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1

Surface-electrode point Paul trap  

E-print Network

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 ...

Chuang, Isaac L.

2

Surface-electrode point Paul trap  

SciTech Connect

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 trap design is compatible with microfabrication and offers a simple method by which the height of the trapped ions above the surface may be changed in situ. We demonstrate trapping of single {sup 88}Sr{sup +} ions over an ion height range of 200-1000 {mu}m for several hours under Doppler laser cooling and use these to characterize the trap, finding good agreement with our model.

Kim, Tony Hyun; Herskind, Peter F.; Chuang, Isaac L. [Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Kim, Taehyun; Kim, Jungsang [Department of Electrical and Computer Engineering, Duke University Durham, North Carolina 27708 (United States)

2010-10-15

3

Arc electrode interaction study  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

4

Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning.  

PubMed

The aim of the study was to investigate the uniformity of the muscle motor point location for lower limb muscles in healthy subjects. Fifty-three subjects of both genders (age range: 18-50 years) were recruited. The muscle motor points were identified for the following ten muscles of the lower limb (dominant side): vastus medialis, rectus femoris, and vastus lateralis of the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus of the hamstring muscles, tibialis anterior, peroneus longus, lateral and medial gastrocnemius. The muscle motor point was identified by scanning the skin surface with a stimulation pen electrode and corresponded to the location of the skin area above the muscle in which an electrical pulse evoked a muscle twitch with the least injected current. For each investigated muscle, 0.15 ms square pulses were delivered through the pen electrode at low current amplitude (<10 mA) and frequency (2 Hz). 16 motor points were identified in the 10 investigated muscles of almost all subjects: 3 motor points for the vastus lateralis, 2 motor points for rectus femoris, vastus medialis, biceps femoris, and tibialis anterior, 1 motor point for the remaining muscles. An important inter-individual variability was observed for the position of the following 4 out of 16 motor points: vastus lateralis (proximal), biceps femoris (short head), semimembranosus, and medial gastrocnemius. Possible implications for electrical stimulation procedures and electrode positioning different from those commonly applied for thigh and leg muscles are discussed. PMID:21796408

Botter, Alberto; Oprandi, Gianmosè; Lanfranco, Fabio; Allasia, Stefano; Maffiuletti, Nicola A; Minetto, Marco Alessandro

2011-10-01

5

GLAS Spacecraft Pointing Study  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

6

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

NASA Astrophysics Data System (ADS)

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 spatial resolution approximately 0.039 in. (1 mm). Such high spatial resolution was necessary to study the behavior of thermohaline columns in the vicinity of convective/conductive zone interfaces. The point-electrode conductivity instrument was designed for use in up to 25% (by weight) salinities with immersion times on the order of magnitude of 0.1 year or longer. Drift in the instrument, 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.

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

1983-12-01

7

AC impedance study of degradation of porous nickel battery electrodes  

NASA Technical Reports Server (NTRS)

AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.

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

1987-01-01

8

Alkali metal thermoelectric converter (AMTEC) electrode lifetime studies  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

9

Chemically modified electrodes and related solution studies  

SciTech Connect

This report is divided into 5 sections: Ru[sub 4]/Fe complexes of tetra(4[prime]-methyl-2,2[prime]-bipyridine)porphyrin--catalytic epoxidation of olefins; water oxidation catalysis by doubly linked [mu]-oxo ruthenium complexes; polymer films formed by oxidation of transition metal electrodes into solutions of bisbipyridinealkane ligands; polymer films containing [CpMo([mu]-S)][sub 2]S[sub 2]CHR dinuclear clusters;and conducting polymer films for catalyst incorporation.

Elliott, C.M.

1993-04-01

10

Point of zero potential of single-crystal electrode/inert electrolyte interface.  

PubMed

Most of the environmentally important processes occur at the specific hydrated mineral faces. Their rates and mechanisms are in part controlled by the interfacial electrostatics, which can be quantitatively described by the point of zero potential (PZP). Unfortunately, the PZP value of specific crystal face is very difficult to be experimentally determined. Here we show that PZP can be extracted from a single-crystal electrode potentiometric titration, assuming the stable electrochemical cell resistivity and lack of specific electrolyte ions sorption. Our method is based on determining a common intersection point of the electrochemical cell electromotive force at various ionic strengths, and it is illustrated for a few selected surfaces of rutile, hematite, silver chloride, and bromide monocrystals. In the case of metal oxides, we have observed the higher PZP values than those theoretically predicted using the MultiSite Complexation Model (MUSIC), that is, 8.4 for (001) hematite (MUSIC-predicted ~6), 8.7 for (110) rutile (MUSIC-predicted ~6), and about 7 for (001) rutile (MUSIC-predicted 6.6). In the case of silver halides, the order of estimated PZP values (6.4 for AgCl<6.5 for AgBr) agrees well with sequence estimated from the silver halide solubility products; however, the halide anions (Cl(-), Br(-)) are attracted toward surface much stronger than the Ag(+) cations. The observed PZPs sequence and strong anions affinity toward silver halide surface can be correlated with ions hydration energies. Presented approach is the complementary one to the hysteresis method reported previously [P. Zarzycki, S. Chatman, T. Preo?anin, K.M. Rosso, Langmuir 27 (2011) 7986-7990]. A unique experimental characterization of specific crystal faces provided by these two methods is essential in deeper understanding of environmentally important processes, including migration of heavy and radioactive ions in soils and groundwaters. PMID:22277245

Zarzycki, Piotr; Preo?anin, Tajana

2012-03-15

11

Electrochemical charge transfer at a metallic electrode: A simulation study  

SciTech Connect

The calculation of the Marcus free energy curves for electron transfer events between a redox species and a metallic electrode in an atomistic simulation designed to model the electrochemical interface with an ionic liquid is described. The calculation is performed on a system comprising a molten salt mixture confined between model metallic electrodes [Reed et al., J. Chem. Phys. 126, 084704 (2007)] which are maintained at a constant electrical potential. The calculation therefore includes a self-consistent description of the screening of the electrode potential by the liquid and the polarization of the electrode by the ions (image charge effects). The purpose of the study was to examine how the Marcus curves depend on the applied potential and on the distance of the redox species from an electrode. The pronounced oscillations in the mean electrical potential seen in molten salt systems in the ''double-layer'' region are not reflected in the reaction free energy for the electron transfer event. The reorganization energy depends markedly on the distance of the redox ion from the electrode surface because of image charge effects.

Reed, Stewart K.; Madden, Paul A. [School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ (United Kingdom); Papadopoulos, Aristides [Edinburgh Parallel Computer Centre, University of Edinburgh, Edinburgh EH9 3JZ (United Kingdom)

2008-03-28

12

Potentiometric studies at ORNL with hydrogen electrode concentration cells  

SciTech Connect

The absence of suitably stable reference electrodes for and to 300 C led ORNL to develop hydrogen electrode concentration cells for studies of equilibria of interest in reactor and steam generator systems to about 300 C during the late 1960`s and seventies. During the intervening two dozen years over twenty scientists have participated in potentiometric studies at Oak Ridge and much of that work will be summarized in this paper. A description of hydrogen electrode concentration cells developed in the late sixties and currently in use at Oak Ridge is given. The method of measurement, data interpretation, and published results are reviewed for studies of acid-base ionization, metal ion hydrolysis, and metal complexation reactions using principally such cells in titration or flow modes. 41 refs.

Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

1994-12-31

13

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

PubMed Central

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

2013-01-01

14

Quantitative study of non-covalent interactions at the electrode-electrolyte interface using cyanide-modified Pt(111) electrodes.  

SciTech Connect

Cations at the outer Helmholtz plane (OHP) can interact through non-covalent interactions with species at the inner Helmholtz plane (IHP), which are covalently bonded to the electrode surface, thereby affecting the structure and the properties of the electrochemical double layer. These non-covalent interactions can be studied quantitatively using cyanide-modified Pt(111) electrodes.

Escudero-Escribano, M.; Michoff, M. E. Z.; Leiva, E. P. M.; Markovic, N. M.; Gutierrez, C.; Cuesta, A. (Materials Science Division); (CSIC); (Universidad Nacional de Cordoba)

2011-08-22

15

Traceability of pH measurements by glass electrode cells: performance characteristic of pH electrodes by multi-point calibration  

Microsoft Academic Search

Routine pH measurements are carried out with pH meter-glass electrode assemblies. In most cases the glass and reference electrodes are thereby fashioned into a single probe, the so-called 'combination electrode' or simply 'the pH electrode'. The use of these electrodes is subject to various effects, described below, producing uncertainties of unknown magnitude. Therefore, the measurement of pH of a sample

R. Naumann; Ch. Alexander-Weber; R. Eberhardt; J. Giera; P. Spitzer

2002-01-01

16

STUDIES OF POINT DEFECTS IN SILVER CHLORIDE  

Microsoft Academic Search

Experiments were made on excess point defects introduced into single ; crystals of silver chloride by pulsed elastic extension or by rapid cooling from ; high temperature. Point defects are created by plastic deformation much less ; efficiently in silver chloride than in other substances that have been studied. ; Interstitial silver ions so produced have a lifetime of the

Howard Layer; Lawrence Slifkin

1962-01-01

17

a Study of Cobalt Electrodes in Alkaline Media.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. This thesis is a study of the anodic oxidation of cobalt in alkaline solution. The main interest is on the electrochemical behaviour of the Co/Co(OH) _2 couple as a potentially high energy density anode in rechargeable batteries. Fundamental studies on solid cobalt electrodes were carried out to determine its kinetics of oxidation. The anodic formation of cobalt hydroxide films at different current densities showed that the film thickness varied with changing current and that the films were most likely to be formed by a nucleation and growth mechanism. Steady state measurements provided kinetic parameters such as Tafel slopes and reaction order. Two Tafel slopes were observed and it was deduced from theoretically predicted Tafel slopes that the oxidation of the cobalt metal electrode was initially dominated by an electrodissolution of the metal followed by the formation of the hydroxide film. Potentiostatic experiments performed in conjunction with a.c. impedance measurements confirmed that the formation of the hydroxide film was a solid phase reaction involving the nucleation and growth of cobalt hydroxide crystallites on the metal surface. The effect of adding lithium hydroxide to the electrolyte was also examined. Better discharge performance was observed from both galvanostatic and potentiostatic studies for the oxidation of cobalt in lithiated electrolyte. Investigations on the dissolution accompanying the passivation of Co showed the presence of a higher concentration of Co(II) ions in the lithiated electrolyte. It is concluded that the slower rate of nucleation in the presence of LiOH results in the more severe corrosion of the metal. The evaluation of the reversibility of the Co/Co ^{2+} couple gave promising results. It was found that the cobalt electrode recharged efficiently even under non gassing conditions. The fact that it is possible to charge the electrode without gassing is of significant importance in that no reserve negative material needs to be included as is normally the case in existing secondary batteries. Finally some preliminary studies were carried out to examine methods of preparing porous cobalt electrodes. Electrodes prepared from high surface area cobalt, obtained by reducing Co_3O_4 in H_2, performed well and initial results indicate that it is the best manufacture method. (Abstract shortened by UMI.).

Yon Hin, Foo Yueh Yin

18

Studies of Low-Current Back-Discharge in Point-Plane Geometry with Dielectric Layer  

NASA Astrophysics Data System (ADS)

The paper presents results of spectroscopic investigations of back-discharges generated in the point-plane electrode geometry in ambient air at atmospheric pressure, with the plane electrode covered with a dielectric layer. Fly ash from an electrostatic precipitator of a coal-fired power plant was used as the dielectric layer in these investigations. The discharges for positive and negative polarities of the needle electrode were studied by measuring optical emission spectra at two regions of the discharge: near the needle electrode and dielectric layer surface. The visual forms of the discharge were recorded and correlated with the current-voltage characteristics and optical emission spectra. The back-arc discharge was of particular interest in these studies due to its detrimental effects it causes in electrostatic precipitators.

Jaworek, Anatol; Rajch, Eryk; Krupa, Andrzej; Czech, Tadeusz; Lackowski, Marcin

2006-01-01

19

A Comparative Study of Lead Oxide Modified Graphite Paste Electrodes and Solid Graphite Electrodes with Mechanically Immobilized Lead Oxides  

Microsoft Academic Search

The cyclic voltammetry of red PbO, -PbO2, -PbO2 and BaPbO3 was studied withtwo different types of electrodes in acidic and al - kaline media. In one case, microcrystalline particles of lead oxides were mechanically immobilized on the surface of paraffin-impreg- nated graphite rod electrodes (PIGE), while in the other case, lead oxides were added to a paste of graphite and

Nina Zakharchuk; Stefan Meyer; Britta Lange; Fritz Scholz

20

Studies of the hydrogen evolution reaction on NiP electrodes  

Microsoft Academic Search

The hydrogen evolution reaction (HER) was studied on Ni-P electrodes containing 8 to 30 atomic percent P prepared by galvanostatic deposition. The electrodes were studied directly after preparation or after pretreatment by heating, leaching in HF solution, anodic oxidation, or potential cycling in the solution. The activity of these electrodes depended on the method of preparation and phosphorus content. The

Reza Karimi Shervedani; A. Lasia

1997-01-01

21

Study on effect of electrode force on resistance spot welding process  

NASA Astrophysics Data System (ADS)

This paper deals with the effect of electrode force on resistance spot welding process. As one of the most important parameters during the process, the electrode force can influence the process in different aspects. Dynamic resistance, which can reflect the internal physical variation of the workpiece, is employed to monitor the characteristic variation of the workpieces. According to theoretical analysis, large electrode force may easily induce surface expulsion. Also, it can decrease the overall dynamic resistance values and postpone the time when first melting point appears, as well as enlarge the duration between times when first melting point and peak value appear. Larger electrode force induces the initial smaller nugget diameter, and then the nugget diameter has a higher growth speed. However, the overall nugget diameter may be smaller and its growth terminates earlier than when smaller electrode force is applied. Final experiments validated all the theoretical analysis.

Zhou, Kang; Cai, Lilong

2014-08-01

22

Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.  

ERIC Educational Resources Information Center

The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

Diamandis, E. P.; And Others

1983-01-01

23

Theoretical study of reactions at the electrode-electrolyte interface  

SciTech Connect

Electron transfer rates are predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have produced a new theory for description of the Jahn Teller effect in the solvation shell of the cuprous ion in aqueous solution, have implemented it in a molecular dynamics simulation and compared the results with experimental neutron scattering measurements on solutions containing the cuprous ion. A large amount of numerical data has been collected on the transition state of the ferrous ferric electron transfer reaction at an electrode. Work was completed on a polarizable and dissociable model of water for use in the electron transfer studies. New calculations of the conductivity in models of oxides have shown the existence of impurity conduction bands in such models for the first time.

Halley, J.W.

1993-01-01

24

Electrochemical study of ricin at glassy carbon electrode.  

PubMed

Ricin, Ricinus communis agglutinin 60 - RCA 60, is a deadly phytotoxic protein which inhibits ribosomes (class II), and there is no known effective antidote in living organisms. Ricin is composed of two polypeptide chains, A and B, linked covalently by a single disulfide bond. The analytical methods for the detection of RCA 60 are commonly laborious, expensive, require skilled labor, and involve sophisticated equipment. Aimed at the development of electroanalytical methods for RCA 60 detection, here we studied the electrochemical oxidation of RCA 60 on a glassy carbon (GC) electrode over a wide pH range, using cyclic voltammetry, differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two quasi-reversible electrochemical RCA 60 oxidation peaks were identified on the GC electrode by SWV. For values of 2.2 ? pH ? 10.2, DPV studies revealed that the peak potentials, EP1 and EP2, display a linear dependence with pH and the reaction mechanism involves the transfer of 2H?/2e? (peak 1) and 1H?/1e? (peak 2). The first and second RCA 60 oxidation steps may correspond to the oxidation of cysteine and tyrosine-tryptophan residues, respectively. The oxidation product of the second RCA 60 oxidation step appears at 7.0 ? pH ? 11.8. For pH ? 10.2, both processes are pH independent, resulting in a pKa of ca. 10.2. A third RCA 60 oxidation peak only appears at acidic pH. RCA 60 samples extracted from different castor seed cultivars showed similar electrochemical behavior, enabling the implementation of an analytical voltammetric method. PMID:23741733

Ribeiro, Williame F; da Costa, Daniel J E; Lourenço, Anabel S; Lopes, Ilanna C; de Medeiros, Everaldo P; Salazar-Banda, Giancarlo R; do Nascimento, Valberes B; de Araújo, Mário C U

2013-08-21

25

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

26

Study of a low temperature plasma generator with a divergent output electrode channel  

Microsoft Academic Search

Results of experimental studies of a plasma generator with a divergent output electrode channel are presented, and a comparative\\u000a analysis is performed of operation of this plasma generator and plasma generator with cylindrical channel of constant cross\\u000a section. Studies of sectioned output electrodes are performed along with plasma generators with solid electrodes. The influence\\u000a of sectioning on the parameters of

E. Kh. Isakaev; O. A. Sinkevich; N. O. Spektor; T. F. Tazikova; A. S. Tyuftyaev; A. G. Khachaturova

2010-01-01

27

Advanced PowerPoint Self Study  

NSDL National Science Digital Library

In order to recieve credit for the Advanced PowerPoint Night, you will need to complete *ALL* of the following activities. 1. Please search for of Advanced PowerPoint Features on Google. These examples demonstrate how PowerPoint can function in other ways besides a linear presentation. (Notice how button and hyperlinks are used to navigate through the slideshows.) 2. Read pages 1-8 in your Advanced PowerPoint Module . ...

Murphy, Rachel

2005-11-28

28

Study of catalase electrode for organic peroxides assays.  

PubMed

The catalytic activity of immobilized catalase (EC 1.11.1.6) for two model peroxide compounds (dibenzoyl peroxide and 3-chloroperoxibenzoic acid) in a non-aqueous medium was used to prepare an organic-phase enzyme electrode (OPEE). The enzyme was immobilized within a polymeric film on spectrographic graphite. The amperometric signal of the enzyme electrode in substrate solutions was found to be due to the reduction of oxygen generated in the enzyme layer. The electrode response is proportional to peroxide concentrations up to about 40 microM within the potential range from -450 to -650 mV (vs. Ag/AgCl), and the response time is at most 90 s. The enzyme electrode retains about 35% of its initial activity after a 3-week storage at room temperature. PMID:12414324

Horozova, Elena; Dimcheva, Nina; Jordanova, Zinaida

2002-12-01

29

Dedicated phantom to study susceptibility artifacts caused by depth electrode in magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The susceptibility artifacts can degrade of magnetic resonance image quality. Electrodes are an important source of artifacts when performing brain imaging. A dedicated phantom was built using a depth electrode to study the susceptibility effects under different pulse sequences. T2-weighted images were acquired with both gradient-and spin-echo sequences. The spin-echo sequences can significantly attenuate the susceptibility artifacts allowing a straightforward visualization of the regions surrounding the electrode.

Garcia, J.; Hidalgo, S. S.; Solis, S. E.; Vazquez, D.; Nuñez, J.; Rodriguez, A. O.

2012-10-01

30

Study on Spraying Corona Discharge Technology with Grounding 1 Discharge Electrodes for Purifying Flue-gas  

Microsoft Academic Search

This study focused on a new electrostatic precipitation technology of spraying corona discharges with grounding discharge electrodes for purifying flue-gas. DC positive high-voltage was connected to collecting electrodes and water discharge electrodes were grounded. A lasting and effective electrostatic removal of dust with minimized drain water would be achieved by wet or semi-wet spraying corona discharges. The experimental researches on

Dexuan Xu; Shanshan Lin; Yujia Wang; Zhiming Guo; Weili Ge

31

Transport across poly( o-aminophenol) modified electrodes in contact with media containing redox active couples. A study using rotating disc electrode voltammetry  

Microsoft Academic Search

The electrochemistry of poly(o-aminophenol) modified electrodes in the presence of different electroactive solutes (Fe(CN)64?\\/3?, hydroquinone\\/benzoquinone (HQ\\/Q), Sn2+) able to diffuse through the polymer film was studied by rotating disc electrode voltammetry. Experimental results relating to the diffusion of these electroactive species through the polymer were interpreted on the basis of the membrane–diffusion theory for the rotating disc electrode. The electron

A Bonfranceschi; A Pérez Córdoba; S Keunchkarian; S Zapata; R Tucceri

1999-01-01

32

An electrode kinetics study of H 2 oxidation on Ni\\/Y 2O 3–ZrO 2 cermet electrode of the solid oxide fuel cell  

Microsoft Academic Search

Hydrogen oxidation on Ni\\/3 mol% Y2O3–ZrO2 (Ni\\/Y-TZP) cermet electrodes has been studied in moist H2 environments. The impedance behaviour is characterised by two clearly separated arcs in the frequency domain, indicating that the overall electrode reaction is controlled by at least two rate limiting processes in series. The electrode process associated with the low frequency arc is mainly dependent on

S. P Jiang; S. P. S Badwal

1999-01-01

33

Point process models in line transect studies  

Microsoft Academic Search

In visual line transecting, whales are observed when surfacing to breath. Surfacings are short. Point process models for surfacing times are com- bined with a model for the hazard probability of initial sighting to obtain a likelihood for the observed encounters. Point processes are also useful for describing the clustering of encounters along the track line due to spatial clustering

Tore Schweder

34

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid  

NASA Astrophysics Data System (ADS)

The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.

Zhou, Yuan; Hao, Miao; Chen, George; Wilson, Gordon; Jarman, Paul

2014-07-01

35

Point defects in silicon crystals studied via complexes with hydrogen  

Microsoft Academic Search

We studied the properties of irradiation-induced point defects and thermal equilibrium vacancies in Si by detecting hydrogen interacting with these point defects. First, we show the irradiation temperature dependence of the point defect concentration. We studied the optical absorption spectra of complexes of hydrogen and point defects generated by electron irradiation of hydrogenated Si crystals at low temperatures. The concentrations

M Suezawa; N Fukata; Y Takada; R Taniguchi; F Hori; R Oshima

2003-01-01

36

Radio-frequency ablation electrode displacement elastography: A phantom study  

PubMed Central

This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio-frequency (rf) ablation-induced lesions. The method involves use of the radio-frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easyin vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single-inclusion tissue-mimicking phantom containing a radio-frequency ablation electrode rigidly attached to the inclusion center. Full-frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One-dimensional cross-correlation analysis between pre-and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast-to-noise ratio, and signal-to-noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single-inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue-mimicking phantom and on in vitro rf-ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation. PMID:18649476

Bharat, Shyam; Varghese, Tomy; Madsen, Ernest L.; Zagzebski, James A.

2008-01-01

37

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

38

Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.  

PubMed

In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes. PMID:23035436

Dhiman, Mopsy; Kapur, Pawan; Ganguli, Abhijit; Singla, Madan Lal

2012-09-01

39

The fabrication of low-impedance nanoporous gold multiple-electrode arrays for neural electrophysiology studies  

PubMed Central

Neural electrodes are essential tools for the study of the nervous system and related diseases. Low electrode impedance is a figure of merit for sensitive detection of neural electrical activity and numerous studies have aimed to reduce impedance. Unfortunately, most of these efforts have been tethered by a combination of poor functional coating adhesion, complicated fabrication techniques, and poor fabrication repeatability. We address these issues with a facile method for reliably producing multiple-electrode arrays with low impedance by patterning highly adherent nanoporous gold films using conventional microfabrication techniques. The high surface area-to-volume ratio of self-assembled nanoporous gold results in a more than 25-fold improvement in the electrode-electrolyte impedance, where at 1 kHz, 850 k? impedance for conventional Au electrodes is reduced to 30 k? for nanoporous gold electrodes. Low impedance provides a superior signal-to-noise ratio for detection of neural activity in noisy environments. We systematically studied the effect of film morphology on electrode impedance and successfully recorded field potentials from rat hippocampal slices. Here, we present our fabrication approach, the relationship between film morphology and impedance, and field potential recordings. PMID:20203356

Seker, Erkin; Berdichevsky, Yevgeny; Begley, Matthew R; Reed, Michael L; Staley, Kevin J; Yarmush, Martin L

2011-01-01

40

Study of nickel hydroxide electrodes. 2: Oxidation products of nickel (2) hydroxides  

NASA Technical Reports Server (NTRS)

Pure phases of some oxidized Ni oxides were prepared galvanimetrically with the Ni(2) hydroxide electrode of an alkaline battery. The crystallographic data of these phases, their chemical behavior, and conditions of transition were studied.

Bode, H.; Demelt, K.; White, J.

1986-01-01

41

Improved separability of dipole sources by tripolar versus conventional disk electrodes: A modeling study using independent component analysis  

Microsoft Academic Search

Tripolar electrodes have been shown to have less mutual information and higher spatial resolution than disc electrodes. In this work, a four-layer anisotropic concentric spherical head computer model was programmed, then four configurations of time-varying dipole signals were used to generate the scalp surface signals that would be obtained with tripolar and disc electrodes. Finally, a fast fixed-point algorithm was

H. Caol; W. Besio; S. Jones; A. Medvedev

2009-01-01

42

Immobilization of DNA at Glassy Ccarbon Electrodes: A Critical Study of Adsorbed Layer  

PubMed Central

In this work we present a critical study of the nucleic acid layer immobilized at glassy carbon electrodes. Different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface. The adsorption and electrooxidation of DNA demonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. The DNA layer immobilized at a freshly polished glassy carbon electrode was very stable even after applying highly negative potentials. The electron transfer of potassium ferricyanide, catechol and dopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlled potential conditions) and thick (obtained by casting the glassy carbon surface with highly concentrated DNA solutions) DNA layers was slower than that at the bare glassy carbon electrode, although this effect was dependent on the thickness of the layer and was not charge selective. Raman experiments showed an important decrease of the vibrational modes assigned to the nucleobases residues, suggesting a strong interaction of these residues with the electrode surface. The hybridization of oligo(dG)21 and oligo(dC)21 was evaluated from the guanine oxidation signal and the reduction of the redox indicator Co(phen)33+. In both cases the chronopotentiometric response indicated that the compromise of the bases in the interaction of DNA with the electrode surface is too strong, preventing further hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in a direct and very sensitive way, but not to be used for the preparation of biorecognition layers by direct adsorption of the probe sequence on the electrode surface for detecting the hybridization event.

Pedano, M. L.; Rivas, G. A.

2005-01-01

43

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

NASA Technical Reports Server (NTRS)

Voltammetry of partially oxidized porous molybdenum alkali metal thermoelectric converter (AMTEC) electrodes from about 600 to 1000 K revealed a series of redox processes within the AMTEC operational voltage range which can be used to establish the electronic and ionic conductivities of these electrodes. Improved estimates of the free energies of formation of Na2Mo3O6, NaMoO2, and Na3MoO4 are obtained. Evidence is provided for the slow corrosive attack by Na2MoO4 on molybdenum. The ionic conductivity of Na2MoO4 is found to be sufficiently large at temperatures of greater than 700 K to explain the observed electrochemical phenomena in addition to the enhanced sodium transport in AMTEC electrodes below the freezing point of Na2MoO4.

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

1986-01-01

44

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

PubMed Central

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

Liu, Xiaoping; Zweier, Jay L.

2012-01-01

45

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

E-print Network

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

Togelius, Julian

46

Simulation studies of optimized electrode designs for a cylindrical IEC  

SciTech Connect

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.

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

47

Electrode temperature gradients in the electroslag process  

Microsoft Academic Search

A self-consistent model for electrode temperature gradients in an ESR process has been tested against experimental results.\\u000a The results indicate that when melting steels in the electrode and mold sizes studied, the electrode material spends approximately\\u000a 30 sec in the temperature gradient 1000‡C to the melting point. It is suggested that this would lead to a significant nonequilibrium\\u000a retention of

A. Mitchell; S. Joshi; J. Cameron

1971-01-01

48

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

E-print Network

- energy loss spectroscopy (HREELS) and electrochemical-scanning tunneling microscopy (EC-STM) on a smooth polycrystalline and well-defined (single-crystalline) Pd(100) electrode surface. The results point to the following more critical conclusions...

Chen, Xiaole

2006-04-12

49

Updates on R2E FLUKA studies for Point 1 and Point 5  

E-print Network

This report integrates and updates our former studies on possible shielding for the electronics located in the UJs and ULs of Point 1 and Point 5. Up on the results of those studies, the EN/MEF group has proposed new possible shieldings for Point 1, which have been evaluated with FLUKA simulations. We have also performed an evaluation of the attenuation of the high energy hadrons fluence with the distance along the ULs. This work has been realized within the compass of the Radiation To Electronics issue.

Versaci, R

2010-01-01

50

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

NASA Astrophysics Data System (ADS)

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.

Gu, Y.; Levin, C. S.

2014-06-01

51

R2E FLUKA studies for Point 1 and Point 5  

E-print Network

This report presents a summary of the studies we have performed on possible shielding for the electronics located in the UJs of Point 1 and Point 5, within the compass of the Radiation To Electronics working group. We have considered the present status of the shielding and the proposal by EN/MEF group. We have also studied possible improved shielding, based on the results of the first simulations. All the calculations were performed with the Monte Carlo particle transport code FLUKA.

Versaci, R; Brugger, M; Mereghetti, A; Cerutti, F; Vlachoudis, V; Ferrari, A; CERN. Geneva. ATS Department

2010-01-01

52

Fundamental Studies and Potential Applications of Cloud Point Extraction .  

E-print Network

??FUNDAMENTAL STUDIES AND POTENTIAL APPLICATIONS OF CLOUD POINT EXTRACTION Abstract by MELISSA ENSOR FREIDERICH, Ph.D. Washington State University DECEMBER 2011 Chair: Kenneth L. Nash Separation… (more)

[No author

2011-01-01

53

Dithiooxamide Modified Glassy Carbon Electrode for the Studies of Non-Aqueous Media: Electrochemical Behaviors of Quercetin on the Electrode Surface  

PubMed Central

Electrochemical oxidation of quercetin, as an important biological molecule, has been studied in non-aqueous media using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. To investigate the electrochemical properties of quercetin, an important flavonoid derivative, on a different surface, a new glassy carbon electrode has been developed using dithiooxamide as modifier in non-aqueous media. The surface modification of glassy carbon electrode has been performed within the 0.0 mV and +800 mV potential range with 20 cycles using 1 mM dithioxamide solution in acetonitrile. However, the modification of quercetin to both bare glassy carbon and dithiooxamide modified glassy carbon electrode surface was carried out in a wide +300 mV and +2,800 mV potential range with 10 cycles. Following the modification process, cyclic voltammetry has been used for the surface characterization in aqueous and non-aqueous media whereas electrochemical impedance spectroscopy has been used in aqueous media. Scanning electron microscopy has also been used to support the surface analysis. The obtained data from the characterization and modification studies of dithioxamide modified and quercetin grafted glassy carbon electrode showed that the developed electrode can be used for the quantitative determination of quercetin and antioxidant capacity determination as a chemical sensor electrode. PMID:22666010

Mulaz?moglu, Aysen Demir; Y?lmaz, Ecir; Mulaz?moglu, Ibrahim Ender

2012-01-01

54

An IPE back-end study for Turkey Point plant  

Microsoft Academic Search

This paper describes a study of Turkey Point plant's large dry containment as part of a response to the US Nuclear Regulatory Commission's individual plant examination Generic Letter 88-20. Two unique features of Turkey Point containment are discussed. This study includes an evaluation of the containment response to the physical processes occurring during an accident and probabilistic analysis of the

C. Guey; J. Kabadi

1991-01-01

55

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

SciTech Connect

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/.

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

1986-11-01

56

Exploring the electrocatalytic sites of carbon nanotubes for NADH detection: an edge plane pyrolytic graphite electrode study.  

PubMed

The electrocatalytic properties of multi-walled carbon nanotube modified electrodes toward the oxidation of NADH are critically evaluated. Carbon nanotube modified electrodes are examined and compared with boron-doped diamond and glassy carbon electrodes, and most importantly, edge plane and basal pyrolytic graphite electrodes. It is found that CNT modified electrodes are no more reactive than edge plane pyrolytic graphite electrodes with the comparison with edge plane and basal plane pyrolytic graphite electrodes allowing the electroactive sites for the electrochemical oxidation of NADH to be unambiguously determined as due to edge plane sites. Using these highly reactive edge plane sites, edge plane pyrolytic graphite electrodes are examined with cyclic voltammetry and amperometry for the electroanalytical determination of NADH. It is demonstrated that a detection limit of 5 microM is possible with cyclic voltammetry or 0.3 microM using amperometry suggesting that edge plane pyrolytic graphite electrodes can conveniently replace carbon nanotube modified glassy carbon electrodes for biosensing applications with the relative advantages of reactivity, cost and simplicity of preparation. We advocate the routine use of edge plane and basal plane pyrolytic graphite electrodes in studies utilising carbon nanotubes particularly if 'electrocatalytic' properties are claimed for the latter. PMID:16096667

Banks, Craig E; Compton, Richard G

2005-09-01

57

Potentiostatic and ac impedance studies of the hydrogen electrodes used in Ni/H2 batteries  

NASA Technical Reports Server (NTRS)

In a study of electrode activity for hydrogen evolution and hydrogen ionization, knowledge of the detailed kinetics and of the surface coverage by adsorbed hydrogen is essential. In the Ni/H2 battery, the hydrogen electrode is subjected to high hydrogen pressure; elucidation of the variation of kinetic parameters with hydrogen pressure is therefore of interest. Potentiostatic and ac impedance spectroscopic techniques were used in the present study. The equivalent circuit of the reaction, the kinetic parameters, and their pressure dependence have been determined.

Le Helloco, Jean-Guy; Bojkov, Hristo; Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.

1992-01-01

58

First-Principles Study of Contact Resistance between Graphene and Metal Electrodes  

NASA Astrophysics Data System (ADS)

Graphene attracts much interest for post-silicon electronics material due to its outstanding electronic transport properties such as considerably high mobility at room temperature. For the application of electronics devices, contacting of metal electrodes is necessary and decreasing of contact resistance between graphene and the metal electrodes is regarded as one of a key issue. In this study, we investigate the contact resistance using DFT+NEGF method. We consider the Ni and Cu electrode within LDA and TM-type norm-conserving pseudo-potential. We employed PHASE code [1] to determine the interface structures. Then, we constructed two terminal device structures in which current flows from metals to graphene. The electron transport properties were calculated using ASCOT code[2]. For Ni electrode, the dependence of the electrode size qualitatively agrees well with that obtained by the experiments. But our results suggest that contact resistance can be reduced considerably. [1] http://www.ciss.iis.u-tokyo.ac.jp/english/project/device/. [2] H. Kondo, J. Nara, H. Kino and T. Ohno, Jpn. J. Appl. Phys. 47, 4792 (2008).

Kaneko, Tomoaki; Ohno, Takahisa

2013-03-01

59

In situ STM studies of electrochemically polished Cd(0001) electrode in aqueous electrolyte solutions  

NASA Astrophysics Data System (ADS)

The in situ STM studies of electrochemically polished Cd(0001) electrode in the H3PO4 aqueous solution have been performed under negative electrode potentials from - 1.4 to - 0.9 V (versus Ag|AgCl in sat. KCl aqueous solution) in the 0.1 M Na2SO4 + 1 × 10- 5 M H2SO4 aqueous solution. The atomic resolution parameters of Cd(0001) surface have been calculated. The in situ STM data show that there are no surface reconstruction processes and the surface structure of electrochemically polished Cd(0001) is stable within the potential region investigated.

Pikma, P.; Grozovski, V.; Kasuk, H.; Lust, E.

2014-10-01

60

Point and non-point microbial source pollution: A case study of Delhi  

NASA Astrophysics Data System (ADS)

The present study identifies major point and non-point sources of microbial pollution during dry and wet weather in Delhi watershed which is the first prerequisite for planning and management of water quality of the river Yamuna. Fecal coliforms (FC) and fecal streptococci (FS) levels were determined from two types of sources - point source (effluent from sewage treatment plants) and non-point source (stormwater runoff during dry and wet weather). FC and FS levels in the river Yamuna were also monitored, which is an ultimate sink for all microbial loads in Delhi watershed. Effluent from sewage treatment plants (STPs) employing different treatment technologies were evaluated. FC and FS levels greater than the effluent discharge standard (1000 MPN/100 ml) were observed in the effluents from all STPs except “oxidation pond Timarpur”. This study also involved field program for characterization of urban runoff from different land-uses. Results indicated that the microbial quality of urban runoff produced during wet weather from different land-uses was similar to that of raw sewage. Sewage overflows along with human and animal sources were responsible for high FC and FS levels in the runoff samples. Wet weather FC and FS levels in river Yamuna were higher as compared to the dry weather levels suggesting that dilution of the river water during wet weather does not affect its microbiological quality. Thus on the basis of this study it was found that urban runoff also contributes to the microbial quality of the river Yamuna.

Jamwal, Priyanka; Mittal, Atul K.; Mouchel, Jean-Marie

61

Kinetic study of the formation of oxygen vacancy on lanthanum manganite electrodes  

Microsoft Academic Search

Strontium doped lanthanum manganite (LSM) has been considered one of the most promising cathode materials for solid oxide fuel cells (SOFC). The electrochemical reduction of oxygen on lanthanum manganite (LSM) electrodes has been investigated by cyclic voltammetry, alternating current (ac) impedance, and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of

Yi Jiang; Shizhong Wang; Yahong Zhang; Jingwang Yan; Wenzhao Li

1998-01-01

62

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

Microsoft Academic Search

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 mm3) head model from individual MRI data was adopted to describe accurately thin tissues, such as bone marrow and skin. The RF

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

2004-01-01

63

Kinetic Studies of the Hydrogen Electrode with the Rotating Disk Technique.  

National Technical Information Service (NTIS)

The work was undertaken to elucidate some aspects of the anodic oxidation of hydrogen on a rotating platinum disk electrode under conditions which allowed polarization studies at atmospheric and elevated pressures up to 60 atm. Solutions of 1 N HBr, H2SO4...

M. P. Makowski, E. Heitz, E. Yeager

1964-01-01

64

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

E-print Network

Journal of Luminescence 126 (2007) 225­229 A comparative study of electrode effects on the electrical and luminescent characteristics of Alq3/TPD OLED: Improvements due to conductive polymer (PEDOT luminescence devices 1. Introduction Efficient organic light emitting devices (OLEDs) based on small molecular

Klotzkin, David

65

A Pilot Study of Robot-Assisted Cochlear Implant Surgery Using Steerable Electrode Arrays  

Microsoft Academic Search

This paper presents results of a pilot study evaluating the efficacy of robotic assistance using novel steerable electrode arrays for cochlear implant surgery. The current surgical setup of cochlear implant surgery is briefly re- viewed and its limitations are highlighted. In an effort to reduce trauma to the structure of the cochlea, the kinematics and path planning for novel cochlear

Jian Zhang; Kai Xu; Nabil Simaan; Spiros Manolidis

2006-01-01

66

Electrochemical studies of hydrogen evolution, storage and oxidation on carbon nanotube electrodes  

Microsoft Academic Search

Carbon nanotube films produced on a Si(100) substrate without any metal catalyst were used as electrodes in galvanic cells. The electrochemical mechanism of hydrogen evolution, storage and oxidation was studied using cyclic voltammetry and galvanostatic polarisation. Cyclic voltammetry showed that hydrogen is easily produced on the carbon nanotube surface, but a significant overvoltage was observed for hydrogen oxidation. The kinetics

Pier Paolo Prosini; Alfonso Pozio; Sabina Botti; Roberto Ciardi

2003-01-01

67

Review and Evaluation of the Indian Point Probabilistic Safety Study.  

