational modifications, 11 protein translocation events and 8 activation/inhibition events. In addition, 65 gene regulation events at the mRNA levels induced by MIF signaling have also been catalogued. This signaling pathway has been integrated into NetPath ( http://www.netpath.org ), a freely available human signaling pathway resource developed previously by our group. The MIF pathway data is freely available online in various community standard data exchange formats. We expect that data on signaling events and a detailed signaling map of MIF will provide the scientific community with an improved platform to facilitate further molecular as well as biomedical investigations on MIF. PMID:27139435
A model study of sequential enzyme reactions and electrostatic channeling
NASA Astrophysics Data System (ADS)
Eun, Changsun; Kekenes-Huskey, Peter M.; Metzger, Vincent T.; McCammon, J. Andrew
We study models of two sequential enzyme-catalyzed reactions as a basic functional building block for coupled biochemical networks. We investigate the influence of enzyme distributions and long-range molecular interactions on reaction kinetics, which have been exploited in biological systems to maximize metabolic efficiency and signaling effects. Specifically, we examine how the maximal rate of product generation in a series of sequential reactions is dependent on the enzyme distribution and the electrostatic composition of its participant enzymes and substrates. We find that close proximity between enzymes does not guarantee optimal reaction rates, as the benefit of decreasing enzyme separation is countered by the volume excluded by adjacent enzymes. We further quantify the extent to which the electrostatic potential increases the efficiency of transferring substrate between enzymes, which supports the existence of electrostatic channeling in nature. Here, a major finding is that the role of attractive electrostatic interactions in confining intermediate substrates in the vicinity of the enzymes can contribute more to net reactive throughput than the directional properties of the electrostatic fields. These findings shed light on the interplay of long-range interactions and enzyme distributions in coupled enzyme-catalyzed reactions, and their influence on signaling in biological systems.
Speeding chemical reactions by focusing
NASA Astrophysics Data System (ADS)
Lacasta, A. M.; Ramírez-Piscina, L.; Sancho, J. M.; Lindenberg, K.
We present numerical results for a chemical reaction of colloidal particles which are transported by a laminar fluid and are focused by periodic obstacles in such a way that the two components are well mixed and consequently the chemical reaction is speeded up. The roles of the various system parameters (diffusion coefficients, reaction rate, and obstacles sizes) are studied. We show that focusing speeds up the reaction from the diffusion limited rate ˜t-1/2 to very close to the perfect mixing rate, ˜t-1.
Anaphylactoid reactions to radiocontrast media.
Cochran, Sachiko T
Adverse reactions to contrast material are a concern because iodinated contrast materials are commonly used drugs. The risk for adverse reaction is 4% to 12% with ionic contrast materials and 1% to 3% with nonionic contrast materials. The risk for severe adverse reaction is 0.16% with ionic contrast materials and 0.03% with nonionic contrast materials. The death rate, one to three per 100,000 contrast administrations, is similar for both ionic and nonionic agents. More than 90% of adverse reactions with nonionic contrast materials are anaphylactoid. The types of severe reactions seen with nonionic contrast administration were initially predominantly anaphylactoid. With the advent of helical CT angiography, the reactions are now predominantly attributable to cardiopulmonary decompensation. With the widespread use of nonionic contrast materials, adverse reactions are now seen less frequently. Skills involved in evaluating and treating adverse reactions are not as frequently used. Periodic reviews and updates of specific treatment plans for various reactions with the physicians and staff who use contrast material are very important to ensure optimal preparedness. The key to successful treatment is preparation and early intervention. PMID:15659260
Dearomatization Reactions Using Phthaloyl Peroxide.
Eliasen, Anders M; Christy, Mitchell; Claussen, Karin R; Besandre, Ronald; Thedford, Randal P; Siegel, Dionicio
A new oxidative dearomatization reaction has been developed using phthaloyl peroxide to chemoselectively install two oxygen-carbon bonds into aromatic precursors. The oxidation reaction proceeds only once; addition of superstoichiometric equivalents of phthaloyl peroxide does not react further with the newly generated 1,3-cyclohexadiene. The reaction has been challenged by the addition of different functional groups and shown to maintain chemoselectivity. Due to the broad reactivity with 1,2-methylenedioxybenzene derivatives, linear free energy correlations were determined and support a mechanism proceeding through diradicals analogous to arene-hydroxylation reactions using phthaloyl peroxide. PMID:26333308
The reaction of an iridium PNP complex with parahydrogen facilitates polarisation transfer without chemical change† †Electronic supplementary information (ESI) available: Sample preparation, signal enhancements and raw data. CCDC 1026865. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt03088e Click here for additional data file. Click here for additional data file.
Holmes, Arthur J.; Rayner, Peter J.; Cowley, Michael J.; Green, Gary G. R.; Whitwood, Adrian C.
The short lived pincer complex [(C5H3N(CH2P(tBu)2)2)Ir(H)2(py)]BF4 is shown to be active for signal amplification by reversible exchange. This catalyst formulation enables the efficient transfer of polarization from parahydrogen to be placed into just a single molecule of the hyperpolarisation target, pyridine. When the catalysts 1H nuclei are replaced by 2H, increased levels of substrate hyperpolarization result and when the reverse situation is examined the catalyst itself is clearly visible through hyperpolarised signals. The ligand exchange pathways of [(C5H3N(CH2P(tBu)2)2)Ir(H)2(py)]BF4 that are associated with this process are shown to involve the formation of 16-electron [(C5H3N(CH2P(tBu)2)2)Ir(H)2]BF4 and the 18-electron H2 addition product [(C5H3N(CH2P(tBu)2)2)Ir(H)2(H2)]BF4. PMID:25410259
(Reaction mechanism studies of heavy ion induced nuclear reactions)
Mignerey, A.C.
This report discusses the following research projects; decay of excited nuclei formed in La-induced reactions at E/A = 45 MeV; mass and charge distributions in Cl-induced heavy ion reactions; and mass and charge distributions in {sup 56}Fe + {sup 165}Ho at E/A = 12 MeV.
Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions
ERIC Educational Resources Information Center
Schultz, Emeric
A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…
Analog and digital signal processing
NASA Astrophysics Data System (ADS)
Baher, H.
The techniques of signal processing in both the analog and digital domains are addressed in a fashion suitable for undergraduate courses in modern electrical engineering. The topics considered include: spectral analysis of continuous and discrete signals, analysis of continuous and discrete systems and networks using transform methods, design of analog and digital filters, digitization of analog signals, power spectrum estimation of stochastic signals, FFT algorithms, finite word-length effects in digital signal processes, linear estimation, and adaptive filtering.
Microglia Ontology and Signaling
ElAli, Ayman; Rivest, Serge
Microglia constitute the powerhouse of the innate immune system in the brain. It is now widely accepted that they are monocytic-derived cells that infiltrate the developing brain at the early embryonic stages, and acquire a resting phenotype characterized by the presence of dense branching processes, called ramifications. Microglia use these dynamic ramifications as sentinels to sense and detect any occurring alteration in brain homeostasis. Once a danger signal is detected, such as molecular factors associated to brain damage or infection, they get activated by acquiring a less ramified phenotype, and mount adequate responses that range from phagocyting cell debris to secreting inflammatory and trophic factors. Here, we review the origin of microglia and we summarize the main molecular signals involved in controlling their function under physiological conditions. In addition, their implication in the pathogenesis of multiple sclerosis and stress is discussed. PMID:27446922
General stress response signaling
Huo, Yi-Xin; Rosenthal, Adam Z.; Gralla, Jay D.
E. coli responds to stress by a combination of specific and general transcription signaling pathways. The general pathways typically require the master stress regulator sigma38 (rpoS). Here we show that the signaling from multiple stresses that relax DNA is processed by a non-conserved 8 amino acid tail of the sigma 38 C-terminal domain (CTD). By contrast, responses to stresses that accumulate potassium glutamate do not rely on this short tail, but still require the overall CTD. In vitro transcription and footprinting studies suggest that multiple stresses can target a poised RNA polymerase and activate it by unwrapping DNA from a nucleosome-like state, allowing the RNA polymerase to escape into productive mode. This transition can be accomplished by either the DNA relaxation or potassium glutamate accumulation that characterizes many stresses. PMID:18761624
NASA Astrophysics Data System (ADS)
Meyer, G.
The theory, realization techniques, and applications of digital filtering are surveyed, with an emphasis on the development of software, in a handbook for advanced students of electrical and electronic engineering and practicing development engineers. The foundations of the theory of discrete signals and systems are introduced. The design of one-dimensional linear systems is discussed, and the techniques are expanded to the treatment of two-dimensional discrete and multidimensional analog systems. Numerical systems, quantification and limitation, and the characteristics of particular signal-processing devices are considered in a section on design realization. An appendix contains definitions of the basic mathematical concepts, derivations and proofs, and tables of integration and differentiation formulas.
Baker, John; Archer, Daniel E.; Luke, Stanley John; Decman, Daniel J.; White, Gregory K.
A tailpulse signal generating/simulating apparatus, system, and method designed to produce electronic pulses which simulate tailpulses produced by a gamma radiation detector, including the pileup effect caused by the characteristic exponential decay of the detector pulses, and the random Poisson distribution pulse timing for radioactive materials. A digital signal process (DSP) is programmed and configured to produce digital values corresponding to pseudo-randomly selected pulse amplitudes and pseudo-randomly selected Poisson timing intervals of the tailpulses. Pulse amplitude values are exponentially decayed while outputting the digital value to a digital to analog converter (DAC). And pulse amplitudes of new pulses are added to decaying pulses to simulate the pileup effect for enhanced realism in the simulation.
Regulation of inflammasome signaling
Rathinam, Vijay A K; Vanaja, Sivapriya Kailasan; Fitzgerald, Katherine A
Innate immune responses have the ability to both combat infectious microbes and drive pathological inflammation. Inflammasome complexes are a central component of these processes through their regulation of interleukin 1β (IL-1β), IL-18 and pyroptosis. Inflammasomes recognize microbial products or endogenous molecules released from damaged or dying cells both through direct binding of ligands and indirect mechanisms. The potential of the IL-1 family of cytokines to cause tissue damage and chronic inflammation emphasizes the importance of regulating inflammasomes. Many regulatory mechanisms have been identified that act as checkpoints for attenuating inflammasome signaling at multiple steps. Here we discuss the various regulatory mechanisms that have evolved to keep inflammasome signaling in check to maintain immunological balance. PMID:22430786
RASSP signal processing architectures
NASA Astrophysics Data System (ADS)
Shirley, Fred; Bassett, Bob; Letellier, J. P.
The rapid prototyping of application specific signal processors (RASSP) program is an ARPA/tri-service effort to dramatically improve the process by which complex digital systems, particularly embedded signal processors, are specified, designed, documented, manufactured, and supported. The domain of embedded signal processing was chosen because it is important to a variety of military and commercial applications as well as for the challenge it presents in terms of complexity and performance demands. The principal effort is being performed by two major contractors, Lockheed Sanders (Nashua, NH) and Martin Marietta (Camden, NJ). For both, improvements in methodology are to be exercised and refined through the performance of individual 'Demonstration' efforts. The Lockheed Sanders' Demonstration effort is to develop an infrared search and track (IRST) processor. In addition, both contractors' results are being measured by a series of externally administered (by Lincoln Labs) six-month Benchmark programs that measure process improvement as a function of time. The first two Benchmark programs are designing and implementing a synthetic aperture radar (SAR) processor. Our demonstration team is using commercially available VME modules from Mercury Computer to assemble a multiprocessor system scalable from one to hundreds of Intel i860 microprocessors. Custom modules for the sensor interface and display driver are also being developed. This system implements either proprietary or Navy owned algorithms to perform the compute-intensive IRST function in real time in an avionics environment. Our Benchmark team is designing custom modules using commercially available processor ship sets, communication submodules, and reconfigurable logic devices. One of the modules contains multiple vector processors optimized for fast Fourier transform processing. Another module is a fiberoptic interface that accepts high-rate input data from the sensors and provides video-rate output data to a
NASA Astrophysics Data System (ADS)
Morgera, Salvatore D.; Krishna, Hari
Computationally efficient digital signal-processing algorithms over finite fields are developed analytically, and the relationship of these algorithms to algebraic error-correcting codes is explored. A multidisciplinary approach is employed, in an effort to make the results accessible to engineers, mathematicians, and computer scientists. Chapters are devoted to systems of bilinear forms, efficient finite-field algorithms, multidimensional methods, a new class of linear codes, and a new error-control scheme.
Plant peptide hormone signalling.
Motomitsu, Ayane; Sawa, Shinichiro; Ishida, Takashi
The ligand-receptor-based cell-to-cell communication system is one of the most important molecular bases for the establishment of complex multicellular organisms. Plants have evolved highly complex intercellular communication systems. Historical studies have identified several molecules, designated phytohormones, that function in these processes. Recent advances in molecular biological analyses have identified phytohormone receptors and signalling mediators, and have led to the discovery of numerous peptide-based signalling molecules. Subsequent analyses have revealed the involvement in and contribution of these peptides to multiple aspects of the plant life cycle, including development and environmental responses, similar to the functions of canonical phytohormones. On the basis of this knowledge, the view that these peptide hormones are pivotal regulators in plants is becoming increasingly accepted. Peptide hormones are transcribed from the genome and translated into peptides. However, these peptides generally undergo further post-translational modifications to enable them to exert their function. Peptide hormones are expressed in and secreted from specific cells or tissues. Apoplastic peptides are perceived by specialized receptors that are located at the surface of target cells. Peptide hormone-receptor complexes activate intracellular signalling through downstream molecules, including kinases and transcription factors, which then trigger cellular events. In this chapter we provide a comprehensive summary of the biological functions of peptide hormones, focusing on how they mature and the ways in which they modulate plant functions. PMID:26374891
Phytosulfokine peptide signalling.
Sauter, Margret
Phytosulfokine (PSK) belongs to the group of plant peptide growth factors. It is a disulfated pentapeptide encoded by precursor genes that are ubiquitously present in higher plants, suggestive of universal functions. Processing of the preproprotein involves sulfonylation by a tyrosylprotein sulfotransferase in the trans-golgi and proteolytic cleavage in the apoplast. The secreted peptide is perceived at the cell surface by a membrane-bound receptor kinase of the leucine-rich repeat family. The PSK receptor PSKR1 from Arabidopsis thaliana is an active kinase and has guanylate cyclase activity resulting in dual-signal outputs. Receptor activity is regulated by calmodulin. While PSK may be an autocrine growth factor, it also acts non-cell autonomously by promoting growth of cells that are receptor-deficient. In planta, PSK has multiple functions. It promotes cell growth, acts in the quiescent centre cells of the root apical meristem, contributes to funicular pollen tube guidance, and differentially alters immune responses depending on the pathogen. It has been suggested that PSK integrates growth and defence signals to balance the competing metabolic costs of these responses. This review summarizes our current understanding of PSK synthesis, signalling, and activity. PMID:25754406
Photosynthetic reaction center of green sulfur bacteria studied by EPR
Nitschke, W.; Rutherford, A.W. ); Fieler, U. )
Membrane preparations of two species of the green sulfur bacteria Chlorobium have been studied be EPR. Three signals were detected which were attributed to iron-sulfur centers acting as electron acceptors in the photosynthetic reaction center. (1) A signal from a center designated F{sub B}, was photoinduced at 4K. (2) A similar signal, F{sub A}, was photoinduced in addition to the F{sub B} signal upon a short period of illumination at 200 K. (3) Further illumination at 200 K resulted in the appearance of a broad feature at g=1.78. This is attributed to the g{sub x} component of an iron-sulfur center designated F{sub X}. The designations of these signals as F{sub B}, F{sub A}, and F{sub X} are based on their spectroscopic similarities to signals in photosystem I (PS I). The orientation dependence of these EPR signals in ordered Chlorobium membrane multilayers is remarkably similar to that of their PS I homologues. A magnetic interaction between the reduced forms of F{sub B} and F{sub A} occurs, which is also very similar to that seen in PS I. The triplet state of P{sub 840}, the primary electron donor, could be photoinduced at 4 K in samples which had been preincubated with sodium dithionite and methyl viologen and then preilluminated at 200 K. The preillumination reduces the iron-sulfur centers while the preincubation is thought to result in the inactivation of an earlier electron acceptor. Orientation studies of the triplet signal in ordered multilayers indicate that the bacteriochlorophylls which act as the primary electron donor in Chlorobium are arranged with a structural geometry almost identical with that of the special pair in purple bacteria. The Chlorobium reaction center appears to be similar in some respects to both PS I and to the purple bacterial reaction center. This is discussed with regard to the evolution of the different types of reaction centers from a common ancestor.
Entropy Effects in Chelation Reactions.
ERIC Educational Resources Information Center
Chung, Chung-Sun
The entropy change for a reaction in aqueous solution can be evaluated as a combination of entropy factors. Valuable insight or understanding can be obtained from a detailed examination of these factors. Several entropy effects of inorganic chemical reactions are discussed as examples. (Author/JN)
Free Radical Reactions in Food.
ERIC Educational Resources Information Center
Taub, Irwin A.
Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…
The Variance Reaction Time Model
ERIC Educational Resources Information Center
Sikstrom, Sverker
The variance reaction time model (VRTM) is proposed to account for various recognition data on reaction time, the mirror effect, receiver-operating-characteristic (ROC) curves, etc. The model is based on simple and plausible assumptions within a neural network: VRTM is a two layer neural network where one layer represents items and one layer…
Chemistry of heavy ion reactions
Hoffman, D.C.
The use of heavy ions to induce nuclear reactions was reported as early as 1950. Since that time it has been one of the most active areas of nuclear research. Intense beams of ions as heavy as uranium with energies high enough to overcome the Coulomb barriers of even the heaviest elements are available. The wide variety of possible reactions gives rise to a multitude of products which have been studied by many ingenious chemical and physical techniques. Chemical techniques have been of special value for the separation and unequivocal identification of low yield species from the plethora of other nuclides present. Heavy ion reactions have been essential for the production of the trans-Md elements and a host of new isotopes. The systematics of compound nucleus reactions, transfer reactions, and deeply inelastic reactions have been elucidated using chemical techniques. A review of the variety of chemical procedures and techniques which have been developed for the study of heavy ion reactions and their products is given. Determination of the chemical properties of the trans-Md elements, which are very short-lived and can only be produced an ''atom-at-a-time'' via heavy ion reactions, is discussed. 53 refs., 19 figs.
Adverse Reactions to Hallucinogenic Drugs.
ERIC Educational Resources Information Center
Meyer, Roger E. , Ed.
This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…
Enantioselective oxidative boron Heck reactions.
Lee, A-L
This review highlights the use of the oxidative boron Heck reaction in enantioselective Heck-type couplings. The enantioselective oxidative boron Heck reaction overcomes several limitations of the traditional Pd(0)-catalysed Heck coupling and has subsequently allowed for intermolecular couplings of challenging systems such as cyclic enones, acyclic alkenes, and even site selectively on remote alkenes. PMID:26529247
"Greening up" the Suzuki Reaction
ERIC Educational Resources Information Center
Aktoudianakis, Evangelos; Chan, Elton; Edward, Amanda R.; Jarosz, Isabel; Lee, Vicki; Mui, Leo; Thatipamala, Sonya S.; Dicks, Andrew P.
This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous…
Isosinglet approximation for nonelastic reactions
NASA Technical Reports Server (NTRS)
Wilson, J. W.
Group theoretic relations are derived between different combinations of projectile and secondary particles which appear to have a broad range of application in spacecraft shielding or radiation damage studies. These relations are used to reduce the experimental effort required to obtain nuclear reaction data for transport calculations. Implications for theoretical modeling are also noted, especially for heavy-heavy reactions.
Statistical Factors in Complexation Reactions.
ERIC Educational Resources Information Center
Chung, Chung-Sun
Four cases which illustrate statistical factors in complexation reactions (where two of the reactants are monodentate ligands) are presented. Included are tables showing statistical factors for the reactions of: (1) square-planar complexes; (2) tetrahedral complexes; and (3) octahedral complexes. (JN)
Integrin endosomal signalling suppresses anoikis.
