Sample records for point electrode studies

  1. Electric wind in electrode systems with corona points

    Microsoft Academic Search

    B. A. Kozlov; V. I. Solovyov

    2007-01-01

    The characteristics of the electric wind attendant on the corona initiation are studied with the aim of reaching a maximal\\u000a velocity and flow rate. Systems with a single corona point and multi-in-line electrode are used. The dependences of the gas\\u000a flow rate on the current, voltage, voltage polarity, electrode spacing, corona point geometry, and corona-free electrode design\\u000a are determined.

  2. Accurate pointing of tungsten welding electrodes

    NASA Technical Reports Server (NTRS)

    Ziegelmeier, P.

    1971-01-01

    Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.

  3. Surface-electrode point Paul trap

    E-print Network

    Chuang, Isaac L.

    We present a model as well as experimental results for a surface electrode radiofrequency Paul trap that has a circular electrode geometry well suited for trapping single ions and two-dimensional planar ion crystals. The ...

  4. Arc electrode interaction study

    NASA Technical Reports Server (NTRS)

    Zhou, X.; Berns, D.; Heberlein, J.

    1994-01-01

    The project consisted of two parts: (1) the cathode interaction studies which were a continuation of previous work and had the objective of increasing our understanding of the microscopic phenomena controlling cathode erosion in arc jet thrusters, and (2) the studies of the anode attachment in arc jet thrusters. The cathode interaction studies consisted of (1) a continuation of some modeling work in which the previously derived model for the cathode heating was applied to some specific gases and electrode materials, and (2) experimental work in which various diagnostics was applied to the cathode. The specific diagnostics used were observation of the cathode tip during arcing using a Laser Strobe Video system in conjunction with a tele-microscope, a monochromator with an optical multichannel analyzer for the determination of the cathode temperature distribution, and various ex situ materials analysis methods. The emphasis of our effort was shifted to the cathode materials analysis because a parallel project was in place during the second half of 1993 with a visiting scientist pursuing arc electrode materials studies. As a consequence, the diagnostic investigations of the arc in front of the cathode had to be postponed to the first half of 1994, and we are presently preparing these measurements. The results of last year's study showed some unexpected effects influencing the cathode erosion behavior, such as increased erosion away from the cathode tip, and our understanding of these effects should improve our ability to control cathode erosion. The arc jet anode attachment studies concentrated on diagnostics of the instabilities in subsonic anode attachment arc jet thrusters, and were supplemental measurements to work which was performed by one of the authors who spent the summer as an intern at NASA Lewis Research Center. A summary of the results obtained during the internship are included because they formed an integral part of the study. Two tasks for 1994, the diagnostics of the anode closure phenomenon, and the use of arc jet thrusters for the deposition of c-BN, are being prepared.

  5. Weld electrode cooling study

    NASA Astrophysics Data System (ADS)

    Masters, Robert C.; Simon, Daniel L.

    1999-03-01

    The U.S. auto/truck industry has been mandated by the Federal government to continuously improve their fleet average gas mileage, measured in miles per gallon. Several techniques are typically used to meet these mandates, one of which is to reduce the overall mass of cars and trucks. To help accomplish this goal, lighter weight sheet metal parts, with smaller weld flanges, have been designed and fabricated. This paper will examine the cooling characteristics of various water cooled weld electrodes and shanks used in resistance spot welding applications. The smaller weld flanges utilized in modern vehicle sheet metal fabrications have increased industry's interest in using one size of weld electrode (1/2 inch diameter) for certain spot welding operations. The welding community wants more data about the cooling characteristics of these 1/2 inch weld electrodes. To hep define the cooling characteristics, an infrared radiometer thermal vision system (TVS) was used to capture images (thermograms) of the heating and cooling cycles of several size combinations of weld electrodes under typical production conditions. Tests results will show why the open ended shanks are more suitable for cooling the weld electrode assembly then closed ended shanks.

  6. Modeling deep brain stimulation: point source approximation versus realistic representation of the electrode

    NASA Astrophysics Data System (ADS)

    Zhang, Tianhe C.; Grill, Warren M.

    2010-12-01

    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.

  7. Study of the local repolarization currents and charge carrier injection on an LiNbO 3 surface scanned with a mobile point electrode

    Microsoft Academic Search

    V. G. Zalesskii; A. B. Sherman; S. O. Fregatov

    2001-01-01

    A method of the potential relief recording and reading in a subsurface region of Z-cut monodomain lithium niobate crystals of congruent composition was developed. The method is based on scanning the crystal\\u000a surface with a point (needle-like) electrode. The injection and polarization switching currents were measured in the course\\u000a of scanning. It was found that the characteristic time of the

  8. A point defect model for nickel electrode structures

    NASA Technical Reports Server (NTRS)

    Loyselle, Patricia L.; Karjala, Philip J.; Cornilsen, Bahne C.

    1986-01-01

    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.

  9. Alternating current cloud point extraction on a microchip: the effect of electrode geometry.

    PubMed

    Sasaki, Naoki; Maekawa, Chisaki; Sato, Kae

    2015-02-01

    We report on the effect of electrode geometry on alternating current cloud point extraction (ACPE). ACPE is a technique utilized to extract membrane-associated biomolecules in an electrode-integrated microfluidic channel. In this study, we investigated the effect of gap size (4?22 ?m) between microband electrodes on ACPE. A decrease in gap size resulted in efficient and rapid concentration of fluorescent-labeled phospholipids, a model of membrane-associated biomolecules. We also investigated the effect of applied voltage amplitude on ACPE using devices with decreased electrode gap size. When the gap was small, ACPE was achieved with low applied voltages. ACPE of membrane proteins extracted from HeLa cells was also studied to demonstrate the applicability of the ACPE to real samples. The results provide a guideline to improve the performance of ACPE and facilitate application of the ACPE technique as part of an overall analytical process. PMID:25224325

  10. AC impedance studies on metal hydride electrodes

    SciTech Connect

    Zhang, W.; Sridhar Kumar, M.P.; Srinivasan, S.; Ploehn, H.J. [Texas A and M Univ., College Station, TX (United States)

    1995-09-01

    The metal hydride (MH{sub x}) electrode is the negative electrode in one of the most advanced secondary batteries (i.e., nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydriding reaction in the battery by using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MH{sub x} electrode reaction is proposed. The rate capability of charge and discharge of the MH{sub x} electrode is determined by the kinetics of the charge-transfer reaction at the allow surface, which is mainly represented by the EIS responses in the low frequency region. Transient and pseudo-steady-state analyses (cyclic voltammetry and potential vs. current density behavior) qualitatively and quantitatively support the EIS results. EIS studies on electrodes with (1) three types of binding additives, (2) varying amounts of active materials, and (3) two types of alloys as active materials demonstrate the usefulness of this technique for developing electrodes with the optimum composition and structure.

  11. Effects of electrode design on null point motion of spheres suspended in the electrodynamic balance

    Microsoft Academic Search

    J. D. Eversole; H.-B. Lin

    1987-01-01

    Three similar but geometrically distinct electrode designs for an electrodynamic balance or quadrupole particle levitation cell have been compared in terms of the minimum periodic motion, or ‘‘null point’’ motion of single, suspended glass spheres of either 30 or 11 ?m in diameter. The three electrode surface designs included the ideal hyperbolic shape, similar but spherical surfaces, and spherical surfaces

  12. Nanosecond-pulse gliding discharges between point-to-point electrodes in open air

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Shao, Tao; Yan, Ping; Zhou, Yuanxiang

    2014-06-01

    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.

  13. Preliminary kerr electro-optic field mapping measurements in propylene carbonate using point-plane electrodes

    Microsoft Academic Search

    T. J. Gung; A. Üstundag; M. Zahn

    1999-01-01

    Propylene carbonate is used in Kerr electro-optic field mapping measurements because of its non-toxic chemical nature and very high Kerr constant. We describe the experimental design and chemical purification procedure that minimizes reactions with the electrodes and removes particles and moisture. We measure the optical characteristic parameters using the ac modulation method with point-plane electrodes that allows calculation of the

  14. An Alternative Empirical Formula for Positive Corona Discharge I-V Characteristics in Point-to-Plate Electrode Geometry

    NASA Astrophysics Data System (ADS)

    A. Azooz, A.; Sabah, I. Waysi

    2014-03-01

    Experimental data are presented for a study on the dependence of the I-V characteristics of the corona discharge on pressure and electrode spacing using point-to-plane electrode configuration. These experimental data are obtained by a fast, automatic computer data-acquisition system. The data are used to suggest an alternative dimensionally self-consistent empirical equation for the parameterization of the I-V curves. The formula eliminates the need for any prior assumptions concerning the inception voltage, as is customary in this type of work.

  15. Electrochemical charge transfer at a metallic electrode: a simulation study 

    E-print Network

    Pounds, Michael A.

    2010-01-01

    Part I Electrochemical charge transfer at a metallic electrode: a simulation study The factors which affect the rate of heterogeneous electron transfer at a metallic electrode in the context of Marcus theory are ...

  16. Raman structural studies of the nickel electrode

    NASA Technical Reports Server (NTRS)

    Cornilsen, B. C.

    1985-01-01

    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.

  17. Optical Studies of Surface-Modified Electrodes

    NASA Astrophysics Data System (ADS)

    Cowen, Simon

    Available from UMI in association with The British Library. The technique of surface plasmon-polariton (SPP) excitation has been used as a sensitive probe of the metal/electrolyte interface, with particular emphasis on surface-modified electrodes; these being electrodes with some electrochemically active surface layer present. The aim of the project was to study the oxidation and reduction processes undergone by two electrochromic materials. The results obtained are the first of their kind, providing new information on the optical properties of the two compounds. The reduction of Prussian blue (PB) to Prussian white has been studied in the visible spectrum. The work consists of two parts, the first being carried out at the single wavelength of 632.8 nm. This has provided information about the changes which occur in the film when it is reduced. The results indicate that an optically thin PB film (about 12 nm) can be modelled adequately as a homogeneous film during the reduction process, since the Fe^ {2+} ions have greater mobility in this case. The film also appears to undergo spectroscopic and compositional changes, indicated by dielectric function changes. This is confirmed by the second part of the study, which was performed in the wavelength range 550 to 800 nm. The relative permittivity of the PB film changes upon potential cycling. This is related to the exchange of K^{+} ions for Fe ^{3+} in the lattice. A study has been carried out on polybithiophene (PBT), a conducting polymer. Information has been obtained about the optical constants of this material in the wavelength range 550 to 800 nm, these being the first such measurements. A first attempt at the construction of a solid-state electrochemical cell using the ionic conducting material Nafion is also reported. The cell consists of two thin gold film electrodes modified with PB and PBT. Cyclic voltammetry implies that the expected colour switch occurs, but this is not revealed by SPP measurements.

  18. Alkali metal thermoelectric converter (AMTEC) electrode lifetime studies

    Microsoft Academic Search

    C. Perry Bankston; Roger M. Williams; Barbara Jeffries-Nakamura; Terry Colle

    1987-01-01

    Experimental studies are being conducted at JPL to identify long life, high area power density electrodes for AMTEC. Power versus time measurements are being made in a demountable electrode test cell and, for longer term experiments, a self-contained recirculating cell. The experimental apparatus and procedures are described in detail. The results show that thin film molybdenum electrodes can be designed

  19. AC impedance study of degradation of porous nickel battery electrodes

    NASA Technical Reports Server (NTRS)

    Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.

    1987-01-01

    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.

  20. Development of a point-electrode conductivity salinometer with high-spatial-resolution for use in very-saline solutions

    SciTech Connect

    Jones, G.F.; Grimmer, D.P.; Tafoya, J.; Fitzgerald, T.J.

    1983-01-01

    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.

  1. Study of the contributions of the electrode materials to the plasma of a high-current vacuum spark

    SciTech Connect

    Bashutin, O. A.; Vovchenko, E. D.; Dodulad, E. I.; Savjolov, A. S.; Sarantsev, S. A. [National Nuclear Research University Moscow Engineering Physics Institute (Russian Federation)

    2012-03-15

    The contribution of the electrode material to the formation of the plasma of a low-inductive high-current vacuum spark and its influence on the process of discharge micropinching were studied using X-ray spectroscopy and laser diagnostics. Electrode system configurations are determined in which the contributions of the materials of both electrodes to the plasma emitting X-rays are comparable and in which the contribution of one electrode is dominating. It is found that discharge pinching occurs primarily in the vapor of the pointed electrode independently of its polarity. The experimental results indicate the formation of a suprathermal electron beam in the micropinch region.

  2. GLAS Spacecraft Pointing Study

    NASA Technical Reports Server (NTRS)

    Born, George H.; Gold, Kenn; Ondrey, Michael; Kubitschek, Dan; Axelrad, Penina; Komjathy, Attila

    1998-01-01

    Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 m of the location of the previous repeat ground track. The satellite will be flown in a repeat orbit of 182 days. Operationally, the required pointing information will be determined on the ground using the nominal ground track, to which pointing is desired, and the current propagated orbit of the satellite as inputs to the roll computation algorithm developed by CCAR. The roll profile will be used to generate a set of fit coefficients which can be uploaded on a daily basis and used by the on-board attitude control system. In addition, an algorithm has been developed for computation of the associated command quaternions which will be necessary when pointing at targets of opportunity. It may be desirable in the future to perform the roll calculation in an autonomous real-time mode on-board the spacecraft. GPS can provide near real-time tracking of the satellite, and the nominal ground track can be stored in the on-board computer. It will be necessary to choose the spacing of this nominal ground track to meet storage requirements in the on-board environment. Several methods for generating the roll profile from a sparse reference ground track are presented.

  3. Study of the near-electrode processes in quasi-steady plasma accelerators with impenetrable electrodes

    SciTech Connect

    Kozlov, A. N. [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation)

    2012-01-15

    Near-electrode processes in a coaxial plasma accelerator with equipotential impenetrable electrodes are simulated using a two-dimensional (generally, time-dependent) two-fluid MHD model with allowance for the Hall effect and the plasma conductivity tensor. The simulations confirm the theoretically predicted mechanism of the so-called 'crisis of current' caused by the Hall effect. The simulation results are compared with available experimental data. The influence of both the method of plasma supply to the channel and an additional longitudinal magnetic field on the development of near-electrode instabilities preceding the crisis of current is studied.

  4. AC-impedance studies on metal hydride electrodes

    SciTech Connect

    Zhang, W.; Kumar, M.P.S.; Visintin, A.; Srinivasan, S. [Texas A and M Univ., College Station, TX (United States)

    1994-12-31

    The metal hydride (MH{sub x}) electrode is the negative electrode in one of the most advanced rechargeable batteries (i.e. nickel/metal hydride). The objective of this study is to obtain insight on the mechanism of the hydriding/dehydriding reaction in the battery, using the electrochemical impedance spectroscopy (EIS) technique. An equivalent circuit for the MH{sub x} electrode reaction is proposed. The rate capabilities of charge/discharge reaction of MH{sub x} electrode are determined by the kinetics of charge transfer reaction at the alloy surface. Transient and pseudo steady-state analyses (cyclic voltammetry and potential vs. current density behavior) qualitatively and quantitatively support the EIS results. EIS studies on electrodes with (i) three types of binding additives, (ii) varying amounts of active material, and (iii) two types of alloys as active materials demonstrate the usefulness of this technique to develop electrodes with the optimum compositions and structures.

  5. Study of Influence of Electrode Geometry on Impedance Spectroscopy

    SciTech Connect

    Ahmed, Riaz; Reifsnider, Kenneth L

    2011-01-01

    Electrochemical Impedance Spectroscopy (EIS) is a powerful and proven tool for analyzing AC impedance response. A conventional three electrode EIS method was used to perform the investigation in the present study. Saturated potassium chloride solution was used as the electrolyte and three different material rods were used as working electrodes. Different configurations of electrode area were exposed to the electrolyte as an active area to investigate electrode geometry effects. Counter to working electrode distance was also altered while keeping the working electrode effective area constant to explore the AC response dependence on the variation of ion travel distance. Some controlled experiments were done to validate the experimental setup and to provide a control condition for comparison with experimental results. A frequency range of 100 mHz to 1 MHz was used for all experiments. In our analysis, we have found a noteworthy influence of electrode geometry on AC impedance response. For all electrodes, impedance decreases with the increase of effective area of the electrolyte. High frequency impedance is not as dependent on geometry as low frequency response. The observed phase shift angle drops in the high frequency region with increased working electrode area, whereas at low frequency the reverse is true. Resistance and capacitive reactance both decrease with an increase of area, but resistance response is more pronounce than reactance. For lower frequencies, small changes in working area produce very distinctive EIS variations. Electrode material as well as geometry was systematically varied in the present study. From these and other studies, we hope to develop a fundamental foundation for understanding specific changes in local geometry in fuel cell (and other) electrodes as a method of designing local morphology for specific performance.

  6. Porous nickel electrodes in water electrolysis. I - Electrode preparation and polarisation studies in strong alkali. II - Use of porous nickel electrodes in multicell module

    NASA Astrophysics Data System (ADS)

    Ragunathan, P.; Mitra, S. K.; Nayar, M. G.

    Replacement of 'plate' electrodes in water electrolysis cells by porous nickel electrodes leads to many advantages resulting in reduced specific energy consumption for hydrogen production. This paper describes the techniques developed to prepare the porous electrodes, their physical characteristics and their performance in strong alkali as hydrogen and oxygen gas electrodes. Steady state cell polarization studies over a range of 100 to 10,000 ASM at different temperatures were carried out in 6N K OH solution for different electrode samples prepared by alloy electrodeposition and powder metallurgy methods. Electrodes from these two methods were compared with respect to their electrochemical performance. The current carrying capacity at a given overvoltage was evaluated for different electrode thicknesses. Use of porous electrodes in electrolysis modules permits high current density operation at reduced cell voltages because the specific surface area in porous electrodes increases manifold due to fine pores and large pore densities. But the use of porous electrodes also imposes certain restrictions in design and operation of the module. The increased current densities cause high heat and gas generation fluxes within a small cell space, with the gases being released in the form of very fine bubbles. The above aspects are discussed in detail and the experimental studies carried out on the porous nickel electrodes to determine the bubble size, gas release and separation at different current densities are reported. Description of an electrolyzer of 1.5 cu nm/hr capacity and operation of the module with porous electrodes are given.

  7. Alkali metal thermoelectric converter (AMTEC) electrode lifetime studies

    NASA Technical Reports Server (NTRS)

    Bankston, C. Perry; Williams, Roger M.; Jeffries-Nakamura, Barbara; Colle, Terry

    1987-01-01

    Experimental studies are being conducted at JPL to identify long life, high area power density electrodes for AMTEC. Power versus time measurements are being made in a demountable electrode test cell and, for longer term experiments, a self-contained recirculating cell. The experimental apparatus and procedures are described in detail. The results show that thin film molybdenum electrodes can be designed to produce power near 0.5 W/sq cm for over two hundred hours. Also, platinum/tungsten electrodes exhibit power densities that are stable near 0.5 W/sq cm. If the performance of these electrodes is verified for longer periods (thousands of hours), then practical AMTEC systems will be possible.

  8. A study of the glow discharge characteristics of contact electrodes at atmospheric pressure in air

    SciTech Connect

    Liu, Wenzheng, E-mail: wzhliu@bjtu.edu.cn; Sun, Guangliang, E-mail: 11121659@bjtu.edu.cn; Li, Chuanhui; Zhang, Rongrong [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China)] [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China)

    2014-04-15

    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.

  9. Study of multi-electrodes structure in CdTe nuclear radiation detectors

    Microsoft Academic Search

    Madan Niraula; Yasunori Agata; Kazuhito Yasuda

    2004-01-01

    We studied CdTe nuclear radiation detectors with multi-electrodes structure. The detector consists of a common cathode, while the anode has been separated into three electrodes: the central collecting anode, a guard ring electrode, and a guiding electrode. The detector was biased in such a way that the central anode collects electrons while the guiding electrode repel electrons and guide them

  10. Studies of an artificially generated electrode effect at ground level

    Microsoft Academic Search

    E. A. Mareev; S. Israelsson; E. Knudsen; A. V. Kalinin; M. M. Novozhenov

    1997-01-01

    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

  11. Experimental study of time-varying current flow between electrodes immersed in a laboratory magnetoplasma

    SciTech Connect

    Urrutia Paez, J.M.

    1987-01-01

    The flow of current between electrodes immersed in plasmas is a topic of fundamental importance in the operation of plasma probes, plasma confinement research, and space-based experiments. To date, however, research has been limited to time-stationary treatments of the regions immediate to the electrodes themselves. For the case of non-emitting electrodes, positive and negative charge carriers are predicted to flow from the entire plasma into the oppositely charged electrodes, while only one species is involved if one of the electrodes emits charged particles. If the charge carriers are magnetized, the current flow is restricted to the reattachment point, resulting in a more-efficient data acquisition and it providing a detailed description of the instantaneous spatial relationship of the flow field. Intense studies were conducted using a 2.9-Hz sinusoidal flow with a frequency parameter of 7.5 and with mean and modulation Reynolds numbers of 575 and 350, respectively. For flow through mild occlusions, a 45% axisymmetric and a 38% asymmetric stenoses, the flow-separation pattern displayed oscillation of both the separation boundary and the reattachment point with some nonperiodic components.

  12. The development of a micropatterned electrode for studies of zinc electrodeposition

    SciTech Connect

    Sutija, D.P.; Muller, R.H.; Tobias, C.W.

    1986-12-01

    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.

  13. Electrode, current collector, and electrolyte studies for AMTEC cells

    SciTech Connect

    Ryan, M.A.; Williams, R.M.; Underwood, M.L.; Jeffries-Nakamura, B.; O'Connor, D. (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States))

    1993-01-15

    Studies of components for AMTEC devices at JPL have focussed on electrode materials, materials and construction of the current collection network, and the [beta][double prime]-alumina solid electrolyte. Electrode materials include thin films of molybdenum metal and metal alloys such as PtW and RhW. Surface self-diffusion coefficients have been determined for Mo electrodes in the temperature range 1050--1200 K, and for RhW at 1125 K. The diffusion coefficients have been used in a grain growth model to predict electrode operating lifetimes at temperatures in this range. Current collection networks sputtered with a thin film of platinum have decreased total electrical resistance in an operating device by 35%. Electrolyte studies have found no mechanical stress or chemical degradation induced by long term operation. Further electrolyte studies have focussed on synthesis of both sodium and potassium [beta][double prime]-alumina ceramic. Potassium [beta][double prime]-alumina solid electrolyte has potential application in a potassium-based AMTEC device which operates at a hot side temperature of [similar to]1000 K.

  14. Study on erosion mechanism of graphite electrode in two-electrode spark gap switch

    NASA Astrophysics Data System (ADS)

    Zeng, Han; Lin, Fuchang; Cai, Li; Li, Lee; Zhou, Zhengyang; Qi, Xiangdong

    2012-01-01

    In a high-powered single pulse system, the graphite electrode is better than other common metal electrodes for high energy transfer and pulse discharge. In this paper, the erosion mechanism of graphite electrode is investigated with the thermodynamics theory and the experimental results. Based on a simplified mathematical model, the graphite electrode erosion process of high-powered spark gap switch is also analyzed. The analysis results show that the relationship of the graphite electrode erosion and the charge transfer is linear, which is accordant with the experimental results.

  15. Study on erosion mechanism of graphite electrode in two-electrode spark gap switch.

    PubMed

    Zeng, Han; Lin, Fuchang; Cai, Li; Li, Lee; Zhou, Zhengyang; Qi, Xiangdong

    2012-01-01

    In a high-powered single pulse system, the graphite electrode is better than other common metal electrodes for high energy transfer and pulse discharge. In this paper, the erosion mechanism of graphite electrode is investigated with the thermodynamics theory and the experimental results. Based on a simplified mathematical model, the graphite electrode erosion process of high-powered spark gap switch is also analyzed. The analysis results show that the relationship of the graphite electrode erosion and the charge transfer is linear, which is accordant with the experimental results. PMID:22299948

  16. Factors Associated with Incomplete Insertion of Electrodes in Cochlear Implant Surgery: A Histopathologic Study

    PubMed Central

    Lee, Joonhan; Nadol, Joseph B.; Eddington, Donald K.

    2011-01-01

    Objectives Atraumatic and complete insertion of the electrode array is a stated objective of cochlear implant surgery. However, it is known that obstructions within the cochlea such as new bone formation, cochlear otosclerosis, temporal bone fracture, and cochlear anomalies may limit the depth of insertion of the electrode array. In addition, even among patients without obvious clinical or radiographic indicators of obstruction, incomplete insertion may occur. The current study is a histopathologic evaluation of possible sources of resistance to insertion of the electrode array using the temporal bone collection of the Massachusetts Eye and Ear Infirmary. Methods Forty temporal bones from patients who in life had undergone cochlear implantation were evaluated. Temporal bones were removed at autopsy and fixed and prepared for histologic study by standard techniques. Specimens were then serially sectioned and reconstructed by 2-dimensional methods. Two electrode metrics were determined for each bone: the inserted length (IL: the distance measured from the cochleostomy site to the apical tip of the electrode) and the active electrode length (AEL: the distance between the most basal and most apical electrodes on the electrode array). The ratio of these two metrics (IL/AEL) was used to split the temporal bones into two groups: those with incomplete insertion (n = 27, IL/AEL <1.0) and those with complete insertion (n = 13, IL/AEL ?1.0). Seven possible histopathologic indicators of resistance to insertion of the electrode due to contact with the basilar membrane, osseous spiral lamina and/or spiral ligament were evaluated by analysis of serial sections from the temporal bones along the course of the electrode tracks. Results Obvious obstruction by abnormal intracochlear bone or soft tissue accounted for only 6 (22%) of the 27 partial insertions. Of the remaining 21 bones with incomplete insertions and 13 bones with complete insertions, dissection of the spiral ligament to the lateral cochlear wall was the only histopathologic indicator of insertion resistance identified with significantly higher frequency in the partial-insertion bones than in the complete-insertion bones (p = 0.003). An observed trend for the percentage of complete insertions to decrease with the number of times the electrode penetrated the basilar membrane did not reach significance. In the bones without an obvious obstruction, the most frequently observed indicator of insertion resistance was dissection of the spiral ligament (with no contact of the lateral cochlear wall) identified in 67% (14/21) of partial-insertion bones and in 92% (12/13) of complete-insertion bones. Conclusion These results are consistent with the view that (1) electrode contact with cochlear structures resulting in observable trauma to the basilar membrane, osseous spiral lamina and/or spiral ligament does not necessarily impact the likelihood of complete insertion of the electrode array and (2) once contact trauma to the spiral ligament reaches the point of dissection to the cochlear wall, the likelihood of incomplete insertion increases dramatically. PMID:20571258

  17. Response to high-energy photons of PTW31014 PinPoint ion chamber with a central aluminum electrode

    SciTech Connect

    Agostinelli, S.; Garelli, S.; Piergentili, M.; Foppiano, F. [S. S. Fisica Medica, National Cancer Research Institute, 16132 Genova (Italy)

    2008-07-15

    Since its introduction the PinPoint (PTW-Freiburg) micro-ionization chamber has been proposed for relative dosimetry (output factors, depth dose curves, and beam profiles) as well as for determination of absolute dose of small high-energy photon beams. This paper investigates the dosimetric performance of a new design (type 31014) of the PinPoint ion chamber with a central aluminum electrode. The study included characterization of inherent and radiation-induced leakage, ion collection efficiency and polarity effect, relative response of the chamber, measurement of beam profiles, and depth dose curves. The 6 and 15 MV photon beams of a Varian 2100 C/D were considered. At the nominal operating voltage of 400 V the PinPoint type 31014 chamber was found to present a strong field size dependence of the polarity correction factor and an excess of the collected charge, which can lead to an underestimation of the collection efficiency if determined with the conventional ''two-voltage'' method. In comparison to the original PinPoint design (type 31006) the authors found for type 31014 chamber no overresponse to large-area fields if polarity correction is applied. If no correction is taken into consideration, the authors found the chamber's output to be inaccurate for large-area fields (0.5% accuracy limited up to the 12x12 and 20x20 cm{sup 2} field for the 6 and 15 MV beams, respectively), which is a direct consequence of the stem and polarity effects due to the chamber's very small sensitive volume (0.015 cc) and cable irradiation. Beam profiles and depth dose curves measured with type 31014 PinPoint chamber for small and medium size fields were compared to data measured with a 0.125 cc ion chamber and with high-resolution Kodak EDR2 films. Analysis of the penumbra (80%-20% distance) showed that the spatial resolution of type 31014 PinPoint ion chamber approaches (penumbra broadening {<=}0.6 mm) EDR2 film results.

  18. Comparison of resistive switching characteristics using copper and aluminum electrodes on GeOx/W cross-point memories

    PubMed Central

    2013-01-01

    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 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/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 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/GeOx/W devices, while a low operation voltage of ±2 V 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 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/GeOx/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. PMID:24305116

  19. Array electrode design for transcutaneous electrical stimulation: A simulation study

    Microsoft Academic Search

    Andreas Kuhn; Thierry Keller; Silvestro Micera; Manfred Morari

    2009-01-01

    Array electrodes are a promising technology that is likely to bring transcutaneous electrical stimulation (TES) a step forward. The dynamic adaptation of electrode size and position helps to simplify the use of electrical stimulation systems and to increase their clinical efficacy. However, up to now array electrodes were built by trial and error and it is unclear how, for example,

  20. Alternative Electrode Materials and Ceramic Filter Minimize Disinfection Byproducts in Point-of-Use Electrochemical Water Treatment.

    PubMed

    Yoon, Yeojoon; Jung, Youmi; Kwon, Minhwan; Cho, Eunha; Kang, Joon-Wun

    2013-12-01

    Effects of various electrodes and prefiltration to minimize disinfection byproducts (DBPs) in electrochemical water disinfection was evaluated. The target microorganism, Escherichia coli O157:H7, was effectively inactivated even applying a solar-charged storage battery for the electrolysis process. Extent of microbial inactivation decreased with lower water temperature and higher pH in the free chlorine disinfection system. The RuO2/Ti electrode was most efficient because it produced the lowest concentration of chlorate and the highest generation of free chlorine. Prefiltration using a ceramic filter inhibited formation of halogenated DBPs because it removed precursors of DBPs. For safe point-of-use water treatment, the use of a hybrid prefiltration stage with the electrolysis system is strongly recommended to reduce risks from DBPs. The system is particularly suited to use in developing regions. PMID:24381482

  1. Advances in Studies of Electrode Kinetics and Mass Transport in AMTEC Cells (abstract)

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Kisor, A.; O'Connor, D.; Kikkert, S.

    1993-01-01

    Previous work reported from JPL has included characterization of electrode kinetics and alkali atom transport from electrodes including Mo, W, WRh(sub x), WPt(sub x)(Mn), in sodium AMTEC cells and vapor exposure cells, and Mo in potassium vapor exposure cells. These studies were generally performed in cells with small area electrodes (about 1 to 5 cm(sup 2)), and device geometry had little effect on transport. Alkali diffusion coefficients through these electrodes have been characterized, and approximate surface diffusion coefficients derived in cases of activated transport. A basic model of electrode kinetic at the alkali metal vapor/porous metal electrode/alkali beta'-alumina solid electrolyte three phase boundary has been proposed which accounts for electrochemical reaction rates with a collision frequency near the three phase boundary and tunneling from the porous electrode partially covered with adsorbed alkali metal atoms. The small electrode effect in AMTEC cells has been discussed in several papers, but quantitative investigations have described only the overall effect and the important contribution of electrolyte resistance. The quantitative characterization of transport losses in cells with large area electrodes has been limited to simulations of large area electrode effects, or characterization of transport losses from large area electrodes with significant longitudinal temperature gradients. This paper describes new investigations of electrochemical kinetics and transport, particularily with WPt(sub 3.5) electrodes, including the influence of electrode size on the mass transport loss in the AMTEC cell. These electrodes possess excellent sodium transport properties making verification of device limitations on transport much more readily attained.

  2. Study for Electrode Metals on Taste Sensor with LB film

    NASA Astrophysics Data System (ADS)

    Yokoya, Takahiro; Hirata, Takamichi; Akiya, Masahiro

    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.

  3. First principles studies of silicon as a negative electrode material

    NASA Astrophysics Data System (ADS)

    Chevrier, Vincent L.

    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.

  4. Stimulation of the Human Lumbar Spinal Cord With Implanted and Surface Electrodes: A Computer Simulation Study

    Microsoft Academic Search

    Josef Ladenbauer; Karen Minassian; Ursula S. Hofstoetter; Milan R. Dimitrijevic; Frank Rattay

    2010-01-01

    Human lumbar spinal cord networks controlling stepping and standing can be activated through posterior root stimulation using implanted electrodes. A new stimulation method utilizing surface electrodes has been shown to excite lumbar posterior root fibers similarly as with implants, an unexpected finding considering the distance to these target neurons. In the present study we apply computer modeling to compare the

  5. Comprehensive study of noise processes in electrode electrolyte interfaces Arjang Hassibi,a)

    E-print Network

    Lee, Thomas H.

    Comprehensive study of noise processes in electrode electrolyte interfaces Arjang Hassibi,a) Reza equilibrium noise created by conductors, or nonequilibrium excess noise caused by charge transfer processes varying fluc- tuation, which substantiates the presence of noise processes. The noise of the electrode

  6. Influence of electrodes on the photon energy deposition in CVD-diamond dosimeters studied with the Monte Carlo code PENELOPE.

    PubMed

    Górka, B; Nilsson, B; Fernández-Varea, J M; Svensson, R; Brahme, A

    2006-08-01

    A new dosimeter, based on chemical vapour deposited (CVD) diamond as the active detector material, is being developed for dosimetry in radiotherapeutic beams. CVD-diamond is a very interesting material, since its atomic composition is close to that of human tissue and in principle it can be designed to introduce negligible perturbations to the radiation field and the dose distribution in the phantom due to its small size. However, non-tissue-equivalent structural components, such as electrodes, wires and encapsulation, need to be carefully selected as they may induce severe fluence perturbation and angular dependence, resulting in erroneous dose readings. By introducing metallic electrodes on the diamond crystals, interface phenomena between high- and low-atomic-number materials are created. Depending on the direction of the radiation field, an increased or decreased detector signal may be obtained. The small dimensions of the CVD-diamond layer and electrodes (around 100 microm and smaller) imply a higher sensitivity to the lack of charged-particle equilibrium and may cause severe interface phenomena. In the present study, we investigate the variation of energy deposition in the diamond detector for different photon-beam qualities, electrode materials and geometric configurations using the Monte Carlo code PENELOPE. The prototype detector was produced from a 50 microm thick CVD-diamond layer with 0.2 microm thick silver electrodes on both sides. The mean absorbed dose to the detector's active volume was modified in the presence of the electrodes by 1.7%, 2.1%, 1.5%, 0.6% and 0.9% for 1.25 MeV monoenergetic photons, a complete (i.e. shielded) (60)Co photon source spectrum and 6, 18 and 50 MV bremsstrahlung spectra, respectively. The shift in mean absorbed dose increases with increasing atomic number and thickness of the electrodes, and diminishes with increasing thickness of the diamond layer. From a dosimetric point of view, graphite would be an almost perfect electrode material. This study shows that, for the considered therapeutic beam qualities, the perturbation of the detector signal due to charge-collecting graphite electrodes of thicknesses between 0.1 and 700 microm is negligible within the calculation uncertainty of 0.2%. PMID:16861769

  7. Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter

    NASA Astrophysics Data System (ADS)

    Guo, Yuyan

    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.

  8. Characterization of piezoresistive PEDOT:PSS pressure sensors with inter-digitated and cross-point electrode structures.

    PubMed

    Wang, Jer-Chyi; Karmakar, Rajat Subhra; Lu, Yu-Jen; Huang, Chiung-Yin; Wei, Kuo-Chen

    2015-01-01

    The piezoresistive characteristics of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pressure sensors with inter-digitated (IDE) and cross-point electrode (CPE) structures have been investigated. A small variation of the resistance of the pressure sensors with IDE without bottom indium-tin-oxide (b-ITO) film and with CPE structures was observed owing to the single carrier-conducting pathway. For the IDE pressure sensors with b-ITO, the piezoresistive characteristics at low and high pressure were similar to those of the pressure sensors with IDE without b-ITO and with CPE structures, respectively, leading to increased piezoresistive pressure sensitivity as the PEDOT:PSS film thickness decreased. A maximum sensitivity of more than 42 k?/Pa was achieved. When the normal pressure was applied, the increased number of conducting points or the reduced distance between the PEDOT oligomers within the PEDOT:PSS film resulted in a decrease of the resistance. The piezoresistive pressure sensors with a single carrier-conducting pathway, i.e., IDE without b-ITO and CPE structures, exhibited a small relaxation time and a superior reversible operation, which can be advantageous for fast piezoresistive response applications. PMID:25569756

  9. Characterization of Piezoresistive PEDOT:PSS Pressure Sensors with Inter-Digitated and Cross-Point Electrode Structures

    PubMed Central

    Wang, Jer-Chyi; Karmakar, Rajat Subhra; Lu, Yu-Jen; Huang, Chiung-Yin; Wei, Kuo-Chen

    2015-01-01

    The piezoresistive characteristics of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pressure sensors with inter-digitated (IDE) and cross-point electrode (CPE) structures have been investigated. A small variation of the resistance of the pressure sensors with IDE without bottom indium-tin-oxide (b-ITO) film and with CPE structures was observed owing to the single carrier-conducting pathway. For the IDE pressure sensors with b-ITO, the piezoresistive characteristics at low and high pressure were similar to those of the pressure sensors with IDE without b-ITO and with CPE structures, respectively, leading to increased piezoresistive pressure sensitivity as the PEDOT:PSS film thickness decreased. A maximum sensitivity of more than 42 k?/Pa was achieved. When the normal pressure was applied, the increased number of conducting points or the reduced distance between the PEDOT oligomers within the PEDOT:PSS film resulted in a decrease of the resistance. The piezoresistive pressure sensors with a single carrier-conducting pathway, i.e., IDE without b-ITO and CPE structures, exhibited a small relaxation time and a superior reversible operation, which can be advantageous for fast piezoresistive response applications. PMID:25569756

  10. Studying the Performance of Conductive Polymer Films as Textile Electrodes for Electrical Bioimpedance Measurements

    NASA Astrophysics Data System (ADS)

    Cunico, F. J.; Marquez, J. C.; Hilke, H.; Skrifvars, M.; Seoane, F.

    2013-04-01

    With the goal of finding novel biocompatible materials suitable to replace silver in the manufacturing of textile electrodes for medical applications of electrical bioimpedance spectroscopy, three different polymeric materials have been investigated. Films have been prepared from different polymeric materials and custom bracelets have been confectioned with them. Tetrapolar total right side electrical bioimpedance spectroscopy (EBIS) measurements have been performed with polymer and with standard gel electrodes. The performance of the polymer films was compared against the performance of the gel electrodes. The results indicated that only the polypropylene 1380 could produce EBIS measurements but remarkably tainted with high frequency artefacts. The influence of the electrode mismatch, stray capacitances and large electrode polarization impedance are unclear and they need to be clarified with further studies. If sensorized garments could be made with such biocompatible polymeric materials the burden of considering textrodes class III devices could be avoided.

  11. Lunar libration point flight dynamics study

    NASA Technical Reports Server (NTRS)

    1969-01-01

    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.

  12. Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study Ramya Balachandran1

    E-print Network

    Webster III, Robert James

    Insertion of electrode array using percutaneous cochlear implantation technique: a cadaveric study-invasive technique, called percutaneous cochlear implantation (PCI), has been proposed that involves drilling: Percutaneous cochlear implantation, microstereotactic frame, minimally-invasive surgery. 1. INTRODUCTION

  13. Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter

    Microsoft Academic Search

    Yuyan Guo

    2006-01-01

    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\\

  14. A Study in Enzyme Kinetics Using an Ion-Specific Electrode.

    ERIC Educational Resources Information Center

    Turchi, Sandra; And Others

    1989-01-01

    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)

  15. Application of Electrode Methods in Studies of Nitric Oxide Metabolism and Diffusion Kinetics

    PubMed Central

    Liu, Xiaoping; Zweier, Jay L.

    2012-01-01

    Nitric oxide (NO) has many important physiological roles in the body. Since NO electrodes can directly measure NO concentration in the nM range and in real time, NO electrode methods have been generally used in laboratories for measuring NO concentration in vivo and in vitro. This review focuses on the application of electrode methods in studies of NO diffusion and metabolic kinetics. We have described the physical and chemical properties that need to be considered in the preparation of NO stock solution, discussed the effect of several interfering factors on the measured curves of NO concentration that need to be eliminated in the experimental setup for NO measurements, and provided an overview of the application of NO electrode methods in measuring NO diffusion and metabolic kinetics in solution and in biological systems. This overview covers NO metabolism by oxygen (O2), superoxide, heme proteins, cells and tissues. Important conclusions and physiological implication of these studies are discussed. PMID:23730264

  16. A new method of studying buried steel corrosion and its inhibition using the wire beam electrode

    Microsoft Academic Search

    Naing Naing Aung; Yong-Jun Tan

    2004-01-01

    An electrochemically integrated multi-electrode system namely the wire beam electrode (WBE) has been applied for the first time to study corrosion of mild steel buried in sand, with and without the presence of corrosion inhibitor potassium dichromate (K2Cr2O7). Measurements of galvanic current distribution maps have been carried out during the exposure of the WBE to dry, damp and chlorinated sand

  17. The adsorption of paraquat on silver electrode surfaces: a SERS microprobe study

    Microsoft Academic Search

    S. Kreisig; A. Tarazona; E. Koglin

    1997-01-01

    Surface-enhanced Raman microprobe spectroscopy (micro-SERS) has been used to study, in situ, the adsorption process of the bipyridylium herbicide paraquat (1,1?-dimethyl-4,4?-dipyridylium dichloride, PQ2+) on roughened silver electrode surfaces. The electrogeneration of the paraquat cation PQ+. and its interaction with the silver surface was investigated. The micro-SERS method permits the acquisition of surface Raman spectra from electrode surface spots down to

  18. Simulation studies of optimized electrode designs for a cylindrical IEC

    SciTech Connect

    Miley, G.H.; DeMora, J.; Stubbers, R.A.; Zich, R. [Univ. of Illinois, Urbana, IL (United States). Fusion Studies Lab.; Sved, J. [DASA, Bremmen (Germany); Anderl, R.; Hartwell, J. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1997-12-31

    The cylindrical version (c-device) of the single grid inertial electrostatic confinement (IEC) device is of strong interest for various neutron activation analysis (NAA) applications. The present version produces {approximately} 10{sup 6} D-D fusion neutron/s steady-state, and a higher yield pulsed version is under development. In both designs the grid configuration must be optimized for maximum neutron yield. An ion tracking code, SIMION has been adapted for this purpose. While it includes several key approximations (e.g., neglects self-fields and collisions), it still predicts trends well for the present regime of operation, and provides improved physical insight. Recent simulations have examined variations of the reference electrode design, covering a wide range of diameters and lengths. Thus, for example, with a 10-cm long cathode and 3-cm long anodes the optimum diameter is predicted to be 60--80 mm. As the diameter is reduced further, the ion beam focus is lost. Further, the plasma sheath at the inside cathode wall begins to distort the beam path. These simulations will be described along with results for several novel designs, including a modular cathode and multiple segmented electrode concept will be presented.

  19. Study on the distortion of apparent resistivity curves caused by the 'infinite' electrode space of a Pole-Pole array and its correction

    NASA Astrophysics Data System (ADS)

    Xiao, Le-Le; Wei, Jiu-Chuan; Niu, Chao; Shi, Long-Qing; Zhai, Pei-He; Yin, Hui-Yong; Xie, Dao-Lei

    2015-07-01

    The Pole-Pole (PP) array is widely used for measurements that incorporate two-dimensional (2-D) and three-dimensional (3-D) multi-electrode electrical resistivity surveys, although an effective equilibrium has not yet been achieved between two factors, the location of 'infinite' electrodes and the data utilisation of the effective resistivity, which affects the detection accuracy; thus, the data collected under the conditions of 'infinite' electrodes that are as finite as possible are maximally effective. Studies have shown that the optimum 'infinite' electrode distance must be greater than 20 times the current-potential electrode distance AM; this value is much greater than the currently used value of 5 to 10 times AM. However, limitations imposed by landforms and topographic conditions, such as mountainous areas and coal mine roadways, often prevent the 'infinite' condition from being satisfied. In this study, a field test was designed and performed by adopting a particular PP array to collect sounding data under different 'infinite' electrode distances, and the differences were analysed in the apparent resistivity curves calculated with different geometric coefficients. The results reveal that when the 'infinite' electrode space is finite relative to AM, significant distortion may occur, and a minimum inflection point may appear in the sounding curve of apparent resistivity that is calculated with the geometric coefficient Kpp. Although the data past the minimum inflection point of ?s-mpp curve lose their value for the sounding application, a portion of the first segment of the distorted curve can be used, therefore, a correction formula under the condition of non-infinite electrode (Bing and Greenhalgh, 1998) space in a PP array is derived based on traditional electric field theories and formulas of apparent resistivity under different electrode arrays. The error analysis after correction indicates that the data utilisation ratio in the corrected effective apparent resistivity is significantly improved, and all the data that appear before the minimum inflection point can be effectively corrected. Additionally, the error between the corrected apparent resistivity and the value under an ideal state (when BM is at least 20 times AM) is less than 5%. Engineering application cases are conducted to validate the effectiveness of this correction formula, and the results indicate that this formula can be applied to process the resistivity sounding data affected by the 'infinite' electrodes.

  20. Mass-transfer study of carbon felt, flow-through electrode

    NASA Astrophysics Data System (ADS)

    Kinoshita, K.; Leach, S. C.

    1982-09-01

    The mass-transfer characteristics of a carbon felt, flow-through electrode that has potential application for the positive electrode in zinc-bromine batteries were studied. The electrochemical technique of limiting current measurements for the cathodic reduction of 0.0055-.062 M bromine in excess supporting electrolytes was used. In an electrochemical cell with perpendicular flow of electrolyte and current, limiting currents that were proportional to the electrolyte velocity, which was dependent on the electrode thickness but independent of the concentration of reactant species, were obtained at low Reynolds numbers. Analysis of the data using a model that relates the conversion efficiency of a porous electrode to a dimensionless group which contains experimental parameters such as porosity, pore diameter, flow rate, and diffusion coefficient, showed good agreement.

  1. Study of electrode pattern design for a CZT-based PET detector

    PubMed Central

    Gu, Y; Levin, C S

    2014-01-01

    We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3-D positioning Cadmium Zinc Telluride (CZT) photon detectors comprising 40 mm × 40 mm × 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 mm 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 ns to ~127.5 ns 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 ns 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 strips’ weighting functions, which indicated a stronger “small pixel” 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 V to ?80 V w.r.t the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 ?m vs. 100 ?m) 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

  2. Study of electrode pattern design for a CZT-based PET detector.

    PubMed

    Gu, Y; Levin, C S

    2014-06-01

    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 × 40 mm × 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 strips' weighting functions, which indicated a stronger 'small pixel' 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 µm) 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

  3. Study of the influence of transducer-electrode and electrode-wall gaps on the acoustic field inside a sonoelectrochemical reactor by FEM simulations

    Microsoft Academic Search

    Ignacio Tudela; Verónica Sáez; María Deseada Esclapez; Pedro Bonete; Hassen Harzali; Fabien Baillon; José González-García; Olivier Louisnard

    2011-01-01

    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

  4. Point-process analysis of neural spiking activity of muscle spindles recorded from thin-film longitudinal intrafascicular electrodes

    E-print Network

    Citi, Luca

    Recordings from thin-film Longitudinal Intra-Fascicular Electrodes (tfLIFE) together with a wavelet-based de-noising and a correlation-based spike sorting algorithm, give access to firing patterns of muscle spindle afferents. ...

