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1

Photoconductivity of high voltage space insulating materials: Measurements with metal electrodes  

NASA Technical Reports Server (NTRS)

The electrical conductivities of high voltage insulating materials were measured in the dark and under various intensities of illumination. The materials investigated included FEP Teflon, Kapton-H, fused quartz, and parylene. Conductivities were determined as functions of temperature between 22 and 100 C and light intensity between 0 and 2.5 kW/m2. The thickness dependence of the conductivity was determined for Teflon and Kapton, and the influence of spectral wavelengths on the conductivity was determined in several cases. All measurements were made in a vacuum to simulate a space environment, and all samples had metallic electrodes. The conductivity of Kapton was permanently increased by exposure to light; changes as great as five orders of magnitude were observed after six hours of illumination.

Coffey, H. T.; Nanevicz, J. E.

1975-01-01

2

Determining resistivity of a formation adjacent to a borehole having casing by generating constant current flow in portion of casing and using at least two voltage measurement electrodes  

DOEpatents

Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information related to the resistivity of adjacent geological formations from within the cased well are described. The multiple electrode apparatus has a minimum of two spaced apart voltage measurement electrodes that electrically engage a first portion of the interior of the cased well and that provide at least first voltage information. Current control means are used to control the magnitude of any selected current that flows along a second portion of the interior of the casing to be equal to a predetermined selected constant. The first portion of the interior of the cased well is spaced apart from the second portion of the interior of the cased well. The first voltage information and the predetermined selected constant value of any selected current flowing along the casing are used in part to determine a magnitude related to the formation resistivity adjacent to the first portion of the interior of the cased well. Methods and apparatus having a plurality of voltage measurement electrodes are disclosed that provide voltage related information in the presence of constant currents flowing along the casing which is used to provide formation resistivity.

Vail, III, William Banning (Bothell, WA)

2000-01-01

3

Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes  

SciTech Connect

This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.

Malík, M., E-mail: michal.malik@tul.cz; Primas, J.; Kopecký, V.; Svoboda, M. [Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec, Liberec, 461 17 (Czech Republic)] [Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec, Liberec, 461 17 (Czech Republic)

2014-01-15

4

Noncontact, Electrode-free Capacitance/Voltage Measurement Based on General Theory of Metal-Oxide-Semiconductor (MOS) Structure  

NASA Astrophysics Data System (ADS)

In this paper, we discussed a novel approach to semiconductor surface inspection, which is analysis using the C--V curve measured in a noncontact method by the metal-air-semiconductor (MAIS) technique. A new gap sensing method using the so-called Goos-Haenchen effect was developed to achieve the noncontact C--V measurement. The MAIS technique exhibited comparable sensitivity and repeatability to those of conventional C--V measurement, and hence, good reproducibility and resolution for quantifying the electrically active impurity on the order of 1× 109/cm2, which is better than most spectrometric techniques, such as secondary ion mass spectroscopy (SIMS), electron spectroscopy for chemical analysis (ESCA) and Auger electron spectrocopy (AES) which are time-consuming and destructive. This measurement without preparation of any electrical contact metal electrode suggested, for the first time, the possibility of measuring an intrinsic characteristic of the semiconductor surface, using the examples of a concrete examination.

Sakai, Takamasa; Kohno, Motohiro; Hirae, Sadao; Nakatani, Ikuyoshi; Kusuda, Tatsufumi

1993-09-01

5

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

6

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

7

Arc voltage distribution skewness as an indicator of electrode gap during vacuum arc remelting  

DOEpatents

The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap.

Williamson, Rodney L. (Albuquerque, NM); Zanner, Frank J. (Sandia Park, NM); Grose, Stephen M. (Glenwood, WV)

1998-01-01

8

Evaluation of Niobium as Candidate Electrode Material for DC High Voltage Photoelectron Guns  

NASA Technical Reports Server (NTRS)

The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (< 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

BastaniNejad, M.; Mohamed, Abdullah; Elmustafa, A. A.; Adderley, P.; Clark, J.; Covert, S.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Mammei, R.; Surles-Law, K.; Williams, P.

2012-01-01

9

Application of active electrode compensation to perform continuous voltage-clamp recordings with sharp microelectrodes  

NASA Astrophysics Data System (ADS)

Objective. Electrophysiological recordings of single neurons in brain tissues are very common in neuroscience. Glass microelectrodes filled with an electrolyte are used to impale the cell membrane in order to record the membrane potential or to inject current. Their high resistance induces a high voltage drop when passing current and it is essential to correct the voltage measurements. In particular, for voltage clamping, the traditional alternatives are two-electrode voltage-clamp technique or discontinuous single electrode voltage-clamp (dSEVC). Nevertheless, it is generally difficult to impale two electrodes in a same neuron and the switching frequency is limited to low frequencies in the case of dSEVC. We present a novel fully computer-implemented alternative to perform continuous voltage-clamp recordings with a single sharp-electrode. Approach. To reach such voltage-clamp recordings, we combine an active electrode compensation algorithm (AEC) with a digital controller (AECVC). Main results. We applied two types of control-systems: a linear controller (proportional plus integrative controller) and a model-based controller (optimal control). We compared the performance of the two methods to dSEVC using a dynamic model cell and experiments in brain slices. Significance. The AECVC method provides an entirely digital method to perform continuous recording and smooth switching between voltage-clamp, current clamp or dynamic-clamp configurations without introducing artifacts.

Gómez-González, J. F.; Destexhe, A.; Bal, T.

2014-10-01

10

The effect of electrode temperature on the sparking voltage of short spark gaps  

NASA Technical Reports Server (NTRS)

This report presents the results of an investigation to determine what effect the temperature of spark plug electrodes might have on the voltage at which a spark occurred. A spark gap was set up so that one electrode could be heated to temperatures up to 700 degrees C., while the other electrode and the air in the gap were maintained at room temperature. The sparking voltages were measured both with direct voltage and with voltage impulse from ignition coil. It was found that the sparking voltage of the gap decreased materially with increase of temperature. This change was more marked when the hot electrode was of negative polarity. The phenomena observed can be explained by the ionic theory of gaseous conduction, and serve to account for certain hitherto unexplained actions in the operation of internal combustion engines. These results indicate that the ignition spark will pass more readily when the spark-plug design is such as to make the electrodes run hot. This possible gain is, however, very closely limited by the danger of producing preignition. These experiments also show that sparking is somewhat easier when the hot electrode (which is almost always the central electrode) is negative than when the polarity is reversed.

Silsbee, F B

1924-01-01

11

Improving membrane voltage measurements  

E-print Network

as fluorescence resonance energy transfer (FRET) donor and acceptor to develop a voltage sensor, named Mermaid activities in cultured excitable cells. Notably, Mermaid has fast on-off kinetics at warm (B33 1C

Cai, Long

12

Measuring Breakdown Voltage.  