Alanko, Jonna; Mai, Anja; Jacquemet, Guillaume; Schauer, Kristine; Kaukonen, Riina; Saari, Markku; Goud, Bruno; Ivaska, Johanna
Integrin-containing focal adhesions transmit extracellular signals across the plasma membrane to modulate cell adhesion, signalling and survival. Although integrins are known to undergo continuous endo/exocytic traffic, the potential impact of endocytic traffic on integrin-induced signals is unknown. Here, we demonstrate that integrin signalling is not restricted to cell-ECM adhesions and identify an endosomal signalling platform that supports integrin signalling away from the plasma membrane. We show that active focal adhesion kinase (FAK), an established marker of integrin-ECM downstream signalling, localizes with active integrins on endosomes. Integrin endocytosis positively regulates adhesion-induced FAK activation, which is early endosome antigen-1 and small GTPase Rab21 dependent. FAK binds directly to purified endosomes and becomes activated on them, suggesting a role for endocytosis in enhancing distinct integrin downstream signalling events. Finally, endosomal integrin signalling contributes to cancer-related processes such as anoikis resistance, anchorage independence and metastasis. PMID:26436690
Tuff reaction vessel experiment
Bazan, F.; Rego, J.H.
A laboratory leaching test has been performed as part of a project to evaluate the suitability of tuff rocks at Yucca Mountain, Nevada, as a site for a high-level nuclear waste repository. Glass samples of the kind that will be used to store nuclear waste were placed in water inside tuff vessels, and then the tuff vessels were placed in water inside Teflon containers. Glass-component leach rates and migration through the tuff were measured for samples of the ATM-8 actinide glass, which is a PNL 76-68 based glass with low levels of {sup 99}Tc, {sup 237}Np, {sup 238}U, and {sup 239}Pu to simulate wastes. Disc samples of this glass were leached at 90{sup 0}C to 30, 90, and 1983 days inside tuff vessels using a natural groundwater (J-13 well-water) as the leachant. Some samples were held by 304L stainless steel supports to evaluate the effect of this metal on the release rate of glass constituents. At the end of each leaching interval, the J-13 water present inside and outside the rock vessel was analyzed for glass components in solution. On the basis of these analyses, B, Mo, and Tc, appear to migrate through the rock at rates that depend on the porosity of each vessel and the time of reaction. U, Np, and Pu were found only in the inner leachate. Na, Si, and Sr are present in the rock as well as in the J-13 water, and the addition of these elements from the glass could not be determined. Normalized elemental mass loss values for B, Mo, and Tc were calculated using the combined concentrations of the inner and outer leachates and assuming a negligible retention on the rock. The maximum normalized release was 2.3 g/m{sup 2} for Tc. B, Mo, Tc, and Np were released linearly with respect to each other, with B and Mo released at about 85% of the Tc rate, and Np at 5-10% of the Tc rate. Plutonium was found at low levels in the inner leachate but was strongly sorbed on the steel and Teflon supports. Neptunium was sorbed to a lesser extent.
Oxysterols and mechanisms of survival signaling.
Vurusaner, Beyza; Leonarduzzi, Gabriella; Gamba, Paola; Poli, Giuseppe; Basaga, Huveyda
Oxysterols, a family of oxidation products of cholesterol, are increasingly drawing attention of scientists to their multifaceted biochemical properties, several of them of clear relevance to human pathophysiology. Taken up by cells through both vesicular and non-vesicular ways or often generated intracellularly, oxysterols contribute to modulate not only the inflammatory and immunological response but also cell viability, metabolism and function by modulating several signaling pathways. Moreover, they have been recognized as elective ligands for the most important nuclear receptors. The outcome of such a complex network of intracellular reactions promoted by these cholesterol oxidation products appears to be largely dependent not only on the type of cells, the dynamic conditions of the cellular and tissue environment but also on the concentration of the oxysterols. Here focus has been given to the cascade of molecular events exerted by relatively low concentrations of certain oxysterols that elicit survival and functional signals in the cells, with the aim to contribute to further expand the knowledge about the biological and physiological potential of the biochemical reactions triggered and modulated by oxysterols. PMID:27017897
Enzymatic reactions in confined environments
NASA Astrophysics Data System (ADS)
Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter
Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.
[Anaphylactic reaction following hair bleaching].
Babilas, P; Landthaler, M; Szeimies, R-M
Ammonium persulphate is a potent bleach and oxidizing agent that is commonly present in hair bleaches. Because bleaching is so commonly performed, hairdressers often develop allergic contact dermatitis to ammonium persulphate. In addition to this delayed reaction, asthma and rhinitis may develop as immediate reactions in those exposed to the fumes. Severe anaphylactic reactions are rare. We report a 24-year-old woman who acquired dermatitis following contact with bleaching substances while working as a hairdresser. After changing her profession, the dermatitis disappeared. Following the private use of a hairdressing bleach containing ammonium persulphate, she suffered a severe anaphylactic reaction with unconsciousness. The patient also developed an anaphylactic reaction three hours following patch testing with the hairdresser battery. The rub test with ammonium persulphate (2.5%) in a 1:100 solution was positive. PMID:15688222
[Skin reactions to tattoo ink].
Piérard-Franchimont, C; Hermanns, J-F; Piérard, G E
Ritual and artistic tattoos rely on the use of numerous pigments which are not all entirely inert once placed in the dermis. The compositions of some tattoo inks are identified. However, new but less well identified compounds appear on the market. Allergic reactions can be present under different aspects. They may correspond to allergic contact dermatitis or to photodermatitis. Other reactions include allergic hypersensitivity reactions as well as lichenoid, granulomatous or pseudolymphoma reactions. Pulsed light and laser are typically used for regular tattoo removal. These procedures are not indicated in inflamed tattoos. Indeed, the pigment dispersed during photolysis may perpetuate the reaction. Pseudotattoos due to the stratum corneum staining are frequently responsible for photoeczema. PMID:21942077
Fundamental reaction pathways during coprocessing
Stock, L.M.; Gatsis, J.G.
The objective of this research was to investigate the fundamental reaction pathways in coal petroleum residuum coprocessing. Once the reaction pathways are defined, further efforts can be directed at improving those aspects of the chemistry of coprocessing that are responsible for the desired results such as high oil yields, low dihydrogen consumption, and mild reaction conditions. We decided to carry out this investigation by looking at four basic aspects of coprocessing: (1) the effect of fossil fuel materials on promoting reactions essential to coprocessing such as hydrogen atom transfer, carbon-carbon bond scission, and hydrodemethylation; (2) the effect of varied mild conditions on the coprocessing reactions; (3) determination of dihydrogen uptake and utilization under severe conditions as a function of the coal or petroleum residuum employed; and (4) the effect of varied dihydrogen pressure, temperature, and residence time on the uptake and utilization of dihydrogen and on the distribution of the coprocessed products. Accomplishments are described.
Enzymatic reactions in confined environments.
Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter
Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems. PMID:27146955
Allergic reactions, "spillover' reactions, and T-cell subsets.
Bruynzeel, D P; Nieboer, C; Boorsma, D M; Scheper, R J; van Ketel, W G
A strong positive, allergic patch-test reaction was elicited in 15 patients with an established allergy for a particular allergen. Patches with a marginally irritating concentration of sodium lauryl sulfate (SLS) were applied at fixed distances. The SLS patch situated adjacent to the allergic reaction was significantly enhanced in 12 of 15 patients (P less than 0.01) compared to more distant SLS reactions ("spillover'). Only quantitative differences were observed in the histologic pictures of the different types of reaction. The infiltrate consisted of lymphocytes and histiocytes, mainly located perivascular in the upper dermis. T-cell subsets were assessed with monoclonal antibodies using an immunoperoxidase technique. The distribution of the different T cells was the same for both reaction types. T cells located outside the perivascular infiltrates (e.g., in the epidermal vesicles) were OKT-8-positive (cytotoxic/suppressor T lymphocytes). Immunofluorescence examination did not show different patterns for the allergic or "enhanced toxic' reactions with regard to the presence of immunoglobulins and complement. The "spillover' phenomenon may cause false-positive patch-test reactions. PMID:6223603
Antitumor immune reaction elicited by photodynamic therapy
NASA Astrophysics Data System (ADS)
Korbelik, Mladen
This work examines why photodynamic therapy (PDT) is capable of eliciting a strong immune reaction against treated solid tumors. It is postulated that this phenomenon originates from the basic charter of the insult inflicted by the photodynamic treatment, which is dominated by singlet oxygen-mediated oxidative stress. The early event associated with this initial impact, which is of major relevance for the development of immune response, is the generation of photo-oxidative lesions responsible for the activation of cellular signal transduction pathways and consequent induction of stress proteins. Importantly, these lesions, as well as other types of PDT mediated oxidative injury, have a strong pro-inflammatory character. It is suggested that the antitumor immune response is primed and propagated by the PDT-induced inflammatory process. Of critical importance for the immune recognition of treated tumor is the generation of large amounts of cancer cell debris that occurs rapidly following PDT treatment.
Structures and reaction mechanisms of GTP cyclohydrolases.
Gräwert, Tobias; Fischer, Markus; Bacher, Adelbert
GTP cyclohydrolases generate the first committed intermediates for the biosynthesis of certain vitamins/cofactors (folic acid, riboflavin, deazaflavin, and tetrahydrobiopterin), deazapurine antibiotics, some t-RNA bases (queuosine, archaeosine), and the phytotoxin, toxoflavin. They depend on divalent cations for hydrolytic opening of the imidazole ring of the substrate, guanosine triphosphate (GTP). Surprisingly, the ring opening reaction is not the rate-limiting step for GTP cyclohydrolases I and II whose mechanism have been studied in some detail. GTP cyclohydrolase I, Ib, and II are potential targets for novel anti-infectives. Genetic factors modulating the activity of human GTP cyclohydrolase are highly pleiotropic, since the signal transponders whose biosyntheses require their participation (nitric oxide, catecholamines) impact a very wide range of physiological phenomena. Recent studies suggest that human GTP cyclohydrolase may become an oncology target. PMID:23457054
Dynamic Vibrotactile Signals for Forward Collision Avoidance Warning Systems
Meng, Fanxing; Gray, Rob; Ho, Cristy; Ahtamad, Mujthaba
Objective: Four experiments were conducted in order to assess the effectiveness of dynamic vibrotactile collision-warning signals in potentially enhancing safe driving. Background: Auditory neuroscience research has demonstrated that auditory signals that move toward a person are more salient than those that move away. If this looming effect were found to extend to the tactile modality, then it could be utilized in the context of in-car warning signal design. Method: The effectiveness of various vibrotactile warning signals was assessed using a simulated car-following task. The vibrotactile warning signals consisted of dynamic toward-/away-from-torso cues (Experiment 1), dynamic versus static vibrotactile cues (Experiment 2), looming-intensity- and constant-intensity-toward-torso cues (Experiment 3), and static cues presented on the hands or on the waist, having either a low or high vibration intensity (Experiment 4). Results: Braking reaction times (BRTs) were significantly faster for toward-torso as compared to away-from-torso cues (Experiments 1 and 2) and static cues (Experiment 2). This difference could not have been attributed to differential responses to signals delivered to different body parts (i.e., the waist vs. hands; Experiment 4). Embedding a looming-intensity signal into the toward-torso signal did not result in any additional BRT benefits (Experiment 3). Conclusion: Dynamic vibrotactile cues that feel as though they are approaching the torso can be used to communicate information concerning external events, resulting in a significantly faster reaction time to potential collisions. Application: Dynamic vibrotactile warning signals that move toward the body offer great potential for the design of future in-car collision-warning system. PMID:25850161
Interplant signalling through hyphal networks.
Johnson, David; Gilbert, Lucy
Mycorrhizal fungi can form common mycelial networks (CMNs) that interconnect plants. Here, we provide an insight into recent findings demonstrating that CMNs can be conduits for interplant signalling, influencing defence against insect herbivores and foliar necrotrophic fungi. A likely mechanism is direct transfer of signalling molecules within hyphae. However, electrical signals, which can be induced by wounding, may also enable signalling over relatively long distances, because the biophysical constraints imposed by liquid transport in hyphae and interaction with soil are relieved. We do not yet understand the ecological, evolutionary and agronomic implications of interplant signalling via CMNs. Identifying the mechanism of interplant signalling will help to address these gaps. PMID:25421970
Digital processing of bandpass signals
NASA Astrophysics Data System (ADS)
Jackson, M. C.; Matthewson, P.
Modern radar and radio systems rely on digital signal processing to enhance the quality of received signals. Prior to such processing, these signals must be converted to digital form. The historical development of signal digitization is briefly discussed in this paper and leads to a description of some current work on digital mixing. A method of directly sampling a band-limited intermediate frequency (i.f.) signal is presented, using a pair of digital mixer channels to produce complex low-pass samples of the signal envelope. The method is found to produce well matched channel outputs. Finally, the applicability of the method to radar is discussed.
GEANT4 simulations of Cherenkov reaction history diagnostics.
Rubery, M S; Horsfield, C J; Herrmann, H W; Kim, Y; Mack, J M; Young, C S; Caldwell, S E; Evans, S C; Sedilleo, T J; McEvoy, A; Miller, E K; Stoeffl, W; Ali, Z; Toebbe, J
This paper compares the results from a GEANT4 simulation of the gas Cherenkov detector 1 (GCD1) with previous simulations and experimental data from the Omega laser facility. The GCD1 collects gammas emitted during a deuterium-tritium capsule implosion and converts them, through several processes, to Cherenkov light. Photon signals are recorded using subnanosecond photomultiplier tubes, producing burn reaction histories. The GEANT4 GCD1 simulation is first benchmarked against ACCEPT, an integrated tiger series code, with good agreement. The simulation is subsequently compared with data from the Omega laser facility, where experiments have been performed to measure the effects of Hohlraum materials on reaction history signals, in preparation for experiments at the National Ignition Facility. PMID:21033850
GEANT4 simulations of Cherenkov reaction history diagnostics
Rubery, M. S.; Horsfield, C. J.; Herrmann, H. W.; Kim, Y.; Mack, J. M.; Young, C. S.; Caldwell, S. E.; Evans, S. C.; Sedilleo, T. J.; McEvoy, A.; Miller, E. K.; Stoeffl, W.; Ali, Z.
This paper compares the results from a GEANT4 simulation of the gas Cherenkov detector 1 (GCD1) with previous simulations and experimental data from the Omega laser facility. The GCD1 collects gammas emitted during a deuterium-tritium capsule implosion and converts them, through several processes, to Cherenkov light. Photon signals are recorded using subnanosecond photomultiplier tubes, producing burn reaction histories. The GEANT4 GCD1 simulation is first benchmarked against ACCEPT, an integrated tiger series code, with good agreement. The simulation is subsequently compared with data from the Omega laser facility, where experiments have been performed to measure the effects of Hohlraum materials on reaction history signals, in preparation for experiments at the National Ignition Facility.
Liu, Zhi-Yan; Wu, Tao; Li, Qing; Wang, Min-Cong; Jing, Li; Ruan, Zhi-Ping; Yao, Yu; Nan, Ke-Jun; Guo, Hui
Abstract Non-small-cell lung cancer (NSCLC) is a lethal and aggressive malignancy. Currently, the identities of prognostic and predictive makers of NSCLC have not been fully established. Dysregulated Notch signaling has been implicated in many human malignancies, including NSCLC. However, the prognostic value of measuring Notch signaling and the utility of developing Notch-targeted therapies in NSCLC remain inconclusive. The present study investigated the association of individual Notch receptor and ligand levels with lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC) prognosis using the Kaplan-Meier plotte database. This online database encompasses 2437 lung cancer samples. Hazard ratios with 95% confidence intervals were calculated. The results showed that higher Notch1, Notch2, JAG1, and DLL1 mRNA expression predicted better overall survival (OS) in lung ADC, but showed no significance in SCC patients. Elevated Notch3, JAG2, and DLL3 mRNA expression was associated with poor OS of ADC patients, but not in SCC patients. There was no association between Notch4 and OS in either lung ADC or SCC patients. In conclusion, the set of Notch1, Notch2, JAG1, DLL1 and that of Notch3, JAG2, DLL3 played opposing prognostic roles in lung ADC patients. Neither set of Notch receptors and ligands was indicative of lung SCC prognosis. Notch signaling could serve as promising marker to predict outcomes in lung ADC patients. The distinct features of lung cancer subtypes and Notch components should be considered when developing future Notch-targeted therapies. PMID:27196489
Magnetic Resonance Current Density Imaging of Chemical Processes and Reactions
NASA Astrophysics Data System (ADS)
Beravs, Katarina; Demš Ar, Alojz; Demsar, Franci
Electric current density imaging was used to image conductivity changes that occur as a chemical process or reaction progresses. Feasibility was assessed in two models representing the dissolving of an ionic solid and the formation of an insoluble precipitate. In both models, temporal and spatial changes in ionic concentrations were obtained on current density images. As expected, the images showed significant signal enhancement along the ionization/dissociation sites.
System and process for pulsed multiple reaction monitoring
Belov, Mikhail E
A new pulsed multiple reaction monitoring process and system are disclosed that uses a pulsed ion injection mode for use in conjunction with triple-quadrupole instruments. The pulsed injection mode approach reduces background ion noise at the detector, increases amplitude of the ion signal, and includes a unity duty cycle that provides a significant sensitivity increase for reliable quantitation of proteins/peptides present at attomole levels in highly complex biological mixtures.
Herzel, H.; Reuter, R.
Irregularities in voiced speech are often observed as a consequence of vocal fold lesions, paralyses, and other pathological conditions. Many of these instabilities are related to the intrinsic nonlinearities in the vibrations of the vocal folds. In this paper, a specific nonlinear phenomenon is discussed: The appearance of two independent fundamental frequencies termed biphonation. Several narrow-band spectrograms are presented showing biphonation in signals from voice patients, a newborn cry, a singer, and excised larynx experiments. Finally, possible physiological mechanisms of instabilities of the voice source are discussed. {copyright} {ital 1996 American Institute of Physics.}
Neural Membrane Signaling Platforms
Wallace, Ron
Throughout much of the history of biology, the cell membrane was functionally defined as a semi-permeable barrier separating aqueous compartments, and an anchoring site for proteins. Little attention was devoted to its possible regulatory role in intracellular molecular processes and neuron electrical signaling. This article reviews the history of membrane studies and the current state of the art. Emphasis is placed on natural and artificial membrane studies of electric field effects on molecular organization, especially as these may relate to impulse propagation in neurons. Implications of these studies for new designs in artificial intelligence are briefly examined. PMID:20640161
Growth hormone signaling pathways.
Carter-Su, Christin; Schwartz, Jessica; Argetsinger, Lawrence S
Over 20years ago, our laboratory showed that growth hormone (GH) signals through the GH receptor-associated tyrosine kinase JAK2. We showed that GH binding to its membrane-bound receptor enhances binding of JAK2 to the GHR, activates JAK2, and stimulates tyrosyl phosphorylation of both JAK2 and GHR. The activated JAK2/GHR complex recruits a variety of signaling proteins, thereby initiating multiple signaling pathways and cellular responses. These proteins and pathways include: 1) Stat transcription factors implicated in the expression of multiple genes, including the gene encoding insulin-like growth factor 1; 2) Shc adapter proteins that lead to activation of the grb2-SOS-Ras-Raf-MEK-ERK1,2 pathway; 3) insulin receptor substrate proteins implicated in the phosphatidylinositol-3-kinase and Akt pathway; 4) signal regulatory protein α, a transmembrane scaffold protein that recruits proteins including the tyrosine phosphatase SHP2; and 5) SH2B1, a scaffold protein that can activate JAK2 and enhance GH regulation of the actin cytoskeleton. Our recent work has focused on the function of SH2B1. We have shown that SH2B1β is recruited to and phosphorylated by JAK2 in response to GH. SH2B1 localizes to the plasma membrane, cytoplasm and focal adhesions; it also cycles through the nucleus. SH2B1 regulates the actin cytoskeleton and promotes GH-dependent motility of RAW264.7 macrophages. Mutations in SH2B1 have been found in humans exhibiting severe early-onset childhood obesity and insulin resistance. These mutations impair SH2B1 enhancement of GH-induced macrophage motility. As SH2B1 is expressed ubiquitously and is also recruited to a variety of receptor tyrosine kinases, our results raise the possibility that effects of SH2B1 on the actin cytoskeleton in various cell types, including neurons, may play a role in regulating body weight. PMID:26421979
Sphingosine in apoptosis signaling.