National Technical Information Service (NTIS)

This report summarizes the review of the internal and external event portions of the Indian Point Probabilistic Safety Study (IPPSS). The review was conducted by Sandia National Laboratories and Sandia contractors over approximately a 6-month period. The ...

A. M. Kolaczkowski, D. L. Berry, G. J. Kolb, J. W. Hickman, R. G. Easterling

1982-01-01

68

An IPE back-end study for Turkey Point plant  

SciTech Connect

This paper describes a study of Turkey Point plant's large dry containment as part of a response to the US Nuclear Regulatory Commission's individual plant examination Generic Letter 88-20. Two unique features of Turkey Point containment are discussed. This study includes an evaluation of the containment response to the physical processes occurring during an accident and probabilistic analysis of the spectrum of severe-accident progressions.

Guey, C.; Kabadi, J. (Florida Power and Light Co., Juno Beach (United States))

1991-01-01

69

Combined in situ EC-AFM and CV measurement study on lead electrode for lead–acid batteries  

Microsoft Academic Search

An electrochemical atomic force microscope (EC-AFM) was used to study the reaction of a lead electrode in sulfuric acid electrolyte, when the reaction corresponding to what occurs at the negative electrode of a lead–acid battery took place. At first, the AFM was applied to observation of the lead electrode during cyclic-voltammetry (CV) measurement, and was found to be useful to

Yoshiaki Yamaguchi; Masashi Shiota; Yasuhide Nakayama; Nobumitsu Hirai; Shigeta Hara

2001-01-01

70

Repassivation studies of aluminum using a rotating strip electrode.  

National Technical Information Service (NTIS)

In this work a technique was described to study the repassivation of bare metal surfaces. The advantage of this approach over other techniques is the ease with which multiple repassivation events can be studied. The repassivation rate of aluminum was foun...

Aldykiewicz Isaacs

1977-01-01

71

An improved cochlear implant electrode array for use in experimental studies.  

PubMed

Experimental studies play an important role in establishing the safety and efficacy of cochlear implants and they continue to provide insight into a new generation of electrode arrays and stimulation strategies. One drawback has been the limited depth of insertion of an electrode array in experimental animals. We compared the insertion depth and trauma associated with the insertion of Cochlear Ltd's Hybrid-L (HL) array with a standard 8 ring array in cat cochleae. Both arrays were inserted into cadaver cochleae and an X-ray recorded their anatomical location. The implanted cochlea was serially sectioned and photographed at 300 ?m intervals for evidence of electrode insertion trauma. Subsequently two cats were chronically implanted with HL arrays and electrically-evoked potentials recorded over a three month period. Mean insertion depth for the HL arrays was 334.8° (SD = 21°; n = 4) versus 175.5° (SD = 6°; n = 2) for the standard array. This relates to ?10.5 mm and 6 mm respectively. A similar insertion depth was measured in a chronically implanted animal with an HL array. Histology from each cadaver cochleae showed that the electrode array was always located in the scala tympani; there was no evidence of electrode insertion trauma to the basilar membrane, the osseous spiral lamina or the spiral ligament. Finally, evoked potential data from the chronically implanted animals exhibited significantly lower thresholds compared with animals implanted with a standard 8 ring array, with electrical thresholds remaining stable over a three-month observation period. Cochlear Ltd's HL electrode array can be safely inserted ?50% of the length of the cat scala tympani, placing the tip of the array close to the 4 kHz place. This insertion depth is considerably greater than is routinely achieved using a standard 8-ring electrode array (?12 kHz place). The HL array evokes low thresholds that remain stable over three months of implantation. This electrode array has potential application in a broad area of cochlear implant related research. PMID:21540098

Shepherd, Robert; Verhoeven, Kristien; Xu, Jin; Risi, Frank; Fallon, James; Wise, Andrew

2011-07-01

72

Operando studies of all-vanadium flow batteries: Easy-to-make reference electrode based on silver-silver sulfate  

NASA Astrophysics Data System (ADS)

In-depth evaluation of the electrochemical performance of all-vanadium redox flow batteries (VRFBs) under operando conditions requires the insertion of a reliable reference electrode in the battery cell. In this work, an easy-to-make reference electrode based on silver-silver sulfate is proposed and described for VRFBs. The relevance and feasibility of the information obtained by inserting the reference electrode is illustrated with the study of ammoxidized graphite felts. In this case, we show that the kinetic of the electrochemical reaction VO2+/VO2+ is slower than that of V2+/V3+ at the electrode. While the slow kinetics at the positive electrode limits the voltage efficiency, the operating potential of the negative electrode, which is outside the stability widow of water, reduces the coulombic efficiency due to the hydrogen evolution.

Ventosa, Edgar; Skoumal, Marcel; Vázquez, Francisco Javier; Flox, Cristina; Morante, Joan Ramon

2014-12-01

73

Motion control of the ankle joint with a multiple contact nerve cuff electrode: a simulation study.  

PubMed

The flat interface nerve electrode (FINE) has demonstrated significant capability for fascicular and subfascicular stimulation selectivity. However, due to the inherent complexity of the neuromuscular skeletal systems and nerve-electrode interface, a trajectory tracking motion control algorithm of musculoskeletal systems for functional electrical stimulation using a multiple contact nerve cuff electrode such as FINE has not yet been developed. In our previous study, a control system was developed for multiple-input multiple-output (MIMO) musculoskeletal systems with little prior knowledge of the system. In this study, more realistic computational ankle/subtalar joint model including a finite element model of the sciatic nerve was developed. The control system was tested to control the motion of ankle/subtalar joint angles by modulating the pulse amplitude of each contact of a FINE placed on the sciatic nerve. The simulation results showed that the control strategy based on the separation of steady state and dynamic properties of the system resulted in small output tracking errors for different reference trajectories such as sinusoidal and filtered random signals. The proposed control method also demonstrated robustness against external disturbances and system parameter variations such as muscle fatigue. These simulation results under various circumstances indicate that it is possible to take advantage of multiple contact nerve electrodes with spatial selectivity for the control of limb motion by peripheral nerve stimulation even with limited individual muscle selectivity. This technology could be useful to restore neural function in patients with paralysis. PMID:24939581

Park, Hyun-Joo; Durand, Dominique M

2014-08-01

74

Electrochemical reduction of an anion for ionic-liquid molecules on a lithium electrode studied by first-principles calculations  

NASA Astrophysics Data System (ADS)

We report ab initio molecular dynamics studies with electric field that reveal chemical stability of room temperature ionic liquid for charge transfer from lithium and nickel electrodes. Bis(trifluoromethanesulfonyl)imide (TFSI) is oxidized on the nickel electrode under a high positive bias condition as expected. However, TFSI is reduced on the lithium electrode under both positive and negative bias conditions, because the lithium electrode acts as a strong reductant. The decomposition of TFSI anion might induce the formation of LiF as a solid electrolyte interphase, which could restrain the TFSI reduction. The stability of an cation under reductant conditions is presented.

Ando, Yasunobu; Kawamura, Yoshiumi; Ikeshoji, Tamio; Otani, Minoru

2014-09-01

75

Model electrode structures for studies of electrocatalyst degradation  

Microsoft Academic Search

Proton exchange membrane fuel cells are being extensively studied as power sources because of their technological advantages such as high energy efficiency and environmental friendliness. The most effective catalyst in these systems consists of nanoparticles of Pt or Pt-based alloys on carbon supports. Understanding the role of the nanoparticle size and structure on the catalytic activity and degradation is needed

Jean St. Pierre; Plamen Borissov Atanassov; Abhaya K. Datye; Ronald S. Goeke

2010-01-01

76

Electrode-polarization studies in hot corrosion systems. Progress report, June 1, 1982-May 31, 1983  

SciTech Connect

Electrode polarization studies in molten sodium sulfide: polarization of nickel electrodes in molten 25% FeS - 75% Na/sub 2/S was found to be linear in current, with the major part due to ohmic electrolyte resistance. Nickel was observed to undergo nonelectrodic dissolution in this electrolyte at the rate of 1.6 x 10/sup -6/g cm/sup -2/sec/sup -1/, with anomalous initial behavior attributed to the presence of polysulfide in the melt. Electrode polarization studies in molten sodium carbonate: this task is proceeding in the direction of a complete mechanistic and kinetic understanding of electrode reactions at the H/sub 2//H/sub 2/S/CO/CO/sub 2/, Ni electrode in molten sodium carbonate. Progress is hampered in working with H/sub 2/S. Gas/metal reactions in mixed oxidants: the kinetics of scale formation on iron in H/sub 2//H/sub 2/S/CO/CO/sub 2/ mixtures at 900/sup 0/C was studied over a range of P/sub O/sub 2// values encompassing thermodynamic stability of FeS and Fe/sub 3/O/sub 4/. All scales, however, were FeS, and all behavior seen could be treated as a perturbation of sulfidation kinetics in H/sub 2//H/sub 2/S alone. During this period a highly successful model was developed which invokes an initial period in which islands of scale form and grow laterally and in thickness. After the surface is entirely covered, i.e., the islands impinge, the scale undergoes a period of diffusion-controlled, parabolic growth, following which the outer portion of the scale ceases to be a diffusion barrier by some process, such as recrystallization, which progresses linearly with time. The inner, barrier portion of the scale thus diminishes in thickness until a steady state condition, with linear scale growth, is attained.

Devereux, O.F.

1983-01-01

77

Study of thin calcium electrode degradation by ion beam analysis  

NASA Astrophysics Data System (ADS)

Organic materials used in organic light emitting diodes (OLED) and organic solar cells are easily degraded under atmospheric conditions. Indeed, these devices require encapsulation with a barrier material which exhibits extremely low permeation rates for water vapour and oxygen. In order to determine these low permeation rates, the degradation of a metallic calcium layer encapsulated with the barrier material is usually monitored. However, the individual contributions of oxygen and water vapour to this degradation cannot be clearly distinguished. In this study, the corrosion of metallic calcium was investigated using isotopic markers in connection with ion beam analysis. We have shown that calcium reacts only with water at room temperature.

Cros, S.; Firon, M.; Lenfant, S.; Trouslard, P.; Beck, L.

2006-09-01

78

The acetabular point: a morphological and ontogenetic study  

PubMed Central

The acetabular point was analysed by studying human pelvic bones from 326 individuals ranging from newborns to age 97 y. The bones were categorised into 3 groups according to the degree of fusion for the 3 elements of the pelvis: nonfused (59), semifused (5) and fused (262). The acetabular point in immature pelvic bones is clearly represented by the point of the fusion lines for each bony element at the level of the acetabular fossa. In adult pelvic bones the acetabular fossa has an irregular clover-leaf shape, the superior lobe being smaller than the anterior and posterior lobes. Cross-sectional analysis of acetabular morphology suggested that the acetabular point in adult pelvic bones is always represented by the indentation between the superior and the anterior lobes of the acetabular fossa. PMID:11465866

RISSECH, C.; SAÑUDO, J. R.; MALGOSA, A.

2001-01-01

79

The Use of an Anode Probe Hole Technique to Study Conditioning Processes between Arced Copper Electrodes in Vacuum  

Microsoft Academic Search

The high voltage breakdown strength of pre-arced copper electrodes in vacuum is studied using a novel technique. The conditioning effect of arcing on the arc anode and arc cathode is correlated with the subsequent behavior of the gap under high dc voltages. It is found that the arc cathode is the least conditioned electrode and that under the conditions of

G. J. Rushton; C. Christopoulos; P. A. Chatterton

1978-01-01

80

Using Ion-Selective Electrodes to Study the Drug Release from Porous Cellulose Matrices  

PubMed Central

Polyvinyl chloride (PVC)-based solid-contact ion-selective electrodes (SC-ISEs), responding to propranolol hydrochloride (Pr+) and lidocaine hydrochloride (Ld+) cations as the model drugs with potassium tetrakis(4-chlorophenyl) borate (KTpClPB) as the ion exchanger, were studied. Different drug-polymer solutions were prepared with the model drugs, using different blend ratios of ethylcellulose (EC) and hydroxypropyl cellulose (HPC). Two different solid dosage forms were used. Polymer films were produced by solvent casting method and drug containing porous cellulose samples were prepared by depositing the drug-polymer solutions onto filter paper substrates. The quality of the electrodes and the release profile of Pr+ and Ld+ were investigated with the potentiometric method. The results were compared to UV spectrophotometry. The electrodes were found to be sensitive, precise and functional with a Nernstian behavior over the range of 1.0 × 10?3–3.1 × 10?6 M (9.2 × 10?4–3.0 × 10?1 mg/mL) and 1 × 10?3–2 × 10?6 M (5.4 × 10?4–2.7 × 10?1 mg/mL) at 25 °C for Pr+ and Ld+ sensitive electrodes, respectively. The dynamic response time for the electrodes was less than 10 s. The Pr+ release from porous filter paper was always higher than its equivalent film formulation. Also, lidocaine had higher and faster release from the samples with higher drug concentration. The comparison of the two analytical methods showed near identical results. The ISEs provided a powerful and flexible alternative to UV method in determination of drug release from porous cellulose substrates in a small scale dissolution testing. PMID:24300297

Vakili, Hossein; Genina, Natalja; Ehlers, Henrik; Bobacka, Johan; Sandler, Niklas

2012-01-01

81

Voltammetric studies of the behavior of carbon black during phenol oxidation on Ti/Pt electrodes  

SciTech Connect

Oxidation of phenol on platinum electrodes rapidly leads to the formation of a passivating film on the surface of these electrodes. Studies of cyclic voltammetry and chronoamperometry combined with high-performance liquid chromatography (HPLC) analyses have shown that the presence of carbon black avoids these phenomena of passivation and thus allows the complete mineralization of phenol. The nature of carbon black and the pH value are two important factors which are studied here. VULCAN XC-72 R, an intrinsic p-type semiconductor, having a large specific area, showed all its efficiency when cyclic voltammetry experiments were carried out in an acid medium (pH 2.2). HPLC analyses revealed the appearance of several by-products such as hydroquinone and benzoquinone, and maleic and fumaric acids.

Boudenne, J.L.; Cerclier, O.; Bianco, P. [Univ. de Provence, Marseille (France)

1998-08-01

82

In situ IR spectroscopic study of water at a polycrystalline gold electrode surface  

Microsoft Academic Search

The effect of the electrolyte anions on the water structure at the interface between a polycrystalline gold electrode and aqueous electrolyte solutions was studied using in situ Fourier transform IR reflection absorption spectroscopy (FT-IRAS). Considerably sharp absorption bands due to OH stretching modes of water were observed in the 3600–3500 cm?1 range in solutions containing F?, Cl?, Br?, I?, BF?4,

Fusao Kitamura; Noritoshi Nanbu; Takeo Ohsaka; Koichi Tokuda

1998-01-01

83

Electrochemical studies on gold electrodes in acidic solutions of thiourea containing gold (I) thiourea complex ions  

Microsoft Academic Search

Electrochemical studies were made of the behaviour of gold electrodes in degassed acidic solutions containing between 0.00l to 0.03 M thiourea and between 10-5 to 10-3 M gold(I)thiourea. At anodic overpotentials of up to 0.3 V the dissolution of gold was rapid, and nearly reached the maximum diffusioncontrolled rate. The exchange current density was greater than 10-6 A cm-2, and

T. Groenewald

1975-01-01

84

A study of the electrocatalytic oxidation of aspirin on a nickel hydroxide-modified nickel electrode  

Microsoft Academic Search

The electrocatalytic oxidation of aspirin has been investigated on a nickel oxide-modified nickel electrode in alkaline solution.\\u000a The process of oxidation and its kinetics have been investigated by using cyclic voltammetry, chronoamperometry, and electrochemical\\u000a impedance spectroscopy techniques and also steady-state polarization measurements. Voltammetric studies have indicated that\\u000a in the presence of aspirin, the anodic peak current of low-valence nickel species

S. Majdi; A. Jabbari; H. Heli

2007-01-01

85

Studies on electrochemical oxidation of azithromycin and Hemomycin ® at gold electrode in neutral electrolyte  

Microsoft Academic Search

The aim of the present study was to examine the oxidative properties and an assay of azithromycin and Hemomycin® at a gold electrode in neutral electrolyte using cyclic linear sweep voltammetry. The maximum value of the current of the oxidation peak of pure azithromycin and azithromycin from Hemomycin® at 0.6V versus SCE in 0.05M NaHCO3 and in a mixture methanol

M. L. Avramov Ivi?; S. D. Petrovi?; D. Ž. Mijin; P. M. Živkovi?; I. M. Kosovi?; K. M. Drljevi?; M. B. Jovanovi?

2006-01-01

86

Numerical study on the effect of electrode force in small-scale resistance spot welding  

Microsoft Academic Search

Since electrode force is an important process parameter in small-scale resistance spot welding (SSRSW), its effects on the electrical, thermal and mechanical behavior of the welding process when using direct current have been studied numerically in the present paper using the finite element method. The variations of contact radius, current density distribution and temperature profile at the sheet\\/sheet (S\\/S) and

B. H. Chang; Y. Zhou

2003-01-01

87

TIPPING POINT (Synopsis) (Roy Thompson, Open Studies Summer Course, 2010)  

E-print Network

(Complication) The Industrial age Soffiel's former beauty and poise are in inexorable decline. As more and more tries, despite her declining strength, to raise herself up, and to urge for a curb on technologicalTIPPING POINT (Synopsis) (Roy Thompson, Open Studies Summer Course, 2010) Act I (Set-up)The Iron-Age

88

Locate QCD Critical End Point in a Continuum Model Study  

E-print Network

With a modified chemical potential dependent effective model for the gluon propagator, we try to locate the critical end point (CEP) of strongly interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond the chiral limit, we find that Nambu solution and Wigner solution could coexist in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we show that these two phases are connected by a first order phase transition. We then locate CEP as the end point of the first order phase transition line. Meanwhile, based on CJT effective action, we give a direct calculation for the chiral susceptibility and thereby study the crossover.

Chao Shi; Yong-Long Wang; Yu Jiang; Zhu-Fang Cui; Hong-Shi Zong

2014-03-15

89

Locate QCD critical end point in a continuum model study  

NASA Astrophysics Data System (ADS)

With a modified chemical potential dependent effective model for the gluon propagator, we try to locate the critical end point (CEP) of strongly interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond the chiral limit, we find that Nambu solution and Wigner solution could coexist in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we show that these two phases are connected by a first order phase transition. We then locate CEP as the end point of the first order phase transition line. Meanwhile, based on CJT effective action, we give a direct calculation for the chiral susceptibility and thereby study the crossover.

Shi, Chao; Wang, Yong-long; Jiang, Yu; Cui, Zhu-fang; Zong, Hong-Shi

2014-07-01

90

Studies on a lead-acid cell with electrodeposited lead and lead dioxide electrodes on carbon  

NASA Astrophysics Data System (ADS)

Performance characteristics of a lead-acid cell with electrodeposited lead and lead dioxide electrodes on carbon are evaluated in aqueous sulfuric acid at concentrations ranging from 1 to 4 M. The discharge capacity is practically independent of the discharge rate within the current range studied (˜1 to 15 mA cm -2). The capacity increases with cycling, possibly due to slow attainment of a 'spongy' character for the negative electrode active mass. The capacity also increases with the amount of deposition, reaching a more or less limiting value beyond an optimum deposition. Steady-state discharge behavior, represented by a voltage plateau, shows a nearly Nernstian response, which indicates that the basic electron-transfer processes are quite fast. Experiments involving less than full charge-discharge cycles showed the charging efficiency to pass through a maximum with charging current.

Das, Kaushik; Mondal, Aparesh

91

Pointing Treatments Are Task Relevant: A Visuomotor Priming Study  

PubMed Central

The present study focused on priming effects on pointing with everyday objects. In a set of four experiments, a visuomotor priming paradigm was used to investigate the nature of visuomotor processing (automatic versus task relevant). By manipulating congruency of orientation and location we found that location congruency facilitates the initiation time of pointing whereas orientation congruency does not. We provide evidence to show that motor planning is influenced by the goal of the action, and that how visual information is processed and held in memory depends on the task relevance. These data are consistent with the proposed interaction between visuomotor and higher processes during the planning and execution of actions such as pointing. PMID:24777029

Roche, Kevin; Chainay, Hanna

2014-01-01

92

Lung Radiofrequency Ablation: In Vivo Experimental Study with Low-Perfusion-Rate Multitined Electrodes  

SciTech Connect

The purpose of this study was to investigate the feasibility and safety of lung radiofrequency (RF) ablation by using low-perfusion-rate, expandable, multitined electrodes in an in vivo animal model. Ten New Zealand White rabbits underwent RF ablation using low-perfusion-rate, expandable, multitined electrodes (Starburst Talon; RITA Medical Systems, Mountain View, CA) and a 200-W RF generator. The electrode was positioned under fluoroscopy guidance and a single percutaneous RF ablation was performed. Saline perfusate was doped with nonionic iodinated contrast agent to render it visible on computed tomography (CT). The pump infused the saline doped with contrast agent into the lateral tines at a rate of 0.1ml/min. The planned ablation was of 3 min, with the hooks deployed to 2 cm at a target temperature of 105{sup o}C. An immediate posttreatment CT scan documented the distribution of the doped saline and the presence of immediate complications. The animals were monitored for delayed complications and sacrificed within 72 h (n = 4), 2 weeks (n = 3), or 4 weeks (n = 3). Assessment of ablation zone and adjacent structures was done at autopsy. Major complications consisted of pneumothorax requiring drainage (n = 2) and skin burn (n = 1). Immediately after the procedure the area of ablation was depicted at CT as a round, well-demarcated area, homogeneously opacified by iodinated contrast medium (mean size, 2.3 {+-} 0.8 cm). The presence of a sharply demarcated area of coagulation necrosis (mean size, 2.1 {+-} 0.4 cm) without severe damage to adjacent structures was confirmed at autopsy. In one case, euthanized at 4 weeks, in whom pneumothorax and pleural effusion were depicted, pleural fibrinous adhesions were demonstrated at autopsy. In conclusion, lung RF ablation performed in an in vivo animal model using low-perfusion-rate, expandable, multitined electrodes is feasible and safe. No severe damage to adjacent structures was demonstrated.

Crocetti, Laura, E-mail: l.crocetti@med.unipi.it; Lencioni, Riccardo; Bozzi, Elena [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplant and Advanced Technologies in Medicine (Italy); Sbrana, Alberto [University of Pisa (Italy); Bartolozzi, Carlo [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplant and Advanced Technologies in Medicine (Italy)

2008-05-15

93

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

SciTech Connect

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.

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

94

Dry electrodes for electrocardiography.  

PubMed

Patient biopotentials are usually measured with conventional disposable Ag/AgCl electrodes. These electrodes provide excellent signal quality but are irritating for long-term use. Skin preparation is usually required prior to the application of electrodes such as shaving and cleansing with alcohol. To overcome these difficulties, researchers and caregivers seek alternative electrodes that would be acceptable in clinical and research environments. Dry electrodes that operate without gel, adhesive or even skin preparation have been studied for many decades. They are used in research applications, but they have yet to achieve acceptance for medical use. So far, a complete comparison and evaluation of dry electrodes is not well described in the literature. This work compares dry electrodes for biomedical use and physiological research, and reviews some novel systems developed for cardiac monitoring. Lastly, the paper provides suggestions to develop a dry-electrode-based system for mobile and long-term cardiac monitoring applications. PMID:24137716

Meziane, N; Webster, J G; Attari, M; Nimunkar, A J

2013-09-01

95

Hubble Space Telescope Pointing Control System design improvement study  

NASA Technical Reports Server (NTRS)

As part of the NASA Controls/Structures Integration Program, a study was undertaken to determine if improvements to the performance of the Hubble Space Telescope Pointing Control System could be obtained when advanced control system design techniques were applied using simulation models and telemetry data from the spacecraft. The study was managed through the Marshall Space Flight Center. Four universities and one aerospace company developed controller designs and tested their performance. This paper summarizes the goals and provides an overview of the study.

Bukley, Angelia P.

1993-01-01

96

Use of surfactant-specific electrodes in the study of adsorption of cationic amphiphilic ions onto clays  

SciTech Connect

The adsorption isotherms of dodecyltrimethylammonium ions (DTA{sup +}) adsorbed onto a laponite clay colloid were studied in water and in NaBr solution (at 0.1, 0.3, and 0.5 mol/liter), at 298 K, using amphiphilic ion-specific electrodes. This potentiometric method can be used to measure concentrations in situ and to follow the decrease in the amount of surfactant in the solution as the surfactant is adsorbed onto the clay. This paper describes a method for characterizing adsorption isotherms of DTA{sup +} onto laponite by determining the amount adsorbed at a fixed surfactant activity in solution. By repeating this process for various DTA{sup +} activities, the adsorption isotherm can be plotted. Adsorption isotherms obtained with or without NaBr in the solution were continuous curves which increased with the surfactant activity. The field of study is limited by the CMC value for the surfactant and the curves have a common intersection point, which can be attributed to the isoelectrical point of the laponite/adsorbed surfactant system. This method can be generalized to other cations and obviously to other solids.

Gloton, M.P.; Mayaffre, A.; Turmine, M.; Letellier, P.; Suquet, H. [Univ. Pierre et Marie Curie, Paris (France)] [Univ. Pierre et Marie Curie, Paris (France)

1995-06-01

97

Theoretical and experimental study of the bending influence on the capacitance of interdigitated micro-electrodes patterned on flexible substrates  

NASA Astrophysics Data System (ADS)

Interdigitated electrodes are common structures in the fields of microelectronics and MEMS. Recent developments in flexible electronics compel an understanding of such structures under bending constraints. In this work, the behavior of interdigitated micro-electrodes when subjected to circular bending has been theoretically and experimentally studied through changes in capacitance. An analytical model has been developed to calculate the expected variation in capacitance of such structures while undergoing outward and inward bending along the direction perpendicular to the electrodes. The model combines conformal mapping techniques to account for the electric field redistribution and fundamental aspects of solid mechanics in order to define the geometrical deformation of the electrodes while bending. To experimentally verify our theoretical predictions, several interdigitated electrode structures with different geometries were fabricated on polymeric substrates by means of photolithography. The samples, placed in a customized bending setup, were bent to controlled radii of curvature while measuring their capacitance. A maximum variation in capacitance of less than 3% was observed at a minimum radius of curvature of 2.5 mm for all the devices tested with very thin electrodes whereas changes of up to 7% were found on stiffer, plated electrodes. Larger or smaller variations would be possible, in theory, by adjusting the geometry of the device. This work establishes a useful predictive tool for the design and evaluation of truly flexible/bendable electronics consisting of interdigitated structures, allowing one to tune the bending influence on the capacitance value through geometrical design.

Molina-Lopez, F.; Kinkeldei, T.; Briand, D.; Tröster, G.; de Rooij, N. F.

2013-11-01

98

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

99

Theoretical and experimental study of the bending influence on the capacitance of interdigitated micro-electrodes patterned on flexible substrates  

SciTech Connect

Interdigitated electrodes are common structures in the fields of microelectronics and MEMS. Recent developments in flexible electronics compel an understanding of such structures under bending constraints. In this work, the behavior of interdigitated micro-electrodes when subjected to circular bending has been theoretically and experimentally studied through changes in capacitance. An analytical model has been developed to calculate the expected variation in capacitance of such structures while undergoing outward and inward bending along the direction perpendicular to the electrodes. The model combines conformal mapping techniques to account for the electric field redistribution and fundamental aspects of solid mechanics in order to define the geometrical deformation of the electrodes while bending. To experimentally verify our theoretical predictions, several interdigitated electrode structures with different geometries were fabricated on polymeric substrates by means of photolithography. The samples, placed in a customized bending setup, were bent to controlled radii of curvature while measuring their capacitance. A maximum variation in capacitance of less than 3% was observed at a minimum radius of curvature of 2.5?mm for all the devices tested with very thin electrodes whereas changes of up to 7% were found on stiffer, plated electrodes. Larger or smaller variations would be possible, in theory, by adjusting the geometry of the device. This work establishes a useful predictive tool for the design and evaluation of truly flexible/bendable electronics consisting of interdigitated structures, allowing one to tune the bending influence on the capacitance value through geometrical design.

Molina-Lopez, F.; Briand, D.; Rooij, N. F. de [Ecole Polytechnique Fédérale de Lausanne (EPFL) - Institute of Microengineering (IMT) – Sensors, Actuators and Microsystems Laboratory - SAMLAB, 2002 Neuchâtel (Switzerland); Kinkeldei, T.; Tröster, G. [Eidgenössische Technische Hochschule Zürich (ETHZ) – Electronics Laboratory, 8092 Zurich (Switzerland)

2013-11-07

100

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

E-print Network

in sensing electrodes, shot noise in electrochemical batteries, and 1/f noise in corrosive interfaces electrodes. Their reports all indicated the presence of shot noise in batteries and galvanic processes

Lee, Thomas H.

101

Ancient Astronomy: A Study of the Point Remove Mound Complex  

NASA Astrophysics Data System (ADS)

Artificial solstice markers are a common thread across many early civilizations. With the beginnings of early agriculture, the need to be able to predict the changes in season became an issue of utmost importance. Many Native American groups used artificial mounds to mark different astronomical events. Toltec Mounds (located southeast of Little Rock, AR) is a complex set of structures left behind by the area's native people that is known to have alignments with the summer and winter solstice as well as an equinox alignment. The Point Remove mound complex (located outside Morrilton, Arkansas, also known as site 3CN4) is a known archeological site that has not been well studied, therefore has never been checked for any form of astronomical alignment. The purpose of this project is to study the Point Remove Mound site and look for features of astronomical significance. Study of Toltec Mounds will serve as a baseline for comparison. Study of the site consists of aerial photographs, topographic maps, and GPS measurements. In addition to studying alignments within the site, the location of the mound complex will be studied with respect to other known complexes like Toltec Mounds and Spiro Mounds (Oklahoma).

Hankins, Matt; Burris, D. L.

2012-01-01

102

Plasma meniscus and extraction electrode studies of the ISIS H{sup -} ion source  

SciTech Connect

In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H{sup -} ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.

Lawrie, S. R.; Faircloth, D. C.; Letchford, A. P.; Gabor, C. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Pozimski, J. K. [ISIS Pulsed Spallation Neutron Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX (United Kingdom); Department of Physics, Imperial College of Science and Technology, London SW7 2AZ (United Kingdom)

2010-02-15

103

Parametric study of the preparation of gas-diffusion electrodes for alkaline fuel cells by a filtration method  

NASA Astrophysics Data System (ADS)

The effects of various parameters in preparing Raney-Ni/PTFE anodes for alkaline fuel-cells are investigated. A partial factorial experiment design (2 5-1) analysis reveals that the important parameters are PTFE content and milling time, and their interaction. Thus, one parameter at a time is varied to study its effect on electrode performance. Electrodes prepared with 8 wt.% PTFE and with milling for 60 s exhibit the best performance.

Sleem-ur-Rahman; Al-Saleh, M. A.; Al-Zakri, A. S.

104

Study of selectivity of iodide membrane electrode in autooscillatory potassium iodate-hydrogen peroxide-cysteine-sulfuric acid systems  

SciTech Connect

In the potassium iodate-hydrogen peroxide-cysteine-sulfuric acid system, the authors studied the selectivity of the membrane electrode for a given type of ions at variable concentrations of other components, with particular attention to the influence of the initial concentrations of the various acids on the shift of the iodide selective electrode potential, taking into account the redox reactions between these components in an oscillatory system.

Protopopov, E.V.; Zueva, T.S.

1985-05-01

105

Field experience and dew point studies of a retrofitted roof  

SciTech Connect

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.

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

1997-11-01

106

First-principles study of point defects in thorium carbide  

NASA Astrophysics Data System (ADS)

Thorium-based materials are currently being investigated in relation with their potential utilization in Generation-IV reactors as nuclear fuels. One of the most important issues to be studied is their behavior under irradiation. A first approach to this goal is the study of point defects. By means of first-principles calculations within the framework of density functional theory, we study the stability and formation energies of vacancies, interstitials and Frenkel pairs in thorium carbide. We find that C isolated vacancies are the most likely defects, while C interstitials are energetically favored as compared to Th ones. These kind of results for ThC, to the best authors' knowledge, have not been obtained previously, neither experimentally, nor theoretically. For this reason, we compare with results on other compounds with the same NaCl-type structure.

Pérez Daroca, D.; Jaroszewicz, S.; Llois, A. M.; Mosca, H. O.

2014-11-01

107

Fundamental studies of water oxidation at model hematite electrodes prepared by atomic layer deposition  

NASA Astrophysics Data System (ADS)

An increasing global demand for energy, combined with an awareness of anthropogenic climate change, has recently fueled the search for abundant, carbon neutral energy sources. The sun offers an enormous amount of energy that is practically inexhaustible and well distributed across Earth. Thus, it is an ideal source for meeting our future energy needs in a carbon neutral fashion. This work focuses on using hematite and sunlight to oxidize water, which is the rate limiting step of splitting water into the energy dense fuel, hydrogen, and the byproduct, oxygen. Hematite is abundant, absorbs a large fraction of the solar spectrum and has an appropriately placed valence band for water oxidation. However, the often cited poor bulk properties, and slow charge transfer kinetics require large applied potentials to oxidize water. Atomic layer deposition (ALD) was utilized to deposit uniform thin films of hematite on transparent conductive substrates as model electrodes to better understand the nature of the limitations in the bulk and at the surface. Comparison of the oxidation of water to the oxidation of fast redox shuttles allowed for the separation of bulk and surface processes. A combination of electrochemical impedance spectroscopy, photoelectrochemical and electrochemical measurements were employed to determine the cause of the large required applied potential. It was found that photogenerated holes initially oxidize the electrode surface under water oxidation conditions, which is attributed to the first step in water oxidation. A critical number of these surface intermediates need to be generated in order for subsequent hole-transfer steps to proceed. At low applied potentials, these intermediates are subject to recombination from the large concentration of electrons in the conduction band due to low band bending. At higher applied potentials, high band bending eliminates surface recombination and the charge collection efficiency of the electrolyte reaches unity. A water oxidation mechanism is proposed to interpret these results. In addition, fundamental studies of hematite electrodes coated with the phosphate mediated cobalt oxide catalyst were performed. The catalyst was found to reduce the surface recombination mentioned above. However, oxidized cobalt oxide was still subject to electron recombination at low applied potentials. This recombination was reduced with the use of an alumina blocking layer, which resulted in a modified hematite electrode capable of oxidizing water with a near unity charge collection efficiency at low applied potentials.

Klahr, Benjamin M.

108

Point Contact Andreev Reflection Studies on Iron Pnictide Superconductors  

NASA Astrophysics Data System (ADS)

We have systematically investigated the temperature, doping and the directional dependence of the gap structure for various types of single crystal iron pnictide superconductors by point contact Andreev reflection spectroscopy. Our studies were performed on highly transparent junctions evidenced by sharp and dramatic conductance enhancements at low temperatures. For the 122 family, despite some small features occasionally observed on the spectroscopy curves which may originate from the multiband superconductivity, a more conclusive characteristic of our obtained spectra is the presence of one predominant superconducting gap. By applying the BTK model, we find that the determined gap size scales well with the transition temperature, resulting in the 2?/kBTC value of ˜ 3.1 for both potassium doped and cobalt doped single crystals. Directional studies suggest that this gap is highly isotropic. Results on chalcogenide and nickel doped 122 superconductors will also be discussed. [X. H. Zhang et al., Phys. Rev. B 81, 024518 (2010)].

Zhang, Xiaohang; Saha, S. R.; Butch, N. P.; Kirshenbaum, K.; Paglione, J.; Greene, R. L.; Takeuchi, I.; Oh, Y.-S.; Liu, Y.; Yan, L. Q.; Kim, K.-H.

2011-03-01

109

Structural and electrochemical study of positive electrode materials for rechargeable lithium ion batteries  

NASA Astrophysics Data System (ADS)

The research presented in this dissertation focuses on a combined study of the electrochemistry and the structure of positive electrode materials for Li ion batteries. Li ion batteries are one of the most advanced energy storage systems and have been the subject of numerous scientific studies in recent decades. They have been widely used for various mobile devices such as cell phones, laptop computers and power tools. They are also promising candidates as power sources for automotive applications. Although intensive research has been done to improve the performance of Li ion batteries, there are still many remaining challenges to overcome so that they can be used in a wider range of applications. In particular, cheaper and safer electrodes are required with much higher reversible capacity. The series of layered nickel manganese oxides [NixLi 1/3-2x/3Mn2/3- x/3]O2 (0 < x < 1/2) are promising alternatives for Li2CoO2, the commercial positive electrode materials in Li ion batteries, because of their lower cost and higher safety and abuse tolerance, when lithium is removed from their structure. Compounds with x<1/2, in which the total Li content is higher than transition metal content, are referred as "Li-excess" materials. The "Li2MnO3-like" region is always present in this type of materials, and the overcapacity is obtained in the first charge process, which is not reversible in the following cycles. A combined X-ray diffraction, solid state nuclear magnetic resonance and X-ray absorption spectroscopy study is performed to investigate the effect of synthetic methods on the structure, to probe the structural change of the materials during cycling and to understand the electrochemical reaction mechanism. The conversion compounds are also investigated because of their high capacities. Since the various compounds have different voltage windows, they can have potential applications as both cathodes and anodes. Solid state nuclear magnetic resonance is used to study the change in the local environment of the structure during the cycling process. Two systems are included in this work, including iron fluorides and Cu-containing materials. A comparison study has been performed on FeF3 and FeF2. Different discharge reaction mechanisms are clarified for each compound, and possible phase transitions are proposed as well. As for the Cu-containing systems, three compounds were chosen with different anions: CuS, CuO and CuF2. The reaction mechanisms are studied by 63Cu, 7Li and 19F NMR and supported by powder X-ray diffraction.

Jiang, Meng

110

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

PubMed

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. PMID:24522116

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

2014-03-01

111

Surface roughness analysis and magnetic property studies of nickel thin films electrodeposited onto rotating disc electrodes  

NASA Astrophysics Data System (ADS)

Ni films were electrodeposited onto polycrystalline gold substrates mounted on a rotating disc electrode. The effects of rotation speed, film thickness and current density on the kinetic roughening and magnetic properties of the films were investigated. The film surface roughness was imaged using an atomic force microscope (AFM). The results indicate that the film roughness increases as the film thickness or deposition current density increases. We found that the electrodeposited Ni films exhibit anomalous scaling since both local and large-scale roughnesses show a power-law dependence on the film thickness. The effect of electrode rotation speed on the film surface roughness was also investigated. Scanning electron microscopy studies (SEM) had a good agreement with the AFM results. The average crystalline size of the film surfaces is also calculated from X-ray line broadening using (220) peak and Debye-Scherrer formula. The obtained results agree with that of AFM and SEM. The Ni thin films which are grown at different deposition current densities and rotation speeds exhibit in-plane magnetization with coercivities less than 110 Oe.

Hedayati, K.; Nabiyouni, G.

