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Modeling deep brain stimulation: point source approximation versus realistic representation of the electrode
NASA Astrophysics Data System (ADS)
Deep brain stimulation (DBS) has emerged as an effective treatment for movement disorders; however, the fundamental mechanisms by which DBS works are not well understood. Computational models of DBS can provide insights into these fundamental mechanisms and typically require two steps: calculation of the electrical potentials generated by DBS and, subsequently, determination of the effects of the extracellular potentials on neurons. The objective of this study was to assess the validity of using a point source electrode to approximate the DBS electrode when calculating the thresholds and spatial distribution of activation of a surrounding population of model neurons in response to monopolar DBS. Extracellular potentials in a homogenous isotropic volume conductor were calculated using either a point current source or a geometrically accurate finite element model of the Medtronic DBS 3389 lead. These extracellular potentials were coupled to populations of model axons, and thresholds and spatial distributions were determined for different electrode geometries and axon orientations. Median threshold differences between DBS and point source electrodes for individual axons varied between -20.5% and 9.5% across all orientations, monopolar polarities and electrode geometries utilizing the DBS 3389 electrode. Differences in the percentage of axons activated at a given amplitude by the point source electrode and the DBS electrode were between -9.0% and 12.6% across all monopolar configurations tested. The differences in activation between the DBS and point source electrodes occurred primarily in regions close to conductor-insulator interfaces and around the insulating tip of the DBS electrode. The robustness of the point source approximation in modeling several special casesŚtissue anisotropy, a long active electrode and bipolar stimulationŚwas also examined. Under the conditions considered, the point source was shown to be a valid approximation for predicting excitation of populations of neurons in response to DBS.
Zhang, Tianhe C.; Grill, Warren M.
Modeling Deep Brain Stimulation: Point Source Approximation vs. Realistic Representation of the Electrode
PubMed Central
Deep brain stimulation (DBS) has emerged as an effective treatment for movement disorders; however, the fundamental mechanisms by which DBS works are not well understood. Computational models of DBS can provide insights into these fundamental mechanisms and typically require two steps: calculation of the electrical potentials generated by DBS and, subsequently, determination of the effects of the extracellular potentials on neurons. The objective of this study was to assess the validity of using a point source electrode to approximate the DBS electrode when calculating the thresholds and spatial distribution of activation of a surrounding population of model neurons in response to monopolar DBS. Extracellular potentials in a homogenous isotropic volume conductor were calculated using either a point current source or a geometrically accurate finite element model of the Medtronic DBS 3389 lead. These extracellular potentials were coupled to populations of model axons, and thresholds and spatial distributions were determined for different electrode geometries and axon orientations. Median threshold differences between DBS and point source electrodes for individual axons varied between ?20.5% and 9.5% across all orientations, monopolar polarities, and electrode geometries utilizing the DBS 3389 electrode. Differences in the percentage of axons activated at a given amplitude by the point source electrode and the DBS electrode were between ?9.0% and 12.6% across all monopolar configurations tested. The differences in activation between the DBS and point source electrodes occurred primarily in regions close to conductor-insulator interfaces and around the insulating tip of the DBS electrode. The robustness of the point source approximation in modeling several special cases--tissue anisotropy, a long active electrode, and bipolar stimulation--was also examined. Under the conditions considered, the point source was shown to be a valid approximation for predicting excitation of populations of neurons in response to DBS.
Zhang, Tianhe C; Grill, Warren M
A point defect model for nickel electrode structures
NASA Technical Reports Server (NTRS)
The Raman spectra for nickel electrode active mass indicate a single formula-unit crystallographic unit cell of the layered NiOOH-type. Empirical stoichiometric formulas require that extensive point defects, cation dopants and nickel vacancies, be incorporated on nickel sites. Structural differences between the alpha/gamma and beta/beta cycles, and the influence of cobalt addition on the structure will be discussed in terms of the point defect model. Other empirical data supporting the point defect model will be considered.
Loyselle, Patricia L.; Karjala, Philip J.; Cornilsen, Bahne C.
Vesicovaginal Fistula Repair Using a Transurethral Pointed Electrode
The most common cause of vesicovaginal fistulasis injury to the bladder at the time of surgery. The operation most frequently responsible for vesicovaginal fistula formation is hysterectomy. The first successful transvaginal approach to vesicovaginal fistula repair was reported by Sims in 1838. Although many surgical procedures exist, there is no best approach for all patients with vesicovaginal fistula. However, it is an essential surgical principle that the fistulous tract and scar should be excised completely. Here we report our technique using a transurethral pointed electrode for the treatment of multiple, small vesicovaginal fistulas and its outcome.
Hong, Hye-Min; Lee, Jea-Whan; Han, Dong-Youp
Nanosecond-pulse gliding discharges between point-to-point electrodes in open air
In this paper, gliding discharges with a point-to-point electrode geometry were produced by a repetitively pulsed power supply with a rise time of ?100 ns and a full-width at half-maximum of ?200 ns. The characteristics of such discharges were investigated by measuring their voltage¢current waveforms and taking photographs of their discharge images. Experimental results showed that once the breakdown occurred, the nanosecond-pulse gliding discharges went into a stable stage at all air gaps, behaving in a mode of repetitive sparks. Under certain conditions, a non-stable stage would appear some time after the discharge went into the stable stage, in which the gliding discharges transitioned from repetitive sparks to diffuse discharges. Furthermore, several factors (gap spacing, pulse repetition frequency (PRF) and gas flow rate) influencing the discharge characteristics were investigated. It was observed that both the breakdown voltage and ignition voltage increased with the gap spacing, and a diffuse discharge was absent when the gap spacing was less than 6 mm. The breakdown voltage decreased with the increase in the PRF and its decrease ratio was larger in large gap spacing than in small gap spacing. Discharges would transit from repetitive sparks to diffuse discharges as the flow rate increased. Furthermore, a comparison of nanosecond-pulse and ac gliding discharges was conducted with respect to the power supply. The consumption and energy, the relationship between the power supply and the load, and the time interval between two pulses were three main factors which could lead to different characteristics between the nanosecond-pulse and ac gliding discharges.
Zhang, Cheng; Shao, Tao; Yan, Ping; Zhou, Yuanxiang
Studies of enzyme electrode and its response using alkanethiols materials
Self-assembled monolayers (SAMs) of alkanthiols have been studied and applied to enzyme modification on metal electrode. The construction of enzyme electrode using SAM is one of the considerable approaches for enzyme sensors. Glucose electrode and lactate electrode were fabricated on gold electrode by alkanthiols. The electrode response allowed to differentiate between long and short alkyl chains of alkanthiols. This result suggests that SAM with different chain length change their surface properties and affect electrochemical response of enzyme modified electrodes. On the basis of the result, micro machined glucose electrode was fabricated and its response was measured.
Joko, Shigeki; Komatsu, Shinya; Peng, Jin; Shiota, Masahiro; Oi, Fumika; Matsuo, Shigeki; Misawa, Hiroaki
Carbon nanotube growth on a pointed bulk electrode using femtosecond laser nonlinear lithography
Carbon nanotube (CNT) bundles were synthesized on pointed bulk electrodes using femtosecond laser nonlinear lithography. A resist mask of 1.5 ?m diameter was formed on a pointed bulk cathode by translating a laser focus three-dimensionally inside the spherical photoresist. Metal masks obtained by pattern transfers of the resists effectively suppressed CNT growth during plasma-enhanced chemical vapor deposition, resulting in synthesis of CNT bundles only at the electrode tip. Irradiation of field emission currents from the pointed cathode enables local melting and subsequent removal of anode materials. The damaged region size and the threshold voltage for this removal process were reduced by spatial limitations of emission sites using the metal mask.
Nishiyama, Hiroaki; Iba, Tomohiro; Hirata, Yoshinori
Development of a point-electrode conductivity salinometer with high-spatial-resolution for use in very-saline solutions
SciTech Connect
A conductivity probe and circuit were developed to measure salinities in sodium chloride salt-gradient solar ponds. A point-electrode salinometer design was chosen to give a spatial resolution of approximately 1 mm (0.039 in.). Such high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective/conductive zone boundaries. The point-electrode conductivity instrument was designed for use in up to 25 wt % salinities with immersion times of about 0.1 year or longer. Drift in the instrument, however, caused principally by changes in the surface condition of the platinum probe tip and reflected by changes in the probe cell constant, required periodic in situ calibration against the measured specific gravity of withdrawn fluid samples.
Jones, G.F.; Grimmer, D.P.; Tafoya, J.; Fitzgerald, T.J.
Super-resolution imaging using multi- electrode CMUTs: theoretical design and simulation using point targets.
This paper investigates a low computational cost, super-resolution ultrasound imaging method that leverages the asymmetric vibration mode of CMUTs. Instead of focusing on the broadband received signal on the entire CMUT membrane, we utilize the differential signal received on the left and right part of the membrane obtained by a multi-electrode CMUT structure. The differential signal reflects the asymmetric vibration mode of the CMUT cell excited by the nonuniform acoustic pressure field impinging on the membrane, and has a resonant component in immersion. To improve the resolution, we propose an imaging method as follows: a set of manifold matrices of CMUT responses for multiple focal directions are constructed off-line with a grid of hypothetical point targets. During the subsequent imaging process, the array sequentially steers to multiple angles, and the amplitudes (weights) of all hypothetical targets at each angle are estimated in a maximum a posteriori (MAP) process with the manifold matrix corresponding to that angle. Then, the weight vector undergoes a directional pruning process to remove the false estimation at other angles caused by the side lobe energy. Ultrasound imaging simulation is performed on ring and linear arrays with a simulation program adapted with a multi-electrode CMUT structure capable of obtaining both average and differential received signals. Because the differential signals from all receiving channels form a more distinctive temporal pattern than the average signals, better MAP estimation results are expected than using the average signals. The imaging simulation shows that using differential signals alone or in combination with the average signals produces better lateral resolution than the traditional phased array or using the average signals alone. This study is an exploration into the potential benefits of asymmetric CMUT responses for super-resolution imaging. PMID:24158286
You, Wei; Cretu, Edmond; Rohling, Robert
Raman structural studies of the nickel electrode
Raman spectroscopy is sensitive to empirically controlled nickel electrode structural variations, and has unique potential for structural characterization of these materials. How the structure relates to electrochemical properties is examined so that the latter can be more completely understood, controlled, and optimized. Electrodes were impregnated and cycled, and cyclic voltammetry is being used for electrochemical characterization. Structural variation was observed which has escaped detection using other methods. Structural changes are induced by: (1) cobalt doping, (2) the state of change or discharge, (3) the preparation conditions and type of buffer used, and (4) the formation process. Charged active mass has an NiOOH-type structure, agreeing with X-ray diffraction results. Discharged active mass, however, is not isostructural with beta-Ni(OH)2. Chemically prepared alpha phases are not isostructural either. A disordered structural model, containing point defects, is proposed for the cycled materials. This model explains K(+) incorporation. Band assignments were made and spectra interpreted for beta-Ni(OH)2, electrochemical NiOOH and chemically precipitated NiOOH.
Cornilsen, B. C.
Removable Interdigital Electrodes for Surface Wave Studies.
National Technical Information Service (NTIS)
The authors have fabricated interdigital electrode structures on polished glass plaques. By placing the plaques next to the surface of a piezoelectric material and exciting the electrode of the transmitting plaque with pulsed rf energy of the appropriate ...
F. P. Lipschultz I. N. Greenberg
AC impedance study of degradation of porous nickel battery electrodes
AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.
Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.
The focal spot shape and point spread function of liquid crystal microlens with different pattern electrodes
In this paper, we present a new LC lens with different pattern electrodes including triangle electrode, square electrode, pentagon electrode, hexagon and octagon electrodes. We demonstrate the focusing process of LC lens, when the electrodes are driven by the voltage signal, all the LC lens with different pattern electrodes have good focusing characters along the optical axis. In addition, a LC lens with different sub-electrode pattern is also introduced, the sub-electrodes are designed to circular pattern and each sub-electrode can be driven separately. If the sub-electrodes are driven by the same voltage signal, the LC lens can focus along the axis, while they are controlled separately, it can make the focus swing off the axis over the focal plane. We show the Interference patterns of LC lens with various pattern electrodes. The different focal spot shapes and the optical properties of LC microlens are also demonstrated experimentally.
Kang, Shengwu; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng
Raman Structural Studies of the Nickel Electrode.
Raman spectroscopy is sensitive to empirically controlled nickel electrode structural variations, and has unique potential for structural characterization of these materials. How the structure relates to electrochemical properties is examined so that the ...
B. C. Cornilsen
A comparison study of electrodes for neonate electrical impedance tomography
Microsoft Academic Search
Electrical impedance tomography (EIT) is an imaging technique that has the potential to be used for studying neonate lung function. The properties of the electrodes are very important in multi-frequency EIT (MFEIT) systems, particularly for neonates, as the skin cannot be abraded to reduce contact impedance. In this work, the impedance of various clinical electrodes as a function of frequency
Mohamad Rahal; Joo Moy Khor; Andreas Demosthenous; Andrew Tizzard; Richard Bayford
Mechanistic studies of ion-selective electrodes.
A knowledge of the chemical composition of blood, urine and other body fluids is a daily requirement for departments of biochemistry. Electronic circuitry and computers to process the data are readily available, but satisfactory transducers to convert chemical composition into electrical signals are frequently the weakest link in the chain of measurement. This review is concerned with one group of transducers: ion-selective electrodes. Since the commercial success of the calcium and fluoride ions-selective electrodes in the mid-sixties, a range of other electrodes has become available. Their use has already conferred considerable benefits upon medicine, e.g. rapid, low-cost, multiple assay of major blood components; diagnostic surveys of chloride sweat levels relating to cystic fibrosis; and monitoring blood fluorides during and after halothane administration. Their adoption for indirectly sensing enzymes and associated substrates is particularly noteworthy. Recent advances in electronics, coupled with flow injection schemes based on ion-selective electrodes, have facilitated the management of hundreds of samples daily. However, developments in the mechanistic knowledge of these sensors have not matched the increase in their application, although definite progress can be reported; for example with regard to the origin of the potential signals induced by ion activities in solution. Numerous techniques have been devised to unravel mechanistic problems, among which radioisotope tracer and impedance measurements may be cited as especially valuable. Selectivity performance, particularly in complex biological media, and undesirable features such as protein poisoning, need further research. Organic chemists are now better placed to synthesize new designs of acyclic and cyclic molecules as mobile site, ion-selective, sensor materials which, with appropriate mediator solvents, provide improved sensor cocktails. This design feature is well illustrated by the continuing guest for a lithium ion-selective electrode compatible with the high levels of sodium interference in blood. PMID:3897710
Moody, G J
Bioleaching of pyrite by Thiobacillus ferrooxidans: fixed grains electrode to study superficial oxidized compounds
An electrode with fixed pyrite grains on a graphite and silicon paste has been used to study the electrochemical processes at the surface of powdered pyrite during bioleaching by Thiobacillus ferrooxidans. The study of an air-oxidized pyrite shows that the fixed grains electrode (FGE) is more sensitive than the classical Carbon Paste Electrode (CPE) already used by different authors to characterize various oxides and sulfurs. On the other hand, the concommitant Raman and electrochemical analysis of autoclaved pyrite shows that the cleaned mineral FeS 2 has no electrochemical reactivity, and points out that the electrochemical response of the oxidized mineral is exclusively due to the chemical compounds present at its surface. Therefore, the electrode acts as an efficient sensor for pyrite superficial oxidized phases, which are fundamental for the biooxidation process and is consequently very well adapted for the control of the oxidation state of pyrite powder during bioleaching by Thiobacillus ferrooxidans.
Toniazzo, Valķrie; Lazaro, Isabelle; Humbert, Bernard; Mustin, Christian
A comparative study of Prussian-Blue-modified graphite paste electrodes and solid graphite electrodes with mechanically immobilized Prussian Blue
The cyclic voltammetry of Prussian Blue was studied using two different types of electrodes. In one case microcrystalline particles of Prussian Blue were mechanically immobilized on the surface of a paraffin-impregnated solid graphite electrode, whereas in the other the Prussian Blue was added to a paste of graphite and silicone oil. The overall behaviour of Prussian Blue in both electrodes
Nina F. Zakharchuk; Birgit Meyer; Horst Henning; Fritz Scholz; Aleksander Jaworksi; Zbigniew Stojek
A study of the glow discharge characteristics of contact electrodes at atmospheric pressure in air
Electric field distributions and discharge properties of rod-rod contact electrodes were studied under the condition of DBD for the steady generation of atmospheric pressure glow discharge plasma (APGD) in air. We found that under the effect of the initial electrons generated in a nanometer-scale gap, the rod-rod cross-contact electrodes yielded APGD plasma in air. Regarding the rod-rod cross-contact electrodes, increasing the working voltage expanded the strong electric field area of the gas gap so that both discharge area and discharge power increased, and the increase in the number of contact points kept the initial discharge voltage unchanged and caused an increase in the plasma discharge area and discharge power. A mesh-like structure of cross-contact electrodes was designed and used to generate more APGD plasma, suggesting high applicability.
Liu, Wenzheng; Sun, Guangliang; Li, Chuanhui; Zhang, Rongrong
The objectives of this investigation have been to define the structures of charged active mass, discharged active mass, and related precursor materials (alpha-phases), with the purpose of better understanding the chemical and electrochemical reactions, including failure mechanisms and cobalt incorporation, so that the nickel electrode may be improved. Although our primary tool has been Raman spectroscopy, the structural conclusions drawn from the Raman data have been supported and augmented by three other analysis methods: infrared spectroscopy, powder X-ray Diffraction (XRD), and x-ray absorption spectroscopy (in particular EXAFS, Extended X-ray Absorption Fine Structure spectroscopy).
Cornilsen, Bahne C.
Studies of an artificially generated electrode effect at ground level
The outdoor experiments, using a metallic grid above the ground surface, have yielded well-defined vertical profiles of the space-charge density. The profiles showed strong evidence for the existence of an electrode effect, which could be named the artificial electrode effect and can serve as a very useful and well-controlled model for the study of atmospheric electric processes in the atmospheric surface layer. The build-up or break-down of an electrode-effect layer occurred in a time of the order of 10 s under the experimental conditions realized. The artificially generated electrode effect is dependent on the electrical field strength supplied, wind speed, turbulent mixing and ion mobilities. Wind speed and ion mobility seem to be the dominant factors, defining space-charge density profiles. A theoretical model for the artificial electrode effect has been developed, taking into account turbulent mixing of charged particles in the air flow with the logarithmic profile of the wind velocity. The numerical analysis of the boundary value problem for the two-dimensional equations for the light ion concentrations has been performed. The model presented shows a qualitative agreement of calculated space-charge profiles with measured ones, and explains the dependence of the artificial electrode effect on the dominant control parameters. The limiting conditions for the developed theory are discussed.
Mareev, E. A.; Israelsson, S.; Knudsen, E.; Kalinin, A. V.; Novozhenov, M. M.
Bismuth film electrodes for the study of metal thiolate complexation: an alternative to mercury electrodes.
A comparative study of the usual static mercury drop electrode (SMDE) and the bismuth film electrode (BiFE) as applied to the analysis of metal complexation by thiol-rich peptides is done. Preliminary experiments on BiFE by differential pulse voltammetry showed that Cd(II) and Pb(II)-ions behave in a similar way as using stripping voltammetry and stripping chronopotentiometry with regard to some splitting effects of the signals. Additionally, on BiFE glutathione (GSH) and some phytochelatins (PC(n)) produce quite irregular signals related to the anodic oxidation of bismuth, which restricted the studies to a narrower concentration range than on SMDE. In the presence of both metal ion and peptide the same characteristic signals were observed on BiFE and SMDE, but better resolution was achieved in the first one, allowing a qualitative analysis of the complexation process for the Pb-GSH system which was not possible on SMDE. This suggests that BiFE may be a complementary tool to Hg electrodes, if not a valuable alternative, in the study of metal complexation. PMID:19269466
Alberich, ArĒstides; Serrano, N·ria; Ari±o, Cristina; DĒaz-Cruz, Josķ Manuel; Esteban, Miquel
The development of a micropatterned electrode for studies of zinc electrodeposition
A micropatterned electrode was prepared for the study of electrocrystallization. Using microphotolithography, in conjunction with evaporation and pulse electrodeposition of thin films, a set of artificially roughened electrodes with hemispherical surface features five microns in diameter was developed. Voltammetric studies were conducted to determine the best electrode material. Gold, platinum, and various carbon surfaces were evaluated for zinc nucleation density and hydrogen overpotential. Surface homogeneity was examined by both light and scanning electron microscopy. Gold was determined to possess the best combination of material properties: chemical inertness, low melting point, and a high work function allowing underpotential deposition of zinc which reduces the rate of hydrogen evolution. Stripping coulometry was employed to determine zinc limiting currents, and evaluate effective diffusion coefficients in concentrated zinc chloride solutions. Although the method worked well for dilute zinc chloride and copper sulfate solutions, it failed at higher current densities; the emergence of surface roughness obscured actual limiting current plateaus.
Sutija, D.P.; Muller, R.H.; Tobias, C.W.
Comparison of resistive switching characteristics using copper and aluminum electrodes on GeOx/W cross-point memories.
Comparison of resistive switching memory characteristics using copper (Cu) and aluminum (Al) electrodes on GeOx/W cross-points has been reported under low current compliances (CCs) of 1ĀnA to 50Ā?A. The cross-point memory devices are observed by high-resolution transmission electron microscopy (HRTEM). Improved memory characteristics are observed for the Cu/GeOx/W structures as compared to the Al/GeOx/W cross-points owing to AlOx formation at the Al/GeOx interface. The RESET current increases with the increase of the CCs varying from 1ĀnA to 50Ā?A for the Cu electrode devices, while the RESET current is high (>1ĀmA) and independent of CCs varying from 1ĀnA to 500Ā?A for the Al electrode devices. An extra formation voltage is needed for the Al/GeOx/W devices, while a low operation voltage of ▒2ĀV is needed for the Cu/GeOx/W cross-point devices. Repeatable bipolar resistive switching characteristics of the Cu/GeOx/W cross-point memory devices are observed with CC varying from 1ĀnA to 50Ā?A, and unipolar resistive switching is observed with CC >100Ā?A. High resistance ratios of 102 to 104 for the bipolar mode (CCs of 1ĀnA to 50Ā?A) and approximately 108 for the unipolar mode are obtained for the Cu/GeOx/W cross-points. In addition, repeatable switching cycles and data retention of 103Ās are observed under a low current of 1ĀnA for future low-power, high-density, nonvolatile, nanoscale memory applications. PMID:24305116
Rahaman, Sheikh Ziaur; Maikap, Siddheswar
Comparison of resistive switching characteristics using copper and aluminum electrodes on GeOx/W cross-point memories
Comparison of resistive switching memory characteristics using copper (Cu) and aluminum (Al) electrodes on GeO x /W cross-points has been reported under low current compliances (CCs) of 1 nA to 50 ?A. The cross-point memory devices are observed by high-resolution transmission electron microscopy (HRTEM). Improved memory characteristics are observed for the Cu/GeO x /W structures as compared to the Al/GeO x /W cross-points owing to AlO x formation at the Al/GeO x interface. The RESET current increases with the increase of the CCs varying from 1 nA to 50 ?A for the Cu electrode devices, while the RESET current is high (>1 mA) and independent of CCs varying from 1 nA to 500 ?A for the Al electrode devices. An extra formation voltage is needed for the Al/GeO x /W devices, while a low operation voltage of ▒2 V is needed for the Cu/GeO x /W cross-point devices. Repeatable bipolar resistive switching characteristics of the Cu/GeO x /W cross-point memory devices are observed with CC varying from 1 nA to 50 ?A, and unipolar resistive switching is observed with CC >100 ?A. High resistance ratios of 102 to 104 for the bipolar mode (CCs of 1 nA to 50 ?A) and approximately 108 for the unipolar mode are obtained for the Cu/GeO x /W cross-points. In addition, repeatable switching cycles and data retention of 103 s are observed under a low current of 1 nA for future low-power, high-density, nonvolatile, nanoscale memory applications.
Potentiometric studies at ORNL with hydrogen electrode concentration cells
The absence of suitably stable reference electrodes for and to 300 C led ORNL to develop hydrogen electrode concentration cells for studies of equilibria of interest in reactor and steam generator systems to about 300 C during the late 1960`s and seventies. During the intervening two dozen years over twenty scientists have participated in potentiometric studies at Oak Ridge and much of that work will be summarized in this paper. A description of hydrogen electrode concentration cells developed in the late sixties and currently in use at Oak Ridge is given. The method of measurement, data interpretation, and published results are reviewed for studies of acid-base ionization, metal ion hydrolysis, and metal complexation reactions using principally such cells in titration or flow modes. 41 refs.
Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.
First-principles study of III-V electrode interfaces for photoelectrochemical hydrogen production
Photoelectrochemical (PEC) cells promise clean, sustainable production of hydrogen fuel using water and sunlight. However, combining solar conversion efficiency with durability in electrolyte solution has proven difficult, in part because the complex chemistry active at the electrode-electrolyte interface remains poorly understood. We use first-principles molecular dynamics simulations and model density-functional calculations to study the structure, stability, and chemical activity of GaP/InP semiconductor electrodes in contact with water. We find that a local bond-topological model is able to capture much of the basic surface chemistry. Interpretation of our results points to the particular importance of surface-adsorbed oxygen in determining the available reaction pathways for photocorrosion and water dissociation. Electronic signatures of the local bond topologies are compared to data from X-ray absorption and emission spectroscopy for insight into actual electrode structure.
Wood, Brandon; Ogitsu, Tadashi; Choi, Wooni; Schwegler, Eric
Pressure-independent point in current-voltage characteristics of coplanar electrode microplasma devices operated in neon
We introduce the idea of a pressure-independent point (PIP) in a group of current-voltage curves for the coplanar electrode microplasma device (CEMPD) at neon pressures ranging from 15 to 95 kPa. We studied four samples of CEMPDs with different sizes of the microcavity and observed the PIP phenomenon for each sample. The PIP voltage depends on the area of the microcavity and is independent of the height of the microcavity. The PIP discharge current, I{sub PIP}, is proportional to the volume (Vol) of the microcavity and can be expressed by the formula I{sub PIP}=I{sub PIP0}+DxVol. For our samples, I{sub PIP0} (the discharge current when Vol is zero) is about zero and D (discharge current density) is about 3.95 mA mm{sup -3}. The error in D is 0.411 mA mm{sup -3} (less than 11% of D). When the CEMPD operates at V{sub PIP}, the discharge current is quite stable under different neon pressures.
Meng Lingguo; Lin Zhaojun [School of Physics, Shandong University, Jinan 250100 (China); Xing Jianping [School of Information Science and Engineering, Shandong University, Jinan 250100 (China); Liang Zhihu; Liu Chunliang [Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China)
Cyclic voltammetric studies of stabilized ?-nickel hydroxide electrode
Substitution of aluminum for nickel in the lattice of nickel hydroxide, prepared by co-precipitation, leads to hydrofalcite-like compound of ?-nickel hydroxide. This compound has been used as the electrochemical active material in the positive electrodes of rechargeable alkaline batteries. Cyclic voltammetric studies suggest that ?-nickel hydroxide displays better reversibility of the Ni(OH) 2/NiOOH redox couple. The mechanism of the electrode reaction is still found to be controlled by proton diffusion, and the proton diffusion coefficient differs with the content of aluminium.
Bing, Liu; Huatang, Yuan; Yunshi, Zhang; Zuoxiang, Zhou; Deying, Song
Quantitative study of non-covalent interactions at the electrode-electrolyte interface using cyanide-modified Pt(111) electrodes.
Cations at the outer Helmholtz plane (OHP) can interact through non-covalent interactions with species at the inner Helmholtz plane (IHP), which are covalently bonded to the electrode surface, thereby affecting the structure and the properties of the electrochemical double layer. These non-covalent interactions can be studied quantitatively using cyanide-modified Pt(111) electrodes.
Escudero-Escribano, M.; Michoff, M. E. Z.; Leiva, E. P. M.; Markovic, N. M.; Gutierrez, C.; Cuesta, A. (Materials Science Division); (CSIC); (Universidad Nacional de Cordoba)
A study of electrode passivation during aqueous phenol electrolysis
The process of electrode passivation during phenol electrolysis at a platinum electrode was studied in a sulfuric acid electrolyte (pH0-1). Passive film growth and the effects of concentration and potential were investigated using chronoamperometry, x-ray photoelectron spectroscopy, and gel permeation chromatography. The main products of the phenol oxidation are oligomers/polymers with weight-averaged molecular weights typically around 1000 g/mol after a 30 ms anodic pulse. X-ray photoelectron spectroscopy shows that the passivating polymer film is oxidized incompletely with many hydroxyl groups present. Increased potential increased the polymerization rate, but above 1.0 V vs. SCE film decomposition reactions also occurred. Increased phenol concentration increased the charge required to initiate passivation. Potential steps to the open-circuit potential or to mo9re cathodic values can interfere with the passivation process. Chronamperometric results show that the current decay at the passivated electrode is roughly inversely proportional to time and that the currents for a fixed amount of polymerization reaction follow a Tafel relationship. This t;type of decay is not due to a limitation caused b;y reactant diffusion through, nor IR drop across, a growing film but is more characteristic of electron tunneling through a growing insulating barrier layer. The model proposed for the observed behavior involves the formation of a region of high molecular weight, oxidized material at the electrode surface which blocks further reaction at the electrode. The rate-determining step at the passivated electrode is therefore electron tunneling through this unreactive material.
Gattrell, M.; Kirk, D.W. (Univ. of Toronto, ON (Canada))
Nanostructured electrode surfaces studied by electrochemical NMR
Electrochemical nuclear magnetic resonance (EC-NMR) is a powerful local probe, which combines solid state NMR with electrochemistry. It is a unique technique that permits a unified, electronic-level study of the metal and adsorbate side of the electrochemical interface. Experiments can be performed either under direct potentiostatic control and in situ potential adjustment, or with samples prepared in a separate electrochemical
P. K. Babu; Y. Y. Tong; H. S. Kim; A. Wieckowski
External reflection studies of CO on platinized platinum electrodes
Several studies have shown a difference in the electrochemical response of bare platinum vs platinized platinum electrodes. We have found that the thickness of the platinum black coverage on a Pt electrode also changes the spectroscopic response of CO adsorbed on such a surface. A polycrystalline electrode was platinized at 2.75 V in a solution of chloroplatinic acid/lead acetate for time periods of 10 to 30 s. External reflection spectra were calculated using a single-beam spectrum collected with a monolayer of CO on the electrode and a single beam spectrum without the adsorbed CO as a reference. At lower platinization times, the CO peak existed as the expected upward-going band. As the platinization time was increased, the band shape became dispersive and the intensity of the band increased. At the highest platinization time, the peak appeared to invert itself into a downward going band, i.e., the reflection increased in the region of the CO absorption. This surprising phenomenon appears to be directly related to the change in the surface features with increased platinization time.
Bjerke, Amy E.; Griffiths, Peter R. [Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343 (United States)
Voltammetric study of an iron electrode in alkaline electrolytes
The electrochemical behaviour of a pure iron electrode was studied by cyclic voltammetry in solutions of KOH containing LiOH, Na 2S or SeO 2. The maximum charge delivered by the electrode in one cycle was observed in the concentration ranges 1.1 - 2.4 M KOH and 10 -4 - 10 -3 M Na 2S. Sulphide ions enhance the anodic reaction, while LiOH enhances the cathodic reduction of Fe(OH) 2. The effect of SeO 2 is similar to that of Na 2S, but it is considerably weaker; its advantage compared to the sulphide is that the reduction of Fe(OH) 2 is better separated from the hydrogen evolution peak, thus improving the charging efficiency.
?ern², J.; Micka, K.
Potentiometric studies of the rutile¢water interface: hydrogen-electrode concentration-cell versus glass-electrode titrations
This paper represents a comparison of surface protonation studies of rutile in NaCl media obtained using a conventional glass-electrode autotitrator system from 10 to 50░C, and hydrogen-electrode concentration cells from 25 to 250░C [J. Colloid Interface Sci., 200 (1998) 298]. Experimental conditions were matched as closely as possible between the two techniques, permitting a direct comparison of the results. Values
Moira K. Ridley; Michael L. Machesky; Donald A. Palmer; David J. Wesolowski
Detection of p53 gene point mutation using sequence-specific molecularly imprinted PoPD electrode.
An amperometric sequence-specific molecularly imprinted single-stranded oligodeoxyribonucleotide (ss-ODN) biosensor was fabricated and characterised in this study. Using ss-ODN as the template and o-phenylenediamine as the functional monomer, the ODN biosensor was fabricated by an electropolymerisation process on an indium-tin oxide (ITO) coated glass substrate. The template ss-ODN was washed out of the ss-ODN/poly(o-phenylenediamine)(PoPD)/ITO electrode using sterilised basic ethanol-water. The resulting ss-ODN imprinted PoPD/ITO electrode was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The amperometric responses, i.e., ?i as a function of the target ss-ODN concentration was studied. The biosensor using ss-ODN imprinted PoPD/ITO as the working electrode showed a linear ? current response to the target ss-ODN concentration within the range of 0.01-300 fM. The biosensor showed a sensitivity of 0.62 ?A/fM, with a response time of 14s. The present novel molecularly imprinted ss-ODN biosensor could greatly benefit in terms of cost-effectiveness, storage stability, ultra sensitivity and selectivity together with the potential for improved commercial genetic sensors. PMID:22484234
Tiwari, Ashutosh; Deshpande, Swapneel R; Kobayashi, Hisatoshi; Turner, Anthony P F
An optimization based study of equivalent circuit models for representing recordings at the neuron-electrode interface
Extracellular neuroelectronic interfacing is an emerging field with important applications in the fields of neural prosthetics, biological computation and biosensors. Traditionally, neuron-electrode interfaces have been modeled as linear point or area contact equivalent circuits but it is now being increasingly realized that such models cannot explain the shapes and magnitudes of the observed extracellular signals. Here, results were compared and contrasted from an unprecedented optimization based study of the point contact models for an extracellular æon-cellÆ neuron-patch electrode and a planar neuron-microelectrode interface. Concurrent electrophysiological recordings from a single neuron simultaneously interfaced to three distinct electrodes (intracellular, æon-cellÆ patch and planar microelectrode) allowed novel insights into the mechanism of signal transduction at the neuron-electrode interface. After a systematic isolation of the nonlinear neuronal contribution to the extracellular signal, a consistent underestimation of the simulated supra-threshold extracellular signals compared to the experimentally recorded signals was observed. This conclusively demonstrated that the dynamics of the interfacial medium contribute nonlinearly to the process of signal transduction at the neuron-electrode interface. Further, an examination of the optimized model parameters for the experimental extracellular recordings from sub- and supra-threshold stimulations of the neuron-electrode junctions revealed that ionic transport at the æon-cellÆ neuron-patch electrode is dominated by diffusion whereas at the neuron-microelectrode interface the electric double layer (EDL) effects dominate. Based on this study, the limitations of the equivalent circuit models in their failure to account for the nonlinear EDL and ionic electrodiffusion effects occurring during signal transduction at the neuron-electrode interfaces are discussed.
Thakore, Vaibhav; Molnar, Peter; Hickman, James J.
Lunar libration point flight dynamics study
Two satellite concepts, Halo and Hummingbird, for a lunar libration point satellite to be used as a tracking and communications link with the far side of the moon were evaluated. Study areas included flight dynamics, communications, attitude control, propulsion, and system integration. Both concepts were proved feasible, but Halo was shown to be the better concept.
Studies of Novel Electrode Materials for Anodic Oxidations.
Electrode material plays an important role in electrochemical reaction rates. Such electrode processes as nickel oxide, lead dioxide, platinum, carbon paste and glassy carbon anodes have been investigated. Oxidation of benzyl amine and 2-phenylethylamine ...
I. ul Haque
Ab initio study of metal gate electrode work function
The work function of metal multilayers and monolayers on bulk metals was studied using the first principle pseudopotential method within the local density approximation in order to find a way to modulate the work function of metal gate electrodes. Various multilayer stacks and bilayer stacks of two systems, Al-Pt and Al-Ni, were examined. It was found that two or three layers of the metal are enough to shift the work function to that of the surface metal. Also, it was found that even a submonolayer could affect the work function of the bulk metal significantly.
Park, Seongjun; Colombo, Luigi; Nishi, Yoshio; Cho, Kyeongjae
Graphene as transparent conducting electrodes in organic photovoltaics: studies in graphene morphology, hole transporting layers, and counter electrodes.
In this work, organic photovoltaics (OPV) with graphene electrodes are constructed where the effect of graphene morphology, hole transporting layers (HTL), and counter electrodes are presented. Instead of the conventional poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) PEDOT:PSS HTL, an alternative transition metal oxide HTL (molybdenum oxide (MoO(3))) is investigated to address the issue of surface immiscibility between graphene and PEDOT:PSS. Graphene films considered here are synthesized via low-pressure chemical vapor deposition (LPCVD) using a copper catalyst and experimental issues concerning the transfer of synthesized graphene onto the substrates of OPV are discussed. The morphology of the graphene electrode and HTL wettability on the graphene surface are shown to play important roles in the successful integration of graphene films into the OPV devices. The effect of various cathodes on the device performance is also studied. These factors (i.e., suitable HTL, graphene surface morphology and residues, and the choice of well-matching counter electrodes) will provide better understanding in utilizing graphene films as transparent conducting electrodes in future solar cell applications. PMID:22107487
Park, Hyesung; Brown, Patrick R; Bulovi?, Vladimir; Kong, Jing
The unusual adsorption states of Pt(111) electrodes studied by an iodine displacement method: comparison with Au(111) electrodes
The process of iodine adsorption on Pt(111) and Au(111) electrodes is utilized to identify the nature of unusual adsorption states on the Pt(111) electrode. The application of iodine allows the adsorbate replacement measurements at higher potentials than it has previously been practised with CO, thus enabling the study of Pt(111) in perchloric acid medium. The comparison between the results obtained with the two probes leads to self-consistency of the previous and present results. The data obtained with the two electrodes (and in the two supporting electrolytes) are mutually consistent. In sulphuric acid, we confirm that adsorption of an anion (sulfate or bisulfate) accounts for the unique features of the Pt(111) voltammetry. We also provide experimental results for identifying the origin of the unusual adsorption states in perchloric acid solution.
Herrero, E.; Feliu, J. M.; Wieckowski, A.; Clavilier, J.
Studies with porous zinc electrodes with additives for secondary alkaline batteries
The effect of the presence of additives like ZnO, V 2O 5, PbO and (NH 4) 2CS in solution phase on the performance of solid zinc electrode has already been reported. Small additions of HgO, Sb 2O 3, TiO 2 and Pb 3O 4 to the pasted zinc electrodes have been evaluated using Cyclic Voltammetry, Potentiodynamic Polarization (with temperature effect), A.C. Impedance measurements, Solution Analysis, and Porosity measurements. Though the additives HgO and Sb 2O 3 are known for their high hydrogen overpotential, HgO additive has the beneficial effect of imparting minimum standby corrosion, enhanced ageing behaviour and minimum shape change. As regards the additive TiO 2, its behaviour is superior to that of HgO as far as the ageing and high temperature performance are concerned. For Pb 3O 4, the corrosion behaviour as well as ageing are fairly good. However, this additive imparts a disadvantage of lead getting deposited on the counter electrode which would become a setback from the battery point of view. Details of the study are discussed in this paper.
Shivkumar, R.; Kalaignan, G. Paruthimal; Vasudevan, T.
Peripheral phlebitis: a point-prevalence study.
The purpose of this research study was to determine the factors influencing peripheral phlebitis in the adult medical-surgical population. The authors would then be able to use those data to determine whether a change in practice was warranted. Data collection and analysis of 188 intravenous sites revealed that females with higher doses of medications in intravenous sites of longer dwell times and suboptimal nutrition were at greater risk of developing peripheral phlebitis. The point prevalence was greater than the recommended 5%, which led the authors to review their facility's patient care and documentation practices. PMID:22759829
Washington, Georgita T; Barrett, Robin
Spatial bifurcations of fixed points and limit cycles during the electrochemical oxidation of H2 on Pt ring-electrodes.
Pattern formation during the oscillatory oxidation of H2 on Pt ring-electrodes in the presence of electrosorbing ions was studied under potentiostatic control for three different positions of the reference electrode (RE). The position of the RE crucially affects the degree of the global feedback which is imposed by the potentiostatic operation mode, and the three configurations selected corresponded to zero, maximum and intermediate global coupling. In the absence of global coupling, 'communication' among different positions occurs exclusively through migration coupling (the electrochemical counterpart to diffusion in reaction-diffusion systems). In this case, spatially inhomogeneous oscillations that were attributed to a spatial bifurcation of the homogeneous limit cycle were observed throughout. This implies that the system is Benjamin-Feir unstable. For the strongest global coupling adjustable, travelling pulses were found that emerged in a wave bifurcation with n = 1 from the homogeneous steady state. The pulses exhibited modulations in velocity and width that most likely resulted from the interaction between inhomogeneities of the catalytic surface and the nonlinear reaction dynamics. In the case of an intermediate global coupling strength, a diversity of spatio-temporal motions was observed. The dynamics ranged from pulses over target patterns and so-called asymmetric target patterns to mixed states where two or three of these states alternate. For some parameters these mixed states were in addition separated by bursts of the system to a nearly homogeneous unreactive state. PMID:11901673
Grauel, P; Varela, H; Krischer, K
A Comparative Study on Cutting Electrodes for Batteries with Lasers
E-mobility is still one of the most discussed topics within the automotive industry. Electric powered vehicles can drive emissionfree and present consequently the future propulsion. Nearly all global players in the automotive industry are making great efforts to develop cost-efficient electric drives, which are suitable for series production. The national governments support this evolution progressively. For example the mobility research programme of the Federal Republic of Germany looks at the production of Li- Ion cells in its entirety. Within this programme the cutting of electrodes for Li-Ion cells by lasers is an issue, too. This paper provides a comparative study on cutting materials relevant for Li-Ion cells with beam sources operating in a cw mode and a pulsed mode respectively.
Luetke, Matthias; Franke, Volker; Techel, Anja; Himmer, Thomas; Klotzbach, Udo; Wetzig, Andreas; Beyer, Eckhard
Theoretical study of reactions at the electrode-electrolyte interface
Electron transfer rates are predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have produced a new theory for description of the Jahn Teller effect in the solvation shell of the cuprous ion in aqueous solution, have implemented it in a molecular dynamics simulation and compared the results with experimental neutron scattering measurements on solutions containing the cuprous ion. A large amount of numerical data has been collected on the transition state of the ferrous ferric electron transfer reaction at an electrode. Work was completed on a polarizable and dissociable model of water for use in the electron transfer studies. New calculations of the conductivity in models of oxides have shown the existence of impurity conduction bands in such models for the first time.
Halley, J.W.
Electrochemical study of ricin at glassy carbon electrode.
Ricin, Ricinus communis agglutinin 60 - RCA 60, is a deadly phytotoxic protein which inhibits ribosomes (class II), and there is no known effective antidote in living organisms. Ricin is composed of two polypeptide chains, A and B, linked covalently by a single disulfide bond. The analytical methods for the detection of RCA 60 are commonly laborious, expensive, require skilled labor, and involve sophisticated equipment. Aimed at the development of electroanalytical methods for RCA 60 detection, here we studied the electrochemical oxidation of RCA 60 on a glassy carbon (GC) electrode over a wide pH range, using cyclic voltammetry, differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two quasi-reversible electrochemical RCA 60 oxidation peaks were identified on the GC electrode by SWV. For values of 2.2 ? pH ? 10.2, DPV studies revealed that the peak potentials, EP1 and EP2, display a linear dependence with pH and the reaction mechanism involves the transfer of 2H?/2e? (peak 1) and 1H?/1e? (peak 2). The first and second RCA 60 oxidation steps may correspond to the oxidation of cysteine and tyrosine-tryptophan residues, respectively. The oxidation product of the second RCA 60 oxidation step appears at 7.0 ? pH ? 11.8. For pH ? 10.2, both processes are pH independent, resulting in a pKa of ca. 10.2. A third RCA 60 oxidation peak only appears at acidic pH. RCA 60 samples extracted from different castor seed cultivars showed similar electrochemical behavior, enabling the implementation of an analytical voltammetric method. PMID:23741733
Ribeiro, Williame F; da Costa, Daniel J E; Lourenńo, Anabel S; Lopes, Ilanna C; de Medeiros, Everaldo P; Salazar-Banda, Giancarlo R; do Nascimento, Valberes B; de Ara·jo, Mßrio C U
Advanced PowerPoint Self Study
NSDL National Science Digital Library
In order to recieve credit for the Advanced PowerPoint Night, you will need to complete *ALL* of the following activities. 1. Please search for of Advanced PowerPoint Features on Google. These examples demonstrate how PowerPoint can function in other ways besides a linear presentation. (Notice how button and hyperlinks are used to navigate through the slideshows.) 2. Read pages 1-8 in your Advanced PowerPoint Module . ...