Cuvillier, Olivier
The sphingolipid metabolites ceramide, sphingosine, and sphingosine 1-phosphate contribute to controlling cell proliferation and apoptosis. Ceramide and its catabolite sphingosine act as negative regulators of cell proliferation and promote apoptosis. Conversely, sphingosine 1-phosphate, formed by phosphorylation of sphingosine by a sphingosine kinase, has been involved in stimulating cell growth and inhibiting apoptosis. As the phosphorylation of sphingosine diminishes apoptosis, while dephosphorylation of sphingosine 1-phosphate potentiates it, the role of sphingosine as a messenger of apoptosis is of importance. Herein, the effects of sphingosine on diverse signaling pathways implicated in the apoptotic process are reviewed. PMID:12531549
Toward Direct Reaction-in-Flight Measurements
NASA Astrophysics Data System (ADS)
Wilhelmy, Jerry; Bredeweg, Todd; Fowler, Malcolm; Gooden, Matthew; Hayes, Anna; Rusev, Gencho; Caggiano, Joseph; Hatarik, Robert; Henry, Eugene; Tonchev, Anton; Yeaman, Charles; Bhike, Megha; Krishichayan, Krishi; Tornow, Werner
At the National Ignition Facility (NIF) neutrons having energies greater than the equilibrium 14.1 MeV value can be produced via Reaction-in-Flight (RIF) interactions between plasma atoms and upscattered D or T ions. The yield and spectrum of these RIF produced neutrons carry information on the plasma properties as well as information on the stopping power of ions under plasma conditions. At NIF the yield of these RIF neutrons is predicted to be 4-7 orders of magnitude below the peak 14 MeV neutron yield. The current generation of neutron time of flight (nTOF) instrumentation has so far been incapable of detecting these low-yield neutrons primarily due to high photon backgrounds. To date, information on RIF neutrons has been obtained in integral activation experiments using reactions with high energy thresholds such as 169Tm(n,3n)167Tm and 209Bi(n,4n) 206Bi. Initial experiments to selectively suppress photon backgrounds have been performed at TUNL using pulsed monoenergetic neutron beams of 14.9, 18.5, 24.2, and 28.5 MeV impinging on a Bibenzyl scintillator. By placing 5 cm of Pb before the scintillator we were able to selectively suppress the photons from the flash occurring at the production target and enhance the n/_signal by ~6 times.
Integrated Microreactors for Reaction Automation: New Approaches to Reaction Development
NASA Astrophysics Data System (ADS)
McMullen, Jonathan P.; Jensen, Klavs F.
Applications of microsystems (microreactors) in continuous-flow chemistry have expanded rapidly over the past two decades, with numerous reports of higher conversions and yields compared to conventional batch benchtop equipment. Synthesis applications are enhanced by chemical information gained from integrating microreactor components with sensors, actuators, and automated fluid handling. Moreover, miniaturized systems allow experiments on well-defined samples at conditions not easily accessed by conventional means, such as reactions at high pressure and temperatures. The wealth of synthesis information that could potentially be acquired through use of microreactors integrated with physical sensors and analytical chemistry techniques for online reaction monitoring has not yet been well explored. The increased efficiency resulting from use of continuous-flow microreactor platforms to automate reaction screening and optimization encourages a shift from current batchwise chemical reaction development to this new approach. We review advances in this new area and provide application examples of online monitoring and automation.
Thermally multiplexed polymerase chain reaction
Phaneuf, Christopher R.; Pak, Nikita; Saunders, D. Curtis; Holst, Gregory L.; Birjiniuk, Joav; Nagpal, Nikita; Culpepper, Stephen; Popler, Emily; Shane, Andi L.; Jerris, Robert; Forest, Craig R.
Amplification of multiple unique genetic targets using the polymerase chain reaction (PCR) is commonly required in molecular biology laboratories. Such reactions are typically performed either serially or by multiplex PCR. Serial reactions are time consuming, and multiplex PCR, while powerful and widely used, can be prone to amplification bias, PCR drift, and primer-primer interactions. We present a new thermocycling method, termed thermal multiplexing, in which a single heat source is uniformly distributed and selectively modulated for independent temperature control of an array of PCR reactions. Thermal multiplexing allows amplification of multiple targets simultaneously—each reaction segregated and performed at optimal conditions. We demonstrate the method using a microfluidic system consisting of an infrared laser thermocycler, a polymer microchip featuring 1 μl, oil-encapsulated reactions, and closed-loop pulse-width modulation control. Heat transfer modeling is used to characterize thermal performance limitations of the system. We validate the model and perform two reactions simultaneously with widely varying annealing temperatures (48 °C and 68 °C), demonstrating excellent amplification. In addition, to demonstrate microfluidic infrared PCR using clinical specimens, we successfully amplified and detected both influenza A and B from human nasopharyngeal swabs. Thermal multiplexing is scalable and applicable to challenges such as pathogen detection where patients presenting non-specific symptoms need to be efficiently screened across a viral or bacterial panel. PMID:26339317
Reactions and properties of clusters
NASA Astrophysics Data System (ADS)
Castleman, A. W., Jr.
The elucidation from a molecular point of view of the differences and similarities in the properties and reactivity of matter in the gaseous compared to the condensed state is a subject of considerable current interest. One of the promising approaches to this problem is to utilize mass spectrometry in conjunction with laser spectroscopy and fast-flow reaction devices to investigate the changing properties, structure and reactivity of clusters as a function of the degree of solvation under well-controlled conditions. In this regard, an investigation of molecular cluster ions has provided considerable new insight into the basic mechanisms of ion reactions within a cluster, and this paper reviews some of the recent advances in cluster production, the origin of magic numbers and relationship to cluster ion stabilities, and solvation effects on reactions. There have been some notable advances in the production of large cluster ions under thermal reaction conditions, enabling a systematic study of the influence of solvation on reactions to be carried out. These and other new studies of magic numbers have traced their origin to the thermochemical stability of cluster ions. There are several classes of reaction where solvation has a notable influence on reactivity. A particularly interesting example comes from recent studies of the reactions of the hydroxyl anion with CO2 and SO2, studied as a function of the degree of hydration of OH-. Both reactions are highly exothermic, yet the differences in reactivity are dramatic. In the case of SO2, the reaction occurs at near the collision rate. By contrast, CO2 reactivity plummets dramatically for clusters having more than four water molecules. The slow rate is in accord with observations in the liquid phase.
Nuclear Structure and Reaction Mechanism Studies with Multinucleon Reactions
Regan, P. H.; Jones, G. A.; Podolyak, Zs.; Abdullah, M.; Gelletly, W.; Langdown, S. D.; Wollel, G.; De Angelis, G.; Gadea, A.; Kroell, Th.; Marginean, N.; Martinez, T.; Napoli, D. R.; Rusu, C.; Tonev, D.; Zhang, Y. H.; Ur, C. A.; Axiotis, M.; Bazzacco, D.; Farnea, E.
This contribution reports on the results of an experiment to study the near-yrast states in selenium- and osmium-like nuclei, following their population in thick-target, multinucleon transfer reactions between an 82Se beam and a 192Os target. The experimental results for the level scheme for 84Se are presented together with investigations into the use of multi-dimensional gamma-ray energy gating to investigate angular momentum population in such heavy-ion binary reactions.
Signal quality of endovascular electroencephalography
NASA Astrophysics Data System (ADS)
He, Bryan D.; Ebrahimi, Mosalam; Palafox, Leon; Srinivasan, Lakshminarayan
Objective, Approach. A growing number of prototypes for diagnosing and treating neurological and psychiatric diseases are predicated on access to high-quality brain signals, which typically requires surgically opening the skull. Where endovascular navigation previously transformed the treatment of cerebral vascular malformations, we now show that it can provide access to brain signals with substantially higher signal quality than scalp recordings. Main results. While endovascular signals were known to be larger in amplitude than scalp signals, our analysis in rabbits borrows a standard technique from communication theory to show endovascular signals also have up to 100× better signal-to-noise ratio. Significance. With a viable minimally-invasive path to high-quality brain signals, patients with brain diseases could one day receive potent electroceuticals through the bloodstream, in the course of a brief outpatient procedure.
Recurrent Infections May Signal Immunodeficiencies
... Search AAAAI Breadcrumb navigation Home ▸ Conditions & Treatments ▸ Library ▸ Primary Immunodeficiency Disease Library ▸ Recurrent Infections May Signal Immunodeficiencies Share | Recurrent Infections May Signal Immunodeficiencies This article has been reviewed by Thanai Pongdee, MD, FAAAAI ...
Calcium Signaling in the Liver
Amaya, Maria Jimena; Nathanson, Michael H.
Intracellular free Ca2+ ([Ca2+]i) is a highly versatile second messenger that regulates a wide range of functions in every type of cell and tissue. To achieve this versatility, the Ca2+ signaling system operates in a variety of ways to regulate cellular processes that function over a wide dynamic range. This is particularly well exemplified for Ca2+ signals in the liver, which modulate diverse and specialized functions such as bile secretion, glucose metabolism, cell proliferation, and apoptosis. These Ca2+ signals are organized to control distinct cellular processes through tight spatial and temporal coordination of [Ca2+]i signals, both within and between cells. This article will review the machinery responsible for the formation of Ca2+ signals in the liver, the types of subcellular, cellular, and intercellular signals that occur, the physiological role of Ca2+ signaling in the liver, and the role of Ca2+ signaling in liver disease. PMID:23720295
Tilting mode in nuclear reactions
Dossing, T.; Randrup, J.
The relation between tilting relaxation and the reaction plane dynamics is discussed, providing an intuitive understanding of the expression for the cross section close to the beam direction, which has recently been derived. Second, the tilting relaxation time and the related wriggling relaxation time are discussed, based upon nucleon exchange transport (window friction). Finally, recent experimental information on the tilting mode relaxation is discussed, and the dynamics of the tilting mode is discussed qualitatively for the three different types of nuclear reactions considered, compound nucleus fission, quasifission, and damped nuclear reactions. 9 refs., 3 figs.
Renormalized reaction and relaxation rates
NASA Astrophysics Data System (ADS)
Gorbachev, Yuriy E.
Impact of the non-equilibrium on the reaction and relaxation rates (called as generalized relaxation rates - GRR), for the spatially inhomogeneous gas mixture is considered. Discarding the assumption that the 'chemical' part of the collisional integral is a small correction to non-reactive part, the expression for the zero-order GRR is derived. They are represented as a renormalization of the traditional reaction and relaxation rates, which means mixing of all corresponding processes. Thus all reactions and relaxation processes are entangled.
Leukemoid Reaction in Chikungunya Fever
Charaniya, Riyaz; Sahoo, Ratnakar; Tansir, Ghazal; Sasmal, Gargi
Chikungunya is a viral illness caused by an arbovirus which is transmitted by Aedes mosquito. Fever and polyarthralgia are hallmark of this viral illness. Viral infections are generally associated with leucopenia and bacterial infections with leukocytosis. Leukemoid Reaction (LR) is defined by reactive increase in leukocyte count of more than 50,000/cu mm with increase in mature leukocytes on peripheral blood. Leukocytosis is common in Chikungunya but leukemoid reaction has not been reported in medical literature. Our patient presented with high grade fever and symmetrical polyarthritis. Blood investigation showed Leukemoid reaction and after extensive work up a diagnosis of chikungunya was made. PMID:27437276
Catalytic Organometallic Reactions of Ammonia
Klinkenberg, Jessica L.
Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen-containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross-coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity. PMID:20857466
Hypersensitivity reaction associated with phenytoin
Indu, T. H.; Basutkar, Roopa Satyanarayan
Hypersensitivity reactions with antiepileptic drugs (AEDs) are generally associated with aromatic AEDs. We present a case of hypersensitivity reactions followed by administration of phenytoin with diazepam and ranitidine in a patient with generalized tonic-clonic seizures. Antigen-antibody reactions or decreased levels of epoxide hydrolase are well known with phenytoin. Increased level of serum phenytoin causing toxicities due to competitive inhibition with diazepam on co-administration was also reported in the literature. Prevention of the adverse effects with AEDs is a multi-stage process, which requires implementation of preventive measures through careful monitoring and prompts interventions. PMID:26692739
Magnetically suspended reaction wheel assembly
NASA Technical Reports Server (NTRS)
Stocking, G.
The magnetically suspended reaction wheel assembly (MSRWA) is the product of a development effort funded by the Air Force Materials Laboratory (AFML) at Wright Patterson AFB. The specific objective of the project was to establish the manufacturing processes for samarium cobalt magnets and demonstrate their use in a space application. The development was successful on both counts. The application portion of the program, which involves the magnetically suspended reaction wheel assembly, is emphasized. The requirements for the reaction wheel were based on the bias wheel requirements of the DSP satellite. The tasks included the design, fabrication, and test of the unit to the DSP program qualification requirements.
Hypersensitivity reaction associated with phenytoin.
Indu, T H; Basutkar, Roopa Satyanarayan
Hypersensitivity reactions with antiepileptic drugs (AEDs) are generally associated with aromatic AEDs. We present a case of hypersensitivity reactions followed by administration of phenytoin with diazepam and ranitidine in a patient with generalized tonic-clonic seizures. Antigen-antibody reactions or decreased levels of epoxide hydrolase are well known with phenytoin. Increased level of serum phenytoin causing toxicities due to competitive inhibition with diazepam on co-administration was also reported in the literature. Prevention of the adverse effects with AEDs is a multi-stage process, which requires implementation of preventive measures through careful monitoring and prompts interventions. PMID:26692739
Nuclear reactions at intermediate energies
NASA Astrophysics Data System (ADS)
Shyam, Radhey
In the domain of Nuclear reactions at intermediate energies, the QCD coupling constant αs is large enough (~ 0.3 - 0.5) to render the perturbative calculational techniques inapplicable. In this regime the quarks are confined into colorless hadrons and it is expected that effective field theories of hadron interactions via exchange of hadrons, provide useful tools to describe such reactions. In this contribution we discuss the application of one such theory, the effective Lagrangian model, in describing the hadronic reactions at intermediate energies whose measurements are the focus of a vast international experimental program.
Siloxy alkynes in annulation reactions.
Qian, Hui; Zhao, Wanxiang; Sun, Jianwei
Siloxy alkynes are a family of versatile species in organic synthesis. This account reviews the annulation reactions of siloxy alkynes for the synthesis of a variety of carbo- and heterocyclic products. With various dipolarophiles or dipolarophile-like reaction partners, siloxy alkynes are capable of forming small (three- to six-membered) rings. Recently, we have expanded the scope to the synthesis of medium- and large-ring lactones, enabled by the design of new amphoteric molecules as well as a new ring-expansion strategy. These annulation reactions provide not only practically useful syntheses of cyclic molecules, but also important understanding of the fundamental reactivity of siloxy alkynes. PMID:25171137
Chemical potential and reaction electronic flux in symmetry controlled reactions.
Vogt-Geisse, Stefan; Toro-Labbé, Alejandro
In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc. PMID:27237470
Signal processing in magnetoencephalography.
Vrba, J; Robinson, S E
The subject of this article is detection of brain magnetic fields, or magnetoencephalography (MEG). The brain fields are many orders of magnitude smaller than the environmental magnetic noise and their measurement represent a significant metrological challenge. The only detectors capable of resolving such small fields and at the same time handling the large dynamic range of the environmental noise are superconducting quantum interference devices (or SQUIDs). The SQUIDs are coupled to the brain magnetic fields using combinations of superconducting coils called flux transformers (primary sensors). The environmental noise is attenuated by a combination of shielding, primary sensor geometry, and synthetic methods. One of the most successful synthetic methods for noise elimination is synthetic higher-order gradiometers. How the gradiometers can be synthesized is shown and examples of their noise cancellation effectiveness are given. The MEG signals measured on the scalp surface must be interpreted and converted into information about the distribution of currents within the brain. This task is complicated by the fact that such inversion is nonunique. Additional mathematical simplifications, constraints, or assumptions must be employed to obtain useful source images. Methods for the interpretation of the MEG signals include the popular point current dipole, minimum norm methods, spatial filtering, beamformers, MUSIC, and Bayesian techniques. The use of synthetic aperture magnetometry (a class of beamformers) is illustrated in examples of interictal epileptic spiking and voluntary hand-motor activity. PMID:11812209
TGIF inhibits retinoid signaling.
Bartholin, Laurent; Powers, Shannon E; Melhuish, Tiffany A; Lasse, Samuel; Weinstein, Michael; Wotton, David
TGIF (TG-interacting factor) represses transforming growth factor beta (TGF-beta)-activated gene expression and can repress transcription via a specific retinoid response element. Mutations in human TGIF are associated with holoprosencephaly, a severe defect of craniofacial development with both genetic and environmental causes. Both TGF-beta and retinoic acid signaling are implicated in craniofacial development. Here, we analyze the role of TGIF in regulating retinoid responsive gene expression. We demonstrate that TGIF interacts with the ligand binding domain of the RXRalpha retinoid receptor and represses transcription from retinoid response elements. TGIF recruits the general corepressor, CtBP, to RXRalpha, and this recruitment is required for full repression by TGIF. Interaction between TGIF and RXRalpha is reduced by the addition of retinoic acid, consistent with a role for TGIF as an RXRalpha transcriptional corepressor. We created a Tgif null mutation in mice and tested the sensitivity of mutant mice to increased levels of retinoic acid. Tgif mutant embryos are more sensitive to retinoic acid-induced teratogenesis, and retinoid target genes are expressed at a higher level in tissues from Tgif null mice. These results demonstrate an important role for TGIF as a transcriptional corepressor, which regulates developmental signaling by retinoic acid, and raises the possibility that TGIF may repress other RXR-dependent transcriptional responses. PMID:16428452
Endocannabinoid Signaling in Autism.
Chakrabarti, Bhismadev; Persico, Antonio; Battista, Natalia; Maccarrone, Mauro
Autism spectrum disorder (ASD) is a complex behavioral condition with onset during early childhood and a lifelong course in the vast majority of cases. To date, no behavioral, genetic, brain imaging, or electrophysiological test can specifically validate a clinical diagnosis of ASD. However, these medical procedures are often implemented in order to screen for syndromic forms of the disorder (i.e., autism comorbid with known medical conditions). In the last 25 years a good deal of information has been accumulated on the main components of the "endocannabinoid (eCB) system", a rather complex ensemble of lipid signals ("endocannabinoids"), their target receptors, purported transporters, and metabolic enzymes. It has been clearly documented that eCB signaling plays a key role in many human health and disease conditions of the central nervous system, thus opening the avenue to the therapeutic exploitation of eCB-oriented drugs for the treatment of psychiatric, neurodegenerative, and neuroinflammatory disorders. Here we present a modern view of the eCB system, and alterations of its main components in human patients and animal models relevant to ASD. This review will thus provide a critical perspective necessary to explore the potential exploitation of distinct elements of eCB system as targets of innovative therapeutics against ASD. PMID:26216231
Universal signal conditioning amplifier
NASA Technical Reports Server (NTRS)
Medelius, Pedro J.; Hallberg, Carl; Cecil, Jim
A state-of-the-art instrumentation amplifier capable of being used with most types of transducers has been developed at the Kennedy Space Center. This Universal Signal Conditioning Amplifier (USCA) can eliminate costly measurement setup item and troubleshooting, improve system reliability and provide more accurate data than conventional amplifiers. The USCA can configure itself for maximum resolution and accuracy based on information read from a RAM chip attached to each transducer. Excitation voltages or current are also automatically configured. The amplifier uses both analog and digital state-of-the-art technology with analog-to-digital conversion performed in the early stages in order to minimize errors introduced by offset and gain drifts in the analog components. A dynamic temperature compensation scheme has been designed to achieve and maintain 12-bit accuracy of the amplifier from 0 to 70 C. The digital signal processing section allows the implementation of digital filters up to 511th order. The amplifier can also perform real-time linearizations up to fourth order while processing data at a rate of 23.438 kS/s. Both digital and analog outputs are available from the amplifier.
Brown, J.; Wang, H.; Hajishengallis, G.N.; Martin, M.