2014-09-01

112

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

113

Point of View: Leadership Studies from Different Perspectives  

ERIC Educational Resources Information Center

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…

Harter, Nathan

2012-01-01

114

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

ERIC Educational Resources Information Center

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…

Butterworth, George; Adamson-Macedo, Elvidina

115

Chalk Point auxiliary pump study: 1981. Final report  

SciTech Connect

In July 1981, the Academy of Natural Sciences of Philadelphia undertook a study to examine the numbers of finfish and blue crabs (Callinectes sapidus) entrained through the auxiliary cooling pumps at the Chalk Point Steam Electric Station (SES) operated by the Potomac Electric Power Company. Samples were collected by positioning a net attached to a hinged steel frame directly in the discharge of the auxiliary pumps. Concurrently, impingement rates of fish and blue crabs on the travelling screens were estimated by collecting the organisms washed into the troughs that lead to the discharge canal. A total of 6673 fish and blue crabs, representing 13 species, was collected in auxiliary pump samples at the Chalk Point generating station during July and August 1981. A total of 2154 fish and blue crabs representing seven species was collected in concurrent impingement samples. Blue crabs represented almost all of the total. The numbers of individuals entrained through auxiliary pumps showed a diel effect, with most individuals entrained at night.

Hirshfield, M.F.; Hixson, J.H. III; Perry, E.S.

1982-03-26

116

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

SciTech Connect

A literature review is presented on the field of polymer modified electrodes which can be electrochemically generated. It is suggested that a possible application of these polymer modified electrodes is as a regeneratable catalysis packing material for use in couter-current exchange columns. Secondly, there is a presentation of experimental results dealing with possible electrode modification using difluoro- and dimethyl- phenols and fluorinated derivatives of styrene, benzoquinone and hydroquinone. It appears that dimethylphenol shows the most potential of the monomers experimentally tested in providing a stable polymer modified electrode surface. 170 refs., 31 figs., 1 tab.

Jayanta, P.S.; Ishida, Takanobu.

1991-05-01

117

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

NASA Technical Reports Server (NTRS)

A detailed electrochemical model of the alkali metal thermoelectric converter (AMTEC) electrode and current collector grid has been developed recently. Comparative evaluations of the resulting differences in model predictions reveal that the new detailed model predicts up to 50 percent higher electrode power densities at condenser operating temperatures above 600 K. The new model, with experimentally determined parameters, was used to recalculate the projected system performance of previously reported 1- and 100-kWe AMTEC space power systems that had incorporated earlier electrolyte/electrode models. It was found that when the detailed model was used to determine the electrode power densities, enhanced specific power and efficiencies are predicted.

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

1992-01-01

118

Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries  

SciTech Connect

Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous oxidation of Fe{sup 2+} and Mn{sup 2+} in a small range of compositions. Black-Right-Pointing-Pointer Surface analysis from XPS allows reveals slight differences at the surface of the electrode with respect to the bulk.

Perea, A. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Castro, L. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Aldon, L., E-mail: laurent.aldon@um2.fr [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Stievano, L. [Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France); Dedryvere, R.; Gonbeau, D. [IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France); Tran, N.; Nuspl, G. [Sued-Chemie AG, Ostenriederstr. 15, D-85368 Moosburg (Germany); Breger, J.; Tessier, C. [SAFT, 111-113 bd. Alfred Daney, 33074 Bordeaux, Cedex (France)

2012-08-15

119

A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells  

PubMed Central

This study describes a systematic approach of TiO2/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO2 and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO2 to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized. PMID:23672498

2013-01-01

120

A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

This study describes a systematic approach of TiO2/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO2 and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO2 to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized.

Lim, Jeongmin; Ryu, Sang Yeoul; Kim, Jeonghun; Jun, Yongseok

2013-05-01

121

Cobalt (hydro)oxide electrodes under electrochemical conditions: a first principle study  

NASA Astrophysics Data System (ADS)

There is currently much interest in photoelectrochemical water splitting as a promising pathway towards sustainable energy production. A major issue of such photoelectrochemical devices is the limited efficiency of the anode, where the oxygen evolution reaction (OER) takes place. Cobalt (hydro)oxides, particularly Co3O4 and Co(OH)2, have emerged as promising candidates for use as OER anode materials. Interestingly, recent in-situ Raman spectroscopy studies have shown that Co3O4 electrodes undergo progressive oxidation and transform into oxyhydroxide, CoO(OH), under electrochemical working conditions. (Journal of the American Chemical Society 133, 5587 (2011))Using first principle electronic structure calculations, we provide insight into these findings by presenting results on the structural, thermodynamic, and electronic properties of cobalt oxide, hydroxide and oxydroxide CoO(OH), and on their relative stabilities when in contact with water under external voltage.

Chen, Jia; Selloni, Annabella

2013-03-01

122

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

NASA Technical Reports Server (NTRS)

Localized corrosion in welded samples of 2219-T87 Al alloy (2319 filler), 2090 Al-Li alloy (4043 and 2319 fillers), and 2195 Al-Li alloy (4043 and 2319 fillers) has been investigated using the relatively new scanning reference electrode technique. The weld beads are cathodic in all cases, leading to reduced anode/cathode ratios. A reduction in anode/cathode ratio leads to an increase in the corrosion rates of the welded metals, in agreement with results obtained in previous electrochemical and stress corrosion studies involving the overall corrosion rates of welded samples. The cathodic weld beads are bordered on both sides by strong anodic regions, with high propensity for corrosion.

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

1995-01-01

123

Binding studies and anion-selective electrodes with neutral isophthalamide-based receptors.  

PubMed

Two acyclic isophthalamide-based hosts have been synthesised and their anion binding properties have been evaluated by (1)H-NMR titrations. Different binding modes have been detected for the series of tested anions. The attachment of aminomethylpyrrole groups resulted in an improved binding selectivity. Additionally, the receptors have been incorporated as ionophores in plasticised polymeric membrane-based anion-selective electrodes. The potentiometric studies were in agreement with the NMR experiments and revealed a good sensing ability, considering the structural simplicity of the receptors and their interactions purely based on hydrogen bonding. These preliminary experiments have revealed an interesting selectivity towards highly hydrophilic anions such as fluoride and sulfate. Moreover, a particularly low detection limit (9 × 10(-7) M) has been determined for the fluoride anion. PMID:25368872

Más-Montoya, Miriam; Cuartero, María; Curiel, David; Ortuño, Joaquín A; Soledad García, M; Tárraga, Alberto

2014-12-01

124

Chalk Point steam electric station studies Patuxent Estuary studies: ichthyoplankton population studies, 1979. Final report  

SciTech Connect

Two years of riverwide ichthyoplankton data were collected as a part of a series of studies at the Chalk Point Steam Electric Station (SES) to contribute data necessary to evaluate information to be presented in the 316 variance demonstration document scheduled for Units 1 and 2 of this facility during 1981. These studies also provided information on the regional spatial and temporal distribution of fish eggs and larvae required to put nearfield studies conducted by the Potomac Electric Power Company into regional context. The principal species collected were white perch, striped bass, bay anchovy, sliversides, naked goby, yellow perch, and clupeids.

Mihursky, J.A.; Wood, K.V.; Kerig, S.; Setzler-Hamilton, E.M.

1980-04-01

125

Electrode and Langmuir probe tools used for flow damping studies in the Helically Symmetric Experiment  

SciTech Connect

A system of electrodes and Langmuir probes has been developed for the measurement of plasma flow damping in the Helically Symmetric Experiment (HSX) stellarator. A biased electrode is used to apply a JxB torque to the plasma. The fast switching electrode power supply allows the electrode voltage to be applied in {approx}1 {mu}s, which is much faster than any of the plasma time scales; the electrode current is terminated on a similar time scale at the end of the electrode pulse. A pair of multitipped Mach probes have been designed to measure the plasma flows in a magnetic surface with good spatial and time resolution ({delta}t>20 {mu}s). The unmagnetized model by Hutchinson is used to analyze the Mach probe data, and radial force balance is found to be well satisfied during electrode bias. These probes allow for measurements of the transient response of the plasma flows and floating potential when the electrode is energized. An example of using the system for the estimation of viscous damping times in HSX is provided.

Gerhardt, S.P.; Anderson, D.T.; Anderson, F.S.B.; Talmadge, J.N. [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53703 (United States)

2004-11-01

126

Tricritical point in ferroelastic ammonium titanyl fluoride: NMR study  

NASA Astrophysics Data System (ADS)

Ionic mobility and phase transitions in ammonium titanyl pentafluoride (NH 4) 3TiOF 5 were studied using the 19F and 1H NMR data. The high-temperature phase (I) is characterized by spherically symmetric (isotropic) reorientation of [TiOF 5] 3- anions and by uniaxial reorientation of these anions in the ferroelastic phase II. A previously unknown second-order phase transition to the low-temperature modification (NH 4) 3TiOF 5(III) was found at 205 K. The transition is accompanied by hindering of uniaxial rotations of [TiOF 5] 3- anions and by noticeable change of 19F magnetic shielding tensor associated with the influence of pseudo-Jahn-Teller effect. A pressure-induced tricritical point with coordinates pTCR?2 kbar and TTCR?170 K is estimated on the base of 19F NMR chemical shift data, and previously studied p- T diagram of (NH 4) 3TiOF 5.

Kavun, V. Ya.; Kozlova, S. G.; Laptash, N. M.; Tkachenko, I. A.; Gabuda, S. P.

2010-09-01

127

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

NASA Astrophysics Data System (ADS)

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.

Zhang, Xulong

128

Electrode compositions  

DOEpatents

An electrode composition for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C.sub.8 -C.sub.15 alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5-4.5 volts.

Block, Jacob (Rockville, MD); Fan, Xiyun (Orange, TX)

1998-01-01

129

Electrode compositions  

DOEpatents

An electrode composition is described for use as an electrode in a non-aqueous battery system. The electrode composition contains an electrically active powder in a solid polymer and, as a dispersant, a C{sub 8}-C{sub 15} alkyl capped oligomer of a hexanoic acid that is electrochemically inert at 2.5--4.5 volts.

Block, J.; Fan, X.

1998-10-27

130

[Surface-enhanced raman spectroscopy study of vitamin B12 on copper electrode].  

PubMed

The vitamin B12 molecule has long fascinated chemists because of its exclusive complex structure and unusual reactivities in biological systems. In order to achieve a better understanding of the structural attribute of the Vitamin B12 molecule when it interacted with metal, in the present paper, the vitamin B12 molecules adsorbed on variation of copper electrode potential from 0 to -1.0 V was studied by surface-enhanced Raman spectroscopy (SERS). An excellent SERS substrate was obtained with insitu electrochemical oxidation-reduction cycle (ORC), and its surface roughness was characterized by atomic force microscope (AFM). Assignments of Raman peaks observed by normal Raman spectrum (NRS) and SERS spectra of vitamin B12 molecule were given based on previous literatures. It was found that the potential-dependent relative intensity changed in SERS spectra which depended on the vitamin B12 molecular orientation with respect to the copper surface according to the surface selection rule (SSR). It was concluded that the corrin ring was adsorbed in tilt form on copper surface and the Co-CN group was farther away from the copper surface at higher potentials. With the decrease in potential, the tilt angle between the corrin ring and copper surface became smaller, then the Co-N group and 5,6 dimethylbenzimidazole group got close to the copper surface. The results offered an important structural attribute of vitamin B12 molecule when it interacted with copper electrode for the first time, and supplied a meaningful reference for the electrochemical bioactivity of the vitamin B12 molecule. PMID:24369644

Wang, Bo; Chang, Da-hu; Lu, Gang; Wang, Tian-hu; Zhang, Zhen-long; Mo, Yu-jun

2013-09-01

131

Study of freezing-point depression of selected food extracts  

SciTech Connect

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.

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

132

A rapid method for determining standard 10/10 electrode positions for high resolution EEG studies.  

PubMed

This report describes the basic principle and examines the comparative accuracy of a novel method for locating 3-D coordinates of electrode positions on the head. The method involves calculation of the 3-D coordinates for any array of 10/10 electrode positions from 14 straight-line distances between 11 10/10 electrodes. In 11 subjects the 3-D coordinates of 64 scalp electrodes embedded in an electrode cap were identified with the novel method, and also with a standard commercial magnetic field digitizer. The outcomes from the two methods were compared with directly measured coordinates of all 64 positions (cf. De Munck, J.C., Vijn, P.C.M. and Spekreijse, H. A practical method for determining electrode positions on the head. Electroenceph. clin. Neurophysiol., 1991, 89: 85-87). Coordinates in 3 dimensions obtained using the new method were significantly closer to the directly measured values than those from the magnetic field digitizer. The new method was also quicker and requires less specialized instrumentation than the magnetic field digitization method. The novel method appears to be a valid and convenient tool for use with EEG analysis techniques that require specific information about 10/10 electrode positions. PMID:9741756

Le, J; Lu, M; Pellouchoud, E; Gevins, A

1998-06-01

133

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

SciTech Connect

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.

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

2010-08-01

134

A comparative study of nano-scale coatings on gold electrodes for bioimpedance studies of breast cancer cells.  

PubMed

The relative sensitivity of standard gold microelectrodes for electric cell-substrate impedance sensing was compared with that of gold microelectrodes coated with gold nanoparticles, carbon nanotubes, or electroplated gold to introduce nano-scale roughness on the surface of the electrodes. For biological solutions, the electroplated gold coated electrodes had significantly higher sensitivity to changes in conductivity than electrodes with other coatings. In contrast, the carbon nanotube coated electrodes displayed the highest sensitivity to MDA-MB-231 metastatic breast cancer cells. There was also a significant shift in the peak frequency of the cancer cell bioimpedance signal based on the type of electrode coating. The results indicate that nano-scale coatings which introduce varying degrees of surface roughness can be used to modulate the frequency dependent sensitivity of the electrodes and optimize electrode sensitivity for different bioimpedance sensing applications. PMID:24867593

Srinivasaraghavan, Vaishnavi; Strobl, Jeannine; Wang, Dong; Heflin, James R; Agah, Masoud

2014-10-01

135

Working Electrodes  

NASA Astrophysics Data System (ADS)

In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution; however, solid electrolytes and ionic melts can be used as well. The term "electrode" is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term "electrode" is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term "electrode" usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9].

Komorsky-Lovri?, Šebojka

136

An electrode array study of electrochemical inhomogeneity of zinc in zinc\\/steel couple during galvanic corrosion  

Microsoft Academic Search

The local electrochemical properties of anodic metal within a zinc\\/steel couple immersed in seawater was studied via an electrode array composed of zinc and mild steel wire sensors. It showed that the potential and current density distribution of zinc wires were inhomogeneous, and the main anodic area moved from the zinc wires adjacent to the steel wires and even further

Da-Lei Zhang; Wei Wang; Yan Li

2010-01-01

137

Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon nanotube dispersed polythiophene-fullerene  

E-print Network

Nanostructured electrodes for organic bulk heterojunction solar cells: Model study using carbon for organic pseudo-bilayer solar cells J. Appl. Phys. 112, 084511 (2012) Addition of regiorandom poly(3 (2012) Tunable open-circuit voltage in ternary organic solar cells Appl. Phys. Lett. 101, 163302 (2012

Hone, James

138

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

E-print Network

in continuous flow. Parasitic current flow did not appreciably impact reactor performance. a r t i c l e i n fElectrochemical study of multi-electrode microbial fuel cells under fed-batch and continuous flow connections. Polarization tests were needed to compare individual reactors with combined MFCs. Same power

139

RESEARCH ON SPUTTERING PHENOMENA, SURFACE STABILITY AND VOLTAGE BREAKDOWN FOR ALKALI-COATED REFRACTORY ELECTRODES. Quarterly Report No. 2, August 1, 1961October 31, 1961  

Microsoft Academic Search

Studies of voltage breakdown in ion propulsion systems are described. ; Results of microscopic examinations of Cs deposited on W electrodes indicate that ; under ion propulsion conditions, Cs intercepted by the electrodes can accumulate ; and apread readily from the point of impact, thus enhancing the breakdown ; likelinood by spreading on the electrode support insulation. Plans for examining

R. L. Strayer; F. M. Charbonnier; E. C. Cooper

1963-01-01

140

Fabrication and heating rate study of microscopic surface electrode ion traps  

E-print Network

We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with a trapping height of approximately 240 ?m. Using the Doppler recooling method, we characterize the trap heating rates ...

Daniilidis, N.

141

Cyclic voltammetric study of alpha-methyldopa at carbon paste electrode.  

PubMed

The cyclic voltammetric behaviour of alpha-methyldopa at a silicon oil carbon paste electrode has been reported. This allowed the development of a quantitative method to determine alpha-methyldopa in LiCl, KCl, NaCl, HCl, H2SO4 and CH3COOH as supporting electrolytes. For qualitative characteristics, alpha-methyldopa showed an ECC mechanism in terms of electron transfer reaction (placing it in DPI zone) at carbon paste electrode. The values of transfer coefficients alpha and beta were determined. The larger DeltaEp values were obtained due to the use of unmodified carbon paste electrode (CPE) has decreased the rate of electron transfer at the surface of the test electrode. The first order rate constant values (ko) were within 0.10-7.78 +/- 0.1x10(-3) s(-1). Adsorption of analyte was also determined at CPE using repeated scan method. PMID:16431377

Ali, S Azhar; Sami, M A

2005-01-01

142

STUDIES ON TWO CLASSES OF POSITIVE ELECTRODE MATERIALS FOR LITHIUM-ION BATTERIES  

E-print Network

4) Lithium Battery Cathode. Electrochemical and Solid-StateBattery Electrodes Utilizing Fibrous Conductive Additives. Electrochemical and Solid-Statesolid state, these effects can become limiting in some systems. 1.3 Battery

Wilcox, James D.

2010-01-01

143

Electrochemical study of the interaction between dsDNA and copper(II) using carbon paste and hanging mercury drop electrodes  

Microsoft Academic Search

The interaction of copper(II) with double-stranded (ds) calf thymus DNA was studied in solution as well as at the electrode\\u000a surface by means of differential pulse stripping voltammetry and alternating current voltammetry, using carbon paste electrode\\u000a and hanging mercury drop electrode, respectively. As a result of the interaction of Cu(II) with dsDNA, the characteristic\\u000a peak of dsDNA, due to the

Zorka Stani?; Stella Girousi

2009-01-01

144

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

Microsoft Academic Search

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

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

1995-01-01

145

Topology Study of Photovoltaic Interface for Maximum Power Point Tracking  

Microsoft Academic Search

This paper looks at the performance of photovoltaic modules in nonideal conditions and proposes topologies to minimize the degradation of performance caused by these conditions. It is found that the peak power point of a module is significantly decreased due to only the slightest shading of the module, and that this effect is propagated through other nonshaded modules connected in

Weidong Xiao; Nathan Ozog; William G. Dunford

2007-01-01

146

REGIONAL AIR POLLUTION STUDY. POINT SOURCE EMISSION INVENTORY  

EPA Science Inventory

Emission data from stationary point sources in the St. Louis Interstate Air Quality Control Region were gathered during 1975. Data for 'criteria' pollutants were obtained on an hourly basis. Emissions from large sources were based on hourly, measured values at pertinent operating...

147

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

PubMed

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

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

2012-03-15

148

A Printed Superoxide Dismutase Coated Electrode for the Study of Macrophage Oxidative Burst  

PubMed Central

The miniaturization of electrochemical sensors allows for the minimally invasive and cost effective examination of cellular responses at a high efficacy rate. In this work, an ink-jet printed superoxide dismutase electrode was designed, characterized, and utilized as a novel microfluidic device to examine the metabolic response of a 2D layer of macrophage cells. Since superoxide production is one of the first indicators of oxidative burst, macrophage cells were exposed within the microfluidic device to phorbol myristate acetate (PMA), a known promoter of oxidative burst, and the production of superoxide was measured. A 46 ± 19% increase in current was measured over a 30 min time period demonstrating successful detection of sustained macrophage oxidative burst, which corresponds to an increase in the superoxide production rate by 9 ± 3 attomoles/cell/sec. Linear sweep voltammetry was utilized to show the selectivity of this sensor for superoxide over hydrogen peroxide. This novel controllable microfluidic system can be used to study the impact of multiple effectors from a large number of bacteria or other invaders along a 2D layer of macrophages, providing an in vitro platform for improved electrochemical studies of metabolic responses. PMID:22257735

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

2012-01-01

149

Study of a layered iron(III) phosphate phase Na3Fe3(PO4)4 used as positive electrode in lithium batteries  

E-print Network

prepared by solid-state reaction was studied as positive electrode in lithium batteries. Up to 1.9 Li and lithium batteries. 1. Introduction : Recently, a new class of cathodic material based on iron phosphatesStudy of a layered iron(III) phosphate phase Na3Fe3(PO4)4 used as positive electrode in lithium

Paris-Sud XI, Université de

150

Liquid electrode  

DOEpatents

A dropping electrolyte electrode for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions.

Ekechukwu, Amy A. (Augusta, GA)

1994-01-01

151

A new disposable electrode for electrochemical study of leukemia K562 cells and anticancer drug sensitivity test.  

PubMed

Developing cost-effective and simple analysis tools is of vital importance for practical applications in bioanalysis. In this work, a new disposable electrochemical cell sensor with low cost and simple fabrication was proposed to study the electrochemical behavior of leukemia K562 cells and the effect of anticancer drugs on cell viability. The analytical device was integrated by using ITO glass as the substrate of working electrodes and paper as the electrolytic cell. The cyclic voltammetry of the K562 cells at the disposable electrode exhibited an irreversible anodic peak and the peak current is proportional to the cell number. This anodic peak is attributed to the oxidation of guanine in cells involving two protons per transfer of two electrons. For the drug sensitivity tests, arsenic trioxide and cyclophosphamide were added to cell culture media. As a result, the electrochemical responses of the K562 cells decreased significantly. The cytotoxicity curves and results obtained corresponded well with the results of CCK-8 assays. In comparison to conventional methods, the proposed method is simple, rapid and inexpensive. More importantly, the developed sensor is supposed to be a single-use disposable device and electrodes were prepared "as new" for each experiment. We think that such disposable electrodes with these characteristics are suitable for experimental study with cancer cells or other types of pathogens for disease diagnosis, drug selection and on-site monitoring. PMID:24140828

Yu, Chunmei; Zhu, Zhenkun; Wang, Li; Wang, Qiuhong; Bao, Ning; Gu, Haiying

2014-03-15

152

Studies of calcium channels in rat clonal pituitary cells with patch electrode voltage clamp  

PubMed Central

1. The properties of the Ca channel in tissue cultured clonal cells (GH3) isolated from a rat anterior pituitary tumour were studied with the patch electrode voltage-clamp technique. 2. To isolate the current through the Ca channel, the currents through the Na channel, the delayed K channel and the Ca2+ induced K channel were minimized by replacing the external Na+ with TEA+ and adding EGTA to the K-free solution inside the patch electrode. 3. The selectivity ratios through the Ca channel with different cations were 2·7 (Ba2+):1·6 (Sr2+):1·0 (Ca2+) and the m2 form of the activation kinetics and the relationships between the time constant and the membrane potential were common to the three divalent cations. 4. The amplitude of the Ba2+ current increased linearly with [Ba2+]o up to 25 mM and thereafter tended to show saturation. 5. The current—voltage relation showed a positive shift along the voltage axis as [Ba2+]o increased, probably due to the screening effect of Ba2+ on the negative surface charges. 6. The time constant of activation as a function of the membrane potential showed a parallel shift as [Ba2+]o was increased, suggesting that the activation kinetics were independent of the permeant ion concentration. 7. The time constant of the tail current was consistent with m2 kinetics for opening and closing of the Ca channel. 8. The extrapolated `instantaneous' tail current rapidly increased as the activating membrane potential became more positive and reached an apparent saturation at membrane potentials substantially more positive than the potential that gave the maximum peak inward current, and suggested that the single channel has a sigmoidal current—voltage relationship. 9. The power density spectrum obtained during the steady-state inward Ba2+ current had a cut-off frequency which was nearly voltage independent; this is expected if the fluctuation of the current originates from m2 activation kinetics. 10. The results of noise analysis suggest that the amplitude of the single Ca channel current was about 0·2 pA at 25 mM-Ba2+ and 0·7 pA at 100 mM-Ba2+ for membrane potentials in the vicinity of the maximum inward current. PMID:6296367

Hagiwara, Susumu; Ohmori, Harunori

1982-01-01

153

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

SciTech Connect

Materials that undergo a conversion reaction with lithium (e.g., metal fluorides MF{sub 2}: M = Fe, Cu, ...) often accommodate more than one Li atom per transition-metal cation, and are promising candidates for high-capacity cathodes for lithium ion batteries. However, little is known about the mechanisms involved in the conversion process, the origins of the large polarization during electrochemical cycling, and why some materials are reversible (e.g., FeF{sub 2}) while others are not (e.g., CuF{sub 2}). In this study, we investigated the conversion reaction of binary metal fluorides, FeF{sub 2} and CuF{sub 2}, using a series of local and bulk probes to better understand the mechanisms underlying their contrasting electrochemical behavior. X-ray pair-distribution-function and magnetization measurements were used to determine changes in short-range ordering, particle size and microstructure, while high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) were used to measure the atomic-level structure of individual particles and map the phase distribution in the initial and fully lithiated electrodes. Both FeF{sub 2} and CuF{sub 2} react with lithium via a direct conversion process with no intercalation step, but there are differences in the conversion process and final phase distribution. During the reaction of Li{sup +} with FeF{sub 2}, small metallic iron nanoparticles (<5 nm in diameter) nucleate in close proximity to the converted LiF phase, as a result of the low diffusivity of iron. The iron nanoparticles are interconnected and form a bicontinuous network, which provides a pathway for local electron transport through the insulating LiF phase. In addition, the massive interface formed between nanoscale solid phases provides a pathway for ionic transport during the conversion process. These results offer the first experimental evidence explaining the origins of the high lithium reversibility in FeF{sub 2}. In contrast to FeF{sub 2}, no continuous Cu network was observed in the lithiated CuF{sub 2}; rather, the converted Cu segregates to large particles (5-12 nm in diameter) during the first discharge, which may be partially responsible for the lack of reversibility in the CuF{sub 2} electrode.

Wang, Feng; Robert, Rosa; Chernova, Natasha A.; Pereira, Nathalie; Omenya, Fredrick; Badway, Fadwa; Hua, Xiao; Ruotolo, Michael; Zhang, Ruigang; Wu, Lijun; Volkov, Vyacheslav; Su, Dong; Key, Baris; Whittingham, M. Stanley; Grey, Clare P.; Amatucci, Glenn G.; Zhu, Yimei; Graetz, Jason (Rutgers); (SBU); (Cambridge); (SUNY-Binghamton); (BNL)

2012-03-15

154

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

NASA Astrophysics Data System (ADS)

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..

Yang, Xiaoling; Miley, George H.

2009-03-01

155

Study of Point Blast wave Instability in Numerical Experiment  

NASA Astrophysics Data System (ADS)

The detection of cases demonstrating an unstable evolution of the point blast wave in perfect gas was the problem actually formulated since 1980s when it was found with the help of self-similar approach to stability problem that for cases of gas specific ratio ? being less than 1.20 bllast wave became unstable: the Rayleigh-Taylor type instability showed up at the shock front (Ref.1-3). Later these results were confirmed in computer experiments when 2D hydrodynamic code was used. This code selected shock wave front and used the 1-st order Godunov scheme. In this paper we set ourselves the task of doing that using 3D hydrodynamic code. So we carry out computer simulation of blast wave using 3D Eulerian code TREK (Ref.5,6). The other objective of computation is to determine if the regime of perturbation evolution depends on the second (angular) number of spherical harmonic. The computation geometry is as follows: At t=0, the initial pressure is set constant in the centre region, and the pressure is equal to zero beyond this region. The central region presents a slightly perturbed sphere: the value of sphere radius has a small perturbation proportional to spherical harmonic (Legendre polynomial). The entire material is ideal gas with density being equal of unit and ? = 1.1- 1.2. The perturbations considered are of reasonably high harmonic polar numbers n: n=16 and higher. Computation results are as follows: We prove the perturbation amplitude increase in case of n=16 and ? < 1.2 i.e. we get the direct proof of blast wave instability in these cases. We prove also that the perturbations evolution mode converts to the self-similar pattern in a short time (i.e. when the shock front radius increased by 3-4 times) independently from initial conditions and further proceeds according to the self-similar theory. We prove that oscillations period of non-axially symmetric harmonics is equal to that of axially symmetric ones with the same polar number n. We prove also that these periods are equal to that in self-similar theory (Ref.1-3). The non linear stage of evolution of blast wave axially symmetric perturbations is also studied. The computation of raising perturbations evolution is continued until the formation of singularities and jets on the axis of symmetry and their turbulizations. 1. V.Ktitorov, Voprosy Atomnoi Nauki i Tekhniki, Ser.TPF, No2, p.28, (1984); 2. D.Ryu and E.T.Vishniac, Astr.J, 313, p.820 (1987); 3. V.Ktitorov, Khimich. Fizika (Chem Phys Issues) V.14, No 2-3, p.169, (1995); 4. V.Ktitorov, V.Meltzas, Proceedings of the 6th IWPTM, p.251-258. 5. A.Stadnik, V.Tarasov, Yu. Yanilkin, Voprosy Atomnoi Nauki i Tekhniki, Ser.MMFP, No3, p.52, (1995); 6. Yu.Yanilkin et al., Proceedings of the 6th IWPTM,. p.520-526.

Ktitorov, Vladimir; Yanilkin, Yurii

1999-06-01

156

A study on the ignition characteristics of inductively coupled electrode-less lamp  

NASA Astrophysics Data System (ADS)

Almost twenty years have passed since the first electrode-less lamp operated at 13.56MHz was put on the market. Since then, it has come to be expected that the lumen output and the efficiency of these lamp systems would be improved. The present electrode-less lamp system operated at 135kHz has higher efficiency and output than the high pressure mercury lamp system which is very popular in the market. However, the ignition mechanism of the electrode-less lamp has not yet been completely worked out. To grasp the ignition voltage and time is very important for designing this lamp system, because these influence the cost of the system. The authors investigated how to reduce the ignition time. With regard to the ignition for magnetic coupled electrode-less lamp, it was reported that there are theoretically two types of ignition, E-discharge and H-discharge. However, the definition of the ignition actually is regarded as the time when the H-discharge occurs. The authors observed the starting state of the electrode-less lamp and found that the performance of the circuit influenced the transition from E- discharge to H- discharge. The large current is necessary for the smooth transition from E- discharge to H- discharge right after the E- discharge occurs.

Uetsuki, Tadao; Fujita, Masao; Saimi, Motohiro; Kakehashi, Hidenori

2009-10-01

157

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

NASA Astrophysics Data System (ADS)

For the first time silver wire electrodes have been coated with carbon nanotubes using floating catalyst chemical vapor deposition (CVD) method. The production of CNTs has been conducted in a horizontal tubular reactor. Acetylene gas was used as a carbon source. Ferrocene has been used as a catalyst precursor for the growth of CNT. Different parameters have been optimized to get a high yield of CNTs and ensure their growth on the silver electrodes using univariate method. The parameters studied include the hydrogen flow rate, acetylene flow rate, temperature of the furnace, time of the reaction and the location of the electrodes in the reactor tube. The optimum conditions for those parameters were: for hydrogen and acetylene, the flow rates were 25 mL /min and 75 mL / min respectively. The furnace temperature was found to be 700 °C and the reaction time was 15 minutes. Regarding the location of the silver wires it should be located in the first 10 cm of the front side of the tube. Scanning electron microscopy (SEM) and transition electron microscopy (TEM) have been used to characterize carbon on silver electrodes. According to the experimental results, TEM figures show that CNT produced on Silver wire is multiwall carbon nanotubes MWCNT. Silver electrodes either pure or coated with CNT were used as indicating systems in micro titration using both dc differential electrolytic potentiometry (DEP) and mark-space bias DEP techniques. All types of titrimetric reactions were investigated using different types of electrodes like Pt and gold for oxidation reduction titrations, antimony electrodes for acid base titrations, silver electrodes for precipitation titrations in addition to Ag-CNT electrodes. End points at volumes of 1 microL were determined. Different parameters were optimized like the current density, the percentage bias, the volume of the sample and the concentrations of the reactants. Microtitrimetry has been applied on several types of analytes; Ferrous, Ascorbic acid, chloride, Cyanide, Sodium Bicarbonate and Ketoconazole in aqueous and non- aqueous medium. The performance of Ag-CNT electrodes was found to be much better than the normal silver electrodes. The differential titration curves obtained were symmetrical with significant heights. For silver electrodes coated with CNT the first derivative of the potential was found to give better curves than the normal differential curves, hence the end point location was successfully achieved. A micro liter injector that can deliver volumes at a micro liter level was designed and fabricated. Microtitrimetry which requires volumes of reagents at the micro liter level can offer a solution to the large consumption of reagents in all classical titrimetric processes. Hence, large savings in reagents as well as less waste will reach the environment.

Amro, Abdulaziz Nabil

158

Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials  

NASA Astrophysics Data System (ADS)

Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and deuterium-intercalated pyrolusite and ramsdellite were detected by NMR, for the first time, and their locations and motions in the structures were analyzed by applying variable temperature NMR techniques. Discharge mechanisms of EMD in alkaline (aqueous) electrolytes were studied, in conjunction with step potential electrochemical spectroscopic (SPECS) method, and five distinctive discharge processes were proposed. EMD is usually heat-treated at about 300--400°C to remove water to be used in lithium batteries. Details of the effects of heat-treatment, such as structural and compositional changes as a function of heat-treatment temperature, were studied by a combination of MAS NMR, XRD, and thermogravimetric analysis. Lithium local environments in heat-treated EMD (HEMD) that were discharged in lithium cells, were described in terms of related environments found in model compounds pyrolusite and ramsdellite where specific Li + sites were detected by MAS NMR and the hyperfine shift scale method of Grey et al. Acid-leaching of Li2MnO3 represents an approach for synthesizing new or modified manganese oxide electrode materials for lithium rechargeable batteries. Progressive removal of lithium from specific crystallographic sites, followed by a gradual change of the crystal structure, was monitored by a combination of NMR and XRD techniques.

Paik, Younkee

159

Precision pointing control for SPICA: risk mitigation phase study  

NASA Astrophysics Data System (ADS)

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and far-infrared astronomy with a 3-m class telescope which is cryogenically cooled to be less than 6 K. The SPICA mechanical cooling system is indispensable for the mission but, generates micro-vibrations which could affect to the pointing stability performances. Activities to be undertaken during a risk mitigation phase (RMP) include consolidation of micro-vibration control design for the satellite, as well as a number of breadboarding activities centered on technologies that are critical to the success of the mission. This paper presents the RMP activity results on the microvibration control design.

Mitani, Shinji; Kawakatsu, Yasuhiro; Sakai, Shin-ichiro; Murakami, Naomi; Yamawaki, Toshihiko; Mizutani, Tadahito; Komatsu, Keiji; Kataza, Hirokazu; Enya, Keigo; Nakagawa, Takao

2014-08-01

160

Photovoltaic concentrator pointing dynamics and plasma interaction study  

NASA Technical Reports Server (NTRS)

The objectives of this experiment are to use the Space Technology Experiments Platform (STEP) system to demonstrate the viability of concentrator photovoltaic arrays by: (1) configuring a deployable mast on the STEP pallet with concentrator mass models and some active photovoltaic modules; (2) measuring the array pointing dynamics under normal rotation as well as disturbance conditions; (3) performing an array plasma interaction experiment to determine the steady-state plasma losses under various voltage conditions; and (4) providing active distributed control of the support truss to determine the improvement in dynamic response. Experiment approach and test control and instrumentation are described.

Stern, T. G.

1984-01-01

161

Geometrically asymmetric electrodes for probing electrochemical reaction kinetics: a case study of hydrogen at the Pt-CsH2PO4 interface.  

PubMed

Electrochemical reactions can exhibit considerable asymmetry, with the polarization behavior of oxidation at a given metal|electrolyte interface differing substantially from that of reduction. The reference-less, microcontact electrode geometry, in which the electrode overpotentials are geometrically constrained to the working electrode (by limiting its area) is experimentally convenient, particularly for fuel cell studies, because the results do not rely on accurate placement of a reference electrode nor must oxidant and reductant gases be sealed off from one another. Here, the conditions under which the critical assumption of this geometry applies-that the overpotential at the large-area counter electrode can be ignored-is numerically assessed. It is found that, for cells of sufficiently large area, the effective radius of the counter electrode (which defines the area through which the majority of the current passes) can be expressed directly as a function of electrolyte thickness and the materials properties, sigma, the conductivity of the electrolyte, and k, the reaction rate constant for the electrochemical reaction at zero-bias. From this effective radius and the true radius of the working electrode, the fraction of electrode overpotential at the latter, defined as the extent of isolation, can be readily computed. Experimental studies of hydrogen electro-oxidation/proton electro-reduction at the Pt|CsH(2)PO(4) interface using two cells of differing dimensions both validate the computational results and demonstrate that asymmetry in such reactions are readily revealed in the micro-electrode, reference-less geometry. The study furthermore confirms the insensitivity of the results to the precise placement of the working electrode, while indicating the importance of very high isolation values (>99%) to ensure that overpotential contributions of the counter electrode do not influence the measurements, particularly as bias is increased. PMID:19756291

Sasaki, Kenji A; Hao, Yong; Haile, Sossina M

2009-10-01

162

Study of the ultraviolet emission of the electrode coatings of arc welding.  

PubMed

The optical emission properties of several minerals components employed in electrode coatings of arc welding have been investigated. The X-ray diffraction analysis shows that the composition of 14 commercial electrode coatings collected from different countries (Spain, France, UK, Poland, Argentina and Germany), consists of quartz, calcite, sodium and potassium rich feldspars, muscovite and rutile. The natural thermal stimulated luminescence (TSL) of these mineral phases, measured in the range of 200-800 nm at different temperatures (from room temperature to 400 degrees C) displays UV-A (wavelengths of 320 nm to 400 nm) and UV-B (from 280 nm to 320 nm) emissions, with the exception of rutile. The UV-B radiation, commonly described as the most dangerous form of radiation to human life, is here associated with structural defects in the crystallographic lattice of the mineral components of electrode coatings. PMID:15369993

Garcia-Guinea, J; Correcher, V; Lombardero, M; Gonzalez-Martin, R

2004-08-01

163

Advanced electrodes for AMTEC  

SciTech Connect

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.}

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

164

Geometrically asymmetric electrodes for probing electrochemical reaction kinetics: a case study of hydrogen at the PtCsH2PO4 interface  

E-print Network

for fuel cell studies, because the results do not rely on accurate placement of a reference electrode nor, the conductivity of the electrolyte, and k, the reaction rate constant for the electrochemical reaction at zero-bias of the counter electrode do not influence the measurements, particularly as bias is increased. 1. Introduction

165

In vivo mechanical study of helical cardiac pacing electrode interacting with canine myocardium  

NASA Astrophysics Data System (ADS)

Cardiac pacing is a medical device to help human to overcome arrhythmia and to recover the regular beats of heart. A helical configuration of electrode tip is a new type of cardiac pacing lead distal tip. The helical electrode attaches itself to the desired site of heart by screwing its helical tip into the myocardium. In vivo experiments on anesthetized dogs were carried out to measure the acute interactions between helical electrode and myocardium during screw-in and pull-out processes. These data would be helpful for electrode tip design and electrode/myocardium adherence safety evaluation. They also provide reliability data for clinical site choice of human heart to implant and to fix the pacing lead. A special design of the helical tip using strain gauges is instrumented for the measurement of the screw-in and pull-out forces. We obtained the data of screw-in torques and pull-out forces for five different types of helical electrodes at nine designed sites on ten canine hearts. The results indicate that the screw-in torques increased steplike while the torque time curves presente saw-tooth fashion. The maximum torque has a range of 0.3 1.9 N mm. Obvious differences are observed for different types of helical tips and for different test sites. Large pull-out forces are frequently obtained at epicardium of left ventricle and right ventricle lateral wall, and the forces obtained at right ventricle apex and outflow tract of right ventricle are normally small. The differences in pull-out forces are dictated by the geometrical configuration of helix and regional structures of heart muscle.