  5. Numerical Study of the Buoyancy-Driven Flow in a Four-Electrode Rectangular Electrochemical Cell

    NASA Astrophysics Data System (ADS)

    Sun, Zhanyu; Agafonov, Vadim; Rice, Catherine; Bindler, Jacob

    2009-11-01

    Two-dimensional numerical simulation is done on the buoyancy-driven flow in a four-electrode rectangular electrochemical cell. Two kinds of electrode layouts, the anode-cathode-cathode-anode (ACCA) and the cathode-anode-anode-cathode (CAAC) layouts, are studied. In the ACCA layout, the two anodes are placed close to the channel outlets while the two cathodes are located between the two anodes. The CAAC layout can be converted from the ACCA layout by applying higher electric potential on the two middle electrodes. Density gradient was generated by the electrodic reaction I3^-+2e^- =3I^-. When the electrochemical cell is accelerated axially, buoyancy-driven flow occurs. In our model, electro-neutrality is assumed except at the electrodes. The Navier-Stokes equations with the Boussinesq approximation and the Nernst-Planck equations are employed to model the momentum and mass transports, respectively. It is found that under a given axial acceleration, the electrolyte density between the two middle electrodes determines the bulk flow through the electrochemical cell. The cathodic current difference is found to be able to measure the applied acceleration. Other important electro-hydrodynamic characteristics are also discussed.

  6. Impedance spectroscopy of nonactive metal electrodes at low potentials in propylene carbonate solutions: A comparison to studies of Li electrodes

    SciTech Connect

    Aurbach, D.; Zaban, A. (Bar-Ilan Univ., Ramat Gan (Israel). Dept. of Chemistry)

    1994-07-01

    Surface films formed on nonactive metals (nickel, gold, and silver) in propylene carbonate solutions were investigated using impedance spectroscopy. The salts used included LiClO[sub 4], LiAsF[sub 6], LiBF[sub 4], and LiPF[sub 6], and the impact of their concentration on the properties of the surface films was explored. In addition, the influence of the presence of additives such as O[sub 2], H[sub 2]O, and CO[sub 2] in solutions and the potential of formation on the properties of these surface films was rigorously studied. Using simple methods and simulation programs, it was possible to separate the time constants of the impedance spectra, relate them to different parts of the metal-solution interface, and to calculate the thickness of these surface films from the interfacial capacitances. Following variations of the thickness calculated for the surface films formed in the different systems as a function of applied potential and solution composition, it was possible to study the stability of the surface films, their dissolution rates and the influence of different additives on their stability. For a few systems, ex situ Fourier transform infrared spectroscopy (external reflectance mode) was also applied. The results thus obtained were correlated to previous studies of Li electrodes in the same solutions.

  7. Voltammetric studies of porous molybdenum electrodes for the alkali metal thermoelectric converter

    SciTech Connect

    Williams, R.M.; Bankston, C.P.; Khanna, S.K.; Cole, T.

    1986-11-01

    Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from --600 to --1000 K revealed a series of redox processes within the operational voltage range of the AMTEC device. The most important of these processes involve reactions that add sodium to MoO/sub 2/, Na/sub 2/Mo/sub 3/O/sub 6/, and Na/sub 2/MoO/sub 4/. The redox processes can be used as an in situ analytical probe of oxide species in porous molybdenum electrodes. These constituents are important in establishing the electronic and ionic conductivities of AMTEC electrodes. The estimated equilibrium potentials of these reactions provide improved estimates of the free energies of formation of Na/sub 2/Mo/sub 3/O/sub 6/, NaMoO/sub 2/, and Na/sub 3/MoO/sub 4/. In the AMTEC operating regime, there is evidence for the comparatively slow corrosive attack by Na/sub 2/MoO/sub 4/ on molybdenum. The ionic conductivity of Na/sub 2/MoO/sub 4/ measured from 600 to over 1000 K shows sharp increases in conductivity at --750, 865, and 960 K. The conductivity is sufficiently large at T > 700 K to explain the observed electrochemical phenomena, as well as enhanced sodium transport in AMTEC electrodes below the freezing point (960 K) of Na/sub 2/MoO/sub 4/.

  8. Studies of the interface between lithium electrodes and polymeric electrolyte systems using in situ FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Chusid, O.; Gofer, Y.; Aurbach, D.; Watanabe, M.; Momma, T.; Osaka, T.

    This paper describes studies of the interface between lithium electrodes and solid electrolyte systems using in situ FTIR spectroscopy in a single internal reflectance mode. In this method, the masking effect of the electrolyte matrix components is largely avoided. We studied gel electrolytes based on polyvinylidene difluoride-hexafluoropropylene with cyclic alkyl carbonates as plasticizers, suitable for ambient temperatures, and a solvent free polymer, derivatives of polyethylene oxide (PEO) with a branched structure: poly[ethyleneoxide-2-(2-methoxyethoxy)ethyl glycidyl ether] at elevated temperatures. We found that the surface chemistry of Li electrodes in contact with the gel matrixes is dominated by alkyl carbonate solvent reduction to ROCO 2Li surface species. In the case of the PEO-based polymer, the surface reactions of Li electrodes are dominated by salt and trace water reduction. The polymer itself seems to be stable with lithium even at 60°C.

  9. The use of carbon paste electrodes with non-conducting binder for the study of minerals: Chalcopyrite

    Microsoft Academic Search

    Isabel Lázaro; Norma Martínez-Medina; Israel Rodríguez; Elsa Arce; Ignacio González

    1995-01-01

    A pulverized chalcopyrite mixture with graphite and silicon was subjected to electrochemical studies and found to have similar behaviour to that of chalcopyrite massive electrodes, with the advantage of excellent reproducibility, since the problems of polishing deficiency, fracture and lack of homogeneity that solid electrodes present, are avoided. From voltammetric studies of these carbon paste-chalcopyrite electrodes in H2SO4, HNO3 and

  10. Metallic electrodes and leads in simultaneous EEG-MRI: specific absorption rate (SAR) simulation studies.

    PubMed

    Angelone, Leonardo M; Potthast, Andreas; Segonne, Florent; Iwaki, Sunao; Belliveau, John W; Bonmassar, Giorgio

    2004-05-01

    The purpose of this study was to investigate the changes in specific absorption rate (SAR) in human-head tissues while using nonmagnetic metallic electroencephalography (EEG) electrodes and leads during magnetic resonance imaging (MRI). A realistic, high resolution (1 mm(3)) head model from individual MRI data was adopted to describe accurately thin tissues, such as bone marrow and skin. The RF power dissipated in the human head was evaluated using the FDTD algorithm. Both surface and bird cage coils were used. The following numbers of EEG electrodes/leads were considered: 16, 31, 62, and 124. Simulations were performed at 128 and 300 MHz. The difference in SAR between the electrodes/leads and no-electrodes conditions was greater with the bird cage coil than with the surface coil. The peak 1 g averaged SAR values were highest at 124 electrodes, increasing to as much as two orders of magnitude (x172.3) at 300 MHz compared to the original value. At 300 MHz, there was a fourfold (x3.6) increase of SAR averaged over the bone marrow, and a sevenfold (x7.4) increase in the skin. At 128 MHz, there was a fivefold (x5.6) increase of whole head SAR. Head models were obtained from two different subjects, with an inter-subject whole head SAR variability of 3%. . PMID:15114638

  11. A Magnetic Bright Point Case Study

    NASA Astrophysics Data System (ADS)

    Utz, D.; Jur?ák, J.; Bellot-Rubio, L.; del Toro Iniesta, J. C.; Thonhofer, S.; Hanslmeier, A.; Veronig, A.; Muller, R.; Lemmerer, B.

    Due to its magnetic fields our host star - the Sun - becomes the interesting object for research as we know it. The magnetic fields themselves cover different spatial, lifetime and strength scales and reach down from enormous flux concentrations like active sunspot groups to single isolated magnetic flux tubes and even weaker, predominantly inclined intranetwork structures. Flux tubes can be seen in filtergram observations as magnetic bright points (MBPs). They are of interest for research not only due to their sheer existence but due to their important role in atmospheric heating (wave heating as well as reconnection processes), to their role in the understanding of creation and annihilation of magnetic fields as well as to their influence on the total solar irradiance variation. In this study we present a close look onto an evolutionary track of an MBP from its formation to its disintegration. Physical quantities of MBPs like their magnetic field strength and inclination, their line-of-sight velocity, and their temperature at different heights are inferred from the inversion of spectropolarimetric data. Original data are taken from the Sunrise/IMaX instrument and constitute a time series of some 60 min. The presented case resembles the convective collapse model and is in agreement with previous studies.

  12. Studies on Mechanical Alloying of Copper-Tungsten Carbide Composite for Spot Welding Electrode

    NASA Astrophysics Data System (ADS)

    Zuhailawati, H.; Jamaludin, S. B.

    2009-12-01

    This article presents a study on the properties and performance of copper-based composite reinforced with recycled tungsten carbide powder as spot welding electrode. The copper-tungsten carbide composite electrode was prepared by mechanical alloying and powder forging before being machined into truncated cone-face geometry. The welding operation was conducted on galvanized steel using a pedestal-type spot welding machine. Composites with higher density and electrical conductivity were obtained after mechanical alloying for shorter time. In contrast, a higher hardness is shown in the composite, which was mechanically alloyed to longer time. The strength of the welded steel coupon was found to increase with decreasing milling time due to an increase in density and electrical conductivity. The wear behavior of the composite revealed that the deformation of the spot weld electrode increased with increasing milling time.

  13. Two and Three-Electrode Impedance Studies on 18650 Li-Ion Cells

    SciTech Connect

    Nagasubramanian, Ganesan

    1999-08-11

    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).

  14. Efficiency of Timing Delays and Electrode Positions in Optimization of Biventricular Pacing: A Simulation Study

    Microsoft Academic Search

    Iulia M. Graf; Olaf DÖssel

    2009-01-01

    Electrode positions and timing delays influence the efficacy of biventricular pacing (BVP). Accordingly, this study focuses on BVP optimization, using a detailed 3-D electrophysiological model of the human heart, which is adapted to patient-specific anatomy and pathophysiology. The research is effectuated on ten heart models with left bundle branch block and myocardial infarction derived from magnetic resonance and computed tomography

  15. Nanopore Patterned Pt Array Electrodes for Triple Phase Boundary Study in Low Temperature SOFC

    E-print Network

    Cui, Yi

    Nanopore Patterned Pt Array Electrodes for Triple Phase Boundary Study in Low Temperature SOFC structural integrity and thermal stability at the solid oxide fuel cell SOFC operating temperature of 450, Meeting of the Society, October 4­9, 2009. Solid oxide fuel cells SOFCs are efficient energy conversion

  16. Catalytic study of SOFC electrode materials in engine exhaust gas Pauline Briaulta

    E-print Network

    Paris-Sud XI, Université de

    1 Catalytic study of SOFC electrode materials in engine exhaust gas atmosphere Pauline Briaulta Fuel Cell (SC-SOFC) is a device able to produce electricity from a mixture of hydrocarbons and oxidant for conventional SOFCs. Anode material was a cermet composed of nickel and Ce0.9Gd0.1O1.95 (GDC) which was also

  17. A study on electrode for amperometric measurement of human stress with flow injection analysis biosensing system

    Microsoft Academic Search

    Lee Yoot Khuan; M. Hurairah Adha b Kamaruddin; Mohd Firdaus Abdullah; N. K. Madzhi; Anuar Ahmad

    2010-01-01

    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

  18. Nickel and nickel based alloys as oxygen electrodes for alkaline water electrolysis: Electrochemical and ellipsometric studies

    Microsoft Academic Search

    W. T. P. Lu

    1976-01-01

    The major objectives of the present study are: (1) to obtain electrode kinetic parameters for hydrogen and oxygen evolution reactions as a function of temperature and to ascertain the efficiency gain at higher operating temperature for water electrolysis; (2) to investigate the kinetics of the OER on Ni-based alloys or intermetallic compounds and to elucidate effects of electronic structure of

  19. Degradation of Li/S Battery Electrodes Studied Using X-ray Phase Contrast Tomography

    E-print Network

    Schmidt, Volker

    1 Degradation of Li/S Battery Electrodes Studied Using X-ray Phase Contrast Tomography L. Zielkea. Zengerlea,f and S. Thielea,g Lithium/sulphur batteries are promising candidates for future energy storage passivation and increasing charge transfer resistance. Broader Context Lithium/sulphur batteries are currently

  20. Electrode-polarization studies in hot-corrosion systems. Progress report, 1 June 1980-31 May 1981

    SciTech Connect

    Devereux, O.F.

    1981-02-01

    The following tasks are reported on: electrode polarization studies in molten sodium carbonate, liquid line corrosion, and gas/metal reactions in mixed oxidants. Two previously unpublished papers are included as appendices: Reactions at the CO, CO/sub 2//Ni electrode in Molten Sodium Carbonate; and Reactions at the Corroding Nickel Electrode in Molten Sodium Carbonate under CO, CO/sub 2/ Atmospheres. (DLC)

  1. Different Influences of Hematocrit on the Results of Two Point-Of-Care Platelet Function Tests, the VerifyNow Assay and Multiple Electrode Platelet Aggregometry

    PubMed Central

    Kim, Yun Gi; Suh, Jung-Won; Park, Jin Joo; Oh, Il-Young; Yoon, Chang-Hwan; Cho, Young-Seok; Youn, Tae-Jin; Chae, In-Ho; Choi, Dong-Ju

    2014-01-01

    Objective Previous studies have reported a considerable association between the VerifyNow (Accumetrics, San Diego, CA, USA) P2Y12 assay results and hematocrit. No reports, however, have described an association between the multiple electrode platelet aggregometry (MEA; Dynabyte, Munich, Germany) adenosine diphosphate (ADP) assay results and hematocrit. This study was conducted to evaluate the influence of hematocrit on the results of 2 different point-of-care platelet function tests. Methods A total of 462 consecutive patients who were undergoing percutaneous coronary intervention were enrolled. Platelet function was evaluated with both the VerifyNow P2Y12 and MEA ADP assays. Results Anemic patients (n?=?152, 32.9%) demonstrated a significantly higher rate of cardiac death, myocardial infarction, and stroke (5.3% vs. 2.3%, p?=?0.046) during the follow-up (median: 18.8 months). Although the VerifyNow P2Y12 assay results demonstrated a significant inverse correlation with hematocrit (r?=??0.409, p<0.001), there was no such correlation between the MEA ADP assay results and hematocrit (r?=?0.039, p?=?0.401). In the multivariate analysis, anemia was an independent predictor of high on-treatment platelet reactivity, defined as a VerifyNow P2Y12 reaction unit level of ?252.5 (odds ratio?=?2.21, 95% confidence interval?=?1.39–3.52; p?=?0.001). Importantly, this association was independent of an intrinsic change in platelet reactivity as measured by the MEA ADP assay. Adjusting for the influence of hematocrit improved the strength of the correlation between the VerifyNow P2Y12 and MEA ADP assay results. Conclusions Hematocrit significantly influenced the VerifyNow P2Y12 assay results, a phenomenon that was presumably in-vitro. Hematocrit level should therefore be considered when interpreting results of the VerifyNow P2Y12 assay. PMID:25427105

  2. Astrometric Telescope Facility isolation and pointing study

    NASA Technical Reports Server (NTRS)

    Hibble, William; Allen, Terry; Jackson, Louis; Medbery, James; Self, Richard

    1988-01-01

    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.

  3. Case study of AES Barbers Point, Inc.

    SciTech Connect

    Ryan, S.

    1994-12-31

    The AES Barbers Point plant is a $383 million coal-fired cogeneration facility. The plant is the first major coal-fired electric power producer in the Hawaiian Islands, and is the largest single supplier of electricity to Hawaiian Electric Company (BECO). The plant is capable of supplying over 189 megawatts of electricity, approximately 18 percent of the electricity needs of Oahu, the most densely populated island in the Hawaiian chain. In addition to the electricity generated, the state-of-the-art plant produces 30,000 pounds of steam per hour for the Chevron USA oil refinery at Barbers Point.

  4. Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter

    E-print Network

    Guo, Yuyan

    2009-05-15

    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...

  5. Lipid-membrane modified electrodes to study quinone oxidoreductases

    PubMed Central

    Weiss, Sophie A.; Jeuken, Lars J. C.

    2013-01-01

    Quinone oxidoreductases are a class of membrane enzymes that catalyse the oxidation or reduction of membrane-bound quinols/quinones. The conversion of quinone/quinol by these enzymes is difficult to study due to the hydrophobic nature of the enzymes and their substrates. We describe some biochemical properties of quinones and quinone oxidoreductases and then look in more detail at two model membranes that can be used to study quinone oxidoreductases in a native-like membrane environment with their native lipophylic quinone substrates. The results obtained with these model membranes are compared to classical enzyme assays that use water-soluble quinone analogues. PMID:19614580

  6. Electrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow conditions

    E-print Network

    Electrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow November 2013 Available online 18 December 2013 Keywords: Multi-electrode Microbial fuel cells Hydraulic connected microbial fuel cells (MFCs) was compared with the reactors operated using individual electrical

  7. Electrochemical studies of an unsupported PtIr electrocatalyst as a bifunctional oxygen electrode in a unitized regenerative fuel cell

    Microsoft Academic Search

    Ho-Young Jung; Branko N. Popov

    2009-01-01

    The electrochemical performance of an unsupported PtIr electrocatalyst was evaluated as a bifunctional oxygen electrode in a unitized regenerative fuel cell (URFC). The catalyst was a mixture of unsupported Pt black and Ir black catalysts in varying proportions. The performance of the unsupported PtIr catalyst was studied by using a rotating ring disc electrode (RRDE) and linear sweep voltammetry (LSV).

  8. ICESat Spacecraft Pointing Support Study Grant

    NASA Technical Reports Server (NTRS)

    2000-01-01

    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.

  9. A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique

    NASA Technical Reports Server (NTRS)

    Donford, M. D.; Ding, R. J.

    1998-01-01

    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.

  10. A 100 electrode intracortical array: structural variability.

    PubMed

    Campbell, P K; Jones, K E; Normann, R A

    1990-01-01

    A technique has been developed for fabricating three dimensional "hair brush" electrode arrays from monocrystalline silicon blocks. Arrays consist of a square pattern of 100 penetrating electrodes, with 400 microns interelectrode spacing. Each electrode is 1.5mm in length and tapers from about 100 microns at its base to a sharp point at the tip. The tips of each electrode are coated with platinum and the entire structure, with the exception of the tips, is insulated with polyimide. Electrical connection to selected electrodes is made by wire bonding polyimide insulated 25 microns diameter gold lead wires to bonding pads on the rear surface of the array. As the geometrical characteristics of the electrodes in such an aray will influence their electrical properties (such as impedance, capacitance, spreading resistance in an electrolyte, etc.) it is desirable that such an array have minimal variability in geometry from electrode to electrode. A study was performed to determine the geometrical variability resulting from our micromachining techniques. Measurements of the diameter of each of the 100 electrodes were made at various planes above the silicon substrate of the array. For the array that was measured, the standard deviation of the diameters was approximately 9% of the mean diameter near the tip, 8% near the middle, and 6% near the base. We describe fabrication techniques which should further reduce these variabilities. PMID:2334761

  11. Study on erosion mechanism of graphite electrode in two-eletrode spark gap

    Microsoft Academic Search

    Han Zeng; Fuchang Lin; Cai Li; Li Li; Gang Liu; Feng Yu

    2011-01-01

    In a high-powered single pulse system, the graphite electrode is better than other ordinary metal electrodes for high energy transfer and pulse discharge. The erosion mechanism of graphite electrode is investigated in the paper with the theory of thermodynamics and the results of experiment. The graphite electrode erosion process of high-powered spark gap switch is analyzed, based on the set

  12. A study of the effect of magnetized water on enzyme activities by potentiometric enzyme electrode method.

    PubMed

    Ma, Y L; Ren, H; Ren, S; Zhen, E K; Hao, G; Zhao, Y W

    1992-01-01

    A very promising glutamate decarboxylase electrode, which has linear response range of 5.6 x 10(-5)-1.2 x 10(-2) mol/L. Nernstian slope of 50 mV/decade, detection limit of 3.2 x 10(-5) mol/L and response time less than 3 min, has been designed to observe and evaluate quantitatively the effect of magnetized water on enzyme activities by potentiometric enzyme electrode method. It was found that the activity of glutamate decarboxylase can increase by 30% in magnetized water. The mechanism of increased enzyme activity was discussed in the present paper. Such a new finding will probably lead to some new explanations for the physiological and biological mechanism of the effect of magnetized water on living organisms, thus providing a new approach to the study of the effect of magnetized water. PMID:1289564

  13. Thermal-stability studies of electrode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Jiang, Junwei

    2005-07-01

    The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ? x ? 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ? y ? 1/4, 1/6 ? z ? 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

  14. Point-to-Point Car Racing: an Initial Study of Evolution Versus Temporal Difference Learning

    E-print Network

    Togelius, Julian

    Point-to-Point Car Racing: an Initial Study of Evolution Versus Temporal Difference Learning Simon, jtogel}@essex.ac.uk Abstract-- This paper considers variations on an extremely simple form of car racing-evaluation neural networks, and these were greatly superior to human drivers. Keywords: Car racing, reinforcement

  15. Electrochemical Behavior and Li Diffusion Study of LiCoO? Thin Film Electrodes Prepared by PLD

    E-print Network

    Xia, H.

    Preferred c-axis oriented LiCoO? thin films were prepared on the SiO?/Si (SOS) substrates by pulsed laser deposition (PLD). Thin film electrodes without carbon and binder are ideal samples to study the electrochemical ...

  16. Chemisorption and anodic oxidation of aromatic molecules on Pd electrode surfaces: studies by UHV-EC-STM

    E-print Network

    Chen, Xiaole

    2006-04-12

    The chemisorption and anodic oxidation of hydroquinone (H2Q) and benzoquinone (BQ) at palladium electrode surfaces was studied by a combination of electrochemistry (EC), Auger electron spectroscopy (AES), high-resolution electron...

  17. Chemisorption and anodic oxidation of aromatic molecules on Pd electrode surfaces: studies by UHV-EC-STM 

    E-print Network

    Chen, Xiaole

    2006-04-12

    The chemisorption and anodic oxidation of hydroquinone (H2Q) and benzoquinone (BQ) at palladium electrode surfaces was studied by a combination of electrochemistry (EC), Auger electron spectroscopy (AES), high-resolution electron...

  18. Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide

    PubMed Central

    Lin, Jyh-Ling; Hsu, Hsiang-Yi

    2010-01-01

    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. PMID:22294900

  19. REACTION KINETICS AND X-RAY ABSORPTION SPECTROSCOPY STUDIES OF YTTRIUM CONTAINING METAL HYDRIDE ELECTRODES

    SciTech Connect

    TICIANELLI,E.A.; MUKERJEE,S.; MCBREEN,J.; ADZIC,G.D.; JOHNSON,J.R.; REILLY,J.J.

    1998-11-01

    This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)}, (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.

  20. Reaction kinetics and x-ray absorption spectroscopy studies of yttrium containing metal hydride electrodes

    SciTech Connect

    Ticianelli, E.A.; Mukerjee, S.; McBreen, J.; Adzic, G.D.; Johnson, J.R.; Reilly, J.J. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science

    1998-12-31

    This was a study of electrode degradation mechanisms and the reaction kinetics of LaNi{sub 4.7}Sn{sub 0.3}, La{sub (1{minus}x)} Y{sub x}Ni{sub 4.7}Sn{sub 0.3} (x = 0.1, 0.2, and 0.3) and La{sub 0.7}Y{sub 0.3}Ni{sub 4.6}Sn{sub 0.3}Co{sub 0.1} metal hydride electrodes. Alloy characterization included x-ray diffraction (XRD), x-ray absorption (XAS), hydrogen absorption in a Sieverts apparatus, and electrochemical cycling of alloy electrodes. The atomic volume of H was determined for two of the alloys. Electrochemical kinetic measurements were made using steady state galvanostatic measurements, galvanodynamic sweep, and electrochemical impedance techniques. XAS was used to examine the degree of corrosion of the alloys with cycling. Alloying with Y decreased the corrosion rate. The results are consistent with corrosion inhibition by a Y containing passive film. The increase in the kinetics of the hydrogen oxidation reaction (HOR) with increasing depth of discharge was much greater on the Y containing alloys. This may be due to the dehydriding of the catalytic species on the surface of the metal hydride particles.

  1. Numerical study on the electron—wall interaction in a Hall thruster with segmented electrodes placed at the channel exit

    NASA Astrophysics Data System (ADS)

    Qing, Shao-Wei; E, Peng; Duan, Ping; Xu, Dian-Guo

    2013-08-01

    Electron—wall interaction is always recognized as an important physical problem because of its remarkable influences on thruster discharge and performance. Based on existing theories, an electrode is predicted to weaken electron—wall interaction due to its low secondary electron emission characteristic. In this paper, the electron—wall interaction in an Aton-type Hall thruster with low-emissive electrodes placed near the exit of discharge channel is studied by a fully kinetic particle-in-cell method. The results show that the electron—wall interaction in the region of segmented electrode is indeed weakened, but it is significantly enhanced in the remaining region of discharge channel. It is mainly caused by electrode conductive property which makes equipotential lines convex toward channel exit and even parallel to wall surface in near-wall region; this convex equipotential configuration results in significant physical effects such as repelling electrons, which causes the electrons to move toward the channel center, and the electrons emitted from electrodes to be remarkably accelerated, thereby increasing electron temperature in the discharge channel, etc. Furthermore, the results also indicate that the discharge current in the segmented electrode case is larger than in the non-segmented electrode case, which is qualitatively in accordance with previous experimental results.

  2. Two-dimensional numerical study of an atmospheric pressure helium plasma jet with dual-power electrode

    NASA Astrophysics Data System (ADS)

    Yan, Wen; Liu, Fu-Cheng; Sang, Chao-Feng; Wang, De-Zhen

    2015-06-01

    In this paper, the characteristics of an atmospheric pressure helium plasma jet generated by a dual-power electrode (DPE) configuration are investigated by using a two-dimensional fluid model. The effect of a needle electrode on the discharge is studied by comparing the results of the DPE configuration with those of the single ring electrode configuration. It is found that the existence of the needle leads to the generation of a helium plasma jet with a higher propagation velocity, higher species density, and larger discharge width. Furthermore, the influences of the needle radius and needle-to-ring discharge gap on the generation of a plasma jet are also studied. The simulation results indicate that the needle electrode has an evident influence on the plasma jet characteristics. Project supported by the National Natural Science Foundation of China (Grant Nos. 10775026, 11275042, 11305026, and 11405042).

  3. Studies on electrochemical oxidation of non-aqueous electrolyte on the LiCoO 2 thin film electrode

    Microsoft Academic Search

    Kiyoshi Kanamura; Shigetaka Toriyama; Soshi Shiraishi; Masahiro Ohashi; Zen-ichiro Takehara

    1996-01-01

    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

  4. Studies on a non-thermal pulsed corona plasma between two parallel-plate electrodes in water

    Microsoft Academic Search

    M M Sein; Z Bin Nasir; U Telgheder; T C Schmidt

    2012-01-01

    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

  5. A study of fullerene-quantum dot composite structure on substrates with a transparent electrode layer

    NASA Astrophysics Data System (ADS)

    Pavlov, S. I.; Kirilenko, D. A.; Nashchekin, A. V.; Sokolov, R. V.; Konnikov, S. G.

    2015-02-01

    We have studied the structure of films consisting of fullerene clusters and a related fullerene-based composite with incorporated quantum dots. The films were obtained by electrophoretic deposition from solution onto glass substrates with a transparent indium-doped tin oxide (ITO) electrode layer. The average cluster size, as measured by electron microscopy, amounts to 300 nm in pure fullerene films and 800 nm in the composite material. Electron diffraction measurements showed that pure fullerene clusters had an fcc lattice, while the introduction of quantum dots rendered the fullerene matrix predominantly amorphous.

  6. Origins of the Human Pointing Gesture: A Training Study

    ERIC Educational Resources Information Center

    Matthews, Danielle; Behne, Tanya; Lieven, Elena; Tomasello, Michael

    2012-01-01

    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 with…

  7. Ion exchange at the electrode/electrolyte interface studied by probe beam deflection techniques.

    PubMed

    Barbero, César A

    2005-05-01

    Probe beam deflection (PBD) techniques are a set of in situ electrochemical methods based on the measurement of refractive index gradients in front of the electrode/electrolyte interface. Here, the details of the techniques are described. First, the theory of potential step chronodeflectometry and pulse voltadeflectometry is discussed. Later, different numerical procedures used for data processing and/or simulation of cyclic voltadeflectometry experiments are described. Then, an overview is performed of the techniques use to study electrochemical systems. The systems described are limited to surface species in binary electrolytes, where a clear interpretation of the data is possible. Among the systems studied are: surface reactions on solid electrodes, electrochromic oxides, conducting polymers, redox polymers, double layer charging in nanostructured carbons and ion exchange in layer-by-layer self assembled multilayers. It is shown that PBD techniques have been able to ascertain the effect of different factors on ion exchange: anion size, pH, solvent, film composition, covalent modification, etc. The capability of the techniques to perform fast measurements was also used with success to find out kinetic effects on the ion exchange. PMID:19787889

  8. An impedimetric study of DNA hybridization on paper-supported inkjet-printed gold electrodes

    NASA Astrophysics Data System (ADS)

    Ihalainen, Petri; Pettersson, Fredrik; Pesonen, Markus; Viitala, Tapani; Määttänen, Anni; Österbacka, Ronald; Peltonen, Jouko

    2014-03-01

    In this study, two different supramolecular recognition architectures for impedimetric detection of DNA hybridization have been formed on disposable paper-supported inkjet-printed gold electrodes. The gold electrodes were fabricated using a gold nanoparticle based ink. The first recognition architecture consists of subsequent layers of biotinylated self-assembly monolayer (SAM), streptavidin and biotinylated DNA probe. The other recognition architecture is constructed by immobilization of thiol-functionalized DNA probe (HS-DNA) and subsequent backfill with 11-mercapto-1-undecanol (MUOH) SAM. The binding capacity and selectivity of the recognition architectures were examined by surface plasmon resonance (SPR) measurements. SPR results showed that the HS-DNA/MUOH system had a higher binding capacity for the complementary DNA target. Electrochemical impedance spectroscopy (EIS) measurements showed that the hybridization can be detected with impedimetric spectroscopy in picomol range for both systems. EIS signal indicated a good selectivity for both recognition architectures, whereas SPR showed very high unspecific binding for the HS-DNA/MUOH system. The factors affecting the impedance signal were interpreted in terms of the complexity of the supramolecular architecture. The more complex architecture acts as a less ideal capacitive sensor and the impedance signal is dominated by the resistive elements.

  9. Experimental Study of Diamond Like Carbon (DLC) Coated Electrodes for Pulsed High Gradient Electron Gun

    E-print Network

    Paraliev, M; Ivkovic, S; Le Pimpec, F

    2010-01-01

    For the SwissFEL Free Electron Laser project at the Paul Scherrer Institute, a pulsed High Gradient (HG) electron gun was used to study low emittance electron sources. Different metals and surface treatments for the cathode and anode were studied for their HG suitability. Diamond Like Carbon (DLC) coatings are found to perform exceptionally well for vacuum gap insulation. A set of DLC coated electrodes with different coating parameters were tested for both vacuum breakdown and photo electron emission. Surface electric fields over 250MV/m (350 - 400kV, pulsed) were achieved without breakdown. From the same surface, it was possible to photo-emit an electron beam at gradients up to 150MV/m. The test setup and the experimental results are presented

  10. Preparation of polymer-modified electrodes: A literature and experimental study

    SciTech Connect

    Jayanta, P.S.; Ishida, Takanobu

    1991-05-01

    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.

  11. Impedance-based study of capacitive porous carbon electrodes with hierarchical and bimodal porosity

    E-print Network

    Santiago, Juan G.

    hierarchical and bimodal supercapacitor electrodes. First detailed characterization of hierarchical carbon Supercapacitor Capacitive deionization Electrochemical impedance spectroscopy Hierarchical carbon a b s t r a c

  12. AMTEC system performance studies using the detailed electrode kinetic and transport model

    NASA Astrophysics Data System (ADS)

    Sievers, Robert K.; Williams, Roger M.; Underwood, Mark L.; Jeffries-Nakamura, Barbara; Bankston, C. P.

    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.

  13. AMTEC system performance studies using the detailed electrode kinetic and transport model

    NASA Technical Reports Server (NTRS)

    Sievers, Robert K.; Williams, Roger M.; Underwood, Mark L.; Jeffries-Nakamura, Barbara; Bankston, C. P.

    1992-01-01

    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.

  14. Sodium glass electrode in propylene carbonate for study of uranyl ion complexed to 18-crown-6 and substituted derivatives

    SciTech Connect

    Fux, P.; Lagrange, J.; Lagrange, P.

    1984-02-01

    Complexation of the uranyl ion (UO/sub 2//sup 2 +/) by 18-crown-6 and its substituted derivatives (dibenzo and dicyclohexyl) has been studied in propylene carbonate (0.1 M TEACIO/sub 4/) at 25/sup 0/C, using Na/sup +/ as a competing ion and a Na/sup +/ glass selective electrode. The response of the Na/sup +/ glass electrode in propylene carbonate with H/sup +/ as an interfering ion has been studied. Concentrations of Na/sup +/-free ions were calculated by using the extended Nicolsky equation. The stability constants determined by this method agree with those determined spectrophotometrically. 24 references, 3 figures, 1 table.

  15. A Newly Developed Perfused Umbrella Electrode for Radiofrequency Ablation: An Ex Vivo Evaluation Study in Bovine Liver

    SciTech Connect

    Bruners, Philipp, E-mail: bruners@hia.rwth-aachen.de; 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)

    2007-09-15

    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.

  16. Connectivity patterns of pallidal DBS electrodes in focal dystonia: a diffusion tensor tractography study.

    PubMed

    Rozanski, Verena E; Vollmar, Christian; Cunha, João Paulo; Tafula, Sérgio Miguel Neves; Ahmadi, Seyed-Ahmad; Patzig, Maximilian; Mehrkens, Jan-Hinnerk; Bötzel, Kai

    2014-01-01

    Deep brain stimulation (DBS) of the internal pallidal segment (GPi: globus pallidus internus) is gold standard treatment for medically intractable dystonia, but detailed knowledge of mechanisms of action is still not available. There is evidence that stimulation of ventral and dorsal GPi produces opposite motor effects. The aim of this study was to analyse connectivity profiles of ventral and dorsal GPi. Probabilistic tractography was initiated from DBS electrode contacts in 8 patients with focal dystonia and connectivity patterns compared. We found a considerable difference in anterior-posterior distribution of fibres along the mesial cortical sensorimotor areas between the ventral and dorsal GPi connectivity. This finding of distinct GPi connectivity profiles further confirms the clinical evidence that the ventral and dorsal GPi belong to different functional and anatomic motor subsystems. Their involvement could play an important role in promoting clinical DBS effects in dystonia. PMID:24045076

  17. Studies of localized corrosion in welded aluminum alloys by the scanning reference electrode technique

    NASA Technical Reports Server (NTRS)

    Danford, M. D.; Nunes, A. C.

    1995-01-01

    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.

  18. Nano-Ag-Nafion modified Pt electrode for oxidation of volatile organic compounds: an electrochemical study.

    PubMed

    Muthuraman, G; Chung, Sang Joon; Moon, Il Shik

    2011-08-01

    In this work, we describe Nano-Ag-Nafion coated pt electrode for oxidation of volatile organic compound (VOC), here acetaldehyde. Electrochemically synthesized Nano-Ag-Nafion film on Pt was analyzed by electrochemically in various electrolyte solutions like nitric acid, sulfuric acid, potassium nitrate, and potassium hydroxide for its stability. High stability of Nano-Ag-Nafion film appeared in potassium hydroxide medium among electrolyte solutions studied. Electrocatalysis of acetaldehyde was occurred only in acid and neutral medium. A catalytic oxidative peak during cathodic voltammetric reduction scan was observed at 1.75 V, which, unusual redox behavior, follows EC' reaction path way between electrogenerated Ag(II) and acetaldehyde. For Nano-Ag potential applicability, a calibration plot was drawn from various concentration range of acetaldehyde to check the maximum concentration level of acetaldehyde degradation in air. PMID:22103205

  19. Electrode materials for lithium rechargeable batteries: Synthesis, spectroscopic studies and electrochemical performance

    NASA Astrophysics Data System (ADS)

    Zhang, Xulong

    The lithium rechargeable battery is the newest member of the rechargeable battery family and is best known for its high energy density, long battery life, low self-discharge rate and light weight. This battery may become one of the most important energy sources in consumer market, industrial and military applications. Intercalation compounds play a critical role in determining the overall performance of a lithium rechargeable battery. The common intercalation materials for battery applications are layered structure Lisb{x}CoOsb2, spinel Lisb{x}Mnsb2Osb4 and lithium vanadium oxides, Lisb{x}Vsb2Osb5 and Lisb{x}Vsb3Osb8. Three distinct Lisb{x}Vsb2Osb5 phases, delta,\\ varepsilon, and gamma-Lisb{x}Vsb2Osb5, were obtained through a chemical intercalation reaction and solid state reactions. Infrared and Raman spectra were recorded for the three phases. The spectral changes were interpreted in terms of the local structural changes of the vanadium-oxygen polyhedra. Although the delta and varepsilon phases have very similar powder x-ray diffraction patterns, IR and Raman studies showed these two phases adopt distinctive local structural environments. These results demonstrate that IR and Raman spectroscopy are important techniques for the structural analysis of intercalation materials. Single crystals of Lisb{1.1}Vsb3Osb8 and sp6Lisb{1.1}Vsb3Osb8 were prepared using solid state synthesis techniques. IR spectra and polarized Raman spectra were recorded on the Lisb{1.1}Vsb3Osb8 and sp6Lisb{1.1}Vsb3Osb8 crystals and a lithiated phase, Lisb4Vsb3Osb8. Factor group analysis method was used to interpret the spectral changes. These spectroscopic results provide insight into the structural modifications originating from lithium intercalation/deintercalation processes. In situ Raman spectra of Lisb{x}Vsb2Osb5 were successfully recorded on a operating lithium rechargeable battery. Distinctive spectral changes were observed at different lithium intercalation levels and interpreted in terms of the slight rearrangements of the V-O structural units. The results show that in situ Raman spectroscopy may become an important nondestructive technique in investigating the irreversible structural changes in electrode materials and evaluating battery performance. For the first time novel mesostructural materials were synthesized as electrode materials for the lithium rechargeable battery. The well-ordered mesostructural materials provide an ideal host for lithium transport processes. The preliminary results on the manganese oxide-based cathode and tin oxide-based anode show that the templating synthesis technique may provide important electrode materials for battery applications.

  20. Application of surface enhanced Raman spectroscopy to the study of SOFC electrode surfaces.

    PubMed

    Li, Xiaxi; Blinn, Kevin; Fang, Yingcui; Liu, Mingfei; Mahmoud, Mahmoud A; Cheng, Shuang; Bottomley, Lawrence A; El-Sayed, Mostafa; Liu, Meilin

    2012-05-01

    SERS provided by sputtered silver was employed to detect trace amounts of chemical species on SOFC electrodes. Considerable enhancement of Raman signal and lowered detection threshold were shown for coked nickel surfaces, CeO(2) coatings, and cathode materials (LSM and LSCF), suggesting a viable approach to probing electrode degradation and surface catalytic mechanism. PMID:22441570

  1. The Surface Organometallic Chemistry of Pd Electrodes: Studies with Aromatic Compounds 

    E-print Network

    Cruz, Juan

    2012-10-19

    -liquid electrochemistry interfaces ............................................. 27 2.3 Potential-step coulometry ................................................................. 30 2.4 Volume of thin-layer cell.... Therefore, the electrochemical process is dependent on the potential of the electrode and the distance of the species to the electrode surface. 2.3 Potential-step coulometry In the potential-step coulometry method, a constant potential is applied...

  2. Application of the A.C. Admittance technique to double layer studies on polycrystalline gold electrodes

    NASA Astrophysics Data System (ADS)

    Fawcett, W. R.; Kovacova, Zuzana; Motheo, Arthur J.; Foss, Colby A., Jr.

    1992-02-01

    A detailed examination of the dependence of the a.c. admittance of a cell containing a polycrystalline gold electrode has been made in the double layer region as a function of d.c. potential, a.c. frequency, and electrode history. It is shown that the interfacial impedance of a gold electrode with a carefully prepared surface can be treated under these circumstances as a constant phase element when it is in contact with an aqueous solution containing 0.05 M KClO4. Analysis of the frequency dependence of the cell impedance gives the surface inhomogeneity parameter n which turns out to be very close to unity. Although the electrode surface is only slightly inhomogeneous on a microscopic scale, a very large frequency dispersion of the impedance is observed experimentally. A method of estimating the true specific capacity of the electrode is presented, and conditions for carrying out the experiments in a reproducible manner are discussed.

  3. Electrode compositions

    DOEpatents

    Block, J.; Fan, X.

    1998-10-27

    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.

  4. Olivine electrode engineering impact on the electrochemical performance of lithium-ion batteries.

    SciTech Connect

    Lu, W.; Jansen, A.; Dees, D.; Henriksen, G.; Chemical Sciences and Engineering Division

    2010-08-01

    High energy and power density lithium iron phosphate was studied for hybrid electric vehicle applications. This work addresses the effects of porosity in a composite electrode using a four-point probe resistivity analyzer, galvanostatic cycling, and electrochemical impedance spectroscopy (EIS). The four-point probe result indicates that the porosity of composite electrode affects the electronic conductivity significantly. This effect is also observed from the cell's pulse current discharge performance. Compared to the direct current (dc) methods used, the EIS data are more sensitive to electrode porosity, especially for electrodes with low porosity values.

  5. A study of the effect of BTA on flow electrification using rotating cylindrical electrodes

    SciTech Connect

    Washabaugh, A.P.; Zahn, M. [Massachusetts Institute of Technology, Cambridge, MA (United States)

    1995-05-01

    A rotating cylindrical electrode apparatus was used to simulate flow electrification in an electric power transformer and study the effects of the additive 1,2,3 benzotriazole (BTA). The experiments had Shell Diala A transformer oil filling the annulus between coaxial cylindrical (stainless steel) electrodes and EHV-Weidmann HiVal pressboard covering a thin copper sheet epoxied to the inner cylinder. Time transient and steady state measurements of the charge density in the core region of the fluid flow and the terminal current or voltage were performed over temperatures ranging from 15-70{degrees}C, inner cylinder rotation rates of 100-1400 rpm (Reynolds numbers of 5x10{sup 3}-5x10{sup 5}), and oil BTA concentrations of 0-60 ppm. The BTA appeared to cause competing effects: it reduced the volume charge density on the liquid side of the interface (by a factor of 10) which reduces the electrification but also decreased the oil conductivity (by a factor of 10), which increases the electrification. The BTA also had both long term and short term effects on the electrification. The steady state charge density, short-circuit current and open-circuit voltage had a minimum magnitude for a BTA concentration between 5 and 8 ppm. This paper also develops a physical model for the electrification which uses established representations for the interfacial charge transfer boundary condition. Based on the model, the steady state experimental data shows the largest magnitudes when the diffusion sublayer thickness is small compared to the Debye length. Interfacial volume charge densities ({rho}{sup w}`s) were estimated from the open-circuit data. From the short-circuit data, rate constants for the interfacial charge transfer appear to be large, but cannot always be taken as infinite.

  6. Methanol electrooxidation at mesoporous Pt and Pt-Ru electrodes: A comparative study with carbon supported materials

    NASA Astrophysics Data System (ADS)

    García, Gonzalo; Florez-Montaño, Jonathan; Hernandez-Creus, Alberto; Pastor, Elena; Planes, Gabriel A.

    2011-03-01

    The electrochemical behaviour of fuel cell catalysts (mesoporous Pt (MPPt), MPPtRu, MPPt modified by adsorbed Ru (MPPt/Ru) and carbon supported PtRu alloy) was studied using the thin layer flow cell differential electrochemical mass spectrometry (TLFC-DEMS) technique. The catalysts present high catalytic activity towards the methanol oxidation reaction (MOR), being the PtRu/C electrode the least active for MOR, while MPPt/Ru presents higher current densities for this reaction than MPPtRu. The results suggest that the diffusion properties obtained in the porous structure of the MP electrodes and the surface atomic arrangement in the electrode are the main reasons for the higher catalytic activity achieved. Finally, TLFC-DEMS was proved to be a powerful technique which evaluates and correlates the CO2 efficiency with the catalytic activity and the porous structure of the catalysts.

  7. Study and evaluation of a single differential sensor design based on electro-textile electrodes for ECG biometrics applications

    Microsoft Academic Search

    Hugo Silva; Andre Lourenco; Renato Lourenco; Paulo Leite; David Coutinho; Ana Fred

    2011-01-01

    In this paper we present a study and evaluation of a custom single differential sensor design for ECG data acquisition, recurring to electro-textile electrodes as the interface between the sensor and the skin. Our work is focused on improving current signal acquisition methods for ECG biometrics, targeting wearable, continuous and unobtrusive applications. A circuit with virtual ground was also devised

  8. Comparative Study of the Thermodynamics and Kinetics of the Ion Transfer Across the LiquidjLiquid Interface by Means of Three-Phase Electrodes

    Microsoft Academic Search

    Francois Quentel; Valentin Mirceski; Maurice L'Her; Mitko Mladenov; Fritz Scholz; Catherine Elleouet; S V. Kiril

    2005-01-01

    A comparative study of the behavior of different sorts of three-phase electrodes applied for assessing the thermodynamics and kinetics of the ion transfer across the liquidjliquid (LjL) interface is presented. Two types of three-phase electrodes are compared, that is, a paraffin-impregnated graphite electrode at the surface of which a macroscopic droplet of an organic solvent is attached and an edge

  9. Cloud reflectance calculations using DAK: study on required integration points

    E-print Network

    Stoffelen, Ad

    Cloud reflectance calculations using DAK: study on required integration points E.L.A. Wolters, R reflectance as calculated by the Dou- bling Adding KNMI (DAK) radiative transfer model with an abso- lute accuracy within 0.005. Cloud reflectance calculations at 0.632 and 1.605 µm are performed for a plane

  10. Stereo Visual Servoing with a Single Point: a Comparative Study

    Microsoft Academic Search

    E. Cervera; F. Berry; P. Martinet Robotic; Blaise Pascal

    A comparative study of a stereo visual servoing sys- tem is presented. The visual feature is the pair of images of an object, for which there not exists a ge- ometrical model. Instead, the image of the object is segmented, and its center of gravity is computed. The developed control laws use either the raw image points, or the estimated

  11. Monochromatic imaging studies of sustained metal vapor arcs burning on 150 mm diameter molten iron electrodes

    SciTech Connect

    Williamson, R.L.; Schlienger, M.E.

    1996-07-01

    Monochromatic imaging was used to investigate the excited-state density distributions of Fe and Fe{sup +} in the inter-electrode gap region of a 3,100 A dc metal vapor arc burning between molten iron surfaces in a vacuum arc furnace. Multiple images were acquired at four wavelengths. The images were corrected and Abel inverted to yield the absolute radial intensity distributions for Fe and Fe{sup +} in the inter-electrode gap region. The results show a structured, axisymmetric plasma consisting of a high density `core` of Fe{sup +} emitters centered between the electrode surfaces situated against a relatively broad, flat excited-state Fe distribution.

  12. Multifactorial comparative study of spatial point pattern analysis methods.

    PubMed

    Wallet, F; Dussert, C

    1997-08-01

    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, Voronoï 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

  13. Analytical study of the structure of chaos near unstable points

    E-print Network

    G. Contopoulos; C. Efthymiopoulos; M. Katsanikas

    2014-10-10

    In a 2D conservative Hamiltonian system there is a formal integral $\\Phi$ besides the energy H. This is not convergent near a stable periodic orbit, but it is convergent near an unstable periodic orbit. We explain this difference and we find the convergence radius along the asymptotic curves. In simple mappings this radius is infinite. This allows the theoretical calculation of the asymptotic curves and their intersections at homoclinic points. However in more complex mappings and in Hamiltonian systems the radius of convergence is in general finite and does not allow the theoretical calculation of any homoclinic point. Then we develop a method similar to analytic continuation, applicable in systems expressed in action-angle variables, that allows the calculation of the asymptotic curves to an arbitrary length. In this way we can study analytically the chaotic regions near the unstable periodic orbit and near its homoclinic points.