Toll-like receptors play a critical role in innate immunity by detecting invading pathogens. The ability of TLRs to engage different intracellular signaling molecules and cross-talk with other regulatory pathways is an important factor in shaping the type, magnitude, and duration of the inflammatory response. The present review will cover the fundamental signaling pathways utilized by TLRs and how these pathways regulate the innate immune response to pathogens. Abbreviations: TLR, Toll-like receptor; PRR, pattern recognition receptor; PAMP, pathogen-associated molecular pattern; LPS, lipopolysaccharide; APC, antigen-presenting cell; IL, interleukin; TIR, Toll/IL-1R homology; MyD88, myeloid differentiation factor 88; IFN, interferon; TRIF, TIR-domain-containing adapter-inducing interferon-β; IRAK, IL-1R-associated kinase; TAK1, TGF-β-activated kinase; TAB1, TAK1-binding protein; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B-cells; MAPK, mitogen-activated protein kinase; NLR, NOD-like receptors; LRR, leucine-rich repeats; DC, dendritic cell; PI3K, phosphoinositide 3-kinases; GSK3, glycogen synthase kinase-3; mTOR, mammalian target of rapamycin; DAF, decay-accelerating factor; IKK, IκB kinase; IRF, interferon regulatory factors; TBK1, TANK-binding kinase 1; CARD, caspase activation and recruitment domain; PYD, pyrin N-terminal homology domain; ATF, activating transcription factor; and PTEN, phosphatase and tensin homolog. PMID:20940366
Roles of phosphotase 2A in nociceptive signal processing
Multiple protein kinases affect the responses of dorsal horn neurons through phosphorylation of synaptic receptors and proteins involved in intracellular signal transduction pathways, and the consequences of this modulation may be spinal central sensitization. In contrast, the phosphatases catalyze an opposing reaction of de-phosphorylation, which may also modulate the functions of crucial proteins in signaling nociception. This is an important mechanism in the regulation of intracellular signal transduction pathways in nociceptive neurons. Accumulated evidence has shown that phosphatase 2A (PP2A), a serine/threonine specific phosphatase, is implicated in synaptic plasticity of the central nervous system and central sensitization of nociception. Therefore, targeting protein phosphotase 2A may provide an effective and novel strategy for the treatment of clinical pain. This review will characterize the structure and functional regulation of neuronal PP2A and bring together recent advances on the modulation of PP2A in targeted downstream substrates and relevant multiple nociceptive signaling molecules. PMID:24010880
Regulation of redox signaling by selenoproteins.
Hawkes, Wayne Chris; Alkan, Zeynep
The unique chemistry of oxygen has been both a resource and threat for life on Earth for at least the last 2.4 billion years. Reduction of oxygen to water allows extraction of more metabolic energy from organic fuels than is possible through anaerobic glycolysis. On the other hand, partially reduced oxygen can react indiscriminately with biomolecules to cause genetic damage, disease, and even death. Organisms in all three superkingdoms of life have developed elaborate mechanisms to protect against such oxidative damage and to exploit reactive oxygen species as sensors and signals in myriad processes. The sulfur amino acids, cysteine and methionine, are the main targets of reactive oxygen species in proteins. Oxidative modifications to cysteine and methionine can have profound effects on a protein's activity, structure, stability, and subcellular localization. Non-reversible oxidative modifications (oxidative damage) may contribute to molecular, cellular, and organismal aging and serve as signals for repair, removal, or programmed cell death. Reversible oxidation events can function as transient signals of physiological status, extracellular environment, nutrient availability, metabolic state, cell cycle phase, immune function, or sensory stimuli. Because of its chemical similarity to sulfur and stronger nucleophilicity and acidity, selenium is an extremely efficient catalyst of reactions between sulfur and oxygen. Most of the biological activity of selenium is due to selenoproteins containing selenocysteine, the 21st genetically encoded protein amino acid. The most abundant selenoproteins in mammals are the glutathione peroxidases (five to six genes) that reduce hydrogen peroxide and lipid hydroperoxides at the expense of glutathione and serve to limit the strength and duration of reactive oxygen signals. Thioredoxin reductases (three genes) use nicotinamide adenine dinucleotide phosphate to reduce oxidized thioredoxin and its homologs, which regulate a plethora of
Sum Frequency Generation Studies of Hydrogenation Reactions on Platinum Nanoparticles
Krier, James M.
Sum Frequency Generation (SFG) vibrational spectroscopy is used to characterize intermediate species of hydrogenation reactions on the surface of platinum nanoparticle catalysts. In contrast to other spectroscopy techniques which operate in ultra-high vacuum or probe surface species after reaction, SFG collects information under normal conditions as the reaction is taking place. Several systems have been studied previously using SFG on single crystals, notably alkene hydrogenation on Pt(111). In this thesis, many aspects of SFG experiments on colloidal nanoparticles are explored for the first time. To address spectral interference by the capping agent (PVP), three procedures are proposed: UV cleaning, H2 induced disordering and calcination (core-shell nanoparticles). UV cleaning and calcination physically destroy organic capping while disordering reduces SFG signal through a reversible structural change by PVP.
Selective effects of physical exercise on choice reaction processes.
Arcelin, R; Delignieres, D; Brisswalter, J
The aim of the present study was to examine the effects of an exercise of moderate intensity (60% of maximal aerobic power) on specific information-processing mechanisms. 22 students completed 3 10-min. exercise bouts on a bicycle ergometer. Concomitantly, participants performed six manual-choice-reaction tasks manipulating task variables (Signal Intensity, Stimulus-Response Compatibility, and Time Uncertainty) on two levels. Reaction tests, randomly ordered, were administered at rest and during exercise. A significant underadditive interaction between Time Uncertainty and exercise was found for the highest quartiles of the distribution of reaction times. No other interaction effects were obtained for the other variables. These results reasonably support that moderate aerobic exercise showed selective rather than general influences on information processing. PMID:9760644
Salicylic acid signaling inhibits apoplastic reactive oxygen species signaling
Background Reactive oxygen species (ROS) are used by plants as signaling molecules during stress and development. Given the amount of possible challenges a plant face from their environment, plants need to activate and prioritize between potentially conflicting defense signaling pathways. Until recently, most studies on signal interactions have focused on phytohormone interaction, such as the antagonistic relationship between salicylic acid (SA)-jasmonic acid and cytokinin-auxin. Results In this study, we report an antagonistic interaction between SA signaling and apoplastic ROS signaling. Treatment with ozone (O3) leads to a ROS burst in the apoplast and induces extensive changes in gene expression and elevation of defense hormones. However, Arabidopsis thaliana dnd1 (defense no death1) exhibited an attenuated response to O3. In addition, the dnd1 mutant displayed constitutive expression of defense genes and spontaneous cell death. To determine the exact process which blocks the apoplastic ROS signaling, double and triple mutants involved in various signaling pathway were generated in dnd1 background. Simultaneous elimination of SA-dependent and SA-independent signaling components from dnd1 restored its responsiveness to O3. Conversely, pre-treatment of plants with SA or using mutants that constitutively activate SA signaling led to an attenuation of changes in gene expression elicited by O3. Conclusions Based upon these findings, we conclude that plants are able to prioritize the response between ROS and SA via an antagonistic action of SA and SA signaling on apoplastic ROS signaling. PMID:24898702
Signal and Image Processing Operations
VIEW is a software system for processing arbitrary multidimensional signals. It provides facilities for numerical operations, signal displays, and signal databasing. The major emphasis of the system is on the processing of time-sequences and multidimensional images. The system is designed to be both portable and extensible. It runs currently on UNIX systems, primarily SUN workstations.
Isolated transfer of analog signals
NASA Technical Reports Server (NTRS)
Bezdek, T.
Technique transfers analog signal levels across high isolation boundary without circuit performance being affected by magnetizing reactance or leakage inductance. Transfers of analog information across isolated boundary are made by interrupting signal flow, with switch, in such a manner as to produce alternating signal which is applied to transformer.
Multiple source navigation signal generator
NASA Astrophysics Data System (ADS)
Bojda, Petr
The paper presents a FPGA based digital VOR/LOC signal generator. It provides the composite signal, which consists of the particular signals of several predefined navigation sources - VOR beacons. Design of the generator is implemented into the two different FPGA DSP platforms.
SIG. Signal Processing, Analysis, & Display
Hernandez, J.; Lager, D.; Azevedo, S.
SIG is a general-purpose signal processing, analysis, and display program. Its main purpose is to perform manipulations on time- and frequency-domain signals. However, it has been designed to ultimately accommodate other representations for data such as multiplexed signals and complex matrices. Two user interfaces are provided in SIG - a menu mode for the unfamiliar user and a command mode for more experienced users. In both modes errors are detected as early as possible and are indicated by friendly, meaningful messages. An on-line HELP package is also included. A variety of operations can be performed on time- and frequency-domain signals including operations on the samples of a signal, operations on the entire signal, and operations on two or more signals. Signal processing operations that can be performed are digital filtering (median, Bessel, Butterworth, and Chebychev), ensemble average, resample, auto and cross spectral density, transfer function and impulse response, trend removal, convolution, Fourier transform and inverse window functions (Hamming, Kaiser-Bessel), simulation (ramp, sine, pulsetrain, random), and read/write signals. User definable signal processing algorithms are also featured. SIG has many options including multiple commands per line, command files with arguments,commenting lines, defining commands, and automatic execution for each item in a repeat sequence. Graphical operations on signals and spectra include: x-y plots of time signals; real, imaginary, magnitude, and phase plots of spectra; scaling of spectra for continuous or discrete domain; cursor zoom; families of curves; and multiple viewports.
SIG. Signal Processing, Analysis, & Display
Hernandez, J.; Lager, D.; Azevedo, S.
SIG is a general-purpose signal processing, analysis, and display program. Its main purpose is to perform manipulations on time and frequency-domain signals. However, it has been designed to ultimately accommodate other representations for data such as multiplexed signals and complex matrices. Two user interfaces are provided in SIG; a menu mode for the unfamiliar user and a command mode for more experienced users. In both modes errors are detected as early as possible and are indicated by friendly, meaningful messages. An on-line HELP package is also included. A variety of operations can be performed on time and frequency-domain signals including operations on the samples of a signal, operations on the entire signal, and operations on two or more signals. Signal processing operations that can be performed are digital filtering (median, Bessel, Butterworth, and Chebychev), ensemble average, resample, auto and cross spectral density, transfer function and impulse response, trend removal, convolution, Fourier transform and inverse window functions (Hamming, Kaiser-Bessel), simulation (ramp, sine, pulsetrain, random), and read/write signals. User definable signal processing algorithms are also featured. SIG has many options including multiple commands per line, command files with arguments, commenting lines, defining commands, and automatic execution for each item in a `repeat` sequence. Graphical operations on signals and spectra include: x-y plots of time signals; real, imaginary, magnitude, and phase plots of spectra; scaling of spectra for continuous or discrete domain; cursor zoom; families of curves; and multiple viewports.
SIG. Signal Processing, Analysis, & Display
Hernandez, J.; Lager, D.; Azevedo, S.
SIG is a general-purpose signal processing, analysis, and display program. Its main purpose is to perform manipulations on time-and frequency-domain signals. However, it has been designed to ultimately accommodate other representations for data such as multiplexed signals and complex matrices. Two user interfaces are provided in SIG - a menu mode for the unfamiliar user and a command mode for more experienced users. In both modes errors are detected as early as possible and are indicated by friendly, meaningful messages. An on-line HELP package is also included. A variety of operations can be performed on time and frequency-domain signals including operations on the samples of a signal, operations on the entire signal, and operations on two or more signals. Signal processing operations that can be performed are digital filtering (median, Bessel, Butterworth, and Chebychev), ensemble average, resample, auto and cross spectral density, transfer function and impulse response, trend removal, convolution, Fourier transform and inverse window functions (Hamming, Kaiser-Bessel), simulation (ramp, sine, pulsetrain, random), and read/write signals. User definable signal processing algorithms are also featured. SIG has many options including multiple commands per line, command files with arguments, commenting lines, defining commands, and automatic execution for each item in a repeat sequence. Graphical operations on signals and spectra include: x-y plots of time signals; real, imaginary, magnitude, and phase plots of spectra; scaling of spectra for continuous or discrete domain; cursor zoom; families of curves; and multiple viewports.
Asymmetry In Biphase Data Signals
NASA Technical Reports Server (NTRS)
Nguyen, Tien M.
Report presents analysis of some effects of asymmetry in Manchester (biphase) binary data signal transmitted by phase modulation of sinusoidal carrier signal. Report extends analysis described in article, "Effects of Asymmetry of NRZ Data Signals on Performance" (NPO-18261), to include case where data biphase-modulated directly on residual carrier.
Radiative capture reactions in astrophysics
Brune, Carl R.; Davids, Barry
Here, the radiative capture reactions of greatest importance in nuclear astrophysics are identified and placed in their stellar contexts. Recent experimental efforts to estimate their thermally averaged rates are surveyed.
Experimental Study of Serpentinization Reactions
NASA Technical Reports Server (NTRS)
Cohen, B. A.; Brearley, A. J.; Ganguly, J.; Liermann, H.-P.; Keil, K.
Current carbonaceous chondrite parent-body thermal models [1-3] produce scenarios that are inconsistent with constraints on aqueous alteration conditions based on meteorite mineralogical evidence, such as phase stability relationships within the meteorite matrix minerals [4] and isotope equilibration arguments [5, 6]. This discrepancy arises principally because of the thermal runaway effect produced by silicate hydration reactions (here loosely called serpentinization, as the principal products are serpentine minerals), which are so exothermic as to produce more than enough heat to melt more ice and provide a self-sustaining chain reaction. One possible way to dissipate the heat of reaction is to use a very small parent body [e.g., 2] or possibly a rubble pile model. Another possibility is to release this heat more slowly, which depends on the alteration reaction path and kinetics.
Method for conducting exothermic reactions
Smith, L. Jr.; Hearn, D.; Jones, E.M. Jr.
A liquid phase process for oligomerization of C[sub 4] and C[sub 5] isoolefins or the etherification thereof with C[sub 1] to C[sub 6] alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120 to 300 F. wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.
Transfer reactions in nuclear astrophysics
NASA Astrophysics Data System (ADS)
Bardayan, D. W.
To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star's fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.
Solar-thermal reaction processing
Weimer, Alan W; Dahl, Jaimee K; Lewandowski, Allan A; Bingham, Carl; Raska Buechler, Karen J; Grothe, Willy
In an embodiment, a method of conducting a high temperature chemical reaction that produces hydrogen or synthesis gas is described. The high temperature chemical reaction is conducted in a reactor having at least two reactor shells, including an inner shell and an outer shell. Heat absorbing particles are included in a gas stream flowing in the inner shell. The reactor is heated at least in part by a source of concentrated sunlight. The inner shell is heated by the concentrated sunlight. The inner shell re-radiates from the inner wall and heats the heat absorbing particles in the gas stream flowing through the inner shell, and heat transfers from the heat absorbing particles to the first gas stream, thereby heating the reactants in the gas stream to a sufficiently high temperature so that the first gas stream undergoes the desired reaction(s), thereby producing hydrogen or synthesis gas in the gas stream.
The Retro-Hydroformylation Reaction.
Kusumoto, Shuhei; Tatsuki, Toshiumi; Nozaki, Kyoko
Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon-carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91% yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation-dehydrogenation or dehydrogenation-decarbonylation process. PMID:26089259
Medications and Drug Allergic Reactions
... Drug Guide Conditions Dictionary Just for Kids Library School Tools Videos Virtual Allergist Education & Training Careers in ... reaction to a medication. These include: genetics, body chemistry, frequent drug exposure or the presence of an ...
Method for conducting exothermic reactions
Smith, Jr., Lawrence; Hearn, Dennis; Jones, Jr., Edward M.
A liquid phase process for oligomerization of C.sub.4 and C.sub.5 isoolefins or the etherification thereof with C.sub.1 to C.sub.6 alcohols wherein the reactants are contacted in a reactor with a fixed bed acid cation exchange resin catalyst at an LHSV of 5 to 20, pressure of 0 to 400 psig and temperature of 120.degree. to 300.degree. F. wherein the improvement is the operation of the reactor at a pressure to maintain the reaction mixture at its boiling point whereby at least a portion but less than all of the reaction mixture is vaporized. By operating at the boiling point and allowing a portion of the reaction mixture to vaporize, the exothermic heat of reaction is dissipated by the formation of more boil up and the temperature in the reactor is controlled.
Adverse reactions to food additives.
Simon, R A
There are thousands of agents that are intentionally added to the food that we consume. These include preservatives, stabilizers, conditioners, thickeners, colorings, flavorings, sweeteners, antioxidants, etc. etc. Yet only a surprisingly small number have been associated with hypersensitivity reactions. Amongst all the additives, FD&C dyes have been most frequently associated with adverse reactions. Tartrazine is the most notorious of them all; however, critical review of the medical literature and current Scripps Clinic studies would indicate that tartrazine has been confirmed to be at best only occasionally associated with flares of urticaria or asthma. There is no convincing evidence in the literature of reactivity to the other azo or nonazo dyes. This can also be said of BHA/BHT, nitrites/nitrates and sorbates. Parabens have been shown to elicit IgE mediated hypersensitivity reactions when used as pharmaceutical preservatives; however, as with the other additives noted above, ingested parabens have only occasionally been associated with adverse reactions. MSG, the cause of the 'Chinese restaurant syndrome' has only been linked to asthma in one report. Sulfiting agents used primarily as food fresheners and to control microbial growth in fermented beverages have been established as the cause of any where from mild to severe and even fatal reactions in at least 5% of the asthmatic population. Other reactions reported to follow sulfite ingestion include anaphylaxis, gastro intestinal complaints and dermatological eruptions. The prevalence of these non asthmatic reactions is unknown. The mechanism of sulfite sensitive asthma is also unknown but most likely involves hyperreactivity to inhale SO2 in the great majority of cases; however, there are reports of IgE mediated reactions and other sulfite sensitive asthmatics have been found with low levels of sulfite oxidase; necessary to oxidize endogenous sulfite to sulfate. PMID:3302664
Features for instantaneous emissions of low-level infrared signals of glucokinase enzyme from Pyrococcus furiosus.
Torres, Sergio; Mella, Héctor; Reyes, Claudio; Meza, Pablo; Gallardo, Maria J; Staforelli, Juan P
A noncontact infrared (IR) imaging-based methodology and signal recovery tools are applied on an enzyme reaction as a test target. The method is implemented by a long-wave (8-12 μm) IR microbolometer imaging array and a germanium-based IR optical vision. The reaction is carried out by the glucokinase, which produces a rapid exothermal release of energy that is weak, and, even worse, the IR video captured by the uncooled microbolometer detector is affected by spatial and temporal noise with specific complexities. Hitherto, IR-based signal recovery tools have worked with a standard acquisition frequency, which is clearly beyond the time scale of a real scenario. The implications of this (and similar) rapid reactions motivate the designs of a signal recovery method using prior information of the processes to extract and quantify the spontaneity of the enzymatic reaction in a three-dimensional (space and time) single and noncontact online measurement. PMID:25968383
NASA Technical Reports Server (NTRS)
Griebeler, Elmer L.
Binary communication through long cables, opto-isolators, isolating transformers, or repeaters can become distorted in characteristic ways. The usual solution is to slow the communication rate, change to a different method, or improve the communication media. It would help if the characteristic distortions could be accommodated at the receiving end to ease the communication problem. The distortions come from loss of the high-frequency content, which adds slopes to the transitions from ones to zeroes and zeroes to ones. This weakens the definition of the ones and zeroes in the time domain. The other major distortion is the reduction of low frequency, which causes the voltage that defines the ones or zeroes to drift out of recognizable range. This development describes a method for recovering a binary data stream from a signal that has been subjected to a loss of both higher-frequency content and low-frequency content that is essential to define the difference between ones and zeroes. The method makes use of the frequency structure of the waveform created by the data stream, and then enhances the characteristics related to the data to reconstruct the binary switching pattern. A major issue is simplicity. The approach taken here is to take the first derivative of the signal and then feed it to a hysteresis switch. This is equivalent in practice to using a non-resonant band pass filter feeding a Schmitt trigger. Obviously, the derivative signal needs to be offset to halfway between the thresholds of the hysteresis switch, and amplified so that the derivatives reliably exceed the thresholds. A transition from a zero to a one is the most substantial, fastest plus movement of voltage, and therefore will create the largest plus first derivative pulse. Since the quiet state of the derivative is sitting between the hysteresis thresholds, the plus pulse exceeds the plus threshold, switching the hysteresis switch plus, which re-establishes the data zero to one transition
Expert system for predicting reaction conditions: the Michael reaction case.