Zhang, Xiangming; Ma, Nianke; Fan, Hualin; Niu, Guodong; Yang, Wei

2007-06-01

166

Numerical Studies and Equipment Development for Single Point Incremental Forming  

NASA Astrophysics Data System (ADS)

This paper summarizes the achievements obtained so far in the context of a research project carried out at the University of Aveiro, Portugal on both numerical and experimental viewpoints concerning Single Point Incremental Forming (SPIF). On the experimental side, the general guidelines on the development of a new SPIF machine are detailed. The innovation features are related to the choice of a six-degrees-of-freedom, parallel kinematics machine, with a high payload, to broad the range of materials to be tested, and allowing for a higher flexibility on tool-path generation. On the numerical side, preliminary results on simulation of SPIF processes resorting to an innovative solid-shell finite element are presented. The final target is an accurate and fast simulation of SPIF processes by means of numerical methods. Accuracy is obtained through the use of a finite element accounting for three-dimensional stress and strain fields. The developed formulation allows for an unlimited number of integration points through its thickness direction, which promotes accuracy without loss of CPU efficiency. Preliminary results and designs are shown and discussions over the obtained solutions are provided in order to further improve the research framework.

Marabuto, S. R.; Sena, J. I. V.; Afonso, D.; Martins, M. A. B. E.; Coelho, R. M.; Ferreira, J. A. F.; Valente, R. A. F.; de Sousa, R. J. Alves

2011-05-01

167

An in situ x-ray absorption spectroscopy study of InSb electrodes in lithium batteries.  

SciTech Connect

We present a detailed in situ extended X-ray absorption fine-structure spectroscopy (EXAFS) study of structural and compositional changes in InSb intermetallic electrodes under electrochemical cycling conditions in a lithium battery. Analysis of the EXAFS data shows that Li is inserted into and In is extruded from the zinc-blende-type InSb network during the first discharge from 1.5 to 0.5 V, yielding changing Li{sub x+y}In{sub 1-y}Sb compositions (0 < x {le} 2, 0 < y {le} 1), with a lattice parameter that varies between that of InSb (a = 6.478 A) and Li{sub 3}Sb (a = 6.572 A). The structural features of tetragonal metallic In and lithiated (i.e., In depleted) InSb are evident. The fully recharged electrode, at 1.2 V, has a zinc-blende framework closely resembling InSb. However, 40% of the In remains permanently outside the face-centered-cubic Sb lattice, explaining a loss in capacity after the first discharge. After the second discharge, at 0.51 V, Li has replaced about 80% of the indium in the InSb lattice, while the Li{sub x}In{sub y}Sb volume has expanded less than 4% compared to the initial electrode. Finally, as the cell is discharged below 0.51 V, Li reacts with the In metal, forming LiIn. Our results indicate that intermetallic electrodes are promising alternative negative electrodes for Li batteries.

Kropf, A. J.; Tostmann, H.; Johnson, C. S.; Vaughey, J. T.; Thackeray, M. M.; Chemical Engineering; Univ. of Florida

2001-11-01

168

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

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

169

A structural study of solid electrolyte interface on negative electrode of lithium-Ion battery by electron microscopy.  

PubMed

For the last decades, the performance of the lithium-ion battery (LIB) has been significantly improved and its applications have been expanding rapidly. However, its performance has yet to be enhanced.In the lithium-ion battery development, it is important to elucidate the electrode structure change in detail during the charge and discharge cycling. In particular, solid electrolyte interface (SEI) formed by decomposition of the electrolytes on the graphite negative electrode surface should play an important role for battery properties. Therefore, it is essential to control the structure and composition of SEI to improve the battery performance. Here, we conducted a scanning electron microscope (SEM) and transmission electron microscope (TEM) study to elucidate the structures of the SEI during the charge and discharge process using LiNi1/3Co1/3Mn1/3O2 [1] cathode and graphite anode. [2] Since SEI is a lithium-containing compound with high activity, it was observed without being exposed to the atmosphere. The electrodes including SEI were sampled after dismantling batteries with cutoff voltages of 3V and 4.2V for the charge process and 3V for the discharge process. Fig.1 shows SEM images of the graphite electrode surface during the charge and discharge process. The change of the SEI structure during the process was clearly observed. Further, TEM images showed that the SEI grew thicker during the charge process and becomes thinner when discharged. These results with regard to the reversible SEI structure could give a new insight for the battery development.jmicro;63/suppl_1/i21/DFU056F1F1DFU056F1Fig. 1.SEM images of the graphite electrode surface:(a) before charge process;(b) with charge-cutoff voltage of 3.0V; (c) with charge-cutoff voltage of 4.2V; (d) with discharge-cutoff voltage of 3.0V. PMID:25359815

Matsushita, Tadashi; Watanabe, Jiro; Nakao, Tatsuya; Yamashita, Seiichi

2014-11-01

170

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

E-print Network

, 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..., 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...

Guo, Yuyan

2009-05-15

171

Phase transition in porous electrodes.  

PubMed

It is shown by Monte Carlo simulation that electrochemical thermodynamics of electrolytes in a porous electrode is qualitatively different from that in the bulk with a planar electrode. In particular, first order phase transitions occur in porous electrodes when the pore size is comparable to the ion size of the electrolytes: as the voltage is increased from zero, the surface charge density and the ion density in the porous electrodes discontinuously change at a specific voltage. The critical points for those phase transitions are identified. PMID:21513411

Kiyohara, Kenji; Sugino, Takushi; Asaka, Kinji

2011-04-21

172

The effects of ECT stimulus dose and electrode placement on the ictal electroencephalogram: an intraindividual crossover study.  

PubMed

Recent evidence suggests that electroconvulsive therapy (ECT) efficacy depends upon both electrode placement and the degree to which stimulus dosage exceeds seizure threshold (T), and not simply on surpassing a minimum seizure duration as has been assumed. In light of these findings and studies reporting ictal electroencephalogram (EEG) differences between bilateral and unilateral ECT, we performed this 19-subject intraindividual crossover study of the effects of dose and electrode placement on the ictal EEG. We found ictal EEG evidence of greater seizure intensity with bilateral than unilateral ECT and with higher dosage (2.25 T) compared with barely suprathreshold stimuli. Seizure duration was not longer with bilateral than unilateral ECT and actually decreased with increased dose. A number of ictal EEG variables separated the unilateral 2.25 T and unilateral T conditions, which reportedly differ in efficacy, and therefore, these EEG measures show promise as markers of treatment adequacy. PMID:8292679

Krystal, A D; Weiner, R D; McCall, W V; Shelp, F E; Arias, R; Smith, P

1993-12-01

173

The oxidation of tyrosine and tryptophan studied by a molecular dynamics normal hydrogen electrode  

SciTech Connect

The thermochemical constants for the oxidation of tyrosine and tryptophan through proton coupled electron transfer in aqueous solution have been computed applying a recently developed density functional theory (DFT) based molecular dynamics method for reversible elimination of protons and electrons. This method enables us to estimate the solvation free energy of a proton (H{sup +}) in a periodic model system from the free energy for the deprotonation of an aqueous hydronium ion (H{sub 3}O{sup +}). Using the computed solvation free energy of H{sup +} as reference, the deprotonation and oxidation free energies of an aqueous species can be converted to pK{sub a} and normal hydrogen electrode (NHE) potentials. This conversion requires certain thermochemical corrections which were first presented in a similar study of the oxidation of hydrobenzoquinone [J. Cheng, M. Sulpizi, and M. Sprik, J. Chem. Phys. 131, 154504 (2009)]. Taking a different view of the thermodynamic status of the hydronium ion, these thermochemical corrections are revised in the present work. The key difference with the previous scheme is that the hydronium is now treated as an intermediate in the transfer of the proton from solution to the gas-phase. The accuracy of the method is assessed by a detailed comparison of the computed pK{sub a}, NHE potentials and dehydrogenation free energies to experiment. As a further application of the technique, we have analyzed the role of the solvent in the oxidation of tyrosine by the tryptophan radical. The free energy change computed for this hydrogen atom transfer reaction is very similar to the gas-phase value, in agreement with experiment. The molecular dynamics results however, show that the minimal solvent effect on the reaction free energy is accompanied by a significant reorganization of the solvent.

Costanzo, Francesca; Valle, Raffaele Guido Della [Dipartimento di Chimica Fisica e Inorganica, Universita di Bologna and INSTM-UdR Bologna, Viale Risorgimento 4, I-40136 Bologna (Italy); Sulpizi, Marialore; Sprik, Michiel [Department of Chemistry, University of Cambridge, Cambridge CB2 1EW (United Kingdom)

2011-06-28

174

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

PubMed Central

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

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

2014-01-01

175

Studies on paired packed-bed electrode reactor: Modeling and experiments  

Microsoft Academic Search

Experiments are carried out in a paired packed-bed electrode reactor with the cathodic reduction of potassium ferricyanide coupled with the anodic oxidation of potassium ferrocyanide as the working system. Eight probes are used to determine the potential distribution. A two-dimensional model is developed and solved by the finite element method. Good agreement is observed between the experimental data and the

Xin-Sheng Zhang; Guo-Bin Wu; Ping Ding; Xing-Gui Zhou; Wei-Kang Yuan

1999-01-01

176

An in situ X-ray absorption spectroscopy study of InSb electrodes in lithium batteries  

Microsoft Academic Search

We present a detailed in situ extended X-ray absorption fine-structure spectroscopy (EXAFS) study of structural and compositional changes in InSb intermetallic electrodes under electrochemical cycling conditions in a lithium battery. Analysis of the EXAFS data shows that Li is inserted into and In is extruded from the zinc-blende-type InSb network during the first discharge from 1.5 to 0.5 V, yielding

A. J. Kropf; H. Tostmann; C. S. Johnson; J. T. Vaughey; M. M. Thackeray

2001-01-01

177

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

Microsoft Academic Search

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

Qun-jie Xu; Guo-ding Zhou

2008-01-01

178

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

Microsoft Academic Search

The capacity fading mechanism of lithium-ion cell was studied by disassembling the charge–discharged cells and analyzing their electrodes using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. Cu ion dissolved from current collector of anode and Mn ion dissolved from LiMn2O4 spinel (cathode) were all existing in solid electrolyte interface (SEI) layer on carbon anode as Cu2O and

Li Yang; Michio Takahashi; Baofeng Wang

2006-01-01

179

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

NASA Technical Reports Server (NTRS)

A two-component Point Doppler Velocimeter (PDV) which has recently been developed is described, and a series of velocity measurements which have been obtained to quantify the accuracy of the PDV system are summarized. This PDV system uses molecular iodine vapor cells as frequency discriminating filters to determine the Doppler shift of laser light which is scattered off of seed particles in a flow. The majority of results which have been obtained to date are for the mean velocity of a rotating wheel, although preliminary data are described for fully-developed turbulent pipe flow. Accuracy of the present wheel velocity data is approximately +/- 1 % of full scale, while linearity of a single channel is on the order of +/- 0.5 % (i.e., +/- 0.6 m/sec and +/- 0.3 m/sec, out of 57 m/sec, respectively). The observed linearity of these results is on the order of the accuracy to which the speed of the rotating wheel has been set for individual data readings. The absolute accuracy of the rotating wheel data is shown to be consistent with the level of repeatability of the cell calibrations. The preliminary turbulent pipe flow data show consistent turbulence intensity values, and mean axial velocity profiles generally agree with pitot probe data. However, there is at present an offset error in the radial velocity which is on the order of 5-10 % of the mean axial velocity.

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

1997-01-01

180

From a child's point of view: Studying Thailand and Nigeria  

Microsoft Academic Search

Young children enjoy studying about other cultures when they experience them in a concrete, hands-on manner. Cross-cultural study by young children should encourage them to experience a culture from an indigenous child's viewpoint. Learning facts and information about a culture is less important than experiencing how children from other places might play a game or what they might eat for

Cynthia Szymanski Sunal; Barbara Gibson Warash

1992-01-01

181

Exposures from thorium contained in thoriated tungsten welding electrodes.  

PubMed

Information provided in this article can be used for estimating the radiation dose associated with the use of thoriated tungsten electrodes in tungsten inert gas welding. Area and breathing zone concentrations of 232Th generated by welding and electrode sharpening along with particle size information; isotopic composition of electrodes from two domestic manufacturers and one European manufacturer; and process variables and estimates on the number of thoriated tungsten electrodes manufactured are presented. Past literature is reviewed and compared with the results of this study. Isotopic analysis of a nominal 2% thoriated electrode found 0.6 ppm +/- 0.4 ppm 230Th and less than 0.1 ppm 228Th. Analysis of a ceriated tungsten electrode and a lanthanated tungsten electrode for 232Th found 124 ppm and 177 ppm, respectively. Electrode consumption during welding was primarily the result of tip sharpening. Less than 3% of the weight loss was attributable to the welding process. The in-mask concentration of respirable thorium particulate in the welder's breathing zone was 0.002 x 10(-12) microCi 232Th/mL. The concentration of respirable thorium particulate from electrode sharpening was 1.3 x 10(-12) microCi 232Th/mL. The measured sharpening time was 20 sec per electrode. Estimates of the activity median aerodynamic diameters for the respirable fraction of the welding and electrode sharpening aerosols were 3.5 and 5 microns, respectively, when measured in the breathing zone at 0.3 m (12 inches) from the point of operation. The respirable fraction of the total welding and sharpening aerosols was 45 and 60%. PMID:10386359

Jankovic, J T; Underwood, W S; Goodwin, G M

1999-01-01

182

Polyaniline-Supported Atomic Gold Electrodes: Comparison with Macro Electrodes  

SciTech Connect

Under precisely controlled conditions, atomic gold electrodes with even or odd number of Au atoms per polyaniline repeat unit (Pt/PANI/AuN for 0 electrodes is compared with that of macro gold and PANI coated platinum electrodes by testing electrochemical oxidation of n-propanol and iso-propanol. This study allowed us to separate the behavior dominated by that of macroscopic gold in strongly alkaline medium and by that of the quantized odd–even effect of atomic gold. Within this overarching scope, there is a specific oxidation pattern attributable to the structural differences between the two isomers of propanol. The significance of this research lies in the recognition of high specific catalytic activity of atomic gold, which is at least three orders of magnitude higher than that of bulk gold for the oxidation of alcohols. It points to a substantial saving of the precious metal without the loss of catalytic activity, which is important in fuel cells and in other energy conversion device applications.

Schwartz, Ilana; Jonke, Alex P.; Josowicz, Mira A.; Janata, Jiri

2012-11-01

183

Application of branching point process models to the study of invasive red banana  

E-print Network

Application of branching point process models to the study of invasive red banana plants in Costa models, ecological modeling, epidemic type aftershock sequence models, invasive species, point processes grid-based birth-and-death rather than branching point process models (Keeling et al. 2001; Keeling

Schoenberg, Frederic Paik (Rick)

184

A cross-cultural study of reference point adaptation: Evidence from China, Korea, and the US  

Microsoft Academic Search

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 after a gain than after an equal-sized loss. When we

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

2010-01-01

185

Streamer initiation in mineral oil. Part I: electrode surface effect under impulse voltage  

Microsoft Academic Search

Presents a study of streamer inception in mineral transformer oil, in point-plane and rod-plane geometry under impulse voltage. The measurements performed with points and rods over a wide range of tip radii show a marked decrease of initiation fields when the electrode radius is increased. The initiation field is divided by 30 over the investigated range (from 1 ?m points

O. Lesaint; T. V. Top

2002-01-01

186

Radiofrequency electrode vibration-induced shear wave imaging for tissue modulus estimation: A simulation study  

PubMed Central

Quasi-static electrode displacement elastography, used for in-vivo imaging of radiofrequency ablation-induced lesions in abdominal organs such as the liver and kidney, is extended in this paper to dynamic vibrational perturbations of the ablation electrode. Propagation of the resulting shear waves into adjoining regions of tissue can be tracked and the shear wave velocity used to quantify the shear (and thereby Young’s) modulus of tissue. The algorithm used utilizes the time-to-peak displacement data (obtained from finite element analyses) to calculate the speed of shear wave propagation in the material. The simulation results presented illustrate the feasibility of estimating the Young’s modulus of tissue and is promising for characterizing the stiffness of radiofrequency-ablated thermal lesions and surrounding normal tissue. PMID:20968329

Bharat, Shyam; Varghese, Tomy

2010-01-01

187

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

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

2013-01-01

188

Electrochemical characteristics of nanostructured platinum electrodes--a cyclic voltammetry study.  

PubMed

Platinum surfaces play a decisive role in catalysis in sensors, fuel cells, solar cells and other applications like neuronal stimulation and recording. Technical advances in nanotechnology contributed tremendously to the progress in these fields. A fundamental understanding of the chemical and physical interactions between the nanostructured surfaces and electrolytes is essential, but was barely investigated up to now. In this article, we present a wet-chemical process for the deposition of nanostructures on polycrystalline platinum surfaces. The electrochemically active surface area was increased by a factor of over 1000 times with respect to the geometrical surface. The influence of the nanostructures was examined in different acidic, alkaline, and neutral electrolytes. Comparing cyclic voltammograms of nanostructured and planar polycrystalline platinum revealed new insights into the microenvironment at the electrode-electrolyte interface. The characteristic features of the cyclic voltammograms were altered in their shape and strongly shifted with respect to the applied potential. In neutral buffered and unbuffered electrolytes the water window was expanded from 1.4 V to more than 2 V. The shifts were interpreted as local pH-changes and exhausted buffer capacity in direct proximity of the electrode surface due to the strong release and binding of protons, respectively. These polarized electrodes induce significant changes in the electrochemical potential of the electrolyte due to the high roughness of their surface. The electrochemical phenomena and the observed voltage shifts are crucial for the understanding of the basic mechanism at nanostructured electrodes and mandatory for designing fuel cells, sensors and many other devices. PMID:24664444

Daubinger, P; Kieninger, J; Unmüssig, T; Urban, G A

2014-05-14

189

Chemically modified electrodes and related solution studies. Final technical report, January 15, 1991--January 14, 1992  

SciTech Connect

This report is divided into 5 sections: Ru{sub 4}/Fe complexes of tetra(4{prime}-methyl-2,2{prime}-bipyridine)porphyrin--catalytic epoxidation of olefins; water oxidation catalysis by doubly linked {mu}-oxo ruthenium complexes; polymer films formed by oxidation of transition metal electrodes into solutions of bisbipyridinealkane ligands; polymer films containing [CpMo({mu}-S)]{sub 2}S{sub 2}CHR dinuclear clusters;and conducting polymer films for catalyst incorporation.

Elliott, C.M.

1993-04-01

190

Study of enzyme biosensor based on carbon nanotubes modified electrode for detection of pesticides residue  

Microsoft Academic Search

The paper describes a controllable layer-by-layer (LBL) self-assembly modification technique of multi-walled carbon nanotubes (MWNTs) and poly(diallyldimethylammonium chloride) (PDDA) towards glassy carbon electrode (GCE), Acetylcholinesterase (AChE) was immobilized directly to the modified GCE by LBL self-assembly method, the activity value of AChE was detected by using i-t technique based on the modified Ellman method. Then the composition of carbaryl were

Shu Ping Zhang; Lian Gang Shan; Zhen Ran Tian; Yi Zheng; Li Yi Shi; Deng Song Zhang

2008-01-01

191

EIS Studies of Porous Oxygen Electrodes with Discrete II. Transmission Line Modeling  

E-print Network

were derived from experimental data for Pt4Ru4Ir-coated Ti0.9Nb0.1O2 and Ebonex electrodes prepared and the reduction of oxygen in re- generative fuel cells.8 These materials consist of Pt4Ru4Ir metals-rich environments at high temperatures or high anodic potentials. It has been hypothesized that the perfor- mance

192

Prototype as a Referential Point: A Case Study.  

ERIC Educational Resources Information Center

Using cognitive linguistics to study the subjective lexicon of second-language (L2) learners of English, this article examines two questions: whether cognitive processes such as metonymy, metaphor, generalization, and specialization are used for expansion in the L2 lexicon; and what other factors work in understanding prototypical…

Ueda, Norifumi

1999-01-01

193

Translating point of view: A corpus-based study  

Microsoft Academic Search

The issue of the presence of translators as discursive subjects and the relationship between translation and reported discourse have only recently received attention in translation studies. Mossop (1983; 1998) regards translation as reported discourse in which the target text is the reporting discourse and the source text the reported discourse; Folkart (1991) argues that a translation differs from an original

Charlotte Bosseaux

2004-01-01

194

Oxidized graphene in ionic liquids for assembling chemically modified electrodes: a structural and electrochemical characterization study.  

PubMed

Dispersions of graphene oxide (GO) nanoribbons in ionic liquids, ILs (either 1-butyl-3-methylimidazolium chloride (BMIM-Cl-) or 1-butylpyridinium chloride (-Bupy-Cl-)) have been used to assemble modified screen printed electrodes (SPEs). The graphene oxide/ionic liquid dispersions have been morphologically and structurally characterized by the use of several techniques: X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR) spectroscopy, high-resolution-transmission electron microscopy (HR-TEM). The assembled modified SPEs have then been challenged with various compounds and compared to several electro-active targets. In all cases high peak currents were detected, as well as significant potential shifts, especially in the detection of catecholamines and NADH, compared with the bare SPE and the conventional electrodes, such as glassy carbon (GC) and highly oriented pyrolitic graphite (HOPG). This opens the way to the assembly of new types of sensors and biosensors. The enhanced performances observed are attributed to electrocatalytic effects related to the high electrode surface area, to oxygen-assisted electron transfer, as well as to the disordering effect of the ILs, this latter related to the favorable ?-? interactions with the ILs and the GO plane. PMID:22726213

Valentini, F; Roscioli, D; Carbone, M; Conte, V; Floris, B; Palleschi, G; Flammini, R; Bauer, E M; Nasillo, G; Caponetti, E

2012-07-01

195

Space tug point design study. Volume 1: Summary  

NASA Technical Reports Server (NTRS)

The design and characteristics of a space tug are discussed. The primary objective of the study is to verify the performance capability of a baseline design to deliver and retrieve payloads between 100 nautical miles, 28.5 degrees inclination, and geosynchronous. The space tug is ground based, reusable for 20 mission cycles, and is shuttled to and from low earth orbit by an earth orbital shuttle (EOS) with a 65,000 pound payload capability. It is shown that the baseline concept can meet the target performance goals. The design analysis encompassed: (1) definition of the vehicle primary structure, (2) thermal control, (3) meteoroid protection, (4) propulsion and mechanical subsystems, and (5) avionics including power generation and distribution.

1972-01-01

196

Do Changes in Electrical Skin Resistance of Acupuncture Points Reflect Menstrual Pain? A Comparative Study in Healthy Volunteers and Primary Dysmenorrhea Patients  

PubMed Central

Electrical skin resistance (ESR) measurements were performed with a four-electrode impedance detector at 10 points bilaterally on the first day of and the third day after menstruation in 48 healthy volunteers and 46 primary dysmenorrhea (PD) patients, to assess whether ESR changes of acupuncture points can reflect menstrual pain or not. The results showed statistical reductions in ESR imbalance ratio between left and right side that were detected at SP8 (Diji) and GB39 (Xuanzhong) (P < 0.05), and a statistical increase was detected at SP6 (Sanyinjiao) (P = 0.05) on the first day of menstruation compared with those values on the third day after menstruation in dysmenorrhea group. No significant differences were detected at other points within and between two groups (P > 0.05). This study showed that the imbalance of ESR at uterine-relevant points in PD patients is not significantly different from those of healthy women on both the 1st day of and the 3rd day after menstruation. The ESR imbalance ratio of certain points can either be lower or higher during menstruation in PD patients. The ESR property of acupuncture points needs to be investigated in further clinical trials with appropriate points, diseases, larger sample sizes, and optimal device. PMID:24876879

She, Yan-Fen; Ma, Liang-Xiao; Qi, Cong-Hui; Wang, Yan-Xia; Tang, Ling; Li, Chun-Hua; Yuan, Hong-Wen; Liu, Yu-Qi; Song, Jia-Shan; Zhu, Jiang

2014-01-01

197

Study on the influence of the B4C layer thickness on the neutron flux and energy distribution shape in multi-electrode ionisation chamber.  

PubMed

A model of a multi-electrode ionisation chamber, with polypropylene electrodes coated with a thin layer of B4C was created within Monte Carlo N-Particle Transport Code (MCNPX) and Fluktuierende Kaskade (FLUKA) codes. The influence of the layer thickness on neutron absorption in B4C and on the neutron spectra in the consecutive intra-electrode gas volumes has been studied using the MCNPX and FLUKA codes. The results will be used for designing the new type of the ionisation chamber. PMID:24729596

Tymi?ska, K; Maciak, M; O?ko, J; Tulik, P; Zielczy?ski, M; Gryzi?ski, M A

2014-10-01

198

Surface-enhanced resonance hyper-Raman scattering and surface-enhanced resonance Raman scattering of dyes adsorbed on silver electrode and silver colloid: a comparison study  

NASA Astrophysics Data System (ADS)

Surface-enhanced resonance hyper-Raman scattering (SERHRS) and surface-enhanced resonance Raman scattering (SERRS) of three dyes, rhodamine 6G, crystal violet and basic fuchsin, are studied comparatively on electrochemically roughened silver electrode and silver colloid, respectively. All three dyes show a better SERHRS efficiency on the silver colloid than on the silver electrode, a phenomenon just opposite to what we have recently observed for pyridine and pyrazine [Chem. Phys. Lett. 305 (1999) 303]. These results suggest that the efficiency of SEHRS depends not only on the active surfaces employed (colloidal metals versus roughened electrodes) but also on the types of the adsorbed molecules.

Li, Wu-Hu; Li, Xiao-Yuan; Yu, Nai-Teng

1999-10-01

199

First-Principles Study of Point Defects in LaAlO?  

E-print Network

In this study, the native point defects including oxygen vacancy and interstitial, metal (La, Al) vacancy and interstitial, and metal antisite in perovskite LAO are studied. Defect formation energies are studied as a ...

Zheng, J.X.

200

[Study of solanesol adsorbed on platinum electrode by surface enhanced Raman scattering].  

PubMed

The normal Raman spectrum (RRS) of solanesol molecules and surface enhanced raman scattering (SERS) of these molecules adsorbted on Pt electrode surface are reported in this paper. By comparison that the results show that the molecules of solanesol is adsorbed on the Pt surface through the C=C bond. The large difference between RRS and SERS demonstrates that the interaction between the molecules and Pt surface is rather strong and this interaction leads to a large disturbance to the molecules structure of solanesol. PMID:12953530

Yin, Guo-sheng; Zhao, Ge; Du, Yin-xiao; Zhang, Jing-lai; Liu, Kuai-zhi; Mo, Yu-jun

2003-06-01

201

The future of labor studies, from a labor lawyer's point of view. 1.How might future labor studiesevolve, from a French labor lawyer's point of view?  

E-print Network

the two types of employment contract, fixed term contract and open-ended term contract, by a "sole laborThe future of labor studies, from a labor lawyer's point of view. 1.How might future labor studiesevolve, from a French labor lawyer's point of view? I would first point out several factors that may

Paris-Sud XI, Université de

202

Electrode immersion depth determination and control in electroslag remelting furnace  

DOEpatents

An apparatus and method for controlling an electroslag remelting furnace comprising adjusting electrode drive speed by an amount proportional to a difference between a metric of electrode immersion and a set point, monitoring impedance or voltage, and calculating the metric of electrode immersion depth based upon a predetermined characterization of electrode immersion depth as a function of impedance or voltage.

Melgaard, David K. (Albuquerque, NM); Beaman, Joseph J. (Austin, TX); Shelmidine, Gregory J. (Tijeras, NM)

2007-02-20

203

Experimental Study of Saddle Point of Attachment in Laminar Juncture Flow  

NASA Technical Reports Server (NTRS)

An experimental study of laminar horseshoe vortex flows upstream of a cylinder/flat plate juncture has been conducted to verify the existence of saddle-point-of-attachment topologies. In the classical depiction of this flowfield, a saddle point of separation exists on the flat plate upstream of the cylinder, and the boundary layer separates from the surface. Recent computations have indicated that the topology may actually involve a saddle point of attachment on the surface and additional singular points in the flow. Laser light sheet flow visualizations have been performed on the symmetry plane and crossflow planes to identify the saddle-point-of-attachment flowfields. The visualizations reveal that saddle-point-of-attachment topologies occur over a range of Reynolds numbers in both single and multiple vortex regimes. An analysis of the flow topologies is presented that describes the existence and evolution of the singular points in the flowfield.

Coon, Michael D.; Tobak, Murray

1995-01-01

204

New Low Contact Resistance Electrode  

Microsoft Academic Search

STUDY was made of the contact resistance developed at a ferrite-electrode interface using for comparative purposes a variety of different electrode materials and methods of application. In this study individual samples measuring 0.565 in.XO.31O in. XO.065 in. were sectioned from a high-density homogeneous nickel ferrite ceramic body. Samples were cleaned in acetone immedi­ ately prior to application of electrodes. Measured

S. S. Flaschen; L. G. van Uitert

1956-01-01

205

CONJUGATE POINTS IN FORMATION CONSTRAINED OPTIMAL MULTI-AGENT COORDINATION: A CASE STUDY  

E-print Network

CONJUGATE POINTS IN FORMATION CONSTRAINED OPTIMAL MULTI-AGENT COORDINATION: A CASE STUDY JIANGHAI HU, MARIA PRANDINI, AND CLAIRE TOMLIN§ Abstract. In this paper, an optimal coordinated motion conjugate point. We study a particular instance of the formation constrained optimal coordinated motion

Tomlin, Claire

206

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

SciTech Connect

Techniques have been developed and implemented to gain insight into fundamental factors that affect the performance of electrodes in Li and Li-ion batteries and other energy storage devices. These include experimental strategies for monitoring the Raman scattering spectra of single microparticles of carbon and transition metal oxides as a function of their state of charge. Measurements were performed in electrolytes of direct relevance to Li and Li-Ion batteries both in the static and dynamic modes. In addition, novel strategies were devised for performing conventional experiments in ultrahigh vacuum environments under conditions which eliminate effects associated with presence of impurities, using ultrapure electrolytes, both of the polymeric and ionic liquid type that display no measurable vapor pressure. Also examined was the reactivity of conventional non aqueous solvent toward ultrapure Li films as monitored in ultrahigh vacuum with external reflection Fourier transform infrared spectroscopy. Also pursued were efforts toward developing applying Raman-scattering for monitoring the flow of charge of a real Li ion battery. Such time-resolved, spatially-resolved measurements are key to validating the results of theoretical simulations involving real electrode structures.

Daniel A Scherson

2013-03-14

207

Spectroscopic study of the proton dynamics in manganese dioxide electrode materials  

SciTech Connect

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 ({alpha}-MnO{sub 2}{lg_bullet}nH{sub 2}O; n{approx}0.2-0.33), the heat-treated products (n{approx}0-0.1), as well as their more stable lithia-doped derivatives, {alpha}-[xLi{sub 2}O]{lg_bullet}MnO{sub 2} (0 {le} x {le} 0.25), have been investigated. Inelastic neutron scattering was used as a means to differentiate and interrogate the key proton or water interactions in these MnO{sub 2} structures. The neutron spectra reveal excitations associated with the hydrogen vibrations centered at 4, 13, 16, 26, 36, 65, 90, 110, 140, 200, 420, and 490 meV in the alpha-phase and 14, 24, 65, 84, 100, 202, and 425 meV in the lithia-doped derivatives. Band assignments were carried out by comparing these frequencies with those reported for structurally similar hydrated {gamma}-MnO{sub 2} compounds and comparison with infrared data.

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

1997-10-01

208

Mass Transfer Studies of Geobacter sulfurreducens Biofilms on Rotating Disk Electrodes  

PubMed Central

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

Babuta, Jerome T.; Beyenal, Haluk

2014-01-01

209

Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes  

Microsoft Academic Search

A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has

Keun Su Kim; Jin Myung Park; Sooseok Choi; Jongin Kim; Sang Hee Hong

2008-01-01

210

EDM electrodes  

Microsoft Academic Search

A precision molded electrical discharge machining electrode is made by shaping a preform from granules of carbon and granules of a refractory material selected from the group consisting of tungsten, molybdenum, carbides thereof, and stoichiometric and hyperstoichiometric carbides of the other elements of the groups IVB, VB, and VIB of the Periodic Table of the Elements, the carbon and refractory

Th. E. Haskett; J. J. Schmitt

1984-01-01

211

Charging efficiency improvement by structuring lithium battery electrodes  

NASA Astrophysics Data System (ADS)

For atomic intercalation into an infinite long solid electrode, Haftbaradaran et al. [Appl. Phys. Lett. 96, 091909 (2010)] have pointed out that a coupling between internal stresses and activation energy for diffusion may result in surface locking instability accompanied by very large stresses near the electrode surface, significantly limiting the overall charging rate for high energy density lithium batteries. In the present study, we applied this model to the cylindrical electrode with finite length and found that free ends of the electrode may help to release surface stress within certain extent to each of them and postpone the surface locking of diffusion to occur. Following this finding, we further created parallel grooves on the electrode surface and quantitatively investigated the influences of the groove size and interval to the stress distribution and critical charging current density under galvanostatic charging and discharging conditions. It shows that such treatment of surface slotting to electrodes can significantly decrease the mechanical stresses during atomic intercalation and extraction, and improve the electrode charging efficiency, providing some beneficial inspirations to the Lithium battery technology.

Liu, Xiaojing; Zhou, Youhe; Zheng, Xiaojing; Wang, Jizeng

2012-06-01

212

A novel approach to surface electromyography: an exploratory study of electrode-pair selection based on signal characteristics.  

PubMed

A 3×4 electrode array was placed over each of seven muscles and surface electromyography (sEMG) data were collected during isometric contractions. For each array, nine bipolar electrode pairs were formed off-line and sEMG parameters were calculated and evaluated based on repeatability across trials and comparison to an anatomically placed electrode pair. The use of time-domain parameters for the selection of an electrode pair from within a grid-like array may improve upon existing electrode placement methodologies. PMID:22537650

Kendell, Cynthia; Lemaire, Edward D; Losier, Yves; Wilson, Adam; Chan, Adrian; Hudgins, Bernie

2012-01-01

213

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

PubMed

Electrical impedance tomography is an attractive functional imaging method. It is currently limited in resolution and sensitivity due to the complexity of the inverse problem and the safety limits of introducing current. Recently, internal electrodes have been proposed for some clinical situations such as intensive care or RF ablation. This paper addresses the research question related to the benefit of one or more internal electrodes usage since these are invasive. Internal electrodes would be able to reduce the effect of insulating boundaries such as fat and bone and provide improved internal sensitivity. We found there was a measurable benefit with increased numbers of internal electrodes in saline tanks of a cylindrical and complex shape with up to two insulating boundary gel layers modeling fat and muscle. The internal electrodes provide increased sensitivity to internal changes, thereby increasing the amplitude response and improving resolution. However, they also present an additional challenge of increasing sensitivity to position and modeling errors. In comparison with previous work that used point sources for the internal electrodes, we found that it is important to use a detailed mesh of the internal electrodes with these voxels assigned to the conductivity of the internal electrode and its associated holder. A study of different internal electrode materials found that it is optimal to use a conductivity similar to the background. In the tank with a complex shape, the additional internal electrodes provided more robustness in a ventilation model of the lungs via air filled balloons. PMID:24845453

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

2014-06-01

214

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

NASA Technical Reports Server (NTRS)

Localized corrosion in 2219-T87 aluminum (Al) alloy, 2195 aluminum-lithium (Al-Li) alloy, and welded 2195 Al-Li alloy (4043 filler) have been investigated using the relatively new scanning reference electrode technique (SRET). Anodic sites are more frequent and of greater strength in the 2195 Al-Li alloy than in the 2219-T87 Al alloy, indicating a greater tendency toward pitting for the latter. However, the overall corrosion rates are about the same for these two alloys, as determined using the polarization resistance technique. In the welded 2195 Al-Li alloy, the weld bean is entirely cathodic, with rather strongly anodic heat affected zones (HAZ) bordering both sides, indicating a high probability of corrosion in the HAZ parallel to the weld bead.

Danford, M. D.

1995-01-01

215

Fabrication and heating rate study of microscopic surface electrode ion traps  

E-print Network

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.

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

216

Os layers spontaneously deposited on the Pt(111) electrode : XPS, STM and GIF-XAS study.  

SciTech Connect

Scanning tunneling microscopy (STM) characterized adlayers of spontaneously deposited osmium on a Pt(111) electrode were investigated using ex-situ X-ray photoemission spectroscopy (XPS) and in-situ grazing incidence fluorescence X-ray absorption spectroscopy (GIF-XAS). After a single spontaneous deposition, monoatomic (or nearly monoatomic) nanoislands of osmium are formed. The island diameter varies from 2 to 5 nm depending on the Os coverage, which in turn is adjusted by varying the concentration of the Os precursor salt (OsCl3) in the deposition bath and/or by the deposition time. XPS reveals three oxidation states: a metallic Os (the 4f7/2 core level binding energy of 50.8 eV), Os(IV) (51.5 eV) and Os(VIII) (52.4 eV). The metallic osmium exists at potentials below 500 mV (vs. RHE) while above 500 mV osmium is oxidized to Os(IV). Electrodissolution of osmium begins above 900 mV and occurs simultaneously with platinum oxidation. At ca. 1200 mV V versus the RHE reference, the oxidation state of some small amounts of osmium that survive dissolution is the Os(VIII). We demonstrate, for the first time, that mixed or odd valencies of osmium exist on the platinum surface at potentials higher that 800 mV. In-situ GIF-XAS measurements of an Os LIII edge also reveal the presence of three Os oxidation states. Namely, below the electrode potential of 400 mV, the X-ray fluorescent energy at maximum absorption is 10.8765 keV, and is characteristic of the metallic Os. In the potential range between 500 and 1000 mV this energy is gradually shifted to higher values, assignable to higher valencies of osmium, like Os(IV). This tendency continues to higher potentials consistent with the third, highly oxidized osmium form present, most likely Os(VIII). The variation of the 'raw edge jump height' of Os with the electrode potential, which is equivalent to a drop in osmium surface concentration, demonstrates that the electrochemical stripping of Os begins below 1.0 V versus RHE, as expected from voltammetry. Also, the observed intensity of the white line of Os in the 100-400 mV region is larger than the value reported for metallic bulk Os. This discrepancy may result from the difference in the electronic properties of the metallic Os layers on Pt(111) and the metallic bulk Os: in the potential region between 100 and 400 mV, the 5d electrons in Os and Pt form a mixed electronic band, and the density of electronic states near the Fermi level, the main factor determining the white line intensity, may not be the same as in metallic bulk. The presented results on osmium adlayers are much more comprehensive than those available in our previous work due to the combined STM, GIF-XAS and XPS investigations. A nearly perfect convergence of the in situ and ex situ data is one of the main research outcomes of this project. Finally, platinum XPS spectra taken in the context of Os electrooxidation from the electrode surface are also presented and conclusions are made, that up to 900 mV platinum remain metallic, irrespective of a significant osmium oxidation on its surface.