  14. Electrochemical study of uranium cations in LiCl-KCl melt using a rotating disk electrode

    SciTech Connect

    Bae, Sang-Eun; Kim, Dae-Hyun; Kim, Jong-Yoon; Park, Tae-Hong; Cho, Young Hwan; Yeon, Jei-Won; Song, Kyuseok [Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute,989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of)

    2013-07-01

    A rotating disk electrode (RDE) measurement technique was employed to investigate the electrochemical REDOX reactions of actinide (An) and lanthanide (Ln) ions in LiCl-KCl molten salt. By using RDE, it is possible to access more exact values of the diffusion coefficient, Tafel slope, and exchange current density. In this work, we constructed RDE setup and electrodes for RDE measurements in high temperature molten salt and measured the electrochemical parameters of the An and Ln ions. The RDE setup is composed of a Pine model MSRX rotator equipped with a rod type of W electrode. The active electrode area was confined to the planar part of the W rod by making meniscus at the LiCl-KCl melt surface.

  15. Studies of electrical breakdown processes across vacuum gaps between metallic electrodes

    E-print Network

    Gilson, Erik

    could outgas organic or other complex molecules which might coat electrodes. These techni- ques, all field strength. It is also apparent in the curious and non-intuitive scaling of the voltage difference

  16. Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter 

    E-print Network

    Guo, Yuyan

    2009-05-15

    , which are covered by thin porous electrode on the inner and outer surface as anode and cathode films respectively. High pressure sodium vapor is oxidized within the BASE tube causing sodium ions to pass through the BASE to the outer surface. Sodium....5 Schematic drawing of the sputtering process.??????????..? 37 2.6 Schematic diagram of the Coulter counter???????..?????. 40 3.1 Schematic diagram of SETC electrodes??.??????????..? 49 3.2 Chemical potential diagrams for (a) the Na...

  17. Studies of three-dimensional electrodes in the FMO1LC laboratory electrolyser

    Microsoft Academic Search

    C. J. Brown; D. Pletcher; F. C. Walsh; J. K. Hammond; D. Robinson

    1994-01-01

    A FMO1-LC parallel plate, laboratory electrochemical reactor has been modified by the incorporation of stationary, flow-by, three-dimensional electrodes which fill an electrolyte compartment. The performance of several electrode configurations including stacked nets, stacked expanded metal grids and a metal foam (all nickel) is compared by (i) determining the limiting currents for a mass transport controlled reaction, the reduction of ferricyanide

  18. An experimental study of conductive heating using a concentric double-electrode applicator

    Microsoft Academic Search

    Takashi Tanaka; Tadaoki Morimoto; Yohsuke Kinouchi; Tadamitsu Iritani; Yasumasa Monden

    1995-01-01

    With hyperthermia for treatment of superficial tumors in mind, a prototype applicator with two electrodes arranged concentrically\\u000a on a disk was designed for efficient local heating, and a basic heating test was carried out. Frequencies as low as 200 kHz\\u000a were used in order to simplify the configuration of the power device. The applicator consists of two electrodes, a circular

  19. A printed superoxide dismutase coated electrode for the study of macrophage oxidative burst.

    PubMed

    Hiatt, Leslie A; McKenzie, Jennifer R; Deravi, Leila F; Harry, Reese S; Wright, David W; Cliffel, David E

    2012-03-15

    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/s. 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. PMID:22257735

  20. A semi-analytical study of positive corona discharge in wire-plane electrode configuration

    NASA Astrophysics Data System (ADS)

    Yanallah, K.; Pontiga, F.; Chen, J. H.

    2013-08-01

    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.

  1. Electrochemical properties of a cell with solid oxide electrolyte and a gastight platinum electrode

    SciTech Connect

    Glumov, M.V.

    1985-12-01

    The use of electrodes of different structure is one method by which one can attain predominance of one of the steps of an electrode process so that one can examine it in more detail. To this end a point electrode and a compact electrode with solid electrolyte in the form of powder have been previously proposed in order to minimize the importance of processes evolving in the electrolyte. The other limiting case also is possible, viz., a compact electrolyte and a gastight electrode were the solid electrolyte is expected to have the predominant effect on the electrode process, and it is this system which is studied in the present work. Steady-state polarization characteristics of the gas-tight electrode in atmospheres with different oxygen levels are shown.

  2. Microparticle electrodes and single particle microbatteries: electrochemical and in situ microRaman spectroscopic studies.

    PubMed

    Jebaraj, Adriel Jebin Jacob; Scherson, Daniel A

    2013-05-21

    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

  3. Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes

    SciTech Connect

    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)

    2012-03-15

    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.

  4. A mortality cohort study among workers in a graphite electrode production plant in Italy

    PubMed Central

    Merlo, D; Garattini, S; Gelatti, U; Simonati, C; Covolo, L; Ceppi, M; Donato, F

    2004-01-01

    Aims: To investigate mortality from cancer and other diseases among workers in a graphite electrode production plant in Italy. Methods: A total of 1291 males actively employed between 1 January 1950 and 31 December 1989 who had worked at the plant for at least one year were studied. The follow up extended from 1950 to 1997. Standardised mortality ratios (SMR) and their 95% confidence intervals (CI) were computed using mortality rates for the Italian and regional male population. Results: Excess mortality was observed for all causes (SMR 1.44, CI 1.32 to 1.56), all cancers (SMR 1.27, CI 1.07 to 1.50), liver cancer (SMR 4.19, CI 2.68 to 6.23), silicosis (SMR 66.39, CI 52.56 to 82.7), and cirrhosis and other chronic diseases of the liver (SMR 1.87, CI 1.31 to 2.59) in comparison with the national male population. When regional rates were used to calculate the number of expected deaths, SMRs remained higher for silicosis (SMR 57.32, 42.11 to 76.22), and liver cancer (SMR 2.57, 1.57 to 3.97). Mortality from silicosis was increased in workers hired at young ages (<25 years, SMR 81.79; 25–34 years, SMR 82.73), and in workers aged <45 at death (SMR 333.3, CI 159.8 to 613). Mortality from liver cancer increased threefold (SMR 3.11, CI 1.78 to 5.05) in workers with more than 10 years of employment at the plant during the manufacture of Karbate products. Conclusions: Results support the association between excess mortality from silicosis and occupational exposure to siliceous sands experienced during graphite electrode manufacturing. The observed excess mortality from liver cancer is compatible, to some extent, with exposures that may have occurred during the manufacture of phenolic and furfuryl resins treated products, although a role of lifestyle factors and viral infections cannot be excluded. PMID:14739393

  5. Drug-selective electrode for ketamine determination in pharmaceutical preparations and electrochemical study of drug with BSA.

    PubMed

    Alizadeh, Naader; Mehdipour, Rasoul

    2002-10-15

    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

  6. Tunnel magnetoresistance effect and interface study in magnetic tunnel junctions using epitaxial Fe2CrSi Heusler alloy electrode

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Pu; Han, Gu-Chang; Lu, Hui; Qiu, Jinjun; Yap, Qi-Jia; Ji, Rong; Teo, Kie-Leong

    2013-07-01

    We report the studies of magnetic tunnel junctions (MTJs) using epitaxially grown Fe2CrSi (FCS) as a bottom electrode. A tunnel magnetoresistance (TMR) ratio of 2.5% was obtained for MTJ at room temperature. The low TMR ratio is attributed to the oxidation of FCS at the interface with MgO barrier. With the insertion of 0.3 nm Mg layer between the FCS and MgO barrier layers, the TMR ratio increases to 8.1%. X-ray Photoelectron Spectroscopy results show that the FCS film is most likely terminated at Fe and Si atomic layers, which is found to be bonded to oxygen at the interface, while Cr remains at metallic state. Post-annealing effect shows that TMR first increases with annealing temperature (Ta) due to improvement in crystalline structure of MgO and top electrode and then decreases due to oxidation of the bottom electrode. The TMR finally disappears due to the depinning of top electrode induced by Mn diffusion at high Ta.

  7. Investigation and Design Studies of SOFC Electrode Performance at Elevated Pressure

    SciTech Connect

    Ted Ohrn; Shung Ik Lee

    2010-07-31

    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.

  8. Study of methods to increase cluster/dislocation loop densities in electrodes

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoling; Miley, George H.

    2009-03-01

    Recent research has developed a technique for imbedding ultra-high density deuterium ``clusters'' (50 to 100 atoms per cluster) in various metals such as Palladium (Pd), Beryllium (Be) and Lithium (Li). It was found the thermally dehydrogenated PdHx retained the clusters and exhibited up to 12 percent lower resistance compared to the virginal Pd samplesootnotetextA. G. Lipson, et al. Phys. Solid State. 39 (1997) 1891. SQUID measurements showed that in Pd these condensed matter clusters approach metallic conditions, exhibiting superconducting propertiesootnotetextA. Lipson, et al. Phys. Rev. B 72, 212507 (2005ootnotetextA. G. Lipson, et al. Phys. Lett. A 339, (2005) 414-423. If the fabrication methods under study are successful, a large packing fraction of nuclear reactive clusters can be developed in the electrodes by electrolyte or high pressure gas loading. This will provide a much higher low-energy-nuclear- reaction (LENR) rate than achieved with earlier electrodeootnotetextCastano, C.H., et al. Proc. ICCF-9, Beijing, China 19-24 May, 2002..

  9. Surface study of stainless steel electrode deposition from soil electrokinetic (EK) treatment using X-ray photoelectron spectroscopy (XPS)

    NASA Astrophysics Data System (ADS)

    Embong, Zaidi; Johar, Saffuwan; Tajudin, Saiful Azhar Ahmad; Sahdan, Mohd Zainizan

    2015-04-01

    Electrokinetic (EK) remediation relies upon application of a low-intensity direct current through the soil between stainless steel electrodes that are divided into a cathode array and an anode array. This mobilizes charged species, causing ions and water to move toward the electrodes. Metal ions and positively charged organic compounds move toward the cathode. Anions such as chloride, fluoride, nitrate, and negatively charged organic compounds move toward the anode. Here, this remediation techniques lead to a formation of a deposition at the both cathode and anode surface that mainly contributed byanion and cation from the remediated soil. In this research, Renggam-Jerangau soil species (HaplicAcrisol + RhodicFerralsol) with a surveymeter reading of 38.0 ± 3.9 ?R/hr has been investigation in order to study the mobility of the anion and cation under the influence electric field. Prior to the EK treatment, the elemental composition of the soil and the stainless steel electrode are measured using XRF analyses. Next, the soil sample is remediated at a constant electric potential of 30 V within an hour of treatment period. A surface study for the deposition layer of the cathode and anode using X-ray Photoelectron spectroscopy (XPS) revealed that a narrow photoelectron signal from oxygen O 1s, carbon, C 1s silica, Si 2p, aluminium, Al 2p and chromium, Cr 2p exhibited on the electrode surface and indicate that a different in photoelectron intensity for each element on both electrode surface. In this paper, the mechanism of Si2+ and Al2+ cation mobility under the influence of voltage potential between the cathode and anode will be discussed in detail.

  10. Microtitrimetry by differential electrolytic potentiometry using metallic electrodes and nanomaterials modified metallic electrodes

    NASA Astrophysics Data System (ADS)

    Amro, Abdulaziz Nabil

    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.

  11. Advanced electrodes for AMTEC

    SciTech Connect

    Fiebig, Brad; Schuller, Michael; Hudson, Patricia [Center for Space Power, Texas AM University, College Station, Texas 77843 (United States); Williams, Roger [Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, California 91109 (United States)

    1999-01-01

    Texas A&M University has begun an investigation of materials and fabrication methods which will improve AMTEC electrode performance. The study currently involves gathering data on materials which meet the basic requirements of operating in an AMTEC cell, and sorting out candidates possessing characteristics conducive to efficient AMTEC operation. An initial assessment has shown Iridium as a promising metal electrode candidate. Sodium-containing double-oxides, with melting temperatures above AMTEC operating temperatures, including NaNbO{sub 3} and Na{sub 2}Ti{sub 3}O{sub 7}, have been identified as possible electrode dopants, to enhance the sodium conductivity of an electrode. Photo-deposition and Evaporative-deposition will be investigated further as electrode fabrication techniques. {copyright} {ital 1999 American Institute of Physics.}

  12. Effects of Electrode Position on Spatiotemporal Auditory Nerve Fiber Responses: A 3D Computational Model Study

    PubMed Central

    2015-01-01

    A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance. PMID:25755675

  13. Effects of electrode position on spatiotemporal auditory nerve fiber responses: a 3D computational model study.

    PubMed

    Kang, Soojin; Chwodhury, Tanmoy; Moon, Il Joon; Hong, Sung Hwa; Yang, Hyejin; Won, Jong Ho; Woo, Jihwan

    2015-01-01

    A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance. PMID:25755675

  14. Ancient Astronomy: A Study of the Point Remove Mound Complex

    NASA Astrophysics Data System (ADS)

    Hankins, Matt; Burris, D. L.

    2012-01-01

    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).

  15. Application of iron electrode corrosion enhanced electrokinetic-Fenton oxidation to remediate diesel contaminated soils: A laboratory feasibility study

    NASA Astrophysics Data System (ADS)

    Tsai, Tzai-Tang; Sah, Jygau; Kao, Chih-Ming

    2010-01-01

    SummaryDiesel soil contamination on gas stations or refinery plants is a worldwide environmental problem. The main objectives of this study were to (1) evaluate the efficiency of electrokinetic (EK) by using different electrode materials (graphite and iron rods) and electrolytes (tap water, 0.01 M NaCl, and 0.1 M NaCl) on the remediation of diesel contaminated soils, and (2) evaluate the feasibility of total petroleum hydrocarbon-diesel (TPH-D) reducing in soils via EK-Fenton oxidation enhanced by corroded iron electrode. The EK and EK-Fenton experiments were conducted in batch and sand box experiments, respectively. Batch experiments reveal that the most appropriate electrolyte was 0.1 M NaCl when iron electrode was used in the EK system. Sand box experiments indicate that the TPH-D concentration dropped from 10,000 to 300 mg kg -1 when amorphous iron/total iron (Fe o/Fe t) ratio increased from 0.1 to 0.33, with the addition of 8% of H 2O 2 and 0.1 M NaCl after 60 days of EK-Fenton operation. Electrokinetically enhanced oxidation with the presence of both H 2O 2 and Fe 3O 4 (iron electrode corrosion) resulted in higher TPH-D removal efficiency (97%) compared to the efficiencies observed from EK (55%) or Fenton oxidation (27%) alone. This demonstrates that EK-Fenton oxidation catalyzed by iron electrode corrosion is a valuable direction to efficiently and effectively remediate diesel contaminated soils.

  16. Study on monatomic fraction improvement with alumina layer on metal electrode in hydrogen plasma ion source

    SciTech Connect

    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)

    2012-02-15

    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.

  17. Application of Gold Electrodes for the Study of Nickel Based Homogeneous Catalysts for Hydrogen Oxidation

    SciTech Connect

    Nepomnyashchii, Alexander B.; Liu, Fei; Roberts, John A.; Parkinson, Bruce A.

    2013-08-12

    Gold and glassy carbon working electrode materials are compared as suitable substrates for the hydrogen oxidation reaction with Ni(PCy2Nt-Bu2)2(BF4)2 used as a catalyst. Voltammetric responses showing electrocatalytic hydrogen oxidation mediated by the homogeneous electrocatalyst Ni(PCy2Nt-Bu2)2(BF4)2 are identical at glassy carbon and gold electrodes, which shows that gold electrode can be used for hydrogen oxidation reaction. This work is supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under FWP 56073.

  18. Intraorbital optic nerve stimulation with penetrating electrodes: in vivo electrophysiology study in rabbits

    Microsoft Academic Search

    Liming Li; Pengjia Cao; Mingjie Sun; Xinyu Chai; Kaijie Wu; Xun Xu; Xiaoxin Li; Qiushi Ren

    2009-01-01

    Purpose  To investigate the response properties of the electrically evoked potentials (EEPs) elicited by intraorbital optic nerve stimulation\\u000a with penetrating electrodes using different stimulus parameters.\\u000a \\u000a \\u000a \\u000a Methods  Visually evoked potentials (VEPs) were recorded as a control and for comparative purposes. Teflon-coated tungsten wire electrodes\\u000a (100 ?m core-diameter, 300 ?m exposed tip) were inserted intraorbitally into the optic nerve. A charge-balanced biphasic current\\u000a was delivered to

  19. Superconducting molybdenum-rhenium electrodes for single-molecule transport studies

    NASA Astrophysics Data System (ADS)

    Gaudenzi, R.; Island, J. O.; de Bruijckere, J.; Burzurí, E.; Klapwijk, T. M.; van der Zant, H. S. J.

    2015-06-01

    We demonstrate that electronic transport through single molecules or molecular ensembles, commonly based on gold (Au) electrodes, can be extended to superconducting electrodes by combining gold with molybdenum-rhenium (MoRe). This combination induces proximity-effect superconductivity in the gold to temperatures of at least 4.6 K and magnetic fields of 6 T, improving on previously reported aluminum based superconducting nanojunctions. As a proof of concept, we show three-terminal superconductive transport measurements through an individual Fe4 single-molecule magnet.

  20. A study of adsorption kinetics and thermodynamics of ?-mercaptoalkylhydroquinone self-assembled monolayer on a gold electrode

    Microsoft Academic Search

    Hun-Gi Hong

    2005-01-01

    The adsorption kinetics and thermodynamics for the formation of redox active self-assembled monolayer (SAM) of 2-(n-mercaptoalkyl)hydroquinone (abbreviated as H2Q(CH2)nSH, where n=4, 6, 8, 10, and 12) on gold electrode has been investigated by cyclic voltammetry to study the effects of concentration and alkyl chain length. The time dependence of surface coverage, differential capacitance, and formal potential of electroactive hydroquinone(H2Q) moiety

  1. Electrocatalytic oxidation of sodium levothyroxine with phenyl hydrazine as a mediator at carbon paste electrode: A cyclic voltammetric study

    Microsoft Academic Search

    S. Chitravathi; B. E. Kumara Swamy; Umesh Chandra; G. P. Mamatha; B. S. Sherigara

    2010-01-01

    The electrochemical oxidation of sodium levothyroxine (T4) has been studied on carbon paste electrode (CPE) with phenyl hydrazine homogenous as mediator, using cyclic voltammetric technique in presence of 0.1M HCl as supporting electrolyte. The charge transfer coefficient (?n?) for T4 in the presence and absence of phenyl hydrazine was determined. The oxidation peak currents represented a linear dependence on T4

  2. A method for direct thalamic stimulation in fMRI studies using a glass-coated carbon fiber electrode

    Microsoft Academic Search

    Bai-Chuang Shyu; Chun-Yu Lin; Jyh-Jang Sun; Sergiy Sylantyev; Chen Chang

    2004-01-01

    Recent fMRI studies are of interest in exploring long-range interactions between different brain structures and the functional activation of specific brain regions by known neuroanatomical pathways. One of the experimental approaches requires the invasive implantation of an intracranial electrode to excite specific brain structures. In the present report, we describe a procedure for the production of a glass-coated carbon fiber

  3. A study of the behavior of copper electrodes in buffered borax solutions containing BTA-type inhibitors by photoelectrochemical methods

    Microsoft Academic Search

    Qun-jie Xu; Guo-ding Zhou

    2008-01-01

    Purpose – The purpose of this paper is to provide useful information pertaining to the corrosion inhibition mechanism of BTA and its derivatives on copper. Design\\/methodology\\/approach – The photoelectrochemical behavior of copper electrodes in buffered borax solutions (pH 9.2) containing BTA and its derivatives was comparatively studied by using a photoelectrochemical technique. It was possible to analyze the inhibition mechanism

  4. A study on capacity fading of lithium-ion battery with manganese spinel positive electrode during cycling

    Microsoft Academic Search

    Li Yang; Michio Takahashi; Baofeng Wang

    2006-01-01

    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

  5. Nonaqueous Inhibition of Iron-Boron-Silicon Amorphous Electrodes in Hydrochloric Acid: An Alternating Current Impedance Study

    Microsoft Academic Search

    K. Habib; A. Abdullah

    1994-01-01

    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

  6. Surface studies of the jalpaite-based copper(II) ion-selective electrode membrane in seawater

    Microsoft Academic Search

    Roland De Marco

    1996-01-01

    Ageing of the jalpaite Cu(II) ion-selective electrode (ISE) membrane in saline solutions and seawater has been studied using X-ray photoelectron spectroscopy (XPS), and it is shown that the membrane surface composition is altered after exposure to these media. XPS evidence shows that the change in membrane surface composition in a saline Cu(II) ion buffer involves the transformation of jalpaite (i.e.

  7. Field experience and dew point studies of a retrofitted roof

    SciTech Connect

    Carlson, A.R. [Univ. of Alaska, Fairbanks, AK (United States). Cooperative Extension Service

    1997-11-01

    A symposium on insulating materials would not be complete without discussing the effect of the thermal and vapor performance on potential condensation problems in insulated assemblies. Retrofitting the top of an existing insulated roof with an impermeable rigid or foamed insulation can lead to serious condensation-related maintenance problems. Dew point studies in Alaska indicate that the thermal resistance of retrofitted assemblies should be at least two times greater than the existing insulated wall, or roof to avoid condensation in the cavity, depending on local heating degree days. Further, an exterior impervious insulated wall or roof assembly should be provided with some type of natural venting to relieve vapor pressure and allow excess condensate to drain and evaporate. Unfortunately, most condensation problems do not become apparent for 5 to 10 years, long after the one year warranty is null and void. A computer spreadsheet will be presented that simulates dew point conditions in an insulated roof assembly to determine the proper selection and placement of the vapor retarder, insulation, and ventilation of the exterior skin to prevent further deterioration of the roof. This necessitated the computation and tabulation of surface temperatures, dew point temperatures, vapor pressures and relative humidities at various structural components of the insulated assemblies, particularly near the outer skin.

  8. A spatiotemporal study of gliosis in relation to depth electrode tracks in drug-resistant epilepsy

    PubMed Central

    Goc, Joanna; Liu, Joan Y W; Sisodiya, Sanjay M; Thom, Maria

    2014-01-01

    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 4–301 days 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: 0–350 ?m), zone 2 (350–700 ?m) and zone 3 (remote ?2000 ?m) in relation to the ICE injury site. Microglial/macrophage cell densities peaked at 28–30 days 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

  9. Properties of implanted electrodes for functional electrical stimulation.

    PubMed

    Popovic, D; Gordon, T; Rafuse, V F; Prochazka, A

    1991-01-01

    Implanted wire electrodes are increasingly being used for the functional electrical stimulation of muscles in partially paralysed patients, yet many of their basic characteristics are poorly understood. In this study we investigated the selectivity, recruitment characteristics and range of control of several types of electrode in triceps surae and plantaris muscles of anaesthetized cats. We found that nerve cuffs are more efficient and selective (i.e., cause less stimulus spread to surrounding muscles) than intramuscular electrodes. Bipolar intramuscular stimulation was more efficient and selective than monopolar stimulation, but only if the nerve entry point was between the electrodes. Monopolar electrodes are efficient and selective if located close to the nerve entry point, but their performance declines with distance from it. Nonetheless, for a variety of reasons monopolar stimulation provides the best compromise in many current applications. Short duration pulses offer the best efficiency (least charge per pulse to elicit force) but high peak currents, increasing the risk of electrode corrosion and tissue damage. Electrode size has little effect on recruitment and should therefore be maximised because this minimises current density. PMID:1928872

  10. Journal of Luminescence 126 (2007) 225229 A comparative study of electrode effects on the electrical and

    E-print Network

    Klotzkin, David

    2007-01-01

    on the carrier injection efficiency from both electrodes, and on the charge balance in a controlled electron current injection almost linear after turn-on, whiles devices incorporating a LiF and CuPc layers­V injection. This is attributed to the reduced barrier at the organic-organic interface in PEDOT, the `ladder

  11. Study on the treatment of photovoltaic wastewater using electrocoagulation: fluoride removal with aluminium electrodes--characteristics of products.

    PubMed

    Drouiche, N; Aoudj, S; Hecini, M; Ghaffour, N; Lounici, H; Mameri, N

    2009-09-30

    In this work, treatment of synthetic fluoride-containing solutions by electrocoagulation method using aluminium electrodes has been studied. Electrocoagulation was investigated for applied potential (10-30 V), electrolysis time and supporting electrolyte (NaCl) concentration (0-100mg/L). The results showed that with increasing applied potential and electrolysis time, the Al(3+) dosage increases, and thereby favouring the fluoride ions removal. It was also observed that defluoridation is dependant on the concentration of supporting electrolyte. Finally, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy of X-rays and Fourier transform infrared spectroscopy were used to characterize the solid products formed by aluminium electrodes during the EC process. PMID:19395167

  12. Alloy corrosion studied by a combination of stripping voltammetry and the rotating ring-disk electrode. Lead-cadmium alloy

    SciTech Connect

    Zhdanov, V.V.; Filanovskii, B.K.

    1984-08-01

    The authors have used the rotating ring-disk electrode (RRDE) in combination with stripping voltammetry (SVA) at solid electrodes in order to determine partial dissolution rates of alloy components in the vicinity of the steady potential and also under cathodic and anodic polarization. The method of SVA is used in the analytical determination of trace amounts of heavy metals dissolved in electrolytes. The method was used to investigate the electrolytic dissolution of lead-cadmium alloy in the vicinity of the steady potential and under cathodic polarization. Results obtained when studying the corrosion behavior of the lead-cadmium alloy are given. The results indicate that selective cadmium dissolution occurs initially, but then this is replaced by uniform alloy dissolution. The data shows that the partial currents of alloy component dissolution can be determined by a combination of SVA and RRDE.

  13. A feasibility study of a rotary planar electrode array for electrical impedance mammography using a digital breast phantom.

    PubMed

    Zhang, X; Chatwin, C; Barber, D C

    2015-06-01

    A feasibility study of an electrical impedance mammography (EIM) system with a rotary planar electrode array, named RPEIM, is presented. The RPEIM system is an evolution of the Sussex MK4 system, which is a prototype instrument for breast cancer detection. Comparing it with the other planar electrode EIM systems, the rotation feature enables a dramatic increase in the number of independent measurements. To assist impedance evaluation exploiting electrode array rotation, a synchronous mesh method is proposed. Using the synchronous mesh method, the RPEIM system is shown to have superior performance in image accuracy, spatial resolution and noise tolerance over the MK4 system. To validate the study, we report simulations based on a close-to-realistic 3D digital breast phantom, which comprises of: skin, nipple, ducts, acinus, fat and tumor. A digital breast phantom of a real patient is constructed, whose tumor was detected using the MK4 system. The reconstructed conductivity image of the breast phantom indicates that the breast phantom is a close replica of the patient's real breast as assessed by the MK4 system in a clinical trial. A comparison between the RPEIM system and the MK4 system is made based on this phantom to assess the advantages of the RPEIM system. PMID:26007201

  14. Liquid electrode

    DOEpatents

    Ekechukwu, A.A.

    1994-07-05

    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.

  15. Numerical study on the spark ignition characteristics of a methane-air mixture using detailed chemical kinetics. Effect of equivalence ratio, electrode gap distance, and electrode radius on MIE, quenching distance, and ignition delay

    SciTech Connect

    Han, Jilin; Yamashita, Hiroshi; Hayashi, Naoki [Department of Mechanical Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi (Japan)

    2010-07-15

    The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. Even though the formation of flame kernels in quiescent methane-air mixtures has been simulated numerically, the ignition mechanism has never been satisfactorily explained. This study investigated the spark ignition of methane-air mixtures through a numerical analysis using detailed chemical kinetics consisting of 53 species and 325 elementary reactions while considering the heat loss to the electrode. The simulation was used to investigate the quenching distance and the effects on the MIE of the electrode size, electrode gap distance, ignition duration, and equivalence ratio. The effect of the equivalence ratio on the ignition delay time was also examined. The simulated results showed the same trend as previous experimental results. (author)

  16. Skimming electronic newspaper headlines: a study of typeface, point size, screen resolution, and monitor size

    Microsoft Academic Search

    David Kingery; Richard Furuta

    1997-01-01

    The effects of typeface, point size, screen resolution and monitor size on legibility were studied in a task-setting similar to skimming headlines in an electronic newspaper. Times New Roman, Book Antiqua, Century Gothic, and Arial were the four typefaces used in the study. The point sizes used to present the headlines were 14 point, 20 point, and 24 point sizes.

  17. Control of electrode depth in electroslag remelting

    DOEpatents

    Melgaard, David K. (Albuquerque, NM); Shelmidine, Gregory J. (Tijeras, NM); Damkroger, Brian K. (Albuquerque, NM)

    2002-01-01

    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.

  18. Rotational thromboelastometry and multiple electrode platelet aggregometry in four patients with abnormal routine coagulation studies before removal of epidural catheters after major surgery: a case series and research study

    PubMed Central

    2013-01-01

    Introduction Routine coagulation tests have a low predictability for perioperative bleeding complications, and spinal hematoma after removal of epidural catheters is very infrequent. Thromboelastometry and point-of-care platelet aggregometry may improve hemostatic monitoring but have not been studied in the context of safety around epidural removal. Methods Twenty patients who received an epidural catheter for major thoracoabdominal and abdominal surgery were included prospectively. In addition to routine coagulation tests, rotational thromboelastometry and multiple electrode platelet aggregometry were carried out. Results A coagulation deficit was suggested by routine coagulation tests on the intended day of epidural catheter removal in four out of 20 patients. Prothrombin time-international normalized ratio was elevated to 1.5 in one patient (normal range: 0.9 to 1.2) while rotational thromboelastometry and multiple electrode platelet aggregometry parameters were within normal limits. Activated partial thromboplastin time was elevated to 47 to 50 seconds in the remaining three patients (normal range 28 to 45 seconds). Rotational thromboelastometry showed that one of the patients’ results was due to heparin effect: the clotting time with the HEPTEM® activator was 154 seconds as compared to 261 seconds with INTEM. The three remaining patients with prolonged routine coagulation test results had all received over 1L of hydroxyethyl starch (Venofundin®) and thrombosis prophylaxis with low-molecular-weight heparin (enoxaparin). Rotational thromboelastometry and multiple electrode platelet aggregometrygave normal or hypercoagulative signals in most patients. Conclusions This case series is new in that it examines rotational thromboelastometry and multiple electrode platelet aggregometry postoperatively in the context of epidural analgesia and shows that they may be clinically useful. These methods should be validated before they can be used for standard patient care. PMID:24377397

  19. Bifunctional electrodes for unitised regenerative fuel cells

    Microsoft Academic Search

    Sebastian Altmann; Till Kaz; Kaspar Andreas Friedrich

    2011-01-01

    The effects of different configurations and compositions of platinum and iridium oxide electrodes for the oxygen reaction of unitised regenerative fuel cells (URFC) are reported. Bifunctional oxygen electrodes are important for URFC development because favourable properties for the fuel cell and the electrolysis modes must be combined into a single electrode. The bifunctional electrodes were studied under different combinations of

  20. Subdural Electrodes

    PubMed Central

    Lesser, Ronald P.; Crone, Nathan E.; Webber, W.R.S.

    2010-01-01

    Subdural electrodes are frequently used to aid in the neurophysiological assessment of patients with intractable seizures. We review the indications for these, their uses for localizing epileptogenic regions and for localizing cortical regions supporting movement, sensation, and language. PMID:20573543

  1. Point McIntyre Field, Alaska: An integrated reservoir study

    SciTech Connect

    Kosich, D.F. (Exxon Co., Houston, TX (United States)); Frank, K.J. (ARCO, Anchorage, AK (United States)); Hunter, R.B. (BP Exploration Inc., Anchorage, AK (United States))

    1996-01-01

    The geologic model of the Kuparuk Formation at Point McIntyre Field is the result of an integrated reservoir study. Data from 7000 feet of evenly distributed cores are the foundation for a lithofacies model, chronostratigraphic correlations, 2-D and 3-D mapping, and the geostatistical distribution of reservoir parameters. The resulting cellular model provides improved input to the simulator model used for reservoir management. The depositional lithofacies model is divided into 14 categories. These range from bioturbated, very fine-grained sandstone to conglomerates with abundant lithic mudstone clasts. Depositional lithofacies control reservoir quality, with the highest potential in massive or trough cross-bedded sandstones. The reservoir sandstones represent the marine portion of a fan-delta. No shales thicker than one inch are preserved within the Kuparuk Formation in the Point McIntyre cores. Accurate correlation and mapping of chronostratigraphic surfaces is essential to preserve porosity and permeability trends within the model. Sequence stratigraphic correlations show a complex depositional history and define twenty-one mappable zones with five major truncation surfaces. New zonal mapping methodologies honor the chronostratigraphy. Isochore maps contain strong depositional trends that influence reservoir management. A 3-D cellular model captures onlap and truncation relationships within the zones, preserving internal geometries. Lithofacies distributed within the 3-D model form a template tied to core and well control. The lithofacies template guides the geostatistical distribution of reservoir parameters.

  2. Point McIntyre Field, Alaska: An integrated reservoir study

    SciTech Connect

    Kosich, D.F. [Exxon Co., Houston, TX (United States); Frank, K.J. [ARCO, Anchorage, AK (United States); Hunter, R.B. [BP Exploration Inc., Anchorage, AK (United States)

    1996-12-31

    The geologic model of the Kuparuk Formation at Point McIntyre Field is the result of an integrated reservoir study. Data from 7000 feet of evenly distributed cores are the foundation for a lithofacies model, chronostratigraphic correlations, 2-D and 3-D mapping, and the geostatistical distribution of reservoir parameters. The resulting cellular model provides improved input to the simulator model used for reservoir management. The depositional lithofacies model is divided into 14 categories. These range from bioturbated, very fine-grained sandstone to conglomerates with abundant lithic mudstone clasts. Depositional lithofacies control reservoir quality, with the highest potential in massive or trough cross-bedded sandstones. The reservoir sandstones represent the marine portion of a fan-delta. No shales thicker than one inch are preserved within the Kuparuk Formation in the Point McIntyre cores. Accurate correlation and mapping of chronostratigraphic surfaces is essential to preserve porosity and permeability trends within the model. Sequence stratigraphic correlations show a complex depositional history and define twenty-one mappable zones with five major truncation surfaces. New zonal mapping methodologies honor the chronostratigraphy. Isochore maps contain strong depositional trends that influence reservoir management. A 3-D cellular model captures onlap and truncation relationships within the zones, preserving internal geometries. Lithofacies distributed within the 3-D model form a template tied to core and well control. The lithofacies template guides the geostatistical distribution of reservoir parameters.

  3. A study on pitting corrosion of aluminum alloy 2024-T3 by scanning microreference electrode technique

    Microsoft Academic Search

    Minhua Shao; Yan Fu; Ronggang Hu; Changjian Lin

    2003-01-01

    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

  4. Thermal-stability studies of electrode materials for lithium-ion batteries

    Microsoft Academic Search

    Junwei Jiang

    2005-01-01

    The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes

  5. Interfacial Properties of Ultrathin- Film Metal Electrodes: Studies by Combined Electron Spectroscopy and Electrochemistry

    E-print Network

    Cummins, Kyle

    2012-07-16

    gratitude to my mentor and advisor, Dr. M. P. Soriaga, for the countless hours of collaboration and advice. Imparted to me, through his encouragement and scholastic stewardship, were the virtues of academic creativity and intellectual accountability. A.... viii NOMENCLATURE ADC Analog-to-Digital Converter AES Auger Electron Spectroscopy CE Counter Electrode CHA Concentric Hemispheric Analyzer CMA Cylindrical Mirror Analyzer CPD Controlled-Potential Deposition CV Cyclic Voltammetry...

  6. In-situ acoustic emission study of Si-based electrodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Tranchot, A.; Etiemble, A.; Thivel, P.-X.; Idrissi, H.; Roué, L.

    2015-04-01

    The mechanical degradation of a Si powder (?2 ?m) based electrode is investigated by acoustic emission (AE). AE signals are mainly detected during the first lithiation, suggesting that electrode cracking mainly occurs during this period. The formation of the solid electrolyte interface (SEI) is not very acoustically emissive, in contrast to the Si particle cracking which is initiated in the early stage of the lithiation in accordance with a core-shell lithiation mechanism. An increase of the AE activity is observed at the end of the discharge when the c-Li15Si4 phase is formed and during the charge when the potential reaches ?0.45 V, corresponding to the delithiation of c-Li15Si4. From a clustering procedure, three types of signals are identified: type-1 signals consisting of a succession of very short waveforms with high peak frequency (?700 kHz) are primarily detected when the Si lithiation is initiated and are ascribed to the nucleation of surface microcracks on the Si particles; type-2 signals (peak frequency ?400 kHz), present all during the Si lithiation, are attributed to the propagation of cracks through the Si particles and into the composite film; type-3 signals (peak frequency ?200 kHz), detected when the potential reaches 60 mV, are ascribed to the accentuation of the electrode cracking due to the c-Li15Si4 formation.

  7. On the Origins of Pointing in Infancy: A Pilot Study.

    ERIC Educational Resources Information Center

    Butterworth, George; Adamson-Macedo, Elvidina

    Observations were made of the incidence of pointing behavior among infants differing in age when a radio-controlled truck entered the room in which mother and infant were seated. Infants' reactions over 5 to 6 minutes were recorded on videotape. Recordings were analyzed to establish the incidence of pointing, handedness of pointing, whether…

  8. Point of View: Leadership Studies from Different Perspectives

    ERIC Educational Resources Information Center

    Harter, Nathan

    2012-01-01

    By adopting the dictum that all knowledge is knowledge from a point of view, educators can arrange the literature on leadership into nine categories from three conceptually distinct points of view, namely the Leader, the Follower, and the Investigator. Students who come to appreciate and account for point of view not only increase their…

  9. Critical sampling points methodology: case studies of geographically diverse watersheds.

    PubMed

    Strobl, Robert O; Robillard, Paul D; Debels, Patrick

    2007-06-01

    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

  10. Study on Thickness Effect of Three-Point-Bend Specimen

    NASA Astrophysics Data System (ADS)

    Kikuchi, Masanori; Ishihara, Takehito

    The thickness effect of a three-point-bend (3PB) specimen on dimple fracture behavior is studied experimentally and numerically. At first, fracture toughness tests were conducted using 3PB specimens of different thicknesses. Fracture toughness values and R-curves are obtained, and the thickness effect is discussed. Using scanning electron microscopy (SEM), dimple fracture surfaces are observed precisely. It is found that the thickness effect appears clearly in the void growth process. Finite element (FEM) analyses are conducted based on these experimental data. Using Gurson’s constitutive equation, the nucleation and growth of voids during the dimple fracture process are simulated. The distribution patterns of stress triaxiality and the crack growth process are obtained. The results show a good agreement with experimental ones qualitatively. The effects of specimen thickness on R-curves are explained well on the basis of these numerical simulations.

  11. Optical Studies of Pure Fluids about Their Critical Points

    NASA Astrophysics Data System (ADS)

    Pang, Kian Tiong

    Three optical experiments were performed on pure fluids near their critical points. In the first two setups, CH_3F and H_2C:CF _2 were each tested in a temperature -controlled, prism-shaped cell and a thin parallel-windows cell. In the prism cell, a laser beam was additionally deflected by the fluid present. From the deflection data, the refractive index was related to the density to find the Lorentz-Lorenz function. Critical temperature (T _{c}), density, refractive index and electronic polarizability were found. In the second experiment, a critically-filled, thin parallel-windows cell was placed in one arm of a Mach-Zehnder interoferometer. Fluid density was monitored by changes in the fringe pattern with changing cell temperature. The aim was to improve on the precision of T_{c}: T_{c}{rm (CH}_3 F) = (44cdot9087 +/- 0cdot0002)C; T _{c}{rm(H}_2C:CF _2) = (29cdot7419 +/- 0cdot0001)C; and, to study the coexistence curve and diameter as close to T_{c} as possible. The critical behaviour was compared to the theoretical renormalization group calculations. The derived coefficients were tested against a proposed three-body interaction to explain the field-mixing term in the diameter near the critical point. It was found that H_2C:CF_2 behaved as predicted by such an interaction; CH _3F (and CHF_3) did not. The third experiment was a feasibility study to find out if (critical) isotherms could be measured optically in a setup which combined the prism and parallel-windows cells. The aim was to map isotherms in as wide a range of pressure and density as possible and to probe the critical region directly. Pressure was monitored by a precise digital pressure gauge. CH_3F and CHF _3 were tested in this system. It was found that at low densities, the calculated second and third virial coefficients agreed with reference values. However, the data around the critical point were not accurate enough for use to calculate the critical exponent, delta . The calculated value was consistently smaller than the expected value. It was believed that the present setup had thermal isolation problems. Suggestions were made as to the improvements of this isotherm cell setup. Lastly, a joint project with the Department of Ophthalmology, UBC to assemble a vitreous fluorophotometer is discussed in Appendix F. The upgrading of the instrument took up the initial two years of this PhD programme.

  12. Radiofrequency Ablation with a New Perfused-Cooled Electrode Using a Single Pump: An Experimental Study in Ex Vivo Bovine Liver

    SciTech Connect

    Kim, Seung Kwon [Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Department of Radiology (Korea, Republic of)], E-mail: radi@lycos.co.kr; Seo, Jung Wook [Ilsan Paik Hospital, Inje University School of Medicine, Department of Diagnostic Radiology (Korea, Republic of)

    2005-12-15

    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.

  13. Cluster Multi-Point Studies of the Auroral Acceleration Region

    NASA Astrophysics Data System (ADS)

    Marklund, G. T.

    2014-12-01

    Multi-point studies of the auroral acceleration region (AAR) by the Cluster spacecraft has enabled a number of open issues on the auroral acceleration to be addressed and revealed. Data from AAR crossings of Inverted-V aurora, by the C1 and C3 spacecraft at different altitudes, enabled a detailed reconstruction of the acceleration potential and a verification of its stability on a five min time scale. The relative role of quasi-static and Alfvénic acceleration behind aurora are addressed in two event studies. In one of these, the two processes are shown to operate jointly on the plasma population within the polar cap boundary. In the other, the electron energy flux producing multiple arcs within a surge is found to be generally dominated by the quasi-static contribution. Acceleration features and the FAC closure associated with surge-horn aurora crossed by the Cluster fleet were derived in another event study. A study of the density distribution within the auroral cavity, showed for all included events, exponential density decreases, relative to the ambient densities, from the mid to top of the AAR. In another study, cavities were found to extend well beyond the top of the AAR. Finally, statistical high-latitude electric field and plasma density distributions are presented based on 10 years of Cluster data collected between 2 and 4 RE altitudes. Intense electric fields appear in two altitude regimes on the nightside, separated by a gap at 2.8 RE. The upper altitude fields were interpreted to be Alfvénic and the lower altitude fields quasi-static, related to the AAR. The gap in the electric field intensity indicates a partial closure of the potentials in the lower region, with similarities to model results of reflected Alfvén waves and earlier reported observations

  14. Space Shuttle Earth Observation sensors pointing and stabilization requirements study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    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.

  15. 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

    Microsoft Academic Search

    Guo-Ding Zhou; Hua Shao; B. H. Loo

    1997-01-01

    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

  16. Neutron Depth Profiling benchmarking and analysis of applications to lithium ion cell electrode and interfacial studies research

    NASA Astrophysics Data System (ADS)

    Whitney, Scott M.

    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.

  17. Electrochemical, AFM and QCM studies on ferritin immobilized onto a self-assembled monolayer-modified gold electrode

    Microsoft Academic Search

    Masato Tominaga; Akihiro Ohira; Yoshihisa Yamaguchi; Masashi Kunitake

    2004-01-01

    A ferritin-immobilized electrode based on self-assembled monolayer (SAM)-modified gold electrodes was developed. Various alkane thiols containing functional groups as the terminal group were used for the SAMs. The ferritin-immobilized SAM-modified electrodes were characterized by electrochemical, atomic force microscopy (AFM) and quartz crystal microbalance (QCM) techniques. The results indicated that ferritin was selectively immobilized onto amino terminal alkane thiol-modified electrodes by

  18. A study on oxidized glassy carbon sheets for bipolar supercapacitor electrodes

    SciTech Connect

    Braun, A.; Baertsch, M.; Geiger, F. [and others

    2000-07-01

    Electrochemical Double Layer Capacitors (EDLC) for high energy and power density applications, based on glassy carbon (GC) electrodes, are being developed in this laboratory. In the context of this project, GC sheets were oxidized and investigated with Small Angle X-ray Scattering (SAXS), Electrochemical Impedance Spectroscopy (EIS) and Nitrogen Gas Adsorption (BET). During oxidation on active film with open pores is built on the surface of the GC. Upon oxidation, the internal volumetric surface area of the active film decreases, whereas the volumetric electrochemical double layer capacitance increases. The authors show that this effect is correlated with the opening, the growth and the coalescence of the pores.

  19. Improvements and artifact analysis in conductivity images using multiple internal electrodes.

    PubMed

    Farooq, Adnan; Tehrani, Joubin Nasehi; McEwan, Alistair Lee; Woo, Eung Je; Oh, Tong In

    2014-06-01

    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

  20. Comparative study of the effect of some macro-molecules and some simple molecules on dropping mercury electrode capacity

    Microsoft Academic Search

    S. L. Gupta

    1954-01-01

    Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a A comparative study of the effect of some macromolecules such as invertase, insulin, and albumin on the one hand and the simple\\u000a molecules like isobutyl alcohol and isopropyl alcohol on the other, on the dropping mercury electrode capacity has been investigated.\\u000a Effect of shift of the electro-capillary zero on the magnitude of the desorption peaks have been examined

  1. Reliability of cone beam computed tomography in scalar localization of the electrode array: a radio histological study.

    PubMed

    Marx, Mathieu; Risi, Frank; Escudé, Bernard; Durmo, Irfan; James, Christopher; Lauwers, Frédéric; Deguine, Olivier; Fraysse, Bernard

    2014-04-01

    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

  2. Electrochemical and kinetic studies of ultrafast laser structured LiFePO4 electrodes

    NASA Astrophysics Data System (ADS)

    Mangang, M.; Gotcu-Freis, P.; Seifert, H. J.; Pfleging, W.

    2015-03-01

    Due to a growing demand of cost-efficient lithium-ion batteries with an increased energy and power density as well as an increased life-time, the focus is set on intercalation cathode materials like LiFePO4. It has a high practical capacity, is environmentally friendly and has low material costs. However, its low electrical conductivity and low ionic diffusivity are major drawbacks for its use in electrochemical storage devices or electric vehicles. By adding conductive agents, the electrical conductivity can be enhanced. By increasing the surface of the cathode material which is in direct contact with the liquid electrolyte the lithium-ion diffusion kinetics can be improved. A new approach to increase the surface of the active material without changing the active particle packing density or the weight proportion of carbon black is the laser-assisted generation of 3D surface structures in electrode materials. In this work, ultrafast laser radiation was used to create a defined surface structure in LiFePO4 electrodes. It was shown that by using ultrashort laser pulses instead of nanosecond laser pulses, the ablation efficiency could be significantly increased. Furthermore, melting and debris formation were reduced. To investigate the diffusion kinetics, electrochemical methods such as cyclic voltammetry and galvanostatic intermittent titration technique were applied. It could be shown that due to a laser generated 3D structure, the lithium-ion diffusion kinetic, the capacity retention and cell life-time can be significantly improved.

  3. In-situ Spectroscopic and Structural Studies of Electrode Materials for Advanced Battery Applications

    SciTech Connect

    Daniel A Scherson

    2013-03-14

    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.