Marcou, G; Aires de Sousa, J; Latino, D A R S; de Luca, A; Horvath, D; Rietsch, V; Varnek, A
A generic chemical transformation may often be achieved under various synthetic conditions. However, for any specific reagents, only one or a few among the reported synthetic protocols may be successful. For example, Michael β-addition reactions may proceed under different choices of solvent (e.g., hydrophobic, aprotic polar, protic) and catalyst (e.g., Brønsted acid, Lewis acid, Lewis base, etc.). Chemoinformatics methods could be efficiently used to establish a relationship between the reagent structures and the required reaction conditions, which would allow synthetic chemists to waste less time and resources in trying out various protocols in search for the appropriate one. In order to address this problem, a number of 2-classes classification models have been built on a set of 198 Michael reactions retrieved from literature. Trained models discriminate between processes that are compatible and respectively processes not feasible under a specific reaction condition option (feasible or not with a Lewis acid catalyst, feasible or not in hydrophobic solvent, etc.). Eight distinct models were built to decide the compatibility of a Michael addition process with each considered reaction condition option, while a ninth model was aimed to predict whether the assumed Michael addition is feasible at all. Different machine-learning methods (Support Vector Machine, Naive Bayes, and Random Forest) in combination with different types of descriptors (ISIDA fragments issued from Condensed Graphs of Reactions, MOLMAP, Electronic Effect Descriptors, and Chemistry Development Kit computed descriptors) have been used. Models have good predictive performance in 3-fold cross-validation done three times: balanced accuracy varies from 0.7 to 1. Developed models are available for the users at http://infochim.u-strasbg.fr/webserv/VSEngine.html . Eventually, these were challenged to predict feasibility conditions for ∼50 novel Michael reactions from the eNovalys database (originally
Polarization phenomena in collinear reactions
NASA Astrophysics Data System (ADS)
Moravcsik, Michael J.; Arash, Firooz
It is shown for a collinear reaction containing four particles with arbitrary spins which amplitudes remain nonzero and how they are related to the observables. In terms of primary observables all submatrices relating products of amplitudes to observables either vanish or turn into one-by-one submatrices, except the 8i types which may turn into three-by-three submatrices, but these latter submatrices are mostly avoidable when determining amplitudes. In terms of the secondary observables the 1M and 2i submatrices are slightly larger. Specifically, it is shown that in collinear reactions all observables in which only one particle is polarized (no matter how) vanish. Since reactions at very high energies are expected to be predominantly very close to being collinear, the smallness of such observables in such reactions can be expected on general grounds but polarization effects involving observables with more than one polarized particle can very well be very large. An iterative approximation method for the polarization analysis of reactions at very high energies is suggested. The results of this paper are also applicable to all models in which helicity conservation holds, since they are, for all t values, formally identical with collinear reactions.
Kinetics of actinide complexation reactions
Nash, K.L.; Sullivan, J.C.
Though the literature records extensive compilations of the thermodynamics of actinide complexation reactions, the kinetics of complex formation and dissociation reactions of actinide ions in aqueous solutions have not been extensively investigated. In light of the central role played by such reactions in actinide process and environmental chemistry, this situation is somewhat surprising. The authors report herein a summary of what is known about actinide complexation kinetics. The systems include actinide ions in the four principal oxidation states (III, IV, V, and VI) and complex formation and dissociation rates with both simple and complex ligands. Most of the work reported was conducted in acidic media, but a few address reactions in neutral and alkaline solutions. Complex formation reactions tend in general to be rapid, accessible only to rapid-scan and equilibrium perturbation techniques. Complex dissociation reactions exhibit a wider range of rates and are generally more accessible using standard analytical methods. Literature results are described and correlated with the known properties of the individual ions.
Signaling Pathways in Osteoclast Differentiation.
Kim, Jung Ha; Kim, Nacksung
Osteoclasts are multinucleated cells of hematopoietic origin that are responsible for the degradation of old bone matrix. Osteoclast differentiation and activity are controlled by two essential cytokines, macrophage colony-stimulating factor (M-CSF) and the receptor activator of nuclear factor-κB ligand (RANKL). M-CSF and RANKL bind to their respective receptors c-Fms and RANK to stimulate osteoclast differentiation through regulation of delicate signaling systems. Here, we summarize the critical or essential signaling pathways for osteoclast differentiation including M-CSF-c-Fms signaling, RANKL-RANK signaling, and costimulatory signaling for RANK. PMID:26865996
Emerging Trends in Retrograde Signaling.
Suvarna, Yashasvi; Maity, Nivedita; Shivamurthy, M C
Retrograde signaling is defined as the signaling events leading from the plastids to the nucleus in plants and across the chemical synapse, from the postsynaptic neuron to the presynaptic neuron in animals. The discovery of various retrograde messengers has opened many avenues and clouds of thoughts as to the role of retrograde signaling. They have been implicated particularly in long-term potentiation (LTP) and synaptic plasticity. But the basic assumptions about retrograde signaling have not been studied upon for many years. This review focuses on established facts and hypothesis put forward in retrograde signaling. PMID:26081150
Notch Signaling in Pancreatic Development
Li, Xu-Yan; Zhai, Wen-Jun; Teng, Chun-Bo
The Notch signaling pathway plays a significant role in embryonic cell fate determination and adult tissue homeostasis. Various studies have demonstrated the deep involvement of Notch signaling in the development of the pancreas and the lateral inhibition of Notch signaling in pancreatic progenitor differentiation and maintenance. The targeted inactivation of the Notch pathway components promotes premature differentiation of the endocrine pancreas. However, there is still the contrary opinion that Notch signaling specifies the endocrine lineage. Here, we review the current knowledge of the Notch signaling pathway in pancreatic development and its crosstalk with the Wingless and INT-1 (Wnt) and fibroblast growth factor (FGF) pathways. PMID:26729103
Eph/ephrin signaling: networks
Arvanitis, Dina; Davy, Alice
Bidirectional signaling has emerged as an important signature by which Ephs and ephrins control biological functions. Eph/ephrin signaling participates in a wide spectrum of developmental processes, and cross-regulation with other communication pathways lies at the heart of the complexity underlying their function in vivo. Here, we review in vitro and in vivo data describing molecular, functional, and genetic interactions between Eph/ephrin and other cell surface signaling pathways. The complexity of Eph/ephrin function is discussed in terms of the pathways that regulate Eph/ephrin signaling and also the pathways that are regulated by Eph/ephrin signaling. PMID:18281458
Multiparticle collision dynamics for diffusion-influenced signaling pathways
NASA Astrophysics Data System (ADS)
Strehl, R.; Rohlf, K.
An efficient yet accurate simulation method for modeling diffusion-influenced reaction networks is presented. The method extends existing reactive multiparticle collision dynamics by incorporating species-dependent diffusion coefficients, and developing theoretical expressions for the reactant-dependent diffusion control. This off-lattice particle-based mesoscopic simulation tool is particularly suited for problems in which detailed descriptions of particle trajectories and local reactions are required. Numerical simulations of an intracellular signaling pathway for bacterial chemotaxis are carried out to validate our approach, and to demonstrate its efficiency.
Interactive digital signal processor
NASA Technical Reports Server (NTRS)
Mish, W. H.; Wenger, R. M.; Behannon, K. W.; Byrnes, J. B.
The Interactive Digital Signal Processor (IDSP) is examined. It consists of a set of time series analysis Operators each of which operates on an input file to produce an output file. The operators can be executed in any order that makes sense and recursively, if desired. The operators are the various algorithms used in digital time series analysis work. User written operators can be easily interfaced to the sysatem. The system can be operated both interactively and in batch mode. In IDSP a file can consist of up to n (currently n=8) simultaneous time series. IDSP currently includes over thirty standard operators that range from Fourier transform operations, design and application of digital filters, eigenvalue analysis, to operators that provide graphical output, allow batch operation, editing and display information.
[Signal Processing Suite Design
NASA Technical Reports Server (NTRS)
Sahr, John D.; Mir, Hasan; Morabito, Andrew; Grossman, Matthew
Our role in this project was to participate in the design of the signal processing suite to analyze plasma density measurements on board a small constellation (3 or 4) satellites in Low Earth Orbit. As we are new to space craft experiments, one of the challenges was to simply gain understanding of the quantity of data which would flow from the satellites, and possibly to interact with the design teams in generating optimal sampling patterns. For example, as the fleet of satellites were intended to fly through the same volume of space (displaced slightly in time and space), the bulk plasma structure should be common among the spacecraft. Therefore, an optimal, limited bandwidth data downlink would take advantage of this commonality. Also, motivated by techniques in ionospheric radar, we hoped to investigate the possibility of employing aperiodic sampling in order to gain access to a wider spatial spectrum without suffering aliasing in k-space.
Collider Signal I :. Resonance
NASA Astrophysics Data System (ADS)
Tait, Tim M. P.
These TASI lectures were part of the summer school in 2008 and cover the collider signal associated with resonances in models of physics beyond the Standard Model. I begin with a review of the Z boson, one of the best-studied resonances in particle physics, and review how the Breit-Wigner form of the propagator emerges in perturbation theory and discuss the narrow width approximation. I review how the LEP and SLAC experiments could use the kinematics of Z events to learn about fermion couplings to the Z. I then make a brief survey of models of physics beyond the Standard Model which predict resonances, and discuss some of the LHC observables which we can use to discover and identify the nature of the BSM physics. I finish up with a discussion of the linear moose that one can use for an effective theory description of a massive color octet vector particle.
Feijó, José A; Costa, Sílvia S; Prado, Ana Margarida; Becker, Jörg D; Certal, Ana Catarina
New molecules, including protein kinases, lipids and molecules that have neurotransmitter activities in animals have emerged as important players in tip-growing cells. Transcriptomics analysis reveals that the largest single class of genes expressed in pollen tubes encode signal transducers, reflecting the necessity to decode complex and diverse pathways that are associated with tip growth. Many of these pathways may use common intracellular second messengers, with ions and reactive oxygen species emerging as two major common denominators in many of the processes involved in tip growth. These second messengers might influence the actin cytoskeleton through known interactions with actin-binding proteins. In turn, changes in the dynamic properties of the cytoskeleton would define the basic polarity events needed to shape and modify tip-growing cells. PMID:15337103
Antunes, Gabriela; Simoes de Souza, Fabio Marques
The guanine nucleotide protein (G protein)-coupled receptors (GPCRs) superfamily represents the largest class of membrane protein in the human genome. More than a half of all GPCRs are dedicated to interact with odorants and are termed odorant-receptors (ORs). Linda Buck and Richard Axel, the Nobel Prize laureates in physiology or medicine in 2004, first cloned and characterized the gene family that encode ORs, establishing the foundations to the understanding of the molecular basis for odor recognition. In the last decades, a lot of progress has been done to unravel the functioning of the sense of smell. This chapter gives a general overview of the topic of olfactory receptor signaling and reviews recent advances in this field. PMID:26928542
NASA Technical Reports Server (NTRS)
Zahzah, Mohamad (Inventor); Korkosz, Gregory J. (Inventor); Bohr, Gerald (Inventor)
A current-driven signal conditioning system comprising a first terminal, a second terminal, a strain gauge, and an instrumentation amplifier is disclosed. The strain gauge is adapted to measure a deformation of a structure and to generate a resistance which corresponds to the measured deformation. The instrumentation amplifier is adapted to be connected between the first terminal and the second terminal. The instrumentation amplifier is further adapted to be connected to the strain gauge and to place an output current on the second terminal. The output current is proportional to the resistance generated by the strain gauge. An output resister is coupled between the strain gauge and the second terminal, and a capacitor is coupled between the resister and the first terminal. A zenor diode is coupled between the first terminal and the strain gauge, and a diode is also coupled between the first terminal and the strain gauge.
Elementary signals in ptychography.
da Silva, Julio Cesar; Menzel, Andreas
Ptychographic imaging has gained popularity for its high resolving power and sensitivity as well as for its ability to map simultaneously the sample's complex-valued refractive index and the illumination. Yet, despite significant progress that allows for reliable practical implementation, some of the technique's fundamentals remain poorly understood, and oftentimes successful data acquisition is either overly conservative or relies more on experimenters experience than on rational data acquisition strategies. Here, we propose a theoretical framework of ptychography, which is based on Gabor's notion of decomposition into elementary signals and the concept of frames. We demonstrate how this framework can straightforwardly be used to derive sampling requirements or to provide arguments on how to optimize the ptychographic scan. More generally, our theoretical framework can serve as a bridge between the experimental technique and the rich and well established mathematical disciplines of wavelets decomposition and spectrogram analysis. PMID:26832042
Epigenetic signaling in schizophrenia.
Ibi, Daisuke; González-Maeso, Javier
Histone modifications and DNA methylation represent central dynamic and reversible processes that regulate gene expression and contribute to cellular phenotypes. These epigenetic marks have been shown to play fundamental roles in a diverse set of signaling and behavioral outcomes. Psychiatric disorders such as schizophrenia and depression are complex and heterogeneous diseases with multiple and independent factors that may contribute to their pathophysiology, making challenging to find a link between specific elements and the underlying mechanisms responsible for the disorder and its treatment. Growing evidences suggest that epigenetic modifications in certain brain regions and neural circuits represent a key mechanism through which environmental factors interact with individual's genetic constitution to affect risk of psychiatric conditions throughout life. This review focuses on recent advances that directly implicate epigenetic modifications in schizophrenia and antipsychotic drug action. PMID:26120009
Quantitative measures for redox signaling.
Pillay, Ché S; Eagling, Beatrice D; Driscoll, Scott R E; Rohwer, Johann M
Redox signaling is now recognized as an important regulatory mechanism for a number of cellular processes including the antioxidant response, phosphokinase signal transduction and redox metabolism. While there has been considerable progress in identifying the cellular machinery involved in redox signaling, quantitative measures of redox signals have been lacking, limiting efforts aimed at understanding and comparing redox signaling under normoxic and pathogenic conditions. Here we have outlined some of the accepted principles for redox signaling, including the description of hydrogen peroxide as a signaling molecule and the role of kinetics in conferring specificity to these signaling events. Based on these principles, we then develop a working definition for redox signaling and review a number of quantitative methods that have been employed to describe signaling in other systems. Using computational modeling and published data, we show how time- and concentration- dependent analyses, in particular, could be used to quantitatively describe redox signaling and therefore provide important insights into the functional organization of redox networks. Finally, we consider some of the key challenges with implementing these methods. PMID:27151506
Nuclear Reactions for Astrophysics and Other Applications
Escher, J E; Burke, J T; Dietrich, F S; Scielzo, N D; Ressler, J J
Cross sections for compound-nuclear reactions are required for many applications. The surrogate nuclear reactions method provides an indirect approach for determining cross sections for reactions on unstable isotopes, which are difficult or impossible to measure otherwise. Current implementations of the method provide useful cross sections for (n,f) reactions, but need to be improved upon for applications to capture reactions.
Signaling on the endocytic pathway.
McPherson, P S; Kay, B K; Hussain, N K
Ligand binding to receptor tyrosine kinases and G-protein-coupled receptors initiates signal transduction events and induces receptor endocytosis via clathrin-coated pits and vesicles. While receptor-mediated endocytosis has been traditionally considered an effective mechanism to attenuate ligand-activated responses, more recent studies demonstrate that signaling continues on the endocytic pathway. In fact, certain signaling events, such as the activation of the extracellular signal-regulated kinases, appear to require endocytosis. Protein components of signal transduction cascades can assemble at clathrin coated pits and remain associated with endocytic vesicles following their dynamin-dependent release from the plasma membrane. Thus, endocytic vesicles can function as a signaling compartment distinct from the plasma membrane. These observations demonstrate that endocytosis plays an important role in the activation and propagation of signaling pathways. PMID:11389765
EEG signal analysis: a survey.
Subha, D Puthankattil; Joseph, Paul K; Acharya U, Rajendra; Lim, Choo Min
The EEG (Electroencephalogram) signal indicates the electrical activity of the brain. They are highly random in nature and may contain useful information about the brain state. However, it is very difficult to get useful information from these signals directly in the time domain just by observing them. They are basically non-linear and nonstationary in nature. Hence, important features can be extracted for the diagnosis of different diseases using advanced signal processing techniques. In this paper the effect of different events on the EEG signal, and different signal processing methods used to extract the hidden information from the signal are discussed in detail. Linear, Frequency domain, time - frequency and non-linear techniques like correlation dimension (CD), largest Lyapunov exponent (LLE), Hurst exponent (H), different entropies, fractal dimension(FD), Higher Order Spectra (HOS), phase space plots and recurrence plots are discussed in detail using a typical normal EEG signal. PMID:20433058
A network map of Interleukin-10 signaling pathway.
Verma, Renu; Balakrishnan, Lavanya; Sharma, Kusum; Khan, Aafaque Ahmad; Advani, Jayshree; Gowda, Harsha; Tripathy, Srikanth Prasad; Suar, Mrutyunjay; Pandey, Akhilesh; Gandotra, Sheetal; Prasad, T S Keshava; Shankar, Subramanian
Interleukin-10 (IL-10) is an anti-inflammatory cytokine with important immunoregulatory functions. It is primarily secreted by antigen-presenting cells such as activated T-cells, monocytes, B-cells and macrophages. In biologically functional form, it exists as a homodimer that binds to tetrameric heterodimer IL-10 receptor and induces downstream signaling. IL-10 is associated with survival, proliferation and anti-apoptotic activities of various cancers such as Burkitt lymphoma, non-Hodgkins lymphoma and non-small scell lung cancer. In addition, it plays a central role in survival and persistence of intracellular pathogens such as Leishmania donovani, Mycobacterium tuberculosis and Trypanosoma cruzi inside the host. The signaling mechanisms of IL-10 cytokine are not well explored and a well annotated pathway map has been lacking. To this end, we developed a pathway resource by manually annotating the IL-10 induced signaling molecules derived from literature. The reactions were categorized under molecular associations, activation/inhibition, catalysis, transport and gene regulation. In all, 37 molecules and 76 reactions were annotated. The IL-10 signaling pathway can be freely accessed through NetPath, a resource of signal transduction pathways previously developed by our group. PMID:26253919
Amyloplast Distribution Directs a Root Gravitropic Reaction
NASA Astrophysics Data System (ADS)
Kordyum, Elizabeth
Immobile higher plants are oriented in the gravitational field due to gravitropim that is a physiological growth reaction and consists of three phases: reception of a gravitational signal by statocytes, its transduction to the elongation zone, and finally the organ bending. As it is known, roots are characterized with positive gravitropism, i. e. they grow in the direction of a gravitational vector, stems - with negative gravitropism, i. e. they grow in the direction opposite to a gravitational vector. According to the Nemec's and Haberlandt's starch-statolith hypothesis, amyloplasts in diameter of 1.5 - 3 μ in average, which appear to act as gravity sensors and fulfill a statolythic function in the specialized graviperceptive cells - statocytes, sediment in the direction of a gravitational vector in the distal part of a cell, while a nucleus is in the proximal one. There are reasonable data that confirm the amyloplasts-statoliths participation in gravity perception: 1) correlation between the statoliths localization and the site of gravity sensing, 2) significant redistribution (sedimentation) of amyloplasts in statocytes under gravistimulation in comparison with other cell organelles, 3) root decreased ability to react on gravity under starch removal from amyloplasts, 4) starchless Arabidopsis thaliana mutants are agravitropic, 5) amyloplasts-statoliths do not sediment in the absence of the gravitational vector and are in different parts or more concentrated in the center of statocytes. Plant tropisms have been intensively studied for many decades and continue to be investigated. Nevertheless, the mechanisms by which plants do so is still not clearly explained and many questions on gravisensing and graviresponse remain unanswered. Even accepted hypotheses are now being questioned and recent data are critically evaluated. Although the available data show the Ca2+ and cytoskeleton participation in graviperception and signal transduction, the clear evidence
Reaction rates for a generalized reaction-diffusion master equation
Hellander, Stefan; Petzold, Linda
It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model, and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is on the order of the reaction radius of a reacting pair of molecules. PMID:26871190
Reaction rates for a generalized reaction-diffusion master equation
NASA Astrophysics Data System (ADS)
Hellander, Stefan; Petzold, Linda
It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.
Nonenzymatic catalytic signal amplification for nucleic acid hybridization assays
NASA Technical Reports Server (NTRS)
Fan, Wenhong (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)
Devices, methods, and kits for amplifying the signal from hybridization reactions between nucleic acid probes and their cognate targets are presented. The devices provide partially-duplexed, immobilized probe complexes, spatially separate from and separately addressable from immobilized docking strands. Cognate target acts catalytically to transfer probe from the site of probe complex immobilization to the site of immobilized docking strand, generating a detectable signal. The methods and kits of the present invention may be used to identify the presence of cognate target in a fluid sample.