ERIC Educational Resources Information Center

The article discusses an aspect of conductivity, one of the electrical properties subdivisions, and describes a tester that can be shop-built. Breakdown voltage of an insulation material is specifically examined. Test procedures, parts lists, diagrams, and test data form are included. (MF)

Auer, Herbert J.

1978-01-01

13

Technique eliminates high voltage arcing at electrode-insulator contact area  

NASA Technical Reports Server (NTRS)

Coating the electrode-insulator contact area with silver epoxy conductive paint and forcing the electrode and insulator tightly together into a permanent connection, eliminates electrical arcing in high-voltage electrodes supplying electrical power to vacuum facilities.

Mealy, G.

1967-01-01

14

High speed electric field and voltage measurements with field coupled sensors  

SciTech Connect

In this paper, we introduce the concept of displacement vector (D) measurements with floating electrodes, discuss measurements with resistively grounded electrodes, and explore how measurements of voltage and electric field are related. Finally, we discuss errors in measurements with floating electrodes.

Di Capua, M.S.

1984-12-12

15

Wide-aperture plasma jet source based on low-voltage spark discharge with ferroelectric electrode  

NASA Astrophysics Data System (ADS)

Low-voltage vacuum spark discharge initiated at a storage capacitor voltage of 75-600 V using a metal grid cathode situated on the front surface of a polarized ferroelectric (FE) electrode has been experimentally studied. The discharge was initiated when a control voltage pulse with an amplitude of 1 kV and a duration of 100 ns at only negative polarity was applied to the rear FE surface (irrespective of the direction of its polarization vector). Optical measurements showed that the emitting surface area on the cathode increases approximately in proportion to the discharge voltage. According to the collector measurements, the ion plasma flux has slow and fast components, the velocities of which remain almost constant when the discharge current amplitude varies in a wide interval.

Korobkin, Yu. V.; Gorbunov, S. P.; Myaekivi, V. V.; Paperny, V. L.

2010-05-01

16

Field Emission Measurements from Niobium Electrodes  

SciTech Connect

Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and/or ion bombardment and high levels of field emission can damage the ceramic insulator. Niobium electrodes (single crystal, large grain and fine grain) were characterized using a DC high voltage field emission test stand at maximum voltage -225kV and electric field gradient > 10MV/m. Niobium electrodes appear to be superior to diamond-paste polished stainless steel electrodes.

M. BastaniNejad, P.A. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, R. Mammei, M. Poelker

2011-03-01

17

Calculation of potential distribution and voltage drop at electrodes on high-rate discharge: literature survey and computer-aided approach  

NASA Astrophysics Data System (ADS)

While the electrical resistance of the electrodes in lead/acid batteries can be neglected on low-rate discharges in comparison with other resistive contributions, the minimization of electrode resistance is an important goal to optimize high-rate performance. High electrode resistance has two undesired effects: (i) reduced cell voltage, and (ii) inhomogeneous current distribution across the electrode plane. In addition, the current inhomogeneity reduces cell voltage even more, and the electrode capacity is diminished. Using finite element analysis (FEA), potential distribution and electrode resistance are calculated even at the time of planning a new electrode geometry that employs only the technical drawing of the grid design. Unnecessary manufacture of test electrodes, only for measurement of electrode resistance and evaluation of high-rate performance, can be avoided. Consequently, electrode development and grid optimization for high-rate discharges becomes more effective, faster and less expensive.

Meissner, Eberhard

18

Low voltage and high transmittance blue-phase liquid crystal displays with corrugated electrodes  

E-print Network

Low voltage and high transmittance blue-phase liquid crystal displays with corrugated electrodes BPLC display is proposed. The periodic corrugated electrodes generate a strong horizontal field along the beam path is large, resulting in low voltage and high transmittance. This approach enables

Wu, Shin-Tson

19

Electrodic voltages accompanying stimulated bioremediation of a uranium-contaminated aquifer  

SciTech Connect

The inability to track the products of subsurface microbial activity during stimulated bioremediation has limited its implementation. We used spatiotemporal changes in electrodic potentials (EP) to track the onset and persistence of stimulated sulfate-reducing bacteria in a uranium-contaminated aquifer undergoing acetate amendment. Following acetate injection, anomalous voltages approaching -900 mV were measured between copper electrodes within the aquifer sediments and a single reference electrode at the ground surface. Onset of EP anomalies correlated in time with both the accumulation of dissolved sulfide and the removal of uranium from groundwater. The anomalies persisted for 45 days after halting acetate injection. Current-voltage and current-power relationships between measurement and reference electrodes exhibited a galvanic response, with a maximum power density of 10 mW/m{sup 2} during sulfate reduction. We infer that the EP anomalies resulted from electrochemical differences between geochemically reduced regions and areas having higher oxidation potential. Following the period of sulfate reduction, EP values ranged from -500 to -600 mV and were associated with elevated concentrations of ferrous iron. Within 10 days of the voltage decrease, uranium concentrations rebounded from 0.2 to 0.8 {mu}M, a level still below the background value of 1.5 {mu}M. These findings demonstrate that EP measurements provide an inexpensive and minimally invasive means for monitoring the products of stimulated microbial activity within aquifer sediments and are capable of verifying maintenance of redox conditions favorable for the stability of bioreduced contaminants, such as uranium.

Williams, K.H.; N'Guessan, A.L.; Druhan, J.; Long, P.E.; Hubbard, S.S.; Lovley, D.R.; Banfield, J.F.

2009-11-15

20

Electrode-less measurement of cell layers impedance.  

PubMed

This paper is devoted to yet unpublished electrode-less methods (ELM) of cell layers impedance measurement based on transformer principle. The main advantage of ELM is elimination uncertainties caused by interface between electrodes and measured electrolyte. The method of avoiding distortion caused by non-ideal transformer transfer function ("deconvolution") and errors caused by residual voltage is described. The modification of original transformer based method allowing to measure an impedance of inserted object is proposed. Results of several calibration measurements confirming the proper function of ELM including example of transepithelial resistance of cells layer are presented. Crucial parts of measuring system and recommendation for their realization are included. PMID:25157656

Kr?šek, J; ?a?o, S

2014-01-01

21

Total Electrode Fall Measurement in a Parallel-Plate Magnetoplasmadynamic Thruster  

NASA Astrophysics Data System (ADS)

The total electrode fall voltage in a channel of magnetoplasmadynamic (MPD) thruster was determined by using "zero-limit approximating method", which is one of the classical methods widely used in the arc welding field. A new five-channel parallel-plate MPDT was designed and operated in a quasi-steady mode. This paper presents the measurement of the discharge voltage vs. the electrode gap for gaps from 1 mm to 4 mm. The extrapolated zero-gap intercept resulted in 18 V, which was considered as the total electrode-fall voltage. The electrode-fall voltage did not depend on the discharge current unless the discharge current exceeded onset threshold. It is considered that most of the electrode fall is deposited on the cathode side since the space potential at the inter-electrode region was almost equal to the anode potential.