Murphy, Rachel
Study on the Realization of Indium Point
Indium point cells are fabricated using ingots of various forms from a variety of sources (manufacturers). Using these cells, newly built indium point furnaces are evaluated and their reliability is confirmed. The indium point realizations based on the single solid-liquid method (SSL method) and multi solid-liquid method (MSL method) are evaluated. The effect of impurities in the ingots is evaluated from the dependency of the slope of the freezing curve on the change in furnace temperature, the indium point depression based on the impurity analysis, and the cell comparison. The results show equality among the cells. Based on the results obtained, the uncertainty in realizing the indium point using the described indium point cells and indium point furnaces is estimated. The new uncertainty budget introduces uncertainties coming from plateau repeatability and chemical impurity derived by the present work, the values of which are significantly lower than those adopted in the current calibration service.
Widiatmo, Januarius V.; Yamazawa, Kazuaki; Satou, Kouichi; Tamba, Jun; Arai, Masaru
Study for Electrode Metals on Taste Sensor with LB film
In this paper, sensor responses with only metal electrode as Au, Cr, Ti and more with LB film were described. LB film material was the Dioctadecyldimethylammonium bromide combined by PVSK as an underlayer. To detect five basic taste substances, sensor parameters were defined as maximum voltage change and response time. Response time for sourness and umami with Ti and Cr evaporated metal electrode was larger than that of usual Au electrode. LB film effect was finally found to increase response time for five basic taste materials.
Yokoya, Takahiro; Hirata, Takamichi; Akiya, Masahiro
Some Studies into Electrical Discharge Machining of Nimonic75 Super Alloy Using Rotary Copper Disk Electrode
The present study reports the rotary disk electrical discharge machining of Nimonic75 super alloy, extensively used in aerospace industries. The experiments have been performed using Taguchi's orthogonal array L18 (21 ū 35) with copper disk electrode. The control factors considered were, viz., peak current, pulse on time, pulse off-time, gap voltage, and rotational speed of disk electrode with three levels each, and aspect ratio (AR) of the disk electrode having two levels, as noise factor. The novel approach of this article is to study the effect of the AR of the disk electrode on the performance measures, viz., material removal rate, disk electrode wear rate, and surface roughness. The results based on Taguchi's analysis show that among the considered process parameters, the AR and peak current significantly affect the machining characteristics. Furthermore, the rotating disk electrode easily flushes off the debris, resulting in better machining and reducing the chances of re-solidified layer formation.
Singh, S.; Pandey, A.
A comparative study of solid and liquid inner contact benzalkonium chloride ion-selective electrode membranes.
A comparative study was made between two designs of benzalkonium ion (Bz)-selective electrodes: a silver-coated (solid contact) called electrode A and a PVC membrane (liquid inner contact) called electrode B based on benzalkonium-phosphomolybdate (Bz-PM) as ion-exchanger complex. Electrode A has a linear dynamic range from 2.0ū10(-8) to 1.0ū10(-2) mol L(-1), with a Nernstian slope of 60▒0.3 mV/decade and a detection limit of 2.0ū10(-8) mol L(-1). Electrode B shows linearity over the concentration range from 2.0ū10(-7) to 1.0ū10(-2) mol L(-1), with a Nernstian slope of 55▒1.2 mV/decade and a limit of detection of 1.5ū10(-7) mol L(-1). Electrode A showed better performance than electrode B. The detection limit of benzalkonium chloride (BzCl) was effectively improved by a solid contact ion-selective electrode (SC-ISE), rather than the traditional liquid inner contact electrode that gives lower detection limits because of diminished ion fluxes. The present electrodes show clear discrimination of BzCl from several inorganic, organic ions, sugars and some common drug excipients. The sensors were applied efficiently for determination of BzCl in its pharmaceutical preparations (eye, ear and nasal drops) using standard addition and the calibration curve methods. PMID:23158314
Abu Shawish, Hazem M; Khedr, Abdalla M; Abed-Almonem, Khalid I; Gaber, M
Alternating current electrode polarization
Summary This article summarizes principles of alternating current electrode polarization. The importance of alternating current electrode polarization in biological impedance studies is discussed. The following topics are treated in detail: Definition of Electrode Polarization Impedance; Linearity and Superpositioning Principle; Frequency Dependence of Electrode Impedance; Preparation of Electrodes (Optimal current density for platinum black application, Stability of electrode impedance, Cell design
H. P. Schwan
Studies of Oxygen Reduction at a Rotating Disk Electrode.
The kinetics and mechanism of oxygen reduction at platinum were investigated by means of rotating disc electrode for potential applicability to measurement of dissolved oxygen. A kinetic expression for the current for oxygen reduction was developed, takin...
M. Forbes S. Lynn
Contribution to the study of the electric arc: Erosion of metallic electrodes. Thesis
A procedure is described for determining the extent of arc electrode erosion (excluding erosion due to transfer of material) from measurements of emitted spectral beam intensity. The relation between emission intensity and plasma temperature is ascertained. Experimental study of several combinations of monometallic electrodes shows that the method is suitable for determining cathode erosion, although the anode metal affects the extent of erosion. Combinations of electrodes which lead to low erosion of silver are reported.
Castro, A.
X-ray photoelectron and scanning auger electron spectroscopic studies of oxidized graphite electrode surfaces
The surfaces of electrochemically modified graphite electrodes have been studied using ESCA, scanning Auger microscopy, and chemical titration. Quantitative evaluation of surface functionalities after electro-oxidation in sulfuric acid provides an understanding of their mechanistic role in synthetic uses of the carbon electrode. Specifically concentrations of acid and phenolic groups are correlated with the level of oxidation on the electrode. A plateau is reached at between 4 and 22 C/cm/sup 2/.
Wandass, J.H.; Gardello, J.A. Jr.; Weinberg, N.L.; Bolster, M.E.; Salvati, L. Jr.
Speech perception with mono- and quadrupolar electrode configurations: a crossover study
OBJECTIVE: To study the effect of two multipolar electrode configurations on speech perception, pitch perception, and the intracochlear electrical field. STUDY DESIGN: Crossover design; within subject. SETTING: Tertiary referral center. PATIENTS: Eight experienced adult cochlear implant users. INTERVENTION: Each subject used each of three experimental processors for 3 weeks. The following processors were compared that differed only in electrode configuration:
Lucas H M Mens; Carlo K Berenstein
First principles studies of silicon as a negative electrode material
Batteries with higher volumetric and specific energy capacities are needed. Silicon is a promising candidate to replace graphite as the negative electrode material in Li-ion batteries. Silicon alloys with lithium, meaning its structure changes significantly during lithiation. Unlike other lithium alloys, lithiated silicon is amorphous when created electrochemically at room temperature. However, when lithiated at 415░C, crystalline Li-Si phases are experimentally found. This thesis focused on the study of the Li-Si crystalline phases and the lithiation of amorphous LixSi using first-principles calculations. A novel protocol to model the lithiation of amorphous silicon was developed, yielding results in good agreement with experiment. This represents the first time the lithiation of an amorphous alloy material has been modeled using first-principles calculations. Density functional theory calculations yielded formation energies for the crystalline and amorphous structures, from which potential-composition curves were calculated and compared to experiment. Good agreement with experiment was found, providing validation of the calculation methods and proposed protocol. Charge transfer studies and calculations of electronic densities of states for crystalline and amorphous structures were also completed. These confirmed the understanding of Li-Si structures as Zintl phases and quantified the charge transferred from Li to Si atoms. Phonon studies were completed for the crystalline Li-Si phases and helped explain their stability as a function of temperature. The phonon studies revealed that the Li15Si4 phase is unstable with respect to the other crystalline phases at elevated temperature, in agreement with experiment. Finally, experimental thermal studies of lithiated Si were used to obtain activation energies of the various crystallization events that occur when heating lithiated Si.
Chevrier, Vincent L.
Study of a guarded electrode system in the dc conductivity measurement of insulating liquid
The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.
Zhou, Yuan; Hao, Miao; Chen, George; Wilson, Gordon; Jarman, Paul
Astrometric Telescope Facility isolation and pointing study
The Astrometric Telescope Facility (ATF), an optical telescope designed to detect extrasolar planetary systems, is scheduled to be a major user of the Space Station's Payload Pointing System (PPS). However, because the ATF has such a stringent pointing stability specification and requires + or - 180 deg roll about its line of sight, mechanisms to enhance the basic PPS capability are required. The ATF pointing performance achievable by the addition of a magnetic isolation and pointing system (MIPS) between the PPS upper gimbal and the ATF, and separately, by the addition of a passive isolation system between the Space Station and the PPS base was investigated. The candidate MIPS can meet the ATF requirements in the presence of a 0.01 g disturbance. It fits within the available annular region between the PPS and the ATF while meeting power and weight limitations and providing the required roll motion, payload data and power services. By contrast, the passive base isolator system must have an unrealistically low isolation bandwidth on all axes to meet ATF pointing requirements and does not provide roll about the line of sight.
Hibble, William; Allen, Terry; Jackson, Louis; Medbery, James; Self, Richard
Glassy Carbon Rotating Ring-Disc Electrode for Molten Salt Studies.
A description of the procedure for fabricating a glassy carbon ring disc electrode for molten salt studies is described. The electrode has been employed in NaAlCl4 melts at 175 C and in KCl-LiCl melts at 450 C. (Author)
J. Phillips R. J. Gale R. G. Wier R. A. Osteryoung
ICESat Spacecraft Pointing Support Study Grant
The Geodetic Laser Altimeter System (GLAS) mission is designed to measure changes in the elevations of the polar ice sheets. The ICESat satellite will carry the GLAS altimeter, and will have a nominal orbit altitude of 600 km and orbit inclination of 94deg. The groundtrack repeat period is 182 days and will be maintained to less than 1 km at the equator via routine orbit adjustments. Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 meters of a predetermined reference groundtrack. As the actual ICESat groundtrack drifts away from the reference groundtrack, the attitude must be controlled such that the altimeter boresight is pointed, crosstrack, at the reference groundtrack. This orientation may be described by a rotation, theta, about the instantaneous geodetic local horizontal direction vector, which lies in the orbit plane and is oriented in the direction of motion of the satellite. The attitude is further complicated by requirements related to thermal and power considerations for various instruments, spacecraft components, and solar array orientation. In order to keep battery temperatures within the specified operating range, and maintain near normal pointing of the solar array with respect to the sunline direction vector as the orbit precesses relative to the sun, the satellite will be oriented in one of four fixed yaw modes. Each of these yaw modes depends upon the angle between the orbit plane and the sunline direction vector; this angle is designated Beta'. Table 1 shows the satellite yaw angle, Psi, for a given Beta' range. The angle Psi represents a rotation about the satellite z-axis, which points in the geodetic nadir direction; for Psi = 0deg the satellite x-axis points in the direction of motion.
Study of the adsorbed layer on a solid electrode surface by specular reflection measurement
Specular reflection measurements were carried out to study the adsorbed layers of certain heterocyclic compounds such as adenine, barbital, 2'-deoxyadenosine, phenobarbital, pyridine and thymine. When pyridine was present in 0.1M NaClO 4, a marked decrease in the reflectivity of a gold electrode was observed. In the potential range near the point of zero charge on the reflectivity-potential curve, the decrease was due to the adsorption of pyridine. Assuming the reflectivity change to be proportional to the surface coverage, the potential and concentration dependence of pyridine adsorption was determined and analysed on the basis of a Langmuir-type adsorption isotherm. The refractive indices and extinction coefficients for the adsorbed layers of the compounds investigated were evaluated using the observed reflectivity change, according to relations proposed by McIntyre and Aspnes.
Kusu, Fumiyo; Takamura, Kiyoko
Experimental and theoretical study of an internally cooled bipolar electrode for RF coagulation of biological tissues.
Although some types of bipolar electrodes have been broadly employed in clinical practice to coagulate biological tissue by means of radiofrequency (RF) currents, there is still scanty available information about their electrical-thermal behaviour. We are focused on internally cooled bipolar electrodes. The goal of our study was to know more about the behavior of this kind of electrodes. For that, we planned an experimental and theoretical model. The experimental study was based on bovine hepatic ex vivo tissue and the theoretical model was based on the Finite Element Method (FEM). In order to check the feasibility of the theoretical model, we assessed both theoretically and experimentally the effect of the internal cooling characteristics of the bipolar electrode (flow rate and coolant temperature) on the impedance progress during RF heating and coagulation zone dimensions. The experimental and theoretical results were in good agreement, which suggests that the theoretical model could be useful to improve the design of cooled bipolar electrodes. PMID:22255919
Gonzßlez-Sußrez, A; Alba, J; Trujillo, M; Berjano, E
Experimental study of tunnelling through nanogap electrodes in neural networks
Calf-thymus DNA sodium salt and polyallylamine hydrochloride a weak polyelectrolyte form a complex wire-like network, where interconnection is due to electrostatic forces during self-assembly. Tunnelling is believed to be responsible for conduction through the films spun on a series of specially designed nanogap electrodes.
Asim K. Ray; Anirban Bandyopadhyay; Saiful I. Khondaker
Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter
This research focuses on preparation, kinetics, and performance studies of mixed ionic and electronic conducting electrodes (MIEE) applied in an alkali metal thermal to electric converter (AMTEC). Two types of MIEE, metal/sodium titanate and metal/beta?-alumina were investigated, using Ni, Cu, Co and W as the metal components. Pure metal electrodes (PME) were also studied, including Ta, Ni, Nb, Ir, W and MoRe electrodes. The stability of MIEE/beta?-alumina solid electrolyte (BASE) interface was studied in terms of the chemical potential of Na-Al-Ti-O system at 1100K (typical AMTEC operating temperature). Ni metal was compatible with sodium titanate and BASE and displayed the best initial performance among all tested PMEs. Ni/sodium titanate electrodes with 4/1 mass ratios of metal/ceramic performed best among all tested electrodes. Scanning Electron Microscope (SEM) observations showed that grain agglomeration, which is the main mechanism for electrode degradation, occurred in all tested electrodes. Ceramic components were able to effectively limit the growth of metal grains and resulted in a long lifetime for MIEEs. Ni particles in the MIEE formed a network microstructure that was close to the theoretical morphology of the ideal electrode. A model based on percolation theory was constructed to interpret and predict the performance of MIEEs. The electrode kinetics was studied and a theoretical expression for the interface impedance was derived for both PME and MIEE, using electrochemical impedance spectroscopy (EIS). The conductivity of the Na2Ti 3O7 and Na2Ti6O13 mixture was measured. The average activation energy for the bulk conductivity was 0.87ev. Finally, theoretical analysis clarified that the transfer coefficient alpha value change would cause at most a few percent change in the electrode performance parameter B.
Guo, Yuyan
A simulation study of generation of unidirectionally propagated action potentials with bipolar electrodes
Electrical stimulation of unmyelinated nerve fibers was analyzed, using bipolar point electrodes in a simple volume conductor model and a dynamic model of Hodgkin-Huxley. The cathodal excitation threshold, the anodal block threshold and the virtual cathodal excitation threshold were calculated by a numerical method with axons of different radii. The results show that the rectangular stimulation pulse should have an
Changfeng Tai; Dazong Jiang
Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.
In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436
Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal
Abdominal wall trigger point case study.
Myofascial trigger points (TrPs) are posited to be an element in the etiology of both musculoskeletal and visceral pain. However, the recognition of TrPs as a causative factor in a patient's pain presentation varies amongst physicians and therapists. When myofascial pain syndrome is responsible for a patient's condition and is not recognized by the patient's medical advisors, the patient may be put through a plethora of testing procedures to find the cause of the patient's pain, and prescribed medications in an effort to treat the patient's symptoms. The case review presented here involves a patient with severe anterior abdominal pain, with a history of Crohn's disease, who experienced a long and difficult medical process before a diagnosis of myofascial pain syndrome was made. PMID:23561860
Muscolino, Joseph E
Evaluating object and region of concentric electrode in bio-electrical impedance measurement
Concentric electrode is easy to use and used widely for measuring bio-electrical impedance. But, its evaluating region was not investigated in detail. Then, the characteristics of concentric electrode were studied from various points of view. In case of use without electrode paste, impedance is determined with the contacting condition between electrode and skin surface over all frequency range. In case
Yoshitake YAMAMOTO; Kiyoko SHIRAI; Noriko GODA; Takao NAKAMURA; Toshimasa KUSUHARA; Hiroyuki OKUDA
Study of nickel hydroxide electrodes. 2: Oxidation products of nickel (2) hydroxides
Pure phases of some oxidized Ni oxides were prepared galvanimetrically with the Ni(2) hydroxide electrode of an alkaline battery. The crystallographic data of these phases, their chemical behavior, and conditions of transition were studied.
Bode, H.; Demelt, K.; White, J.
A Study in Enzyme Kinetics Using an Ion-Specific Electrode.
ERIC Educational Resources Information Center
Describes an undergraduate biochemistry laboratory experiment on enzyme kinetics using the D-amino acid oxidase system and an ammonia electrode. Preparation of an ammonia standard curve, a sample preparation, and inhibition studies are discussed. (YP)
Turchi, Sandra; And Others
Voltammetric studies of porous molybdenum electrodes for the alkali metal thermoelectric converter
Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from about 600 to 1000 K revealed a series of redox processes within the AMTEC operational voltage range which can be used to establish the electronic and ionic conductivities of these electrodes. Improved estimates of the free energies of formation of Na2Mo3O6, NaMoO2, and Na3MoO4 are obtained. Evidence is provided for the slow corrosive attack by Na2MoO4 on molybdenum. The ionic conductivity of Na2MoO4 is found to be sufficiently large at temperatures of greater than 700 K to explain the observed electrochemical phenomena in addition to the enhanced sodium transport in AMTEC electrodes below the freezing point of Na2MoO4.
Williams, R. M.; Bankston, C. P.; Khanna, S. K.; Cole, T.
Development and electrochemical studies of gas diffusion electrodes for polymer electrolyte fuel cells
Electrochemical studies on low catalyst loading gas diffusion electrodes for polymer electrolyte fuel cells are reported. The best performance is obtained with an electrode formed from 20 wt% Pt\\/C, 0.4 mg Pt cm-2 and 1.1 mg Nafion« cm-2 in the catalyst layer and 15% PTFE in a diffusion layer of 50 Ąm thickness, for both the cathode and the anode.
V. A. Paganin; E. A. Ticianelli; E. R. Gonzalez
AFM study of surface film formation on a composite graphite electrode in lithium-ion batteries
An in situ electrochemical atomic force microscopy (AFM) observation of a composite graphite electrode surface was performed in 1moldm?3 LiClO4 dissolved in a mixture of ethylene carbonate (EC)+diethyl carbonate (DEC), and propylene carbonate (PC) to show the applicability of scanning probe microscopy (SPM) to studies using composite graphite electrodes. In EC+DEC, three kinds of morphological changes (curling, swelling, and exfoliation)
Soon-Ki Jeong; Minoru Inaba; Yasutoshi Iriyama; Takeshi Abe; Zempachi Ogumi
Morphology and capacity of a cadmium electrode - Studies on a simulated pore.
Conditions in a single pore of a battery plate were simulated by using a cadmium chip of millimeter dimensions covered with an electrolyte film of micron thickness. In situ microscopy was applied to study changes in the electrode morphology during charge and discharge. Passivation and increases in particle sizes due to precipitation and electrodeposition of dissolved cadmium species were found to cause profound loss in electrode capacity on repeated charge and discharge.
Will, F. G.; Hess, H. J.
Modeling of Solid Oxide Fuel Cell functionally graded electrodes and a feasibility study of fabrication techniques for functionally graded electrodes
With the large energy demands, finite natural resources, and concern about carbon emissions, a more efficient method to produce energy for the electrical power grid is needed. Solid Oxide Fuel Cells (SOFC) have demonstrated nearly 70% efficiency in full scale trials. Much time has been spent reducing the cost of SOFCs, but little investigative focus has been put on optimal power output based on electrode microstructure. Moreover, it appears that no modeling has investigated optimization behavior of functionally graded SOFC electrodes. Also, nonlinear functional grading of SOFC electrodes has not been explored. In this work, a complete SOFC electrode model from literature was adapted for use in analyzing and comparing the losses between homogeneous, linearly, and nonlinearly graded electrodes. The model is based on a coupled differential equation system that was iteratively solved for three dependent variables: voltage, electronic current, and reactant gas pressure. It was found that particle size and porosity functional grading reduce diffusion losses near the electrode's free surface, while decreasing activation loss levels near the electrolyte interface. A range of particle sizes was identified around the optimal homogenous electrode particles size, where particle size grading is beneficial. Outside of this range, homogeneous structured electrodes show better performance. Nonlinear porosity grading shows an improvement over linear grading in voltage losses at small particle diameters (300 nm); little to no benefit is seen for larger particle diameters (3 mum). This work discusses (1) relative loss contribution in a SOFC electrode, (2) particle size and porosity grading ranges and their associated grading profiles for optimal performance, and (3) design criteria for the efficacy of particle size graded verses homogeneous electrodes. This work can be used to further explore the contribution of individual losses in a SOFC electrode. This information can then be used to further understand how to optimize SOFCs.
Flesner, Reuben Richard
High-freezing-point fuel studies
Considerable progress in developing the experimental and analytical techniques needed to design airplanes to accommodate fuels with less stringent low temperature specifications is reported. A computer technique for calculating fuel temperature profiles in full tanks was developed. The computer program is being extended to include the case of partially empty tanks. Ultimately, the completed package is to be incorporated into an aircraft fuel tank thermal analyser code to permit the designer to fly various thermal exposure patterns, study fuel temperatures versus time, and determine holdup.
Tolle, F. F.
Combined operando studies of new electrode materials for Li-ion batteries
The performances of Li-ion batteries depend on many factors amongst which the important ones are the electrode materials and their structural and electronic evolution upon cycling. For a better understanding of lithium reactivity mechanism of many materials the combination of X-Ray Powder Diffraction (XRPD) and Transmission M÷ssbauer Spectroscopy (TMS) providing both structural and electronic information during the electrochemical cycling has been carried out. Thanks to the design of a specific electrochemical cell, derived from a conventional Swagelock cell, such measurements have been realised in operando mode. Two examples illustrate the greatness of combining XRPD and TMS for the study of LiFe0.75Mn0.25PO4 as positive electrode and TiSnSb as negative electrode. Different kinds of insertion or conversion reactions have been identified leading to a better optimization and design of performing electrodes.
Jumas, Jean-Claude; Sougrati, Moulay Tahar; Perea, Alexis; Aldon, Laurent; Olivier-Fourcade, Josette
Experimental study and finite element analyses of electrode wear mechanisms during the resistance spot welding of galvannealed steel
The wear mechanisms of electrodes used on resistance spot welding of galvannealed steels were studied. The study focused on the inter-relationship among the steel properties, welding parameters and electrode wear. Six different galvannealed steels were studied using a standard constant current welding test. With the same kind of Cu-Zr electrode, the tests were performed with the electrode force fixed at 600 lbs and the welding time fixed at 12 cycles for all the steels studied. The welding current is set at just below the expulsion limit for each of the steels. The microstructure and mechanical properties of these steels were examined by SEM and microhardness tests. The face profiles for electrodes subjected to various numbers of welds were examined using carbon imprint tests and low magnification optical microscopy. The alloys formed on the electrode face were studied by the EDS and WDS quantitative analyses and linescans. Changes in the microhardness of the electrode material near the electrode face during the electrode wear process were also studied. Combined with the experimental examination, a sequentially coupled finite element analysis procedure was used to analyze the detailed distribution and evolution of the electrical current, temperature and stress throughout the process of making a weld. These analyses have greatly enhanced the understanding of the experimental observations. The results of this study indicate that the welding current is the dominant factor influencing electrode life. When the electrode force and the welding time are fixed, the welding current is determined by the steel properties. Thicker steel sheets and higher steel sheet surface hardnesses will result in smaller welding current. When the electrode force and welding time are fixed, steels requiring higher welding currents will yield shorter electrode lives. With increasing welding current, the top and bottom electrodes in this study showed increasingly different wear behaviors. Electrodes used on steels requiring higher welding current developed an edge pit near the top electrode periphery, that gradually evolved into a large pit at the bottom electrode face center. Toward the end of the electrode life, these electrodes result in a "three spots" feature nuggets that are shifted toward the top electrode. This kind of electrode failure is characterized by "nugget shifting". In contrast, under smaller welding current, the top and bottom electrode wear approximately the same. As the electrode face diameter increases gradually, not all the face area is in good contact with the steel sheet during welding. The localized contact areas for the top and bottom electrodes are symmetric and become fragmented gradually toward the end of the electrode life. The fragmentation of the electrode face areas which can be in good contact with the steel sheet results in the shunting of the welding current. When the electrical current density is reduced to a certain level by the shunting effect, the nugget can not be formed and the electrodes are declared to be failed. This kind of electrode failure is characterized by nugget shrinking. The welding current also has a big influence on the other electrode wear mechanism as the electrode mushrooming, face alloying, etc.
Lu, Feng
Study of electrode pattern design for a CZT-based PET detector.
We are developing a 1Āmm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40ĀmmĀūĀ40ĀmmĀūĀ5Āmm crystals metalized with a cross-strip electrode pattern with a 1Āmm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5Āmm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3Āmm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (?26 to ?127.5Āns full width at half maximum (FWHM) for 0.5Āmm and 4.2Āmm depths, respectively). 5Āmm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (?34 to ?83Āns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3Āmm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3Āmm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 toĀ-80ĀV w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100ĀĄm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns. PMID:24786208
Gu, Y; Levin, C S
Study of electrode pattern design for a CZT-based PET detector
We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm ū 40 mm ū 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (?26 to ?127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (?34 to ?83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode stripsÆ weighting functions, which indicated a stronger æsmall pixelÆ effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to ?80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 Ąm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.
Gu, Y.; Levin, C. S.
Study of the influence of transducer-electrode and electrode-wall gaps on the acoustic field inside a sonoelectrochemical reactor by FEM simulations
The influence of transducer-electrode and electrode-wall gaps on the spatial distribution of the acoustic pressure inside a sonoelectrochemical reactor has been studied by employing a linear acoustics-based model accounting for vibrations of the reactor walls. A FEM (Finite Elements Method) software package was used in order to simulate the response curves of the system, the distribution of the acoustic pressure
Ignacio Tudela; Ver¾nica Sßez; MarĒa Deseada Esclapez; Pedro Bonete; Hassen Harzali; Fabien Baillon; Josķ Gonzßlez-GarcĒa; Olivier Louisnard
Improvement of the interface integrity between a high-k dielectric film and a metal gate electrode by controlling point defects and residual stress
In this study, the influence of composition of thin films on the interface integrity between a hafnium dioxide thin film and a gate electrode was investigated by using a quantum chemical molecular dynamics method. Effect of the fluctuation of the composition around the HfO2▒x\\/metal interface on the formation of the interfacial layer was analyzed quantitatively. Post-oxidation annealing after deposition of
Ken Suzuki; Tatsuya Inoue; Hideo Miura
Origins of the Human Pointing Gesture: A Training Study
Despite its importance in the development of children's skills of social cognition and communication, very little is known about the ontogenetic origins of the pointing gesture. We report a training study in which mothers gave children one month of extra daily experience with pointing as compared with a control group who had extra experience withģ
Matthews, Danielle; Behne, Tanya; Lieven, Elena; Tomasello, Michael
Study of the arc-electrode interaction in a SF6 self-blast circuit breaker
To study the interaction between the electrode and the electrical arc in a SF6 self-blast circuit breaker, a coupling between experimental and theoretical approaches is proposed. The experimental approach allows physical variables such as the temperature just below the contact surface and the total metallic vapour mass in the electrical arc to be measured. The theoretical study is based on a hydrodynamic model for electrical arc modelling, which takes into account Joule heating, radiation and real-gas effects. The arc/electrode interaction model is built on an energy balance at the boundary between the gas flow (the arc) and the electrode (cathode or anode). The validation is obtained through comparisons between measured and calculated results.
Chķvrier, P.; Fiķvet, C.; Ciobanu, S. S.; Fleurier, C.; Scarpa, P.
Review and Evaluation of the Indian Point Probabilistic Safety Study.
This report summarizes the review of the internal and external event portions of the Indian Point Probabilistic Safety Study (IPPSS). The review was conducted by Sandia National Laboratories and Sandia contractors over approximately a 6-month period. The ...
A. M. Kolaczkowski D. L. Berry G. J. Kolb J. W. Hickman R. G. Easterling
First-Principles Study of Contact Resistance between Graphene and Metal Electrodes
Graphene attracts much interest for post-silicon electronics material due to its outstanding electronic transport properties such as considerably high mobility at room temperature. For the application of electronics devices, contacting of metal electrodes is necessary and decreasing of contact resistance between graphene and the metal electrodes is regarded as one of a key issue. In this study, we investigate the contact resistance using DFT+NEGF method. We consider the Ni and Cu electrode within LDA and TM-type norm-conserving pseudo-potential. We employed PHASE code [1] to determine the interface structures. Then, we constructed two terminal device structures in which current flows from metals to graphene. The electron transport properties were calculated using ASCOT code[2]. For Ni electrode, the dependence of the electrode size qualitatively agrees well with that obtained by the experiments. But our results suggest that contact resistance can be reduced considerably. [1] http://www.ciss.iis.u-tokyo.ac.jp/english/project/device/. [2] H. Kondo, J. Nara, H. Kino and T. Ohno, Jpn. J. Appl. Phys. 47, 4792 (2008).
Kaneko, Tomoaki; Ohno, Takahisa
An IPE back-end study for Turkey Point plant
This paper describes a study of Turkey Point plant's large dry containment as part of a response to the US Nuclear Regulatory Commission's individual plant examination Generic Letter 88-20. Two unique features of Turkey Point containment are discussed. This study includes an evaluation of the containment response to the physical processes occurring during an accident and probabilistic analysis of the spectrum of severe-accident progressions.
Guey, C.; Kabadi, J. (Florida Power and Light Co., Juno Beach (United States))
Phenothiazine-modified electrodes: a useful platform for protein adsorption study.
Using glucose oxidase (GOx) as a target protein, we studied the adsorption of protein on the phenothiazine-modified electrodes and assessed the potential of using the electrodes in biochemical applications. Experiment results showed that thionine chloride (TC) and its structural analogues, such as toluidine blue and methylene blue, fluoresced under photochemical excitation after being immobilized on indium-doped tin oxide (ITO) electrodes fabricated using either diazotization-reduction or oxidative polymerization. The surface-bound phenothiazines exhibited substantial binding affinities to the protein. At a pH > 5, the adsorbate showed no sign of desorption even the electrodes were electrically biased with voltages between ▒0.3 V vs SCE. Thus, emission decay occurred while GOx was injected over the electrodes, which was consistent with the observations made using conductive-mode atomic force microscopy (CM-AFM). Under a quiescent condition, the protein interacted with the immobilized TC via a pseudo-first-order kinetic mechanism. The reaction reached a maximum rate at a pH > 5, at which the rate constant was approximately 7 ū 10(-8) L/(U s). Under this condition, the adsorption rate increased as the level of the protein increased, regardless of pH, revealing application potential for GOx quantitation. The adsorption rate, however, decreased with a decrease in pH if the pH < 5. We concluded that static interactions played a crucial role. By monitoring Fe(CN)6(3-/4-) taking place at the TC-modified electrodes in pH 7 solutions, we observed that the adsorption of GOx imposed impedance on Fe(CN)6(3-/4-). The resulting charge-transfer resistance (RCT) increased as the amount of the protein increased, leading to a conclusion that the protein could reach the maximum surface coverage when its concentrations were greater than 100 U/mL. The protein molecules were likely repel each other as approaching the TC sites. Despite this, they maintained the native bioactivity after being adsorbed, enabling the TC-modified electrodes to function as glucose sensors. Glucose concentrations between 1 and 60 mM could be detected. Long-term analysis, in addition, showed that the electrode responses to the analyte were consistent and reproducible. Phenothiazine-modified electrodes are evident as a useful tool for understanding the adsorption of protein on solid surfaces and quantifying proteins. PMID:24460092
Chiou, Bo-Hao; Tsai, Yi-Ting; Wang, Chong Mou
The chemistry of Li/SOCl2 cells - An ESR study of carbon electrodes
Carbon electrodes from Li/SOCl2 cells were studied by electron spin resonance after various stages of discharge. Different behavior was observed in the temperature-dependent part of the ESR linewidth, defined as 'intrinsic linewidth', Delta H(int), when two different electrolytes were used. With one electrolyte, 1.5M LiAlCl4/SoCl2, the Delta H(int) value stayed constant or slightly decreased whereas with another electrolyte, 1.0M LiAlCl4/14 percent BrClin SOCl2, the value increased as discharge progressed. The carbon electrodes are modified differently during discharge with these two electrolytes, and it is speculated that this may be due to changes in the carbon matrix functional groups. This difference in the carbon electrodes may explain the claimed differences in safety performance of the cells.
Kim, S. S.; Carter, B. J.; Tsay, F. D.
Chemistry of Li/SOCl2 cells - an ESR study of carbon electrodes
Carbon electrodes from Li/SOCl2 cells were studied by electron spin resonance after various stages of discharge. Different behavior was observed in the temperature-dependent part of the ESR linewidth, defined as intrinsic linewidth, Delta H(int), when two different electrolytes were used. With one electrolyte, 1.5M LiAlCl4/SoCl2, the Delta H(int) value stayed constant or slightly decreased whereas with another electrolyte, 1.0M LiAlCl4/14 percent BrClin SOCl2, the value increased as discharge progressed. The carbon electrodes are modified differently during discharge with these two electrolytes, and it is speculated that this may be due to changes in the carbon matrix functional groups. This difference in the carbon electrodes may explain the claimed differences in safety performance of the cells. 19 references.
Kim, S.S.; Carter, B.J.; Tsay, F.D.
Two and Three-Electrode Impedance Studies on 18650 Li-Ion Cells
Two and three electrode impedance measurements were made on 18650 Li-ion cells at different QB temperatures ranging from 35 C to {minus}40 C. The ohmic resistance of the cell is nearly constant the temperature range studied although the total cell impedance increases by an order of magnitude in the same temperature range. In contrast to what is commonly believed, we show from our three-electrode impedance results that, the increase in cell impedance comes mostly from the cathode and not from the anode. Further, the anode and cathode contribute to both the impedance loops (in the NyQuist plot).
Nagasubramanian, Ganesan
Pointing Treatments Are Task Relevant: A Visuomotor Priming Study
The present study focused on priming effects on pointing with everyday objects. In a set of four experiments, a visuomotor priming paradigm was used to investigate the nature of visuomotor processing (automatic versus task relevant). By manipulating congruency of orientation and location we found that location congruency facilitates the initiation time of pointing whereas orientation congruency does not. We provide evidence to show that motor planning is influenced by the goal of the action, and that how visual information is processed and held in memory depends on the task relevance. These data are consistent with the proposed interaction between visuomotor and higher processes during the planning and execution of actions such as pointing.
Roche, Kevin; Chainay, Hanna
A study on electrode for amperometric measurement of human stress with flow injection analysis biosensing system
This paper presents a study on electrode for the amperometric detection of human stress based on salivary alpha amylase, emulated with different concentration of glucose, with the flow injection analysis biosensing system. Amperometric detection is an electrochemical voltammetric measurement approach, where the current intensity in a detection cell is regarded as a function of the concentration of the analyte. Flow
Lee Yoot Khuan; M. Hurairah Adha b Kamaruddin; Mohd Firdaus Abdullah; N. K. Madzhi; Anuar Ahmad
Studies on degradation of traditional Chinese medicine wastewater by a novel doped Ti\\/PbO2 electrode
In this study, we prepared a novel lead dioxide electrodes doped with Bi and Cu on Ti substrate by electro- deposition, and applied this electrode in electro-catalytic tests to treat traditional Chinese medicine wastewater. The electrode was characterized by using the Scanning Electron Microscope (SEM), Energy Dispersive X-ray Detector (EDX), and X-ray Diffraction (XRD). The results showed that this novel
Xudong Xu; Zhongqi Wang; Nannan Huang; Haixia Fu; Nailei Zhou
Study of Waverider-based Point-to-Point Suborbital Rocketplane
As a high-speed manned transportation system in the future, point-to-point (P2P) suborbital rocketplane is currently studied in Japan Aerospace Exploration Agency (JAXA) space transportation mission directorate. The vehicle was designed on the basis of the concept of waverider allowing high L/D in hypersonic regime, which is required for longer flight range and smaller load factor. Compared with an ideal waverider, the designed P2P suborbital rocketplane has outer wings for the improvement of the low-speed aerodynamic performance, finite thickness in the leading edge for the reduction of the aerodynamic heating, and twin vertical tails for directional stability. The aerodynamic performance of the P2P vehicle was investigated through numerical simulation of both subsonic and hypersonic flows, and the baseline aerodynamic shape of the P2P vehicle was discussed. The L/D in the trim condition at hypersonic speed was 2.6.
Takama, Yoshiki; Ishimoto, Shinji
The acetabular point: a morphological and ontogenetic study
The acetabular point was analysed by studying human pelvic bones from 326 individuals ranging from newborns to age 97 y. The bones were categorised into 3 groups according to the degree of fusion for the 3 elements of the pelvis: nonfused (59), semifused (5) and fused (262). The acetabular point in immature pelvic bones is clearly represented by the point of the fusion lines for each bony element at the level of the acetabular fossa. In adult pelvic bones the acetabular fossa has an irregular clover-leaf shape, the superior lobe being smaller than the anterior and posterior lobes. Cross-sectional analysis of acetabular morphology suggested that the acetabular point in adult pelvic bones is always represented by the indentation between the superior and the anterior lobes of the acetabular fossa.
The acetabular point: a morphological and ontogenetic study.
The acetabular point was analysed by studying human pelvic bones from 326 individuals ranging from newborns to age 97 y. The bones were categorised into 3 groups according to the degree of fusion for the 3 elements of the pelvis: nonfused (59), semifused (5) and fused (262). The acetabular point in immature pelvic bones is clearly represented by the point of the fusion lines for each bony element at the level of the acetabular fossa. In adult pelvic bones the acetabular fossa has an irregular clover-leaf shape, the superior lobe being smaller than the anterior and posterior lobes. Cross-sectional analysis of acetabular morphology suggested that the acetabular point in adult pelvic bones is always represented by the indentation between the superior and the anterior lobes of the acetabular fossa. PMID:11465866
Rissech, C; Sa±udo, J R; Malgosa, A
Motion control of the ankle joint with a multiple contact nerve cuff electrode: a simulation study.
The flat interface nerve electrode (FINE) has demonstrated significant capability for fascicular and subfascicular stimulation selectivity. However, due to the inherent complexity of the neuromuscular skeletal systems and nerve-electrode interface, a trajectory tracking motion control algorithm of musculoskeletal systems for functional electrical stimulation using a multiple contact nerve cuff electrode such as FINE has not yet been developed. In our previous study, a control system was developed for multiple-input multiple-output (MIMO) musculoskeletal systems with little prior knowledge of the system. In this study, more realistic computational ankle/subtalar joint model including a finite element model of the sciatic nerve was developed. The control system was tested to control the motion of ankle/subtalar joint angles by modulating the pulse amplitude of each contact of a FINE placed on the sciatic nerve. The simulation results showed that the control strategy based on the separation of steady state and dynamic properties of the system resulted in small output tracking errors for different reference trajectories such as sinusoidal and filtered random signals. The proposed control method also demonstrated robustness against external disturbances and system parameter variations such as muscle fatigue. These simulation results under various circumstances indicate that it is possible to take advantage of multiple contact nerve electrodes with spatial selectivity for the control of limb motion by peripheral nerve stimulation even with limited individual muscle selectivity. This technology could be useful to restore neural function in patients with paralysis. PMID:24939581
Park, Hyun-Joo; Durand, Dominique M
Microwave absorption studies of interface phenomena at ZnO electrodes
In order to explore the feasibility of microwave absorption techniques as a tool for the study of interfaces and electrode reactions we have measured the electrochemical and photochemical properties of ZnO in contact with an aqueous electrolyte by conventional electrochemical procedures and simultaneously by electrodeless detection of microwave absorption at 9.5 GHz in a resonant cavity. Pronounced potential dependent microwave absorption signals were found which proved to be influenced by illumination and electrochemical surface reactions. The comparison of microwave absorption with the electrochemically measured electrode behavior indicates, that microwave absorption data can provide interesting complementary information on the nature and reactivity of charge carriers and dipoles in the electrode/electrolyte interface. The proposed method is so sensitive that signals arising from fractions of monolayers will be detectable. A comprehensive interpretation of the results is not yet attempted. Further experimental studies on simple electrode systems are needed to clarify the mechanism. Because of its nondestructive nature, the microwave method could develop into a valuable new technique in surface chemistry.
Bogomolni, R.A.; Tributsch, H.; Petermann, G.; Klein, M.P.
Using ion-selective electrodes to study the drug release from porous cellulose matrices.
Polyvinyl chloride (PVC)-based solid-contact ion-selective electrodes (SC-ISEs), responding to propranolol hydrochloride (Pr+) and lidocaine hydrochloride (Ld+) cations as the model drugs with potassium tetrakis(4-chlorophenyl) borate (KTpClPB) as the ion exchanger, were studied. Different drug-polymer solutions were prepared with the model drugs, using different blend ratios of ethylcellulose (EC) and hydroxypropyl cellulose (HPC). Two different solid dosage forms were used. Polymer films were produced by solvent casting method and drug containing porous cellulose samples were prepared by depositing the drug-polymer solutions onto filter paper substrates. The quality of the electrodes and the release profile of Pr+ and Ld+ were investigated with the potentiometric method. The results were compared to UV spectrophotometry. The electrodes were found to be sensitive, precise and functional with a Nernstian behavior over the range of 1.0 ū 10-3-3.1 ū 10-6 M (9.2 ū 10-4-3.0 ū 10-1 mg/mL) and 1 ū 10-3-2 ū 10-6 M (5.4 ū 10-4-2.7 ū 10-1 mg/mL) at 25 ░C for Pr+ and Ld+ sensitive electrodes, respectively. The dynamic response time for the electrodes was less than 10 s. The Pr+ release from porous filter paper was always higher than its equivalent film formulation. Also, lidocaine had higher and faster release from the samples with higher drug concentration. The comparison of the two analytical methods showed near identical results. The ISEs provided a powerful and flexible alternative to UV method in determination of drug release from porous cellulose substrates in a small scale dissolution testing. PMID:24300297
Vakili, Hossein; Genina, Natalja; Ehlers, Henrik; Bobacka, Johan; Sandler, Niklas
Using Ion-Selective Electrodes to Study the Drug Release from Porous Cellulose Matrices
Polyvinyl chloride (PVC)-based solid-contact ion-selective electrodes (SC-ISEs), responding to propranolol hydrochloride (Pr+) and lidocaine hydrochloride (Ld+) cations as the model drugs with potassium tetrakis(4-chlorophenyl) borate (KTpClPB) as the ion exchanger, were studied. Different drug-polymer solutions were prepared with the model drugs, using different blend ratios of ethylcellulose (EC) and hydroxypropyl cellulose (HPC). Two different solid dosage forms were used. Polymer films were produced by solvent casting method and drug containing porous cellulose samples were prepared by depositing the drug-polymer solutions onto filter paper substrates. The quality of the electrodes and the release profile of Pr+ and Ld+ were investigated with the potentiometric method. The results were compared to UV spectrophotometry. The electrodes were found to be sensitive, precise and functional with a Nernstian behavior over the range of 1.0 ū 10?3¢3.1 ū 10?6 M (9.2 ū 10?4¢3.0 ū 10?1 mg/mL) and 1 ū 10?3¢2 ū 10?6 M (5.4 ū 10?4¢2.7 ū 10?1 mg/mL) at 25 ░C for Pr+ and Ld+ sensitive electrodes, respectively. The dynamic response time for the electrodes was less than 10 s. The Pr+ release from porous filter paper was always higher than its equivalent film formulation. Also, lidocaine had higher and faster release from the samples with higher drug concentration. The comparison of the two analytical methods showed near identical results. The ISEs provided a powerful and flexible alternative to UV method in determination of drug release from porous cellulose substrates in a small scale dissolution testing.