Rhee, C. K.; Wakisaka, M.; Tolmachev, Y.; Johnston, C.; Haasch, R.; Attenkofer, K.; Lu, G. Q.; You, H.; Wieckowski, A.; Univ. of Illinois Champaigh-Urbana

2003-01-01

217

Masking mechanisms of bitter taste of drugs studied with ion selective electrodes.  

PubMed

The masking mechanisms of the bitter taste of propantheline bromide (PB) and oxyphenonium (OB) bromide by native and modified cyclodextrins, saccharides, surfactants, organic acids, nonionic and anionic polymers, and other compounds were investigated with ion selective electrodes. The intensity of the bitter taste for a mixed solution of cyclodextrin with PB or OB was quantitatively explained from the observed electromotive force with the following assumptions: the complex and the masking agent do not have any tastes and the bitter taste is independent of other tastes. Sodium dodecyl sulfate reduced the bitter taste remarkably, and this reduction was also explicable on the basis of the same mechanism. Sodium taurodeoxycholate enhanced the bitter taste, because of its strong bitterness, although it formed 1 : 1 complexes with PB and OB. The masking mechanism of saccharides was ascribed to overcoming the weak bitterness of the drug by the strong sweetness. Lambda-carrageenan suppressed the bitter taste remarkably. This suppression was ascribed to the binding of PB and OB to lambda-carrageenan, the effect of the solution viscosity on the bitter taste, and the covering of the bitter taste receptor by lambda-carrageenan. It was suggested that the moderate masking by other polymers was attributable to the effect of the solution viscosity or the receptor covering. Native and modified beta-cyclodextrins, sodium dodecyl sulfate, lambda-carrageenan, Tween 20, and sodium carboxymethyl cellulose are good masking agents for the bitter tastes of PB and OB. The drug ion selective electrode is a useful tool for understanding of the masking mechanism of the bitter taste, screening of masking agents, and estimation of appropriate concentrations of the masking agents. PMID:16880661

Funasaki, Noriaki; Uratsuji, Ikumi; Okuno, Takashi; Hirota, Shun; Neya, Saburo

2006-08-01

218

Microfluidic device with tunable post arrays and integrated electrodes for studying cellular release.  

PubMed

In this paper, we describe the development of a planar, pillar array device that can be used to image either side of a tunable membrane, as well as sample and detect small molecules in a cell-free region of the microchip. The pores are created by sealing two parallel PDMS microchannels (a cell channel and a collector channel) over a gold pillar array (5 or 10 ?m in height), with the device being characterized and optimized for small molecule cross-over while excluding a flowing cell line (here, red blood cells, RBCs). The device was characterized in terms of the flow rate dependence of analyte cross-over and cell exclusion as well as the ability to perform amperometric detection of catechol and nitric oxide (NO) as they cross-over into the collector channel. Using catechol as the test analyte, the limits of detection (LOD) of the cross-over for the 10 ?m and 5 ?m pillar array heights were shown to be 50 nM and 105 nM, respectively. Detection of NO was made possible with a glassy carbon detection electrode (housed in the collector channel) modified with Pt-black and Nafion, to enhance sensitivity and selectivity, respectively. Reproducible cross-over of NO as a function of concentration resulted in a linear correlation (r(2) = 0.995, 7.6-190 ?M), with an LOD for NO of 230 nM on the glassy carbon/Pt-black/0.05% Nafion electrode. The applicability of the device was demonstrated by measuring the NO released from hypoxic RBCs, with the device allowing the released NO to cross-over into a cell free channel where it was detected in close to real-time. This type of device is an attractive alternative to the use of 3-dimensional devices with polycarbonate membranes, as either side of the membrane can be imaged and facile integration of electrochemical detection is possible. PMID:25105251

Selimovic, Asmira; Erkal, Jayda L; Spence, Dana M; Martin, R Scott

2014-10-15

219

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

NASA Astrophysics Data System (ADS)

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.

Wu, Jingjie

220

DFT and MM calculation: the performance mechanism of pour point depressants study  

Microsoft Academic Search

Adding pour point depressants (PPDs) to lower the cold filter plugging point (CFPP) of oils has been widely used as the most valuable way in the world. To develop the new type of PPDs according to the oils of different kinds, many researchers have tried to study the performance mechanism of PPDs with different methods. In this article, we have

Jinli Zhang; Chuanjie Wu; Wei Li; Yiping Wang; Hui Cao

2004-01-01

221

Kinetics of electrode processes on cadmium electrode of a sealed nickel-cadmium accumulator  

Microsoft Academic Search

The kinetics of electrode processes on cadmium electrode of an alkali accumulator related to the variations of concentration of cadmium species in the near-electrode layers of electrolyte under the primary current-generating process as well as the mechanism of contamination of separation material under the conditions when an electrode is operated as a part of a sealed accumulators are studied. The

L. S. Nadezhina; B. A. Borisov; L. N. Gerasimenko

1995-01-01

222

Electrode Architecture  

Microsoft Academic Search

Retinal prosthesis presents a unique design challenge: how to form an electrical stimulation interface to a curved surface?\\u000a The challenge is primarily the lack of fabrication methods to pattern conductive material onto a spherical or curved surface.\\u000a The proximity of the electrodes to the retina is important because increased distance requires increased stimulation charge\\u000a and reduces acuity. Even flexible substrates,

Lee J. Johnson; Dean A. Scribner

223

STUDIES ON TWO CLASSES OF POSITIVE ELECTRODE MATERIALS FOR LITHIUM-ION BATTERIES  

SciTech Connect

The development of advanced lithium-ion batteries is key to the success of many technologies, and in particular, hybrid electric vehicles. In addition to finding materials with higher energy and power densities, improvements in other factors such as cost, toxicity, lifetime, and safety are also required. Lithium transition metal oxide and LiFePO{sub 4}/C composite materials offer several distinct advantages in achieving many of these goals and are the focus of this report. Two series of layered lithium transition metal oxides, namely LiNi{sub 1/3}Co{sub 1/3-y}M{sub y}Mn{sub 1/3}O{sub 2} (M=Al, Co, Fe, Ti) and LiNi{sub 0.4}Co{sub 0.2-y}M{sub y}Mn{sub 0.4}O{sub 2} (M = Al, Co, Fe), have been synthesized. The effect of substitution on the crystal structure is related to shifts in transport properties and ultimately to the electrochemical performance. Partial aluminum substitution creates a high-rate positive electrode material capable of delivering twice the discharge capacity of unsubstituted materials. Iron substituted materials suffer from limited electrochemical performance and poor cycling stability due to the degradation of the layered structure. Titanium substitution creates a very high rate positive electrode material due to a decrease in the anti-site defect concentration. LiFePO{sub 4} is a very promising electrode material but suffers from poor electronic and ionic conductivity. To overcome this, two new techniques have been developed to synthesize high performance LiFePO{sub 4}/C composite materials. The use of graphitization catalysts in conjunction with pyromellitic acid leads to a highly graphitic carbon coating on the surface of LiFePO{sub 4} particles. Under the proper conditions, the room temperature electronic conductivity can be improved by nearly five orders of magnitude over untreated materials. Using Raman spectroscopy, the improvement in conductivity and rate performance of such materials has been related to the underlying structure of the carbon films. The combustion synthesis of LiFePO4 materials allows for the formation of nanoscale active material particles with high-quality carbon coatings in a quick and inexpensive fashion. The carbon coating is formed during the initial combustion process at temperatures that exceed the thermal stability limit of LiFePO{sub 4}. The olivine structure is then formed after a brief calcination at lower temperatures in a controlled environment. The carbon coating produced in this manner has an improved graphitic character and results in superior electrochemical performance. The potential co-synthesis of conductive carbon entities, such as carbon nanotubes and fibers, is also briefly discussed.

Wilcox, James D.

2008-12-18

224

Electrochemical and STM studies of 1-thio-?-D-glucose self-assembled on a Au(111) electrode surface.  

PubMed

In this study, a Au(111) electrode is functionalized with a monolayer of 1-thio-?-D-glucose (?-Tg), producing a hydrophilic surface. A monolayer of ?-Tg was formed on a Au(111) surface by either (1) potential-assisted deposition with the thiol in a supporting electrolyte or (2) passive incubation of a gold substrate in a thiol-containing solution. For each method, the properties of the ?-Tg monolayer were investigated using cyclic voltammetry (CV), differential capacitance (DC), and chronocoulometry. In addition, electrochemical scanning tunneling microscopy (EC-STM) was used to obtain images of the self-assembled monolayer with molecular resolution. Potential-assisted assembly of ?-Tg onto a Au(111) electrode surface was found to be complicated by oxidation of ?-Tg molecules. The EC-STM images revealed formation of a passive layer containing honeycomb-like domains characteristic of a formation of S(8) rings, indicating the S-C bond may have been cleaved. In contrast, passive self-assembly of thioglucose from a methanol solution was found to produce a stable, disordered monolayer of ?-Tg. Since the passive assembly method was not complicated by the presence of a faradaic process, it is the method of choice for modifying the gold surface with a hydrophilic monolayer. PMID:21939277

Kycia, Annia H; Sek, Slawomir; Su, Zhangfei; Merrill, A Rod; Lipkowski, Jacek

2011-11-01

225

PHOTOGALVANIC EFFECTS WITH ANODIZED ZIRCONIUM AND NIOBIUM ELECTRODES  

Microsoft Academic Search

Attempts were made to elucidate the nature of photoeffects by studying ; anodized Zr and Nb electrodes. A freshly polished Zr electrode when immersed in ; solution showed an initial potential, relative to the reference electrode, of ; about -1.2 v. As oxide began to form on the electrode surface the potential ; became less negative. Zr electrodes that were

Robert E. Salomon; George B. Adams; Wendell M. Graven

1963-01-01

226

Evaluating policy and service interventions: framework to guide selection and interpretation of study end points  

Microsoft Academic Search

The effect of many cost effective policy and service interventions cannot be detected at the level of the patient. This new framework could help improve the design (especially choice of primary end point) and interpretation of evaluative studies

Richard J Lilford; Peter J Chilton; Karla Hemming; Alan J Girling; Celia A Taylor; Paul Barach

2010-01-01

227

Empirical Correlates of Frequently Occurring Two-Point MMPI Code Types: A Replicated Study  

ERIC Educational Resources Information Center

The results of this study are consistent with previous research that has indicated that a large proportion of MMPI protocols obtained in a psychiatric setting can be classified into a relatively small number of two point code types. (Author)

Lewandowski, Denis; Graham, John R.

1972-01-01

228

Young's Modulus Reconstruction for Radio-frequency Ablation Electrode-induced Displacement Fields: A Feasibility Study  

PubMed Central

Radiofrequency (RF) ablation is a minimally invasive treatment for tumors in various abdominal organs. It is effective if good tumor localization and intra-procedural monitoring can be done. In this paper, we investigate the feasibility of using an ultrasound-based Young’s modulus reconstruction algorithm to image an ablated region whose stiffness is elevated due to tissue coagulation. To obtain controllable tissue deformations for abdominal organs during and/or intermediately after the RF ablation, the proposed modulus imaging method is specifically designed for using tissue deformation fields induced by the RF electrode. We have developed a new scheme under which the reconstruction problem is simplified to a two-dimensional problem. Based on this scheme, an iterative Young’s modulus reconstruction technique with edge-preserving regularization was developed to estimate the Young’s modulus distribution. The method was tested in experiments using a tissue-mimicking phantom and on ex vivo bovine liver tissues. Our preliminary results suggest that high contrast modulus images can be successfully reconstructed. In both experiments, the geometries of the reconstructed modulus images of thermal ablation zones match well with the phantom design and the gross pathology image, respectively. PMID:19258195

Jiang, Jingfeng; Varghese, Tomy; Brace, Chris L.; Madsen, Ernest L.; Hall, Timothy J.; Bharat, Shyam; Hobson, Maritza A.; Zagzebski, James A.; Lee, Fred T.

2009-01-01

229

Atomic resolution study of reversible conversion reaction in metal oxide electrodes for lithium-ion battery.  

PubMed

Electrode materials based on conversion reactions with lithium ions have shown much higher energy density than those based on intercalation reactions. Here, nanocubes of a typical metal oxide (Co3O4) were grown on few-layer graphene, and their electrochemical lithiation and delithiation were investigated at atomic resolution by in situ transmission electron microscopy to reveal the mechanism of the reversible conversion reaction. During lithiation, a lithium-inserted Co3O4 phase and a phase consisting of nanosized Co-Li-O clusters are identified as the intermediate products prior to the subsequent formation of Li2O crystals. In delithiation, the reduced metal nanoparticles form a network and breakdown into even smaller clusters that act as catalysts to prompt reduction of Li2O, and CoO nanoparticles are identified as the product of the deconversion reaction. Such direct real-space, real-time atomic-scale observations shed light on the phenomena and mechanisms in reaction-based electrochemical energy conversion and provide impetus for further development in electrochemical charge storage devices. PMID:25337887

Luo, Langli; Wu, Jinsong; Xu, Junming; Dravid, Vinayak P

2014-11-25

230

Study of styrene butadiene rubber and sodium methyl cellulose as binder for negative electrodes in lithium-ion batteries  

Microsoft Academic Search

Graphite and nano-silicon-based negative electrodes in lithium-ion batteries with low binder content were evaluated. The effectiveness of styrene butadiene rubber (SBR) and various types of cellulose containing electrodes were compared to standard electrodes containing PVdF as binder. The cycling performance of lithium-based half cells in EC:DMC (1:1), 1M LiPF6 shows that styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (Na-CMC), or

H. Buqa; M. Holzapfel; F. Krumeich; C. Veit; P. Novák

2006-01-01

231

Study of interaction between a cationic surfactant and two anionic azo dyes by ion-selective electrode technique and spectrophotometry  

Microsoft Academic Search

Interaction between a cationic surfactant, hexadecyltrimethylammonium bromide (HTAB), and two anionic azo dyes, C.I. Direct Orange 26 (DO26) and Direct Red 16 (DR16) has been investigated using surfactant-selective electrode and spectrophotometry techniques. In ion-selective electrode technique an HTAB surfactant-selective membrane electrode has been used. The electromotive force versus total surfactant concentration has been plotted for the systems of HTAB\\/DR16 and

S. M. Ghoreishi; M. Behpour; A. Ghafari Farsani

2007-01-01

232

Analysis of non-point and point source pollution in China: case study in Shima Watershed in Guangdong Province  

NASA Astrophysics Data System (ADS)

China economy has been rapidly increased since 1978. Rapid economic growth led to fast growth of fertilizer and pesticide consumption. A significant portion of fertilizers and pesticides entered the water and caused water quality degradation. At the same time, rapid economic growth also caused more and more point source pollution discharge into the water. Eutrophication has become a major threat to the water bodies. Worsening environment problems forced governments to take measures to control water pollution. We extracted land cover from Landsat TM images; calculated point source pollution with export coefficient method; then SWAT model was run to simulate non-point source pollution. We found that the annual TP loads from industry pollution into rivers are 115.0 t in the entire watershed. Average annual TP loads from each sub-basin ranged from 0 to 189.4 ton. Higher TP loads of each basin from livestock and human living mainly occurs in the areas where they are far from large towns or cities and the TP loads from industry are relatively low. Mean annual TP loads that delivered to the streams was 246.4 tons and the highest TP loads occurred in north part of this area, and the lowest TP loads is mainly distributed in middle part. Therefore, point source pollution has much high proportion in this area and governments should take measures to control point source pollution.

Fang, Huaiyang; Lu, Qingshui; Gao, Zhiqiang; Shi, Runhe; Gao, Wei

2013-09-01

233

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

Microsoft Academic Search

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

Amy M. Wolaver

2002-01-01

234

Readout electrode assembly for measuring biological impedance  

NASA Technical Reports Server (NTRS)

The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.

Montgomery, L. D.; Moody, D. L., Jr. (inventors)

1976-01-01

235

Modeling of Impedance of Porous Electrodes  

NASA Astrophysics Data System (ADS)

Porous electrodes are very important in practical applications of electrocatalysis, where an increase in the real surface area leads to an increase in catalytic activity. Porous electrodes are used in gas evolution (water electrolysis, hydrogen and oxygen evolution, chlorine evolution), electrocatalytic hydrogenation or oxidation of organic compounds, in batteries, fuel cells, etc. Good knowledge of the porous electrode theory permits for the construction of the electrodes with optimal utilization of the active electrode material. The porous electrode model was first developed by several authors for dc conditions (1-6) and later applied to the impedance studies.

Lasia, Andrzej

236

Theoretical study of reactions at the electrode-electrolyte interface. Progress report, August 1, 1991--January 31, 1993  

SciTech Connect

Electron transfer rates are predicted by numerical methods, in a collaboration with Argonne National Laboratory . Emphasis is on electron transfer involving ions known to be important in enhancing stress corrosion cracking in light water reactors and on electron transfer at oxide surfaces. We have produced a new theory for description of the Jahn Teller effect in the solvation shell of the cuprous ion in aqueous solution, have implemented it in a molecular dynamics simulation and compared the results with experimental neutron scattering measurements on solutions containing the cuprous ion. A large amount of numerical data has been collected on the transition state of the ferrous ferric electron transfer reaction at an electrode. Work was completed on a polarizable and dissociable model of water for use in the electron transfer studies. New calculations of the conductivity in models of oxides have shown the existence of impurity conduction bands in such models for the first time.

Halley, J.W.

1993-02-01

237

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

NASA Technical Reports Server (NTRS)

Electrochemical studies indicate that poly(Isothianaphthene) or PITN, can be p-doped only. Electrochemical properties of PITN and Nafion-PITN in acetonitrile solutions containing tetra-phenyl Phosphonium chloride as supporting electrolyte are compared. In both cases, the electrochemical behavior of thin films are different from that of thick films. In addition, Nafion does not seem to alter the electrochemical properties of PITN. Cyclic voltammetric and chronocoulometric measurements were made to compute the diffusion coefficient of the counter ions. Electrochemical behavior of both PITN and Nafion-PITN in acetonitrile solution containing different counter ions are described. PITN, when electrochemically deposited, apparently neither passivates surface states present nor forms ohmic contacts with p-Si or p(+)Si single-crystal electrodes.

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

1987-01-01

238

A study of impulsive multiterm fractional differential equations with single and multiple base points and applications.  

PubMed

We discuss the existence and uniqueness of solutions for initial value problems of nonlinear singular multiterm impulsive Caputo type fractional differential equations on the half line. Our study includes the cases for a single base point fractional differential equation as well as multiple base points fractional differential equation. The asymptotic behavior of solutions for the problems is also investigated. We demonstrate the utility of our work by applying the main results to fractional-order logistic models. PMID:24578623

Liu, Yuji; Ahmad, Bashir

2014-01-01

239

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

NASA Astrophysics Data System (ADS)

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.

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

240

(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)

The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

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

1993-01-01

241

The TITAN Reversed-Field Pinch Reactor: Design-point determination and parametric studies  

SciTech Connect

The multi-institutional TITAN study has examined the physics, technology, safety, and economics issues associated with the operation of a Reversed-Field Pinch (RFP) magnetic fusion reactor at high power density. A comprehensive system and trade study have been conducted as an integral and ongoing part of the reactor assessment. Attractive design points emerging from these parametric studies are subjected to more detailed analysis and design integration, the results of which are used to refine the parametric systems model. The design points and tradeoffs for two TITAN/RFP reactor embodiments are discussed. 14 refs.

Miller, R.L.

1987-01-01

242

Effect of acupuncture-point stimulation on diastolic blood pressure in hypertensive subjects: a preliminary study.  

PubMed

Electrical stimulation of four specific acupuncture points (Liver 3, Stomach 36, Large Intestine 11, and the Groove for Lowering Blood Pressure) was examined in order to determine the effect of this stimulation on diastolic blood pressure in 10 subjects with diastolic hypertension. Subjects were randomly divided into two groups: (1) an Acu-ES group, which received electrical stimulation applied to the four antihypertensive acupuncture points, and (2) a Sham-ES group, which received electrical stimulation applied to non-acupuncture-point areas. A repeated-measures analysis of variance revealed a significant, immediate poststimulation reduction of diastolic blood pressure for the Acu-Es group versus the Sham-ES group. Further studies are needed to determine whether there are other acupuncture points, stimulation characteristics, or modalities that can enhance this treatment effect and whether the treatment effect can last for a clinically significant period of time. PMID:2052631

Williams, T; Mueller, K; Cornwall, M W

1991-07-01

243

Studying of the nuclear fission rate from the point of view of Brownian motion  

SciTech Connect

The problem of the nuclear fission rate is studied from the point of view of Brownian motion. The Fokker-Planck equation is solved by means of the rate eigenvalue method. The viscosity tensors, the inertia parameters, and the temperature are functions of nuclear deformation. Their effects on the fission rate are also studied.

Wu, X.Z.; Zhou, Y.Z.

1981-07-01

244

Work in Progress: A Quantitative Study of the Effectiveness of PowerPoint in the Classroom  

Microsoft Academic Search

At New Mexico State University (NMSU), a quantitative study has begun of the effectiveness of PowerPoint for learning in introductory physics. The study is expected to run for a total of five years and the final results will include data for more than 1000 engineering and computer science students completing the mechanics and electricity and magnetism portions of beginning physics.

Michael DeAntonio; Luis Martin Sandoval; Roberto Arceo

2006-01-01

245

Inexpensive and Disposable pH Electrodes  

ERIC Educational Resources Information Center

Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H[superscript +] concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH…

Goldcamp, Michael J.; Conklin, Alfred; Nelson, Kimberly; Marchetti, Jessica; Brashear, Ryan; Epure, Emily

2010-01-01

246

Impedance studies of nickel/cadmium and nickel/hydrogen cells using the cell case as a reference electrode  

NASA Technical Reports Server (NTRS)

Impedance measurements have been made on several Ni/Cd and Ni/H2 flight-weight cells using the case as a reference electrode. For these measurements, the voltage of the case with respect to the anode or cathode is unimportant provided that it remains stable during the measurement of the impedance. In the cells measured so far, the voltage of the cell cases with respect to the individual electrodes differ from cell to cell, even at the same overall cell voltage, but they remain stable with time. The measurements can thus be used to separate the cell impedance into the contributions of each electrode, allowing improved diagnosis of cell problems.

Reid, Margaret A.

1990-01-01

247

Cryogenic Propellant Storage and Transfer Technology Demonstration: Prephase A Government Point-of-Departure Concept Study  

NASA Technical Reports Server (NTRS)

The primary purpose of this study was to define a point-of-departure prephase A mission concept for the cryogenic propellant storage and transfer technology demonstration mission to be conducted by the NASA Office of the Chief Technologist (OCT). The mission concept includes identification of the cryogenic propellant management technologies to be demonstrated, definition of a representative mission timeline, and definition of a viable flight system design concept. The resulting mission concept will serve as a point of departure for evaluating alternative mission concepts and synthesizing the results of industry- defined mission concepts developed under the OCT contracted studies

Mulqueen, J. A.; Addona, B. M.; Gwaltney, D. A.; Holt, K. A.; Hopkins, R. C.; Matis, J. A.; McRight, P. S.; Popp, C. G.; Sutherlin, S. G.; Thomas, H. D.; Baysinger, M. F.; Maples, C. D.; Capizzo, P. D.; Fabisinski, L. L.; Hornsby, L. S.; Percy, T. K.; Thomas, S. D.

2012-01-01

248

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

NASA Astrophysics Data System (ADS)

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.

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

249

A system-based study of the variation in the amplitude of the compound sensory nerve action potential recorded using surface electrodes  

Microsoft Academic Search

This study arose from the impression that there is a wide variation in the amplitude of the compound sensory nerve action potential (SNAP) when recorded using surface electrodes. Both the physiological factors influencing the SNAP and the method of measurement itself can be viewed as inputs to a system that produces the recorded value as its output. Taking a systems

Matthew C. Pitt

1996-01-01

250

Studying and evaluating anti-corrosion coatings and inhibitors using the wire beam electrode method in conjunction with electrochemical noise analysis  

Microsoft Academic Search

Purpose – To provide a summary of research work carried out mainly in the authors' group for evaluating various protective coatings including rustproofing oils, and also for studying corrosion inhibitors using the wire beam electrode (WBE) method. Design\\/methodology\\/approach – A range of published papers published during the past 15 years was summarised and reviewed. Recent research work in the authors'

Yong-Jun Tan; Ting Wang; Tie Liu; Naing-Naing Aung

2006-01-01

251

Electrochemical lithiation and passivation mechanisms of iron monosulfide thin film as negative electrode material for lithium-ion batteries studied by surface analytical techniques  

NASA Astrophysics Data System (ADS)

The lithiation/delithiation reaction mechanism of iron monosulfide (troilite Fe(1-x)S, x = 0.07) as negative electrode material for lithium-ion batteries and the electrode passivation induced by reductive decomposition of the electrolyte were studied by combining surface (X-ray photoelectron spectroscopy, XPS, and time-of-flight secondary ion mass spectrometry, ToF-SIMS) and electrochemical analysis (cyclic voltammetry, CV) of thin films grown by thermal sulfidation of metal iron substrate. XPS analysis performed at different stages of the first lithiation/delithiation cycle shows that the reversible formation of metallic iron and lithium sulfide is not solely limited to the principal cathodic/anodic peaks at 1.23/1.89 V and that disulfide products, possibly Li2FeS2, are also formed at lower cathodic potentials. ToF-SIMS depth profiling of the thin film electrode confirms an incomplete process of conversion/deconversion and reveals an expansion/shrinkage of the material induced by electrochemical lithiation/delithiation. The solid electrolyte interphase (SEI) layer formed on the iron monosulfide thin film electrode is mostly composed of Li2CO3 with some presence of ROCO2Li. For the first time, it is shown that the SEI layer thickness varies upon conversion/deconversion, between 9 and 4.5 nm in the lithiated and delithiated states, respectively, on a conversion-type electrode. Moreover, the electrolyte decomposition products penetrate the bulk electrode until the current collector owing to pulverization/cracking caused by expansion and shrinkage of the thin film material upon cycling.

Liao, Feng; ?wiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Klein, Lorena H.; Zanna, Sandrine; Marcus, Philippe

2013-10-01

252

Photochemical Quartz Crystal Microbalance Study of the Nanocrystalline Titanium Dioxide Semiconductor Electrode/Water Interface: Simultaneous Photoaccumulation of Electrons  

E-print Network

Semiconductor Electrode/Water Interface: Simultaneous Photoaccumulation of Electrons and Protons Buford I. Lemon: protons in the case of water, small electrolyte cations in the case of aprotic solvents. The cations

253

A Statistical Mechanical Study of Current Spikes Due to Phase Transitions at Electrode-Electrolyte Interfaces  

Microsoft Academic Search

We develop a statistical mechanical description of current spikes experimentally measured during first-order phase transitions\\u000a on electrode surfaces. We interpret an experimental current spike as an averaged result of the finite-size effects for a large\\u000a ensemble of crystalline domains (crystals) that are formed on the electrode surface, i.e., as an envelope of mutually shifted\\u000a single-crystal spikes of various heights and

Igor Medved; Dale A. Huckaby

2007-01-01

254

Voltammetric study of polyviologen and the application of polyviologen-modified glassy carbon electrode in amperometric detection of vitamin C  

Microsoft Academic Search

The voltammetric behavior of viologen oligomers prepared from butylviologen dibromide and the factors influencing polyviologen\\u000a film formation were investigated at a glassy carbon electrode (GCE). Based on the voltammetric observations, phosphoric acid\\u000a is crucial to the formation of a stable polyviologen film on a GCE. The polyviologen-modified glassy carbon electrode (PVGCE)\\u000a was employed to determine vitamin C (i.e., ascorbic acid)

P.-F. Hsu; W.-L. Ciou; P.-Y. Chen

2008-01-01

255

Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter  

Microsoft Academic Search

Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optinum performance as AMTEC electrodes at thicknesses less than 1.0 µm when used with molybdenum or nickel current collector grids. Power densities of 0.40 W cm-2 for 0.5 µm molybdenum films at 1200 K and 0.35 W cm-2 for 0.5 µm tungsten films at 1180 K were obtained at electrode maturity after

B. L. Wheeler; R. M. Williams; B. Jeffries-Nakamura; J. L. Lamb; M. E. Loveland; C. P. Bankston; T. Cole

1988-01-01

256

A gas electrode - Behavior of the chlorine injection electrode in fused alkali chlorides  

NASA Astrophysics Data System (ADS)

The electroreduction of chlorine in fused alkali chlorides was studied by transient electrochemical techniques on graphite and carbon electrodes. Two types of experiments were carried out. First, on massive electrodes, the separate contributions of dissolved chlorine and of chlorine from bubbles at the electrode surface were detected. Second, injection electrodes were used to improve the efficiency of the reduction; the chlorine gas introduced inside the electrode flowed through the wall of the electrode. A model is presented to describe the behavior of this gas electrode; the model takes into consideration the main parameters which influence the electrode process: the properties of carbon and graphite (density, porosity, pore distribution), the wetting properties or the electrode process, the chlorine pressure, and the temperature.

Lantelme, Frederic; Alexopoulos, Hiraclis; Devilliers, Didier; Chemla, Marius

1991-06-01

257

A COMPUTATIONAL STUDY OF ENZYME PATTERNING ON MICROFLUIDIC BIOFUEL CELL ELECTRODES  

Microsoft Academic Search

The specific character of biological enzyme catalysts enables combined fuel and oxidant channels and simple non-compartmentalized fuel cell assemblies. In this work, a microstructured multi-step enzymatic biofuel cell architecture is proposed, and the species transport phenomena and chemical reactions are studied computationally in order to provide guidelines for optimization. This is the first computational study of this technology, and a

E. Kjeang; D. Sinton; D. Harrington; N. Djilali

258

Low Resistance Electrode Construction  

SciTech Connect

An electrochemical cell having a cathode and an anode in contact with an electrolyte. Both electrodes or one of them has an electrically conducting non-metal receptacle defining a chamber with a first metal having a melting point in the range of from about room temperature to about 800 C inside said receptacle chamber. A second metal with a melting point greater than about 800 C is in contact with the first metal inside the receptacle chamber and extends outside of the receptacle chamber to form a terminal for the anode. The electrolyte may include the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides. Metal may be produced at the cathode during operation of the cell and oxygen or chlorine at the anode.

Redey, Laszlo; Karell, Eric

2000-01-20

259

PLANT-ANIMAL INTERACTIONS -ORIGINAL PAPER Point and interval estimation of pollinator importance: a study  

E-print Network

PLANT-ANIMAL INTERACTIONS - ORIGINAL PAPER Point and interval estimation of pollinator importance: a study using pollination data of Silene caroliniana Richard J. Reynolds Ã? Charles B. Fenster Received: 4 Abstract Pollinator importance, the product of visitation rate and pollinator effectiveness

Fenster, Charles B.

260

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

E-print Network

adsorbed-molecule orientations; in a few cases, verification was obtained via surface vibrational (high-resolution electron-energy loss) spectroscopy. Eleven aromatic compounds were studied: [hydroquinone (1), benzoquinone (2), methylhydroquinone (3), 2...

Cruz, Juan

2012-10-19

261

Oxygen electrode reaction on Nd 2NiO 4+ ? cathode materials: impedance spectroscopy study  

Microsoft Academic Search

The oxygen reduction at the surface of Nd2NiO4+? mixed conducting cathodes has been studied in the temperature range 400–1100 K using two kinds of cells: (i) porous cathodes deposited on a standard electrolyte pellet of yttria-stabilized zirconia (YSZ) and (ii) YSZ films sputtered on dense pellets of Nd2NiO4+?. The studies on dense cathodes allowed to determine their electrical conductivity characteristics

F. Mauvy; J.-M. Bassat; E. Boehm; J.-P. Manaud; P. Dordor; J.-C. Grenier

2003-01-01

262

transparent electrode  

NASA Astrophysics Data System (ADS)

We report a new semitransparent inverted polymer solar cell (PSC) with a structure of glass/FTO/nc-TiO2/P3HT:PCBM/MoO3/Ag/MoO3. Because high-temperature annealing which decreased the conductivity of indium tin oxide (ITO) must be handled in the process of preparation of nanocrystalline titanium oxide (nc-TiO2), we replace glass/ITO with a glass/fluorine-doped tin oxide (FTO) substrate to improve the device performance. The experimental results show that the replacing FTO substrate enhances light transmittance between 400 and 600 nm and does not change sheet resistance after annealing treatment. The dependence of device performances on resistivity, light transmittance, and thickness of the MoO3/Ag/MoO3 film was investigated. High power conversion efficiency (PCE) was achieved for FTO substrate inverted PSCs, which showed about 75% increase compared to our previously reported ITO substrate device at different thicknesses of the MoO3/Ag/MoO3 transparent electrode films illuminated from the FTO side (bottom side) and about 150% increase illuminated from the MoO3/Ag/MoO3 side (top side).

Li, Fumin; Chen, Chong; Tan, Furui; Li, Chunxi; Yue, Gentian; Shen, Liang; Zhang, Weifeng

2014-10-01

263

Localization of neurosurgically implanted electrodes via photograph-MRI-radiograph coregistration  

PubMed Central

Intracranial electroencephalography (iEEG) is clinically indicated for medically refractory epilepsy and is a promising approach for developing neural prosthetics. These recordings also provide valuable data for cognitive neuroscience research. Accurate localization of iEEG electrodes is essential for evaluating specific brain regions underlying the electrodes that indicate normal or pathological activity, as well as for relating research findings to neuroimaging and lesion studies. However, electrodes are frequently tucked underneath the edge of a craniotomy, inserted via a burr hole, or placed deep within the brain, where their locations cannot be verified visually or with neuronavigational systems. We show that one existing method, registration of postimplant CT with preoperative MRI, can result in errors exceeding 1 cm. We present a novel method for localizing iEEG electrodes using routinely acquired surgical photographs, X-ray radiographs, and magnetic resonance imaging (MRI) scans. Known control points are used to compute projective transforms that link the different image sets, ultimately allowing hidden electrodes to be localized, in addition to refining the location of manually registered visible electrodes. As the technique does not require any calibration between the different image modalities, it can be applied to existing image databases. The final result is a set of electrode positions on the patient’s rendered MRI yielding locations relative to sulcal and gyral landmarks on individual anatomy, as well as MNI coordinates. We demonstrate the results of our method in eight epilepsy patients implanted with electrode grids spanning the left hemisphere. PMID:18657573

Dalal, Sarang S.; Edwards, Erik; Kirsch, Heidi E.; Barbaro, Nicholas M.; Knight, Robert T.; Nagarajan, Srikantan S.

2008-01-01

264

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

SciTech Connect

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.

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

2008-08-10

265

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

E-print Network

-Chinchilla, Xiaole Chen, Juan Cruz, Ding Li, and Alnald Javier. Akhtar Mohammed Hossain deserves a special thanks for his collaborative work. Thanks also to Stephanus Axnanda, a co- worker in the study of alloy cathodes. I am ever-so-grateful for the support... Efficiency As an Oxygen Cathode ......................................... 69 ? Cyclic Voltammetric Behavior .............................................................. 73 ? Potential-Dependent Corrosion...

Cummins, Kyle

2012-07-16

266

Use of platinum electrodes for the electrochemical detection of bacteria  

NASA Technical Reports Server (NTRS)

Platinum electrodes with surface area ratios of four to one were used to detect and enumerate a variety of gram-positive and gram-negative organisms. Linear relationships were established between inoculum size and detection time. End points for platinum electrodes were similar to those obtained with a platinum-reference electrode combination. Shape of the overall response curves and length of detection times for gram-positive organisms were markedly different than those for the majority of gram-negative species. Platinum electrodes are better than the platinum-reference electrode combination because of cost, ease of handling, and clearer definition of the end point.

Wilkins, J. R.

1978-01-01

267

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

Microsoft Academic Search

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

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

2002-01-01

268

In-situ STM study of phosphate adsorption on Cu(111), Au(111) and Cu/Au(111) electrodes  

NASA Astrophysics Data System (ADS)

The interaction of Cu(111), Au(111) and Cu-covered Au(111) electrodes with a neutral phosphate buffer solution has been studied by means of cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). Under low potential conditions, both the Cu(111) and the Au(111) surface appear apparently adsorbate free, indicated by the presence of a (4 × 4) structure and the herringbone surface reconstruction, respectively. Upon potential increase, phosphate anions adsorb on both surfaces and for Cu(111) the formation of a ?{3}×?{3}R30 structure is found, whereas on Au(111) a "?{3}×?{7}" structure is formed. For a Cu-submonolayer on Au(111), coadsorption of phosphate anions leads to the formation of a (2 × 2) vacancy structure within an assumed pseudomorphic structure of the Cu-submonolayer with the phosphate anions occupying the vacancies. When desorbing the phosphate anions at low potentials, the Cu-submonolayer first becomes mobile and eventually undergoes an irreversible transition to a coalescent nonpseudomorphic structure.

Schlaup, Christian; Horch, Sebastian

2013-02-01

269

Bioanalysis with Potentiometric Membrane Electrodes.  

ERIC Educational Resources Information Center

Discusses major themes and interrelationships common to bioselective potentiometric membrane electrodes including the nature of bioselective electrodes, applications, and future prospects. Includes tables on traditional ion-selective membrane electrodes, nontraditional electrodes, and typical biocatalytic potentiometric electrodes. (Author/JN)

Rechnitz, G. A.

1982-01-01

270

Novel electrodes for underwater ECG monitoring.  

PubMed

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

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

271

Partially filled electrodes for digital microfluidic devices  

NASA Astrophysics Data System (ADS)

As digital microfluidics technology evolves, the need for integrating additional elements (e.g., sensing/detection and heating elements) on the electrode increases. Consequently, electrode area for droplet actuation is reduced to create space for accommodating these additional elements, which undesirably affects force generation. Electrodes cannot simply be scaled larger to compensate for this loss of force, as this would also increase droplet volume and thereby compromise the advantages thought in miniaturization. Here, we present a study evaluating, numerically with preliminary experimental verification, different partially filled electrode designs and suggesting designs that combine high actuation forces with a large reduction in electrode area.

Pyne, D. G.; Salman, W. M.; Abdelgawad, M.; Sun, Y.

2013-07-01

272

The ARIES-I high-field-tokamak reactor: Design-point determination and parametric studies  

SciTech Connect

The multi-institutional ARIES study has examined the physics, technology, safety, and economic issues associated with the conceptual design of a tokamak magnetic-fusion reactor. The ARIES-I variant envisions a DT-fueled device based on advanced superconducting coil, blanket, and power-conversion technologies and a modest extrapolation of existing tokamak physics. A comprehensive systems and trade study has been conducted as an integral and ongoing part of the reactor assessment in order to identify an acceptable design point to be subjected to detailed analysis and integration as well as to characterize the ARIES-I operating space. Results of parametric studies leading to the identification of such a design point are presented. 15 refs., 6 figs., 2 tabs.