Nakata, Daisuke; Toki, Kyoichiro; Shimizu, Yukio; Funaki, Ikkoh; Kuninaka, Hitoshi; Arakawa, Yoshihiro

22

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

23

Novel high-voltage power lateral MOSFET with adaptive buried electrodes  

NASA Astrophysics Data System (ADS)

A new high-voltage and low-specific on-resistance (Ron,sp) adaptive buried electrode (ABE) silicon-on-insulator (SOI) power lateral MOSFET and its analytical model of the electric fields are proposed. The MOSFET features are that the electrodes are in the buried oxide (BOX) layer, the negative drain voltage Vd is divided into many partial voltages and the output to the electrodes is in the buried oxide layer and the potentials on the electrodes change linearly from the drain to the source. Because the interface silicon layer potentials are lower than the neighboring electrode potentials, the electronic potential wells are formed above the electrode regions, and the hole potential wells are formed in the spacing of two neighbouring electrode regions. The interface hole concentration is much higher than the electron concentration through designing the buried layer electrode potentials. Based on the interface charge enhanced dielectric layer field theory, the electric field strength in the buried layer is enhanced. The vertical electric field EI and the breakdown voltage (BV) of ABE SOI are 545 V/?m and -587 V in the 50 ?m long drift region and the 1 ?m thick dielectric layer, and a low Ron,sp is obtained. Furthermore, the structure also alleviates the self-heating effect (SHE). The analytical model matches the simulation results.

Zhang, Wen-Tong; Wu, Li-Juan; Qiao, Ming; Luo, Xiao-Rong; Zhang, Bo; Li, Zhao-Ji

2012-07-01

24

Voltage clamping of Xenopus laevis oocytes utilizing agarose-cushion electrodes  

Microsoft Academic Search

Two-electrode voltage clamping of expressed ion channels in intact oocytes of the South African clawed frog Xenopus laevis has been refined to allow stable, low-resistance electrical access to the cytosol (50–800 kO). Glass microelectrodes were filled with a cushion of 1 % agarose at their tips to prevent KC1 leakage (agarose-cushion electrodes). Insertion of these electrodes into X. laevis oocytes

Wolfgang Schreibmayer; Henry A. Lester; Nathan Dascal

1994-01-01

25

PEDOT–CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities  

NASA Astrophysics Data System (ADS)

Objective. The aim of this study was to compare two different microelectrode materials—the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)–carbon nanotube(CNT) and titanium nitride (TiN)—at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. Approach. Retinal ganglion cell spikes were recorded by a central electrode (30 ?m diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1–1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 ?m). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. Main results. Stimulation of retinal interneurons using PEDOT–CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT–CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. Significance. In neuroprosthetic implants, PEDOT–CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy.

Samba, R.; Herrmann, T.; Zeck, G.

2015-02-01

26

PEDOT-CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities.  

PubMed

Objective. The aim of this study was to compare two different microelectrode materials-the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)-carbon nanotube(CNT) and titanium nitride (TiN)-at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. Approach. Retinal ganglion cell spikes were recorded by a central electrode (30 ?m diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1-1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 ?m). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. Main results. Stimulation of retinal interneurons using PEDOT-CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT-CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. Significance. In neuroprosthetic implants, PEDOT-CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy. PMID:25588201

Samba, R; Herrmann, T; Zeck, G

2015-02-01

27

Total voltage drops in electrode fall regions of ?, argon and air arcs in current range from 10 to 20 000 A  

NASA Astrophysics Data System (ADS)

Measurements were made of the sum of cathode fall and anode fall voltages, i.e. electrode fall voltages for 0022-3727/29/5/020/img8, argon and air arcs at a pressure of 0.1 MPa in wide current range from 10 to 20 000 A. For each arc, copper - tungsten, copper, iron and tungsten were used as electrode materials. The 0022-3727/29/5/020/img8 arcs proved to have electrode fall voltages of 17.5, 17.5, 17.5 and 13.8 V at the Cu - W, Cu, Fe and W electrodes respectively. The electrode fall voltage of each arc was affected by the electrode material. It was also found that the electrode fall voltage of each arc at a given electrode was independent of current in the above range. Further, the electric field strength at cathode surface and thickness of cathode fall region were estimated on the basis of Temperature-and-Field emission theory.

Yokomizu, Y.; Matsumura, T.; Henmi, R.; Kito, Y.

1996-05-01

28

Current-voltage characteristics of organic semiconductors: Interfacial control between organic layers and electrodes  

NASA Astrophysics Data System (ADS)

Current-voltage (I-V) characteristics of organic molecular glasses and solution processable materials embedded between two electrodes were studied to find materials possessing high charge-carrier mobilities and to design organic memory devices. The comparison studies between TOF, FET and SCLC measurements confirm the validity of using analyses of I-V characteristics to determine the mobility of organic semiconductors. Hexaazatrinaphthylene derivatives tri-substituted by electron withdrawing groups were characterized as potential electron transporting molecular glasses. The presence of two isomers has important implications for film morphology and effective mobility. The statistical isomer mixture of hexaazatrinaphthylene derivatized with pentafluoro-phenylmethyl ester is able to form amorphous films, and electron mobilities with the range of 10--2 cm2/Vs are observed in their I-V characteristics. Single-layer organic memory devices consisting of a polymer layer embedded between an Al electrode and ITO modified with Ag nanodots (Ag-NDs) prepared by a solution-based surface assembly demonstrated a potential capability as nonvolatile organic memory device with high ON/OFF switching ratios of 10 4. This level of performance could be achieved by modifying the ITO electrodes with some Ag-NDs that act as trapping sites, reducing the current in the OFF state. Based upon the observed electrical characteristics, the currents of the low-resistance state can be attributed to a tunneling through low-resistance pathways of metal particles originating from the metal top electrode in the organic layer and that the high-resistance state is controlled by charge trapping by the metal particles including Ag-NDs. In an alternative approach, complex films of AgNO3: hexaazatrinaphthylene derivatives were studied as the active layers for all-solution processed and air-stable organic memory devices. Rewritable memory effects were observed in the devices comprised of a thin polymer dielectric layer deposited on the bottom electrode, the complex film, and a conducting polymer film as the top electrode. The electrical characteristics indicate that the accumulation of Ag+ ions at the interface of the complex film and the top electrode may contribute to the switching effect.