Phosphorelays Provide Tunable Signal Processing Capabilities for the Cell
Kothamachu, Varun B.; Feliu, Elisenda; Wiuf, Carsten; Cardelli, Luca; Soyer, Orkun S.
Achieving a complete understanding of cellular signal transduction requires deciphering the relation between structural and biochemical features of a signaling system and the shape of the signal-response relationship it embeds. Using explicit analytical expressions and numerical simulations, we present here this relation for four-layered phosphorelays, which are signaling systems that are ubiquitous in prokaryotes and also found in lower eukaryotes and plants. We derive an analytical expression that relates the shape of the signal-response relationship in a relay to the kinetic rates of forward, reverse phosphorylation and hydrolysis reactions. This reveals a set of mathematical conditions which, when satisfied, dictate the shape of the signal-response relationship. We find that a specific topology also observed in nature can satisfy these conditions in such a way to allow plasticity among hyperbolic and sigmoidal signal-response relationships. Particularly, the shape of the signal-response relationship of this relay topology can be tuned by altering kinetic rates and total protein levels at different parts of the relay. These findings provide an important step towards predicting response dynamics of phosphorelays, and the nature of subsequent physiological responses that they mediate, solely from topological features and few composite measurements; measuring the ratio of reverse and forward phosphorylation rate constants could be sufficient to determine the shape of the signal-response relationship the relay exhibits. Furthermore, they highlight the potential ways in which selective pressures on signal processing could have played a role in the evolution of the observed structural and biochemical characteristic in phosphorelays. PMID:24244132
Study of char gasification reactions
Ballal, G.D.
A Texas lignite, an anthracite and two bituminous coals, Pittsburgh number8 and Illinois number6, were pyrolyzed in a nitrogen atmosphere to prepare chars. Optical microscopy, mercury porosimetry and gas adsorption techniques using nitrogen, CO/sub 2/ and CO, were employed for pore structure characterization. The lignite char exhibited the fastest rates of gaseous diffusion, followed in order of decreasing diffusivities by the Illinois number6, Pittsburgh number8 and anthracite chars. The changes in reactivities and pore structures of chars were measured experimentally during their reaction with oxygen (400-550C) and CO/sub 2/ (800-1000C). For a particular char-gas system, the normalized rate-conversion pattern was invariant with respect to temperature and gaseous concentration. In the case of lignite and Pittsburgh number8 chars, the rate-conversion pattern was similar during reaction with oxygen and CO/sub 2/. Adsorption experiments on partially reacted chars indicated that the micropores in the lignite char were accessible to both reactants. The micropores in the Illinois number6 char were, however, not accessible during its reaction with oxygen. The evolution of pore structure during reaction was modeled by using a probabilistic approach which accounts for overlapping pores with different shapes and sizes. The kinetics of gasification of the lignite and the Pittsburgh number8 chars was studied using a Langmuir-Hinshelwood type kinetic expression to correlate the experimental data. CO was found to inhibit the reaction substantially. The effect of a potassium carbonate catalyst on the reaction of these two chars was also investigated. Substantial increases in reaction rates were observed, and the enhancement was approximately proportional to the catalyst loading.
Reaction pathways of propene pyrolysis.
Qu, Yena; Su, Kehe; Wang, Xin; Liu, Yan; Zeng, Qingfeng; Cheng, Laifei; Zhang, Litong
The gas-phase reaction pathways in preparing pyrolytic carbon with propene pyrolysis have been investigated in detail with a total number of 110 transition states and 50 intermediates. The structure of the species was determined with density functional theory at B3PW91/6-311G(d,p) level. The transition states and their linked intermediates were confirmed with frequency and the intrinsic reaction coordinates analyses. The elementary reactions were explored in the pathways of both direct and the radical attacking decompositions. The energy barriers and the reaction energies were determined with accurate model chemistry method at G3(MP2) level after an examination of the nondynamic electronic correlations. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K for all the reaction steps were reported. Those at any temperature can be developed with classical thermodynamics by using the fitted (as a function of temperature) heat capacities. It was found that the most favorable paths are mainly in the radical attacking chain reactions. The chain was proposed with 26 reaction steps including two steps of the initialization of the chain to produce H and CH(3) radicals. For a typical temperature (1200 K) adopted in the experiments, the highest energy barriers were found in the production of C(3) to be 203.4 and 193.7 kJ/mol. The highest energy barriers for the production of C(2) and C were found 174.1 and 181.4 kJ/mol, respectively. These results are comparable with the most recent experimental observation of the apparent activation energy 201.9 +/- 0.6 or 137 +/- 25 kJ/mol. PMID:20082392
Integrin endosomal signalling suppresses anoikis
Alanko, Jonna; Mai, Anja; Jacquemet, Guillaume; Schauer, Kristine; Kaukonen, Riina; Saari, Markku; Goud, Bruno; Ivaska, Johanna
Integrin containing focal adhesions (FAs) transmit extracellular signals across the plasma membrane to modulate cell adhesion, signalling and survival. Although integrins are known to undergo continuous endo/exocytic traffic, potential impact of endocytic traffic on integrin-induced signals is unknown. Here, we demonstrate that integrin signalling is not restricted to cell-ECM adhesions and identify an endosomal signalling platform that supports integrin signalling away from the plasma membrane. We show that active focal adhesion kinase (FAK), an established marker of integrin-ECM downstream signalling, localises with active integrins on endosomes. Integrin endocytosis positively regulates adhesion-induced FAK activation, which is early endosome antigen-1 (EEA1) and small GTPase Rab21 dependent. FAK binds directly to purified endosomes and becomes activated on them, suggesting a role for endocytosis in enhancing distinct integrin downstream signalling events. Finally, endosomal integrin signalling contributes to cancer-related processes such as anoikis resistance, anchorage-independence and metastasis. Integrins are heterodimeric cell surface adhesion receptors functioning as integrators of the extra-cellular matrix (ECM) driven cues, the cellular cytoskeleton and the cellular signalling apparatus 1.Upon adhesion, integrins trigger the formation of plasma-membrane proximal large mechanosensing and signal-transmitting protein clusters depicted as "adhesomes" 2, 3. In addition, integrins undergo constant endocytic traffic to facilitate focal adhesion turnover, cell migration, invasion and cytokinesis 4. For other receptor systems it is well established that endocytic membrane traffic regulates bioavailability of cell-surface molecules and therefore the intensity and/or specificity of receptor-initiated signals 5, 6. Although active integrins and their ligands have been detected in endosomes 7–9 and increased integrin recycling to the plasma membrane contributes
Efficient signal transmission by synchronization through compound chaotic signal
NASA Astrophysics Data System (ADS)
Murali, K.; Lakshmanan, M.
The idea of synchronization of chaotic systems is further extended to the case where all the drive system variables are combined suitably to obtain a compound chaotic signal. An appropriate feedback loop is constructed in the response system to achieve synchronization among the variables of the drive and response systems. We apply this approach to transmit both analog and digital data signals in which the quality of the recovered signal is higher and the encoding is more secure.
Reactions in water: alkyl nitrile coupling reactions using Fenton's reagent.
Keller, Christopher L; Dalessandro, James D; Hotz, Richard P; Pinhas, Allan R
The coupling reaction of water-soluble alkyl nitriles using Fenton's reagent (Fe(II) and H2O2) is described. The best metal for the reaction is iron(II), and the greatest yields are obtained when the concentration of the metal is kept low. Hydrogen-atom abstraction is selective, preferentially producing the radical alpha to the nitrile. In order to increase the production of dinitrile, in situ reduction of iron(III) to iron(II), using a variety of reducing agents, was investigated. PMID:18363368
The principle of conformational signaling.
Tompa, Peter
Signal transduction is the primary process by which cells respond to changes in their physical and chemical environments. Cellular response is initiated through a signaling protein (a receptor), which interacts with the "signal", most often a novel molecule outside or inside the cell. The mechanism of activation of the receptor is a conformational change and/or covalent modification, which then sets in motion a signaling pathway, i.e. a cascade of modification and binding events that relay and amplify the message to eventually alter the state of the cell. In reflection of this general perception, concepts such as the "second messenger" and the "phosphorylation cascade" dominate our views of signal transduction. The idea I advocate here is that the non-covalent change in protein conformation itself might serve as the initial or intermittent "signal" in the cascade, and it is often the primary event being recognized and interpreted by downstream receptor(s). This signaling principle is intertwined with many other cellular regulatory concepts, such as (pathway) allostery, conformational spread, induced folding/unfolding, conformational memory, the hierarchical assembly of complexes, and the action of regulatory chaperones and prions. By elaborating on many examples and also recent advances in experimental methodology, I show that conformational signaling, although thus far underappreciated, is a general and robust signaling principle that most of the time operates in close interplay with covalent signals in the cell. PMID:27242242
Regulation of Hippo signalling by p38 signalling.
Huang, Dashun; Li, Xiaojiao; Sun, Li; Huang, Ping; Ying, Hao; Wang, Hui; Wu, Jiarui; Song, Haiyun
The Hippo signalling pathway has a crucial role in growth control during development, and its dysregulation contributes to tumorigenesis. Recent studies uncover multiple upstream regulatory inputs into Hippo signalling, which affects phosphorylation of the transcriptional coactivator Yki/YAP/TAZ by Wts/Lats. Here we identify the p38 mitogen-activated protein kinase (MAPK) pathway as a new upstream branch of the Hippo pathway. In Drosophila, overexpression of MAPKK gene licorne (lic), or MAPKKK gene Mekk1, promotes Yki activity and induces Hippo target gene expression. Loss-of-function studies show that lic regulates Hippo signalling in ovary follicle cells and in the wing disc. Epistasis analysis indicates that Mekk1 and lic affect Hippo signalling via p38b and wts We further demonstrate that the Mekk1-Lic-p38b cascade inhibits Hippo signalling by promoting F-actin accumulation and Jub phosphorylation. In addition, p38 signalling modulates actin filaments and Hippo signalling in parallel to small GTPases Ras, Rac1, and Rho1. Lastly, we show that p38 signalling regulates Hippo signalling in mammalian cell lines. The Lic homologue MKK3 promotes nuclear localization of YAP via the actin cytoskeleton. Upregulation or downregulation of the p38 pathway regulates YAP-mediated transcription. Our work thus reveals a conserved crosstalk between the p38 MAPK pathway and the Hippo pathway in growth regulation. PMID:27402810
Nonlocality in deuteron stripping reactions.
Timofeyuk, N K; Johnson, R C
We propose a new method for the analysis of deuteron stripping reactions, A(d,p)B, in which the nonlocality of nucleon-nucleus interactions and three-body degrees of freedom are accounted for in a consistent way. The model deals with equivalent local nucleon potentials taken at an energy shifted by ∼40 MeV from the "E(d)/2" value frequently used in the analysis of experimental data, where E(d) is the incident deuteron energy. The "E(d)/2" rule lies at the heart of all three-body analyses of (d, p) reactions performed so far with the aim of obtaining nuclear structure properties such as spectroscopic factors and asymptotic normalization coefficients that are crucial for our understanding of nuclear shell evolution in neutron- and proton-rich regions of the nuclear periodic table and for predicting the cross sections of stellar reactions. The large predicted shift arises from the large relative kinetic energy of the neutron and proton in the incident deuteron in those components of the n+p+A wave function that dominate the (d, p) reaction amplitude. The large shift reduces the effective d-A potentials and leads to a change in predicted (d, p) cross sections, thus affecting the interpretation of these reactions in terms of nuclear structure. PMID:25166525
Combustion kinetics and reaction pathways
Klemm, R.B.; Sutherland, J.W.
This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.
Thermal reactions of brushite cements.
Bohner, M; Gbureck, U
The thermal reactions of a brushite cement made of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and an aqueous solution were followed in situ with an isothermal calorimeter at 37 degrees C. The investigated parameters were the beta-TCP/MCPM weight ratio, the liquid-to-powder ratio, the synthesis route and milling duration of the beta-TCP powder, as well as the presence of sulfate, citrate, and pyrophosphate ions in the mixing liquid. The thermograms were complex, particularly for mixtures containing an excess of MCPM or additives in the mixing solution. Results suggested that the endothermic MCPM dissolution and the highly exothermic beta-TCP dissolution occurred simultaneously, thereby leading to the formation of a large exothermic peak at early reaction time. Both reactions were followed by the exothermic crystallization of brushite and in the presence of an excess of MCPM by the endothermic crystallization of monetite. Additives generally widened the main exothermic reaction peak, or in some cases with pyrophosphate ions postponed the main exothermic peak at late reaction time. Generally, the results could be well explained and understood based on thermodynamic and solubility data. PMID:17618509
[Recipients adverse reactions: guidance supports].
Bazin, A
Since 1994, adverse effects of transfusion transmitted to the French haemovigilance network are registered on "e-fit", the database of the French agency for the safety of health products (Afssaps). In order to improve their analysis, guidance supports have been made by Afssaps working groups. Each support deals with a blood transfusion side effect and is composed of five parts including pathophysiological mechanisms, diagnostic criteria, management recommendations, etiologic investigations and rules of filing the notification form on e-fit. The major characteristics of sheets published or soon-to-be published are presented: transfusion-related acute lung injury, transfusion-transmitted bacterial infection, non-haemolytic febrile reaction, allergic reaction, transfusion-associated circulatory overload, hypotensive transfusion reaction, alloimmunization, erythrocyte incompatibility reaction and hemosiderosis. These new supports give relevant guidelines allowing a better analysis and evaluation of recipients' adverse reactions, particularly their diagnosis, gravity and accountability. They could also initiate studies in European and international haemovigilance and transfusion networks. PMID:21051267
Studies of heavy-ion reactions and transuranic nuclei
NASA Astrophysics Data System (ADS)
Schroeder, W. U.
Papers on the following topics are included: The Cold-Fusion Saga; Decay Patterns of Dysprosium Nuclei Produced in S-32 + Sn-118,124 Fusion Reactions; Unexpected Features of Reactions Between Very Heavy Ions at Intermediate Bombarding Energies; Correlations Between Neutrons and Charged Products from the Dissipative Reaction Au-197 + Pb-208 at E/A = 29 MeV; Dissipative Dynamics of Projectile-Like Fragment Production in the Reaction Bi-209 + Xe-136 at E/A = 28.2 MeV; Dynamical Production of Intermediate-Mass Fragments in Peripheral Bi-209 + Xe-136 Collisions at E(sub lab)/A = 28.2 MeV; The Rochester 960-Liter Neutron Multiplicity Meter; A Simple Pulse Processing Concept for a Low-Cost Pulse-Shape-Based Particle Identification; A One-Transistor Preamplifier for PMT Anode Signals; A Five-Channel Multistop TDC/Event Handler for the SuperBall Neutron Multiplicity Meter; Construction of the SuperBall - a 16,000-Liter Neutron Detector for Calorimetric Studies of Intermediate-Energy Heavy-Ion Reactions; A Computer Code for Light Detection Efficiency Calculations for Photo-multipliers of a Neutron Detector; Evaluation of Gd-Loaded Liquid Scintillators for the SuperBall Neutron Calorimeter; and Measurement of the Interaction of Cosmic-Ray mu(-) with a Muon Telescope.
Signaling during Kidney Development.
Krause, Mirja; Rak-Raszewska, Aleksandra; Pietilä, Ilkka; Quaggin, Susan E; Vainio, Seppo
The kidney plays an essential role during excretion of metabolic waste products, maintenance of key homeostasis components such as ion concentrations and hormone levels. It influences the blood pressure, composition and volume. The kidney tubule system is composed of two distinct cell populations: the nephrons forming the filtering units and the collecting duct system derived from the ureteric bud. Nephrons are composed of glomeruli that filter the blood to the Bowman's capsule and tubular structures that reabsorb and concentrate primary urine. The collecting duct is a Wolffian duct-derived epithelial tube that concentrates and collects urine and transfers it via the renal pelvis into the bladder. The mammalian kidney function depends on the coordinated development of specific cell types within a precise architectural framework. Due to the availability of modern analysis techniques, the kidney has become a model organ defining the paradigm to study organogenesis. As kidney diseases are a problem worldwide, the understanding of mammalian kidney cells is of crucial importance to develop diagnostic tools and novel therapies. This review focuses on how the pattern of renal development is generated, how the inductive signals are regulated and what are their effects on proliferation, differentiation and morphogenesis. PMID:25867084
Li, Panyun; Zhang, Kai; Bao, Yuan; Ren, Yuqi; Ju, Zaiqiang; Wang, Yan; He, Qili; Zhu, Zhongzhu; Huang, Wanxia; Yuan, Qingxi; Zhu, Peiping
Microscopy techniques using visible photons, x-rays, neutrons, and electrons have made remarkable impact in many scientific disciplines. The microscopic data can often be expressed as the convolution of the spatial distribution of certain properties of the specimens and the inherent response function of the imaging system. The x-ray grating interferometer (XGI), which is sensitive to the deviation angle of the incoming x-rays, has attracted significant attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the comprehensive and analytical theoretical framework is yet to be presented. Herein, we propose a theoretical framework termed angular signal radiography (ASR) to describe the imaging process of the XGI system in a classical, comprehensive and analytical manner. We demonstrated, by means of theoretical deduction and synchrotron based experiments, that the spatial distribution of specimens' physical properties, including absorption, refraction and scattering, can be extracted by ASR in XGI. Implementation of ASR in XGI offers advantages such as simplified phase retrieval algorithm, reduced overall radiation dose, and improved image acquisition speed. These advantages, as well as the limitations of the proposed method, are systematically investigated in this paper. PMID:27136780
Purinergic signaling in epilepsy.
Rassendren, François; Audinat, Etienne
Until recently, analysis of the mechanisms underlying epilepsy was centered on neuron dysfunctions. Accordingly, most of the available pharmacological treatments aim at reducing neuronal excitation or at potentiating neuronal inhibition. These therapeutic options can lead to obvious secondary effects, and, moreover, seizures cannot be controlled by any known medication in one-third of the patients. A purely neurocentric view of brain functions and dysfunctions has been seriously questioned during the past 2 decades because of the accumulation of experimental data showing the functional importance of reciprocal interactions between glial cells and neurons. In the case of epilepsy, our current knowledge of the human disease and analysis of animal models clearly favor the involvement of astrocytes and microglial cells during the progression of the disease, including at very early stages, opening the way to the identification of new therapeutic targets. Purinergic signaling is a fundamental feature of neuron-glia interactions, and increasing evidence indicates that modifications of this pathway contribute to the functional remodeling of the epileptic brain. This Review discusses the recent experimental results indicating the roles of astrocytic and microglial P2X and P2Y receptors in epilepsy. © 2016 Wiley Periodicals, Inc. PMID:27302739
Signaling during Kidney Development
Krause, Mirja; Rak-Raszewska, Aleksandra; Pietilä, Ilkka; Quaggin, Susan E.; Vainio, Seppo
The kidney plays an essential role during excretion of metabolic waste products, maintenance of key homeostasis components such as ion concentrations and hormone levels. It influences the blood pressure, composition and volume. The kidney tubule system is composed of two distinct cell populations: the nephrons forming the filtering units and the collecting duct system derived from the ureteric bud. Nephrons are composed of glomeruli that filter the blood to the Bowman's capsule and tubular structures that reabsorb and concentrate primary urine. The collecting duct is a Wolffian duct-derived epithelial tube that concentrates and collects urine and transfers it via the renal pelvis into the bladder. The mammalian kidney function depends on the coordinated development of specific cell types within a precise architectural framework. Due to the availability of modern analysis techniques, the kidney has become a model organ defining the paradigm to study organogenesis. As kidney diseases are a problem worldwide, the understanding of mammalian kidney cells is of crucial importance to develop diagnostic tools and novel therapies. This review focuses on how the pattern of renal development is generated, how the inductive signals are regulated and what are their effects on proliferation, differentiation and morphogenesis. PMID:25867084
SUMO chains: polymeric signals.
