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Method of barrier voltages in cyclic accelerators
NASA Astrophysics Data System (ADS)
Principle of operation of barrier RF voltage systems that are used for stacking and acceleration of charged particles in proton synchrotrons and storage rings is presented. The description is based on two sample models of such systems: with rectangular and quasi-sinusoidal barriers. Two different methods are used for description of particle dynamics in synchrotrons with barrier RF voltage. The first method is "stepwise" analysis of particle motion in the "momentum-phase" space. This method allows to give a clear and simple description of physical principles of the method and to obtain its main properties in analytical form. However, this method is not always efficient. Therefore, a method of analysis of phase motion of particles in barrier systems based on solution of differential equations of phase motion is presented in the paper and is widely used in practice. This method allows both analytical calculations and numeric simulation, which is illustrated with the aid of supplied examples.
Meshkov, I. N.
Exposure to stallion accelerates the onset of mares' cyclicity.
Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses. PMID:24815602
Wespi, B; Sieme, H; Wedekind, C; Burger, D
Accelerated kinetics and mechanism of growth of boride layers on titanium under isothermal and cyclic diffusion
NASA Astrophysics Data System (ADS)
The tendency of titanium (Ti) and its alloys to wear, gall and seize during high contact stresses between sliding surfaces severely limits their applications in bearings, gears etc. One way to mitigate these problems is to modify their surfaces by applying hard and wear resistant surface coatings. Boriding, which involves solid state diffusion of boron (B) into Ti, thereby forming hard surface layers consisting of TiB2 and TiB compounds has been shown to produce extremely high wear resistant surfaces in Ti and its alloys. The growth kinetics of these layers are, however, limited by the low diffusivities of B in the high melting TiB2 and TiB compounds. On the basis of the fact that HCP metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the first hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of B atoms, thereby accelerating the growth of the hard boride layers. Isothermal boriding experiments were performed close to phase transition temperature (890, 910, and 915�C) for time periods ranging from 3 to 24 hours. It was found that indeed a much deeper growth of TiB into the Ti substrate (�75 mum) occurred at temperatures very close to the transition temperature (910�C), compared to that obtained at 1050�C. A diffusion model based on error-function solutions of Fick's second law was developed to quantitatively illustrate the combined effects of the normal B diffusion in the TiB phase and the anomalous B diffusion in Ti phase in accelerating TiB layer growth. Furthermore, isothermal boriding experiments close to transition temperature (900�C) for a period of 71 hours resulted in coating thickness well above 100 mum, while at 1050�C, the layer growth saturated after about 24 hours of treatment time. In the second part of this work, a novel approach named "cyclic-phase-changediffusion, (CPCD)," to create deeper TiB2 and TiB coating layers on CP-Ti by cyclic thermal processing, has been investigated. It was found that thermal cyclic B diffusion in Ti across the alpha(alpha)-beta(beta) phase transition temperature led to highly hardened surface layers enriched with TiB whiskers that grow to depths exceeding 120 mum. By solving the transient heat transport problem for cyclic changes in surface temperatures, it was found that there is a "heat-packet" that travels back and forth from the surface to the interior of the material. This heat-packet appears to transport B dissolved in beta-Ti into interior causing increased coating depths.
Sarma, Biplab
e-/e+ Accelerating Structure with Cyclic Variation of Azimuth Asymmetry
A classical electron/positron accelerating structure is a disk-loaded cylindrical waveguide. The accelerator structure here has azimuth symmetry. The proposed structure contains a disk-loaded cylindrical waveguide where there is a periodical change of RF-field vs. azimuth. The modulation deforms the rf-field in such a manner that the accelerated particles undergo transverse focusing forces. The new class of accelerator structures covers the initial part of e+/e- linacs where a bunch is not rigid and additional transverse focusing fields are necessary. We discuss a bunch formation with a high transverse aspect ratio in the proposed structure and particularly in the photoinjector part of a linac.
Krasnykh, A.; /SLAC
Daily Exposure to Di(2-ethylhexyl) Phthalate Alters Estrous Cyclicity and Accelerates Primordial Follicle Recruitment Potentially Via Dysregulation of the Phosphatidylinositol 3-Kinase Signaling Pathway in Adult Mice.
Humans are exposed daily to di(2-ethylhexyl) phthalate (DEHP), a plasticizer found in many consumer, medical, and building products containing polyvinyl chloride. Large doses of DEHP disrupt normal ovarian function; however, the effects of DEHP at environmentally relevant levels, the effects of DEHP on folliculogenesis, and the mechanisms by which DEHP disrupts ovarian function are unclear. The present study tested the hypothesis that relatively low levels of DEHP disrupt estrous cyclicity as well as accelerate primordial follicle recruitment by dysregulating phosphatidylinositol 3-kinase (PI3K) signaling. Adult CD-1 mice were orally dosed with DEHP (20 ?g/kg/day-750 mg/kg/day) daily for 10 and 30 days. Following dosing, the effects on estrous cyclicity were examined, and follicle numbers were histologically quantified. Further, the ovarian mRNA and protein levels of PI3K signaling factors that are associated with early folliculogenesis were quantified. The data indicate that 10- and 30-day exposure to DEHP prolonged the duration of estrus and accelerated primordial follicle recruitment. Specifically, DEHP exposure decreased the percentage of primordial follicles and increased the percentage of primary follicles counted following 10-day exposure and increased the percentage of primary follicles counted following 30-day exposure. DEHP exposure, at doses that accelerate folliculogenesis, increased the levels of 3-phosphoinositide-dependent protein kinase-1, mammalian target of rapamycin complex 1, and protein kinase B and decreased the levels of phosphatase and tensin homolog, potentially driving PI3K signaling. Collectively, relatively low levels of DEHP disrupt estrous cyclicity and accelerate primordial follicle recruitment potentially via a mechanism involving dysregulation of PI3K signaling. PMID:24804967
Hannon, Patrick R; Peretz, Jackye; Flaws, Jodi A
Alterations in collagen fiber crimp morphology with accelerated cyclic loading and transvalvular pressure fixation in porcine aortic valves
It is known that changes in the collagen fiber orientation of porcine bioprosthetic heart valves (PBHV) occur with (i) cyclic loading and (ii) fixation pressure. These changes correlate to alterations in biaxial extensibility, as reported by Wells et al. (2002). It is hypothesized that the increased collagen fiber alignment detected by small angle light scattering in (i) and (ii) is
G. J. Fulchiero; S. M. Wells; M. S. Sacks
NSDL National Science Digital Library
What is the purpose of particle accelerators? On this web page, part of a particle physics tutorial, students read that accelerators solve two problems. The accelerators provide an increase in momentum to produce particles of small wavelength, and the fast-moving particles can create new particles when smashed together. A photograph of the inside of a particle accelerator is provided. Copyright 2005 Eisenhower National Clearinghouse
Group, Lawrence B.
The paper proposes a digital compensation by imposing real-time compensation voltage to Vin Pin of VCOXCO while device vibrating. The embedded digital compensating circuit includes a MEMS three-axes acceleration sensor, a FPGA and a D\\/A converter. G-sensitivity vector can be computed based on the MEMS sensor. A proportion digital compensation model is built to generate voltage which can compensate frequency
QingXiao Shan; Yang Jun; JianYun Chen; Tang Qian; LongZhe Ji
Making Ends Meet: Microwave-Accelerated Synthesis of Cyclic and Disulfide Rich Proteins Via In Situ Thioesterification and Native Chemical Ligation.
The development of synthetic methodologies for cyclic peptides is driven by the discovery of cyclic peptide drug scaffolds such as the plant-derived cyclotides, sunflower trypsin inhibitor 1 (SFTI-1) and the development of cyclized conotoxins. Currently, the native chemical ligation reaction between an N-terminal cysteine and C-terminal thioester group remains the most robust method to obtain a head-to-tail cyclized peptide. Peptidyl thioesters are effectively generated by Boc SPPS. However, their generation is challenging using Fmoc SPPS because thioester linkers are not stable to repeated piperidine exposure during deprotection. Herein we describe a Fmoc-based protocol for synthesizing cyclic peptides adapted for microwave assisted solid phase peptide synthesis. The protocol relies on the linker Di-Fmoc-3,4-diaminobenzoic acid, and we demonstrate the use of Gly, Ser, Arg and Ile as C-terminal amino acids (using HBTU and HATU as coupling reagents). Following synthesis, an N-acylurea moiety is generated at the C-terminal of the peptide; the resin bound acylurea peptide is then deprotected and cleaved from the resin. The fully deprotected peptide undergoes thiolysis in aqueous buffer, generating the thioester in situ. Ultimately, the head-to-tail cyclized peptide is obtained via native chemical ligation. Two naturally occurring cyclic peptides, the prototypical M�bius cyclotide kalata B1 and SFTI-1 were synthesized efficiently, avoiding potential branching at the diamino linker, using the optimized protocol. In addition, we demonstrate the possibility to use the approach for the synthesis of long and synthetically challenging linear sequences, by the ligation of two truncated fragments of a 50-residue long plant defensin. PMID:23504256
Gunasekera, Sunithi; Aboye, Teshome L; Madian, Walid A; El-Seedi, Hesham R; G�ransson, Ulf
Accelerated atmospheric corrosion testing using a cyclic wet/dry exposure test; Galvanic couples of aluminum with graphite neoprene rubber, galvanized steel, and steel
Aluminum corrosion is important in overhead electrical conductors constructed from aluminum wire centrally reinforced by galvanized steel strands. Inspection of conductor after long service has implicated rubber bushing material, on the outside, and the galvanized strands, on the inside, as providing potential galvanic sites for the initiation of rapid aluminum corrosion. Therefore, the galvanic corrosion of aluminum in contact with graphite-loaded neoprene rubber, hot-dip galvanized steel and steel was assessed in a cyclic wet/dry exposure test using mixed-salts spray solutions containing appropriate ratios of sulfate and chloride ion. Aluminum was found to corrode at between 3 to 6 times its uncoupled rate when associated with the rubber material. While the eta-phase, relatively pure Zn, galvanized layer remained intact, galvanic corrosion of aluminum was slow. However, on exposure of the zeta-phase, Zn/Fe intermetallic layer, aluminum corroded about 35 times faster than expected in a solution with a high level of Cl{sup -} ion. The importance of these data to conductor lifetime is discussed.
Lyon, S.B.; Thompson, G.E.; Johnson, J.E.; Wood, G.C. (Manchester Univ. (UK). Inst. of Science and Technology); Ferguson, J.M. (Central Electricity Generating Board, Guildford (UK))
Enumeration of Cyclic Graphs and Cyclic Designs.
National Technical Information Service (NTIS)
The close relationship of cyclic graphs and cyclic designs is pointed out and used in the enumeration of cyclic graphs. An explicit formula is given for graphs with a prime number of vertices and a general constructive method of enumeration is developed. ...
H. A. David
Low Perturbation Electron Injector for Cyclic Accelerators.
National Technical Information Service (NTIS)
This invention relates to transporting electron beams without disturbance, and more particularly to a means of transporting an electron beam across magnetic field lines without adding much perpendicular velocity to the electrons. Discussed is a tapered z-...
F. Mako W. Manheimer C. A. Kapetanokos F. Sandel
Molecular Biology: Cyclic Nucleotides.
National Technical Information Service (NTIS)
The Cancergram concerns the role of cyclic nucleotides and their derivatives in a wide variety of cellular processes in neoplastic cells and tissues, and related studies in normal cell systems which contribute to an understanding of cyclic nucleotide meta...
Molecular Biology: Cyclic Nucleotides.
National Technical Information Service (NTIS)
The Cancergram concerns the role of cyclic nucleotides and their derivatives in a wide variety of cellular processes in neoplastic cells and tissues, and related studies in normal cell systems which contribute to an understanding of cyclic nucleotide meta...
Beyond Inflation: A Cyclic Universe Scenario
NSDL National Science Digital Library
Inflation is typically seen in current Big Bang models of the universe, however this paper proposes a cyclic universe without high energy inflation. It proposes that the universe lived in a long attractor state that is determined by the laws of physics. The universe is made homogenouse and flat and scale-invariant adiabatic pertubations are generated through an epoch of low energy acceleration.
Turok, Neil; Steinhardt, Paul
Cosmic evolution in a cyclic universe
NASA Astrophysics Data System (ADS)
Based on concepts drawn from the ekpyrotic scenario and M theory, we elaborate our recent proposal of a cyclic model of the universe. In this model, the universe undergoes an endless sequence of cosmic epochs which begin with the universe expanding from a ``big bang'' and end with the universe contracting to a ``big crunch.'' Matching from ``big crunch'' to ``big bang'' is performed according to the prescription recently proposed with Khoury, Ovrut and Seiberg. The expansion part of the cycle includes a period of radiation and matter domination followed by an extended period of cosmic acceleration at low energies. The cosmic acceleration is crucial in establishing the flat and vacuous initial conditions required for ekpyrosis and for removing the entropy, black holes, and other debris produced in the preceding cycle. By restoring the universe to the same vacuum state before each big crunch, the acceleration ensures that the cycle can repeat and that the cyclic solution is an attractor.
Steinhardt, Paul J.; Turok, Neil
We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We also provide an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392 GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.
Whittum, David H.; Tantawi, Sami G.
Finite element forced vibration analysis of rotating cyclic structures
NASA Technical Reports Server (NTRS)
A capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axes of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical development of this capability is presented.
Elchuri, V.; Smith, G. C. C.
No Arithmetic Cyclic Quadrilaterals
ERIC Educational Resources Information Center
A quadrilateral is arithmetic if its area is an integer and its sides are integers in an arithmetic progression, and it is cyclic if it can be inscribed in a circle. The author shows that no quadrilateral is both arithmetic and cyclic.
Beauregard, Raymond A.
The cyclic universe model is a modification of the ekpyrotic universe and the pyrotechnic universe models. The cyclic universe goes through the six transitions: the triplet universe, the inflation, the big bang, the quintessence, the big crush, and the deflation transitions. The universe starts with eleven dimensional space-time with two boundary 9-branes separated by a finite gap spanning an intervening
Ding-Yu Chung
ERIC Educational Resources Information Center
The cyclical nature of mathematics grades was studied for a cohort of elementary school students from a large metropolitan school district in Texas over six years (average cohort size of 8495). The study used an autoregressive integrated moving average (ARIMA) model. Results indicate that grades do exhibit a significant cyclical pattern. (SLD)
Adams, Gerald J.; Dial, Micah
ERIC Educational Resources Information Center
Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction�
Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.
A cyclic control stick of the type used in helicopters for reducing the safety hazards associated with such a mechanism in the event of a crewman being thrown violently into contact with the cyclic control stick resulting from a crash or the like. The cyclic control stick is configured to break away upon the exertion of an impact force which exceeds a predetermined value and/or is exerted for more than a momentary time duration. The cyclic control stick is also configured to be adjustable so as to locate the grip thereof as far away from the crewman as possible for safety reasons without comprising the comfort of the crewman or the use of the control stick, and a crushable pad is provided on the top of the grip for impact energy absorbing purposes.
Whitaker, Charles N. (2834 S. Extension Rd., No. 2024, Mesa, AZ 85202); Zimmermann, Richard E. (425 E. Greenway, Tempe, AZ 85282)
In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as ekpyrotic and cyclic models. We show that the inflationary flow equations are invariant under the duality and therefore apply equally well to inflation or to cyclic cosmology. We construct a self-consistent small-parameter approximation dual to the slow-roll approximation in inflation, and calculate the power spectrum of perturbations in this limit. We also recover the matter-dominated contracting solution of Wands, and the recently proposed adiabatic ekpyrosis solution.
Kinney, William H.; Dizgah, Azadeh Moradinezhad [Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260-1500 (United States)
Cyclic networks of quantum gates
In this paper initial steps in an analysis of cyclic networks of quantum logic gates will be given. Cyclic networks are those in which the qubit lines are loops. In our investigations of cyclic networks of quantum gates we have studied one- and two-qubit systems plus two-qubit systems connected to another qubit on an acyclic line. The analysis includes classifying networks into groups, the dynamics of the qubits in the cyclic network, and the perturbation effects of an acyclic qubit acting on a cyclic network of quantum gates. This will be followed by a discussion on quantum algorithms and quantum information processing with cyclic networks of quantum gates. An implementation of a cyclic network quantum memory and quantum sensors via cyclic networks will also be discussed.
Cabauy, Peter [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA (United States); Applied Physics Department, University of Michigan, Ann Arbor, Michigan 48109, USA (United States); Benioff, Paul [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA (United States)
Cyclic and chronic neutropenia.
Patients with severe chronic neutropenia have blood neutrophil level <0.5 � 10(9)/L, predisposing them to increased susceptibility to life-threatening bacterial infections. This chapter focuses on cyclic and congenital neutropenia, two very interesting and rare hematological conditions causing severe chronic neutropenia. Both disorders respond well to treatment with the myeloid growth factor, granulocyte colony-stimulating factor (G-CSF). This chapter describes the basic features of these diseases and addresses several current clinical issues regarding their diagnosis and management. Cyclic neutropenia is a rare, inherited autosomal dominant disorder due to mutations in the gene for neutrophil elastase (ELA-2 or ELANE). Usually these patients have regular oscillation of blood neutrophil counts with periods of severe neutropenia occurring every 21 days. During these periods, they have painful mouth ulcers, fevers, and bacterial infections. The most severe consequences are gangrene, bacteremia, and septic shock. Cyclic neutropenia patients respond well to treatment with granulocyte colony-stimulating factor (G-CSF) given by subcutaneous injections on a daily or alternate-day basis. Severe congenital neutropenia is also a rare hematological disease, but it is probably more common than cyclic neutropenia. Blood neutrophils are extremely low on a continuing basis; the levels may be <0.2 � 10(9)/L, and the risk of severe bacterial infections is even greater than in cyclic neutropenia. The majority of cases are due to autosomal dominant inheritance of mutations in the ELA-2 or ELANE gene. Less commonly, mutations in HAX-1, G6PC3, and other genes cause this disorder. Treatment with G-CSF is usually effective, but the dose of G-CSF required to normalize blood neutrophils varies greatly. Ten to thirty percent of severe congenital neutropenia patients evolve to develop acute myeloid leukemia, necessitating careful clinical monitoring. PMID:21052952
Dale, David C; Welte, Karl
Turnaround in cyclic cosmology.
It is speculated how dark energy in a brane world can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model is described, in which dark energy with w<-1 equation of state leads to a turnaround at a time, extremely shortly before the would-be big rip, at which both volume and entropy of our Universe decrease by a gigantic factor, while very many independent similarly small contracting universes are spawned. The entropy of our model decreases almost to zero at turnaround but increases for the remainder of the cycle by a vanishingly small amount during contraction, empty of matter, then by a large factor during inflationary expansion. PMID:17359014
Baum, Lauris; Frampton, Paul H
NASA Astrophysics Data System (ADS)
An extension of a basic model, initially made for sand modeling is developed with the object of using it for clays. The formal principles of elastoplasticity as well as the origin of plasticity surface forms that are commonly used for soils are reviewed. This basic model was applied to study the behavior of clay by cyclic torsion experiments. The results show that it is not possible to reproduce dilatancy appearance in undrained cyclic experiments if the clay is normally consolidated. An analysis on how to introduce a Cam-Clay type closed surface into the basic model is given. The consolidation mechanisms as well as the deviatoric mechanisms of the proposed model extension are described. The identification process of the parameters for the proposed model is summarized. An analytical process of identification from drained and undrained experiments is given. The analysis of the simulation results conducted is included.
Dubujet, Philippe
NASA Astrophysics Data System (ADS)
In this work, which is a supplemental to previous one, we undertake to establish some cosmological thermodynamic equations in the context of the cyclical universe as the scenario in which the universe itself is considered like an adiabatic thermodynamical system enclosed in physical volume characterized by periodic reversible transitions. Our model is based on the combination of local and global cosmological time-dependent temperatures { T 0( ? 0), T( ?)} and volumes { V 0( ? 0), V( ?)} instead of the critical temperature T c and volume V c; and the infinitesimal relative variations { dT/ T, dV/ V}, which are mainly due to the cosmological chaotic fluctuations that are generally ignored in certain oscillating models. By taking into account all these factors, certain equations in the form of d ?/ ?=� ? d ?/ ? H have been established and from them we derive some others to provide a mechanism that is responsible for the thermodynamic evolution of the cyclical universe.
Hassani, Mohamed E.
Metallo-supramolecular cyclic polymers.
Cyclic brush polymers represent an exciting new macromolecular topology. For the first time, this new topology has been combined with metallo-supramolecular interactions to construct novel cyclic brush polymers. Here, ring-expansion metathesis polymerization was used to synthesize a universal cyclic template with a polynorbornene backbone, which was further modified with the metal-chelating synthon terpyridine. The terpyridine side chains served as the key supramolecular unit for the creation of cyclic polymer brushes and gels. This metallo-supramolecular functionality allowed direct visualization of the cyclic brush polymers by transmission electron microscopy for the first time. This demonstration should open a new area in which supramolecular interactions are used to build an array of novel cyclic brush copolymers as well as other cyclic-polymer-based architectures generating new materials. PMID:23930776
Zhang, Ke; Zha, Yongping; Peng, Bo; Chen, Yongming; Tew, Gregory N
Can Accelerators Accelerate Learning?
The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ)[1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.
Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil, Caixa Postal 68528, 21941-972 (Brazil)
National Technical Information Service (NTIS)
The accelerator has potential applications in aerodynamic testing, as a source of high-speed plasma for research and as a propulsion system for space vehicles. The accelerator is capable of steady flow operation. The arrangement includes an accelerating c...
G. P. Wood A. F. Carter A. Busemann
Method of controlling cyclic variation in engine combustion
Cyclic variation in combustion of a lean burning engine is reduced by detecting an engine combustion event output such as torsional acceleration in a cylinder (i) at a combustion event (k), using the detected acceleration to predict a target acceleration for the cylinder at the next combustion event (k+1), modifying the target output by a correction term that is inversely proportional to the average phase of the combustion event output of cylinder (i) and calculating a control output such as fuel pulse width or spark timing necessary to achieve the target acceleration for cylinder (i) at combustion event (k+1) based on anti-correlation with the detected acceleration and spill-over effects from fueling. 27 figs.
Davis, L.I. Jr.; Daw, C.S.; Feldkamp, L.A.; Hoard, J.W.; Yuan, F.; Connolly, F.T.
Computer simulation of cyclic oxidation
NASA Technical Reports Server (NTRS)
A computer program has been developed which simulates the cyclic oxidation behavior of materials. The simulation is based on the assumption that the weight fraction of scale that spalls in any thermal cycle is proportional to the amount of scale present on the surface at the beginning of the cycle. The program provides plots as well as tabular data which describe the cyclic oxidation behavior of a given material. Individual input parameters can be selectively altered and the resulting change in cyclic kinetics determined, allowing the user to quickly survey a wide range of cyclic conditions on the kinetics of a given material.
Probst, H. B.; Lowell, C. E.
GAF Domains: Cyclic Nucleotides Come Full Circle
NSDL National Science Digital Library
Cyclic nucleotides are ubiquitous signaling molecules that are present in life forms ranging from bacteria to yeast to humans. In higher eukaryotes, conserved molecular machinery processes signals through both cyclic adenosine monophosphate (AMP) and cyclic guanosine monophosphate (GMP). Hurley describes how one widespread cyclic nucleotide recognition module, the GAF (cyclic GMP, adenylyl cyclase, FhlA) domain, formerly thought to bind only cyclic GMP, has now been found to bind cyclic AMP as well. Recent structural analysis of a cyclic GMP-binding GAF domain shows how conserved elements among the cyclic nucleotide-binding subgroup of GAF domains recognize the common chemical moieties in the two compounds.
James H. Hurley (National Institutes of Health;Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases REV)
Cyclic Configurations of Pentagon Linkages
We investigate cyclic configurations of planar polygon and relate them to the topology of moduli space of the corresponding polygonal linkage. The main attention is given to quadrilateral and pentagon linkages. For a nondegenerate quadrilateral linkage, we prove that cyclic configurations are critical points of the signed area function on moduli space and their number is determined by the topology
Eka Elerdashvili; Mamuka Jibladze; Giorgi Khimshiashvili
The effects of aging on the cyclic stress-strain behavior and hysteresis loop evolution of lead free solders
Solder joints in electronic assemblies are typically subjected to thermal cycling, either in actual application or in accelerated life testing used for qualification. Mismatches in the thermal expansion coefficients of the assembly materials leads to the solder joints being subjected to cyclic (positive\\/negative) mechanical strains and stresses. This cyclic loading leads to thermomechanical fatigue damage that involves damage accumulation, crack
Muhannad Mustafa; Zijie Cai; Jeffrey C. Suhling; Pradeep Lall
Synthesis and properties of cyclic acetal biomaterials.
There is an increasing need to develop new biomaterials as tissue engineering scaffolds. Unfortunately, many of the materials that have been studied for these purposes are polyesters that hydrolytically degrade into acidic products, which may harm the surrounding tissue, and lead to accelerated degradation of the biomaterial. To overcome this disadvantage, a novel class of biomaterials based on a cyclic acetal unit has been created. Specifically, materials based upon the monomer 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) is examined. This study investigates the effects of fabrication parameters, including initiator content, volume of diluent, and volume of accelerant, on several properties of EHD networks. Twelve different formulations were fabricated by varying the three parameters in a factorial design. The effects of the fabrication parameters on properties of the EHD networks were examined. Results show that the volume of accelerant most affected the EHD network gelation time, while the volume of diluent most affected the maximum reaction temperature, sol fraction, and degree of swelling. Cell viability on the EHD networks varied between (18 +/- 6)% and (57 +/- 10)% of the control at 4 h, and between (36 +/- 14)% and (140 +/- 50)% of the control at 8 h. These results indicate that it is possible to control the properties of the EHD networks by varying the fabrication parameters, and that EHD networks support a viable cell population. PMID:17177269
Moreau, Jennifer L; Kesselman, Dafna; Fisher, John P
NASA Astrophysics Data System (ADS)
A summary of the accelerator topics (CW electron accelerators, heavy ion colliders, kaon factories, polarized proton beams, and cooling rings) discussed in the 1984 conference on ``Intersections Between Particle and Nuclear Physics'' (Steamboat Springs) is presented. (AIP)
Mills, F. E.
A summary of the accelerator topics (CW electron accelerators, heavy ion colliders, kaon factories, polarized proton beams, and cooling rings) discussed in the 1984 conference on ''Intersections Between Particle and Nuclear Physics'' (Steamboat Springs) is presented. (AIP)
Mills, F.E.
I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.
John Womersley
NASTRAN forced vibration analysis of rotating cyclic structures
NASA Technical Reports Server (NTRS)
Theoretical aspects of a new capability developed and implemented in NASTRAN level 17.7 to analyze forced vibration of a cyclic structure rotating about its axis of symmetry are presented. Fans, propellers, and bladed shrouded discs of turbomachines are some examples of such structures. The capability includes the effects of Coriolis and centripetal accelerations on the rotating structure which can be loaded with: (1) directly applied loads moving with the structure and (2) inertial loas due to the translational acceleration of the axis of rotation (''base' acceleration). Steady-state sinusoidal or general periodic loads are specified to represent: (1) the physical loads on various segments of the complete structure, or (2) the circumferential harmonic components of the loads in (1). The cyclic symmetry feature of the rotating structure is used in deriving and solving the equations of forced motion. Consequently, only one of the cyclic sectors is modelled and analyzed using finite elements, yielding substantial savings in the analysis cost. Results, however, are obtained for the entire structure. A tuned twelve bladed disc example is used to demonstrate the various features of the capability.
Elchuri, V.; Smith, G. C. C.; Gallo, A. M.
Cyclic Amplification of Prion Protein Misfolding
Protein Misfolfing Cyclic amplification (PMCA) is a technique that take advantage of the nucleation-dependent prion replication process to accelerate the conversion of PrPC into PrPSc in the test tube. PMCA uses ultrasound waves to fragment the PrPSc polymers, increasing the amount of seeds present in the infected sample without affecting their ability to act as conversion nucleus. Over the past 5 years PMCA has became an invaluable technique to study diverse aspects of prions. The PMCA technology has been used by several groups to understand the molecular mechanism of prion replication, the cellular factors involved in prion propagation, the intriguing phenomena of prion strains and species barriers, to detect PrPSc in tissues and biological fluids and to screen for inhibitors against prion replication. In this article we describe a detailed protocol of the PMCA technique, highlighting some of the important technical aspects to obtain a successful and reproducible application of the technology.
Barria, Marcelo A; Gonzalez-Romero, Dennisse; Soto, Claudio
Computer Simulation Of Cyclic Oxidation
NASA Technical Reports Server (NTRS)
Computer model developed to simulate cyclic oxidation of metals. With relatively few input parameters, kinetics of cyclic oxidation simulated for wide variety of temperatures, durations of cycles, and total numbers of cycles. Program written in BASICA and run on any IBM-compatible microcomputer. Used in variety of ways to aid experimental research. In minutes, effects of duration of cycle and/or number of cycles on oxidation kinetics of material surveyed.
Probst, H. B.; Lowell, C. E.
Cyclic spectral analysis in practice
NASA Astrophysics Data System (ADS)
This paper addresses the spectral analysis of cyclostationary (CS) signals from a generic point of view, with the aim to provide the practical conditions of success in a wide range of applications, such as in mechanical vibrations and acoustics. Specifically, it points out the similarities, differences and potential pitfalls associated with cyclic spectral analysis as opposed to classical spectral analysis. It is shown that non-parametric cyclic spectral estimators can all be derived from a general quadratic form, which yields as particular cases "cyclic" versions of the smoothed, averaged, and multitaper periodograms. The performance of these estimators is investigated in detail on the basis of their frequency resolution, cyclic leakage, systematic and stochastic estimation errors. The results are then extended to more advanced spectral quantities such as the cyclic coherence function and the Wigner-Ville spectrum of CS signals. In particular an optimal estimator of the Wigner-Ville spectrum is found, with remarkable properties. Several examples of cyclic spectral analyses, with an emphasis on mechanical systems, are finally presented in order to illustrate the value of such a general treatment for practical applications.
Antoni, J�r�me
Five cases of cyclical Cushing's syndrome
Reported cases of cyclical Cushing's syndrome are rare. Of 14 successive patients with Cushing's syndrome nine collected sequential urine samples for the estimation of cortisol:creatinine ratio. Five had cyclical Cushing's syndrome while two had considerable variation in urinary cortisol excretion without a cyclical pattern being established. Two of the five patients with a cyclical syndrome had paradoxical responses to dexamethasone.
A B Atkinson; A L Kennedy; D J Carson; D R Hadden; J A Weaver; B Sheridan
Cyclic nucleotide phosphodiesterases in pancreatic islets
Cyclic nucleotide phosphodiesterases (PDEs) comprise a family of enzymes (PDE1-PDE11) which hydrolyse cyclic AMP and cyclic GMP to their biologically inactive 5 derivatives. Cyclic AMP is an important physiological amplifier of glucose-induced insulin secretion. As PDEs are the only known mechanism for inactivating cyclic nucleotides, it is important to characterise the PDEs present in the pancreatic islet beta cells. Several
N. J. Pyne; B. L. Furman
Cyclic vomiting syndrome: treatment options.
Cyclic vomiting syndrome is a disorder characterized by recurrent episodes of severe nausea and vomiting separated by symptom-free periods. Our aims were to review treatments of adult cyclic vomiting syndrome as well as to identify areas for further clinical research and the unanswered questions in this field. We conducted a PubMed search using such keywords as "cyclic vomiting syndrome," "nausea," "vomiting," "treatment," "trigger factors" and "tricyclic antidepressants" and combined this information with the knowledge and clinical research from the authors. Available data show that in adult cyclic vomiting syndrome, there is an impressive and sustained response to high-dose tricyclic antidepressants. In up to 13�% who are regarded as poor responders to tricyclic antidepressants, a predictable profile can be identified related to coexisting psychological disorders, marijuana use, poorly controlled migraine headache or chronic narcotic use. Cyclic vomiting syndrome in adults is being an increasingly recognized entity. Tricyclic antidepressants are the main treatment for controlling symptoms. Eliminating and addressing trigger factors are an essential part of management. PMID:24862509
Hejazi, Reza A; McCallum, Richard W
3':5'Cyclic AMP and Hormonal Control of Puparium Formation in the Fleshfly Sarcophaga bullata
Injection of 3':5'-cyclic AMP (cAMP) into larvae of the fly Sarcophaga bullata 3-4 hr before the beginning of puparium formation (red-spiracle stage) greatly accelerates the onset of tanning without affecting initiation of puparium formation (anterior retraction). Accelerated tanning resembles real tanning in two important respects: the solubility of cuticular proteins becomes reduced and [U-14C]tyrosine is incorporated into the cuticle. Of
G. Fraenkel; Ann Blechl; James Blechl; Paul Herman; Morris I. Seligman
Note on Fast Cyclic Convolution.
National Technical Information Service (NTIS)
The note presents a new algorithm for computing the cyclic convolution of two vectors over a commutative ring. The algorithm requires n((n sub 1)+1)...((n sub k)+1)/(2 to the kth power) multiplications for the convolution of two n-vectors, where n=(n sub ...
Y. Zalcstein
Color visualization of cyclic magnitudes
NASA Astrophysics Data System (ADS)
We exploit the perceptual, circular ordering of the hues in a technique for the visualization of cyclic variables. The hue is thus meaningfully used for the indication of variables such as the azimuth and the units of the measurement of time. The cyclic (or circular) variables may be both of the continuous type or the discrete type; among the first there is azimuth and among the last you find the musical notes and the days of the week. A correspondence between the values of a cyclic variable and the chromatic hues, where the natural circular ordering of the variable is respected, is called a color code for the variable. We base such a choice of hues on an assignment of of the unique hues red, yellow, green and blue, or one of the 8 even permutations of this ordered list, to 4 cardinal values of the cyclic variable, suitably ordered; color codes based on only 3 cardinal points are also possible. Color codes, being intuitive, are easy to remember. A possible low accuracy when reading instruments that use this technique is compensated by fast, ludic and intuitive readings; also, the use of a referential frame makes readings precise. An achromatic version of the technique, that can be used by dichromatic people, is proposed.
Restrepo, Alfredo; Estupi��n, Viviana
Cyclic pelvic pain and dysmenorrhea.
Primary dysmenorrhea, secondary dysmenorrhea, and cyclic pelvic pain syndromes represent a special subset of CPP. Although more common and no less debilitating, these conditions are better understood, more easily diagnosed, and more successfully treated than chronic pain states. It should be the expectation of both the physician and the patient that successful resolution of these complaints is possible. PMID:8115089
Smith, R P
From Calculus to Cyclic Cohomology.
National Technical Information Service (NTIS)
The main object of this talk is to point out how homology theory arose, in a perfectly natural way, from the calculus, and to trace the main thread of ideas which led, about a hundred years later, to the consideration of its cyclic variants. Also, motivat...
K. S. Sarkaria
Nonlinear, Nonbinary Cyclic Group Codes.
National Technical Information Service (NTIS)
New cyclic group codes of length 2(exp m) - 1 over (m - j)-bit symbols are introduced. These codes can be systematically encoded and decoded algebraically. The code rates are very close to Reed-Solomon (RS) codes and are much better than Bose-Chaudhuri-Ho...
G. Solomon
NSDL National Science Digital Library
The Podcast: Acceleration is a segment of the Force and Motion Short Course. The podcast is 2 minutes 13 seconds in duration. Presented by science experts and NSTA staff, the NSTA Online Short Courses are professional development opportunities de
Sequencing cyclic peptides by multistage mass spectrometry.
Some of the most effective antibiotics (e.g. Vancomycin and Daptomycin) are cyclic peptides produced by non-ribosomal biosynthetic pathways. While hundreds of biomedically important cyclic peptides have been sequenced, the computational techniques for sequencing cyclic peptides are still in their infancy. Previous methods for sequencing peptide antibiotics and other cyclic peptides are based on Nuclear Magnetic Resonance spectroscopy, and require large amount (miligrams) of purified materials that, for most compounds, are not possible to obtain. Recently, development of MS-based methods has provided some hope for accurate sequencing of cyclic peptides using picograms of materials. In this paper we develop a method for sequencing of cyclic peptides by multistage MS, and show its advantages over single-stage MS. The method is tested on known and new cyclic peptides from Bacillus brevis, Dianthus superbus and Streptomyces griseus, as well as a new family of cyclic peptides produced by marine bacteria. PMID:21751357
Mohimani, Hosein; Yang, Yu-Liang; Liu, Wei-Ting; Hsieh, Pei-Wen; Dorrestein, Pieter C; Pevzner, Pavel A
Sequencing Cyclic Peptides by Multistage Mass Spectrometry
Some of the most effective antibiotics (e.g., Vancomycin and Daptomycin) are cyclic peptides produced by non-ribosomal biosynthetic pathways. While hundreds of biomedically important cyclic peptides have been sequenced, the computational techniques for sequencing cyclic peptides are still in their infancy. Previous methods for sequencing peptide antibiotics and other cyclic peptides are based on Nuclear Magnetic Resonance spectroscopy, and require large amount (miligrams) of purified materials that, for most compounds, are not possible to obtain. Recently, development of mass spectrometry based methods has provided some hope for accurate sequencing of cyclic peptides using picograms of materials. In this paper we develop a method for sequencing of cyclic peptides by multistage mass spectrometry, and show its advantages over single stage mass spectrometry. The method is tested on known and new cyclic peptides from Bacillus brevis, Dianthus superbus and Streptomyces griseus, as well as a new family of cyclic peptides produced by marine bacteria.
Mohimani, Hosein; Yang, Yu-Liang; Liu, Wei-Ting; Hsieh, Pei-Wen; Dorrestein, Pieter C.; Pevzner, Pavel A.
Cyclic polygons with rational sides and area
We generalise the notion of Heron triangles to rational-sided, cyclic n-gons with rational area using Brahmagupta's formula for the area of a cyclic quadrilateral and Robbins' formul� for the area of cyclic pentagons and hexagons. We use approximate techniques to explore rational area n-gons for n greater than six. Finally, we produce a method of generating non-Eulerian rational area cyclic
Ralph H. Buchholz; James A. MacDougall
40 CFR 721.2120 - Cyclic amide.
Code of Federal Regulations, 2010 CFR
...2009-07-01 2009-07-01 false Cyclic amide. 721.2120 Section 721.2120...Specific Chemical Substances § 721.2120 Cyclic amide. (a) Chemical substance and...The chemical substance identified as a cyclic amide (PMN P-92-131) is...
Robust tracking of cyclic nonrigid motion
Cyclic motion underlies several human activities including exercising,running, and walking. Accurate tracking of such motion in video data helps in developing computer-aided applications such as gait analysis, person identification, pa- tient rehabilitation, etc. This paper presents a set of novel techniques for tracking cyclic human motion based on de- composing complex cyclic motion into simpler motion com- ponents and introducing
Cheng Chang; Rashid Ansari; Ashfaq A. Khokhar
Collective Focusing Ion Accelerator
NASA Astrophysics Data System (ADS)
The principal subject of this dissertation is the trapping and confinement of pure electron plasmas in bumpy toroidal magnetic fields, with particular attention given to the trapping procedure and the behavior of the plasma during the final equilibrium. The most important aspects of the equilibrium which were studied were the qualitative nature of the plasma configuration and motion and its density, distribution, and stability. The motivation for this study was that an unneutralized cloud of electrons contained in a toroidal system, sufficiently dense and stable, may serve to electrostatically focus ions (against centrifugal and self space-charge forces) in a cyclic ion accelerator. Such an accelerator, known as a Collective Focusing Ion Accelerator (C.F.I.A.), could be far smaller than conventional designs (which use external magnetic fields directly to focus the ions) due to the smaller gyro-radius of an electron in a magnetic field of given strength. A toroidal electric field, induced by a changing magnetic flux, would accelerate the ions. To prevent the electrons from being accelerated and shorting out this field (and possibly instigating a two-stream instability), the strength of the toroidal magnetic field which contains the electrons is given spacial periodicity in the toroidal direction. Suitably prepared electrons will not circulate toroidally in such a "bumpy" field due to the mirror effect of the field maxima. These experiments, then, have involved essentially independent electron clouds contained within the magentic "cells" formed by the bumpy field. Supporting experiments performed in a linear mirror system eliminated the complexity of the gradient inherent in a toroidal field and admitted experiments not possible in a torus. These included performing measurements on electrons ejected out one end. Technical developments in injection were also carried out in this simpler system. The electron cloud generally drifted poloidally at a finite radius from the toroidal minor axis. As this would preclude focusing ions with such clouds, damping this motion was investigated. Finite resistance in the normally perfectly conductive vessel wall did this. In further preparation for a working C.F.I.A., additional experiments studied the effect of ions on the stability of the electron cloud.