Kondo, Takeshi

2007-12-01

29

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines  

DOEpatents

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2000-01-01

30

Electrical voltages and resistances measured to inspect metallic cased wells and pipelines  

DOEpatents

A cased well in the earth is electrically energized with A.C. current. Voltages are measured from three voltage measurement electrodes in electrical contact with the interior of the casing while the casing is electrically energized. In a measurement mode, A.C. current is conducted from a first current carrying electrode within the cased well to a remote second current carrying electrode located on the surface of the earth. In a calibration mode, current is passed from the first current carrying electrode to a third current carrying electrode located vertically at a different position within the cased well, where the three voltage measurement electrodes are located vertically in between the first and third current carrying electrodes. Voltages along the casing and resistances along the casing are measured to determine wall thickness and the location of any casing collars present so as to electrically inspect the casing. Similar methods are employed to energize a pipeline to measure the wall thickness of the pipeline and the location of pipe joints to electrically inspect the pipeline.

Vail, III, William Banning (Bothell, WA); Momii, Steven Thomas (Seattle, WA)

2001-01-01

31

Thermoelectric corrections to quantum voltage measurement  

NASA Astrophysics Data System (ADS)

A generalization of Büttiker's voltage probe concept for nonzero temperatures is an open third terminal of a quantum thermoelectric circuit. An explicit analytic expression for the thermoelectric correction to an ideal quantum voltage measurement in linear response is derived and interpreted in terms of local Peltier cooling/heating within the nonequilibrium system. The thermoelectric correction is found to be large (up to ±24 % of the peak voltage) in a prototypical ballistic quantum conductor (graphene nanoribbon). The effects of measurement nonideality are also investigated. Our findings have important implications for precision local electrical measurements.

Bergfield, Justin P.; Stafford, Charles A.

2014-12-01

32

Sheath expansion of two-dimensional grid electrodes subjected to short pulses of negative high-voltage  

NASA Astrophysics Data System (ADS)

Sheath expansion was investigated for two-dimensional (2D) grid electrodes which consist of a periodic array of cylindrical electrodes when short pulses of negative high-voltage were applied to the electrodes immersed in plasmas. In the sheath expansion model, a geometric function which describes the electrode system is crucial to numerically calculate the temporal evolution of a sheath boundary. In this paper, the 2D geometric function of grid electrodes was obtained by using XOOPIC (particle-in-cell) simulation. When the ratio between the diameter of cylindrical electrodes and grid spacing is fixed, we found that the geometric functions and the temporal evolutions of the sheath boundary for grid electrodes are identical in normalized coordinates. The numerical calculation results of the temporal evolutions of the sheath boundary showed reasonable agreements with the experimental measurements carried out in argon plasmas produced by hot filament discharges with neutral gas pressure of ?0.4 mTorr and plasma density in the order of 1010 cm?3 in a multi-dipole device.

Yi, Changho; Lee, Huijea; Park, Byungjae; Namkung, Won; Cho, Moohyun

2015-02-01

33

Improving the performance of stainless-steel DC high voltage photoelectron gun cathode electrodes via gas conditioning with helium or krypton  

NASA Astrophysics Data System (ADS)

Gas conditioning was shown to eliminate field emission from cathode electrodes used inside DC high voltage photoelectron guns, thus providing a reliable means to operate photoguns at higher voltages and field strengths. Measurements and simulation results indicate that gas conditioning eliminates field emission from cathode electrodes via two mechanisms: sputtering and implantation, with the benefits of implantation reversed by heating the electrode. We have studied five stainless steel electrodes (304L and 316LN) that were polished to approximately 20 nm surface roughness using diamond grit, and evaluated inside a high voltage apparatus to determine the onset of field emission as a function of voltage and field strength. The field emission characteristics of each electrode varied significantly upon the initial application of voltage but improved to nearly the same level after gas conditioning using either helium or krypton, exhibiting less than 10 pA field emission at -225 kV bias voltage with a 50 mm cathode/anode gap, corresponding to a field strength of ~13 MV/m. Field emission could be reduced with either gas, but there were conditions related to gas choice, voltage and field strength that were more favorable than others.

BastaniNejad, M.; Elmustafa, A. A.; Forman, E.; Clark, J.; Covert, S.; Grames, J.; Hansknecht, J.; Hernandez-Garcia, C.; Poelker, M.; Suleiman, R.

2014-10-01

34

Improving the performance of stainless-steel DC high voltage photoelectron gun cathode electrodes via gas conditioning with helium or krypton  

SciTech Connect

Gas conditioning was shown to eliminate field emission from cathode electrodes used inside DC high voltage photoelectron guns, thus providing a reliable means to operate photoguns at higher voltages and field strengths. Measurements and simulation results indicate that gas conditioning eliminates field emission from cathode electrodes via two mechanisms: sputtering and implantation, with the benefits of implantation reversed by heating the electrode. We have studied five stainless steel electrodes (304L and 316LN) that were polished to approximately 20 nm surface roughness using diamond grit, and evaluated inside a high voltage apparatus to determine the onset of field emission as a function of voltage and field strength. The field emission characteristics of each electrode varied significantly upon the initial application of voltage but improved to nearly the same level after gas conditioning using either helium or krypton, exhibiting less than 10 pA field emission at ?225 kV bias voltage with a 50 mm cathode/anode gap, corresponding to a field strength of ~13 MV/m. Field emission could be reduced with either gas, but there were conditions related to gas choice, voltage and field strength that were more favorable than others.

Bastaninejad, Mahzad [ODU; Elmustafa, Abdelmageed [ODU; Forman, Eric I. [JLAB; Clark, James [JLAB; Covert, Steven R. [JLAB; Grames, Joseph M. [JLAB; Hansknecht, John C. [JLAB; Hernandez-Garcia, Carlos [JLAB; Poelker, Bernard [JLAB; Suleiman, Riad S. [JLAB

2014-10-01

35

Rapidly prototyped multi-scale electrodes to minimize the voltage requirements for bacterial cell lysis.  

PubMed

Lab-on-a-chip systems used for nucleic acid based detection of bacteria rely on bacterial lysis for the release of cellular material. Although electrical lysis devices can be miniaturized for on-chip integration and reagent-free lysis, they often suffer from high voltage requirements, and rely on the use of off-chip voltage supplies. To overcome this barrier, we developed a rapid prototyping method for creating multi-scale electrodes that are structurally tuned for lowering the voltage needed for electrical bacterial lysis. These three-dimensional multi-scale electrodes - with micron scale reaction areas and nanoscale features - are fabricated using benchtop methods including craft cutting, polymer-induced wrinkling, and electrodeposition, which enable a lysis device to be designed, fabricated, and optimized in a matter of hours. These tunable electrodes show superior behaviour compared to lithographically-prepared electrodes in terms of lysis efficiency and voltage requirement. Successful extraction of nucleic acids from bacterial samples processed by these electrodes demonstrates the potential for these rapidly prototyped devices to be integrated within practical lab-on-a-chip systems. PMID:25597363

Gabardo, Christine M; Kwong, Aaron M; Soleymani, Leyla

2015-03-01

36

High-Voltage Measurements and Isolation  

NSDL National Science Digital Library

This tutorial is part of the National Instruments Measurement Fundamentals series. Each tutorial in this series teaches you a specific topic of common measurement applications by explaining theoretical concepts and providing practical examples. There are many issues to consider when measuring high voltage. When specifying a data acquisition (DAQ) system, the first question one should ask is whether the system will be safe. Making high-voltage measurements can be hazardous to the equipment, to the unit under test, and to you and your colleagues. This tutorial covers the concept of isolation, as well as discussing National Instruments' isolated products. A PDF of the material is available for download as well.