  4. Spectroscopic study of the proton dynamics in manganese dioxide electrode materials

    NASA Astrophysics Data System (ADS)

    Johnson, C. S.; Thackeray, M. M.; Nipko, J. C.; Loong, C.-K.

    1998-04-01

    Proton or lithium diffusion is a critical electrode process that occurs in manganese dioxide electrode materials during cycling of either aqueous (alkaline) or non-aqueous (lithium) batteries. The structural and electrochemical properties of a number of hydrated alpha-phase manganese dioxide compounds (?-MnO2.nH2O n~0.2-0.33), the heat-treated products (n~0-0.1), as well as their more stable lithia-doped derivatives, ?-[xLi2O].MnO2 (0

  5. Mass Transfer Studies of Geobacter sulfurreducens Biofilms on Rotating Disk Electrodes

    PubMed Central

    Babuta, Jerome T.; Beyenal, Haluk

    2014-01-01

    Electrochemical impedance spectroscopy has received significant attention recently as a method to measure electrochemical parameters of Geobacter sulfurreducens bio-films. Here, we use electrochemical impedance spectroscopy to demonstrate the effect of mass transfer processes on electron transfer by G.sulfurreducens biofilms grown in situ on an electrode that was subsequently rotated. By rotating the biofilms up to 530 rpm, we could control the microscale gradients formed inside G.sulfurreducens biofilms. A 24% increase above a baseline of 82 ?A could be achieved with a rotation rate of 530 rpm. By comparison, we observed a 340% increase using a soluble redox mediator (ferrocyanide) limited by mass transfer. Control of mass transfer processes was also used to quantify the change in biofilm impedance during the transition from turnover to non-turnover. We found that only one element of the biofilm impedance, the interfacial resistance, changed significantly from 900 to 4,200 ? under turnover and non-turnover conditions, respectively. We ascribed this change to the electron transfer resistance overcome by the biofilm metabolism and estimate this value as 3,300 ?. Additionally, under non-turnover, the biofilm impedance developed pseudocapacitive behavior indicative of bound redox mediators. Pseudocapacitance of the biofilm was estimated at 740 ?F and was unresponsive to rotation of the electrode. The increase in electron transfer resistance and pseudocapacitive behavior under non-turnover could be used as indicators of acetate limitations inside G.sulfurreducens biofilms. PMID:23996084

  6. Comparative study of multi walled carbon nanotubes-based electrodes in micellar media and their application to micellar electrokinetic capillary chromatography.

    PubMed

    Chicharro, Manuel; Arribas, Alberto Sánchez; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio

    2007-12-15

    This work reports on a comparative study of the electrochemical performance of carbon nanotubes-based electrodes in micellar media and their application for amperometric detection in micellar electrokinetic capillary chromatography (MEKC) separations. These electrodes were prepared in two different ways: immobilization of a layer of carbon nanotubes dispersed in polyethylenimine (PEI), ethanol or Nafion onto glassy carbon electrodes or preparation of paste electrodes using mineral oil as binder. Scanning electron microscopy (SEM) was employed for surface morphology characterization while cyclic voltammetry of background electrolyte was used for capacitance estimation. The amperometric responses to hydrogen peroxide, amitrol, diuron and 2,3-dichlorophenol (2,3CP) in the presence and in the absence of sodium dodecylsulphate (SDS) were studied by flow injection analysis (FIA), demonstrating that the electrocatalytic activity, background current and electroanalytical performance were strongly dependent on the electrodes preparation procedure. Glassy carbon electrodes modified with carbon nanotubes dispersed in PEI (GC/(CNT/PEI)) displayed the most adequate performance in micellar media, maintaining good electrocatalytic properties combined with acceptable background currents and resistance to passivation. The advantages of using GC/(CNT/PEI) as detectors in capillary electrophoresis were illustrated for the MEKC separations of phenolic pollutants (phenol, 3-chlorophenol, 2,3-dichlorophenol and 4-nitrophenol) and herbicides (amitrol, asulam, diuron, fenuron, monuron and chlortoluron). PMID:18371652

  7. The secondary alkaline zinc electrode

    Microsoft Academic Search

    Frank R. McLarnon; Elton J. Cairns

    1991-01-01

    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

  8. Study of freezing-point depression of selected food extracts

    SciTech Connect

    Tanaka, Fumihiko [Kagoshima Univ. (Japan). Dept. of Agricultural Systems Engineering; Murata, Satoshi; Habara, Kazuhiro; Amaratunga, K.S.P. [Kyushu Univ., Fukuoka (Japan). Dept. of Agricultural Engineering

    1996-12-31

    The phenomenon of freezing-point depression that accompanies the solute concentration of selected food extracts was investigated to reveal the characteristics of solid-liquid phase equilibrium. The freezing curves of various food extracts did not exhibit ideal solution behavior in the higher concentration range. The experimental data were fitted to new freezing-point depression equations by the method of nonlinear least squares, and the results clearly indicated that the calculated freezing points at various concentrations were in good agreement with the experimental data. Furthermore, by using the determined parameters, the freezing ratio and the activation coefficient were derived.

  9. Studies on the Behavior of Water Triple-Point Cells

    Microsoft Academic Search

    Shu-Fei Tsai

    2003-01-01

    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

  10. Using compound electrodes in electrical impedance tomography.

    PubMed

    Hua, P; Woo, E J; Webster, J G; Tompkins, W J

    1993-01-01

    In electrical impedance tomography, we inject currents and measure voltages to estimate an object's resistivity distribution. The electrode configuration affects measured voltage data because the electrode-skin contact impedance is high and varies with electrode location. We developed a compound electrode which is composed of two electrodes: a large outer electrode to inject current and a small inner electrode to sense voltage. We used these compound electrodes to measure voltages from a physical phantom. We showed that the measured voltages from the compound electrodes are smaller in amplitude than those from conventional electrodes. This demonstrates that the compound electrode can minimize contact impedance voltage drop from the measured data. We used a finite element model for the compound electrode and incorporated the model into the regularized Newton-Raphson reconstruction algorithm. We performed a sensitivity study and showed that the reconstructed resistivity distributions are less dependent on the unknown contact resistance values for a compound electrode than a conventional electrode and that the use of a compound electrode results in improved images for the reconstruction algorithm. PMID:8468073

  11. Electrochemical, interfacial, and surface studies of the conversion of carbon dioxide to liquid fuels on tin electrodes

    NASA Astrophysics Data System (ADS)

    Wu, Jingjie

    The electrochemical reduction of carbon dioxide (CO2) into liquid fuels especially coupling with the intermittent renewable electricity offers a promising means of storing electricity in chemical form, which reduces the dependence on fossil fuels and mitigates the negative impact of anthropogenic CO2 emissions on the planet. Although converting CO2 to fuels is not in itself a new concept, the field has not substantially advanced in the last 30 years primarily because of the challenge of discovery of structural electrocatalysts and the development of membrane architectures for efficient collection of reactants and separation of products. An efficient catalyst for the electrochemical conversion of CO2 to fuels must be capable of mediating a proton-coupled electron transfer reaction at low overpotentials, reducing CO2 in the presence of water, selectively converting CO 2 to desirable chemicals, and sustaining long-term operations (Chapter 1). My Ph.D. research was an investigation of the electroreduction of CO2 on tin-based electrodes and development of an electrochemical cell to convert CO2 to liquid fuels. The initial study focused on understanding the CO2 reduction reaction chemistry in the electrical double layer with an emphasis on the effects of electrostatic adsorption of cations, specific adsorption of anion and electrolyte concentration on the potential and proton concentration at outer Helmholtz plane at which reduction reaction occurs. The variation of potential and proton concentration at outer Helmholtz plane accounts for the difference in activity and selectivity towards CO2 reduction when using different electrolytes (Chapter 2). Central to the highly efficient CO2 reduction is an optimum microstructure of catalyst layer in the Sn gas diffusion electrode (GDE) consisting of 100 nm Sn nanoparticles to facilitate gas diffusion and charge transfer. This microstructure in terms of the proton conductor fraction and catalyst layer thickness was optimized to maximize the triple phase boundary length for simultaneous high current density and selectivity towards formate formation (Chapter 3). The Sn GDEs was incorporated into a home-designed scalable full electrochemical cell which features a buffer layer of circulating liquid electrolyte mediating the proton concentration at cathode electrode surface. The Sn GDEs exhibited excellent short-term performance for CO2 reduction with high selectivity towards formate formation at low overpotentials in the full electrochemical cell. Additionally, coupling water oxidation and CO2 reduction was demonstrated in this full electrochemical cell to mimic biosynthesis (Chapter 4). The rapid degradation of selectivity towards formate formation on Sn GDEs in the full electrochemical cell, however, was observed during long-term operation. The degradation mechanism was unraveled due to the decrease of electrode potential resulted from substantial increase of internal ohmic resistance of the full electrochemical cell. The unexpected rise of internal ohmic resistance was attributed to the pulverization of 100 nm Sn nanoparticles due to the hydrogen diffusion induced stress. Based on the understanding of the origin of Sn nanoparticles pulverization, SnO2 nanoparticles of 3˜3.5 nm close to the critical size were utilized and reduced in situ to form Sn catalyst for electrochemical reduction of CO2. The pulverization was suppressed and subsequently a stable performance of electrodes was obtained (Chapter 5). Due to the affinity to oxygen, Sn nanoparticle surface is covered by a native thin oxide layer. The performance of Sn GDEs towards CO2 reduction strongly depends on the initial thickness of the surface oxide layer. The selectivity towards formate production dropped while the hydrogen yield increased as the initial thickness of the oxide layer increased (Chapter 6). These results suggest the underlying of surface structure on the selectivity of Sn electrode for CO2 reduction and provide insight into the development of more efficient catalysts.

  12. First-principles studies of ultrathin ferroelectric capacitors with Ru-based perovskite electrodes

    NASA Astrophysics Data System (ADS)

    He, Jun; Nakhmanson, Serge

    2010-03-01

    First-principles calculations are used to investigate the electrostatics and polarization screening effects in ultrathin PbTiO3 films capped with SrRuO3 or CaRuO3 electrodes under short-circuit boundary conditions. In accordance with previous results, we find that the SrRuO3/PbTiO3/SrRuO3 system without antiferrodistortive octahedral rotations is ``non-pathological'' with respect to the metal/ferroelectric band alignment across the interface. Such rotations, however, have to be explicitly considered to correctly determine the band alignment and polarization screening in the SrRuO3/PbTiO3/SrRuO3 nanocapacitor. (*) Present address: Vanderbilt University, Nashville, Tennessee 37235 and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

  13. Fabrication and heating rate study of microscopic surface electrode ion traps

    E-print Network

    N. Daniilidis; S. Narayanan; S. A. Möller; R. Clark; T. E. Lee; P. J. Leek; A. Wallraff; St. Schulz; F. Schmidt-Kaler; H. Häffner

    2010-09-15

    We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with trapping height of approximately 240 micron. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found in the literature and possible relation of anomalous heating to sources of noise and dissipation in other systems, namely impurity atoms adsorbed on metal surfaces and amorphous dielectrics.

  14. Study of localized corrosion in aluminum alloys by the scanning reference electrode technique

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1995-01-01

    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.

  15. Electrochemical impedance spectroscopy study of a hydrogen electrode reaction at a Zn electrode in a molten LiCl-KCl-LiH system.

    PubMed

    Nakajima, Hironori; Nohira, Toshiyuki; Ito, Yasuhiko

    2005-05-19

    The hydrogen electrode reaction involving hydride ion, H-, at a Zn electrode is investigated in a molten LiCl-KCl-LiH system at 673 K. The charge-transfer resistances were measured by electrochemical impedance spectroscopy in the overpotential region of 0.10 < or = eta < or = 0.35 V and over the H- concentrations of 1.5 x 10(-4) < or = C(H)- < or = 1.2 x 10(-3) mol cm(-3). The logarithm plot of the charge-transfer resistance against the overpotential at C(H)- = 3.0 x 10(-4) mol cm(-3) gives the symmetry factor, beta, of 0.50 and the exchange current density, j0, of 5.8 x 10(-3)A cm(-2), respectively. Analysis of the dependence of j0 on H- concentration independently gives a beta of 0.55. The reasonable beta values indicate that the H- <==> H(ad)(M) + e- step is rate-determining. PMID:16852161

  16. Investigation of the effects of shear on arc-electrode erosion using a modified arc-electrode mass loss model

    NASA Astrophysics Data System (ADS)

    Webb, Bryan T.

    The electrodes are the attachment points for an electric arc where electrons and positive ions enter and leave the gas, creating a flow of current. Electrons enter the gas at the cathode and are removed at the anode. Electrons then flow out through the leads on the anode and are replenished from the power supply through the leads on the cathode. Electric arc attachment to the electrode surface causes intensive heating and subsequent melting and vaporization. At that point a multitude of factors can contribute to mass loss, to include vaporization (boiling), material removal via shear forces, chemical reactions, evaporation, and ejection of material in jets due to pressure effects. If these factors were more thoroughly understood and could be modeled, this knowledge would guide the development of an electrode design with minimal erosion. An analytic model was developed by a previous researcher that models mass loss by melting, evaporation and boiling with a moving arc attachment point. This pseudo one-dimensional model includes surface heat flux in periodic cycles of heating and cooling to model motion of a spinning arc in an annular electrode where the arc periodically returns to the same spot. This model, however, does not account for removal of material due to shear or pressure induced effects, or the effects of chemical reactions. As a result of this, the model under-predicts material removal by about 50%. High velocity air flowing over an electrode will result in a shear force which has the potential to remove molten material as the arc melts the surface on its path around the electrode. In order to study the effects of shear on mass loss rate, the model from this previous investigator has been altered to include this mass loss mechanism. The results of this study have shown that shear is a viable mechanism for mass loss in electrodes and can account for the mismatch between theoretical and experimental rates determined by previous investigators. The results of a parametric study of arc attachment factors - including spot size, fall voltage, arc spot rotation rate, ambient bore heat rate, and air mass flow rate - are presented. The parametric study resulted in improving estimates of both the arc spot size and electrode fall voltage, two critical factors affecting electrode heating. Little sensitivity of electrode erosion rate to ambient bore heat rate and rotation rate was found. The erosion rate is found to be sensitive to the mass flow rate of air injected in the arc heater and validation of the model by comparison with more run condition data should be carried out as the data become available.

  17. Study plans a) Study plan for Specialization in Financial Mathematics (CP is credit points)

    E-print Network

    Ulm, Universität

    Study plans a) Study plan for Specialization in Financial Mathematics (CP is credit points) Term Financial Mathematics Mathematics Financial Economics Other CP 1 Financial Mathematics I 9 CP Optional modules 9 CP Asset Pricing 7 CP Additional Key Qualification 3 CP 28 2 Financial Mathematics II 9 CP

  18. Potential dependence of self-assembled porphyrin layers on a Cu(111) electrode surface: In-situ STM study

    NASA Astrophysics Data System (ADS)

    Phan, Thanh Hai; Kosmala, Tomaz; Wandelt, Klaus

    2015-01-01

    The adsorption of redox-active 5,10,15,20-Tetrakis(4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate) molecules, abbreviated as [H2TTMAPP]4+, on a chloride pre-covered Cu(111) electrode surface was studied in an electrochemical environment by means of combined cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). The [H2TTMAPP]4+ molecules adsorb spontaneously on the c(p ×?{ 3}) Cl/Cu(111) surface and form a highly ordered 2D monolayer once the supporting electrolyte (10 mM HCl) is replaced by the molecule containing electrolyte (10 mM HCl + 0.1 mM H2TTMAPP) at a potential of E = + 20 mV vs. RHE (reversible hydrogen electrode). This ordered phase undergoes a phase transition into a disordered one once the [H2TTMAPP]4+ molecules pass through the first reduction step at negative potentials. In contrast, at positive potentials, the copper corrosion process, taking place at step-edges with predominant < 2 bar 11 > directions, is not prevented by the presence of the [H2TTMAPP]4+ adlayer.

  19. Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes

    PubMed Central

    2014-01-01

    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 cells’ distributions demonstrate the method’s 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. PMID:24903282

  20. Two-point bend studies of glass fibers

    NASA Astrophysics Data System (ADS)

    Tang, Zhongzhi

    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 ˜40% 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.

  1. A STUDY OF PRECONDITIONERS FOR NETWORK INTERIOR POINT METHODS

    E-print Network

    Resende, Mauricio G. C.

    for the minimum cost network flow problem. A computational comparison using a set of standard problems improves A number of implementations of interior point methods for the minimum cost network flow (MCNF) problem have) AA x = b, where A is the m×n matrix of the coefficients and is a n×n diagonal matrix of positive

  2. Study Points to Acid Rain in Decline of Songbirds

    NSDL National Science Digital Library

    Seabrook, Charles.

    2002-01-01

    New research from the Cornell Lab of Ornithology points to acid rain as a major cause of songbird decline, where previous research focused on forest fragmentation. This Web site is a brief article highlighting the research findings from the Atlanta Journal-Constitution, published on the Natural Resources Defense Council's Web page.

  3. A Theoretical Study of Stagnation-Point Ablation

    NASA Technical Reports Server (NTRS)

    Roberts, Leonard

    1959-01-01

    A simplified analysis is made of ablation cooling near the stagnation point of a two-dimensional or axisymmetric body which occurs as the body vaporizes directly from the solid state. The automatic shielding mechanism Is discussed and the important thermal properties required by a good ablation material are given. The results of the analysis are given in terms of dimensionless parameters.

  4. Study of QCD critical point using the canonical ensemble method

    E-print Network

    Anyi Li

    2010-03-06

    The existence of the QCD critical point at non-zero baryon density is not only of great interest for experimental physics but also a challenge for the theory. Any hint of the existence of the first order phase transition and, particularly, its critical point will be valuable towards a full understanding of the QCD phase diagram. We use lattice simulation based on the canonical ensemble method to explore the finite baryon density and finite temperature region and look for the QCD critical point. As a benchmark, we run simulations for the four degenerate flavor QCD where we observe a clear signal of the expected first order phase transition. In the two flavor case, we do not see any signal for temperatures as low as $0.83 \\rm{T_c}$. Although our real world contains two light quarks and one heavier quark, three degenerate flavor case shares a lot of similar phase structures as the QCD. We scan the phase diagram using clover fermions with $m_\\pi \\approx 700{MeV}$ on $6^3\\times4$ lattices. The baryon chemical potential is measured as we increase the baryon number and we see the characteristic "S-shape" that signals the first order phase transition. We determine the phase boundaries by Maxwell construction and report our preliminary results for the location of critical point for the present lattice.

  5. Particle Transportation Using Programmable Electrode Arrays

    E-print Network

    Kua, C.H.

    This study presents a technique to manipulate particles in microchannels using arrays of individually excitable electrodes. These electrodes were energized sequentially to form a non-uniform electric field that moved along ...

  6. Fabrication of ion-conducting carbon-polymer composite electrodes by spin-coating

    NASA Astrophysics Data System (ADS)

    Põldsalu, Inga; Mändmaa, Sven-Erik; Peikolainen, Anna-Liisa; Kesküla, Arko; Aabloo, Alvo

    2015-04-01

    We report a fabricating method for ion-conducting carbon electrodes on top of industrially produced PVDF membrane by spin-coating. Spin-coating is desirable due to its potential application in large-scale actuator manufacturing and its possibility to produce very thin electrodes. The industrial grade membrane was chosen in order to investigate more accurately the results of spin-coating without considering the deviations present in a hand-made membrane. Spin-coating and surface resistivity measurements via four-point probe were described in further detail. The production process of electrode suspension and suspension dispensing were developed and fine-tuned. The spin coater was programmed to obtain electrodes with uniform electrical properties. The arrangement of the spin coater was slightly altered to remove swelling and bubble formation effects concurrent with usage of the porous membrane. Electrodes produced with the developed method were measured and analyzed. Thickness of the film was measured with micrometer screw gauge and four-point probe was used to measure sheet resistivity, in addition film was studied under scanning electron microscope. In best cases the coefficient of variation for sheet conductivity was 6.2%. For all electrode sheet conductivities the median coefficient of variation was 7%. The thickness of the electrodes varied from 6 to 23 ?m. As a proof of concept for the developed method a working actuator with spin-coated electrodes was produced.

  7. Studies on Conducting Polypyrrole/Graphene Oxide Composites as Supercapacitor Electrode

    NASA Astrophysics Data System (ADS)

    Konwer, Surajit; Boruah, Ratan; Dolui, Swapan K.

    2011-11-01

    An electrode material based on polypyrrole (PPy) doped with graphene oxide (GO) sheets was synthesized via in situ polymerization of pyrrole in the presence of GO in various proportions (5% and 10%). The synthesized samples were characterized by Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, and electrical conductivity measurements. FTIR spectroscopy and XRD revealed the interaction between GO and PPy. The direct-current (DC) electrical conductivity (75.8 S/cm) of the prepared composites was dramatically enhanced compared with pure PPy (1.18 S/cm). High specific capacitance of PPy/GO composite of 421.4 F/g was obtained in the potential range from 0 V to 0.50 V at 2 mA compared with 237.2 F/g for pure PPy by galvanostatic charge-discharge analysis. Incorporation of GO into the PPy matrix has a pronounced effect on the electrical conductivity and electrochemical capacitance performance of PPy/GO nanocomposites.

  8. Studies on Supercapacitor Electrode Material from Activated Lignin-Derived Mesoporous Carbon

    SciTech Connect

    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

    2014-01-01

    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.

  9. A study of purely astrometric selection of extragalactic point sources

    E-print Network

    Heintz, Kasper E; Høg, Erik

    2015-01-01

    Selection of extragalactic point sources, e.g. QSOs, is often hampered by significant selection effects causing existing samples to have rather complex selection functions. We explore whether a purely astrometric selection of extragalactic point sources, e.g. QSOs, is feasible with the ongoing Gaia mission. Such a selection would be interesting as it would be unbiased in terms of colours of the targets and hence would allow selection also with colours in the stellar sequence. We have analyzed a total of 18 representative regions of the sky by using \\textit{GUMS}, the simulator prepared for ESAs Gaia mission, both in the range of $12\\le G \\le 20$ mag and $12\\le G \\le 18$ mag. For each region we determine the density of apparently stationary stellar sources, i.e. sources for which Gaia cannot measure a significant proper motion. The density is contrasted with the density of extragalactic point sources, e.g. QSOs, in order to establish in which celestial directions a pure astrometric selection is feasible. When ...

  10. Physiologic Responses to Acupuncture Point Stimulation: A Pilot Study to Evaluate Methods and

    E-print Network

    Physiologic Responses to Acupuncture Point Stimulation: A Pilot Study to Evaluate Methods Abstract-- The physiological responses to needle stimulation of an acupuncture point and a nearby control, unexpected noise, etc were annotated. Keywords-- Acupuncture stimulation, physiologic response to acupuncture

  11. Electrochemical studies of thin films of conducting polymers and conducting polymer composites deposited on metal and semiconductor electrodes

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, G.; Di Stefano, S.; Moacanin, J.

    1987-01-01

    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.

  12. Study of the ion-channel behavior on glassy carbon electrode supported bilayer lipid membranes stimulated by perchlorate anion.

    PubMed

    Zhang, Zhiquan; Shi, Jun; Huang, Weimin

    2015-10-01

    In this paper, a kind of didodecyldimethylammonium bromide (DDAB) layer membranes was supported on a glassy carbon electrode (GCE). We studied the ion channel behavior of the supported bilayer lipid membrane by scanning electrochemical microscopy (SCEM) in tris(2,2'-bipyridine) ruthenium(II) solution. Perchlorate anion was used as a presence of stimulus and ruthenium(II) complex cations as the probing ions for the measurement of SECM, the lipid membrane channel was opened and exhibited the behavior of distinct SECM positive feedback curve. The channel was in a closed state in the absence of perchlorate anions while reflected the behavior of SECM negative feedback curve. The rates of electron transfer reaction in the lipid membranes surface were detected and it was dependant on the potential of SECM. PMID:26117774

  13. Experimental and theoretical study of the efficiency of a three-electrode reactor for the removal of NO

    NASA Astrophysics Data System (ADS)

    Gallego, J. L.; Minotti, F.; Grondona, D.

    2014-05-01

    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.

  14. A study of the fatigue properties of small diameter wires used in intramuscular electrodes.

    PubMed

    Scheiner, A; Mortimer, J T; Kicher, T P

    1991-05-01

    Single and multi-strand stainless steel and cobalt-nickel alloy wires, with strand diameters from 26 to 46 microns, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi-stranded wires have the same average fatigue life as their individual constituent strands, but the variance of that life is smaller. (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure. (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life. PMID:1869576

  15. Defect electrochemistry of oxide electrodes

    NASA Astrophysics Data System (ADS)

    Wirtz, G. P.; Isaacs, H. S.

    1983-10-01

    The polarization in an electrochemical cell may be represented by the sum of a number of overpotentials which arise during the passage of current through the cell. The product of this sum and the cell current is the energy loss during cell operation. At the oxygen electrode in a stabilized zirconia based cell the polarization process is often markedly dependent on the electrode material as evidenced in point contact measurements. In many cases the observations may be rationalized in terms of a model based on a Langmuir adsorption isotherm for oxygen in which the rate limiting step in the electrode reaction is the adsorption-desorption of oxygen on the electrode surface. This model predicts cathodic and anodic currents limited respectively by the complete depletion and complete coverage of the surface by adsorbed oxygen.

  16. Alloy corrosion studied by a combination of stripping voltammetry and the rotating ring-disk electrode. Lead-cadmium alloy

    Microsoft Academic Search

    V. V. Zhdanov; B. K. Filanovskii

    1984-01-01

    The authors have used the rotating ring-disk electrode (RRDE) in combination with stripping voltammetry (SVA) at solid electrodes in order to determine partial dissolution rates of alloy components in the vicinity of the steady potential and also under cathodic and anodic polarization. The method of SVA is used in the analytical determination of trace amounts of heavy metals dissolved in

  17. The relationship between early afterdepolarization and the occurrence of torsades de pointes--an in vivo canine model study.

    PubMed

    Sato, T; Hirao, K; Hiejima, K

    1993-06-01

    The relationship between early afterdepolarization (EAD) and the occurrence of torsades de pointes (TdP) was studied in a canine model. Twelve dogs of both sexes, weighing 9.9-16 Kg, were studied. After reducing the concentration of serum potassium to 3.0-4.0 mEq/l, by administration of calcium polystyrene sulfonate at 15-20 g/day for 1 or 2 weeks, a 6F electrode catheter was introduced via the femoral vein and positioned at the atrioventricular (AV) junction. Complete AV block was produced by catheter ablation using a high frequency current. A Franz 6F catheter was introduced into the right ventricle to record monophasic action potentials (MAPs) using the contact electrode technique. After a stable recording of the MAPs was achieved, cesium chloride (CsCl; 1 mM/Kg) was administered as an intravenous bolus over 15 sec. The MAPs and electrocardiogram (ECG) changes were simultaneously recorded for 30 min after the administration of CsCl. The administration was repeated several times at intervals 30 min. Sustained or non-sustained ventricular tachycardia was produced in all dogs. EAD appeared in 8 of 12 dogs. When EAD developed sufficiently high amplitude, ventricular premature beats occurred near the peak of EAD and TdP was induced in 3 of 8 EAD-positive dogs. TdP was not induced in EAD-negative dogs. Although TdP was comparatively difficult to induce, EAD-triggered activity was suggested to be one of the necessary conditions for TdP, because TdP occurred only when EAD reached a sufficiently high amplitude to produce ventricular premature beats. PMID:8341001

  18. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    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.

  19. Detection of EEG electrodes in brain volumes.

    PubMed

    Graffigna, Juan P; Gómez, M Eugenia; Bustos, José J

    2010-01-01

    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

  20. Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Cavallari, Marco Roberto; Zanchin, Vinicius Ramos; Pojar, Mariana; Seabra, Antonio Carlos; de Assumpção Pereira-da-Silva, Marcelo; Fonseca, Fernando Josepetti; de Andrade, Adnei Melges

    2014-05-01

    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 (˜0.01 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.

  1. Enhancing Electrochemical Water-Splitting Kinetics by Polarization-Driven Formation of Near-Surface Iron(0): An In?Situ XPS Study on Perovskite-Type Electrodes**

    PubMed Central

    Opitz, Alexander K; Nenning, Andreas; Rameshan, Christoph; Rameshan, Raffael; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; Rupprechter, Günther; Fleig, Jürgen; Klötzer, Bernhard

    2015-01-01

    In the search for optimized cathode materials for high-temperature electrolysis, mixed conducting oxides are highly promising candidates. This study deals with fundamentally novel insights into the relation between surface chemistry and electrocatalytic activity of lanthanum ferrite based electrolysis cathodes. For this means, near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and impedance spectroscopy experiments were performed simultaneously on electrochemically polarized La0.6Sr0.4FeO3?? (LSF) thin film electrodes. Under cathodic polarization the formation of Fe0 on the LSF surface could be observed, which was accompanied by a strong improvement of the electrochemical water splitting activity of the electrodes. This correlation suggests a fundamentally different water splitting mechanism in presence of the metallic iron species and may open novel paths in the search for electrodes with increased water splitting activity. PMID:25557533

  2. Studying 21cm power spectrum with one-point statistics

    NASA Astrophysics Data System (ADS)

    Shimabukuro, Hayato; Yoshiura, Shintaro; Takahashi, Keitaro; Yokoyama, Shuichiro; Ichiki, Kiyotomo

    2015-07-01

    The redshifted 21cm line signal from neutral hydrogens is a promising tool to probe the cosmic dawn and the epoch of reionization. Ongoing and future low-frequency radio experiments are expected to detect its fluctuations, especially through the power spectrum. In this paper, we give a physical interpretation of the time evolution of the power spectrum of the 21cm brightness temperature fluctuations, which can be decomposed into dark matter density, spin temperature and neutral fraction of hydrogen fluctuations. From the one-point statistics of the fluctuations, such as variance and skewness, we find that the peaks and dips in the time evolution are deeply related to X-ray heating of the intergalactic gas, which controls the spin temperature. We suggest the skewness of the brightness temperature distribution is a key observable to identify the onset of X-ray heating.

  3. Study on the service life and deactivation mechanism of Ti\\/SnO 2 Sb electrode by physical and electrochemical methods

    Microsoft Academic Search

    Hai-Yang Ding; Yu-Jie Feng; Jiang-Wei Lu

    2010-01-01

    The Sb doped tin dioxide electrode (Sb-doped SnO2) inter-layer was prepared using electroposition layer-by-layer onto a titanium plate, and the Sb-doped SnO2 surface catalytic layer (Ti\\/SnO2-Sb) was prepared using thermo-decomposition method. Accelerated service life tests were carried out in 0.5 M H2SO4 solution and 1.0 M NaOH solution, respectively. The deactivation mechanism of the electrodes is studied using oxygen evolution

  4. A Cross-Cultural Study of Reference Point Adaptation: Evidence from China, Korea, and the US

    ERIC Educational Resources Information Center

    Arkes, Hal R.; Hirshleifer, David; Jiang, Danling; Lim, Sonya S.

    2010-01-01

    We examined reference point adaptation following gains or losses in security trading using participants from China, Korea, and the US. In both questionnaire studies and trading experiments with real money incentives, reference point adaptation was larger for Asians than for Americans. Subjects in all countries adapted their reference points more…

  5. The technical study of integration of Flash animation in PowerPoint

    Microsoft Academic Search

    You-Rong Xiao; Quan-Jun Zheng; Xue Gong

    2010-01-01

    PowerPoint and Flash are very popular courseware at present. This thesis mainly studies the practical technology and theoretical knowledge of Integration of Flash animation in PowerPoint. It mainly introduces the contents of the course of practice, technical theory and technical features of integrating Flash animation into PowerPoint using hyperlinks objects controls and plug-ins.

  6. Activated transport in AMTEC electrodes

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1992-01-01

    Transport of alkali, metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. The temperature dependence of the diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and preexponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process.

  7. Plated Metal Powders for Electrode Pastes

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.

    1984-01-01

    Metal grains to be sintered precoated with frit metal. Coated metal powders used to make ink-like electrode pastes for printing and sintering electrode-fabrication process. Grains of base metal coated with lowmelting-point--, lead or tin-- by electroless deposition.

  8. Accuracy Study of a 2-Component Point Doppler Velocimeter (PDV)

    NASA Technical Reports Server (NTRS)

    Kuhlman, John; Naylor, Steve; James, Kelly; Ramanath, Senthil

    1997-01-01

    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.

  9. Impedance studies of Ni/Cd and Ni/H2 cells using the cell case as a reference electrode

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1989-01-01

    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.

  10. Semiclassical Green's functions of magnetic point contacts

    NASA Astrophysics Data System (ADS)

    Useinov, N. Kh.

    2015-05-01

    We propose a method for constructing the semiclassical symmetric and antisymmetric Green's functions of magnetic point contacts with uniform magnetization of different ferromagnetic electrodes. The obtained antisymmetric Green's function permits studying the ballistic and diffusion transport of electrons through the magnetic contact with the electrochemical potential inhomogeneity taken into account.

  11. Parametric study on instabilities in a two-layer electromagnetohydrodynamic channel flow confined between two parallel electrodes.

    PubMed

    Reddy, P Dinesh Sankar; Bandyopadhyay, Dipankar; Joo, Sang Woo; Sharma, Ashutosh; Qian, Shizhi

    2011-03-01

    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

  12. Studies on the Electrochemical Behaviour of Hydroquinone at L-cysteine Self-Assembled Monolayers Modified Gold Electrode

    Microsoft Academic Search

    Shengfu Wang; Dan Du

    2002-01-01

    L-Cysteine is combined onto gold electrode to form a self-assembled monolayers modified electrode (L-Cys\\/Au SAMs) by taking advantage of strong sulfur-gold interaction. ATR-FTIR, SEM, cyclic voltammetry (CV) and impedance were used for the characterization of the film. It shows excellent stability upon voltametric scanning and a good voltametric response towards hydroquinone with the potential ranged from 0.8 to -0.2 V

  13. Electrochemical study on the TiO2 porous electrodes for metal-free dye-sensitized solar cells

    Microsoft Academic Search

    D. W. Zhang; S. Chen; X. D. Li; Z. A. Wang; J. H. Shi; Z. Sun; X. J. Yin; S. M. Huang

    2009-01-01

    Nanocrystalline TiO2 porous electrodes were prepared by screen-printing method in order to efficiently control the fabrication process. TiO2 viscous pastes were prepared from commercial TiO2 nano powder using ethyl cellulose as a porosity controlling agent. A metal-free organic dye (indoline dye D102) was used as a sensitizer. TiO2 porous electrodes with different thicknesses were investigated. The optical and physical properties

  14. Space tug point design study. Volume 4: Program requirements

    NASA Technical Reports Server (NTRS)

    1973-01-01

    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.

  15. Numerical and experimental study of SnOx | Ag | SnOx multilayer as indium-free transparent electrode for organic solar cells

    NASA Astrophysics Data System (ADS)

    Bou, Adrien; Torchio, Philippe; Barakel, Damien; Thierry, François; Thoulon, Pierre-Yves; Ricci, Marc

    2014-03-01

    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.

  16. Muscle channelopathies and critical points in functional and genetic studies

    PubMed Central

    Jurkat-Rott, Karin; Lehmann-Horn, Frank

    2005-01-01

    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. PMID:16075040

  17. ELLIPSOMETRIC AND ELECTROCHEMICAL STUDIES OF THE STATE OF THE SURFACE OF COBALT, NICKEL AND INDIUM ELECTRODES

    E-print Network

    Paris-Sud XI, Université de

    ELLIPSOMETRIC AND ELECTROCHEMICAL STUDIES OF THE STATE OF THE SURFACE OF COBALT, NICKEL AND INDIUM'ellipsométrie est utilisée pour suivre le comportement anodique du cobalt, du nickel et de l'indium en solution

  18. Single-phase dielectrophoretic and electrorotation studies using three dimensional electrodes for cell characterization.

    PubMed

    Kumar, Rajeshwari Taruvai Kalyana; Cherukuri, Kavya; Prasad, Shalini

    2014-08-01

    A novel electrokinetic approach using single-phase electrorotation for the label-free manipulation and characterization of biological cells is presented. A single shell model was used to theoretically design and develop an experimental strategy for biological particle characterization. As a study model, electro-rotation of glutathione agarose (GA) beads was studied using three- dimensional spatially oriented micro-needle setup. Effect of electrical parameters (i) voltage: from 0-10 Vpp and (ii) frequency: 0-100 MHz was evaluated on a heterogeneous mixture of GA beads (35-150 microns). The relationship of the electrical parameters to rotational frequency of the beads was studied. This paper demonstrates a simple and easy to implement prototype for electrokinetic characterization of particles with translational potential for biological cells. PMID:25571112

  19. A Novel In-situ Electrochemical Cell for Neutron Diffraction Studies of Phase Transitions in Small Volume Electrodes of Li-ion Batteries

    SciTech Connect

    Vadlamani, Bhaskar S [ORNL; An, Ke [ORNL; Jagannathan, M. [University of Utah; Ravi Chandran, K. [University of Utah

    2014-01-01

    The design and performance of a novel in-situ electrochemical cell that greatly facilitates the neutron diffraction study of complex phase transitions in small volume electrodes of Li-ion cells, is presented in this work. Diffraction patterns that are Rietveld-refinable could be obtained simultaneously for all the electrodes, which demonstrates that the cell is best suited to explore electrode phase transitions driven by the lithiation and delithiation processes. This has been facilitated by the use of single crystal (100) Si sheets as casing material and the planar cell configuration, giving improved signal-to-noise ratio relative to other casing materials. The in-situ cell has also been designed for easy assembly and to facilitate rapid experiments. The effectiveness of cell is demonstrated by tracking the neutron diffraction patterns during the charging of graphite/LiCoO2 and graphite/LiMn2O4 cells. It is shown that good quality neutron diffraction data can be obtained and that most of the finer details of the phase transitions, and the associated changes in crystallographic parameters in these electrodes, can be captured.

  20. A study on reception electrodes for the vital-sign monitor using near-field intra-body communication enhanced by spread spectrum technique.

    PubMed

    Kobayashi, Takumi; Shimatani, Yuichi; Kyoso, Masaki

    2013-01-01

    As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication (NF-IBC) technique. However, it was hard to ensure communication reliability because transmission channel is noisy and unstable. In order to solve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. In previous study, we have already developed an ECG monitor using NF-IBC enhanced by SS. In this paper, we evaluated on structure of the reception electrode for reliable communication. Based on the evaluations with bit error rate, we suggested the reception electrode structure which can keep the communication reliability. As the results we considered that we can expand the reception electrode up to 2.25 m(2). Moreover, we proposed the structure of the reception electrodes that can keep the communication reliability. Finally we suggested how to use the SS NF-IBC vital-sign monitor in room that larger than 2.25 m(2), and we had shown the practicability of the systems. PMID:24109918

  1. Structural changes of the KcsA potassium channel upon application of the electrode potential studied by surface-enhanced IR absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamakata, Akira; Shimizu, Hirofumi; Osawa, Masatoshi; Oiki, Shigetoshi

    2013-06-01

    Structural changes of the KcsA potassium channel fixed on gold electrode surface in the upright orientation were studied by surface-enhanced IR absorption spectroscopy (SEIRAS). Measurements were performed at neutral pH, where the activation gate is kept closed. Band intensities were enhanced for the asymmetric (1565 cm-1) and symmetric (1405 cm-1) OCO-carboxylate groups at negative electrode potentials in the K+ solution, but not in the Na+ solution. Even for the reverse-oriented channel, the enhanced OCO-carboxylate band was evident at negative potential. When TBA was loaded in the central cavity, the K+-specific OCO band was not elicited. These results indicate that the negative electrode potential renders the local K+ concentration accumulated at the vicinity of the electrode surface, and the KcsA channel bathed in high K+ changes conformation of the selectivity filter from the collapsed to the open, and OCO-carboxylate groups (D80 and E71) in the back of the filter were rearranged.

  2. Structural variations of CO adlayers on a Pt(100) electrode in 0.1 M HClO4 solution: an in situ STM study.

    PubMed

    Wakisaka, Mitsuru; Yoneyama, Toshiki; Ashizawa, Shuichi; Hyuga, Yohei; Ohkanda, Takaharu; Uchida, Hiroyuki; Watanabe, Masahiro

    2013-07-14

    In the present study, we have investigated structures of a CO adlayer on a well-defined Pt(100) electrode surface in 0.1 M HClO4 aqueous solutions saturated with N2, 1% CO/He and 100% CO by using in situ STM. The in situ STM images with molecular resolution demonstrated that highly ordered structures of the CO adlayer, denoted (2 × n) - 2(n - 1)CO with CO coverages of (n - 1)/n, dynamically varied with the electrode potential and the CO partial pressure in solution. As the CO partial pressure increased, more compressed structures of the CO adlayer formed on the electrode surface. In each solution, a phase transition of the CO adlayer on the terrace site was observed to be triggered by increasing the electrode potential, accompanied by a partial desorption of surface CO without charge transfer. A series of in situ STM images revealed transient local structures during the phase transition of the CO adlayer. Specifically, unique structures were found to appear in the vicinity of monoatomic steps in N2- and 1% CO/He-saturated solution, but not in 100% CO-saturated solution. PMID:23715199

  3. Study of the impedance behavior of surface layers formed on lithium electrodes in a propylene carbonate electrolyte

    SciTech Connect

    Thevenin, J.G.; Muller, R.H.

    1986-01-01

    Different models of homogeneous and heterogeneous interphases have been investigated for the interpretation of impedance measurements of surface layers formed on lithium electrodes in an organic electrolyte. These models are based on the assumption that the surface layer consists of organic and inorganic compounds with the properties of solid and polymer electrolytes. The models discussed are compact, porous and multilayer systems. The analysis of the models is derived from a study of the equivalent circuits and the corresponding impedance diagrams for the different interphase models. This analysis leads to the determination of impedance parameters for the evaluation of the thickness of surface layers. The impedance measurements for lithium in propylene carbonate lithium perchlorate solution can be fitted by two interphase models. (1) The surface layer can be assumed to consist of two sublayers of different permittivities and conductivities according to the Compact-Stratified Layer (CSL) Model. (2) The surface layer can also be assumed to consist of a mixture of solid and polymer electrolytes according to the Solid-Polymer Interphase (SPI) Model. The thickness of surface layers deduced from the impedance data appears in agreement with the thicknesses which have been obtained by ellipsometric measurements in previous work.

  4. Novel electrodes for underwater ECG monitoring.

    PubMed

    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

    2014-06-01

    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 > 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

  5. Interfacial Properties of Ultrathin- Film Metal Electrodes: Studies by Combined Electron Spectroscopy and Electrochemistry 

    E-print Network

    Cummins, Kyle

    2012-07-16

    A pair of studies investigating the deposition and surface chemical properties of ultrathin metal films were pursued: (i) Pt-Co alloys on Mo(110); and (ii) Pd on Pt(111). Experimental measurement was based on a combination of electron spectroscopy...

  6. Albumin adsorption on alkanethiols self-assembled monolayers on gold electrodes studied by chronopotentiometry

    Microsoft Academic Search

    M. C. L. Martins; C. Fonseca; M. A. Barbosa; B. D. Ratner

    2003-01-01

    Chronopotentiometry was used to study the adsorption of human serum albumin (HSA) to self-assembled monolayers with the following terminal functional groups: CH3, COOH and OH. Surfaces were characterized by X-ray photoelectron spectroscopy, water contact angle measurements and cyclic voltammetry. HSA coverage of the different SAMs was investigated by chronopotentiometry and the total amount of adsorbed protein was determined using radiolabelled

  7. X-ray absorption spectroscopy studies of nickel oxide thin film electrodes for supercapacitors

    Microsoft Academic Search

    Kyung-Wan Nam; Won-Sub Yoon; Kwang-Bum Kim

    2002-01-01

    Nickel oxide films were synthesized by electrochemical precipitation of Ni(OH)2 followed by heat-treatment in air at various temperatures (200–600°C). Their structure and electrochemical properties were studied by cyclic voltammetry, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). XRD results showed that the nickel oxide obtained at 250°C or above has a crystalline NiO structure. The specific capacitance of the oxide

  8. Hairy carbon electrodes studied by cyclic voltammetry and battery discharge testing

    NASA Technical Reports Server (NTRS)

    Chung, Deborah D. L.; Shui, Xiaoping; Frysz, Christine A.

    1993-01-01

    Hairy carbon is a new material developed by growing submicron carbon filaments on conventional carbon substrates. Typical substrate materials include carbon black, graphite powder, carbon fibers, and glassy carbon. A catalyst is used to initiate hair growth with carbonaceous gases serving as the carbon source. To study the electrochemical behavior of hairy carbons, cyclic voltammetry (CV) and discharge testing were conducted. In both cases, hairy carbon results surpassed those of the substrate material alone.

  9. Chemical Modification of Electrodes.

    ERIC Educational Resources Information Center

    Bard, Allen J.

    1983-01-01

    Methods of preparing and characterizing modified electrodes are outlined and several applications are described. Topics include how electrodes are modified, characterization of such electrodes, and why it is necessary to modify electrodes. Reasons include use in electrocatalysis and display devices and in analytical/photoelectrochemical…

  10. Activated transport in AMTEC electrodes

    NASA Astrophysics Data System (ADS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Oconnor, D.; Kikkert, S.

    1992-08-01

    Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of the diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process.

  11. Activated transport in AMTEC electrodes

    SciTech Connect

    Williams, R.M.; Jeffries-Nakamura, B.; Ryan, M.A.; Underwood, M.L.; O`Connor, D.; Kikkert, S.

    1992-07-01

    Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process. 17 refs.

  12. Activated transport in AMTEC electrodes

    SciTech Connect

    Williams, R.M.; Jeffries-Nakamura, B.; Ryan, M.A.; Underwood, M.L.; O'Connor, D.; Kikkert, S.

    1992-01-01

    Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process. 17 refs.

  13. Influence of potential's electrode selection on physical modeling of time domain induced polarization (TDIP), case studies of homogeneous isotropic medium

    NASA Astrophysics Data System (ADS)

    Yatini, Laesanpura, A.

    2013-09-01

    The relationship between metal mineral content and induced polarization response is not well known. Mathematical and physical modeling in laboratory scale was applied to find out those relationship. Their relationship was obtained by curve mathching. The physical modeling data quality was very importand in obtaining the relationship, therefore accurate and precise measurements are needed. Physical modeling data quality depend on the type of electrode, measurement techniques and equipment. Therefore, it is important to know the characteristics of the utilized potential electrode materials. The results show that porouspot is the most excellent potential electrodes used for TDIP physical modeling. The obtained resistivity and chargeability of the TDIP response of the porouspot electrodes and copper electrodes are 16.11 Ohm-m and 0.015 mSec, and 16 Ohm-m and 0.36 mSec, respectively. It is concluded that the groundwater can be used in homogeneous isotropic medium approach and also it is a good method for host medium in physical modeling.

  14. A study of the comparative accuracy of two methods of locating acupuncture points

    Microsoft Academic Search

    Mark Aird; Meaghan Coyle; DM Cobbin; C Zaslawski

    2000-01-01

    SummaryThe ability to locate an acupuncture point accurately is an essential component of both effective treatment and meaningful acupuncture research. This study examined the comparative accuracy of two commonly used mechanical methods of acupuncture point location: directional and proportional. Twenty final-year acupuncture students attempted to locate the points LI.10 (Shousanli) and ST.40 (Fenglong) using each method contralaterally on a volunteer.