Goldin, Fletcher Joshua
Cyclic AMP signaling in trypanosomatids.
Curative interference with signal transduction pathways is a spectacularly successful concept in many domains of modern pharmacology; indeed, the 'wonder drug' Viagra is but a humble inhibitor of a cyclic GMP (cGMP)-specific phosphodiesterase and, thus, interferes with cGMP-signaling in a strategic organ. In fact, about half of the 100 most successful drugs currently on the market act through modulating cellular signal transduction. Despite these encouraging findings, signal transduction pathways as potential drug targets in trypanosomatids have remained largely unexplored. However, what little is known indicates that adenylyl cyclases of trypanosomatids, and probably other enzymes of the cyclic nucleotide signaling pathways, are significantly different from their mammalian counterparts. Here, Christina Naula and Thomas Seebeck summarize what is known about cAMP signal transduction in trypanosomatids. PMID:10637587
Naula, C; Seebeck, T
Long Memory in Cyclical Fluctuations
Conventional macroeconomic theory treats output fluctuations as merely transitory deviations around a deterministic pattern, the natural output trend. From such a perspective, output fluctuations can only be short-lived, thus giving economic shocks no lasting impact on long-term output. A rescaled range (R\\/S) approach is used in the context of cyclical fluctuations to explore these fluctuations. The analysis extends to other
Ali Abderrezak
Cyclic volume changes in rubber
The present paper deals with the volume variation in filled crystallizable natural (F-NR) and uncrystallizable styrene-butadiene (F-SBR) rubbers subjected to cyclic loadings. During their deformation, such materials exhibit volume variation induced by the cavitation phenomenon and the decohesion between particles and the rubber matrix. In this study, we propose to measure this volume variation over the first mechanical cycles by
J.-B. Le Cam; E. Toussaint
Solidphase synthesis of cyclic polyamines
A method for the synthesis of cyclic polyamines based on solid-phase chemistry is shown. Linear polyamines are stepwise synthesized on solid support from the center by repetitive alkylations at benzylic N-atoms. Cyclizations at the resins were effected conventionally by direct intramolecular SN2 reactions between sulfonyl-protected terminal amino groups and primary alkyl bromides or by intramolecular Mitsunobu reactions between sulphonamides and
Pascal Bisegger; Nikolay Manov; Stefan Bienz
NASA Technical Reports Server (NTRS)
Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.
Rogers, Melissa J. B.
Cyclic Game Dynamics Driven by Iterated Reasoning
Recent theories from complexity science argue that complex dynamics are ubiquitous in social and economic systems. These claims emerge from the analysis of individually simple agents whose collective behavior is surprisingly complicated. However, economists have argued that iterated reasoning�what you think I think you think�will suppress complex dynamics by stabilizing or accelerating convergence to Nash equilibrium. We report stable and efficient periodic behavior in human groups playing the Mod Game, a multi-player game similar to Rock-Paper-Scissors. The game rewards subjects for thinking exactly one step ahead of others in their group. Groups that play this game exhibit cycles that are inconsistent with any fixed-point solution concept. These cycles are driven by a �hopping� behavior that is consistent with other accounts of iterated reasoning: agents are constrained to about two steps of iterated reasoning and learn an additional one-half step with each session. If higher-order reasoning can be complicit in complex emergent dynamics, then cyclic and chaotic patterns may be endogenous features of real-world social and economic systems.
Frey, Seth; Goldstone, Robert L.
Protein misfolding cyclic amplification of infectious prions
Prions are proteinaceous infectious agents responsible for the transmission of prion diseases. The lack of a procedure for cultivating prions in the laboratory has been a major limitation to the study of the unorthodox nature of this infectious agent and the molecular mechanism by which the normal prion protein (PrPC) is converted into the abnormal isoform (PrPSc). Protein misfolding cyclic amplification (PMCA ), described in detail in this protocol, is a simple, fast and efficient methodology to mimic prion replication in the test tube. PMCA involves incubating materials containing minute amounts of infectious prions with an excess of PrPC and boosting the conversion by cycles of sonication to fragment the converting units, thereby leading to accelerated prion replication. PMCA is able to detect the equivalent of a single molecule of infectious PrPSc and propagate prions that maintain high infectivity, strain properties and species specificity. A single PMCA assay takes little more than 3 d to replicate a large amount of prions, which could take years in an in vivo situation. Since its invention 10 years ago, PMCA has helped to answer fundamental questions about this intriguing infectious agent and has been broadly applied in research areas that include the food industry, blood bank safety and human and veterinary disease diagnosis.
Morales, Rodrigo; Duran-Aniotz, Claudia; Diaz-Espinoza, Rodrigo; Camacho, Manuel V; Soto, Claudio
NASA Technical Reports Server (NTRS)
Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.
Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.
There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.
Wang, Zhehui (Los Alamos, NM); Barnes, Cris W. (Santa Fe, NM)
National Technical Information Service (NTIS)
These lectures contain (a) an overview of what might be learned from experiments at future (e bar)e, pp and ep colliders, (b) a review of limitations on circular and linear colliders, and (c) a description of some novel ideas for acceleration.
C. H. Llewellyn Smith
ERIC Educational Resources Information Center
Use of the term "acceleration" to describe interventions to enhance children's intellectual potential is inappropriate, as the term cannot by justified from the standpoint of mental measurement, mental growth, genetics, or education. Maximizing a child's potential through creation of stimulating environments is recommended rather than�
Elkind, David
NASA Astrophysics Data System (ADS)
I'll overview the past, present, and future of the GRAPE project, which started as the effort to design and develop specialized hardware for gravitational N-body problem. The current hardware, GRAPE-DR, has an architecture quite different from previous GRAPEs, in the sense that it is a collection of small, but programmable processors, while previous GRAPEs had hardwired pipelines. I'll discuss pros and cons of these two approaches, comparisons with other accelerators and future directions.
Makino, Junichiro
One of the major motivations driving recent interest in FFAGs is their use for the cost-effective acceleration of muons. This paper summarizes the progress in this area that was achieved leading up to and at the FFAG workshop at KEK from July 7-12, 2003. Much of the relevant background and references are also given here, to give a context to the progress we have made.
Electrochemical oxidation of cyclic polysilanes
During the past decade, the electrochemical properties of cyclic polysilane derivatives, namely [Mes2Si]3 (I), [t-Bu(Me)Si]4 (IIa), [Et2Si]4 (IIb), [(n-Pr)2Si]5 (IIIa), [Et2Si]5 (IIIb), [Me2Si]6 (IVa), [Et2Si]6 (IVb), [Et2Si]7 (V), [Me2Si]8 (VI), and [Me2Si]9 (VII), have been explored in our laboratory. Various parameters have been investigated, such as anodic peak potentials, the effect of anode material, nature of supporting electrolyte, atmosphere under
James Y Becker
Advances in targeting cyclic nucleotide phosphodiesterases.
Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants. PMID:24687066
Maurice, Donald H; Ke, Hengming; Ahmad, Faiyaz; Wang, Yousheng; Chung, Jay; Manganiello, Vincent C
Rhodopsin phosphorylation as a mechanism of cyclic GMP phosphodiesterase regulation by S-modulin
DURING light-adaptation by the vertebrate eye, the rods are desensitized and the light response is accelerated1,2. When light is absorbed by the rods, a phosphodiesterase is activated that hydrolyses cyclic GMP3,4. A light-induced decrease in cytoplasmic Ca2+ concentration5-7 is part of this light-adaptation process8,9. The protein S-modulin (Mr 26,000) is known to increase the fraction of light-activated cyclic GMP-phosphodiesterase (PDE)
Satoru Kawamura
Cyclic Imide Dioxime: Formation and Hydrolytic Stability
Poly(acrylamidoximes) play an important role in the uranium extraction from seawater. The present work reports solution studies of simple analogs to address the formation and stability of two binding sites present in these polymers, open-chain amidoximes and cyclic imide dioximes, including: 1) conditions that maximize the formation of the cyclic form, 2) existence of a base-induced conversion from open-chain to cyclic form, and 3) degradation under acid and base conditions.
Kang, S.O. [University of Kansas; Vukovic, Sinisa [ORNL; Custelcean, Radu [ORNL; Hay, Benjamin [ORNL
Cyclic Polygons with Rational Sides and Area
We generalise the notion of Heron triangles to rational-sided, cyclic n-gons with rational area using Brahmagupta's formula for the area of a cyclic quadrilateral and Robbins' formul for the area of cyclic pentagons and hexagons. We use approximate techniques to explore rational area n-gons for n greater than six. Finally, we pro- duce a method of generating non-Eulerian rational area
Ralph H. Buchholz; James A. MacDougall
Morse index of a cyclic polygon
It is known that cyclic configurations of a planar polygonal linkage are critical points of the signed area function. In the\\u000a paper we give an explicit formula of the Morse index for the signed area of a cyclic configuration. We show that it depends\\u000a not only on the combinatorics of a cyclic configuration, but also on its metric properties.
Gaiane Panina; Alena Zhukova
Income dispersion and counter-cyclical markups
Recent advances in measuring cyclical changes in the income distribution raise new questions: How might these distributional changes affect the business cycle itself? We show how counter-cyclical income dispersion can generate counter-cyclical markups in the goods market, without any preference shocks or price-setting frictions. In recessions, idiosyncratic labor productivity shocks raise income dispersion, lower the price elasticity of demand, and
Chris Edmond; Laura Veldkamp
Genetics Home Reference: Cyclic vomiting syndrome
Cyclic vomiting syndrome Mitochondrial DNA References Quick links to this topic MedlinePlus Health information Genetic and Rare Diseases Information Center Information about genetic conditions and ...
Accelerators and the Accelerator Community
In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.
Malamud, Ernest; Sessler, Andrew
Durability of concrete�accelerated carbonation and weathering studies
In this paper we report on some laboratory testing on the carbonation and weathering of concrete. Each study involves accelerated test methods. In the carbonation study the effects of humidity level, grade of concrete and pore size on carbonation depths are investigated. Experiments using mechanical and thermal cyclic loading have been carried out to study deterioration of concrete by weathering;
S. K. Roy; K. B. Poh; D. o. Northwood
Cyclic response of axially loaded pile groups
This paper presents a total stress hybrid load-transfer analysis for the response of pile groups in clay under either uniform or irregular cyclic loading. The soil mass may be arbitrarily layered and the nonlinear pile response is represented by a simple cyclic hyperbolic interface soil model. The reduction of shaft stress and accumulation of displacement are considered using the degradation
C. Y. Lee
Engineered piles to improve cyclic load capacity
Theoretical analyses have been carried out on five different pile types in two hypothetical soils representing offshore calcareous sediment profiles. It is demonstrated that both static and cyclic performance can be improved, over that of a conventional uniform pile, by altering the distribution of diameter and\\/or stiffness along the pile. To optimize performance under cyclic loading, a pile should be
H. G. Poulos; K. B. Sim
Cyclic electron flow in C3 plants
This paper summarized our present view on the mechanism of cyclic electron flow in C3 plants. We propose that cyclic and linear pathways are in competition for the reoxidation of the soluble primary PSI acceptor, Ferredoxin (Fd), that freely diffuses in the stromal compartment. In the linear mode, Fd binds ferredoxin-NADP-reductase and electrons are transferred to NADP+ and then to
Pierre Joliot; Anne Joliot
Synthesis of cyclic disulfide-rich peptides.
In this chapter we describe two SPPS approaches for producing cyclic disulfide-rich peptides in our laboratory, including cyclotides from plants, cyclic conotoxins from cone snail venoms, chlorotoxin from scorpion venom, and the sunflower trypsin inhibitor peptide, SFTI-1. PMID:23943480
Akcan, Muharrem; Craik, David J
Cyclic Oxidation Evaluation Approaching Application Conditions.
National Technical Information Service (NTIS)
A survey is presented of the cyclic furnace and burner rig oxidation facilities at NASA-Lewis Research Center together with a review of selected test results and an initial interpretation of the data obtained. Cyclic furnace tests are used to conveniently...
C. A. Barrett E. B. Evans
Fractionalization of cyclic transformations in optics
In this paper we consider fractional transforms that are based on cyclic linear transformations, and which have been actively used during the last decade in optical information processing. Some general algorithms for the fractionalization of cyclic transforms are discussed. In particular we consider the fractional Fourier transformation and its relatives (the cosine, sine, Hartley, and Hankel transformation), convolutional transformations like
Tatiana Aliev; Martin J. Bastiaans; Mar � i; Luisa Calvo
Fractionalization of cyclic transformations in optics
ABSTRACT In this paper we consider fractional transforms that are based on cyclic linear transformations, and which have been actively used during the last decade in optical information processing. Some general algorithms for the fractionalization of cyclic transforms are discussed. In particular we consider the fractional Fourier transformation and its relatives (the cosine, sine, Hartley, and Hankel transformation), convolutional transformations
T Alieva; MJ Bastiaans; ML Calvo
A Cyclic Universe Numerically Realized
NASA Astrophysics Data System (ADS)
A unique way of realizing inflation has been proposed recently in the context of cyclic cosmology where the universe grows by a constant factor in each cycle. This leads to an overall exponential growth over many cycles. In a given cycle such a growth is possible if, for instance, ``heavy particles'' can decay into radiation (photons) leading to an increase in entropy. However, to sustain this mechanism over successive cycles, it is crucial to reproduce the heavy particles back through quantum scattering processes and re-establish thermal equilibrium between all the species. We attempt to prove the viability of a ``multiple bang'' scenario to produce known cosmological data as well as use it to predict fluctuations in the upcoming higher resolution plank telescope data. This paradigm opens doors for new investigations into the principles surrounding the content and origin of the universe.
Duhe, William; Biswas, Tirthbar
Cell reorientation under cyclic stretching.
Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations--cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell's passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity. PMID:24875391
Livne, Ariel; Bouchbinder, Eran; Geiger, Benjamin
Cyclic olefin copolymer plasma millireactors.
The novelty of this paper lies in the development of a multistep process for the manufacturing of plasma millireactors operating at atmospheric pressure. The fabrication process relies on the integration of metallic electrodes over a cyclic olefin copolymer chip by a combination of photopatterning and sputtering. The developed plasma millireactors were successfully tested by creating air discharges in the gas volume of the millichannel. A sputtered silica layer was deposited on the channel walls to provide a barrier between the plasma and the polymer in order to prevent the alteration of polymer surfaces during the plasma treatment. Interest in this process of employing plasma millireactor as a high reactive environment is demonstrated here by the degradation of a volatile organic compound (acetaldehyde) in ambient air. In this miniaturized device, we obtained a high acetaldehyde conversion (98%) for a specific input energy lower than 200 J L(-1). PMID:24957952
Schelcher, G; Guyon, C; Ognier, S; Cavadias, S; Martinez, E; Taniga, V; Malaquin, L; Tabeling, P; Tatoulian, M
In recent years, the focus of the U.S. Department of Energy (DOE) complex has shifted from defense production to facility stabilization, decommissioning, and environmental restoration. This shift from production to cleanup requires a parallel shift from operations-focused management to project-focused management for an efficient facility deactivation. In the operation-focused management organization, activities are planned and executed based on production goals and are typically repetitive and cyclic. In the project-focused management environment, activities are based on a defined scope/end objective, start date, and completion date. Since the workforce used to perform production operations is also usually relied onto perform facility deactivation, it is important to shift from an operations management approach to a project management approach. It is best if the transition is accomplished quickly so the project can move forward and workers don't spend a lot of energy anticipating change. Therefore, it is essential that managers, planners, and other workers understand the key elements associated with planning a deactivation project. This paper describes a planning approach that has been used successfully to plan deactivation projects consistent with the requirements provided in DOE Order 430.1A Life Cycle Asset Management and the companion Deactivation Implementation Guide, G430. 1A-3, while exceeding schedule expectations and reducing costs. Although the planning of a deactivation project closely mirrors the classic project planning for construction projects, there are unique variations associated with facility deactivation. The key elements of planning a deactivation project are discussed relative to scope, schedule, and cost. Management tools such as project metrics and histograms are discussed as desired outputs from the planning process. In addition, lessons learned from planning deactivation projects across the DOE complex are discussed relative to making the transition from operations management to project management and the implications for deactivation project planning.
Amide bonds -NH-CO- preferentially exist in trans conformations, the cis conformation being thermodynamically unfavored with respect to the trans by about 2 kcal/mol. Yet, the main reason most proteins or peptides cannot be made from cis-peptide plaques only lies in that connecting them into open chains appears to be sterically impracticable. It is possible, however, to build all-cis cyclic peptides in which all cis-plaques are efficiently locked. The present work examines, through quantum calculations, the structural and energetic issues associated with these peculiar arrangements. Systematic exploration at DFT-B3LYP level of the potential-energy surfaces for all-cis cyclopolyglycines cG(n)(c) (n = 2-10,15), and to a lesser extent, for all-cis cyclopolyalanines and all-cis cyclopolyphenylalanines confirms that all these structures are true minima. Optimal ring size occurs around eight peptide units, resulting in planar cG7(c), cG8(c), and cG9(c). In smaller systems, the ring strain is relieved through nonplanar cup-like distortions, particularly in cG6(c). From 10 peptide units and beyond, the ring framework distorts into a saddle-edge shape. These molecules disclose some molecular flexibility, as combinatorial tilting of the plaques may give sets of minima close in energy. Indexes based on isodesmic reactions are used to estimate the energy for joining all-cis or all-trans plaques into cyclic peptides. One of them, the mean plaque-junction energy (MPJE) suggests that within sensible sizes from six peptide units and beyond, all-cis plaque association is almost equally favorable as all-trans one. The frame of radiating cis-amide bonds can be considered as defining a new kind of peptidic material, endowed with specific self-assembling properties. PMID:16201809
Poteau, Romuald; Trinquier, Georges
Accelerator system and method of accelerating particles
NASA Technical Reports Server (NTRS)
An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.
Wirz, Richard E. (Inventor)
Information Processing and Movement Optimization During Development: Kinematics of Cyclical Pointing in 5- to 11YearOld Children
The authors studied the development of movement control in speed-accuracy tradeoff conditions in children aged 5�11 years and in adults performing cyclical pointings. Twelve difficulty levels (IDs), ranging from 2 to 6.58 bits, were defined (P. M. Fitts, 1954). Peak and time to peak velocity, acceleration, and deceleration, and acceleration profiles as a function of hand position (Hooke's portraits) were
Fr�d�ric Bourgeois; Laurette Hay
Pressure solution creep under cyclic loading
NASA Astrophysics Data System (ADS)
Pressure solution creep was studied on sodium chloride, calcium carbonate and ammonium nitrate in respective saturated aqueous solutions under static loading and cyclic unloading. Ball indentation and powder compaction curves show that each transition from static to cyclic regime produces an increase�sometimes manifold�in creep rate which lasts over the whole time of cyclic impact. After returning to static regime, the initial creep rate reappears. Over longer-term tests, both in static and cyclic regime, the creep gradually slows down. Increasing impact frequency enhances the effect. Any noticeable changes in strain rate are absent in a pure inert medium (paraffin oil). Possible mechanisms of the cyclic unloading effect are discussed.
Traskine, Vladimir; Skvortsova, Zoya; Muralev, Alexey; Zubov, Dmitry
Mutations in the cyclic AMP binding site of the cyclic AMP receptor protein of Escherichia coli.
Mutants in the cyclic AMP binding site of the cyclic AMP receptor protein (CRP) of Escherichia coli have been constructed by oligonucleotide-directed mutagenesis. They have been phenotypically characterized and their ability to enhance the expression of catabolite-repressible operons has been tested. In addition, the binding of cyclic nucleotides to the mutants has been investigated. It is shown that the six mutants made fall into one of three classes: (i) those that bind cyclic AMP better than the wild type protein (Ser-62----Ala) and result in greater transcription enhancement; (ii) those that bind cyclic AMP similarly to wild type (Ser-83----Ala, Ser-83----Lys, Thr-127----Ala, Ser-129----Ala); and (iii) those that do not bind cyclic AMP at all (Arg-82----Leu). Implications of these findings with respect to present models of the cyclic nucleotide binding pocket of CRP are discussed. Images Fig. 1.
Gronenborn, A M; Sandulache, R; Gartner, S; Clore, G M
Cyclic AMP and cyclic GMP concentrations in serum- and density-restricted fibroblast cultures.
Mouse fibroblasts transformed by simian virus 40 (SV3T3 cells) are characterized by cyclic AMP and cyclic GMP levels, respectively, about half and twice those found in growing untransformed 3T3 cells. Density-dependent inhibition of growth is correlated with reduced cyclic GMP concentrations in 3T3 and four different density-restricted revertant lines derived from SV3T3. The levels of cyclic AMP are not increased at confluence. Upon serum restriction, serum-dependent cell lines show a greater increase in intracellular cAMP than serum-insensitive lines. Cyclic GMP levels are greatly reduced, even in serum-insensitive density revertants, but not in SV3T3. Serum readdition to all serum-dependent lines is followed by a rapid decrease in cyclic AMP and increase in cyclic GMP concentrations. The magnitude of these responses is decreased in SV3T3 and density revertants.
Moens, W; Vokaer, A; Kram, R
Cyclic AMP and cyclic GMP concentrations in serum- and density-restricted fibroblast cultures.
Mouse fibroblasts transformed by simian virus 40 (SV3T3 cells) are characterized by cyclic AMP and cyclic GMP levels, respectively, about half and twice those found in growing untransformed 3T3 cells. Density-dependent inhibition of growth is correlated with reduced cyclic GMP concentrations in 3T3 and four different density-restricted revertant lines derived from SV3T3. The levels of cyclic AMP are not increased at confluence. Upon serum restriction, serum-dependent cell lines show a greater increase in intracellular cAMP than serum-insensitive lines. Cyclic GMP levels are greatly reduced, even in serum-insensitive density revertants, but not in SV3T3. Serum readdition to all serum-dependent lines is followed by a rapid decrease in cyclic AMP and increase in cyclic GMP concentrations. The magnitude of these responses is decreased in SV3T3 and density revertants. PMID:165482
Moens, W; Vokaer, A; Kram, R
40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.
Code of Federal Regulations, 2010 CFR
...2010-07-01 false Haloalkyl substituted cyclic ethers. 721.3440 Section 721... § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and...chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...
40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.
Code of Federal Regulations, 2010 CFR
...2009-07-01 false Haloalkyl substituted cyclic ethers. 721.3440 Section 721... § 721.3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and...chemical substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...
The use of the high-frequency fatigue test as a method for accelerated estimation of endurance characteristics of materials
NASA Astrophysics Data System (ADS)
It is shown that the methods for accelerated estimation of endurance characteristics of materials involving high-frequency cyclic loading have certain advantages as compared to other "accelerated" methods. The effect of cyclic loading frequency on the endurance limit is considered for a number of metallic materials and the possibility is shown to plot a single fatigue curve independent of the number of cycles. The most promising areas of application for high-frequency fatigue test methods are noted.
Kuz'menko, V. A.
Cyclic Nucleotides and Phosphodiesterases in Monocytic Differentiation
Monocytes are immune cells that can differentiate into a number of cell types including macrophages, dendritic cells, and osteoclasts upon exposure to various cytokines. The phenotypes of these differentiated cells are highly heterogeneous and their differentiation can be affected by the cyclic nucleotides, 3?�5?-cyclic adenosine monophosphate (cAMP) and 3? �5?-cyclic guanosine monophosphate (cGMP). The intracellular levels of cAMP and cGMP are controlled through regulation of production by adenylyl and guanylyl cyclases and through degradation by cyclic nucleotide phosphodiesterases (PDEs). PDE inhibition and subsequent changes in cyclic nucleotide levels can alter the final phenotype of a differentiating monocyte with regards to surface marker expression, gene expression, or changes in secreted chemokine and cytokine levels. The differentiation process itself can also be either inhibited or augmented by changes in cyclic nucleotide levels, depending on the system being studied and the timing of cyclic nucleotide elevation. This chapter explores the effects of PDE inhibition and increases in cGMP and cAMP on monocytic differentiation into osteoclasts, dendritic cells, and macrophages.
Hertz, Angie L.
Platelet cyclic AMP in essential hypertension.
Various abnormalities in platelet metabolism, including increased sensitivity to several aggregating agents, have been described in essential hypertension. Platelet response is controlled by Ca2+ and cyclic AMP-dependent mechanisms (stimulatory and inhibitory, respectively) which oppose one another. In the present study, the cyclic AMP contents of unstimulated platelets were measured by radio-immunoassay and observed to be lower in hypertensive than in normotensive subjects, either in the basal state or after prostaglandin E1 (PGE1) stimulation. In the presence of 7-bromo-1,5,dihydro-3,6-dimethylimidazo [2,1-b] quinazolin-2(3H)-one (Ro 15-2041), a specific inhibitor of phosphodiesterase, the increases in cyclic AMP content were similar in platelets from both groups, indicating that this enzyme was not responsible for the alterations in cyclic AMP metabolism observed in hypertension. Low external Ca2+ reduced basal and PGE1-stimulated cyclic AMP content in both normotensive and hypertensive groups but cyclic AMP levels remained lower in hypertensive patients than in normotensive subjects, indicating that Ca2+ influx is not responsible for this altered metabolism of cyclic AMP in hypertension. These data suggest that the reduced platelet cAMP content may participate in the hyperreactivity to various aggregating agents previously reported to accompany essential hypertension. PMID:2550542
Mazeaud, M M; Le Quan Sang, K H; Devynck, M A
Cyclic creep of Type 304 stainless steel during unbalanced tension-compression loading at elevated temperature
Samples of Type 304 stainless steel were subjected to cyclic stresses with a positive mean stress at 300 and 560/sup 0/C. Very rapid net elongation was observed whenever the stress limits were such as to produce a plastic strain amplitude of the same order of magnitude as the elastic strain at the peak stress. The maximum mean strain-rate, or cyclic creep rate, for a given peak tensile stress was achieved when the mean stress was just slightly above zero. Increasing the mean stress caused the mean strain rate to decrease. The sensitive dependence of the mean strain-rate on the plastic strain amplitude and inverse dependence on the mean stress indicates that remobilization of dislocations by the reverse strain is an important mechanism for cyclic-creep acceleration. Although rapid cyclic creep was observed at both temperatures, a measurable mean strain rate was found for a much narrower range of stress conditions at 560 than at 300/sup 0/C. The strain accumulated during cyclic creep did not produce any strain hardening, but did influence the shape of the stress-strain curve in a subsequent tensile test.
Turner, A.P.L.; Martin, T.J.
Nanosecond Temperature Jump Relaxation Dynamics of Cyclic ?-Hairpin Peptides
The thermal unfolding of a series of 6-, 10-, and 14-mer cyclic ?-hairpin peptides was studied to gain insight into the mechanism of formation of this important secondary structure. The thermodynamics of the transition were characterized using temperature dependent Fourier transform infrared spectroscopy. Thermodynamic data were analyzed using a two-state model which indicates increasing cooperativity along the series. The relaxation kinetics of the peptides in response to a laser induced temperature jump were probed using time-resolved infrared spectroscopy. Single exponential relaxation kinetics were observed and fit with a two-state model. The folding rate determined for these cyclic peptides is accelerated by some two orders of magnitude over the rate of a linear peptide that forms a ?-hairpin. This observation supports the argument that the rate limiting step in the linear system is either stabilization of compact collapsed structures or rearrangement of collapsed structures over a barrier to achieve the native interstrand registry. Small activation energies for folding of these peptides obtained from an Arrhenius analysis of the rates imply a primarily entropic barrier, hence an organized transition state having specific stabilizing interactions.
Maness, Shelia J.; Franzen, Stefan; Gibbs, Alan C.; Causgrove, Timothy P.; Dyer, R. Brian
Cyclic crack resistance of an anticorrosion surfacing steel joint
An investigation was made of the cyclic crack resistance of the austenitic surfacing - 15Kh2MFA steel transition zone taking into consideration the fatigue crack geometry, the fracture mechanism, and the effect of crack closure. Microstructural analysis showed significant heterogeneity of the surfacing-base metal transition zone. An analysis of the base metal showed that in the area of low-fatigue crack growth rates, there is a significant spread in the experimental data obtained in tests of three specimens. Under steady service conditions, an increased loading asymmetry sharply accelerates failure of the alloy as the result of growth only of the subsurfacing crack, which is partically insensitive to the direction of crack development and to structural changes in the transition zone materials.
Zuezdin, Y.I.; Andrusiv, B.N.; Nikiforchin, G.N.; Timofeev, B.T.; Zima, Y.V.
Diurnal Variation in Cyclic Nucleotide Levels in Normal and Phorbol Myristate Acetate Treated Mouse Epidermis
The diurnal variations in cyclic AMP, cyclic GMP and cyclic GMP\\/cyclic AMP were determined in mouse epidermis. Slight (60%) diurnal fluctuations were observed in the levels of cyclic AMP and cyclic GMP\\/cyclic AMP while cyclic GMP showed a more substantial (250%) variation. All 3 parameters showed peaks between 10 AM and 2 PM. The tumor promoter phorbol myristate acetate had
Seymour J. Garte; Sidney Belman
Synchronization in chaotic oscillators by cyclic coupling
NASA Astrophysics Data System (ADS)
We introduce a type of cyclic coupling to investigate synchronization of chaotic oscillators. We derive analytical solutions of the critical coupling for stable synchronization under the cyclic coupling for the R�ssler system and the Lorenz oscillator as paradigmatic illustration. Based on the master stability function (MSF) approach, the analytical results on critical coupling are verified numerically. An enhancing effect in terms of lowering the critical coupling or enlarging the synchronization window in a critical coupling space is noticed. The cyclic coupling is also applied in other models, Hindmarsh-Rose model, Sprott system, Chen system and forced Duffing system to confirm the enhancing effect. The cyclic coupling allows tuning of two coupling constants in reverse directions when an optimal control of synchronization is feasible.
Olusola, O. I.; Njah, A. N.; Dana, S. K.
Cyclic response of axially loaded pile groups
This paper presents a total stress hybrid load-transfer analysis for the response of pile groups in clay under either uniform or irregular cyclic loading. The soil mass may be arbitrarily layered and the nonlinear pile response is represented by a simple cyclic hyperbolic interface soil model. The reduction of shaft stress and accumulation of displacement are considered using the degradation of the soil secant modulus and shaft limiting stress. The shaft-stress-degradation factor is related to the cyclic strain in a hyperbolic form. The formulation of the analysis is relatively simple and the soil parameters required are relatively few and have physical meaning. The method is used to analyze the response of model pile-group tests in soft clay under cyclic loading. In addition, a repeated monotonic loading on a full-scale pile-group test in stiff overconsolidated clay is analyzed. The measured and computed results are in reasonably good agreement.
Lee, C.Y. (Univ. of Sydney, New South Wales (Australia). School of Civil and Mining Engineering)
Cyclic hardening in bundled actin networks.
Nonlinear deformations can irreversibly alter the mechanical properties of materials. Most soft materials, such as rubber and living tissues, display pronounced softening when cyclically deformed. Here we show that, in contrast, reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear. As a consequence, they exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain. This unique response is crucially determined by the network architecture: at lower crosslinker concentrations networks do not harden, but soften showing the classic Mullins effect known from rubber-like materials. By simultaneously performing macrorheology and confocal microscopy, we show that cyclic shearing results in structural reorganization of the network constituents such that the maximum applied strain is encoded into the network architecture. PMID:21139579
Schmoller, K M; Fern�ndez, P; Arevalo, R C; Blair, D L; Bausch, A R
Fine Structure Produced by Cyclic Martensitic Transformation.
National Technical Information Service (NTIS)
The results are presented of investigations of the enhancement of martensitic transformation after cyclic martensitic transformation, and the FCC to BCC transformation in iron-nickel alloys containing between 7 and 25 percent nickel.
G. Krauss
A Compact Electromagnetic Accelerator.
National Technical Information Service (NTIS)
An electromagnetic pellet accelerator for the injection of glass beads into a plasma accelerator is used to simulate cometary dust for collection method development. The accelerator is described and a schematic diagram given. Its operational characteristi...
E. Igenbergs H. Kuczera P. Lell
Fractionalization of the linear cyclic transforms.
In this study the general algorithm for the fractionalization of the linear cyclic integral transforms is established. It is shown that there are an infinite number of continuous fractional transforms related to a given cyclic integral transform. The main properties of the fractional transforms used in optics are considered. As an example, two different types of fractional Hartley transform are introduced, and the experimental setups for their optical implementation are proposed. PMID:11140494
Alieva, T; Calvo, M L
New Sylostic Architectures for Cyclic Code Encoding
In this paper, we develop three systolic architectures for the encoding of cyclic codes. Our discussion is limited to codes over the finite field GF(2\\u000am). Contrary to those published in the litterature, our encoders use the check polynomial H(x) of the code. For an (n,k) cyclic code, the first and second encoder consist respectively of (n-k) and k cells
Menouer Diab; Paul Sabatier
Consecutive exotropia following surgically corrected cyclic esotropia.
Introduction: Cyclic esotropia is a rare form of strabismus consisting of regular intervals of esotropia alternating with periods of orthophoria in a rhythmic/cyclic manner. In the vast majority of cases, surgery appears to permanently correct the esotropia, with no sequelae after years of follow-up. We report a case of consecutive exotropia in a patient five years after bilateral medial rectus recessions for cyclic esotropia. Methods: A case report involving review of a clinical chart. Results: A two-year-old male presented with right esotropia and mild amblyopia. He was treated with patching and following resolution of the amblyopia he developed a cyclic esotropia. Surgical correction was performed for the full amount measured on a "manifest" day. Following the surgery, he was orthophoric and demonstrated binocular vision. He remained stable for five years, and then returned with occasional diplopia and an intermittent exotropia. Conclusion: Cyclic esotropia is a rare disorder of ocular motility that spontaneously appears and disappears at regular intervals. After surgical correction, the deviation disappears and recurrence of esotropia is very infrequent. We present the first reported case of consecutive exotropia following surgical correction of a cyclic esotropia. PMID:21149164
Post, Joel; Eidsness, Ryan B; Romanchuk, Kenneth G
Cyclic arsenic-nitrogen cations.
A series of different cyclo-diarsa-diazenium salts bearing several bulky groups such as supermesityl (Mes* = 2,4,6-tBu(3)C(6)H(2)) and m-terphenyl (2,6-Mes(2)-C(6)H(3), Mes = 2,4,6-Me(3)C(6)H(2)) and anions such as triflate (OTf = SO(3)CF(3) = trifluoromethylsulfonate) and tetrachloridogallate (GaCl(4)(-)) were synthesized and fully characterized. The novel 1-chloro-cyclo-1,3-diarsa-2,4-diazenium cation represents the first example of a binary cyclic As(III)/N four-membered heterocyclic cation, with a di- and tricoordinated As atom and a delocalized pi bond along the NAs((+))N unit. The addition of excess Me(3)SiN(3) yields the fully characterized cationic arsenic azide, 1-azido-cyclo-1,3-diarsa-2,4-diazenium-mu-azido-hexachlorido-digallate. The Cl(-)/N(3)(-) exchange is triggered by the action of the Lewis acid GaCl(3). Depending on the Me(3)SiN(3) stoichiometry, different mu-azido-hexachlorido-digallate salts with either 1-chloro- or 1-azido-cyclo-1,3-diarsa-2,4-diazenium cations or even a mixture of both are observed. Moreover, it was of special interest to study the distances between the cationic arsenic center and the anion in cyclo-diarsa-diazenium salts. A correlation between the color of the salt and the anion/cation distance, ranging between 2 and 8 A in cyclo-diarsa-diazenium salts of the type [R(2)N(2)As(2)Y](+)X(-) depending on the bulky group R (R = Mes*, Ter), the substituent Y (Y = Cl, N(3), OTf), and the anion X(-) (X = OTf, GaCl(4), Cl(3)Ga-N(3)-GaCl(3)), was established. PMID:19586007
Schulz, Axel; Villinger, Alexander
Pile shaft capacity in sand has been observed to decrease significantly under cyclic wave loading. While the characteristics of the load transfer behavior have been replicated in the laboratory, there is limited understanding of the microscale mechanisms that govern this behavior. Cyclic interface shear tests were performed in which the cementation, soil type, cyclic displacement magnitude, and cyclic loading mode
Jason T. DeJong; David J. White; Mark F. Randolph
Measuring Cyclic Error in Laser Heterodyne Interferometers
NASA Technical Reports Server (NTRS)
An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-
Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter
Cyclic nucleotides of cone-dominant retinas. Reduction of cyclic AMP levels by light and by cone degeneration.
Dark-adapted retinas or whole eyes of 13-line ground squirrels (Citellus tridecemlineatus) and western fence lizards (Sceloporus occidentalis) contain higher levels of cyclic AMP than of cyclic GMP. In these cone-dominant retinas, light reduces cyclic AMP content selectively. Freezing of dark- or light-adapted retinas or eyes also reduces cyclic AMP content, with only minimal changes in cyclic GMP levels. In addition, exposure of frozen retinas of dark-adapted ground squirrel to light results in a significant decrease in cyclic AMP content. The destruction of cone visual cells of ground squirrel retina by iodoacetic acid injection decreases the cyclic nucleotide content of the dark-adapted retina. Considering the relative loss of cyclic nucleotides from cone degeneration, we estimate that the content of cyclic AMP in visual cells of ground squirrel retina is about four times greater than that of cyclic GMP. PMID:6256308
Farber, D B; Souza, D W; Chase, D G; Lolley, R N
A general discussion is presented of the acceleration of particles. Upon this foundation is built a categorization scheme into which all accelerators can be placed. Special attention is devoted to accelerators which employ a wake-field mechanism and a restricting theorem is examined. It is shown how the theorem may be circumvented. Comments are made on various acceleration schemes.
Sessler, A.M.
Further studies on cyclic erythropoiesis in mice
When young adult female W/Wv mice are given 0.5 micro+Ci /sup 89/Sr/g body weight intravenously, their hematocrit values oscillate from nadirs of 26% to zeniths of 42% with a periodicity of 16 days. The response of the W/Wv mouse to an assortment of radioactive and hematologic stresses have been examined in an effort to understand better the pathophysiology of cyclic erythropoiesis. When the dose of /sup 89/Sr is increased, the amplitude of cycling increases as nadirs are lowered, but periodicity is unchanged. When the dose of /sup 89/Sr is lowered to 0.3 microCi or less, cyclic erythropoiesis of substantial amplitude is observed only after five or six microoscillations. A single hematopoietic insult of 80 rad x-irradiation coupled with phlebotomy produces a transient form of cyclic erythropoiesis, namely, a series of dampened oscillations prior to recovery. Finally, we report that Wv/Wv mice exhibit a form of cyclic erythropoiesis in response to 0.5 microCi /sup 89/Sr/g body weight, in which the hematocrit values of successive nadirs gradually increase, and stabilize at about 100 days. /sup 89/Sr does not induce cyclic erythropoiesis in the +/+, W/+, or W/v/+ mice, the Hertwig strain of anemic mice, or in normal BDF1 mice.
Gibson, C.M.; Gurney, C.W.; Simmons, E.L.; Gaston, E.O.
Loop quantum gravity and the cyclic universe
Loop quantum gravity introduces strong nonperturbative modifications to the dynamical equations in the semiclassical regime, which are responsible for various novel effects, including resolution of the classical singularity in a Friedman universe. Here we investigate the modifications for the case of a cyclic universe potential, assuming that we can apply the four-dimensional loop quantum formalism within the effective four-dimensional theory of the cyclic scenario. We find that loop quantum effects can dramatically alter the near-collision dynamics of the cyclic scenario. In the kinetic-dominated collapse era, the scalar field is effectively frozen by loop quantum friction, so that the branes approach collision and bounce back without actual collision.