37

High voltage, rechargeable lithium batteries using newly-developed carbon for negative electrode material  

NASA Astrophysics Data System (ADS)

Carbon is a good candidate for negative electrodes because it can take the form of lithium intercalation compounds. We discussed the characteristics of typical carbon materials which have been studied as negative electrode materials. We have found that the mesophase pitch-based carbon microbead (MCMB) of high graphitization stage which have been graphitized at a high temperature such as 2800 C gives good characteristics as a negative electrode for rechargeable lithium batteries. The cylindrical 'AA-size' batteries of our trial products using LiCoO2 as the positive electrode and the M CMB graphitized at 2800 C as the negative electrode have been found to provide large capacities of 500 mA h and high voltages of 3.7 V with high energy densities of 240 W h/l, 100 W h/kg.

Yamaura, Junichi; Ozaki, Yoshiyuki; Morita, Akiyoshi; Ohta, Akira

1993-03-01

38

Formation of an out-of-electrode plasma in a high-voltage gas discharge  

NASA Astrophysics Data System (ADS)

The formation of an out-of-electrode plasma in a high-voltage gas discharge is studied. The occurrence and self-maintenance of a gas discharge and its associated plasma fluxes on the straight portions of electrical field lines are predicted theoretically and confirmed experimentally. It is shown that the focusing of the gas discharge and plasma fluxes is provided by increasing the length of the field line straight portions toward the symmetry axis of a hole in the anode. It is found that, when the discharge power (more specifically, an accelerating voltage applied to the electrodes of the gas-discharge tube) rises, the straight portions of the field lines elongate and concentrate near the symmetry axis of the hole in the anode. Recommendations are given on using the out-of-electrode plasma in surface micro- and nanostructuring.

Kolpakov, V. A.; Kolpakov, A. I.; Podlipnov, V. V.

2013-04-01

39

Performance evaluation of the electrode configuration in bioelectrical impedance analysis for visceral fat measurement.  

PubMed

Excessive amount of visceral fat is considered as a crucial indicator for the metabolic syndrome (MS). Visceral fat area (VFA) at the umbilicus level measured by CT is adopted as the gold standard, but it has many limitations. Recently, Application of bioelectrical impedance analysis (BIA) for measuring VFA is widely used. However, the correlation between impedance and VFA is highly dependent on the measurement conditions. Therefore, we evaluate its measurement conditions here. In our experiment, we choose 5 different electrode configurations with changes of current and its frequency for evaluating its performance to distinguish fat and thin group with impedance. Our results indicated that electrode arrangement with fixed waist ratio is better in its performance than fixed distance electrode arrangement. Current electrode on each flank side is better than on the front and rear side. Shorter distance between current electrode and voltage electrode is better than longer distance in its performance. Our experiment results are presented. PMID:19965130

Kim, Kwangsoo; Lee, Mi-Hee; Kim, Jungchae; Jung, Seok Myung; Jee, Sun Ha; Yoo, Sun K

2009-01-01

40

Utilizing a handheld electrode array for localized muscle impedance measurements  

PubMed Central

Introduction Electrical impedance myography (EIM) is a non-invasive technique used for assessment of muscle health in which a high-frequency, low-amplitude electric current is applied to the skin overlying a muscle, and the resulting surface voltage is measured. We have previously used adhesive electrodes, application of which is inconvenient. We present data using a handheld electrode array (HEA) that we devised to expedite the EIM procedure in a clinical setting. Methods Thirty-four healthy volunteers and 24 radiculopathy subjects underwent EIM testing using the HEA and adhesive electrodes. Results The HEA was shown to have good test-retest reproducibility, with intraclass correlation coefficients as high as 0.99. HEA data correlated strongly with data from adhesive electrodes, ? = 0.85 in healthy volunteers (p < 0.001) and ? = 0.75 in radiculopathy subjects (p < 0.001). Discussion These data support the potential use of a handheld array for performing rapid localized surface impedance measurements. PMID:22806375

Narayanaswami, Pushpa; Spieker, Andrew J.; Mongiovi, Phillip; Keel, John C.; Muzin, Stefan C.; Rutkove, Seward B.

2012-01-01

41

Programming voltage reduction in phase change memory cells with tungsten trioxide bottom heating layer/electrode.  

PubMed

A phase change memory cell with tungsten trioxide bottom heating layer/electrode is investigated. The crystalline tungsten trioxide heating layer promotes the temperature rise in the Ge(2)Sb(2)Te(5) layer which causes the reduction in the reset voltage compared to a conventional phase change memory cell. Theoretical thermal simulation and calculation for the reset process are applied to understand the thermal effect of the tungsten trioxide heating layer/electrode. The improvement in thermal efficiency of the PCM cell mainly originates from the low thermal conductivity of the crystalline tungsten trioxide material. PMID:21832748

Rao, Feng; Song, Zhitang; Gong, Yuefeng; Wu, Liangcai; Feng, Songlin; Chen, Bomy

2008-11-01

42

Programming voltage reduction in phase change memory cells with tungsten trioxide bottom heating layer/electrode  

NASA Astrophysics Data System (ADS)

A phase change memory cell with tungsten trioxide bottom heating layer/electrode is investigated. The crystalline tungsten trioxide heating layer promotes the temperature rise in the Ge2Sb2Te5 layer which causes the reduction in the reset voltage compared to a conventional phase change memory cell. Theoretical thermal simulation and calculation for the reset process are applied to understand the thermal effect of the tungsten trioxide heating layer/electrode. The improvement in thermal efficiency of the PCM cell mainly originates from the low thermal conductivity of the crystalline tungsten trioxide material.

Rao, Feng; Song, Zhitang; Gong, Yuefeng; Wu, Liangcai; Feng, Songlin; Chen, Bomy

2008-11-01

43

Loss measurement in high voltage thyristor valves  

SciTech Connect

No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter stations and Static VAR controllers. This paper presents a measuring method to be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to a sophisticated calorimetric technique. An uncertainty of 1% was achieved at conditions simulating full load operation. Voltage across and current through the valve are recorded in discrete steps and digitized. The loss is then calculated as their product. Special current and voltage sensors were developed to cover a very high dynamic range of the measured quantities. A high resolution, multichannel digital recorder was used for simultaneous registration of two voltage and two current signals. The method is of a general application, since the valve is treated as a two port circuit. Therefore, it can be used to measure loss in other non-linear components and apparatus, where large dynamic changes of the measured quantities preclude application of conventional techniques.