A study of the interaction between two triple points
In the Mach reflection of plane shock on a concave double wedge, after two triple points collide with each other, the wave pattern is usually complicated. In this paper, firstly, a shock dynamic approach is used for studying this problem. In this approach, the method of shock-shock polar is used for better understanding the pattern of disturbance propagation. A downward-traveling
P. Xie; Z. Y. Han; K. Takayama
Multifactorial comparative study of spatial point pattern analysis methods.
A way of studying cooperative behaviour of biological entities (proteins, cells, etc.) is by using topographical analysis: the quantification of the spatial patterns formed by the entities considered as points. Five methods of topographical analysis were compared in terms of discriminant power, stability of parameters, methodological bias and algorithms. We tested five methods (nearest neighbour distribution, radial distribution, Vorono' paving, quadrat count, minimal spanning tree graph) which generated nine parameters on four simulated models (random point process, hardcore model and two cluster models) and on experimental cellular models. The method which offers the best discrimination power and stability seems to be the minimal spanning tree graph edge length distribution. PMID:9245582
Wallet, F; Dussert, C
Studies on the Behavior of Water Triple-Point Cells
Several triple point of water (TPW) cells from four different manufacturers were investigated in the same TPW maintenance bath with three standard platinum resistance thermometers. Temperature differences between the water triple point among cells were analyzed and found to be within 0.319 mK and repeatability to 0.015 mK over four to five months. The variations of temperature with height in different cells were compared with each other and also with the expected value of -7.3ū10-4 K.m-1. The effect of the depth of immersion of the TPW cell in the maintenance bath on the water triple-point was studied and discussed here.
Tsai, Shu-Fei
Metal-sheet-beam formation using an impregnated electrode-type liquid-metal ion source with a linear array of emission points
High current and sheet-shaped metal beams are required in ion implanters which utilize a mass separator. The present paper describes the profiles of the ion beams extracted from the impregnated electrode-type liquid-metal ion source with linear array of emission points (array source) and the formation of the sheet beams with a rectangular lens system. The experimental results indicated that the profiles of the extracted beamlet of array source without use of lens system have smaller divergences along the parallel direction with respect to the ion emission array. Since it has been clarified that the beamlet was convergent along the parallel direction, the focusing lens system was designed so as to converge the ion beam along the perpendicular direction. The profiles of the converged beams were also measured. As a result, it was found that the sheet beams were successfully formed and the thickness of the sheet-shaped beam is found to be about 2 mm. The present results demonstrated that this type of ion source could be utilized in a practical implanter.
Gotoh, Yasuhito; Ishikawa, Junzo; Tsuji, Hiroshi; Fukayama, Norihisa; Ogata, Yasushi
[In-situ FTIR study of hybrid copper-cobalt hexacyanoferrate film modified electrode].
The study on the in-situ FTIR spectroelectrochemistry of a hybrid copper-cobalt hexacyanoferrate film modified platinum electrode was carried out. The variation of the FTIR spectra was well correlated to the redox process of CuCoHCF. The relative contribution of Cu(II) and Co(II) to the stretching vibration of CN was found to vary with the applied potential. PMID:12953554
Cui, Xing-pin; Wang, Xia-yan; Lin, Xiang-qin
Study of hypothermia on cultured neuronal networks using multi-electrode arrays
Efficient and safe use of hypothermia during various neuro-medical procedures requires sound understanding of low temperature effects on the neuronal network's activity. In this report, we introduce the use of cultivated dissociated neuronal networks on temperature controlled multi-electrode arrays (MEAs) as a simple methodology for studying the long-term effects of hypothermia. The networks exhibit spontaneous activity in the form of
Liel Rubinsky; Nadav Raichman; Itay Baruchi; Mark Shein; Jacob Lavee; Hanan Frenk; Eshel Ben-Jacob
Material removal rate and electrode wear study on the EDM of silicon carbide
In this work, a material removal rate (MRR) and electrode wear (EW) study on the die-sinking electrical discharge machining (EDM) of siliconised or reaction-bonded silicon carbide (SiSiC) has been carried out. The selection of the above-mentioned conductive ceramic was made taking into account its wide range of applications in the industrial field: high-temperature gas turbines, bearings, seals and lining of
C. J. Luis; I. Puertas; G. Villa
Study of camphor-pyrolysed carbon electrode in a lithium rechargeable cell
Pure camphor pyrolysed at 900░C for 2h in different gaseous environments yields graphite-like carbons which were used as a negative electrode in rechargeable carbon\\/Li cells. These cells were continuously cycled at a constant current of 300?Acm?2 for 10¢20 days and reversible Li+ intercalation capacities of 0.45¢0.61 were observed. Kinetic analysis of such a cell was studied by complex impedance spectroscopy
Mukul Kumar; P. D Kichambare; Maheshwar Sharon; Neil R Avery; Krista J Black
A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique
A study of the corrosion of friction stir welded 2195 Al-Li alloy has been carried out using the scanning reference electrode technique (SRET). The results are compared to those obtained from a study of heterogeneously welded samples.
Donford, M. D.; Ding, R. J.
Martian Aerocapture Terminal Point Guidance: A Reference Path Optimization Study
An effective method of terminal point guidance is to employ influence coefficients, which are solved from a set of differential equations adjoint to the linearized perturbations of the equations of motion about a reference trajectory. Hence, to optimize this type of guidance, one must first optimize the reference trajectory that the guidance is based upon. This study concentrates on various methods to optimize a reference trajectory for a Martian aerocapture maneuver, including a parametric analysis and first order gradient method. Resulting reference trajectories were tested in separate 2000 6-DOF Monte Carlo runs, using the Atmospheric Guidance Algorithm Testbed for the Mars Surveyor Program 2001 (MSP '01) Orbiter. These results were compared to an August 1998 study using the same terminal point control guidance algorithm and simulation testbed. Satisfactory improvements over the 1998 study are amply demonstrated.
Ro, Theodore U.; Queen, Eric M.; Striepe, Scott A.
Can bismuth film screen printed carbon electrodes be used to study complexation?
Ex- situ bismuth film on commercial screen-printed carbon electrodes (BiSPCE) has been used for the first time for the analysis of the complexation of Cd(2+) by thiol containing compounds as glutathione (GSH) and phytochelatin (?-Glu-Cys)2-Gly (PC2). Reproducibility of data is quite satisfactory and allows their treatment by multivariate curve resolution by alternating least squares (MCR-ALS). Unitary voltammograms and concentration profiles provided by MCR-ALS confirm the formation of 1:1 and 1:2 Cd(2+):GSH and 1:2 Cd(2+):PC2 complexes. These results are in agreement with those previously obtained by mercury electrodes, and allow us to propose the use of BiSPCE for further studies on complexation. PMID:23598234
Sosa, Velia; Serrano, N·ria; Ari±o, Cristina; Manuel DĒaz-Cruz, Josķ; Esteban, Miquel
In Situ X-Ray Absorption Spectroscopy Study of the LiNiO2 Electrode
LiNiO2 is one of the most promising active material for the development of novel 4V rechargeable lithium batteries. Recent x-ray diffraction studies showed that the electrochemical reactivity of this electrode is sensitive to the structure of the starting material as well as the charged products. To further examine this material, we have conducted an x-ray absorption spectroscopy (XAS) study to determine the structure of this electrode as a function of its charge state. Specifically, the x-ray absorption Ni K-edge energy, the pre-edge structure, and local structure parameters such as bond lengths, coordination numbers and disorders were investigated at various states of charge corresponding to Li_(1-x)NiO2 for x values of 0.0, 0.11, 0.23, 0.34, 0.45, 0.82, and 0.99. The charging which proceeds via lithium de-intercalation was conducted using constant current anodization at 0.5 mA in a non aqueous electrolyte consisting of 1M LiPF6 in 1:1:3 propylene ! carbonate, ethylene carbonate and dimethyl carbonate. The XAS results for this electrode will be compared with those of ?-NiOOH and KNiIO_6, the latter being used as a reference for quadrivalent nickel.
Mansour, A. N.; McBreen, J.; Melendres, C. A.
Impact of point-source injection methodologies on injection studies
Effective interdiction of illicit radioactive material requires decision criteria that are sensitive to the material of interest, while insensitive to material of lesser interest. Injection studies are used to assess the sensitivities of decision criteria to radioactive threat scenarios. Configuring injection studies requires decisions about methodological factors that represent or simplify actual field conditions. Understanding the relative impact of different source injection methods on alarm rates and other outcome measures is vital for interpreting results of injection studies. The most complete and realistic way to inject point-source counts into a vehicle count profile is with the randomly positioned source profile approach. In this paper, we report a study of the impacts of methodological simplifications to this approach. We assessed relative sensitivity of two field-deployed detection algorithms to two experimental factors in point-source injection studies. The first factor featured "centered" versus "random" point-source position along the vehicle count profile. The second factor featured either adding the entire injection profile ("profile injection") or adding only the central "spike" portion of the injection profile nearest to the point-source position ("spike injection"). A collection of 75 059 archived vehicle count profiles from an operating border crossing were injected with a simulated low-energy gamma-ray point-source intended to emulate surrogates of highly enriched uranium or plutonium. Outcomes were assessed by means of injection curves (alarm rate vs. injection source size) and a derived measure, minimum detectable count rates (MDC) required to attain a detection probability of 95%. Results show that injection methodology combined with algorithm impacts study outcomes in different ways. For gross count results, centered spike injections yield higher detection sensitivity than centered profile injections, and random spike injections yield even higher detection sensitivity than centered spike injections. Conversely, for energy window ratio results, centered spike injections yield less sensitivity than centered profile injections, and random spike injections yield even less sensitivity than centered spike injections. These effects may be partially attributable to background suppression in the vehicle profile of detection statistics. Although the observed effects (up to 10%) are not large, the injection method impacts alarm rates from the two detection algorithms in opposite directions. These results inform methodological decisions and assessments of results in injection studies.
Weier, Dennis R.; Lo Presti, Charles A.; Bates, Derrick J.
A semi-automatic method to determine electrode positions and labels from gel artifacts in EEG/fMRI-studies.
The analysis of simultaneous EEG and fMRI data is generally based on the extraction of regressors of interest from the EEG, which are correlated to the fMRI data in a general linear model setting. In more advanced approaches, the spatial information of EEG is also exploited by assuming underlying dipole models. In this study, we present a semi automatic and efficient method to determine electrode positions from electrode gel artifacts, facilitating the integration of EEG and fMRI in future EEG/fMRI data models. In order to visualize all electrode artifacts simultaneously in a single view, a surface rendering of the structural MRI is made using a skin triangular mesh model as reference surface, which is expanded to a "pancake view". Then the electrodes are determined with a simple mouse click for each electrode. Using the geometry of the skin surface and its transformation to the pancake view, the 3D coordinates of the electrodes are reconstructed in the MRI coordinate frame. The electrode labels are attached to the electrode positions by fitting a template grid of the electrode cap in which the labels are known. The correspondence problem between template and sample electrodes is solved by minimizing a cost function over rotations, shifts and scalings of the template grid. The crucial step here is to use the solution of the so-called "Hungarian algorithm" as a cost function, which makes it possible to identify the electrode artifacts in arbitrary order. The template electrode grid has to be constructed only once for each cap configuration. In our implementation of this method, the whole procedure can be performed within 15 min including import of MRI, surface reconstruction and transformation, electrode identification and fitting to template. The method is robust in the sense that an electrode template created for one subject can be used without identification errors for another subject for whom the same EEG cap was used. Furthermore, the method appears to be robust against spurious or missing artifacts. We therefore consider the proposed method as a useful and reliable tool within the larger toolbox required for the analysis of co-registered EEG/fMRI data. PMID:21784161
de Munck, Jan C; van Houdt, Petra J; Verdaasdonk, Ruud M; Ossenblok, Pauly P W
Studying the glial cell response to biomaterials and surface topography for improving the neural electrode interface
Neural electrode devices hold great promise to help people with the restoration of lost functions, however, research is lacking in the biomaterial design of a stable, long-term device. Current devices lack long term functionality, most have been found unable to record neural activity within weeks after implantation due to the development of glial scar tissue (Polikov et al., 2006; Zhong and Bellamkonda, 2008). The long-term effect of chronically implanted electrodes is the formation of a glial scar made up of reactive astrocytes and the matrix proteins they generate (Polikov et al., 2005; Seil and Webster, 2008). Scarring is initiated when a device is inserted into brain tissue and is associated with an inflammatory response. Activated astrocytes are hypertrophic, hyperplastic, have an upregulation of intermediate filaments GFAP and vimentin expression, and filament formation (Buffo et al., 2010; Gervasi et al., 2008). Current approaches towards inhibiting the initiation of glial scarring range from altering the geometry, roughness, size, shape and materials of the device (Grill et al., 2009; Kotov et al., 2009; Kotzar et al., 2002; Szarowski et al., 2003). Literature has shown that surface topography modifications can alter cell alignment, adhesion, proliferation, migration, and gene expression (Agnew et al., 1983; Cogan et al., 2005; Cogan et al., 2006; Merrill et al., 2005). Thus, the goals of the presented work are to study the cellular response to biomaterials used in neural electrode fabrication and assess surface topography effects on minimizing astrogliosis. Initially, to examine astrocyte response to various materials used in neural electrode fabrication, astrocytes were cultured on platinum, silicon, PMMA, and SU-8 surfaces, with polystyrene as the control surface. Cell proliferation, viability, morphology and gene expression was measured for seven days in vitro. Results determined the cellular characteristics, reactions and growth rates of astrocytes grown on PMMA resembled closely to that of cells grown on the control surface, thus confirming the biocompatibility of PMMA. Additionally, the astrocyte GFAP gene expressions of cells grown on PMMA were lower than the control, signifying a lack of astrocyte reactivity. Based on the findings from the biomaterials study, it was decided to optimize PMMA by changing the surface characteristic of the material. Through the process of hot embossing, nanopatterns were placed on the surface in order to test the hypothesis that nanopatterning can improve the cellular response to the material. Results of this study agreed with current literature showing that topography effects protein and cell behavior. It was concluded that for the use in neural electrode fabrication and design, the 3600mm/gratings pattern feature sizes were optimal. The 3600 mm/gratings pattern depicted cell alignment along the nanopattern, less protein adsorption, less cell adhesion, proliferation and viability, inhibition of GFAP and MAP2k1 compared to all other substrates tested. Results from the initial biomaterials study also indicated platinum was negatively affected the cells and may not be a suitable material for neural electrodes. This lead to pursuing studies with iridium oxide and platinum alloy wires for the glial scar assay. Iridium oxide advantages of lower impedance and higher charge injection capacity would appear to make iridium oxide more favorable for neural electrode fabrication. However, results of this study demonstrate iridium oxide wires exhibited a more significant reactive response as compared to platinum alloy wires. Astrocytes cultured with platinum alloy wires had less GFAP gene expression, lower average GFAP intensity, and smaller glial scar thickness. Results from the nanopatterning PMMA study prompted a more thorough investigation of the nanopatterning effects using an organotypic brain slice model. PDMS was utilized as the substrate due to its optimal physical properties. Confocal and SEM imaging illustrated cells from the brain tissue slices were aligned along the nanopatt
Ereifej, Evon S.
Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide
The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10?4 M to 1 M, and 29.96 mV/decade for 10?7 M to 10?4 M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10?4 M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 10?5 M and 10?4 M.
Lin, Jyh-Ling; Hsu, Hsiang-Yi
Ancient Astronomy: A Study of the Point Remove Mound Complex
Artificial solstice markers are a common thread across many early civilizations. With the beginnings of early agriculture, the need to be able to predict the changes in season became an issue of utmost importance. Many Native American groups used artificial mounds to mark different astronomical events. Toltec Mounds (located southeast of Little Rock, AR) is a complex set of structures left behind by the area's native people that is known to have alignments with the summer and winter solstice as well as an equinox alignment. The Point Remove mound complex (located outside Morrilton, Arkansas, also known as site 3CN4) is a known archeological site that has not been well studied, therefore has never been checked for any form of astronomical alignment. The purpose of this project is to study the Point Remove Mound site and look for features of astronomical significance. Study of Toltec Mounds will serve as a baseline for comparison. Study of the site consists of aerial photographs, topographic maps, and GPS measurements. In addition to studying alignments within the site, the location of the mound complex will be studied with respect to other known complexes like Toltec Mounds and Spiro Mounds (Oklahoma).
Hankins, Matt; Burris, D. L.
Examination of Iontophoretic Transport of Ionic Drugs Across Skin. 1. Baseline Studies with the Four-Electrode System.
Recently there has been increased interest in the possibility of utilizing iontophoresis for drug transport across skin. Although previous studies with conventional two electrode systems have shown that it is feasible to obtain flux enhancement of drugs a...
S. Pons T. Masada W. I. Higuchi U. Rohr J. Fox
Application of various electrodes in potentiometric titration of calcium.
In complexometric titrations various indicator electrodes may be employed for monitoring the course of titration and for detection of the end-point. Several of them, including the silver, mercury, bivalent cation membrane, calcium membrane and manganese dioxide electrodes were investigated and compared in their usefulness. As titrant, EDTA was mostly used, but results with similar chelating titrants were also obtained. The practical utility of the electrodes in titrations depends on their selectivity, magnitude of the end-point break and precision in determination of the end-point. For the electrodes studied, in some instances there is good correlation between the theoretical and experimental titration curves, but it is not always possible to predict the electrode response in the low activity range. In other cases poor correlation does not mean that reasonably good analytical results may not be obtained. PMID:18961322
Hulanicki, A; Trojanowicz, M
The study of lithium insertion¢deinsertion processes into composite graphite electrodes by in situ atomic force microscopy (AFM)
Li insertion¢deinsertion into composite graphite electrodes, comprising synthetic graphite flakes (6 ?m average size), polyvinylidene difluoride binder (PVdF), and copper current collectors, in commonly used alkyl carbonate solutions were studied by in situ atomic force microscopy (AFM). In this study, we were able to probe by in situ AFM the behavior of practical, composite graphite electrodes in ethylene carbonate¢dimethyl carbonate
Maxim Koltypin; Yaron S Cohen; Boris Markovsky; Yair Cohen; Doron Aurbach
The study of electron transfer in advanced materials (electrodes for Li-ion batteries or catalysts)
M÷ssbauer Spectroscopy (MS) is really suitable to study local electronic structures. Its hyperfine parameters, isomer shift (IS) and quadrupole splitting (QS) allow to characterize the oxidation state and coordination of the probed element. So, the capabilities of this powerful technique have been highlighted for the study of electron transfer occurring during electrochemical or catalytic processes. Several examples illustrate how MS can be used for the determination of reaction mechanisms in new electrode materials of Li-ion batteries (Sb or Sn-based, Ti oxides) or reforming catalysts (supported bimetallic PtSn catalysts). Deeper insight into the mechanisms determining the electrochemical or catalytic performances can be expected.
Jumas, Jean-Claude; Womes, Manfred; Lippens, Pierre-Emmanuel; Olivier-Fourcade, Josette
Chalk Point Steam Electric Station Studies Patuxent Estuary Studies: Ichthyoplankton Population Studies, 1978 Data Report.
The surveys are part of a series of studies designed to help evaluate the effect of the Chalk Point Generating Station on the Patuxent Estuary. Objectives of the study were to determine spatial and temporal distribution of fish eggs and larvae in the rive...
E. M. Setzler K. V. Wood D. Shelton G. Drewry
Impact of Point-Source Injection Methodologies on Injection Studies
Effective interdiction of illicit radioactive material requires detection algorithms that are sensitive to material of interest while insensitive to material of no interest. Injection studies are used to assess the detection sensitivities to threat scenarios by various detection algorithms. In injection studies, gamma-ray spectra for varying source strengths representing particular radioisotopes and shielding configurations are added to archived vehicle count time-profiles. Observed alarm rates are calculated and analyzed to address experimental questions. Numerous decisions need to be made about configuring injection studies, including two important methodological factors that emulate actual field conditions: point-source position and temporal shape. Understanding the relative impact of different methods on outcome measures is vital for comparing results of injection studies.
Weier, Dennis R.; Lopresti, Charles A.; Bates, Derrick J.
Comprehensive Study of Microgel Electrode for On-Chip Electrophoretic Cell Sorting
We have developed an on-chip cell sorting system and microgel electrode for applying electrostatic force in microfluidic pathways in the chip. The advantages of agarose electrodes are 1) current-driven electrostatic force generation, 2) stability against pH change and chemicals, and 3) no bubble formation caused by electrolysis. We examined the carrier ion type and concentration dependence of microgel electrode impedance, and found that CoCl2 has less than 1/10 of the impedance from NaCl, and the reduction of the impedance of NaCl gel electrode was plateaued at 0.5 M. The structure control of the microgel electrode exploiting the surface tension of sol-state agarose was also introduced. The addition of 1% (w/v) trehalose into the microgel electrode allowed the frozen storage of the microgel electrode chip. The experimental results demonstrate the potential of our system and microgel electrode for practical applications in microfluidic chips.
Akihiro Hattori,; Kenji Yasuda,
A blister-test apparatus for studies on the adhesion of materials used for neural electrodes.
A blister test apparatus has been developed, which allows a quantitative adhesion analysis of thin-film metallizations on polymers manufactured in cleanroom conditions suitable for micromachining of neural electrode arrays. The device is capable of pressurizing metallic membranes at wafer level, monitoring the pressure and the height of the developing blister while detecting the moment of delamination, allowing the calculation of the adhesion energy between metal film and polymer. The machine is designed for quantitative long-term studies of materials used in neural microelectrode arrays. PMID:22254960
Ordonez, Juan; Boehler, Christian; Schuettler, Martin; Stieglitz, Thomas
Plasma meniscus and extraction electrode studies of the ISIS H- ion source
In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H- ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.
Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Gabor, C.; Pozimski, J. K.
Plasma meniscus and extraction electrode studies of the ISIS H- ion source.
In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H(-) ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam. PMID:20192377
Lawrie, S R; Faircloth, D C; Letchford, A P; Gabor, C; Pozimski, J K
Plasma meniscus and extraction electrode studies of the ISIS H{sup -} ion source
In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H{sup -} ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.
Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Gabor, C. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Pozimski, J. K. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Department of Physics, Imperial College of Science and Technology, London SW7 2AZ (United Kingdom)
Computational study of the pressure-driven flow in a four-electrode rectangular micro-electrochemical accelerometer with an infinite aspect ratio
Numerical simulation is done on the pressure-driven flow in a four-electrode rectangular micro-electrochemical accelerometer with an infinite aspect ratio. The pressure gradient is proportional to the applied acceleration. Two kinds of electrode arrangements along the channel, the anode¢cathode¢cathode¢anode (ACCA) and the cathode¢anode¢anode¢cathode (CAAC) layouts, are studied. With the imposed electric potential difference between the electrodes, the electrode reaction, I3?+2e??3I?, occurs
Zhanyu Sun; Vadim M. Agafonov
A study on characteristic and reliability of fabricated microfluidic three electrodes sensor based on randle-sevcik equation
A simple fabrication method on wet etching and thermal evaporator had been used to fabricate microfluidic three gold (Au) electrodes assembled with polydimethylsiloxane (PDMS) was reported in the present work. In this work, we studied the suitable size of electrode area that can fulfill the Randle-Sevcik equation for reversible redox process. The voltammograms of 0.01 M K3Fe(CN)6 in 0.1M KCl
I. H. Hamzah; Asrulnizam Abd Manaf; O. Sidek
Studies on electrochemical oxidation of non-aqueous electrolyte on the LiCoO 2 thin film electrode
In this study, we demonstrated an in situ FTIR measurement for an electrochemical oxidation of propylene carbonate with 1.0 mol dm?3 LiClO4 on LiCoO2 cathode active material used in rechargeable lithium batteries. A thin film electrode of LiCoO2 was prepared by an r.f. sputtering method. The prepared LiCoO2 film had high quality as an electrode for the in situ FTIR
Kiyoshi Kanamura; Shigetaka Toriyama; Soshi Shiraishi; Masahiro Ohashi; Zen-ichiro Takehara
Studies on a non-thermal pulsed corona plasma between two parallel-plate electrodes in water
A non-thermal plasma generated between two parallel-plate electrodes submerged in water was studied in this work. The surface of one of the stainless-steel electrodes (the cathode) was coated with a ceramic layer of Al2O3. This reactor cell was connected to a water cycle and the discharge was carried out in a closed loop and therefore an equilibrium was established during
M M Sein; Z Bin Nasir; U Telgheder; T C Schmidt
a Finite Element Study of Diffusion-Induced Mechanics in Li-Ion Battery Electrode Materials
In this paper, a Finite Element (FE) framework for studying diffusion induced mechanics of Li-ion battery electrode materials is presented. In a previous study [Vanimisetti and Ramakrishnan (2011), Proc. IMechE, Part C: J. Mech. Eng. Sci. 0954406211432668], a set of analytical expressions for the stress distribution in ideal geometries, such as slab and cylindrical shaped particles, were derived using thermal stress analogy while solutions for spherical particles already exist. However, the limitations of the analytical study in handling complex geometries, the material behavior and the functional parameters necessitated the development of an FE model based approach. A multi-physics model was developed in COMSOL« package linking diffusion phenomenon to stress development. The model was verified comparing the results with those of the earlier analytical studies. As an illustration, we use the model to make inferences with regard to the effect of electrode particle shape. Along similar lines, the diffusion-induced mechanics in silicon rod structures grown on copper current collector is also demonstrated.
Vanimisetti, Sampath K.; Ramakrishnan, N.
A locked, non-rotating, completely embedded, moveable electrode for chronic brain stimulation studies in freely moving, fighting rats.
A light-weight, yet rugged moveable electrode assembly is described for chronic brain stimulation studies in small-brained animals. The assembly can be completely embedded in a smooth, unobtrusive dental cement cap and is therefore suitable for use in fighting experiments, where collisions with partners and cage walls will limit the use of other assemblies. It permits a variable electrode distance penetration of 3 mm in 75 mu-steps by using a separate unlocking turning-key. This design excludes the possibility of inadvertent displacement of the electrode tips by the animal itself. Since the electrode itself does not rotate during displacement, extra damage arising from possible eccentricity is avoided. The assembly has been used in a number of hypothalamic penetrations, demonstrating its usefulness and reliability. PMID:6685324
van der Poel, A M; van der Hoef, H; Meelis, W; Vletter, G; Mos, J; Kruk, M R
Chalk Point Steam Electric Station Studies Patuxent Estuary Studies: Ichthyoplankton Population Studies, 1979.
Two years of riverwide ichthyoplankton data were collected as a part of a series of studies at the Chalk Point Steam Electric Station (SES) to contribute data necessary to evaluate information to be presented in the 316 variance demonstration document sch...
J. A. Mihursky K. V. Wood S. Kerig E. M. Setzler-Hamilton
Design and study of the characteristics of a three electrode experimental ionization chamber for gamma ray dosimetry of spent fuel
The ( I, V) characteristics of two and three electrode ionization chamber filled with argon gas have been studied. To determine the sensitivity and the response with increase in exposure rate, the chamber was tested with a 60Co commercial irradiator. The response is linear up to more than 1.5 krad/h. The experimentally measured sensitivity of the chamber is 1.849ū10 -13 A/cm 3 per rad/h when the argon gas pressure in the chamber is 1.24 GPa (180 psi). The effect of transparency of the intermediate electrod on the saturation current due to 137Cs gamma-rays has also been studied. The experimental results show that the electrode with holes of small diameter acts as a better intermediate electrode as compared to the electrodes without holes or with holes of a larger diameter. The chamber has also been teste with fission product gamma-rays from spent fuel elements of a typical pool type research reactor. The results indicate that the presence of an intermediate electrode lowers the operating voltage by 50% and reduces the slope in the plateau region.
Ahmad, N.; Mirza, Nasir M.; Mirza, Sikander M.; Rashid, T.; Tufail, M.; Khan, Liaquat A.
Electrochemical and in situ spectroelectrochemical studies on the gold nanoparticles co-deposited with cobalt hexacyanoferrate modified electrode and its application in sensor.
Gold nanoparticles (Aunano) co-deposited with cobalt hexacyanoferrate (CoHCF) modified electrode was prepared by electrodeposition on glassy carbon electrode (represented as GC/Aunano-CoHCF) and characterized. The surface morphology of the modified electrode was studied by AFM and the electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The co-deposition of Aunano with CoHCF improved the electrochemical behavior of the Aunano-CoHCF modified electrode when compared to CoHCF modified electrode. The in-situ spectroelectrochemical changes of Aunano-CoHCF modified electrode was studied to understand the redox switching of CoHCF in the presence of Aunano. The in-situ spectral study showed that the co-deposited Aunano with CoHCF acted as nanoelectrode and improved the electron transfer and redox switching processes when compared to CoHCF modified electrode. An enhanced electrocatalytic oxidation of hydrogen peroxide (H2O2) was observed at the GC/Aunano-CoHCF electrode with an onset potential of 0.5 V when compared to GC/CoHCF electrode. The poly Au electrode did not show a similar oxidation peak for H2O2 oxidation. The Aunano co-deposited with CoHCF (GC/Aunano-CoHCF) significantly enhanced the electrocatalytic property of CoHCF. The amperometric detection of H2O2 was studied at the CoHCF modified electrode in the presence and absence of Aunano and poly Au electrode. The GC/Aunano-CoHCF electrode showed fast sensing response and lower detection limit for H2O2 when compared to GC/CoHCF and poly Au electrode. The electrochemical, in situ spectroelectrochemical and electrocatalytic properties of Aunano co-deposited with CoHCF clearly showed that the GC/Aunano-CoHCF electrode could be used as an electrochemical sensor. PMID:19437975
Thangavel, Subramani; Ramaraj, Ramasamy
Virtual electrode effects in defibrillation
This modeling study demonstrates that a re-entrant activity in a sheet of myocardium can be extinguished by a defibrillation shock delivered via extracellular point-source electrodes which establish spatially non-uniform applied field. The tissue is represented as a homogeneous bidomain with unequal anisotropy ratios in the cardiac conductivities. Spiral wave re-entry is initiated in the bidomain sheet following an S1¢S2 stimulation
Natalia Trayanova; Kirill Skouibine; Peter Moore
Application of drug selective electrode in the drug release study of pH-responsive microgels.
The colloidal phenomenon of soft particles is becoming an important field of research due to the growing interest in using polymeric system in drug delivery. Previous studies have focused on techniques that require intermediate process step such as dialysis or centrifugation, which introduces additional errors in obtaining the diffusion kinetic data. In this study, a drug selective electrode was used to directly measure the concentration of procaine hydrochloride (PrHy) released from methacrylic acid-ethyl acrylate (MAA-EA) microgel, thereby eliminating the intermediate process step. PrHy selective membrane constructed using a modified poly (vinyl chloride) (PVC) membrane and poly (ethylene-co-vinyl acetate-co-carbon monoxide) as plasticizer exhibited excellent reproducibility and stability. The response was reproducible at pH of between 3 to 8.5 and the selectivity coefficients against various organic and inorganic cations were evaluated. Drug release was conducted using the drug electrode under different pHs and the release rate increased with pH. The release behavior of the system under different pH exhibited obvious gradient release characteristics. PMID:17250922
Tan, Jeremy P K; Tam, Kam C
Study of electrode slice forming of bicycle dynamo hub power connector
Taiwan's bicycle industry has been an international reputation as bicycle kingdom, but the problem in the world makes global warming green energy rise, the development of electrode slice of hub dynamo and power output connector to bring new hope to bike industry. In this study connector power output to gather public opinion related to patent, basis of collected documents as basis for design, structural components in least drawn to power output with simple connector. Power output of this study objectives connector hope at least cost, structure strongest, highest efficiency in output performance characteristics such as use of computer-aided drawing software Solid works to establish power output connector parts of 3D model, the overall portfolio should be considered part types including assembly ideas, weather resistance, water resistance, corrosion resistance to vibration and power flow stability. Moreover the 3D model import computer-aided finite element analysis software simulation of expected the power output of the connector parts manufacturing process. A series of simulation analyses, in which the variables relied on first stage and second stage forming, were run to examine the effective stress, effective strain, press speed, and die radial load distribution when forming electrode slice of bicycle dynamo hub.
Chen, Dyi-Cheng; Jao, Chih-Hsuan
Ab initio study of solvent effects on electrical transport of molecular bridge between electrodes
The electrical conductance of benzene dithiolate (BDT) between gold electrodes has been actively investigated to realize single molecular devices. However, almost all of previous theoretical studies for the electrical conductance of BDT were done assuming 0K and vacuum in spite that many measurements have been performed at room temperature in solution [1,2]. In this study, we have investigated the electrical transport of BDT molecule between gold electrodes in water solution using ab initio nonequilibrium Green's function method and Car-Parrinello molecular dynamics at room temperature. The calculated time-averaged conductance of the BDT in water solution, 0.190 G0, is clearly different from the value calculated without water, 0.201 G0. Detailed analysis shows that this difference can be attributed to the effect of dipole moments of water molecules on the potential profile of the BDT molecule. [1] X. Xiao et al., Nano Lett. 4, 267 (2004). [2] M. Kiguchi et al., Appl. Phys. Lett. 89, 213104 (2006).
Tawara, Arihiro; Tada, Tomofumi; Watanabe, Satoshi
Kinetic study of the formation of oxygen vacancy on lanthanum manganite electrodes
Strontium doped lanthanum manganite (LSM) has been considered one of the most promising cathode materials for solid oxide fuel cells (SOFC). The electrochemical reduction of oxygen on lanthanum manganite (LSM) electrodes has been investigated by cyclic voltammetry, alternating current (ac) impedance, and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of oxygen vacancy, which is shown to be the main cause for the reversed hysteresis in cyclic voltammograms and for the increase in the electrochemical activity of oxygen reduction on the cathodically polarized LSM electrode observed in both ac impedance and in potential step experiments. The potential step experiments show that the oxygen vacancy concentration increases exponentially with time when the LSM is under a cathodic polarization. In the present study, the rate controlling step for the formation of oxygen vacancies is the oxygen vacancy generation step. The cathodic current rising from the reaction on oxygen vacancies can make a significant contribution to the total reduction current.
Jiang, Y.; Wang, S.; Zhang, Y.; Yan, J.; Li, W. [Chinese Academy of Sciences, Dalian (China). Dalian Inst. of Chemical Physics
Fundamental studies of water oxidation at model hematite electrodes prepared by atomic layer deposition
An increasing global demand for energy, combined with an awareness of anthropogenic climate change, has recently fueled the search for abundant, carbon neutral energy sources. The sun offers an enormous amount of energy that is practically inexhaustible and well distributed across Earth. Thus, it is an ideal source for meeting our future energy needs in a carbon neutral fashion. This work focuses on using hematite and sunlight to oxidize water, which is the rate limiting step of splitting water into the energy dense fuel, hydrogen, and the byproduct, oxygen. Hematite is abundant, absorbs a large fraction of the solar spectrum and has an appropriately placed valence band for water oxidation. However, the often cited poor bulk properties, and slow charge transfer kinetics require large applied potentials to oxidize water. Atomic layer deposition (ALD) was utilized to deposit uniform thin films of hematite on transparent conductive substrates as model electrodes to better understand the nature of the limitations in the bulk and at the surface. Comparison of the oxidation of water to the oxidation of fast redox shuttles allowed for the separation of bulk and surface processes. A combination of electrochemical impedance spectroscopy, photoelectrochemical and electrochemical measurements were employed to determine the cause of the large required applied potential. It was found that photogenerated holes initially oxidize the electrode surface under water oxidation conditions, which is attributed to the first step in water oxidation. A critical number of these surface intermediates need to be generated in order for subsequent hole-transfer steps to proceed. At low applied potentials, these intermediates are subject to recombination from the large concentration of electrons in the conduction band due to low band bending. At higher applied potentials, high band bending eliminates surface recombination and the charge collection efficiency of the electrolyte reaches unity. A water oxidation mechanism is proposed to interpret these results. In addition, fundamental studies of hematite electrodes coated with the phosphate mediated cobalt oxide catalyst were performed. The catalyst was found to reduce the surface recombination mentioned above. However, oxidized cobalt oxide was still subject to electron recombination at low applied potentials. This recombination was reduced with the use of an alumina blocking layer, which resulted in a modified hematite electrode capable of oxidizing water with a near unity charge collection efficiency at low applied potentials.
Klahr, Benjamin M.
Critical sampling points methodology: case studies of geographically diverse watersheds.
Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations. For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania, Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide. PMID:16957843
Strobl, Robert O; Robillard, Paul D; Debels, Patrick
Surface roughness analysis and magnetic property studies of nickel thin films electrodeposited onto rotating disc electrodes
Ni films were electrodeposited onto polycrystalline gold substrates mounted on a rotating disc electrode. The effects of rotation speed, film thickness and current density on the kinetic roughening and magnetic properties of the films were investigated. The film surface roughness was imaged using an atomic force microscope (AFM). The results indicate that the film roughness increases as the film thickness or deposition current density increases. We found that the electrodeposited Ni films exhibit anomalous scaling since both local and large-scale roughnesses show a power-law dependence on the film thickness. The effect of electrode rotation speed on the film surface roughness was also investigated. Scanning electron microscopy studies (SEM) had a good agreement with the AFM results. The average crystalline size of the film surfaces is also calculated from X-ray line broadening using (220) peak and Debye-Scherrer formula. The obtained results agree with that of AFM and SEM. The Ni thin films which are grown at different deposition current densities and rotation speeds exhibit in-plane magnetization with coercivities less than 110 Oe.
Hedayati, K.; Nabiyouni, G.
MoS2 Field Effect Transistors with different polarity: study of electrode work functions
The transfer characteristics of Molybdenum disulfide (MoS2) field effect transistors (FETs) depend on the Schottky barrier formed between the metal electrode and the semiconducting MoS2. We obtained p-type behavior for Pd-contacted MoS2 FETs and n-type with both Au and Nb [1] contacts. We study the work function of these electrode metals to understand their effect on the Schottky barrier and therefore the polarity of the MoS2 FETs. The work function of the above metals is measured using a non-contact Kelvin Probe technique under different ambient conditions. We will discuss the observed n-type and p-type behavior of MoS2 FETs in relation to the measured metal work functions.[4pt] [1] M. Fontana, T. Deppe, A. Boyd, M. Rinzan, A. Liu, M. Paranjape, P. Barbara, Photovoltaic effect in gated MoS2 Schottky junctions, in, arXiv:1206.6125v1 [cond-mat.mtrl-sci
Dube, Isha; Boyd, Anthony K.; Fontana, Marcio; Gayduchenko, Igor; Fedorov, Georgy; Liu, Amy; Paranjape, Makarand; Barbara, Paola
Space Shuttle Earth Observation sensors pointing and stabilization requirements study
The shuttle orbiter inertial measurement unit (IMU), located in the orbiter cabin, is used to supply inertial attitude reference signals; and, in conjunction with the onboard navigation system, can provide a pointing capability of the navigation base accurate to within plus or minus 0.5 deg for earth viewing missions. This pointing accuracy can degrade to approximately plus or minus 2.0 deg for payloads located in the aft bay due to structural flexure of the shuttle vehicle, payload structural and mounting misalignments, and calibration errors with respect to the navigation base. Drawbacks to obtaining pointing accuracy by using the orbiter RCS jets are discussed. Supplemental electromechanical pointing systems are developed to provide independent pointing for individual sensors, or sensor groupings. The missions considered and the sensors required for these missions and the parameters of each sensor are described. Assumptions made to derive pointing and stabilization requirements are delineated.
Turbulent mixing and deposition studies for single point aerosol sampling
A generic mixing system has been developed which creates suitable conditions for single point stack sampling of effluent air emission points. Results show that the system performance is well within the EPA mixing criteria---the COVs for velocity, tracer gas concentration and 10 mum AD aerosol particles are less than half of the EPA permissible level of 20%. Experiments were conducted to characterize the degree of mixing at downstream locations as affected by several types of flow disturbances, including 90░ elbows and commercial static mixing devices. It was found that the mixing is impacted by the upstream flow turbulence and that the use of static mixing elements can greatly enhance the mixing process. A stack system has been characterized which creates conditions suitable for single point representative sampling. The stack system could be used in both existing and new stack or duct configurations. It could also be used as an aerosol wind tunnel for testing various sampling devices. Results show that the system performance is well within the EPA permissible limits. A mixing model has been developed which can predict mixing of tracer gas in turbulent air flows in piping systems comprised of a series of 90░ elbows. The model uses the concept of an equivalent length of straight pipe that would produce the same degree of mixing as the mixing element under consideration. There is good agreement between experimental and predicted results. Aerosol penetration through flow splitters was experimentally and numerically investigated. A surface plot was generated from the experimental data to predict aerosol penetration as a function of the Stokes number and the bifurcation angle between the two outlets of the splitters. The developed correlation is valid in the ranges of 0.034 ? Stk ? 1.248; 2,556 ? Re ? 13,630; and, 30░ ? theta ? 180░, and should be a useful sub-model for predicting aerosol particle losses in flow splitters in software programs, e.g., DEPOSITION. Numerical studies were conducted with a commercial computational fluid dynamics (CFD) software, FLUENT, and a Lagrangian particle tracking code. Good agreement was found between the experimental and numerical results.
Gupta, Rajiv
The self-discharge of the NiOOH/Ni(OH)2 electrode constant potential study
Hydrogen oxidation currents at a NiOOH/Ni(OH)2 electrode were measured directly at constant potentials for various hydrogen pressures and states of charge. It was found that the hydrogen oxidation current is linearly proportional to the hydrogen pressure at all electrode potentials and that the logarithm of the anodic current is a linear function of electrode potential. It was also found that hydrogen oxidation on the nickel substrate material was strongly inhibited by the presence of nickel hydroxide on the substrate surface. By comparing the currents for hydrogen oxidation and oxygen evolution on the NiOOH/Ni(OH)2 electrode and a nickel substrate, it is suggested that the self-discharge of the NiOOH/Ni(OH)2 electrode is mainly due to electrochemical oxidation of hydrogen on the active electrode material.
Mao, Z.; White, R. E.
Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries
Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous oxidation of Fe{sup 2+} and Mn{sup 2+} in a small range of compositions. Black-Right-Pointing-Pointer Surface analysis from XPS allows reveals slight differences at the surface of the electrode with respect to the bulk.
Perea, A. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Castro, L. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Aldon, L., E-mail: firstname.lastname@example.com [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Stievano, L. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Dedryvere, R.; Gonbeau, D. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Tran, N.; Nuspl, G. [Sued-Chemie AG, Ostenriederstr. 15, D-85368 Moosburg (Germany); Breger, J.; Tessier, C. [SAFT, 111-113 bd. Alfred Daney, 33074 Bordeaux, Cedex (France)
Electrochemical ascorbic acid\\/hydroquinone detection on graphene electrode and the electro-active site study
In this article, graphite oxide (GO) and graphene have been prepared by chemical method and applied to modify electrodes in electrochemical detection of hydroquinone and ascorbic acid (AA). It is confirmed that the as-prepared GO- and graphene-modified electrodes own good electro-sensitivity for detecting hydroquinone and AA by cyclic voltammogram measurements. The detection limit of hydroquinone on graphene electrode was 3.8?ū?10?mol?L
Lili Feng; Guo Gao; Chunlei Zhang; Jiebing Ma; Daxiang Cui
In situ STM studies of Sb(111) electrodes in aqueous electrolyte solutions
The in situ STM studies of Sb(111), which was cleaved at the temperature of liquid nitrogen inside the glove box, and of Sb(111), which was electrochemically polished in the KI + HCl aqueous solution, have been performed under negative polarizations from - 0.8 to - 0.15 V (versus Ag|AgCl in sat. KCl aqueous solution) in the 0.5 M Na2SO4 + 0.0003 M H2SO4 aqueous solution. The atomic resolution has been achieved. The in situ STM data show that there are no quick surface reconstruction processes and the surface structure of cleaved and electrochemically polished Sb(111) is stable within the potential region investigated, similarly for Bi(111) single crystal electrode, previously studied [S. Kallip, E. Lust, Electrochem. Comm. 7 (2005) 863].