Bojowald, Martin [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany); Maartens, Roy [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG (United Kingdom); Singh, Parampreet [IUCAA, Ganeshkhind, Pune 411 007 (India); Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, London E1 4NS (United Kingdom)
Cyclic and low temperature effects on microcircuits
NASA Technical Reports Server (NTRS)
Cyclic temperature and low temperature operating life tests, and pre-/post-life device evaluations were used to determine the degrading effects of thermal environments on microcircuit reliability. Low power transistor-transistor-logic gates and linear devices were included in each test group. Device metallization systems included aluminum metallization/aluminum wire, aluminum metallization/gold wire, and gold metallization/gold wire. Fewer than 2% electrical failures were observed during the cyclic and low temperature life tests and the post-life evaluations revealed approximately 2% bond pull failures. Reconstruction of aluminum die metallization was observed in all devices and the severity of the reconstruction appeared to be directly related to the magnitude of the temperature excursion. All types of bonds except the gold/gold bonds were weakened by exposure to repeated cyclic temperature stress.
Weissflug, V. A.; Sisul, E. V.
The nature of solar cyclicity. I
NASA Astrophysics Data System (ADS)
The report contains a critical survey of work devoted to the study of the nature of solar cyclicity. The inconsistency of the representation of cyclic curves using a frequency spectrum is indicated. The useful contribution of the ideas of Wolf, Newcomb, and Waldmeier to the solution of the problem is noted. Data are cited in favor of the theory of the tidal nature of solar cyclicity developed by the author, which also takes into account the ideas of the above-mentioned authors: the continuous paired and single tidal actions of the planets and the resonance character of this action, thanks to which the approximately 10-year period of action of Jupiter and Saturn is transformed into the 11-year activity cycle.
Romanchuk, P. R.
Cyclic Oxonitriles: Stereodivergent Grignard Addition-Alkylations
Sequential carbonyl addition-conjugate addition of Grignard reagents to cyclic 5�7�membered oxoalkenenitriles efficiently generates cyclic magnesiated nitriles. Alkylations of these magnesiated nitriles exhibit diastereoselectivities that depend intimately on the size of the carbocyclic ring: 5-membered oxonitriles generate magnesiated nitriles whose alkylations are controlled by steric constraints whereas 6- and 7-membered oxonitriles generate internally coordinated, C-magnesiated nitriles whose alkylations are controlled by stereoelectronic effects. Reversing the alkylation selectivity of 6-membered C-magnesiated nitriles is achieved by conversion to an N-metalated nitrile in which steric, rather than electronic, effects direct the electrophile trajectory. Collectively, the conjugate addition-alkylation generates highly substituted, cyclic 5�7-membered nitriles containing three new stereocenters with selective access to diastereomers at the quaternary nitrile-bearing carbon.
Fleming, Fraser F.; Wei, Guoqing; Zhang, Zhiyu; Steward, Omar W.
mMass as a Software Tool for the Annotation of Cyclic Peptide Tandem Mass Spectra
Natural or synthetic cyclic peptides often possess pronounced bioactivity. Their mass spectrometric characterization is difficult due to the predominant occurrence of non-proteinogenic monomers and the complex fragmentation patterns observed. Even though several software tools for cyclic peptide tandem mass spectra annotation have been published, these tools are still unable to annotate a majority of the signals observed in experimentally obtained mass spectra. They are thus not suitable for extensive mass spectrometric characterization of these compounds. This lack of advanced and user-friendly software tools has motivated us to extend the fragmentation module of a freely available open-source software, mMass (http://www.mmass.org), to allow for cyclic peptide tandem mass spectra annotation and interpretation. The resulting software has been tested on several cyanobacterial and other naturally occurring peptides. It has been found to be superior to other currently available tools concerning both usability and annotation extensiveness. Thus it is highly useful for accelerating the structure confirmation and elucidation of cyclic as well as linear peptides and depsipeptides.
Niedermeyer, Timo H. J.; Strohalm, Martin
Cyclic unequal error protection codes constructed from cyclic codes of composite length
NASA Technical Reports Server (NTRS)
The distance structure of cyclic codes of composite length was investigated. A lower bound on the minimum distance for this class of codes is derived. In many cases, the lower bound gives the true minimum distance of a code. Then the distance structure of the direct sum of two cyclic codes of composite length were investigated. It was shown that, under certain conditions, the direct-sum code provides two levels of error correcting capability, and hence is a two-level unequal error protection (UEP) code. Finally, a class of two-level UEP cyclic direct-sum codes and a decoding algorithm for a subclass of these codes are presented.
Lin, Shu
Synthesis and characterization of cyclic acetal based degradable hydrogels.
While many synthetic, hydrolytically degradable hydrogels have been developed for biomedical applications, there are only a few examples whose polymer backbone does not form acidic products upon degradation. In order to address this concern, we proposed to develop a hydrogel based on a cyclic acetal unit that produces diols and propanals upon hydrolytic degradation. In particular, we proposed the fabrication of hydrogels formed by the free radical polymerization of two diacrylate monomers, 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD), a cyclic acetal having two acryl groups, and poly(ethylene glycol)diacrylate (PEGDA). However, the hydrophobicity of the EHD monomer inhibits hydrogel fabrication. Therefore this work develops a strategy to form hydrogels with a co-monomer system, one of which is hydrophobic, and subsequently describes the properties of the resulting hydrogel. Using benzoyl peroxide as an initiator and N,N-dimethyl-p-toluidine as an accelerator, the EHD and PEGDA monomers were reacted in an acetone/water co-solvent system. The chemical structure of the resulting EH-PEG [5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol-co-PEG] hydrogel was then characterized by FT-IR. Physicochemical properties of the EH-PEG hydrogel, including swelling degree, sol fraction, and contact angle, were determined so as to characterize the properties of these materials and ultimately investigate their use in drug delivery and tissue engineering applications. Results showed that EH-PEG hydrogel may be formed using the co-solvent system. Further results indicated that swelling degree is dependent upon initiator concentration, monomer concentration, and molar ratios of monomers, while sol fraction significantly depended on initiator concentration and monomer concentration, only. These results demonstrate the ability to fabricate hydrogels using EHD and PEGDA system as well as to control the properties of the resulting hydrophilic networks. PMID:17888640
Kaihara, Sachiko; Matsumura, Shuichi; Fisher, John P
Antibacterial Cyclic d,l-?-Glycopeptides
We report the design, synthesis, membrane activity, biophysical characterization, and in vitro antibacterial activities of cationic cyclic d,l-?-glycopeptides bearing side chains derivatized with d-glucosamine (GlcNH2), d-galactose (Gal), or d-mannose (Man).
Motiei, Leila; Rahimipour, Shai; Thayer, Desiree A.; Wong, Chi-Huey; Ghadiri, M. Reza
Raft and Pile Foundations under Cyclic Loading
The paper presents typical phenomena which can occur due to cyclic loading in granular soil. Numerical analysis with different material laws shows the challenges to simulate the ground behaviour realistically. Results of numerical analysis by means of the Finite-Element-Method are presented and the limitation of material laws discussed.
S. Meissner; H. Quick; U. Arslan
PZT behavior in cyclic strain environments
NASA Astrophysics Data System (ADS)
This paper presents results of an experiment designed to determine the impact of repeated strain cycles on lead ziconate titanate (PZT) transducers affixed to an aluminum test specimen. The goal of this research effort is to determine the impact of three cyclic strain levels on PZTs affixed with two different glue types. PZT transducers are evaluated because they are one of the leading health monitoring technologies used in aircraft structures due to their ability to transmit and receive Lamb Waves. Analysis of changes in the received signals can indicate the presence of structural damage. This monitoring paradigm can only be successful if signal changes due to exposure to aircraft environmental factors (temperature/strain/pressure cycles, etc) over time can be clearly identified and characterized. This paper presents the results and initial analysis of experiments to determine the changes in signal responses due to cyclic mechanical strain. Results indicate cyclic strain at 800 ?? has no effect to 510K cycles, while cyclic strain at 1700 and 2600 ?? both cause signal loss to varying degrees.
Kuhn, Jeffrey D.; Swenson, Eric D.; Soni, Som R.
Modelling cyclic voltammetry without digital simulation
A semi-analytical method of modelling cyclic voltammetry is described, derived, exemplified, verified, and advocated. A listing of the mechanistic schemes that can be addressed by the procedure includes E, EE, CE, EC and ECE, all with various degrees of reversibility. The approach has advantages and disadvantages when compared with digital simulation.
Keith B. Oldham; Jan C. Myland
One pot solution synthesis of cyclic oligodeoxyribonucleotides.
Several cyclic oligodeoxynucleotides with different base composition and size have been prepared from 5',3'-unprotected linear precursors, using a bifunctional phosphorylating reagent. The final deprotected oligomers have been characterized by 1H- and 31P-NMR. The present procedure is particularly useful for millimolar scale syntheses.
Capobianco, M L; Carcuro, A; Tondelli, L; Garbesi, A; Bonora, G M
Loop quantum gravity and the cyclic universe
Loop quantum gravity introduces strong nonperturbative modifications to the dynamical equations in the semiclassical regime, which are responsible for various novel effects, including resolution of the classical singularity in a Friedman universe. Here we investigate the modifications for the case of a cyclic universe potential, assuming that we can apply the four-dimensional loop quantum formalism within the effective four-dimensional theory
Martin Bojowald; Roy Maartens; Parampreet Singh
Boston University Physics Applets: Cyclic Processes
NSDL National Science Digital Library
This web page is an interactive physics simulation on cyclic processes. The user can put an engine through four steps, returning it to its original conditions. The work done by the engine is graphed after each step, showing the net work done. This is part of a collection of similar simulation-based student activities.
Duffy, Andrew
Development of a cyclic damage evaluation method
An effective method of measuring the state of fatigue damage accumulation in a pressure vessel, steel, A508, was identified by microstructural examinations. Selective angle diffraction (SAD), based on electron beam technique is utilized. SAD had been proved to be effective for detecting cumulative damage (CD) in samples cyclicly deformed at two levels of constant strain amplitudes. The objectives of this study are to validate the SAD method with a composite of cyclic strains simulating LWR plant service strains, and to transform the SAD method, which requires expert operation and data analysis of electron microscopy, to a nonexpert inspection procedure. Fatigue damage was induced in test bars under cyclic conditions intended to simulate the service conditions of a BWR feedwater nozzle. Three types (A, B, C) of cyclic strains were superimposed. B and C represent events associated with scram and normal transients, respectively. The degree of damage due to those events are insignificant, and thus used as pre-fatigue conditions. Type A damage originates from pressure tests and startup/shutdown events, and control the usage factor. One of the samples (Sample 11) was made to represent the case of probable CD (0.7%), for the plant life time ({approximately}40 years). Three other samples (12, 13, 14) represented the cases of cycle up to failure, having CD of 15, 43, and 100%, respectively. 19 figs., 3 tabs.
Nakagawa, Y.G.; Yoshizawa, H.; Umemoto, T. (Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan))
NASA Technical Reports Server (NTRS)
Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.
Cheng, D. Y.
A 'Universal Accelerator Libraries' (UAL) environment is described. Its purpose is to facilitate program modularity and inter-program and inter-process communication among heterogeneous programs. The goal ultimately is to facilitate model-based control of accelerators.
Malitsky, Nikolay; Talman, Richard [Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (United States)
National Technical Information Service (NTIS)
The great diversity of possible applications of accelerators has been demonstrated in the past few years. Apart from the more familiar uses of accelerators for fundamental particle, nuclear, and solid state physics research, the applications range from mi...
J. S. Fraser
Collective Acceleration of Ions.
National Technical Information Service (NTIS)
The collective method for acceleration of ions is described. The problem of the formation of an electron ring cluster charged with ions, its stability and focusing, and some questions of acceleration are discussed. (Author)
A. B. Kuznetsov E. A. Parelshtein I. N. Ivanov K. A. R. Reshetnikov V. A. Preizendorf
Cyclic Peptides as Therapeutic Agents and Biochemical Tools
There are many cyclic peptides with diverse biological activities, such as antibacterial activity, immunosuppressive activity, and anti-tumor activity, and so on. Encouraged by natural cyclic peptides with biological activity, efforts have been made to develop cyclic peptides with both genetic and synthetic methods. The genetic methods include phage display, intein-based cyclic peptides, and mRNA display. The synthetic methods involve individual synthesis, parallel synthesis, as well as split-and-pool synthesis. Recent development of cyclic peptide library based on split-and-pool synthesis allows on-bead screening, in-solution screening, and microarray screening of cyclic peptides for biological activity. Cyclic peptides will be useful as receptor agonist/antagonist, RNA binding molecule, enzyme inhibitor and so on, and more cyclic peptides will emerge as therapeutic agents and biochemical tools.
Joo, Sang Hoon
We present a solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal. Acceleration gradients of order 100 GV/cm are theoretically possible, but channeling radiation limits the maximum attainable energy to 10/sup 5/ TeV for protons. Beam dechanneling due to multiple scattering is substantially reduced by the high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed.
Chen, P.; Noble, R.J.
We present a solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal. Acceleration gradients of order 100 GV/cm are theoretically possible, but channeling radiation limits the maximum attainable energy to 10/sup 5/ TeV for protons. Beam dechanneling due to multiple scattering is substantially reduced by the high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed.
Chen, P.; Noble, R.J.
NASA Technical Reports Server (NTRS)
Cycle life regression model, cycle life prediction model, and acceleration factors are discussed. A method was presented to: (1) select a mathematical model; (2) determine model coefficients using accelerated test data; (3) test model fit of the accelerated test data; and (4) predict normal packs.
Schwartz, D.
NSDL National Science Digital Library
In this short lab, students observe the movement of an air bubble in a small level, attached to a toy truck, as it is moved from a stop, to a steady speed and back to a stop. This gives a visual to the concepts positive acceleration, zero acceleration and negative acceleration.
Mary Spaulding, Clearbrook-Gonvick Public School, Clearbrook Minnesota, based on an original activity from Physics Principles and Problems (1995) page 75.
NASA Technical Reports Server (NTRS)
The subjective effects of sustained acceleration are discussed, including positive, negative, forward, backward, and lateral acceleration effects. Physiological effects, such as retinal and visual response, unconsciousness and cerebral function, pulmonary response, and renal output, are studied. Human tolerance and performance under sustained acceleration are ascertained.
Fraser, T. M.
Angular Acceleration without Torque?
ERIC Educational Resources Information Center
Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.
Kaufman, Richard D.
Covariant Uniform Acceleration
NASA Astrophysics Data System (ADS)
We derive a 4D covariant Relativistic Dynamics Equation. This equation canonically extends the 3D relativistic dynamics equation , where F is the 3D force and p = m0?v is the 3D relativistic momentum. The standard 4D equation is only partially covariant. To achieve full Lorentz covariance, we replace the four-force F by a rank 2 antisymmetric tensor acting on the four-velocity. By taking this tensor to be constant, we obtain a covariant definition of uniformly accelerated motion. This solves a problem of Einstein and Planck. We compute explicit solutions for uniformly accelerated motion. The solutions are divided into four Lorentz-invariant types: null, linear, rotational, and general. For null acceleration, the worldline is cubic in the time. Linear acceleration covariantly extends 1D hyperbolic motion, while rotational acceleration covariantly extends pure rotational motion. We use Generalized Fermi-Walker transport to construct a uniformly accelerated family of inertial frames which are instantaneously comoving to a uniformly accelerated observer. We explain the connection between our approach and that of Mashhoon. We show that our solutions of uniformly accelerated motion have constant acceleration in the comoving frame. Assuming the Weak Hypothesis of Locality, we obtain local spacetime transformations from a uniformly accelerated frame K' to an inertial frame K. The spacetime transformations between two uniformly accelerated frames with the same acceleration are Lorentz. We compute the metric at an arbitrary point of a uniformly accelerated frame. We obtain velocity and acceleration transformations from a uniformly accelerated system K' to an inertial frame K. We introduce the 4D velocity, an adaptation of Horwitz and Piron s notion of "off-shell." We derive the general formula for the time dilation between accelerated clocks. We obtain a formula for the angular velocity of a uniformly accelerated object. Every rest point of K' is uniformly accelerated, and its acceleration is a function of the observer's acceleration and its position. We obtain an interpretation of the Lorentz-Abraham-Dirac equation as an acceleration transformation from K' to K.
Friedman, Yaakov; Scarr, Tzvi
Effect of Cyclic Straining on the Diffusivity of Zinc in a Magnesium-5.1%Zinc-0.6%Zirconium Alloy.
National Technical Information Service (NTIS)
The work shows that cyclic straining at 310C enhances the diffusivity of zinc in Mg-5.1%Zn-O.6%Zr grain-refined nondendritic alloy, due to an increased concentration of vacancies in the lattice. This enhancement of diffusivity accelerates the dissolution ...
T. Z. Kattamis
Some fixed point results for multi-valued cyclic mappings
NASA Astrophysics Data System (ADS)
This paper investigates the fixed points and best proximity points of multivalued cyclic self-mappings in metric spaces under a generalized contractive condition involving Hausdorff distances. Some previous results for cyclic self-mappings or for multivalued self-mappings in metric fixed point theory are extended to cyclic multivalued self-mappings.
De la Sen, M.; Singh, S. L.; Gordji, M. E.
Regulation of Cyclic GMP, Cyclic amp and Lactate Dehydrogenase by Putative Neutrotransmitters in the C6 Rat Glioma Cell Line.
National Technical Information Service (NTIS)
In C6 cells norepinephrine and dopamine caused transient increases in cyclic GMP and cyclic AMP, as well as an induction of lactate dehydrogenase. All of these responses were blocked by 1-propranolol, suggesting mediation by a beta -receptor. Phentolamine...
J. E. Bottenstein J. de Vellis
Role of Ecdysone, Pupariation Factors, and Cyclic AMP in Formation and Tanning of the Puparium of the Fleshfly Sarcophaga bullata
Two pupariation factors, anterior retraction factor (ARF) and puparium tanning factor (PTF), are absent from the hemolymph of larvae at the time of tanning accelerated by ARF\\/PTF, cyclic AMP, or dopamine. ARF and PTF are not involved in derepression of dopa decarboxylase (aromatic L-amino-acid decarboxylase, aromatic L-amino-acid carboxy-lyase, EC 188.8.131.52) synthesis initiated by ecdysone. Tanning is entirely inhibited by injection
Morris Seligman; Ann Blechl; James Blechl; Paul Herman; G. Fraenkel
On Development Model based on Intra-county Cyclic Economy under Low-carbon Economy for Northeast China
Northeast China as the old industrial base is still under the development stage of resource-consuming. In order to rejuvenate northeast China, it is necessary to actively accelerate the transformation of economic growth mode. The development mode of intra-county cyclic economy under low-carbon economy should be strived to develop. Based experiences on development of intra-county economy, the scientific and effective low-carbon
Guo Zhen; Liu Qieyi; Wang Xiaoxu
Mechanisms of damage accumulation in time-dependent cyclic deformation. Progress report, January 1, 1984-December 31, 1984
Problems of cyclic creep and time-dependent cyclic deformation are being increasingly recognized in machines used for energy conversion and storage, but few studies have been done in exploration of the relevant damage phenomena. Accordingly, the proposal called for the parallel study of various kinds of damage produced in cyclic creep: (1) change in dislocation density and arrangement, to be studied in copper; (2) development of fracture mechanisms under cyclic creep in pure copper and (3) damage phenomena perhaps involving precipates in Cr-Mo-V rotor steel. Furthermore, we have attempted to involve more micro-mechanics in the research. Progress in the last year has ben encouraging. We have successfully developed a quadratic programming procedure for the calculation of single crystal plastic response, and can thus use the results previously reported on cyclic response to develop realistic predictions of polycrystalline failure behavior. We have also completed our studies on Cr-Mo-V steel - the development of damage at various elevated temperatures has been assessed for regular cycling and cycling with holds. Damage takes several forms of which two of the most important are (1) cavitation and (2) accelerated (> X100) secondary hardening, which has the effect of depleting the matrix of Mo and thereby inducing embrittlement.
Laird, C.; Bassani, J.L.
This note intends to motivate our effort toward the advent of new methods of particle acceleration, utilizing the fast rising laser technology. By illustrating the underlying principles in an intuitive manner and thus less jargon-clad fashion, we seek a direction in which we shall be able to properly control and harness the promise of laser acceleration. First we review the idea behind the laser wakefield. We then go on to examine ion acceleration by laser. We examine the sheath acceleration in particular and look for the future direction that allows orderly acceleration of ions in high energies.
Tajima, T. [Kansai Photon Science Institute and Photon Medical Research Center Japan Atomic Energy Agency Kyoto, 619-0215 (Japan)
NASA Technical Reports Server (NTRS)
A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.
Foster, John E.
High brightness electron accelerator
A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.
Sheffield, Richard L. (Los Alamos, NM); Carlsten, Bruce E. (Los Alamos, NM); Young, Lloyd M. (Los Alamos, NM)
The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.
Colgate, S.A.
UHECR acceleration in dark matter filaments of cosmological structure formation
NASA Astrophysics Data System (ADS)
A mechanism for proton acceleration to ~ 1021 eV is suggested. It may operate in accretion flows onto thin dark matter filaments of cosmic structure formation. The flow compresses the ambient magnetic field to strongly increase and align it with the filament. Particles begin the acceleration by E � B drift with the accretion flow. The energy gain in the drift regime is limited by the conservation of the adiabatic invariant p?2/B(r). Upon approaching the filament, the drift turns into the gyro-motion around the filament so that the particle moves parallel to the azimuthal electric field. In this `betatron' regime the acceleration speeds up to rapidly reach the electrodynamic limit cpmax = eBR for an accelerator with magnetic field B and the orbit radius R (Larmor radius). The periodic orbit becomes unstable and the particle slings out of the filament to the region of a weak (uncompressed) magnetic field, which terminates the acceleration. To escape the filament, accelerated particles must have gyro-radii comparable with the filament radius. Therefore, the mechanism requires pre-acceleration that is likely to occur in large scale shocks upstream or nearby the filament accretion flow. Previous studies identify such shocks as efficient proton accelerators, with a firm upper limit ~ 1019.5 eV placed by the catastrophic photo-pion losses. The present mechanism combines explosive energy gain in its final (betatron) phase with prompt particle release from the region of strong magnetic field. It is this combination that allows protons to overcome both the photo-pion and the synchrotron-Compton losses and therefore attain energy ~ 1021 eV. A customary requirement on accelerator power to reach a given Emax, which is placed by the accelerator energy dissipation proptoEmax2/Z0 due to the finite vacuum impedance Z0, is circumvented by the cyclic operation of the accelerator.
Malkov, M. A.; Sagdeev, R. Z.; Diamond, P. H.
Surface and interface properties of carbon fiber composites under cyclical aging
NASA Astrophysics Data System (ADS)
Carbon fiber-reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have been characterized by FTIR, SEM/EDXA, XRD, and moisture-uptake determination. The results indicated that combination accelerated aging had great effects on the mechanical properties of the composite, the network structure of the BMI matrix, and the moisture uptake by the composite. After a third cycle of accelerated aging, moisture reached the center layer of the composite and as a result led to an obvious decrease in ILSS due to deterioration of the carbon fiber-BMI interface. Sufficient moisture absorption on the composite surface made the network structure of the BMI matrix more open, which facilitated stress relaxation and the creation of micro-cracks, with a consequent obvious decrease in flexural strength. With increasing number of combined-action accelerated aging cycles, ever more moisture was absorbed during each hygrothermal process due to the plasticizing effect of water, and micro-cracks propagated as a result of internal stresses caused by the hygrothermal process, the thermal-oxidative process, and the freezing process of each cycle. XRD analysis indicated that moisture penetrated through the amorphous region of the BMI matrix.
Lv, Xinying; Wang, Rongguo; Liu, Wenbo; Jiang, Long
Cyclic Oxidation Modeling and Life Prediction
NASA Technical Reports Server (NTRS)
The cyclic oxidation process can be described as an iterative scale growth and spallation sequence by a number of similar models. Model input variable include oxide scale type and growth parameters, spalling geometry, spall constant, and cycle duration. Outputs include net weight change, the amounts of retained and spalled oxide, the total oxygen and metal consumed, and the terminal rates of weight loss and metal consumption. All models and their variations produce a number of similar characteristic features. In general, spalling and material consumption increase to a steady state rate, at which point the retained scale approaches a constant and the rate of weight loss becomes linear. For one model, this regularity was demonstrated as dimensionless, universal expressions, obtained by normalizing the variables by critical performance factors. These insights were enabled through the use of the COSP for Windows cyclic oxidation spalling program.
Smialek, James L.
Cyclic debonding of adhesively bonded composites
NASA Technical Reports Server (NTRS)
The fatigue behavior of a simple composite to composite bonded joint was analyzed. The cracked lap shear specimen subjected to constant amplitude cyclic loading was studied. Two specimen geometries were tested for each bonded system: (1) a strap adherend of 16 plies bonded to a lap adherend of 8 plies; and (2) a strap adherend of 8 plies bonded to a lap adherend of 16 plies. In all specimens the fatigue failure was in the form of cyclic debonding with some 0 deg fiber pull off from the strap adherend. The debond always grew in the region of adhesive that had the highest mode (peel) loading and that region was close to the adhesive strap interface.
Mall, S.; Johnson, W. S.; Everett, R. A., Jr.
Improved cyclic reduction for solving queueing problems
NASA Astrophysics Data System (ADS)
The cyclic reduction technique (Buzbee et al., 1970), rephrased in functional form (Bini and Meini, 1996), provides a numerically stable, quadratically convergent method for solving the matrix equation X = ?+ ? iD0 Xi Ai, where the Ai's are nonnegative k k matrices such that ?+ ? iD0 Ai is column stochastic. In this paper we propose a further improvement of the above method, based on a point-wise evaluation/interpolation at a suitable set of Fourier points, of the functional relations defining each step of cyclic reduction (Bini and Meini,1996). This new technique allows us to devise an algorithm based on FFT having a lower computational cost and a higher numerical stability. Numerical results and comparisons are provided.
Bini, Dario; Meini, Beatrice
Combustion oscillation control by cyclic fuel injection
A number of recent articles have demonstrated the use of active control to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract the periodic heat release that contributes to undesired pressure oscillations. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characterized by acoustic modes that do not exist in the final engine configuration. To address this issue, the present paper reports on active control of a subscale, atmospheric pressure nozzle/combustor arrangement. The fuel is natural gas. Cyclic injection of 14% control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitude by a factor of 0.30 (i.e., {approximately}10 dB) at 300 Hz. Measurement of the oscillating heat release is also reported.
Richards, G.A.; Yip, M.J. [USDOE Morgantown Energy Technology Center, WV (United States); Robey, E. [EG& G Technical Services of West Virginia, Morgantown Energy Technology Center, WV (United States); Cowell, L.; Rawlins, D. [Solar Turbines, Inc., San Diedgo, CA (United States)
An introduction to acceleration mechanisms
This paper discusses the acceleration of charged particles by electromagnetic fields, i.e., by fields that are produced by the motion of other charged particles driven by some power source. The mechanisms that are discussed include: Ponderamotive Forces, Acceleration, Plasma Beat Wave Acceleration, Inverse Free Electron Laser Acceleration, Inverse Cerenkov Acceleration, Gravity Acceleration, 2D Linac Acceleration and Conventional Iris Loaded Linac Structure Acceleration. (LSP)
Palmer, R.B.
Representing cyclic human motion using functional analysis
We present a robust automatic method for modeling cyclic 3D human motion such as walking using motion-capture data. The pose of the body is represented by a time-series of joint angles which are automatically segmented into a sequence of motion cycles. The mean and the principal components of these cycles are computed using a new algorithm that enforces smooth transitions
Dirk Ormoneit; Michael J. Black; Trevor Hastie; Hedvig Kjellstr�m
The cyclic AMP system and Drosophila learning
The cyclic AMP (cAMP) system plays a critical role in olfactory learning in the fruit fly,Drosophila melanogaster, as evidenced by the following: [1] The dunce gene encodes a form of cAMP phosphodiesterase (PDE). Flies carrying mutations at this gene show reduced PDE activity, high cAMP levels, and deficits in olfactory learning and memory [2]. The rutabaga gene encodes one type
Ronald L. Davis; Jim Cherry; Brigitte Dauwalder; Pyung-Lim Han; Efthimios Skoulakis
Precoder for DMT with insufficient cyclic prefix
Multi-carrier modulation is a modulation technique that enables higher transmission rate than traditional techniques, such as single-carrier quadrature amplitude modulation (QAM) systems. One implementation of multi-carrier modulation technique is discrete multi-tone (DMT). DMT used in asymmetric digital subscriber lines (ADSL) and very high speed DSL (VDSL) systems has a fixed cyclic prefix length. When the impulse response of the channel
Kok-Wui Cheong; J. M. Cioffi
Cyclic onium compounds and glucosidase inhibitors
US Patent & Trademark Office Database
Cyclic onium compounds reresented by the following structural formula (I), glucosidase inhibitors using such compounds, and antidiabetic drugs or food containing such glucosidase inhibitor. ##STR00001## wherein A.sup.- is an aniom; m is an interger between 1 and 6, n is 0 or 1, X.sup.+ is S.sup.+ or N.sup.+Q (where Q is H or an alkyl of 1 to 4 carbon atoms).
Discrepancy of Hyperplane Nets and Cyclic Nets
Digital nets are very important representatives in the family of low-discrepancy point sets which are often used as underlying\\u000a nodes for quasi-Monte Carlo integration rules. Here we consider a special sub-class of digital nets known as cyclic nets and,\\u000a more general, hyperplane nets. We show the existence of such digital nets of good quality with respect to star discrepancy\\u000a in
Friedrich Pillichshammer; Gottlieb Pirsic
Modeling of cyclic-nitramine combustion
The theoretical and experimental data on the combustion of cyclic nitramines published in the past 30 years are systematized\\u000a and critically reviewed. Results of studies of combustion-wave parameters and flame chemical structure are presented. Simplified\\u000a and detailed models of nitramine combustion are examined. Reduction of the chemical mechanism in a flame and general problems\\u000a of the adequate description of nitramine-combustion
N. E. Ermolin; V. E. Zarko
Cyclic Tritrpticin Analogs with Distinct Biological Activities
Tritrpticin is a Trp-, Arg-, and Pro-rich cathelicidin peptide with promising antimicrobial activity. Cyclic analogs of tritrpticin\\u000a were designed using two different approaches: circularization of the backbone by a head-to-tail peptide bond (TritrpCyc) or\\u000a disulfide bridging between two Cys residues introduced at the termini of the peptide (TritrpDisu). Compared to the parent\\u000a peptide, TritrpCyc has greatly improved therapeutic potential, showing
Leonard T. Nguyen; Johnny K. Chau; Sebastian A. J. Zaat; Hans J. Vogel
The Hodge Filtration and Cyclic Homology
We relate the �Hodge filtration� of the cohomology of a complex algebraic variety X to the �Hodge decomposition� of its cyclic homology. If X is smooth and projective,\\u000a$$HC_n^{(i)} (X) $$\\u000a is the quotient of the Betti cohomology\\u000a$$H^{2i - n} (X(\\\\mathbb{C});\\\\mathbb{C}) $$\\u000a by the \\u000a$$(i + 1)^{st} $$\\u000a piece of the Hodge filtration.
Charles Weibel
Behavior of rigid plastics under cyclic loading
Research progress on the dynamic fatigue of plastics is briefly reviewed. Attention is concentrated on the problems of damage accumulation and self-heating. The effect of various factors on the fatigue of plastics is considered. The possibility of predicting the cyclic life-time from the results of long-time static strength tests is examined. The prospects for the construction of a theory of
V. P. Tamuzh
Highly Efficient Protein Misfolding Cyclic Amplification
Protein misfolding cyclic amplification (PMCA) provides faithful replication of mammalian prions in vitro and has numerous applications in prion research. However, the low efficiency of conversion of PrPC into PrPSc in PMCA limits the applicability of PMCA for many uses including structural studies of infectious prions. It also implies that only a small sub-fraction of PrPC may be available for
Nuria Gonzalez-Montalban; Natallia Makarava; Valeriy G. Ostapchenko; Regina Savtchenk; Irina Alexeeva; Robert G. Rohwer; Ilia V. Baskakov
Solid-phase synthesis of cyclic imides.
A cyclative cleavage strategy for the synthesis of cyclic imides on a polystyrene resin is described. After optimization of the cleavage conditions, a small array of succinimides and phthalimides was synthesized. The methodology was then applied to a drug discovery project, in which it was used to synthesize a new class of delta-opioid receptor ligand by both automated and manual methods. PMID:10746011
Barn, D R; Morphy, J R
Universal Responses of Cyclic-Oxidation Models Studied
NASA Technical Reports Server (NTRS)
Oxidation is an important degradation process for materials operating in the high-temperature air or oxygen environments typical of jet turbine or rocket engines. Reaction of the combustion gases with the component material forms surface layer scales during these oxidative exposures. Typically, the instantaneous rate of reaction is inversely proportional to the existing scale thickness, giving rise to parabolic kinetics. However, more realistic applications entail periodic startup and shutdown. Some scale spallation may occur upon cooling, resulting in loss of the protective diffusion barrier provided by a fully intact scale. Upon reheating, the component will experience accelerated oxidation due to this spallation. Cyclic-oxidation testing has, therefore, been a mainstay of characterization and performance ranking for high-temperature materials. Models simulate this process by calculating how a scale spalls upon cooling and regrows upon heating (refs. 1 to 3). Recently released NASA software (COSP for Windows) allows researchers to specify a uniform layer or discrete segments of spallation (ref. 4). Families of model curves exhibit consistent regularity and trends with input parameters, and characteristic features have been empirically described in terms of these parameters. Although much insight has been gained from experimental and model curves, no equation has been derived that can describe this behavior explicitly as functions of the key oxidation parameters.
Smialek, James L.
Cyclic transition to turbulence in rigid abdominal aortic aneurysm models
NASA Astrophysics Data System (ADS)
The hydrodynamic stability of cyclic flows inside rigid abdominal aortic aneurysm (AAA) models was investigated. Rectified sine waveforms were used to simulate aortic flow conditions (Re mean=1600-2100 and ?=7.2-12.2). Depending on the bulge geometry ( D/ d and L/ d ratios), AAA flows can be broadly classified into three regimes, namely types A, B and C, respectively. While type A has no vortex formation, type B and C have distinctive laminar vortical structures that are very different from one another. The type of flow regimes would also determine where and when the transition to turbulence would occur and the portion of the cycle at which the flow remains turbulent in the bulge. The stability characteristics of types B and C are obtained from the linear stability analysis performed on the unsteady velocity profiles measured at different phases of a cycle. Based on the linear stability analyses, instability is found to initiate in the bulge for types B and C through the formation of vortical structures. Instability grows progressively during the acceleration phase and transition to turbulence in the bulge occurs shortly after the commencement of the deceleration phase in all cases investigated. The mechanisms of transition to turbulence for types B and C are discussed. Although transition to turbulence appears in all the cases investigated here, fully laminar flows in types B and C are predicted to exist by the linear stability theory under extreme flow conditions. Finally, the in vivo biological implications of the in vitro results were discussed.
Yip, T. H.; Yu, S. C. M.
Cyclic viscoelastoplasticity of polypropylene/nanoclay composites
NASA Astrophysics Data System (ADS)
Observations are reported on isotactic polypropylene/organically modified nanoclay hybrids with concentrations of filler ranging from 0 to 5 wt.% in cyclic tensile tests with a stress-controlled program (oscillations between various maximum stresses and the zero minimum stress). A pronounced effect of nanofiller is demonstrated: reinforcement with 2 wt.% of clay results in strong reduction of maximum and minimum strains per cycle and growth of number of cycles to failure compared with neat polypropylene. To rationalize these findings, a constitutive model is developed in cyclic viscoelasticity and viscoplasticity of polymer nanocomposites. Adjustable parameters in the stress-strain relations are found by fitting experimental data. The model correctly describes the growth of the ratcheting strain and shows that fatigue failure is driven by a pronounced increase in plastic strain in the crystalline phase. To assess the influence of loading conditions on the changes in the material parameters, experimental data on polypropylene are studied in cyclic tests with a strain-controlled program (oscillations between fixed maximum and minimum strains) and a mixed program (oscillations between various maximum strains and the zero minimum stress). Numerical simulation confirms the ability of the model to predict the evolution of stress-strain diagrams with the number of cycles.
Drozdov, A. D.; deC. Christiansen, J.
High-affinity Cyclic Peptide Matriptase Inhibitors*
The type II transmembrane serine protease matriptase is a key activator of multiple signaling pathways associated with cell proliferation and modification of the extracellular matrix. Deregulated matriptase activity correlates with a number of diseases, including cancer and hence highly selective matriptase inhibitors may have therapeutic potential. The plant-derived cyclic peptide, sunflower trypsin inhibitor-1 (SFTI-1), is a promising drug scaffold with potent matriptase inhibitory activity. In the current study we have analyzed the structure-activity relationships of SFTI-1 and Momordica cochinchinensis trypsin inhibitor-II (MCoTI-II), a structurally divergent trypsin inhibitor from Momordica cochinchinensis that also contains a cyclic backbone. We show that MCoTI-II is a significantly more potent matriptase inhibitor than SFTI-1 and that all alanine mutants of both peptides, generated using positional scanning mutagenesis, have decreased trypsin affinity, whereas several mutations either maintain or result in enhanced matriptase inhibitory activity. These intriguing results were used to design one of the most potent matriptase inhibitors known to date with a 290 pm equilibrium dissociation constant, and provide the first indication on how to modulate affinity for matriptase over trypsin in cyclic peptides. This information might be useful for the design of more selective and therapeutically relevant inhibitors of matriptase.
Quimbar, Pedro; Malik, Uru; Sommerhoff, Christian P.; Kaas, Quentin; Chan, Lai Y.; Huang, Yen-Hua; Grundhuber, Maresa; Dunse, Kerry; Craik, David J.; Anderson, Marilyn A.; Daly, Norelle L.
Plasma inverse transition acceleration
It can be proved fundamentally from the reciprocity theorem with which the electromagnetism is endowed that corresponding to each spontaneous process of radiation by a charged particle there is an inverse process which defines a unique acceleration mechanism, from Cherenkov radiation to inverse Cherenkov acceleration (ICA) [1], from Smith-Purcell radiation to inverse Smith-Purcell acceleration (ISPA) [2], and from undulator radiation to inverse undulator acceleration (IUA) [3]. There is no exception. Yet, for nearly 30 years after each of the aforementioned inverse processes has been clarified for laser acceleration, inverse transition acceleration (ITA), despite speculation [4], has remained the least understood, and above all, no practical implementation of ITA has been found, until now. Unlike all its counterparts in which phase synchronism is established one way or the other such that a particle can continuously gain energy from an acceleration wave, the ITA to be discussed here, termed plasma inverse transition acceleration (PITA), operates under fundamentally different principle. As a result, the discovery of PITA has been delayed for decades, waiting for a conceptual breakthrough in accelerator physics: the principle of alternating gradient acceleration [5, 6, 7, 8, 9, 10]. In fact, PITA was invented [7, 8] as one of several realizations of the new principle.
Xie, Ming
Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing
NASA Technical Reports Server (NTRS)
Evaluation of metal-based structures has long relied on atmospheric exposure test sites to determine corrosion resistance in marine environments. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions of the corrosive environment. Their success for correlation to atmospheric exposure is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated laboratory testing, which often focuses on the electrochemical reactions that occur during corrosion conditions, has yet to be universally accepted as a useful tool in predicting the long term service life of a metal despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard and their use is imperative, a method that correlates timescales from atmospheric exposure to accelerated testing would be very valuable. This work uses surface chemistry to interpret the chemical changes occurring on low carbon steel during atmospheric and accelerated corrosion conditions with the objective of finding a correlation between its accelerated and long-term corrosion performance. The current results of correlating data from marine atmospheric exposure conditions at the Kennedy Space Center beachside corrosion test site, alternating seawater spray, and immersion in typical electrochemical laboratory conditions, will be presented. Key words: atmospheric exposure, accelerated corrosion testing, alternating seawater spray, marine, correlation, seawater, carbon steel, long-term corrosion performance prediction, X-ray photoelectron spectroscopy.
Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerone C.; Kolody, Mark R.
The conformations of cyclic polymers in bidisperse blends of cyclic polymers
NASA Astrophysics Data System (ADS)
The size of cyclic polymers in bidisperse blends of chemically identical molecules is analyzed by computer simulations. The compression of entangled rings can be explained by the changes in the penetrable fraction of the surface bounded by the ring. Corrections for small rings can be approximated by a concatenation probability 1-POO that a cyclic polymer entraps at least one other cyclic polymer. Both results are in line with a previous work [1] on the compression of entangled cyclic polymers in monodisperse melts. For entangled cyclic polymers, bond-bond correlations show a constant anti-correlation peak at a curvilinear distance of about ten segments that coincides with a horizontal tangent in the normalized mean square internal distances along the ring for sufficiently large degrees of polymerization. In consequence, the length scale of topological interactions must be considered as constant in contrast to a recent proposal by Sakaue [2]. Our data is not in accord with an extension of the model of Cates and Deutsch [3] to bidiperse blends of ring polymers.[4pt] [1] M. Lang, J. Fischer, J.-U. Sommer, Macromolecules 45 (2012) 7642-7648.[0pt] [2] T. Sakaue, Phys. Rev. Lett. 2011, 106, 167802.[0pt] [3] M. E. Cates, J. M. Deutsch, J. Phys. (Paris) 1986, 47, 2121- 2128.
Lang, Michael
The Dielectric Wall Accelerator (DWA), a class of induction accelerators, employs a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge to mass ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.
Caporaso, G J; Chen, Y; Sampayan, S E
Optically pulsed electron accelerator
An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.
Fraser, John S. (Los Alamos, NM); Sheffield, Richard L. (Los Alamos, NM)
Optically pulsed electron accelerator
An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.
Fraser, J.S.; Sheffield, R.L.
The foxhole accelerating structure
This report examines some properties of a new type of open accelerating structure. It consists of a series of rectangular cavities, which we call foxholes, joined by a beam channel. The power for accelerating the particles comes from an external radiation source and enters the cavities through their open upper surfaces. Analytic and computer calculations are presented showing that the foxhole is a suitable structure for accelerating relativistic electrons.
Fernow, R.C.; Claus, J.
A Mechanochemical Model of Cell Reorientation on Substrates under Cyclic Stretch
We report a theoretical study on the cyclic stretch-induced reorientation of spindle-shaped cells. Specifically, by taking into account the evolution of sub-cellular structures like the contractile stress fibers and adhesive receptor-ligand clusters, we develop a mechanochemical model to describe the dynamics of cell realignment in response to cyclically stretched substrates. Our main hypothesis is that cells tend to orient in the direction where the formation of stress fibers is energetically most favorable. We show that, when subjected to cyclic stretch, the final alignment of cells reflects the competition between the elevated force within stress fibers that accelerates their disassembly and the disruption of cell-substrate adhesion as well, and an effectively increased substrate rigidity that promotes more stable focal adhesions. Our model predictions are consistent with various observations like the substrate rigidity dependent formation of stable adhesions and the stretching frequency, as well as stretching amplitude, dependence of cell realignment. This theory also provides a simple explanation on the regulation of protein Rho in the formation of stretch-induced stress fibers in cells.
Qian, Jin; Liu, Haipei; Lin, Yuan; Chen, Weiqiu; Gao, Huajian
The design of high-intensity accelerators is described, using examples of machines being built at the Los Alamos National Laboratory. The major design problem with these accelerators is associated with control of beam loss when accelerator intensity is increased. Beam dynamics, beam loss, and the radio-frequency quadrupole structure are discussed in the first part of the chapter followed by an explanation of plans to achieve high-intensity operation in three projects: the Fusion Material Irradiation Tests (a joint effort with the Hanford Development Laboratory in Richland, Washington), the Proton Storage Ring (an addition to the LAMPF accelerator), and the Racetrack Microtron Project (with the National Bureau of Standards).
Knapp, E.A.
Various resonances important in accelerators are analyzed, with the intention of demonstrating their essential similarity. Transverse instabilities of bunched electron beams are emphasized, including beam--beam effects.
Talman, R.
Various resonances important in accelerators are analyzed, with the intention of demonstrating their essential similarity. Transverse instabilities of bunched electron beams are emphasized, including beam-beam effects.
Talman, R.
Particle acceleration in flares
NASA Technical Reports Server (NTRS)
Particle acceleration is intrinsic to the primary energy release in the impulsive phase of solar flares, and we cannot understand flares without understanding acceleration. New observations in soft and hard X-rays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements exhibit at least five different time scales in flares. In addition, some new observations of delayed acceleration signatures are also presented. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.
Benz, Arnold O.; Kosugi, Takeo; Aschwanden, Markus J.; Benka, Steve G.; Chupp, Edward L.; Enome, Shinzo; Garcia, Howard; Holman, Gordon D.; Kurt, Victoria G.; Sakao, Taro
The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases. PMID:24365468
Kreiner, A J; Baldo, M; Bergueiro, J R; Cartelli, D; Castell, W; Thatar Vento, V; Gomez Asoia, J; Mercuri, D; Padulo, J; Suarez Sandin, J C; Erhardt, J; Kesque, J M; Valda, A A; Debray, M E; Somacal, H R; Igarzabal, M; Minsky, D M; Herrera, M S; Capoulat, M E; Gonzalez, S J; Del Grosso, M F; Gagetti, L; Suarez Anzorena, M; Gun, M; Carranza, O
Due to their finite lifetime, muons must be accelerated very rapidly. It is challenging to make the magnets ramp fast enough to accelerate in a synchrotron, and accelerating in a linac is very expensive. One can use a recirculating accelerator (like CEBAF), but one needs a different arc for each turn, and this limits the number of turns one can use to accelerate, and therefore requires significant amounts of RF to achieve the desired energy gain. An alternative method for muon acceleration is using a fixed field alternating gradient (FFAG) accelerator. Such an accelerator has a very large energy acceptance (a factor of two or three), allowing one to use the same arc with a magnetic field that is constant over time. Thus, one can in principle make as many turns as one can tolerate due to muon decay, therefore reducing the RF cost without increasing the arc cost. This paper reviews the current status of research into the design of FFAGs for muon acceleration. Several current designs are described and compared. General design considerations are also discussed.
Android Acceleration Application
NSDL National Science Digital Library
In the first of two sequential lessons, students create mobile apps that collect data from an Android device's accelerometer and then store that data to a database. This lesson provides practice with MIT's App Inventor software and culminates with students writing their own apps for measuring acceleration. In the second lesson, students are given an app for an Android device, which measures acceleration. They investigate acceleration by collecting acceleration vs. time data using the accelerometer of a sliding Android device. Then they use the data to create velocity vs. time graphs and approximate the maximum velocity of the device.
IMPART RET Program, College of Information Science & Technology,
Charged particle accelerator grating
A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.
Palmer, Robert B. (Shoreham, NY)
Accelerators and Nobel Laureates
NSDL National Science Digital Library
This online article written by Sven Kullander at the Nobel e-Museum discusses the importance of particle accelerators to physics in a historical context. After studying their basic operatation, users can then learn about the many accelerator inventions and their assistance in various discoveries such as x-rays and electrons. The website provides links to descriptions of the many Nobel Prize winners who have utilized accelerators in their important work. Users can view images of the large accelerators from all over the world including the United Kingdom, Sweden, and the United State.
Kullander, Sven
Acceleration of polarized protons in circular accelerators
The theory of depolarization in circular accelerators is presented. The spin equation is first expressed in terms of the particle orbit and then converted to the equivalent spinor equation. The spinor equation is then solved for three different situations: (1) a beam on a flat top near a resonance, (2) uniform acceleration through an isolated resonance, and (3) a model of a fast resonance jump. Finally, the depolarization coefficient, epsilon, is calculated in terms of properties of the particle orbit and the results are applied to a calculation of depolarization in the AGS.
Courant, E.D.; Ruth, R.D.
Interactions of cyclic and non-cyclic naphthalene diimide derivatives with different nucleic acids.
Recently, strategy based on stabilization of G-quadruplex telomeric DNA by small organic molecule has been realized by naphthalene diimide derivatives (NDIs). At the same time NDIs bind to DNA duplex as threading intercalators. Here we present cyclic derivative of naphthalene diimide (ligand 1) as DNA-binding ligand with ability to recognition of different structures of telomeric G-quadruplexes and ability to bis-intercalate to double-stranded helixes. The results have been compared to non-cyclic derivative (ligand 2) and revealed that preferential binding of ligands to nucleic acids strongly depends on their topology and structural features of ligands. PMID:24726302
Czerwinska, Izabella; Sato, Shinobu; Juskowiak, Bernard; Takenaka, Shigeori
Angular velocities, angular accelerations, and coriolis accelerations
NASA Technical Reports Server (NTRS)
Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.
Graybiel, A.
Cyclic Nucleotide Signaling in Polycystic Kidney Disease
Increased levels of 3��5�-cyclic adenosine monophosphate (cAMP) stimulate cell proliferation and fluid secretion in polycystic kidney disease (PKD). Since hydrolytic capacity of phosphodiesterases (PDE) far exceeds maximum rate of synthesis by adenylyl cyclases (AC), cellular levels of cAMP are more sensitive to PDE inhibition than to AC activity changes. We have used enzymatic, western blot, immunohistochemistry, PCR and biochemical assays to study activity and expression of PDE families and isoforms and expression of downstream effectors of cAMP signaling in wildtype and PKD rat and mouse kidneys. The results indicate: 1) Species specific differences in PDE expression; higher PDE activity in kidneys from mice compared to rats; higher contribution of PDE1, relative to PDE4 and PDE3, to total PDE activity of kidney lysate and lower PDE1, PDE3 and PDE4 activities in murine cystic compared to wildtype kidneys. 2) Reduced levels of several PDE1, PDE3 and PDE4 proteins despite mRNA upregulation, possibly due to increased protein degradation. 3) Increased cGMP levels in polycystic kidneys, suggesting in vivo downregulation of PDE1 activity. 4) Additive stimulatory effect of cAMP and cGMP on cystogenesis in vitro. 5) Upregulation of cAMP-dependent protein kinase (PKA) subunits I? and II?, PKare, CREB-1 mRNA, and CREM, ATF-1 and ICER proteins in cystic compared to wildtype kidneys. In summary, the results of this study suggest that alterations in cyclic nucleotide catabolism may render the cystic epithelium particularly susceptible to factors acting on Gs coupled receptors, account at least in part for the upregulation of cyclic nucleotide signaling in PKD, and contribute substantially to the progression of this disease.
Wang, Xiaofang; Ward, Christopher J.; Harris, Peter C.; Torres, Vicente E.
Universal Behavior of a Cyclic Oxidation Model
NASA Technical Reports Server (NTRS)
A mathematical model has been generated to represent the iterative, discrete growth and spallation processes associated with cyclic oxidation. Parabolic growth kinetics (k(sub p)) over and a constant spall area (F(sub A)) were assumed, with spalling occurring interfacially at the thickest regions of the scale. Although most models require numerical techniques, the regularity and simplicity of this progression permitted an approximation by algebraic expressions. Normalization could now be performed to reflect all parametric effects, and a universal cyclic oxidation response was generated: W(sub u) = 1/2 {3J(sub u)(sup 1/2)+ J(sub u)(sup 3/2)} where W, is weight change normalized by the maximum and J(sub u) is the cycle number normalized by the number to reach maximum. Similarly, the total amount of metal consumed was represented by a single normalized curve. The factor [(S(sub c)-l)(raised dot)sqrt(F(sub A)k(sub p)DELTAt)] was identified as a general figure of merit, where S(sub c) is the mass ratio of oxide to oxygen and DELTAt is the cycle duration. A cyclic oxidation failure map was constructed, in normalized k(sub p)-F(sub A) space, as defined by the locus of points corresponding to a critical amount of metal consumption in a given time. All three constructions describe behavior for every value of growth rate, spall fraction, and cycle duration by means of single curves, but with two branches corresponding to the times before and after steady state is achieved.
Smialek, James L.
Antioxidants block cyclic loading induced chondrocyte death.
Articular cartilage in congruous joints benefits from the moderate stresses and strains associated with normal cyclic loading. However, loading of joints with surface incongruities can lead to local stress and strain elevation at "step-off' sites where cartilage is not fully buttressed b ysurrounding matrix. Excessive stresses and strains predicted to occur at such sites may induce apoptosis, a process thought to promote cartilage degeneration and osteoarthritis (OA) through chondrocyte attrition. We hypothesized that the induction of apoptosis is mediated by oxidants, and that antioxidants can reduce elevated stress-induced chondrocyte attrition. To test this we exposed cylindrical cartilage explants from human articular cartilage to radially unconfined cyclic axial compression (3600 cycles, 1 Hz, 50% duty cycle) using two different physiologic loads (2MPa and 5 MPa). We found that 30% of chondrocytes in the superficial zone died within 24 hours of exposure to loading with 5 MPa axial compression, whereas mortality was limited to less than 15% with 2 MPa axial compression. Similarly, lactate accumulation in the medium was suppressed by compression with 5 MPa, but not 2 MPa. Approximately 80% of cell death induced by 5 MPa compression was blocked by pre-incubation of the explants in a variety of anti-oxidants including vitamin E, n-acetyl cysteine (NAC), and a superoxide dismutase mimetic (SOD). SOD and NAC also prevented the suppression of lactate secretion after 5 MPa compression. These observations support the hypothesis that the harmful effects of abnormal cyclic loading are mediated by oxidants and suggest that treatments to prevent OA may include methods of minimizing oxidative damage to chondrocytes. PMID:17907423
Beecher, B R; Martin, J A; Pedersen, D R; Heiner, A D; Buckwalter, J A
Accelerators for energy production
NASA Astrophysics Data System (ADS)
A tremendous progress of accelerators for these several decades, has been motivated mainly by the research on subnuclear physics. The culmination in high energy accelerators might be SSC, 20 TeV collider in USA, probably the ultimate accelerator being built with the conventional principle. The technology cultivated and integrated for the accelerator development, can now stably offer the high power beam which could be used for the energy problems. The Inertial Confinement Fusion (ICF) with high current, 10 kA and short pulse, 20 ns heavy ion beam (HIB) of mass number approximately 200, would be the most promising application of accelerators for energy production. In this scenario, the fuel containing D-T mixture, will be compressed to the high temperature, approximately 10 keV and to the high density state, approximately 1000 times the solid density with the pressure of ablative plasma or thermal X ray produced by bombarding of high power HIB. The efficiency, beam power/electric power for accelerator, and the repetition rate of HIB accelerators could be most suitable for the energy production. In the present paper, the outline of HIB ICF (HIF) is presented emphasizing the key issues of high current heavy ion accelerator system.
Katayama, Takeshi
NASA Astrophysics Data System (ADS)
Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.
Birx, Daniel
Diagnostics for induction accelerators
The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960`s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore`s Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail.
Fessenden, T.J.
A {open_quotes}Universal Accelerator Libraries{close_quotes} (UAL) environment is described. Its purpose is to facilitate program modularity and inter-program and inter-process communication among heterogeneous programs. The goal ultimately is to facilitate model-based control of accelerators. {copyright} {ital 1997 American Institute of Physics.}
Malitsky, N.; Talman, R. [Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (United States)
1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.
Microscale acceleration history discriminators
A new class of micromechanical acceleration history discriminators is claimed. These discriminators allow the precise differentiation of a wide range of acceleration-time histories, thereby allowing adaptive events to be triggered in response to the severity (or lack thereof) of an external environment. Such devices have applications in airbag activation, and other safety and surety applications.
Polosky, Marc A. (Albuquerque, NM); Plummer, David W. (Albuquerque, NM)
Accelerators Beyond The Tevatron?
Following the successful operation of the Fermilab superconducting accelerator three new higher energy accelerators were planned. They were the UNK in the Soviet Union, the LHC in Europe, and the SSC in the United States. All were expected to start producing physics about 1995. They did not. Why?.
Lach, Joseph [Fermi National Accelerator Laboratory, P.O Box 500, Batavia Illinois (United States)
1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.
1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.
NASA Astrophysics Data System (ADS)
The description of beams in RF and induction accelerators share many common features. Likewise, there is considerable commonality between electron induction accelerators (see Chap. 7) and ion induction accelerators. However, in contrast to electron induction accelerators, there are fewer ion induction accelerators that have been operated as application-driven user facilities. Ion induction accelerators are envisioned for applications (see Chap. 10) such as Heavy Ion Fusion (HIF), High Energy Density Physics (HEDP), and spallation neutron sources. Most ion induction accelerators constructed to date have been limited scale facilities built for feasibility studies for HIF and HEDP where a large numbers of ions are required on target in short pulses. Because ions are typically non-relativistic or weakly relativistic in much of the machine, space-charge effects can be of crucial importance. This contrasts the situation with electron machines, which are usually strongly relativistic leading to weaker transverse space-charge effects and simplified longitudinal dynamics. Similarly, the bunch structure of ion induction accelerators relative to RF machines results in significant differences in the longitudinal physics.
Barnard, John J.; Horioka, Kazuhiko
National Technical Information Service (NTIS)
The Two-Beam Accelerator (TBA) consists of a long high-gradient accelerator structure (HGS) adjacent to an equal-length Free Electron Laser (FEL). In the FEL, a beam propagates through a long series of undulators. At regular intervals, waveguides couple m...
A. M. Sessler D. B. Hopkins
National Technical Information Service (NTIS)
The Two-Beam Accelerator (TBA) consists of a long high-gradient accelerator structure (HGS) adjacent to an equal-length Free Electron Laser (FEL). In the FEL, a beam propagates through a long series of undulators. At regular intervals, waveguides couple m...
A. M. Sessler D. B. Hopkins
Physics of Particle Acceleration.
National Technical Information Service (NTIS)
The development of particle accelerators was reviewed with regard to energy and cost. The problems of funding much larger and slower particle accelerators was considered. The question of new ideas and techniques was raised and, with this in mind, the vari...
J. D. Lawson
The Japan Proton Accelerator Research Complex (J-PARC) is under construction in Tokai site. The linac beam commissioning started last fall, while the beam commissioning of the 3-GeV Rapid-Cycling Synchrotron (RCS) will start this fall. The status of the J-PARC accelerator is reported with emphasis on the technical development accomplished for the J-PARC.
Yamazaki, Yoshishige [J-PARC Center High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Organization (JAEA) Shirakata-Shirane, Tokai-Mura, Naka-Gun, Ibaraki-Ken (Japan)
NASA Astrophysics Data System (ADS)
The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA) is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.
Iwashita, T.; Adachi, T.; Takayama, K.; Leo, K. W.; Arai, T.; Arakida, Y.; Hashimoto, M.; Kadokura, E.; Kawai, M.; Kawakubo, T.; Kubo, Tomio; Koyama, K.; Nakanishi, H.; Okazaki, K.; Okamura, K.; Someya, H.; Takagi, A.; Tokuchi, A.; Wake, M.
Repressible extracellular phosphodiesterases showing cyclic 2',3'- and cyclic 3',5'-nucleotide phosphodiesterase activities in Neurospora crassa.
Two molecular species of repressible extracellular phosphodiesterases showing cyclic 2',3'- and cyclic 3',5'-nucleotide phosphodiesterase activities were detected in mycelial culture media of wild-type Neurospora crassa and purified. The two molecular species were found to be monomeric and polymeric forms of an enzyme constituted of identical subunits having molecular weights of 50,000. This enzyme had the same electrophoretic mobility as repressible acid phosphatase. The enzyme designated repressible cyclic phosphodiesterase showed pH optima of 3.2 to 4.0 with a cyclic 3',5'-AMP substrate and 5.0 to 5.6 with a cyclic 2',3'-AMP substrate. Repressible cyclic phosphodiesterase was activated by MnCl2 and CoCl2 with cyclic 2',3'-AMP as substrate and was slightly activated by MnCl2 with cyclic 3',5'-AMP. The enzyme hydrolyzed cyclic 3',5'- and cyclic 2',3'-nucleotides, in addition to bis-rho-nitrophenyl phosphate, but not certain 5' -and 3'-nucleotides. 3'-GMP and 3'-CMP were hydrolyzed less efficiently. Mutant strains A1 (nuc-1) and B1 (nuc-2), which cannot utilize RNA or DNA as a sole source of phosphorus, were unable to produce repressible cyclic phosphodiesterase. The wild type (74A) and a heterocaryon between strains A1 and B1 produced the enzyme and showed growth on orthophosphate-free media containing cyclic 2',3'-AMP or cyclic 3',5'-AMP, whereas both mutants showed little or no growth on these media. Images
Hasunuma, K
A case of cyclic neutropenia in adults.
A 22 years old patient presented with recurrent episodes of diarrhoea, pharyngitis, apthous ulcers and fever for the past 6 months. The episodes lasted a week each time. The patient was admitted and blood studies revealed neutropenia with increased number of Large Granular Lymphocytes. Later on it was found out that his neutrophil count dropped to less than 0.2 x 10(9)/L after every 3 weeks. Bone marrow study revealed decreases neutrophil precursors during these episodes. He was diagnosed with adult onset cyclic neutropenia and his episodes were treated with G-CSF and Ceftriaxone. PMID:22764469
Mansoor, Muhammad Sohail; Khan, Muhammad Bilal Salman
Model for Cyclically Astable Third Sound Resonance
NASA Astrophysics Data System (ADS)
Third sound in a circular resonator is capable of rich behavior due to the coincidence of several characteristics: a high quality factor; the capability for wave-induced circulation changes; vortex pinning on the substrate; and the Doppler shifting of modes. One dimensional models for each of these components have previously been used to reproduce highly nonlinear third sound CW lineshapes using a steady-state approximation. We now include oscillator transients to account for cyclical amplitude modulations of third sound recently observed under conditions of a drive force where both the amplitude and frequency are fixed.
Ellis, F. M.; Carbone, Ian; Dang, Hoan
Collinear wake field acceleration
NASA Astrophysics Data System (ADS)
In the Voss-Weiland scheme of wake field acceleration a high current, ring shaped driving bunch is used to accelerate a low current beam following along an axis. In such a structure, the transformer ratio, i.e., the ratio of maximum voltage that can be gained by the on-axis beam and the voltage lost by the driving beam, can be large. In contrast, it was observed that for an arrangement in which driving and driven bunches follow the same path, and where the current distribution of both bunches is gaussian, the transformer ratio is not normally greater than two. Some of the possibilities and limitations of a collinear acceleration scheme are explored. In addition to its application to wake field acceleration in structures, this study is also of interest for the understanding of the plasma wake field accelerator.
Bane, K. I. F.; Chen, P.; Wilson, P. B.
Collinear wake field acceleration
In the Voss-Weiland scheme of wake field acceleration a high current, ring-shaped driving bunch is used to accelerate a low current beam following along on axis. In such a structure, the transformer ratio, i.e., the ratio of maximum voltage that can be gained by the on-axis beam and the voltage lost by the driving beam, can be large. In contrast, it has been observed that for an arrangement in which driving and driven bunches follow the same path, and where the current distribution of both bunches is gaussian, the transformer ratio is not normally greater than two. This paper explores some of the possibilities and limitations of a collinear acceleration scheme. In addition to its application to wake field acceleration in structures, this study is also of interest for the understanding of the plasma wake field accelerator. 11 refs., 4 figs.
Bane, K.L.F.; Chen, P.; Wilson, P.B.
Technology evaluation of man-rated acceleration test equipment for vestibular research
NASA Technical Reports Server (NTRS)
The considerations for eliminating acceleration noise cues in horizontal, linear, cyclic-motion sleds intended for both ground and shuttle-flight applications are addressed. the principal concerns are the acceleration transients associated with change in direction-of-motion for the carriage. The study presents a design limit for acceleration cues or transients based upon published measurements for thresholds of human perception to linear cyclic motion. The sources and levels for motion transients are presented based upon measurements obtained from existing sled systems. The approaches to a noise-free system recommends the use of air bearings for the carriage support and moving-coil linear induction motors operating at low frequency as the drive system. Metal belts running on air bearing pulleys provide an alternate approach to the driving system. The appendix presents a discussion of alternate testing techniques intended to provide preliminary type data by means of pendulums, linear motion devices and commercial air bearing tables.
Taback, I.; Kenimer, R. L.; Butterfield, A. J.
Limiting curves for the onset of cyclic creep
1.We empirically established the existence of a certain limiting plastic strain amplitude ?apm for a given material. With the attainment of this amplitude, cyclic creep increases abruptly during the course of cyclic softening. The ?apm-P relation was established for steels 12010, 14331, and 10GN2MFA in the form of limiting curves for the onset of cyclic creep.2.We found a connection between
Ya. Pokluda; P. Stanek
Deformation Behavior of Zircaloy4 Cladding under Cyclic Pressurization
The deformation behavior of Zircaloy-4 cladding was investigated under cyclic pressurization. A cyclic pressurization test for a cladding tube was carried out and a stress-life diagram of the cladding tube was constructed. The result showed that the O'Donnell and Langer relationship can be fitted to the fatigue behavior of the Zircaloy-4 cladding under cyclic pressurization with the frequency of 1
Jun Hwan KIM; Myoung Ho LEE; Byoung Kwon CHOI; Yong Hwan JEONG
Potential synthetic lubricants: Esters of C 18 -saturated cyclic acids
A series of 16 esters of C18-saturated cyclic acids (HCal) were prepared, and partial evaluation showed that several have qualities that recommend them\\u000a as potential low-temp lubricants. Starting materials used were primary, straight, and branched chain alcohols C4�C7; perfluoro alcohols; phenol; cyclohexanol; and C18-saturated cyclic alcohols prepared from cyclic acids. Viscosities were measured at ?40, 100, and 210F. Their viscosity
J. P. Friedrich; E. W. Bell; L. E. Gast
Interpretation of tandem mass spectra obtained from cyclic nonribosomal peptides.
Natural and non-natural cyclic peptides are a crucial component in drug discovery programs because of their considerable pharmaceutical properties. Cyclosporin, microcystins, and nodularins are all notable pharmacologically important cyclic peptides. Because these biologically active peptides are often biosynthesized nonribosomally, they often contain nonstandard amino acids, thus increasing the complexity of the resulting tandem mass spectrometry data. In addition, because of the cyclic nature, the fragmentation patterns of many of these peptides showed much higher complexity when compared to related counterparts. Therefore, at the present time it is still difficult to annotate cyclic peptides MS/MS spectra. In this current work, an annotation program was developed for the annotation and characterization of tandem mass spectra obtained from cyclic peptides. This program, which we call MS-CPA is available as a web tool (http://lol.ucsd.edu/ms-cpa_v1/Input.py). Using this program, we have successfully annotated the sequence of representative cyclic peptides, such as seglitide, tyrothricin, desmethoxymajusculamide C, dudawalamide A, and cyclomarins, in a rapid manner and also were able to provide the first-pass structure evidence of a newly discovered natural product based on predicted sequence. This compound is not available in sufficient quantities for structural elucidation by other means such as NMR. In addition to the development of this cyclic annotation program, it was observed that some cyclic peptides fragmented in unexpected ways resulting in the scrambling of sequences. In summary, MS-CPA not only provides a platform for rapid confirmation and annotation of tandem mass spectrometry data obtained with cyclic peptides but also enables quantitative analysis of the ion intensities. This program facilitates cyclic peptide analysis, sequencing, and also acts as a useful tool to investigate the uncommon fragmentation phenomena of cyclic peptides and aids the characterization of newly discovered cyclic peptides encountered in drug discovery programs. PMID:19413302
Liu, Wei-Ting; Ng, Julio; Meluzzi, Dario; Bandeira, Nuno; Gutierrez, Marcelino; Simmons, Thomas L; Schultz, Andrew W; Linington, Roger G; Moore, Bradley S; Gerwick, William H; Pevzner, Pavel A; Dorrestein, Pieter C
Synthesis of cyclic oligodeoxyribonucleotides via the 'filtration' approach.
The synthesis of cyclic di-, tri-, tetra-, penta- and hexa-thymidylic acids (16; n = 2, 3, 4, 5 and 6) and the cyclic hexadeoxyribonucleotide [d(CpCpTpApGpGp)], via the "filtration" approach, is reported. Some of the physical properties of the cyclic oligonucleotides are discussed, and their susceptibility to digestion in the presence of phosphorylytic enzymes has been studied. Images
Rao, M V; Reese, C B
Acceleration of exp 14 C BEAMS in Electrostatic Accelerators.
National Technical Information Service (NTIS)
Operational problems in the production and acceleration of exp 14 C beams for nuclear structure research in Los Alamos National Laboratory's Van de Graaff accelerators are discussed. Methods for the control of contamination in ion sources, accelerators an...
L. J. Rowton J. R. Tesmer
Analyzing radial acceleration with a smartphone acceleration sensor
NASA Astrophysics Data System (ADS)
This paper continues the sequence of experiments using the acceleration sensor of smartphones (for description of the function and the use of the acceleration sensor, see Ref. 1) within this column, in this case for analyzing the radial acceleration.
Vogt, Patrik; Kuhn, Jochen
Dependence of the Excitability of Pituitary Cells on Cyclic Nucleotides
Cyclic 3?,5?-adenosine monophosphate and cyclic 3?,5?-guanosine monophosphate are intracellular (second) messengers that are produced from the nucleotide triphosphates by a family of enzymes consisting of adenylyl and guanylyl cyclases. These enzymes are involved in a broad array of signal transduction pathways mediated by the cyclic nucleotide monophosphates and their kinases, which control multiple aspects of cell function through the phosphorylation of protein substrates. Here, we review the findings and working hypotheses on the role of the cyclic nucleotides and their kinases in the control of electrical activity of the endocrine pituitary cells and the plasma membrane channels involved in this process.
Stojilkovic, Stanko S.; Kretschmannova, Karla; Tomic, Melanija; Stratakis, Constantine A.
Theoretical Studies of Some HEDM Species: Cyclic O4, Cyclic O3 and Cubane
NASA Technical Reports Server (NTRS)
Calculations have been carried out for the HEDM species (cyclic O4, cyclic O3, and cubane) using CASSCF/derivative and CASSCF/ICCI methods. Cyclic O4 is of interest both as a potential HEDM species and because of its possible role in the ozone deficit problem in atmospheric chemistry. We have studied the pathway for decomposition from the D(2d) minimum and also have found the approximate location of the singlet triplet crossing. The barrier to decomposition is found to be about 9 kcal/mol and is not limited by the singlet triplet crossing. For cyclic O3 we have focused on the crossings between the lowest five surfaces (X(1)A(1), s(1)A(1), (1)A(2), (1)B(1), and (1)B(2)) to provide some insight into ways to form cyclic O3 photochemically. The crossing region between the X(1)A(1) and 2(1)A(1) surfaces is in agreement with the work of Xantheas et al. The calculations show that vertical excitation from the ground state to the (1)A(2) state leads to a crossing with the (1)A(1) manifold near the crossing region of the X(1)A(1) and 2(1)A(1) surfaces. We have studied the decomposition pathways for cubane to benzene plus acetylene and to cyclooctatetraene. We have also studied the ground and excited states for the photochemical ring closure step. The state which closes to cubane can be described as a double triplet pi to pi* excitation with respect to the ground state. Thus, this state has only a small oscillator strength with respect to the ground state. However, there is a singlet pi to pi* state at nearly the same energy and excitation to this state followed by intersystem crossing could lead to the triplet pi to pi* state.
Walch, Stephen P.; Langhoff, Steve R. (Technical Monitor)
Cyclic Nucleotide Mapping of Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channels.
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play a central role in the regulation of cardiac and neuronal firing rate, and these channels can be dually activated by membrane hyperpolarization and by binding of cyclic nucleotides. cAMP has been shown to directly bind HCN channels and modulate their activity. Despite this, while there are selective inhibitors that block the activation potential of the HCN channels, regulation by cAMP analogs has not been well investigated. A comprehensive screen of 47 cyclic nucleotides with modifications in the nucleobase, ribose moiety, and cyclic phosphate was tested on the three isoforms HCN1, HCN2, and HCN4. 7-CH-cAMP was identified to be a high affinity binder for HCN channels and crosschecked for its ability to act on other cAMP receptor proteins. While 7-CH-cAMP is a general activator for cAMP- and cGMP-dependent protein kinases as well as for the guanine nucleotide exchange factors Epac1 and Epac2, it displays the highest affinity to HCN channels. The molecular basis of the high affinity was investigated by determining the crystal structure of 7-CH-cAMP in complex with the cyclic nucleotide binding domain of HCN4. Electrophysiological studies demonstrate a strong activation potential of 7-CH-cAMP for the HCN4 channel in vivo. So, this makes 7-CH-cAMP a promising activator of the HCN channels in vitro whose functionality can be translated in living cells. PMID:24605759
M�ller, Stefan; Alfieri, Andrea; Bertinetti, Daniela; Aquila, Marco; Schwede, Frank; Lolicato, Marco; Rehmann, Holger; Moroni, Anna; Herberg, Friedrich W
Triality between inflation, cyclic, and phantom cosmologies
NASA Astrophysics Data System (ADS)
It is shown that any spatially flat and isotropic universe undergoing accelerated expansion driven by a self-interacting scalar field can be directly related to a contracting, decelerating cosmology. The duality is made manifest by expressing the scale factor and Hubble parameter as functions of the scalar field and simultaneously interchanging these two quantities. The decelerating universe can be twinned with a cosmology sourced by a phantom scalar field by inverting the scale factor and leaving the Hubble parameter invariant. The accelerating model can be related to the same phantom universe by identifying the scale factor with the inverse of the Hubble parameter. The duality between accelerating and decelerating backgrounds can be extended to spatially curved cosmologies and models containing perfect fluids. A similar triality and associated scale factor duality is found in the Randall-Sundrum type II braneworld scenario.
Lidsey, James E.
Large electrostatic accelerators
The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.
Jones, C.M.
Accelerator Toolbox for MATLAB
This paper introduces Accelerator Toolbox (AT)--a collection of tools to model particle accelerators and beam transport lines in the MATLAB environment. At SSRL, it has become the modeling code of choice for the ongoing design and future operation of the SPEAR 3 synchrotron light source. AT was designed to take advantage of power and simplicity of MATLAB--commercially developed environment for technical computing and visualization. Many examples in this paper illustrate the advantages of the AT approach and contrast it with existing accelerator code frameworks.
Terebilo, Andrei
We are investigating the possibility of accelerating particles with high gradients in a ''Wake Field Transformer'' (1,2). The progress of this experiment will be described. The development of the high current hollow beam electron gun was continued. In the conventional linac, the hollow beam was accelerated to about 6 MeV. Beam monitors came into operation, two gap monitors, two fluorescent monitors and a C-hacekerenkov monitor. Calculations with the computer code WAKTRACK(3) gave the final details for the high energy section of the accelerator that will be installed during 1986.
Bialowons, W.; Bremer, H.D.; Decker, F.h.; Hartrott, M.v.; Lewin, H.C.; Voss, G.h.; Weiland, T.; Wilhelm, P.; Chengde, X.; Yokoya, K.; and others
NRL Compact Accelerator Theory Studies.
National Technical Information Service (NTIS)
NRL compact accelerator theory studies in support of the Spiral Line Induction Accelerator (SLIA) and the Recirculating Linear Accelerator (RLA) are summarized in a series of short papers. The first of these papers describes the ELBA three-dimensional bea...
A. W. Ali F. Mako G. Joyce J. Krall R. F. Hubbard
Interplay between cyclic AMP-cyclic AMP receptor protein and cyclic di-GMP signaling in Vibrio cholerae biofilm formation.
Vibrio cholerae is a facultative human pathogen. The ability of V. cholerae to form biofilms is crucial for its survival in aquatic habitats between epidemics and is advantageous for host-to-host transmission during epidemics. Formation of mature biofilms requires the production of extracellular matrix components, including Vibrio polysaccharide (VPS) and matrix proteins. Biofilm formation is positively controlled by the transcriptional regulators VpsR and VpsT and is negatively regulated by the quorum-sensing transcriptional regulator HapR, as well as the cyclic AMP (cAMP)-cAMP receptor protein (CRP) regulatory complex. Transcriptome analysis of cyaA (encoding adenylate cyclase) and crp (encoding cAMP receptor protein) deletion mutants revealed that cAMP-CRP negatively regulates transcription of both VPS biosynthesis genes and genes encoding biofilm matrix proteins. Further mutational and expression analysis revealed that cAMP-CRP negatively regulates transcription of vps genes indirectly through its action on vpsR transcription. However, negative regulation of the genes encoding biofilm matrix proteins by cAMP-CRP can also occur independent of VpsR. Transcriptome analysis also revealed that cAMP-CRP regulates the expression of a set of genes encoding diguanylate cyclases (DGCs) and phosphodiesterases. Mutational and phenotypic analysis of the differentially regulated DGCs revealed that a DGC, CdgA, is responsible for the increase in biofilm formation in the Deltacrp mutant, showing the connection between of cyclic di-GMP and cAMP signaling in V. cholerae. PMID:18708497
Fong, Jiunn C N; Yildiz, Fitnat H
Amps particle accelerator definition study
NASA Technical Reports Server (NTRS)
The Particle Accelerator System of the AMPS (Atmospheric, Magnetospheric, and Plasmas in Space) payload is a series of charged particle accelerators to be flown with the Space Transportation System Shuttle on Spacelab missions. In the configuration presented, the total particle accelerator system consists of an energetic electron beam, an energetic ion accelerator, and both low voltage and high voltage plasma acceleration devices. The Orbiter is illustrated with such a particle accelerator system.
Sellen, J. M., Jr.
Learning about Accelerated Learning.
ERIC Educational Resources Information Center
When accelerated learning programs succeed, they do so in part because they invoke and integrate skills and basic information, theoretical understanding, and natural knowledge. The trainer must blend these elements appropriately. (JOW)
Caine, Geoffrey; Caine, Renate Nummela
Modulational effects in accelerators.
National Technical Information Service (NTIS)
We discuss effects of field modulations in accelerators, specifically those that can be used for operational beam diagnostics and beam halo control. In transverse beam dynamics, combined effects of nonlinear resonances and tune modulations influence diffu...
T. Satogata
Acceleration of Logarithmic Convergence
NASA Technical Reports Server (NTRS)
In this paper, we shall give a characterization of all monotonically decreasing sequence of positive terms, whose sum converge and then introduce a Transformation which can be used to accelerate the convergence of a large class of logarithmically convergent series.
Gaskin, J. G.; Ford, W. F.
Accelerating Translational Research
Accelerating Translational Research Coordinating and facilitating translational research initiatives across the NCI and the cancer research community. NCI Translational Science Meetings NCI Translates - July 28-29, 2011 NCI Translates - 2009 NCI Translates
ACCLIB: Accelerators as libraries
Accelerator based computing is a popular design paradigm employed by designers to help meet the power-performance requirements of modern System-on-chips (SoCs). However, the non-recurring costs (hardware design, HW\\/SW integration, logic and physical design, and mask generation) required to design SoCs have significantly increased, to the point where only very high-volume products are now able to invest in accelerator-based computing. The
Yue Du
APT accelerator. Topical report
The Accelerator Production of Tritium (APT) project, sponsored by Department of Energy Defense Programs (DOE\\/DP), involves the preconceptual design of an accelerator system to produce tritium for the nation`s stockpile of nuclear weapons. Tritium is an isotope of hydrogen used in nuclear weapons, and must be replenished because of radioactive decay (its half-life is approximately 12 years). Because the annual
G. Lawrence; D. Rusthoi
A rolamite acceleration sensor which has a failsafe feature including a housing, a pair of rollers, a tension band wrapped in an S shaped fashion around the rollers, wherein the band has a force-generation cut out and a failsafe cut out or weak portion. The failsafe cut out or weak portion breaks when the sensor is subjected to an excessive acceleration so that the sensor fails in an open circuit (non-conducting) state permanently.