Miller, R.L.

1989-01-01

273

Separation of electrode reactions in multi electrode amperometric sensors  

Microsoft Academic Search

Multi electrode amperometric sensors based on stabilized zirconia have been studied with respect to the simultaneous detection\\u000a of oxygen and NO. Both gases are of particular interest in oxygen rich exhaust gases. With a setup consisting of two subsequent\\u000a electrodes it was possible to separate the reduction of oxygen and the reduction of NO spatially. Hence the currents of the

S. L. Somov; G. Reinhardt; U. Guth; U. Schonauer; W. Göpel

1995-01-01

274

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)

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.

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

2013-06-01

275

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

SciTech Connect

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.

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

2014-01-01

276

Comparative study of oxidation ability between boron-doped diamond (BDD) and lead oxide (PbO2) electrodes  

NASA Astrophysics Data System (ADS)

The electrochemical oxidation capabilities of two high-performance electrodes, the boron-doped diamond film on Ti (Ti/BDD) and the lead oxide film on Ti (Ti/PbO2), were discussed. Hydroxyl radicals (·HO) generated on the electrode surface were detected by using p-nitrosodimethylaniline (RNO) as the trapping reagent. Electrochemical oxidation measurements, including the chemical oxygen demand (COD) removal and the current efficiency (CE), were carried out via the degradation of p-nitrophenol (PNP) under the galvanostatic condition. The results indicate that an indirect reaction, which is attributed to free hydroxyl radicals with high activation, conducts on the Ti/BDD electrode, while the absorbed hydroxyl radicals generated at the Ti/PbO2 surface results in low degradation efficiency. Due to quick mineralization which combusts PNP to CO2 and H2O absolutely by the active hydroxyl radical directly, the CE obtained on the Ti/BDD electrode is much higher than that on the Ti/PbO2 electrode, notwithstanding the number of hydroxyl radicals produced on PbO2 is higher than that on the BDD surface.

Wei, Jun-Jun; Zhu, Xiu-Ping; Lü, Fan-Xiu; Ni, Jin-Ren

2011-10-01

277

Soft X-ray absorption spectroscopic studies with different probing depths: Effect of an electrolyte additive on electrode surfaces  

NASA Astrophysics Data System (ADS)

A solid electrolyte interphase (SEI) formed on a model LiCoO2 electrode was analyzed by the ultra-soft X-ray absorption spectroscopy (XAS). The data of Li K-, B K-, C K-, O K-, and Co L-edges spectra for the SEI film on the electrode were collected using three detection methods with different probing depths. The electrode was prepared by a pulsed laser deposition method. All the spectral data consistently indicated that the SEI film containing lithium carbonate was instantly formed just after the soak of the electrode into the electrolyte solution and that it decomposed during the repeated charge-discharge reactions. The decomposition of the SEI film seems to cause the deterioration in lithium ion battery cycle performance. By adding lithium bis(oxalate) borate (LiBOB) to the electrolyte the decomposition could be suppressed leading to longer cycle life. It was found that some of the Co ions at the electrode surface were reduced to Co(II) during the charge-discharge reactions and this reaction could also be suppressed by the addition of LiBOB.

Yogi, Chihiro; Takamatsu, Daiko; Yamanaka, Keisuke; Arai, Hajime; Uchimoto, Yoshiharu; Kojima, Kazuo; Watanabe, Iwao; Ohta, Toshiaki; Ogumi, Zenpachi

2014-02-01

278

Activated transport in AMTEC electrodes  

SciTech Connect

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.

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

1992-01-01

279

Activated transport in AMTEC electrodes  

SciTech Connect

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.

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

1992-07-01

280

HSPES membrane electrode assembly  

NASA Technical Reports Server (NTRS)

An improved fuel cell electrode, as well as fuel cells and membrane electrode assemblies that include such an electrode, in which the electrode includes a backing layer having a sintered layer thereon, and a non-sintered free-catalyst layer. The invention also features a method of forming the electrode by sintering a backing material with a catalyst material and then applying a free-catalyst layer.

Kindler, Andrew (Inventor); Yen, Shiao-Ping (Inventor)

2000-01-01

281

Study of Near-Neighbor Structure of Point Defects in ?-FE by Displacement Cascade  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have been performed to study the primary damage formation in ?-Fe by collision cascades in the recoil energy range 0.5-20 keV. Two near-neighbor analysis methods including the near-neighbor defect density (NPDD) analysis and cluster analysis were introduced to characterize the spatial aggregation of point defects and the morphologies of clusters, respectively. It is found that the NPDD of self-interstitial atom (SIA) and the number of Frenkel pairs show a similar variation trend, while the NPDD of vacancy exhibits a peak at shorter time than that of SIA. Furthermore, we find that the clusters of point defects exist mostly in the form of chainlike structure in the course and the end of cascades, but the proportion of chainlike clusters decreases with increasing the number of point defects included in one cluster. Therefore, the present methods are found to be effective to characterize the aggregation and the near-neighbor structure of point defects by displacement cascades at any time.

Wang, Wei-Lu; Liu, Wei; Wu, Xuebang; Fang, Q. F.; Liu, C. S.; Huang, Qun-Ying; Wu, Y. C.

2012-07-01

282

Using GENIE to study a tipping point in the climate system.  

PubMed

We have used the Grid ENabled Integrated Earth system modelling framework to study the archetypal example of a tipping point in the climate system; a threshold for the collapse of the Atlantic thermohaline circulation (THC). eScience has been invaluable in this work and we explain how we have made it work for us. Two stable states of the THC have been found to coexist, under the same boundary conditions, in a hierarchy of models. The climate forcing required to collapse the THC and the reversibility or irreversibility of such a collapse depends on uncertain model parameters. Automated methods have been used to assimilate observational data to constrain the pertinent parameters. Anthropogenic climate forcing leads to a robust weakening of the THC and increases the probability of crossing a THC tipping point, but some ensemble members collapse readily, whereas others are extremely resistant. Hence, we test general methods that have been developed to directly diagnose, from time-series data, the proximity of a 'tipping element', such as the THC to a bifurcation point. In a three-dimensional ocean-atmosphere model exhibiting THC hysteresis, despite high variability in the THC driven by the dynamical atmosphere, some early warning of an approaching tipping point appears possible. PMID:19087945

Lenton, Timothy M; Myerscough, Richard J; Marsh, Robert; Livina, Valerie N; Price, Andrew R; Cox, Simon J; Genie Team

2009-03-13

283

Glucose oxidase electrodes of polyaniline, poly( o -anisidine) and their co-polymer as a biosensor: a comparative study  

Microsoft Academic Search

Polyaniline (PA), poly(o-anisidine) (POA) and their co-polymer poly(aniline-co-o-anisidine) (PA-co-POA) thin films were electropolymerized in solution containing 0.1 M monomer(s) and 1 M H2SO4 as a electrolyte by applying sequential linear potential scan rate 50 mV\\/s between ?0.2 and 1.0 V vs. Ag\\/AgCl electrode on\\u000a platinum electrode. A simple technique is described for constructing a glucose sensor by the entrapment of glucose oxidase\\u000a (GOD) in

D. D. Borole; U. R. Kapadi; P. P. Mahulikar; D. G. Hundiwale

2007-01-01

284

AC susceptibility and temperature modulation studies of gadolinium near the Curie point  

Microsoft Academic Search

Measurements of the ac susceptibility and temperature modulation studies of the ac and dc magnetic properties of polycrystalline gadolinium in the vicinity of the Curie point Tc are reported. Field-independent exchange-enhanced paramagnetism was observed above Tc. Below Tc the initial field-independent susceptibility was observed for applied fields < 8 A\\/m rms and exhibited a frequency dependence characteristic of a magnetic

K. R. Sydney; D. H. Chaplin; G. V. H. Wilson

1976-01-01

285

Improving nickel metal hydride batteries through research in negative electrode corrosion control and novel electrode materials  

E-print Network

IMPROVING NICKEL METAL HYDRIDE BATTERIES THROUGH RESEARCH IN NEGATIVE ELECTRODE CORROSION CONTROL AND NOVEL ELECTRODE MATERIALS A Thesis by MICHAEL SCOTT ALEXANDER 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 1997 Major Subject: Chemical Engineering IMPROVING NICKEL METAL HYDRIDE BATTERIES THROUGH RESEARCH IN NEGATIVE ELECTRODE CORROSION CONTROL AND NOVEL ELECTRODE...

Alexander, Michael Scott

2012-06-07

286

Advanced treatment of cephalosporin pharmaceutical wastewater by nano-coated electrode and perforated electrode.  

PubMed

The objective of this study was to investigate the degradation of nonbiodegradable organic pollutants in biologically cephalosporin pharmaceutical wastewater using different electrodes such as non-nano-scale electrode (traditional coated), nano-scale (nano-coated) electrode, and perforated electrode after biotreatment. The traditional coated electrode plate, nano-coated electrode plate, and two different perforated titanium dioxide (TiO2) electrode plates with an average pore size of 10 ?m and 20 ?m were chosen as the anode. The results demonstrated that traditional coated electrode, nano-scale electrode, and perforated electrode could effectively remove nonbiodegradable organic pollutants from pharmaceutical wastewater. The perforated electrode with an average pore size of 10 ?m exhibited the best degradation effect with a 90 % decrease in the chemical oxygen demand (COD) (COD content reduced from 320 mg L(-1) to 32 mg L(-1)). During catalytic degradation, the electrical conductivity of pharmaceutical wastewater increased and the pH increased and finally reached equilibrium. It was also found that the perforated TiO2 electrode produced relatively large amounts of dissolved oxygen during the catalytic oxidation process, reaching above 4 mg L(-1), whereas the nano-coated electrode produced little dissolved oxygen. The biotoxicities of all wastewater samples increased firstly then decreased slightly during the electrical catalytic oxidation, but the final biotoxicities were all higher than initial ones. PMID:24967559

Yang, Bo; Zuo, Jiane; Gan, Lili; Yu, Xin; Liu, Fenglin; Tang, Xinyao; Wang, Yajiao

2014-09-19

287

Amperometry with Two Polarizable Electrodes. Chelometric Determination of Rare Earths  

Microsoft Academic Search

The method of determining rare earths by chelometric EDTA titration with biamperometric end-point indication using two stationary platinum electrodes was studied. The convenient pH range for the determination of lanthanum is 5.0 – 8.0, for yttrium 3.5 – 8.0 and for ytterbium 3.0 – 8.0. Rare earths have been determined in the presence of iron and thorium. Iron and thorium

Frantisek Vydra; Jan Horácek

1967-01-01

288

An equivalent system for studying periodic points of the beta-transformation for a Pisot or a Salem number  

E-print Network

An equivalent system for studying periodic points of the beta-transformation for a Pisot or a Salem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Chapter 3 Pisot numbers, Salem numbers and periodic points 18 3.1 Introduction.3 Pisot numbers and Salem numbers . . . . . . . . . . . . . . . . . . . . 20 3.4 Periodic points under

Manning, Anthony

289

Reading Different Orthographic Structures in the Shallow-Pointed Hebrew Script: A Cross-Grade Study in Elementary School  

ERIC Educational Resources Information Center

Hebrew-speaking children learn to read using a transparent, pointed writing system, but by grade three, they gradually begin using the non-pointed version of Hebrew script. The current study examined the development of reading, in the pointed script, of a nationally representative sample of children in grades two, four, and six. Rate and accuracy…

Shany, Michal; Bar-On, Amalia; Katzir, Tami

2012-01-01

290

Thin film fuel cell electrodes.  

NASA Technical Reports Server (NTRS)

Earlier work shows that fuel cell electrodes prepared by sputtering thin films of platinum on porous vycor substrates avoid diffusion limitations even at high current densities. The presented study shows that the specific activity of sputtered platinum is not unusually high. Performance limitations are found to be controlled by physical processes, even at low loadings. Catalyst activity is strongly influenced by platinum sputtering parameters, which seemingly change the surface area of the catalyst layer. The use of porous nickel as a substrate shows that pore size of the substrate is an important parameter. It is noted that electrode performance increases with increasing loading for catalyst layers up to two microns thick, thus showing the physical properties of the sputtered layer to be different from platinum foil. Electrode performance is also sensitive to changing differential pressure across the electrode. The application of sputtered catalyst layers to fuel cell matrices for the purpose of obtaining thin total cells appears feasible.

Asher, W. J.; Batzold, J. S.

1972-01-01

291

The secondary alkaline zinc electrode  

NASA Astrophysics Data System (ADS)

The worldwide studies conducted between 1975 and 1990 with the aim of improving cell lifetimes of secondary alkaline zinc electrodes are overviewed. Attention is given the design features and characteristics of various secondary alkaline zinc cells, including four types of zinc/nickel oxide cell designs (vented static-electrolyte, sealed static-electrolyte, vibrating-electrode, and flowing-electrolyte); two types of zinc/air cells (mechanically rechargeable consolidated-electrode and mechanically rechargeable particulate-electrode); zinc/silver oxide battery; zinc/manganese dioxide cell; and zinc/ferric cyanide battery. Particular consideration is given to recent research in the fields of cell thermodynamics, zinc electrodeposition, zinc electrodissolution, zinc corrosion, electrolyte properties, mathematical and phenomenological models, osmotic pumping, nonuniform current distribution, and cell cycle-life perforamnce.

McLarnon, Frank R.; Cairns, Elton J.

1991-02-01

292

Reading different orthographic structures in the shallow-pointed Hebrew script: a cross-grade study in elementary school  

Microsoft Academic Search

Hebrew-speaking children learn to read using a transparent, pointed writing system, but by grade three, they gradually begin\\u000a using the non-pointed version of Hebrew script. The current study examined the development of reading, in the pointed script,\\u000a of a nationally representative sample of children in grades two, four, and six. Rate and accuracy for four different pointed\\u000a orthographic structures: letter-diacritic

Michal Shany; Amalia Bar-On; Tami Katzir

293

Auricular Point Acupressure for Chronic Low Back Pain: A Feasibility Study for 1-Week Treatment  

PubMed Central

Objectives. The objective of this one-group, repeated-measures design was to explore the acceptance of auricular point acupressure (APA) to reduce chronic low back pain (CLBP) and estimate minimum clinically important differences (MCIDs) for pain intensity change. Methods. Subjects received 7-day APA treatment. After appropriate acupoints were identified, vaccaria seeds were carefully taped onto each selected auricular point for 7-day. The Brief Pain Inventory Short Form (BPI) was used to collect outcome data. Results. A total of 74 subjects participated in the study. Ten subjects dropped out and the retention rate was 87%. Subjects reported a 46% reduction in BPI worst pain, and over 50% reduction in BPI average pain, overall pain severity and pain interference by the end of study, and 62.5% subjects also reported less pain medication use. The MCIDs for the subscale of BPI ranged from .70 to 1.86 points. The percentage improvement of MCIDs from baseline was between 14.5–24.9%. Discussion. APA appears to be highly acceptable to patients with CLBP. A sham group is needed in order to differentiate the true effects of APA from the possible psychological effects of more frequent visits by the auricular therapist and patients' expectation of the APA treatment. PMID:22811745

Yeh, Chao-Hsing; Chien, Lung-Chang; Chiang, Yi-Chien; Huang, Li-Chun

2012-01-01

294

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

PubMed

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

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

2010-02-01

295

Flexible retinal electrode array  

DOEpatents

An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

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

2006-10-24

296

Micromachined electrode array  

DOEpatents

An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

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

2007-12-11

297

High frequency reference electrode  

DOEpatents

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.

Kronberg, James W. (Aiken, SC)

1994-01-01

298

Synaptic dysfunction in hippocampus of transgenic mouse models of Alzheimer's disease: a multi-electrode array study.  

PubMed

APP.V717I and Tau.P301L transgenic mice develop Alzheimer's disease pathology comprising important aspects of human disease including increased levels of amyloid peptides, cognitive and motor impairment, amyloid plaques and neurofibrillary tangles. The combined model, APP.V717I×Tau.P301L bigenic mice (biAT mice) exhibit aggravated amyloid and tau pathology with severe cognitive and behavioral defects. In the present study, we investigated early changes in synaptic function in the CA1 and CA3 regions of acute hippocampal slices of young APP.V717I, Tau.P301L and biAT transgenic animals. We have used planar multi-electrode arrays (MEA) and improved methods for simultaneous multi-site recordings from two hippocampal sub-regions. In the CA1 region, long-term potentiation (LTP) was severely impaired in all transgenic animals when compared with age-matched wild-type controls, while basal synaptic transmission and paired-pulse facilitation were minimally affected. In the CA3 region, LTP was normal in Tau.P301L and APP.V717I but clearly impaired in biAT mice. Surprisingly, frequency facilitation in CA3 was significantly enhanced in Tau.P301L mice, while not affected in APP.V717I mice and depressed in biAT mice. The findings demonstrate important synaptic changes that differ considerably in the hippocampal sub-regions already at young age, well before the typical amyloid or tau pathology is evident. PMID:21807097

Chong, Seon-Ah; Benilova, Iryna; Shaban, Hamdy; De Strooper, Bart; Devijver, Herman; Moechars, Dieder; Eberle, Wolfgang; Bartic, Carmen; Van Leuven, Fred; Callewaert, Geert

2011-12-01

299

Theoretical and experimental study of Differential Pulse Voltammetry at spherical electrodes: Measuring diffusion coefficients and formal potentials  

Microsoft Academic Search

Rigorous and approximate analytical expressions are deduced for Differential Pulse Voltammetry at spherical electrodes of any size, including microelectrodes, when the electrogenerated species is soluble in the electrolytic solution. From these, we examine the utility of DPV for the determination of diffusion coefficients and formal potentials, establishing the optimum conditions for this purpose. The experimental validation of the theoretical results

Ángela Molina; Eduardo Laborda; Emma I. Rogers; Francisco Martínez-Ortiz; Carmen Serna; Juan G. Limon-Petersen; Neil V. Rees; Richard G. Compton

2009-01-01

300

Study of the Nano-Size Silica Sol–Gel Film as the Matrix of Chemically Modified Electrode  

Microsoft Academic Search

This paper reports a new method to make the sol–gel film from silicate. It provided more profitable conditions than hydrolysis of alkoxyl silane to prepare the high-quality nanometers thin film. The thin film could be applied as the matrix to directly modify the molecules of methylene blue on electrode surface and kept their electrochemical activity excellently. It exhibited the remarkable

Yi-Feng Tu; Jun-Wei Di; Xiao-Jun Chen

2005-01-01

301

A comparative study of the determination of sulphide in tannery waste water by ion selective electrode (ISE) and iodimetry  

Microsoft Academic Search

The determination of sulphide present in tannery waste water by two different methods namely, iodimetry and ion selective electrode (ISE) has been critically analysed. The results obtained from iodimetry are fairly accurate, while there is a considerable deviation in the values obtained by ISE. The accuracy of the values obtained from the latter method depends on the different effluent streams

S Balasubramanian; V Pugalenthi

2000-01-01

302

Drug–GSH interaction on GSH–Au modified electrodes: A cyclic voltammetry and electrochemical impedance spectroscopy study  

Microsoft Academic Search

Gold electrode was functionalized with glutathione (GSH) by adsorption and analyzed by cyclic voltammetry and electrochemical impedance techniques. The structure and properties of the surface film are strongly dependent on the modification procedure, pH value and supporting electrolyte. The blocking properties and the electron transfer through the GSH film and the «ion gating» effect of Ca2+ ions was analyzed in

Alina Latus; Mirela Enache; Elena Volanschi

2011-01-01

303

First long term in vivo study on subdurally implanted micro-ECoG electrodes, manufactured with a novel laser technology.  

PubMed

A novel computer aided manufacturing (CAM) method for electrocorticography (ECoG) microelectrodes was developed to be able to manufacture small, high density microelectrode arrays based on laser-structuring medical grade silicone rubber and high purity platinum. With this manufacturing process, we plan to target clinical applications, such as presurgical epilepsy monitoring, functional imaging during cerebral tumor resections and brain-computer interface control in paralysed patients, in the near future. This paper describes the manufacturing, implantation and long-term behaviour of such an electrode array. In detail, we implanted 8-channel electrode arrays subdurally over rat cerebral cortex over a period of up to 25 weeks. Our primary objective was to ascertain the electrode's stability over time, and to analyse the host response in vivo. For this purpose, impedance measurements were carried out at regular intervals over the first 18 weeks of the implantation period. The impedances changed between day 4 and day 7 after implantation, and then remained stable until the end of the implantation period, in accordance with typical behaviour of chronically implanted microelectrodes. A post-mortem histological examination was made to assess the tissue reaction due to the implantation. A mild, chronically granulated inflammation was found in the area of the implant, which was essentially restricted to the leptomeninges. Overall, these findings suggest that the concept of the presented ECoG-electrodes is promising for use in long-term implantations. PMID:20838900

Henle, C; Raab, M; Cordeiro, J G; Doostkam, S; Schulze-Bonhage, A; Stieglitz, T; Rickert, J

2011-02-01

304

Study of point spread in the aberration-corrected transmission electron microscopy.  

PubMed

High precision determination of atomic position is necessary for quantitative electron microscopy so that small width of peaks, which represent atoms in structural images, adequate resolution, and sufficiently strong image contrast are needed. The width of peak is usually determined by the point spread (PS) of instruments, but the PS of objects should also be taken into consideration in aberration-corrected transmission electron microscopy when point resolution of a microscope reaches the sub-angstrom scale, and thus the PS of the instrument is comparable with that of the object. In this article, PS is investigated by studying peak width with variation of atomic number, sample thickness, and spherical aberration coefficients in both negative Cs (NCSI) and positive Cs imaging (PCSI) modes by means of dynamical image simulation. Through comparing the peak width with various atomic number, thickness, and values of spherical aberration, NCSI mode is found to be superior to PCSI considering the smaller width. PMID:25256649

Ge, Binghui; Wang, Yumei; Chang, Yunjie; Yao, Yuan

2014-10-01

305

A companion matrix approach to the study of zeros and critical points of a polynomial  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a new type of companion matrices, namely, D-companion matrices. By using these D-companion matrices, we are able to apply matrix theory directly to study the geometrical relation between the zeros and critical points of a polynomial. In fact, this new approach will allow us to prove quite a number of new as well as known results on this topic. For example, we prove some results on the majorization of the critical points of a polynomial by its zeros. In particular, we give a different proof of a recent result of Gerhard Schmeisser on this topic. The same method allows us to prove a higher order Schoenberg-type conjecture proposed by M.G. de Bruin and A. Sharma.

Cheung, Wai Shun; Ng, Tuen Wai

2006-07-01

306

Effect of tin on point defects and oxygen precipitation in Czochralski silicon: Experimental and theoretical studies  

NASA Astrophysics Data System (ADS)

The effect of tin (Sn)-doping on point defects and oxygen precipitation (OP) in Czochralski (CZ) silicon has been investigated by experiment and theoretical calculations based on density functional theory (DFT). It is found that Sn plays different roles in affecting OP according to the amount of introduced vacancies. That is, Sn suppresses OP in vacancy-lean CZ silicon but promotes OP in vacancy-rich CZ silicon. The effects of Sn-doping on the formation and annihilation of point defects as well as on the evolution of vacancy- and oxygen-related complexes have been systematically studied using DFT calculations. Based on the experimental and theoretical results, it is postulated that Sn atoms in silicon act as vacancy reservoirs which modify the formation and annihilation of vacancies as well as the evolution of vacancy-related complexes. The mechanism for the different roles of Sn in affecting OP is discussed based on the DFT calculations.

Gao, Chao; Ma, Xiangyang; Zhao, Jianjiang; Yang, Deren

2013-03-01

307

Etching of titanium nitride electrode for DRAM capacitors of high capacitance  

NASA Astrophysics Data System (ADS)

As design rules of DRAM shrink, metal electrodes for capacitors to achieve high capacitance are required. Among the proposed metal electrodes, TiN has attracted much interest due to the chemical stability and good electrical properties. However, the absence of the node formation method for TiN electrode restricts the introduction of MIM capacitor. In this work, we fabricated the MIM capacitor with TiN electrode with a structure of cylindrical stack. Especially, the node separation process of TiN electrode is deeply studied using CF4/O2 and Cl2/Ar chemistries in an ICP chamber. In a Cl2/Ar chemistry, TiN is etched at room temperature because the Cl radicals easily react with TiN forming volatile products such as TiClx and NClx. However, the etched profile has a sharp point at the top of the electrode node caused by the spacer-shaped profile along the sidewall of the hole. A capacitor having such a sharp point could have characteristics of high leakage degrading the data retention time. On the other hand, in a CF4/O2 chemistry, TiN can be etched at specific condition because the etch product, TiFx, is nonvolatile at room temperature. The profile etched with the CF4/O2 chemistry shows an isotropic etched shape without any sharp point at the top of electrode nodes. The rounded top of the electrode shows good electrical properties showing low leakage current. However, certain byproducts may remain on the SiO2 surface with the CF4/O2 process. From the analysis of gas phase reaction by OES, we found that the etching of SiO2 is accelerated during the byproduct formation. It is found that the power is the most effective parameter to determine the amount of the byproducts. We also found the robust process window without any byproducts under a certain threshold power.

Cho, Sung-Il; Kim, Jong-Kyu; Chi, Kyeong-Koo; Kang, Chang-Jin; Cho, Han-Ku; Moon, Joo-Tae

2004-09-01

308

Time-resolved in situ ATR-SEIRAS study of adsorption and 2D phase formation of uracil on gold electrodes  

Microsoft Academic Search

The adsorption and phase formation of uracil on massive Au[n(111)–(110)] single crystal and Au(111-20 nm) film electrodes in 0.1 M H2SO4 was studied by electrochemical measurements and ATR surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS). At E<0.15 V uracil molecules are disordered and planar oriented, co-adsorbed with weakly hydrogen-bonded interfacial water (region I). Around the potential of zero charge a

S Pronkin; Th Wandlowski

2003-01-01

309

Study of the electrochemical performance of spinel LiMn 2O 4 at high temperature based on the polymer modified electrode  

Microsoft Academic Search

A novel method improving the performance of spinel LiMn2O4 at high temperature is studied. The copolymer was put into the interspaces of the LiMn2O4 electrode layer prepared by maleic anhydride and acrylamide for decorating LiMn2O4, involving groups to compound with the manganese-ion. It is found that with the act of modification of the functional copolymer, the 45th discharge capacity was

Guohe Hu; Xiaobing Wang; Fang Chen; Jianyin Zhou; Rengui Li; Zhenghua Deng

2005-01-01

310

Electrochemical oxidation of adsorbed alkenoic acids as a function of chain length at Pt(111) electrodes. Studies by cyclic voltammetry, EELS and Auger spectroscopy  

Microsoft Academic Search

Studies of the electrochemical oxidation of a series of straight-chain terminal alkenoic acids adsorbed at a Pt(111) electrode surface are reported. Compounds adsorbed were: propenoic acid (acrylic acid, PPA); 3-butenoic acid (vinylacetic acid, 3BTA); 4-pentenoic acid (allylacetic acid, 4PTA); 6-heptenoic acid (6HPA); and 10-undecenoic acid (10UDA). Vibrational spectra of adsorbed layers were obtained by use of electron energy-loss spectroscopy (EELS).

Nikola Batina; Scott A. Chaffins; Bruce E. Kahn; Frank Lu; James W. McCargar; John W. Rovang; Donald A. Stern; Arthur T. Hubbard

1989-01-01

311

Computational Study on Subdural Cortical Stimulation - The Influence of the Head Geometry, Anisotropic Conductivity, and Electrode Configuration  

PubMed Central

Subdural cortical stimulation (SuCS) is a method used to inject electrical current through electrodes beneath the dura mater, and is known to be useful in treating brain disorders. However, precisely how SuCS must be applied to yield the most effective results has rarely been investigated. For this purpose, we developed a three-dimensional computational model that represents an anatomically realistic brain model including an upper chest. With this computational model, we investigated the influence of stimulation amplitudes, electrode configurations (single or paddle-array), and white matter conductivities (isotropy or anisotropy). Further, the effects of stimulation were compared with two other computational models, including an anatomically realistic brain-only model and the simplified extruded slab model representing the precentral gyrus area. The results of voltage stimulation suggested that there was a synergistic effect with the paddle-array due to the use of multiple electrodes; however, a single electrode was more efficient with current stimulation. The conventional model (simplified extruded slab) far overestimated the effects of stimulation with both voltage and current by comparison to our proposed realistic upper body model. However, the realistic upper body and full brain-only models demonstrated similar stimulation effects. In our investigation of the influence of anisotropic conductivity, model with a fixed ratio (1?10) anisotropic conductivity yielded deeper penetration depths and larger extents of stimulation than others. However, isotropic and anisotropic models with fixed ratios (1?2, 1?5) yielded similar stimulation effects. Lastly, whether the reference electrode was located on the right or left chest had no substantial effects on stimulation. PMID:25229673

Kim, Donghyeon; Seo, Hyeon; Kim, Hyoung-Ihl; Jun, Sung Chan

2014-01-01

312

Local Effects of Biased Electrodes in the Divertor of NSTX  

SciTech Connect

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.

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

2012-05-07

313

Application of Ultrasound-Guided Trigger Point Injection for Myofascial Trigger Points in the Subscapularis and Pectoralis Muscles to Post-Mastectomy Patients: A Pilot Study  

PubMed Central

Purpose To investigate the therapeutic effectiveness of ultrasound (US)-guided trigger point injection for myofascial trigger points (MTrPs) in the internal rotator muscles of the shoulder in post-mastectomy patients. Materials and Methods This pilot study was a non-controlled, prospective, clinical trial. Nineteen post-mastectomy patients with a diagnosis of at least one active MTrP in the subscapularis and/or pectoralis muscles were included. We performed trigger point injections into the subscapularis muscle deep behind the scapula as well as the pectoralis muscle for diagnostic and therapeutic purpose by the newly developed US-guided method. Results Visual analogue scale and range of motion of the shoulder for external rotation and of abduction showed significant improvement immediately after the first injection and 3 months after the last injection compared with baseline (p<0.05 for both). Duration from onset to surgery and duration of myofascial pain syndrome in the good responder group were significantly shorter than in the bad responder group (p<0.05). Patients did not report any complications related to the procedure or serious adverse events attributable to the treatment. Conclusion In post-mastectomy patients with shoulder pain, US-guided trigger point injections of the subscapularis and/or pectoralis muscles are effective for both diagnosis and treatment when the cause of shoulder pain is suspected to originate from active MTrPs in these muscles, particularly, the subscapularis. PMID:24719150

Shin, Hyuk Jai; Shin, Ji Cheol; Kim, Wan Sung; Chang, Won Hyuk

2014-01-01

314

Study of a New Working Point for the CERN PS Booster  

E-print Network

This paper reports on experiments with a new working point for the CERN PS Booster (PSB), performed during a dedicated machine development (MD) session following the 2003 run. For the experiments, we have set up the PSB with (Qh = 4.17,Qv = 4.23), and compensated only the 2Qv = 9 resonance. We compare the performance of the PSB to the one using operational settings (Qh = 4.17,Qv = 5.23). We have studied the performance using ISOLDE and LHC type beams. Furthermore, we have measured the strength of some of the resonance driving terms.

Benedikt, Michael; Carli, Christian; Chanel, M; Fiebiger, H; Findlay, A; Hanke, K; Sanchez-Alvarez, J L; Tan, J; Urschütz, Peter; CERN. Geneva. AB Department

2004-01-01

315

Cohort protocol paper: The Pain and Opioids In Treatment (POINT) study  

PubMed Central

Background Internationally, there is concern about the increased prescribing of pharmaceutical opioids for chronic non-cancer pain (CNCP). In part, this is related to limited knowledge about the long-term benefits and outcomes of opioid use for CNCP. There has also been increased injection of some pharmaceutical opioids by people who inject drugs, and for some patients, the development of problematic and/or dependent use. To date, much of the research on the use of pharmaceutical opioids among people with CNCP, have been clinical trials that have excluded patients with complex needs, and have been of limited duration (i.e. fewer than 12 weeks). The Pain and Opioids In Treatment (POINT) study is unique study that aims to: 1) examine patterns of opioid use in a cohort of patients prescribed opioids for CNCP; 2) examine demographic and clinical predictors of adverse events, including opioid abuse or dependence, medication diversion, other drug use, and overdose; and 3) identify factors predicting poor pain relief and other outcomes. Methods/Design The POINT cohort comprises around 1,500 people across Australia prescribed pharmaceutical opioids for CNCP. Participants will be followed-up at four time points over a two year period. POINT will collect information on demographics, physical and medication use history, pain, mental health, drug and alcohol use, non-adherence, medication diversion, sleep, and quality of life. Data linkage will provide information on medications and services from Medicare (Australia’s national health care scheme). Data on those who receive opioid substitution therapy, and on mortality, will be linked. Discussion This study will rigorously examine prescription opioid use among CNCP patients, and examine its relationship to important health outcomes. The extent to which opioids for chronic pain is associated with pain reduction, quality of life, mental and physical health, aberrant medication behavior and substance use disorders will be extensively examined. Improved understanding of the longer-term outcomes of chronic opioid therapy will direct community-based interventions and health policy in Australia and internationally. The results of this study will assist clinicians to better identify those patients who are at risk of adverse outcomes and who therefore require alternative treatment strategies. PMID:24646721

2014-01-01

316

Corneal-shaping electrode  

SciTech Connect

The disclosure relates to a circulating saline electrode for changing corneal shape in eyes. The electrode comprises a tubular nonconductive electrode housing having an annular expanded base which has a surface substantially matched to a subject corneal surface. A tubular conductive electrode connected to a radiofrequency generating source is disposed within the electrode housing and longitudinally aligned therewith. The electrode has a generally hemispherical head having at least one orifice. Saline solution is circulated through the apparatus and over the cornea to cool the corneal surface while radiofrequency electric current emitted from the electrode flows therefrom through the cornea to a second electrode, on the rear of the head. This current heats the deep corneal stroma and thereby effects corneal reshaping as a biological response to the heat.

Doss, J.D.; Hutson, R.L.

1982-04-27

317

Nanostructured Electrodes For Organic Bulk Heterojunction Solar Cells: Model Study Using Carbon Nanotube Dispersed Polythiophene-fullerene Blend Devices  

SciTech Connect

We test the feasibility of using nanostructured electrodes in organic bulk heterojunction solar cells to improve their photovoltaic performance by enhancing their charge collection efficiency and thereby increasing the optimal active blend layer thickness. As a model system, small concentrations of single wall carbon nanotubes are added to blends of poly(3-hexylthiophene): [6,6]-phenyl-C{sub 61}-butyric acid methyl ester in order to create networks of efficient hole conduction pathways in the device active layer without affecting the light absorption. The nanotube addition leads to a 22% increase in the optimal blend layer thickness from 90 nm to 110 nm, enhancing the short circuit current density and photovoltaic device efficiency by as much as {approx}10%. The associated incident-photon-to-current conversion efficiency for the given thickness also increases by {approx}10% uniformly across the device optical absorption spectrum, corroborating the enhanced charge carrier collection by nanostructured electrodes.

Nam, C.Y.; Wu, Q.; Su, D.; Chiu, C.-y; Tremblay, N.J.; Nuckolls, C,; Black, C.T.

2011-09-19

318

Cloud point, fluorimetric and 1H NMR studies of ibuprofen-polymer systems  

NASA Astrophysics Data System (ADS)

Influence of six polymers viz. hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), sodium carboxy methyl cellulose (NaCMC) and dextran sulfate (DxS) on solution properties of amphiphilic drug ibuprofen (IBF) has been described in this work. As only HPMC showed the clouding behavior (among the polymers employed herein), its cloud point (CP) was studied in detail in presence of varying amounts of IBF containing different fixed concentrations of inorganic salts (NaCl, NaNO3, Na2SO4, KBr and KNO3). Presence of all these salts had CP reducing effect. By means of steady state fluorescence quenching studies, average aggregation number of IBF aggregates (Nagg) in the presence of varying amounts of the mentioned polymers were evaluated and discussed. 1H NMR studies show that the magnitude of chemical shifts (?) varies with the nature of the polymer.

Khan, Iqrar Ahmad; Anjum, Kahkashan; Koya, P. Ajmal; Qadeer, Atiytul; Kabir-ud-Din

2014-01-01

319

Low resistance fuel electrodes  

DOEpatents

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.

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

1989-01-01

320

A study of pencil-lead bismuth-film electrodes for the determination of trace metals by anodic stripping voltammetry  

Microsoft Academic Search

This work reports the utility of inexpensive and disposable pencil-lead graphite as a substrate for bismuth-film electrodes (BFEs) for the simultaneous determination of Cd(II), Pb(II) and Zn(II) by square-wave anodic stripping voltammetry (SWASV). The BFE was generated in situ by depositing simultaneously the bismuth film and the metal cations by reduction at ?1.4V on the pencil graphite substrate. Then, the

D Demetriades; A Economou; A Voulgaropoulos

2004-01-01

321

Low-temperature study of lithium-ion cells using a Li ySn micro-reference electrode  

Microsoft Academic Search

Lithium-ion batteries are considered to be the next battery system for hybrid electric vehicles (HEVs) due to their high power density. However, their power is severely limited at ?30°C and the concern exists that lithium metal could plate on the negative electrode during regen (charge) pulses. The goal of this work is to determine the reason for this poor low-temperature

Andrew N. Jansen; Dennis W. Dees; Daniel P. Abraham; Khalil Amine; Gary L. Henriksen

2007-01-01

322

Multiscale porous fuel cell electrodes  

NASA Astrophysics Data System (ADS)

Porous electrodes are widely used in fuel cells to enhance electrode performance due to their high surface area. Increasingly, such electrodes are designed with both micro-scale and nano-scale features. In the current work, carbon based porous materials have been synthesized and utilized as bioelectrode support for biofuel cells, analysis of such porous electrodes via rotating disk electrode has been enhanced by a numerical model that considers diffusion and convection within porous media. Finally, porous perovskite metal oxide cathodes for solid oxide fuel cell have been modeled to simulate impedance response data obtained from symmetric cells. Carbon fiber microelectrodes (CFME) were fabricated to mimic the microenvironment of carbon fiber paper based porous electrodes. They were also miniature electrodes for small-scale applications. As observed by scanning electron microscopy (SEM), carbon nanotubes (CNTs) formed a homogeneously intertwined matrix. Biocatalysts can fully infiltrate this matrix to form a composite, with a significantly enhanced glucose oxidation current---that is 6.4 fold higher than the bare carbon fiber electrodes. Based on the CNT based porous matrix, polystyrene beads of uniform diameter at 500 nm were used as template to tune the porous structure and enhance biomolecule transport. Focused ion beam (FIB) was used to observe the morphology both at the surface and the cross-section. It has been shown that the template macro-pores enhanced the fuel transport and the current density has been doubled due to the improvement. Like commonly used rotating disk electrode, the porous rotating disk electrode is a system with analytically solved flow field. Although models were proposed previously with first order kinetics and convection as the only mass transport at high rotations, some recent findings indicated that diffusion could play an important role at all disk rotation rates. In the current proposed model, enzymatic kinetics that follow a Ping Pong Bi Bi mechanism was considered, diffusional transport included, and the electrolyte transport of substrate outside the porous media discussed as well. Composite solid oxide fuel cells have good power generation due to enhanced ion conductivity in the cathode achieved by inclusion of high oxygen ion conductivity materials. Impedance spectroscopies of such cathodes were modeled to study the underlying transport and kinetic mechanisms. The effects of electronic conductor loading were studied, including loading values below the percolation threshold. The conductivity and oxygen surface exchange reaction rate were fitted to experimental data and percolation theory was utilized to explain the fitted trends.