Grozovski, V.; Kallip, S.; Lust, E.
AMTEC system performance studies using the detailed electrode kinetic and transport model
A detailed electrochemical model of the alkali metal thermoelectric converter (AMTEC) electrode and current collector grid has been developed recently. Comparative evaluations of the resulting differences in model predictions reveal that the new detailed model predicts up to 50 percent higher electrode power densities at condenser operating temperatures above 600 K. The new model, with experimentally determined parameters, was used to recalculate the projected system performance of previously reported 1- and 100-kWe AMTEC space power systems that had incorporated earlier electrolyte/electrode models. It was found that when the detailed model was used to determine the electrode power densities, enhanced specific power and efficiencies are predicted.
Sievers, Robert K.; Williams, Roger M.; Underwood, Mark L.; Jeffries-Nakamura, Barbara; Bankston, C. P.
Preparation of polymer-modified electrodes: A literature and experimental study
A literature review is presented on the field of polymer modified electrodes which can be electrochemically generated. It is suggested that a possible application of these polymer modified electrodes is as a regeneratable catalysis packing material for use in couter-current exchange columns. Secondly, there is a presentation of experimental results dealing with possible electrode modification using difluoro- and dimethyl- phenols and fluorinated derivatives of styrene, benzoquinone and hydroquinone. It appears that dimethylphenol shows the most potential of the monomers experimentally tested in providing a stable polymer modified electrode surface. 170 refs., 31 figs., 1 tab.
Jayanta, P.S.; Ishida, Takanobu.
Comparative study of maximum power point tracking algorithms
Maximum power point trackers (MPPTs) play an important role in photovoltaic (PV) power systems because they maximize the power output from a PV system for a given set of conditions, and therefore maximize the array efficiency. Thus, an MPPT can minimize the overall system cost. MPPTs find and maintain operation at the maxi- mum power point, using an MPPTalgorithm. Many
D. P. Hohm; M. E. Ropp
Numerical study of a novel dew point evaporative cooling system
Dew point evaporative cooling system is an alternative to vapor compression air conditioning system for sensible cooling of ventilation air. This paper presents the theoretical performance of a novel dew point evaporative cooling system operating under various inlet air conditions (covering dry, moderate and humid climate) and influence of major operating parameters (namely, velocity, system dimension and the ratio of
B. Riangvilaikul; S. Kumar
A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells
This study describes a systematic approach of TiO2/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO2 and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO2 to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized.
The Leidenfrost point: Experimental study and assessment of existing models
Recent demands for superior material properties and more efficient use of materials and production time are forcing manufacturers to develop intelligent processing techniques for enhanced process control in order to better dictate the end product. In the heat treatment and processing of metallic alloys, the desire to obtain parts of enhanced and uniform mechanical properties is requiring increased control over heat removal rates and enhanced temperature control. In particular, spray quenching has been shown to be an effective means to control and enhance the cooling rates of heat treatable aluminum alloys. This study presents a detailed and thorough parametric study of the Leidenfrost point (LFP), which serves as the temperature boundary between the transition and film boiling regimes. Sessile drop evaporation experiments were conducted with acetone, benzene, FC-72, and water on heated aluminum surfaces with either polished, particle blasted, or rough sanded finishes to observe the influential effects of fluid properties, surface roughness, and surface contamination on the LFP. A weak relationship between surface energies and the LFP was observed by performing droplet evaporation experiments with water on polished copper, nickel, and silver surfaces. Additional parameters which were investigated and found to have negligible influence on the LFP included liquid subcooling, liquid degassing, surface roughness on the polished level, and the presence of polishing paste residues. The accumulated LFP data of this study were used to assess several existing models which attempt to identify the mechanisms which govern the LFP. The disagreement between the experimental LFP values and those predicted by the various models suggests that an accurate and robust theoretical model which effectively captures the LFP mechanisms is currently unavailable.
Bernardin, J.D.; Mudawar, I.
Vanadium pentoxide thin films used as positive electrode in lithium microbatteries: An XPS study during cycling
Vanadium pentoxide thin films, usable as positive electrode in microbatteries, have been prepared by radio frequency magnetron sputtering in a pure argon or mixed argon/oxygen atmosphere using a V2O5 target. Depending on the oxygen partial pressure in the discharge gas, we have obtained either crystallized or amorphous thin films, with different morphologies. These two kinds of thin films having different electrochemical behavior, an extensive XPS study was carried out. The main redox processes and their reversibility occurring during the 1st, 10th, and 30th discharge charge cycles were discussed in relation with the electrochemical properties. Our results have revealed a good reversibility of the redox process for amorphous thin films and degradation for crystallized ones, in agreement with the discharge capacity evolution. Furthermore, the growth of a surface layer between the cathode and the liquid electrolyte was evidenced upon the discharge as well as its partial dissolution upon the charge.
Benayad, A.; Martinez, H.; Gies, A.; Pecquenard, B.; Levasseur, A.; Gonbeau, D.
Experimental and theoretical studies of the electrode impedance effect in capacitive discharges
It is widely acknowledged that one can observe a strong harmonics content in the current of an asymmetric capacitive discharge, even in case of a strongly sinusoidal driving voltage. This particular phenomenon is directly connected to the heating of electrons.footnotetextT. Mussenbrock et al., Phys. Rev. Lett 101, 085004 (2008). It has been shown by means of careful measurements that the increase of certain harmonics indicates an increase of the electron density.footnotetextY. Yamazawa et al., Jpn. J. Appl. Phys. 46, 7453 (2007). In this paper we revisit these experiments. We also propose a model to study the possibility of controlling the excitation of current harmonics using an external circuit and its effect on the electron density (which is often referred to as the electrode impedance effect).
Ziegler, Dennis; Mussenbrock, Thomas; Brinkmann, Ralf Peter; Yamazawa, Yohei
Mechanistic study of photoelectrochemical reactions at a p-gap electrode
The photocurrent-potential relations of a p-GaP electrode in various solutions are studied potentiostatically. Both the cathodic and anodic photocurrents are observed, i.e., the sign of photocurrent changes at a certain potential which we name the potential of zero photocurrent, V/sub zp/. The potential of zero photocurrent is close but not equal to the flatband potential. The origin of the anodic photocurrent is presented. The log (photocurrent)-potential relations follow the Tafel line at medium bias potentials and deviate from it at large and small bias potentials. The mechanism of the cathodic reactions is proposed based on the experimental results. The rate-determining step is the supply of photoexcited electrons to the semiconductor surface at large bias potentials and is the electrochemical, i.e., surface, process at medium and small bias potentials. 34 refs.
Uosaki, K.; Kita, H.
Studies of localized corrosion in welded aluminum alloys by the scanning reference electrode technique
Localized corrosion in welded samples of 2219-T87 Al alloy (2319 filler), 2090 Al-Li alloy (4043 and 2319 fillers), and 2195 Al-Li alloy (4043 and 2319 fillers) has been investigated using the relatively new scanning reference electrode technique. The weld beads are cathodic in all cases, leading to reduced anode/cathode ratios. A reduction in anode/cathode ratio leads to an increase in the corrosion rates of the welded metals, in agreement with results obtained in previous electrochemical and stress corrosion studies involving the overall corrosion rates of welded samples. The cathodic weld beads are bordered on both sides by strong anodic regions, with high propensity for corrosion.
Danford, M. D.; Nunes, A. C.
Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study
There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.
Chen, Jia; Selloni, Annabella
Study of GEM-like detectors with resistive electrodes for RICH applications
We have developed prototypes of GEM-like detectors with resistive electrodes to be used as RICH photodetectors equipped with CsI photocathodes. The main advantages of these detectors are their intrinsic spark-protection and possibility to operate at high gain (ś10 5) in many gases including poorly quenched ones, allowing for the adoption of windowless configurations in which the radiator gas is also used in the chamber. Results of systematic studies of the resistive GEMs combined with CsI photocathodes are presented: their quantum efficiency, rate characteristics, long-term stability, etc. On the basis of the obtained results, we believe that the new detector will be a promising candidate for upgrading the ALICE RICH detector.
Ag¾cs, A. G.; Di Mauro, A.; Ben David, A.; Clark, B.; Martinengo, P.; Nappi, E.; Peskov, V.
Rotating ring¢disk electrode studies of the oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond electrodes
The stepwise electrochemical oxidation of p-methoxyphenol and hydroquinone at boron-doped diamond (BDD) electrodes was investigated in perchloric acid media using rotating ring¢disk electrode (RRDE) and hydrodynamic modulation techniques. Initial oxidation of these compounds to p-benzoquinone at the disk may be confirmed by reduction of the quinone at the ring electrode. Further oxidation, ultimately to CO2, can be followed by the
David Sopchak; Barry Miller; Yitzhak Avyigal; Rafi Kalish
A newly developed perfused umbrella electrode for radiofrequency ablation: an ex vivo evaluation study in bovine liver.
The purpose of this study was to evaluate the effectiveness of a newly developed perfused monopolar radiofrequency (RF) probe with an umbrella-shaped array. A perfused umbrella-shaped monopolar RF probe based on a LeVeen electrode (Boston Scientific Corp., Natick, MA, USA) with a 3-cm array diameter was developed. Five different configurations of this electrode were tested: (a) perfusion channel/endhole, (b) perfusion channel/endhole + sideholes, (c) 1 cm insulation removed at the tip, (d) 1 cm insulation removed at the tip + perfusion channel/endhole, and (e) 1 cm insulation removed at the tip + perfusion channel/endhole + sideholes. An unmodified LeVeen electrode served as a reference standard. RF ablations were performed in freshly excised bovine liver using a commercial monopolar RF system with a 200-W generator (RF 3000; Boston Scientific Corp.). Each electrode was tested 10 times applying the vendor's recommended ablation protocol combined with the preinjection of 2 ml 0.9% saline. Volumes and shapes of the lesions were compared. Lesions generated with the original LeVeen electrode showed a mean volume of 12.74 +/- 0.52 cm(3). Removing parts of the insulation led to larger coagulation volumes (22.65 +/- 2.12 cm(3)). Depending on the configuration, saline preinjection resulted in a further increase in coagulation volume (25.22 +/- 3.37 to 31.28 +/- 2.32 cm(3)). Besides lesion volume, the shape of the ablation zone was influenced by the configuration of the electrode used. We conclude that saline preinjection in combination with increasing the active tip length of the umbrella-shaped LeVeen RF probe allows the reliable ablation of larger volumes in comparison to the originally configured electrode. PMID:17647060
Bruners, Philipp; Pfeffer, Jochen; Kazim, Rana M; G³nther, Rolf W; Schmitz-Rode, Thomas; Mahnken, Andreas H
A Newly Developed Perfused Umbrella Electrode for Radiofrequency Ablation: An Ex Vivo Evaluation Study in Bovine Liver
The purpose of this study was to evaluate the effectiveness of a newly developed perfused monopolar radiofrequency (RF) probe with an umbrella-shaped array. A perfused umbrella-shaped monopolar RF probe based on a LeVeen electrode (Boston Scientific Corp., Natick, MA, USA) with a 3-cm array diameter was developed. Five different configurations of this electrode were tested: (a) perfusion channel/endhole, (b) perfusion channel/endhole + sideholes, (c) 1 cm insulation removed at the tip, (d) 1 cm insulation removed at the tip + perfusion channel/endhole, and (e) 1 cm insulation removed at the tip + perfusion channel/endhole + sideholes. An unmodified LeVeen electrode served as a reference standard. RF ablations were performed in freshly excised bovine liver using a commercial monopolar RF system with a 200-W generator (RF 3000; Boston Scientific Corp.). Each electrode was tested 10 times applying the vendor's recommended ablation protocol combined with the preinjection of 2 ml 0.9% saline. Volumes and shapes of the lesions were compared. Lesions generated with the original LeVeen electrode showed a mean volume of 12.74 {+-} 0.52 cm{sup 3}. Removing parts of the insulation led to larger coagulation volumes (22.65 {+-} 2.12 cm{sup 3}). Depending on the configuration, saline preinjection resulted in a further increase in coagulation volume (25.22 {+-} 3.37 to 31.28 {+-} 2.32 cm{sup 3}). Besides lesion volume, the shape of the ablation zone was influenced by the configuration of the electrode used. We conclude that saline preinjection in combination with increasing the active tip length of the umbrella-shaped LeVeen RF probe allows the reliable ablation of larger volumes in comparison to the originally configured electrode.
Bruners, Philipp, E-mail: email@example.com; Pfeffer, Jochen; Kazim, Rana M. [Helmholtz Institute for Biomedical Engineering, Applied Medical Engineering (Germany); Guenther, Rolf W. [RWTH Aachen University Hospital, Department of Diagnostic Radiology (Germany); Schmitz-Rode, Thomas; Mahnken, Andreas H. [Helmholtz Institute for Biomedical Engineering, Applied Medical Engineering (Germany)
Application of the flooded-agglomerate model to study oxygen reduction on thin porous coating rotating disk electrode
The study of the oxygen reduction reaction on dispersed platinum on carbon catalysts has been the object of several publications for over 20 years, because of the importance of these materials for application in various kinds of fuel cells. In this work, the thin-film/flooded-agglomerate model of gas diffusion electrodes was used to study the oxygen reduction reaction (ORR) on rotating disk electrodes with thin porous coating in alkaline solutions. Vulcan XC-72 carbon and 10, 20, and 30% w/w Pt/C catalysts were used as electrode materials. Fitting of the theoretical equations to the experimental data was employed to simulate the polarization characteristics of the ORR on the catalysts and to obtain the oxygen concentration profiles along the thickness of the flooded agglomerate as a function of the electrode potential and the structural parameters of the electrodes. The method was found to be a simple and adequate way to evaluate the performance of the supported catalysts. The predicted effect of doubling of the Tafel slope of the ORR due to diffusion of the reactant in the flooded agglomerate was confirmed experimentally. The kinetic parameters obtained for the ORR in alkaline media indicated that, for the lower Pt/C ratios, there is a strong participation of the carbon substrate in the catalysis of the reaction.
Perez, J.; Tanaka, A.A.; Gonzalez, E.R.; Ticianelli, E.A. (Sao Paulo Univ., Sao Carlos (Brazil). Inst. de Fisica e Quimica de Sao Carlos)
Electrode compositions
An electrode composition for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C.sub.8 -C.sub.15 alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5-4.5 volts.
Block, Jacob (Rockville, MD); Fan, Xiyun (Orange, TX)
An electrode composition is described for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C{sub 8}-C{sub 15} alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5--4.5 volts.
Block, J.; Fan, X.
Electrochemical impedance study of the polymerization of pyrrole on high surface area carbon electrodes.
Polymerization of pyrrole on a Vulcan XC-72 carbon black coated glassy carbon electrode was performed using potentiodynamic and galvanostatic regimes in an aqueous solution of 0.5 M pyrrole and 0.5 M NaClO(4). Responses of the electrodes prepared under different conditions were recorded using cyclic voltammetry and electrochemical impedance spectroscopy. It was found that voltammograms of electrodes prepared galvanostatically showed a reversible oxidation-reduction of the polypyrrole. The redox waves became less reversible, characterized by greater peak separations, when the electrodes were prepared potentiodynamically. These observations were investigated by electrochemical impedance spectroscopy, which revealed significant charge transfer resistances for the electrodes prepared potentiodynamically. The bulk resistances of the electrodes prepared by the two methods also differed, both in magnitude and their dependence on the polypyrrole loading and potential. These differences, in combination with scanning electron microscopy and voltammograms recorded during potentiodynamic polymerization, were used to elucidate differences in the structures of the polypyrrole-carbon black composites. The polymerization voltammograms showed a two-step nucleation on the carbon black coated electrodes rather than the one-step polymerization on a bare electrode. This was attributed to initial polymerization on the carbon particles followed by sustained polymerization on top of the carbon black layer. More uniform deposition of polypyrrole on the full area of the carbon particles was achieved by slow galvanostatic polymerization. PMID:20428553
Moghaddam, Reza B; Pickup, Peter G
Midland/Penetang Limiting Set-Point Thermostat Study.
This report was initiated to evaluate the validity of limiting set point thermostats as an economical means of conserving energy in low density public housing. The investigation was based on the following assumption: a certain proportion of public housing...
[Surface-enhanced raman spectroscopy study of vitamin B12 on copper electrode].
The vitamin B12 molecule has long fascinated chemists because of its exclusive complex structure and unusual reactivities in biological systems. In order to achieve a better understanding of the structural attribute of the Vitamin B12 molecule when it interacted with metal, in the present paper, the vitamin B12 molecules adsorbed on variation of copper electrode potential from 0 to -1.0 V was studied by surface-enhanced Raman spectroscopy (SERS). An excellent SERS substrate was obtained with insitu electrochemical oxidation-reduction cycle (ORC), and its surface roughness was characterized by atomic force microscope (AFM). Assignments of Raman peaks observed by normal Raman spectrum (NRS) and SERS spectra of vitamin B12 molecule were given based on previous literatures. It was found that the potential-dependent relative intensity changed in SERS spectra which depended on the vitamin B12 molecular orientation with respect to the copper surface according to the surface selection rule (SSR). It was concluded that the corrin ring was adsorbed in tilt form on copper surface and the Co-CN group was farther away from the copper surface at higher potentials. With the decrease in potential, the tilt angle between the corrin ring and copper surface became smaller, then the Co-N group and 5,6 dimethylbenzimidazole group got close to the copper surface. The results offered an important structural attribute of vitamin B12 molecule when it interacted with copper electrode for the first time, and supplied a meaningful reference for the electrochemical bioactivity of the vitamin B12 molecule. PMID:24369644
Wang, Bo; Chang, Da-hu; Lu, Gang; Wang, Tian-hu; Zhang, Zhen-long; Mo, Yu-jun
New Advances in the Study of the Proximal Point Algorithm
Consider in a real Hilbert space H the inexact, Halpern-type, proximal point algorithm xn+1 = ?nu+(1-?n)J?nxn+en, n = 0,1,..., (H-PPA) where u, x?H are given points, J?n = (I+?na) for a given maximal monotone operator A, and (en) is the error sequence, under new assumptions on ?n?(0,1) and ?n?(0,1). Several strong convergence results for the H-PPA are presented under the general condition that the error sequence converges strongly to zero, thus improving the classical Rockafellar's summability condition on (||en||) that has been extensively used so far for different versions of the proximal point algorithm. Our results extend and improve some recent ones. These results can be applied to approximate minimizers of convex functionals. Convergence rate estimates are established for a sequence approximating the minimum value of such a functional.
Moro?anu, Gheorghe
Photoelectrocatalytic study and scaling up of titanium dioxide electrodes for wastewater treatment.
Different TiO2 photoelectrodes have been characterized and tested for the photoelectrocatalytic oxidation of methanol. Particulate electrodes (TiO2/Ti and TiO2/ITO) have been shown to notably favour charge-carrier transfer at the electrolyte interface while a thermal electrode (Ti) has been shown to favour charge-carrier separation when applying an electric potential bias according to cyclic voltammetry technique, as a consequence of differences in TiO2 surface between particulate and thermal electrodes. Particulate electrodes lead to a higher photoelectrocatalytic activity for methanol oxidation compared to that of the thermal electrode, probably due to the pure-rutile TiO2 phase composition of the latter and its lower surface area. TiO2/Ti electrode has been shown to be the most effective photoelectrode tested for methanol oxidation since its activity was improved by the combination of the particulate TiO2 layer and the high electrical conductivity of the support. Generally, photocurrent density measured in the photoelectrochemical cell seems to correlate with activity, whereas this correlation is not observed when using a larger photoelectrocatalytic reactor. In contrast, the activity obtained for the scaled-up electrode is found to be similar in terms of surface kinetic constant to that obtained at laboratory scale. PMID:24037149
Pablos, C; van Grieken, R; Marugßn, J; Adßn, C; Osuna, M; Palma, J
Working Electrodes
In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].
Komorsky-Lovri?, Ŗebojka
Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode
DFT-B3LYP\\/6-31G (d, p) and HF\\/6-31G (d, p) calculations are performed for deoxidized norepinephrineat (NP(R)) and its oxidized form (NP(O)). The electrochemistry of norepinephrineat (NP) was studied by cyclic voltammetry (CV) at a pyrolytic graphite electrode modified by Nafion multi-walled carbon nanotubes (MWNTs) in phosphate buffers at pH 6.0, showing that the standard electrode potential of half reaction for NP(O), H+\\/NP(R)
Yuanzhi Song
A study on transmission characteristics and specific absorption rate using impedance-matched electrodes for various human body communication.
Human body communication (HBC) is a new communication technology that has presented potential applications in health care and elderly support systems in recent years. In this study, which is focused on a wearable transmitter and receiver for HBC in a body area network (BAN), we performed electromagnetic field analysis and simulation using the finite difference time domain (FDTD) method with various models of the human body. Further we redesigned a number of impedance-matched electrodes to allow transmission without stubs or transformers. The specific absorption rate (SAR) and transmission characteristics S21 of these electrode structures were compared for several models. PMID:24110079
Machida, Yuta; Yamamoto, Takahiko; Koshiji, Kohji
Laparoscopic implantation of neural electrodes on pelvic nerves: an experimental study on the obturator nerve in a chronic minipig model
BackgroundĀĀLaparoscopic exposure of pelvic nerves has opened a new area in the field of neuromodulation. However, electrode design and\\u000a material deterioration remain issues that limit clinical application. The objective of this study was to evaluate experimentally\\u000a the laparoscopic implantation of different types of neural electrodes in order to achieve functional and selective electrical\\u000a stimulation of pelvic nerves.\\u000a \\u000a \\u000a \\u000a \\u000a MethodsĀĀThis was a
Demetrio LarraĒn; Pierre Rabischong; Revaz Botchorishvili; Georges Fraisse; Stephane Gallego; Philippe Gaydier; Jean Michel Chardigny; Paul Avan
Two-point bend studies of glass fibers
The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of glasses, including glass composition, thermal history of melts and environmental conditions during the failure tests. Understanding how these conditions affect failure helps us understand how glass fails. In this dissertation, failure strains for many different silicate and borate glasses were measured under a variety of experimental conditions. Failure stresses for various silicate glasses were calculated using values of the nonlinear elastic moduli reported in the literature. Inert intrinsic strengths for alkali silicate glasses were related to the structure and corresponding bond strengths, and the dependence of the inert strengths on faceplate velocity is discussed. Inert failure strains were also obtained for sodium borate glasses. Up to ś40% failure strain was measured for vitreous B2O 3. The addition of soda to boron oxide increases the dimensionality and connectivity of the glass structure and hence increases its resistance to deformation, as was observed in elasticity and brittleness measurements reported in the literature. The increase in deformation resistance produces lower failure strains, a behavior also seen for alkali silicate and aluminosilicate glasses where the reduction of non-bridging oxygen increases the structure stiffness and leads to lower inert failure strain. Fatigue effects on silicate glasses were studied by measuring the failure strains in water at different temperatures and at different loading rates, and in air with a range of relative humidities. The dominant fatigue reaction for cross-linked network glasses is bond hydrolysis, whereas for alkali modified depolymerized glasses is ion-exchange reaction between alkali ions and water species. The fatigue mechanism difference results in the difference in the humidity sensitivity of the reaction rate. The dominant fatigue reaction also changes at around 50% relative humidity.
Tang, Zhongzhi
A study of carbon steel corrosion inhibition by phosphate ions and by an organic buffer using a scanning vibrating electrode
The scanning vibrating reference electrode technique (SVET) has been used to map anodic and cathodic currents in solutions over freely corroding type Cl020 carbon steel. All solutions contained millimolar concentrations of chloride and were sterilized. The effect of phosphate and an organic buffer on the corrosion of carbon steel in liquid media were studied because they were added to promote
A study of the electro-catalytic oxidation of methanol on a cobalt hydroxide modified glassy carbon electrode
Cobalt hydroxide modified glassy carbon electrodes (CHM\\/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of
M. Jafarian; M. G. Mahjani; H. Heli; F. Gobal; H. Khajehsharifi; M. H. Hamedi
An electrode array study of electrochemical inhomogeneity of zinc in zinc\\/steel couple during galvanic corrosion
The local electrochemical properties of anodic metal within a zinc\\/steel couple immersed in seawater was studied via an electrode array composed of zinc and mild steel wire sensors. It showed that the potential and current density distribution of zinc wires were inhomogeneous, and the main anodic area moved from the zinc wires adjacent to the steel wires and even further
Da-Lei Zhang; Wei Wang; Yan Li
Studies of LaSn{sub 3} as a negative electrode for lithium ion batteries.
The intermetallic compound LaSn{sub 3} has been explored as a possible negative electrode for lithium-ion batteries. A combination of experiment and density functional theory calculations provides evidence that the structure is intolerant to lithium insertion and that the electrochemical reaction occurs via a displacement mechanism. Experiment shows that approximately six Li react initially with LaSn{sub 3}; calculated energetics suggest that during the reaction La{sub 3}Sn{sub 5} and lithiated tin are formed and that the electrode operates by delithiation and relithiation of the Sn particles within an inert lanthanum-tin matrix. LaSn{sub 3} electrodes provide a reversible specific capacity of 200-250 mAh/g, whereas In-substituted electrodes that form a solid solution with LaSn{sub 3}, such as LaSn{sub 2.7}In{sub 0.3}, yield a slightly lower capacity.
Vaughey, J. T.; Thackeray, M. M.; Shin, D.; Wolverton, C.; Northwestern Univ.
Basic Study of Sorption of Organic Fuels During Oxidation at Electrodes.
The objective of this program was an improved understanding of the role of sorption processes at electrodes in the electrochemical oxidation of carbonaceous fuels with special emphasis on the development of novel experimental approaches to this end. Of th...
R. J. Flannery G. Aronowitz E. M. Banas M. J. Den Herder J. A. Donohue
Carbon Paste Electrodes Made from Different Carbonaceous Materials: Application in the Study of Antioxidants
This work describes the sensing properties of carbon paste electrodes (CPEs) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, l-ascorbic acid and l-glutathione have been analyzed and compared. It has been demonstrated that the electrodes based on carbon microspheres show the best performances in terms of kinetics and stability, whereas G-CPEs presented the smallest detection limit for all the antioxidants analyzed. An array of electrodes has been constructed using the three types of electrodes. As demonstrated by means of Principal Component Analysis, the system is able to discriminate among antioxidants as a function of their chemical structure and reactivity.
Apetrei, Constantin; Apetrei, Irina Mirela; De Saja, Jose Antonio; Rodriguez-Mendez, Maria Luz
Voltammetric and Potentiometric Study of Cysteine at Cobalt(II) Phthalocyanine Modified Carbon-paste Electrode
Cyclic voltammetry and potentiometry were used to investigate the electrochemical behavior of cysteine at a chemically modified electrode prepared by incorporating cobalt(II) phthalocyanine (Co(II)Pc) into carbon paste matrix. The modified electrode showed high electrocatalytic activity toward cysteine; the overpotential for the oxidation of cysteine was decreased by more than 100 mV, and the corresponding peak current increased significantly. The electrocatalytic
S. S. Khaloo; M. K. Amini; S. Tangestaninejad; S. Shahrokhian; R. Kia
Study of salt permeation process into Vigna angularis using Ag\\/AgCl electrodes
In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag\\/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag\\/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary
Satoshi Sasaki; Kazunori Yokota; Nobutaka Hanagata
A Raman spectroscopic and electrochemical study of the photoinduced crystallization of triethylenediamine triiodide upon a silver electrode
When a silver electrode, electrochemically coated with AgI, is immersed in an electrolyte containing NaI and the diprotonated form of 1,4-diazabicyclo 2.2.2 octane (abbreviated DABCO-H22+), and is bathed in 514.5 nm radiation from an argon ion laser through the objective of the microscope attachment of the DILOR Omars-89 Raman spectrophotometer, crystals form from the focal point. These are attributed to DABCO-h22+ 213-. Both spectroscopic and electrochemical experiments are described and interrelated. A mechanism for this photoinduced electrochemical crystal growth is presented.
Ozek, Toru; Irish, Donald E.
A Printed Superoxide Dismutase Coated Electrode for the Study of Macrophage Oxidative Burst
The miniaturization of electrochemical sensors allows for the minimally invasive and cost effective examination of cellular responses at a high efficacy rate. In this work, an ink-jet printed superoxide dismutase electrode was designed, characterized, and utilized as a novel microfluidic device to examine the metabolic response of a 2D layer of macrophage cells. Since superoxide production is one of the first indicators of oxidative burst, macrophage cells were exposed within the microfluidic device to phorbol myristate acetate (PMA), a known promoter of oxidative burst, and the production of superoxide was measured. A 46 ▒ 19% increase in current was measured over a 30 min time period demonstrating successful detection of sustained macrophage oxidative burst, which corresponds to an increase in the superoxide production rate by 9 ▒ 3 attomoles/cell/sec. Linear sweep voltammetry was utilized to show the selectivity of this sensor for superoxide over hydrogen peroxide. This novel controllable microfluidic system can be used to study the impact of multiple effectors from a large number of bacteria or other invaders along a 2D layer of macrophages, providing an in vitro platform for improved electrochemical studies of metabolic responses.
Hiatt, Leslie A.; McKenzie, Jennifer R.; Deravi, Leila F.; Harry, Reese S.; Wright, David W.; Cliffel, David E.
A semi-analytical study of positive corona discharge in wire-plane electrode configuration
Wire-to-plane positive corona discharge in air has been studied using an analytical model of two species (electrons and positive ions). The spatial distributions of electric field and charged species are obtained by integrating Gauss's law and the continuity equations of species along the Laplacian field lines. The experimental values of corona current intensity and applied voltage, together with Warburg's law, have been used to formulate the boundary condition for the electron density on the corona wire. To test the accuracy of the model, the approximate electric field distribution has been compared with the exact numerical solution obtained from a finite element analysis. A parametrical study of wire-to-plane corona discharge has then been undertaken using the approximate semi-analytical solutions. Thus, the spatial distributions of electric field and charged particles have been computed for different values of the gas pressure, wire radius and electrode separation. Also, the two dimensional distribution of ozone density has been obtained using a simplified plasma chemistry model. The approximate semi-analytical solutions can be evaluated in a negligible computational time, yet provide precise estimates of corona discharge variables.
Yanallah, K.; Pontiga, F.; Chen, J. H.
Liquid electrode
A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.
Ekechukwu, Amy A. (Augusta, GA)
Electrode catalyst
An electrode catalyst for a fuel cell comprising at least one boride of molybdenum is disclosed. The electrode catalyst is far more excellent than conventional catalysts such as platinum black in that the resistance to acids is very high, that the polarization is little, that the price is low, etc. It is particularly suitable as an electrode catalyst for a fuel cell employing an acidic electrolyte.
Kudo, T.; Obayashi, H.
NASA Office of Space Sciences and Applications study on Space Station attached payload pointing
A study has been conducted to determine the articulated-pointing requirements of a suite of instruments carried by the NASA Space Station, and define a pointing system architecture accomodating those requirements. It is found that these pointing requirements are sufficiently exacting, and the Space Station's disturbance environment sufficiently severe, to preclude the successful use of a conventional gimbal-pointing system; a gimbaled system incorporating an isolation stage is judged capable of furnishing the requisite levels of pointing performance.
Laskin, R. A.; Estus, J. M.; Lin, Y. H.; Spanos, J. T.; Satter, C. M.
Reference Electrodes
In most electrochemical measurements, it is necessary to keep one of the electrodes in an electrochemical cell at a constant potential. This so-called reference electrode allows control of the potential of a working electrode (e.g. in voltammetry) or the measurement of an indicator electrode (e.g. in potentiometry, see Chap. II.9). The standard hydrogen electrode plays the role of a basic reference element in electrochemical devices; however, in practice, it is difficult to handle. Therefore, secondary reference electrodes are preferred in most experiments. A secondary reference electrode must fulfil the following criteria: (i) it should be chemically and electrochemically reversible, i.e. its potential is governed by the Nernst equation and does not change in time; (ii) the potential must remain almost constant when a small current passes through the electrode and reverse to its original value after such small current flow (i.e. a non-polarisable electrode); and (iii) the thermal coefficient of potential should be small.
Kahlert, Heike
A new disposable electrode for electrochemical study of leukemia K562 cells and anticancer drug sensitivity test.
Developing cost-effective and simple analysis tools is of vital importance for practical applications in bioanalysis. In this work, a new disposable electrochemical cell sensor with low cost and simple fabrication was proposed to study the electrochemical behavior of leukemia K562 cells and the effect of anticancer drugs on cell viability. The analytical device was integrated by using ITO glass as the substrate of working electrodes and paper as the electrolytic cell. The cyclic voltammetry of the K562 cells at the disposable electrode exhibited an irreversible anodic peak and the peak current is proportional to the cell number. This anodic peak is attributed to the oxidation of guanine in cells involving two protons per transfer of two electrons. For the drug sensitivity tests, arsenic trioxide and cyclophosphamide were added to cell culture media. As a result, the electrochemical responses of the K562 cells decreased significantly. The cytotoxicity curves and results obtained corresponded well with the results of CCK-8 assays. In comparison to conventional methods, the proposed method is simple, rapid and inexpensive. More importantly, the developed sensor is supposed to be a single-use disposable device and electrodes were prepared "as new" for each experiment. We think that such disposable electrodes with these characteristics are suitable for experimental study with cancer cells or other types of pathogens for disease diagnosis, drug selection and on-site monitoring. PMID:24140828
Yu, Chunmei; Zhu, Zhenkun; Wang, Li; Wang, Qiuhong; Bao, Ning; Gu, Haiying
Electron transfer at the contact between Al electrode and gold nanoparticles of polymer: Nanoparticle resistive switching devices studied by alternating current impedance spectroscopy
Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO3/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.
Ouyang, Jianyong
Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO{sub 3}/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.
Ouyang, Jianyong, E-mail: email@example.com [Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore)] [Department of Materials Science and Engineering, National University of Singapore, Singapore 117576 (Singapore)
Microparticle electrodes and single particle microbatteries: electrochemical and in situ microRaman spectroscopic studies.
Studies of the intrinsic electrochemical, structural, and electronic propertiesof microparticles of energy storage materials can provide much needed insight into the factors that control various aspects of the performance of technical electrodes for battery applications. This Account summarizes efforts made in our laboratories toward the development and implementation of methods for the in situ electrical, optical, and spectroscopic characterization of microparticles of a variety of such materials, including Ni hydroxide, Zn, carbon, and lithiated Mn and Co oxides. In the case of Ni hydroxide, the much darker appearance of NiOOH compared to the virtually translucent character of virgin Ni(OH)2 allowed for the spatial and temporal evolution of charge flow within spherical microparticles of Ni(OH)2 to be monitored in real time during the first scan toward positive potentials using computer-controlled video imaging. In situ Raman scattering measurements involving single microparticles of Zn harvested from a commercial Zn|MnO2 battery revealed that passive films formed in strongly alkaline solutions by stepping the potential from 1.55 V to either 0.7 or 0.8 V vs SCE displayed a largely enhanced feature at ca. 565 cm(-1) ascribed to a longitudinal optical phonon mode of ZnO, an effect associated with the presence of interstitial Zn and oxygen deficiencies in the lattice. In addition, significant amounts of crystalline ZnO could be detected only for passive films formed at the same two potentials after the electrodes had been roughened by a single passivation-reduction step. Quantitative correlations were found in the case of LiMn2O4 and KS-44 graphite between the Raman spectral properties and the state of charge. In the case of KS-44, a chemometrics analysis of the spectroscopic data in the potential region in which the transition between dilute phase 1 and phase 4 of lithiated graphite is known to occur made it possible to determine independently the fraction of each of the two phases present as a function of potential without relying on the coulometric information. Also featured in this Account are methods we developed for the assembly and electrochemical characterization of Zn|MnO2 and nickel|metal-hydride Ni|MH alkaline batteries incorporating single microparticles of the active materials. As evidenced from the data collected, the voltage-time profiles for constant current operation for both types of devices were found to be similar to those of commercially available batteries involving the same chemistries. The ability to monitor the state of charge of individual particles based strictly on spectroscopic data is expected to open exciting new prospects for visualizing the flow of charge within electrodes in Li-ion batteries, an area that is being vigorously pursued in our laboratories. PMID:23530836
Jebaraj, Adriel Jebin Jacob; Scherson, Daniel A
Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes
Materials that undergo a conversion reaction with lithium (e.g., metal fluorides MF{sub 2}: M = Fe, Cu, ...) often accommodate more than one Li atom per transition-metal cation, and are promising candidates for high-capacity cathodes for lithium ion batteries. However, little is known about the mechanisms involved in the conversion process, the origins of the large polarization during electrochemical cycling, and why some materials are reversible (e.g., FeF{sub 2}) while others are not (e.g., CuF{sub 2}). In this study, we investigated the conversion reaction of binary metal fluorides, FeF{sub 2} and CuF{sub 2}, using a series of local and bulk probes to better understand the mechanisms underlying their contrasting electrochemical behavior. X-ray pair-distribution-function and magnetization measurements were used to determine changes in short-range ordering, particle size and microstructure, while high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) were used to measure the atomic-level structure of individual particles and map the phase distribution in the initial and fully lithiated electrodes. Both FeF{sub 2} and CuF{sub 2} react with lithium via a direct conversion process with no intercalation step, but there are differences in the conversion process and final phase distribution. During the reaction of Li{sup +} with FeF{sub 2}, small metallic iron nanoparticles (<5 nm in diameter) nucleate in close proximity to the converted LiF phase, as a result of the low diffusivity of iron. The iron nanoparticles are interconnected and form a bicontinuous network, which provides a pathway for local electron transport through the insulating LiF phase. In addition, the massive interface formed between nanoscale solid phases provides a pathway for ionic transport during the conversion process. These results offer the first experimental evidence explaining the origins of the high lithium reversibility in FeF{sub 2}. In contrast to FeF{sub 2}, no continuous Cu network was observed in the lithiated CuF{sub 2}; rather, the converted Cu segregates to large particles (5-12 nm in diameter) during the first discharge, which may be partially responsible for the lack of reversibility in the CuF{sub 2} electrode.
Wang, Feng; Robert, Rosa; Chernova, Natasha A.; Pereira, Nathalie; Omenya, Fredrick; Badway, Fadwa; Hua, Xiao; Ruotolo, Michael; Zhang, Ruigang; Wu, Lijun; Volkov, Vyacheslav; Su, Dong; Key, Baris; Whittingham, M. Stanley; Grey, Clare P.; Amatucci, Glenn G.; Zhu, Yimei; Graetz, Jason (Rutgers); (SBU); (Cambridge); (SUNY-Binghamton); (BNL)
Photovoltaic concentrator pointing dynamics and plasma interaction study
The objectives of this experiment are to use the Space Technology Experiments Platform (STEP) system to demonstrate the viability of concentrator photovoltaic arrays by: (1) configuring a deployable mast on the STEP pallet with concentrator mass models and some active photovoltaic modules; (2) measuring the array pointing dynamics under normal rotation as well as disturbance conditions; (3) performing an array plasma interaction experiment to determine the steady-state plasma losses under various voltage conditions; and (4) providing active distributed control of the support truss to determine the improvement in dynamic response. Experiment approach and test control and instrumentation are described.
Stern, T. G.
Point Contact Spectroscopy Study of ZrZn2
We have performed point contact spectroscopy on spark-cut single crystals of ferromagnetic ZrZn2, using normal-metal tips in a dilution refrigerator down to 100mK. The differential conductance spectra show low-energy peak structures which evolve systematically with temperature below 1.1 K. We associate these state-conserving peak spectra with the surface superconductivity recently observed in ZrZn2. Implications of our data on the electron pairing in ZrZn2 are discussed.
Turel, C. S.; Tanatar, M. A.; Hill, R. W.; Yelland, E. A.; Hayden, S. M.; Wei, J. Y. T.
Effect of silicate ions on electrode overvoltage
The influence of the addition of a silicate to a caustic solution (KOH) is studied in order to determine the degree to which silicates inhibit the corrosion of chrysotile under conditions of electrolysis at working temperatures of 100 C and above. In an alkaline solution containing various silicate concentrations, current density was increased and electrode overvoltage was measured. Results show that silicate ion concentrations in the electrolyte increase with temperature without effecting electrochemical performance up to 115 C at 700 MA/sqcm. At this point the concentration is about 0.5 g Si/100 g KOH. Beyond this limit, electrolytic performance rapidly degenerates due to severe oxidation of the electrodes.
Gras, J. M.; Seite, C.
Electrosynthesis of trifluorochloroethylene on porous hydrophobized electrodes with different electrocatalysts
The promising perspectives for the production of trifluorochloroethylene by the electrochemical dechlorination of 1,1,2-trifluorotrichloroethane (khladon 113, Freon-113) have been pointed out. Trifluorochloroethylene was obtained with high current and substance yields on zinc electrodes; however, destruction of the electrodes takes place, due to interaction of zinc with the freon. In the present study they have investigated other electrocatalysts which are chemically resistant to the freon and which give to the electrodes the necessary mechanical strength. Cadmium, lead, copper, BAU carbon, and acetylene carbon black (Technical specification TU-14-7-24-80) were selected from the materials recommended in the literature. The most promising for the electrochemical dechlorination of Freon-113 the electrodes with a catalyst-carrier and the carbon black electrodes.
Kolyagin, G.A.; Kornienko, V.L.
Investigation and Design Studies of SOFC Electrode Performance at Elevated Pressure
An experimental program was set forth to study fuel cell performance at pressure and under various compositions. Improvement in cathode electrode performance is on the order of 33-40% at pressures of 6.4 Bara compared to atmospheric pressure. Key cathode operational parameters are the concentration and partial pressure of O2, and temperature. The effect of partial pressure of oxygen (PO2) decreases the activation polarization, although there appears to be a secondary effect of absolute pressure as well. The concentration of oxygen impacts the diffusion component of the polarization, which is largely insensitive to absolute pressure. The effect of pressure was found to reduce the total polarization resistance of full fuel-cells beyond the reduction determined for the cathode alone. The total reduction in ASR was on the order of 0.10 ohm-cm2 for a pressure increase from 1 to 6.5 Bara, with about 70% of the improvement being realized from 1 to 4 Bara. An important finding was that there is an effect of steam on the cathode that is highly temperature dependent. The loss of performance at temperatures below 850 C was very large for the standard LSM + YSZ cathodes.
Ted Ohrn; Shung Ik Lee
Initiation from a point anode in a dielectric liquid
Many previous studies of electrical breakdowns in dielectric liquids in point-plane geometry have examined the relationships among the breakdown structure (or speed), the electrode geometry (point radius, gap length), and\\/or voltage. This paper explores the hypothesis that, for streamers initiating from a point anode, the critical volume model used for similar geometry in gaseous dielectrics is useful in liquids. The
M. Kim; R. E. Hebner
Finite element modeling of electrode-skin contact impedance in electrical impedance tomography.
In electrical impedance tomography (EIT), we inject currents through and measure voltages from an array of surface electrodes. The measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through this contact impedance are both high. We used large electrodes to provide a more uniform current distribution and reduce the contact impedance. A large electrode differs from a point electrode in that it has shunting and edge effects which cannot be modeled by a single resistor. We used the finite element method (FEM) to study the electric field distributions underneath an electrode, and developed three models: a FEM model, a simplified FEM model and a weighted load model. We showed that the FEM models considered both shunting and edge effects and matched closely the experimental measurements. FEM models for electrodes can be used to improve the performance of an electrical impedance tomography reconstruction algorithm. PMID:8375870
Hua, P; Woo, E J; Webster, J G; Tompkins, W J
Potential Distribution About an Electrode on the Surface of the Earth
An analytical study is made of the potential distribution about an electrode on a stratified earth, from the point of view of developing special formulas appropriate for computation at small and large distances from the electrode. Power series in the distance for small distances and simple asymptotic expansions for large separations are derived first for a two layer earth, from
Morris Muskat
Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode.