Abbin, Joseph P. (Albuquerque, NM); Briner, Clifton F. (Albuquerque, NM); Martin, Samuel B. (Albuquerque, NM)
CEBAF accelerator achievements
In the past decade, nuclear physics users of Jefferson Lab's Continuous Electron Beam Accelerator Facility (CEBAF) have benefited from accelerator physics advances and machine improvements. As of early 2011, CEBAF operates routinely at 6 GeV, with a 12 GeV upgrade underway. This article reports highlights of CEBAF's scientific and technological evolution in the areas of cryomodule refurbishment, RF control, polarized source development, beam transport for parity experiments, magnets and hysteresis handling, beam breakup, and helium refrigerator operational optimization.
Y.C. Chao, M. Drury, C. Hovater, A. Hutton, G.A. Krafft, M. Poelker, C. Reece, M. Tiefenback
Microgravity Acceleration Measurement System
NASA Technical Reports Server (NTRS)
Microgravity Acceleration Measurement System (MAMS) is an ongoing study of the small forces (vibrations and accelerations) on the ISS that result from the operation of hardware, crew activities, as well as dockings and maneuvering. Results will be used to generalize the types of vibrations affecting vibration-sensitive experiments. Investigators seek to better understand the vibration environment on the space station to enable future research.
Foster, William
The Vacuum Beat Wave Accelerator (VBWA) utilizes two laser beams with differing wavelengths to accelerate particles in vacuo.(Sprangle et al., Opt. Comm. 124), 69 (1996); Esarey et al., Phys. Rev. E 52, 5443 (1995). The mechanism relies on the v�B force, circumventing the so-called Lawson-Woodward theorem. A proof-of-principle experiment will be performed at the Naval Research Laboratory, based on design
C. I. Moore; B. Hafizi; E. Esarey; P. Sprangle; A. Ganguly; J. L. Hirshfield
An intense electromagnetic pulse can create weak plasma oscillations through the action of the nonlinear ponderomotive force. Electrons trapped in the wake can be accelerated to high energy. Existing glass lasers of power density 10 to the 18th W\\/sq cm shone on plasmas of densities 10 to the 18th\\/cu cm can yield gigaelectronvolts of electron energy per centimeter of acceleration
T. Tajima; J. M. Dawson
Acceleration for the ?+?- collider
We discuss possible acceleration scenarios and methods for a ? +-?- collider. The accelerator must take the beams from ~100 MeV to 2 TeV energies within the muon life-time (2.2�10-6E?\\/m? ?S), while compressing bunches of ~1012 muons from m to cm bunch lengths. A linac, recirculating linac, and very rapid-cycling synchrotron approaches are studied. A multiple recirculating linac approach is
D. Summers; D. Neuffer; Q.-S. Shu; E. Willen
Biomedical accelerator mass spectrometry
NASA Astrophysics Data System (ADS)
Ultrasensitive SIMS with accelerator based spectrometers has recently begun to be applied to biomedical problems. Certain very long-lived radioisotopes of very low natural abundances can be used to trace metabolism at environmental dose levels ( [greater-or-equal, slanted] z mol in mg samples). 14C in particular can be employed to label a myriad of compounds. Competing technologies typically require super environmental doses that can perturb the system under investigation, followed by uncertain extrapolation to the low dose regime. 41Ca and 26Al are also used as elemental tracers. Given the sensitivity of the accelerator method, care must be taken to avoid contamination of the mass spectrometer and the apparatus employed in prior sample handling including chemical separation. This infant field comprises the efforts of a dozen accelerator laboratories. The Center for Accelerator Mass Spectrometry has been particularly active. In addition to collaborating with groups further afield, we are researching the kinematics and binding of genotoxins in-house, and we support innovative uses of our capability in the disciplines of chemistry, pharmacology, nutrition and physiology within the University of California. The field can be expected to grow further given the numerous potential applications and the efforts of several groups and companies to integrate more the accelerator technology into biomedical research programs; the development of miniaturized accelerator systems and ion sources capable of interfacing to conventional HPLC and GMC, etc. apparatus for complementary chemical analysis is anticipated for biomedical laboratories.
Freeman, Stewart P. H. T.; Vogel, John S.
Cyclic deformation and dynamic compressive properties of copper bicrystals
Cyclic deformation and dynamic compressive tests of three copper bicrystals were carried out on a Shimadzu servo-hydraulic testing machine and a split Hopkinson pressure bar (SHPB) apparatus respectively. The post-deformation dislocation structures, grain boundary (GB) serrations and adiabatic shear bands (ASBs) were examined using electron channeling contrast (ECC) imaging in a scanning electron microscope (SEM). After cyclic straining the secondary
R. Q. Yang; S. X. Li; Z. F. Zhang
ON INFINITE p-GROUPS WITH CYCLIC SUBGROUPS
NASA Astrophysics Data System (ADS)
For each odd prime p, continuum many nonisomorphic simple groups are constructed having isomorphic subgroup lattices and having the property that every proper subgroup is a cyclic p-group. Also constructed is a periodic group of infinite width where every proper subgroup is cyclic. The proofs are based on papers by A. Yu. Ol'shanski?.Figures: 2. Bibliography: 6 titles.
Deryabina, G. S.
Consecutive isocyanide-based multicomponent reactions: synthesis of cyclic pentadepsipeptoids.
The synthesis of six cyclic depsipeptoids inspired by the natural depsipeptide sansalvamide A is described. An efficient and fast synthetic strategy was developed using a combination of consecutive isocyanide-based multicomponent reactions (Ugi and Passerini reactions). This methodology can be used to access a variety of cyclic oligodepsipeptoids. PMID:24991252
Barreto, Ang�lica de F�tima S; Vercillo, Otilie E; Wessjohann, Ludger A; Andrade, Carlos Kleber Z
Consecutive isocyanide-based multicomponent reactions: synthesis of cyclic pentadepsipeptoids
Summary The synthesis of six cyclic depsipeptoids inspired by the natural depsipeptide sansalvamide A is described. An efficient and fast synthetic strategy was developed using a combination of consecutive isocyanide-based multicomponent reactions (Ugi and Passerini reactions). This methodology can be used to access a variety of cyclic oligodepsipeptoids.
Barreto, Angelica de Fatima S; Vercillo, Otilie E; Wessjohann, Ludger A
Dietary cyclic dipeptides, apoptosis and psychiatric disorders: A hypothesis.
Cyclic dipeptides from food and intestinal yeast cyclic dipeptides may play a role in causing psychiatric disorders such as schizophrenia. From cancer research, cyclic dipeptides such as cyclo (proline-phenylalanine) have been found to activate the pathways of apoptosis and to cause programmed cell death. Activation of such pathways is also thought to be important in causing the neurodevelopmental abnormalities seen in disorders such as schizophrenia and autistic disorder, and also may be important in Alzheimer's. Cyclic dipeptides are found in foods such as malt and cocoa and beer. The intestinal yeast Candida albicans also synthesizes cyclic dipeptides. These dipeptides may be activating apoptosis pathways throughout fetal development and postnatal development, leading to some of the changes seen in brain in schizophrenia and in other psychiatric disorders. These compounds should be researched further to see if they play a role in causing these brain changes. In addition, these cyclic dipeptides are considered within the larger context of research on amino acids and other cyclic dipeptides in neurotransmission and neurophysiology. A better understanding of the role of these cyclic dipeptides in psychiatric disorders could lead to strategies for prevention and treatment of these disorders. PMID:24717821
Semon, Bruce A
Cyclic LTI Systems and the Paraunitary Interpolation Problem.
National Technical Information Service (NTIS)
Cyclic signal processing refers to situations where all the time indices are interpreted modulo some integer L. Since the frequency domain is a uniform discrete grid, there is more freedom in theoretical and design aspects. The basics of cyclic L miltirat...
P. P. Vaidyanathan A. Kirac
The cyclic prefix of OFDM\\/DMT - an analysis
We address the impact of a too short cyclic prefix on multicarrier systems such as orthogonal frequency division multiplexing (OFDM) and discrete multitone (DMT). The main result is that the intersymbol interference (ISI) and intercarrier interference (ICI) may be spectrally concentrated and analytical expressions showing this are given. A practical implication is, e.g., that the cyclic prefix in some xDSL
Werner Henkel; Georg Taubock; Per Odling; Per Ola Borjesson; Niklas Petersson
High-Temperature Cyclic Oxidation Data, Volume 1
NASA Technical Reports Server (NTRS)
This first in a series of cyclic oxidation handbooks contains specific-weight-change-versus-time data and X-ray diffraction results derived from high-temperature cyclic tests on high-temperature, high-strength nickel-base gamma/gamma' and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.
Barrett, C. A.; Garlick, R. G.; Lowell, C. E.
Effect of cyclic horizontal loads on the behavior of piles
Simultaneously with thepiles tests soil specimens were investigated by a cyclic load in unconfined compression apparatuses to reveal the main regularities of the behavior of the soil under the given type of loading. During the tests the stress conditions and duration of the loading cycles were varied. The investigations established the character of development of total strains during cyclic loading.
B. L. Fayans; V. A. Barvashov; I. Ya. Luchkovskii; G. S. Lekumovich; M. A. Mets
Behavior of monopile foundations under cyclic lateral load
This paper describes the development and application of design charts for monopile foundations of offshore wind turbines in sandy soil under long-term cyclic lateral load. It outlines a numerical model, working with a numerical concept, which makes the calculation of accumulated displacements based on cyclic triaxial test results possible, and it describes important factors affecting the deformation response of a
Martin Achmus; Yu-Shu Kuo; Khalid Abdel-Rahman
Earth Pressure on Caissons in Marine Clay Under Cyclic Loading
Coastal protection is proposed to be made out of a contiguous caisson type of wall. These caissons can be designed to resist both lateral static and cyclic loading. With adequate depth of embedment, the walls can be designed to offer significant lateral passive resistance to counteract the lateral static and cyclic loading arising out of wave action. This article describes
S. Narasimha Rao; N. Darga Kumar
Multiplefiltering device for the estimation of cyclical DSGE models
We propose a method to estimate cyclical DSGE models using the information provided by a variety of filtering methods. We treat cyclical data obtained with different filtering methods as contaminated measurement of the relevant modelbased quantities and estimate structural and nonstructural parameters jointly using an unobservable component structure. We emply simu? lated data to illustrate the properties of the procedure
Fabio Canova; Filippo Ferroni
Yawing of wind turbines with blade cyclic-pitch variation
The control system horizontal axis wind turbine is discussed. It incorporates two features: the application of blade cyclic pitch variation adopted from rotorcraft technology, and the use of yaw angle control, not only for wind direction following, but also for rotor speed or torque control. Cyclic pitch variation in a two-bladed rotor relieves the blades of all the gyroscopic and
K. H. Hohenemser; A. H. P. Swift; D. A. Peters
Neutrophil elastase in cyclic and severe congenital neutropenia
Mutations in ELA2 encoding the neutro- phil granule protease, neutrophil elastase (NE), are the major cause of the 2 main forms of hereditary neutropenia, cyclic neutropeniaandseverecongenitalneutro- penia (SCN). Genetic evaluation of other forms of neutropenia in humans and model organisms has helped to illumi- nate the role of NE. A canine form of cyclic neutropenia corresponds to hu- man Hermansky-Pudlak
Marshall S. Horwitz; Zhijun Duan; Brice Korkmaz; Hu-Hui Lee; Matthew E. Mealiffe; Stephen J. Salipante
Damage constitutive for high strength concrete in triaxial cyclic compression
A constitutive relationship for high strength concrete in triaxial monotonic and cyclic compressions is developed based on the continuum damage mechanics. The bounding surface concept is employed in the formulation of the theoretical model. An experimental program was undertaken in order to establish databases for high strength concrete under triaxial monotonic and cyclic compressions. The stress-strain responses of high strength
Qingbin Li; Lixiang Zhang; Farhad Ansari
Adaptive feedforward control of cyclic movements using artificial neural networks
An adaptive neural network control system has been designed for the purpose of controlling cyclic movements of nonlinear dynamic systems with input time delays (as found in functional neuromuscular stimulation). The adaptive feedforward (FF) controller is implemented as a two-stage neural network. The first stage, the pattern generator (PG), generates a cyclic pattern of activity. The signals from the PG
James J. Abbas; H. J. Chizeck
Numerical Simulations of RC Hollow Piers Under Horizontal Cyclic Loading
This article addresses numerical simulations of experimentally tested RC hollow-section piers prone to shear problems under cyclic loading. Detailed nonlinear modeling was applied with 3D FEM discretization using a damage model for concrete and a cyclic behavior model for steel bars represented by uniaxial elements Analyses were supported by parameter calibration based on experimental pier test data. The results confirmed
P. Delgado; A. Monteiro; A. Ar�de; N. Vila Pouca; R. Delgado; A. Costa
The Development of Children's Understanding of Cyclic Aspects of Time
ERIC Educational Resources Information Center
This study examines the development of children's understanding of temporal cycles and the relationship between cyclic concepts and cognitive development. A sample of 62 children, ranging in age from 4 to 10 years, were administered Piagetian tests of classification and seriation and a variety of specially designed cyclic tasks. (Author/JMB)
Friedman, William J.
Finite cyclic quantum state machines: a topological perspective
Finite cyclic quantum state machines (FCQSMs) are characterized by free actions of finite cyclic groups upon odd-dimensional spheres. This provides for a covering space representation for all such machines. FCQSM simulation, as well as simple, quotient, and split FCQSMs are defined within this context. The notions of dynamical and process symmetries for FCQSMs are introduced and it is shown that
A. D. Parks
FRPC reinforced concrete beam-column joints under cyclic excitation
An investigation on the performance of reinforced concrete beam-column joints under cyclic loading is reported. Joints have been cast with adequate and deficient bond of reinforcements at the beam-column joint. FRP sheets and strips have been applied on the joints in different configurations. The columns are subjected to an axial force while the beams are subjected to a cyclic load
Abhijit Mukherjee; Mangesh Joshi
Cyclic grain boundary migration in aluminum during high temperature fatigue
Earlier observations of cyclic grain boundary migration during the reverse bending of Pb at room temperature have been confirmed through similar experiments on Al at 300/sup 0/C. It is suggested that cyclic grain boundary migration is a general phenomenon of high temperature fatigue, especially at very low frequencies.
Yavari, P.; Langdon, T.G.
Janus cyclic peptide-polymer nanotubes
NASA Astrophysics Data System (ADS)
Self-assembled nanotubular structures have numerous potential applications but these are limited by a lack of control over size and functionality. Controlling these features at the molecular level may allow realization of the potential of such structures. Here we report a new generation of self-assembled cyclic peptide-polymer nanotubes with dual functionality in the form of either a Janus or mixed polymeric corona. A �relay� synthetic strategy is used to prepare nanotubes with a demixing or mixing polymeric corona. Nanotube structure is assessed in solution using 1H-1H nuclear Overhauser effect spectroscopy NMR, and in bulk using differential scanning calorimetry. The Janus nanotubes form artificial pores in model phospholipid bilayers. These molecules provide a viable pathway for the development of intriguing nanotubular structures with dual functionality via a demixing or a mixing polymeric corona and may provide new avenues for the creation of synthetic transmembrane protein channel mimics.
Danial, Maarten; My-Nhi Tran, Carmen; Young, Philip G.; Perrier, S�bastien; Jolliffe, Katrina A.
Statistical cyclicity of the supercontinent cycle
NASA Astrophysics Data System (ADS)
Supercontinents like Pangea impose a first-order control on Earth's evolution as they modulate global heat loss, sea level, climate, and biodiversity. In a traditional view, supercontinents form and break up in a regular, perhaps periodic, manner in a cycle lasting several 100 Myr as reflected in the assembly times of Earth's major continental aggregations: Columbia, Rodinia, and Pangea. However, modern views of the supercontinent cycle propose a more irregular evolution on the basis of an improved understanding of the Precambrian geologic record. Here we use fully dynamic spherical mantle convection models featuring plate-like behavior and continental drift to investigate supercontinent formation and breakup. We further dismiss the concept of regularity but suggest a statistical cyclicity in which the supercontinent cycle may have a characteristic period imposed by mantle and lithosphere properties, but this is hidden in immense fluctuations between different cycles that arise from the chaotic nature of mantle flow.
Rolf, T.; Coltice, N.; Tackley, P. J.
Entropy of Contracting Universe in Cyclic Cosmology
NASA Astrophysics Data System (ADS)
Following up a recent proposal1 for a cyclic model based on phantom dark energy, we examine the content of the contracting universe (cu) and its entropy Scu. We find that beyond dark energy, the universe contains on average zero or an unlikely single photon which if present immediately after turnaround would have infinitesimal energy that blue shifts eventually to produce e+e- pairs. These statements are independent of the equation of state ? = p/? of dark energy provided ? < -1. Thus Scu = 0 and if observations confirm ? < -1, the entropy problem is solved. We discuss the absence of a theoretical lower bound on ? = |?+1|, then describe an anthropic fine tuning argument that renders unlikely extremely small ?. The present bound ? ? 0.1 already implies a time until turnaround of (tT - t0) ? 100 Gy.
Baum, Lauris; Frampton, Paul H.
Sildenafil accelerates fracture healing in mice.
Sildenafil, a cyclic guanosine monophosphate (cGMP)-dependent phospodiesterase-5 inhibitor, has been shown to be a potent stimulator of angiogenesis through upregulation of pro-angiogenic factors and control of cGMP concentration. Herein, we determined whether sildenafil also influences angiogenic growth factor expression and bone formation during the process of fracture healing. Bone healing was studied in a murine closed femur fracture model using radiological, biomechanical, histomorphometric, and protein biochemical analysis at 2 and 5 weeks after fracture. Thirty mice received 5?mg/kg body weight sildenafil p.o. daily. Controls (n? = 30) received equivalent amounts of vehicle. After 2 weeks of fracture healing sildenafil significantly increased osseous fracture bridging, as determined radiologically and histologically. This resulted in an increased biomechanical stiffness compared to controls. A smaller callus area with a slightly reduced amount of cartilaginous tissue indicated an accelerated healing process. After 5 weeks the differences were found blunted, demonstrating successful healing in both groups. Western blot analysis showed a significantly higher expression of the pro-angiogenic and osteogenic cysteine-rich protein (CYR) 61, confirming the increase of bone formation. We show for the first time that sildenafil treatment accelerates fracture healing by enhancing bone formation, most probably by a CYR61-associated pathway. PMID:21246617
Histing, Tina; Marciniak, Kerstin; Scheuer, Claudia; Garcia, Patric; Holstein, Joerg H; Klein, Moritz; Matthys, Romano; Pohlemann, Tim; Menger, Michael D
Computational properties and convergence analysis of BPNN for cyclic and almost cyclic learning with penalty.
Weight decay method as one of classical complexity regularization methods is simple and appears to work well in some applications for backpropagation neural networks (BPNN). This paper shows results for the weak and strong convergence for cyclic and almost cyclic learning BPNN with penalty term (CBP-P and ACBP-P). The convergence is guaranteed under certain relaxed conditions for activation functions, learning rate and under the assumption for the stationary set of error function. Furthermore, the boundedness of the weights in the training procedure is obtained in a simple and clear way. Numerical simulations are implemented to support our theoretical results and demonstrate that ACBP-P has better performance than CBP-P on both convergence speed and generalization ability. PMID:22622263
Wang, Jian; Wu, Wei; Zurada, Jacek M
Cyclic-AMP and bacterial cyclic-AMP receptor proteins revisited: adaptation for different ecological niches?
Escherichia coli cyclic-AMP receptor protein (CRP) represents one of the paradigms of bacterial gene regulation. Yet despite decades of intensive study, new information continues to emerge that prompts reassessment of this classic regulatory system. Moreover, in recent years CRPs from several other bacterial species have been characterized, allowing the general applicability of the CRP paradigm to be tested. Here the properties of the E. coli, Mycobacterium tuberculosis and Pseudomonas putida CRPs are considered in the context of the ecological niches occupied by these bacteria. It appears that the cyclic-AMP-CRP regulatory system has been adapted to respond to distinct external and internal inputs across a broad sensitivity range that is, at least in part, determined by bacterial lifestyles.
Green, Jeffrey; Stapleton, Melanie R; Smith, Laura J; Artymiuk, Peter J; Kahramanoglou, Christina; Hunt, Debbie M; Buxton, Roger S
EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators
This special issue on laser and plasma accelerators illustrates the rapid advancement and diverse applications of laser and plasma accelerators. Plasma is an attractive medium for particle acceleration because of the high electric field it can sustain, with studies of acceleration processes remaining one of the most important areas of research in both laboratory and astrophysical plasmas. The rapid advance
Robert Bingham
Accelerator-based Neutron Sources
Since the earliest experiments defining the properties of the neutron, accelerators have played an important role in providing neutrons for research and applications. For many years, neutrons produced at accelerator facilities have complemented capabilities available from reactor-based sources. Now, with the declining availability of reactor facilities, upgrades of existing accelerator facilities and proposed new, more powerful accelerator-based sources will be
James B. Ball
Plasma-based accelerator structures
Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.
Schroeder, Carl B.
The development of linear induction accelerators has been motivated by applications requiring high-pulsed currents of charged particles at voltages exceeding the capability of single-stage, diode-type accelerators and at currents too high for rf accelerators. In principle, one can accelerate charged particles to arbitrarily high voltages using a multi-stage induction machine, but the 50-MeV, 10-kA Advanced Test Accelerator (ATA) at LLNL is the highest voltage machine in existence at this time. The advent of magnetic pulse power systems makes sustained operation at high-repetition rates practical, and this capability for high-average power is very likely to open up many new applications of induction machines in the future. This paper surveys the US induction linac technology with primary emphasis on electron machines. A simplified description of how induction machines couple energy to the electron beam is given, to illustrate many of the general issues that bound the design space of induction linacs.
Briggs, R.J.
Advanced accelerator theory development
A new accelerator technology, the dielectric wall accelerator (DWA), is potentially an ultra compact accelerator/pulsed power driver. This new accelerator relies on three new components: the ultra-high gradient insulator, the asymmetric Blumlein and low jitter switches. In this report, we focused our attention on the first two components of the DWA system the insulators and the asymmetric Blumlein. First, we sought to develop the necessary design tools to model and scale the behavior of the high gradient insulator. To perform this task we concentrated on modeling the discharge processes (i.e., initiation and creation of the surface discharge). In addition, because these high gradient structures exhibit favorable microwave properties in certain accelerator configurations, we performed experiments and calculations to determine the relevant electromagnetic properties. Second, we performed circuit modeling to understand energy coupling to dynamic loads by the asymmetric Blumlein. Further, we have experimentally observed a non-linear coupling effect in certain asymmetric Blumlein configurations. That is, as these structures are stacked into a complete module, the output voltage does not sum linearly and a lower than expected output voltage results. Although we solved this effect experimentally, we performed calculations to understand this effect more fully to allow better optimization of this DWA pulse-forming line system.
Sampayan, S.E.; Houck, T.L.; Poole, B.; Tishchenko, N.; Vitello, P.A.; Wang, I.
Heparin Accelerates Gelsolin Amyloidogenesis�
The chemical environment of the extracellular matrix may influence the tissue-selective deposition observed there in gelsolin amyloid disease. Previously, we have identified the proteases that generate the amyloidogenic fragments from the full length gelsolin variants, and demonstrated that heparin is capable of accelerating gelsolin amyloidogenesis. Herein, we identify the structural features of heparin that promote the 8 kDa disease-associated gelsolin fragments (residues 173-243) generated at the cell surface to form amyloid. In conjunction with electron microscopy analyses, our kinetic studies demonstrate that heparin efficiently accelerates the formation of gelsolin amyloid by enabling intermolecular ?-sheet formation. The use of heparin analogues reveal that sulfation is important in accelerating amyloidogenesis and that the extent of acceleration is proportional to the molecular weight of heparin. In addition, heparin accelerated aggregation at both early and late stages of amyloidogenesis. Dynamic light scattering coupled to size exclusion chromatography showed that heparin promotes the formation of soluble aggregates. Collectively, these data reveal that heparin templates fibril formation and affords solubility to the aggregating peptides through its sulfated structure. By extension, the biochemical results herein suggest that tissue-selective deposition characteristic of the gelsolin amyloidoses are likely influenced by the extracellular localization of distinct glycosaminoglycans.
Suk, Ji Young; Zhang, Fuming; Balch, William E.; Linhardt, Robert J.; Kelly, Jeffery W.
Laser acceleration with open waveguides
A unified framework based on solid-state open waveguides is developed to overcome all three major limitations on acceleration distance and hence on the feasibility of two classes of laser acceleration. The three limitations are due to laser diffraction, acceleration phase slippage, and damage of waveguide structure by high power laser. The two classes of laser acceleration are direct-field acceleration and ponderomotive-driven acceleration. Thus the solutions provided here encompass all mainstream approaches for laser acceleration, either in vacuum, gases or plasmas.
Xie, Ming
Phorbol esters modulate cyclic AMP accumulation in porcine thyroid cells
In cultured porcine thyroid cells, during 60 min incubation phorbol 12-myristate 13-acetate (PMA) had no effect on basal cyclic AMP accumulation and slightly stimulated cyclic AMP accumulation evoked by thyroid stimulating hormone (TSH) or forskolin. Cholera toxin-induced cyclic AMP accumulation was significantly stimulated by PMA. On the other hand, cyclic AMP accumulation evoked by prostaglandin E/sub 1/ or E/sub 2/ (PGE/sub 1/ and PGE/sub 2/) was markedly depressed by simultaneous addition of PMA. These opposing effects of PMA on cyclic AMP accumulation evoked by PGE and cholera toxin were observed in a dose-related fashion, with half-maximal effect of around 10/sup -9/ M in either case. The almost same effects of PMA on cyclic AMP accumulation in basal and stimulated conditions were also observed in freshly prepared thyroid cells. The present study was performed in the presence of phosphodiesterase inhibitor, 3-iso-butyl-1-methylxanthine (IBMX), indicating that PMA affected adenylate cyclase activity. Therefore, it is suggested that PMA may modulate the production of cyclic AMP in response to different stimuli, possibly by affecting several sites in the adenylate cyclase complex in thyroid cells.
Emoto, T.; Kasai, K.; Hiraiwa, M.; Shimoda, S.
Reversible cyclic peptide libraries for the discovery of affinity ligands.
A novel strategy is presented for the identification of cyclic peptide ligands from combinatorial libraries of reversible cyclic depsipeptides. A method for the solid-phase synthesis of individual cyclic depsipeptides and combinatorial libraries of these compounds is proposed, which employs lactic acid (Lact) and the dipeptide ester (N?-Ac)-Ser(Ala)- as linkers for dilactonization. Upon alkaline treatment of the beads selected by screening a model library, the cyclic depsipeptides are linearized and released from the solid support to the liquid phase, to be sequenced via single-step tandem mass spectrometry (MS/MS). The protocol presented for library synthesis provides for wide structural diversity. Two model sequences, VVWVVK and AAWAAR, were chosen to present different structural examples for depsipeptide libraries and demonstrate the process of sequence determination by mass spectrometry. Further, a case study using the IgG binding cyclic depsipeptide cyclo[(N?-Ac)-S(A)-RWHYFK-Lact-E] is presented to demonstrate the process of library screening and sequence determination on the selected beads. Finally, a method is shown for synthesis of the irreversible cyclic peptide corresponding to the proposed depsipeptide structure, to make the ligand stable to the aqueous acid and alkaline conditions encountered in affinity chromatographic applications. The cyclic peptide ligand was synthesized on a poly(methacrylate) resin and used for chromatographic binding of the target IgG. PMID:24000940
Menegatti, Stefano; Ward, Kevin Lawrence; Naik, Amith Dattatray; Kish, William Stanley; Blackburn, Robert Kevin; Carbonell, Ruben Guillermo
A variety of particle accelerators have either potential or already demonstrated uses in connection with medically-related research, diagnosis, and treatment. For cancer radiotherapy, nuclear particles including protons, neutrons, heavy ions, and negative pi mesons have advantages compared to conventional radiations in terms of dose localization and/or biological effectiveness. Clinical evaluations of these particles are underway at a number of institutions. Accelerator-produced radionuclides are in widespread use for research and routine diagnostic purposes. Elemental analysis techniques with charged particles and neutrons are being applied to bone, blood, and other tissues. Finally, low-dose medical imaging can be accomplished with accelerated protons and heavy ions. The status and future of these programs are discussed.
Bradbury, J.N.
An accelerator technology legacy
Accelerator technology has been a major beneficiary of the investment made over the last decade. It is the intention of this paper to provide the reader with a glimpse of the broad nature of those advances. Development has been on a broad front and this paper can highlight only a few of those. Two spin-off applications will be outlined -- a concept for a compact, active, beam probe for solar body exploration and the concept for an accelerator-driven transmutation system for energy production.
Heighway, E.A.
Electrostatics of pyroelectric accelerators
NASA Astrophysics Data System (ADS)
Derivations for equations for calculating the potential and field strength in both single-crystal and two-crystal pyroelectric accelerators are presented. Such expressions for the single-crystal system are well established in the literature, but with cursory derivations. We provide a rigorous derivation of the single-crystal system and expand upon this physical understanding to derive expressions for the potential and field in a two-crystal system. The expressions are verified with finite element modeling and compared with experimental results. This allows for better understanding of pyroelectric accelerators.
Fullem, T. Z.; Danon, Y.
NSDL National Science Digital Library
As the US part of the Large Hadron Collider Program, US LHC "consists of efforts of Brookhaven National Laboratory (BNL), Fermi National Accelerator Laboratory (FNAL), and Lawrence Berkeley National Laboratory (LBNL) to support the construction of the LHC at CERN." This Web site provides visitors with links to each of the three participating laboratories as well as information on recent papers, reports, and other materials related to the project. While a bit dated, there is also a press release covering the production of the highest energy producing superconducting accelerator in the world; it utilizes over 6,000 superconducting magnets.
NSDL National Science Digital Library
Some may argue that gifted children have many education options, but these options do not always help gifted students learn science. Unfortunately, gifted students often do not reach their full academic potential--they are frequently less motivated to succeed because they are not being academically challenged in regular classrooms (McCoach and Siegle 2003). To counter these problems, a strong option for educating gifted students is acceleration. This article describes the challenges that more and more gifted students face when accelerating, particularly when skipping an entire academic year. Strategies to lessen their intensity and duration and, ultimately, help gifted students to succeed are also included.
Chapman, Christine
Accelerated molecular dynamics methods
The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.
Perez, Danny [Los Alamos National Laboratory
A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.
Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Nunnally, W; Paul, A; Poole, B; Rhodes, M; Sanders, D; Selenes, K; Sullivan, J; Wang, L; Watson, J
Effects of cyclic flexural fatigue on porcine bioprosthetic heart valve heterograft biomaterials.
Although bioprosthetic heart valves (BHV) remain the primary treatment modality for adult heart valve replacement, continued problems with durability remain. Several studies have implicated flexure as a major damage mode in porcine-derived heterograft biomaterials used in BHV fabrication. Although conventional accelerated wear testing can provide valuable insights into BHV damage phenomena, the constituent tissues are subjected to complex, time-varying deformation modes (i.e., tension and flexure) that do not allow for the control of the amount, direction, and location of flexure. Thus, in this study, customized fatigue testing devices were developed to subject circumferentially oriented porcine BHV tissue strips to controlled cyclic flexural loading. By using this approach, we were able to study layer-specific structural damage induced by cyclic flexural tensile and compressive stresses alone. Cycle levels of 10 x 10(6), 25 x 10(6), and 50 x 10(6) were used, with resulting changes in flexural stiffness and collagen structure assessed. Results indicated that flexural rigidity was markedly reduced after only 10 x 10(6) cycles, and progressively decayed at a lower rate with cycle number thereafter. Moreover, the against-curvature fatigue direction induced the most damage, suggesting that the ventricularis and fibrosa layers have low resistance to cyclic flexural compressive and tensile loads, respectively. The histological analyses indicated progressive collagen fiber delamination as early as 10 x 10(6) cycles but otherwise no change in gross collagen orientation. Our results underscore that porcine-derived heterograft biomaterials are very sensitive to flexural fatigue, with delamination of the tissue layers the primary underlying mechanism. This appears to be in contrast to pericardial BHV, wherein high tensile stresses are considered to be the major cause of structural failure. These findings point toward the need for the development of chemical fixation technologies that minimize flexure-induced damage to extend porcine heterograft biomaterial durability. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010. PMID:20166221
Mirnajafi, Ali; Zubiate, Brett; Sacks, Michael S
Interactions between cyclic cell penetrating peptides and lipid membranes
NASA Astrophysics Data System (ADS)
Cyclic peptides exhibit strong enhancement in receptor-binding affinity, specificity, and stability relative to their linear counterparts, partially due to their reduced conformational freedom. In this work, we examine cyclic versions of cell penetrating peptides. Using small-angle x-ray scattering (SAXS) measurements, we show that cyclic polyarginine peptides generate saddle-splay curvature more efficiently than their linear counterparts, We show how this increase in induced saddle splay curvature impinges on the efficiency of cell penetration in a series of giant vesicle and intracellular trafficking experiments.
Zhao, Kun; Liu, Tao; Choe, Mike; Kamei, Daniel; Pei, Dehua; Wong, Gerard
Cyclic behavior at quasi-parallel collisionless shocks
NASA Technical Reports Server (NTRS)
Large scale one-dimensional hybrid simulations with resistive electrons have been carried out of a quasi-parallel high-Mach-number collisionless shock. The shock initially appears stable, but then exhibits cyclic behavior. For the magnetic field, the cycle consists of a period when the transition from upstream to downstream is steep and well defined, followed by a period when the shock transition is extended and perturbed. This cyclic shock solution results from upstream perturbations caused by backstreaming gyrating ions convecting into the shock. The cyclic reformation of a sharp shock transition can allow ions, at one time upstream because of reflection or leakage, to contribute to the shock thermalization.
Burgess, D.
A novel pathway in the photooxygenation of cyclic allenes.
[equation--see text] The photooxidation of cyclic allenes gives rise to cyclic 1,2, 3-trione hydrates. The formation of these compounds points to a novel photooxidation mechanism involving both singlet and triplet oxygen. Upon placement of a methyl group on the allene, the mechanism shifts to predominantly an "ene" reaction. The corresponding cycloadditions with 4-methyl-1,3,4-triazoline-3, 5-dione (MTAD) with cyclic allenes involve 2 equiv of MTAD. The dipolar intermediates are trapped with H(2)O to give alpha-urazole-substituted 2-cycloalkenones. PMID:10814453
Erden, I; Song, J; Cao, W
Cyclic plasticity models and application in fatigue analysis
NASA Technical Reports Server (NTRS)
An analytical procedure for prediction of the cyclic plasticity effects on both the structural fatigue life to crack initiation and the rate of crack growth is presented. The crack initiation criterion is based on the Coffin-Manson formulae extended for multiaxial stress state and for inclusion of the mean stress effect. This criterion is also applied for the accumulated damage ahead of the existing crack tip which is assumed to be related to the crack growth rate. Three cyclic plasticity models, based on the concept of combination of several yield surfaces, are employed for computing the crack growth rate of a crack plane stress panel under several cyclic loading conditions.
Kalev, I.
The cyclic fatigue behavior of adhesive joints
NASA Astrophysics Data System (ADS)
In the last six months we have: (1) Concentrated our efforts on the fatigue failure of carbon-fiber PEEK/AFl63 lap joints, and in particular we have started to predict the life time of single-lap joints under cyclic fatigue loading. The analysis is based on data obtained from double cantilever beam (DCB) fracture mechanics tests; (2) Further, we have been successful in measuring the rate of crack growth in lap joints during fatigue fracture using ultrasonic scanning; (3) Preliminary test data on the static fracture of glass-fiber reinforced poly(phenylene sulphide) (PPS)/AF163 joints have also been studied; and (4) A comparison has been made in computing the critical strain energy release rate G(sub c) for the glass-fiber PPS/AF163 joints based on the compliance method, beam theory and corrected beam theory. The last method accounts for large non-linear deflections and the associated crack root rotations along with the necessary corrections for the increase in stiffness introduced by the presence of end blocks.
Kinloch, A. J.; Toh, T.
Opposite effects of different hexachlorocyclohexane (lindane) isomers on cerebellar cyclic GMP: relation of cyclic GMP accumulation to seizure activity
A number of different depressant and convulsant agents have been shown to alter accumulation of cerebellar cyclic GMP. Since the different hexachlorocyclohexane (HCH) isomers elicit different pharmacological responses in mammals, the authors examined their effects on the accumulation of cerebellar cyclic GMP. Mice received one of the HCH isomers and were sacrificed for determination of cyclic GMP concentrations one hour later. Gamma-HCH increased cyclic GMP while alpha and delta -HCH decreased it. In addition, alpha and delta -HCH prevented the increase in cyclic GMP due to the gamma isomer. Picrotoxin increased cyclic GMP in a manner similar to that of gamma-HCH while strychnine produced only a small increase. All three HCH isomers inhibited the binding of /sup 3/H-TBOB (a ligand for the GABA-A-receptor linked chloride channel) in mouse cerebellum. It is concluded the different HCH isomers can have different effects on cerebellar cyclic GMP accumulation and that these effects may mediated through actions at the GABA-A receptor linked chloride channel. 15 references, 1 figure, 3 tables.
Fishman, B.E.; Gianutsos, G.
Precipitation in solution-treated Al-4wt%Cu under cyclic strain
Solution-treated Al-4wt%Cu was strain-cycled at ambient temperature and above and the precipitation behavior investigated by TEM. In the temperature range 100 C to 200 C precipitation of {Theta}'' appears to have been suppressed and precipitation of {Theta}' promoted via cyclic strain. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy supersaturation generated by dislocation motion, with a diminishing effect observed at higher temperatures due to the faster recovery of non-equilibrium vacancy concentrations. {Theta}' precipitates generated under cyclic strain are considerably smaller and more finely dispersed than those typically produced via quench-aging due to their heterogeneous nucleation on dislocations, and possess a low aspect ratio and rounded edges of the broad faces due to the introduction of ledges into the growing precipitates by dislocation cutting. Frequency effects indicate that dislocation motion, rather than the extremely small precipitate size, is responsible for the observed reduction in aspect ratio. Accelerated formation of grain boundary precipitates appears partially responsible for rapid intergranular fatigue failure following cycling at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.
Farrow, Adam M [Los Alamos National Laboratory; Laird, Campbell [U PENN
Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol
NASA Astrophysics Data System (ADS)
Surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4'-dimercaptoazobenzene (DMAB) have been investigated by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O2 (as an electron acceptor) is essential and H2O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H2O (or H2) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. This SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions.
Xu, Ping; Kang, Leilei; Mack, Nathan H.; Schanze, Kirk S.; Han, Xijiang; Wang, Hsing-Lin
Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol.
Surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4'-dimercaptoazobenzene (DMAB) have been investigated by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O? (as an electron acceptor) is essential and H?O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H?O (or H?) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. This SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions. PMID:24141289
Xu, Ping; Kang, Leilei; Mack, Nathan H; Schanze, Kirk S; Han, Xijiang; Wang, Hsing-Lin
Microassay of cyclic nucleotides in vessel wall. IV. Cyclic GMP phosphodiesterase activity.
Following our microassay for cyclic AMP phosphodiesterase (1978, Microvascular Res. 15:229), a new microassay for cyclic GMP phosphodiesterase (c-GMPPDE) activity was devised, combining the quantitative histochemical method of O.H. Lowry and J.V. Passonneau (1971, A Flexible System of Enzymatic Analysis, Academic Press, New York) with the thin-layer chromatography method of W.A. Scott and B. Solomon (1973, Biochem. Biophys. Res. Comm., 53, 1024). Using this method, c-GMPPDE activity can be accurately measured in a 250 microgram dry weight sample of tissue from the aortic wall. The optimal amount of sample and incubation time were studied, and two Km values were obtained. Low Km is 4.00 x 10(-6) and high Km is 1.25 x 10(-5). The activity of this enzyme was measured in the intima and media of the aorta of three rabbits, three cows and three pigs. The cyclic GMPPDE activities in tissue from cows, pigs and rabbits were 26.61 +/- 2.19, 20.40 +/- 1.35, 43.08 +/- 4.11 pmole/mg dry weight/min in the intima; 52.56 +/- 2.73, 16.07 +/- 3.30 and 66.51 +/- 4.60 pmole/mg dry weight/min in the media. With regard to the relationship between levels of cAMP and cGMP, the activities of cGMPPDE were 10-20 times higher than those of cAMPPDE. These assay systems should provide accurate tools for researching biological, physiological and pathological states of arterial tissues, particularly in the case of atherosclerosis. PMID:231754
Watabiki, S; Numano, F; Yokota, K; Watanabe, Y; Numano, F
Accelerated Learning Takes Off.