  15. Studies of 18650 cylindrical cells made with doped LiNiO 2 positive electrodes for military applications

    NASA Astrophysics Data System (ADS)

    Fan, Jiang

    We studied GP 18650 cylindrical cells made with doped LiNiO 2 positive electrode for military application. The studied cells should deliver about 184 Wh/kg according to the military specification MIL-PRF-320521 while it delivers about 201 Wh/kg according to the general commercial standard. The difference in the cell specific energy is mainly caused by the difference in the charging voltage. It is 4.1 V in the military specification compared to 4.2 V in the general commercial standard. Clearly, to take full advantage of the commercial lithium-ion cell, either the military increases the voltage limit to 4.2 V from 4.1 V or the cell manufacturers redesign their cells according to the 4.1 V charging voltage limit. The studied cell exceeds all major military requirements including high rate discharging, high current pulse discharging, low temperature discharging, cycle life, high temperature storage, and abuse tolerances such as the overcharging, forced discharging, and external short. Specifically, the capacity of the cell exceeds the requirement by 51% at a high discharging rate (3.3 A) and by 39% with a high current (6 A) pulse. The cell can discharge not only ˜62% of the expected capacity at -30 °C but also ˜47% at -40 °C and at 0.67 A, which means that the military can extend their specification to -40 °C. The cell still retained 1.97 Ah (or 92%) after 224 cycles, which exceeds the requirement by ˜9%. The cell retained 1.95 Ah (or 95%) after one-week storage at 50 °C and at 4.1 V, which exceeds the requirement by 8%. The abuse tolerance is also very high. The maximum cell temperature ranged only from 62 to 70 °C during overcharging, external short, and forced discharging. Directions for the improvement are also discussed.

  16. Scanning probe microscopy studies of dissolution and deposition processes on electrode surfaces

    SciTech Connect

    Cruickshank, B.J.

    1993-01-01

    Recently, it has been shown that scanning probe microscopes, particularly the scanning tunneling microscope (STM) and the atomic force microscope (AFM), are ideal methods for analyzing surface chemistry in situ. Both instruments allow for atomic resolution in many different environments, including electrolyte, air, cryogen, and vacuum. The authors have built a variable temperature STM, capable of operating at liquid helium temperatures. Initial results show the utility of the instrument in imaging inorganic adsorbates on ordered conductive substrates. Further work will focus on using scanning tunneling spectroscopy (STS) to map out the occupied and unoccupied molecular orbitals of the inorganic adsorbates. Atomic Force Microscopy studies have focused on monitoring corrosion and deposition processes on copper surfaces. In one study, the AFM was used to examine the anodic dissolution of polycrystalline copper in acid media with and without a corrosion inhibitor. An amorphous overlayer and preferential grain boundary etching were observed. The addition of benzotriazole formed a protective film that inhibited copper dissolution. In situ Atomic Force Microscopy (AFM) images of Cu(100) single crystals in dilute acid solutions reveals that a ([radical]2 [times] [radical]2)R45[degrees] adlattice is formed on this material. The authors associate the overlayer with adsorbed O or OH[sup [minus

  17. Experimental and DFT theoretical studies of surface enhanced Raman scattering effect on the silver nano arrays modified electrode.

    PubMed

    Zhang, Lisheng; Fang, Yan; Wang, Peijie

    2012-07-01

    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

  18. CETF Space Station payload pointing system design and analysis feasibility study. [Critical Evaluation Task Force

    NASA Technical Reports Server (NTRS)

    Smagala, Tom; Mcglew, Dave

    1988-01-01

    The expected pointing performance of an attached payload coupled to the Critical Evaluation Task Force Space Station via a payload pointing system (PPS) is determined. The PPS is a 3-axis gimbal which provides the capability for maintaining inertial pointing of a payload in the presence of disturbances associated with the Space Station environment. A system where the axes of rotation were offset from the payload center of mass (CM) by 10 in. in the Z axis was studied as well as a system having the payload CM offset by only 1 inch. There is a significant improvement in pointing performance when going from the 10 in. to the 1 in. gimbal offset.

  19. The secondary alkaline zinc electrode

    NASA Astrophysics Data System (ADS)

    McLarnon, Frank R.; Cairns, Elton J.

    1991-02-01

    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.

  20. Spectrophotometric calibration of pH electrodes in seawater using purified m-cresol purple.

    PubMed

    Easley, Regina A; Byrne, Robert H

    2012-05-01

    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

  1. Material removal rate and electrode wear ratio study on the powder mixed electrical discharge machining of cobalt-bonded tungsten carbide

    Microsoft Academic Search

    Kuang-Yuan Kung; Jenn-Tsong Horng; Ko-Ta Chiang

    2009-01-01

    In this article, a material removal rate (MRR) and electrode wear ratio (EWR) study on the powder mixed electrical discharge\\u000a machining (PMEDM) of cobalt-bonded tungsten carbide (WC-Co) has been carried out. This type of cemented tungsten carbide was\\u000a widely used as moulding material of metal forming, forging, squeeze casting, and high pressure die casting. In the PMEDM process,\\u000a the aluminum

  2. Alternating current anodic stripping voltammetry in the study of cadmium complexation by a reference Suwannee river fulvic acid: a model case with strong electrode adsorption and weak binding

    Microsoft Academic Search

    Anna Maria Garrigosa; Cristina Ariño; José Manuel Díaz-Cruz; Miquel Esteban

    2008-01-01

    The possibilities of anodic stripping voltammetry (ASV) using an alternating current (AC) scan in the stripping step have\\u000a been checked through the study of the complexation of cadmium by Suwannee river fulvic acid (SRFA), a reference fulvic acid\\u000a from the International Humic Substances Society. Because of the strong electrode adsorption of SRFA, AC mode appears to be\\u000a a good approach

  3. The influence of Triton-X-100 surfactant on the electroanalysis of lead and cadmium at carbon film electrodes – An electrochemical impedance study

    Microsoft Academic Search

    Carla Gouveia-Caridade; Christopher M. A. Brett

    2006-01-01

    The influence of the model surfactant Triton-X-100 on the electroanalysis of trace lead and cadmium ions by anodic stripping voltammetry at Nafion-coated carbon film electrodes has been studied by electrochemical impedance spectroscopy. Spectra were recorded before and after metal deposition, without and with the presence of surfactant. Plots of the imaginary part of the impedance vs. the logarithm of the

  4. In-situ STM study of the initial stages of corrosion of Cu(100) electrodes in sulfuric and hydrochloric acid solution

    Microsoft Academic Search

    M. R. Vogt; A. Lachenwitzer; O. M. Magnussen; R. J. Behm

    1998-01-01

    An in-situ scanning tunneling microscopy (STM) study of Cu(100) electrode surfaces in sulfuric and hydrochloric acid solutions in the potential range ?0.6 to ?0.1 V versus AgAgCl (KClsat) is presented, revealing the surface structure and dynamics in the double-layer region and providing detailed structural data on the initial stages of anodic Cu dissolution. After preparation by electropolishing in phosphoric acid,

  5. Micromachined electrode array

    DOEpatents

    Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

    2007-12-11

    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.

  6. Flexible retinal electrode array

    DOEpatents

    Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

    2006-10-24

    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.

  7. High frequency reference electrode

    DOEpatents

    Kronberg, James W. (Aiken, SC)

    1994-01-01

    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.

  8. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    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.

  9. Experimental study of discharge with liquid non-metallic (tap-water) electrodes in air at atmospheric pressure

    Microsoft Academic Search

    P. Andre; Yu Barinov; G. Faure; V. Kaplan; A. Lefort; S. Shkol'nik; D. Vacher

    2001-01-01

    The discharge with liquid non-metallic electrodes (DLNME) was investigated. The discharge burnt steadily with a DC power supply between two streams of weakly conducting liquid (tap water) in open air at atmospheric pressure. The metallic current leads were inserted into the streams and were covered by a 5 mm thick water layer. The discharge burnt in volumetric (diffuse) form with

  10. EFFECTS OF HEAVY DRINKING IN COLLEGE ON STUDY EFFORT, GRADE POINT AVERAGE, AND MAJOR CHOICE

    Microsoft Academic Search

    Amy M. Wolaver

    2002-01-01

    This article measures the effects of college drinking on study hours, grade point average (GPA), and major choice using simultaneous equation models and data from the 1993 College Alcohol Study. Binging and intoxication decrease GPA directly and indirectly by reducing study hours. Greater frequency of drinking increases the effect on study hours but not the total effect on GPA. College

  11. Study of infrared point source simulator for generating the multi-decoy

    NASA Astrophysics Data System (ADS)

    Zeng, Chang-e.; Yang, Di; Su, Jian-gang; Huang, Yan-jun; Wang, Zhi-sheng

    2013-08-01

    The hardware-in-loop test system for infrared point-type guide missile was introduced;The decoy irradiation and motion characteristics were analyzed; multi-decoy generation mode and principle were studied.

  12. A study of the point reactor dynamics equations as applied to large nuclear excursions

    E-print Network

    Perry, Robert Terrell

    1967-01-01

    A STUDY OF THE POINT REACTOR DYNAMICS EQUATIONS AS APPLIED TO LARGE NUCLEAR EXCURSIONS A Thesis By ROBERT TERRELL PERRY, JR, Submitted to the Graduate College of the Texas ARM University xn partial fulfillment of the requirements i...' or the degree of MASTER OF SCIENCE May, 1967 Major Subject: Nuclear Engineering A STUDY OF THE POINT REACTOR DYNAMICS EQUATIONS AS APPLIED TO LARGE NUCLEAR EXCURSIONS A Thesis By ROBERT TERRELL PERRY, JR. Approved as to style and content by...

  13. A comparative measurement study the workload of wireless access points in campus networks

    Microsoft Academic Search

    Felix Hernandez-Campos; Maria Papadopouli

    2005-01-01

    Our goal is to perform a system-wide characterization of the workload of wireless access points (APs) in a production 802.11 infrastructure. The key issues of this study are the characterization of the traffic at each access point (AP), its modeling, and a comparison among APs of different wireless campus-wide infrastructures. Unlike most other studies, we compare two networks using similar

  14. High performance cermet electrodes

    DOEpatents

    Isenberg, Arnold O. (Forest Hills Boro, PA); Zymboly, Gregory E. (Penn Hills, PA)

    1986-01-01

    Disclosed is a method of increasing the operating cell voltage of a solid oxide electrochemical cell having metal electrode particles in contact with an oxygen-transporting ceramic electrolyte. The metal electrode is heated with the cell, and oxygen is passed through the oxygen-transporting ceramic electrolyte to the surface of the metal electrode particles so that the metal electrode particles are oxidized to form a metal oxide layer between the metal electrode particles and the electrolyte. The metal oxide layer is then reduced to form porous metal between the metal electrode particles and the ceramic electrolyte.

  15. Local Effects of Biased Electrodes in the Divertor of NSTX

    SciTech Connect

    Zweben, S.; Campanell, M. D.; Lyons, B. C.; Maqueda, R. J.; Raitses, Y.; Roquemore, A. L.; Scotti, F.

    2012-05-07

    The goal of this paper is to characterize the effects of small non-axisymmetric divertor plate electrodes on the local scrape-off layer plasma. Four small rectangular electrodes were installed into the outer divertor plates of NSTX. When the electrodes were located near the outer divertor strike point and biased positively, there was an increase in the nearby probe currents and probe potentials and an increase in the LiI light emission at the large major radius end of these electrodes. When an electrode located farther outward from the outer divertor strike point was biased positively, there was sometimes a significant decrease in the LiI light emission at the small major radius end of this electrode, but there were no clear effects on the nearby probes. No non-local effects were observed with the biasing of these electrodes.

  16. PEDOT Electrochemical Polymerization Improves Electrode Fidelity and Sensitivity

    PubMed Central

    Frost, Christopher M.; Wei, Benjamin; Baghmanli, Ziya; Cederna, Paul S.; Urbanchek, Melanie G.

    2015-01-01

    Background The goal of the authors is to restore fine motor control and sensation for high-arm amputees. They developed a regenerative peripheral nerve interface with the aim of attaining closed loop neural control by integrating directly with the amputee's residual motor and sensory peripheral nerves. PEDOT, poly(3,4-ethylenedioxythiophene), has both electrical and ionic conduction characteristics. This hybrid character could help bridge the salutatory conduction of the nervous system to an electrode. The purpose of this study was to determine whether electrodes polymerized with PEDOT have improved ability to both record and stimulate peripheral nerve action potentials. Methods Impedance spectroscopy and cyclic voltammetry were performed on electrodes before and after polymerization to measure electrode impedance and charge capacity. Both recording needle and bipolar stimulating electrodes were polymerized with PEDOT. Plain and PEDOT electrodes were tested using rat (n = 18) in situ nerve conduction studies. The peroneal nerve was stimulated using a bipolar electrode at multiple locations along the nerve. Action potentials were measured in the extensor digitorum longus muscle. Results Bench testing showed PEDOT electrodes had a higher charge capacity and lower impedance than plain electrodes, indicating significantly improved electrode fidelity. Nerve conduction testing indicated a significant reduction in the stimulus threshold for both PEDOT recording and PEDOT stimulatory electrodes when compared with plain electrodes, indicating an increase in sensitivity. Conclusions PEDOT electrochemical polymerization improves electrode fidelity. Electrodes that have been electropolymerized with PEDOT show improved sensitivity when recording or stimulating action potentials at the tissue–electrode interface. PMID:22456363

  17. A Mixed-Methods Study Investigating the Relationship between Media Multitasking Orientation and Grade Point Average

    ERIC Educational Resources Information Center

    Lee, Jennifer

    2012-01-01

    The intent of this study was to examine the relationship between media multitasking orientation and grade point average. The study utilized a mixed-methods approach to investigate the research questions. In the quantitative section of the study, the primary method of statistical analyses was multiple regression. The independent variables for the…

  18. Dielectric elastomer actuators with elastomeric electrodes

    NASA Astrophysics Data System (ADS)

    Bozlar, Michael; Punckt, Christian; Korkut, Sibel; Zhu, Jian; Chiang Foo, Choon; Suo, Zhigang; Aksay, Ilhan A.

    2012-08-01

    For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.

  19. Improved biomedical electrode

    NASA Technical Reports Server (NTRS)

    Frost, J. D., Jr.

    1972-01-01

    Newly designed electrode is prefilled, disposable, electrolyte-saturated spong. New design permits longe periods of storage without deterioration, and readiness in matter of seconds. Electrodes supply signals for electroencephalogram, electro-oculogram, and electrocardiogram.

  20. An interaction of 1,10-phenantroline with the copper electrode in neutral and acidic aqueous solutions: a surface enhanced Raman scattering study

    NASA Astrophysics Data System (ADS)

    Zawada, K.; Bukowska, J.

    2000-11-01

    This paper presents the investigations of the Cu electrode/1,10-phenanthroline interface by using surface enhanced Raman scattering (SERS) method. Both neutral and acidic aqueous solutions of 1,10-phenanthroline have been studied. In order to characterise the adsorbed film its SERS spectrum was compared with the normal Raman spectra of 1,10-phenanthroline monohydrate and its complex with copper (I) chloride in a solid state. Both frequency values and relative intensities are considerably changed in the SERS spectra in comparison to the Raman spectrum of non-adsorbed molecules. The general pattern of the SERS spectrum is similar to that of the Raman spectrum of the Cu (I)-phenanthroline complex, thus suggesting that the Cu electrode surface is modified by some kind of surface complex. This surface complex was shown to be stable in a wide range of electrode potentials (up to -1.2 V). As evidenced by electrochemical experiments (cyclic voltammetry) the modification of the Cu surface by phenanthroline molecules significantly inhibits the hydrogen evolution at negative potentials. The inhibiting effect is more pronounced in acidic solutions. The appearance of the bands assigned to the out-of-plane vibrations in the surface Raman spectrum suggests that the plane of the adsorbed molecules is tilted from the normal to the metal surface.

  1. Study on the sonic point in unsteady shock reflections via numerical flowfield analysis

    NASA Astrophysics Data System (ADS)

    Hakkaki-Fard, Ali

    A current literature review revealed that unsteady shock reflection is an active research field in terms of the number of still unanswered questions in this area. One of the unresolved aspects of unsteady shock reflection is the relationship between the catch-up and sonic points. In a recent experiment, Skews and Kleine found that the catch-up point is reached at a higher wall angle than the theoretical sonic point predicted by the steady-state two-shock theory. This thesis attempts to shed some light on these matters via numerical flowfield analysis of unsteady shock reflections. Two-dimensional computations are performed using a locally adaptive unstructured unsteady Euler/Navier-Stokes code. At the first stage, a general guideline for numerical modeling of shock wave front structure using the Navier-Stokes equations on adaptive unstructured grid is presented. Obtained results can be directly used for selection of grid resolution required to study shock reflection problems in a viscous flowfields. Then, various techniques for determination of the location of the sonic/catch-up points in unsteady shock reflection based on numerical flowfield analysis are introduced. The results obtained with these techniques regarding the sonic/catch-up points locations are not in agreement with the experimental results of Skews and Kleine. The causes of this disagreement between the experiments and the present CFD study are studied by imitating the experimental technique used for catch-up point determination. It is shown that the reason for this disagreement is that the shock thickness captured in experimental images exceeds the shock physical thickness by a few orders of magnitude, which leads to detection of the catch-up point at higher wall angles. Three flow models are studied to investigate the location of the sonic/catch-up points on a circular cylinder. The first model is based on the Euler (inviscid, non-heat-conducting) equations and an ideal reflecting surface (impermeable wall boundary condition). The computational experiment for this case shows that the sonic and catch-up points are actually the same points, which approach to the theoretical sonic point with grid refinement. The other two models are intend to study the effect of viscosity on the sonic/catch-up points. At first, the ideal reflecting surface (slip boundary condition) is considered. It is shown that for this case the sonic and catch-up points are again the same points, but the viscous effects (finite shock thickness) cause the sonic/catch-up point to be delayed (to occur at lower wall angles) as compared to the two-shock theory predictions. The final model employs the non-slip reflecting surface. Since in this model the flow velocity at the wall is zero, the sonic point cannot be obtained on the reflection surface; however, the catch-up point can be defined and analyzed. The results of the simulations show that even larger delay for the catch-up point is obtained for the viscous case with the non-slip reflecting surface (in the presence of the boundary layer) as compared to the viscous case with the ideal reflecting surfaces.

  2. Low resistance fuel electrodes

    DOEpatents

    Maskalick, Nichols J. (Pittsburgh, PA); Folser, George R. (Lower Burrell, PA)

    1989-01-01

    An electrode 6 bonded to a solid, ion conducting electrolyte 5 is made, where the electrode 6 comprises a ceramic metal oxide 18, metal particles 17, and heat stable metal fibers 19, where the metal fibers provide a matrix structure for the electrode. The electrolyte 5 can be bonded to an air electrode cathode 4, to provide an electrochemical cell 2, preferably of tubular design.

  3. Preliminary Study on Applications of an Atmospheric-Pressure Argon Plasma Discharge With a Single-Electrode Configuration

    Microsoft Academic Search

    Wen-Tong Huang; Shou-Zhe Li

    2010-01-01

    An atmospheric-pressure (AP) argon plasma discharge generated in a single-electrode configuration with the power supply operating at a frequency of 45 kHz is employed to perform some applications, such as the treatment of the interior surface of a medical infusion tube, hydrophilic modification of insulator surface, hardening of metal surface, and acidification treatment of water. It is shown that the

  4. A comparative study of the electrochemical behavior of complementary polymer electrochromic devices based on different counter-electrodes

    NASA Astrophysics Data System (ADS)

    Du, Qing; Mi, Sai; Zheng, Jianming; Xu, Chunye

    2013-12-01

    8,11-di-(4-thiophen-2-yl)acenaphtho[1,2-b]quinoxaline (DTAQ) was successfully synthesized via a Stille coupling reaction and the corresponding polymer (PDTAQ) was prepared electrochemically. The spectroelectrochemical and electrochromic properties of the polymer film reveal that PDTAQ film shows distinct color states (purple in the neutral state and blue in the oxidized state), and optical contrast (?T%) of 45.16% at 772 nm and 49.39% at 1100 nm with switching times of 2.5 and 0.5 s. Complementary electrochromic devices, which are based on the PDTAQ film as the working electrode, Prussian blue (PB) and V2O5 as counter-electrodes, respectively, and LiClO4/PC solution as the electrolyte, were assembled and characterized. The results illustrate that the properties of the PDTAQ/PB and PDTAQ/V2O5 devices (including the absorption, color changes, ?T% and response times) can be modified by the counter-electrodes. Furthermore, the PDTAQ/V2O5 device exhibits a significantly higher contrast ratio in the visible region (34.92% at 771 nm) and much faster response time (0.4 s) than the PDTAQ/PB device (21.32% at 552 nm).

  5. Design and validation of a multi-electrode bioimpedance system for enhancing spatial resolution of cellular impedance studies.

    PubMed

    Alexander, Frank A; Celestin, Michael; Price, Dorielle T; Nanjundan, Meera; Bhansali, Shekhar

    2013-07-01

    This paper reports the design and evaluation of a multi-electrode design that improves upon the statistical significance and spatial resolution of cellular impedance data measured using commercial electric cell-substrate impedance sensing (ECIS) systems. By evaluating cellular impedance using eight independent sensing electrodes, position-dependent impedance measurements can be recorded across the device and compare commonly used equivalent circuit and mathematical models for extraction of cell parameters. Data from the 8-electrode device was compared to data taken from commercial electric cell-substrate impedance sensing (ECIS) system by deriving a relationship between equivalent circuit and mathematically modelled parameters. The impedance systems were evaluated and compared by investigating the effects of arsenic trioxide (As2O3), a well-established chemotherapeutic agent, on ovarian cancer cells. Impedance spectroscopy, a non-destructive, label-free technique, was used to continuously measure the frequency-dependent cellular properties, without adversely affecting the cells. The importance of multiple measurements within a cell culture was demonstrated; and the data illustrated that the non-uniform response of cells within a culture required redundant measurements in order to obtain statistically significant data, especially for drug discovery applications. Also, a correlation between equivalent circuit modelling and mathematically modelled parameters was derived, allowing data to be compared across different modelling techniques. PMID:23689543

  6. A Study of Impulsive Multiterm Fractional Differential Equations with Single and Multiple Base Points and Applications

    PubMed Central

    Liu, Yuji; Ahmad, Bashir

    2014-01-01

    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

  7. Protein coated electrodes

    Microsoft Academic Search

    E. E. Uzgiris; J. H. Kaplan

    1974-01-01

    We describe a simple method for coating platinized Pt electrodes with bovine serum albumin. The coating does not alter the electrical properties of the electrodes in dilute salt solutions, seems to be durable enough for extended use, and, most importantly, prevents a specific type of surface reaction from occurring between the Pt surface and a sucrose buffer. These electrodes are

  8. Longitudinal discharge laser electrodes

    DOEpatents

    Warner, B.E.; Miller, J.L.; Ault, E.R.

    1994-08-23

    The improved longitudinal discharge laser electrode with IR baffle includes an electrode made up of washers spaced along the laser axis in order to form inter-washer spaces for hollow cathode discharge to take place and for IR radiation to be trapped. Additional IR baffles can be placed between the electrode ann the window. 2 figs.

  9. Near-Electrode Imager

    SciTech Connect

    Rathke, Jerome W.; Klingler, Robert J.; Woelk, Klaus; Gerald, Rex E.,II

    1999-05-01

    An apparatus, near-electrode imager, for employing nuclear magnetic resonance imaging to provide in situ measurements of electrochemical properties of a sample as a function of distance from a working electrode. The near-electrode imager use the radio frequency field gradient within a cylindrical toroid cavity resonator to provide high-resolution nuclear magnetic resonance spectral information on electrolyte materials.

  10. Insulated ECG electrodes

    NASA Technical Reports Server (NTRS)

    Portnoy, W. M.; David, R. M.

    1973-01-01

    Insulated, capacitively coupled electrode does not require electrolyte paste for attachment. Other features of electrode include wide range of nontoxic material that may be employed for dielectric because of sputtering technique used. Also, electrode size is reduced because there is no need for external compensating networks with FET operational amplifier.

  11. Near-electrode imager

    DOEpatents

    Rathke, Jerome W. (Lockport, IL); Klingler, Robert J. (Westmont, IL); Woelk, Klaus (Wachtberg, DE); Gerald, II, Rex E. (Brookfield, IL)

    2000-01-01

    An apparatus, near-electrode imager, for employing nuclear magnetic resonance imaging to provide in situ measurements of electrochemical properties of a sample as a function of distance from a working electrode. The near-electrode imager uses the radio frequency field gradient within a cylindrical toroid cavity resonator to provide high-resolution nuclear magnetic resonance spectral information on electrolyte materials.

  12. Advances in lightweight nickel electrode technology

    NASA Technical Reports Server (NTRS)

    Coates, Dwaine; Paul, Gary; Daugherty, Paul

    1989-01-01

    Studies are currently underway to further the development of lightweight nickel electrode technology. Work is focused primarily on the space nickel-hydrogen system and nickel-iron system but is also applicable to the nickel-cadmium and nickel-zinc systems. The goal is to reduce electrode weight while maintaining or improving performance, thereby increasing electrode energy density. Two basic electrode structures are being investigated. The first is the traditional nickel sponge produced from sintered nickel-carbonyl powder. The second is a new material for this application which consists of a non-woven mat of nickel fiber. Electrodes are being manufactured, tested, and evaluated at the electrode and cell level.

  13. Studies on interaction of porphyrin and its complexes with DNA at interface on gold electrode modified by thiol-porphyrin self-assembled monolayer

    Microsoft Academic Search

    Yan Zhang; Xiaoquan Lu; Tianlu Liao; Yina Cheng; Xiuhui Liu; Limin Zhang

    2007-01-01

    The interaction of 5-[p-(mercaptopropyloxy)-phenyl]-10, 15, 20-triphenylporphyrin (H2MPTPP) and its metalloporphyrin (Co, Ni-MPTPP) with calf thymus deoxyribonucleic acid (DNA) has been studied on gold electrode\\u000a modified by thiol-porphyrin self-assembled monolayer (SAM). The mode and characteristics of their interaction with DNA have\\u000a been studied by cyclic voltammetry, scanning electrochemical microscope (SECM), and alternating current (AC) impedance. Some\\u000a electrochemical parameters have been determined,

  14. Potentiometric titration of thallium(I) with sodium tetraphenylborate, using ion-selective electrodes.

    PubMed

    Selig, W

    1980-11-01

    Thallium(I) has been determined by potentiometric titration with sodium tetraphenylborate. The titrations were monitored with a double-junction reference electrode and various liquid-membrane and solid-state ion-selective electrodes. The largest end-point breaks were obtained with the liquid-membrane fluoroborate and nitrate electrodes. The cyanide electrode yielded the largest break of the solid-state electrodes tested. Although the magnitude of the end-point break for the cyanide electrode is considerably less than for the above-mentioned liquid-membrane electrodes, routine use of this electrode is preferred because no conditioning is required for the solid-state electrodes. Precision was satisfactory for all electrodes investigated. Thallium(I) can be titrated with tetraphenylborate at any pH from 1.3 to at least 10.2. Other cations that can be precipitated with tetraphenylborate interfere. PMID:18962822

  15. Skimming Electronic Newspaper Headlines: A Study of Typeface, Point Size, Screen Resolution, and Monitor Size.

    ERIC Educational Resources Information Center

    Kingery, David; Furuta, Richard

    1997-01-01

    Describes a study that suggests the perception of words while skimming a newspaper headline on a computer screen is affected by typeface, point size, screen resolution, and monitor size. Limitations of the study are discussed and further research is suggested. (LRW)

  16. Capacitive transducers with curved electrodes

    Microsoft Academic Search

    Robert B. McIntosh; Philip E. Mauger; Steven R. Patterson

    2006-01-01

    The design, performance, and potential applications are described for capacitive transducers with curved electrodes. A curved electrode governs the deflection of a compliant electrode under applied stress. A dielectric film on one electrode provides a variable region of fixed electrode spacing. The sensitivity and linear dynamic range of the transducers are higher and wider than devices with parallel electrodes. An

  17. Preliminary study on the self-patterning and self-registration of metal electrodes by exploiting the chemical and optical traits of an organic silver compound in conjunction with polyaniline

    NASA Astrophysics Data System (ADS)

    Shin, Dong-Youn; Grassia, Paul

    2010-02-01

    The advent of printed electronics has shown the incessant requirement for the reduction of printed features less than tens of micrometers, where conventional printing technologies have not easily reached. To augment the resolution and registration capabilities of conventional printing technologies, surface energy patterning techniques have been explored. However, they require additional pre-patterning processes to differentiate regions with low or high surface energy and do not completely prevent electrical defects, which frequently occur when conducting ink coalesces across two adjacent electrodes. In addition, they do not provide an appropriate solution to precisely place the channel electrode between them. In this study, novel fabrication techniques for the self-patterning of two adjacent electrodes without the aid of surface energy patterning and the self-registration of the channel electrode between them have been demonstrated by exploiting the chemical and optical traits of an organic silver compound in conjunction with polyaniline. It is found that the combination of self-patterning and self-registration techniques could form two adjacent electrodes as narrow as 13.3 ± 1.5 µm and precisely place the channel electrode between them. The sheet resistance of resulting electrodes is found to be as low as 2.57 ± 0.06 ?/squ.

  18. Reduction of electrode polarization capacitance in low-frequency impedance spectroscopy by using mesh electrodes.

    PubMed

    Padmaraj, Divya; Miller, John H; Wosik, Jarek; Zagozdzon-Wosik, Wanda

    2011-11-15

    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 probes, thereby reducing the area of the double layer. The design decreases the electrode-electrolyte contact area by almost 40% while keeping the bulk sample capacitance the same. Interrogation electric fields away from the electrode surface and sensitivity are unaffected. Electrodes were microfabricated (600?m×50?m, spacing of 100?m) with and without mesh holes 7.5?m×7.5?m in size. Simulations of electric field performed using Comsol Multiphysics showed non-uniformity of the electric field within less than 1.5?m from the electrode surface, which encompasses the double layer region, but at greater distance the solid and mesh electrodes gave the same results. Mesh electrodes reduced capacitance measurements for water and KCl solutions of different concentrations at low frequencies (<10kHz), while higher frequency capacitance remained the same for both electrode types, confirming our hypothesis that this design leaves the electric field mainly unaffected. Impedance measurements at low frequencies for water and mice heart mitochondrial suspension were lower for mesh than for solid electrodes. Comsol simulations confirmed these results by showing that mesh electrodes have a greater charge density than solid electrodes, which affects conductance. These electrodes are being used for mitochondrial membrane potential studies. PMID:21872464

  19. Cervical Detachment Using Monopolar SupraLoop™ Electrode versus Monopolar Needle in Laparoscopic Supracervical Hysterectomy (LSH): An Interventional, Comparative Cohort Study.

    PubMed

    Brucker, S; Rothmund, R; Krämer, B; Neis, F; Schönfisch, B; Zubke, W; Taran, F A; Wallwiener, M

    2013-11-01

    Objective: Currently available monopolar loop electrodes are difficult to handle in laparoscopic supracervical hysterectomy (LSH) and are entirely disposable devices, generating additional operating costs. The aim of this interventional study was the comparison of the efficiency and safety of cervical detachment with a newly developed monopolar loop electrode (SupraLoop™) with a conventional method of cervical detachment in LSH. Material and Methods: Our study sample included 1598 patients; 1070 patients that underwent LSH with cervical detachment using the monopolar SupraLoop™ (study group) and 528 patients that underwent LSH with cervical detachment using the monopolar needle (control group). We also assessed cervical detachment time and total device application and cutting time in a subgroup of 49 patients (23 patients from the study group and 26 patients from the control group). Results: Total operation time for LSH was significantly shorter among SupraLoop™ patients (93?±?41 minutes) when compared to patients in whom cervical detachment was performed with the needle (105?±?44 minutes) (p?electrode (SupraLoop™) is both an effective and safe instrument for cervical detachment in laparoscopic supracervical hysterectomy, and performed better than the needle, offering a significantly shorter operating time and less complications for the hysterectomy compared to the conventional method. PMID:24771898

  20. A study on the influence of operating circuit on the position of emission point of fluorescent lamp

    NASA Astrophysics Data System (ADS)

    Uetsuki, Tadao; Genba, Yuki; Kanda, Takashi

    2009-10-01

    High efficiency fluorescent lamp systems driven by high frequency are very popular for general lighting. Therefore it is very beneficial to be able to predict the lamp's life before the lamp dying, because people can buy a new lamp just before the lamp dying and need not have stocks. In order to judge the lifetime of a lamp it is very useful to know where the emission point is on the electrode filament. With regard to a method for grasping the emission point, it has been reported that the distance from the emission point to the end of the filament can be calculated by measuring the voltage across the filament and the currents flowing in both ends of the filament. The lamp's life can be predicted by grasping the movement of the emission point with operating time. Therefore it is very important to confirm whether the movement of the emission point changes or not when the operating circuit is changed. The authors investigated the difference in the way the emission points moved for two lamp systems which are very popular. One system had an electronic ballast having an auxiliary power source for the heating cathode. Another system had an electronic ballast with no power source, but with a capacitor connected to the lamp in parallel. In this presentation these measurement results will be reported.

  1. Task 1: Modeling Study of CO Effects on Polymer Electrolyte Fuel Cell Anodes Task 2: Study of Ac Impedance as Membrane/Electrode Manufacturing Diagnostic Tool

    SciTech Connect

    Thomas E. Springer

    1998-01-30

    Carbon monoxide poisoning of polymer electrolyte fuel cell anodes is a key problem to be overcome when operating a polymer electrolyte fuel cell (PEFC) on reformed fuels. CO adsorbs preferentially on the precious metal surface leading to substantial performance losses. Some recent work has explored this problem, primarily using various Pt alloys in attempts to lower the degree of surface deactivation. In their studies of hydrogen oxidation on Pt and Pt alloy (Pt/Sn, Pt/Ru) rotating disk electrodes exposed to H{sub 2}/CO mixtures, Gasteiger et al. showed that a small hydrogen oxidation current is observed well before the onset of major CO oxidative stripping (ca. 0.4 V) on Pt/Ru. However, these workers concluded that such current observed at low anode overpotentials was too low to be of practical value. Nonetheless, MST-11 researchers and others have found experimentally that it is possible to run a PEFC, e.g., with a Pt/Ru anode, in the presence of CO levels in the range 10--100 ppm with little voltage loss. Such experimental results suggest that, in fact, PEFC operation at significant current densities under low anode overpotentials is possible in the presence of such levels of CO, even before resorting to air bleeding into the anode feed stream. The latter approach has been shown to be effective in elimination of Pt anode catalyst poisoning effects at CO levels of 20--50 ppm for cells operating at 80 C with low Pt catalyst loading. The effect of oxygen bleeding is basically to lower P{sub CO} down to extremely low levels in the anode plenum thanks to the catalytic (chemical) oxidation of CO by dioxygen at the anode catalyst. In this modeling work the authors do not include specific description of oxygen bleeding effects and concentrate on the behavior of the anode with feed streams of H{sub 2} or reformate containing low levels of CO. The anode loss is treated in this work as a hydrogen and carbon monoxide electrode kinetics problem, but includes the effects of dilution of the feedstream with significant fractions of carbon dioxide and nitrogen and of mass transport losses in the gas diffusion backing. Not included in the anode model are ionic resistance and diffusion losses in the catalyst layer. They are looking to see if the overall pattern of polarization curves calculated based on such a purely kinetic model indeed mimics the central features of polarization curves observed for PEFCs operating on hydrogen with low levels of CO.

  2. A theoretical study on native point defects and dopants in cuprous oxide

    NASA Astrophysics Data System (ADS)

    Wang, Weichao; Wu, Dangxin; Zhang, Qiming; Tao, Meng

    2007-03-01

    We have performed a first-principle study on the electronic structures, atomic configurations, and formation energies of native point defects in cuprous oxide, i.e. vacancies(VCu,VO), interstitials (Cui,Oi) and antisite defects (CuO,OCu) by using Density Function Theory based VASP package with PAW potentials. We have carefully studied the formation of native point defects under different chemical environments and Fermi level positions. We have also calculated the electronic structures of dopants such as F, Cl, N, Ca and Mg in the cuprous oxide crystal. Their formation at different chemical environments and Fermi level positions will be presented as well.

  3. Voltammetric studies on the HIV1 inhibitory drug Efavirenz: The interaction between dsDNA and drug using electrochemical DNA biosensor and adsorptive stripping voltammetric determination on disposable pencil graphite electrode

    Microsoft Academic Search

    Burcu Dogan-Topal; Bengi Uslu; Sibel A. Ozkan

    2009-01-01

    The interaction of Efavirenz (EFV) with fish sperm dsDNA immobilized onto pencil graphite electrode (PGE) has been studied by using differential pulse voltammetric technique using an electrochemical DNA biosensor. The guanine signal was lower with (double stranded-DNA) dsDNA-treated PGE than the untreated electrode after the interaction with EFV occurred. The changes in the experimental parameters such as the accumulation time

  4. Electrochemistry at Nanometer-Scaled Electrodes

    ERIC Educational Resources Information Center

    Watkins, John J.; Bo Zhang; White, Henry S.

    2005-01-01

    Electrochemical studies using nanometer-scaled electrodes are leading to better insights into electrochemical kinetics, interfacial structure, and chemical analysis. Various methods of preparing electrodes of nanometer dimensions are discussed and a few examples of their behavior and applications in relatively simple electrochemical experiments…

  5. Study of transition metal oxide doped LaGaO 3 as electrode materials for LSGM-based solid oxide fuel cells

    Microsoft Academic Search

    Fanglin Chen; Meilin Liu

    1998-01-01

    Transition metal oxide doped lanthanum gallates, La0.9Sr0.1Ga0.8M0.2O3 (where M=Co, Mn, Cr, Fe, or V), are studied as mixed ionic-electronic conductors (MIECs) for electrode applications. The\\u000a electrochemical properties of these materials in air and in H2 are characterized using impedance spectroscopy, open cell voltage measurement, and gas permeation measurement. Three single\\u000a cells based on La0.9Sr0.1Ga0.8 Mg0.2O3 (LSGM) electrolyte (1.13 to 1.65?mm

  6. Lifetime studies of high power rhodium\\/tungsten and molybdenum electrodes for application to AMTEC (alkali metal thermal-to-electric converter)

    Microsoft Academic Search

    R. M. Williams; B. Jeffries-Nakamura; M. L. Underwood; D. O'Connor; M. A. Ryan; S. Kikkert; C. P. Bankston

    1990-01-01

    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

  7. A quantitative study on accumulation of age mass around stagnation points in nested flow systems

    NASA Astrophysics Data System (ADS)

    Jiang, Xiao-Wei; Wan, Li; Ge, Shemin; Cao, Guo-Liang; Hou, Guang-Cai; Hu, Fu-Sheng; Wang, Xu-Sheng; Li, Hailong; Liang, Si-Hai

    2012-12-01

    The stagnant zones in nested flow systems have been assumed to be critical to accumulation of transported matter, such as metallic ions and hydrocarbons in drainage basins. However, little quantitative research has been devoted to prove this assumption. In this paper, the transport of age mass is used as an example to demonstrate that transported matter could accumulate around stagnation points. The spatial distribution of model age is analyzed in a series of drainage basins of different depths. We found that groundwater age has a local or regional maximum value around each stagnation point, which proves the accumulation of age mass. In basins where local, intermediate and regional flow systems are all well developed, the regional maximum groundwater age occurs at the regional stagnation point below the basin valley. This can be attributed to the long travel distances of regional flow systems as well as stagnancy of the water. However, when local flow systems dominate, the maximum groundwater age in the basin can be located around the local stagnation points due to stagnancy, which are far away from the basin valley. A case study is presented to illustrate groundwater flow and age in the Ordos Plateau, northwestern China. The accumulation of age mass around stagnation points is confirmed by tracer age determined by 14C dating in two boreholes and simulated age near local stagnation points under different dispersivities. The results will help shed light on the relationship between groundwater flow and distributions of groundwater age, hydrochemistry, mineral resources, and hydrocarbons in drainage basins.

  8. Socioeconomic impacts of nuclear generating stations: Nine Mile Point and Fitzpatrick case study

    Microsoft Academic Search

    K. Branch; R. Cochran; R. Meale

    1982-01-01

    This report documents a case study of the socio-economic impacts of the construction and operation of the Nine Mile Point and Fitzpatrick nuclear power stations. It is part of a major post-licensing study of the socio-economic impacts at twelve nuclear power stations. The case study covers the period beginning with the announcement of plans to construct the reactor and ending

  9. Lithium-ion drifting: Application to the study of point defects in floating-zone silicon

    SciTech Connect

    Walton, J.T.; Wong, Y.K. [Lawrence Berkeley National Lab., CA (United States); Zulehner, W. [Wacker-Siltronic GmbH, Burghausen (Germany)] [and others

    1997-04-01

    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 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{sup +} drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li{sup +} compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

  10. Electrochemical pretreatment of polycrystalline gold electrodes to produce a reproducible surface roughness for self-assembly: a study in phosphate buffer pH 7.4

    PubMed

    Hoogvliet; Dijksma; Kamp; van Bennekom WP

    2000-05-01

    It has been emphasized in several studies that the state of the surface, including the surface roughness, is very important for the reproducible formation of high-quality self-assembled monolayers on gold. The pulsed-potential pretreatment procedure described in this paper can, in a reproducible way, reduce the surface roughness of mechanically polished polycrystalline gold electrodes by a factor 2. The developed procedure, in which the gold is alternately oxidized and reduced, has been optimized for use in a flow system (100 mM phosphate buffer pH 7.4). The influence of the pretreatment procedure on the surface roughness of the electrodes has been studied by in-situ oxygen adsorption measurements using cyclic voltammetry. The most effective pulse regime in producing a gold surface with a reproducible and relatively low surface roughness is a triple-potential pulse waveform, with potentials of +1.6, 0.0, and -0.8 Vvs SCE and pulse widths of 100 ms for each potential. Prolonged pulsing for 2000-5000 s with the gold working electrode in a flow-through cell showed an electropolishing effect, i.e., a decrease of the roughness in time. Flow conditions are very important: the roughness decreased faster at higher flow rates, while an increase was observed without flow. A process of reconstruction and dissolution of gold during application of the potential pulses under flow conditions is assumed to account for the observed phenomena. A self-assembled monolayer of thioctic acid with reproducible characteristics, determined with impedance measurements, could be formed on a pretreated gold surface. PMID:10815959

  11. Saur Viddyut Kosh. IV - Study of a rechargeable solar battery with n-Pb3O4 electrodes

    NASA Astrophysics Data System (ADS)

    Sharon, M.; Kumar, S.; Sathe, N. P.; Jawalekar, S. R.

    1984-09-01

    The design, fabrication, and performance of a rechargeable solar battery with storage capability (a Saur Viddyut Kosh, SVK) are reported. Electrodes of n-Pb3O4 are produced by thermal decomposition of lead citrate in O2 for 2 h at 350 C and sintering of 2-mm-thick 1-cm-diameter pellets in H2 for 2 h at 300 C and characterized photolectrochemically using various redox couples. Using the couple 0.1 M Fe(3+)/saturated Fe(2+), photocurrent density 175.2 microA/sq cm, bandgap 2.0 eV at wavelength 575 nm, flat-band potential -310 mV, fill factor 38 percent, and power efficiency 0.09 percent are determined. An SVK using the same redox pair in one compartment and 0.1 M IO3(-)/0.1 M I(-) in the other is constructed and found to have charged dark potential (after 1 h) 840 mV, current density 408.0 microA/sq cm, output voltage 93 mV, and SHE flat-band potential -170 mV (in contrast with the -290 mV calculated by Butler and Ginley, 1978). The electrode is found to become photoelectrochemically unstable after about 12 h if the Fe(3+)/Fe(2+) concentrations are maintained.

  12. Ni-composite microencapsulated graphite as the negative electrode in lithium-ion batteries. I. Initial irreversible capacity study

    SciTech Connect

    Yu, P.; Ritter, J.A.; White, R.E.; Popov, B.N.

    2000-04-01

    A novel approach for suppressing the solvated lithium intercalation in graphite was developed by microencapsulating graphite with nanosized Ni-composite particles. The Ni-composite graphite showed great improvement in charge-discharge performance, coulomb efficiency, and cycling behavior when used as the negative electrode in a Li-ion cell with propylene carbonate (PC)-based electrolyte. For example, a 10 wt % Ni-composite coating increased the initial charge-discharge coulomb efficiency of SFG75 graphite (75 {micro}m, Timcal America) from 59 to 84% and the reversible capacity by 30--40 mAh/g. The Ni-composite coating consisted of nanosized particles distributed over the surface of the graphite particle, which effectively blocked some of the edge surfaces exposed to the electrolyte. this minimized solvated lithium intercalation at these edge sites, which subsequently minimized the PC reduction within the graphite and the exfoliation of the graphene layers, and also gas evolution. Corresponding improvements in both the charge-discharge performance and safety of the negative electrode in a rechargeable Li-ion cell resulted.

  13. Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode

    PubMed Central

    Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

    2013-01-01

    Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200?nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. PMID:24170960

  14. Impact of Field of Study, College and Year on Calculation of Cumulative Grade Point Average

    ERIC Educational Resources Information Center

    Trail, Carla; Reiter, Harold I.; Bridge, Michelle; Stefanowska, Patricia; Schmuck, Marylou; Norman, Geoff

    2008-01-01

    A consistent finding from many reviews is that undergraduate Grade Point Average (uGPA) is a key predictor of academic success in medical school. Curiously, while uGPA has established predictive validity, little is known about its reliability. For a variety of reasons, medical schools use different weighting schemas to combine years of study

  15. Contingency Management to Increase Grade Point Average among Fraternity Members: A Feasibility Study

    ERIC Educational Resources Information Center

    Van Patten, Ryan A.; Irons, Jessica G.; Apple, Kevin J.

    2015-01-01

    Contingency management is an incentive-based intervention strategy that has been demonstrated to be effective for inducing behavior change among a variety of populations and for a variety of behaviors. The current study examined whether contingency management techniques can help students change behaviors in an effort to raise their grade point…

  16. Study of the Onset of Deconfinement and Search for the Critical Point of Strongly Interacting Matter

    E-print Network

    Peter Seyboth

    2013-01-24

    Collisions of lead nuclei have been studied at the CERN SPS since 1994. A review is presented of the evidence for the production of deconfined matter, the location of the energy of the onset of deconfinement and the search for the critical point of stronly interacting matter

  17. Innovations fields from corporate studies to socio-ecological indicators : a point of review

    E-print Network

    Boyer, Edmond

    ). As a mirrored response to corporate innovation field classification, sustainability pillars combinations canInnovations fields from corporate studies to socio-ecological indicators : a point of review concept, through exploring the both corporate and territorial significations of this notion. Next, we list

  18. A Theoretical Study of the Two-Dimensional Point Focusing by Two Multilayer Laue Lenses.

    SciTech Connect

    Yan,H.; Maser, J.; Kang, H.C.; Macrader, A.; Stephenson, B.

    2008-08-10

    Hard x-ray point focusing by two crossed multilayer Laue lenses is studied using a full-wave modeling approach. This study shows that for a small numerical aperture, the two consecutive diffraction processes can be decoupled into two independent ones in respective directions. Using this theoretical tool, we investigated adverse effects of various misalignments on the 2D focus profile and discussed the tolerance to them. We also derived simple expressions that described the required alignment accuracy.

  19. Pocket ECG electrode

    NASA Technical Reports Server (NTRS)

    Lund, G. F. (inventor)

    1980-01-01

    A low noise electrode suited for sensing electrocardiograms when chronically and subcutaneously implanted in a free ranging subject is described. The electrode comprises a pocket shaped electrically conductive member with a single entrance adapted to receive body fluids. The exterior of the member and the entrance region is coated with electrical insulation so that the only electrolyte/electrode interface is within the member, remote from artifact-generating tissue. Cloth straps are bonded to the member to permit the electrode to be sutured to tissue and to provide electrical lead flexure relief.

  20. Pocket ECG electrode

    NASA Technical Reports Server (NTRS)

    Lund, Gordon F. (Inventor)

    1982-01-01

    A low-noise electrode suited for sensing electrocardiograms when chronically and subcutaneously implanted in a free-ranging subject. The electrode comprises a pocket-shaped electrically conductive member with a single entrance adapted to receive body fluids. The exterior of the member and the entrance region is coated with electrical insulation so that the only electrolyte/electrode interface is within the member remote from artifact-generating tissue. Cloth straps are bonded to the member to permit the electrode to be sutured to tissue and to provide electrical lead flexure relief.