DFT-B3LYP/6-31G (d, p) and HF/6-31G (d, p) calculations are performed for deoxidized norepinephrineat (NP(R)) and its oxidized form (NP(O)). The electrochemistry of norepinephrineat (NP) was studied by cyclic voltammetry (CV) at a pyrolytic graphite electrode modified by Nafion multi-walled carbon nanotubes (MWNTs) in phosphate buffers at pH 6.0, showing that the standard electrode potential of half reaction for NP(O), H+/NP(R) is 0.75l V. This experimental standard electrode potential of half reaction is consistent with that calculated using the energies of solvation and sum of electronic and thermal free energies of NP(R) and NP(O). The frontier orbital theory and M³lliken charges of molecular explain the electrochemical behavior of CV at modified electrode well. The singlet vertical excited states for NP(R) and NP(O) are also discussed. PMID:17141559
Song, Yuanzhi
Coverage and potential dependent CO adsorption on Pt(1111), (711) and (100) electrode surfaces studied by infrared reflection absorption spectroscopy
The structure of CO adsorbed on stepped electrode surfaces was studied by infrared reflection absorption method. Three kinds of (100) terrace surfaces which exhibited different step densities, Pt(1111)[6(100) ū (111)], Pt(711)[4(100) ū (111)] and Pt(100), were examined. At least four kinds of absorption bands of CO were found on each electrode surface: on-top CO on steps at 2045 cm -1, on-top CO on terraces at 2060 cm -1, symmetric bridge CO at 1880 cm -1, and asymmetric bridge CO at 1920 cm -1. The population at each CO adsorption site could be controlled by changing the electrode potential and CO coverage. At negative electrode potentials, CO preferred a bridge site on terrace atoms and an on-top site on step atoms, while at positive potentials, on-top CO on terraces predominated. The coverages at which on-top CO on the terrace surface started to appear were 0.40 on Pt(100), 0.35 on Pt(1111) and 0.25 on Pt(711).
Watanabe, S.; Inukai, J.; Ito, M.
Drug-selective electrode for ketamine determination in pharmaceutical preparations and electrochemical study of drug with BSA.
Ion-selective membrane electrode to the drug ketamine hydrochloride has been constructed using a modified PVC membrane which has ionic end-groups as ion-exchanger sites and which was cast using plasticized with ortho-nitrophenyloctyl ether (o-NPOE) as plastisizer. This drug electrode show excellent Nernstian responses (59 mV per decade) in the concentration range 1 x 10(-5)-1 x 10(-2) M with a detection limit of 5 x 10(-6) M. Response time was about 10 s for ketamine concentrations between 1 x 10(-5) and 1 x 10(-2) M. The response is not affected by pH between 4 and 8.5. Selectivity coefficients against various organic and inorganic cations were evaluated. The electrode was applied for determination of ketamine hydrochloride in pharmaceutical preparations using direct potentiometry. The drug electrode has also been used to study the interaction of bovine serum albumin (BSA) with ketamine in buffer solution (phosphate, pH 7). The saturated quantities of ketamine binding were 114, 32 and 25 mol/mol in 0.01, 0.02 and 0.1% of protein, respectively. The Hill equations were applied to obtain co-operative drug bindings to BSA at 27 degrees C. PMID:12367698
Alizadeh, Naader; Mehdipour, Rasoul
Microtitrimetry by differential electrolytic potentiometry using metallic electrodes and nanomaterials modified metallic electrodes
For the first time silver wire electrodes have been coated with carbon nanotubes using floating catalyst chemical vapor deposition (CVD) method. The production of CNTs has been conducted in a horizontal tubular reactor. Acetylene gas was used as a carbon source. Ferrocene has been used as a catalyst precursor for the growth of CNT. Different parameters have been optimized to get a high yield of CNTs and ensure their growth on the silver electrodes using univariate method. The parameters studied include the hydrogen flow rate, acetylene flow rate, temperature of the furnace, time of the reaction and the location of the electrodes in the reactor tube. The optimum conditions for those parameters were: for hydrogen and acetylene, the flow rates were 25 mL /min and 75 mL / min respectively. The furnace temperature was found to be 700 ░C and the reaction time was 15 minutes. Regarding the location of the silver wires it should be located in the first 10 cm of the front side of the tube. Scanning electron microscopy (SEM) and transition electron microscopy (TEM) have been used to characterize carbon on silver electrodes. According to the experimental results, TEM figures show that CNT produced on Silver wire is multiwall carbon nanotubes MWCNT. Silver electrodes either pure or coated with CNT were used as indicating systems in micro titration using both dc differential electrolytic potentiometry (DEP) and mark-space bias DEP techniques. All types of titrimetric reactions were investigated using different types of electrodes like Pt and gold for oxidation reduction titrations, antimony electrodes for acid base titrations, silver electrodes for precipitation titrations in addition to Ag-CNT electrodes. End points at volumes of 1 microL were determined. Different parameters were optimized like the current density, the percentage bias, the volume of the sample and the concentrations of the reactants. Microtitrimetry has been applied on several types of analytes; Ferrous, Ascorbic acid, chloride, Cyanide, Sodium Bicarbonate and Ketoconazole in aqueous and non- aqueous medium. The performance of Ag-CNT electrodes was found to be much better than the normal silver electrodes. The differential titration curves obtained were symmetrical with significant heights. For silver electrodes coated with CNT the first derivative of the potential was found to give better curves than the normal differential curves, hence the end point location was successfully achieved. A micro liter injector that can deliver volumes at a micro liter level was designed and fabricated. Microtitrimetry which requires volumes of reagents at the micro liter level can offer a solution to the large consumption of reagents in all classical titrimetric processes. Hence, large savings in reagents as well as less waste will reach the environment.
Amro, Abdulaziz Nabil
Ionization EM calorimetry with accordion electrodes and liquid krypton or argon.
The results of a study and tests of a liquid krypton/argon electromagnetic calorimeter with accordion electrode structure are briefly summarized. This includes the calorimeter response to electrons and muons, energy, pointing and timing resolution, and a ...
V. Radeka
Photovoltage response to temperature change at oxide semiconductor electrodes
A study has been carried out on single crystal electrodes of TiO2, SrTiO3, and alpha-Fe2O3 and polycrystalline WO3 to investigate the effect of cell temperature on the onset potential of n-type oxide semiconductor electrodes. It is found that the change of the onset potential with temperature is due to the potential change across the Helmholtz layer. The amount of this change depends on the point of zero zeta potential (pzzp) of the semiconductor electrode. The possibility of increasing the solar-to-chemical energy conversion efficiency of a photochemical cell by increasing the cell temperature is discussed.
Reichman, B.; Byvik, C. E.
Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source
A high monatomic beam fraction is an important factor in a hydrogen ion source to increase the application efficiency. The monatomic fraction of hydrogen plasmas with different plasma electrode materials is measured in a helicon plasma ion source, and aluminum shows the highest value compared to that with the other metals such as copper and molybdenum. Formation of an aluminum oxide layer on the aluminum electrode is determined by XPS analysis, and the alumina layer is verified as the high monatomic fraction. Both experiments and numerical simulations conclude that a low surface recombination coefficient of the alumina layer on the plasma electrode is one of the most important parameters for increasing the monatomic fraction in hydrogen plasma ion sources.
Jung, Bong-Ki; Chung, Kyoung-Jae; Dang, Jeong-Jeung; Hwang, Y. S. [Department of Nuclear Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)
DFT Study of Oxygen Reduction Reaction on N-substituted Carbon Electrodes. Adsorption
Carbon alloys attract attention as metal-free cathode catalysts. Mechanisms of oxygen reduction reactions are investigated using the DFT calculations and molecular models such as N-substituted coronene, circum pyrene, and corannulene. The overall oxygen reduction reaction (ORR) is decomposed into five elementary reactions. Adsorption of O2 is important as the first step of reduction, and it depends strongly on the spin density on C atoms, introduced by the N atom. Secondly the peripheral C atoms have an advantage due to the rehybridization freedom to the sp3 configuration. Based on the reversible electrode potential (REP) for each elementary reaction, the overpotential is expected for the first reduction of O2 to OOH and the final reduction of OH to H2O. These features indicate that N-substituted carbon electrode resembles Pt electrode compared to other less active metals, such as Au.
Kobayashi, Hisayoshi; Tomoya, Nakzono; Miyazaki, Soichi; Miura, Toshiko; Takeuchi, Nobuyuki; Yamabe, Tokio
Stiffness properties for Nucleus standard straight and contour electrode arrays.
Trauma and damage during insertion of electrode arrays into the human cochlea are strongly related to the stiffness of the array. The stiffness properties of electrode arrays, which were determined by three-point flexural bending and buckling tests, are reported in this paper. To date there has been limited publication on mechanical properties of these electrode arrays. Previous studies mainly focused on characterizing the stiffness of the tip of the Nucleus straight array with little emphasis on characterizing the stiffness of its whole length. In this study, stiffnesses of the Nucleus straight and contour electrode arrays have been determined along their length. Young's modulus of elasticity of the Nucleus straight array has been found to increase from the tip (182 MPa) to the rear end (491 MPa), whereas the stiffness of the contour array is greatest near the tip (480 MPa) and is fairly uniform in the middle and rear sections of the electrode array (380-400 MPa). Buckling experiments have shown that the contour array has much higher critical buckling load (about four times) than the Nucleus straight array. The results from three-point flexural bending and buckling experiments provide significant data for the development of electrode arrays, from which new array designs with improved flexibility can be developed. The results of stiffness properties are also important input for use in finite element models to predict the trajectories during insertion and to help evaluate the effects of different electrode array designs on damage sustained during insertion. PMID:15471696
Kha, H N; Chen, B K; Clark, G M; Jones, R
In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium
Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque time curves presente saw-tooth fashion. The maximum torque has a range of 0.3 1.9 N mm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.
Zhang, Xiangming; Ma, Nianke; Fan, Hualin; Niu, Guodong; Yang, Wei
Comparison and correlation of surface and sphenoidal electrodes with simultaneous intracranial recording: an interictal study.
We prospectively compared and correlated interictal spikes recorded with simultaneous surface, sphenoidal, depth and subdural electrodes in 21 patients. Although the amplitude of sphenoidal spikes was often larger than that of surface spikes in patients with mesial basal temporal ictal and interictal foci, only 1 patient had exclusively sphenoidal spikes. Spikes with maximal amplitude at the sphenoidal electrode arose from mesial temporal, temporal neocortical and orbital frontal foci. An inferior vertical temporal dipole (hippocampal positive and inferior temporal neocortex negative) was associated with surface and sphenoidal spikes. PMID:1370140
Marks, D A; Katz, A; Booke, J; Spencer, D D; Spencer, S S
Studies on conducting polymer and conducting polymerinorganic composite electrodes prepared via a new cathodic polymerization method
A novel approach for the electrodeposition of conducting polymers and conducting polymer-inorganic composite materials is presented. The approach shows that conducting polymers, such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) can be electrodeposited by the application of a cathodic bias that generates an oxidizing agent, NO+, via the in-situ reduction of nitrate anions. This new cathodic polymerization method allows for the deposition of PPy and PEDOT as three dimensional, porous films composed of spherical polymer particles. The method is also suitable for the co-deposition of inorganic species producing conducting polymer-inorganic composite electrodes. Such composites are used as high surface area electrodes in Li-ion batteries, electrochemical hydrogen evolution and in the development of various other conducting polymer-inorganic composite electrodes. New Sn-PPy and Sb-PPy composite electrodes where Sn and Sb nanoparticles are well dispersed among the PPy framework are reported. These structures allow for decreased stress during expansion and contraction of the active material (Sn, Sb) during the alloying and de-alloying processes of a Li-ion battery anode, significantly alleviating the loss of active material due to pulverization processes. The new electrochemical synthesis mechanism allows for the fabrication of Sn-PPy and Sb-PPy composite electrodes directly from a conducting substrate and eliminates the use of binding materials and conducting carbon used in modern battery anodes, which significantly simplifies their fabrication procedures. Platinum (Pt) has long been identified as the most efficient catalyst for electrochemical water splitting, while nickel (Ni) is a cheaper, though less efficient alternative to Pt. A new morphology of PPy attained via the aforementioned cathodic deposition method allows for the use of minimal quantities of Pt and Ni dispersed over a very high surface area PPy substrate. These composite electrodes show significantly improved performance over bulk Pt or Ni electrodes in electrochemical hydrogen evolution applications. A variety of conducting polymer-inorganic composite materials are considered, showing that the obtained results are not limited to the mentioned inorganic materials and polymers. Various conducting polymer-inorganic composite electrodes with silver (Ag), gold (Au) and PEDOT are also reported and discussed in detail. The results presented herein open new pathways into the exploration, fabrication and applications of conducting polymer and conducting polymer-based inorganic composites in the field of energy storage and electrocatalysis.
Singh, Nikhilendra
An in situ x-ray absorption spectroscopy study of InSb electrodes in lithium batteries.
We present a detailed in situ extended X-ray absorption fine-structure spectroscopy (EXAFS) study of structural and compositional changes in InSb intermetallic electrodes under electrochemical cycling conditions in a lithium battery. Analysis of the EXAFS data shows that Li is inserted into and In is extruded from the zinc-blende-type InSb network during the first discharge from 1.5 to 0.5 V, yielding changing Li{sub x+y}In{sub 1-y}Sb compositions (0 < x {le} 2, 0 < y {le} 1), with a lattice parameter that varies between that of InSb (a = 6.478 A) and Li{sub 3}Sb (a = 6.572 A). The structural features of tetragonal metallic In and lithiated (i.e., In depleted) InSb are evident. The fully recharged electrode, at 1.2 V, has a zinc-blende framework closely resembling InSb. However, 40% of the In remains permanently outside the face-centered-cubic Sb lattice, explaining a loss in capacity after the first discharge. After the second discharge, at 0.51 V, Li has replaced about 80% of the indium in the InSb lattice, while the Li{sub x}In{sub y}Sb volume has expanded less than 4% compared to the initial electrode. Finally, as the cell is discharged below 0.51 V, Li reacts with the In metal, forming LiIn. Our results indicate that intermetallic electrodes are promising alternative negative electrodes for Li batteries.
Kropf, A. J.; Tostmann, H.; Johnson, C. S.; Vaughey, J. T.; Thackeray, M. M.; Chemical Engineering; Univ. of Florida
Accuracy Study of a 2-Component Point Doppler Velocimeter (PDV)
A two-component Point Doppler Velocimeter (PDV) which has recently been developed is described, and a series of velocity measurements which have been obtained to quantify the accuracy of the PDV system are summarized. This PDV system uses molecular iodine vapor cells as frequency discriminating filters to determine the Doppler shift of laser light which is scattered off of seed particles in a flow. The majority of results which have been obtained to date are for the mean velocity of a rotating wheel, although preliminary data are described for fully-developed turbulent pipe flow. Accuracy of the present wheel velocity data is approximately +/- 1 % of full scale, while linearity of a single channel is on the order of +/- 0.5 % (i.e., +/- 0.6 m/sec and +/- 0.3 m/sec, out of 57 m/sec, respectively). The observed linearity of these results is on the order of the accuracy to which the speed of the rotating wheel has been set for individual data readings. The absolute accuracy of the rotating wheel data is shown to be consistent with the level of repeatability of the cell calibrations. The preliminary turbulent pipe flow data show consistent turbulence intensity values, and mean axial velocity profiles generally agree with pitot probe data. However, there is at present an offset error in the radial velocity which is on the order of 5-10 % of the mean axial velocity.
Kuhlman, John; Naylor, Steve; James, Kelly; Ramanath, Senthil
Ab initio study of point defects in magnesium oxide
Energetics of a variety of point defects in MgO have been considered from an ab initio perspective using density functional theory. The considered defects are isolated Schottky and Frenkel defects and interstitial pairs, along with a number of Schottky defects and di-interstitials. Comparisons were made between the density functional theory results and results obtained from empirical potential simulations and these generally showed good agreement. Both methodologies predicted the first nearest neighbor Schottky defects to be the most energetically favorable of the considered Schottky defects and that the first, second, and fifth nearest neighbor di-interstitials were of similar energy and were favored over the other di-interstitial configurations. Relaxed structures of the defects were analyzed, which showed that empirical potential simulations were accurately predicting the displacements of atoms surrounding di-interstitials, but were overestimating O atom displacement for Schottky defects. Transition barriers were computed for the defects using the nudged elastic band method. Vacancies and Schottky defects were found to have relatively high energy barriers, the majority of which were over 2 eV, in agreement with conclusions reached using empirical potentials. The lowest barriers for di-interstitial transitions were found to be for migration into a first nearest neighbor configuration. Charges were calculated using a Bader analysis and this found negligible charge transfer during the defect transitions and only small changes in the charges on atoms surrounding defects, indicating why fixed charge models work as well as they do.
Gilbert, C. A.; Kenny, S. D.; Smith, R.; Sanville, E. [Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU (United Kingdom)
Numerical and Analytical Studies of AC Electric Field in Dielectrophoretic Electrode Arrays
Manipulation of micro-sized particles and biological cells using dielectrophoresis (DEP) is an emerging technique in MEMS and nano technology(3). This paper presents an exact solution of dielectrophoretic motion of a polarized particle in the vicinity of interdigitated bar electrodes fabricated on pla- nar insulating surfaces which have been widely employed in conjunction with hydrodynamic forces and gravity to sepa- rate
J. J. Feng; S. Krishnamoorthy; Z. J. Chen; V. B. Makhijani
Self-healing processes in coil-coated cladding studied by the scanning vibrating electrode
The ability of the zinc layer in coil-coated cladding to protect the underlying metal substrate exposed to the environment through a sub-centimeter circular defect was established by using the scanning vibrating electrode technique (SVET). The onset of electrochemical corrosion is observed through the development of local anodes and cathodes in the defective system, with the formation of soluble zinc species.
R. M. Souto; B. Normand; H. Takenouti; M. Keddam
Photo electrochemical study of ferrioxalate actinometry at a glassy carbon electrode
An alternative photo electrochemical approach of potassium ferrioxalate actinometry has been investigated via the amperometric detection of product (Fe2+) formation at a glassy carbon electrode. The corresponding oxidation current response of [Fe2+] formed due to the photolysis of ferrioxalate, was monitored as a function of illumination time, which allowed the intensity of the illumination source to be determined. To validate
Samina Ahmed
Raman Spectroscopic and Electrochemical Study of the Photoinduced Crystallization of Triethylenediamine Triiodide upon a Silver Electrode.
When a silver electrode, electrochemically coated with AgI, is immersed in an electrolyte containing NaI and the diprotonated form of 1,4-diazabicyclo2.2.2octane (abbreviated DABCO-H22+), and is bathed in 514.5 nm radiation from an argon ion laser through...
D. E. Irish T. Ozek
Study of Plasma Arc Welded Reactor Materials. Plasma Arc Welding Using Hot Wire Electrodes.
The effects of single-run and double-run plasma arc welding using a hot wire electrode on the structure of the HAZ of the fine-grained structural steels 22 NiMoCr 3 7 and 20 MnMoNi 5 5 were investigated, with particular regard to the behaviour of that reg...
K. O. Trarbach
EHD study of the corona wind between wire and plate electrodes
The corona wind, with a velocity of several meters per second, is caused by applying high electric tension to bring about corona discharge in gases. In this paper the corona wind is experimentally and theoretically analyzed from an electrohydrodynamical (EHD) standpoint. Experiments have been performed mainly in nitrogen by a two-dimensional electrode arrangement of a fine wire anode and a
A. Yabe; Y. Mori; K. Hijikata
Modeling of EEG electrode artifacts and thermal ripples in human radiofrequency exposure studies.
The effects of radiofrequency (RF) exposure on wake and sleep electroencephalogram (EEG) have been in focus since mobile phone usage became pervasive. It has been hypothesized that effects may be explained by (1) enhanced induced fields due to RF coupling with the electrode assembly, (2) the subsequent temperature increase around the electrodes, or (3) RF induced thermal pulsing caused by localized exposure in the head. We evaluated these three hypotheses by means of both numerical and experimental assessments made with appropriate phantoms and anatomical human models. Typical and worst-case electrode placements were examined at 900 and 2140?MHz. Our results indicate that hypothesis 1 can be rejected, as the induced fields cause <20% increase in the 10?g-averaged specific absorption rate (SAR). Simulations with an anatomical model indicate that hypothesis 2 is also not supported, as the realistic worst-case electrode placement results in a maximum skin temperature increase of 0.31?░C while brain temperature elevations remained <0.1?░C. These local short-term temperature elevations are unlikely to change brain physiology during the time period from minutes to several hours after exposure. The maximum observed temperature ripple due to RF pulses is <0.001?░C for GSM-like signals and <0.004?░C for 20-fold higher pulse energy, and offers no support for hypothesis 3. Thus, the mechanism of interaction between RF and changes in the EEG power spectrum remains unknown. PMID:24523224
Murbach, Manuel; Neufeld, Esra; Christopoulou, Maria; Achermann, Peter; Kuster, Niels
Study on a novel manufacturing process of membrane electrode assemblies for solid polymer electrolyte water electrolysis
A novel manufacturing process for catalyst coated membrane (CCM) was utilized to fabricate the membrane electrode assemblies (MEA) for solid polymer electrolyte (SPE) water electrolysis. The properties and performance of the modified CCM were analyzed and evaluated by SEM, electrochemistry impedance spectroscopy (EIS) and I¢V curves. The characterizations reveal that the sprayed Nafion layers are very effective for increasing the
Yangjian Zhang; Cheng Wang; Nianfang Wan; Zhixiang Liu; Zongqiang Mao
Degradation studies of transparent conductive electrodes on electroactive poly(vinylidene fluoride) for uric acid measurements
Biochemical analysis of physiological fluids using, for example, lab-on-a-chip devices requires accurate mixing of two or more fluids. This mixing can be assisted by acoustic microagitation using a piezoelectric material, such as the ?-phase of poly(vinylidene fluoride) (?-PVDF). If the analysis is performed using optical absorption spectroscopy and ?-PVDF is located in the optical path, the material and its conductive electrodes must be transparent. Moreover, if, to improve the transmission of the ultrasonic waves to the fluids, the piezoelectric transducer is placed inside the fluidic structures, its degradation must be assessed. In this paper, we report on the degradation properties of transparent conductive oxides, namely, indium tin oxide (ITO) and aluminum-doped zinc oxide, when they are used as electrodes for providing acoustic microagitation. The latter promotes mixing of chemicals involved in the measurement of uric acid concentration in physiological fluids. The results are compared with those for aluminum electrodes. We find that ?-PVDF samples with ITO electrodes do not degrade either with or without acoustic microagitation.
Cardoso, Vanessa F.; Martins, Pedro; Botelho, Gabriela; Rebouta, Luis; Lanceros-Mķndez, Senentxu; Minas, Graca
The oxidation of tyrosine and tryptophan studied by a molecular dynamics normal hydrogen electrode
The thermochemical constants for the oxidation of tyrosine and tryptophan through proton coupled electron transfer in aqueous solution have been computed applying a recently developed density functional theory (DFT) based molecular dynamics method for reversible elimination of protons and electrons. This method enables us to estimate the solvation free energy of a proton (H{sup +}) in a periodic model system from the free energy for the deprotonation of an aqueous hydronium ion (H{sub 3}O{sup +}). Using the computed solvation free energy of H{sup +} as reference, the deprotonation and oxidation free energies of an aqueous species can be converted to pK{sub a} and normal hydrogen electrode (NHE) potentials. This conversion requires certain thermochemical corrections which were first presented in a similar study of the oxidation of hydrobenzoquinone [J. Cheng, M. Sulpizi, and M. Sprik, J. Chem. Phys. 131, 154504 (2009)]. Taking a different view of the thermodynamic status of the hydronium ion, these thermochemical corrections are revised in the present work. The key difference with the previous scheme is that the hydronium is now treated as an intermediate in the transfer of the proton from solution to the gas-phase. The accuracy of the method is assessed by a detailed comparison of the computed pK{sub a}, NHE potentials and dehydrogenation free energies to experiment. As a further application of the technique, we have analyzed the role of the solvent in the oxidation of tyrosine by the tryptophan radical. The free energy change computed for this hydrogen atom transfer reaction is very similar to the gas-phase value, in agreement with experiment. The molecular dynamics results however, show that the minimal solvent effect on the reaction free energy is accompanied by a significant reorganization of the solvent.
Costanzo, Francesca; Valle, Raffaele Guido Della [Dipartimento di Chimica Fisica e Inorganica, Universita di Bologna and INSTM-UdR Bologna, Viale Risorgimento 4, I-40136 Bologna (Italy); Sulpizi, Marialore; Sprik, Michiel [Department of Chemistry, University of Cambridge, Cambridge CB2 1EW (United Kingdom)
Electrochemical and XPS Study of the Nickel-Titanium Electrode Surface.
A Ni-Ti alloy with a 50:50 atomic composition has shown exceptional properties as a fixed potential LCEC detector for carbohydrates and related substances. It exhibited excellent sensitivity and superior long-term stability compared to pure Ni. A study was therefore undertaken by means of cyclic voltammetry (CV), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to understand the role of Ti and the respective surface oxides of Ni and Ti in the catalytic stability of the detector. CV results showed that Ti is initially oxidized, most likely to TiO(2) in 0.1 M NaOH solution. The oxidation of Ni to nickel(II) oxide also occurs at potentials close to that of Ti. At higher potentials in the range of +0.4 to +0.5 V vs Ag/AgCl reference, nickel(II) oxide undergoes further oxidation to the Ni(III) oxidation state. This state is responsible for the catalysis of carbohydrates, amino acids and other biosubstances. When Ni-Ti and Ni are repetitively CV cycled in the potential range of 0.0 to +0.6 V, a second wave appears at more negative potentials during the reverse cathodic scan for Ni but not for Ni-Ti. SEM images of these two electrodes in the oxidized form show the Ni-Ti surface remains smoother in appearance. This smoothness is consistent with the fact that the thickness of the surface "oxide" layer increases less rapidly, as Ni-Ti is repetitively CV cycled, compared to pure Ni. XPS results for the nature of the surface oxides are consistent with oxidized Ti as TiO(2), Ni(II) predominantly as Ni(OH)(2), and Ni(III) possibly as NiOOH. Possible reasons for Ti stabilizing the Ni-Ti alloy as a LCEC detector are discussed. PMID:21619268
Luo, P F; Kuwana, T; Paul, D K; Sherwood, P M
A spatiotemporal study of gliosis in relation to depth electrode tracks in drug-resistant epilepsy.
Key questions remain regarding the processes governing gliogenesis following central nervous system injury that are critical to understanding both beneficial brain repair mechanisms and any long-term detrimental effects, including increased risk of seizures. We have used cortical injury produced by intracranial electrodes (ICEs) to study the time-course and localization of gliosis and gliogenesis in surgically resected human brain tissue. Seventeen cases with ICE injuries of 4-301Ādays age were selected. Double-labelled immunolabelling using a proliferative cell marker (MCM2), markers of fate-specific transcriptional factors (PAX6, SOX2), a microglial marker (IBA1) and glial markers (nestin, GFAP) was quantified in three regions: zone 1 (immediate vicinity: 0-350Ā?m), zone 2 (350-700Ā?m) and zone 3 (remote ?2000Ā?m) in relation to the ICE injury site. Microglial/macrophage cell densities peaked at 28-30Ādays post-injury (dpi) with a significant decline in proliferating microglia with dpi in all zones. Nestin-expressing cells (NECs) were concentrated in zones 1 and 2, showed the highest regenerative capacity (MCM2 and PAX6 co-expression) and were intimately associated with capillaries within the organizing injury cavity. There was a significant decline in nestin/MCM2 co-expressing cells with dpi in zones 1 and 2. Nestin-positive fibres remained in the chronic scar, and NECs with neuronal morphology were noted in older injuries. GFAP-expressing glia were more evenly distributed between zones, with no significant decline in density or proliferative capacity with dpi. Colocalization between nestin and GFAP in zone 1 glial cells decreased with increasing dpi. In conclusion, NECs at acute injury sites are a proliferative, transient cell population with capacity for maturation into astrocytes with possible neuronal differentiation observed in older injuries. PMID:24666402
Goc, Joanna; Liu, Joan Y W; Sisodiya, Sanjay M; Thom, Maria
A Comparative Mechanical Analysis of the Pointe Shoe Toe BoxAn In Vitro Study
Dancing en pointe requires the ballerina to stand on her toes, which are protected only by the pointe shoe toe box. This protection diminishes when the toe box loses its structural integrity. The objectives of this study were 1) to quantify the comparative structural static and fatigue properties of the pointe shoe toe box, and 2) to evaluate the preferred
Bryan W. Cunningham; Andrea F. DiStefano; Natasha A. Kirjanov; Stuart E. Levine; Lew C. Schon
Applying Function Point to Unified Modeling Language: Conversion Model and Pilot Study
We consider convertibility of the elements of the unified modeling language into entities of the function point analysis, introduces a model for establishing the link, and presents a pilot study for comparing the function point counts provided by the model with those provided by a function point certified expert. In order to map the unified modeling language elements to function
Giovanni Cantone; Davide Pace; Giuseppe Calavaro
The Study of Educational Administration: A Developmental Point of View.
This paper presents arguments for the notion that as a field of study, educational administration is necessarily undergoing change and development within the context of the culture in which it is being studied. For this reason the paper concludes that the field cannot justifiably be viewed as producing conclusive end products (rules for effectiveģ
Riffel, J. Anthony
A dropping electrolyte electrode is described for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions. 2 figures.
Ekechukwu, A.A.
First-principles study of high-conductance DNA sequencing with carbon nanotube electrodes
Rapid and cost-effective DNA sequencing at the single nucleotide level might be achieved by measuring a transverse electronic current as single-stranded DNA is pulled through a nanometer-sized pore. In order to enhance the electronic coupling between the nucleotides and the electrodes and hence the current signals, we employ a pair of single-walled close-ended (6,6) carbon nanotubes (CNTs) as electrodes. We then investigate the electron transport properties of nucleotides sandwiched between such electrodes by using first-principles quantum transport theory. In particular, we consider the extreme case where the separation between the electrodes is the smallest possible that still allows the DNA translocation. The benzene-like ring at the end cap of the CNT can strongly couple with the nucleobases and therefore it can both reduce conformational fluctuations and significantly improve the conductance. As such, when the electrodes are closely spaced, the nucleobases can pass through only with their base plane parallel to the plane of CNT end caps. The optimal molecular configurations, at which the nucleotides strongly couple to the CNTs, and which yield the largest transmission, are first identified. These correspond approximately to the lowest energy configurations. Then the electronic structures and the electron transport of these optimal configurations are analyzed. The typical tunneling currents are of the order of 50 nA for voltages up to 1 V. At higher bias, where resonant transport through the molecular states is possible, the current is of the order of several ?A. Below 1 V, the currents associated to the different nucleotides are consistently distinguishable, with adenine having the largest current, guanine the second largest, cytosine the third and, finally, thymine the smallest. We further calculate the transmission coefficient profiles as the nucleotides are dragged along the DNA translocation path and investigate the effects of configurational variations. Based on these results, we propose a DNA sequencing protocol combining three possible data analysis strategies.
Chen, X.; Rungger, I.; Pemmaraju, C. D.; Schwingenschl÷gl, U.; Sanvito, S.
Study of hydrogen nanobubbles in solution in the vicinity of a platinum wire electrode using double-potential step chronoamperometry
A solution supersaturated with hydrogen around a platinum wire electrode was studied by double-potential step chronoamperometry. The time¢current curve at the hydrogen oxidation potential obtained with double-potential step increased with a shift of the hydrogen evolution potential to the cathodic potential. The initial slope of the chronoamperogram at the oxidation potential increased to zero with the shift from the hydrogen
Kenji Kikuchi; Yoshinori Tanaka; Yasuhiro Saihara; Zempachi Ogumi
Comparative study of hydrogen peroxide electro-generation on gas-diffusion electrodes in undivided and membrane cells
The generation of hydrogen peroxide by means of the cathodic reduction of oxygen at gas-diffusion electrodes with a near 100%\\u000a current efficiency was achieved in concentrations sufficient for the mineralization of refractory organics in Fenton treatment.\\u000a A decrease in current efficiency over time at high temperatures and high current densities was observed. The polarization\\u000a study carried out in potentiostatic, potentiodynamic
G. R. Agladze; G. S. Tsurtsumia; B.-I. Jung; J.-S. Kim; G. Gorelishvili
Study of engineering ceramic machining with a new design of ripple controlled microdetonation of electrode arc striking
Based on the principle of strong shock wave generating transient dynamic high-pressure, physical theory of vacuum discharge,\\u000a and high-power pulse technology, this study developed a new machining system of ripple controlled microdetonation of electrode\\u000a arc striking (MDEAS), which was specially used to machine hard and crisp materials, such as ceramic. The topographies such\\u000a as hole, ladder plane, column surface, and
Xinli Tian; Junfei Yang; Chao Liu; Baoguo Zhang; Fang Guo; Aibing Yu
Studies on Me\\/Al-layered double hydroxides (Me = Ni and Co) as electrode materials for electrochemical capacitors
Me\\/Al-layered double hydroxides (Me=Ni and Co) prepared by the chemical co-precipitation method have been shown to be outstanding novel materials for electrochemical capacitors. The crystalline structure and the electrochemical properties of the electrodes have been studied by considering the effect of the mole ratio of nickel\\/cobalt. X-ray diffraction analysis shows that the materials belong to hexagonal system with layered structure.
Xian-Ming Liu; Yi-He Zhang; Xiao-Gang Zhang; Shao-Yun Fu
A study on capacity fading of lithium-ion battery with manganese spinel positive electrode during cycling
The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge¢discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn2O4 spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu2O and
Li Yang; Michio Takahashi; Baofeng Wang
Reversible Oxygen Electrodes.
Some possible mechanisms of O dissolution are reviewed and briefly discussed. The role of rotating disk electrode with a ring for discriminating between various possible mechanisms is illustrated. In the study of the catalytic activity for the reduction o...
M. Genshaw V. Brusic A. Damjanovic J. O. Bockris
Exposures from thorium contained in thoriated tungsten welding electrodes.
Information provided in this article can be used for estimating the radiation dose associated with the use of thoriated tungsten electrodes in tungsten inert gas welding. Area and breathing zone concentrations of 232Th generated by welding and electrode sharpening along with particle size information; isotopic composition of electrodes from two domestic manufacturers and one European manufacturer; and process variables and estimates on the number of thoriated tungsten electrodes manufactured are presented. Past literature is reviewed and compared with the results of this study. Isotopic analysis of a nominal 2% thoriated electrode found 0.6 ppm +/- 0.4 ppm 230Th and less than 0.1 ppm 228Th. Analysis of a ceriated tungsten electrode and a lanthanated tungsten electrode for 232Th found 124 ppm and 177 ppm, respectively. Electrode consumption during welding was primarily the result of tip sharpening. Less than 3% of the weight loss was attributable to the welding process. The in-mask concentration of respirable thorium particulate in the welder's breathing zone was 0.002 x 10(-12) microCi 232Th/mL. The concentration of respirable thorium particulate from electrode sharpening was 1.3 x 10(-12) microCi 232Th/mL. The measured sharpening time was 20 sec per electrode. Estimates of the activity median aerodynamic diameters for the respirable fraction of the welding and electrode sharpening aerosols were 3.5 and 5 microns, respectively, when measured in the breathing zone at 0.3 m (12 inches) from the point of operation. The respirable fraction of the total welding and sharpening aerosols was 45 and 60%. PMID:10386359
Jankovic, J T; Underwood, W S; Goodwin, G M
Control of electrode depth in electroslag remelting
A method of and apparatus for controlling an electroslag remelting furnace by driving the electrode at a nominal speed based upon melting rate and geometry while making minor proportional adjustments based on a measured metric of the electrode immersion depth. Electrode drive speed is increased if a measured metric of electrode immersion depth differs from a set point by a predetermined amount, indicating that the tip is too close to the surface of a slag pool. Impedance spikes are monitored to adjust the set point for the metric of electrode immersion depth based upon one or more properties of the impedance spikes.
Melgaard, David K. (Albuquerque, NM); Shelmidine, Gregory J. (Tijeras, NM); Damkroger, Brian K. (Albuquerque, NM)
Experimental study on the fixed points of the RANK filter
The effects of iterations of the RANK filter are studied experimentally. The RANK filters are a new family of nonlinear filters. The effects of the RANK filters are significant because of their local adaptivity, i.e. flexibility of the shape of the filter window. Images of random values that are uniformly independently distributed are processed by the RANK filters iteratively, and
Akira Asano; Leonid P. Yaroslavsky
Space tug point design study. Volume 4: Program requirements
A study was conducted to determine the configuration of a space tug and to predict the performance parameters. The program plans and planning data generated in support of the tug development program are presented. The preliminary plans and supporting planning data emphasize the following requirements: (1) maintenance and refurbishment, (2) technology development, (3) production, (4) test facilities, (5) quality control, and (6) scheduling.
Case Study ¢ surface reconstruction from point clouds for prosthesis production
Currently, the production of a high-quality and highly aesthetic prosthesis is still mainly based on handwork and subjective comparison to get the proper shape and colour of the prosthesis, likely not by a first attempt. This article describes a case study whose goal was to investigate the possibilities of computer-aided surface reconstruction and supplementation to improve the quality and reduce
N. VukaÜinovi?; T. KolÜek; J. Duhovnik
Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes
Under precisely controlled conditions, atomic gold electrodes with even or odd number of Au atoms per polyaniline repeat unit (Pt/PANI/AuN for 0 electrodes is compared with that of macro gold and PANI coated platinum electrodes by testing electrochemical oxidation of n-propanol and iso-propanol. This study allowed us to separate the behavior dominated by that of macroscopic gold in strongly alkaline medium and by that of the quantized odd¢even effect of atomic gold. Within this overarching scope, there is a specific oxidation pattern attributable to the structural differences between the two isomers of propanol. The significance of this research lies in the recognition of high specific catalytic activity of atomic gold, which is at least three orders of magnitude higher than that of bulk gold for the oxidation of alcohols. It points to a substantial saving of the precious metal without the loss of catalytic activity, which is important in fuel cells and in other energy conversion device applications.
Schwartz, Ilana; Jonke, Alex P.; Josowicz, Mira A.; Janata, Jiri
Nonaqueous inhibition of iron-boron-silicon amorphous electrodes in hydrochloric acid: An alternating current impedance study
Iron-boron-silicon (Fe-B-Si) amorphous electrodes were studied using electrochemical impedance spectroscopy (EIS) to determine the alternating current (AC) impedance and the capacitance of four Fe-B-Si alloys in various acid solutions. The AC impedance and the capacitance of Fe-B-Si, Fe-B-Si with carbon (C), Fe-B-Si with cobalt (Co), and Fe-B-Si with chromium (Cr) were obtained in 25%, 50%, 75%, and 100% hydrochloric acid (HCl) at room temperature. The electrochemical parameters (i.e., impedance) varied depending on additions of C, Co, and Cr to the Fe-B-Si alloy; the acid concentration; and the nanoscopic surface roughness of the electrodes. Consequently, a correlation between the data obtained was established.
Habib, K.; Abdullah, A. (Kuwait Inst. for Scientific Research, Safat (Kuwait))
Muscle channelopathies and critical points in functional and genetic studies
Muscle channelopathies are caused by mutations in ion channel genes, by antibodies directed against ion channel proteins, or by changes of cell homeostasis leading to aberrant splicing of ion channel RNA or to disturbances of modification and localization of channel proteins. As ion channels constitute one of the only protein families that allow functional examination on the molecular level, expression studies of putative mutations have become standard in confirming that the mutations cause disease. Functional changes may not necessarily prove disease causality of a putative mutation but could be brought about by a polymorphism instead. These problems are addressed, and a more critical evaluation of the underlying genetic data is proposed.
Jurkat-Rott, Karin; Lehmann-Horn, Frank
Lifetime studies of high power rhodium/tungsten and molybdenum electrodes for application to AMTEC (alkali metal thermal-to-electric converter)
A detailed and fundamental model for the electrochemical behavior of AMTEC electrodes is developed which can aid in interpreting the processes which occur during prolonged operation of these electrodes. Because the sintering and grain growth of metal particles is also a well-understood phenomenon, the changes in electrode performance which accompany its morphological evolution may be anticipated and modeled. The grain growth rate observed for porous Mo AMTEC electrodes is significantly higher than that predicted from surface diffusion data obtained at higher temperatures and incorporated into the grain growth model. The grain growth observed under AMTEC conditions is also somewhat higher than that measured for Mo films on BASE (beta-alumina solid electrolyte) substrates in vacuum or at similar temperatures. Results of modeling indicate that thin Mo electrodes may show significant performance degradation for extended operation (greater than 10,000 h) at higher operating temperatures (greater than 1150 K), whereas W/Rh and W/Pt electrodes are expected to show adequate performance at 1200 K for lifetimes greater than 10,000 h. It is pointed out that current collection grids and leads must consist of refractory metals such as Mo and W which do not accelerate sintering or metal migration.
Williams, R. M.; Jeffries-Nakamura, B.; Underwood, M. L.; O'Connor, D.; Ryan, M. A.; Kikkert, S.; Bankston, C. P.
Do Changes in Electrical Skin Resistance of Acupuncture Points Reflect Menstrual Pain? A Comparative Study in Healthy Volunteers and Primary Dysmenorrhea Patients
Electrical skin resistance (ESR) measurements were performed with a four-electrode impedance detector at 10 points bilaterally on the first day of and the third day after menstruation in 48 healthy volunteers and 46 primary dysmenorrhea (PD) patients, to assess whether ESR changes of acupuncture points can reflect menstrual pain or not. The results showed statistical reductions in ESR imbalance ratio between left and right side that were detected at SP8 (Diji) and GB39 (Xuanzhong) (P < 0.05), and a statistical increase was detected at SP6 (Sanyinjiao) (P = 0.05) on the first day of menstruation compared with those values on the third day after menstruation in dysmenorrhea group. No significant differences were detected at other points within and between two groups (P > 0.05). This study showed that the imbalance of ESR at uterine-relevant points in PD patients is not significantly different from those of healthy women on both the 1st day of and the 3rd day after menstruation. The ESR imbalance ratio of certain points can either be lower or higher during menstruation in PD patients. The ESR property of acupuncture points needs to be investigated in further clinical trials with appropriate points, diseases, larger sample sizes, and optimal device.
She, Yan-Fen; Ma, Liang-Xiao; Qi, Cong-Hui; Wang, Yan-Xia; Tang, Ling; Li, Chun-Hua; Yuan, Hong-Wen; Liu, Yu-Qi; Song, Jia-Shan; Zhu, Jiang
Radiofrequency electrode vibration-induced shear wave imaging for tissue modulus estimation: A simulation study
Quasi-static electrode displacement elastography, used for in-vivo imaging of radiofrequency ablation-induced lesions in abdominal organs such as the liver and kidney, is extended in this paper to dynamic vibrational perturbations of the ablation electrode. Propagation of the resulting shear waves into adjoining regions of tissue can be tracked and the shear wave velocity used to quantify the shear (and thereby YoungÆs) modulus of tissue. The algorithm used utilizes the time-to-peak displacement data (obtained from finite element analyses) to calculate the speed of shear wave propagation in the material. The simulation results presented illustrate the feasibility of estimating the YoungÆs modulus of tissue and is promising for characterizing the stiffness of radiofrequency-ablated thermal lesions and surrounding normal tissue.
Bharat, Shyam; Varghese, Tomy
Radiofrequency electrode vibration-induced shear wave imaging for tissue modulus estimation: a simulation study.