Wen, Hao

323

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

PubMed

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

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

2013-07-01

324

Near-Electrode Imager  

SciTech Connect

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.

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

1999-05-01

325

Insulated ECG electrodes  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

326

Near-electrode imager  

DOEpatents

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.

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

2000-01-01

327

Magnetization reversal via bloch points nucleation in nanowires and dots: a micromagnetic study  

NASA Astrophysics Data System (ADS)

Micromagnetic studies of the reversal of stripe domains in elements of different geometries are reported. Various 2D and 3D codes are used in order to allow comparison between an infinite slab, nanowires and dots. Starting from a saturated state the establishment of stripe domains through the sample is first studied. Contrary to the thin film case, the nucleation of this pattern is not uniform and is very different to the geometry of a wire or an isolated dot. Special attention is paid to the reversal of the core of the vortex (the remnants of inner walls between up and down domains) which requires the insertion of point singularities called Bloch points (BP) either at surfaces or created in a pair depending on the length allowed for the stripe in the corresponding element. The magnetization distribution around the core of the various BP is described in detail as well as the key characteristics of their motion. Finally, some experiments are suggested predicting the behaviour of stripe domains under an applied field.

Niedoba, H.; Labrune, M.

2005-10-01

328

Three electrode measurements on solid electrolytes  

SciTech Connect

AC impedance spectroscopy and chronopotentiometry have been used to study solid-state ionic conductors. Results obtained using three electrodes are compared to those using a two-electrode configuration. The uncompensated resistance was shown to depend strongly on the geometric placement of the electrodes. The optimal configuration for minimized uncompensated resistance effects is similar to the Luggin capillary arrangement in the liquid phase. The effect of non-negligible geometric capacitance on interpretation of results is discussed.

Pham, A.Q.; Glass, R.S.

1995-12-01

329

Space science/space station attached payload pointing accommodation study: Technology assessment white paper  

NASA Technical Reports Server (NTRS)

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.

Lin, Richard Y.; Mann, Kenneth E.; Laskin, Robert A.; Sirlin, Samuel W.

1987-01-01

330

Feasibility study of a novel dew point air conditioning system for China building application  

Microsoft Academic Search

The paper investigated the feasibility of a novel dew point evaporative cooling for air conditioning of buildings in China regions. The issues involved include analyses of China weather conditions, investigation of availability of water for dew point cooling, and assessment of cooling capacity of the system within various regions of China. It is concluded that the dew point system is

Xudong Zhao; Shuang Yang; Zhiyin Duan; Saffa B. Riffat

2009-01-01

331

A regression study of the number of efficient extreme points in multiple objective linear programming  

Microsoft Academic Search

In this paper we employ regression analysis to construct relationships for predicting the number of ecient extreme points in MOLPs (multiple objective linear programs) with up to 120,000 ecient extreme points, and the CPU time to compute them. Principal among the factors aecting the number of ecient extreme points and CPU time are the number of objectives, criterion cone size,

Ralph E. Steuer; Craig A. Piercy

2005-01-01

332

Point-contact study of soft magnetic CoSiBFeNb amorphous alloys  

NASA Astrophysics Data System (ADS)

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.

Seinige, Heidi; Wang, Cheng; Tsoi, Valerii; Tsoi, Maxim

2013-03-01

333

Studying field emission characteristics of point and wedge–shaped surface defects  

NASA Astrophysics Data System (ADS)

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.

Nikiforov, K. A.; Zartdinov, A. N.

2014-10-01

334

Forced Magnetic Reconnection at an X-point: A Fully Kinetic Study  

NASA Astrophysics Data System (ADS)

We will present electromagnetic Particle-In-Cell (PIC) simulation of the current sheet formation and resulting magnetic reconnection at an X-point of an initially potential field closed by conducting wall boundaries. The reconnection we study is driven by forcing that is far from the initial separatrices and is slow compared to a characteristic Alfvén speed. The effects of two types of forcing will be investigated separately: (i) convergent flows at two opposite boundaries, and (ii) enhanced pressure gradient in two spatial domains on opposite sides of the initial separatrix. For both cases, we will present the time dependence of the reconnecting electric field (suitably normalized), energy partitioning, and dependence on system size. Our results will be compared with fluid simulations of the same setup to seek suitable closure relation with necessary kinetic effects in the fluid models. This challenge problem is carried out under the auspices of a Focus Team in the NASA Living With a Star Targeted Research and Technology Program.; Reconnecting electric field Ey in the case of forcing by boundary convergent flows. Change of sign of Ey is observed. Note that the value shown is unnormalized and that if normalized by upstream B and outflow velocity, the value can be of order 0.1. ; The out-of-plane current along two axes passing the X-point at two times. The signs are opposite for the two times. The length of the current sheet is in tens of di while the width is about 1di.

Wang, L.; Bhattacharjee, A.; Bessho, N.; Germaschewski, K.

2012-12-01

335

A Randomized Clinical Trial of Auricular Point Acupressure for Chronic Low Back Pain: A Feasibility Study  

PubMed Central

Objectives. This prospective, randomized clinical trial (RCT) was designed to investigate the feasibility and effects of a 4-week auricular point acupressure (APA) for chronic low back pain (CLBP). Methods. Participants were randomized to either true APA (true acupoints with taped seeds on the designated ear points for CLBP) or sham APA (sham acupoints with taped seeds but on different locations than those designated for CLBP). The duration of treatment was four weeks. Participants were assessed before treatment, weekly during treatment, and 1 month following treatment. Results. Participants in the true APA group who completed the 4-week APA treatment had a 70% reduction in worst pain intensity, a 75% reduction in overall pain intensity, and a 42% improvement in disability due to back pain from baseline assessment. The reductions of worst pain and overall pain intensity in the true APA group were statistically greater than participants in the sham group (P < 0.01) at the completion of a 4-week APA and 1 month followup. Discussion. The preliminary findings of this feasibility study showed a reduction in pain intensity and improvement in physical function suggesting that APA may be a promising treatment for patients with CLBP. PMID:23554825

Yeh, Chao Hsing; Chien, Lung Chang; Balaban, Devora; Sponberg, Rebecca; Primavera, Jaclyn; Morone, Natalia E.; Glick, Ronald; Albers, Kathryn M.; Cohen, Susan M.; Ren, Dianxu; Huang, Li Chun; Suen, Lorna Kwai-Ping

2013-01-01

336

Point defects engineering in graphene/h-BN bilayer: A first principle study  

NASA Astrophysics Data System (ADS)

Point defects engineering in a new type hetero bilayer consisting of graphene and hexagonal boron-nitrogen (h-BN) sheet, including vacancy, substitutional C/B/N doping and the possible combinations of the former two, was theoretically studied using first-principles calculations. The optimized geometry, formation energy, magnetic moment, and electronic property of these systems are discussed. It was found that N vacancy is more likely to form than B vacancy in graphene/h-BN bilayer and their electronic properties exhibit n-type and p-type conductivity, respectively. Divacancy of N and C in hetero bilayer shows high stability and induces direct band gap in up and down spin, respectively. Combined by N substitutional doping in graphene and B vacancy in h-BN layer, this substitution-vacancy combination shows low formation energy and changes the semiconductor property of pristine graphene/h-BN bilayer to metallic. In contrast, the graphene/h-BN bilayer with the combinated defect of C-substitution in B site and C vacancy in graphene shows half-metallic electronic property. The calculated magnetic moments are in reasonable agreement with the available theoretical analysis on atomic charge distribution. This work reveals that the electronic and magnetic properties of graphene/h-BN bilayer can be effectively tuned by above proposed point defects engineering.

Yuan, Jianmei; Wei, Zhe; Zhong, Jianxin; Huang, Yanping; Mao, Yuliang

2014-11-01

337

x Left electrode Right electrode  

E-print Network

University Center, SE-10691 Stockholm, Sweden Received 11 June 2003; published 8 January 2004 We study- late, and the prospects for large-scale manufacturing are comparatively good. However, they suffer from

Haviland, David

338

Ion-exchange studies on poly-o-anisidine Sn(IV) phosphate nano composite and its application as Cd(II) ion-selective membrane electrode  

Microsoft Academic Search

An organic-inorganic composite, poly-o-anisidine Sn(IV) phosphate, was chemically synthesized by mixing ortho-anisidine into\\u000a gels of Sn(IV) phosphate with different mixing volume ratios. Studies on the effect of eluant concentration, elution behavior\\u000a and separation of metal ions were carried out to understand the ion-exchange capabilities. Due to Cd(II) selective nature\\u000a of composite, revealed by distribution studies, Cd(II) ion selective membrane electrode

Asif Ali Khan; Anish Khan

2010-01-01

339

Electrode potential studies of liquid-solid equilibrium in Na{sub 3}Bi-saturated Na-Bi melts  

SciTech Connect

Liquid binary Na-Bi alloys have been studied extensively because of the interest in possible uses as electrochemically active couples in regenerative electrochemical cells, in high-energy batteries, and as potential heat-transfer media in nuclear reaction processes. Techniques used previously for thermodynamic measurements on the system have included the transpiration method, quasi-static and boiling point methods, the electromotive force (emf) method using molten salt mixtures and various solid electrolytes, and thermal analysis. Most of the thermodynamic data on Bi-Na alloys were recently assessed by Sangster and Pelton. However, no experimental thermodynamic data for liquid-solid equilibrium in liquid Na-Bi alloys saturated with solid Na{sub 3}Bi have been reported in the literature. The aim of the present work was to investigate experimentally the equilibrium between Na-Bi melts and solid Na{sub 3}Bi by the emf method in the range 638 to 973 K.

Yan, X.Y.; Langberg, D.E.; Rankin, W.J.

2000-04-01

340

Effects of Stimulation Level and Electrode Pairing on The Binaural Interaction Component of The Electrically Evoked Auditory Brain Stem Response  

PubMed Central

Objectives The purpose of this study was to investigate the effects of stimulation level and electrode pairing on the binaural interaction component (BIC) of the electrically evoked auditory brain stem response (EABR) in Nucleus cochlear implant users. Design Ten postlingually deafened adult cochlear implant users participated in this study. EABRs were measured using loudness balanced, biphasic current pulses presented in the left monaural, right monaural and bilateral stimulation conditions. BICs were computed based on measures of the EABR obtained for each subject by pairing the electrode 12 (out of 22 intracochlear electrodes) in the right ear with each of 11 electrodes spaced across the electrode array in the left ear. The effect of stimulation level on the amplitude of the BIC was investigated by measuring growth functions of the BIC from six subjects. The effect of electrode pairing on the amplitude of the BIC was studied at high stimulation levels in ten subjects and at low stimulation levels in seven subjects. The high stimulation level was chosen as the 90% point of the subject’s dynamic range (DR) or the highest stimulation level where the electrophysiological recordings were not contaminated by muscle artifacts. The low stimulation level was chosen as a level that was 10% point of subject’s DR higher than the BIC threshold for six of these seven subjects. For one subject, BIC thresholds were not available and the low stimulation level was referred to the 70% point of her DR. Results BICs were successfully recorded from all 11 interaural electrode pairs for a majority of subjects tested at both stimulation levels. BIC amplitudes increased with stimulation level. The effect of stimulation level on latencies of the BIC was less robust. At high stimulation levels, BIC amplitudes did not change significantly as the stimulating electrode used in the left ear was systematically varied. When low stimulation levels were used, BIC amplitude was maximal for interaural electrode pairs with similar intracochlear positions and decreased when the offset between interaural electrodes increased. Conclusions This study demonstrates that stimulation level affects amplitudes of the BIC response. It is possible to record the BIC of the EABR in bilateral CI users even from interaural electrode pairs that have large interaural offsets. This finding suggests that when high-level stimuli are used, there is a broad pattern of current spread within the two cochleae. At lower stimulation levels the spread of excitation within the cochlea is reduced making the effect of electrode pairing on the amplitude of the BIC more pronounced. PMID:20418771

He, Shuman; Brown, Carolyn J.; Abbas, Paul J.

2012-01-01

341

Study on gutta-percha points using scanning electron microscopy and analysis with electron microprobe.  

PubMed

A comparative study of the apical morphology and contour was performed with the scanning electron microscope at 45x, 70x and 300x, while the chemical composition of eight gutta-percha point brands was surveyed with an EDAX 9100 electron microprobe. They were classified according to their apical morphology as conical (25%) and truncate (75%), based on their contour as regular (50%) and irregular (50%) and according to their surface as without defects (50%) and with defects (50%). The analysis of inorganic compounds revealed the presence of varying proportions of Zn, Ba, Si, Mg. Ca, P, Cl and Al, possibly implying that the presence of Ba and Al could interfere with postendodontic repair or at least irritate the periapical area if inadvertently overfilled. PMID:11885233

Fernández Monjes, J; Lopreite, H; Maresca, B M; Sierra, L

1994-01-01

342

Comparison of temperature and work function measurements obtained with different GTA electrodes  

Microsoft Academic Search

This work was carried out on one standard electrode (W-ThO2,) and other electrodes developed by additions of La2O3, CeO2, and Y2O3,. The effect of rare-earth metal oxides on GTAW electrode phenomena, concerning electrode temperature, emissivity, and work function, was analyzed and compared from the point of view of those oxides' behavior during arcing. The experimental results indicate that the electrode

Masao Ushio; Alber A. Sadek; Fukuhisa Matsuda

1991-01-01

343

Characteristics study of multimode directional coupler by elliptical point contacts and CMT  

NASA Astrophysics Data System (ADS)

The developed directional coupler using polymer optical fiber performance is studied analytically where related theories are integrated and the outcomes are analyzed. Important theories such as simplified coupled mode theory and elliptical point contacts are integrated where the parameters such as coupling length, distance between the two fibers cores and forces are varied. Using simplified coupled mode theory, coupling coefficient and coupling efficiency is obtained based on the parameters of multimode fiber coupler such as the operating wavelength, numerical apertures, coupling length and diameter of the cores. The two fibers are initially tapered at certain length at most 20 mm and attached to geometrical blocks with certain radii and the middle tapered regions of the fibers are brought closed in proximity and they are lapped to each other. Investigation of different radii of the geometrical blocks represents the effect of macro-bending when the fibers are bent when attached to the circular blocks. This concept is used to transfer the modes from first fiber to the second. Then a particular amount of load force is exerted upon one side of the blocks so that the gap is closed and leads to increment of coupling length between the two fibers. The various load force amount will give different coupling lengths and distances between the two cores, thus leading to different coupling efficiencies. Analytically the expression that represents the coupling efficiency with force is an integrated expression from simplified coupled mode theory and Hertz's Law of elliptical point contacts. Optimized coupling efficiency obtained is as high as 70% for this study.

Supian, L. S.; Ramza, Harry; Ab-Rahman, Mohd Syuhaimi; Arsad, Norhana

2014-08-01

344

Genetic thinking in the study of social relationships: Five points of entry  

PubMed Central

For nearly a generation, researchers studying human behavioral development have combined genetically informed research designs with careful measures of social relationships: parenting, sibling relationships, peer relationships, marital processes, social class stratifications and patterns of social engagement in the elderly. In what way have these genetically informed studies altered the construction and testing of social theories of human development? We consider five points where genetic thinking is taking hold. First, genetic findings suggest an alternative scenario for explaining social data. Associations between measures of the social environment and human development may be due to genes that influence both. Second, genetic studies add to other prompts to study the early developmental origins of current social phenomena in mid-life and beyond. Third, genetic analyses promise to bring to the surface understudied social systems, such as sibling relationships, that have an impact on human development independent of genotype. Fourth, genetic analyses anchor in neurobiology individual differences in resilience and sensitivity to both adverse and favorable social environments. Finally, genetic analyses increase the utility of laboratory simulations of human social processes and of animal models. PMID:25419225

Reiss, David

2014-01-01

345

The Economic Intelligence process : A study according to the point of view of the infomediary and of the information retrieval  

E-print Network

1 The Economic Intelligence process : A study according to the point of view of the infomediary and of the information retrieval problem Stéphane GORIA and Audrey KNAUF CEIS (Compagnie Européenne d'Intelligence Intelligence, user model, watcher. Abstract The information universe from a company point of view has changed

Paris-Sud XI, Université de

346

Statistical implications of end-point selection and inspection interval in the Daphnia reproduction test -- a simulation study  

Microsoft Academic Search

In order to protect an ecosystem against anthropogenic stressors such as xenobiotics, potential impacts on its sensitive populations must be investigated. A general simulation approach was developed for validating biotest end points in the Daphnia reproduction test. Various toxic-effect scenarios, sample sizes, and inspection regimes were used to study the behavior and robustness of different end points. The intrinsic rate

Hans Toni Ratte

1996-01-01

347

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

SciTech Connect

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.

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

2000-04-01

348

The Dependence of Auditory Nerve Rate Adaptation on Electric Stimulus Parameters, Electrode Position, and Fiber Diameter: A Computer Model Study  

PubMed Central

This paper describes results from a stochastic computational neuron model that simulates the effects of rate adaptation on the responses to electrical stimulation in the form of pulse trains. We recently reported results from a single-node computational model that included a novel element that tracks external potassium ion concentration so as to modify membrane voltage and cause adaptation-like responses. Here, we report on an improved version of the model that incorporates the anatomical components of a complete feline auditory nerve fiber (ANF) so that conduction velocity and effects of manipulating the site of excitation can be evaluated. Model results demonstrate rate adaptation and changes in spike amplitude similar to those reported for feline ANFs. Changing the site of excitation from a central to a peripheral axonal site resulted in plausible changes in latency and relative spread (i.e., dynamic range). Also, increasing the distance between a modeled ANF and a stimulus electrode tended to decrease the degree of rate adaptation observed in pulse-train responses. This effect was clearly observed for high-rate (5,000 pulse/s) trains but not low-rate (250 pulse/s) trains. Finally, for relatively short electrode-to-ANF distances, increases in modeled ANF diameter increased the degree of rate adaptation. These results are compared against available feline ANF data, and possible effects of individual parameters are discussed. PMID:20033248

Woo, Jihwan; Abbas, Paul J.

2009-01-01

349

Real-time measurement of electrode impedance during intracochlear electrode insertion  

PubMed Central

Objectives This pilot study details the use of a software tool that uses continuous impedance measurement during electrode insertion, with the eventual potential to assess and optimize electrode position and reduce insertional trauma. Study Design Software development and experimental study with human cadaveric cochleae and two live surgeries. Methods A prototype program to measure intracochlear electrode impedance and display it graphically in real time has been developed. The software was evaluated in human cadaveric temporal bones while simultaneously making real time fluoroscopic recordings, and in two live surgeries during intracochlear electrode insertion. Results Impedance changes were observed with various scalar positions, and values were consistent with those obtained using clinically available software. Using Contour Advance™ electrodes, impedance values increased after stylet removal, particularly when using the monopolar mode. Conclusion Impedance values seem systematically affected by electrode position, with higher values being associated with proximity to the cochlear wall. The new software is capable of acquiring impedance measurements during electrode insertion and this data may be useful to guide surgeons to achieve optimal and atraumatic electrode insertion, to guide robotic electrode insertion, and to provide insights about electrode position in the cochlea. PMID:23529884

Tan, Chin-Tuan; Svirsky, Mario; Anwar, Abbas; Kumar, Shaun; Caessens, Bernie; Carter, Paul; Treaba, Claudiu; Roland, J. Thomas

2013-01-01

350

Myofascial trigger point needling for whiplash associated pain--a feasibility study.  

PubMed

Clinicians claim that myofascial trigger points (MTrPs) are a primary cause of pain in whiplash injured patients. Pain from MTrPs is often treated by needling, with or without injection. We conducted a placebo controlled study to test the feasibility of a phase III randomised controlled trial investigating the efficacy of MTrP needling in patients with whiplash associated pain. Forty-one patients referred for physiotherapy with a recent whiplash injury, were recruited. Patients were randomised to receive standardised physiotherapy plus either acupuncture or a sham needle control. A trial was judged feasible if: i) the majority of eligible patients were willing to participate; ii) the majority of patients had MTrPs; iii) at least 75% of patients provided completed self-assessment data; iv) no serious adverse events were reported and v) the end of treatment attrition rate was less than 20%. 70% of those patients eligible to participate volunteered to do so; all participants had clinically identified MTrPs; a 100% completion rate was achieved for recorded self-assessment data; no serious adverse events were reported as a result of either intervention; and the end of treatment attrition rate was 17%. A phase III study is both feasible and clinically relevant. This study is currently being planned. PMID:20580303

Tough, Elizabeth A; White, Adrian R; Richards, Suzanne H; Campbell, John L

2010-12-01

351

Impact of field of study, college and year on calculation of cumulative grade point average.  

PubMed

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. Additional concerns relate to the equivalence of grades obtained from different fields of study and institutions, with little hard data to guide conclusions. At the Michael G. DeGroote School of Medicine Class of 2007 at McMaster University, every undergraduate grade of 2,138 applicants, along with field of study and post-secondary educational institution, was analyzed. Individual grades were aggregated into an overall uGPA using published algorithms from several medical school, and correlated with a non-weighted sum. Correlations of the different schemas with equal weights ranged from 0.973 to 0.990. The extent of the difference between fields of study was small, accounting for only 1.5% of the variance. However, differences among 16 Ontario universities were larger, and accounted for 9.3% of the variance. The results of this study suggest that all weighting schemas are virtually equivalent, making any formulation reasonable. Differences by field of study are small, but do not show any bias against non-science students. Differences by institution are larger, amounting to a range in average score from 78.7 to 84.6; however it is not clear whether this reflects candidate ability or institutional policy, so attempts to correct for institution may be difficult. PMID:17063382

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

2008-08-01

352

Calorimetric study of the smectic-Ad-smectic-A2 critical point  

Microsoft Academic Search

High-resolution heat-capacity measurements are reported for the vicinity of the smectic-Ad-smectic-A2 critical point in mixtures of undecyloxyphenyl-cyanobenzyloxy benzoate (11OPCBOB) and nonyloxybiphenyl cyanobenzoate (9OBCB). This type of critical point, which has similarities to the familiar liquid-gas (Ising) critical point, is predicted to belong to a new universality class. The variation of Cpx in two near-critical mixtures with 11OPCBOB mole fractions X=0.655

Y. H. Jeong; G. Nounesis; C. W. Garland; R. Shashidhar

1989-01-01

353

a Comparative Study Between Pair-Point Clique and Multi-Point Clique Markov Random Field Models for Land Cover Classification  

NASA Astrophysics Data System (ADS)

Markov random field (MRF) is an effective method for description of local spatial-temporal dependence of image and has been widely used in land cover classification and change detection. However, existing studies only use pair-point clique (PPC) to describe spatial dependence of neighbouring pixels, which may not fully quantify complex spatial relations, particularly in high spatial resolution images. In this study, multi-point clique (MPC) is adopted in MRF model to quantitatively express spatial dependence among pixels. A modified least squares fit (LSF) method based on robust estimation is proposed to calculate potential parameters for MRF models with different types. The proposed MPC-MRF method is evaluated and quantitatively compared with traditional PPCMRF in urban land cover classification using high resolution hyperspectral HYDICE data of Washington DC. The experimental results revealed that the proposed MPC-MRF method outperformed the traditional PPC-MRF method in terms of classification details. The MPC-MRF provides a sophisticated way of describing complex spatial dependence for relevant applications.

Hu, B.; Li, P.

2013-07-01

354

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

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

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

2009-01-01

355

The study of the electrooxidation of chloride at RuO 2\\/TiO 2 electrode using CV and radiotracer techniques and evaluating by electrochemical kinetic simulation methods  

Microsoft Academic Search

The mechanism of the chloride electrooxidation was investigated by CV and radiotracer techniques, as well as PC simulation methods on RuO2\\/TiO2 mixed oxide electrodes. The voltammetric behavior of an adsorbed intermediate was studied.Both the experimental and simulation results show that the electrooxidation of chloride is going through the steps of the Volmer–Heyrovsky mechanism on this working electrode.

L. Tomcsányi; A. De Battisti; G. Hirschberg; K. Varga; J. Liszi

1999-01-01

356

Electrochemistry at Nanometer-Scaled Electrodes  

ERIC Educational Resources Information Center

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…

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

2005-01-01

357

THE ISOTOPE EFFECT ON HYDROGEN ELECTRODES  

Microsoft Academic Search

The electrochemical hydrogen isotope separation at cathodic and anodic ; electrodes was studied for the purpose of understanding reaction rate mechanisms ; and providing data for a proposed heavy water enrichment plant. The dependence ; of the separation factor. S, on: the cathode material, the cathode surface ; (porous vs smooth electrodes), the cathode potential, and the cathode temperature ;

1962-01-01

358

The Relationship between Electrically Evoked Compound Action Potential and Speech Perception : A Study in Cochlear Implant Users with Short Electrode Array  

PubMed Central

Objectives To determine the extent to which electrically evoked compound action potential (ECAP) measurements were related with speech perception performance in implant users with a short electrode array and to investigate the relationship between ECAP measures and performance according to specific devices. Design Prospective study. Setting Tertiary referral center. Patients Seventeen Hybrid cochlear implant users were tested in this study. Subjects were divided into 2 groups: 1) 8 using the Nucleus Hybrid M, 2) 9 using the Nucleus Hybrid RE. In addition, 21 Nucleus Freedom long electrode implant (CI24RE) users were also tested to compare with the results of the old device (CI24M). Main Outcome measures ECAP growth functions were recorded using either an interphase gap (IPG) of 8 or 45 us. We then calculated 1) the slope of the growth function, and 2) changes in sensitivity with IPG. For each subject, these measures were compared with performance on tests of word recognition. Results The changes in sensitivity using two IPGs showed no correlation with results of word recognition test in Hybrid cochlear implant users. In contrast, relatively strong correlations have been found between the slope of ECAP growth functions and performance on word recognition test. Additionally, when we separate the results of Hybrid M and RE, the slopes of ECAP growth functions from only Hybrid RE CI recipients were significantly correlated with speech performance. The slopes of ECAP growth function in CI24RE users with long electrode were also significantly correlated with performance. However, comparing between two independent correlations in RE devices, correlation was higher in Hybrid RE group. Conclusion The results presented in this paper support the view that slope of the ECAP growth can show significant correlation to performance with a cochlear implant. Further, these results suggest that the strength of the correlation may be related to the specific device. These results suggest that ECAP measures may be useful in developing a test to predict outcomes with the implant. PMID:20634770

Kim, Jae-Ryong; Abbas, Paul J.; Brown, Carolyn J.; Etler, Christine P.; O'Brien, Sara; Kim, Lee-Suk

2010-01-01

359

Simultaneous Measurement of Dopamine and Ascorbic Acid at Cnt Electrode  

NASA Astrophysics Data System (ADS)

Electrochemical behaviors of dopamine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for dopamine redox reactions at the carbon nanotube electrode in comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. The important discover was that the carbon nanotube electrode can be used to detect low level of dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution as well.

Hu, C. G.; Wang, W. L.; Feng, B.; Wang, H.

360

A CMB foreground study in WMAP data: Extragalactic point sources and zodiacal light emission  

NASA Astrophysics Data System (ADS)

The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. It serves as a primary tool to understand the global properties, content and evolution of the universe. Since 2001, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite has been napping the full sky anisotropy with unprecedented accuracy, precision and reliability. The CMB angular power spectrum calculated from the WMAP full sky maps not only enables accurate testing of cosmological models, but also places significant constraints on model parameters. The CMB signal in the WMAP sky maps is contaminated by microwave emission from the Milky Way and from extragalactic sources. Therefore, in order to use the maps reliably for cosmological studies, the foreground signals must be well understood and removed from the maps. This thesis focuses on the separation of two foreground contaminants from the WMAP maps: extragalactic point sources and zodiacal light emission. Extragalactic point sources constitute the most important foreground on small angular scales. Various methods have been applied to the WMAP single frequency maps to extract sources. However, due to the limited angular resolution of WMAP, it is possible to confuse positive CMB excursions with point sources or miss sources that are embedded in negative CMB fluctuations. We present a novel CMB-free source finding technique that utilizes the spectrum difference of point sources and CMB to form internal linear combinations of multifrequency maps to suppress the CMB and better reveal sources. When applied to the WMAP 41, 64 and 94 GHz maps, this technique has not only enabled detection of sources that are previously cataloged by independent methods, but also allowed disclosure of new sources. Without the noise contribution from the CMB, this method responds rapidly with the integration time. The number of detections varies as 0( t 0.72 in the two-band search and 0( t 0.70 in the three-band search from one year to five years, separately, in comparison to t 0.40 from the WMAP catalogs. Our source catalogs are a good supplement to the existing WMAP source catalogs, and the method itself is proven to be both complementary to and competitive with all the current source finding techniques in WMAP maps. Scattered light and thermal emission from the interplanetary dust (IPD) within our Solar System are major contributors to the diffuse sky brightness at most infrared wavelengths. For wavelengths longer than 3.5 mm, the thermal emission of the IPD dominates over scattering, and the emission is often referred to as the Zodiacal Light Emission (ZLE). To set a limit of ZLE contribution to the WMAP data, we have performed a simultaneous fit of the yearly WMAP time-ordered data to the time variation of ZLE predicted by the DIRBE IPD model (Kelsallet al. 1998) evaluated at 240 mm, plus [cursive l] = 1 - 4 CMB components. It is found that although this fitting procedure can successfully recover the CMB dipole to a 0.5% accuracy, it is not sensitive enough to determine the ZLE signal nor the other multipole moments very accurately.

Chen, Xi

361

Bifunctional alkaline oxygen electrodes  

NASA Technical Reports Server (NTRS)

The authors describe the identification and testing of electrocatalysts and supports for the positive electrode of moderate-temperature, single-unit, rechargeable alkaline fuel cells. Recent work on Na(x)Pt3O4, a potential bifunctional catalyst, is described, as well as the application of novel approaches to the development of more efficient bifunctional electrode structures. The three dual-character electrodes considered here showed similar superior performance; the Pt/RhO2 and Rh/RhO2 electrodes showed slightly better performance than the Pt/IrO2 electrode. It is concluded that Na(x)Pt3O4 continues to be a promising bifunctional oxygen electrode catalyst but requires further investigation and development.

Swette, L.; Kackley, N.; Mccatty, S. A.

1991-01-01

362

Study of antibacterial activity by capillary electrophoresis using multiple UV detection points.  

PubMed

A new methodology for an antibacterial assay based on capillary electrophoresis with multiple UV detection points has been proposed. The possible antibacterial activity of cationic molecules on bacteria (Gram-positive and Gram-negative) is studied by detecting the bacteria before, during, and after their meeting with the cationic antibacterial compound. For that, a UV area imaging detector having two loops and three detection windows was used with a 95 cm ×100 ?m i.d. capillary. In the antibacterial assay, the bacteria (negatively charged) and the cationic molecules were injected separately from each end of the capillary. The bacteria were mobilized by anionic ITP mode while cationic molecules migrate in the opposite direction under conditions close to CZE. The cationic molecules were injected into the capillary as a broad band (injected volume about 16% of the volume of the capillary) to prevent dilution of the sample during the electrophoretic process. Bacteriolytic activity, as well as strong interactions between the small antibacterial molecules and the bacteria, can be investigated within a few minutes. The assay was used to study the antibacterial activity of dendrigraft poly-L-lysines on Micrococcus luteus and Erwinia carotovora. Because dendrigraft poly-L-lysines are nonimmunogenic and have low toxicity, this new class of dendritic biomacromolecules is very promising for antibacterial applications. PMID:22448657

Oukacine, Farid; Romestand, Bernard; Goodall, David M; Massiera, Gladys; Garrelly, Laurent; Cottet, Hervé

2012-04-01

363

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

NASA Technical Reports Server (NTRS)

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 controls system over the 5.2 msec round-trip time for a realistic spacecraft environment was = 0.3 micro rad, rms, within the specified value of less than 0.5 micro rad, rms, derived in a 2 micron LAWS System Study. Disturbance modes were defined for: (1) the Bearing and Power Transfer Assembly (BAPTA) scan bearing, (2) the spacecraft reaction wheel torques, and (3) the solar array drive torques. The scan bearing disturbance was found to be the greatest contributing noise source to the jitter performance. Disturbances from the fast steering mirror reaction torques and a boom-mounted cross-link antenna clocking were also considered but were judged to be small compared to the three principal disturbance sources above and were not included in the final controls analysis.

Manlief, Scott

1995-01-01

364

An Observational Study on the Effectiveness of Point-Of-Use Chlorination  

PubMed Central

Although the efficacy of chlorine disinfection under controlled laboratory conditions is well known, the effectiveness of chlorine under field point-of-use (POU) conditions is still not clearly understood and may be impacted by a variety of factors. This study evaluated the effectiveness of POU chlorine disinfection in rural Ecuador under typical use conditions and compared this effectiveness with the efficacy in controlled laboratory conditions. While reductions of indicator organisms were slightly higher in households that used chlorination, no significant differences were seen between households employing POU chlorination and the households with no chlorination (1–1.5 log10 median reductions for chlorinating households and 0.31–0.55 log10 for nonchlorinating households, depending on the indicator organism). In contrast, significant reduction of all test organisms was found when simulating POU conditions in the laboratory. This study demonstrates that POU chlorination can be considerably less effective under actual field conditions than would be predicted based on its laboratory efficacy (3–5 log10 median reductions for chlorinated and 0–0.3 log10 for non-chlorinated samples). Human factors (including improper storage and chlorine dosing) and uncontrolled water quality effects are hypothesized to impact significantly the effectiveness of chlorine disinfection. PMID:19408433

McLaughlin, Laura A.; Levy, Karen; Beck, Nicola K.; Shin, Gwy-Am; Meschke, J. Scott; Eisenberg, Joseph N.

2010-01-01

365

A Simulation Study Comparison of Bayesian Estimation with Conventional Methods for Estimating Unknown Change Points  

ERIC Educational Resources Information Center

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…

Wang, Lijuan; McArdle, John J.

2008-01-01

366

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

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

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

2013-01-01

367

Nanoscopic electrode molecular probes  

DOEpatents

The present invention relates to a method and apparatus for enhancing the electron transport property measurements of a molecule when the molecule is placed between chemically functionalized carbon-based nanoscopic electrodes to which a suitable voltage bias is applied. The invention includes selecting a dopant atom for the nanoscopic electrodes, the dopant atoms being chemically similar to atoms present in the molecule, and functionalizing the outer surface and terminations of the electrodes with the dopant atoms.

Krstic, Predrag S. (Knoxville, TN); Meunier, Vincent (Knoxville, TN)

2012-05-22

368

Radiation effects on silver and zinc battery electrodes. II. July-October 1965  

Microsoft Academic Search

The study of the effects of radiation on silver and zinc electrodes was continued with specific attention being given to the silver electrode. Cadmium counter electrodes were used with the silver electrodes in the study pending the availability of suitable zinc electrodes. Material losses from irradiated silver electrodes of 3.0 g total weight averaged 60.2, 77.7, and 52.9 mg at

G. R. Argue; H. L. Recht; W. A. McCollum

1965-01-01

369

Pocket ECG electrode  

NASA Technical Reports Server (NTRS)

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.

Lund, G. F. (inventor)

1980-01-01

370

Pocket ECG electrode  

NASA Technical Reports Server (NTRS)

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.

Lund, Gordon F. (Inventor)

1982-01-01

371

Origin of Capacity Fading in Nano-Sized Co3O4 Electrodes: Electrochemical Impedance Spectroscopy Study  

NASA Astrophysics Data System (ADS)

Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4 with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4 anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.

Kang, Jin-Gu; Ko, Young-Dae; Park, Jae-Gwan; Kim, Dong-Wan

2008-10-01

372

Performance of temporary epicardial stainless steel wire electrodes used to treat atrial fibrillation: a study in patients following open heart surgery.  

PubMed

AF is the most common arrhythmia following open heart surgery. Transthoracic cardioversion is used when pharmacological treatment fails to restore SR, or is ineffective in controlling ventricular response rate. We report on the performance of temporary atrial defibrillation wire electrodes implanted on the epicardium of patients undergoing open heart surgery. Epicardial stainless steel wire electrodes for both pacing/sensing and atrial defibrillation were placed at the left and right atrium during open heart surgery in 100 consecutive patients (age 65 +/- 9 years; male/female 77/23). Electrophysiological studies performed postoperatively revealed a test shock (0.3 J) impedance of 96 +/- 12 omega (monophasic) and 97 +/- 13 omega (biphasic). AF was induced by burst stimulation in 84 patients. All patients were successfully converted to SR. The mean energy of successful shocks was 3.1 +/- 1.9 J. Atrial pacing and sensing were accomplished in all patients. Pacing threshold was 1.9 +/- 1.7 V (0.5 ms) in the left atrium and 2.1 +/- 2 V in the right atrium. P wave sensing was 2.5 +/- 1.6 mV in the left atrium and 2.3 +/- 1.4 mV in the right atrium. No complications were observed with shock application, nor with lead extraction. Atrial defibrillation using temporary epicardial wire electrodes can be performed successfully and safely in patients following cardiac operations. The shock energy required to restore SR is low. Electrical cardioversion in the absence of anesthesia should be feasible. PMID:10087546

Liebold, A; Rödig, G; Birnbaum, D E

1999-02-01

373

Structural in situ study of the thermal behavior of manganese dioxide materials: toward selected electrode materials for supercapacitors.  