Vertegaal, Alfred C O
Ubiquitin and ubiquitin-like proteins are conjugated to a wide variety of target proteins that play roles in all biological processes. Target proteins are conjugated to ubiquitin monomers or to ubiquitin polymers that form via all seven internal lysine residues of ubiquitin. The fate of these target proteins is controlled in a chain architecture-dependent manner. SUMO (small ubiquitin-related modifier) shares the ability of ubiquitin to form chains via internal SUMOylation sites. Interestingly, a SUMO-binding site in Ubc9 is important for SUMO chain synthesis. Similar to ubiquitin-polymer cleavage by USPs (ubiquitin-specific proteases), SUMO chain formation is reversible. SUMO polymers are cleaved by the SUMO proteases SENP6 [SUMO/sentrin/SMT3 (suppressor of mif two 3)-specific peptidase 6], SENP7 and Ulp2 (ubiquitin-like protease 2). SUMO chain-binding proteins including ZIP1, SLX5/8 (synthetic lethal of unknown function 5/8), RNF4 (RING finger protein 4) and CENP-E (centromere-associated protein E) have been identified that interact non-covalently with SUMO chains, thereby regulating target proteins that are conjugated to SUMO multimers. SUMO chains play roles in replication, in the turnover of SUMO targets by the proteasome and during mitosis and meiosis. Thus signalling via polymers is an exciting feature of the SUMO family. PMID:20074033
Steganography in arrhythmic electrocardiogram signal.
Edward Jero, S; Ramu, Palaniappan; Ramakrishnan, S
Security and privacy of patient data is a vital requirement during exchange/storage of medical information over communication network. Steganography method hides patient data into a cover signal to prevent unauthenticated accesses during data transfer. This study evaluates the performance of ECG steganography to ensure secured transmission of patient data where an abnormal ECG signal is used as cover signal. The novelty of this work is to hide patient data into two dimensional matrix of an abnormal ECG signal using Discrete Wavelet Transform and Singular Value Decomposition based steganography method. A 2D ECG is constructed according to Tompkins QRS detection algorithm. The missed R peaks are computed using RR interval during 2D conversion. The abnormal ECG signals are obtained from the MIT-BIH arrhythmia database. Metrics such as Peak Signal to Noise Ratio, Percentage Residual Difference, Kullback-Leibler distance and Bit Error Rate are used to evaluate the performance of the proposed approach. PMID:26736533
Requirements for signaling channel authentication
Tarman, T.D.
This contribution addresses requirements for ATM signaling channel authentication. Signaling channel authentication is an ATM security service that binds an ATM signaling message to its source. By creating this binding, the message recipient, and even a third party, can confidently verify that the message originated from its claimed source. This provides a useful mechanism to mitigate a number of threats. For example, a denial of service attack which attempts to tear-down an active connection by surreptitiously injecting RELEASE or DROP PARTY messages could be easily thwarted when authenticity assurances are in place for the signaling channel. Signaling channel authentication could also be used to provide the required auditing information for accurate billing which is impervious to repudiation. Finally, depending on the signaling channel authentication mechanism, end-to-end integrity of the message (or at least part of it) can be provided. None of these capabilities exist in the current specifications.
Hedgehog signaling in skin cancers
Li, Chengxin; Chi, Sumin; Xie, Jingwu
An increasing progress on the role of Hedgehog (Hh) signaling for carcinogenesis has been achieved since the link of Hh pathway to human cancer was firstly established. In particular, the critical role of Hh signaling in the development of Basal cell carcinoma (BCC) has been convincingly demonstrated by genetic mutation analyses, mouse models of BCCs, and successful clinical trials of BCCs using Hh signaling inhibitors. In addition, the Hh pathway activity is also reported to be involved in the pathogenesis of Squamous Cell Carcinoma (SCC), melanoma and Merkel Cell Carcinoma. These findings have significant new paradigm on Hh signaling transduction, its mechanisms in skin cancer and even therapeutic approaches for BCC. In this review, we will summarize the major advances in the understanding of Hh signaling transduction, the roles of Hh signaling in skin cancer development, and the current implications of "mechanism-based" therapeutic strategies. PMID:21397013
Algorithm evolution for signal understanding
Teller, A.
Automated program evolution has existed in some form for over thirty years. Signal understanding (e.g., signal classification) has been a scientific concern for even longer than that. Interest in generating, through machine learning techniques, a general signal understanding system is a newer topic, but has recently attracted considerable attention. First, I have proposed to define and create a machine learning mechanism for generating signal understanding systems independent of the signal`s type and size. Second, I have proposed to do this through an evolutionary strategy that is an extension of genetic programming. Third, I have proposed to introduce a suite of sub-mechanisms that not only contribute to the power of the thesis mechanism, but are also contributions to the understanding of the learning technique developed.
Calcium signalling remodelling and disease.
Berridge, Michael J
A wide range of Ca2+ signalling systems deliver the spatial and temporal Ca2+ signals necessary to control the specific functions of different cell types. Release of Ca2+ by InsP3 (inositol 1,4,5-trisphosphate) plays a central role in many of these signalling systems. Ongoing transcriptional processes maintain the integrity and stability of these cell-specific signalling systems. However, these homoeostatic systems are highly plastic and can undergo a process of phenotypic remodelling, resulting in the Ca2+ signals being set either too high or too low. Such subtle dysregulation of Ca2+ signals have been linked to some of the major diseases in humans such as cardiac disease, schizophrenia, bipolar disorder and Alzheimer's disease. PMID:22435804
A unified diabatic description for electron transfer reactions, isomerization reactions, proton transfer reactions, and aromaticity.
Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S
While diabatic approaches are ubiquitous for the understanding of electron-transfer reactions and have been mooted as being of general relevance, alternate applications have not been able to unify the same wide range of observed spectroscopic and kinetic properties. The cause of this is identified as the fundamentally different orbital configurations involved: charge-transfer phenomena involve typically either 1 or 3 electrons in two orbitals whereas most reactions are typically closed shell. As a result, two vibrationally coupled electronic states depict charge-transfer scenarios whereas three coupled states arise for closed-shell reactions of non-degenerate molecules and seven states for the reactions implicated in the aromaticity of benzene. Previous diabatic treatments of closed-shell processes have considered only two arbitrarily chosen states as being critical, mapping these states to those for electron transfer. We show that such effective two-state diabatic models are feasible but involve renormalized electronic coupling and vibrational coupling parameters, with this renormalization being property dependent. With this caveat, diabatic models are shown to provide excellent descriptions of the spectroscopy and kinetics of the ammonia inversion reaction, proton transfer in N2H7(+), and aromaticity in benzene. This allows for the development of a single simple theory that can semi-quantitatively describe all of these chemical phenomena, as well as of course electron-transfer reactions. It forms a basis for understanding many technologically relevant aspects of chemical reactions, condensed-matter physics, chemical quantum entanglement, nanotechnology, and natural or artificial solar energy capture and conversion. PMID:26193994
Surface reactions of natural glasses
White, A.F.
Reactions at natural glass surfaces are important in studies involving nuclear waste transport due to chemical control on ground water in host rocks such as basalt and tuff, to potential diffusion into natural hydrated glass surfaces and as natural analogs for waste glass stability. Dissolution kinetics can be described by linear surface reaction coupled with cation interdiffusion with resulting rates similar to those of synthetic silicate glasses. Rates of Cs diffusion into hydrated obsidian surfaces between 25{sup 0} and 75{sup 0}C were determined by XPS depth profiles and loss rates from aqueous solutions. Calculated diffusion coefficients were ten others of magnitude more rapid than predicted from an Arrhenius extrapolation of high temperature tracer diffusion data due to surface hydration reactions.
Catalytic, enantioselective, vinylogous aldol reactions.
Denmark, Scott E; Heemstra, John R; Beutner, Gregory L
In 1935, R. C. Fuson formulated the principle of vinylogy to explain how the influence of a functional group may be felt at a distant point in the molecule when this position is connected by conjugated double-bond linkages to the group. In polar reactions, this concept allows the extension of the electrophilic or nucleophilic character of a functional group through the pi system of a carbon-carbon double bond. This vinylogous extension has been applied to the aldol reaction by employing "extended" dienol ethers derived from gamma-enolizable alpha,beta-unsaturated carbonyl compounds. Since 1994, several methods for the catalytic, enantioselective, vinylogous aldol reaction have appeared, with which varying degrees of regio- (site), enantio-, and diastereoselectivity can be attained. In this Review, the current scope and limitations of this transformation, as well as its application in natural product synthesis, are discussed. PMID:15940727
Anaphylactoid reactions to radiocontrast media.
Canter, Lauren M
As the role for diagnostic and therapeutic contrast-enhanced imaging increases, review of the epidemiology, mechanisms, risk factors, and pretreatment for radiocontrast-mediated anaphylactoid reactions becomes more and more pertinent. Ongoing research has failed to elucidate the precise mechanisms of both early and late reactions, though the current data point to a multifactorial pathogenesis. The risk of reactions has decreased over time as contrast media have evolved from ionic, high-osmolality to nonionic, low-osmolality formulations; however, the expense of the low-osmolality agents limit their universal use. Today, 1-12% of patients exhibit adverse responses ranging from mild to severe, with individual risk depending on the type of contrast administered and certain baseline patient characteristics. For those high-risk patients who must receive contrast, effective pretreatment guidelines have been established. PMID:16119034
Spatial model of autocatalytic reactions
NASA Astrophysics Data System (ADS)
de Anna, Pietro; di Patti, Francesca; Fanelli, Duccio; McKane, Alan J.; Dauxois, Thierry
Biological cells with all of their surface structure and complex interior stripped away are essentially vesicles—membranes composed of lipid bilayers which form closed sacs. Vesicles are thought to be relevant as models of primitive protocells, and they could have provided the ideal environment for prebiotic reactions to occur. In this paper, we investigate the stochastic dynamics of a set of autocatalytic reactions, within a spatially bounded domain, so as to mimic a primordial cell. The discreteness of the constituents of the autocatalytic reactions gives rise to large sustained oscillations even when the number of constituents is quite large. These oscillations are spatiotemporal in nature, unlike those found in previous studies, which consisted only of temporal oscillations. We speculate that these oscillations may have a role in seeding membrane instabilities which lead to vesicle division. In this way synchronization could be achieved between protocell growth and the reproduction rate of the constituents (the protogenetic material) in simple protocells.
Reaction models in nuclear astrophysics
NASA Astrophysics Data System (ADS)
Descouvemont, Pierre
We present different reaction models commonly used in nuclear astrophysics, in particular for the nucleosynthesis of light elements. Pioneering works were performed within the potential model, where the internal structure of the colliding nuclei is completely ignored. Significant advances in microscopic cluster models provided the first microscopic description of the 3He(α,&gamma)7 Be reaction more than thirty years ago. In this approach, the calculations are based on an effective nucleon-nucleon interaction, but the cluster approximation should be made to simplify the calculations. Nowadays, modern microscopic calculations are able to go beyond the cluster approximation, and aim at finding exact solutions of the Schrödinger equation with realistic nucleon-nucleon interactions. We discuss recent examples on the d+d reactions at low energies.
Photonuclear reactions on titanium isotopes
Belyshev, S. S.; Dzhilavyan, L. Z.; Ishkhanov, B. S.; Kapitonov, I. M.; Kuznetsov, A. A. Orlin, V. N.; Stopani, K. A.
The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes {sup 47,48,49,50}Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes {sup 49,50}Ti.
Monitoring biochemical reactions using Y-cut quartz thermal sensors.
Ren, Kailiang; Kao, Ping; Pisani, Marcelo B; Tadigadapa, Srinivas
In this paper, we present a micromachined Y-cut quartz resonator based thermal sensor array which is configured with a reaction chamber that is physically separated but located in close proximity to the resonator for sensitive calorimetric biosensing applications. The coupling of heat from the reaction chamber to the quartz resonator is achieved via radiation and conduction through ambient gas. The sensor was packaged onto a 300 μm thick stainless plate with an opening in the middle. The sensor array was aligned to the opening and mounted from the underside of the plate. A reaction chamber designed for performing (bio)chemical reactions was used in the measurements. This configuration of the sensor allows for a very robust sensing platform with no fouling of the sensor surface or degradation in its performance metrics. Impedance-based tracking of resonance frequency was used for chemical, enzymatic, and cellular activity measurements. The sensor described has an impedance sensitivity of 852 Ω °C(-1) or a frequency sensitivity of 7.32 kHz °C(-1) for the 91 MHz resonator used in this work. Results on exothermic reaction between hydrochloric acid and ammonium hydroxide, the hydrolysis reaction of urea by urease and the catalytic reaction of glucose with glucose dehydrogenase are reported. From the signal to noise ratio analysis of the glucose sensor, <10 μM glucose sensitivity could be obtained improving the detection limit by a factor of 250 in comparison to our previous work using thermopile sensors. Finally, calcium ionophore induced cellular activity was measured in pancreatic cancer cells using the sensor. PMID:21655628
Unraveling reaction pathways and specifying reaction kinetics for complex systems.
Vinu, R; Broadbelt, Linda J
Many natural and industrial processes involve a complex set of competing reactions that include several different species. Detailed kinetic modeling of such systems can shed light on the important pathways involved in various transformations and therefore can be used to optimize the process conditions for the desired product composition and properties. This review focuses on elucidating the various components involved in modeling the kinetics of pyrolysis and oxidation of polymers. The elementary free radical steps that constitute the chain reaction mechanism of gas-phase/nonpolar liquid-phase processes are outlined. Specification of the rate coefficients of the various reaction families, which is central to the theme of kinetics, is described. Construction of the reaction network on the basis of the types of end groups and reactive moieties in a polymer chain is discussed. Modeling frameworks based on the method of moments and kinetic Monte Carlo are evaluated using illustrations. Finally, the prospects and challenges in modeling biomass conversion are addressed. PMID:22468596
Coupled Reactions "versus" Connected Reactions: Coupling Concepts with Terms
ERIC Educational Resources Information Center
Aledo, Juan Carlos
A hallmark of living matter is its ability to extract and transform energy from the environment. Not surprisingly, biology students are required to take thermodynamics. The necessity of coupling exergonic reactions to endergonic processes is easily grasped by most undergraduate students. However, when addressing the thermodynamic concept of…
EDITORIAL: Special section on signal transduction Special section on signal transduction
NASA Astrophysics Data System (ADS)
Shvartsman, Stanislav
This special section of Physical Biology focuses on multiple aspects of signal transduction, broadly defined as the study of the mechanisms by which cells communicate with their environment. Mechanisms of cell communication involve detection of incoming signals, which can be chemical, mechanical or electromagnetic, relaying these signals to intracellular processes, such as cytoskeletal networks or gene expression systems, and, ultimately, converting these signals to responses such as cell differentiation or death. Given the multiscale nature of signal transduction systems, they must be studied at multiple levels, from the identities and structures of molecules comprising signal detection and interpretation networks, to the systems-level properties of these networks. The 11 papers in this special section illustrate some of the most exciting aspects of signal transduction research. The first two papers, by Marie-Anne Félix [1] and by Efrat Oron and Natalia Ivanova [2], focus on cell-cell interactions in developing tissues, using vulval patterning in worm and cell fate specification in mammalian embryos as prime examples of emergent cell behaviors. Next come two papers from the groups of Julio Saez-Rodriguez [3] and Kevin Janes [4]. These papers discuss how the causal relationships between multiple components of signaling systems can be inferred using multivariable statistical analysis of empirical data. An authoritative review by Zarnitsyna and Zhu [5] presents a detailed discussion of the sequence of signaling events involved in T-cell triggering. Once the structure and components of the signaling systems are determined, they can be modeled using approaches that have been successful in other physical sciences. As two examples of such approaches, reviews by Rubinstein [6] and Kholodenko [7], present reaction-diffusion models of cell polarization and thermodynamics-based models of gene regulation. An important class of models takes the form of enzymatic networks
Synchronous Photodiode-Signal Sampler
NASA Technical Reports Server (NTRS)
Primus, Howard K.
Synchronous sampling circuit increases signal-to-noise ratio of measurements of chopped signal of known phase and frequency in presence of low-frequency or dc background noise. Used with linear array of photoelectric sensors for locating edge of metal plate. Multiplexing circuit cycles through 16 light-emitting-diode/photodiode pairs, under computer control. Synchronized with multiplexer so edge detector makes one background-subtracted signal measurement per emitter/detector pair in turn.
Reaction pathway for alkane dehydrocyclization
Shi, Buchang; Davis, B.H.
Naphtha reforming to produce high octane gasoline is an important process. Many reaction mechanisms are involved in this process. For example, the study of the fundamentals of this process led to the concept of bi- or poly-functional catalysis. The results of this study provide additional mechanistic information about the dehydrocyclization of an n-alkane to produce aromatics. The reaction coordinate diagram advanced to account for the observation of irreversible adsorption should be modified to account for the present results. 32 refs., 1 fig.
Learning to predict chemical reactions.
Kayala, Matthew A; Azencott, Chloé-Agathe; Chen, Jonathan H; Baldi, Pierre
Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles, respectively, are not high throughput, are not generalizable or scalable, and lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry data set consisting of 1630 full multistep reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top-ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of nonproductive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system
Some Concepts in Reaction Dynamics
NASA Astrophysics Data System (ADS)
Polanyi, John C.
The objective in this work has been one which I have shared with the two other 1986 Nobel lecturers in chemistry, D. R. Herschbach and Y. T. Lee, as well as with a wide group of colleagues and co-workers who have been responsible for bringing this field to its current state. That state is summarized in the title; we now have some concepts relevant to the motions of atoms and molecules in simple reactions, and some examples of the application of these concepts. We are, however, richer in vocabulary than in literature. The great epics of reaction dynamics remain to be written. I shall confine myself to some simple stories.
Learning to Predict Chemical Reactions
Kayala, Matthew A.; Azencott, Chloé-Agathe; Chen, Jonathan H.
Being able to predict the course of arbitrary chemical reactions is essential to the theory and applications of organic chemistry. Approaches to the reaction prediction problems can be organized around three poles corresponding to: (1) physical laws; (2) rule-based expert systems; and (3) inductive machine learning. Previous approaches at these poles respectively are not high-throughput, are not generalizable or scalable, or lack sufficient data and structure to be implemented. We propose a new approach to reaction prediction utilizing elements from each pole. Using a physically inspired conceptualization, we describe single mechanistic reactions as interactions between coarse approximations of molecular orbitals (MOs) and use topological and physicochemical attributes as descriptors. Using an existing rule-based system (Reaction Explorer), we derive a restricted chemistry dataset consisting of 1630 full multi-step reactions with 2358 distinct starting materials and intermediates, associated with 2989 productive mechanistic steps and 6.14 million unproductive mechanistic steps. And from machine learning, we pose identifying productive mechanistic steps as a statistical ranking, information retrieval, problem: given a set of reactants and a description of conditions, learn a ranking model over potential filled-to-unfilled MO interactions such that the top ranked mechanistic steps yield the major products. The machine learning implementation follows a two-stage approach, in which we first train atom level reactivity filters to prune 94.00% of non-productive reactions with a 0.01% error rate. Then, we train an ensemble of ranking models on pairs of interacting MOs to learn a relative productivity function over mechanistic steps in a given system. Without the use of explicit transformation patterns, the ensemble perfectly ranks the productive mechanism at the top 89.05% of the time, rising to 99.86% of the time when the top four are considered. Furthermore, the system
Vision 2020. Reaction Engineering Roadmap
Klipstein, David H.; Robinson, Sharon
The Reaction Engineering Roadmap is a part of an industry- wide effort to create a blueprint of the research and technology milestones that are necessary to achieve longterm industry goals. This report documents the results of a workshop focused on the research needs, technology barriers, and priorities of the chemical industry as they relate to reaction engineering viewed first by industrial use (basic chemicals; specialty chemicals; pharmaceuticals; and polymers) and then by technology segment (reactor system selection, design, and scale-up; chemical mechanism development and property estimation; dealing with catalysis; and new, nonstandard reactor types).
Reaction theory: Status and perspectives
NASA Astrophysics Data System (ADS)
Moro, A. M.; Gómez-Camacho, J.
The current status of the reaction theory of nuclear collisions involving weakly-bound exotic nuclei is presented. The problem is addressed within the Continuum Discretized Coupled Channel (CDCC) framework, recalling its foundations and applications, as well as its connection with the Faddeev formalism. Recent developments and improvements of the method, such as core and target excitations and the extension to three-body projectiles, are presented. The use of the CDCC wave function in the calculation of inclusive breakup reactions is also introduced.
Protein modules and signalling networks
NASA Astrophysics Data System (ADS)
Pawson, Tony
Communication between cells assumes particular importance in multicellular organisms. The growth, migration and differentiation of cells in the embryo, and their organization into specific tissues, depend on signals transmitted from one cell to another. In the adult, cell signalling orchestrates normal cellular behaviour and responses to wounding and infection. The consequences of breakdowns in this signalling underlie cancer, diabetes and disorders of the immune and cardiovascular systems. Conserved protein domains that act as key regulatory participants in many of these different signalling pathways are highlighted.