Quasi-static electrode displacement elastography, used for in-vivo imaging of radiofrequency ablation-induced lesions in abdominal organs such as the liver and kidney, is extended in this paper to dynamic vibrational perturbations of the ablation electrode. Propagation of the resulting shear waves into adjoining regions of tissue can be tracked and the shear wave velocity used to quantify the shear (and thereby Young's) modulus of tissue. The algorithm used utilizes the time-to-peak displacement data (obtained from finite element analyses) to calculate the speed of shear wave propagation in the material. The simulation results presented illustrate the feasibility of estimating the Young's modulus of tissue and is promising for characterizing the stiffness of radiofrequency-ablated thermal lesions and surrounding normal tissue. PMID:20968329
A sealed optical cell for the study of lithium-electrode|electrolyte interfaces
A sealed, symmetrical, lithium optical cell, which enables optical images of lithium surface deposits and in situ Raman spectra to be obtained simply and conveniently during charge¢discharge cycling of lithium metal electrodes, has been designed and tested. A conventional aprotic liquid, 1M lithium hexafluorophosphate in propylene carbonate, and an experimental ionic liquid, 20mol% lithium bis(trifluoromethanesulfonyl)amide in 1-ethyl 3-methyl imidazolium bis(trifluoromethanesulfonyl)amide,
P. C. Howlett; D. R. MacFarlane; A. F. Hollenkamp
Voltammetric study of nifuroxazide at unmodified and Sephadex-modified carbon paste electrodes
The electrooxidation of nifuroxazide was investigated by cyclic and differential-pulse voltammetry at carbon paste and Sephadex-modified\\u000a carbon paste electrodes. Nifuroxazide is irreversibly oxidized at all pH values and gives rise to a well-defined oxidation\\u000a peak. The modification of the carbon paste surface with Sephadex allowed a preconcentration process to take place for nifuroxazide\\u000a such that higher sensitivity was achieved compared
A. Radi
Studies on the oxygen reduction catalyst for zinc¢air battery electrode
In this paper, perovskite type La0.6Ca0.4CoO3 as a catalyst of oxygen reduction was prepared, and the structure and performance of the catalysts was examined by means of IR, X-ray diffraction (XRD), and thermogravimetric (TG). Mixed catalysts doped, some metal oxides were put also used. The cathodic polarization curves for oxygen reduction on various catalytic electrodes were measured by linear sweep
Xianyou Wang; P. J. Sebastian; Mascha A. Smit; Hongping Yang; S. A. Gamboa
A study on pitting corrosion of aluminum alloy 2024-T3 by scanning microreference electrode technique
Micropitting corrosion of aluminum alloy 2024-T3 was investigated by using scanning microreference electrode technique combined with scanning electron microscopy and X-ray energy dispersive spectroscopy. It was found that the micropitting initiated immediately after the exposure of Al 2024¢T3 to NaCl solution at open-circuit potential. Some corrosion active nuclei developed with time while others disappeared. Most of the micropits were found
Minhua Shao; Yan Fu; Ronggang Hu; Changjian Lin
A rotating disc electrode study of oxygen reduction at platinised nickel and cobalt coatings
Platinized nickel and cobalt coatings, Pt(Ni) and Pt(Co), have been prepared on glassy carbon, GC, rotating disc electrode\\u000a substrates by a two-step room temperature procedure that involved the electrodeposition of nickel and cobalt layers and their\\u000a spontaneous partial replacement by platinum (ōtransmetalationö) when immersed into a chloroplatinic acid solution. By tuning\\u000a the quantity of initially deposited nickel and cobalt, Pt(Ni)
Andromahi Tegou; Sofia Papadimitriou; Georgios Kokkinidis; Sotirios Sotiropoulos
Improved performances of nanosilicon electrodes using the salt LiFSI: a photoelectron spectroscopy study.
Silicon is a very good candidate for the next generation of negative electrodes for Li-ion batteries, due to its high rechargeable capacity. An important issue for the implementation of silicon is the control of the chemical reactivity at the electrode/electrolyte interface upon cycling, especially when using nanometric silicon particles. In this work we observed improved performances of Li//Si cells by using the new salt lithium bis(fluorosulfonyl)imide (LiFSI) with respect to LiPF6. The interfacial chemistry upon long-term cycling was investigated by photoelectron spectroscopy (XPS or PES). A nondestructive depth resolved analysis was carried out by using both soft X-rays (100-800 eV) and hard X-rays (2000-7000 eV) from two different synchrotron facilities and in-house XPS (1486.6 eV). We show that LiFSI allows avoiding the fluorination process of the silicon particles surface upon long-term cycling, which is observed with the common salt LiPF6. As a result the composition in surface silicon phases is modified, and the favorable interactions between the binder and the active material surface are preserved. Moreover a reduction mechanism of the salt LiFSI at the surface of the electrode could be evidenced, and the reactivity of the salt toward reduction was investigated using ab initio calculations. The reduction products deposited at the surface of the electrode act as a passivation layer which prevents further reduction of the salt and preserves the electrochemical performances of the battery. PMID:23763546
Philippe, Bertrand; DedryvĶre, Rķmi; Gorgoi, Mihaela; Rensmo, HÕkan; Gonbeau, Danielle; Edstr÷m, Kristina
Electrochemical characteristics of nanostructured platinum electrodes--a cyclic voltammetry study.
Platinum surfaces play a decisive role in catalysis in sensors, fuel cells, solar cells and other applications like neuronal stimulation and recording. Technical advances in nanotechnology contributed tremendously to the progress in these fields. A fundamental understanding of the chemical and physical interactions between the nanostructured surfaces and electrolytes is essential, but was barely investigated up to now. In this article, we present a wet-chemical process for the deposition of nanostructures on polycrystalline platinum surfaces. The electrochemically active surface area was increased by a factor of over 1000 times with respect to the geometrical surface. The influence of the nanostructures was examined in different acidic, alkaline, and neutral electrolytes. Comparing cyclic voltammograms of nanostructured and planar polycrystalline platinum revealed new insights into the microenvironment at the electrode-electrolyte interface. The characteristic features of the cyclic voltammograms were altered in their shape and strongly shifted with respect to the applied potential. In neutral buffered and unbuffered electrolytes the water window was expanded from 1.4 V to more than 2 V. The shifts were interpreted as local pH-changes and exhausted buffer capacity in direct proximity of the electrode surface due to the strong release and binding of protons, respectively. These polarized electrodes induce significant changes in the electrochemical potential of the electrolyte due to the high roughness of their surface. The electrochemical phenomena and the observed voltage shifts are crucial for the understanding of the basic mechanism at nanostructured electrodes and mandatory for designing fuel cells, sensors and many other devices. PMID:24664444
Daubinger, P; Kieninger, J; Unm³ssig, T; Urban, G A
Study of reticulated vitreous carbon surface treated by plasma immersion ion implantation for electrodes production
RVC samples were treated by nitrogen plasma immersion ion implantation (N-PIII) for electrodes production. High-voltage pulses with amplitudes of -3.0 kV or -10.0 kV were applied to the RVC samples while the treatment time was 10, 20 and 30 min. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The SEM images present an apparent enhancement of the surface roughness after the treatment probably due to the surface sputtering during the PIII process. This observation is in agreement with the specific electrochemical surface area (SESA) of RVC electrodes. An increase was observed of the SESA values for the PIII-treated samples compared to the untreated specimen. Some oxygen and nitrogen containing groups were introduced on the RVC surface after the PIII treatment. Both plasma-induced process: the surface roughening and the introduction of the polar species on the RVC surface are beneficial for the RVC electrodes application.
Silva, L. L. G.; ConceińŃo, D. A. S.; Oishi, S. S.; Toth, A.; Ueda, M.
Study of a lithium-lithium propionate electrode in propylene carbonate
Preliminary data are presented on the electrochemical behaviour of a secondary lithium electrode in propylene carbonate at 25 ░C. The anion of the insoluble lithium propionate salt, whose precipitation is favoured by the anodic dissolution of lithium, was introduced into the solvent as a tetrabutylammonium salt. This was prepared by neutralising tetrabutylammonium hydroxide with an excess of propionic acid followed by vacuum evaporation to remove the unwanted water. The introduction of this salt into the solvent increases its specific conductivity without affecting its compatibility with lithium. All measurements were made with freshly prepared mercury-mercurous propionate reference electrodes to overcome problems involving their stability over prolonged periods. Steady-state potentiostatic polarization curves, anodic galvanostatic, and cyclic voltammetry measurements provided information on the kinetics of the lithium system. It was shown to be reversible, provided that the overpotential does not exceed 60 mV, and may be able to deliver current densities of the order of 0.25 mA/cm 2 without appreciable polarisation. Consideration of the reduction of the electrolyte on platinum and lithium electrodes is also discussed.
SaltŃo, J. M. S.; Sequeira, C. A. C.
NICOŌ electrode material and electrode
A battery plate is made by loading a supporting porous metallic plaque with an electrode paste comprising: (1) NiCOŌ, (2) cobalt additive, (3) sufficient water to form a paste, and optionally (4) a deflocculant.
J. F. Jackovitz; E. A. Pantier; J. Seidel
ATR-SEIRAS study of the adsorption of acetate anions at chemically deposited silver thin film electrodes.
The adsorption of acetate anions at silver thin film electrodes has been studied by in-situ infrared spectroscopy experiments with a Kretschmann internal reflection configuration. Stable silver thin films were chemically deposited on germanium substrates. Ex-situ STM images show mean grain sizes ranging from ca. 20 to 90 nm for deposition times between 2 and 20 min, respectively. The thickness of the silver film, measured by AFM, is typically around 10 nm for a deposition time of 10 min and increases up to 50 nm for a deposition time of 20 min. Roughness factors around 2.3 have been obtained for the silver films from the charge involved in lead underpotential deposition (UPD). A noticeable enhancement of the infrared absorption of adsorbed species (SEIRA effect) is observed when the silver films are used as electrodes under internal total reflection conditions. Maximum intensities of the adsorbate bands were observed for a deposition time of 10 min and an angle of incidence around 65 degrees . The potential-dependent infrared spectra of acetate and interfacial water are consistent with previously proposed models involving the existence of weakly hydrogen-bonded water molecules at potentials below the potential of zero charge and the reorientation of water molecules at potentials above the potential of zero charge. Results reported in this work suggest a weak interaction between acetate and water molecules adsorbed at the silver thin film electrodes. PMID:16142964
Delgado, Josķ Manuel; Orts, Josķ Manuel; Rodes, Antonio
A non-thermal plasma generated between two parallel-plate electrodes submerged in water was studied in this work. The surface of one of the stainless-steel electrodes (the cathode) was coated with a ceramic layer of Al2O3. This reactor cell was connected to a water cycle and the discharge was carried out in a closed loop and therefore an equilibrium was established during discharge. The dependence of hydrogen peroxide formation as an indicator for the generation of most important oxidative species OH radicals on the pulse repetition rate, the solution conductivity and the pH of the solution was investigated. The highest yield of H2O2 (3.5 mg L-1) was obtained at 20 pps in a NaCl solution with a conductivity of 400 ĄS cm-1 and pH 7 in 90 min. The maximum energy efficiency of ś0.1 g kWh-1 H2O2 was obtained. The surface of the coated electrodes, before and after applying of electrical discharges, was analysed by scanning electron microscopy. During the discharge process, the coating was destroyed and the formation of H2O2 decreased to 10% after discharging of nearly 35 h.
Sein, M. M.; Nasir, Z. Bin; Telgheder, U.; Schmidt, T. C.
Comparative Study on Effects of Armchair and Zigzag Graphene Electrodes on Ballistic Transport through C Atomic Chain
We performed theoretical investigations on electronic transport through carbon atomic chain (CAC) attached to relaxed armchair graphene (ACG) and zigzag graphene (ZZG) electrodes with the use of scattering state formalism implemented in PWSCF code of Quantum Espresso package. Our computed results show that the equilibrium conductance of CAC attached to ZZG-electrodes tends to zero over a wide energy range covering Fermi energy. Similar behavior of conductance is not seen when ZZG electrodes are replaced by ACG electrodes. CAC connected to ACG electrode is found better conducting as compared to CAC connected to ZZG electrode.
Ambavale, S. K.; Sharma, A. C.
Low-Temperature Study of a Sputtered Metal Film Gas-Supporting Electrode on Beta-Alumina Solid Electrolyte in the Sodium Heat Engine.
Low temperature (250(DEGREES)C-400(DEGREES)C) studies of sputter-deposited inert-metal film (Molybdenum) electrode processes in the Sodium Heat Engine, which employs a beta''-alumina solid electrolyte, showed that the cell current-voltage relationship could be resolved in terms of the cell polarizations. These include the polarizations due to charge transport and exchange, mass transport (diffusion) in the electrode, in-plane electronic conduction, and in -plane thermal gradients. The experimental techniques for studying these polarizations included current interruption, sodium vapor flux detection in vacuo, back-biasing, and in-plane voltage measurements. Two regimes of differing electrode behavior were studied. These were associated with the submonolayer sodium containing electrode, and the supermonolayer (quasi-liquid) sodium containing electrode. The condensation of quasi -liquid sodium permitted the charge exchange polarization to be distinguished from the overall polarization due to charge transport and exchange. The Butler-Volmer model of charge exchange was critically reviewed, but the data neither supported or denied the appropriateness of the Butler-Volmer model's application to solid electrolyte systems. Other electrode processes had different behavior in the submonolayer and supermonolayer regimes. The relationship between activity (vapor pressure) and concentration (coverage) in the electrode was found to be described by the Temkin isotherm. A novel method for measuring the in-plane sheet resistance was used. Ordinary methods are shown to be inaccurate due to the coupling between the electronic and ionic charge carriers. A perturbation method for the analysis of the variation in current density is presented. The adsorption of sodium in the electrode was studied using absorption and flow measurements along with back-bias measurements. From the analysis of this study emerged a physical model of the electrode. An intergranular phase may account for the strong adsorption and immobilization of several micromoles of sodium in the electrode. The ordered crystalline phase adsorbs about a tenth as much as the intergranular phase. Sodium transport through the electrode is modeled as taking place on the surface of the crystalline phase within the electrode.
Detwiler, Arthur Kyle, III
Pathological Alterations and Stress Responses near DBS Electrodes after MRI Scans at 7.0T, 3.0T and 1.5T: An In Vivo Comparative Study
Objective The purpose of this study was to investigate the pathological alterations and the stress responses around deep brain stimulation (DBS) electrodes after magnetic resonance imaging (MRI) scans at 7.0T, 3.0T and 1.5T. Materials and Methods DBS devices were stereotactically implanted into the brains of New Zealand rabbits, targeting the left nucleus ventralis posterior thalami, while on the right side, a puncture passage pointing to the same target was made. MRI scans at 7.0T, 3.0T and 1.5T were performed using transmit/receive head coils. The pathological alterations of the surrounding tissue were evaluated by hematoxylin and eosin staining (H&E staining) and transmission electron microscopy (TEM). The levels of the 70 kDa heat shock protein (HSP-70), Neuronal Nuclei (NeuN) and Caspase-3 were determined by western-blotting and quantitative polymerase chain reaction (QPCR) to assess the stress responses near the DBS electrodes. Results H&E staining and TEM showed that the injury around the DBS electrodes was featured by a central puncture passage with gradually weakened injurious alterations. Comparisons of the injury across the groups manifested similar pathological alterations near the DBS electrodes in each group. Moreover, western-blotting and QPCR assay showed that the level of HSP-70 was not elevated by MRI scans (p>0.05), and the levels of NeuN and Caspase-3 were equal in each group, regardless of the field strengths applied (p>0.05). Conclusions Based on these findings, it is reasonable to conclude that in this study the MRI scans at multiple levels failed to induce additional tissue injury around the DBS electrodes. These preliminary data furthered our understanding of MRI-related DBS heating and encouraged revisions of the current MRI guidelines for patients with DBS devices.
Meng, Da-Wei; Li, Shao-Wu; Liu, Huan-Guang; Li, Jun-Ju; Wang, Xiu; Zhang, Xin; Zhang, Jian-Guo
Laboratory performance comparison of IEEE 802.11 b, g point-to-point links: a case study
The importance of wireless communications, involving electronic devices, has been growing. Performance is a very important issue. Laboratory measurements are made about several performance aspects of Wi-Fi IEEE 802.11 b, g point-to-point links. A contribution is given to performance evaluation of this technology, using two types of access points from Enterasys Networks (RBTR2 and RBT-4102), and wireless routers from Linksys
J. A. R. Pacheco de Carvalho; P. A. J. Gomes; N. Marques; C. F. F. R. Pacheco; H. Veiga; A. D. Reis
Radiofrequency Ablation with a New Perfused-Cooled Electrode Using a Single Pump: An Experimental Study in Ex Vivo Bovine Liver
The purpose of this study was to assess the efficacy of a new perfused-cooled electrode that uses a single pump for creating a large ablation zone in explanted bovine liver. This was done by comparing with the radiofrequency (RF) ablation zones that were created with a monopolar cooled electrode to the RF ablation zones that were created by the new perfused-cooled electrode. We developed a new perfused-cooled electrode that uses a single pump by modifying a 17-gauge cooled electrode (Radionics) with a 2.5-cm outer metallic sheath (15-gauge) in order to allow use of the internal cooling water (5.85 % hypertonic saline) for the infused saline. Thirty ablation zones were created in explanted bovine livers (12-min ablation cycle; pulsed technique; 2000 mA, maximum) with three different regimens: group A, RF ablation with the 17-gauge cooled electrode; group B, RF ablation with the 15-gauge cooled electrode; group C, RF ablation with the perfused-cooled electrode. T2-weighted magnetic resonance (MR) imaging was obtained immediately after RF ablation for calculating volumes of the ablation zone. Following MR imaging, the ablation zones were excised and measured for transverse diameters and vertical diameters. The transverse diameter, vertical diameter, and the calculated volumes of the ablation zones on MR imaging were compared among the groups. Ablation zones created with the perfused-cooled electrode (group C) were significantly larger than those created with the 17-gauge cooled electrode (group A) and the 15-gauge cooled electrode (group B) according to the transverse diameter and vertical diameter on the gross specimens (p < 0.05): 3.6 {+-} 0.38 cm and 4.4 {+-} 0.20 cm in group A, 3.7 {+-} 0.08 cm and 4.6 {+-} 0.16 cm in group B, and 5.4 {+-} 0.65 cm and 6.0 {+-} 0.56 cm in group C, respectively. On the MR imaging, the calculated volumes of the ablation zones in group C were significantly larger than those in groups A and B (p < 0.05): 23.1 {+-} 8.7 cm{sup 3} in group A, 28.9 {+-} 5.7 cm{sup 3} in group B, and 80.0 {+-} 34 cm{sup 3} in group C, respectively. A new perfused-cooled electrode using a single pump could efficiently increase the size of the ablation zone in liver compared with a monopolar cooled electrode, and this was due to its simultaneous use of internal cooling and saline infusion.
Kim, Seung Kwon [Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Department of Radiology (Korea, Republic of)], E-mail: email@example.com; Seo, Jung Wook [Ilsan Paik Hospital, Inje University School of Medicine, Department of Diagnostic Radiology (Korea, Republic of)
Cermet electrode
Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.
Maskalick, Nicholas J. (Pittsburgh, PA)
Studies on CuTAPc-nanotube-modified electrodes as chemical sensors for NO.
Poly-copper tetraaminophthalocyanine (CuTAPc) nanotubes were successfully fabricated on porous alumina templates by electropolymerization. Their high surface area and simple preparation protocol made them potential candidates as the modification layer of electrodes for sensor application. High sensitivities and improved linear ranges were obtained through different measurements such as differential pulse voltammetry (DPV), differential potential amperometric (DPA) and electrochemical impedance spectroscopy (EIS). Detection limits as low as 10 nM were demonstrated in common voltammetric analysis with ultra-high response current in the microA range. PMID:19581690
Gu, Feng; Xu, Guo Qin; Ang, Siau Gek
An electrochemical and spectroelectrochemical study of pentacoordinated CoTPP on glassy carbon electrode
A glassy carbon electrode (GCE) modified with a monolayer of 4-aminothiophenol (4-ATP) and 5,10,15,20-meso-tetraphenylporphyrin cobalt (CoTPP) was prepared and used to examine the electroreduction of oxygen. Cyclic voltammetry showed that CoTPP chemisorbed on carbon via a 4-ATP monolayer (GCE\\/4-ATP¢CoTPP) displayed a catalytic effect similar to that of physisorbed CoTPP on a GCE (GCE\\/CoTPP). UV¢visible spectra recorded in solution and on
Hķlo'se H. De Paz; Christelle Mķdard; Mario Morin
Electrode immersion depth determination and control in electroslag remelting furnace
An apparatus and method for controlling an electroslag remelting furnace comprising adjusting electrode drive speed by an amount proportional to a difference between a metric of electrode immersion and a set point, monitoring impedance or voltage, and calculating the metric of electrode immersion depth based upon a predetermined characterization of electrode immersion depth as a function of impedance or voltage.
Melgaard, David K. (Albuquerque, NM); Beaman, Joseph J. (Austin, TX); Shelmidine, Gregory J. (Tijeras, NM)
Photoelectrochemical electrodes
The surface of a moderate band gap semiconductor such as p-type molybdenum sulfide is modified to contain an adherent film of charge mediating ionene polymer containing an electroactive unit such as bipyridimium. Electron transport between the electrode and the mediator film is favorable and photocorrosion and recombination processes are suppressed. Incorporation of particles of catalyst such as platinum within the film provides a reduction in overvoltage. The polymer film is readily deposited on the electrode surface and can be rendered stable by ionic or addition crosslinking. Catalyst can be predispersed in the polymer film or a salt can be impregnated into the film and reduced therein.
Williams, R. M.; Rembaum, A. (inventors)
Neutron Depth Profiling benchmarking and analysis of applications to lithium ion cell electrode and interfacial studies research
The role of the lithium ion cell is increasing with great intensity due to global concerns for the decreased use of fossil fuels as well as the growing popularity of portable electronics. With the dramatic increase in demand for these cells follows an outbreak of research to optimize the lithium ion cells in terms of safety, cost, and also performance. The work shown in this dissertation sets out to distinguish the role of Neutron Depth Profiling (NDP) in the expanding research of lithium ion cells. Lithium ions play the primary role in the performance of lithium ion batteries. Moving from anode to cathode, and cathode to anode, the lithium ions are constantly being disturbed during the cell's operation. The ability to accurately determine the lithium's behavior within the electrodes of the cell after different operating conditions is a powerful tool to better understand the faults and advantages of particular electrode compositions and cell designs. NDP has this ability through the profiling of 6Li. This research first validates the ability of The University of Texas NDP (UT-NDP) facility to accurately profile operated lithium ion cell electrodes to a precision within 2% over 10 mum for concentration values, and with a precision for depth measurements within 77 nm. The validation of the UT-NDP system is performed by comparing UT-NDP profiles to those from the NIST-NDP system, from the Secondary Ion Mass Spectrometry (SIMS) technique, and also from Monte Carlo n-Particle (MCNPX) code simulations. All of the comparisons confirmed that the UT-NDP facility is fully capable of providing accurate depth profiles of lithium ion cell electrodes in terms of depth, shape of distribution, and concentration. Following the validation studies, this research investigates three different areas of lithium ion cell research and provides analysis based on NDP results. The three areas of investigation include storage of cells at temperature, cycling of cells, and the charging of cells at different current rates. The results conclude that NDP is a valuable asset to the characterization of the Solid Electrolyte Interface (SEI) growth as a function of storage time. The NDP results were able to conclude that LiFePO4 cell anodes have a factor of 21 times slower rate of SEI growth than anodes from LiFePSO 4. This indicates that the capacity fade of the LiFePO4 cell will be less than that of the LiFePSO4 cell due to storage at 50░C. Furthermore, NDP was able to conclude that cycling of cells had little effect on the lithium concentration within the cathode materials. The lithium concentration was found to be uniform throughout the first 10 mum of the LiFePO4 and LiNi1/3Mn1/3Co1/3O 2 cathodes. These measurements agreed with the initial hypothesis. However, NDP analysis of cells charged at different current rates found that lithium was concentrating within the first 2 mum of the cathode's surface at the electrode-electrolyte interface. This was an unexpected conclusion, but the results also concluded that effect of the lithium concentrating near the surface is amplified by charging the cells at higher current rates. The ultimate conclusion of this research was that NDP is capable of providing invaluable insight to the behavior of lithium within the electrodes of lithium ion cells. It is the author's conclusion that NDP may be most useful in the investigation of SEI layers and their variation according to electrode composition, electrolyte compositions, and the conditions, such as temperature, to which the cells are exposed.
Whitney, Scott M.
The shape measurement of goaf is an important job in mine project. With the rapid development of the measuring equipment, 3D laser scanner, which makes the efficiency of traditional work being improved, is widely used in goaf. The final result of 3D laser scan is a huge collection of points. Although different measuring intervals will lead different point cloud density,
Yuanmin Fang; Jie CHEN; Yonghua XIA
A potentiometric study of the behavior of a carbon-freon (C, CF/sub 4/) electrode in fluorine-containing halide melts
It was previously noted that a graphite carbon electrode washed with gaseous carbon tetrafluoride should, at high temperatures, be reversible to fluoride ion in fluoride-containing melts. Its equilibrium potential should be determined by the partial pressure of the gaseous carbon tetrafluoride and by the activity of the fluoride ion in the melt. Since there was no previous information on specific studies in the electrochemical behavior of this carbon-freon electrode in halide melts, the authors conducted a potentiometric study of the electrochemical cells shown in this paper. In the experiments, the authors used analytical reagent-grade potassium fluoride (dihydrate), ultrapure sodium fluoride, and analytical reagent-grade lithium fluoride and ammonium fluoride. It is shown that the carbon-freon (C,CF/sub 4/) electrode is a reversible, second-order electrode in melts containing fluoride. Measurements using it give stable, reproducible results in fluoride or fluoride-chloride melts with a high fluoride content.
Nekrasov, V.N.; Cherepanov, V.B.; Ivanovskii, L.E.; Zaikov, Yu.P.
In-situ Spectroscopic and Structural Studies of Electrode Materials for Advanced Battery Applications
Techniques have been developed and implemented to gain insight into fundamental factors that affect the performance of electrodes in Li and Li-ion batteries and other energy storage devices. These include experimental strategies for monitoring the Raman scattering spectra of single microparticles of carbon and transition metal oxides as a function of their state of charge. Measurements were performed in electrolytes of direct relevance to Li and Li-Ion batteries both in the static and dynamic modes. In addition, novel strategies were devised for performing conventional experiments in ultrahigh vacuum environments under conditions which eliminate effects associated with presence of impurities, using ultrapure electrolytes, both of the polymeric and ionic liquid type that display no measurable vapor pressure. Also examined was the reactivity of conventional non aqueous solvent toward ultrapure Li films as monitored in ultrahigh vacuum with external reflection Fourier transform infrared spectroscopy. Also pursued were efforts toward developing applying Raman-scattering for monitoring the flow of charge of a real Li ion battery. Such time-resolved, spatially-resolved measurements are key to validating the results of theoretical simulations involving real electrode structures.
Daniel A Scherson
A Study of the Realization of the Melting and Freezing Points of Silver
Freezing and melting behaviour of our silver sample was studied using conventional procedures and also using conditions that were nearly adiabatic in order to obtain an equilibrium melting curve. The results indicate that the freezing point of a silver sample of six-9s purity is reproducible well within one millikelvin, provided that experimental conditions to realize it are reproduced. the melting range from 10% liquid to the liquidus point is about 28 mK, and the freezing point obtained following a supercool can be one to several mK below the liquidus point, depending upon the freezing technique used.
Ancsin, J.
a Study on the Height of the Corona Bright Points on FeXII Radiance Map
By registering SOHO EIT FeXII -19 5 nm coronal images with Kitt Peak magnetograms D A Falconer et al 1998 found that the brightest features in the network lanes which they called network coronal bright points had a highly significant coincidence with magnetic network neutral lines They found that most bright points sit on neutral lines in the network magnetic flux We further studied the height information of the bright points on the FeXII radiance map by comparing the individual pattern of the coronal bright points with the distribution of the top segments of the loops from the 3-D magnetic field force-free extrapolated from the photospheric magnetogram If we assume the source regions of the bright points are all on the top of the loops then the height of bright points of FeXII radiance is between 5Mm-10Mm
Tian, H.; Tu, C.-Y.; He, J.-S.; Marsch, E.
Satellite Power Systems (SPS) concept definition study: SPS point design definition update
The Rockwell International Photovoltaic Satellite Based Satellite Power System (SPS) Point Design as it is defined through July 1978 is described. The point design to be presented is the result of a series of trade studies. The data established during the period May through July 1978 is incorporated in this summary document. The system relationship of the total Satellite Power
G. M. Hanley
An electrochemical study on the human dental enamel with special reference to isoelectric point.
In an attempt to make a dynamic study of the isoelectric point and the chargeability of human dental enamel, an electrochemical approach was utilized. Zeta potential of three kinds of the enamel was measured by a streaming potential method. As a result, these isoelectric points could be decided. PMID:28340
Kambara, M; Asai, T; Kumasaki, M; Konishi, K
Sideropenic Anemia and Celiac Disease (One Study, Two Points of View)
Recent studies have pointed to the relationshipbetween iron deficiency anemia and celiac disease,although data on the prevalence of celiac disease inanemic patients have been conflicting, and there is no agreement on the best screening procedurefor CD in these patients. Our aims were to evaluate therelationship between anemia and celiac disease (CD) fromtwo different points of view Ś the hematology clinic
Antonio Carroccio; Emilio Iannitto; Francesca Cavataio; Giuseppe Montalto; Mario Tumminello; Piero Campagna; Maria Grazia Lipari; Alberto Notarbartolo; Giuseppe Iacono
A study of the copper electrode behavior in borax buffer solutions containing chloride ions and benzotriazole-type inhibitors by voltammetry and the photocurrent response method
The electrochemical behavior of the Cu electrode in borax buffer solutions containing chloride ions and benzotriazole (BTA)-type inhibitors was studied by voltammetry and the photocurrent response method. A p-type photoresponse was observed from the Cu electrode in the pure borax buffer solutions. However, an n-type photoresponse was observed in chloride-containing borax buffer solutions if the Cl? concentration exceeded 0.08%. The
Guo-Ding Zhou; Hua Shao; B. H. Loo
Reliability of cone beam computed tomography in scalar localization of the electrode array: a radio histological study.
Postoperative imaging plays a growing role in clinical studies concerning prognostic factors in cochlear implantation. Indeed, intracochlear position of the cochlear implant has recently been identified as a contributor in functional outcomes and radiological tools must be accurate enough to determine the final placement of the electrode array. The aim of our study was to validate cone beam computed tomography as a reliable technique for scalar localization of the electrode array. We performed therefore a temporal bone study on ten specimens that were implanted with a perimodiolar implant prototype. Cone beam reconstructions were performed and images were analyzed by two physicians both experienced in cochlear implant imaging, who determined the scalar localization of the implant. Temporal bones then underwent histological control to document this scalar localization and hypothetical intracochlear lesions. In four cases, a dislocation from scala tympani to scala vestibuli was suspected on cone beam reconstructions of the ascending part of the basal turn. In three of these four specimens, dislocation in pars ascendens was confirmed histologically. In the remaining temporal bone, histological analysis revealed an elevation with rupture of the basilar membrane. Histological assessment revealed spiral ligament tearing in another bone. We conclude that cone beam is a reliable tool to assess scalar localization of the selectrode array and may be used in future clinical studies. PMID:23536136
Marx, Mathieu; Risi, Frank; Escudķ, Bernard; Durmo, Irfan; James, Christopher; Lauwers, Frķdķric; Deguine, Olivier; Fraysse, Bernard
Improvements and artifact analysis in conductivity images using multiple internal electrodes.
Electrical impedance tomography is an attractive functional imaging method. It is currently limited in resolution and sensitivity due to the complexity of the inverse problem and the safety limits of introducing current. Recently, internal electrodes have been proposed for some clinical situations such as intensive care or RF ablation. This paper addresses the research question related to the benefit of one or more internal electrodes usage since these are invasive. Internal electrodes would be able to reduce the effect of insulating boundaries such as fat and bone and provide improved internal sensitivity. We found there was a measurable benefit with increased numbers of internal electrodes in saline tanks of a cylindrical and complex shape with up to two insulating boundary gel layers modeling fat and muscle. The internal electrodes provide increased sensitivity to internal changes, thereby increasing the amplitude response and improving resolution. However, they also present an additional challenge of increasing sensitivity to position and modeling errors. In comparison with previous work that used point sources for the internal electrodes, we found that it is important to use a detailed mesh of the internal electrodes with these voxels assigned to the conductivity of the internal electrode and its associated holder. A study of different internal electrode materials found that it is optimal to use a conductivity similar to the background. In the tank with a complex shape, the additional internal electrodes provided more robustness in a ventilation model of the lungs via air filled balloons. PMID:24845453
Farooq, Adnan; Tehrani, Joubin Nasehi; McEwan, Alistair Lee; Woo, Eung Je; Oh, Tong In
A study on prevention of an electric discharge at an extraction electrode of an electron cyclotron resonance ion source for cancer therapy.
A compact ECR ion source has utilized for carbon radiotherapy. In order to increase beam intensity with higher electric field at the extraction electrode and be better ion supply stability for long periods, electric geometry and surface conditions of an extraction electrode have been studied. Focusing attention on black deposited substances on the extraction electrode, which were observed around the extraction electrode after long-term use, the relation between black deposited substances and the electrical insulation property is investigated. The black deposited substances were inspected for the thickness of deposit, surface roughness, structural arrangement examined using Raman spectroscopy, and characteristics of electric discharge in a test bench, which was set up to simulate the ECR ion source. PMID:24593429
Kishii, Y; Kawasaki, S; Kitagawa, A; Muramatsu, M; Uchida, T
Experimental studies of X-pinch dynamics and X-ray emission point parameters.
New x-ray and spectroscopic diagnostics on the XP Pulser at Cornell (450 kA, 100 ns) have allowed quantitative measurements important for understanding the behavior of X-pinches. X-pinches produce intense x-ray radiation bursts from spots close to 1 ?m in diameter lasting about 0.5 ns. Using two parallel X-pinches, the radiation burst from each X-pinch was used to generate a magnified X-ray backlighter image of the other [1]. These images allow previously unobserved structure close to the time of x-ray burst emission to be seen. An intial stage is revealed in which a 300 ?m length z-pinch forms between the virtual electrodes of a "mini-diode" located at the crossing-point of the X-pinch. This z-pinch collapses rapidly into a series of narrow necks until an x-ray burst occurs from a spot inside the narrowest neck. After the x-ray burst, the z-pinch disappears quickly leaving only the mini-diode visible. Using a simple technique involving a reference mesh superimposed on the x-ray images, the x-ray emission point is located to within 10 ?m. Calibrated density measurements of Al x-pinches have been made using an Al step wedge in the film pack. K-spectra of H- and He-like Al, Ti, and Ni, as well as Ne-like Mo ions have been registered using FSSR spectrography with spherically bent mica crystals. These spectra yield estimates of Ne > 10^21 cm-3 and Te > 1 keV for the x-ray emission point. 1. T.A.Shelkovenko, S.A.Pikuz, A.R.Mingaleev and D.A.Hammer, Rev. Sci. Instrum., 70, 667 (1999).
Shelkovenko, T. A.; Pikuz, S. A.; Sinars, D. B.; Skobelev, I. Yu.; Hammer, D. A.; Greenly, J. B.; Dimant, Y. S.
Study of localized corrosion in aluminum alloys by the scanning reference electrode technique
Localized corrosion in 2219-T87 aluminum (Al) alloy, 2195 aluminum-lithium (Al-Li) alloy, and welded 2195 Al-Li alloy (4043 filler) have been investigated using the relatively new scanning reference electrode technique (SRET). Anodic sites are more frequent and of greater strength in the 2195 Al-Li alloy than in the 2219-T87 Al alloy, indicating a greater tendency toward pitting for the latter. However, the overall corrosion rates are about the same for these two alloys, as determined using the polarization resistance technique. In the welded 2195 Al-Li alloy, the weld bean is entirely cathodic, with rather strongly anodic heat affected zones (HAZ) bordering both sides, indicating a high probability of corrosion in the HAZ parallel to the weld bead.
Danford, M. D.
A study of calcium zincate as negative electrode materials for secondary batteries
The properties of calcium zincate as negative electrode materials for secondary batteries were examined by powder microelectrode, cyclic voltammetry, charge-discharge cycle measurements and X-ray diffraction (XRD) analysis. The results show that the cycleability of calcium zincate is obviously superior to that of ZnO and that of the mixture of ZnO and Ca(OH) 2 (the molar ratio of Zn:Ca=2:1). Calcium zincate forms zinc metal during the charging and exhibits an initial discharge capacity 230 mAh g -1. With the discharge cut-off voltage of 1.0 V, the discharge capacity of the experimental Zn/NiOOH cell does not decay much during 500 cycles, exhibiting good prospect for practical use.
Yu, Jingxian; Yang, Hanxi; Ai, Xinping; Zhu, Xiaoming
Chronoamperometric study of membrane electrode assembly operation in continuous flow photoelectrochemical water splitting.
Water splitting was performed in a photoelectrochemical cell (PEC) with water oxidation and hydrogen formation reactions in two separate compartments. A photoanode consisting of carbon paper loaded with TiO2 and a cathode made of Pt dispersed on carbon black spread also on carbon paper were fixed on both sides of a Nafion« membrane and electrically coupled via an external circuit. Anode and cathode compartments with serpentine flow field were operated either in the liquid or vapour phase. Electrical current was monitored with chronoamperometry and D2 formation from deuterated water using mass spectrometry. Mapping the photocurrent under a variety of reaction conditions enabled identification of the limiting factors related to proton and photocarrier transport and reaction product evacuation. This comprehensive research approach to the operation of a PEC will assist future optimisation of cell design and development of membrane electrode assemblies. PMID:23660956
Rongķ, Jan; Nijs, Dorien; Kerkhofs, Stef; Masschaele, Kasper; Martens, Johan A
Laser-induced photoelectrochemistry. Time-resolved coulostatic-flash studies of cadmium sulfide electrodes
Coulostatic-flash irradiation of semiconductor-liquid-junction cells with a pulsed laser source permits time-resolved measurements of photopotential transients in the nanosecond time domain. The transients observed with CdS electrodes are unusual in that they exhibit wavelength and solution dependence. Both fast (10 ns) and slow (approx. 100 ns) transients are observed in various aqueous electrolytes with irradiation near the band gap. Similar results in nonaqueous solution and with CdSe suggest that these transient photopotentials are related to processes within the semiconductor itself. A much slower (approx. 1 ..mu..s) transient is observed in polysulfide solution with irradiation in the ultraviolet; it is suggested that this transient photopotential is due to light absorption by polysulfide.
Richardson, J.H.; Perone, S.P.; Deutscher, S.B.
Microwave coagulation using a perfusion microwave electrode: Preliminary experimental study using ex vivo and in vivo liver.
To assess the coagulation capability of a perfusion microwave electrode (PME) as a key component of microwave coagulation therapy, a preliminary experimental study was performed using ex vivo and in vivo livers. For a microwave electrode, a PME was employed. Using a PME, saline was passed through the electrode and injected continuously into the target tissue. Using an ex vivo bovine liver, the range of tissue coagulation was measured for various volumes of infused saline and microwave outputs. Using an in vivo porcine liver, the efficiency of coagulation by a PME was compared with that of radiofrequency ablation (RFA) using a cool-tip needle. In an ex vivo bovine liver, the range of tissue coagulation increased as the flow rate of saline increased. In the in vivo porcine liver, the range of coagulation was similar to that found in the ex vivo bovine liver. With a PME under conditions of a microwave output of 80 W, a flow rate of 3 ml/min and irradiation time of 5 min, the range of coagulation was 44.8▒2.8 mm [maximum vertical diameter: (a)] x 31.2▒2.4 mm [maximum transverse diameter: (b)]. The range of RFA (cool-tip needle) at 12 min was 46.0▒2.0 mm (a) x 30.2▒2.0 mm (b). With only 5 min of microwave irradiation, the use of a PME enabled induction of the same range of coagulation that was obtainable by RFA for 12 min. In comparison with microwave coagulation without saline infusion, the use of a PME made it possible to extend the range of tissue coagulation to a range equal to that of RFA in a short time. Microwave coagulation using a PME may be one of the suitable tissue coagulation systems for local ablation treatment. PMID:22969871
Umehara, Hideto; Seki, Toshihito; Inokuchi, Ryosuke; Tamai, Toru; Kawamura, Rinako; Asayama, Toshiki; Ikeda, Kozo; Okazaki, Kazuichi
Methodic aspects of studies of point defects interaction with implanted impurity atoms by channeling methods.
Methodic of studies of point defects interactions with implanted impurity atoms by channeling methods and mathematical modeling are described. Location of implanted Xe atoms in Ni monocrystal lattice, as well as their interaction with radiation defects, k...
I. M. Neklyudov G. D. Tolstolutskaya I. G. Marchenko V. F. Rybalko I. Kopanets
Analysis of non-point and point source pollution in China: case study in Shima Watershed in Guangdong Province
China economy has been rapidly increased since 1978. Rapid economic growth led to fast growth of fertilizer and pesticide consumption. A significant portion of fertilizers and pesticides entered the water and caused water quality degradation. At the same time, rapid economic growth also caused more and more point source pollution discharge into the water. Eutrophication has become a major threat to the water bodies. Worsening environment problems forced governments to take measures to control water pollution. We extracted land cover from Landsat TM images; calculated point source pollution with export coefficient method; then SWAT model was run to simulate non-point source pollution. We found that the annual TP loads from industry pollution into rivers are 115.0 t in the entire watershed. Average annual TP loads from each sub-basin ranged from 0 to 189.4 ton. Higher TP loads of each basin from livestock and human living mainly occurs in the areas where they are far from large towns or cities and the TP loads from industry are relatively low. Mean annual TP loads that delivered to the streams was 246.4 tons and the highest TP loads occurred in north part of this area, and the lowest TP loads is mainly distributed in middle part. Therefore, point source pollution has much high proportion in this area and governments should take measures to control point source pollution.
Fang, Huaiyang; Lu, Qingshui; Gao, Zhiqiang; Shi, Runhe; Gao, Wei
Human Cell-Based Micro Electrode Array Platform for Studying Neurotoxicity
At present, most of the neurotoxicological analyses are based on in vitro and in vivo models utilizing animal cells or animal models. In addition, the used in vitro models are mostly based on molecular biological end-point analyses. Thus, for neurotoxicological screening, human cell-based analysis platforms in which the functional neuronal networks responses for various neurotoxicants can be also detected real-time are highly needed. Microelectrode array (MEA) is a method which enables the measurement of functional activity of neuronal cell networks in vitro for long periods of time. Here, we utilize MEA to study the neurotoxicity of methyl mercury chloride (MeHgCl, concentrations 0.5¢500?nM) to human embryonic stem cell (hESC)-derived neuronal cell networks exhibiting spontaneous electrical activity. The neuronal cell cultures were matured on MEAs into networks expressing spontaneous spike train-like activity before exposing the cells to MeHgCl for 72?h. MEA measurements were performed acutely and 24, 48, and 72?h after the onset of the exposure. Finally, exposed cells were analyzed with traditional molecular biological methods for cell proliferation, cell survival, and gene and protein expression. Our results show that 500?nM MeHgCl decreases the electrical signaling and alters the pharmacologic response of hESC-derived neuronal networks in delayed manner whereas effects can not be detected with qRT-PCR, immunostainings, or proliferation measurements. Thus, we conclude that human cell-based MEA platform is a sensitive online method for neurotoxicological screening.
Yla-Outinen, Laura; Heikkila, Juha; Skottman, Heli; Suuronen, Riitta; Aanismaa, Riikka; Narkilahti, Susanna
Study of C-coated LiFe0.33Mn0.67PO4 as positive electrode material for Li-ion batteries
Commercial C-LiFe0.33Mn0.67PO4 positive electrode material has been investigated by 57Fe M÷ssbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. 57Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe0.33Mn0.67PO4/Li cells after 50 cycles at 60 ░C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both 57Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances.
Perea, A.; Castro, L.; Aldon, L.; Stievano, L.; DedryvĶre, R.; Gonbeau, D.; Tran, N.; Nuspl, G.; Brķger, J.; Tessier, C.
Perceptual saliency of points along the contour of everyday objects: a large-scale study.
The aim of this large-scale study was to find out which points along the contour of a shape are most salient and why. Many subjects (N=161) were asked to mark salient points on contour stimuli, derived from a large set of line drawings of everyday objects (N=260). The database of more than 200,000 marked points was analyzed extensively to test the hypothesis, first formulated by Attneave (1954), that curvature extrema are most salient. This hypothesis was confirmed by the data: Highly salient points are usually very close to strong curvature extrema (positive maxima and negative minima). However, perceptual saliency of points along the contour is determined by more factors than just local absolute curvature. This was confirmed by an extensive correlational analysis of perceptual saliency in relation to ten different stimulus factors. A point is more salient when the two line segments connecting it with its two neighboring salient points make a sharp turning angle and when the 2-D part defined by the triplet of salient points is less compact and sticks out more. PMID:18306960
De Winter, Joeri; Wagemans, Johan
A comparative study for the estimation of geodetic point velocity by artificial neural networks
Space geodesy era provides velocity information which results in the positioning of geodetic points by considering the time evolution. The geodetic point positions on the Earth's surface change over time due to plate tectonics, and these changes have to be accounted for geodetic purposes. The velocity field of geodetic network is determined from GPS sessions. Velocities of the new structured geodetic points within the geodetic network are estimated from this velocity field by the interpolation methods. In this study, the utility of Artificial Neural Networks (ANN) widely applied in diverse fields of science is investigated in order to estimate the geodetic point velocities. Back Propagation Artificial Neural Network (BPANN) and Radial Basis Function Neural Network (RBFNN) are used to estimate the geodetic point velocities. In order to evaluate the performance of ANNs, the velocities are also interpolated by Kriging (KRIG) method. The results are compared in terms of the root mean square error (RMSE) over five different geodetic networks. It was concluded that the estimation of geodetic point velocity by BPANN is more effective and accurate than by KRIG when the points to be estimated are more than the points known.