Cepek, M.; Douville, J.; Fecteau, G. (Hydro-Quebec Research Inst., Montreal, Quebec (Canada)); Malewski, R.

1994-07-01

44

dc step response of induced-charge electro-osmosis between parallel electrodes at large voltages  

NASA Astrophysics Data System (ADS)

Induced-charge electro-osmosis (ICEO) is important since it can be used for realizing high performance microfluidic devices. Here, we analyze the simplest problem of ion relaxation around a circular polarizable cylinder between parallel blocking electrodes in a closed cell by using a multiphysics coupled simulation technique. This technique is based on a combination of the finite-element method and finite-volume method for the Poisson-Nernst-Planck (PNP) equations having a flow term and the Stokes equation having an electric stress term. Through this analysis, we successfully demonstrate that on application of dc voltages, quadorapolar ICEO vortex flows grow during the charging time of the cylinder for both unbounded and bounded problems and decay during the charging time of the parallel electrodes only for the bounded problem using blocking electrodes. Further, by proposing a simple model that considers the two-dimensional (2D) PNP equations analytically, we successfully explain the step response time of the ICEO flow for the both unbounded and bounded problems. Furthermore, at low applied voltages, we find analytical formulations on steady diffused-ion problems and steady ICEO-flow problems and examine that our numerical results agree well with the analytical results. Moreover, by considering an ion-conserving condition with 2D Poisson-Boltzmann equations, we explain significant decrease of the maximum slip velocity at large applied voltages fairly well. We believe that our analysis will contribute greatly to the realistic designs of prospective high-performance microfluidic devices.

Sugioka, Hideyuki

2014-07-01

45

Origin of voltage decay in high-capacity layered oxide electrodes  

NASA Astrophysics Data System (ADS)

Although Li-rich layered oxides (Li1+xNiyCozMn1?x?y?zO2 > 250 mAh g?1) are attractive electrode materials providing energy densities more than 15% higher than today’s commercial Li-ion cells, they suffer from voltage decay on cycling. To elucidate the origin of this phenomenon, we employ chemical substitution in structurally related Li2RuO3 compounds. Li-rich layered Li2Ru1?yTiyO3 phases with capacities of ~240 mAh g?1 exhibit the characteristic voltage decay on cycling. A combination of transmission electron microscopy and X-ray photoelectron spectroscopy studies reveals that the migration of cations between metal layers and Li layers is an intrinsic feature of the charge–discharge process that increases the trapping of metal ions in interstitial tetrahedral sites. A correlation between these trapped ions and the voltage decay is established by expanding the study to both Li2Ru1?ySnyO3 and Li2RuO3; the slowest decay occurs for the cations with the largest ionic radii. This effect is robust, and the finding provides insights into new chemistry to be explored for developing high-capacity layered electrodes that evade voltage decay.

Sathiya, M.; Abakumov, A. M.; Foix, D.; Rousse, G.; Ramesha, K.; Saubanère, M.; Doublet, M. L.; Vezin, H.; Laisa, C. P.; Prakash, A. S.; Gonbeau, D.; Vantendeloo, G.; Tarascon, J.-M.

2015-02-01

46

Electrochemical dealloying using pulsed voltage waveforms and its application for supercapacitor electrodes  

NASA Astrophysics Data System (ADS)

Dealloying is an important industrial technique for generating nanoporous metallic structures by selectively leaching out the more reactive metal component from an alloy material. A constant voltage is often applied to facilitate the dealloying process. Here we report the first study on dealloying with the application of a voltage waveform-specifically, pulsed voltage waveforms are applied for dealloying Ni-Cu alloys. It is found that pulsed dealloying voltage waveforms can exert a strong impact on the dealloying process by 1) significantly lowering the compositional threshold of the more reactive metal component for the dealloying reaction to take place, 2) more thoroughly removing the more reactive metal component and thus producing a porous metal of higher purity and higher porosity (volume fraction of voids), and 3) greatly affecting the morphology of the generated porous metal structure (e.g., leading to significantly thinner ligaments). The nanoporous metallic materials obtained by the pulsed voltage waveform enable supercapacitor electrodes of significantly better performance than the counterpart dealloyed with a constant voltage.

Zhang, Jie; Zhan, Yawen; Bian, Haidong; Li, Zhe; Tsang, Chun-Kwan; Lee, Chris; Cheng, Hua; Shu, Shiwei; Li, Yang Yang; Lu, Jian

2014-07-01

47

The burning voltage of a high-current vacuum arc in a six-cap rod electrode system  

Microsoft Academic Search

This paper studies the voltage-current characteristics of the six-gap rod electrode system and their dependence on the shape and material of the electrodes and interelectrode gap value. The investigations were carried out for currents up to 200 kA with the rate of its rise up to ~5·109 A\\/s. A number of features were observed concerning arc-burning voltage dynamics depending on

D. F. Alferov; N. I. Korobova; V. A. Sidorov

1997-01-01

48

Superconducting switch permits measurement of small voltages at cryogenic temperatures  

NASA Technical Reports Server (NTRS)

Dual-coil, superconducting, on-off switch measures small, thermoelectrically generated voltages produced by thermocouples in a liquid helium bath. Placed in a shunt configuration between the thermocouple and the measuring device, the measuring device sees the sum of the voltage to be measured and the spurious thermoelectric voltages.

Govednik, R. E.; Huebener, R. P.

1968-01-01

49

Electrodic voltages in the presence of dissolved sulfide: Implications for monitoring natural microbial activity  

SciTech Connect

There is growing interest in the development of new monitoring strategies for obtaining spatially extensive data diagnostic of microbial processes occurring in the earth. Open-circuit potentials arising from variable redox conditions in the fluid local-to-electrode surfaces (electrodic potentials) were recorded for a pair of silver-silver chloride electrodes in a column experiment, whereby a natural wetland soil containing a known community of sulfate reducers was continuously fed with a sulfate-rich nutrient medium. Measurements were made between five electrodes equally spaced along the column and a reference electrode placed on the column inflow. The presence of a sulfate reducing microbial population, coupled with observations of decreasing sulfate levels, formation of black precipitate (likely iron sulfide),elevated solid phase sulfide, and a characteristic sulfurous smell, suggest microbial-driven sulfate reduction (sulfide generation) in our column. Based on the known sensitivity of a silver electrode to dissolved sulfide concentration, we interpret the electrodic potentials approaching 700 mV recorded in this experiment as an indicator of the bisulfide (HS-) concentration gradients in the column. The measurement of the spatial and temporal variation in these electrodic potentials provides a simple and rapid method for monitoring patterns of relative HS- concentration that are indicative of the activity of sulfate-reducing bacteria. Our measurements have implications both for the autonomous monitoring of anaerobic microbial processes in the subsurface and the performance of self-potential electrodes, where it is critical to isolate, and perhaps quantify, electrochemical interfaces contributing to observed potentials.