Chirp signal generator feasibility study
NASA Astrophysics Data System (ADS)
Chomiki, M.; Genauzeau, F.
The feasibility of a signal generator with 100 microsec temporal dispersion, and 330 MHz frequency dispersion, for the ERS-1 (ESA satellite) radar altimeter, with a solid state transmitter, is demonstrated. Two surface wave dispersive filters (20 and 80 microsec dispersion) are cascaded with a frequency multiplier to give a 900 MHz output signal. The first filter receives an impulse which ensures an output signal to noise ratio 20 dB. The chirp signal output level is 0 dBm; amplitude fluctuation 2 dBcc, phase error compared with theory 10 deg rms; short term jitter 100 psec. The generator model occupies 0.5 l, and consumes 7 W.
Amyloplast Distribution Directs a Root Gravitropic Reaction
NASA Astrophysics Data System (ADS)
Kordyum, Elizabeth
Immobile higher plants are oriented in the gravitational field due to gravitropim that is a physiological growth reaction and consists of three phases: reception of a gravitational signal by statocytes, its transduction to the elongation zone, and finally the organ bending. As it is known, roots are characterized with positive gravitropism, i. e. they grow in the direction of a gravitational vector, stems - with negative gravitropism, i. e. they grow in the direction opposite to a gravitational vector. According to the Nemec's and Haberlandt's starch-statolith hypothesis, amyloplasts in diameter of 1.5 - 3 μ in average, which appear to act as gravity sensors and fulfill a statolythic function in the specialized graviperceptive cells - statocytes, sediment in the direction of a gravitational vector in the distal part of a cell, while a nucleus is in the proximal one. There are reasonable data that confirm the amyloplasts-statoliths participation in gravity perception: 1) correlation between the statoliths localization and the site of gravity sensing, 2) significant redistribution (sedimentation) of amyloplasts in statocytes under gravistimulation in comparison with other cell organelles, 3) root decreased ability to react on gravity under starch removal from amyloplasts, 4) starchless Arabidopsis thaliana mutants are agravitropic, 5) amyloplasts-statoliths do not sediment in the absence of the gravitational vector and are in different parts or more concentrated in the center of statocytes. Plant tropisms have been intensively studied for many decades and continue to be investigated. Nevertheless, the mechanisms by which plants do so is still not clearly explained and many questions on gravisensing and graviresponse remain unanswered. Even accepted hypotheses are now being questioned and recent data are critically evaluated. Although the available data show the Ca2+ and cytoskeleton participation in graviperception and signal transduction, the clear evidence
Reactions and reaction intermediates on iron surfaces. III. Reactions of aldehydes and ketones on Fe(100)
Benziger, J.B.; Madix, R.J.
The reactions of formaldehyde, acetaldehyde, and acetone on Fe(100) were studied by temperature-programmed reaction spectroscopy and X-ray photoelectron spectroscopy (XPS). Formaldehyde and acetaldehyde were observed to react with adsorbed hydrogen to form adsorbed alkoxy intermediates. These reactions occurred at low temperature (ca. 200 K). In the absence of adsorbed hydrogen, formaldehyde and acetaldehyde decomposed to adsorbed CO and hydrogen. This reaction was also observed at low temperatures. On an initially clean surface the aldehydes first decomposed, forming adsorbed hydrogen which subsequently reacted with adsorbed aldehyde to form an alkoxy intermediate. The alkoxy intermediates reacted to form CO and H/sub 2/ primarily, with lesser amounts of alcohol, aldehyde, and hydrocarbon products. Acetone reacted differently from the aldehydes and did not appear to form an alkoxy intermediate. XPS results suggested that acetone and acetaldehyde did not adsorb in their keto form on the surface and it is suggested that they adsorbed as enol intermediates. The distinct reaction behavior of acetone may be due to these enol intermediates.
Recognition of a signal peptide by the signal recognition particle
Janda, Claudia Y.; Li, Jade; Oubridge, Chris; Hernández, Helena; Robinson, Carol V.; Nagai, Kiyoshi
Targeting of proteins to appropriate sub-cellular compartments is a crucial process in all living cells. Secretory and membrane proteins usually contain an N-terminal signal peptide, which is recognised by the signal recognition particle (SRP) when nascent polypeptide chains emerge from the ribosome. The SRP-ribosome nascent chain complex is then targeted through its GTP-dependent interaction with SRP-receptor to the protein-conducting channel on endoplasmic reticulum membrane in eukaryotes or plasma membrane in bacteria. A universally conserved component of SRP1, 2, SRP54 or its bacterial homolog, fifty-four homolog (Ffh), binds the signal peptides which have a highly divergent sequence divisible into a positively charged n-region, an h-region commonly containing 8-20 hydrophobic residues and a polar c-region 3-5. No structure has been reported that exemplified SRP54 binding of any signal sequence. We have produced a fusion protein between Sulfolobus solfataricus SRP54 and a signal peptide connected via a flexible linker. This fusion protein oligomerises in solution, through interaction between the SRP54 and signal peptide moieties belonging to different chains, and it is functional, able to bind SRP RNA and SRP-receptor FtsY. Here we present the crystal structure at 3.5 Å resolution of an SRP54-signal peptide complex in the dimer, which reveals how a signal sequence is recognised by SRP54. PMID:20364120
Enhanced reaction rates in NDP analysis with neutron scattering
Downing, R. Gregory
Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.
Neutron-induced reactions in the hohlraum to study reaction in flight neutrons
NASA Astrophysics Data System (ADS)
Boswell, M. S.; Elliott, S. R.; Guiseppe, V.; Kidd, M.; Rundberg, B.; Tybo, J.
We are currently developing the physics necessary to measure the Reaction In Flight (RIF) neutron flux from a NIF capsule. A measurement of the RIF neutron flux from a NIF capsule could be used to deduce the stopping power in the cold fuel of the NIF capsule. A foil irradiated at the Omega laser at LLE was counted at the LANL low-background counting facility at WIPP. The estimated production rate of 195Au was just below our experimental sensitivity. We have made several improvements to our counting facility in recent months. These improvements are designed to increase our sensitivity, and include installing two new low-background detectors, and taking steps to reduce noise in the signals.
Neutron-induced reactions in the hohlraum to study reaction in flight neutrons
Boswell, M. S.; Elliott, S. R.; Tybo, J.; Guiseppe, V.; Rundberg, B.; Kidd, M.
We are currently developing the physics necessary to measure the Reaction In Flight (RIF) neutron flux from a NIF capsule. A measurement of the RIF neutron flux from a NIF capsule could be used to deduce the stopping power in the cold fuel of the NIF capsule. A foil irradiated at the Omega laser at LLE was counted at the LANL low-background counting facility at WIPP. The estimated production rate of {sup 195}Au was just below our experimental sensitivity. We have made several improvements to our counting facility in recent months. These improvements are designed to increase our sensitivity, and include installing two new low-background detectors, and taking steps to reduce noise in the signals.
Computational functions in biochemical reaction networks.
Arkin, A; Ross, J
In prior work we demonstrated the implementation of logic gates, sequential computers (universal Turing machines), and parallel computers by means of the kinetics of chemical reaction mechanisms. In the present article we develop this subject further by first investigating the computational properties of several enzymatic (single and multiple) reaction mechanisms: we show their steady states are analogous to either Boolean or fuzzy logic gates. Nearly perfect digital function is obtained only in the regime in which the enzymes are saturated with their substrates. With these enzymatic gates, we construct combinational chemical networks that execute a given truth-table. The dynamic range of a network's output is strongly affected by "input/output matching" conditions among the internal gate elements. We find a simple mechanism, similar to the interconversion of fructose-6-phosphate between its two bisphosphate forms (fructose-1,6-bisphosphate and fructose-2,6-bisphosphate), that functions analogously to an AND gate. When the simple model is supplanted with one in which the enzyme rate laws are derived from experimental data, the steady state of the mechanism functions as an asymmetric fuzzy aggregation operator with properties akin to a fuzzy AND gate. The qualitative behavior of the mechanism does not change when situated within a large model of glycolysis/gluconeogenesis and the TCA cycle. The mechanism, in this case, switches the pathway's mode from glycolysis to gluconeogenesis in response to chemical signals of low blood glucose (cAMP) and abundant fuel for the TCA cycle (acetyl coenzyme A). Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 FIGURE 10 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 PMID:7948674
Correlation theory-based signal processing method for CMF signals
NASA Astrophysics Data System (ADS)
Shen, Yan-lin; Tu, Ya-qing
Signal processing precision of Coriolis mass flowmeter (CMF) signals affects measurement accuracy of Coriolis mass flowmeters directly. To improve the measurement accuracy of CMFs, a correlation theory-based signal processing method for CMF signals is proposed, which is comprised of the correlation theory-based frequency estimation method and phase difference estimation method. Theoretical analysis shows that the proposed method eliminates the effect of non-integral period sampling signals on frequency and phase difference estimation. The results of simulations and field experiments demonstrate that the proposed method improves the anti-interference performance of frequency and phase difference estimation and has better estimation performance than the adaptive notch filter, discrete Fourier transform and autocorrelation methods in terms of frequency estimation and the data extension-based correlation, Hilbert transform, quadrature delay estimator and discrete Fourier transform methods in terms of phase difference estimation, which contributes to improving the measurement accuracy of Coriolis mass flowmeters.
Specific features of vowel-like signals of white whales
NASA Astrophysics Data System (ADS)
Bel'Kovich, V. M.; Kreichi, S. A.
The set of acoustic signals of White-Sea white whales comprises about 70 types of signals. Six of them occur most often and constitute 75% of the total number of signals produced by these animals. According to behavioral reactions, white whales distinguish each other by acoustic signals, which is also typical of other animal species and humans. To investigate this phenomenon, signals perceived as vowel-like sounds of speech, including sounds perceived as a "bleat," were chosen A sample of 480 signals recorded in June and July, 2000, in the White Sea within a reproductive assemblage of white whales near the Large Solovetskii Island was studied. Signals were recorded on a digital data carrier (a SONY minidisk) in the frequency range of 0.06 20 kHz. The purpose of the study was to reveal the perceptive and acoustic features specific to individual animals. The study was carried out using the methods of structural analysis of vocal speech that are employed in lingual criminalistics to identify a speaking person. It was demonstrated that this approach allows one to group the signals by coincident perceptive and acoustic parameters with assigning individual attributes to single parameters. This provided an opportunity to separate conditionally about 40 different sources of acoustic signals according to the totality of coincidences, which corresponded to the number of white whales observed visually. Thus, the application of this method proves to be very promising for the acoustic identification of white whales and other marine mammals, this possibility being very important for biology.
Stochastic signaling in biochemical cascades and genetic systems in genetically engineered living cells.
Daniel, Ramiz; Almog, Ronen; Shacham-Diamand, Yosi
Living cells, either prokaryote or eukaryote, can be integrated within whole-cell biochips (WCBCs) for various applications. We investigate WCBCs where information is extracted from the cells via a cascade of biochemical reactions that involve gene expression. The overall biological signal is weak due to small sample volume, low intrinsic cell response, and extrinsic signal loss mechanisms. The low signal-to-noise ratio problem is aggravated during initial detection stages and limits the minimum detectable signal or, alternatively, the minimum detection time. Taking into account the stochastic nature of biochemical process, we find that the signal is accompanied by relatively large noise disturbances. In this work, we use genetically engineered microbe sensors as a model to study the biochips output signal stochastic behavior. In our model, the microbes are designed to express detectable reporter proteins under external induction. We present analytical approximated expressions and numerical simulations evaluating the fluctuations of the synthesized reporter proteins population based on a set of equations modeling a cascade of biochemical and genetic reactions. We assume that the reporter proteins decay more slowly than messenger RNA molecules. We calculate the relation between the noise of the input signal (extrinsic noise) and biochemical reaction statistics (intrinsic noise). We discuss in further details two cases: (1) a cascade with large decay rates of all biochemical reactions compared to the protein decay rate. We show that in this case, the noise amplitude has a positive linear correlation with the number of stages in the cascade. (2) A cascade which includes a stable enzymatic-binding reaction with slow decay rate. We show that in this case, the noise strongly depends on the protein decay rate. Finally, a general observation is presented stating that the noise in whole-cell biochip sensors is determined mainly by the first reactions in the genetic system
Stochastic signaling in biochemical cascades and genetic systems in genetically engineered living cells
NASA Astrophysics Data System (ADS)
Daniel, Ramiz; Almog, Ronen; Shacham-Diamand, Yosi
Living cells, either prokaryote or eukaryote, can be integrated within whole-cell biochips (WCBCs) for various applications. We investigate WCBCs where information is extracted from the cells via a cascade of biochemical reactions that involve gene expression. The overall biological signal is weak due to small sample volume, low intrinsic cell response, and extrinsic signal loss mechanisms. The low signal-to-noise ratio problem is aggravated during initial detection stages and limits the minimum detectable signal or, alternatively, the minimum detection time. Taking into account the stochastic nature of biochemical process, we find that the signal is accompanied by relatively large noise disturbances. In this work, we use genetically engineered microbe sensors as a model to study the biochips output signal stochastic behavior. In our model, the microbes are designed to express detectable reporter proteins under external induction. We present analytical approximated expressions and numerical simulations evaluating the fluctuations of the synthesized reporter proteins population based on a set of equations modeling a cascade of biochemical and genetic reactions. We assume that the reporter proteins decay more slowly than messenger RNA molecules. We calculate the relation between the noise of the input signal (extrinsic noise) and biochemical reaction statistics (intrinsic noise). We discuss in further details two cases: (1) a cascade with large decay rates of all biochemical reactions compared to the protein decay rate. We show that in this case, the noise amplitude has a positive linear correlation with the number of stages in the cascade. (2) A cascade which includes a stable enzymatic-binding reaction with slow decay rate. We show that in this case, the noise strongly depends on the protein decay rate. Finally, a general observation is presented stating that the noise in whole-cell biochip sensors is determined mainly by the first reactions in the genetic system
Runaway Reaction: Solving for X.
ERIC Educational Resources Information Center
Bartz, Solveig A.
This article examines the runaway reaction as it was displayed by Barry, a 14-year-old eighth-grade boy with learning disabilities. It identifies some of the common characteristics of this response and proposes school intervention methods. Functional behavioral assessments and strength-based assessments are encouraged, along with using strategy…
Teachers' Reactions to Children's Aggression
ERIC Educational Resources Information Center
Nesdale, Drew; Pickering, Kaye
Drawing on social schema theory (Fiske & Taylor, 1991) and social identity theory (Tajfel & Turner, 1979), this study examined the impact on teachers' reactions to children's aggression of three variables, two of which were related to the aggressors and one was related to the teachers. Experienced female elementary school teachers (N=90) each read…
Severe immediate reaction to nabumetone.
Gonzalo-Garijo, M A; Cordobés-Duran, C; Lamilla-Yerga, A M; Moreno-Gastón, I
Nabumetone is a nonsteroidal antiinflammatory (NSAID) prodrug that inhibits cyclooxygenase-2. It has been recommended as a safe alternative in most patients with hypersensitivity reactions to NSAIDs. Systemic reactions caused by nabumetone are not frequent. We report 2 cases of immediate systemic reactions due to nabumetone. The first case involved a 68-year-old woman who developed immediate generalized pruritus, erythema, morbilliform eruption, swollen tongue sensation, diarrhea, and hypotension after the ingestion of a single dose of nabumetone. In the second case, a 77-year-old woman developed generalized pruritus, palm erythema, colic abdominal pain, diarrhea, dizziness, tightness of the chest, dyspnea, and hypotension immediately after oral intake of nabumetone. Both patients had previously tolerated this drug. Since these episodes, they have avoided nabumetone. Skin prick tests with nabumetone (10 and 100 mg/mL) were negative. Oral challenge tests with other NSAIDs, even of the same group as nabumetone, were negative in both patients. The mechanisms responsible for the reaction were not established. PMID:17694703
Reactions to threatening health messages
Background Threatening health messages that focus on severity are popular, but frequently have no effect or even a counterproductive effect on behavior change. This paradox (i.e. wide application despite low effectiveness) may be partly explained by the intuitive appeal of threatening communication: it may be hard to predict the defensive reactions occurring in response to fear appeals. We examine this hypothesis by using two studies by Brown and colleagues, which provide evidence that threatening health messages in the form of distressing imagery in anti-smoking and anti-alcohol campaigns cause defensive reactions. Methods We simulated both Brown et al. experiments, asking participants to estimate the reactions of the original study subjects to the threatening health information (n = 93). Afterwards, we presented the actual original study outcomes. One week later, we assessed whether this knowledge of the actual study outcomes helped participants to more successfully estimate the effectiveness of the threatening health information (n = 72). Results Results showed that participants were initially convinced of the effectiveness of threatening health messages and were unable to anticipate the defensive reactions that in fact occurred. Furthermore, these estimates did not improve after participants had been explained the dynamics of threatening communication as well as what the effects of the threatening communication had been in reality. Conclusions These findings are consistent with the hypothesis that the effectiveness of threatening health messages is intuitively appealing. What is more, providing empirical evidence against the use of threatening health messages has very little effect on this intuitive appeal. PMID:23171445
Knoevenagel Reaction of Unprotected Sugars
NASA Astrophysics Data System (ADS)
Scherrmann, Marie-Christine
The Knoevenagel reaction of unprotected sugars was investigated in the 1950s using zinc chloride as promoter. The so-called Garcia Gonzalez reaction had been almost forgotten for 50 years, until the emergence of new water tolerant catalysts having Lewis acid behavior. The reaction was thus reinvestigated and optimal conditions have been found to prepare trihydroxylated furan derivatives from pentose or β-tetrahydrofuranylfuran from hexoses with non-cyclic β-keto ester or β-diketones. Other valuable compounds such as β-linked tetrahydrobenzofuranyl glycosides or hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione can be obtained using cyclic β-dicarbonylic derivatives. Apart from one report in the 1950s, the Knoevenagel reaction of unprotected carbohydrate in basic condition has been studied only in the mid-1980s to prepare C-glycosyl barbiturates from barbituric acids and, later on, from non-cyclic β-diketones, β-C-glycosidic ketones. The efficient method exploited to prepare such compounds has found an industrial development in cosmetics.
Adverse drug reactions in dermatology.
Ferner, R E
Adverse drug reactions (ADRs) - that is, unintended and harmful responses to medicines - are important to dermatologists because many present with cutaneous signs and because dermatological treatments can cause serious ADRs. The detection of ADRs to new drugs is often delayed because they have a long latency or are rare or unexpected. This means that ADRs to newer agents emerge only slowly after marketing. ADRs are part of the differential diagnosis of unusual rashes. A good drug history that includes details of drug dose, time-course of the reaction and factors that may make the patient more susceptible, will help. For example, Stevens-Johnson syndrome with abacavir is much commoner in patients with HLA-B*5701, and has a characteristic time course. Newer agents have brought newer reactions; for example, acneiform rashes associated with epidermal growth factor receptor inhibitors such as erlotinib. Older systemic agents used to treat skin disease, including corticosteroids and methotrexate, cause important ADRs. The adverse effects of newer biological agents used in dermatology are becoming clearer; for example, hypersensitivity reactions or loss of efficacy from antibody formation and progressive multifocal leucoencephalopathy due to reactivation of latent JC (John Cunningham) virus infections during efalizumab treatment. Unusual or serious harm from medicines, including ADRs, medication errors and overdose, should be reported. The UK Yellow Card scheme is online, and patients can report their own ADRs. PMID:25622648
Severe allergic reaction to Dermabond.
Perry, Arthur W; Sosin, Michael
The use of 2-octyl cyanoacrylate (Dermabond; Ethicon, Somerville, NJ) for wound closure is increasingly popular. Problems with Dermabond are generally related to application techniques and rarely relate to the chemical nature of the adhesive. This article describes a severe allergic reaction to Dermabond following breast augmentation/mastopexy. PMID:19717065
The Pitfalls of Precipitation Reactions.
ERIC Educational Resources Information Center
Slade, Peter W.; Rayner-Canham, Geoffrey W.
Described are some of the difficulties presented in these reactions by competing equilibria that are usually ignored. Situations involving acid-base equilibria, solubility product calculations, the use of ammonia as a complexing agent, and semiquantitative comparisons of solubility product values are discussed. (CW)