ERIC Educational Resources Information Center
Trainers at Bell Atlantic converted two courses to an accelerated learning format. As a result, the costs of one course were reduced by 42 percent and the other by 57 percent. The satisfaction of students and trainers greatly improved, as did their job performance. (JOW)
Gill, Mary Jane; Meier, David
NSDL National Science Digital Library
Although this lab is not an inquiry activity, it is very important in learning about acceleration and mass. It is a deeply held misconception among students that objects of different masses fall at different rates. Simply explaining that this is not true
Horton, Michael
Pulsed electromagnetic gas acceleration
NASA Technical Reports Server (NTRS)
Detailed measurements of the axial velocity profile and electromagnetic structure of a high power, quasi-steady MPD discharge are used to formulate a gasdynamic model of the acceleration process. Conceptually dividing the accelerated plasma into an inner flow and an outer flow, it is found that more than two-thirds of the total power in the plasma is deposited in the inner flow, accelerating it to an exhaust velocity of 12.5 km/sec. The outer flow, which is accelerated to a velocity of only 6.2 km/sec, appears to provide a current conduction path between the inner flow and the anode. Related cathode studies have shown that the critical current for the onset of terminal voltage fluctuations, which was recently shown to be a function of the cathode area, appears to reach an asymptote for cathodes of very large surface area. Detailed floating potential measurements show that the fluctuations are confined to the vicinity of the cathode and hence reflect a cathode emission process rather than a fundamental limit on MPD performance.
Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.
High intensity hadron accelerators
Accelerators needed to examine the intersections between nuclear and particle physics will require GeV energies with high beam intensities. Concerns about such high intensity machines are beam focusing, intensity limitations, power economics, and heavy ion applicability. These topics are the basis for this discussion. (AIP)
Teng, L.C.
A plasma medium can support a variety of wave motions which may be useful for accelerating charged particles. For highly relativistic beams the longitudinal electrostatic wave is most suitable and may be driven by laser or by particle beams. The basic principles, limitations and prospects for these devices are discussed.
Evans, R.G.
Radioisotope Dating with Accelerators.
ERIC Educational Resources Information Center
Explains a new method of detecting radioactive isotopes by counting their accelerated ions rather than the atoms that decay during the counting period. This method increases the sensitivity by several orders of magnitude, and allows one to find the ages of much older and smaller samples. (GA)
Muller, Richard A.
''Angara-5'' Accelerator System.
National Technical Information Service (NTIS)
Some considerations are given with respect to the accelerating system ''Angara-5,'' which has a beam power of 10 exp 14 W. The system is intended for the experiments of pulse initiation of the controlled fusion reaction by the high-current electron beams ...
E. P. Velikhov V. A. Glukhikh O. A. Gusev
ERIC Educational Resources Information Center
In 1995, South Side Middle School in New York implemented an organizational change and provided accelerated math instruction for all students. It is proposed that taking advance math in high school was strongly associated with successful completion of college, which inturn, correlates with subsequent educational and employment opportunities.
Burris, Carol Corbett; Heubert, Jay P.; Levin, Henry M.
Fermi National Accelerator Laboratory
NSDL National Science Digital Library
Fermilab is a national science laboratory of the U.S. Department of Energy and the home of the Tevatron, the world's second-largest particle accelerator. Through this portal, users can learn about Fermilab's experiments, research, projects, and publications. The lab also sponsors an extensive outreach program for K-20 educators and learners, much of which may be accessed online.
Laboratory, Fermi N.
NASA Astrophysics Data System (ADS)
This paper will review GEANT4 applications and extensions for accelerator studies, both as a general framework and for the simulation of specific accelerators. G4Beamline is a Geant4-based program intended to easily simulate many different aspects of beam-line design. G4Beamline implements accelerator components via an object-oriented ASCII input format. For instance, it allows the definition of a quadrupole magnet by its physical geometry, materials, and also magnetic field (including several models for fringe fields). The Muon Ionization Cooling Experiment (MICE) poses some challenges for simulation not normally found in a particle physics experiment. The G4MICE package is under development to allow a complete simulation of the MICE cooling channel (including the simulation of magnetic and RF fields) and instrumentation. BDSIM is a Geant4 based code that implements fast accelerator-style tracking for particles within the beam-pipe together with the full set of Geant4 physics processes for particles that leave the beam-pipe. The program has been used to simulate and optimize the design of proposed electron positron linear colliders (ILC and CLIC). The input to the code is based on the MAD format and allows definition of geometries, fields and materials. Geometry descriptions common to those used by the ILC detector groups have enabled common studies of the interaction region, specification of the required collimation depths and optimization of the extraction lines.
Ellis, Malcolm; Blair, Grahame; Torun, Yagmur; Roberts, Tom
Accelerating business analytics applications
Business text analytics applications have seen rapid growth, driven by the mining of data for various decision making processes. Regular expression processing is an important component of these applications, consuming as much as 50% of their total execution time. While prior work on accelerating regular expression processing has focused on Network Intrusion Detection Systems, business analytics applications impose different requirements
Valentina Salapura; Tejas Karkhanis; Priya Nagpurkar; Jose Moreira
Acceleration of Time Integration
We outline our strategies for accelerating time integration for long-running simulations, such as those for global climate modeling. The strategies target the Cray XT systems at the National Center for Computational Sciences at Oak Ridge National Laboratory. Our strategies include fully implicit, parallel-in-time, and curvelet methods.
White III, James B [ORNL; Drake, John B [ORNL; Worley, Patrick H [ORNL; Archibald, Richard K [ORNL; Evans, Katherine J [ORNL; Kothe, Douglas B [ORNL
Future accelerator magnet needs
Superconducting magnet technology is continually evolving in order to meet the demanding needs of new accelerators and to provide necessary upgrades for existing machines. A variety of designs are now under development, including high fields and gradients, rapid cycling and novel coil configurations. This paper presents a summary of R&D programs in the EU, Japan and the USA. A performance
Arnaud Devred; Stephen A. Gourlay; Akira Yamamoto
Rapid purification of iodinated ligands for cyclic nucleotide radioimmunoassays
The tyrosine methyl esters of succinyl cyclic AMP and succinyl cyclic GMP were iodinated by the chloramine T method and individually applied to C18 cartridges. A solution of 1-propanol/0.1 M sodium acetate pH 4.75 (17.5:82.5) was then pumped onto each cartridge and the eluate collected. A large peak of radioactivity, containing primarily the monoiodo and diiodo derivatives, was eluted. Radioactivity in peak fractions was greater than or equal to 95% the monoiodo derivative and represented 20 to 25% of the starting radioactivity. Contamination by the native cyclic nucleotide analogs was less than 5%. These peak fractions containing primarily monoiodinated products worked well in cyclic nucleotide radioimmunoassays. This fractionation required less than 30 min.
Wilson, S.P.
Common Cyclical Features Analysis in VAR Models with Cointegration
The paper considers n-dimensional VAR models for variables exhibiting cointegration and common cyclical features. Two specific reduced rank vector error correction models are discussed. In one, named the \\
Alain Hecq; Franz C. Palm; Jean-Pierre Urbain
21 CFR 862.1230 - Cyclic AMP test system.
Code of Federal Regulations, 2012 CFR
...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems � 862.1230 Cyclic AMP test system. (a) Identification....
Cyclic Strength of Undisturbed Sands from Niigata, Japan.
National Technical Information Service (NTIS)
Standard Penetration Tests, undisturbed field sampling, laboratory index property tests and laboratory cyclic triaxial strength tests were performed on cohesionless soils from Niigata, Japan, to determine why some soil deposits failed by liquefaction whil...
M. L. Silver
Circadian Rhythms in Catecholamine Metabolites and Cyclic Nucleotide Production.
National Technical Information Service (NTIS)
Circadian rhythms in noradrenergic (NE) and dopaminergic (DA) metabolites and in cyclic nucleotide production were measured in discrete regions of rat brain. A circadian rhythm was found in the concentration of the NE metabolite, 3-methoxy-4-hydroxyphenyl...
M. S. Kafka, M. A. Benedito, R. H. Roth, L. K. Steele, W. W. Wolfe
Adult Cyclic Vomiting Syndrome Successfully Treated with Intranasal Sumatriptan
Cyclic vomiting syndrome is an increasingly recognized cause of nausea and vomiting in adults. We report the case of a 47-year-old man with recurrent episodes of intractable nausea and vomiting for one year. His symptoms persisted for 4�7�days and then resolved spontaneously, only to return after periods of time ranging from one week up to a month. After an extensive workup, which failed to determine any causative explanation for his symptoms, he was diagnosed with cyclic vomiting syndrome. His episodes of vomiting were successfully terminated with the use of intranasal sumatriptan. In this case, we highlight that sumatriptan effectively aborted symptoms in an adult patient with cyclic vomiting syndrome. Increasing physicians� awareness of adult cyclic vomiting syndrome may improve care of patients suffering from this debilitating condition.
Kowalczyk, Monika; Parkman, Henry
Evaluation of High-Temperature Lubricant Under Cyclic Operating Conditions.
National Technical Information Service (NTIS)
The performance of a candidate high-temperature lubricant was determined under cyclic operating conditions of idle, maximum torque, and maximum power at intermediate and high oil temperatures. The results were compared with previous oil performance result...
E. A. Frame D. M. Yost
Work Hardening of Copper Crystals by Cyclic Straining.
National Technical Information Service (NTIS)
Copper single crystals were strained cyclically between constant plastic strain limits. The mechanical hysteresis loops were plotted. The loop shape became constant after a few cycles while the peak stress increased for a few hundred cycles. The effect of...
N. J. Wadsworth J. Hutchings
Constitutive Modeling of Metal Matrix Composites Under Cyclic Loading.
National Technical Information Service (NTIS)
A micro-mechanical cyclic/fatigue damage model is developed for metal matrix composites. The model is based on thermodynamical principles within the framework of continuum damage mechanics and employs physical principles of damage behavior in metal matrix...
G. Z. Voyiadjis R. Echle
Applications of Energy Density Theory in Cyclic Plasticity.
National Technical Information Service (NTIS)
This paper discusses the application of energy density theory to a variety of problems associated with cyclic plasticity. Attention is focused on problems related to fatigue life enhancement procedures, and on understanding the mechanisms which govern fai...
J. Paul L. Molent
Production of Reactive Oxygen Species by Polyhalogenated Cyclic Hydrocarbons (PCH).
National Technical Information Service (NTIS)
The results of this research strongly support the hypothesis that polyhalogenated cyclic hydrocarbons (PCH) induce production of reactive oxygen species which may contribute to many of the toxic manifestations associated with these xenobiotics. A non-inva...
S. J. Stohs
Effects of cyclic stress distribution models on fatigue life predictions.
National Technical Information Service (NTIS)
The fatigue analysis of a wind turbine component typically uses representative samples of cyclic loads to determine lifetime loads. In this paper, several techniques currently in use are compared to one another based on fatigue life analyses. The generali...
H. J. Sutherland P. S. Veers
21 CFR 862.1230 - Cyclic AMP test system.
Code of Federal Regulations, 2010 CFR
...overactivity of the parathyroid gland). Cyclic AMP measurements may also be used in the diagnosis and treatment of Graves' disease (a disorder of the thyroid) and in the differentiation of causes of hypercalcemia (elevated levels of serum...
Life Prediction Modeling Based on Cyclic Damage Accumulation.
National Technical Information Service (NTIS)
A high temperature, low cycle fatigue life prediction method was developed. This method, Cyclic Damage Accumulation (CDA), was developed for use in predicting the crack initiation lifetime of gas turbine engine materials, where initiation was defined as a...
R. S. Nelson
Cyclic Voltammetry of Polysulfide (Thiokol) Prepolymers and Related Compounds.
National Technical Information Service (NTIS)
The cyclic voltammetry of polysulfide prepolymers and related monomeric sulfur compounds was examined at a gold wire electrode. Electrode processes were assigned to the polysulfide prepolymers on the basis of those occurring in the model compounds. It was...
W. Mazurek
Acceleration of polarized proton beams
The acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian snakes are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible. A similar scheme is being studied for the 800 GeV HERA proton accelerator.
Roser, T.
Stacked insulator induction accelerator gaps
Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.
Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.
Unified constitutive modeling for proportional and nonproportional cyclic plasticity responses
NASA Astrophysics Data System (ADS)
Several features of cyclic plasticity, e.g. cyclic hardening/softening, ratcheting, relaxation, and their dependence on strain range, nonproportionality of loading, time, and temperature determine the stress-strain responses of materials under cyclic loading. Numerous efforts have been made in the past decades to characterize and model these responses. Many of these responses can be simulated reasonably by the existing constitutive models, but the same models would fail in simulating the structural responses, local stress-strain or global deformation. One of the reasons for this deficiency is that the constitutive models are not robust enough to simulate the cyclic plasticity responses when they interact with each other. This deficiency can be understood better or resolved by developing and validating constitutive models against a broad set of experimental responses and two or more of the responses interacting with each other. This dissertation develops a unified constitutive model by studying the cyclic plasticity features in an integrated manner and validating the model by simulating a broad set of proportional and nonproportional cyclic plasticity responses. The study demonstrates the drawbacks of the existing nonlinear kinematic hardening model originally developed by Chaboche and then develop and incorporate novel ideas into the model for improving its cyclic response simulations. The Chaboche model is modified by incorporating strain-range dependent cyclic hardening/softening through the kinematic hardening rule parameters, in addition to the conventional method of using only the isotropic hardening parameters. The nonproportional loading memory parameters of Tanaka and of Benallal and Marquis are incorporated to study the influence of nonproportionality. The model is assessed by simulating hysteresis loop shape, cyclic hardening-softening, cross-effect, cyclic relaxation, subsequent cyclic softening, and finally a series of ratcheting responses under uniaxial and biaxial loading responses. Next, it is demonstrated that the hysteresis loop shape and width can be improved by incorporation of time dependence (visco-effect) and a novel modeling scheme of backstress shift. Overall, this dissertation demonstrates a methodical and systematic development of a constitutive model for simulating a broad set of low-cycle fatigue responses.
Krishna, Shree
The third-order subharmonic oscillations in weakly non-linear cyclic symmetric structures with multiple degrees of freedom are studied. These strongly coupled cyclic structures, in their linear approximation, are known to possess pairwise double-degenerate natural frequencies with orthogonal normal modes. The asymptotic method of averaging is used to study the nonlinear interactions between the pairs of modes with nearly identical natural frequencies
S. Samaranayake; A. K. Bajaj
Self-assembly of cyclic rod-coil diblock copolymers
NASA Astrophysics Data System (ADS)
The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (?N)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more ``symmetrical,'' due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.
He, Linli; Chen, Zenglei; Zhang, Ruifen; Zhang, Linxi; Jiang, Zhouting
Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics.
In the recent past, the design and synthesis of peptide mimics (peptidomimetics) has received much attention. This because they have shown in many cases enhanced pharmacological properties over their natural peptide analogues. In particular, the incorporation of cyclic constructs into peptides is of high interest as they reduce the flexibility of the peptide enhancing often affinity for a certain receptor. Moreover, these cyclic mimics force the molecule into a well-defined secondary structure. Constraint structural and conformational features are often found in biological active peptides. For the synthesis of cyclic constrained peptidomimetics usually a sequence of multiple reactions has been applied, which makes it difficult to easily introduce structural diversity necessary for fine tuning the biological activity. A promising approach to tackle this problem is the use of multicomponent reactions (MCRs), because they can introduce both structural diversity and molecular complexity in only one step. Among the MCRs, the isocyanide-based multicomponent reactions (IMCRs) are most relevant for the synthesis of peptidomimetics because they provide peptide-like products. However, these IMCRs usually give linear products and in order to obtain cyclic constrained peptidomimetics, the acyclic products have to be cyclized via additional cyclization strategies. This is possible via incorporation of bifunctional substrates into the initial IMCR. Examples of such bifunctional groups are N-protected amino acids, convertible isocyanides or MCR-components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection-cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small cyclic peptide mimics (ranging from four- to seven-membered rings), medium-sized cyclic constructs or peptidic macrocycles (>12 membered rings). This review describes the developments since 2002 of IMCRs-cyclization strategies towards a wide variety of small cyclic mimics, medium sized cyclic constructs and macrocyclic peptidomimetics. PMID:24605172
Koopmanschap, Gijs; Ruijter, Eelco; Orru, Romano Va
Template-constrained cyclic sulfopeptide HIV-1 entry inhibitors�
Template-constrained cyclic sulfopeptides that inhibit HIV-1 entry were rationally designed based on a loop from monoclonal antibody (mAb) 412d. A focused set of sulfopeptides was synthesized using Fmoc-Tyr(SO3DCV)-OH (DCV = 2,2-dichlorovinyl). Three cyclic sulfopeptides that inhibit entry of HIV-1 and complement the activity of known CCR5 antagonists were identified.
Rudick, Jonathan G.; Laakso, Meg M.; Schloss, Ashley C.; DeGrado, William F.
Channel equalization for DMT with insufficient cyclic prefix
In discrete multi-tone (DMT) systems a cyclic prefix is added to the front of each modulated symbol-frame in order to partition the whole channel into many narrow independent sub-channels. When the length of the cyclic prefix is shorter than the channel length, inter-carrier interference (ICI) and inter-symbol interference (ISI) will occur in the output signal. This paper presents a decision
Jie Zhu; Wee Ser; Arye Nehorai
Evaluation of Gas Permeability of CFRP Laminates under Cyclic Loadings
NASA Astrophysics Data System (ADS)
This paper describes the experimental assessment of gas permeability of carbon fiber/toughened epoxy laminates under cyclic loadings as a fundamental research for the development of composite cryogenic propellant tank for reusable space transportation system. A thin-ply technique, which may contribute to the enhancement of damage resistance of CFRP laminates, is introduced herein, and the damage accumulation behaviors and gas permeability are compared between thin-ply laminates and standard laminates subjected to cyclic tension and impact.
Yokozeki, Tomohiro; Kuroda, Akiko; Yoshimura, Akinori; Ogasawara, Toshio; Aoki, Takahira
Phantom energy accretion onto black holes in a cyclic universe
Black holes pose a serious problem in cyclic or oscillating cosmology. It is speculated that, in the cyclic universe with phantom turnarounds, black holes will be torn apart by phantom energy prior to turnaround before they can create any problems. In this paper, using the mechanism of phantom accretion onto black holes, we find that black holes do not disappear before phantom turnaround. But the remanent black holes will not cause any problems due to Hawking evaporation.
Sun Chengyi [Institute of Modern Physics, Northwest University Xian, 710069 (China)
A computer program for cyclic plasticity and structural fatigue analysis
NASA Technical Reports Server (NTRS)
A computerized tool for the analysis of time independent cyclic plasticity structural response, life to crack initiation prediction, and crack growth rate prediction for metallic materials is described. Three analytical items are combined: the finite element method with its associated numerical techniques for idealization of the structural component, cyclic plasticity models for idealization of the material behavior, and damage accumulation criteria for the fatigue failure.
Kalev, I.
Self-assembly of cyclic rod-coil diblock copolymers.
The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (?N)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly. PMID:23485326
He, Linli; Chen, Zenglei; Zhang, Ruifen; Zhang, Linxi; Jiang, Zhouting
The Role of Opportunistic Migration in Cyclic Games
We study cyclic evolutionary games in a spatial diluted grid environment in which agents strategically interact locally but can also opportunistically move to other positions within a given migration radius. We find that opportunistic migration can inverse the cyclic prevalence between the strategies when the frequency of random imitation is large enough compared to the payoff-driven imitation. At the transition the average size of the patterns diverges and this threatens diversity of strategies.
Buesser, Pierre; Tomassini, Marco
Creep and damage accumulation in orthotropic composites under cyclic loading
Experimental results and theoretical prediction of the response of glassfiber-reinforced polyester under quasi-static, static (creep), and cyclic (fatigue) loading are presented. The nonlinear strain component at static loading and the strain amplitude rate at cyclic off-axis loading of an orthotropic composite are shown to follow the associated flow rule with a single-parameter quadratic potential function. The influence of fatigue damage
V. Tamu�s; J. Andersons; K. Aniskevich; J. Jansons; J. Korsgaard
Accelerated Stress Testing of SiC MEMS-DCA Pressure Transducers
Preliminary accelerated stress tests (AST) have been performed on 6H-SiC pn-junction piezoresistive pressure transducers that were packaged by Microelectromechanical Systems Direct Chip Attach (MEMS-DCA) process for the purpose of evaluating their long-term operational stability and reliability under cyclic pressure and temperature. Finite element analysis (FEA) was used to understand the stress distribution at critical sensor\\/Aluminum nitride (AlN) header and AlN
Ender Savrun; Vu Nguyen; Robert Okojie; Charles Blaha
Zaprinast accelerates recovery from established acute renal failure in the rat
Zaprinast accelerates recovery from established acute renal failure in the rat. Atrial natriuretic factor (ANF) has been demonstrated to be effective in the treatment of acute renal failure (ARF) in both rat and humans. The biological effects of ANF are presumed to be mediated by the generation of intracellular 3?,5?-cyclic guanosine monophosphate (cGMP). Therefore, the current investigation examined whether zaprinast
Zhonghong Guan; Steven B Miller; James E Greenwald
Structural characterization of the cyclic cystine ladder motif of ?-defensins.
The ?-defensins are, to date, the only known ribosomally synthesized cyclic peptides in mammals, and they have promising antimicrobial bioactivities. The characteristic structural motif of the ?-defensins is the cyclic cystine ladder, comprising a cyclic peptide backbone and three parallel disulfide bonds. In contrast to the cyclic cystine knot, which characterizes the plant cyclotides, the cyclic cystine ladder has not been as well described as a structural motif. Here we report the solution structures and nuclear magnetic resonance relaxation properties in aqueous solution of three representative ?-defensins from different species. Our data suggest that the ?-defensins are more rigid and structurally defined than previously thought. In addition, all three ?-defensins were found to self-associate in aqueous solution in a concentration-dependent and reversible manner, a property that might have a role in their mechanism of action. The structural definition of the ?-defensins and the cyclic cystine ladder will help to guide exploitation of these molecules as structural frameworks for the design of peptide drugs. PMID:23148585
Conibear, Anne C; Rosengren, K Johan; Harvey, Peta J; Craik, David J
[Etiology and precipitating factors of cyclic vomiting].
The aim of the study was to determine the nature, severity, precipitants and associated features of attacks and the incidence of potential aetiological factors of cyclic vomiting syndrome (CVS). Ten patients (6 boys and 4 girls aged 2-12 years) with CVS, defined as recurrent episodes of vomiting with symptom-free intervals occurring two or more times per year, with episodes having a similar pattern and for which no other cause could be found, ten patients (7 boys and 3 girls aged 7-14 years) with migraine, defined as recurrent headache with symptom-free intervals and at least three of the following symptoms or associated findings: abdominal pain, nausea or vomiting, throbbing headache, unilateral location, associated aura (visual, sensory, motor), relief after sleeping and ten controls (6 boys and 4 girls aged 4-13 years) were studied. The mean age at onset of symptoms in patients with CVS was 3.9 years and the mean number of attacks per year was 4, the average duration of episodes was 20.5 hours and the mean number of school missed days were 6 per year. The mean age at onset of symptoms in patients with migraine was 7.6 years and the mean number of attacks per year was 9.9, the average duration of episodes was 8 hours and the mean number of school missed days were 6.4 per year. A family history of migraine was significantly higher in both groups of patients, compared with controls (p = 0.009). A personal history of headache and/or migraine and associated sign or symptoms like recurrent abdominal pains, limb pain and kinetosis was significantly higher in both patients compared with controls (p < 0.001). CVS is a chronic, disabling condition and is a migraine variant, with attacks usually precipitated by stress and intercurrent infections. PMID:11387762
Scarcia, S; Fiumana, E; Gnoato, R; Pieri, E; Brunelli, P; Pocecco, M
Highly efficient protein misfolding cyclic amplification.
Protein misfolding cyclic amplification (PMCA) provides faithful replication of mammalian prions in vitro and has numerous applications in prion research. However, the low efficiency of conversion of PrP(C) into PrP(Sc) in PMCA limits the applicability of PMCA for many uses including structural studies of infectious prions. It also implies that only a small sub-fraction of PrP(C) may be available for conversion. Here we show that the yield, rate, and robustness of prion conversion and the sensitivity of prion detection are significantly improved by a simple modification of the PMCA format. Conducting PMCA reactions in the presence of Teflon beads (PMCAb) increased the conversion of PrP(C) into PrP(Sc) from ?10% to up to 100%. In PMCAb, a single 24-hour round consistently amplified PrP(Sc) by 600-700-fold. Furthermore, the sensitivity of prion detection in one round (24 hours) increased by 2-3 orders of magnitude. Using serial PMCAb, a 10��-fold dilution of scrapie brain material could be amplified to the level detectible by Western blotting in 3 rounds (72 hours). The improvements in amplification efficiency were observed for the commonly used hamster 263K strain and for the synthetic strain SSLOW that otherwise amplifies poorly in PMCA. The increase in the amplification efficiency did not come at the expense of prion replication specificity. The current study demonstrates that poor conversion efficiencies observed previously have not been due to the scarcity of a sub-fraction of PrP(C) susceptible to conversion nor due to limited concentrations of essential cellular cofactors required for conversion. The new PMCAb format offers immediate practical benefits and opens new avenues for developing fast ultrasensitive assays and for producing abundant quantities of PrP(Sc)in vitro. PMID:21347353
Gonzalez-Montalban, Nuria; Makarava, Natallia; Ostapchenko, Valeriy G; Savtchenk, Regina; Alexeeva, Irina; Rohwer, Robert G; Baskakov, Ilia V
Effects of cyclic loading on internal shear strength of unreinforced geosynthetic clay liner
Stress-controlled static and cyclic shear tests were performed by using a direct simple shear device on samples of a geomembrane-supported geosynthetic clay liner (GCL). The dry material showed no degradation in shear strength during cyclic loading as long as the peak shear stress was less than the static shear strength of the GCL with no cyclic loading. Furthermore, cyclic loading
Jiunnren Lai; David E. Daniel; Stephen G. Wright
Laser-driven electron accelerators
The following possibilities are discussed: inverse free electron laser (wiggler accelerator); inverse Cerenkov effect; plasma accelerator; dielectric tube; and grating linac. Of these, the grating acceleraton is considered the most attractive alternative. (GHT)
Palmer, R.B.
Particle Acceleration in Hypernova Explosion
NASA Astrophysics Data System (ADS)
The relativistic shock break out at the surface of Hypernova star is considered. The hydrodynamical acceleration of outer layers of Hypernova envelope is investigated. The characteristics of accelerated particles are estimated.
Marchenko, V. V.; Hnatyk, B. I.; Pekur, D. V.
Particle Acceleration in Hypernova Explosion
The relativistic shock break out at the surface of Hypernova star is considered. The hydrodynamical acceleration of outer layers of Hypernova envelope is investigated. The characteristics of accelerated particles are estimated.
V. V. Marchenko; B. I. Hnatyk; D. V. Pekur
Characterization of a calmodulin-dependent high-affinity cyclic AMP and cyclic GMP phosphodiesterase from male mouse germ cells.
Two cyclic nucleotide phosphodiesterase activities were separated by ion-exchange chromatography of cytosol from male mouse germ cells. A form eluted at low salt concentration showed high affinity (Km congruent to 2 microM) and low affinity (Km congruent to 20 microM) for cyclic AMP, and high affinity (Km congruent to 3.5 microM) for cyclic GMP. A second form, eluted at high salt concentration, showed high affinity (Km congruent to 5 microM) for cyclic AMP and was similar to a phosphodiesterase activity described in rat germ cells. The present study was performed to characterize the first form, which represents most of the phosphodiesterase activity in mouse germ cells. The enzyme was sensitive to Ca2+ and calmodulin stimulation, which increased its activity 3-4-fold. Calmodulin stimulation depended on direct interaction of the activator with the enzyme, as indicated by the reversible changes in the chromatographic elution pattern in the presence of Ca2+, as well as by the increase in the sedimentation coefficient in the presence of calmodulin. Reciprocal inhibition kinetics between cyclic AMP and cyclic GMP for the calmodulin-dependent form demonstrated a non-competitive inhibition between the two substrates, suggesting the presence of separate catalytic sites. This is in agreement with kinetic parameters and different thermal stabilities of cyclic AMP- and cyclic GMP-hydrolysing activities. Furthermore, the relevant change in s value, depending on the absence or presence of Ca2+ and calmodulin, suggested that the enzyme is composed of subunits, which aggregate in the presence of the activator. A model for catalytic site composition and reciprocal interaction is also proposed.
Geremia, R; Rossi, P; Mocini, D; Pezzotti, R; Conti, M
The field of ion acceleration to higher energies has grown rapidly in the last years. Many new facilities as well as substantial upgrades of existing facilities have extended the mass and energy range of available beams. Perhaps more significant for the long-term development of the field has been the expansion in the applications of these beams, and the building of facilities dedicated to areas outside of nuclear physics. This review will cover many of these new developments. Emphasis will be placed on accelerators with final energies above 50 MeV/amu. Facilities such as superconducting cyclotrons and storage rings are adequately covered in other review papers, and so will not be covered here.
Alonso, J.
Hypervelocity plate acceleration
Shock tubes have been used to accelerate 1.5-mm-thick stainless steel plates to high velocity while retaining their integrity. The fast shock tubes are 5.1-cm-diameter, 15.2-cm-long cylinders of PBX-9501 explosive containing a 1.1-cm-diameter cylindrical core of low-density polystyrene foam. The plates have been placed directly in contact with one face of the explosive system. Plane-wave detonation was initiated on the opposite face. A Mach disk was formed in the imploding styrofoam core, which provided the impulse required to accelerate the metal plate to high velocity. Parametric studies were made on this system to find the effect of varying plate metal, plate thickness, foam properties, and addition of a barrel. A maximum plate velocity of 9.0 km/s has been observed. 6 refs., 17 figs.
Marsh, S.P.; Tan, T.H.
Hardware Accelerated Simulated Radiography
We present the application of hardware accelerated volume rendering algorithms to the simulation of radiographs as an aid to scientists designing experiments, validating simulation codes, and understanding experimental data. The techniques presented take advantage of 32 bit floating point texture capabilities to obtain validated solutions to the radiative transport equation for X-rays. An unsorted hexahedron projection algorithm is presented for curvilinear hexahedra that produces simulated radiographs in the absorption-only regime. A sorted tetrahedral projection algorithm is presented that simulates radiographs of emissive materials. We apply the tetrahedral projection algorithm to the simulation of experimental diagnostics for inertial confinement fusion experiments on a laser at the University of Rochester. We show that the hardware accelerated solution is faster than the current technique used by scientists.
Laney, D; Callahan, S; Max, N; Silva, C; Langer, S; Frank, R
The pulsed drift-tube accelerator (DTA) concept was revived by Joe Kwan and John Staples and is being considered for the HEDP/WDM application. It could be used to reach the full energy or as an intermediate accelerator between the diode and a high gradient accelerator such as multi-beam r.f. In the earliest LBNL HIF proposals and conceptual drivers it was used as an extended injector to reach energies where an induction linac with magnetic quadrupoles is the best choice. For HEDP, because of the very short pulse duration, the DTA could provide an acceleration rate of about 1MV/m. This note is divided into two parts: the first, a design based on existing experience; the second, an optimistic extrapolation. The first accelerates 16 parallel K{sup +} beams at a constant line charge density of 0.25{micro} C/m per beam to 10 MeV; the second uses a stripper and charge selector at around 4MeV followed by further acceleration to reach 40 MeV. Both benefit from more compact sources than the present 2MV injector source, although that beam is the basis of the first design and is a viable option. A pulsed drift-tube accelerator was the first major HIF experiment at LBNL. It was designed to produce a 2{micro}s rectangular 1 Ampere C{sub s}{sup +} beam at 2MeV. It ran comfortably at 1.6MeV for several years, then at lower voltages and currents for other experiments, and remnants of that experiment are in use in present experiments, still running 25 years later. The 1A current, completely equivalent to 1.8A K{sup +}, was chosen to be intermediate between the beamlets appropriate for a multi-beam accelerator, and a single beam of, say, 10A, at injection energies. The original driver scenarios using one large beam on each side of the reactor rapidly fell out of favor because of the very high transverse and longitudinal fields from the beam space charge, circa 1MV/cm and 250 kV/cm respectively, near the chamber and because of aberrations in focusing a large diameter beam down to a 1mm radius spot at a distance of 10m. Almost all subsequent work and the present concept have invoked multiple beams. For HEDP the major differences are that the focal distance can be centimeters instead of meters, provided strong-enough lenses exist and they do, thereby allowing much higher transverse and longitudinal emittances than driver concepts, and focusing parallel small beams is easier than one big beam.
Faltens, A.
The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy under grant number DE-FG05-91ER40642, is currently in the first year of a three-year funding cycle. The program consists of the following three tasks: TASK A, Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams, TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams; TASK C, Study of a Gyroklystron High-power Microwave Source for Linear Colliders. In this report we document the progress that has been made during the past year for each of the three tasks.
Not Available
Adaptive control for accelerators
An adaptive feedforward control loop is provided to stabilize accelerator beam loading of the radio frequency field in an accelerator cavity during successive pulses of the beam into the cavity. A digital signal processor enables an adaptive algorithm to generate a feedforward error correcting signal functionally determined by the feedback error obtained by a beam pulse loading the cavity after the previous correcting signal was applied to the cavity. Each cavity feedforward correcting signal is successively stored in the digital processor and modified by the feedback error resulting from its application to generate the next feedforward error correcting signal. A feedforward error correcting signal is generated by the digital processor in advance of the beam pulse to enable a composite correcting signal and the beam pulse to arrive concurrently at the cavity.
Eaton, Lawrie E. (Los Alamos, NM); Jachim, Stephen P. (Los Alamos, NM); Natter, Eckard F. (Santa Fe, NM)
But a glance at the Livingston chart, Fig. 1, of accelerator particle energy as a function of time shows that the energy has steadily, exponentially, increased. Equally significant is the fact that this increase is the envelope of diverse technologies. If one is to stay on, or even near, the Livingston curve in future years then new acceleration techniques need to be developed. What are the new acceleration methods? In these two lectures I would like to sketch some of these new ideas. I am well aware that they will probably not result in high energy accelerators within this or the next decade, but conversely, it is likely that these ideas will form the basis for the accelerators of the next century. Anyway, the ideas are stimulating and suffice to show that accelerator physicists are not just 'engineers', but genuine scientists deserving to be welcomed into the company of high energy physicists. I believe that outsiders will find this field surprisingly fertile and, certainly fun. To put it more personally, I very much enjoy working in this field and lecturing on it. There are a number of review articles which should be consulted for references to the original literature. In addition there are three books on the subject. Given this material, I feel free to not completely reference the material in the remainder of this article; consultation of the review articles and books will be adequate as an introduction to the literature for references abound (hundreds are given). At last, by way of introduction, I should like to quote from the end of Ref. 2 for I think the remarks made there are most germane. Remember that the talk was addressed to accelerator physicists: 'Finally, it is often said, I think by physicists who are not well-informed, that accelerator builders have used up their capital and now are bereft of ideas, and as a result, high energy physics will eventually--rather soon, in fact--come to a halt. After all, one can't build too many machines greater than 27 km, and soon one will run out of space or money (almost surely money before space). This argument seems terribly wrong to me, and worse than that possibly destructive, for it will have a serious effect if it causes, as it well might, young people to elect to go into fields other than high energy physics. The proper response, I believe, is to point--in considerable detail--to some of the new concepts which show by example that we are far from being out of new ideas. Some of these concepts shall, in my view, be, or lead to, the 'stocks in trade' of the next century, and thus they will allow high energy physics to be as exciting then as it is now. It is our job to make it all happen.
Sessler, A.M.
Commissioning the GTA accelerator
The Ground Test Accelerator (GTA) is supported by the Strategic Defense command as part of their Neutral Particle Beam (NPB) program. Neutral particles have the advantage that in space they are unaffected by the earth's magnetic field and travel in straight lines unless they enter the earth's atmosphere and become charged by stripping. Heavy particles are difficult to stop and can probe the interior of space vehicles; hence, NPB can function as a discriminator between warheads and decoys. We are using GTA to resolve the physics and engineering issues related to accelerating, focusing, and steering a high-brightness, high-current H{sup -} beam and then neutralizing it. Our immediate goal is to produce a 24-MeV, 50mA device with a 2% duty factor.
Sander, O.R.; Atkins, W.H.; Bolme, G.O.; Bowling, S.; Brown, S.; Cole, R.; Gilpatrick, J.D.; Garnett, R.; Guy, F.W.; Ingalls, W.B.; Johnson, K.F.; Kerstiens, D.; Little, C.; Lohsen, R.A.; Lloyd, S.; Lysenko, W.P.; Mottershead, C.T.; Neuschaefer, G.; Power, J.; Rusthoi, D.P.; Sandoval, D.P. Stevens, R.R. Jr.; Vaughn, G.; Wadlinger, E.A.; Yuan, V. (Los Alamos National Lab., NM (United States)); Connolly, R.; Weiss, R. (Gr
Commissioning the GTA accelerator
The Ground Test Accelerator (GTA) is supported by the Strategic Defense command as part of their Neutral Particle Beam (NPB) program. Neutral particles have the advantage that in space they are unaffected by the earth`s magnetic field and travel in straight lines unless they enter the earth`s atmosphere and become charged by stripping. Heavy particles are difficult to stop and can probe the interior of space vehicles; hence, NPB can function as a discriminator between warheads and decoys. We are using GTA to resolve the physics and engineering issues related to accelerating, focusing, and steering a high-brightness, high-current H{sup -} beam and then neutralizing it. Our immediate goal is to produce a 24-MeV, 50mA device with a 2% duty factor.
Sander, O.R.; Atkins, W.H.; Bolme, G.O.; Bowling, S.; Brown, S.; Cole, R.; Gilpatrick, J.D.; Garnett, R.; Guy, F.W.; Ingalls, W.B.; Johnson, K.F.; Kerstiens, D.; Little, C.; Lohsen, R.A.; Lloyd, S.; Lysenko, W.P.; Mottershead, C.T.; Neuschaefer, G.; Power, J.; Rusthoi, D.P.; Sandoval, D.P. Stevens, R.R. Jr.; Vaughn, G.; Wadlinger, E.A.; Yuan, V. [Los Alamos National Lab., NM (United States); Connolly, R.; Weiss, R. [Grumman Space and Electronics Corp., Princeton, NJ (United States); Saadatmand, K. [Grumman Corp., Bethpage, NY (United States). Corporate Research Center
It was shown that the insertion of a cross magnetic field prevents the particles from getting out of phase with the electric field of the plasma wave in the beat wave accelerator scheme. Thus, using a CO/sub 2/ laser, n/sub c//n/sub e/ = (..omega../sub 0//..omega../sub p/)/sup 2/ approx. 35, and a 300 kG magnetic field, electrons can be (in principle) accelerated to 100 GeV in 2 meters. For comparison without the magnetic field, the same energies may be obtained in a n/sub c//n/sub e/ approx. 10/sup 5/ plasma over a distance of 100 meters.
Mori, W.; Joshi, C.; Dawson, J.M.
Accelerometer: Centripetal Acceleration
NSDL National Science Digital Library
Students work as physicists to understand centripetal acceleration concepts. They also learn about a good robot design and the accelerometer sensor. They also learn about the relationship between centripetal acceleration and centripetal force�governed by the radius between the motor and accelerometer and the amount of mass at the end of the robot's arm. Students graph and analyze data collected from an accelerometer, and learn to design robots with proper weight distribution across the robot for their robotic arms. Upon using a data logging program, they view their own data collected during the activity. By activity end , students understand how a change in radius or mass can affect the data obtained from the accelerometer through the plots generated from the data logging program. More specifically, students learn about the accuracy and precision of the accelerometer measurements from numerous trials.