  1. Design of a Wireless EEG System for Point-of-Care Applications

    PubMed Central

    Jia, Wenyan; Bai, Yicheng; Sun, Mingui; Sclabassi, Robert J.

    2014-01-01

    This study aims to develop a wireless EEG system to provide critical point-of-care information about brain electrical activity. A novel dry electrode, which can be installed rapidly, is used to acquire EEG from the scalp. A wireless data link between the electrode and a data port (i.e., a smartphone) is established based on the Bluetooth technology. A prototype of this system has been implemented and its performance in acquiring EEG has been evaluated. PMID:25419099

  2. Degradation of Li/S Battery Electrodes On 3D Current Collectors Studied Using X-ray Phase Contrast Tomography.

    PubMed

    Zielke, L; Barchasz, C; Walu?, S; Alloin, F; Leprêtre, J-C; Spettl, A; Schmidt, V; Hilger, A; Manke, I; Banhart, J; Zengerle, R; Thiele, S

    2015-01-01

    Lithium/sulphur batteries are promising candidates for future energy storage systems, mainly due to their high potential capacity. However low sulphur utilization and capacity fading hinder practical realizations. In order to improve understanding of the system, we investigate Li/S electrode morphology changes for different ageing steps, using X-ray phase contrast tomography. Thereby we find a strong decrease of sulphur loading after the first cycle, and a constant loading of about 15% of the initial loading afterwards. While cycling, the mean sulphur particle diameters decrease in a qualitatively similar fashion as the discharge capacity fades. The particles spread, migrate into the current collector and accumulate in the upper part again. Simultaneously sulphur particles lose contact area with the conducting network but regain it after ten cycles because their decreasing size results in higher surface areas. Since the capacity still decreases, this regain could be associated with effects such as surface area passivation and increasing charge transfer resistance. PMID:26043280

  3. Degradation of Li/S Battery Electrodes On 3D Current Collectors Studied Using X-ray Phase Contrast Tomography

    PubMed Central

    Zielke, L.; Barchasz, C.; Walu?, S.; Alloin, F.; Leprêtre, J.-C.; Spettl, A.; Schmidt, V.; Hilger, A.; Manke, I.; Banhart, J.; Zengerle, R.; Thiele, S.

    2015-01-01

    Lithium/sulphur batteries are promising candidates for future energy storage systems, mainly due to their high potential capacity. However low sulphur utilization and capacity fading hinder practical realizations. In order to improve understanding of the system, we investigate Li/S electrode morphology changes for different ageing steps, using X-ray phase contrast tomography. Thereby we find a strong decrease of sulphur loading after the first cycle, and a constant loading of about 15% of the initial loading afterwards. While cycling, the mean sulphur particle diameters decrease in a qualitatively similar fashion as the discharge capacity fades. The particles spread, migrate into the current collector and accumulate in the upper part again. Simultaneously sulphur particles lose contact area with the conducting network but regain it after ten cycles because their decreasing size results in higher surface areas. Since the capacity still decreases, this regain could be associated with effects such as surface area passivation and increasing charge transfer resistance. PMID:26043280

  4. Monitoring microbial sulfate reduction in porous media using multipurpose electrodes

    Microsoft Academic Search

    Chi Zhang; Dimitrios Ntarlagiannis; Lee Slater; Rory Doherty

    2010-01-01

    There is growing interest in the application of electrode-based measurements for monitoring microbial processes in the Earth using biogeophysical methods. In this study, reactive electrode measurements were combined to electrical geophysical measurements during microbial sulfate reduction occurring in a column of silica beads saturated with natural river water. Electrodic potential (EP), self potential (SP) and complex conductivity signals were recorded

  5. Behavior of secondary lithium ad aluminium-lithium electrodes in propylene carbonate

    SciTech Connect

    Epelboin, I.; Froment, M.; Garreau, M.; Thevenin, J.; Warin, D.

    1980-01-01

    The improvement of the lithium cyclic efficiency obtained by substituting an aluminum substrate for a lithium substrate is explained by means of morphological and kinetic studies of the electrodes in the molar solution LiClO/sub 4/- propylene carbonate. SEM observations show that the insertion rate of the lithium deposit into aluminum can be sufficiently high to avoid the dendritic growth; ESCA analysis also reveals that the chemical decomposition of propylene carbonate to form a polymeric membrane is reduced on the electrode surface. Electrochemical impedance measurements associated with polarization curves data point out that most of the surface is active giving rise to an exchange current density of about 17 ma/cm/sup 2/. These studies also demonstrate that diffusion processes in the passivating layer and in the bulk of the electrode are responsible for the limited lithium cycling performances with the aluminum substrate. 18 refs.

  6. Electrochemical Determination of Chlorpyrifos on a Nano-TiO2/Cellulose Acetate Composite Modified Glassy Carbon Electrode.

    PubMed

    Kumaravel, Ammasai; Chandrasekaran, Maruthai

    2015-07-15

    A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature. PMID:26075585

  7. Electrode Erosion of a High Energy Impulse Spark Gap Switch

    Microsoft Academic Search

    Xueling Yao; Zhengzhong Zeng; Jinliang Chen

    2005-01-01

    Based on the principle of thermal conduction, three metal alloys (stainless steel, copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indicate that the mass loss and surface erosion morphology of the electrode are related with the electrode material (conductivity sigma, melting point Tm, density rho and thermal capacity c) and the

  8. Reviving common standards in point-count surveys for broad inference across studies

    USGS Publications Warehouse

    Matsuoka, Steven M.; Mahon, C. Lisa; Handel, Colleen M.; Solymos, Peter; Bayne, Erin M.; Fontaine, Patricia C.; Ralph, C.J.

    2014-01-01

    We revisit the common standards recommended by Ralph et al. (1993, 1995a) for conducting point-count surveys to assess the relative abundance of landbirds breeding in North America. The standards originated from discussions among ornithologists in 1991 and were developed so that point-count survey data could be broadly compared and jointly analyzed by national data centers with the goals of monitoring populations and managing habitat. Twenty years later, we revisit these standards because (1) they have not been universally followed and (2) new methods allow estimation of absolute abundance from point counts, but these methods generally require data beyond the original standards to account for imperfect detection. Lack of standardization and the complications it introduces for analysis become apparent from aggregated data. For example, only 3% of 196,000 point counts conducted during the period 1992-2011 across Alaska and Canada followed the standards recommended for the count period and count radius. Ten-minute, unlimited-count-radius surveys increased the number of birds detected by >300% over 3-minute, 50-m-radius surveys. This effect size, which could be eliminated by standardized sampling, was ?10 times the published effect sizes of observers, time of day, and date of the surveys. We suggest that the recommendations by Ralph et al. (1995a) continue to form the common standards when conducting point counts. This protocol is inexpensive and easy to follow but still allows the surveys to be adjusted for detection probabilities. Investigators might optionally collect additional information so that they can analyze their data with more flexible forms of removal and time-of-detection models, distance sampling, multiple-observer methods, repeated counts, or combinations of these methods. Maintaining the common standards as a base protocol, even as these study-specific modifications are added, will maximize the value of point-count data, allowing compilation and analysis by regional and national data centers.

  9. Application of double-impedance system and cyclic voltammetry to study the adsorption of fullerols (C60(OH)n) on biological peptide-adsorbed gold electrode.

    PubMed

    Zhou, A; Zhang, J; Xie, Q; Yao, S

    2001-09-01

    The adsorption of fullerols (C60(OH)n) on glutathione-adsorbed gold electrode was characterized by using double-impedance system, i.e., electrochemical quartz crystal impedance and electrochemical impedance spectroscopy, and cyclic voltammetry. The time courses of piezoelectric parameters were used to reflect the changes of interfacial physical properties, such as mass, density-viscosity, and dielectric constant, during the adsorptions of peptide and fullerols onto electrode. The electrochemical impedance based on the simple equivalent electric network were also simultaneously measured and provided electrochemical interface information, e.g., double-layer capacitance and charge-transfer resistance. It was found that the double-impedance responses were varied with the forms of glutathione. It was also shown that the frequency curves due to the adsorption of oxidized (GSSG) and reduced (GSH) glutathione could be exhibited as different kinetic equations. The heterogeneous charge-transfer rate constants of ferricyanide/ferrocyanide before and after the peptide and fullerols adsorption were determined by CV and EIS methods. The results showed that the proposed method has potential applications in interfacial studies of biomaterials, since these combined techniques have advantages in real time providing multidimensional piezoelectric and electrochemical impedance information. PMID:11516084

  10. A Study of the Relationships among Albrecht and Mark II Function Points, Lines of Code 4GL and Effort

    Microsoft Academic Search

    José Javier Dolado

    1997-01-01

    There is a strong interest in finding metrics for replacing the common LOC measure of software size, with most of the interest focusing on the Function Point measures. Mark II Function Points were proposed as a better technique than the original of Albrecht Function Points. In this work, the results of a study comparing those measures are stated, and they

  11. Electrostatic curved electrode actuators

    Microsoft Academic Search

    Rob Legtenberg; John Gilbert; Stephen D. Senturia; Miko Elwenspoek

    1997-01-01

    This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model

  12. Long term flight electrodes

    NASA Technical Reports Server (NTRS)

    Mosier, B.

    1975-01-01

    The reproducibility, stability, and methods of preparation for the various types and forms of biomedical electrodes are discussed. A critical and selective compilation of information on biological and/or physiological electrodes is presented. A discussion of plant hydrocolloids, clays, hydrophyllic colloids, synthetic waxes, and acrylic polymers is included.

  13. Disposable biomedical electrode

    NASA Technical Reports Server (NTRS)

    Frost, J. D., Jr.; Hillman, C. E., Jr.

    1977-01-01

    Reusable recording cap equipped with compressible snap-on bioelectronic electrodes is worn by patient to allow remote monitoring of electroencephalogram and electro-oculogram waveforms. Electrodes can be attached to inside surface of stretch-textile cap at twelve monitoring positions and at one or two ground positions.

  14. Membrane Bioprobe Electrodes

    ERIC Educational Resources Information Center

    Rechnitz, Garry A.

    1975-01-01

    Describes the design of ion selective electrodes coupled with immobilized enzymes which operate either continuously or on drop-sized samples. Cites techniques for urea, L-phenylalanine and amygdalin. Micro size electrodes for use in single cells are discussed. (GH)

  15. Heated graphite cylinder electrodes

    Microsoft Academic Search

    Jian-Jun Sun; Liang Guo; De-Feng Zhang; Wen-Hui Yin; Guo-Nan Chen

    2007-01-01

    A new heated graphite cylinder electrode (HGCE) has been successfully fabricated, which arrangement is similar to that of the heated metal (Pt or Au) wire electrode invented by Grundler. The cylinders’ diameters range from ca. 95 to 300?m obtained by grinding the commercial available pencil graphite. HGCEs demonstrate rapid responses to the heating up and high thermal stability during being

  16. A novel NGFB point mutation: a phenotype study of heterozygous patients

    Microsoft Academic Search

    J Minde; T Andersson; M Fulford; M Aguirre; I Nennesmo; I Nilsson Remahl; O Svensson; M Holmberg; G Toolanen; G Solders

    2009-01-01

    Objective:A family with neurological findings similar to hereditary sensory and autonomic neuropathy type V having a point mutation in the nerve growth factor beta (NGFB) gene was recently described. The homozygous genotype gives disabling symptoms. The purpose of the present study was to evaluate the symptoms in heterozygous patients.Methods:26 patients heterozygous for the NGFB mutation (12 men, mean age 50

  17. Two-micron Laser Atmospheric Wind Sounder (LAWS) pointing\\/tracking study

    Microsoft Academic Search

    Scott Manlief

    1995-01-01

    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

  18. Impact of Field of Study, College and Year on Calculation of Cumulative Grade Point Average

    Microsoft Academic Search

    Carla Trail; Harold I. Reiter; Michelle Bridge; Patricia Stefanowska; Marylou Schmuck; Geoff Norman

    2008-01-01

    A consistent finding from many reviews is that undergraduate Grade Point Average (uGPA) is a key predictor of academic success\\u000a in medical school. Curiously, while uGPA has established predictive validity, little is known about its reliability. For a\\u000a variety of reasons, medical schools use different weighting schemas to combine years of study. Additional concerns relate\\u000a to the equivalence of grades

  19. Study of the point spread function (PSF) for 123I SPECT imaging using Monte Carlo simulation

    Microsoft Academic Search

    A. Cot; J. Sempau; D. Pareto; S. Bullich; J. Pavía; F. Calviño; D. Ros

    2004-01-01

    The iterative reconstruction algorithms employed in brain single-photon emission computed tomography (SPECT) allow some quantitative parameters of the image to be improved. These algorithms require accurate modelling of the so-called point spread function (PSF). Nowadays, most in vivo neurotransmitter SPECT studies employ pharmaceuticals radiolabelled with 123I. In addition to an intense line at 159 keV, the decay scheme of this

  20. Toxicogenomic Studies of the Rat Brain at an Early Time Point Following Acute Sarin Exposure

    Microsoft Academic Search

    Tirupapuliyur V. Damodaran; Stephen T. Greenfield; Anand G. Patel; Holly K. Dressman; Siomon K. Lin; Mohamed B. Abou-Donia

    2006-01-01

    We have studied sarin-induced global gene expression patterns at an early time point (2 h: 0.5×LD50) using Affymetrix Rat Neurobiology U34 chips and male Sprague–Dawley rats. A total of 46 genes showed statistically significant alterations from control levels. Three gene categories contained more of the altered genes than any other groups: ion channel (8 genes) and calcium channel and binding proteins

  1. Low consistency of four brain connectivity measures derived from intracranial electrode measurements.

    PubMed

    Jones, Stephen E; Beall, Erik B; Najm, Imad; Sakaie, Ken E; Phillips, Michael D; Zhang, Myron; Gonzalez-Martinez, Jorge A

    2014-01-01

    Measures of brain connectivity are currently subject to intense scientific and clinical interest. Multiple measures are available, each with advantages and disadvantages. Here, we study epilepsy patients with intracranial electrodes, and compare four different measures of connectivity. Perhaps the most direct measure derives from intracranial electrodes; however, this is invasive and spatial coverage is incomplete. These electrodes can be actively stimulated to trigger electrophysical responses to provide the first measure of connectivity. A second measure is the recent development of simultaneous BOLD fMRI and intracranial electrode stimulation. The resulting BOLD maps form a measure of effective connectivity. A third measure uses low frequency BOLD fluctuations measured by MRI, with functional connectivity defined as the temporal correlation coefficient between their BOLD waveforms. A fourth measure is structural, derived from diffusion MRI, with connectivity defined as an integrated diffusivity measure along a connecting pathway. This method addresses the difficult requirement to measure connectivity between any two points in the brain, reflecting the relatively arbitrary location of the surgical placement of intracranial electrodes. Using a group of eight epilepsy patients with intracranial electrodes, the connectivity from one method is compared to another method using all paired data points that are in common, yielding an overall correlation coefficient. This method is performed for all six paired-comparisons between the four methods. While these show statistically significant correlations, the magnitudes of the correlation are relatively modest (r (2) between 0.20 and 0.001). In summary, there are many pairs of points in the brain that correlate well using one measure yet correlate poorly using another measure. These experimental findings present a complicated picture regarding the measure or meaning of brain connectivity. PMID:25566178

  2. Electrodes for microfluidic applications

    DOEpatents

    Crocker, Robert W. (Fremont, CA); Harnett, Cindy K. (Livermore, CA); Rognlien, Judith L. (Livermore, CA)

    2006-08-22

    An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

  3. Nickel hydroxide electrodes in reduced-alkalinity electrolytes

    SciTech Connect

    Plivelich, R.F.

    1994-04-01

    Ni oxide electrodes cycled to failure in zinc-nickel oxide cells were studied; these cells incorporated novel electrolytes intended to increase the Zn electrode cycle life. The Zn species deposited in the failed Ni electrodes was probably Zn(OH){sub 2} or ZnO. Evidence was found for a strictly mechanical interpretation of the capacity degradation of the Ni oxide electrodes. The gas evolution in failure of Ni electrodes in the zinc-Ni oxide system using a reduced-alkalinity electrolyte, needs to be studied.

  4. A study on fabrication of sulfonated poly(ether ether ketone)-based membrane-electrode assemblies for polymer electrolyte membrane fuel cells

    Microsoft Academic Search

    Jin-Soo Park; Palanichamy Krishnan; Seok-Hee Park; Gu-Gon Park; Tae-Hyun Yang; Won-Yong Lee; Chang-Soo Kim

    2008-01-01

    The porosity effect of catalyst electrodes in membrane-electrode assemblies (MEAs) using a hydrocarbon-based polymer as electrolyte and ionomer was investigated on physical and electrochemical properties by varying the content of ionomer binder (dry condition) in the catalyst electrodes. The MEAs were compared with the Nafion®-based MEA using Nafion® 112 and 5wt.% ionomer solution (EW=1100) in terms of porosity values, scanning

  5. New Approach in Filling of Fixed-Point Cells: Case Study of the Melting Point of Gallium

    NASA Astrophysics Data System (ADS)

    Bojkovski, J.; Hiti, M.; Batagelj, V.; Drnovšek, J.

    2008-02-01

    The typical way of constructing fixed-point cells is very well described in the literature. The crucible is loaded with shot, or any other shape of pure metal, inside an argon-filled glove box. Then, the crucible is carefully slid into a fused-silica tube that is closed at the top with an appropriate cap. After that, the cell is removed from the argon glove box and melted inside a furnace while under vacuum or filled with an inert gas like argon. Since the metal comes as shot, or in some other shape such as rods of various sizes, and takes more volume than the melted material, it is necessary to repeat the procedure until a sufficient amount of material is introduced into the crucible. With such a procedure, there is the possibility of introducing additional impurities into the pure metal with each cycle of melting the material and putting it back into the glove box to fill the cell. Our new approach includes the use of a special, so-called dry-box system, which is well known in chemistry. The atmosphere inside the dry box contains less than 20 ppm of water and less than 3 ppm of oxygen. Also, the size of the dry box allows it to contain a furnace for melting materials, not only for gallium but for higher-temperature materials as well. With such an approach, the cell and all its parts (pure metal, graphite, fused-silica tube, and cap) are constantly inside the controlled atmosphere, even while melting the material and filling the crucible. With such a method, the possibility of contaminating the cell during the filling process is minimized.

  6. Interactions between point defects and dislocations in Al: An ab initio study

    NASA Astrophysics Data System (ADS)

    Lu, Gang; Zhang, Qing; Kioussis, Nicholas; Kaxiras, Efthimios

    2001-06-01

    Interactions of point defects (vacancies and interstitials) and dislocations play an important role in materials mechanical properties. In this paper, we employ the semidiscrete variational Peierls-Nabarro model to study the core properties of various dislocations in Al with and without point defects. In specific, the point defects we study in this paper are vacancy and interstitial H. The material parameters, including elastic constants and generalized stacking fault energy surfaces entering the model are calculated from ab initio approaches with large supercells to simulate the low concentration of vacancy and H interstitial (less than 5 at.properties, such as core energy, Peierls stress and core structure are calculated with and without the point defects and the interactions between them are thus revealed. We find although there is a strong binding between H interstitial and dislocation cores, a weak repulsion is observed for vacancy and dislocations. Moreover while the binding energy of H at dislocation cores increases from screw to edge dislocations, the repulsion between vacancy and dislocations remains almost the same for the various dislocations we studied. The critical stress to move a dislocation, Peierls stress, is calculated and we find that both vacancy and H interstitial can reduce the Peierls stress significantly, while the latter has a more dramatic effect (orders of magnitude), strongly supporting the H-enhanced local plasticity theory of H-embrittlement. For the static dislocation core structure, we find vacancy can facilitate dislocations to dissociate into two partials, with distances between them ranging from 5 to 11 Ådepending on the dislocation characters, while H interstitial can only increase the dislocation width but without any dissociation.

  7. A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS

    NASA Astrophysics Data System (ADS)

    Faria, Paula; Hallett, Mark; Cavaleiro Miranda, Pedro

    2011-12-01

    We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm2), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.

  8. Tender Point Count, Pain, and Mobility in the Older Population: The MOBILIZE Boston Study

    PubMed Central

    Eggermont, Laura H.P.; Shmerling, Robert H.; Leveille, Suzanne G.

    2011-01-01

    Prevalence of tender points (TP), widespread pain and fibromyalgia, as well as the relationship between TP, widespread pain and mobility was examined in 585 community-dwelling older adults (mean age 78.2 years, 63.4% female). Pain was based on location (none, single site, multisite, widespread). Mobility was measured by the Short Physical Performance Battery (SPPB), gait speed, and self-reported (S–R) mobility difficulty. Tender point count and health characteristics (i.e. BMI, chronic conditions, analgesic use, number of medications, depression, and blocks walked per week) were assessed. Results Several participants had 3 or more TP (22.1%) although prevalence of criteria-based fibromyalgia was low (0.3%). Mobility was more limited in persons with higher tender point counts. After adjustment for pain and other risk factors, higher tender point count was associated with poorer SPPB performance (score<10, aOR=1.09 per TP, 95%CI, 1.01–1.17), and slow gait speed (<0.784m/sec, aOR=1.14 per TP, 95%CI, 1.05–1.24), but not with S–R mobility difficulty. S–R mobility difficulty was associated with more disseminated pain (multisite pain, aOR=2.01, 95%CI, 1.21–3.34; widespread pain, aOR=2.47, 95%CI, 1.09–5.62). These findings portray a significant mobility burden related to tender point count and multisite and widespread pain in the older population. Future studies using longitudinal methods are warranted. PMID:19665937

  9. A basic study about multi channel measurement of skin impedance vector loci on the acupuncture points

    Microsoft Academic Search

    Takenori Fukumoto; Shigeo Ohba; Ryoko Futami; H. Tanaka; N. Hoshimiya; K. Sasaki

    2001-01-01

    Acupuncture points have been found to be points of low electrical resistance compared to the surrounding tissue. The significance and detail of the singular electrical properties of acupuncture points are uncertain at present. In this report, we measured the absolute value and the phase of skin impedance on an acupuncture point and non-acupuncture point at many frequencies and current values.

  10. The influence of gold nanoparticle modified electrode on the structure of mercaptopropionic acid self-assembly monolayer

    Microsoft Academic Search

    Shu-feng Liu; Xiao-hong Li; Yun-chao Li; Yong-fang Li; Jin-ru Li; Long Jiang

    2005-01-01

    The comparison of assembly structure and property of mercaptopropionic acid (MPA) self-assembled monolayers (SAMs) on gold nanoparticle modified electrode (nanogold electrode) with that on planar gold electrode was studied by cyclic voltammetry (CV). The electron transfer of through the MPA SAMs and Cu underpotential deposition (UPD) on MPA-covered electrode indicated that MPA molecules assemblied on the planar gold electrode could

  11. Study on cloud points of Triton X-100-cationic gemini surfactants mixtures: a spectroscopic approach.

    PubMed

    Akba?, Halide; Boz, Mesut; Batigöç, Ci?dem

    2010-02-01

    This study investigates the effects of various cationic surfactants on the cloud point (CP) of the nonionic surfactant Triton X-100 (TX-100) in aqueous solutions. Instead of visual observation, a spectrophotometer was used for measurement of the cloud point temperatures. The values of CPs for Triton X-100 can be measured directly because TX-100 has an average number of oxyethylene units per molecule of p approximately 9.5 and a CP=66.0 degrees C. Quaternary ammonium dimeric surfactants (m-s-m, m=10, 12, and 16, and s=2, 6, and 10) were synthesized and used. The melting temperature T(M) and the Krafft temperature T(K) were measured for 1 wt% aqueous solutions of these synthesized surfactants. The melting temperature of the solid gemini surfactants increased with the carbon number of the alkyl chain. The results showed that additions of the gemini surfactants (which are infinitely miscible with water) to Triton X-100 increased the cloud point of the TX-100 solutions. All salts tested in these studies had a large effect on the CPs of nonionic surfactants due to their effect on water structure and their hydrophilicity. The effect of the alkyl chain length of the gemini surfactant on the CP of Triton X-100 is therefore more important than the spacer chain length. PMID:20034845

  12. A study of the turning points of a nems shuttle using td-scc-dftb

    Microsoft Academic Search

    C. Huldt; P. Koskinen; J. Kinaret

    2009-01-01

    Nanoelectromechanical systems, of which the shuttle is one of the most fundamental, have theoretically been described mainly with phenomenological models with simplified interactions between the mobile part and the electrodes. Many microscopic methods, which in principle can give a more realistic picture of the shuttling process, are poorly suited for the dynamic non-equilibrium problem at hand. This is primarily due

  13. Enhancing generalisation in biofeedback intervention using the challenge point framework: A case study

    PubMed Central

    HITCHCOCK, ELAINE R.; BYUN, TARA McALLISTER

    2014-01-01

    Biofeedback intervention can help children achieve correct production of a treatment-resistant error sound, but generalisation is often limited. This case study suggests that generalisation can be enhanced when biofeedback intervention is structured in accordance with a “challenge point” framework for speech-motor learning. The participant was an 11-year-old with residual /r/ misarticulation who had previously attained correct /r/ production through a structured course of ultrasound biofeedback treatment but did not generalise these gains beyond the word level. Treatment difficulty was adjusted in an adaptive manner following predetermined criteria for advancing, maintaining, or moving back a level in a multidimensional hierarchy of functional task complexity. The participant achieved and maintained virtually 100% accuracy in producing /r/ at both word and sentence levels. These preliminary results support the efficacy of a semi-structured implementation of the challenge point framework as a means of achieving generalisation and maintenance of treatment gains. PMID:25216375

  14. In situ Video-STM study of the potential-induced (1 × 1) ? "hex" transition on Au(1 0 0) electrode surfaces in Cl - containing solution

    NASA Astrophysics Data System (ADS)

    Labayen, Miguel; Magnussen, Olaf M.

    2004-12-01

    The potential-induced (1 × 1) ? "hex" transition on Au(1 0 0) electrodes in 0.01 M Na 2SO 4 + 1 mM HCl was studied by in situ scanning tunneling microscopy at high time resolution (Video-STM). According to these observations the elementary units of the "hex" surface reconstruction, hexagonally-ordered strings in the Au surface layer, are highly dynamic nanoscale objects. Isolated "hex" strings exhibit dynamic fluctuations in structure and position on the millisecond timescale. These fluctuations exceed the mobility of multistring "hex" domains by several orders of magnitude and can be explained by collective dynamic processes within the strings. Furthermore, the observations reveal a novel 1D mass transport mechanism along the strings, details on the nucleation and growth of "hex" strings and complex string restructuring processes, facilitating "hex" domain ripening.

  15. Study of the Electrocatalytic Activity of Cerium Oxide and Gold-Studded Cerium Oxide Nanoparticles Using a Sonogel-Carbon Material as Supporting Electrode: Electroanalytical Study in Apple Juice for Babies

    PubMed Central

    Abdelrahim, M. Yahia M.; Benjamin, Stephen R.; Cubillana-Aguilera, Laura Ma; Naranjo-Rodríguez, Ignacio; Hidalgo-Hidalgo de Cisneros, Josè L.; Delgado, Juan Josè; Palacios-Santander, Josè Ma

    2013-01-01

    The present work reports a study of the electrocatalytic activity of CeO2 nanoparticles and gold sononanoparticles (AuSNPs)/CeO2 nanocomposite, deposited on the surface of a Sonogel-Carbon (SNGC) matrix used as supporting electrode and the application of the sensing devices built with them to the determination of ascorbic acid (AA) used as a benchmark analyte. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrocatalytic behavior of CeO2- and AuSNPs/CeO2-modified SNGC electrodes, utilizing different concentrations of CeO2 nanoparticles and different AuSNPs:CeO2 w/w ratios. The best detection and quantification limits, obtained for CeO2 (10.0 mg·mL?1)- and AuSNPs/CeO2 (3.25% w/w)-modified SNGC electrodes, were 1.59 × 10?6 and 5.32 × 10?6 M, and 2.93 × 10?6 and 9.77 × 10?6 M, respectively, with reproducibility values of 5.78% and 6.24%, respectively, for a linear concentration range from 1.5 ?M to 4.0 mM of AA. The electrochemical devices were tested for the determination of AA in commercial apple juice for babies. The results were compared with those obtained by applying high performance liquid chromatography (HPLC) as a reference method. Recovery errors below 5% were obtained in most cases, with standard deviations lower than 3% for all the modified SNGC electrodes. Bare, CeO2- and AuSNPs/CeO2-modified SNGC electrodes were structurally characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). AuSNPs and AuSNPs/CeO2 nanocomposite were characterized by UV-vis spectroscopy and X-ray diffraction (XRD), and information about their size distribution and shape was obtained by transmission electron microscopy (TEM;. The advantages of employing CeO2 nanoparticles and AuSNPs/CeO2 nanocomposite in SNGC supporting material are also described. This research suggests that the modified electrode can be a very promising voltammetric sensor for the determination of electroactive species of interest in real samples. PMID:23584124

  16. Polarization of anthracite electrodes in electrolyte solutions

    SciTech Connect

    A.N. Lopanov; E.V. Blaido; O.V. Smirnova [Shukhov State Technological Academy, Belgorod (Russian Federation)

    2007-10-15

    The regularities of the polarization of anthractie electrodes for the liberation of hydrogen from electrolyte (potassium chloride and hydrogen chloride) solutions were found, and electrode processes occurring at the surface of coals in the Fe{sup 2+}/Fe{sup 3+} redox system were studied. It was found that the deviations of standard electrode potentials from the equilibrium values of redox systems depend on the exchange current densities of electrochemical processes occurring at the surface of coal matter. Low transfer coefficients (0.04-0.051) for the discharge reaction of hydrogen ions on anthracites indicate that the reaction occurs under conditions close to those of an activationless process.

  17. Dual electrode mode electrospinning of biodegradable polymers

    NASA Astrophysics Data System (ADS)

    Li, Mei; He, Yadong; Xin, Chunling; Wei, Xiaopeng; Li, Qingchun; Lu, Chunmeng; Juang, Yi-Je

    2008-05-01

    A high speed dual electrode mode electrospinning was developed in this study. With coexistence of both positively and negatively charged nozzles, the electrospun fibers interact and bridge grafting between nozzles, interconnect with each other, and are stretched on a movable collecting roll. The results demonstrate that a highly intertwined, three-dimensional isotropic network structure can be obtained by using the dual electrode mode. Moreover, the productivity was increased more than 170 times compared to that using the conventional single electrode mode process, which is essential for commercialization of the electrospinning process.

  18. Satisfaction with the local service point for care: results of an evaluation study

    PubMed Central

    Esslinger, Adelheid Susanne; Macco, Katrin; Schmidt, Katharina

    2009-01-01

    Purpose The market of care increases and is characterized by complexity. Therefore, service points, such as the ‘Zentrale Anlaufstelle Pflege (ZAPf)’ in Nuremberg, are helpful for clients to get orientation. The purpose of the presentation is to show the results of an evaluation study about the clients' satisfaction with the offers of ZAPf. Study Satisfaction with service may be measured with the SERVQUAL concept introduced by Parasuraman et al. (1988). They found out five dimensions of quality (tangibles, reliability, responsiveness, assurances and empathy). We took these dimensions in our study. The study focuses on the quality of service and the benefits recognized by clients. In spring 2007, we conducted 67 interviews by phone, based on a half standardized questionnaire. Statistical analysis was conducted using SPSS. Results The clients want to get information about care in general, financial and legal aspects, alternative care arrangement (e.g. ambulant, long-term care) and typical age-related diseases. They show a high satisfaction with the service provided. Their benefits are to get information and advice, to strengthen the ability of decision taking, to cope with changing situations in life, and to develop solutions. Conclusions The results show that the quality of service is on a high level. Critical success factors are the interdisciplinary cooperation at the service point, based on a regularly and open exchange of information. Every member focuses on an optimal individual solution for the client. Local professional service points act as networkers and brokers. They serve not only for the clients' needs but also support the effective and efficient provision of optimized care.

  19. Multifunctional reference electrode

    DOEpatents

    Redey, Laszlo (Lisle, IL); Vissers, Donald R. (Naperville, IL)

    1983-01-01

    A multifunctional, low mass reference electrode of a nickel tube, thermocouple means inside the nickel tube electrically insulated therefrom for measuring the temperature thereof, a housing surrounding the nickel tube, an electrolyte having a fixed sulfide ion activity between the housing and the outer surface of the nickel tube forming the nickel/nickel sulfide/sulfide half-cell. An ion diffusion barrier is associated with the housing in contact with the electrolyte. Also disclosed is a cell using the reference electrode to measure characteristics of a working electrode.

  20. AMTEC electrode development

    NASA Technical Reports Server (NTRS)

    Bankston, C. P.; Williams, R. M.; Nakamura, B. J.; Wheeler, B. L.; Loveland, M. E.; Cole, T.

    1987-01-01

    The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-alumina solid electrolyte. Progress is reported on a long life, high power, porous electrode. Two electrode compositions were identified which have the potential for long life operation at power densities above 0.5 W/sq cm. Longer lifetime testing is being initiated. Successful optimization and demonstration of very long lifetimes for these electrodes will be a major step toward establishing the feasibility of AMTEC space power systems.

  1. Electrode for electrochemical cell

    SciTech Connect

    Kaun, T.D.; Miller, W.E.; Nelson, P.A.

    1981-12-15

    An electrode structure for a secondary electrochemical cell includes an outer enclosure defining a compartment containing electrochemical active material. The enclosure includes a rigid electrically conductive metal sheet with perforated openings over major side surfaces. The enclosure can be assembled as first and second trays each with a rigid sheet of perforated electrically conductive metal at major side surfaces and normally extending flanges at parametric margins. The trays can be pressed together with moldable active material between the two to form an expandable electrode. A plurality of positive and negative electrodes thus formed are arranged in an alternating array with porous frangible interelectrode separators within the housing of the secondary electrochemical cell.

  2. A study of electrode temperature lowering in Dy-containing ceramic metal halide lamps: II. An investigation of the converse effect of Tl and/or Na additives

    NASA Astrophysics Data System (ADS)

    Westermeier, M.; Ruhrmann, C.; Bergner, A.; Denissen, C.; Suijker, J.; Awakowicz, P.; Mentel, J.

    2013-05-01

    The lowering of the gas phase emitter effect of Dy in ceramic metal halide lamps by the admixture of TlI and NaI to the rare earth iodide salt DyI3 is investigated at lamps with different additives. The arcs are operated in an Hg buffer gas atmosphere of 2 MPa between rod-shaped pure tungsten electrodes within transparent YAG lamp tubes with a switched-dc current at operating frequencies from 1 Hz to 1 kHz. The atomic ground state density of Dy is measured phase resolved half way between the electrodes and in front of an electrode by broad band absorption spectroscopy, the Dy ion density in front of an electrode by emission spectroscopy and the electrode tip temperature pyrometrically within lamps seeded with differently composed fillings. The measurements confirm that a strong reduction in the electrode tip temperature is correlated with a high Dy ion density in front of the electrode within the cathodic half period. The Dy ion density is depressed predominantly and with it the reduction in the electrode tip temperature by a competing ionization of Tl, and in addition by a lowering of the Dy vapour pressure above the pool of molten salt by TlI. The influence of Na is of minor importance.

  3. Electro-coagulation treatment efficiency of graphite, iron and aluminum electrodes using alum and wood ash electrolytes on a Kraft pulp and paper mill effluent.

    PubMed

    Orori, O B; Etiégni, L; Senelwa, K; Mwamburi, M M; Balozi, K B; Barisa, G K; Omutange, E S

    2010-01-01

    Specific power consumption and reduction of BOD, COD, TS, pH, and chemical elements were used to determine the treatment efficiency of Fe, graphite and Al electrodes with alum and wood ash as supporting electrolytes on the effluent from a Kraft pulp and paper mill in Kenya. Five sampling points were selected along mill's effluent treatment system: primary settling tank (SP1), first aerated lagoon (SP2), second aerated lagoon (SP3), stabilization pond (SP4), and at discharge point (SP5). Operating costs were also compared between treatments. Graphite electrodes combined with alum showed the lowest power consumption (0.5 to 3.9 mWh/m³), followed by Al and Fe. All the electrodes reduced color from a maximum of 3,200°H to the minimum local standard of 15°H. However Al electrode with alum was the most effective method for BOD and COD reduction by over 60% and 58.8% respectively and generated less sludge at all sampling points. The cost of treatment was lowest with graphite electrode (US$0.006 to 0.0008 per m³ of effluent), but highest with Al electrodes combined with wood ash (US$31.74 to 8.34 per m³). Further study is required for the effectiveness of increasing the concentration of wood ash leachate at higher concentration and current density. PMID:20935369

  4. Determination of dopamine in synthetic cerebrospinal fluid by SWV with a graphite–polyurethane composite electrode

    Microsoft Academic Search

    R. A. de Toledo; M. C. Santos; E. T. G. Cavalheiro; L. H. Mazo

    2005-01-01

    This work describes an electroanalytical investigation of dopamine using cyclic voltammetry (CV) and the graphite–polyurethane composite electrode (GPU). In CV studies, well-defined redox peaks characterize the oxidation process at the GPU electrode, which is indicative of electrocatalytic effects associated with active sites on the GPU electrode surface. A new analytical methodology was developed using the GPU electrode and square wave

  5. Fast and precise positioning of single cells on planar electrode substrates

    Microsoft Academic Search

    H. Thielecke; T. Stieglitz; H. Beutel; T. Matthies; H. H. Ruf; J.-U. Meyer

    1999-01-01

    For cell biosensors and for studying neural networks using planar electrode substrates, a suitable technique for positioning single cells on electrodes was needed. We reported a new method for fast and efficient positioning of single cells on ring electrodes by controlled suction through holes. We described the microfabrication of electrode substrates with microholes and the cell positioning procedure. L929 cells

  6. Comprehensive study of the conditions for obtaining hydrogenated amorphous erbium- and oxygen-doped silicon suboxide films, a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket , by dc-magnetron deposition

    SciTech Connect

    Undalov, Yu. K., E-mail: undalov@mail.ioffe.ru; Terukov, E. I.; Gusev, O. B. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Lebedev, V. M. [Russian Academy of Sciences, Konstantinov Saint Petersburg Institute of Nuclear Physics (Russian Federation); Trapeznikova, I. N. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

    2011-12-15

    The results of a comprehensive study of the conditions for growing a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films are presented. The effect of the composition of various erbium-containing targets (a-SiO{sub x}:H , ErO{sub x}, Er{sub 2}SiO{sub 5}, Er{sub 2}O{sub 3}, and Er), substrate temperature, and annealing temperatures in argon, air, and under conditions of SiH{sub 4} + Ar + O{sub 2} plasma glow is studied. In order to obtain a-SiO{sub x}:H Left-Pointing-Angle-Bracket Er,O Right-Pointing-Angle-Bracket films with the highest photoluminescence intensity of erbium ions, it is recommended for the following technological conditions to be used: the substrate holder should be insulated from dc-magnetron electrodes and the working gas mixture should include silane, argon, and oxygen. Single-crystal silicon and metal erbium should be used as targets. The erbium target should be placed only in the Si-target erosion zone.

  7. First-principles study of point defects at a semicoherent interface

    NASA Astrophysics Data System (ADS)

    Metsanurk, E.; Tamm, A.; Caro, A.; Aabloo, A.; Klintenberg, M.

    2014-12-01

    Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. We show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. We give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials.

  8. A neutron powder diffraction study of. cap alpha. - and. beta. -PbO/sub 2/ in the positive electrode material of lead-acid batteries

    SciTech Connect

    Santoro, A.; Caulder, S.M.; D'Antonio, P.

    1983-07-01

    A neutron powder diffraction study of ..cap alpha..- and ..beta..-PbO/sub 2/, both chemically prepared and electrochemically formed in cycled battery plates, was carried out to correlate the electrochemical activity of the lead-acid battery with the atomic arrangement of the electrode constituents. Our results are consistent with the presence of hydrogen in the structure of ..beta..-PbO/sub 2/, but the departure of the occupancy factors from stoichiometric values are not large enough to unambiguously establish whether there are lead or oxygen deficiencies. If the Pb:O ratio corresponds to exact stoichiometry, any hydrogen which is present must be accompanied by a reduction of Pb/sup +4/. There is a significant increase in the lattice parameter ..cap alpha.. of ..beta..-PbO/sub 2/ in cycled battery electrodes relative to the value found in chemically prepared ..beta..-PbO/sub 2/. No change in the c parameter, however, was detected. These dimensional changes are consistent with a configuration for hydrogen similar to that observed in the rutile type structure of SnO/sub 2/, in which there are OH-ions oriented perpendicular to the c axis. The profile parameters obtained in this analysis show that the crystallites of ..beta..-PbO/sub 2/ in the positive plate material of a battery cycled three times (Y3) are smaller than those in the chemically prepared compound (about 450A vs. 800A), while there are no significant differences between the latter and ..beta..-PbO/sub 2/ in the positive plate material of a battery cycled 36 times (Y36). The average structure of ..cap alpha..-PbO/sub 2/ cannot be accurately determined by profile analysis, at the present time. The difficulties encountered in the refinement may be due to extensive defects, nonspherical crystallites of small size, and/or small departures of the structure from orthorhombic symmetry.

  9. Bifunctional oxygen electrodes

    Microsoft Academic Search

    D. Tryk; W. Aldred; Z. Chen; C. Fierro; J. Hashiguchi; M. Hossain; Z. Zhang; F. Zhao

    1985-01-01

    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

  10. AMTEC electrode development

    Microsoft Academic Search

    C. P. Bankston; R. M. Williams; B. J. Nakamura; B. L. Wheeler; M. E. Loveland; T. Cole

    1987-01-01

    The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-alumina solid electrolyte. Progress is reported on a long life, high power, porous electrode. Two electrode compositions were identified which have the potential for long life operation at power densities above 0.5 W\\/sq cm. Longer lifetime testing

  11. Auricular point acupressure as an adjunct analgesic treatment for cancer patients: a feasibility study.

    PubMed

    Yeh, Chao Hsing; Chien, Lung-Chang; Chiang, Yi Chien; Ren, Dianxu; Suen, Lorna Kwai-Ping

    2015-06-01

    This study aimed (1) to examine the feasibility of an auricular point acupressure (APA) research protocol in terms of recruitment and for the assessment and management of pain and (2) to examine the potential APA analgesic effects for cancer patients. This study was a repeated-measures one-group design. Participants were recruited from the cancer center follow-up clinic affiliated with a large university hospital in the northeastern United States. Participants included 50 patients aged 55-87 years with a diagnosis of cancer. Participants received 7 days of APA treatment for their pain. After appropriate acupoints were identified, vaccaria seeds were carefully taped onto each selected auricular point on each ear. The study recruitment and retention rates were 92% and 91%, respectively. Importantly, the study found preliminary evidence for the analgesic effects of APA for cancer pain management. For example, by the end of the 7-day study, APA reduced pain intensity more than 55% for "worst pain" and about 57% for "average pain" and "pain intensity." Moreover, the use of pain medication was reduced during the APA treatment (e.g., 78% of patients [n = 39] took less pain medication than before the treatment). APA appears to be highly acceptable to patients with cancer-related pain. However, without a placebo control, we cannot draw conclusive evidence for the analgesic effect of APA for cancer patients. A sham group must be added to future studies to differentiate the true effects of APA from the possible psychological effects of the APA treatment. PMID:25439120

  12. Techniques of Electrode Fabrication

    NASA Astrophysics Data System (ADS)

    Guo, Liang; Li, Xinyong; Chen, Guohua

    Electrochemical applications using many kinds of electrode materials as an advanced oxidation/reduction technique have been a focus of research by a number of groups during the last two decades. The electrochemical approach has been adopted successfully to develop various environmental applications, mainly including water and wastewater treatment, aqueous system monitoring, and solid surface analysis. In this chapter, a number of methods for the fabrication of film-structured electrode materials were selectively reviewed. Firstly, the thermal decomposition method is briefly described, followed by introducing chemical vapor deposition (CVD) strategy. Especially, much attention was focused on introducing the methods to produce diamond novel film electrode owing to its unique physical and chemical properties. The principle and influence factors of hot filament CVD and plasma enhanced CVD preparation were interpreted by refereeing recent reports. Finally, recent developments that address electro-oxidation/reduction issues and novel electrodes such as nano-electrode and boron-doped diamond electrode (BDD) are presented in the overview.

  13. Properties of Underwater Coated Electrode Welded Joints

    Microsoft Academic Search

    Constantin Miholc?; Elena Scutelnicu; Aurelia Mihailescu

    The paper presents the results of two comparative studies concerning some properties of underwater air-water coated-electrode welded joints (fillet and butt joints). The testes were performed using normal strength naval steel and hydro-protected medium coated-electrode (Ti). The welding environmental factors were accorded to the Romanian Register of Shipping regulations. The mechanical properties and HV 10 hardness of the welded joints

  14. In situ study of electrochemical activation and surface segregation of the SOFC electrode material La0.75Sr0.25Cr0.5Mn0.5O(3±?).