Yilmaz, M.; Gullu, M.
The voltammetric study of 2-mercapto-5-phenylammino-1,3,4-thiadiazole using carbon paste electrodes.
A rapid and accurate voltammetric method for the quantitative determination of 2-mercapto-5-phenylammino-1,3,4-thiadiazole (MPATD) with carbon paste electrodes (CPE) has been developed. The study was made by cyclic voltammetry between -0.4 and +0.6 V with 50 mV s(-1) sweep rate in aqueous solution. After successive oxidation/reduction cycles we found a total oxidation of MPATD at +0.45 V. As the compound is oxidated, the reduction current peak increases at +0.13 V, indicating an irreversible process. Following only the oxidation process in the -0.1 to +0.6 V range, we investigated the optimum scan rates at different current densities and pH values (realised with buffers, pH between 1.0 and 10.0) with CPE versus Ag/AgCl reference electrode using linear sweep voltammetry. We found a good linear relation between the current peak height and concentration in a 2.5 x 10(-9)-1.25 x 10(-7) mol ml(-1). This method allows the quantitative detection of the MPATD as it or from dosage forms and biological media. PMID:9863945
S?ndulescu, R; Marian, I; Mirel, S; Oprean, R; Roman, L
Electrochemical behavior of sodium azide at Pt and Au electrodes in sodium sulfate electrolyte: A DEMS study
Azides are widely used in chemical technology for a large variety of applications, such as detonators (Pb(N{sub 3}){sub 2}), getters in electric discharge tubes, anticorrosive agents, or additives for the production of foam rubber. The electro-oxidation and -reduction of sodium azide at porous painted platinum and gold electrodes was studied using the multipurpose electrochemical mass spectrometry (MPEMS) which was operated in the differential electrochemical mass spectrometry (DEMS) mode. The platinum electrode was found to be active for electro-oxidation as well as for electroreduction. Above 0.3 V vs. Hg/Hg{sub 2}SO{sub 4}, azide is oxidized to give N{sub 2}, NO, NO{sub 2}, and N{sub 2}O. Reduction of azide takes place below {minus}0.9 V forming N{sub 2}, N{sub 2}H{sub 4}, and possibly NH{sub 3}. In contrast to platinum, gold showed only activity for the electro-oxidation of azide leading to the formation of N{sub 2}, NO, NO{sub 2}, and N{sub 2}O above 0.5 V. Evidence for a reaction without evolution of volatile products was also found taking place above 0.1 V. A reaction mechanism is discussed emphasizing the role of adsorbed hydrogen and oxygen.
Dalmia, A.; Wasmus, S.; Savinell, R.F.; Liu, C.C. [Case Western Reserve Univ., Cleveland, OH (United States)
In situ PM-IRRAS studies of an archaea analogue thiolipid assembled on a au(111) electrode surface.
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) has been applied to determine the conformation, orientation, and hydration of a monolayer of 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-dl-alpha-lipoic acid ester (DPTL) self-assembled at a gold electrode surface. This Archaea analogue thiolipid has been recently employed to build tethered lipid bilayers. By synthesizing DPT(d16)L, a DPTL molecule with a deuterium substituted tetraethylene glycol spacer, it was possible to differentiate the C-H stretch vibrations of the phytanyl chains from the tetraethylene glycol spacer and acquire the characteristic IR spectra for the chains, spacer, and lipoic acid headgroup separately. Our results show that the structure of the monolayer displays remarkable stability in a broad range of electrode potentials and that the phytanyl chains remain in a liquid crystalline state. The tetraethylene glycol chains are coiled, and the IR spectrum for this region shows that it is in the disordered state. The most significant result of this study is the information that in contrast to expectations the spacer region is poorly hydrated. Our results have implications for the design of a tethered lipid membrane based on this thiolipid. PMID:19499931
Leitch, Jay; Kunze, Julia; Goddard, John D; Schwan, Adrian L; Faragher, Robert J; Naumann, Renate; Knoll, Wolfgang; Dutcher, John R; Lipkowski, Jacek
Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes
Background We aimed to investigate the effect of cell-cell dipole interactions in the equilibrium distributions in dielectrophoretic devices. Methods We used a three dimensional coupled Monte Carlo-Poisson method to theoretically study the final distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. The simulated distributions have been compared with experimental ones observed in the case of MDA-MB-231 cells in the same operating conditions. Results The real and simulated distributions are consistent. In both cases the cells distribution near the electrodes is dominated by cell-cell dipole interactions which generate long chains. Conclusions The agreement between real and simulated cellsÆ distributions demonstrate the methodÆs reliability. The distribution are dominated by cell-cell dipole interactions even at low density regimes (105 cell/ml). An improved estimate for the density threshold governing the interaction free regime is suggested.
Strain-based in-situ study of anion and cation insertion into porous carbon electrodes with different pore sizes
The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in-situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Also, the influence of potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into experimental results, which is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.
Black, Jennifer M [ORNL] [ORNL; Feng, Guang [ORNL] [ORNL; Fulvio, Pasquale F [ORNL] [ORNL; Hillesheim, Patrick C [ORNL] [ORNL; Dai, Sheng [ORNL] [ORNL; Gogotsi, Yury G. [Drexel University] [Drexel University; Cummings, Peter T [ORNL] [ORNL; Kalinin, Sergei V [ORNL] [ORNL; Balke, Nina [ORNL] [ORNL
Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.
Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes. The aim was to study how the electrode size and preparation of the electrode (dry electrode/wet electrode/electrode covered with hydrogel membrane) affect the measurement noise, and the skin-electrode impedance. The measurement noise and skin-electrode impedance were determined from surface biopotential measurements. These preliminary results indicate that noise level increases as the electrode size decreases. The noise level is high in dry textile electrodes, as expected. Yet, the noise level of wet textile electrodes is quite low and similar to that of textile electrodes covered with hydrogel. Hydrogel does not seem to improve noise properties, however it may have effects on movement artifacts. Thus, it is feasible to use textile embedded sensors in physiological monitoring applications when moistening or hydrogel is applied. PMID:17946734
Puurtinen, Merja M; Komulainen, Satu M; Kauppinen, Pasi K; Malmivuo, Jaakko A V; Hyttinen, Jari A K
Studies on Supercapacitor Electrode Material from Activated Lignin-Derived Mesoporous Carbon
We synthesized mesoporous carbon from pre-cross-linked lignin gel impregnated with a surfactant as the pore-forming agent, and then activated the carbon through physical and chemical methods to obtain activated mesoporous carbon. The activated mesoporous carbons exhibited 1.5- to 6-fold increases in porosity with a maximum BET specific surface area of 1148 m2/g and a pore volume of 1.0 cm3/g. Slow physical activation helped retain dominant mesoporosity; however, aggressive chemical activation caused some loss of the mesopore volume fraction. Plots of cyclic voltammetric data with the capacitor electrode made from these carbons showed an almost rectangular curve depicting the behavior of ideal double-layer capacitance. Although the pristine mesoporous carbon exhibited the same range of surface-area-based capacitance as that of other known carbon-based supercapacitors, activation decreased the surface-area-based specific capacitance and increased the gravimetric-specific capacitance of the mesoporous carbons. Surface activation lowered bulk density and electrical conductivity. Warburg impedance as a vertical tail in the lower frequency domain of Nyquist plots supported good supercapacitor behavior for the activated mesoporous carbons. Our work demonstrated that biomass-derived mesoporous carbon materials continue to show potential for use in specific electrochemical applications.
Saha, Dipendu [ORNL] [ORNL; Li, Yunchao [ORNL] [ORNL; Bi, Zhonghe [ORNL] [ORNL; Chen, Jihua [ORNL] [ORNL; Keum, Jong Kahk [ORNL] [ORNL; Hensley, Dale K [ORNL] [ORNL; Grappe, Hippolyte A. [Oak Ridge Institute for Science and Education (ORISE)] [Oak Ridge Institute for Science and Education (ORISE); Meyer III, Harry M [ORNL] [ORNL; Dai, Sheng [ORNL] [ORNL; Paranthaman, Mariappan Parans [ORNL] [ORNL; Naskar, Amit K [ORNL] [ORNL
Electrocatalytic studies of covalently immobilized metal tetra-amino phthalocyanines onto derivatized screen-printed gold electrodes
Metal tetra-amino phthalocyanine complexes (MTAPc; where M is Co or Mn) were immobilized on screen-printed gold electrodes\\u000a pre-modified with monolayers of benzylamino groups. The functionalized electrodes were then activated using benzene-1,4-dicarbaldehyde\\u000a as a linker before MTAPc complexes were immobilized. The surface coverages for the modified electrodes confirmed the perpendicular\\u000a orientation of the MTAPcs. The apparent electron transfer constant (kapp) for
Philani Mashazi; Tebello Nyokong
The electrocatalytic activity of Prussian blue in hydrogen peroxide reduction studied using a wall-jet electrode with continuous flow
The kinetics of hydrogen peroxide reduction on electrodes modified with specially deposited Prussian blue were investigated using a wall-jet cell with continuous flow. For this aim a new semi-empirical model for the diffusion limited current distribution holding for narrow wall-jet electrodes was described. In spite of the non-uniform accessibility of the wall-jet electrode surface in terms of mass transport the
Arkady A. Karyakin; Elena E. Karyakina; Lo Gorton
Study of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries
Graphite and nano-silicon-based negative electrodes in lithium-ion batteries with low binder content were evaluated. The effectiveness of styrene butadiene rubber (SBR) and various types of cellulose containing electrodes were compared to standard electrodes containing PVdF as binder. The cycling performance of lithium-based half cells in EC:DMC (1:1), 1M LiPF6 shows that styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (Na-CMC), or
H. Buqa; M. Holzapfel; F. Krumeich; C. Veit; P. Novßk
Accelerating rate calorimetry studies of the reactions between ionic liquids and charged lithium ion battery electrode materials
Using accelerating rate calorimetry (ARC), the reactivity between six ionic liquids (with and without added LiPF6) and charged electrode materials is compared to the reactivity of standard carbonate-based solvents and electrolytes with the same electrode materials. The charged electrode materials used were Li1Si, Li7Ti4O12 and Li0.45CoO2. The experiments showed that not all ionic liquids are safer than conventional electrolytes\\/solvents. Of
Yadong Wang; K. Zaghib; A. Guerfi; Fernanda F. C. Bazito; Roberto M. Torresi; J. R. Dahn
Voltammetric study of interaction of Co(phen) 3 3+ with DNA at gold nanoparticle self-assembly electrode
Modifying electrode surfaces on the molecule scale allow developing new electrochemical biosensors. A new strategy for the immobilization of calf thymus DNA on the surface of gold nanoparticles which are co-immobilized at a gold electrode through 4,4?-bis(methanethiol) biphenyl (MTP) molecule by assembly process is demonstrated. The DNA modified electrode was incubated in Co(phen)33+ solution of an aqueous buffer or an
Baokang Jin; Xueping Ji; Toshio Nakamura
Mediated Knowledge: Reexamining Six Classic Community Studies from a Woman's Point of View
Six studies published in the 1940s have become classics in the analysis of rural community and change: the community stability/instability studies. One of their less recognized features is that their analyses included women. This article revisits these six studies, but from a different vantage point. As a socially constructed enterprise, theģ
Zimmerman, Julie N.
A study of impulsive multiterm fractional differential equations with single and multiple base points and applications.
We discuss the existence and uniqueness of solutions for initial value problems of nonlinear singular multiterm impulsive Caputo type fractional differential equations on the half line. Our study includes the cases for a single base point fractional differential equation as well as multiple base points fractional differential equation. The asymptotic behavior of solutions for the problems is also investigated. We demonstrate the utility of our work by applying the main results to fractional-order logistic models. PMID:24578623
Liu, Yuji; Ahmad, Bashir
A Study of Impulsive Multiterm Fractional Differential Equations with Single and Multiple Base Points and Applications
We discuss the existence and uniqueness of solutions for initial value problems of nonlinear singular multiterm impulsive Caputo type fractional differential equations on the half line. Our study includes the cases for a single base point fractional differential equation as well as multiple base points fractional differential equation. The asymptotic behavior of solutions for the problems is also investigated. We demonstrate the utility of our work by applying the main results to fractional-order logistic models.
First-principles studies of intrinsic point defects in magnesium silicide
We have studied intrinsic point defects in magnesium silicide, Mg2Si, by density-functional theory. Evaluating the formation energies of point defects, we show that n-type electric conductivity of Mg2Si originates from formations of positively charged Mg ions at interstitial sites, regardless of the chemical composition in crystal growth. Moreover, we have calculated the Born effective charge tensors and the valence charge
Akihiko Kato; Takeshi Yagi; Naoto Fukusako
Readout electrode assembly for measuring biological impedance
The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.
Montgomery, L. D.; Moody, D. L., Jr. (inventors)
Use of voltammetric solid-state (micro)electrodes for studying biogeochemical processes: Laboratory measurements to real time measurements with an in situ electrochemical analyzer (ISEA)
Solid-state voltammetric (micro)electrodes have been used in a variety of environments to study biogeochemical processes. Here we show the wealth of information that has been obtained in the study of sediments, microbial mats, cultures and the water column including hydrothermal vents. Voltammetric analyzers have been developed to function with operator guidance and in unattended mode for temporal studies with an
George W. Luther; Brian T. Glazer; Shufen Ma; Robert E. Trouwborst; Tommy S. Moore; Edouard Metzger; Chareonkwan Kraiya; Tim J. Waite; Gregory Druschel; Bj°rn Sundby; Martial Taillefert; Donald B. Nuzzio; Timothy M. Shank; Brent L. Lewis; Paul J. Brendel
A minimal set of electrodes for motor imagery BCI to control an assistive device in chronic stroke subjects: a multi-session study.
The brain-computer interface (BCI) system has been developed to assist people with motor disability. To make the system more user-friendly, it is a challenge to reduce the electrode preparation time and have a good reliability. This study aims to find a minimal set of electrodes for an individual stroke subject for motor imagery to control an assistive device using functional electrical stimulation for 20 sessions with accuracy higher than 90%. The characteristics of this minimal electrode set were evaluated with two popular algorithms: Fisher's criterion and support-vector machine recursive feature elimination (SVM-RFE). The number of calibration sessions for channel selection required for robust control of these 20 sessions was also investigated. Five chronic stroke patients were recruited for the study. Our results suggested that the number of calibration sessions for channel selection did not have a significant effect on the classification accuracy. A performance index devised in this study showed that one training day with 12 electrodes using the SVM-RFE method achieved the best balance between the number of electrodes and accuracy in the 20-session data. Generally, 8-36 channels were required to maintain accuracy higher than 90% in 20 BCI training sessions for chronic stroke patients. PMID:21984520
Tam, Wing-Kin; Tong, Kai-yu; Meng, Fei; Gao, Shangkai
Modeling of Impedance of Porous Electrodes
Porous electrodes are very important in practical applications of electrocatalysis, where an increase in the real surface area leads to an increase in catalytic activity. Porous electrodes are used in gas evolution (water electrolysis, hydrogen and oxygen evolution, chlorine evolution), electrocatalytic hydrogenation or oxidation of organic compounds, in batteries, fuel cells, etc. Good knowledge of the porous electrode theory permits for the construction of the electrodes with optimal utilization of the active electrode material. The porous electrode model was first developed by several authors for dc conditions (1-6) and later applied to the impedance studies.
Lasia, Andrzej
Theoretical study of reactions at the electrode-electrolyte interface. Progress report, August 1, 1991--January 31, 1993
Study of the voltammetric behavior of jatrorrhizine and its sensitive determination at electrochemical pretreatment glassy carbon electrode.
A simple, inexpensive and highly sensitive electrochemical method for the determination of jatrorrhizine was developed using an electrochemically pretreated glassy carbon electrode (EPGCE). The electrochemical behavior of jatrorrhizine was systematically investigated in detail and some kinetic parameters were calculated for the first time. A reasonable reaction mechanism of jatrorrhizine on the EPGCE was also discussed and proposed, which could be a reference for the pharmacological action of jatrorrhizine in clinical study. And the first electroanalytical method of jatrorrhizine was established with a wide linear range from 7.0ū10(-8) to 2.0ū10(-5)mol L(-1) and a low detection limit of 5.0ū10(-8)mol L(-1). The proposed method was successfully applied in determination of jatrorrhizine in pharmaceutical sample, Tinospora capillipes Gagnep (a traditional Chinese medicine), with satisfactory results. PMID:24881532
Ye, Zhuo; Li, Yinfeng; Wen, Jianguo; Li, Kunjing; Ye, Baoxian
Experimental and theoretical study of the efficiency of a three-electrode reactor for the removal of NO
An experimental and theoretical study is presented on the efficiency of the removal of NO in a N2 atmosphere in a novel three-electrode reactor. This reactor combines a dielectric-barrier discharge with a corona discharge, designed to enhance streamer propagation in a relatively large region. Experimentally, the reactor has a good energy yield for the removal of NO, as compared with other discharge methods. A theoretical model is developed for the production of reactive species in the streamers by different reactions that allow to relate simple electrical measurements with the reactor efficiency. This theoretical efficiency resulted in good agreement with the experimental one, validating the model and allowing the evaluation of the contribution of different reactions involved in NO removal.
Gallego, J. L.; Minotti, F.; Grondona, D.
Electrochemical studies of thin films of conducting polymers and conducting polymer composites deposited on metal and semiconductor electrodes
Electrochemical studies indicate that poly(Isothianaphthene) or PITN, can be p-doped only. Electrochemical properties of PITN and Nafion-PITN in acetonitrile solutions containing tetra-phenyl Phosphonium chloride as supporting electrolyte are compared. In both cases, the electrochemical behavior of thin films are different from that of thick films. In addition, Nafion does not seem to alter the electrochemical properties of PITN. Cyclic voltammetric and chronocoulometric measurements were made to compute the diffusion coefficient of the counter ions. Electrochemical behavior of both PITN and Nafion-PITN in acetonitrile solution containing different counter ions are described. PITN, when electrochemically deposited, apparently neither passivates surface states present nor forms ohmic contacts with p-Si or p(+)Si single-crystal electrodes.
Nagasubramanian, G.; Di Stefano, S.; Moacanin, J.
Silver Oxide Electrode Processes.
A cyclic voltammetric study was made of the silver electrode in KOH solutions at room temperature. The presence of carbonate ion has no noticeable effect on the current. The results obtained can quite readily be interpreted in terms of Ag, Ag2O, and AgO a...
T. P. Dirkse
Poly(3-methylthiophene)/palladium sub-micro-modified sensor electrode. Part II: Voltammetric and EIS studies, and analysis of catecholamine neurotransmitters, ascorbic acid and acetaminophen.
Promising voltammetric sensors based on the modification of Pt and poly(3-methylthiophene) (PMT) electrodes with Pd nanoparticles were achieved for the determination of catecholamine neurotransmitters, ascorbic acid and acetaminophen. Electrochemistry of the indicated compounds was studied at these electrodes and interesting electrocatalytic effects were found. Furthermore, simple, easily prepared one electrochemical step Pd-modified Pt electrode (Pt/Pd) is reported for the first time. Cyclic voltammetry (CV) and chronocoulometry (CC) were used for the determination of the apparent diffusion coefficients in different electrolytes at these electrodes and the values are in the range from 10(-4) to 10(-5)cm(2)s(-1). Furthermore, it was found that the method of polymer formation had a substantial effect on the synergism between the polymer film and the loaded metal particles towards the oxidation of dopamine (DA) in different supporting electrolytes. This was confirmed by the CV, CC and EIS (electrochemical impedance spectroscopy) as well as SEM (Scanning Electron Microscopy) results. Pt and PMT electrodes modified with Pd nanoparticles showed excellent results for the simultaneous determination of tertiary and quaternary mixtures of the studied compounds. PMID:19576424
Atta, Nada F; El-Kady, Maher F
We performed theoretical investigations on electronic transport through carbon atomic chain (CAC) attached to relaxed armchair graphene (ACG) and zigzag graphene (ZZG) electrodes with the use of scattering state formalism implemented in PWSCF code of Quantum Espresso package. Our computed results show that the equilibrium conductance of CAC attached to ZZG-electrodes tends to zero over a wide energy range covering
S. K. Ambavale; A. C. Sharma
Electrochemical and surface studies of carbon dioxide reduction to methane and ethylene at copper electrodes in aqueous solutions
The authors describe the electrochemical reduction of COŌ to CHŌ and CŌHŌ in aqueous alkaline solutions at Cu electrodes. The current at the Cu electrodes and the rate of hydrocarbon formation were monitored as a function of time over a temperature range from 0 to 48%C. Solutions of formate, formaldehyde, and methanol, possible intermediates in the reduction process, were also
David W. DeWulf; T. Jin; A. J. Bard
Electrochemically induced surface modifications of boron-doped diamond electrodes: an X-ray photoelectron spectroscopy study
The activity of diamond electrodes depends on the chemical state of the diamond surface, and the present work is focussed on understanding how chemical changes either produced in situ electrochemically, or by ex situ plasma treatments, influence the electrochemical properties. Conductive boron-doped diamond electrodes were produced by depositing adherent boron-doped diamond films on tungsten substrates using a hot filament reactor
Christiaan H. Goeting; Frank Marken; Aurora Gutiķrrez-Sosa; Richard G. Compton; John S. Foord
A comparative study of carbon felt and activated carbon based electrodes for sodium polysulfide\\/bromine redox flow battery
Carbon felt (CF) and activated carbon (AC) based electrodes for sodium polysulfide\\/bromine redox flow battery (PSB) were prepared and compared with a laboratory scale PSB flow cell in terms of structure and application performances. The structural properties of the two types of electrodes were characterized by filamentary analog and BET analysis, respectively. Catalyst coating, discharge behavior analysis and thermogravimetric analysis-mass
Hantao Zhou; Huamin Zhang; Ping Zhao; Baolian Yi
West Point Study: Occurrence of Coronary Artery Disease After 34 Years.
This report reviews the current status of the West Point Study and addresses the prediction of risk of coronary artery disease (CAD) based on cholesterol levels measured at various times during the study. Subjects were grouped into quintiles by their risk...
D. A. Clark W. G. Jackson G. D. Tolan J. R. Hickman
Single camera photogrammetry system for EEG electrode identification and localization.
In this study, photogrammetric coordinate measurement and color-based identification of EEG electrode positions on the human head are simultaneously implemented. A rotating, 2MP digital camera about 20 cm above the subject's head is used and the images are acquired at predefined stop points separated azimuthally at equal angular displacements. In order to realize full automation, the electrodes have been labeled by colored circular markers and an electrode recognition algorithm has been developed. The proposed method has been tested by using a plastic head phantom carrying 25 electrode markers. Electrode locations have been determined while incorporating three different methods: (i) the proposed photogrammetric method, (ii) conventional 3D radiofrequency (RF) digitizer, and (iii) coordinate measurement machine having about 6.5 mum accuracy. It is found that the proposed system automatically identifies electrodes and localizes them with a maximum error of 0.77 mm. It is suggested that this method may be used in EEG source localization applications in the human brain. PMID:20186487
Baysal, U?ur; Seng³l, G÷khan
Applications of infrared spectroscopy in the study of catalytic reactions and related adsorption phenomena on single crystal electrodes: connections between electrochemical and ultra high vacuum surface science
The aim of this review is to describe applications of infrared spectroscopy in the study of catalytic reactions and related adsorption phenomena at single crystal electrodes. The majority of work in this area has focused on reactions that form adsorbed CO as an intermediate, such as the electrochemical oxidation pathways of CO and several small organic molecules. In particular, studies
Carol Korzeniewski; Mark W. Severson
Cryogenic Propellant Storage and Transfer Technology Demonstration: Prephase A Government Point-of-Departure Concept Study
The primary purpose of this study was to define a point-of-departure prephase A mission concept for the cryogenic propellant storage and transfer technology demonstration mission to be conducted by the NASA Office of the Chief Technologist (OCT). The mission concept includes identification of the cryogenic propellant management technologies to be demonstrated, definition of a representative mission timeline, and definition of a viable flight system design concept. The resulting mission concept will serve as a point of departure for evaluating alternative mission concepts and synthesizing the results of industry- defined mission concepts developed under the OCT contracted studies
Mulqueen, J. A.; Addona, B. M.; Gwaltney, D. A.; Holt, K. A.; Hopkins, R. C.; Matis, J. A.; McRight, P. S.; Popp, C. G.; Sutherlin, S. G.; Thomas, H. D.; Baysinger, M. F.; Maples, C. D.; Capizzo, P. D.; Fabisinski, L. L.; Hornsby, L. S.; Percy, T. K.; Thomas, S. D.
Studies on the stripping voltammetric determination and speciation of chromium at a rotating-disc bismuth film electrode.
An adsorptive stripping voltammetric protocol coupled with a rotating-disc bismuth film electrode for the determination and speciation of chromium (III) and chromium (VI) in the presence of diethylenetriaminepentaacetic acid (DTPA) is presented. The developed methodology involves a mass-transport controlled preconcentration step, during which a Cr(III)-DTPA complex is adsorbed onto a pre-plated rotating-disc bismuth film electrode held at -0.4V, followed by a reductive square wave stripping scan. At -1.07 V vs. Ag/AgCl, a peak is recorded due to the catalytic reduction of Cr(III)-DTPA to Cr(II)-DTPA. As a result of different chemical behaviours of Cr(III) and Cr(VI) in the presence of DTPA, the corresponding voltammetric signals presented different stabilities in time. A univariate optimization study was performed with several experimental parameters as variables. For Cr(VI) and total chromium, Cr(III)+Cr(VI), an accumulation time of 60s at -0.4V vs. Ag/AgCl resulted in detection limits of 0.336 and 0.414 nM and quantification limits of 1.12 and 1.40 nM, respectively. The relative standard deviation for 10 measurements of 5.0 nM chromate was 2.4%. Interference of other electroactive trace metals and surfactants was considered. A simple speciation scheme was proposed and satisfactorily applied to Cr(III) and Cr(VI) determinations in river water samples. PMID:20188962
Jorge, E O; Rocha, M M; Fonseca, I T E; Neto, M M M
Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors
A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120 ░C and 1 kgf/cm2 for 2 min, followed by a 10 min post-baking at 100 ░C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-? titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon (ś0.01 cm2/V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.
Cavallari, Marco Roberto; Zanchin, Vinicius Ramos; Pojar, Mariana; Seabra, Antonio Carlos; de AssumpńŃo Pereira-da-Silva, Marcelo; Fonseca, Fernando Josepetti; de Andrade, Adnei Melges
(abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary
The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.
Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.
Pulse voltammetric and ac impedance spectroscopic studies on lithium ion transfer at an electrolyte/Li4/3Ti5/3O4 electrode interface.
Pulse voltammetry and ac impedance spectroscopy were used to study the lithium ion kinetics at a lithium ion insertion electrode consisting of Li4/3Ti5/3O4 thin films in an organic electrolyte. In the cyclic voltammogram, two redox peaks appeared at around 1.56 V vs Li/Li+ due to the insertion and extraction of lithium ion at the electrode. Differential pulse voltammetry gave a large reduction current at approximately 1.56 V during a cathodic scan due to lithium ion insertion into the electrode. From the peak current and potential, the charge-transfer resistance was evaluated by quantitative analysis using approximate equations for irreversible reactions. In the Nyquist plot, one semicircle was observed at 1.56 V, which was assigned to the charge-transfer resistance due to lithium ion transfer at the electrode/electrolyte interface. The value of the charge-transfer resistance at 1.56 V was almost identical to that evaluated by differential pulse voltammetry with an identical characteristic relaxation time. This result shows that both dc differential pulse voltammetry and ac impedance spectroscopy are useful for elucidating the phase transfer kinetics of lithium ion at insertion electrodes. PMID:15762574
Doi, Takayuki; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi
Lithium-ion drifting: Application to the study of point defects in floating-zone silicon
The use of lithium-ion (Li(+)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(+) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li(+) drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li(+) compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.
Walton, J. T.; Wong, Y. K.; Zulehner, W.
Cathodic electrode
This patent describes a cathodic electrode suitable for use in a non-aqueous battery system comprising at least one substantially homogeneous, microporous sheet product having a void volume of from 15 to 25 volume percent and having a composition consisting essentially of from about 90-94 weight percent of particulate material consisting essentially of titanium disulfide having an average particle size of less than about 20 microns, from about 6-10 eight percent of high density polyethylene having a weight average molecular weight of from about 200,000 to 500,000 and from 0 to about 2 weight percent of an organic plasticizer for the polyethylene; and a current collector composed of a conductive material. The collector is in intimate contact with each of the least one microporous sheet product.
Anderman, M.; Lundquist, J.T. Jr.
A cathodic electrode suitable for use in a non-aqueous battery system is described comprising at least one substantially homogeneous, microporous sheet product having a composition of from about 70-98 weight percent of particulate material comprising titanium disulfide having an average particle size of less than about 20 microns with the particulate material having up to about 30 weight percent of a conductive diluent having an average particle size of from 1 to 100 millimicrons, from about 2-30 weight percent of high density polyethylene having a weight average molecular weight of from about 150,000 to 5,000,000 and from 0 to about 5 weight percent of an organic plasticizer for the polyethylene; and a current collector composed of a conductive material. The collector is in intimate contact with each of at least one microporous sheet product.
Anderman, M.; Johnson, S.L.
Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter
Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.
Wheeler, B. L.; Williams, R. M.; Jeffries-Nakamura, B.; Lamb, J. L.; Loveland, M. E.; Bankston, C. P.; Cole, T.
Detection of EEG electrodes in brain volumes.
This paper presents a method to detect 128 EEG electrodes in image study and to merge with the Nuclear Magnetic Resonance volume for better diagnosis. First we propose three hypotheses to define a specific acquisition protocol in order to recognize the electrodes and to avoid distortions in the image. In the second instance we describe a method for segmenting the electrodes. Finally, registration is performed between volume of the electrodes and NMR. PMID:21095810
Graffigna, Juan P; G¾mez, M Eugenia; Bustos, Josķ J
Electrode kinetics and double layer structure
Several electrochemical methods have been developed in recent years for the study of the kinetic parameters of electrode reactions. These methods have been used for obtaining an abundance of experimental data for the standard heterogeneous rate constant, ksh, of electrode reactions, mostly limited to reactions at a mercury electrode. As early as 1933, Frumkin recognized the essential correlation between the
B. Timmer; M. Sluyters-Rehbach; J. H. Sluyters
Impedance studies of nickel/cadmium and nickel/hydrogen cells using the cell case as a reference electrode
Impedance measurements have been made on several Ni/Cd and Ni/H2 flight-weight cells using the case as a reference electrode. For these measurements, the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltage of the cell cases with respect to the individual electrodes differ from cell to cell, even at the same overall cell voltage, but they remain stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.
Reid, Margaret A.
A Raman spectroscopic study of the carbon deposition mechanism on Ni/CGO electrodes during CO/CO2 electrolysis.
In situ and ex situ Raman analyses of porous Ni/CGO electrodes reveal differences in the amount, location and type of carbon formed during CO/CO2 electrolysis. The results demonstrate the limitations of optical in situ techniques applied to Solid Oxide Cells (SOCs) operated in electrolysis conditions. Increased carbon deposition close to the electrode-electrolyte interface is likely to be the result of high charge-transfer current in that area. The positive effect of a CGO interlayer on reducing carbon formation on the fuel electrode is demonstrated. PMID:24871047
Duboviks, V; Maher, R C; Kishimoto, M; Cohen, L F; Brandon, N P; Offer, G J
Impedance studies of Ni/Cd and Ni/H2 cells using the cell case as a reference electrode
Impedance measurements have been made on several Ni/Cd and Ni/H2 flightweight cells using the case as a reference electrode. For these measurements the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltages of the cell cases with respect to the individual electrodes differ from cell to cell even at the same overall cell voltage, but they remains stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.
Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.
To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096
Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki
Experimental and DFT theoretical studies of surface enhanced Raman scattering effect on the silver nano arrays modified electrode
Well-ordered silver nano arrays, prepared using anodic aluminum oxide (AAO) template by laser molecular beam epitaxy (L-MBE) method, were adhered to the work electrode using conductive adhesive to be a Surface-enhanced Raman scattering (SERS) substrate. Variable SERS signals of paranitrobenzoic acid (PNA) on the electrode modified with silver nano arrays were recorded with electric potential ranging from 0.1 to -0.5 V. The SERS spectra of PNA using DFT-B3PW91 with lanl2dz based on two models were calculated. It indicate that the adsorption orientation of probe molecules on the silver nano arrays with potential change of the electrode.
Zhang, Lisheng; Fang, Yan; Wang, Peijie
X-ray Study on the Disordered Structure above the Ferroelectric Curie Point in Potassium Nitrate
The disordered structure (phase I) above the ferroelectric Curie point (ca. 125░C) in KNO3 was studied by analysing X-ray diffuse scattering. The single crystal was prepared by slow cooling from the melt in a small glass tube which was mounted on the sample holder of a camera. The observed intensity distribution of the diffuse scattering in reciprocal space was characterized
Yasuhiro Shinnaka
A blinded pilot study investigating the use of diagnostic ultrasound for detecting active myofascial trigger points
Myofascial trigger points (MFTPs) have been cited by numerous authors as the cause of local and referred pain which arises from muscle and its surrounding fascia. At present there is no reliable objective test which is capable of determining their presence. It was the purpose of this pilot study to assess the use of diagnostic ultrasound in determining any soft
Jeremy Lewis; Philip Tehan
Lithium-ion drifting: Application to the study of point defects in floating-zone silicon.
The use of lithium-ion (Li(sup +)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(sup +) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain ...
J. T. Walton Y. K. Wong W. Zulehner
Two-Micron Laser Atmospheric Wind Sounder (LAWS) Pointing/Tracking Study.
The objective of the study was to identify and model major sources of short-term pointing jitter for a free-flying, full performance 2 micron LAWS system and evaluate the impact of the short-term jitter on wind-measurement performance. A fast steering mir...
S. Manlief
Superconducting energy gap of YB 6 studied by point-contact spectroscopy
Yttrium hexaboride has the second highest critical temperature, Tc?8K, among all borides. The presented paper deals with the experimental study of its superconducting energy gap established by the method of the point-contact spectroscopy. The temperature dependence of the energy gap and the strength of the superconducting coupling is presented.
Pavol Szab¾; Jozef KacmarcĒk; Peter Samuely; Jßn Girovsk²; Slavomir Gabßni; Karol Flachbart; Takao Mori
The programme of the analysis of ethnography as a scientific and educational discipline from the point of view of scientific studies is examined in the article for the first time, the definition of ethnography is given. Science as an integrated phenomenon emerges at the New time as a result of the separation from Philosophy, it passes several stages, at each
G. P. Pirozhkov
Study on the RF Set Point for the PEFP DTL by using a phase scan method
The drift tube linac (DTL) is used to accelerate proton beams from 20 MeV to 100 MeV in the linear accelerator of the Proton Engineering Frontier Project (PEFP). The phase scan signature method is a common technique to determine the radio-frequency (rf) set point, including the rf amplitude and phase, in DTL tanks. In this work, we applied the phase scan method to the first tank of the PEFP's DTL in order to study the procedure for determining the rf set point by using artificial experimental data generated by using the PARMILA code.
Jang, Ji-Ho; Kwon, Hyeok-Jung; Cho, Yong-Sub
Design and characterization of chemically modified electrodes with iron(III) porphyrinic-based polymers: study of their reactivity toward nitrites and nitric oxide in aqueous solution
This study gives new examples of iron porphyrin film electrodes prepared either by electrochemical polymerization or by incorporation in pre-electropolymerized pyrrole derivatives. It shows also the different kinds of interactions between nitric oxide, nitrites and the supported iron porphyrins in acidic and neutral aqueous solutions. It gives clear indications, by cyclic voltammetry and UV-visible spectrophotometry of the formation of the
Fethi Bedioui; Stķphane Trevin; Valķrie Albin; Maria Guadalupe; Gomez Villegas; Jacques Devynck
Low resistance electrode construction
An electrochemical cell having a cathode and an anode in contact with an electrolyte. Both electrodes or one of them has an electrically conducting non-metal receptacle defining a chamber with a first metal having a melting point in the range of from about room temperature to about 800.degree. C. inside said receptacle chamber. A second metal with a melting point greater than about 800.degree. C. is in contact with the first metal inside the receptacle chamber and extends outside of the receptacle chamber to form a terminal for the anode. The electrolyte may include the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides. Metal may be produced at the cathode during operation of the cell and oxygen or chlorine at the anode.
Redey, Laszlo (Downers Grove, IL); Karell, Eric J. (Woodridge, IL)
Raman Spectroscopic and Electrochemical Study on Photoinduced Crystal Growth of DABCO (Triethylenediamine) Polyiodide Upon a Silver Electrode.
Surface Raman spectra of a silver electrode contacting with an acidic solution containing triethylenediamine (DABCO) and sodium iodide showed some new Raman peaks, which were neither the peaks of dissolved DABCO species nor of iodide. These were ascribed ...
D. E. Irish T. Ozeki
Electrochemical lithiation and passivation mechanisms of iron monosulfide thin film as negative electrode material for lithium-ion batteries studied by surface analytical techniques
The lithiation/delithiation reaction mechanism of iron monosulfide (troilite Fe(1-x)S, x = 0.07) as negative electrode material for lithium-ion batteries and the electrode passivation induced by reductive decomposition of the electrolyte were studied by combining surface (X-ray photoelectron spectroscopy, XPS, and time-of-flight secondary ion mass spectrometry, ToF-SIMS) and electrochemical analysis (cyclic voltammetry, CV) of thin films grown by thermal sulfidation of metal iron substrate. XPS analysis performed at different stages of the first lithiation/delithiation cycle shows that the reversible formation of metallic iron and lithium sulfide is not solely limited to the principal cathodic/anodic peaks at 1.23/1.89 V and that disulfide products, possibly Li2FeS2, are also formed at lower cathodic potentials. ToF-SIMS depth profiling of the thin film electrode confirms an incomplete process of conversion/deconversion and reveals an expansion/shrinkage of the material induced by electrochemical lithiation/delithiation. The solid electrolyte interphase (SEI) layer formed on the iron monosulfide thin film electrode is mostly composed of Li2CO3 with some presence of ROCO2Li. For the first time, it is shown that the SEI layer thickness varies upon conversion/deconversion, between 9 and 4.5 nm in the lithiated and delithiated states, respectively, on a conversion-type electrode. Moreover, the electrolyte decomposition products penetrate the bulk electrode until the current collector owing to pulverization/cracking caused by expansion and shrinkage of the thin film material upon cycling.
Liao, Feng; ?wiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Klein, Lorena H.; Zanna, Sandrine; Marcus, Philippe
Parametric study on instabilities in a two-layer electromagnetohydrodynamic channel flow confined between two parallel electrodes.
Instabilities in a two-phase electromagnetohydrodynamic (EMHD) flow between a pair of parallel electrodes are explored. A linear stability analysis has been performed based on a coupled Orr-Sommerfeld system generated from the conservation laws. The study shows the presence of a finite-wave-number EMHD mode of instability in addition to the two commonly observed instability modes in the pressure-driven two-layer flows, namely, the long-wave interfacial mode arising from the viscosity or density stratification and the finite-wave-number shear flow mode engendered by the Reynolds stresses. This extra EMHD mode originates from the additional stresses generated by the Lorenz force acting at the liquid layers and is found to exist under all conditions beyond a critical strength of the externally applied magnetic field. The EMHD mode either can exist as a singular dominant mode or can coexist as a dominant or subdominant mode with the conventional interfacial mode or shear flow instabilities in the two-layer flows. The EMHD flow studied here has numerous potential applications in fluid transport, enhanced heat and mass transfer, mixing, and emulsification because of the low energy requirement, flow reversibility, absence of moving parts, and facile control over flow rate. The parametric study presented here on the instabilities in the two-layer EMHD flow will thus be of great practical use. PMID:21517593
Reddy, P Dinesh Sankar; Bandyopadhyay, Dipankar; Joo, Sang Woo; Sharma, Ashutosh; Qian, Shizhi
First-principles study of self-interstitial point defects in BCC metals
We report a study of the energetics of self-interstitial defects in V and Mo based on plane-wave supercell density functional calculations. We use a 128 atom cubic supercell and 2x2x2 k-point grid for BZ sampling, which we found to be sufficient to obtain accurate results on the basis of a careful convergence study. In our calculations, all the atoms of
Han Seungwu; Zepeda-Ruiza Luis; Car Roberto; Srolovitz David; Ackland Graeme
Experimental study of low-yield-point steel plate shear wall under in-plane load
This paper describes the study of the low-yield-point (LYP) steel plate shear walls under in-plane load. In the LYP steel plate shear wall system, LYP steel was selected for the steel plate wall while the boundary frame was constructed by the high strength structural steel. A series of experimental studies examined the inelastic shear buckling behavior of the LYP steel
Sheng-Jin Chen; Chyuan Jhang
Study of polyaniline doped with trifluoromethane sulfonic acid in gas-diffusion electrodes for proton-exchange membrane fuel cells
Polytetrafluoroethylene (PTFE)-bonded gas-diffusion electrodes (GDEs), modified with polyaniline as an electron and proton conductor in the catalyst layer, are prepared and evaluated for use in proton-exchange membrane fuel cells (PEMFCs). Polyaniline is coated on the GDE by electropolymerization of aniline and trifluoromethane sulfonic acid as the proton-conductive monomer. The electrodes are characterized by cyclic voltammetry, current¢potential measurements, electrochemical impedance spectroscopy,
Hussein Gharibi; Mohammad Zhiani; Ali Akbar Entezami; Rasol Abdullah Mirzaie; Mehdi Kheirmand; Karim Kakaei
L-Cysteine Modified Silver Electrode and Its Application to the Study of the Electrochemistry of Hemoglobin
L-cysteine can be modified onto a silver electrode by covalent binding through the sulphur to give very stable and long-lived chemically modified electrodes(CMEs). Hemoglobin(Hb) exhibits an excellent voltammetric response at the resulting CMEs. Linear sweep voltammetric(LSV) measurements of Hb on the CMEs reveal the existence of a linear relationship between the cathodic peak current and the concentration of Hb in
Genxi Li; Huiqun Fang; Yitao Long; Hongyuan Chen; Dexu Zhu
Study of Li insertion mechanisms in transition metal antimony compounds as negative electrodes for Li-ion battery
MSb (M=Ni, Co, Fe, Mn) alloys with a NiAs type structure were synthesized by ceramic route and evaluate as a negative electrode material for rechargeable lithium batteries. Electrochemical tests demonstrated that initial charge and discharge capacities of this materials were ca. 390 and 330mAhg?1, respectively. Ex situ XRD of MnSb electrodes showed that LiMnSb and Li3Sb were successively formed during
Costana Mihaela Ionica; Pierre Emmanuel Lippens; Josette Olivier Fourcade; Jean-Claude Jumas
Interactive graphics system for locating plunge electrodes in cardiac MRI images
Understanding the mechanisms of ventricular fibrillation and defibrillation requires analysis of epicardial and endocardial potentials throughout the heart. Plunge electrodes permit recording of cardiac potentials at epicardial and endocardial sites, and allow determination of electrical gradients. They also enable us to determine the arrhythmia recurrence sites following failed defibrillation; these sites may be epicardial or endocardial. Therefore, it is necessary to relate the position of the plunge electrodes to the cardiac geometry. We have developed an interactive, computer graphics based system that allows us to locate plunge electrodes on digitized MRI slices of a heart. The system, which can work with any type of image, allows us to identify the epicardial and endocardial points of each plunge electrode on the different MRI slices. Up to 128 different plunge electrodes may be identified to the system. Normalized 3-D coordinates for each epicardial and endocardial electrode point are computed and stored in data files on the computer. Geometry information obtained from this system permits a more thorough understanding of the electrical signals recorded by the plunge electrodes. This information can be used in the study of cardiac excitation and arrhythmias and could help in the development of a more effective lead system for ventricular defibrillation.