Applying Mechatronics to Promote Science (AMPS) GK-12 Program,
The Role of Cyclic Nucleotide Signaling Pathways in Cancer: Targets for Prevention and Treatment
For more than four decades, the cyclic nucleotides cyclic AMP (cAMP) and cyclic GMP (cGMP) have been recognized as important signaling molecules within cells. Under normal physiological conditions, cyclic nucleotides regulate a myriad of biological processes such as cell growth and adhesion, energy homeostasis, neuronal signaling, and muscle relaxation. In addition, altered cyclic nucleotide signaling has been observed in a number of pathophysiological conditions, including cancer. While the distinct molecular alterations responsible for these effects vary depending on the specific cancer type, several studies have demonstrated that activation of cyclic nucleotide signaling through one of three mechanisms�induction of cyclic nucleotide synthesis, inhibition of cyclic nucleotide degradation, or activation of cyclic nucleotide receptors�is sufficient to inhibit proliferation and activate apoptosis in many types of cancer cells. These findings suggest that targeting cyclic nucleotide signaling can provide a strategy for the discovery of novel agents for the prevention and/or treatment of selected cancers.
Fajardo, Alexandra M.; Piazza, Gary A.; Tinsley, Heather N.
Overview of accelerators in medicine
Accelerators used for medicine include synchrotrons, cyclotrons, betatrons, microtrons, and electron, proton, and light ion linacs. Some accelerators which were formerly found only at physics laboratories are now being considered for use in hospital-based treatment and diagnostic facilities. This paper presents typical operating parameters for medical accelerators and gives specific examples of clinical applications for each type of accelerator, with emphasis on recent developments in the field.
Lennox, A.J. [Fermi National Accelerator Lab., Batavia, IL (US)]|[Rush Univ., Chicago, IL (US)
Principles of Charged Particle Acceleration
NSDL National Science Digital Library
This learning resources comprise a healthy introduction to charged particle acceleration. The site, by Stanley Humphries, a professor of electrical and computer engineering at University of New Mexico, amounts to an online textbook (.pdf) introducing the theory of charged particle acceleration. The book's fifteen chapters (with bibliography) summarize "the principles underlying all particle accelerators" and provide "a reference collection of equations and material essential to accelerator development and beam applications."
Phase stability in surfatron acceleration
Particle motion in a laser beat-wave plasma field with a transverse magnetic field is explored. It is determined that stable, phase-space buckets for acceleration are established by these fields and that particles injected near the beat-wave phase velocity can be trapped in these buckets and accelerated indefinitely, with stable phase-energy oscillations about the accelerating phase. Parameters for high-energy accelerators and lower energy demonstration experiments are presented.
Neuffer, D.
Progress on laser plasma accelerators
Several laser plasma accelerator schemes are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA). Theory indicates that a very high acceleration gradient, of order 1 GeV/m, can exist in the plasma wave driven by the beating lasers. Experimental results obtained on the PBWA experiment at UCLA confirms this. Parameters related to the PBWA as an accelerator system are derived, among them issues concerning the efficiency and the laser power and energy requirements are discussed.
Chen, P.
Particle Acceleration Mechanisms
In this paper we review the possible mechanisms for production of non-thermal electrons which are responsible for the observed\\u000a non-thermal radiation in clusters of galaxies. Our primary focus is on non-thermal Bremsstrahlung and inverse Compton scattering,\\u000a that produce hard X-ray emission. We first give a brief review of acceleration mechanisms and point out that in most astrophysical\\u000a situations, and in
V. Petrosian; A. M. Bykov
Multi-TeV Muon Colliders and high intensity Neutrino Factories have captured the imagination of the particle physics community. These new types of facility both require an advanced muon source capable of producing O(10{sup 21}) muons per year. The muons must be captured within bunches, and their phase space manipulated so that they fit within the acceptance of an accelerator. In a Neutrino Factory (NF), muons from this 'front end' are accelerated to a few GeV or a few tens of GeV, and then injected into a storage ring with long straight sections. Muon decays in the straight sections produce an intense neutrino beam. In a Muon Collider (MC) the muons must be cooled by a factor O(10{sup 6}) to produce beams that are sufficiently bright to give high luminosity in the collider. Bunches of positive and negative muons are then accelerated to high energy, and injected in opposite directions into a collider ring in which they collide at one or more interaction points. Over the last decade our understanding of the concepts and technologies needed for Muon Colliders and Neutrino Factories has advanced, and it is now believed that, within a few years, with a well focused R&D effort (i) a Neutrino Factory could be proposed, and (ii) enough could be known about the technologies needed for a Muon Collider to assess the feasibility and cost of this new type of facility, and to make a detailed plan for the remaining R&D. Although these next NF and MC steps are achievable, they are also ambitious, and will require an efficient and dedicated organization to accomplish the desired goals with limited resources. The Muon Accelerator Program (MAP) has recently been created to propose and execute this R&D program.
Geer, Steve; /Fermilab; Zisman, Mike; /LBL, Berkeley
Accelerated predictive-transform
This paper presents a novel accelerated predictive-transform (APT) modeling methodology for use in compression. The APT scheme is illustrated with a monochrome 2D image compression application yielding very promising results. For example, when the Lena image is compressed to 0.056 bits per pixel and the pixel blocks are of dimension 16�16, it is shown that both the design and implementation
Erlan H. Feria; Sos Agaian
A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.
Buttram, M.T.; Ginn, J.W.
NASA Astrophysics Data System (ADS)
In order to greatly expand scientific opportunities with radioactive isotope (RI) beams, RIKEN has constructed a new heavy-ion accelerator facility, called "RI Beam Factory (RIBF)." Three new ring cyclotrons with K-values of 570 MeV, 980 MeV, and 2600 MeV, respectively, boost the energies of the output beams from the existing K540-MeV ring cyclotron up to 440 MeV/u for light ions and 345 MeV/u for very heavy ions. These energetic heavy-ion beams are converted into intense radioactive isotope (RI) beams via projectile fragmentation of stable isotopes or in-flight fission of uranium isotopes by a superconducting fragment separator, BigRIPS. The three ring cyclotrons were commissioned in 2006, and RI beams from uranium were first obtained in 2007. The beam intensities and available ion species are increasing at RIBF, owing to the continuous efforts that have been made since the first beam. So far, we have accelerated deuteron, helium, nitrogen, oxygen, aluminum, calcium, zinc, krypton, xenon, and uranium beams with the superconducting ring cyclotron (SRC). The extracted beam intensities reached 1000 pnA for the helium and oxygen beams, and the calcium beam intensity exceeded 400 pnA recently. The intensities of the xenon and uranium beams are also increasing; they reached 24 and 3.6 pnA, respectively. This paper illustrates the construction, commissioning, and various improvements carried out for the RIBF accelerators, as well as the present accelerator performance.
Okuno, H.; Fukunishi, N.; Kamigaito, O.
Frontiers of accelerator instrumentation
New technology has permitted significant performance improvements of established instrumentation techniques including beam position and profile monitoring. Fundamentally new profile monitor strategies are required for the next generation of accelerators, especially linear colliders (LC). Beams in these machines may be three orders of magnitude smaller than typical beams in present colliders. In this paper we review both the present performance levels achieved by conventional systems and present some new ideas for future colliders.
Ross, M.
We give detailed proofs of several new no-go theorems for constructing flat four-dimensional accelerating universes from warped dimensional reduction. These new theorems improve upon previous ones by weakening the energy conditions, by including time-dependent compactifications, and by treating accelerated expansion that is not precisely de Sitter. We show that de Sitter expansion violates the higher-dimensional null energy condition (NEC) if the compactification manifold M is one-dimensional, if its intrinsic Ricci scalar R-ring vanishes everywhere, or if R-ring and the warp function satisfy a simple limit condition. If expansion is not de Sitter, we establish threshold equation-of-state parameters w below which accelerated expansion must be transient. Below the threshold w there are bounds on the number of e-foldings of expansion. If M is one-dimensional or R-ring everywhere vanishing, exceeding the bound implies the NEC is violated. If R-ring does not vanish everywhere on M, exceeding the bound implies the strong energy condition (SEC) is violated. Observationally, the w thresholds indicate that experiments with finite resolution in w can cleanly discriminate between different models which satisfy or violate the relevant energy conditions.
Wesley, Daniel H., E-mail: email@example.com [Centre for Theoretical Cosmology, DAMTP, Cambridge University, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
Equipartitioning in linear accelerators
Emittance growth has long been a concern in linear accelerators, as has the idea that some kind of energy balance, or equipartitioning, between the degrees of freedom, would ameliorate the growth. M. Prome observed that the average transverse and longitudinal velocity spreads tend to equalize as current in the channel is increased, while the sum of the energy in the system stays nearly constant. However, only recently have we shown that an equipartitioning requirement on a bunched injected beam can indeed produce remarkably small emittance growth. The simple set of equations leading to this condition are outlined below. At the same time, Hofmann, using powerful analytical and computational methods, has investigated collective instabilities in transported beams and has identified thresholds and regions in parameter space where instabilities occur. This is an important generalization. Work that he will present at this conference shows that the results are essentially the same in r-z coordinates for transport systems, and evidence is presented that shows transport system boundaries to be quite accurate in computer simulations of accelerating systems also. Discussed are preliminary results of efforts to design accelerators that avoid parameter regions where emittance is affected by the instabilities identified by Hofmann. These efforts suggest that other mechanisms are present. The complicated behavior of the RFQ linac in this framework also is shown.
Jameson, R.A.
Applications of electrostatic accelerators
Most applications of electrostatic accelerators fit into two main groups, materials analysis and materials modification. Materials analysis includes routine use of Rutherford Backscattering for quality control applications in the semiconductor field. Particle induced x-ray emission (PDCE) is used in fields from art history through environmental sciences. X-ray imaging using 5 MeV DC electron beams and fast pulsed neutron analysis (PFNA) for plastic explosive and drug detection provide promise in the area of security. Accelerator based mass spectrometry (AMS) is having a profound effect in a wide variety of fields which rely on counting extremely rare isotopes in small samples. Materials modification provides a very significant economic impact in the field of semiconductors. Virtually all semiconductor devices now rely on ion implantation with ion beam energies ranging from a few kilovolts to several MeV. With some mention of electron beams, this talk will concentrate primarily on the applications of MeV ion beams from electrostatic accelerators.
Norton, G.A.; Klody, G.M. [National Electrostatics Corp., Middleton, WI (United States)
Cell accelerated cryoablation simulation.
Tumor cryoablation is a clinical procedure where supercooled probes are used to destroy cancerous lesions. Cryoablation is a safe and effective palliative treatment for skeletal metastases, providing immediate and long term pain relief, increasing mobility and improving quality of life. Ideally, lesions are encompassed by an ice ball and frozen to a sufficiently low temperature to ensure cell death. "Lethal ice" is the term used to describe regions within the ice ball where cell death occurs. Failure to achieve lethal ice in all portions of a lesion may explain the high recurrence rate currently observed. Tracking growth of lethal ice is critical to success of percutaneous ablations, however, no practical methods currently exist for non-invasive temperature monitoring. Physicians lack planning tools which provide accurate estimation of the ice formation. Simulation of ice formation, while possible, is computationally demanding and too time consuming to be of clinical utility. We developed the computational framework for the simulation, acceleration strategies for multicore Intel x86 and IBM Cell architectures, and performed preliminary validation of the simulation. Our results demonstrate that the streaming SIMD implementation has better performance and scalability. Both accelerated and non-accelerated algorithms demonstrate good agreement between simulation and manually identified ice ball boundaries in phantom and patient images. Our results show promise for the development of novel cryoablation planning tools with real-time monitoring capability for clinical use. PMID:19854531
Blezek, Daniel J; Carlson, David G; Cheng, Lionel T; Christensen, Jared A; Callstrom, Matthew R; Erickson, Bradley J
Heavy Ion Accelerator (UTI-2).
National Technical Information Service (NTIS)
The design and test results of the 2 MeV ion accelerator designed for science of materials are described. The UTI-2 accelerator is developed on the basis of the UTI-1 accelerator and equipped with an injector of five-charge ions of iron, chromium and othe...
V. V. Bezuglyj M. Y. Bredikhin B. Il'enko I. M. Nekludov V. K. Knorenko
Exponentially Accelerating Jet in Crossflow
Effects of exponential acceleration on penetration and mixing characteristics of a jet in cross�ow have been investigated experimentallyinawatermodel. To imposean exponential acceleration on the �ow, both the injection speed and the nozzle width of the jet increased exponentially in the downstream direction of the cross�ow. An acceleration parameter � is de� ned as the ratio of the revolution time of
Adnan Eroglu; Robert E. Breidenthal
New techniques for particle accelerators
A review is presented of the new techniques which have been proposed for use in particle accelerators. Attention is focused upon those areas where significant progress has been made in the last two years--in particular, upon two-beam accelerators, wakefield accelerators, and plasma focusers. 26 refs., 5 figs., 1 tab.
Sessler, A.M.
Progress on Laser Plasma Accelerators.
National Technical Information Service (NTIS)
Several laser plasma accelerator schemes are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA). Theory indicates that a very high acceleration gradient, of order 1 GeV/m, can exist in the plasma wave driven by the beating lasers. Experime...
P. Chen
Ionization front accelerator: high gradients, demonstrated particle acceleration, and a proposed relativistic accelerator
The Ionization Front Accelerator (IFA) is a collective ion accelerator for which high-gradient particle acceleration has now been demonstrated. In the IFA, the space charge field at the front of an intense relativistic electron beam is controlled by a laser and used to accelerate an ion bunch. Two complete IFA systems have been built (IFA-1 and IFA-2). Here we present initial IFA-2 ion results that demonstrate that ions have been accelerated with controlled accelerating fields of 33 MV/m over 30 cm. Space charge fields of accelerators like the IFA and the plasma beat wave accelerator are compared, and both are shown to be capable of producing fields 1 GV/m and higher. The IFA systems are discussed and initial IFA-2 ion results are presented. Lastly, a relativistic IFA is proposed that should in principle, permit the attainment of virtually unlimited ion energies. 11 references, 8 figures.
Olson, C.L.; Frost, C.A.; Patterson, E.L.; Anthes, J.P.; Poukey, J.W.
The cyclic distortion of thermally grown oxides
NASA Astrophysics Data System (ADS)
Thermal barrier coatings (TBCs) serve to protect critical gas turbine engine components by sustaining large thermal gradients. The coatings are required to maintain their integrity under harsh thermal cycling conditions. Experiments on coatings comprised of a Pt(Ni)-Al diffusion bond coat have revealed a failure mechanism characterized by a continual growth of morphological instabilities of the thermally grown oxide (TGO) that forms at the bond coat-top coat interface, termed rumpling. The goal of this thesis is to elucidate the underlying mechanisms governing the rumpling of Pt(Ni)-Al bond coats and other alloys and to develop experimental protocols designed to validate the predictions of models. First, the fundamental mechanisms of the cyclic distortion of surface imperfections on the surface of a FeCrAlY alloy are explored. For this case, all of the constituent properties of the alloy and the TGO are known from independent measurements, enabling an explicit comparison between the experiments and simulations. The results reveal a peak rumpling-rate, occurring at characteristic imperfection amplitude of order 1 mum. For smaller imperfections, the growth-rates become immeasurably low, explaining the absence of rumpling observed on specimens with initially-polished surfaces. The extension of the model to Pt(Ni)-Al bond coats requires the incorporation of additional phenomena, including bond coat-substrate thermal strain misfit, bond coat martensite phase transformation, and bond coat swelling. As a result, many input parameters are required: complicating validation. A suitable protocol was devised and demonstrated in this study. It involves the measurement of imperfection shape changes as well as independent measurements and calibrations of the transformation temperatures and strains. The model successfully predicts the shape changes of three categories of well-defined initial imperfections: artificial grooves, grain boundary grooves, and intra-grain undulations. For exact correspondence between measurements and simulations, the following three phenomena are all required: a martensite transformation at �700 �C, an oxide lateral growth strain (0.002 ? Deltaepsilong ? 0.008), and a compressive growth stress in the TGO (300MPa ? stgoY ? 200Mpa). The model was then utilized to identify potential system modifications that might suppress rumpling. Effective strategies include decreasing the martensite transformation temperature, bond coat-substrate strain misfits, or the oxide creep strength, or increasing bond coat strength.
Davis, Andrew W.
Cyclic nucleotide phosphodiesterases in Drosophila melanogaster
Cyclic nucleotide PDEs (phosphodiesterases) are important enzymes that regulate intracellular levels of cAMP and cGMP. In the present study, we identify and characterize novel PDEs in the genetic model, Drosophila melanogaster. The Drosophila genome encodes five novel PDE genes in addition to dunce. Predicted PDE sequences of Drosophila show highly conserved critical domains when compared with human PDEs. Thus PDE-encoding genes of D. melanogaster are CG14940-PDE1C, CG8279-PDE6?, CG5411-PDE8A, CG32648-PDE9 and CG10231-PDE11. Reverse transcriptase�PCRs of adult tissues reveal widespread expression of PDE genes. Drosophila Malpighian (renal) tubules express all the six PDEs: Drosophila PDE1, dunce (PDE4), PDE6, PDE8, PDE9 and PDE11. Antipeptide antibodies were raised against PDE1, PDE6, PDE9 and PDE11. Verification of antibody specificity by Western blotting of cloned and expressed PDE constructs allowed the immunoprecipitation studies of adult Drosophila lysates. Biochemical characterization of immunoprecipitated endogenous PDEs showed that PDE1 is a dual-specificity PDE (Michaelis constant Km for cGMP: 15.3�1�?M; Km cAMP: 20.5�1.5�?M), PDE6 is a cGMP-specific PDE (Km cGMP: 37�13�?M) and PDE11 is a dual-specificity PDE (Km cGMP: 6�2�?M; Km cAMP: 18.5�5.5�?M). Drosophila PDE1, PDE6 and PDE11 display sensitivity to vertebrate PDE inhibitors, zaprinast (IC50 was 71�39�?M for PDE1, 0.65�0.015�?M for PDE6 and 1.6�0.5�?M for PDE11) and sildenafil (IC50 was 1.3�0.9�?M for PDE1, 0.025�0.005�?M for PDE6 and 0.12�0.06�?M for PDE11). We provide the first characterization of a cGMP-specific PDE and two dual-specificity PDEs in Drosophila, and show a high degree of similarity in structure and function between human and Drosophila PDEs.
Cyclic nucleotide phosphodiesterases in Drosophila melanogaster.
Cyclic nucleotide PDEs (phosphodiesterases) are important enzymes that regulate intracellular levels of cAMP and cGMP. In the present study, we identify and characterize novel PDEs in the genetic model, Drosophila melanogaster. The Drosophila genome encodes five novel PDE genes in addition to dunce. Predicted PDE sequences of Drosophila show highly conserved critical domains when compared with human PDEs. Thus PDE-encoding genes of D. melanogaster are CG14940-PDE1C, CG8279-PDE6beta, CG5411-PDE8A, CG32648-PDE9 and CG10231-PDE11. Reverse transcriptase-PCRs of adult tissues reveal widespread expression of PDE genes. Drosophila Malpighian (renal) tubules express all the six PDEs: Drosophila PDE1, dunce (PDE4), PDE6, PDE8, PDE9 and PDE11. Antipeptide antibodies were raised against PDE1, PDE6, PDE9 and PDE11. Verification of antibody specificity by Western blotting of cloned and expressed PDE constructs allowed the immunoprecipitation studies of adult Drosophila lysates. Biochemical characterization of immunoprecipitated endogenous PDEs showed that PDE1 is a dual-specificity PDE (Michaelis constant Km for cGMP: 15.3+/-1 microM; Km cAMP: 20.5+/-1.5 microM), PDE6 is a cGMP-specific PDE (Km cGMP: 37+/-13 microM) and PDE11 is a dual-specificity PDE (Km cGMP: 6+/-2 microM; Km cAMP: 18.5+/-5.5 microM). Drosophila PDE1, PDE6 and PDE11 display sensitivity to vertebrate PDE inhibitors, zaprinast (IC50 was 71+/-39 microM for PDE1, 0.65+/-0.015 microM for PDE6 and 1.6+/-0.5 microM for PDE11) and sildenafil (IC50 was 1.3+/-0.9 microM for PDE1, 0.025+/-0.005 microM for PDE6 and 0.12+/-0.06 microM for PDE11). We provide the first characterization of a cGMP-specific PDE and two dual-specificity PDEs in Drosophila, and show a high degree of similarity in structure and function between human and Drosophila PDEs. PMID:15673286
Day, Jonathan P; Dow, Julian A T; Houslay, Miles D; Davies, Shireen-A
Sources of Water to Wells for Transient Cyclic Systems
Many state agencies are currently (1995) developing wellhead protection programs. The thrust of some of these programs is to protect water supplies by determining the areas contributing recharge to water-supply wells and by specifying regulations to minimize the opportunity for contamination of the recharge water by activities at the land surface. The area contributing recharge to a discharging well is the surface area at the water table through which the water flowing to the well entered the ground-water system. In the analyses of ground-water flow systems, steady-state average conditions are commonly used to simplify the problem and make a solution tractable. However, recharge is usually cyclic in nature, with seasonal cycles and longer term climatic cycles. The effect of these cyclic stresses on the area contributing recharge to wells is quantitatively analyzed for a hypothetical alluvial valley aquifer system that is representative of a large class of ground-water systems that are extensively developed for water supply. The analysis shows that, in many cases, these cyclic changes in the recharge rates do not significantly affect the location and size of the areas contributing recharge to wells. The ratio of the mean travel time to the length of the cyclic stress period appears to be an indicator of whether the transient effects of the cyclic stress must be explicitly represented in the analysis of contributing areas to wells. For the cases examined, if the ratio of the mean travel time to the period of the cyclic stress was much greater than one, then the transient area contributing recharge to wells was similar to the area calculated using an average steady-state condition. However, cyclic stresses on systems with ratios less than one do have an effect on the location and size of the areas contributing recharge to wells.
Reilly, T. E.; Pollock, D. W.
Hydrolysis of cyclic phosphoramides. Evidence for syn lone pair catalysis.
Hydrolysis between 1.5 < pH < 4 of five and six membered cyclic phosphoramides has been followed by UV and 3'PNMR spectroscopy. The observed rates fit the equation: k(obs) = k(H2O) [H+]/([H+] + Ka) + k'(H2O), where k(H2O) and k'(H2O) are the pseudo first-order rate constants of water attack on the protonated phosphoramide and its unprotonated form, respectively, and Ka is the phosphoramide acidity equilibrium constant. Although, faster hydrolysis rates on the five membered ring are expected due to the energy released in going from a strained cyclic to a "strained free" trigonal-bipyramidal-pentacoordinated intermediate, with one of the cyclic nitrogens occupying the apical position. these compounds react slightly faster (k(H2O) values) but slower regarding the k'(H2O) values than the six membered analogs. The balance in reactivity is attributed to the additional stability obtained in the six membered cyclic compounds by a syn orientation of the two lone pairs of the cyclic nitrogen to the water attack. This stabilization does not exist in the five membered phospholidines since the water attack is perpendicular to the electron pairs of the cyclic nitrogen. In agreement with the incoming water orientation, the product ratios from the hydrolysis show that in the five membered rings the main product is the one produced by endocyclic cleavage; meanwhile, in the six membered cyclic phospholines the kinetic product is the one produced by exocyclic cleavage. The syn orientation of two electron pairs on nitrogen stabilizes the transition state of water approach to the phosphoramides by ca. 3 kcal mol(-1) when compared to the orthogonal attack. PMID:12945698
N��ez, Andr�s; Berroter�n, Dyanna; N��ez, Oswaldo
Substrate-directable electron transfer reactions. Dramatic rate enhancement in the chemoselective reduction of cyclic esters using SmI2-H2O: mechanism, scope, and synthetic utility.
Substrate-directable reactions play a pivotal role in organic synthesis, but are uncommon in reactions proceeding via radical mechanisms. Herein, we provide experimental evidence showing dramatic rate acceleration in the Sm(II)-mediated reduction of cyclic esters that is enabled by transient chelation between a directing group and the lanthanide center. This process allows unprecedented chemoselectivity in the reduction of cyclic esters using SmI2-H2O and for the first time proceeds with a broad substrate scope. Initial studies on the origin of selectivity and synthetic application to form carbon-carbon bonds are also disclosed. PMID:24079360
Szostak, Michal; Spain, Malcolm; Choquette, Kimberly A; Flowers, Robert A; Procter, David J
Progress toward 10 tesla accelerator dipoles
A 9.1 T central field has been achieved in a Nb-Ti dipole operating in pressurized helium II at 1.8 K. Three different Nb-Ti dipoles, without iron yokes, have achieved central fields of 8.0, 8.6, and 9.1 T - all short sample performance for the conductors at 1.8 K. In helium I, at 4.3 K, the maximum central fields are from 1.5 to 2.0 T lower. Ten-tesla magnets have been designed for both Nb-Ti operating at 1.8 K and Nb/sub 3/Sn operating at 4.2 K. They are based on a very small beam aperture, (40 to 45 mm), very high current density in the superconductors (over 1000 A/mm/sup 2/), and a very low ratio of stabilizing copper to superconductor (about 1). Both layer and block designs have been developed that utilize Rutherford Cable. Magnet cycling from 0 to 6 T has been carried out for field change rate up to 1 T/s; the cyclic heating at 1 T/s is 36 W per meter. At a more representative rate of 0.2 T/s the heating rate is only 2 W/m. Progress in the program to use Nb/sub 3/Sn and NbTi superconductor, in 10 T accelerator magnets is also discussed.
Hassenzahl, W.; Gilbert, G.; Taylor, C.; Meuser, R.
Recent Advances in Plasma Acceleration
The costs and the time scales of colliders intended to reach the energy frontier are such that it is important to explore new methods of accelerating particles to high energies. Plasma-based accelerators are particularly attractive because they are capable of producing accelerating fields that are orders of magnitude larger than those used in conventional colliders. In these accelerators a drive beam, either laser or particle, produces a plasma wave (wakefield) that accelerates charged particles. The ultimate utility of plasma accelerators will depend on sustaining ultra-high accelerating fields over a substantial length to achieve a significant energy gain. More than 42 GeV energy gain was achieved in an 85 cm long plasma wakefield accelerator driven by a 42 GeV electron drive beam in the Final Focus Test Beam (FFTB) Facility at SLAC. Most of the beam electrons lose energy to the plasma wave, but some electrons in the back of the same beam pulse are accelerated with a field of {approx}52 GV/m. This effectively doubles their energy, producing the energy gain of the 3 km long SLAC accelerator in less than a meter for a small fraction of the electrons in the injected bunch. Prospects for a drive-witness bunch configuration and high-gradient positron acceleration experiments planned for the SABER facility will be discussed.
Hogan, Mark
BotEC: Spacecraft Acceleration
NSDL National Science Digital Library
Question Suppose someone offered you a ride to the nearest star in a new spacecraft that could travel at half the speed of light, or about 150,000 km/second. In order to reach such a cruising speed, you and the spacecraft must accelerate from a standstill to half the speed of light. Acceleration means uncomfortable (and maybe even fatal!) "g" forces, that pressed-into-the-seat feeling you get when a car or airplane accelerates. More than 3 g's of acceleration are tough to take for very long, so your spacecraft's engines are designed to accelerate you at not more than 29 meters/second/second (3 times the acceleration due to gravity at the Earth's surface). How long will it take you and your spacecraft to accelerate to half light speed?
Tewksbury, Barb
Synthesis of cyclic Py-Im polyamide libraries.
Cyclic Py-Im polyamides containing two GABA turn units exhibit enhanced DNA binding affinity, but extensive studies of their biological properties have been hindered due to synthetic inaccessibility. A facile modular approach toward cyclic polyamides has been developed via microwave-assisted solid-phase synthesis of hairpin amino acid oligomer intermediates followed by macrocyclization. A focused library of cyclic polyamides 1-7 targeted to the androgen response element (ARE) and the estrogen response element (ERE) were synthesized in 12-17% overall yield. The Fmoc protection strategy also allows for selective modifications on the GABA turn units that have been shown to improve cellular uptake properties. The DNA binding affinities of a library of cyclic polyamides were measured by DNA thermal denaturation assays and compared to the corresponding hairpin polyamides. Fluorescein-labeled cyclic polyamides have been synthesized and imaged via confocal microscopy in A549 and T47D cell lines. The IC(50) values of compounds 1-7 and 9-11 were determined, revealing remarkably varying levels of cytotoxicity. PMID:23106218
Li, Benjamin C; Montgomery, David C; Puckett, James W; Dervan, Peter B
Temperature dependent cyclic deformation mechanisms in Haynes 188 superalloy
NASA Astrophysics Data System (ADS)
The cyclic deformation behavior of a wrought cobalt-base superalloy, Haynes 188, has been investigated over a range of temperatures between 25 and 1000 C under isothermal and in-phase thermomechanical fatigue (TMF) conditions. Constant mechanical strain rates (epsilon-dot) of 10(exp -3)/s and 10(exp -4)/s were examined with a fully reversed strain range of 0.8%. Particular attention was given to the effects of dynamic strain aging (DSA) on the stress-strain response and low cycle fatigue life. A correlation between cyclic deformation behavior and microstructural substructure was made through detailed transmission electron microscopy. Although DSA was found to occur over a wide temperature range between approximately 300 and 750 C the microstructural characteristics and the deformation mechanisms responsible for DSA varied considerably and were dependent upon temperature. In general, the operation of DSA processes led to a maximum of the cyclic stress amplitude at 650 C and was accompanied by pronounced planar slip, relatively high dislocation density, and the generation of stacking faults. DSA was evidenced through a combination of phenomena, including serrated yielding, an inverse dependence of the maximum cyclic hardening with epsilon-dot, and an instantaneous inverse epsilon-dot sensitivity verified by specialized epsilon-dot -change tests. The TMF cyclic hardening behavior of the alloy appeared to be dictated by the substructural changes occuring at the maximum temperature in the TMF cycle.
Rao, K. Bhanu Sankara; Castelli, Michael G.; Allen, Gorden P.; Ellis, John R.
Cannabinoid hyperemesis: cyclical hyperemesis in association with chronic cannabis abuse
Background and aims: To explore the association between chronic cannabis abuse and a cyclical vomiting illness that presented in a series of cases in South Australia. Methods: Nineteen patients were identified with chronic cannabis abuse and a cyclical vomiting illness. For legal and ethical reasons, all patients were counselled to cease all cannabis abuse. Follow up was provided with serial urine drug screen analysis and regular clinical consultation to chart the clinical course. Of the 19 patients, five refused consent and were lost to follow up and five were excluded on the basis of confounders. The remaining nine cases are presented here and compared with a published case of psychogenic vomiting. Results: In all cases, including the published case, chronic cannabis abuse predated the onset of the cyclical vomiting illness. Cessation of cannabis abuse led to cessation of the cyclical vomiting illness in seven cases. Three cases, including the published case, did not abstain and continued to have recurrent episodes of vomiting. Three cases rechallenged themselves after a period of abstinence and suffered a return to illness. Two of these cases abstained again, and became and remain well. The third case did not and remains ill. A novel finding was that nine of the 10 patients, including the previously published case, displayed an abnormal washing behaviour during episodes of active illness. Conclusions: We conclude that chronic cannabis abuse was the cause of the cyclical vomiting illness in all cases, including the previously described case of psychogenic vomiting.
Allen, J H; de Moore, G M; Heddle, R; Twartz, J C
Low severity coal liquefaction promoted by cyclic olefins
Low severity coal liquefaction promoted by cyclic olefins offers a means of liquefying coal at low severity conditions. Lower temperature, 350[degrees]C, and lower hydrogen pressure, 500 psi, have been used to perform liquefaction reactions. The presence of the cyclic olefin, hexahydroanthracene, made a substantial difference in the conversion of Illinois No. 6 coal at these low severity conditions. The Researchperformed this quarter was a parametric evaluation of the effect of different parameters on the coal conversion and product distribution from coal. The effect of the parameters on product distribution from hexahydroanthracene was also determined. The work planned for next quarter includes combining the most effective parametric conditions for the low severity reactions and determining their effect. The second part ofthe research performed this quarter involved performing Fourier transform infrared (FTIR) spectroscopy using cyclic olefins. The objective of this study was to determine the feasibility of using FTIR and a heated cell to determine the reaction pathway that occurs in the hydrogen donation reactions from cyclic olefins. The progress made to date includes evaluating the FTIR spectra of cyclic olefins and their expected reaction products. This work is included in this progress report.
Curtis, C.W.
Temperature Dependent Cyclic Deformation Mechanisms in Haynes 188 Superalloy
NASA Technical Reports Server (NTRS)
The cyclic deformation behavior of a wrought cobalt-base superalloy, Haynes 188, has been investigated over a range of temperatures between 25 and 1000 C under isothermal and in-phase thermomechanical fatigue (TMF) conditions. Constant mechanical strain rates (epsilon-dot) of 10(exp -3)/s and 10(exp -4)/s were examined with a fully reversed strain range of 0.8%. Particular attention was given to the effects of dynamic strain aging (DSA) on the stress-strain response and low cycle fatigue life. A correlation between cyclic deformation behavior and microstructural substructure was made through detailed transmission electron microscopy. Although DSA was found to occur over a wide temperature range between approximately 300 and 750 C the microstructural characteristics and the deformation mechanisms responsible for DSA varied considerably and were dependent upon temperature. In general, the operation of DSA processes led to a maximum of the cyclic stress amplitude at 650 C and was accompanied by pronounced planar slip, relatively high dislocation density, and the generation of stacking faults. DSA was evidenced through a combination of phenomena, including serrated yielding, an inverse dependence of the maximum cyclic hardening with epsilon-dot, and an instantaneous inverse epsilon-dot sensitivity verified by specialized epsilon-dot -change tests. The TMF cyclic hardening behavior of the alloy appeared to be dictated by the substructural changes occuring at the maximum temperature in the TMF cycle.
Rao, K. Bhanu Sankara; Castelli, Michael G.; Allen, Gorden P.; Ellis, John R.
Topological chaos, braiding and bifurcation of almost-cyclic sets.
In certain two-dimensional time-dependent flows, the braiding of periodic orbits provides a way to analyze chaos in the system through application of the Thurston-Nielsen classification theorem (TNCT). We expand upon earlier work that introduced the application of the TNCT to braiding of almost-cyclic sets, which are individual components of almost-invariant sets [Stremler et al., "Topological chaos and periodic braiding of almost-cyclic sets," Phys. Rev. Lett. 106, 114101 (2011)]. In this context, almost-cyclic sets are periodic regions in the flow with high local residence time that act as stirrers or "ghost rods" around which the surrounding fluid appears to be stretched and folded. In the present work, we discuss the bifurcation of the almost-cyclic sets as a system parameter is varied, which results in a sequence of topologically distinct braids. We show that, for Stokes' flow in a lid-driven cavity, these various braids give good lower bounds on the topological entropy over the respective parameter regimes in which they exist. We make the case that a topological analysis based on spatiotemporal braiding of almost-cyclic sets can be used for analyzing chaos in fluid flows. Hence, we further develop a connection between set-oriented statistical methods and topological methods, which promises to be an important analysis tool in the study of complex systems. PMID:23278070
Grover, Piyush; Ross, Shane D; Stremler, Mark A; Kumar, Pankaj
Synthesis of Cyclic Py-Im Polyamide Libraries
Cyclic Py-Im polyamides containing two GABA turn units exhibit enhanced DNA binding affinity, but extensive studies of their biological properties have been hindered due to synthetic inaccessibility. A facile modular approach toward cyclic polyamides has been developed via microwave-assisted solid-phase synthesis of hairpin amino acid oligomer intermediates followed by macrocyclization. A focused library of cyclic polyamides 1�7 targeted to the androgen response element (ARE) and the estrogen response element (ERE) were synthesized in 12�17% overall yield. The Fmoc protection strategy also allows for selective modifications on the GABA turn units that have been shown to improve cellular uptake properties. The DNA binding affinities of a library of cyclic polyamides were measured by DNA thermal denaturation assays and compared to the corresponding hairpin polyamides. Fluorescein-labeled cyclic polyamides have been synthesized and imaged via confocal microscopy in A549 and T47D cell lines. The IC50 values of compounds 1�7 and 9�11 were determined, revealing remarkably varying levels of cytotoxicity.
Family of prokaryote cyclic nucleotide-modulated ion channels
Cyclic nucleotide-modulated ion channels are molecular pores that mediate the passage of ions across the cell membrane in response to cAMP or GMP. Structural insight into this class of ion channels currently comes from a related homolog, MloK1, that contains six transmembrane domains and a cytoplasmic cyclic nucleotide binding domain. However, unlike eukaryote hyperpolarization-activated cyclic nucleotide-modulated (HCN) and cyclic nucleotide-gated (CNG) channels, MloK1 lacks a C-linker region, which critically contributes to the molecular coupling between ligand binding and channel opening. In this study, we report the identification and characterization of five previously unidentified prokaryote homologs with high sequence similarity (24�32%) to eukaryote HCN and CNG channels and that contain a C-linker region. Biochemical characterization shows that two homologs, termed AmaK and SthK, can be expressed and purified as detergent-solubilized protein from Escherichia coli membranes. Expression of SthK channels in Xenopus laevis oocytes and functional characterization using the patch-clamp technique revealed that the channels are gated by cAMP, but not cGMP, are highly selective for K+ ions over Na+ ions, generate a large unitary conductance, and are only weakly voltage dependent. These properties resemble essential properties of various eukaryote HCN or CNG channels. Our results contribute to an understanding of the evolutionary origin of cyclic nucleotide-modulated ion channels and pave the way for future structural and functional studies.
Brams, Marijke; Kusch, Jana; Spurny, Radovan; Benndorf, Klaus; Ulens, Chris
Cyclic beta-glucans of members of the family Rhizobiaceae.
Cyclic beta-glucans are low-molecular-weight cell surface carbohydrates that are found almost exclusively in bacteria of the Rhizobiaceae family. These glucans are major cellular constituents, and under certain culture conditions their levels may reach up to 20% of the total cellular dry weight. In Agrobacterium and Rhizobium species, these molecules contain between 17 and 40 glucose residues linked solely by beta-(1,2) glycosidic bonds. In Bradyrhizobium species, the cyclic beta-glucans are smaller (10 to 13 glucose residues) and contain glucose linked by both beta-(1,6) and beta-(1,3) glycosidic bonds. In some rhizobial strains, the cyclic beta-glucans are unsubstituted, whereas in other rhizobia these molecules may become highly substituted with moieties such as sn-1-phosphoglycerol. To date, two genetic loci specifically associated with cyclic beta-glucan biosynthesis have been identified in Rhizobium (ndvA and ndvB) and Agrobacterium (chvA and chvB) species. Mutants with mutations at these loci have been shown to be impaired in their ability to grow in hypoosmotic media, have numerous alterations in their cell surface properties, and are also impaired in their ability to infect plants. The present review will examine the structure and occurrence of the cyclic beta-glucans in a variety of species of the Rhizobiaceae. The possible functions of these unique molecules in the free-living bacteria as well as during plant infection will be discussed.