    PubMed

    Huber, Anne-Katrin; Falk, Mareike; Rohnke, Marcus; Luerssen, Bjoern; Gregoratti, Luca; Amati, Matteo; Janek, Jürgen

    2012-01-14

    Mixed-conducting perovskite-type electrodes which are used as cathodes in solid oxide fuel cells (SOFCs) exhibit pronounced performance improvement after cathodic polarization. The current in situ study addresses the mechanism of this activation process which is still unknown. We chose the new perovskite-type material La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±?) which is a potential candidate for use in symmetrical solid oxide fuel cells (SFCs). We prepared La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±?) thin film model electrodes on YSZ (111) single crystals by pulsed laser deposition (PLD). Impedance spectroscopy (EIS) measurements show that the kinetics of these electrodes can be drastically improved by applying a cathodic potential. To understand the origin of the enhanced electrocatalytic activity the surfaces of operating LSCrM electrodes were studied in situ (at low pressure) with spatially resolving X-ray photoelectron spectroscopy (?-ESCA, SPEM) and quasi static secondary ion mass spectrometry (ToF-SIMS) after applying different electrical potentials in the SIMS chamber. We observed that the electrode surfaces which were annealed at 600 °C are enriched significantly in strontium. Subsequent cathodic polarization decreases the strontium surface concentration while anodic polarization increases the strontium accumulation at the electrode surface. We propose a mechanism based on the reversible incorporation of a passivating SrO surface phase into the LSCrM lattice to explain the observed activation/deactivation process. PMID:22116198

  15. Free standing carbon nanotube composite bio-electrodes.

    PubMed

    Whitten, Philip G; Gestos, Adrian A; Spinks, Geoffrey M; Gilmore, Kerry J; Wallace, Gordon G

    2007-07-01

    Carbon nanotubes present a new material for the construction of electrodes for electrochemical devices such as batteries, capacitors, and actuators. Such electrodes require high conductivity, strength, and surface area. The latter two requirements are often incompatible. Electrodes composed entirely of carbon nanotubes (bucky paper) have high surface areas but are typically weak, and have insufficient conductivity for practical macroscopic applications. Here we report a technique that uses naturally occurring biopolymers to produce electrodes (free standing films) that exhibit conductivities of 300 S/cm. These composites also have considerable mechanical strength (up to 145 MPa) and sufficient specific capacitance of 19-27 F/g to enable them to be used as freestanding electrodes. One potential application that deserves special attention is that of biocompatible electrodes, where the binder is a biopolymer already used in a range of implants. Preliminary studies reported here show that the new carbon nanotube biopolymer electrodes can foster prolific L929 cell growth. PMID:17078076

  16. A methodological approach to the application of a vermiculite modified carbon paste electrode in interaction studies: Influence of some pesticides on the uptake of Cu(II) from a solution to the solid phase

    Microsoft Academic Search

    I. Grabec Švegl; B. Ogorevc; V. Hudnik

    1996-01-01

    A new methodological approach, for studying metal ion binding interactions with a clay mineral is presented. A carbon paste electrode (CPE) modified with vermiculite clay mineral was used as a model for a soil-like solid phase and Cu(II) ions were chosen as the test ions. The application of this model is demonstrated and explained by investigating the influence of seven

  17. Point-contact study of soft magnetic CoSiBFeNb amorphous alloys

    NASA Astrophysics Data System (ADS)

    Seinige, Heidi; Wang, Cheng; Tsoi, Valerii; Tsoi, Maxim

    2013-03-01

    We study magnetotransport in nanoscale point contacts to soft magnetic CoSiBFeNb ribbons. Such ultrasoft amorphous alloys attracted considerable attention previously because they exhibit Giant Magnetoimpedance (GMI) effect - large variations in the electrical impedance as a function of an external magnetic field [see, for instance, M.-H. Phan, H.-X. Peng, Prog. Mater. Sci. 53, 323 (2008) and references therein]. GMI is attributed to the field-induced variations in alloy permeability and has been established through ac measurements on bulk samples which revealed a strong dependence on ac frequency and amplitude but did not show any variations in dc resistance at all. In our experiments, we use nanocontacts to probe magnetotransport in amorphous CoSiBFeNb at the nanoscale. We use point contacts to inject both ac and dc currents into the alloy ribbons prepared by a melt-spinning technique. Measurements with ac currents revealed GMIs similar to those in macroscopic samples. Interestingly, we also observe a dc magnetoresistance which may be attributed to magnetic domain reorientations in a small contact region. Effects of high dc densities on the magnetoresistance are discussed in terms of spin-transfer torque (STT) effect. We thank A. Serebryakov for providing ribbon samples. We study magnetotransport in nanoscale point contacts to soft magnetic CoSiBFeNb ribbons. Such ultrasoft amorphous alloys attracted considerable attention previously because they exhibit Giant Magnetoimpedance (GMI) effect - large variations in the electrical impedance as a function of an external magnetic field [see, for instance, M.-H. Phan, H.-X. Peng, Prog. Mater. Sci. 53, 323 (2008) and references therein]. GMI is attributed to the field-induced variations in alloy permeability and has been established through ac measurements on bulk samples which revealed a strong dependence on ac frequency and amplitude but did not show any variations in dc resistance at all. In our experiments, we use nanocontacts to probe magnetotransport in amorphous CoSiBFeNb at the nanoscale. We use point contacts to inject both ac and dc currents into the alloy ribbons prepared by a melt-spinning technique. Measurements with ac currents revealed GMIs similar to those in macroscopic samples. Interestingly, we also observe a dc magnetoresistance which may be attributed to magnetic domain reorientations in a small contact region. Effects of high dc densities on the magnetoresistance are discussed in terms of spin-transfer torque (STT) effect. We thank A. Serebryakov for providing ribbon samples. This work was supported in part by NSF grant DMR-1207577

  18. Modiolus-hugging intracochlear electrode array with shape memory alloy.

    PubMed

    Min, Kyou Sik; Jun, Sang Beom; Lim, Yoon Seob; Park, Se-Ik; Kim, Sung June

    2013-01-01

    In the cochlear implant system, the distance between spiral ganglia and the electrodes within the volume of the scala tympani cavity significantly affects the efficiency of the electrical stimulation in terms of the threshold current level and spatial selectivity. Because the spiral ganglia are situated inside the modiolus, the central axis of the cochlea, it is desirable that the electrode array hugs the modiolus to minimize the distance between the electrodes and the ganglia. In the present study, we propose a shape-memory-alloy-(SMA-) embedded intracochlear electrode which gives a straight electrode a curved modiolus-hugging shape using the restoration force of the SMA as triggered by resistive heating after insertion into the cochlea. An eight-channel ball-type electrode array is fabricated with an embedded titanium-nickel SMA backbone wire. It is demonstrated that the electrode array changes its shape in a transparent plastic human cochlear model. To verify the safe insertion of the electrode array into the human cochlea, the contact pressures during insertion at the electrode tip and the contact pressures over the electrode length after insertion were calculated using a 3D finite element analysis. The results indicate that the SMA-embedded electrode is functionally and mechanically feasible for clinical applications. PMID:23762181

  19. Activation of the hypothalamus characterizes the acupuncture stimulation at the analgesic point in human: a positron emission tomography study

    Microsoft Academic Search

    Jen-Chuen Hsieh; Chung-Haow Tu; Fang-Pey Chen; Min-Chi Chen; Tzu-Chen Yeh; Hui-Cheng Cheng; Yu-Te Wu; Ren-Shyan Liu; Low-Tone Ho

    2001-01-01

    We performed a positron emission tomography study, using regional cerebral blood flow as the index of brain activity, to address the specificity of brain activation pattern by acupuncture stimulation of short duration at the classical analgesic point. Needling manipulation at 2 Hz was performed at a classical point of prominent analgesic efficacy (Li 4, Heku) and a near-by non-classical\\/non-analgesic point,

  20. Improving Probe Immobilization for Label-Free Capacitive Detection of DNA Hybridization on Microfabricated Gold Electrodes

    Microsoft Academic Search

    Sandro Carrara; Bruno Riccò; Viale Risorgimento; IC ISIM

    Alternative approaches to labeled optical detection for DNA arrays are actively investigated for low-cost point-of-care applications. In this domain, label-free capacitive detection is one of the most intensely studied techniques. It is based on the idea to detect the Helmholtz ion layer displacements when molecular recognition occurs at the electrodes\\/solution interface. The sensing layer is usually prepared by using thiols

  1. Electrokinetic particle-electrode interactions at high frequencies

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

    We provide a macroscale description of electrokinetic particle-electrode interactions at high frequencies, where chemical reactions at the electrodes are negligible. Using a thin-double-layer approximation, our starting point is the set of macroscale equations governing the “bounded” configuration comprising of a particle suspended between two electrodes, wherein the electrodes are governed by a capacitive charging condition and the imposed voltage is expressed as an integral constraint. In the large-cell limit the bounded model is transformed into an effectively equivalent “unbounded” model describing the interaction between the particle and a single electrode, where the imposed-voltage condition is manifested in a uniform field at infinity together with a Robin-type condition applying at the electrode. This condition, together with the standard no-flux condition applying at the particle surface, leads to a linear problem governing the electric potential in the fluid domain in which the dimensionless frequency ? of the applied voltage appears as a governing parameter. In the high-frequency limit ??1 the flow is dominated by electro-osmotic slip at the particle surface, the contribution of electrode electro-osmosis being O(?-2) small. That simplification allows for a convenient analytical investigation of the prevailing case where the clearance between the particle and the adjacent electrode is small. Use of tangent-sphere coordinates allows to calculate the electric and flows fields as integral Hankel transforms. At large distances from the particle, along the electrode, both fields decay with the fourth power of distance.

  2. 3-D Resistivity Tomography for Cliff Stability Study at the D-Day Pointe du Hoc Historic Site in Normandy, France

    NASA Astrophysics Data System (ADS)

    Udphuay, S.; Everett, M. E.; Guenther, T.; Warden, R. R.

    2007-12-01

    The D-Day invasion site at Pointe du Hoc in Normandy, France is one of the most important World War II battlefields. The site remains today a valuable historic cultural resource. However the site is vulnerable to cliff collapses that could endanger the observation post building and U.S. Ranger memorial located just landward of the sea stack, and an anti-aircraft gun emplacement, Col. Rudder's command post, located on the cliff edge about 200 m east of the observation post. A 3-D resistivity tomography incorporating extreme topography is used in this study to provide a detailed site stability assessment with special attention to these two buildings. Multi-electrode resistivity measurements were made across the cliff face and along the top of the cliff around the two at-risk buildings to map major subsurface fracture zones and void spaces that could indicate possible accumulations and pathways of groundwater. The ingress of acidic groundwater through the underlying carbonate formations enlarges pre-existing tectonic fractures via limestone dissolution and weakens the overall structural integrity of the cliff. The achieved 3-D resistivity tomograms provide diagnostic subsurface resistivity distributions. Resistive zones associated with subsurface void spaces have been located. These void spaces constitute a stability geohazard as they become significant drainage routes during and after periods of heavy rainfalls.

  3. Studying field emission characteristics of point and wedge–shaped surface defects

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Zartdinov, A. N.

    2014-10-01

    Electric field distribution and field emission current over the surface of point (sphere-on-cone) and wedge-shaped defects on a plane substrate are studied. It is found emission current due to wedge-shaped defects is more sensitive to emitter-anode distance than in case of point conical defects. This property is consequence of greater emission area of wedge-shaped defects and has important practical applications. The computer model in Matlab of field electron emission from emitter-defects arrays is used. Electrostatic simulation of electron transport processes with PDE Toolbox finite element solutions is implemented. The effects of the variations in defects geometrical structure and parameters on its potential distribution, electric field, and emission current are discussed. It is found that with increase of distance from the tip or the edge of defect the current density falls very fast and greater part of emission current is in fact produced by a very small area near the emitter tip. The closer the emitter and collector are to each other, the less significant the inter-defect distance becomes.

  4. Ceramic electrodes for an alkali metal thermo-electric converter (AMTEC)

    Microsoft Academic Search

    H. Nakata; T. Nagata; K. Tsuchida; A. Kato

    1993-01-01

    TiN, TiC, TiC\\/TiN, and Mo electrodes for an Alkali Metal Thermo-Electric Converter (AMTEC) were prepared by ceramic processing and their cathodic polarization characteristics were studied at 600–800°C. The polarization characteristics for TiN and TIC electrodes were similar to those for the Mo electrode. Among three kinds of TiC electrodes with different morphologies, the electrode consisting of finer grains gave a

  5. Space science/space station attached payload pointing accommodation study: Technology assessment white paper

    NASA Technical Reports Server (NTRS)

    Lin, Richard Y.; Mann, Kenneth E.; Laskin, Robert A.; Sirlin, Samuel W.

    1987-01-01

    Technology assessment is performed for pointing systems that accommodate payloads of large mass and large dimensions. Related technology areas are also examined. These related areas include active thermal lines or power cables across gimbals, new materials for increased passive damping, tethered pointing, and inertially reacting pointing systems. Conclusions, issues and concerns, and recommendations regarding the status and development of large pointing systems for space applications are made based on the performed assessments.

  6. The bi-variate frequency distribution of two concurrent climatic variables: a study of temperature and dew point

    E-print Network

    Zeitler, Jon William

    1991-01-01

    THE BI-VARIATE FREQUENCY DISTRIBUTION OF TWO CONCURRENT CLIMATIC VARIABLES: A STUDY OF TEMPERATURE AND DEW POINT A Thesis by ION WILLIAM ZEITLER Submitted to the Office of Graduate Studies of Texas ARM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1991 Major Subject: Meteorology THE BI-VARIATE FREQUENCY DISTRIBUTION OF TWO CONCURRENT CLIMATIC VARIABLES: A STUDY OF TEMPERATURE AND DEW POINT A Thesis by JON WILLIAM ZEITLER Approved...

  7. Ice slurry cooling research: Microscale study of ice particles characteristics, role of freezing point depressant, and influence on slurry fluidity

    Microsoft Academic Search

    K. Hayashi; K. Kasza

    2000-01-01

    The influences of freezing-point-depressants on ice slurry characteristics in the form of ice slurry fluidity and on the microscale ice particle features are studied. The results identify microscale features of ice particles such as surface roughness that greatly influence slurry fluidity that are altered favorably by the use of a freezing point depressant. The engineering of a workable and efficient

  8. A study about the fitting curves for the calibration of the Pt/Rh family thermocouples in fixed points

    NASA Astrophysics Data System (ADS)

    del Campo, D.; García, C.

    2013-09-01

    The aim of this paper is to study the suitability of the common procedures used to estimate the calibration fitting curves of noble metal thermocouples, namely from the Pt/Rh family, in fixed points. The objective is to find out the best combination and the minimum number of fixed points that allows obtaining a reasonable interpolation uncertainty.

  9. Electrode pattern design for GaAs betavoltaic batteries

    Microsoft Academic Search

    Chen Haiyang; Yin Jianhua; Li Darang

    2011-01-01

    The sensitivities of betavoltaic batteries and photovoltaic batteries to series and parallel resistance are studied. Based on the study, an electrode pattern design principle of GaAs betavoltaic batteries is proposed. GaAs PIN junctions with and without the proposed electrode pattern are fabricated and measured under the illumination of 63Ni. Results show that the proposed electrode can reduce the backscattering and

  10. Comparative study of different cross-linking agents for the immobilization of functionalized carbon nanotubes within a chitosan film supported on a graphite-epoxy composite electrode.

    PubMed

    Pauliukaite, Rasa; Ghica, Mariana Emilia; Fatibello-Filho, Orlando; Brett, Christopher M A

    2009-07-01

    The effectiveness of immobilization of functionalized carbon nanotubes into chitosan using different cross-linking agents has been evaluated. The cross-linkers used were glyoxal (GO), glutaraldehyde (GA), epichlorohydrin (ECH), and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide together with N-hydroxysuccinimide (EDC-NHS), and the nanotubes were retained on graphite epoxy resin composite electrodes. The nanotube modified electrodes have been characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Using CV and EIS in the presence of potassium hexacyanoferrate(III), the electroactive area of all types of electrodes was determined and the redox process analyzed, leading to the conclusion that ECH and EDC-NHS are better for immobilization of functionalized carbon nanotubes inside the chitosan matrix. The modified electrodes were successfully applied to the determination of hydrogen peroxide by fixed potential amperometry at -0.1 V vs SCE, the highest response being exhibited when using ECH. PMID:19473012

  11. A comparative study of metal-semiconductor-metal photodetectors on GaAs with indium-tin-oxide and Ti\\/Au electrodes

    Microsoft Academic Search

    J.-W. Seo; A. A. Ketterson; D. G. Ballegeer; K.-Y. Cheng; I. Adesida; X. Li; T. Gessert

    1992-01-01

    Metal-semiconductor-metal (MSM) photodiodes with interdigitated indium-tin-oxide (ITO) electrodes have been fabricated on undoped GaAs using reactive-ion-etching in a methane plasma. The responsivity of ITO MSMs is measured to be approximately 0.8 A\\/W, which is twice that of conventional Ti\\/Au MSMs under normal operational bias conditions at ?=850 nm. This higher responsivity is attributed to the transparency of the ITO electrodes.

  12. Study of a gold electrode modified by trans-[Ru(NH 3) 4(Ist)SO 4] + to produce an electrochemical sensor for nitric oxide

    Microsoft Academic Search

    Vanessa N. Santos; Murilo F. Cabral; Jefferson S. Ferreira; Alda K. M. Holanda; Sergio A. S. Machado; Jackson R. Sousa; Luiz G. F. Lopes; Adriana N. Correia; Pedro de Lima Neto

    2011-01-01

    The modification of a gold electrode surface by electropolymerization of trans-[Ru(NH3)4(Ist)SO4]+ to produce an electrochemical sensor for nitric oxide was investigated. The influence of dopamine, serotonin and nitrite as interferents for NO detection was also examined using square-wave voltammetry (SWV). The characterization of the modified electrode was carried out by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and SERS techniques.

  13. In situ STM study of (100) Cu electrodes in sulfuric acid solution in the presence of benzotriazole: Adsorption, Cu corrosion, and Cu deposition

    Microsoft Academic Search

    M. R. Vogt; W. Polewska; O. M. Magnussen; R. J. Behm

    1997-01-01

    Atomic-resolution in situ scanning tunneling microscopy (STM) observations of (100) Cu electrodes in HâSOâ solution containing 10⁻⁶ to 10⁻⁴ M benzotriazole (BTA) are presented. At potentials ⤠-0.6 V vs. a Hg\\/HgâSOâ (KâSOâ sat.) reference electrode ordered superstructures of a chemisorbed BTA adlayer as well as a disordered, chainlike structure, suggesting a polymerized BTA film, were observed. Cu corrosion commences

  14. Design and evaluation of a highly sensitive nanostructure-based surface modification of glassy carbon electrode for electrochemical studies of hydroxychloroquine in the presence of acetaminophen.

    PubMed

    Khoobi, Asma; Ghoreishi, Sayed Mehdi; Behpour, Mohsen; Shaterian, Maryam; Salavati-Niasari, Masoud

    2014-11-01

    N,N'-bis[(E)-(1-pyridyl) methylidene]-1,3-propanediamine (PMPDA) self-assembled monolayer (SAM) was covalently prepared on a glassy carbon electrode (GCE). The electrode surface modification was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Then GC-PMPDA SAM modified electrode was used to investigate the electrochemical behavior of hydroxychloroquine (HQ) using CV, double potential step chronocoulometry and linear sweep voltammetry (LSV) techniques. Using these techniques, the diffusion coefficient (D), electron transfer coefficient (?) and exchanging current density (j0) for HQ were calculated. Furthermore the modified electrode was applied as a high sensitive biosensor for determination of HQ in the presence of acetaminophen (AC). The GC-PMPDA SAM modified electrode provides two linear responses for HQ in the presence of AC in the concentration ranges from 0.09 to 10.21 ?M and 10.21 to 98.29 ?M by differential pulse voltammetry (DPV). The detection limit (three times the signal blank/slope) was 4.65 nM. Finally the modified electrode was satisfactorily used for determining of HQ in human body fluids. PMID:25456984

  15. A new method to study Li-ion cell safety: laser beam initiated reactions on both charged negative and positive electrodes

    NASA Astrophysics Data System (ADS)

    Pérès, J. P.; Perton, F.; Audry, C.; Biensan, Ph; de Guibert, A.; Blanc, G.; Broussely, M.

    The improvement of Li-ion batteries safety in abuse use is one of the key issues for their establishment in future hybrid or electrical vehicles. Such a challenge requires a perfect understanding of phenomena which could occur in abuse situation. A new technique for a better understanding of Li-ion cell safety has been so investigated. Reactions between electrolyte and charged electrodes (positive and negative just recovered from dismantled charged 4/5A cells) have been initiated by a laser beam, having a monitored intensity and time pulse. From such a device, a strong and controlled heating can be generated, in a very short time scale, on a defined electrode surface area. This localized heating, which is supposed to be similar to that could occur from a cell internal short-circuit, is able to initiate "self-propagation reactions" on charged negative and positive electrodes. This new technique has allowed a ranking of charged electrodes in terms of "self-propagation ability". This range of new data has been compared to results obtained from classical thermal characterization methods (DSC, DTA) and results obtained from normalized abuse tests. Global charged negative and positive electrodes degradation mechanisms have been proposed in good agreement with the whole results. The safety of a done Li-ion cell seems mainly related to active negative and positive active materials, but also to other components of the electrodes, and especially additive carbons and aluminum collector of the positive side.

  16. First-principles study of point defects in solar cell semiconductor CuInS2

    NASA Astrophysics Data System (ADS)

    Chen, Hui; Wang, Chong-Yu; Wang, Jian-Tao; Hu, Xiao-Ping; Zhou, Shao-Xiong

    2012-10-01

    The formation energies and transition levels of point defects VCu, VIn, VS, InCu, CuIn, and OS in CuInS2 are studied using the hybrid density functional theory. It is found that the Heyd-Scuseria-Ernzerhof method can accurately describe the electronic structure and gives a band gap of 1.40 eV, in good agreement with the experimental value. On the other hand, we conclude that p-type semiconductor CuInS2 can be obtained under sulfur-rich condition with a certain copper and indium content, while n-type semiconductor CuInS2 can be easily obtained under the copper-rich, indium-rich, sulfur-poor, and non-oxygen conditions. These results provide an excellent account for the modification of the structural and electronic properties of CuInS2.

  17. Redox-switching in a viologen-type adlayer: an electrochemical shell-isolated nanoparticle enhanced Raman spectroscopy study on Au(111)-(1×1) single crystal electrodes.

    PubMed

    Liu, Bo; Blaszczyk, Alfred; Mayor, Marcel; Wandlowski, Thomas

    2011-07-26

    We reported the first application of in situ shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) to an interfacial redox reaction under electrochemical conditions. We construct gap-mode sandwich structures composed of a thiol-terminated HS-6V6H viologen adlayer immobilized on a single crystal Au(111)-(1×1) electrode and covered by Au(60 nm)@SiO(2) core-shell nanoparticles acting as plasmonic antennas. We observed high-quality, potential-dependent Raman spectra of the three viologen species V(2+), V(+?), and V(0) on a well-defined Au(111) substrate surface and could map their potential-dependent evolution. Comparison with experiments on powder samples revealed an enhancement factor of the nonresonant Raman modes of ?3 × 10(5), and up to 9 × 10(7) for the resonance modes. The study illustrates the unique capability of SHINERS and its potential in the entire field of electrochemical surface science to explore structures and reaction pathways on well-defined substrate surfaces, such as single crystals, for molecular, (electro-)catalytic, bioelectrochemical systems up to fundamental double layer studies at electrified solid/liquid interfaces. PMID:21634391

  18. Dual porosity gas evolving electrode

    DOEpatents

    Townsend, C.W.

    1994-11-15

    A dual porosity electrode is described for use in thermoelectrochemical systems where simultaneous transport of gas and liquid into and/or out of the electrode is required. The electrode includes catalytic electrode particles having diameters ranging from about 25 to 100 angstroms. The catalytic electrode particles are anchored to a support network in clusters which have internal pores ranging in size from 25 to 100 angstroms. The pores between the clusters range in size from between about 1 to 20 microns. A method for making the dual porosity electrodes is also disclosed.

  19. Dual porosity gas evolving electrode

    DOEpatents

    Townsend, Carl W. (Los Angeles, CA)

    1994-01-01

    A dual porosity electrode for use in thermoelectrochemical systems where simultaneous transport of gas and liquid into and/or out of the electrode is required. The electrode includes catalytic electrode particles having diameters ranging from about 25 to 100 angstroms. The catalytic electrode particles are anchored to a support network in clusters which have internal pores ranging in size from 25 to 100 angstroms. The pores between the clusters range in size from between about 1 to 20 microns. A method for making the dual porosity electrodes is also disclosed.

  20. Sandwich-type electrode

    DOEpatents

    Lu, Wen-Tong P. (Upper St. Clair, PA); Garcia, Earl R. (Ingram, PA)

    1983-01-01

    Disclosed is an improvement on a method of making an electrode wherein a suspension in a liquid is prepared of a powdered catalyst containing a noble metal, carbon powder and a binder, and the suspension is poured over a carbon substrate dried, compressed and sintered to form a solid catalyst layer bonded to the carbon substrate. The improvement is placing a carbon paper on the catalyst layer prior to compressing. The improved electrode can be used as either a cathode or an anode in a sulfur dioxide depolarized electrolyzer in a process for producing hydrogen from water.

  1. Experimental and Analytical Studies of Shielding Concepts for Point Sources and Jet Noises.

    NASA Astrophysics Data System (ADS)

    Wong, Raymond Lee Man

    This analytical and experimental study explores concepts for jet noise shielding. Model experiments centre on solid planar shields, simulating engine-over-wing installations, and 'sugar scoop' shields. Tradeoff on effective shielding length is set by interference 'edge noise' as the shield trailing edge approaches the spreading jet. Edge noise is minimized by (i) hyperbolic cutouts which trim off the portions of most intense interference between the jet flow and the barrier and (ii) hybrid shields--a thermal refractive extension (a flame); for (ii) the tradeoff is combustion noise. In general, shielding attenuation increases steadily with frequency, following low frequency enhancement by edge noise. Although broadband attenuation is typically only several dB, the reduction of the subjectively weighted perceived noise levels is higher. In addition, calculated ground contours of peak PN dB show a substantial contraction due to shielding: this reaches 66% for one of the 'sugar scoop' shields for the 90 PN dB contour. The experiments are complemented by analytical predictions. They are divided into an engineering scheme for jet noise shielding and more rigorous analysis for point source shielding. The former approach combines point source shielding with a suitable jet source distribution. The results are synthesized into a predictive algorithm for jet noise shielding: the jet is modelled as a line distribution of incoherent sources with narrow band frequency (TURN)(axial distance)('-1). The predictive version agrees well with experiment (1 to 1.5 dB) up to moderate frequencies. The insertion loss deduced from the point source measurements for semi-infinite as well as finite rectangular shields agrees rather well with theoretical calculation based on the exact half plane solution and the superposition of asymptotic closed-form solutions. An approximate theory, the Maggi-Rubinowicz line integral, is found to yield reasonable predictions for thin barriers including cutouts if a certain correction is applied. The more exact integral equation approach (solved numerically) is applied to a more demanding geometry: a half round sugar scoop shield. It is found that the solutions of integral equation derived from Helmholtz formula in normal derivative form show satisfactory agreement with measurements.

  2. Screen-printed diamond electrode: A disposable sensitive electrochemical electrode

    Microsoft Academic Search

    Takeshi Kondo; Hironori Sakamoto; Takayoshi Kato; Masaru Horitani; Isao Shitanda; Masayuki Itagaki; Makoto Yuasa

    A disposable and sensitive screen-printed electrode was fabricated on a polyimide film substrate using an ink containing conductive boron-doped diamond powder (BDDP). The BDDP-printed electrode exhibited a wider potential window and lower background current in an aqueous electrolyte than a carbon-printed electrode, and the signal-to-background ratio of the redox peak for ferri\\/ferrocyanide was greater at the BDDP-printed electrode than at

  3. Reinforcement Mechanisms in Putamen during High Frequency STN DBS: A Point Process Study

    PubMed Central

    Santaniello, Sabato; Gale, John T.; Montgomery, Erwin B.; Sarma, Sridevi V.

    2013-01-01

    Despite a pivotal role in the motor loop, dorsolateral striatum (putamen) has been poorly studied thus far under Parkinsonian conditions and Deep Brain Stimulation (DBS). We analyze the activity of the putamen in a monkey by combining single unit recordings and point process models. The animal received DBS (30–130Hz) in the subthalamic nucleus (STN) while at rest and recordings were acquired both before and after treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which induced Parkinsonian-like motor disorders. 141 neurons were collected and, for each neuron, a point process model captured DBS-evoked discharge patterns. In the normal animal, spike trains at rest had Poisson like distribution with non-stationary recurrent patterns (RPs) of period 3–7ms and were mildly changed by low frequency (LF, i.e., <100Hz) DBS (i.e., <20% of neurons affected). With high frequency (HF, i.e., 100–130Hz) DBS, instead, up to 59% of neurons were affected, the DBS history significantly impacted the neuronal spiking propensity, and the RPs and the post-stimulus activation latency decreased. MPTP evoked inter-neuronal dependencies (INDs) at rest and, compared to normal, LF DBS of the MPTP animal increased RPs and INDs, while HF DBS elicited a faster and wider post-stimulus activation. Overall, HF DBS reduced ongoing non-stationary dynamics by regularizing the discharge patterns both in MPTP and normal putamen, while the combination of MPTP and LF DBS enhanced such dynamics. PMID:23366116

  4. A study of electrode temperature lowering in Dy-containing ceramic metal halide lamps: I. The effect of mixtures of Dy, Tl and Na compared with pure Dy

    NASA Astrophysics Data System (ADS)

    Westermeier, M.; Ruhrmann, C.; Bergner, A.; Denissen, C.; Suijker, J.; Awakowicz, P.; Mentel, J.

    2013-05-01

    The reduction in the electrode temperature by the gas phase emitter effect of dysprosium in ceramic metal halide lamps is investigated within special research lamps in dependence on the operating frequency of switched-dc lamp currents. The lamp tubes are made of transparent YAG material. They are filled with a fixed amount of Hg, which produces a buffer gas during lamp operation at a pressure of 2 MPa, with different amounts of DyI3 and in part with different amounts of NaI plus TlI. The Dy atomic ground state density is measured phase resolved both in the middle of the discharge and in front of the upper electrode by broad band absorption spectroscopy. The Dy ion density in front of the electrode is evaluated from line intensities being measured in absolute units by emission spectroscopy. The electrode tip temperature is determined by a 1? - 2D pyrometric measuring method. It is found that a high Dy ion density in front of the electrode is correlated with a strong reduction in the electrode tip temperature relating to a pure mercury lamp. At low operating frequencies (f ? 100 Hz) the Dy ion density and the temperature reduction is high within the cathodic phase and low within the anodic phase, at higher operating frequencies an increased Dy ion density and a reduction in the electrode tip temperature overlaps onto the anodic phase. The Dy ion density is reduced and with it the tip temperature drop by an addition of Na and Tl vapour to the lamp plasma. The effect of Tl and Na is investigated in more detail in a successive paper.

  5. Magneto-transport study of magnetite (Fe3O4) nanoparticles between Au nanogap electrodes on surface-oxidized Si substrate

    NASA Astrophysics Data System (ADS)

    Kobori, H.; Takata, N.; Fukutome, N.; Yamasaki, A.; Sugimura, A.; Taniguchi, T.; Horie, T.; Naitoh, Y.; Shimizu, T.

    2013-04-01

    We have studied the magneto-transport of magnetite (Fe3O4) nanoparticles (MNPs) between Au nanogap electrodes (ANGEs) on surface-oxidized Si substrate. The MNP sizes are approximately 40 nm and the 100 nm thick magnetite thin film (which is formed of the MNP aggregation) was prepared between and around the ANGEs by use of the RF reactive magnetron sputtering method. The distance between the ANGEs and the bridge width of the ANGEs are approximately 50 nm and 1.5 ?m, respectively. The ANGEs were produced by the tilted-angle-deposition method. The optical microscope, scanning electron microscope and atomic force microscope were used to observe the sample surface structure and morphology. To investigate the crystal structure and crystallinity of the MNPs, the X-ray diffraction measurement was performed. The electrical resistance and magneto-resistance ratio of the MNPs between the ANGEs were measured as a function of temperature. The magneto-transport mechanism is discussed on the basis of the spin dependent transport.

  6. In-vitro broad band impedance study of a biochemical reaction under nanopulses: electrode impedance as a reaction sensor.

    E-print Network

    Boyer, Edmond

    the world, people are immersed in more or less intense electromagnetic fields due to the emergence of global a possible interaction between electromagnetic radiations and some mechanisms involved in brain activity [3,4]. The main difficulty encountered in in vitro and in vivo studies is to master the electromagnetic field

  7. Study on the Generation of Collar Curve Based on 3D Point-Cloud Data

    Microsoft Academic Search

    Xu Xiao-hui; Gu Bing-fei; Su Jun-qiang; Liu Guo-lian

    \\u000a In this paper, non-contact anthropometry is done on the female bodies, and the 3D point-cloud data is got by 3D scanner, and\\u000a then the collar curve of female tight prototype is generation by data processing on point-cloud figures using reverse engineering\\u000a software. The collar curve can be divided into the front and back collar curve. The characteristic points of the

  8. Dual keel Space Station payload pointing system design and analysis feasibility study

    NASA Technical Reports Server (NTRS)

    Smagala, Tom; Class, Brian F.; Bauer, Frank H.; Lebair, Deborah A.

    1988-01-01

    A Space Station attached Payload Pointing System (PPS) has been designed and analyzed. The PPS is responsible for maintaining fixed payload pointing in the presence of disturbance applied to the Space Station. The payload considered in this analysis is the Solar Optical Telescope. System performance is evaluated via digital time simulations by applying various disturbance forces to the Space Station. The PPS meets the Space Station articulated pointing requirement for all disturbances except Shuttle docking and some centrifuge cases.

  9. Pyrolytic carbon electrodes Lithographically Defined Porous Carbon Electrodes**

    E-print Network

    New Mexico, University of

    Pyrolytic carbon electrodes Lithographically Defined Porous Carbon Electrodes** D. Bruce Burckel Polsky* The special nature of the CÀC bond can lead to various polymorphic forms of carbon such as graphite, glassy-carbon, fullerenes (such as buckyballs), carbon nanotubes, and diamond. Electrodes made

  10. Voltammetric studies on the potent carcinogen, 7,12-dimethylbenz[ a]anthracene: Adsorptive stripping voltammetric determination in bulk aqueous forms and human urine samples and detection of DNA interaction on pencil graphite electrode

    Microsoft Academic Search

    Y. Yard?m; E. Keskin; A. Levent; M. Özsöz; Z. ?entürk

    2010-01-01

    7,12-Dimethylbenz[a]anthracene (DMBA), is a widely studied polycyclic aromatic hydrocarbon that has long been recognized as a very potent carcinogen. Initially, the electrochemical oxidation of DMBA at the glassy carbon and pencil graphite electrodes in non-aqueous media (dimethylsulphoxide with lithium perchlorate) was studied by cyclic voltammetry. DMBA was irreversibly oxidized in two steps at high positive potentials, resulting in the ill-resolved

  11. Blocking behavior of self-assembled monolayers on gold electrodes

    Microsoft Academic Search

    Hong Shen; James E. Mark; Carl J. Seliskar; Harry B. Mark Jr.; William R. Heineman

    1997-01-01

    Self-assembled monolayers (SAMs) with metal electrodes, especially thiols on gold, are the subject of this investigation\\u000a because of the unique properties of SAM-modified surfaces. Normal alkanethiols are used to modify the surface of a conventional\\u000a gold electrode to block certain ions such as Pb(II) and Cu(II) from the surface of the electrode. Normal alkanethiols are\\u000a also used to study the

  12. Large-area oranic solar cells with metal electrode

    Microsoft Academic Search

    Jae-Wook Kang; Yong-Jin Kang; Seunghun Lee; Chang Su Kim; Do-Geun Kim; Jong-Kuk Kim

    2011-01-01

    This study examined the effects of the cell area in spray-coated organic solar cells (OSCs) by introducing a metal sub-electrode and grid-electrode to produce large-area cells up to 12.25 cm2. The effects of the cell area were investigated systematically to realize large-area cells. The series resistance could be reduced significantly by inserting a metal grid-electrode onto the indium tin oxide

  13. Battery electrode growth accommodation

    DOEpatents

    Bowen, Gerald K. (Cedarburg, WI); Andrew, Michael G. (Wauwatosa, WI); Eskra, Michael D. (Fredonia, WI)

    1992-01-01

    An electrode for a lead acid flow through battery, the grids including a plastic frame, a plate suspended from the top of the frame to hang freely in the plastic frame and a paste applied to the plate, the paste being free to allow for expansion in the planar direction of the grid.

  14. Dry EEG Electrodes

    PubMed Central

    Lopez-Gordo, M. A.; Sanchez-Morillo, D.; Valle, F. Pelayo

    2014-01-01

    Electroencephalography (EEG) emerged in the second decade of the 20th century as a technique for recording the neurophysiological response. Since then, there has been little variation in the physical principles that sustain the signal acquisition probes, otherwise called electrodes. Currently, new advances in technology have brought new unexpected fields of applications apart from the clinical, for which new aspects such as usability and gel-free operation are first order priorities. Thanks to new advances in materials and integrated electronic systems technologies, a new generation of dry electrodes has been developed to fulfill the need. In this manuscript, we review current approaches to develop dry EEG electrodes for clinical and other applications, including information about measurement methods and evaluation reports. We conclude that, although a broad and non-homogeneous diversity of approaches has been evaluated without a consensus in procedures and methodology, their performances are not far from those obtained with wet electrodes, which are considered the gold standard, thus enabling the former to be a useful tool in a variety of novel applications. PMID:25046013

  15. Seismic mass Top electrode

    E-print Network

    Kraft, Michael

    of which provides loop transducer is described. A bulk-micromachined an accurate measure is that the micromachined, capacitive sensing element had only three connections (top and bottom electrodes and seismic mass domains, (Burstein and Kaiser, 1996). Usually, for an analogue, closed loop accelerometer the latter

  16. In-situ STM study of copper deposition on Cu(111) single-crystal electrode in sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Polewska, Wanda; Vogt, M. R.; Magnussen, O. M.; Behm, R. J.

    2001-04-01

    Results of an in-situ STM study of homoepitaxial copper electro deposition on Cu(111) in 0.01 M H2SO4 solution are presented which show a pronounced change in the growth and morphology of the deposit with increasing potential: while at - 0.40 V vs. SCE Cu multilayer growth is observed, Cu grows via a step-flow mechanism at -0.55 V. This behavior can be explained by the presence of an ordered sulfate adlayer at potentials >=-o.42 V, which causes a pronounced decrease in the Cu surface mobility.

  17. Sphenoidal electrode insertion under local analgesia in children

    Microsoft Academic Search

    Lucia Septien; Pierre Gras; Maurice Giroud; Raymond Dumas

    1992-01-01

    The indications for method and the results of sphenoidal electrode insertion under local analgesia are evaluated in children. This technique makes it possible to study the hippocampal area, which cannot be studied by other extracranial electrodes. It also localizes in a temporal lobe some complex seizures without electrical events on surface recordings, complex sezures with bilateral temporal spikes or a

  18. Stabilization of metal counter electrodes for dye solar cells

    Microsoft Academic Search

    Kati Miettunen; Imran Asghar; Xiaoli Ruan; Janne Halme; Tapio Saukkonen; Peter Lund

    2011-01-01

    The purpose of this study was to identify stable metal based counter electrodes (CE) for dye solar cells (DSC). Previous studies have shown that stainless steel (StS 304) suffers from corrosion when used as a counter electrode. Therefore metals which have inherently higher corrosion resistance, such as stainless steel types 321, 316 and 316L, Inconel 600 and titanium, were investigated

  19. A Simulation Study Comparison of Bayesian Estimation with Conventional Methods for Estimating Unknown Change Points

    ERIC Educational Resources Information Center

    Wang, Lijuan; McArdle, John J.

    2008-01-01

    The main purpose of this research is to evaluate the performance of a Bayesian approach for estimating unknown change points using Monte Carlo simulations. The univariate and bivariate unknown change point mixed models were presented and the basic idea of the Bayesian approach for estimating the models was discussed. The performance of Bayesian…

  20. 21 CFR 882.1340 - Nasopharyngeal electrode.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Nasopharyngeal electrode. 882.1340 Section...Diagnostic Devices § 882.1340 Nasopharyngeal electrode. (a) Identification. A nasopharyngeal electrode is an electrode which...

  1. Electrochemical performance of platinum electrodes within the multi-electrode spiral nerve cuff.

    PubMed

    Rozman, Janez; Pe?lin, Polona; Mehle, Andraž; Šala, Martin

    2014-09-01

    In this study, the electrochemical performance of platinum electrodes within a multi-electrode spiral cuff to be used for selective nerve stimulation was investigated. The original cuff, simplified into a half-cuff, contained a single row of nine electrodes (0.5 × 2 mm) at a distance of 2 mm from its inner surface. Cyclic voltammetry was used to investigate the electrochemical reactions at the electrode-electrolyte interface, to define a potential window within which the electrode could be safely used in selective nerve stimulation, to calculate the charge injection capacity and cathodal charge storage capacity. Voltage transients retrieved during excitation with quasitrapezoidal biphasic current pulses, tested by selective nerve stimulation of the isolated porcine left cervical vagus nerve segment, were used to determine the maximum polarization across the electrode-electrolyte interface and to calculate cathodic charge injection capacity of the electrode. The results show that the most negative and most positive potentials across the electrode-electrolyte interface reached -0.54 and 0.59 V; these did not exceed the safe potential limits for water electrolysis. Furthermore, the time integral of the cathodic current by cyclic voltammetry measured over the potential range of water electrolysis, actually representing the cathodal charge storage capacity, was approximately -4 mC cm(-2). The charge injection capacity, representing the maximum charge density injected in a current stimulation pulse, using only reversible processes, however, was around 75 µC cm(-2). In conclusion, both, the tested stimulation pulse and electrode are suitable for efficient and safe selective nerve stimulation. PMID:24938675

  2. Thermodynamic analysis and experimental study of the effect of atmospheric pressure on the ice point

    SciTech Connect

    Harvey, A. H. [Thermophysical Properties Division National Institute of Standards and Technology, Boulder, Colorado (United States)] [Thermophysical Properties Division National Institute of Standards and Technology, Boulder, Colorado (United States); McLinden, M. O. [Thermophysical Properties Division, National Institute of Standards and Technology, Boulder, Colorado (United States)] [Thermophysical Properties Division, National Institute of Standards and Technology, Boulder, Colorado (United States); Tew, W. L. [Sensor Science Division National Institute of Standards and Technology, Gaithersburg, Maryland (United States)] [Sensor Science Division National Institute of Standards and Technology, Gaithersburg, Maryland (United States)

    2013-09-11

    We present a detailed thermodynamic analysis of the temperature of the ice point as a function of atmospheric pressure. This analysis makes use of accurate international standards for the properties of water and ice, and of available high-accuracy data for the Henry's constants of atmospheric gases in liquid water. The result is an ice point of 273.150 019(5) K at standard atmospheric pressure, with higher ice-point temperatures (varying nearly linearly with pressure) at lower pressures. The effect of varying ambient CO{sub 2} concentration is analyzed and found to be significant in comparison to other uncertainties in the model. The thermodynamic analysis is compared with experimental measurements of the temperature difference between the ice point and the triple point of water performed at elevations ranging from 145 m to 4302 m, with atmospheric pressures from 101 kPa to 60 kPa.

  3. Changes in Antimicrobial Use Prevalence in China: Results from Five Point Prevalence Studies

    PubMed Central

    Li, Chunhui; Ren, Nan; Wen, Ximao; Zhou, Pengcheng; Huang, Xun; Gong, Ruie; Lv, Yixin; Feng, Li; Wu, Hongman; Liu, Zhenru; Fu, Chenchao; Huang, Xin; Li, Jie; Chen, Yuhua; Zeng, Cui; Zuo, Shuangyan; Xiong, Xinrui; Xu, Xiuhua; Wu, Anhua

    2013-01-01

    Objective The abuse of antimicrobials is a serious concern in China. Several measures have been taken to improve the rational use of antimicrobials, including the establishment of a national surveillance network for antimicrobial use. This study describes the dynamic changes in antimicrobial use in China between 2001 and 2010, with the scope of identifying targets to improve the prescription of antimicrobials. Methods Five point prevalence surveys were performed in hospitals across mainland China in 2001, 2003, 2005, 2008, and 2010. All inpatients who were admitted for at least 24 hours were included in the study. Details regarding antimicrobial use by these patients and the collection of samples for bacterial culture from inpatients administered therapeutic antimicrobials were recorded. Results The surveys encompassed tertiary hospitals from all 31 provinces of mainland China. Antimicrobial use prevalence decreased from 54.79% in 2001 to 46.63% in 2010. While this decline was observed in most hospital departments, antimicrobial use remained stable or increased in others. Antimicrobial use prevalence was relatively high in the Pediatrics departments and general intensive care units, whereas it was lower in the Obstetrics (Neonatal group) departments in each survey. The proportion of patients administered a single antimicrobial increased from 60.78% in 2001 to 70.16% in 2010, while the proportion of administration of two or more antimicrobials declined. The bacterial culture rate increased from 25.22% in 2003 to 34.71% in 2010. Antimicrobial use prevalence (47.96% vs 46.16%), bacterial culture rate (36.40% vs 34.19%), and the proportion of administration of a single antimicrobial (71.41% vs 67.33%) were higher in teaching hospitals than in nonteaching hospitals in 2010. Conclusion Although measures for enhancing the rational use of antimicrobials have been effective, further improvements are required. The findings from this study can promote such improvements. PMID:24376580

  4. Resistive switching properties of high crystallinity and low-resistance Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3} thin film with point-contacted Ag electrodes

    SciTech Connect

    Fujimoto, Masayuki; Koyama, Hiroshi; Nishi, Yuji; Suzuki, Toshimasa [Graduate School of Electronic Science and Technology, Shizuoka University, 3-5-1 Jyouhoku, Hamamatsu, Shizuoka 432-8561 (Japan); Taiyo Yuden Company 5607-2 Haruna-machi, Gunma, Gunma 370-3347 (Japan)

    2007-11-26

    A high-crystallinity, low-resistance Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3}(PCMO) thin film deposited by sputtering at 600 deg. C showed no resistive switching with a Pt/Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3}/Pt structure but a remarkable bipolar resistive switching with a Ag paste/Pr{sub 0.7}Ca{sub 0.3}MnO{sub 3}/Pt structure. Observed retention fatigue of the low-resistance state was almost saturated after 24 h. The resistive switching properties were characterized as point contact of Ag grains to PCMO thin film. It was also found that the interface can form interfacial trap states and resistive change active layers. This strongly suggests that the function of the Ag point contact is similar to those of the previously proposed filament path and the nanodomain switch.

  5. Comparison Between Dawson, Trick, and Litzkow Electrode and Contact Lens Electrodes Used in Clinical Electroretinography

    Microsoft Academic Search

    Manami Kuze; Yukitaka Uji

    2000-01-01

    Purpose: To determine the reliability of the Dawson, Trick, and Litzkow (DTL) electrode in electroretinographic recordings (ERG) in subjects of all ages, we evaluated ERG responses obtained with the contact lens (CL) and DTL electrodes and estimated a DTL\\/CL ratio for each sample.Methods: Seventy-nine volunteers aged 2–84 years (79 normal eyes) were recruited for the study. Electroretinographic recordings elicited by

  6. C/NOFS and the Air Force Research Laboratory's Conjugate Point Study

    NASA Astrophysics Data System (ADS)

    Gentile, L. C.; Cooke, D. L.; Huang, C.; Huang, C. Y.; Roddy, P. A.; Sutton, E. K.; Mishin, E. V.; Dao, E. V.; Martinis, C. R.; Burke, W. J.; Lai, P. C.; Pradipta, R.; Valladares, C. E.

    2014-12-01

    The Air Force Research Laboratory's Conjugate Point Study (CPS) seeks to leverage a unique opportunity with the Communication/Navigation Outage Forecasting System (C/NOFS) to make coincident measurements from the satellite and an ever-expanding network of ground stations that can be used to specify effects of atmospheric wave activity on the structure of the ionospheric F-layer. The primary objective of CPS is to integrate plasma density and drift measurements from C/NOFS with ground-based observations of disturbances within magnetic flux tubes to address outstanding scientific questions regarding relationships between plasma fluctuations in the topside ionosphere and wave-like structures generated at bottomside altitudes where satellites have little or no direct access. This project has the potential to generate new insights into the dynamics of ionosphere-neutral atmosphere interactions known to affect operational systems. This could prove particularly valuable in areas where there are no ground stations. Initial results are quite promising, but there is still much work to be done in understanding the mechanisms that couple the topside and bottomside of the ionosphere.

  7. First-principles study of point defects in chalcopyrite ZnSnP2

    NASA Astrophysics Data System (ADS)

    Kumagai, Yu; Choi, Minseok; Nose, Yoshitaro; Oba, Fumiyasu

    2014-09-01

    Chalcopyrite ZnSnP2 is an alternative photoabsorber material for solar cells because of its controllable band gap, high absorption coefficient, and earth abundant constituents. In this study we systematically investigate its native point defects including vacancies, interstitials, and antisites using first-principles calculations with the Heyd-Scuseria-Ernzerhof hybrid functional. We evaluate the defect formation energies and defect single-particle levels at the dilute limit using finite-size image-charge corrections and compare them with those reported for CuInSe2 and CuGaSe2. The most likely donors and acceptors are cation antisites, Sn-on-Zn and Zn-on-Sn, respectively. Because of their significantly low formation energies, they lead to Fermi level pinning in the band gap under any growth condition, and constrain the carrier concentration. The Sn-on-Zn antisite in the neutral charge state becomes an intrinsic DX center, a complex of the Sn interstitial and Zn vacancy, and shows a deep donor level as reported for CuGaSe2.

  8. First-principles study of native point defects in Bi2Se3

    NASA Astrophysics Data System (ADS)

    Xue, L.; Zhou, P.; Zhang, C. X.; He, C. Y.; Hao, G. L.; Sun, L. Z.; Zhong, J. X.

    2013-05-01

    Using first-principles method within the framework of the density functional theory, we study the influence of native point defect on the structural and electronic properties of Bi2Se3. Se vacancy in Bi2Se3 is a double donor, and Bi vacancy is a triple acceptor. Se antisite (SeBi) is always an active donor in the system because its donor level (?(+1/0)) enters into the conduction band. Interestingly, Bi antisite (BiSe1) in Bi2Se3 is an amphoteric dopant, acting as a donor when ?e < 0.119 eV (the material is typical p-type) and as an acceptor when ?e > 0.251 eV (the material is typical n-type). The formation energies under different growth environments (such as Bi-rich or Se-rich) indicate that under Se-rich condition, SeBi is the most stable native defect independent of electron chemical potential ?e. Under Bi-rich condition, Se vacancy is the most stable native defect except for under the growth window as ?e > 0.262 eV (the material is typical n-type) and ??Se < -0.459 eV (Bi-rich), under such growth window BiSe1 carrying one negative charge is the most stable one.