Slater, L.; Ntarlagiannis, D.; Yee, N.; O'Brien, M.; Zhang, C.; Williams, K. H.

2008-10-01

50

Electronic circuit for measuring series connected electrochemical cell voltages  

DOEpatents

An electronic circuit for measuring voltage signals in an energy storage device is disclosed. The electronic circuit includes a plurality of energy storage cells forming the energy storage device. A voltage divider circuit is connected to at least one of the energy storage cells. A current regulating circuit is provided for regulating the current through the voltage divider circuit. A voltage measurement node is associated with the voltage divider circuit for producing a voltage signal which is proportional to the voltage across the energy storage cell.

Ashtiani, Cyrus N. (West Bloomfield, MI); Stuart, Thomas A. (Toledo, OH)

2000-01-01

51

Performance measurements of advanced AMTEC electrodes  

NASA Astrophysics Data System (ADS)

These results are from sodium exposure test cell experiments with advanced AMTEC electrodes performed at Texas A&M University. The majority of the results are for metal electrodes; the minority of the results are for ceramic electrodes. Initial results for iridium and titanate electrodes have been good, but degrade with time. .

Schuller, Michael; Fiebig, Brad; Hudson, Patricia; Kakwan, Imran

2000-01-01

52

Atomic layer deposition encapsulated activated carbon electrodes for high voltage stable supercapacitors.  

PubMed

Operating voltage enhancement is an effective route for high energy density supercapacitors. Unfortunately, widely used activated carbon electrode generally suffers from poor electrochemical stability over 2.5 V. Here we present atomic layer deposition (ALD) encapsulation of activated carbons for high voltage stable supercapacitors. Two-nanometer-thick Al2O3 dielectric layers are conformally coated at activated carbon surface by ALD, well-maintaining microporous morphology. Resultant electrodes exhibit excellent stability at 3 V operation with 39% energy density enhancement from 2.5 V operation. Because of the protection of surface functional groups and reduction of electrolyte degradation, 74% of initial voltage was maintained 50 h after full charge, and 88% of capacitance was retained after 5000 cycles at 70 °C accelerated test, which correspond to 31 and 17% improvements from bare activated carbon, respectively. This ALD-based surface modification offers a general method to enhance electrochemical stability of carbon materials for diverse energy and environmental applications. PMID:25548826

Hong, Kijoo; Cho, Moonkyu; Kim, Sang Ouk

2015-01-28

53

Direct in situ measurements of Li transport in Li-ion battery negative electrodes  

Microsoft Academic Search

We describe the first direct in situ measurements of Li transport in an operating cell. Motion of the lithiation front in the graphite electrode suggests that transport could be controlled by liquid-phase diffusion. The electrochemical (current–voltage) data are successfully modeled with a diffusion equation that contains no material or microstructural information. The model is only qualitatively successful in predicting observed

Stephen J. Harris; Adam Timmons; Daniel R. Baker; Charles Monroe

2010-01-01

54

Sensing Induced Voltage of Electromagnetic Flow Meter with Multi-electrodes  

Microsoft Academic Search

An induced voltage Electromagnetic Flow meter (EMF) in the area of measuring single phase flow rate in pipes has been used in many industrial areas. To measure the continuous phase velocity profile in multiphase flows where the continuous phase is electrical conductive, Electrical capacitance and resistance tomography has been comprehensively investigated, except for continuous phase velocity profile measurement. This paper

Jingzhuo Wang; Chenglong Gong

2006-01-01

55

Gelatin coated electrodes allow prolonged bioelectronic measurements  

NASA Technical Reports Server (NTRS)

Silver electrodes treated with an anodizing electrolyte containing gelatin are used for long term monitoring of bioelectronic potentials in humans. The electrodes do not interact with perspiration, cause skin irritation, or promote the growth of bacteria.

1966-01-01

56

In situ measurements of electron-beam-induced surface voltage of highly resistive materials  

NASA Astrophysics Data System (ADS)

This study presents the development, calibration, characterization, and use of new instrumentation for in situ measurements of electron-beam-induced surface voltage. The instrument capabilities allow for measurements of a full range of insulating materials that are of concern to NASA spacecraft charging experts. These measurements are made using moveable capacitive sensor electrodes that can be swept across the sample using an in vacu stepper motor. Testing has shown a voltage range of more than ±30 kV with a low-voltage resolution of 0.2 V. The movable sensors allow for a radial measurement of surface voltage with spatial resolution as low as 1.5 mm. The instrumentation has response time of ˜7 s from the time the beam is shut off until the probe is in position to take data and uses computer automation to stabilize the system and acquire data over the period of several days or longer. Three types of measurements have been made on two prototypical polymeric spacecraft materials, Low-density Polyethylene (LDPE) and polyimide (Kapton™ HN), to illustrate the research capabilities of the new system. Surface voltage measurements were made periodically during the charging process using a pulsed electron beam and subsequently as the surface voltage discharged to a grounded substrate; these were used to obtain information about the material's electron yields and bulk resistivity. The spatial profile of the voltage across the sample surface was also measured by sweeping the electrode across the surface. Subsequent measurements monitored the time evolution of the magnitude and spatial charge distribution as charge dispersed radially across the sample surface. The results of these measurements are present and compared to literature values validating the instrument's effectiveness.

Hodges, Joshua

57

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium/redox flow cells  

NASA Technical Reports Server (NTRS)

The effect of acid concentration on the performance of the iron-titanium redox flow cell was studied. When the acidity was increased, open-circuit voltages decreased on the titanium side but load voltages increased due to decreased polarization. The best load voltage occurs when there is high acidity on the titanium side coupled with low acidity on the iron side, but such cells show voltage losses with repeated cycling because of the diffusion of acid through the membrane. No membrane tested has been found capable of maintaining the differences in acidity. Chelating agents show some promise in reducing polarization at the Ti electrode and thus improving energy efficiency.

Reid, M. A.; Gahn, R. F.

1977-01-01

58

Non-intrusive high voltage measurement using slab coupled optical sensors  

NASA Astrophysics Data System (ADS)

We present an optical fiber non-intrusive sensor for measuring high voltage transients. The sensor converts the unknown voltage to electric field, which is then measured using slab-coupled optical fiber sensor (SCOS). Since everything in the sensor except the electrodes is made of dielectric materials and due to the small field sensor size, the sensor is minimally perturbing to the measured voltage. We present the details of the sensor design, which eliminates arcing and minimizes local dielectric breakdown using Teflon blocks and insulation of the whole structure with transformer oil. The structure has a capacitance of less than 3pF and resistance greater than 10 G?. We show the measurement of 66.5 kV pulse with a 32.6?s time constant. The measurement matches the expected value of 67.8 kV with less than 2% error.