Breedveld, M W; Miller, K J
APT accelerator. Topical report
The Accelerator Production of Tritium (APT) project, sponsored by Department of Energy Defense Programs (DOE/DP), involves the preconceptual design of an accelerator system to produce tritium for the nation`s stockpile of nuclear weapons. Tritium is an isotope of hydrogen used in nuclear weapons, and must be replenished because of radioactive decay (its half-life is approximately 12 years). Because the annual production requirements for tritium has greatly decreased since the end of the Cold War, an alternative approach to reactors for tritium production, based on a linear accelerator, is now being seriously considered. The annual tritium requirement at the time this study was undertaken (1992-1993) was 3/8 that of the 1988 goal, usually stated as 3/8-Goal. Continued reduction in the number of weapons in the stockpile has led to a revised (lower) production requirement today (March, 1995). The production requirement needed to maintain the reduced stockpile, as stated in the recent Nuclear Posture Review (summer 1994) is approximately 3/16-Goal, half the previous level. The Nuclear Posture Review also requires that the production plant be designed to accomodate a production increase (surge) to 3/8-Goal capability within five years, to allow recovery from a possible extended outage of the tritium plant. A multi-laboratory team, collaborating with several industrial partners, has developed a preconceptual APT design for the 3/8-Goal, operating at 75% capacity. The team has presented APT as a promising alternative to the reactor concepts proposed for Complex-21. Given the requirements of a reduced weapons stockpile, APT offers both significant safety, environmental, and production-fexibility advantages in comparison with reactor systems, and the prospect of successful development in time to meet the US defense requirements of the 21st Century.
Lawrence, G.; Rusthoi, D. [comp.] [ed.
A six-month design study for a future high energy hadron collider was initiated by the Fermilab director in October 2000. The request was to study a staged approach where a large circumference tunnel is built that initially would house a low field ({approx}2 T) collider with center-of-mass energy greater than 30 TeV and a peak (initial) luminosity of 10{sup 34} cm{sup -2}s{sup -1}. The tunnel was to be scoped, however, to support a future upgrade to a center-of-mass energy greater than 150 TeV with a peak luminosity of 2 x 10{sup 34} cm{sup -2} sec{sup -1} using high field ({approx} 10 T) superconducting magnet technology. In a collaboration with Brookhaven National Laboratory and Lawrence Berkeley National Laboratory, a report of the Design Study was produced by Fermilab in June 2001. 1 The Design Study focused on a Stage 1, 20 x 20 TeV collider using a 2-in-1 transmission line magnet and leads to a Stage 2, 87.5 x 87.5 TeV collider using 10 T Nb{sub 3}Sn magnet technology. The article that follows is a compilation of accelerator physics designs and computational results which contributed to the Design Study. Many of the parameters found in this report evolved during the study, and thus slight differences between this text and the Design Study report can be found. The present text, however, presents the major accelerator physics issues of the Very Large Hadron Collider as examined by the Design Study collaboration and provides a basis for discussion and further studies of VLHC accelerator parameters and design philosophies.
Michael Blaskiewicz et al.
Two Stage Light Gas Plasma Projectile Accelerator.
National Technical Information Service (NTIS)
A device for accelerating a projectile to extremely high velocities, composed of a light gas accelerator to impart an initial high velocity to the projectile and a plasma accelerator and compressor receiving the moving projectile and accelerating it to hi...
E. L. Shriver D. W. Jex E. B. Igenbergs
Kinematics: Speed, Velocity & Acceleration
NSDL National Science Digital Library
The following resource is a NFL sponsored, National Science Foundation funded program intended to teach students about scientific concepts by using the popular sport of Football. Each lesson is accompanied by an informative and fast paced video. In this lesson, students will explore kinematics on the playing field. NSF-funded scientists Tony Schmitz from the University of Florida and John Ziegert of Clemson University explain how the kinematic concepts of position, velocity and acceleration can be used to define how a running back moves.
Cyclicity of non-associative products on D-branes
NASA Astrophysics Data System (ADS)
The non-commutative geometry of deformation quantization appears in string theory through the effect of a B-field background on the dynamics of D-branes in the topological limit. For arbitrary backgrounds, associativity of the star product is lost, but only cyclicity is necessary for a description of the effective action in terms of a generalized product. In previous work we showed that this property indeed emerges for a non-associative product that we extracted from open string amplitudes in curved background fields. In the present note we extend our investigation through second order in a complete derivative expansion. We establish cyclicity with respect to the Born-Infeld measure and find a logarithmic correction that modifies the Kontsevich formula in an arbitrary background satisfying the generalized Maxwell equation. This equation is the physical equivalent of a divergence-free Theta, which is required for cyclicity already in the associative case.
Herbst, M.; Kling, A.; Kreuzer, M.
Development of a viscoelastic continuum damage model for cyclic loading
NASA Astrophysics Data System (ADS)
A previously developed spectrum model for linear viscoelastic behavior of solids is used to describe the rate-dependent damage growth of a time dependent material under cyclic loading. Through the use of the iterative solution of a special Volterra integral equation, the cyclic strain history is described. The spectrum-based model is generalized for any strain rate and any uniaxial load history to formulate the damage function. Damage evolution in the body is described through the use of a rate-type evolution law which uses a pseudo strain to express the viscoelastic constitutive equation with damage. The resulting damage function is used to formulate a residual strength model. The methodology presented is demonstrated by comparing the peak values of the computed cyclic strain history as well as the residual strength model predictions to the experimental data of a polymer matrix composite.
Sullivan, R. W.
Yawing of wind turbines with blade cyclic-pitch variation
NASA Astrophysics Data System (ADS)
The control system horizontal axis wind turbine is discussed. It incorporates two features: the application of blade cyclic pitch variation adopted from rotorcraft technology, and the use of yaw angle control, not only for wind direction following, but also for rotor speed or torque control. Cyclic pitch variation in a two-bladed rotor relieves the blades of all the gyroscopic and odd harmonic aerodynamic root moments. It makes rapid yaw rates of a two-bladed rotor possible without causing vibratory hub moments and without causing appreciable angular excursions of the blade tip path plane. Due to the allowable rapid yaw rates of wind turbines with blade cyclic pitch variation, the two conventional separate control systems - yaw control for wind direction following and blade feathering control for regulating rotor speed and torque - can be replaced by a system with only a single control variable, the rotor yaw angle.
Hohenemser, K. H.; Swift, A. H. P.; Peters, D. A.
The development of children's understanding of cyclic aspects of time.
Developmental psychological approaches to the study of time have fallen into 3 categories: studies of time perception; studies of logical, reconstructive abilities; and studies of the understanding of conventional time systems. The present work examines problems spanning the latter 2 categories--the development of children's understanding of temporal cycles and the relationship between cyclic concepts and cognitive development. 62 children, ranging in age from 4 to 10 years, were administered Piagetian tests of classification and seriation and a variety of specially designed cyclic tasks. Results show major progress in the representation of cyclic order and recurrence during the age period examined. For a variety of particular cycles, order responses were shown before continuity responses. The ability to produce a correct order is related to seriation performance but not classification performance when the variance attributable to age is partialed out. Continuity responses appear to be unrelated to performance on either of the Piagetian tasks tested when age is controlled. PMID:608370
Friedman, W J
Application Of Shakedown Analysis To Cyclic Creep Damage Limits
Shakedown analysis may be used to provide a conservative estimate of local rupture and hence cyclic creep damage for use in a creep-fatigue assessment. The shakedown analysis is based on an elastic-perfectly plastic material with a temperature-dependent pseudo yield stress defined to guarantee that a shakedown solution exists which does not exceed rupture stress and temperature for a defined life. The ratio of design life to the estimated maximum cyclic life is the shakedown creep damage. The methodology does not require stress classification and is also applicable to cycles over the full range of temperature above and below the creep regime. Full cyclic creep and damage analysis is the alternative when shakedown analysis appears to be excessively conservative.
Carter, Peter [Stress Engineering Services Inc.; Jetter, Robert I [Consultant; Sham, Sam [ORNL
On the connection between multigrid and cyclic reduction
NASA Technical Reports Server (NTRS)
A technique is shown whereby it is possible to relate a particular multigrid process to cyclic reduction using purely mathematical arguments. This technique suggest methods for solving Poisson's equation in 1-, 2-, or 3-dimensions with Dirichlet or Neumann boundary conditions. In one dimension the method is exact and, in fact, reduces to cyclic reduction. This provides a valuable reference point for understanding multigrid techniques. The particular multigrid process analyzed is referred to here as Approximate Cyclic Reduction (ACR) and is one of a class known as Multigrid Reduction methods in the literature. It involves one approximation with a known error term. It is possible to relate the error term in this approximation with certain eigenvector components of the error. These are sharply reduced in amplitude by classical relaxation techniques. The approximation can thus be made a very good one.
Merriam, M. L.
Broadband accelerator control network
A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating system has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel.
Skelly, J.; Clifford, T.; Frankel, R.
Accelerating the loop expansion
This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.
Ingermanson, R.
Ion Accelerator With Negatively Biased Decelerator Grid
NASA Technical Reports Server (NTRS)
Three-grid ion accelerator in which accelerator grid is biased at negative potential and decelerator grid downstream of accelerator grid biased at smaller negative potential. This grid and bias arrangement reduces frequency of impacts, upon accelerator grid, of charge-exchange ions produced downstream in collisions between accelerated ions and atoms and molecules of background gas. Sputter erosion of accelerator grid reduced.
Brophy, John R.
Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2
NASA Technical Reports Server (NTRS)
Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.
Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.
Computational balance in real-time cyclic spectral analysis
Real-time cyclic spectral analysis is useful in many applications, but is difficult to achieve because of its computational complexity. This paper studies the distribution of complex multipliers in multiprocessor cyclic spectrum analyzers, with the objective of obtaining computational balance. Computationally balanced implementations efficiently use hardware so that computational bottlenecks are reduced and a smooth flow of data between computational sections of the analyzer is maintained. Tables are presented that give the number of complex multipliers required in each section of the analyzer to obtain computational balance.
Roberts, R.S. [Los Alamos National Lab., NM (United States); Loomis, H.H. Jr. [Naval Postgraduate School, Monterey, CA (United States)
Cyclic explosive activity of the Iceland plume in the quaternary
NASA Astrophysics Data System (ADS)
Data on the volcanic ash layers in 70 DSDP and ODP Sites and 100 cores obtained during cruises of the R/V Akademik Kurchatov and Mikhail Lomonosov were used for compiling tephrostratigraphic scale and schematic distribution maps of the pyroclastic material in the Quaternary sediments of the North Atlantic and Norwegian-Greenland Basin. It is revealed that the distribution of pyroclastic material through this region is characterized by cyclic and spatially irregular patterns. Based on their petrochemical and geochemical properties, these ashes are compared with the volcanics of Iceland and the Jan Mayen islands. The relations between the extreme climatic and cyclic explosive events are discussed.
Eroshenko, D. V.; Kharin, G. S.
Geometric phases for mixed states during cyclic evolutions
NASA Astrophysics Data System (ADS)
The geometric phases of cyclic evolutions for mixed states are discussed in the framework of unitary evolution. A canonical 1-form is defined whose line integral gives the geometric phase, which is gauge invariant. It reduces to the Aharonov and Anandan phase in the pure state case. Our definition is consistent with the phase shift in the proposed experiment (Sj�qvist et al 2000 Phys. Rev. Lett. 85 2845) for a cyclic evolution if the unitary transformation satisfies the parallel transport condition. A comprehensive geometric interpretation is also given. It shows that the geometric phases for mixed states share the same geometric sense with the pure states.
Fu, Li-Bin; Chen, Jing-Ling
Pharmacology of cyclic peptides: vancomycin and oxytocin as paradigms.
Cyclic oligopeptides have been introduced into pharmacological use for uses as diverse as selective release of the clotting factor VIII (von Willebrandt factor) by vasopressin, immune modulation by cyclosporin and antibacterial activity by vancomycin. Even now, 60 years after the first isolation of vancomycin (3,4) and the sequencing of oxytocin (48) these compounds have not lost their important role in clinical use. With regard to pharmacological properties oxytocin (as the peptide identic to the human sequence) and vancomycin (as a nonribosomal bacterial peptide) epitomize the swath of cyclic peptide properties. PMID:24559165
Schulze, Johannes
The Cyclic AMP Phenotype of Fragile X and Autism
Cyclic AMP (cAMP) is a second messenger involved in many processes including mnemonic processing and anxiety. Memory deficits and anxiety are noted in the phenotype of fragile X (FX), the most common heritable cause of mental retardation and autism. Here we review reported observations of altered cAMP cascade function in FX and autism. Cyclic AMP is a potentially useful biochemical marker to distinguish autism comorbid with FX from autism per se and the cAMP cascade may be a viable therapeutic target for both FX and autism.
Kelley, Daniel J; Bhattacharyya, Anita; Lahvis, Garet P; Yin, Jerry CP; Malter, Jim; Davidson, Richard J
Cyclic Nucleotides Converge on Brown Adipose Tissue Differentiation
NSDL National Science Digital Library
Brown adipose tissue (BAT) is rich in mitochondria and can uncouple oxidative phosphorylation to produce heat as a by-product of fatty acid metabolism. This thermogenic effect helps to maintain body temperature and also plays a critical role in energy homeostasis and the regulation of body weight. Both cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) contribute to the intracellular regulation of mitochondrial biogenesis and the differentiation of BAT. New evidence has defined the essential role of the cGMP-dependent protein kinase I in a pathway that modulates the RhoA-ROCK pathway and insulin receptor signaling to elicit BAT differentiation and stimulate thermogenesis.
Paul S. Amieux (University of Washington;Department of Pharmacology REV); G. Stanley McKnight (University of Washington;Department of Pharmacology REV)
Some aspects of skin friction of piles in clay under cyclic loading
NASA Astrophysics Data System (ADS)
A number of mode tests on a pile shaft in clay were performed to investigate the influence of cyclic loading on the ultimate skin friction. It is found that the loss of skin friction due to cyclic loading depends on both the cyclic displacement prior to failure and the number of cycles of load. Such loss of skin friction can occur both for one way or two way cyclic loading. The cyclic stiffness of the pile depends on the cyclic displacement of the pile. The rate of loading also influences the skin friction but does not appear to influence the stiffness of the pile.
Poulos, H. G.
Turbulent mixing in accelerating jets
NASA Astrophysics Data System (ADS)
The effects of acceleration on mixing in free turbulent jets are discussed theoretically. If the characteristic time constant of the acceleration is comparable to or less than the large-eddy turnover time, it is postulated that the entrainment rate of ambient fluid into the turbulence is inhibited. Then the engulfment appetite of each vortex is predominantly satisfied by rotational fluid overtaking from behind, thereby displacing the normal entrainment of pure irrotational fluid. This nonstationary condition may be maintained if the acceleration function is exponential. Preliminary experiments with other acceleration functions support the hypothesis. A new class of self-similar accelerating flows is proposed in which the global vorticity remains constant with time. In this sense, the vortices do not age. Hence, the rates of irreversible processes such as dissipation and molecular scale mixing tend to zero. The concept is applied to the temporally stationary but spatially accelerating transverse jet.
Breidenthal, R. E.
Laser acceleration and its future
Laser acceleration is based on the concept to marshal collective fields that may be induced by laser. In order to exceed the material breakdown field by a large factor, we employ the broken-down matter of plasma. While the generated wakefields resemble with the fields in conventional accelerators in their structure (at least qualitatively), it is their extreme accelerating fields that distinguish the laser wakefield from others, amounting to tiny emittance and compact accelerator. The current research largely falls on how to master the control of acceleration process in spatial and temporal scales several orders of magnitude smaller than the conventional method. The efforts over the last several years have come to a fruition of generating good beam properties with GeV energies on a table top, leading to many applications, such as ultrafast radiolysis, intraoperative radiation therapy, injection to X-ray free electron laser, and a candidate for future high energy accelerators.
Tajima, Toshiki
Particle acceleration in pulsar magnetospheres
NASA Technical Reports Server (NTRS)
The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.
Baker, K. B.
Accelerator simulation of astrophysical processes
NASA Technical Reports Server (NTRS)
Phenomena that involve accelerated ions in stellar processes that can be simulated with laboratory accelerators are described. Stellar evolutionary phases, such as the CNO cycle, have been partially explored with accelerators, up to the consumption of He by alpha particle radiative capture reactions. Further experimentation is indicated on reactions featuring N-13(p,gamma)O-14, O-15(alpha, gamma)Ne-19, and O-14(alpha,p)F-17. Accelerated beams interacting with thin foils produce reaction products that permit a determination of possible elemental abundances in stellar objects. Additionally, isotopic ratios observed in chondrites can be duplicated with accelerator beam interactions and thus constraints can be set on the conditions producing the meteorites. Data from isotopic fractionation from sputtering, i.e., blasting surface atoms from a material using a low energy ion beam, leads to possible models for processes occurring in supernova explosions. Finally, molecules can be synthesized with accelerators and compared with spectroscopic observations of stellar winds.
Tombrello, T. A.
Insulin alters the target size of the peripheral cyclic AMP phosphodiesterase but not the integral cyclic GMP-stimulated cyclic AMP phosphodiesterase in liver plasma membranes
Radiation inactivation of the two high affinity cyclic AMP phosphodiesterases (PDE) found in liver plasma membranes afforded an estimation of their molecular target sizes in situ. The activity of the peripheral plasma membrane PDE decayed as a single exponential with a target size corresponding to a monomer of circa 54 kDa. The integral, cyclic GMP-stimulated PDE decayed as a dimer of circa 125 kDa. Preincubation of plasma membranes with insulin (10nM), prior to irradiation, caused the target size of only the peripheral plasma membrane PDE to increase. We suggest that insulin addition causes the peripheral plasma membrane PDE to alter its coupling to an integral plasma membrane protein with a target size of circa 90 kDa.
Wallace, A.V.; Martin, B.R.; Houslay, M.D.
Modern electron accelerators for radiography
Over the past dozen years or so there have been significant advances in electron accelerators designed specifically for radiography of hydrodynamic experiments. Accelerator technology has evolved to accomodate the radiographers' contitiuing quest for multiple images in t h e and space:, improvements in electron beam quality have resulted in smaller radiographic spot sizes for better resolution, while higher radiation do% now provides imprcwed penetration of large, dense objects. Inductive isolation and acceleration techniques have played a ley rob in these advances.
Ekdahl, C. A. (Carl A.)
IFMIF accelerator conceptual design activities
A Conceptual Design Evaluation (CDE) for the International Fusion Materials Irradiation Facility (IFMIF) began in 1997 and will be completed in 1998, as an international program of the IEA involving the European Community, Japan, Russia and the United States. The IFMIF accelerator system, comprising two 125 mA, 40 MeV deuterium accelerators operating at 175 MHz, is a key element of the IFMIF facility. The objectives and accomplishments of the CDE accelerator studies are outlined.
Jameson, R.A. [Los Alamos National Lab., NM (United States); Lagniel, J.M. [CEA Saclay (France); Sugimoto, M. [JAERI (Japan); Kein, H.; Piaszczyk, C.; Tiplyakov, V.
Particle acceleration in solar flares
NASA Technical Reports Server (NTRS)
The most direct signatures of particle acceleration in flares are energetic particles detected in interplanetary space and in the Earth atmosphere, and gamma rays, neutrons, hard X-rays, and radio emissions produced by the energetic particles in the solar atmosphere. The stochastic and shock acceleration theories in flares are reviewed and the implications of observations on particle energy spectra, particle confinement and escape, multiple acceleration phases, particle anistropies, and solar atmospheric abundances are discussed.
Ramaty, R.; Forman, M. A.
Cast dielectric composite linear accelerator
A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.
Sanders, David M. (Livermore, CA) [Livermore, CA; Sampayan, Stephen (Manteca, CA) [Manteca, CA; Slenes, Kirk (Albuquerque, NM) [Albuquerque, NM; Stoller, H. M. (Albuquerque, NM) [Albuquerque, NM
Solar particle acceleration and propagation
NASA Technical Reports Server (NTRS)
The research performed in the period 1983-1986 on solar-particle acceleration and propagation is discussed. Special attention is given to satellite-based observations of large solar energetic particles and (He-3)-rich events; measurements of solar gamma rays, neutrons, and low-energy (1-100-keV) electrons; and observations related to the interplanetary propagation of fast particles. Consideration is also given to theoretical acceleration models based on satellite measurements of accelerated ions.
Lin, R. P.
Status of the FMIT accelerator
The linear accelerator being designed and constructed for the Fusion Materials Irradiation Test (FMIT) facility also has great utility as an R and D program that will provide operating information on large, continuous-wave, high-intensity particle accelerators now being considered for various applications, including electronuclear breeding for fuel, power, or tritium production. A 5-MeV FMIT prototype accelerator is under construction at Los Alamos, with operation to 2 MeV planned in early 1983.
Jameson, R.A.
High field gradient particle accelerator
A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.
Nation, J.A.; Greenwald, S.
High field gradient particle accelerator
A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.
Nation, John A. (Ithaca, NY) [Ithaca, NY; Greenwald, Shlomo (Haifa, IL) [Haifa, IL
Myocardial infarction accelerates atherosclerosis
SUMMARY During progression of atherosclerosis, myeloid cells destabilize lipid-rich plaque in the arterial wall and cause its rupture, thus triggering myocardial infarction and stroke. Survivors of acute coronary syndromes have a high risk of recurrent events for unknown reasons. Here we show that the systemic response to ischemic injury aggravates chronic atherosclerosis. After myocardial infarction or stroke, apoE?/? mice developed larger atherosclerotic lesions with a more advanced morphology. This disease acceleration persisted over many weeks and was associated with markedly increased monocyte recruitment. When seeking the source of surplus monocytes in plaque, we found that myocardial infarction liberated hematopoietic stem and progenitor cells from bone marrow niches via sympathetic nervous system signaling. The progenitors then seeded the spleen yielding a sustained boost in monocyte production. These observations provide new mechanistic insight into atherogenesis and provide a novel therapeutic opportunity to mitigate disease progression.
Dutta, Partha; Courties, Gabriel; Wei, Ying; Leuschner, Florian; Gorbatov, Rostic; Robbins, Clinton; Iwamoto, Yoshiko; Thompson, Brian; Carlson, Alicia L.; Heidt, Timo; Majmudar, Maulik D.; Lasitschka, Felix; Etzrodt, Martin; Waterman, Peter; Waring, Michael T.; Chicoine, Adam T.; van der Laan, Anja M.; Niessen, Hans W.M.; Piek, Jan J.; Rubin, Barry B.; Butany, Jagdish; Stone, James; Katus, Hugo A.; Murphy, Sabina A.; Morrow, David A.; Sabatine, Marc S.; Vinegoni, Claudio; Moskowitz, Michael A.; Pittet, Mikael J.; Libby, Peter; Lin, Charles P.; Swirski, Filip K.; Weissleder, Ralph; Nahrendorf, Matthias
Accelerating Spectrum Sharing Technologies
Spectrum sharing potentially holds the promise of solving the emerging spectrum crisis. However, technology innovators face the conundrum of developing spectrum sharing technologies without the ability to experiment and test with real incumbent systems. Interference with operational incumbents can prevent critical services, and the cost of deploying and operating an incumbent system can be prohibitive. Thus, the lack of incumbent systems and frequency authorization for technology incubation and demonstration has stymied spectrum sharing research. To this end, industry, academia, and regulators all require a test facility for validating hypotheses and demonstrating functionality without affecting operational incumbent systems. This article proposes a four-phase program supported by our spectrum accountability architecture. We propose that our comprehensive experimentation and testing approach for technology incubation and demonstration will accelerate the development of spectrum sharing technologies.
Juan D. Deaton; Lynda L. Brighton; Rangam Subramanian; Hussein Moradi; Jose Loera
Pulsed Plasma Accelerator Modeling
NASA Technical Reports Server (NTRS)
This report presents the main results of the modeling task of the PPA project. The objective of this task is to make major progress towards developing a new computational tool with new capabilities for simulating cylindrically symmetric 2.5 dimensional (2.5 D) PPA's. This tool may be used for designing, optimizing, and understanding the operation of PPA s and other pulsed power devices. The foundation for this task is the 2-D, cylindrically symmetric, magnetohydrodynamic (MHD) code PCAPPS (Princeton Code for Advanced Plasma Propulsion Simulation). PCAPPS was originally developed by Sankaran (2001, 2005) to model Lithium Lorentz Force Accelerators (LLFA's), which are electrode based devices, and are typically operated in continuous magnetic field to the model, and implementing a first principles, self-consistent algorithm to couple the plasma and power circuit that drives the plasma dynamics.
Goodman, M.; Kazeminezhad, F.; Owens, T.
From keV electrons in terrestrial aurorae to Ultra High Energy Cosmic Rays from unidentified "Zevatrons", the cosmos shows a plutocratic proclivity to concentrate energy in a tiny minority of suprathermal particles. The mechanisms involved can be traced back to the ideas of Faraday, Fermi and Alfv�n though we are learning that the details are idiosyncratic to the many environments that we have observed and that much can be learned from comparing and contrasting particle acceleration in laboratory and diverse astronomical locations. It will be argued that new mechanisms are required to account for recent observations of galactic nuclei, pulsar wind nebulae and interplanetary, interstellar and intergalactic media and some candidates will be discussed.
Blandford, Roger [Stanford University
Paraelectric gas flow accelerator
NASA Technical Reports Server (NTRS)
A substrate is configured with first and second sets of electrodes, where the second set of electrodes is positioned asymmetrically between the first set of electrodes. When a RF voltage is applied to the electrodes sufficient to generate a discharge plasma (e.g., a one-atmosphere uniform glow discharge plasma) in the gas adjacent to the substrate, the asymmetry in the electrode configuration results in force being applied to the active species in the plasma and in turn to the neutral background gas. Depending on the relative orientation of the electrodes to the gas, the present invention can be used to accelerate or decelerate the gas. The present invention has many potential applications, including increasing or decreasing aerodynamic drag or turbulence, and controlling the flow of active and/or neutral species for such uses as flow separation, altering heat flow, plasma cleaning, sterilization, deposition, etching, or alteration in wettability, printability, and/or adhesion.
Sherman, Daniel M. (Inventor); Wilkinson, Stephen P. (Inventor); Roth, J. Reece (Inventor)
NASA Astrophysics Data System (ADS)
At 1 AU the fast solar wind reaches speeds that are 2-3 times greater than can be accounted for by the pressure gradient due to the high coronal temperatures. This paper introduces a mechanism that may account for this shortfall, namely, the force due to the gradient of the magnetic pressure of an azimuthal magnetic field, B?, generated by a current jr flowing along the open-ended flux tube guiding the wind. The electromotive force (EMF) driving this current is due to the difference between the thermoelectric force acting on the electron gas within a flux tube and that in the ambient plasma. Using observed values of the magnetic field, we show that this mechanism is capable of accelerating the solar wind up to speeds of 800 km s-1 and higher. It also produces a profile of the radial wind speed v(r) that is nearly flat beyond about 0.15 AU, as is observed.
Ashbourn, J. M. A.; Woods, L. C.
Network acceleration techniques
NASA Technical Reports Server (NTRS)
Splintered offloading techniques with receive batch processing are described for network acceleration. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system ("OS"). The resulting protocol implementation allows the application to bypass the protocol processing of the received data. Such can be accomplished this by moving data from the NIC directly to the application through direct memory access ("DMA") and batch processing the receive headers in the host OS when the host OS is interrupted to perform other work. Batch processing receive headers allows the data path to be separated from the control path. Unlike operating system bypass, however, the operating system still fully manages the network resource and has relevant feedback about traffic and flows. Embodiments of the present disclosure can therefore address the challenges of networks with extreme bandwidth delay products (BWDP).
Crowley, Patricia (Inventor); Awrach, James Michael (Inventor); Maccabe, Arthur Barney (Inventor)
Myocardial infarction accelerates atherosclerosis.
During progression of atherosclerosis, myeloid cells destabilize lipid-rich plaques in the arterial wall and cause their rupture, thus triggering myocardial infarction and stroke. Survivors of acute coronary syndromes have a high risk of recurrent events for unknown reasons. Here we show that the systemic response to ischaemic injury aggravates chronic atherosclerosis. After myocardial infarction or stroke, Apoe-/- mice developed larger atherosclerotic lesions with a more advanced morphology. This disease acceleration persisted over many weeks and was associated with markedly increased monocyte recruitment. Seeking the source of surplus monocytes in plaques, we found that myocardial infarction liberated haematopoietic stem and progenitor cells from bone marrow niches via sympathetic nervous system signalling. The progenitors then seeded the spleen, yielding a sustained boost in monocyte production. These observations provide new mechanistic insight into atherogenesis and provide a novel therapeutic opportunity to mitigate disease progression. PMID:22763456
Dutta, Partha; Courties, Gabriel; Wei, Ying; Leuschner, Florian; Gorbatov, Rostic; Robbins, Clinton S; Iwamoto, Yoshiko; Thompson, Brian; Carlson, Alicia L; Heidt, Timo; Majmudar, Maulik D; Lasitschka, Felix; Etzrodt, Martin; Waterman, Peter; Waring, Michael T; Chicoine, Adam T; van der Laan, Anja M; Niessen, Hans W M; Piek, Jan J; Rubin, Barry B; Butany, Jagdish; Stone, James R; Katus, Hugo A; Murphy, Sabina A; Morrow, David A; Sabatine, Marc S; Vinegoni, Claudio; Moskowitz, Michael A; Pittet, Mikael J; Libby, Peter; Lin, Charles P; Swirski, Filip K; Weissleder, Ralph; Nahrendorf, Matthias
From keV electrons in terrestrial aurorae to Ultra High Energy Cosmic Rays from unidentified "Zevatrons", the cosmos shows a plutocratic proclivity to concentrate energy in a tiny minority of suprathermal particles. The mechanisms involved can be traced back to the ideas of Faraday, Fermi and Alfv�n though we are learning that the details are idiosyncratic to the many environments that we have observed and that much can be learned from comparing and contrasting particle acceleration in laboratory and diverse astronomical locations. It will be argued that new mechanisms are required to account for recent observations of galactic nuclei, pulsar wind nebulae and interplanetary, interstellar and intergalactic media and some candidates will be discussed.
Lectures in accelerator theory
Lecture I deals with the behavior of particles in the nonlinear field arising from the electromagnetic interaction of colliding beams. The case treated, that of counter-rotating proton beams crossing each other at a non-zero angle, has the simple feature that the force between the beam is one dimensional. In lecture II, an analysis of the development of traveling waves on particle beams is presented. The situation studied is that of a uniform beam current in a circular accelerator and the excitation for the coherent motion is induced by the resistivity of the vacuum chamber wall. Finally, in lecture III, a description of the current accumulation process used at the proton storage rings at CERN (The ISR) is given. Particle pulses of rather low average current are injected and stored along the length and width of the vacuum chamber. The efficiency is very high and large currents (over 40 amperes) have been achieved.
Month, M
Effect of thyroid state on cyclic AMP-mediated induction of hepatic phosphoenolpyruvate carboxykinase.
Hepatic phosphoenolpyruvate carboxykinase (PEPCK) is significantly increased in the hyperthyroid starved rat, and moderately decreased in the hypothyroid starved rat. As tri-iodothyronine by itself has only a small and sustained effect on the induction of this enzyme, as was previously shown in the isolated perfused organ, the effect of hypo- and hyper-thyroidism on the increase in cytosolic PEPCK provoked by dibutyryl cyclic AMP (Bt2cAMP) was investigated in vivo and in the isolated perfused liver. Compared with euthyroid fed controls, in hypothyroid fed rats Bt2cAMP provoked in 2 h only a small increase in translatable mRNA coding for PEPCK. In contrast, in hyperthyroid animals PEPCK mRNA as measured by translation in vitro was already increased in the fed state, and further enhanced by Bt2cAMP injection to values as in euthyroid controls. Under all thyroid states a close correlation between PEPCK mRNA activity and PEPCK synthesis was observed. In the isolated perfused liver from the hyperthyroid fed rat, the increase in PEPCK provoked by Bt2cAMP or Bt2cAMP + isobutylmethylxanthine was considerably enhanced compared with those obtained in livers of hypothyroid rats. Also, adrenaline provoked a stimulated induction of PEPCK in hyperthyroid rats compared with hypothyroid rats. To summarize, our data indicate that the primary action of thyroid hormones on the synthesis of hepatic cytosolic PEPCK is to accelerate the cyclic AMP- or adrenaline-induction of the enzyme, acting primarily at a pretranslational level. PMID:2983686
H�ppner, W; S�ssmuth, W; Seitz, H J
Muon Collider Progress: Accelerators
A muon collider would be a powerful tool for exploring the energy-frontier with leptons, and would complement the studies now under way at the LHC. Such a device would offer several important benefits. Muons, like electrons, are point particles so the full center-of-mass energy is available for particle production. Moreover, on account of their higher mass, muons give rise to very little synchrotron radiation and produce very little beamstrahlung. The first feature permits the use of a circular collider that can make efficient use of the expensive rf system and whose footprint is compatible with an existing laboratory site. The second feature leads to a relatively narrow energy spread at the collision point. Designing an accelerator complex for a muon collider is a challenging task. Firstly, the muons are produced as a tertiary beam, so a high-power proton beam and a target that can withstand it are needed to provide the required luminosity of ~1 � 10{sup 34} cm{sup �2}s{sup �1}. Secondly, the beam is initially produced with a large 6D phase space, which necessitates a scheme for reducing the muon beam emittance (�cooling�). Finally, the muon has a short lifetime so all beam manipulations must be done very rapidly. The Muon Accelerator Program, led by Fermilab and including a number of U.S. national laboratories and universities, has undertaken design and R&D activities aimed toward the eventual construction of a muon collider. Design features of such a facility and the supporting R&D program are described.
Zisman, Michael S.
DOE Science Accelerator: Advancing Science by Accelerating Science Access.
National Technical Information Service (NTIS)
To accelerate discovery, it is essential to accelerate the diffusion of science knowledge. This calls for a new era in the sophistication and breadth of the tools to access and use scientific knowledge. Herein, the Office of Scientific and Technical Infor...
Ion acceleration by beating electrostatic waves: Domain of allowed acceleration
The conditions under which a magnetized ion can be accelerated through a nonlinear interaction with a pair of beating electrostatic waves are explored. It has been shown [Benisti et al., Phys. Plasma 5, 3224 (1998)] that the electric field of the beating waves can, under some conditions, accelerate ions from arbitrarily low initial velocity in stark contrast with the well-known
R. Spektor; E. Y. Choueiri
Dynamics of a nonlinear periodic structure with cyclic symmetry
Summary The free and forced motions of a nonlinear periodic structure with cyclic symmetry are studied. The structure consists of a number of identical linear flexural members coupled by means of nonlinear stiffnesses of the third degree. It is found that this system can only possessn �similar� nonlinear modes of free oscillation, and that no other modes are possible. Moreover,
A. F. Vakakis; A. F. Yakakis
Dynamics of Nonlinear Cyclic Systems with Structural Irregularity
The dynamics of weakly coupled, nonlinear cyclic assemblies are investigated in the presence of weak structural mistuning. The method of multiple scales is used to obtain a set of nonlinear algebraic equations which govern the steady-state, synchronous (�modal-like�) motions for the structures. Considering a degenerate assembly of uncoupled oscillators, spatially localized modes are computed corresponding to motions during which vibrational
Melvin E. King; Philip A. Layne
Geometric angles in cyclic evolutions of a classical system
A perturbative method, using Lie transforms, is given for calculating the Hannay angle for slow, cyclic evolutions of a classical system, taking into account the finite rate of change of the Hamiltonian. The method is applied to the generalized harmonic oscillator. The classical Aharonov-Anandan angle is also calculated. The interpretational ambiguity in the definitions of geometrical angles is discussed.
Bhattacharjee, A.; Sen, T.
Geometric angles in cyclic evolutions of a classical system
NASA Technical Reports Server (NTRS)
A perturbative method, using Lie transforms, is given for calculating the Hannay angle for slow, cyclic evolutions of a classical system, taking into account the finite rate of change of the Hamiltonian. The method is applied to the generalized harmonic oscillator. The classical Aharonov-Anandan angle is also calculated. The interpretational ambiguity in the definitions of geometrical angles is discussed.
Bhattacharjee, A.; Sen, Tanaji
Cyclic pulse coding for fast BOTDA fiber sensors.
A cyclic pulse coding technique is proposed and experimentally demonstrated for fast implementation of long-range Brillouin optical time-domain analysis (BOTDA). The proposed technique allows for accurate temperature and strain measurements with meter-scale spatial resolution over kilometers of standard single-mode fiber, with subsecond measurement times. PMID:23903168
Taki, M; Muanenda, Y; Oton, C J; Nannipieri, T; Signorini, A; Di Pasquale, F
Successive Projection under a Quasi-Cyclic Order.
National Technical Information Service (NTIS)
A classical method for finding a point in the intersection of a finite collection of closed convex sets is the successive projection method. It is well-known that this method is convergent if each convex sets is chosen for projection in a cyclical manner....
P. Tseng
Tests on the quarter-scale model of the N. S. Savannah Reactor Vessel ; under cyclic loading conditions were successfully concluded. The investigation ; was specifically directed to the outlet nozzle area because of thc results of ; static tests. Pressurization to 3000 psi (150%, of design pressure) had caused ; yielding on the inside surface of the outlet nozzle. Continuous
T. Stilwell; K. R. Stearns
The Cyclical Nature of Decision Making: An Exploratory Empirical Investigation.
ERIC Educational Resources Information Center
Examined whether different levels of task complexity result in variations in group decision making. Groups (N=7) discussed problems varying in levels of complexity. Findings suggested that group decision making is a cyclical process with the number of cycles affected by task complexity. (RC)
Segal, Uma A.
Common cyclical features analysis in VAR models with cointegration
The paper considers n-dimensional VAR models for variables exhibiting cointegration and common cyclical features. Two specific reduced rank vector error correction models are discussed. In one, named the �strong form� and denoted by SF, the collection of all coefficient matrices of a VECM has rank less than n, in the other, named the �weak form� and denoted by WF, the
Alain Hecq; Franz C. Palm; Jean-Pierre Urbain
Evaluation and Modeling of Delamination under Static and Cyclic Loading.
National Technical Information Service (NTIS)
A part of the VAMAS program on polymer composite delamination in mode 1 and in mode 2 is presented. Glass and carbon fiber reinforced polymers were studied. Monotonic and cyclic loadings are applied at DCB specimens. The results show that the criteria of ...
C. Bathias R. Khoshravan
Finite element analysis of the cyclic indentation of bilayer enamel
NASA Astrophysics Data System (ADS)
Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel.
Jia, Yunfei; Xuan, Fu-zhen; Chen, Xiaoping; Yang, Fuqian
A Simulation of Counter-Cyclical Intervention: Some Practical Lessons
ERIC Educational Resources Information Center
The author introduces a simulation of counter-cyclical interventions that highlights important issues surrounding the practice of government intervention. The simulation provides experiential insight as to why economists have long debated the degree of persistence exhibited by disequilibrating shocks and connects this debate to discussions about�
Grawe, Nathan D.; Watts, Michael, Ed.
High-temperature cyclic oxidation data. Part 2: Turbine alloys
NASA Technical Reports Server (NTRS)
Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.
Barrett, Charles A.; Garlick, Ralph G.
Evaluating cyclic liquefaction potential using the cone penetration test
Soil liquefaction is a major concern for strctures constrcted with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetrtion test (CPT). A method is described t.o estimate grain characteristics directly �om the CPT and to incorporate this into one of
P. K. Robertson
Generating Cyclic Fair Sequences using Aggregation and Stride Scheduling
Fair sequences are useful in a variety of manufacturing and computer systems. This paper considers the generation of cyclic fair sequences for a given set of products, each of which must be produced multiple times in each cycle. The objective is to create a sequence so that, for each product, the variability of the time between consecutive completions is minimized.
Jeffrey W. Herrmann
Efficient DMT\\/OFDM Transmission With Insufficient Cyclic Prefix
In this letter, we describe a new method to eliminate intersymbol interference (ISI) and interchannel interference (ICI) for discrete multitone\\/orthogonal frequency division multiplexing (DMT\\/OFDM) systems with insufficient cyclic prefix (CP). The proposed structure prevents ICI with a preprocessing method that utilizes redundancy in the frequency domain at the transmitter and removes ISI with a simple cancellation method at the receiver.
Cheol-Jin Park; Gi-Hong Im
Synthesis and characterization of cyclic acetal based degradable hydrogels
While many synthetic, hydrolytically degradable hydrogels have been developed for biomedical applications, there are only a few examples whose polymer backbone does not form acidic products upon degradation. In order to address this concern, we proposed to develop a hydrogel based on a cyclic acetal unit that produces diols and propanals upon hydrolytic degradation. In particular, we proposed the fabrication
Sachiko Kaihara; Shuichi Matsumura; John P. Fisher