  9. The characteristic of twin-electrode TIG coupling arc pressure

    NASA Astrophysics Data System (ADS)

    Leng, Xuesong; Zhang, Guangjun; Wu, Lin

    2006-03-01

    The coupling arc of twin-electrode TIG (T-TIG) is a particular kind of arc, which is achieved through the coupling of two arcs generated from two insulated electrodes in the same welding torch. It is therefore different from the single arc of conventional TIG in its physical characteristics. This paper studies the distribution of T-TIG coupling arc pressure, and analyses the influences of welding current, arc length, the distance between electrode tips and electrode shape upon arc pressure on the basis of experiment. It is expected that the T-TIG welding method can be applied in high efficiency welding according to its low arc pressure.

  10. Multivariate meta-analysis of prognostic factor studies with multiple cut-points and/or methods of measurement.

    PubMed

    Riley, Richard D; Elia, Eleni G; Malin, Gemma; Hemming, Karla; Price, Malcolm P

    2015-07-30

    A prognostic factor is any measure that is associated with the risk of future health outcomes in those with existing disease. Often, the prognostic ability of a factor is evaluated in multiple studies. However, meta-analysis is difficult because primary studies often use different methods of measurement and/or different cut-points to dichotomise continuous factors into 'high' and 'low' groups; selective reporting is also common. We illustrate how multivariate random effects meta-analysis models can accommodate multiple prognostic effect estimates from the same study, relating to multiple cut-points and/or methods of measurement. The models account for within-study and between-study correlations, which utilises more information and reduces the impact of unreported cut-points and/or measurement methods in some studies. The applicability of the approach is improved with individual participant data and by assuming a functional relationship between prognostic effect and cut-point to reduce the number of unknown parameters. The models provide important inferential results for each cut-point and method of measurement, including the summary prognostic effect, the between-study variance and a 95% prediction interval for the prognostic effect in new populations. Two applications are presented. The first reveals that, in a multivariate meta-analysis using published results, the Apgar score is prognostic of neonatal mortality but effect sizes are smaller at most cut-points than previously thought. In the second, a multivariate meta-analysis of two methods of measurement provides weak evidence that microvessel density is prognostic of mortality in lung cancer, even when individual participant data are available so that a continuous prognostic trend is examined (rather than cut-points). © 2015 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. PMID:25924725

  11. Study of a plate-electrode XeCl laser with a pulse repetition rate up to 5 kHz

    NASA Astrophysics Data System (ADS)

    Voevodin, Denis D.; Vysotskii, Andrei V.; Lazhintsev, Boris V.; Pisetskaya, Anastasiya V.

    2012-11-01

    The results of the study of a repetitively pulsed XeCl laser with a high rate of pulse repetition and the electrode assembly based on a multi-section discharge gap with inductance-capacitance stabilisation of the discharge are presented. The multi-section discharge gap is formed by 25 pairs of anode — cathode plates. The discharge formed in the interelectrode gap had the dimensions 250 × 12 × 2 mm. The studies were performed using the HCl — Xe — Ne laser mixture at the total pressure up to 3.5 atm. The limit value of the radiation pulse repetition rate was equal to 5 kHz. The meansquare deviation of the pulse energy increased from 0.8 % to 1.6 % in the range of repetition rates from 1 to 4.5 kHz and did not exceed 2.4 % at the frequency 5 kHz. The maximal energy of the laser pulse and the efficiency coefficient were equal to 7.9 mJ and 1.6 %, respectively. The maximal power of laser radiation (31 W) was obtained at the repetition rate 5 kHz. A new technique of measuring the gas flow velocity in the interelectrode gap is proposed. The velocity of gas circulation at the maximal pressure of the mixture did not exceed 18 m s-1. Optical inhomogeneities were observed, caused by a high concentration of electrons in the discharge plasma, by the acoustic wave, arising in the discharge gap, and by the heating of the gas in the discharge.

  12. Study of a plate-electrode XeCl laser with a pulse repetition rate up to 5 kHz

    SciTech Connect

    Voevodin, Denis D; Vysotskii, Andrei V; Lazhintsev, Boris V; Pisetskaya, Anastasiya V [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

    2012-11-30

    The results of the study of a repetitively pulsed XeCl laser with a high rate of pulse repetition and the electrode assembly based on a multi-section discharge gap with inductance-capacitance stabilisation of the discharge are presented. The multi-section discharge gap is formed by 25 pairs of anode - cathode plates. The discharge formed in the interelectrode gap had the dimensions 250 Multiplication-Sign 12 Multiplication-Sign 2 mm. The studies were performed using the HCl - Xe - Ne laser mixture at the total pressure up to 3.5 atm. The limit value of the radiation pulse repetition rate was equal to 5 kHz. The meansquare deviation of the pulse energy increased from 0.8 % to 1.6 % in the range of repetition rates from 1 to 4.5 kHz and did not exceed 2.4 % at the frequency 5 kHz. The maximal energy of the laser pulse and the efficiency coefficient were equal to 7.9 mJ and 1.6 %, respectively. The maximal power of laser radiation (31 W) was obtained at the repetition rate 5 kHz. A new technique of measuring the gas flow velocity in the interelectrode gap is proposed. The velocity of gas circulation at the maximal pressure of the mixture did not exceed 18 m s{sup -1}. Optical inhomogeneities were observed, caused by a high concentration of electrons in the discharge plasma, by the acoustic wave, arising in the discharge gap, and by the heating of the gas in the discharge. (lasers)

  13. Study of characteristic point identification and preprocessing method for pulse wave signals.

    PubMed

    Sun, Wei; Tang, Ning; Jiang, Guiping

    2015-02-01

    Characteristics in pulse wave signals (PWSs) include the information of physiology and pathology of human cardiovascular system. Therefore, identification of characteristic points in PWSs plays a significant role in analyzing human cardiovascular system. Particularly, the characteristic points show personal dependent features and are easy to be affected. Acquiring a signal with high signal-to-noise ratio (SNR) and integrity is fundamentally important to precisely identify the characteristic points. Based on the mathematical morphology theory, we design a combined filter, which can effectively suppress the baseline drift and remove the high-frequency noise simultaneously, to preprocess the PWSs. Furthermore, the characteristic points of the preprocessed signal are extracted according to its position relations with the zero-crossing points of wavelet coefficients of the signal. In addition, the differential method is adopted to calibrate the position offset of characteristic points caused by the wavelet transform. We investigated four typical PWSs reconstructed by three Gaussian functions with tunable parameters. The numerical results suggested that the proposed method could identify the characteristic points of PWSs accurately. PMID:25997292

  14. In vivo impedance spectroscopy of deep brain stimulation electrodes

    NASA Astrophysics Data System (ADS)

    Lempka, Scott F.; Miocinovic, Svjetlana; Johnson, Matthew D.; Vitek, Jerrold L.; McIntyre, Cameron C.

    2009-08-01

    Deep brain stimulation (DBS) represents a powerful clinical technology, but a systematic characterization of the electrical interactions between the electrode and the brain is lacking. The goal of this study was to examine the in vivo changes in the DBS electrode impedance that occur after implantation and during clinically relevant stimulation. Clinical DBS devices typically apply high-frequency voltage-controlled stimulation, and as a result, the injected current is directly regulated by the impedance of the electrode-tissue interface. We monitored the impedance of scaled-down clinical DBS electrodes implanted in the thalamus and subthalamic nucleus of a rhesus macaque using electrode impedance spectroscopy (EIS) measurements ranging from 0.5 Hz to 10 kHz. To further characterize our measurements, equivalent circuit models of the electrode-tissue interface were used to quantify the role of various interface components in producing the observed electrode impedance. Following implantation, the DBS electrode impedance increased and a semicircular arc was observed in the high-frequency range of the EIS measurements, commonly referred to as the tissue component of the impedance. Clinically relevant stimulation produced a rapid decrease in electrode impedance with extensive changes in the tissue component. These post-operative and stimulation-induced changes in impedance could play an important role in the observed functional effects of voltage-controlled DBS and should be considered during clinical stimulation parameter selection and chronic animal research studies.

  15. A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme

    Microsoft Academic Search

    K. K. Tse; Billy M. T. Ho; Henry Shu-Hung Chung; S. Y. Ron Hui

    2004-01-01

    A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc\\/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of

  16. Warm Humid Climate: Methodology to Study Air Temperature Distribution: Mobile Phones Base Stations as Viable Alternative for Fixed Points

    E-print Network

    Araujo, V.; Costa, A.; Labaki, L.

    2006-01-01

    WARM-HUMID CLIMATE: METHODOLOGY TO STUDY AIR TEMPERATURE DISTRIBUTION: MOBILE PHONES BASE STATIONS AS VIABLE ALTERNATIVE FOR FIXED POINTS Angelina Dias Leão Costa (1); Lucila Labaki (2); Virgínia Araújo (3) (1) and (2) School of Civil..., in February 2006, are presented. The fixed points were defined using 20 mobile phone base stations in the city of Natal/RN, distributed along the four administrative zones. Measurements were carried out for seven days, registering air temperature...

  17. Studies on the synthesis and properties of terpene-phenol-aldehyde resin with a high softening point

    Microsoft Academic Search

    Shi-Fa Wang; Takeshi Furuno; Zhi Cheng

    2000-01-01

    Synthesis conditions of terpene-phenol-aldehyde resin with a high softening point were studied based on the reactions among?-pinene, phenol, and formaldehyde. A suitable catalyst system and the best processing conditions were obtained by laboratory\\u000a experiments. The influence of the raw materials ratios, reaction temperature, reaction time, and catalyst dose on the softening\\u000a point, yield, and color of the synthesized resin was

  18. Controlled deposition of nanotubes on opposing electrodes

    NASA Astrophysics Data System (ADS)

    Lu, Shaoning; Chung, Jaehyun; Ruoff, Rodney S.

    2005-09-01

    We report a method of depositing individual 'templated carbon nanotubes' (T-CNTs) on opposing electrodes so that they are suspended across 100 µm deep trenches, and in separate experiments across low profile (70 nm thick) opposing electrodes. The geometry of the electrodes with deep trenches was chosen to be essentially identical to that in a micro-electromechanical system (MEMS) testing stage used for mechanical loading of nanostructures. An electric field was used to attract the T-CNTs dispersed in a solvent and critical point drying was employed to protect them from breaking or deforming. The real-time potential change in the circuit was monitored as a means of characterizing the deposition of an individual T-CNT across this deep trench. For the case of sequential deposition on electrodes that are 70 nm above the substrate surface, a method was developed for counting the number of sequentially deposited T-CNTs. Simultaneous video recording of the deposition of T-CNTs confirmed the measured real-time potential changes for both cases. It was found that the resistance of the circuit changed as each new T-CNT was deposited for the sequential deposition; up to five T-CNTs were sequentially detected. This approach allows for controlled deposition of one-dimensional nanostructures for their potential use in NEMS devices, and may be useful for large-scale integration.

  19. Prevalence of systemic inflammatory response syndrome (SIRS) in hospitalized children: a point prevalence study

    PubMed Central

    Pavare, Jana; Grope, Ilze; Gardovska, Dace

    2009-01-01

    Background In accordance with the 1st International pediatric sepsis consensus conference, where sepsis was defined as SIRS associated with suspected or proven infection, we have identified the need to assess the prevalence of SIRS and sepsis in children with abnormal temperatures hospitalized in The Children's Clinical University Hospital in Latvia. Methods A descriptive prospective point prevalence study (using two time periods, each 24 h, randomly chosen) was conducted on all children (n = 943) treated in the hospital. All children with abnormal temperatures – fever or hypothermia (n = 92) – were included in the study. Questionnaires evaluating age-specific SIRS criteria were completed. The prevalence of SIRS was detected with 95% CI. Results Out of a total of 943 patients treated in the hospital, 10% (n = 92) had abnormal temperatures. In all these cases the abnormal temperature was a fever; hypothermia was not established in any patient. Of the children with fever, 72% (n = 66) had SIRS. Of the SIRS patients, 8% (n = 5) developed sepsis, 5% (n = 3) severe sepsis and 2% (n = 1) septic shock. Seventy-six percent (n = 50) of the SIRS patients had fever in combination with respiratory rate >2 SD above normal for age; 50% (n = 33) had fever with abnormal leukocyte count; 15% (n = 10) had fever with tachycardia >2 SD above normal for age. Most of the SIRS patients (39%, n = 25) were aged 2–5 years. Twenty-one percent (n = 14) of the children with SIRS and 50% (n = 2) of those with severe sepsis and septic shock had an underlying disease. In no case was SIRS and sepsis recognized by doctors and the diagnoses were not recorded on the patients' cards. Conclusion Our results would indicate a high risk for sepsis development in children with SIRS. Early SIRS diagnosis and awareness of risk of developing sepsis could change the medical approach to the patient in everyday clinical practice, eventually leading to early, goal-directed therapy for sepsis. PMID:19344519

  20. Synthesis, characterization and application of electrode materials

    SciTech Connect

    He, L.

    1995-07-07

    It has been known that significant advances in electrochemistry really depend on improvements in the sensitivity, selectivity, convenience, and/or economy of working electrodes, especially through the development of new working electrode materials. The advancement of solid state chemistry and materials science makes it possible to provide the materials which may be required as satisfactory electrode materials. The combination of solid state techniques with electrochemistry expands the applications of solid state materials and leads to the improvement of electrocatalysis. The study of Ru-Ti{sub 4}O{sub 7} and Pt-Ti{sub 4}O{sub 7} microelectrode arrays as introduced in paper 1 and paper 4, respectively, focuses on their synthesis and characterization. The synthesis is described by high temperature techniques for Ru or Pt microelectrode arrays within a conductive Ti{sub 4}O{sub 7} ceramic matrix. The characterization is based on the data obtained by x-ray diffractometry, scanning electron microscopy, voltammetry and amperometry. These microelectrode arrays show significant enhancement in current densities in comparison to solid Ru and Pt electrodes. Electrocatalysis at pyrochlore oxide Bi{sub 2}Ru{sub 2}O{sub 7.3} and Bi{sub 2}Ir{sub 2}O{sub 7} electrodes are described in paper 2 and paper 3, respectively. Details are reported for the synthesis and characterization of composite Bi{sub 2}Ru{sub 2}O{sub 7.3} electrodes. Voltammetric data are examined for evidence that oxidation can occur with transfer of oxygen to the oxidation products in the potential region corresponding to anodic discharge of H{sub 2}O with simultaneous evolution of O{sub 2}. Paper 3 includes electrocatalytic activities of composite Bi{sub 2}Ir{sub 2}O{sub 7} disk electrodes for the oxidation of I{sup -} and the reduction of IO{sub 3}{sup -}.

  1. First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

    NASA Astrophysics Data System (ADS)

    Piochaud, J. B.; Klaver, T. P. C.; Adjanor, G.; Olsson, P.; Domain, C.; Becquart, C. S.

    2014-01-01

    The influence of the local environment on vacancy and self-interstitial formation energies has been investigated in a face-centered-cubic (fcc) Fe-10Ni-20Cr model alloy by analyzing an extensive set of first-principle calculations based on density functional theory. Chemical disorder has been considered by designing special quasirandom structures and four different collinear magnetic structures have been investigated in order to determine a relevant reference state to perform point defect calculations at 0 K. Two different convergence methods have also been used to characterize the importance of the method on the results. Although our fcc Fe-10Ni-20Cr would be better represented in terms of applications by the paramagnetic state, we found that the antiferromagnetic single-layer magnetic structure was the most stable at 0 K and we chose it as a reference state to determine the point defect properties. Point defects have been introduced in this reference state, i.e., vacancies and Fe-Fe, Fe-Ni, Fe-Cr, Cr-Cr, Ni-Ni, and Ni-Cr dumbbell interstitials oriented either parallel or perpendicular to the single layer antiferromagnetic planes. Each point defect studied was introduced at different lattice sites to consider a sufficient variety of local environments and analyze its influence on the formation energy values. We have estimated the point defect formation energies with linear regressions using variables which describe the local environment surrounding the point defects. The number and the position of Ni and Cr first nearest neighbors to the point defects were found to drive the evolution of the formation energies. In particular, Ni is found to decrease and Cr to increase the vacancy formation energy of the model alloy, while the opposite trends are found for the dumbbell interstitials. This study suggested that, to a first approximation, the first nearest atoms to point defects can provide reliable estimates of point defect formation energies.

  2. A study on the effect of inlet turbulence on gas mixing for single point aerosol sampling 

    E-print Network

    Mohan, Anand

    2001-01-01

    The efficiency of certain mixing elements in achieving conditions suited for single point sampling is evaluated. Experimental measurements of velocity and tracer gas concentration are taken to determine the same. Readings are taken under conditions...

  3. An Initial Study of Visuohaptic Simulation of Point-charge Interactions Jaeyoung Park1

    E-print Network

    Tan, Hong Z.

    test showed that both groups benefited from the computer simulation. There were no statistical (Science, Technology, Engineering and Mathematics) topics, with particular emphasis on physics concepts related to the learning of nanotechnology at the undergraduate level. Visuohaptic simulations of point

  4. Study of preparation of ice mantles of triple point of water cells

    Microsoft Academic Search

    K. Kodaira

    2002-01-01

    Ice mantles of triple point of water cells were prepared by a new technique using a remodeled refrigerator with a circulation pump. The work was completed within approximately 10 minutes. No cracks were formed in ice mantles during the preparation.

  5. Study on the Generation of Armhole Curve Based on 3D Point-Cloud Data

    Microsoft Academic Search

    Xu Xiao-hui; Gu Bing-fei; Su Jun-qiang; Liu Guo-lian

    \\u000a In this paper, non-contact anthropometry is done on the female bodies, and the 3D point-cloud data is got by 3D scanner, and\\u000a then the collar curve of female tight prototype is generation by data processing on point-cloud figures using reverse engineering\\u000a software. The armhole curve can be divided into the front and back armhole curve, this paper mainly on the

  6. Ab initio study of boron in ?-iron: Migration barriers and interaction with point defects

    NASA Astrophysics Data System (ADS)

    Bialon, A. F.; Hammerschmidt, T.; Drautz, R.

    2013-03-01

    Boron is a common alloying element in modern steels with a significant influence on the mechanical properties already at concentrations of only a few parts per million. The effect of boron depends on its distribution in the microstructure. Here, we characterize the elemental factors that determine the boron distribution in ?-iron by density functional theory calculations. Boron as point defect has been considered in substitutional and interstitial sites. The calculated migration barriers for the substitutional and interstitial mechanisms show the first nearest-neighbor hops being preferred over second nearest-neighbor hops. A dissociative mechanism shows boron migrating via an interstitial mechanism to be likely trapped by vacancies. In order to characterize the interaction with other point defects, we determined the distance-dependent interaction energy of a boron defect with a vacancy, a second boron, and with hydrogen, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, and sulfur atoms. We find that substitutional boron binds strongly to interstitial point defects with dumbbell formation and weaker to substitutional point defects. Interstitial boron tends to repel substitutional and interstitial point defects. We find a similarity of substitutional boron and vacancies regarding their influence on elastic properties and their interaction with point defects in ?-iron.

  7. Composite electrodes for lithium batteries.

    SciTech Connect

    Hackney, S. A.; Johnson, C. S.; Kahaian, A. J.; Kepler, K. D.; Shao-Horn, Y.; Thackeray, M. M.; Vaughey, J. T.

    1999-02-03

    The stability of composite positive and negative electrodes for rechargeable lithium batteries is discussed. Positive electrodes with spinel-type structures that are derived from orthorhombic-LiMnO{sub 2} and layered-MnO{sub 2} are significantly more stable than standard spinel Li[Mn{sub 2}]O{sub 4} electrodes when cycled electrochemically over both the 4-V and 3-V plateaus in lithium cells. Transmission electron microscope data of cycled electrodes have indicated that a composite domain structure accounts for this greater electrochemical stability. The performance of composite Cu{sub x}Sn materials as alternative negative electrodes to amorphous SnO{sub x} electrodes for lithium-ion batteries is discussed in terms of the importance of the concentration of the electrochemically inactive copper component in the electrode.

  8. Transparent electrode for optical switch

    DOEpatents

    Goldhar, Julius (San Ramon, CA); Henesian, Mark A. (Livermore, CA)

    1986-01-01

    A low pressure gas electrode utilizing ionized gas in a glow discharge regime forms a transparent electrode for electro-optical switches. The transparent electrode comprises a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the electrode is a transparent electrode. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. The plasma can be created either by the main high voltage pulser used to charge up the crystal or by auxiliary discharges or external sources of ionization. A typical configuration utilizes 10 torr argon in the discharge region adjacent to each crystal face.

  9. In-situ STM study of the initial stages of corrosion of Cu(100) electrodes in sulfuric and hydrochloric acid solution

    NASA Astrophysics Data System (ADS)

    Vogt, M. R.; Lachenwitzer, A.; Magnussen, O. M.; Behm, R. J.

    1998-03-01

    An in-situ scanning tunneling microscopy (STM) study of Cu(100) electrode surfaces in sulfuric and hydrochloric acid solutions in the potential range -0.6 to -0.1 V versus {Ag}/{AgCl} (KCl sat) is presented, revealing the surface structure and dynamics in the double-layer region and providing detailed structural data on the initial stages of anodic Cu dissolution. After preparation by electropolishing in phosphoric acid, large, atomically flat terraces, separated by frizzy, almost randomly oriented steps are observed in H 2SO 4 solution in the double-layer region. Atomic-scale observations reveal a (1 × 1) surface lattice in the entire potential range, even during Cu dissolution. In HCl solution this surface morphology and atomic structure are visible only at potentials negative of -0.4 V, whereas above -0.4 V a c(2 × 2) Cl adlattice is observed, together with strong faceting of the steps along the [010] and [001] directions. At low etch rates, the dissolution of clean Cu surfaces proceeds solely by step-flow etching in both electrolytes. In H 2SO 4 solution the dissolution process is accompanied by strong fluctuations in the step positions and by an increase in step roughness. In HCl solution the [010]- and [001]-oriented steps are stabilized by the c(2 × 2) Cl adlayer and Cu dissolution proceeds by the subsequent removal of complete atomic rows consisting of primitive (? a × ?2)R45° units of the (2 × 2) adlattice along these steps. A mechanism is proposed where the dissolution of Cu atoms occurs at two slightly different, structurally well-defined kink sites in the c(2 × 2) lattice, which rapidly travel along the step edge (i.e. along [010] or [001]) during the dissolution process. Adsorbed impurities can locally pin Cu terraces, resulting in the formation of highly anisotropic islands, peninsulas and troughs, or induce the formation of monoatomic etch pits.

  10. Long life reference electrode

    DOEpatents

    Yonco, R.M.; Nagy, Z.

    1989-04-04

    An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservoir and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved. 2 figs.

  11. Long life reference electrode

    DOEpatents

    Yonco, Robert M. (LaGrange, IL); Nagy, Zoltan (Woodridge, IL)

    1989-01-01

    An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservior and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved.

  12. Inert electrode connection

    DOEpatents

    Weyand, J.D.; Woods, R.W.; DeYoung, D.H.; Ray, S.P.

    1985-02-19

    An inert electrode connection is disclosed wherein a layer of inert electrode material is bonded to a layer of conductive material by providing at least one intermediate layer of material therebetween comprising a predetermined ratio of inert material to conductive material. In a preferred embodiment, the connection is formed by placing in a die a layer of powdered inert material, at least one layer of a mixture of powdered inert material and conductive material, and a layer of powdered conductive material. The connection is then formed by pressing the material at 15,000--20,000 psi to form a powder compact and then densifying the powder compact in an inert or reducing atmosphere at a temperature of 1,200--1,500 C. 5 figs.

  13. Flood Management and Protection from the Social Point of View: Case Study from Ukraine

    NASA Astrophysics Data System (ADS)

    Manukalo, V.; Gerasymenko, H.

    2012-12-01

    Defining Issue According to the statistics presented by the Ministry of Emergencies of Ukraine, river floods have imposed the most severe damages to the sectors of economy and the human communities in Ukraine. But, an adaptability and a vulnerability of Ukrainian society to floods are still poorly understood. Results Presentation In the response to increasing flood losses in the country between 1998 and 2008, the State Hydrometeorological Service of Ukraine, which is subordinate to the Ministry of Emergencies, in the cooperation with the National Academy of Sciences of Ukraine have carried out the research study focusing on public views on the problem of river floods for Ukraine. Aims of this study were: a) exploring the main sources of information on water-related hazards and the level of knowledge useful in a flood crisis situation in different groups of peoples; b) learning what the various population groups think of the most significant causes and consequences of flood damages and the role of various central/governmental/ and local authorities in an elaboration and implementation of mitigation measures. Public attitudes towards various prevention and mitigation strategies, as well as sources of emerging conflict were also revealed. The results of study have given a possibility to compare points of view of population groups which: a) living in the low- and high- flood risk areas; b) living in the urban and rural areas; c) having the different levels of education. The responses from 2550 residents have been analyzed and summarized. Among the most important findings of this study can be indicated following: a) on the one hand, the level of knowledge of some aspects of flood problem (impact of climate variation and change, adaptation measures) of the general public should be improved, on the other hand, the most of peoples understand that floods are the significant economical and ecological problem; b) views of the public on the problem differ very much with regard to their regions of residence (low- or high- flood risk areas, cities or villages), education level; c) a lot of peoples don't know distribution of duties between governmental bodies on central and local levels in the field of flood management and protection; d) the most of peoples don't know which Ukrainian governmental bodies are responsible for the elaboration of National adaptation strategy to the expected climate change; e) many recipient estimate as inefficient activities of Ukrainian authorities on local, national and international levels as well as a public participation in the flood management and protection policy. The results of this study have been rather unexpected for Ukrainian central and local governmental bodies responsible for flood management and protection policies. This underlines the importance of having the alternative flood risk management and protection policies studied not only from aspects of technical and economic rational, but also from that of social acceptability, before any decision is made. Practical Application Results of study have been used in preparation of: a) the State Program on the protection against floods in the Dniester, Prut and Siret river basins; b) of the "National Action Plan for Adaptation to Climate Change for period 2011-2015".

  14. Study on light scattering of rf sputtered ZnO:Al thin films as a front electrode of amorphous silicon thin film solar cells

    Microsoft Academic Search

    Jun-Sik Cho; Young Jin Kim; Jeong Chul Lee; Sang Hyun Park; Ji Hoon Jang; Jinsoo Song; Kyung Hoon Yoon

    2009-01-01

    Al-doped ZnO thin films as a front electrode of silicon pin solar cells were prepared on the glass substrates by rf magnetron sputtering in which working pressure and substrate temperature were controlled precisely. After film deposition, the films were etched by dilute acid solution to obtain the textured surfaces. Material properties of the deposited films were investigated by various analytical

  15. Study of electrodeposited nickel-molybdenum, nickel-tungsten, cobalt-molybdenum, and cobalt-tungsten as hydrogen electrodes in alkaline water electrolysis

    SciTech Connect

    Fan, C.; Piron, D.L.; Sleb, A.; Paradis, P. (Ecole Polytechnique de Montreal, Quebec (Canada). Dept. de Metallurgie et de Genie des Materiaux)

    1994-02-01

    Electrodeposited nickel-molybdenum, nickel-tungsten, cobalt-molybdenum, and cobalt-tungsten were characterized for the hydrogen evolution reaction (HER) in the electrolysis of 30 w/o KOH alkaline water at 25 C. The rate-determining step (rds) of the HER was suggested based on the Tafel slope of polarization and the capacitance of electrode-solution interface determined by ac impedance measurement. The HER on the nickel- and cobalt-based codeposits was enhanced significantly compared with that o the electrolytic nickel and cobalt with comparable deposit loadings. The decrease in the HER overpotential was more pronounced on the molybdenum-containing codeposits, particularly on cobalt-molybdenum which also showed a high stability. The enhancement of the HER was attributed to both the synergetic composition and the increased active surface of the codeposits. The real electrocatalytic activity of te electrodes and the effect of their and the increased active surface of the codeposits. The real electrocatalytic activity of the electrodes and the effect of their surface increase were distinguished quantitatively. The linear relations between HER overpotential and surface roughness factor of the electrodes on a Y-log(X) plot were obtained experimentally and interpreted based on the Tafel law.

  16. A Study on a Lightning-Surge Analysis Composite Model of a Reinforced Concrete Pole and a Grounding Electrode in Power Distribution Lines

    Microsoft Academic Search

    Teru Miyazaki; Shigemitsu Okabe; Kenjirou Mori; Kiyoshi Aiba; Takao Hirai; Jun Yoshinaga; Shozo Sekioka

    2006-01-01

    It has been well known for many years that grounding resistance has a current-dependent characteristic due to soil ionization. Moreover reinforced concrete poles should be treated as a kind of grounding electrode against lightning strokes. However, these characteristics were seldom taken into account for lightning-protection designs. If these characteristics are represented in EMTP models for lightning protection designs, the rationalization

  17. In-situ infrared study of the oxidation of SO2 on platinum electrodes. Technical report No. 93, September 1987July 1988

    Microsoft Academic Search

    C. Koreniewski; W. McKenna; S. Pons

    1988-01-01

    The oxidation of sulfur dioxide on metal electrodes is of interest for its application in a variety of industrial processes, particularly in operations involving degradation of automobile emissions, production of energy, and winning of sulfide ores. The oxidation of sulfur dioxide by electrochemical methods is a complex process in which intermediates and products are formed that strongly adsorb on the

  18. Ice electrode electrolytic cell

    DOEpatents

    Glenn, David F. (Idaho Falls, ID); Suciu, Dan F. (Idaho Falls, ID); Harris, Taryl L. (Idaho Falls, ID); Ingram, Jani C. (Idaho Falls, ID)

    1993-01-01

    This invention relates to a method and apparatus for removing heavy metals from waste water, soils, or process streams by electrolytic cell means. The method includes cooling a cell cathode to form an ice layer over the cathode and then applying an electric current to deposit a layer of the heavy metal over the ice. The metal is then easily removed after melting the ice. In a second embodiment, the same ice-covered electrode can be employed to form powdered metals.

  19. Nickel anode electrode

    DOEpatents

    Singh, Prabhakar (Bethel, CT); Benedict, Mark (Monroe, CT)

    1987-01-01

    A nickel anode electrode fabricated by oxidizing a nickel alloying material to produce a material whose exterior contains nickel oxide and whose interior contains nickel metal throughout which is dispersed the oxide of the alloying material and by reducing and sintering the oxidized material to form a product having a nickel metal exterior and an interior containing nickel metal throughout which is dispersed the oxide of the alloying material.

  20. Membrane reference electrode

    DOEpatents

    Redey, L.; Bloom, I.D.

    1988-01-21

    A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

  1. Shielded capacitive electrode

    DOEpatents

    Kireeff Covo, Michel

    2013-07-09

    A device is described, which is sensitive to electric fields, but is insensitive to stray electrons/ions and unlike a bare, exposed conductor, it measures capacitively coupled current while rejecting currents due to charged particle collected or emitted. A charged particle beam establishes an electric field inside the beam pipe. A grounded metallic box with an aperture is placed in a drift region near the beam tube radius. The produced electric field that crosses the aperture generates a fringe field that terminates in the back surface of the front of the box and induces an image charge. An electrode is placed inside the grounded box and near the aperture, where the fringe fields terminate, in order to couple with the beam. The electrode is negatively biased to suppress collection of electrons and is protected behind the front of the box, so the beam halo cannot directly hit the electrode and produce electrons. The measured signal shows the net potential (positive ion beam plus negative electrons) variation with time, as it shall be observed from the beam pipe wall.

  2. Flexible transparent electrode

    NASA Astrophysics Data System (ADS)

    Demiryont, Hulya; Shannon, Kenneth C., III; Moorehead, David; Bratcher, Matthew

    2011-06-01

    This paper presents the properties of the EclipseTECTM transparent conductor. EclipseTECTM is a room temperature deposited nanostructured thin film coating system comprised of metal-oxide semiconductor elements. The system possesses metal-like conductivity and glass-like transparency in the visible region. These highly conductive TEC films exhibit high shielding efficiency (35dB at 1 to 100GHz). EclipseTECTM can be deposited on rigid or flexible substrates. For example, EclipseTECTM deposited on polyethylene terephthalate (PET) is extremely flexible that can be rolled around a 9mm diameter cylinder with little or no reduction in electrical conductivity and that can assume pre-extension states after an applied stress is relieved. The TEC is colorless and has been tailored to have high visible transmittance which matches the eye sensitivity curve and allows the viewing of true background colors through the coating. EclipseTECTM is flexible, durable and can be tailored at the interface for applications such as electron- or hole-injecting OLED electrodes as well as electrodes in flexible displays. Tunable work function and optical design flexibility also make EclipseTECTM well-suited as a candidate for grid electrode replacement in next-generation photovoltaic cells.

  3. Carbon cloth supported electrode

    DOEpatents

    Lu, Wen-Tong P. (Upper St. Clair, PA); Ammon, Robert L. (Baldwin both of, PA)

    1982-01-01

    A flow-by anode is disclosed made by preparing a liquid suspension of about to about 18% by weight solids, the solids comprising about 3.5 to about 8% of a powdered catalyst of platinum, palladium, palladium oxide, or mixtures thereof; about 60 to about 76% carbon powder (support) having a particle size less than about 20 m.mu.m and about 20 to about 33% of an inert binder having a particle size of less than about 500 m.mu.m. A sufficient amount of the suspension is poured over a carbon cloth to form a layer of solids about 0.01 to about 0.05 cm thick on the carbon cloth when the electrode is completed. A vacuum was applied to the opposite side of the carbon cloth to remove the liquid and the catalyst layer/cloth assembly is dried and compressed at about 10 to about 50 MPa's. The binder is then sintered in an inert atmosphere to complete the electrode. The electrode is used for the oxidation of sulfur dioxide in a sulfur based hybrid cycle for the decomposition of water.

  4. Compact Electrochemical System Using On-Chip Sensor Electrodes and Integrated Devices

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tomoyuki; Ikeda, Takaaki; Ishida, Makoto; Sawada, Kazuaki

    2011-04-01

    We report a compact electrochemical sensing system to implement cyclic voltammetry. This type of sensor needs a working electrode, counter electrode, and reference electrode, all of which were integrated on a single chip. The electrochemical system also needs a potentiostat and an input voltage-generating circuit, which were developed using on-chip active devices and a few discrete passive components. This is the first sensor system incorporating electrode-side input voltage generation for electrochemical measurements using an on-chip operational amplifier, which replaces a bulky external voltage controller. A continuous cyclic voltammetry measurement was conducted with a well-studied ferricyanide solution to demonstrate the operation of the intelligent sensor chip. A clear peak was observed and linearity to the target chemical concentration was obtained between the peak height and concentration of the ferricyanide solution. With potential for mass production and small size, this sensor chip could be the best candidate to realize point-of-care testing. This sensor chip is a milestone of a fully integrated electrochemical sensor chip.

  5. Chemical and microstructural transformations in lithium iron phosphate battery electrodes following pulsed laser exposure

    NASA Astrophysics Data System (ADS)

    Lutey, Adrian H. A.; Fiorini, Maurizio; Fortunato, Alessandro; Ascari, Alessandro

    2014-12-01

    Multi-layer lithium iron phosphate (LFP) battery electrodes are exposed to nanosecond pulsed laser radiation of wavelength 1064 nm. Test parameters are chosen to achieve characteristic interaction types ranging from partial incision of the active coating layers only to complete penetration of the electrodes with high visual cut quality. Raman spectroscopy is performed on unexposed regions and at points approaching each incision, highlighting changes in chemical composition and microstructure in the heat affected zone (HAZ). Thermogravimetric analysis is performed on the unexposed electrode active materials to distinguish the development of compositional changes under conditions of slow heating below the melting and sublimation temperatures. A brief theoretical description of the physical phenomena taking place during laser exposure is provided in terms of direct ablation during each laser pulse and vaporization or thermal degradation due to conductive heat transfer on a much longer time-scale, with characteristics of the HAZ reported in terms of these changes. For all laser exposures carried out in the study, chemical and microstructural changes are limited to the visible HAZ. Some degree of oxidation and LFP olivine phase degradation is observed in the cathode, while the polycrystalline graphite structure becomes less ordered in the anode. Where complete penetration is achieved, melting of the cathode active layer and combustion of the anode active layer take place near the cut edge due to thermal conduction from the metallic conductive layers. The presented results provide insight into the effects of laser processing on LFP electrode integrity.

  6. Mechanism of the electrochemical dehydrogenation of hexahydropyrimidine on a boron-doped diamond electrode

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Simakova, A. P.; Kuznetsov, V. V.; Makhova, N. N.; Vedenyapin, A. A.

    2015-04-01

    The electrochemical behavior of hexahydropyrimidine (HHP) on a boron-doped diamond electrode was studied. The obtained data were compared with the results of previous studies on the electrooxidation of HHP on platinum and gold electrodes. It was shown that different products can be obtained from one organic substance using different electrode materials.

  7. Modeling of dielectrophoretic force for moving dielectrophoresis electrodes

    Microsoft Academic Search

    Chin Hock Kua; Yee Cheong Lam; Chun Yang; Kamal Youcef-Toumi; Isabel Rodriguez

    2008-01-01

    Moving dielectrophoresis has been recently introduced by the authors to fractionate and transport cells. This technique allows cells to be fractionated as in the conventional dielectrophoresis technique, but transported like in the traveling wave dielectrophoresis technique. This technique utilizes a series of finite width top electrode, and a common infinite width bottom electrode. This study presents analytical solutions for the

  8. Thermodynamic analysis and experimental study of the effect of atmospheric pressure on the ice point

    NASA Astrophysics Data System (ADS)

    Harvey, A. H.; McLinden, M. O.; Tew, W. L.

    2013-09-01

    We present a detailed thermodynamic analysis of the temperature of the ice point as a function of atmospheric pressure. This analysis makes use of accurate international standards for the properties of water and ice, and of available high-accuracy data for the Henry's constants of atmospheric gases in liquid water. The result is an ice point of 273.150 019(5) K at standard atmospheric pressure, with higher ice-point temperatures (varying nearly linearly with pressure) at lower pressures. The effect of varying ambient CO2 concentration is analyzed and found to be significant in comparison to other uncertainties in the model. The thermodynamic analysis is compared with experimental measurements of the temperature difference between the ice point and the triple point of water performed at elevations ranging from 145 m to 4302 m, with atmospheric pressures from 101 kPa to 60 kPa. At the request of the authors and the Proceedings Editor the above article has been replaced with a corrected version. The original PDF file supplied to AIP Publishing contained several equations with incorrect/missing characters resulting from processes used to create the PDF file. The article has been replaced and the equations now display correctly.

  9. Study on Spot5 remote sensing imagery automatic registration methods based on texture feature points

    NASA Astrophysics Data System (ADS)

    Chu, Chengzan; Yan, Dongmei; Wang, Chao; Zhang, Hong

    2008-11-01

    Due to the problem of lower-efficiency and subjective error generated by manual operation in the process of Spot5 remote sensing satellite imagery matching, a new efficient automatic registration scheme based on imagery characteristic points was proposed. Firstly, the preprocessed 1A level multispectral imagery and panchromatic imagery were registered coarsely based on affine transformation in this workflow using the ephemeris in metadata files. Secondly, the grid constrained feature points were extracted from the two images by improved Forstner operator, and tie-points pairs were obtained by a coarse-to-fine matching using Euclid distance and correlation. Finally, error pairs were eliminated by least median of squares (LSM). After getting enough control point pairs which were high-precision matched and distributed evenly, coarse-registered multispectral imagery was rectified in local small region based on Delaunay triangulation network. Experiments were performed on many volume images, and the results show that the root mean square errors (RMSE) of the check points are less than 0.5 pixels.

  10. Toxicogenomic studies of the rat brain at an early time point following acute sarin exposure.

    PubMed

    Damodaran, Tirupapuliyur V; Greenfield, Stephen T; Patel, Anand G; Dressman, Holly K; Lin, Siomon K; Abou-Donia, Mohamed B

    2006-03-01

    We have studied sarin-induced global gene expression patterns at an early time point (2 h: 0.5 x LD50) using Affymetrix Rat Neurobiology U34 chips and male Sprague-Dawley rats. A total of 46 genes showed statistically significant alterations from control levels. Three gene categories contained more of the altered genes than any other groups: ion channel (8 genes) and calcium channel and binding proteins (6 genes). Alterations were also found in the following gene groups: ATPases and ATP-based transporters (4), growth factors (4), G-protein-coupled receptor pathway-related molecules (3), neurotransmission and neurotransmitter transporters (3), cytoskeletal and cell adhesion molecules (2), hormones (2), mitochondria-associated proteins (2), myelin proteins (2), stress-activated molecules (2), cytokine (1), caspase (1), GABAnergic (1), glutamergic (1), immediate early gene (1), prostaglandin (1), transcription factor (1), and tyrosine phosphorylation molecule (1). Persistent alteration of the following genes also were noted: Arrb1, CaMKIIa, CaMKIId, Clcn5, IL-10, c-Kit, and Plp1, suggesting altered GPCR, kinase, channel, and cytokine pathways. Selected genes from the microarray data were further validated using relative RT-PCR. Some of those genes (GFAP, NF-H, CaMKIIa, Calm, and MBP) have been shown by other laboratories and ours, to be involved in the pathogenesis of sarin-induced pathology and organophosphate-induced delayed neurotoxicity (OPIDN). Induction of both proapoptotic (Bcl2l11, Casp6) and antiapoptotic (Bcl-X) genes, besides suppression of p21, suggest complex cell death/protection-related mechanisms operating early on. Principal component analysis (PCA) of the expression data confirmed that the changes in gene expression are a function of sarin exposure, since the control and treatment groups separated clearly. Our model (based on current and previous studies) indicates that both degenerative and regenerative pathways are activated early and contribute to the level of neurodegeneration at a later time, leading to neuro-pathological alterations. PMID:16733813

  11. Problems associated with the Z-fold region of defibrillation electrodes.

    PubMed

    Cleland, M J; Maloney, J P; Rowe, B H

    1998-01-01

    To examine performance failures of automatic external defibrillator (AED) self-adhesive electrodes, a retrospective analysis of patient reports and electrodes was conducted in a suburban emergency medical service (EMS) system. In all cases, only records from out-of-hospital cardiac arrests (OHCA) were used if the EMS was activated and an AED was used. Electrode failures were assessed as follows: 1) EMS staff returned defibrillation electrodes when they were unable to resolve repeated "Check Electrode" messages, and 2) an audit of selected records was used to determine the frequency of electrode problems during calls. Of 302 OHCA calls during the study period, 22 (7%) resulted in returned electrodes. Defects (cracks or faults) in the internal conductor were present in 37 (86%) of the 43 returned electrodes; 2 (5%) possessed dehydrated conductive gel, and in 4 (9%) electrodes no faults could be identified. Of the 21 complete sets of defective electrodes, 16 (76%) had faults in both electrodes. Chart review revealed at least one "check electrode" message occurring in 21 (60%) of 35 OHCA reports. The electrode checks were present for a total of over 83 min, representing 11% of the call times. Paramedics were required to change electrodes in 9 (26%) of the 35 cases, resolving the malfunction in all instances. Electrode malfunction appears to be a common prehospital problem; the conductor is responsible for the majority of electrode problems and is probably subjected to the most stress during storage and handling. More reliable, durable defibrillation electrodes are required for OHCA treatment. Other strategies for electrode storage and quality control are also discussed. PMID:9543394

  12. Status of the BATSE Enhanced Earth Occultation Analysis Package for Studying Point Sources

    NASA Technical Reports Server (NTRS)

    Skelton, R. T.; Ling, J. C.; Radocinski, R.; Wheaton, Wm. A.

    1993-01-01

    The compton Gama-Ray Observatory's Burst and Transient Source Experiment (BATSE) has a powerful capability to provide nearly uninterrupted monitoring in the 25keV--2MeV range of cosmic point sources using occultation by the Earth.

  13. First-principles study of native point defects in ZnO

    Microsoft Academic Search

    A. F. Kohan; G. Ceder; D. Morgan; Chris G. Van de Walle

    2000-01-01

    The characterization of native point defects in ZnO is still a question of debate. For example, experimental evidence for ZnO with an excess of Zn is inconclusive as to whether the dominant defects are metal interstitials or oxygen vacancies. This information is essential to understand the behavior of the material and to tailor its numerous technological applications. We use the

  14. Using Modification Indexes to Detect Turning Points in Longitudinal Data: A Monte Carlo Study

    ERIC Educational Resources Information Center

    Kwok, Oi-Man; Luo, Wen; West, Stephen G.

    2010-01-01

    Some nonlinear developmental phenomena can be represented by using a simple piecewise procedure in which 2 linear growth models are joined at a single knot. The major problem of using this piecewise approach is that researchers have to optimally locate the knot (or turning point) where the change in the growth rate occurs. A relatively simple way…

  15. A study on the zero moment point measurement for biped walking robots

    Microsoft Academic Search

    K. Erbatur; Akihiro Okazaki; Keisuke Obiya; T. Takahashi; A. Kawamura

    2002-01-01

    The bipedal robot structure is highly suitable for working in human environments due to its advantages in obstacle avoidance and its ability to be employed as a human substitute. However, the complex dynamics involved make biped robot control a challenging task. The zero moment point (ZMP) trajectory in the robot foot support area is a significant criterion for the stability

  16. First-principles study of constitutional and thermal point defects in B2 PdIn

    E-print Network

    Chen, Long-Qing

    structure of B2 PdIn. In agreement with experiments, our calculations show that Pd vacancies and Pd and not of Schottky type. q 2005 Elsevier Ltd. All rights reserved. Keywords: A. intermetallics, miscellaneous; D. defects: point defects; E. ab initio calculations; E. defects: theory 1. Introduction The intermetallic

  17. Public Internet Access Points (PIAPs) and Their Social Impact: A Case Study from Turkey

    ERIC Educational Resources Information Center

    Afacan, Gulgun; Er, Erkan; Arifoglu, Ali

    2013-01-01

    Building public Internet access points (PIAPs) is a significant contribution of governments towards achieving an information society. While many developing countries are investing great amounts to establish PIAPs today, people may not use PIAPs effectively. Yet, the successful implementation of PIAPs is the result of citizens' acceptance to use…

  18. Study of Mathematically Precocious Youth (SMPY). Summary of Points Made in the Symposium.

    ERIC Educational Resources Information Center

    Stanley, Julian C.

    This paper is an overview of some points made at the Annual Meeting of the American Educational Research Association in April of 1987. Gender effects were computed on 82 nationally standardized tests designed to determine precocity among youth. The effect sizes ranged from a magnitude of 0.50 (favoring females) for spelling in grade 12 on the…

  19. Limited energy study, West Point, NY. Executive summary and final report. Final report

    Microsoft Academic Search

    Johnson

    1994-01-01

    In the Holleder Sports Complex at West Point Military Academy, there is an indoor ice skating rink. Due to perceived operational inefficiencies, it was anticipated that energy was being wasted. Furthermore, it was noted that during the normal operation of the ice making plant, heat was being rejected from the building. Questions were asked as to the possibility of recapturing

  20. School Attendance Revisited: A Study of Urban African American Students' Grade Point Averages and Coping Strategies

    ERIC Educational Resources Information Center

    Steward, Robbie J.; Steward, Astin Devine; Blair, Jonathan; Jo, Hanik; Hill, Martin F.

    2008-01-01

    Urban African American first-year high school students' absenteeism was found to be negatively related to grade point average (GPA) and avoidance as a means of coping (use of substances as a way to escape--food, alcohol, smoking, caffeine, etc.) and positively related to use of social support as a means of coping (efforts to stay emotionally…