PubMed

The thermal behavior of a series of MnO2 materials was investigated toward MnO2 microstructures under inert atmospheres. The byproduct formed during MnO2 heat treatments from the room temperature to 800 °C were characterized by in situ X-ray diffraction analyses. It was found that annealing spinel and ramsdellite phases caused the formation of MnO2 pyrolusite at 200 °C, Mn2O3, at 400 °C, and then Mn3O4 at higher temperatures. In the case of cryptomelane and birnessite phases, the heating process resulted in the formation of K0.51Mn0.93O2 at 600 °C, while Mn3O4 was also formed and still present up to 800 °C. Heat-treating Ni-todorokite and OMS-5 up to about 450 °C led to the formation of NiMn2O4 and NaxMnO2, respectively, and again Mn3O4 at higher temperatures. All of these structural transformations were correlated to resulting weight losses of MnO2 powders, measured by thermogravimetric analyses, during the heating process. Cyclic voltammetry measurements were performed in the presence of 0.5 M K2SO4 aqueous solution for annealed cryptomelane, K0.51Mn0.93O2, and Mn3O4-based electrodes. It was found that MnO2 cryptomelane is electrochemically stable upon heating. The long-term charge/discharge voltammetric cycling revealed that the specific capacitance of Mn3O4-based electrode is significantly improved from 14 F·g(-1) (after 20 cycles) to 123 F·g(-1) (after 500 cycles). PMID:21114252

Ghodbane, Ouassim; Pascal, Jean-Louis; Fraisse, Bernard; Favier, Frédéric

2010-12-01

374

Changes in Antimicrobial Use Prevalence in China: Results from Five Point Prevalence Studies  

PubMed Central

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

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

375

An Imaging Spectroscopic Study of Active Region EUV Bright Points by Hinode/EIS  

NASA Astrophysics Data System (ADS)

We have investigated seven Extreme-Ultraviolet (EUV) bright points in the active region AR 0926 on 2006 December 2 by the EUV Imaging spectrometer (EIS) onboard Hinode spacecraft. We determined their Doppler velocities and non-thermal velocities from EUV spectral lines (log T=4.7-7.2) by fitting each line profile to a Gaussian function. We present the Doppler velocity map as a function of temperature which corresponds to a different height. As a result, these active region bright points can be classified into two types according to the pattern of doppler shifts. Type 1 bright point shows a systematic increase of Doppler velocity from -56km/s (blue shift) at log T=5.8 to 12km/s (red shift) at log T=6.7, while type 2 bright points have Doppler velocities in the range of -20km/s and 20km/s. Using MDI magnetograms, we found that only type 1 bright point was associated with the cancelling magnetic feature at the rate of Mx /hour. When assuming that these bright points are caused by magnetic reconnection and the Doppler shift indicates reconnection outflow, the pattern of the Doppler shift implies that type 1 bright point should be related to low atmosphere magnetic reconnection. We also determined their electron densities from line ratio as well as temperatures from emission measure loci using CHIANTI atomic database. The electron densities of all bright points are comparable to typical values of active regions (log Ne=9.9-10.4). The emission loci plots indicate that these bright points should not be isothermal. The DEM (Differential Emission Measure) analysis shows a broad temperature distribution near log T=6.3.

Lee, Kyoung-Sun; Moon, Y.; Kim, S.

2009-05-01

376

Sulfur Tolerant Solid Oxide Fuel Cell for Coal Syngas Application: Experimental Study on Diverse Impurity Effects and Fundamental Modeling of Electrode Kinetics  

NASA Astrophysics Data System (ADS)

With demand over green energy economy, fuel cells have been developed as a promising energy conversion technology with higher efficiency and less emission. Solid oxide fuel cells (SOFC) can utilize various fuels in addition to hydrogen including coal derived sygas, and thus are favored for future power generation due to dependence on coal in electrical industry. However impurities such as sulfur and phosphorous present in coal syngas in parts per million (p.p.m.) levels can severely poison SOFC anode typically made of Ni/yttria-stabilized-zirconia (Ni-YSZ) and limit SOFC applicability in economically derivable fuels. The focus of the research is to develop strategy for application of high performance SOFC in coal syngas with tolerance against trace impurities such as H2S and PH3. To realize the research goal, the experimental study on sulfur tolerant anode materials and examination of various fuel impurity effects on SOFC anode are combined with electrochemical modeling of SOFC cathode kinetics in order to benefit design of direct-coal-syngas SOFC. Tolerant strategy for SOFC anode against sulfur is studied by using alternative materials which can both mitigate sulfur poisoning and function as active anode components. The Ni-YSZ anode was modified by incorporation of lanthanum doped ceria (LDC) nano-coatings via impregnation. Cell test in coal syngas containing 20 ppm H2S indicated the impregnated LDC coatings inhibited on-set of sulfur poisoning by over 10hrs. Cell analysis via X-ray photon spectroscopy (XPS), X-ray diffraction (XRD) and electrochemistry revealed LDC coatings reacted with H2S via chemisorptions, resulting in less sulfur blocking triple--phase-boundary and minimized performance loss. Meanwhile the effects of PH3 impurity on SOFC anode is examined by using Ni-YSZ anode supported SOFC. Degradation of cell is found to be irreversible due to adsorption of PH3 on TPB and further reaction with Ni to form secondary phases with low melting point. The feasibility of mixed ionic and electronic conductive (MIEC) metal oxides with perovskite structure (ABO3) as alternative ceramic SOFC anodes in coal syngas has been examined by PH3 exposure test. The study found although perovskite anodes can be generally more tolerant against H2S, further examination on PH3 tolerance is indispensable before their extensive application in coal syngas. On the theoretical end it is this research's initiative that oxygen reduction reaction at mixed ionic and electronic conductive (MIEC) cathode is a key factor controlling SOFC performance at intermediate temperature (700˜850°C). It is generally recognized that the overall charge-transfer process could occur through both surface pathway at triple-phase boundary (3PB) and bulk pathway at electrolyte/cathode interface (2PB). A modified one-dimensional model is thus developed to predict defect evolution of MIEC cathode under overpotential by incorporating multi-step charge-transfer into the bi-pathway continuum model. Finite volume control method is applied to obtain solutions for the model. The simulation predicted kinetics transition from 3PB control to 2PB control as cathodic overpotential stepping from -0.2V to -0.4V, depending on the material properties parameters. Meanwhile significant activation behavior of the MIEC electrode was also observed as indicated by extension of reaction region towards gas-exposed oxide surface. This model addressed contribution from electrochemical-controlled rate-limiting steps (RLSs) on the reduction kinetics, and identified the role played by multiple material property parameters such as surface oxygen ion concentration and bulk vacancy concentration on the kinetics transition. Combined academic knowledge gained through experimental investigation and theoretical simulation in this research would benefit the future design, development and application strategy of high-performance SOFC in coal syngas fuels.

Gong, Mingyang

377

Seepage study of the Rocky Point Canal and the Grey Mountain-Pleasant Valley Canal systems, Duchesne County, Utah  

USGS Publications Warehouse

This report describes the study of the Rocky Point Canal system in the vicinity of Duchesne and the Grey Mountain-Pleasant Valley Canal system between Duchesne and Myton, in the Uinta Basin, Duchesne County, Utah. The Rocky Point Canal diverts from the left bank of the Duchesne River about 4 mi north of Duchesne. This canal splits into the upper Rocky Point Canal and the lower Rocky Point Canal about 5.2 mi below its head. The Grey Mountain Canal diverts from the right bank of the Duchesne River about 6 mi east of Duchesne. At a point about 7.6 mi below the head, the Pleasant Valley Canal diverts from the right bank of the Grey Mountain Canal.

Cruff, R. W.; Hood, J. W.

1976-01-01

378

New 20-CM Radio-Continuum Study of The Small Magellanic Cloud: Part II - Point Sources Catalogue  

E-print Network

We present a new catalogue of point radio-continuum sources in the field of the Small Magellanic Cloud (SMC). This catalogue also contains point sources previously not found in 2300 MHz (\\lambda=13 cm) with sources found at 1400 MHz (\\lambda=20 cm) and 843 MHz (\\lambda=36 cm). We found 1576 point sources at 20 cm image that is created from new high sensitivity and resolution radio-continuum images of the SMC from Paper I. Some 46 new point sources have been detected at 13 cm as an addition the Filipovi\\'c et al. (2002) catalogue. We also created a 36 cm catalogue to which we listed 1692 point radio-continuum sources. Follow up studies on these sources nature will be presented in Paper III of this series.

Wong, G F; Crawford, E J; Tothill, N F H; Draskovi?, A Y De Horta D; Galvin, T J; Collier, J D; Payne, J L

2011-01-01

379

GGA + U study of native point defects in ZnRh2O4  

NASA Astrophysics Data System (ADS)

ZnRh2O4 spinel is the one of the most promising transparent conducting oxides for applications in optoelectronic technology. Energy levels and formation energies of native point defects, i.e. vacancies (V), interstitials (I), and cation antisites in ZnRh2O4 were analysed. Generalized gradient approximation (GGA) was supplemented by the +U on-site corrections imposed on d(Rh) and p(O) states. The inclusion of the pronounced distortions of the anion sublattice was necessary to obtain the correct band gap. U was treated as a free parameter, which allowed for the systematic study of the U-induced changes of the defect states. A diagram of the thermodynamic phase stability of ZnRh2O4 was obtained. ZnRh is the dominant acceptor that can be responsible for the observed p-type conductivity in ZnRh2O4. The low formation energy of ZnRh can make the intentional n-doping difficult. In the O-rich conditions the second important acceptor is VZn. The two dominant donors that can compensate ZnRh in Zn-rich and O-rich conditions are VO and RhZn, respectively. Growth conditions leading to the lowest concentrations of native defects were identified. Due to the pronounced occupancy dependence of the +U term, VO and RhZn are ‘negative-Ueff’ centres.

Volnianska, O.; Boguslawski, P.

2014-11-01

380

First-principles study of native point defects in Bi2Se3  

NASA Astrophysics Data System (ADS)

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.

Xue, L.; Zhou, P.; Zhang, C. X.; He, C. Y.; Hao, G. L.; Sun, L. Z.; Zhong, J. X.

2013-05-01

381

Vibrational contributions to the stability of point defects in bcc iron: A first-principles study  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate the modes of vibration of the self-interstitial atoms and the vacancy in bcc iron and to estimate how the vibrational properties can affect the stability of these defects. The phonon density of states of the vacancy and the self-interstitials have been calculated within the quasi harmonic approximation using density functional theory calculations. It was observed that self-interstitial atoms have several localized high frequency modes of vibration related to the stretching of the dumbbell bond, but also soft modes favoring their migration. From the phonon density of states, the vibrational contributions to the free energy have been estimated for finite temperatures. Results are compared to previous work performed by others using empirical potentials. We found a rather large formation entropy for the vacancy, SVf=4.08kB. Our results show that the vibrational entropy can have a significant influence on the formation of the point defects even at moderate temperature. Possible consequences on the mobility of these defects are also discussed.

Lucas, G.; Schäublin, R.

2009-09-01

382

Ab initio study of oxygen point defects on tungsten trioxide surface  

NASA Astrophysics Data System (ADS)

The gas response of tungsten trioxide (WO3) based sensors strongly depends on the surface properties. Reconstructed surfaces and oxygen point defects at the surface of the monoclinic WO3 are studied using a self-consistent scheme based on first-principle. The oxygen vacancy is found to be the predominant defect independently of the oxygen partial pressure. Indeed, under rich oxygen atmosphere the formation enthalpies are found to be 1.45 eV in LDA (1.28 eV in GGA) for the oxygen vacancy instead of 2.70 eV (2.42 eV) for the oxygen adatom. When the oxygen partial pressure is lowered, the oxygen vacancy formation enthalpy decreases and becomes exothermic under very O-poor condition (- 1.65 eV in LDA and - 1.36 eV in GGA). On the other hand, the formation enthalpy of an oxygen adatom rises. Finally, the oxygen vacancy formation acts as a n-doping by introducing negative charge carriers at the bottom of the conduction band. All these results can be very helpful in order to explain the electrical resistivity measurements.

Lambert-Mauriat, Caroline; Oison, Vincent; Saadi, Lama; Aguir, Khalifa

2012-01-01

383

Electrode Interaction in Pediatric Cochlear Implant Subjects  

PubMed Central

Multielectrode cochlear implants rely on differential stimulation of the cochlear nerve for presenting the brain with the spectral and timing information required to understand speech. In implant patients, the degree of overlap among cochlear nerve fibers stimulated by the different electrodes constitutes the electrode interaction. Electrode interaction degrades the spectral resolution of the implant’s stimulus. We sought to define electrode interaction in a cohort of pediatric cochlear implant subjects as a function of both stimulus intensity and electrode location along the array. The 27 pediatric subjects that completed the study were implanted with either the Clarion Hi-Focus array with or without positioner, the Nucleus 24 Contour array, or the Nucleus 24 Straight array. All but two of the patients had congenital hearing loss, and none of the patients had meningitis prior to the onset of deafness. The cochlear nerve response was measured with the electrically evoked compound action potential (ECAP). A forward masking protocol was used such that a probe stimulus electrode remained fixed while a preceding masker was moved across the array. Electrode interaction was estimated by measuring the unmasked probe response minus the masked probe response. Three probe locations and three probe intensities were examined for each subject. At all probe locations, electrode interaction increased as probe intensity increased (p < 0.05). Interaction at the basal probe was less than that at either the middle or apical probe locations (p < 0.05), and significant correlation found between probe distance from the basal end of the array and electrode interaction (p < 0.001). These results demonstrate that in this cohort of pediatric subjects, electrode interaction depended on both stimulus intensity and probe location. Implications of these findings on future implant array design and current implant fitting strategies are discussed. The impact of electrode interaction on implant performance is yet to be elucidated. PMID:15952052

Franck, Kevin H.

2005-01-01

384

Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes  

NASA Astrophysics Data System (ADS)

A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones, and the 3D simulation turns out to be more accurate than the 2D simulation as a result of a relatively precise description of the turbulent phenomena inside the torch using a more realistic model of arc root attachment. Finally, it is suggested that the 3D transient formulation is indeed required for describing the real arc discharge phenomena inside the torch, while the 2D stationary approach is sometimes useful for getting practical information about the time-averaged plasma characteristics outside the torch because of its simplicity and rapidness in computation.

Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

2008-02-01

385

The point of Corumbau : a case study in emerging market (Brazil) real estate development feasibility analysis  

E-print Network

In 2003, Renata Oliveira, a young Portuguese architect, has re-discovered the Point of Corumbau in Bahia, Brazil, and, like the Portuguese adventurers who had discovered Brazil 500 years earlier in the same location, found ...

Clayton, Paul B., S.M. Massachusetts Institute of Technology

2007-01-01

386

A study on the effect of inlet turbulence on gas mixing for single point aerosol sampling  

E-print Network

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...

Mohan, Anand

2012-06-07

387

Study on Orbits Near the Triangular Libration Points in the Perturbed Restricted Three Body Problem.  

National Technical Information Service (NTIS)

Periodic orbits of the bicircular problem and their stability; numerical simulations of the motion in an extended neighborhood of the triangular libration points in the Earth-Moon system; the equations of motion; periodic orbits of intermediate equations;...

G. Gomez, J. Llibre, R. Martinez, C. Simo

1987-01-01

388

Study on Dialkylfumarate Terpolymer Lowering Cold Filter Plugging Point for Diesel Fuel  

Microsoft Academic Search

Adding pour point depressants (PPDs) to depress the cold filter plugging point (CFPP) of diesel has been widely used in the petroleum industry. This article describes the synthesis and evaluation of the performance of dialkylfumarate-styrene-vinyl acetate terpolymer (FSV) for improving the cold flow performance of the tested diesel fuels. The n-alkanes carbon distribution in the tested diesel samples was analyzed

Tao Du; Shujun Wang; Hongyan Liu; Ying Zhang; Chengpeng Song

2011-01-01

389

Potential-derived point-charge model study of electrostatic interactions in DNA base components  

NASA Astrophysics Data System (ADS)

Ab initio electrostatic potentials obtained using STO-3G wavefunctions for guanine. cytosine adenine, and thymine are used to calculate potential-derived (PD) point charges for these base components. Calculated PD point charges are used to estimate the electrostatic contributions to hydrogen-bonding and stacking interaction energies of ten sequence isomers of B-DNA. These estimates are in excellent agreement with the results of the more elaborate segmental multipole moment expansion technique.

Ray, Naba K.; Shibata, Masayuki; Bolis, Giorgio; Rein, Robert

1984-08-01

390

A Comprehensive Study of a Hybrid Modulation Technique for the Neutral-Point-Clamped Converter  

Microsoft Academic Search

This paper presents a hybrid modulation technique for the three-level neutral-point-clamped converter. A modulation strategy, based on two modulation signals per phase, was presented previously. This strategy completely removes the low-frequency voltage oscillations that appear at the neutral point (NP) in some operation conditions. However, it also has a major drawback: it significantly increases the switching losses of the converter.

Jordi Zaragoza; Josep Pou; Salvador Ceballos; Eider Robles; P. Ibaez; Jose Luis Villate

2009-01-01

391

Behavioral Synthesis of Double-Precision Floating-Point Adders with Function-Level Transformations: A Case Study  

Microsoft Academic Search

Recently, the continuously growing capacity of FPGAs has enabled us to place floating-point arithmetic IPs on FPGAs. The required\\u000a area for floating-point computations, however, is still high. This paper presents a case study on behavioral synthesis of\\u000a double-precision floating-point adders and adder\\/subtracters for FPGAs. With function-level transformations, we design totally\\u000a 15 adders and 21 adder\\/subtracters from addition and subtraction functions

Yuko Hara; Hiroyuki Tomiyama; Shinya Honda; Hiroaki Takada; Katsuya Ishii

2007-01-01

392

Electrodes with fiber structure  

NASA Technical Reports Server (NTRS)

An electrode framework with a fiber structure, universally applicable in alkaline storage battery systems, was developed and readied for production. Storage batteries with these electrodes present higher energy and power densities and are economical to produce. The design is applicable to all rechargable storage batteries and might replace the previous variety of designs.

Benczur-Uermoessy, G.; Berger, G.; Haschka, F.

1986-01-01

393

Instructions Calomel Reference Electrodes  

E-print Network

. They provide a stable reference potential when used with an appropriate glass pH electrode, ISE (Ion Selec with water to remove any crystals that may have formed on the outer surface during storage. Crystal formation and rinse the electrode with water to remove any crystals that may have formed on the outer surface during

Kleinfeld, David

394

Membrane Bioprobe Electrodes  

ERIC Educational Resources Information Center

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)

Rechnitz, Garry A.

1975-01-01

395

Electrochemistry at Nanometer-Scaled Electrodes  

NASA Astrophysics Data System (ADS)

Advances in the fabrication of nanometer-scaled electrodes during the past decade have created a number of exciting opportunities in both physical chemistry and analytical measurements. This article describes how Pt electrodes of nanometer dimensions are synthesized and characterized in a chemical laboratory. A few examples of their applications in fundamental studies of electron-transfer mechanisms and in analytical chemistry are presented. Examples include investigations of the dependence of electron-transfer kinetics and molecular diffusion on interfacial electric fields and electrochemical detection of very small quantities of a redox-active species (zeptomole detection). The concept of comparing the electrode size to the length scales of various microscopic structures (e.g., the double layer) and chemical steps that define electrochemical reactions is emphasized. This approach allows students to understand why new phenomena appear as the electrode size is reduced to the nanometer scale. A brief overview of literature describing electrochemical experimentation with nanometer-scaled electrodes is also included.

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

2005-05-01

396

Trigger point-related sympathetic nerve activity in chronic sciatic leg pain: a case study.  

PubMed

Sciatica has classically been associated with irritation of the sciatic nerve by the vertebral disc and consequent inflammation. Some authors suggest that active trigger points in the gluteus minimus muscle can refer pain in similar way to sciatica. Trigger point diagnosis is based on Travel and Simons criteria, but referred pain and twitch response are significant confirmatory signs of the diagnostic criteria. Although vasoconstriction in the area of a latent trigger point has been demonstrated, the vasomotor reaction of active trigger points has not been examined. We report the case of a 22-year-old Caucasian European man who presented with a 3-year history of chronic sciatic-type leg pain. In the third year of symptoms, coexistent myofascial pain syndrome was diagnosed. Acupuncture needle stimulation of active trigger points under infrared thermovisual camera showed a sudden short-term vasodilatation (an autonomic phenomenon) in the area of referred pain. The vasodilatation spread from 0.2 to 171.9?cm(2) and then gradually decreased. After needling, increases in average and maximum skin temperature were seen as follows: for the thigh, changes were +2.6°C (average) and +3.6°C (maximum); for the calf, changes were +0.9°C (average) and +1.4°C (maximum). It is not yet known whether the vasodilatation observed was evoked exclusively by dry needling of active trigger points. The complex condition of the patient suggests that other variables might have influenced the infrared thermovision camera results. We suggest that it is important to check if vasodilatation in the area of referred pain occurs in all patients with active trigger points. PMID:24970043

Skorupska, El?bieta; Rychlik, Micha?; Pawelec, Wiktoria; Bednarek, Agata; Samborski, W?odzimierz

2014-10-01

397

Electrodes for microfluidic applications  

DOEpatents

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.

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

2006-08-22

398

GPR study of a prehistoric archaeological site near Point Barrow, Alaska  

NASA Astrophysics Data System (ADS)

A ground penetrating radar (GPR) study was performed on the prehistoric Thule cemetery site near Point Barrow, Alaska. The goals of this study were (a) to test this technology in this type of polar environment, and (b) to search for burials and other archaeological features in a location in imminent danger from ocean erosion. The Nuvuk site is currently eroding at an average rate measured at over 6 m/year. Prior archaeological work at the site had recovered over 80 burials with nearly 100 individuals represented, all of which were less than 1 m below surface, and detectable with small test pits. In addition, the first coastal Ipiutak occupation known north of Point Hope had been recently discovered, at a depth of nearly 2m below surface, in the erosion face. The occupation appeared to have been terminated by a large storm which overwashed the site, leaving a strandline immediately superimposed on the living surface. After that, approximately 1.5 m of sterile gravels had been deposited before the surface on which the Thule people were living formed. Both occupations are of considerable scientific interest. The matrix at the site consists of unconsolidated beach gravels, which necessitates opening large surface areas or use of shoring to test even small units to the depths of the Ipiutak deposit (approximately 8m x 8m at the surface to test 1m x 1m at 2m depth). Such excavations promote erosion, and are very costly in terms of time and labor, so a means to detect features buried at depths greater than those exposed by shovel test pits was desirable. GPR seemed a likely candidate, but it had not been used in such conditions before, and thus it was necessary to test it thoroughly prior to relying on GPR to eliminate areas from physical testing. The GPR imaged the subsurface to a depth of 3 meters at a frequency of 500MHz. Meter-deep test pits were placed at 2-meter intervals in the survey area in a grid pattern since the efficacy of the technology had yet to be shown. The results of the test pits and the GPR were in agreement. It was anticipated that there might be few or no remaining burials in this location since the number of burials had been declining with distance from the center of the larger site. Thus it was surprising when the GPR detected an anomaly that turned out to be the deepest burial in the whole site. In fact, it was so deeply buried that the standard shovel test pitting method might not have detected it. It proved to be a very well-preserved individual, with fairly intact garments. In addition to the burial site, the GPR was used to image a number of "strandlines" as well as other deep (>1m) features in this area. These correspond in depth and orientation to two partial Ipiutak features which have been exposed and recorded in the erosion face in two separate field seasons. It was not possible to test to that depth, but subsequent coastal erosion has exposed additional strandline debris at the depth and location predicted by the GPR data. Two- and three-dimensional images of these features will be presented, along with a detailed technical description of the GPR methods used in this environment.

Herman, R. B.; Jensen, A. M.

2012-12-01

399

An experimental and numerical study of diffusion flames in cross-flow and quiescent environment at smoke point condition  

Microsoft Academic Search

An experimental and numerical study of a turbulent smoke point diffusion flame in a quiescent and cross-flow condition was performed. The fuel mass flow rate of a turbulent smoke point flame was determined at a quiescent condition and in cross-flow with velocity ranging from 2 to 4 m\\/s. This fuel mass flow rate is defined as the Critical Fuel Mass

Sien Fong Goh

2003-01-01

400

Point defects in twisted bilayer graphene: A density functional theory study  

NASA Astrophysics Data System (ADS)

We have used ab initio density functional theory, incorporating van der Waals corrections, to study twisted bilayer graphene (TBLG) where Stone-Wales defects or monovacancies are introduced in one of the layers. We compare these results to those for defects in single-layer graphene or Bernal stacked graphene. The energetics of defect formation is not very sensitive to the stacking of the layers or the specific site at which the defect is created, suggesting a weak interlayer coupling. However, signatures of the interlayer coupling are manifested clearly in the electronic band structure. For the "??" Stone-Wales defect in TBLG, we observe two Dirac cones that are shifted in both momentum space and energy. This up/down shift in energy results from the combined effect of a charge transfer between the two graphene layers and a chemical interaction between the layers, which mimics the effects of a transverse electric field. Charge density plots show that states near the Dirac points have significant admixture between the two layers. For Stone-Wales defects at other sites in TBLG, this basic structure is modified by the creation of minigaps at energy crossings. For a monovacancy, the Dirac cone of the pristine layer is shifted up in energy by ˜0.25 eV due to a combination of the requirement of the equilibration of Fermi energy between the two layers with different numbers of electrons, charge transfer, and chemical interactions. Both kinds of defects increase the density of states at the Fermi level. The monovacancy also results in spin polarization, with magnetic moments on the defect of 1.2-1.8 ?B.

Ulman, Kanchan; Narasimhan, Shobhana

2014-06-01

401

Manufacturing process and electrode properties of palladium-electroded ionic polymer-metal composite  

NASA Astrophysics Data System (ADS)

This paper primarily focuses on the manufacturing process of palladium-electroded ionic polymer-metal composite (IPMC). First, according to the special properties of Pd, many experiments were done to determine several specific procedures, including the addition of a reducing agent and the time consumed. Subsequently, the effects of the core manufacturing steps on the electrode morphology were revealed by scanning electron microscopy studies of 22 IPMC samples treated with different combinations of manufacturing steps. Finally, the effects of electrode characteristics on the electromechanical properties, including the sheet resistivity, the elastic modulus and the electro-active performance, of IPMCs were evaluated experimentally and analyzed according to the electrode morphology.

Chang, Longfei; Chen, Hualing; Zhu, Zicai; Li, Bo

2012-06-01

402

Flood Management and Protection from the Social Point of View: Case Study from Ukraine  

NASA Astrophysics Data System (ADS)

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".

Manukalo, V.; Gerasymenko, H.

2012-12-01

403

Patterning of non-spherical particles onto electrode surface: Study of orientation behavior under viscous fluid and AC electrokinetic forces  

NASA Astrophysics Data System (ADS)

Recently we had proposed a technique called rapid electrokinetic patterning^ (REP), a tool that can manipulate colloidal particles near illuminated spot on an electrode surface. REP utilizes optical landscapes to create gradients in temperature allowing local changes in permittivity and conductivity of the fluid creating a microvortex. However, REP has been demonstrated till now only with spherical particles. We expand upon the initial disclosure of REP and conduct experiments with non-spherical beads. In the presence of linearly polarized field a non-spherical particle experiences frequency dependent alignment torques along three principle axis. This is mainly because of the different polarizability along each direction. In a fluid flow, a non-spherical particle would align itself in order to minimize the viscous drag. But characterizing the orientation behavior of non-spherical particles under the influence of both electric field and viscous fluid drag presents a unique physics problem. We observed the vertical orientation of the cylinders in the REP aggregation. We explore the mobility of the captured particles on the surface with respect to various physical parameters.

Thakur, Raviraj; Williams, Stuart; Cohn, Robert; Rathfon, Jeremy; Berret, Jean-François; Yan, Minhao; Wereley, Steven

2010-11-01

404

Oxidation of carbon monoxide at a platinum film electrode studied by Fourier transform infrared spectroscopy with attenuated total reflection technique  

SciTech Connect

Fourier transform infrared reflection absorption spectroscopy with the attenuated total reflection technique (ATR-FTIR), coupled with cyclic voltammetry (CV) measurement, is used to observe the oxidation process of adsorbed CO at Pt film sputtered on a silicon prism. The interesting bipolar shape of the linearly bonded CO band is observed at high coverage of CO, although no CO band is included in the reference spectrum. This asymmetric shape is ascribed to Fano resonance. In addition to a linear CO and bridged CO, a new absorption band presumably assigned to a carboxyl radical, was detected. This band may be formed by a heterogeneous reaction between adsorbed CO and H{sub 2}O on the Pt surface in the hydrogen adsorption potential region. The adsorbed carboxyl radical was oxidized at a less positive potential than the adsorbed CO, which can be ascribed to a presumable origin for the pre-peak that appeared in a CV reading prior to the oxidation of such a linear or bridged CO. This oxidation led to the rearrangement of CO ad-layers, especially at high coverage of CO. In the case of the low coverage of CO, the conversion from the bridged CO to the linear CO is ascribed to the potential induced electronic effects of the electrode surface on the adsorption states. A consumption of adsorbed H{sub 2}O and a production of CO{sub 2} were also clearly indicated by the spectroscopy when COOH of CO disappeared from the surface.

Zhu, Yimin; Uchida, Hiroyuki; Watanabe, Masahiro

1999-12-07

405

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

Microsoft Academic Search

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

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

2008-01-01

406

Spinal Cord Electrophysiology II: Extracellular Suction Electrode Fabrication  

PubMed Central

Development of neural circuitries and locomotion can be studied using neonatal rodent spinal cord central pattern generator (CPG) behavior. We demonstrate a method to fabricate suction electrodes that are used to examine CPG activity, or fictive locomotion, in dissected rodent spinal cords. The rodent spinal cords are placed in artificial cerebrospinal fluid and the ventral roots are drawn into the suction electrode. The electrode is constructed by modifying a commercially available suction electrode. A heavier silver wire is used instead of the standard wire given by the commercially available electrode. The glass tip on the commercial electrode is replaced with a plastic tip for increased durability. We prepare hand drawn electrodes and electrodes made from specific sizes of tubing, allowing consistency and reproducibility. Data is collected using an amplifier and neurogram acquisition software. Recordings are performed on an air table within a Faraday cage to prevent mechanical and electrical interference, respectively. PMID:21372792

Garudadri, Suresh; Gallarda, Benjamin; Pfaff, Samuel; Alaynick, William

2011-01-01

407

The Effects of Electrode Size and Orientation on the Sensitivity of Myoelectric Pattern Recognition Systems to Electrode Shift  

PubMed Central

Myoelectric pattern recognition systems for prosthesis control are often studied in controlled laboratory settings, but obstacles remain to be addressed before they are clinically viable. One important obstacle is the difficulty of maintaining system usability with socket misalignment. Misalignment inevitably occurs during prosthesis donning and doffing, producing a shift in electrode contact locations. We investigated how the size of the electrode detection surface and placement of electrode poles (electrode orientation) affected system robustness with electrode shift. Electrodes oriented parallel to muscle fibers outperformed electrodes oriented perpendicular to muscle fibers in both shift and no-shift conditions (p<0.01). Another finding was the significant difference (p<0.01) in performance for the direction of electrode shift. Shifts perpendicular to the muscle fibers reduced classification accuracy and real-time controllability much more than shifts parallel to the muscle fibers. Increasing the size of the electrode detection surface was found to help reduce classification accuracy sensitivity to electrode shifts in a direction perpendicular to the muscle fibers but did not improve the real-time controllability of the pattern recognition system. One clinically important result was that a combination of longitudinal and transverse electrodes yielded high controllability with and without electrode shift using only four physical electrode pole locations. PMID:21659017

Young, Aaron J.; Hargrove, Levi J.; Kuiken, Todd A.

2014-01-01

408

Quartz Microbalance Study of 400-angstrom Thick Films near the lambda Point  

NASA Technical Reports Server (NTRS)

In a recent measurement we observed the thinning of an adsorbed helium film induced by the confinement of critical fluctuations a few millikelvin below the lambda point. A capacitor set-up was used to measure this Casimir effect. In this poster we will present our measurement of an adsorbed helium film of 400 angstroms near the lambda point with a quartz microbalance. For films this thick, we must take into account the non-linear dynamics of the shear waves in the fluid. In spite of the added complications, we were able to confirm the thinning of the film due to the Casimir effect and the onset of the superfluid transition. In addition, we observe a sharp anomaly at the bulk lambda point, most likely related to critical dissipation of the first sound. This work is carried out in collaboration with Rafael Garcia, Stephen Jordon and John Lazzaretti. This work is funded by NASA's Office of Biological and Physical Research under grant.

Chan, Moses H. W.

2003-01-01

409

Environmental tipping points in random dynamical systems: a quasigeostrophic case study  

NASA Astrophysics Data System (ADS)

Environmental tipping points (TPs) leading to abrupt state changes are usually considered in an autonomous dynamical systems framework, in which case early warnings may be identified in signals with increased autocorrelation and variance. An essential step toward a more realistic description of abrupt transitions in the environment and climate is to analyze TPs in random dynamical systems. In this context, a case study based on an operational definition of stochastic TPs and on a nonlinear low-order quasigeostrophic model is presented (Pierini, Phys. Rev. E, 2012). Let us suppose that in an autonomous dynamical system (DS), self-sustained relaxation oscillations emerge if (and only if) a control parameter Q is such that Q > Qo: Qo is therefore a (deterministic) TP. The same system perturbed by noise is said to be "excitable" if a range Q < Qo (depending on the noise) exists in which basically the same relaxation oscillations can be noise-induced (such mechanism is usually referred to as "coherence resonance"). In an excitable random DS (a case likely to be quite common in environmental and climate dynamics) a stochastic TP is defined here as the random variable Ro whose realizations satisfy the same conditions required for Qo in the deterministic case. The low-order model (with four degrees of freedom) used in this study describes an excitable DS driven by a stationary forcing with amplitude Q (the deterministic control parameter) plus a colored noise characterized by its amplitude A and autocorrelation time scale Ta. A 10-member ensemble is constructed by performing forward time integrations of length T, and by letting A and Ta vary within a broad parametric range. The ensemble averages and (where the random variable N is the number of relaxation oscillations emerging in T) are then computed. The results suggest that in an excitable random DS coherence resonance may be the predominant transition mechanism, in which case stochastic TPs should be considered instead of their classical deterministic counterpart. Possible early warning signals (different from those of the deterministic case) are investigated: a preliminary analysis shows a variety of possible cases, among which a behavior typical of ramped systems (i.e., excitation arises when the control parameter undergoes a sufficiently fast rate of ramping).

Pierini, S.

2012-04-01

410

Electrodes for sealed secondary batteries  

NASA Technical Reports Server (NTRS)

Self-supporting membrane electrode structures, in which active ingredients and graphite are incorporated in a polymeric matrix, improve performance of electrodes in miniature, sealed, alkaline storage batteries.

Boies, D. B.; Child, F. T.

1972-01-01

411

Technology Dependence In Function Point Analysis: A Case Study And Critical Review  

Microsoft Academic Search

Because Function Point Analysis (FPA) has now been in use for a decade, and in spite of its increasing popularity has met with some recent criticisms, it is time to review how appropriate it still is for today's technologies. A critical review of the FPA approach examines in particular the pioneering and continuing work of Albrecht and more recent work

J. M. Verner; G. Tate; B. Jackson; R. G. Hayward

1989-01-01

412

Using Modification Indexes to Detect Turning Points in Longitudinal Data: A Monte Carlo Study  

ERIC Educational Resources Information Center

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…

Kwok, Oi-Man; Luo, Wen; West, Stephen G.

2010-01-01

413

Public Internet Access Points (PIAPs) and Their Social Impact: A Case Study from Turkey  

ERIC Educational Resources Information Center

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…

Afacan, Gulgun; Er, Erkan; Arifoglu, Ali

2013-01-01

414

EFFECT OF PACKAGE DELAMINATION UNDER 3POINTS BENDING TEST: A CASE STUDY USING CYCLIC LOADING  

Microsoft Academic Search

Generally, thermal cycle tests (TCTs) are applied to under development electronic packages in order to prove their reliability. However, a more effective test is desirable because of the TCTs are time-consuming. This paper present a mechanical cyclic test for the QFN package, namely the three-point cyclic bending test, was proposed into the subject area. This fixture test method is a

S. Abdullah; M. F. Abdullah; A. K. Ariffin; M. N. Baharin; Z. A. Aziz; M. F. Mod Yunoh

2008-01-01

415

Instrument pointing system applicability and orbiter stabilization for EVAL missions. Application studies  

NASA Technical Reports Server (NTRS)

Related aspect of the Earth Viewing Applications Laboratory (EVAL) shuttle missions were investigated. The applicability of the gimballed Instrument Pointing System (IPS) to EVAL missions by comparing the IPS capabilities with the EVAL requirements was evaluated, and a means of stabilizing the shuttle orbiter attitude in earth viewing orientations for prolonged periods without use of the orbiter gas reaction control system was assessed.

Spector, V. A.

1977-01-01

416

REGIONAL AIR POLLUTION STUDY: POINT AND AREA SOURCE ORGANIC EMISSION INVENTORY  

EPA Science Inventory

An inventory of organic emissions from stationary and mobile sources has been assembled for the St. Louis Air Quality Control Region. The inventory covers point and area sources for process, combustion and evaporative emissions. A breakdown into five categories has been assigned ...

417

School Attendance Revisited: A Study of Urban African American Students' Grade Point Averages and Coping Strategies  

ERIC Educational Resources Information Center

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…

Steward, Robbie J.; Steward, Astin Devine; Blair, Jonathan; Jo, Hanik; Hill, Martin F.

2008-01-01

418

Bacteriological monitoring studies to identity sources of fecal pollution at Baby Beach, Dana Point Harbor, California  

Microsoft Academic Search

Summary form only given. Baby Beach, at Dana Point Harbor, CA has had a history of impaired water quality resulting in frequent beach postings and closures due to high fecal indicator bacteria concentrations, especially Enterococcus spp. Numerous Best Management Practices (BMPs) to reduce bacterial levels have been implemented, yet the postings continue. Weekly bacteriological monitoring data indicate a general decline

D. M. Ferguson; M. H. Zhowandai; M. A. Getrich; D. F. Moore; A. Lissner; R. Haimann; D. W. Linger

2003-01-01

419

Point contact Andreev reflection as a probe to study superconductors and ferromagnets  

E-print Network

Ferromagnets with PCAR: SrRuO3 · Good versus bad spectra Pratap Raychaudhuri TIFR Mumbai #12;Collaborators anisotropy in Superconductors kz kx kz kx (k) kx Isotropic gap Ansotropic gap kz kz kx Fermi Surface #12;Unconventional Superconductors Gap function zero at certain points (lines) on the Fermi surface #12;Directional

Raychaudhuri, Pratap

420

A measurement study determining the effect of Internet eXchange points on popular webservers  

Microsoft Academic Search

Internet exchange points (IXPs) are an upcoming and essential component of the Internet infrastructure exhibiting numerous effects on various aspects of Internet topology and packet routing. While IXPs have been shown to play a major role in the evolution of the Internet topology, there has been little prior work in determining their effect on packet routing across the Internet. This

Mohammad Zubair Ahmad; Ratan Guha

2010-01-01

421

Measuring electrode assembly  

DOEpatents

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture.

Bordenick, John E. (West Mifflin, PA)

1989-01-01

422

Measuring electrode assembly  

DOEpatents

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture. 2 figs.

Bordenick, J.E.

1988-04-26

423

Energetics and electronic structure of aluminum point defects in HfO2: A first-principles study  

E-print Network

with respect to the valence electron configuration 5d3 6s1 for hafnium atom, 2s2 2p4 for oxygen atom, and 3s2 3Energetics and electronic structure of aluminum point defects in HfO2: A first-principles study Z approximation, we studied the atomic structure, energetics, and electronic structure of the interstitial

Gong, Xingao

424

Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes  

PubMed Central

Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Zt) and access resistance (Ra) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between Ra and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation suggesting that the level of stimulation applied was creating localised changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation. PMID:21572219

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Seligman, Peter; Cowan, Robert; Shepherd, Robert

2011-01-01

425

AMTEC electrode development  

NASA Technical Reports Server (NTRS)

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.

Bankston, C. P.; Williams, R. M.; Nakamura, B. J.; Wheeler, B. L.; Loveland, M. E.; Cole, T.

1987-01-01

426

Multifunctional reference electrode  

DOEpatents

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.

Redey, Laszlo (Lisle, IL); Vissers, Donald R. (Naperville, IL)

1983-01-01

427

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

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 µM 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 modifi