Laxer, Cary; Johnson, G. A.; Kavanagh, Katherine M.; Simpson, Edward V.; Ideker, Raymond E.; Smith, William M.
Electrode-Skin contact impedance: In vivo measurements on an ovine model
The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 ?, compared to more than 400 ? measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and non-invasive cases. This further prompted us to design a flexible electrode belt using the novel multi-point electrodes for lung EIT on animal models.
Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Jin, C.; Oh, T. I.; Thiagalingam, A.; McEwan, A.
Pain point system scale (PPSS): a method for postoperative pain estimation in retrospective studies
Purpose Pain rating scales are widely used for pain assessment. Nevertheless, a new tool is required for pain assessment needs in retrospective studies. Methods The postoperative pain episodes, during the first postoperative day, of three patient groups were analyzed. Each pain episode was assessed by a visual analog scale, numerical rating scale, verbal rating scale, and a new tool ¢ pain point system scale (PPSS) ¢ based on the analgesics administered. The type of analgesic was defined based on the authorsÆ clinic protocol, patient comorbidities, pain assessment tool scores, and preadministered medications by an artificial neural network system. At each pain episode, each patient was asked to fill the three pain scales. BartlettÆs test and Kaiser¢Meyer¢Olkin criterion were used to evaluate sample sufficiency. The proper scoring system was defined by varimax rotation. SpearmanÆs and PearsonÆs coefficients assessed PPSS correlation to the known pain scales. Results A total of 262 pain episodes were evaluated in 124 patients. The PPSS scored one point for each dose of paracetamol, three points for each nonsteroidal antiinflammatory drug or codeine, and seven points for each dose of opioids. The correlation between the visual analog scale and PPSS was found to be strong and linear (rho: 0.715; P < 0.001 and Pearson: 0.631; P < 0.001). Conclusion PPSS correlated well with the known pain scale and could be used safely in the evaluation of postoperative pain in retrospective studies.
Gkotsi, Anastasia; Petsas, Dimosthenis; Sakalis, Vasilios; Fotas, Asterios; Triantafyllidis, Argyrios; Vouros, Ioannis; Saridakis, Evangelos; Salpiggidis, Georgios; Papathanasiou, Athanasios
The ARIES-I high-field-tokamak reactor: Design-point determination and parametric studies
The multi-institutional ARIES study has examined the physics, technology, safety, and economic issues associated with the conceptual design of a tokamak magnetic-fusion reactor. The ARIES-I variant envisions a DT-fueled device based on advanced superconducting coil, blanket, and power-conversion technologies and a modest extrapolation of existing tokamak physics. A comprehensive systems and trade study has been conducted as an integral and ongoing part of the reactor assessment in order to identify an acceptable design point to be subjected to detailed analysis and integration as well as to characterize the ARIES-I operating space. Results of parametric studies leading to the identification of such a design point are presented. 15 refs., 6 figs., 2 tabs.
Miller, R.L.
Electrochemical Interfaces and Electrode Processes.
This report summarizes ONR research on the development and use of spectroscopic techniques for the study of electrochemical interfaces and electrode processes occurring at such interfaces. A number of in-situ techniques have been used including ultraviole...
E. B. Yeager
M÷ssbauer Spectroscopy (MS) is really suitable to study local electronic structures. Its hyperfine parameters, isomer shift\\u000a (IS) and quadrupole splitting (QS) allow to characterize the oxidation state and coordination of the probed element. So, the\\u000a capabilities of this powerful technique have been highlighted for the study of electron transfer occurring during electrochemical\\u000a or catalytic processes. Several examples illustrate how MS
Jean-Claude Jumas; Manfred Womes; Pierre-Emmanuel Lippens; Josette Olivier-Fourcade
A study on the effect of electrical stimulation on living tissue: potential before, during and after galvanization with constant current of 20 microA through platinum electrodes.
Two platinum needles (therapeutic electrode) were inserted into the rabbit's auricle, and with the medial angle of the eye as the datum point of measurement, the electric potential was measured before, during, and after the galvanization with micro-current (20 microA). With the insertion of the needles alone, the potential between the needles and the datum point showed -0.10 to +0.28 V, which gradually decreased thereafter to reach stable levels ranging from -0.02 to +0.17 V in 3 or 4 days. When galvanized, the potential stood +0.75 to +1.30 V between the anode and the datum point, and -0.37 to -0.50 V between the cathode and the datum point. Then, 3 days later, the voltage rose +1.40 to +1.65V between the anode and the datum point, and went down -0.60 to -0.85 V between the cathode and the datum point. When the micro-current was switched off, the potential immediately decreased, and slight potential endured after 24 hrs. These findings revealed that the insertion of needles generated electric potentials, that galvanization charged the tissue, and that cessation of stimulation led to storage and discharge of electricity. PMID:2348597
Kubota, T; Sato, K
Artifacts of the electrode in cochlea implantation and limits in analysis of deep insertion in cone beam tomography (CBT).
Until now more than 250,000 cochlea implantations have been performed worldwide. The surgical procedure is well standardized. A discussion about the kind of postoperative radiological control has started since cone beam tomography (CBT) has been established in ENT and hearing preservation operations have come more into the focus. Further research has been concentrated on the role of CBT and the insertion of the basal turn. The aim of this study was to look for the possibilities of CBT and deep insertion. The second aim was to analyze the artifacts of cochlea implants in CBT. Three human cadaver ears were implanted with a flex soft electrode of MedEl® in a standard operation procedure with round window insertion and a full insertion. Afterwards 72 CBT sets per ear were performed with different X-ray-tube currents (2-10 mA), voltages (72-90 kV), and exposure times (9 and 17 s). On each data set, the radiological diameter of the electrode 9 (basal), electrode 2 (apical), the diameter of the cable next to the electrodes 9 and 2, and the associated diameter of the cochlea next to the electrodes 9 and 2 were evaluated. Additionally, a comparison to the real diameter was done. The mean radiological diameters of the measure point at electrode 9 were: electrode = 1.19 mm; cable = 0.65 mm; cochlea = 1.77 mm. Results for measure point at electrode 2 were: electrode = 0.98 mm; cable = 0.48 mm; cochlea = 1.21 mm. The real diameters were at electrode 9 in lateral view 0.58 mm and in top view 0.63 mm and at electrode 2 in lateral view 0.36 mm and in top view 0.50 mm. Differences between the diameters of the electrode 9 and 2 were highly significant. Interestingly, the real diameter of the electrode is half in comparison to the radiological one. Also in comparison to the diameter of the cable and the associated electrode is nearly half. Nearly 50% artifact exists on radiologic evaluation of the diameter of the electrode. Varying the X-ray adjustments did not lead to optimized results. The difficulties in evaluating a cochlea electrode with CBT could be shown. The high rate of artifacts (50%) makes it extremely difficult to predict the inserted scale, especially when evaluating the intracochlear position in the medial and apical turn of the cochlea. In conclusion, until now CBT allows a relatively safe evaluation of the electrode in the basal turn, whereas in deep insertion it is not really a useful tool to answer the question of insertion trauma, implanted scale, or scale displacements. PMID:21805178
G³ldner, C; Wiegand, S; Weiss, R; Bien, S; Sesterhenn, A; Teymoortash, A; Diogo, I
Use of platinum electrodes for the electrochemical detection of bacteria
Platinum electrodes with surface area ratios of four to one were used to detect and enumerate a variety of gram-positive and gram-negative organisms. Linear relationships were established between inoculum size and detection time. End points for platinum electrodes were similar to those obtained with a platinum-reference electrode combination. Shape of the overall response curves and length of detection times for gram-positive organisms were markedly different than those for the majority of gram-negative species. Platinum electrodes are better than the platinum-reference electrode combination because of cost, ease of handling, and clearer definition of the end point.
Wilkins, J. R.
Numerical and experimental study of SnOx | Ag | SnOx multilayer as indium-free transparent electrode for organic solar cells
We propose a SnOx | Ag | SnOx multilayer, deposited in a continuous vacuum atmosphere by E-beam evaporation, as transparent anode for a (poly-3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction based Organic Solar Cell (OSC). Optical characterization of the deposited SnOx is performed to determine the dispersion of the complex refractive index. A Transfer Matrix Method (TMM) numerical optimization of the thicknesses of each layer of the electrode is realized to limit the number of manufactured samples. A numerical study using the morphology of the silver inserted between the oxide layers as input data is performed with a Finite Difference Time Domain (FDTD) method to improve the accordance between measurement and optical model. Multilayers are manufactured with the objective to give to the electrode its best conductivity and transparency in the visible spectral range by using the results of the optical optimization. These bare tri-layer electrodes show low sheet resistance (<10 ?/?) and mean transparency on [400-700] nm spectral band as high as 67 % for the whole Glass | SnOx | Ag | SnOx structure. The trilayer is then numerically studied inside a P3HT:PCBM bulk heterojunction based OSC structure. Intrinsic absorption inside the sole active layer is calculated giving the possibility to perform optical optimization on the intrinsic absorption efficiency inside the active area by considering the media embedding the electrodes.
Bou, Adrien; Torchio, Philippe; Barakel, Damien; Thierry, Franńois; Thoulon, Pierre-Yves; Ricci, Marc
Study on the kinetics of ferrocene derivatives in polymer electrolyte\\/electrode interface at microelectrode
Heterogeneous electron transfer rate constants (ks) and diffusion coefficients (D) of the ferrocene and its derivatives, in a new synthetic comb polymer solvent, poly(dimethylsiloxane-g-monomethylether polyethylene glycol) (SCP), and several other polymer solvents were estimated by using microelectrodes. Also, the influence of various supporting electrolytes on ks and D of ferrocene was studied. It was shown that ks and D of
Ningyu Gu; Huafang Zhou; Liming Ding; Zhong Shi; Shaojun Dong
Using GENIE to study a tipping point in the climate system.
We have used the Grid ENabled Integrated Earth system modelling framework to study the archetypal example of a tipping point in the climate system; a threshold for the collapse of the Atlantic thermohaline circulation (THC). eScience has been invaluable in this work and we explain how we have made it work for us. Two stable states of the THC have been found to coexist, under the same boundary conditions, in a hierarchy of models. The climate forcing required to collapse the THC and the reversibility or irreversibility of such a collapse depends on uncertain model parameters. Automated methods have been used to assimilate observational data to constrain the pertinent parameters. Anthropogenic climate forcing leads to a robust weakening of the THC and increases the probability of crossing a THC tipping point, but some ensemble members collapse readily, whereas others are extremely resistant. Hence, we test general methods that have been developed to directly diagnose, from time-series data, the proximity of a 'tipping element', such as the THC to a bifurcation point. In a three-dimensional ocean-atmosphere model exhibiting THC hysteresis, despite high variability in the THC driven by the dynamical atmosphere, some early warning of an approaching tipping point appears possible. PMID:19087945
Lenton, Timothy M; Myerscough, Richard J; Marsh, Robert; Livina, Valerie N; Price, Andrew R; Cox, Simon J; Genie Team
Point defects in YBa2Cu3O7-x studied using positron annihilation
Fast neutron irradiation is a powerful technique for introducing additional pinning centers into high temperature superconductors. The spherical defects with sizes of a few nanometers are considered to be effective pinning centers, enhancing Jc. Their morphology is well-known and has already been investigated by several authors in great detail. However, only very little is known about the nature and density of smaller and point defects, which are invisible in transmission electron microscopy. Positron annihilation lifetime spectroscopy was applied to investigate the nature and the concentration of small point-like defects. In this work, the influence of small point defects, such as vacancies and vacancy clusters, on the superconducting properties of YBa2Cu3O7-x bulks was studied; these were introduced by irradiation in the TRIGA Mark II reactor in Vienna. Jc and Tc measurements were performed prior to and after each irradiation step. The samples were irradiated up to a fast neutron ( > 0.1 MeV) fluence of 6 ū 1021 m-2. The two kinds of defectsŚthe large collision cascades and the small point-like defectsŚcontribute to the decrease of Tc as well as to the Jc enhancement in astonishingly similar ways.
Chudy, Michal; Eisterer, M.; Weber, H. W.; VeternĒkovß, J.; Sojak, S.; Sluge?, V.
Novel Electrodes for Underwater ECG Monitoring.
We have developed hydrophobic electrodes that provide all morphological waveforms without distortion of an ECG signal for both dry and water-immersed conditions. Our electrode is comprised of a mixture of carbon black powder (CB) and polydimethylsiloxane (PDMS). For feasibility testing of the CB/PDMS electrodes, various tests were performed. One of the tests included evaluation of the electrode-to-skin contact impedance for different diameters, thicknesses, and different pressure levels. As expected, the larger the diameter of the electrodes, the lower the impedance and the difference between the large sized CB/PDMS and the similarly-sized Ag/AgCl hydrogel electrodes was at most 200 k?, in favor of the latter. Performance comparison of CB/PDMS electrodes to Ag/AgCl hydrogel electrodes was carried out in three different scenarios: a dry surface, water immersion, and postwater immersion conditions. In the dry condition, no statistical differences were found for both the temporal and spectral indices of the heart rate variability analysis between the CB/PDMS and Ag/AgCl hydrogel (p Ā > 0.05) electrodes. During water immersion, there was significant ECG amplitude reduction with CB/PDMS electrodes when compared to wet Ag/AgCl electrodes kept dry by their waterproof adhesive tape, but the reduction was not severe enough to obscure the readability of the recordings, and all morphological waveforms of the ECG signal were discernible even when motion artifacts were introduced. When water did not penetrate tape-wrapped Ag/AgCl electrodes, high fidelity ECG signals were observed. However, when water penetrated the Ag/AgCl electrodes, the signal quality degraded to the point where ECG morphological waveforms were not discernible. PMID:24845297
Reyes, Bersain A; Posada-Quintero, Hugo F; Bales, Justin R; Clement, Amanda L; Pins, George D; Swiston, Albert; Riistama, Jarno; Florian, John P; Shykoff, Barbara; Qin, Michael; Chon, Ki H
Uranium-involving electrode processes in chloride melts: An x-ray absorption spectroscopy study
Products of anodic dissolution of uranium metal and the cathodic reduction of uranium(IV) ions in a molten eutectic mixture\\u000a of lithium and potassium chlorides are studied at 450?C using x-ray absorption spectroscopy. It is shown that UCl\\u000a 6\\u000a 3?\\u000a Ś ions form in the melt as a result of the metalÆs anodic dissolution, and the metal-ligand distance in the complex
V. A. Volkovich; I. B. Polovov; C. A. Sharrad; I. May; J. M. Charnock
In-situ STM study of phosphate adsorption on Cu(111), Au(111) and Cu/Au(111) electrodes
The interaction of Cu(111), Au(111) and Cu-covered Au(111) electrodes with a neutral phosphate buffer solution has been studied by means of cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). Under low potential conditions, both the Cu(111) and the Au(111) surface appear apparently adsorbate free, indicated by the presence of a (4 ū 4) structure and the herringbone surface reconstruction, respectively. Upon potential increase, phosphate anions adsorb on both surfaces and for Cu(111) the formation of a ?{3}ū?{3}R30 structure is found, whereas on Au(111) a "?{3}ū?{7}" structure is formed. For a Cu-submonolayer on Au(111), coadsorption of phosphate anions leads to the formation of a (2 ū 2) vacancy structure within an assumed pseudomorphic structure of the Cu-submonolayer with the phosphate anions occupying the vacancies. When desorbing the phosphate anions at low potentials, the Cu-submonolayer first becomes mobile and eventually undergoes an irreversible transition to a coalescent nonpseudomorphic structure.
Schlaup, Christian; Horch, Sebastian
Changes in response to antiaggregatory treatment in patients with myeloproliferative neoplasms: a sequential study using multiple electrode aggregometry.
In the present study, we used multiple electrode aggregometry (MEA) to investigate the response to aspirin and clopidogrel treatment, and its potential changes over a long-time disease course in patients with myeloproliferative neoplasms (MPNs). arachidonic acid (ASPI), ADP, and thrombin receptor activating peptide (TRAP) tests were performed at two timepoints between 32-50 months in 21 patients with MPN and 1-46 months in 29 controls. We further checked the medical records of the participants to identify a potential correlation of changes in the treatment response with clinical events. In MPN, four out of 13 patients treated with 100?mg of aspirin, no patients receiving 50?mg of aspirin, and one out of five clopidogrel-treated patients showed a therapeutic antiplatelet effect. In the subsequent examinations, five patients changed from response to nonresponse or vice versa. Initial nonresponse and changes from an initial response to nonresponse were observed in six patients with thrombotic events. In the controls, 25 out of 26 aspirin-treated patients and two out of three clopidogrel-treated patients showed an initially adequate in-vitro response. Except from one patient changing from initial aspirin nonresponse to response, all controls showed a stable response state. One control with two ischemic strokes showed a nonresponse to clopidogrel. In conclusion, MEA detects the response to antiaggregatory treatment, as well as its changes during the disease course in patients with MPN. An initial or subsequent nonresponse was observed in patients with thrombotic events. PMID:24176950
Robier, Christoph; Stettin, Mariana; Neubauer, Manfred
Study of the stability of periodic motions in the vicinity of collinear libration points
The problem of stability of three-dimensional periodic orbits near a collinear libration point is solved in the framework of the three-dimensional circular restricted three-body problem. Special attention is given to the study of the orbital stability of the examined periodic motions since, in the proper sense, all of these are unstable according to Liapunov. It is shown that it is
G. I. Shirmin
Two-micron Laser Atmospheric Wind Sounder (LAWS) pointing\\/tracking study
The objective of the study was to identify and model major sources of short-term pointing jitter for a free-flying, full performance 2 micron LAWS system and evaluate the impact of the short-term jitter on wind-measurement performance. A fast steering mirror controls system was designed for the short-term jitter compensation. The performance analysis showed that the short-term jitter performance of the
Scott Manlief
Study of point spread function and optical transfer function in blind deconvolution
This paper studies the optical diffraction, defocus, and sampling effects on the high speed imaging system. Through detailed analysis, we formulate the point spread function (PSF) and optical transfer function (OTF) which characterize the optical system in the spatial and frequency domain respectively. With the approximate priori knowledge of their PSF, we propose two integer focus operators and analyze their OTFs in association with those of Laplacian and the optimal focus operator. The experimental results and comparison validate our theoretical investigation.
Shen, Bichuan; Chen, C. H.; Wang, Guoyu
Damage states in laminated composite three-point bend specimens: An experimental-analytical correlation study
Damage states in laminated composites were studied by considering the model problem of a laminated beam subjected to three-point bending. A combination of experimental and theoretical research techniques was used to correlate the experimental results with the analytical stress distributions. The analytical solution procedure was based on the stress formulation approach of the mathematical theory of elasticity. The solution procedure is capable of calculating the ply-level stresses and beam displacements for any laminated beam of finite length using the generalized plane deformation or plane stress state assumption. Prior to conducting the experimental phase, the results from preliminary analyses were examined. Significant effects in the ply-level stress distributions were seen depending on the fiber orientation, aspect ratio, and whether or not a grouped or interspersed stacking sequence was used. The experimental investigation was conducted to determine the different damage modes in laminated three-point bend specimens. The test matrix consisted of three-point bend specimens of 0 deg unidirectional, cross-ply, and quasi-isotropic stacking sequences. The dependence of the damage initiation loads and ultimate failure loads were studied, and their relation to damage susceptibility and damage tolerance of the mean configuration was discussed. Damage modes were identified by visual inspection of the damaged specimens using an optical microscope. The four fundamental damage mechanisms identified were delaminations, matrix cracking, fiber breakage, and crushing. The correlation study between the experimental results and the analytical results were performed for the midspan deflection, indentation, damage modes, and damage susceptibility.
Starbuck, J. Michael; Guerdal, Zafer; Pindera, Marek-Jerzy; Poe, Clarence C.
Fluorescence labeling of colloidal core-shell particles with defined isoelectric points for in vitro studies.
In the light of in vitro nanotoxicological studies fluorescence labeling has become standard for particle localization within the cell environment. However, fluorescent labeling is also known to significantly alter the particle surface chemistry and therefore potentially affect the outcome of cell studies. Hence, fluorescent labeling is ideally carried out without changing, for example, the isoelectric point. A simple and straightforward method for obtaining fluorescently labeled spherical metal oxide particles with well-defined isoelectric points and a narrow size distribution is presented in this study. Spherical amorphous silica (SiO2, 161 nm diameter) particles were used as the substrate material and were coated with silica, alumina (Al2O3), titania (TiO2), or zirconia (ZrO2) using sol-gel chemistry. Fluorescent labeling was achieved by directly embedding rhodamine 6G dye in the coating matrix without affecting the isoelectric point of the metal oxide coatings. The coating quality was confirmed by high resolution transmission electron microscopy, energy filtered transmission electron microscopy and electrochemical characterization. The coatings were proven to be stable for at least 240 h under different pH conditions. The well-defined fluorescent particles can be directly used for biomedical investigations, e.g. elucidation of particle-cell interactions in vitro. PMID:22100347
Daberkow, Timo; Meder, Fabian; Treccani, Laura; Schowalter, Marco; Rosenauer, Andreas; Rezwan, Kurosch
Reading Different Orthographic Structures in the Shallow-Pointed Hebrew Script: A Cross-Grade Study in Elementary School
Hebrew-speaking children learn to read using a transparent, pointed writing system, but by grade three, they gradually begin using the non-pointed version of Hebrew script. The current study examined the development of reading, in the pointed script, of a nationally representative sample of children in grades two, four, and six. Rate and accuracyģ
Shany, Michal; Bar-On, Amalia; Katzir, Tami
Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO2) electrodes
The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO2), were discussed. Hydroxyl radicals (ĘHO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode, notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.
Wei, Jun-Jun; Zhu, Xiu-Ping; L³, Fan-Xiu; Ni, Jin-Ren
Two-craft Coulomb formation study about circular orbits and libration points
This dissertation investigates the dynamics and control of a two-craft Coulomb formation in circular orbits and at libration points; it addresses relative equilibria, stability and optimal reconfigurations of such formations. The relative equilibria of a two-craft tether formation connected by line-of-sight elastic forces moving in circular orbits and at libration points are investigated. In circular Earth orbits and Earth-Moon libration points, the radial, along-track, and orbit normal great circle equilibria conditions are found. An example of modeling the tether force using Coulomb force is discussed. Furthermore, the non-great-circle equilibria conditions for a two-spacecraft tether structure in circular Earth orbit and at collinear libration points are developed. Then the linearized dynamics and stability analysis of a 2-craft Coulomb formation at Earth-Moon libration points are studied. For orbit-radial equilibrium, Coulomb forces control the relative distance between the two satellites. The gravity gradient torques on the formation due to the two planets help stabilize the formation. Similar analysis is performed for along-track and orbit-normal relative equilibrium configurations. Where necessary, the craft use a hybrid thrusting-electrostatic actuation system. The two-craft dynamics at the libration points provide a general framework with circular Earth orbit dynamics forming a special case. In the presence of differential solar drag perturbations, a Lyapunov feedback controller is designed to stabilize a radial equilibrium, two-craft Coulomb formation at collinear libration points. The second part of the thesis investigates optimal reconfigurations of two-craft Coulomb formations in circular Earth orbits by applying nonlinear optimal control techniques. The objective of these reconfigurations is to maneuver the two-craft formation between two charged equilibria configurations. The reconfiguration of spacecraft is posed as an optimization problem using the calculus of variations approach. The optimality criteria are minimum time, minimum acceleration of the separation distance, minimum Coulomb and electric propulsion fuel usage, and minimum electrical power consumption. The continuous time problem is discretized using a pseudospectral method, and the resulting finite dimensional problem is solved using a sequential quadratic programming algorithm. The software package, DIDO, implements this approach. This second part illustrates how pseudospectral methods significantly simplify the solution-finding process.
Inampudi, Ravi Kishore
Analytical Study on a Single-Electron Device with Three Islands Connected to One Gate Electrode
We have studied a triple-dot single-electron device that includes four series tunnel junctions connecting a source, three islands and a drain, and three capacitive couplings connecting a gate to the three islands. Algebraic solutions for voltage distribution and Coulomb blockade (CB) conditions were derived for the triple-dot device with a homogeneous tunnel capacitance Cj and a homogeneous gate capacitance Cg. With the help of the established formulas, stability diagrams for the device were drawn and device operating modes were investigated in detail. Stability regions for n \\equiv (n1, n2, n3) = (0, 0, 0) and n = (0, 1, 0) have the shapes of a rhombus and a kite, respectively, and are located along the Vg axis. They overlap and a cycle of alternating gate voltage can transfer a single electron from the source to the drain through the islands, that is, the device works as a single-electron turnstile even though it has uniform capacitances. The turnstile operation is possible for any Cg/Cj ratio. If Cg/Cj is less than \\sqrt{2}-1, stability regions for n = (1, 0, 0) and n = (0, 0, 1) exist but they do not affect the turnstile operation.
Imai, Shigeru; Kawamura, Daichi
HSPES membrane electrode assembly
An improved fuel cell electrode, as well as fuel cells and membrane electrode assemblies that include such an electrode, in which the electrode includes a backing layer having a sintered layer thereon, and a non-sintered free-catalyst layer. The invention also features a method of forming the electrode by sintering a backing material with a catalyst material and then applying a free-catalyst layer.
Kindler, Andrew (Inventor); Yen, Shiao-Ping (Inventor)
Optimization of Wet Radiofrequency Ablation Using a Perfused-Cooled Electrode: A Comparative Study in Ex Vivo Bovine Livers
Objective To determine the optimized protocol for wet monopolar radiofrequency ablation (RFA) using a perfused-cooled electrode to induce coagulation necrosis in the ex vivo bovine liver. Materials and Methods Radiofrequency was applied to excised bovine livers in a monopolar mode using a 200W generator with an internally cooled electrode (groups A and B) or a perfused-cooled electrode (groups C, D, E, and F) at maximum power (150-200 W) for 10 minutes. A total of 60 ablation zones were created with six different regimens: group A - dry RFA using intra-electrode cooling; group B - dry RFA using intra-electrode cooling and a pulsing algorithm; group C - wet RFA using only interstitial hypertonic saline (HS) infusion; group D - wet RFA using interstitial HS infusion and a pulsing algorithm; group E - wet RFA using interstitial HS infusion and intra-electrode cooling; and group F - wet RFA using interstitial HS infusion, intra-electrode cooling and a pulsing algorithm. In groups C, D, E, and F, RFA was performed with the infusion of 6% HS through the perfused cooled electrode at a rate of 2 mL/minute. During RFA, we measured the tissue temperature at a distance of 15 mm from the electrode. The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups. Results During RFA, the mean tissue impedances in groups A (243 ▒ 88 ?) and C (252.5 ▒ 108 ?) were significantly higher than those in groups B (85 ▒ 18.7 ?), D (108.2 ▒ 85 ?), E (70.0 ▒ 16.3 ?), and F (66.5 ▒ 7 ?) (p < 0.05). The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520 ▒ 425 mA in group A, 1163 ▒ 34 mA in group B, 652.5 ▒ 418 mA in group C, 842.5 ▒ 773 mA in group D, 1665 ▒ 295 mA in group E, and 1830 ▒ 109 mA in group F. The mean volumes of the ablation regions in groups E and F were significantly larger than those in the other groups (p < 0.05): 17.7 ▒ 5.6 cm3 in group A, 34.5 ▒ 3.0 cm3 in group B, 20.2 ▒ 15.6 cm3 in group C, 36.1 ▒ 19.5 cm3 in group D, 68.1 ▒ 12.4 cm3 in group E, and 79.5 ▒ 31 cm3 in group F. The final tissue temperatures at a distance of 15 mm from the electrode were higher in groups E and F than those in groups A, C, and D (p < 0.05): 50 ▒ 7.5? in group A, 66 ▒ 13.6? in group B, 60 ▒ 13.4? in group C, 61 ▒12.7? in group D, 78 ▒ 14.2? in group E, and 79 ▒ 12.0? in group F. Conclusion Wet monopolar RFA, using intra-electrode cooling and interstitial saline infusion, showed better performance in creating a large ablation zone than either dry RFA or wet RFA without intra-electrode cooling.
Lee, Jeong Min; Kim, Se Hyung; Lee, Jae Young; Shin, Kyung Sook; Han, Chang Jin; Lee, Min Woo; Choi, Jun Il; Choi, Byung Ihn
Capacity fading of lithiated graphite electrodes studied by a combination of electroanalytical methods, Raman spectroscopy and SEM
We present herein Raman spectroscopy and SEM characterizations of composite graphite electrodes in conjunction with classical electroanalytical characterizations (SSCV and EIS) during prolonged cycling. During cycling, graphite particles crack into smaller pieces that are less oriented than the original platelets, with the possible filling of the cracks thus formed by the reduction products of the electrolyte solution. In addition, the average crystalline size (estimated by Raman spectroscopy) decreases as cycling progresses. The borders between the crystallites may possess dangling bonds and generally contain low-energy (or hollow) sites for irreversible interaction with Li-ions and solution species. The redistribution between the hollow and the shallow sites (i.e. the site for reversible Li-ion storage) occurring during electrode cycling is responsible for the moderate decrease of the reversible capacity of graphite electrodes observed during prolonged cycling.
Markervich, E.; Salitra, G.; Levi, M. D.; Aurbach, D.
Experimental and DFT theoretical studies of surface enhanced Raman scattering effect on the silver nano arrays modified electrode.
Well-ordered silver nano arrays, prepared using anodic aluminum oxide (AAO) template by laser molecular beam epitaxy (L-MBE) method, were adhered to the work electrode using conductive adhesive to be a Surface-enhanced Raman scattering (SERS) substrate. Variable SERS signals of paranitrobenzoic acid (PNA) on the electrode modified with silver nano arrays were recorded with electric potential ranging from 0.1 to -0.5 V. The SERS spectra of PNA using DFT-B3PW91 with lanl2dz based on two models were calculated. It indicate that the adsorption orientation of probe molecules on the silver nano arrays with potential change of the electrode. PMID:22495219
Photoinduction kinetics of electrical potential in a single chloroplast as studied with micro-electrode technique.
1. Using single chloroplasts of Peperomia metallica the kinetics of light-induced potential changes were studied. Three kinetic components (the initial fast rise, the decay in the light and the decay in the dark) were found to be characterized by time constants 4, 220 and 60 ms, respectively at light intensity 5000 1x and temperature 18 degrees C. After flash excitation the potential kept on rising for about 10 ms. Cooling of the medium down to 5 degrees C had no effect on the duration of potential rise after the flash. 2. Variations in the medium temperature in the range 2-23 degrees C had little effect on photoresponse magnitude but resulted in significant acceleration of decay in the light. 3. Addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (5-)0(-6) M) resulted in suppression of the magnitude of the photoresponse but was not accompanied by any change in the rate of initial rise of potential. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea-inhibited photoresponse could be restored and even enhanced by subsequent addition of N-methylphenazonium methosulfate (10(-4) M). N-Methylphenazonium methosulfate essentially influenced the time course and light-intensity curves of photoresponse. 4. The chloroplast photoresponses were of different time-courses when elicited by red (640 nm) or far red (712 nm) light. This fact as well as an enhancement effect of combined illumination by two intermittent light beams indicate on the interaction of two photosynthetic pigment systems when the photoelectric response was formed. 5. An imposed electrical field resulted in stimulation or suppression of chloroplast photoresponse depending on the polarity of the field. No indications for the existance of "reversal potential" for photoelectric response were obtained. 6. A kinetic scheme of photoresponse formation is proposed, which includes two sequential photochemical reactions of photosynthesis. PMID:1276187
Bulychev, A A; Andrianov, V K; Kurella, G A; Litvin, F F
Studies of kinetics of HCOOH oxidation on Pt(100), Pt(110), Pt(111), Pt(510) and Pt(911) single crystal electrodes
The kinetics of HCOOH oxidation via a reactive intermediate on Pt(100), Pt(110), Pt(111), Pt(510) and Pt(911) single crystal electrodes were studied quantitatively. The difficulty due to the self-poisoning involved in HCOOH oxidation has been overcome successfully by designing a programmed potential step procedure, which is based on results of kinetic studies of dissociative adsorption of HCOOH. The data processing method
Shi-Gang Sun; Yi-Yun Yang
Bifunctional oxygen electrodes
The objective of the research on bifunctional oxygen electrodes for alkaline electrolytes was to improve significantly both the cathodic and anodic polarization as well as the cycle life of such electrodes. The research has focused on finding high-efficiency, long-life electrocatalysts for O2 reduction and generation and achieving an understanding of the mechanisms of the catalysis. Catalyst systems which have been examined in alkaline electrolytes have included the following:various types of carbons and graphites; chemically-modified carbons and graphites using adsorptive attachment (e.g., various quinones, macrocycles and chemical linkages); silver and various intermetallics; various oxide systems including perovskites, spinels, pyrochlores and other mixed transition metal oxides; transition metal macrocycles including porphyrins, phthalocyanines, naphthalocyanines and tetraazaannulenes; and thermally-treated macrocycles. Mechanistic studies have particularly focused on the reduction of O2 on various carbon/graphite surfaces and the role of the O2(-) radical ion.
Tryk, D.; Aldred, W.; Chen, Z.; Fierro, C.; Hashiguchi, J.; Hossain, M.; Zhang, Z.; Zhao, F.
A method for better positioning bipolar electrodes for lower limb EMG recordings during dynamic contractions.
To obtain a high quality EMG acquisition, the signal must be recorded as far away as possible from muscle innervations and tendon zones, which are known to shift during dynamic contractions. This study describes a methodology, using commercial bipolar electrodes, to identify better electrode positions for superficial EMG of lower limb muscles during dynamic contractions. Eight female volunteers participated in this study. Myoelectric signals of the vastus lateralis, gastrocnemius medialis, peroneus longus and tibialis anterior muscles were acquired during maximum isometric contractions using bipolar electrodes. The electrode positions of each muscle were selected assessing SENIAM and then, other positions were located along the length of muscle up and down the SENIAM site. The raw signal (density), the linear envelopes, the RMS value, the motor point site, the position of the IZ and its shift during dynamic contractions were taken into account to select and compare electrode positions. For vastus lateralis and peroneus longus, the best sites were 66% and 25% of muscle length, respectively (similar to SENIAM location). The position of the tibialis anterior electrodes presented the best signal at 47.5% of its length (different from SENIAM location). The position of the gastrocnemius medialis electrodes was at 38% of its length and SENIAM does not specify a precise location for signal acquisition. The proposed method should be considered as another methodological step in every EMG study to guarantee the quality of the signal and subsequent human movement interpretations. PMID:19427540
Sacco, Isabel C N; Gomes, Aline A; Otuzi, Mitie E; Pripas, Denise; Onodera, Andrea N
Composite electrodes for electrochemical supercapacitors
Manganese dioxide and Ag-doped manganese dioxide powders were prepared by a chemical precipitation method using KBH4 as a reducing agent. The powders were studied by X-ray analysis, thermogravimetry, and electron microscopy. Composite electrodes\\u000a for electrochemical supercapacitors (ES) were fabricated by impregnation of slurries of the precipitated powders and carbon\\u000a black into porous nickel foam current collectors. In the composite electrodes,
Gideon Moses Jacob; Quan Min Yang; Igor Zhitomirsky
Glucose oxidase electrodes of polyaniline, poly( o -anisidine) and their co-polymer as a biosensor: a comparative study
Polyaniline (PA), poly(o-anisidine) (POA) and their co-polymer poly(aniline-co-o-anisidine) (PA-co-POA) thin films were electropolymerized in solution containing 0.1ĀM monomer(s) and 1ĀM H2SO4 as a electrolyte by applying sequential linear potential scan rate 50ĀmV\\/s between ?0.2 and 1.0ĀV vs. Ag\\/AgCl electrode on\\u000a platinum electrode. A simple technique is described for constructing a glucose sensor by the entrapment of glucose oxidase\\u000a (GOD) in
D. D. Borole; U. R. Kapadi; P. P. Mahulikar; D. G. Hundiwale
Comparative study of atmospheric pressure low and radio frequency microjet plasmas produced in a single electrode configuration
Microsize jet-type plasmas were generated in a single pin electrode structure source for two separate input frequencies of 50 kHz and 13.56 MHz in the ambient air. The copper pin electrode radius was 360 {mu}m, and it was placed in a Pyrex tube with a radius of 3 mm for helium gas supply. Due to the input frequency difference, the generated plasmas showed distinct discharge characteristics for their plasma physical appearances, electrical properties, gas temperatures, and optical properties. Strengths and weaknesses of both plasmas were discussed for further applications.
Kim, Dan Bee; Rhee, J. K.; Gweon, B.; Moon, S. Y.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)
Reduction of electrode polarization capacitance in low-frequency impedance spectroscopy by using mesh electrodes
Dielectric measurements of biological samples are obscured by electrode polarization, which at low frequencies dominates over the actual sample response. Reduction of this artifact is especially necessary in studying interactions of electric field with biological systems in the ?-dispersion range. We developed a method to reduce the influence of electrode polarization by employing mesh instead of solid electrodes as sensing
Divya Padmaraj; John H. Miller; Jarek Wosik; Wanda Zagozdzon-Wosik
Advanced treatment of cephalosporin pharmaceutical wastewater by nano-coated electrode and perforated electrode.
The objective of this study was to investigate the degradation of nonbiodegradable organic pollutants in biologically cephalosporin pharmaceutical wastewater using different electrodes such as non-nano-scale electrode (traditional coated), nano-scale (nano-coated) electrode, and perforated electrode after biotreatment. The traditional coated electrode plate, nano-coated electrode plate, and two different perforated titanium dioxide (TiO2) electrode plates with an average pore size of 10Ā?m and 20Ā?m were chosen as the anode. The results demonstrated that traditional coated electrode, nano-scale electrode, and perforated electrode could effectively remove nonbiodegradable organic pollutants from pharmaceutical wastewater. The perforated electrode with an average pore size of 10Ā?m exhibited the best degradation effect with a 90 % decrease in the chemical oxygen demand (COD) (COD content reduced from 320Āmg L(-1) to 32Āmg L(-1)). During catalytic degradation, the electrical conductivity of pharmaceutical wastewater increased and the pH increased and finally reached equilibrium. It was also found that the perforated TiO2 electrode produced relatively large amounts of dissolved oxygen during the catalytic oxidation process, reaching above 4Āmg L(-1), whereas the nano-coated electrode produced little dissolved oxygen. The biotoxicities of all wastewater samples increased firstly then decreased slightly during the electrical catalytic oxidation, but the final biotoxicities were all higher than initial ones. PMID:24967559
Yang, Bo; Zuo, Jiane; Gan, Lili; Yu, Xin; Liu, Fenglin; Tang, Xinyao; Wang, Yajiao
Thin film fuel cell electrodes.
Earlier work shows that fuel cell electrodes prepared by sputtering thin films of platinum on porous vycor substrates avoid diffusion limitations even at high current densities. The presented study shows that the specific activity of sputtered platinum is not unusually high. Performance limitations are found to be controlled by physical processes, even at low loadings. Catalyst activity is strongly influenced by platinum sputtering parameters, which seemingly change the surface area of the catalyst layer. The use of porous nickel as a substrate shows that pore size of the substrate is an important parameter. It is noted that electrode performance increases with increasing loading for catalyst layers up to two microns thick, thus showing the physical properties of the sputtered layer to be different from platinum foil. Electrode performance is also sensitive to changing differential pressure across the electrode. The application of sputtered catalyst layers to fuel cell matrices for the purpose of obtaining thin total cells appears feasible.
Asher, W. J.; Batzold, J. S.
The secondary alkaline zinc electrode
The worldwide studies conducted between 1975 and 1990 with the aim of improving cell lifetimes of secondary alkaline zinc electrodes are overviewed. Attention is given the design features and characteristics of various secondary alkaline zinc cells, including four types of zinc/nickel oxide cell designs (vented static-electrolyte, sealed static-electrolyte, vibrating-electrode, and flowing-electrolyte); two types of zinc/air cells (mechanically rechargeable consolidated-electrode and mechanically rechargeable particulate-electrode); zinc/silver oxide battery; zinc/manganese dioxide cell; and zinc/ferric cyanide battery. Particular consideration is given to recent research in the fields of cell thermodynamics, zinc electrodeposition, zinc electrodissolution, zinc corrosion, electrolyte properties, mathematical and phenomenological models, osmotic pumping, nonuniform current distribution, and cell cycle-life perforamnce.
McLarnon, Frank R.; Cairns, Elton J.
Experimental study of the expansion dynamic of 9 mm Parabellum hollow point projectiles in ballistic gelatin.
We study in this paper the expanding behaviour of hollow point 9 mm Parabellum projectiles (Hornady XTP(«) and Speer Gold Dot(«)). We defined a deformation rate that takes into account both the diameter increase and the length reduction. We plotted the behaviour of this parameter versus impact velocity (we refer to this curve as the expanding law). This expanding law has been plotted for different gelatin weight ratios and different gelatin block lengths. We completed our experiments with a set of high speed movies in order to correlate the deceleration to the state of expansion and size of the temporary cavity. Our results pointed out that full expansion is reached shortly after the projectile fully penetrates the gelatin. This result shows that the key point to accurately simulate human body interaction with a hollow point projectile is to accurately simulate the interface (skin, skull, clothes thoracic walls). Simulating accurately organs is only an issue if a quantitative comparison between penetration depths is required, but not if we only focus on the state of expansion of the projectile. By varying the gelatin parameters, we discovered that the expanding law exhibits a velocity threshold below which no expansion occurs, followed by a rather linear curve. The parameters of that expanding law (velocity threshold and line slope) vary with the gelatin parameters, but our quantitative results demonstrate that these parameters are not extremely critical. Finally, our experiments demonstrate that the knowledge of the expansion law can be a useful tool to investigate a gunshot in a human body with a semi-jacketed projectile, giving an estimation of the impact velocity and thus the shooting distance. PMID:22269130
Bresson, F; Ducouret, J; Peyrķ, J; Marķchal, C; Delille, R; Colard, T; Demondion, X
High frequency reference electrode
A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.
Kronberg, J.W.
Flexible retinal electrode array
An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.
Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)
Micromachined electrode array
An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.
Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)
Spectrophotometric calibration of pH electrodes in seawater using purified m-cresol purple.
This work examines the use of purified meta-cresol purple (mCP) for direct spectrophotometric calibration of glass pH electrodes in seawater. The procedures used in this investigation allow for simple, inexpensive electrode calibrations over salinities of 20-40 and temperatures of 278.15-308.15 K without preparation of synthetic Tris seawater buffers. The optimal pH range is ?7.0-8.1. Spectrophotometric calibrations enable straightforward, quantitative distinctions between Nernstian and non-Nernstian electrode behavior. For the electrodes examined in this study, both types of behavior were observed. Furthermore, calibrations performed in natural seawater allow direct determination of the influence of salinity on electrode performance. The procedures developed in this study account for salinity-induced variations in liquid junction potentials that, if not taken into account, would create pH inconsistencies of 0.028 over a 10-unit change in salinity. Spectrophotometric calibration can also be used to expeditiously determine the intercept potential (i.e., the potential corresponding to pH 0) of an electrode that has reliably demonstrated Nernstian behavior. Titrations to ascertain Nernstian behavior and salinity effects can be undertaken relatively infrequently (?weekly to monthly). One-point determinations of intercept potential should be undertaken frequently (?daily) to monitor for stable electrode behavior and ensure accurate potentiometric pH determinations. PMID:22463815
Easley, Regina A; Byrne, Robert H
Application of Ultrasound-Guided Trigger Point Injection for Myofascial Trigger Points in the Subscapularis and Pectoralis Muscles to Post-Mastectomy Patients: A Pilot Study
Purpose To investigate the therapeutic effectiveness of ultrasound (US)-guided trigger point injection for myofascial trigger points (MTrPs) in the internal rotator muscles of the shoulder in post-mastectomy patients. Materials and Methods This pilot study was a non-controlled, prospective, clinical trial. Nineteen post-mastectomy patients with a diagnosis of at least one active MTrP in the subscapularis and/or pectoralis muscles were included. We performed trigger point injections into the subscapularis muscle deep behind the scapula as well as the pectoralis muscle for diagnostic and therapeutic purpose by the newly developed US-guided method. Results Visual analogue scale and range of motion of the shoulder for external rotation and of abduction showed significant improvement immediately after the first injection and 3 months a