Stan, Nikola; Chadderdon, Spencer; Selfridge, Richard H.; Schultz, Stephen M.

2014-03-01

59

Small onset voltages in negative corona discharges using the edges of gold and aluminum foils as nano-structured electrodes  

NASA Astrophysics Data System (ADS)

Gold and aluminum foils with nano-structured edges were investigated as electrodes for corona discharges in nitrogen and ambient air. Low onset voltages were observed due to the field enhancement near the edges of the foil. The lowest onset voltage was determined to be about 1.2 kV in ambient air and about 1.1 kV in nitrogen for a 5 mm inter-electrode spacing. This is significantly smaller than the values reported in the literature for sharp tips with similar electrode spacing. The foil-based electrode tips are extremely simple to produce, making them candidates for low-cost, low power consumption and easily available corona-discharge technology.

Eifert, A.; Baier, T.; Hardt, S.

2013-07-01

60

Measurements of high voltage pulses with subnanosecond rise time  

NASA Astrophysics Data System (ADS)

The paper deals with the application features of capacitive probes for subnanosecond voltage pulse measurements. The relation for the amplitude of distortions determined by the finite electrical length of a capacitive divider was obtained. This relation could serve for quantitative estimation of capacitive divider suitability. Probes of various designs were used for recording the high voltage pulses with subnanosecond voltage changes. The pulse shapes with voltage change durations of 0.2 - 20 ns from different voltage probes were compared. It was shown that the use of capacitive divider with high- and low-voltage arms filled with the same material is more appropriate. This divider provides the same voltage ratio for voltage changes of durations from tens to fractions of nanoseconds.

Bykov, N. M.; Kurkan, I. K.; Stepchenko, A. S.

2014-11-01

61

Factors affecting the open-circuit voltage and electrode kinetics of some iron/titanium redox flow cells  

NASA Technical Reports Server (NTRS)

Performance of the iron-titanium redox flow cell was studied as a function of acid concentration. Anion permeable membranes separated the compartments. Electrodes were graphite cloth. Current densities ranged up to 25 mA/square centimeter. Open-circuit and load voltages decreased as the acidity was increased on the iron side as predicted. On the titanium side, open-circuit voltages decreased as the acidity was increased in agreement with theory, but load voltages increased due to decreased polarization with increasing acidity. High acidity on the titanium side coupled with low acidity on the iron side gives the best load voltage, but such cells show voltage losses as they are repeatedly cycled. Analyses show that the bulk of the voltage losses are due to diffusion of acid through the membrane.

Reid, M. A.; Gahn, R. F.

1977-01-01

62

Analysis of NSTX TF Joint Voltage Measurements  

SciTech Connect

This report presents findings of analyses of recorded current and voltage data associated with 72 electrical joints operating at high current and high mechanical stress. The analysis goal was to characterize the mechanical behavior of each joint and thus evaluate its mechanical supports. The joints are part of the toroidal field (TF) magnet system of the National Spherical Torus Experiment (NSTX) pulsed plasma device operating at the Princeton Plasma Physics Laboratory (PPPL). Since there is not sufficient space near the joints for much traditional mechanical instrumentation, small voltage probes were installed on each joint and their voltage monitoring waveforms have been recorded on sampling digitizers during each NSTX ''shot''.

Woolley R

2005-10-07

63

Frequency response measurements in battery electrodes  

NASA Technical Reports Server (NTRS)

Electrical impedance spectroscopy was used to investigate the behavior of porous zinc, silver, cadmium, and nickel electrodes. State of charge could be correlated with impedance data for all but the nickel electrodes. State of health was correlated with impedance data for two AgZn cells, one apparently good and the other bad. The impedance data was fit to equivalent circuit models.

Thomas, Daniel L.

1992-01-01

64

Universality in the low-voltage transport response of molecular wires physisorbed onto graphene electrodes  

NASA Astrophysics Data System (ADS)

We analyze the low-voltage transport response of large molecular wires bridging graphene electrodes, where the molecules are physisorbed onto the graphene sheets by planar anchor groups. In our study, the sheets are pulled away to vary the gap length and the relative atomic positions. The molecular wires are also translated in directions parallel and perpendicular to the sheets. We show that the energy position of the Breit-Wigner molecular resonances is universal for a given molecule, in the sense that it is independent of the details of the graphene edges, gaps lengths, or of the molecule positions. We discuss the need to converge carefully the k sampling to provide reasonable values of the conductance.

García-Suárez, V. M.; Ferradás, R.; Carrascal, D.; Ferrer, J.

2013-06-01

65

Organic dicarboxylate negative electrode materials with remarkably small strain for high-voltage bipolar batteries.  

PubMed

As advanced negative electrodes for powerful and useful high-voltage bipolar batteries, an intercalated metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium, is described which has an organic-inorganic layered structure of ?-stacked naphthalene and tetrahedral LiO4 units. The material shows a reversible two-electron-transfer Li intercalation at a flat potential of 0.8?V with a small polarization. Detailed crystal structure analysis during Li intercalation shows the layered framework to be maintained and its volume change is only 0.33%. The material possesses two-dimensional pathways for efficient electron and Li(+) transport formed by Li-doped naphthalene packing and tetrahedral LiO3C network. A cell with a high potential operating LiNi(0.5)Mn(1.5)O4 spinel positive and the proposed negative electrodes exhibited favorable cycle performance (96% capacity retention after 100 cycles), high specific energy (300?Wh?kg(-1)), and high specific power (5?kW?kg(-1)). An 8?V bipolar cell was also constructed by connecting only two cells in series. PMID:25196994

Ogihara, Nobuhiro; Yasuda, Tomomi; Kishida, Yoshihiro; Ohsuna, Tetsu; Miyamoto, Kaito; Ohba, Nobuko

2014-10-20

66

Current-voltage characteristics of organic photovoltaic cells following deposition of cathode electrode  

PubMed Central

The current-voltage characteristics of benzoporphine-fullerene solar cells were measured subsequent to the deposition of Al as a cathode material. Even in vacuum, a shift in the open circuit voltage was observed at 20 min after Al deposition. Moreover, the displacement of inert gases (N2or Ar) in the evaporation chamber enhanced the photovoltaic parameters. The power conversion efficiency was increased by 24% over the initial characteristics (from 1.04% to 1.29%), which indicates that the structure of the organic-metal interface changed rapidly after Al deposition, even if the process was performed in an air-free glovebox. PMID:21151322

Saeki, Hiroyuki; Hirohara, Kazuto; Koshiba, Yasuko; Horie, Satoshi; Misaki, Masahiro; Takeshita, Kimiya; Ishida, Kenji; Ueda, Yasukiyo

2010-01-01

67

Method for linearizing deflection of a MEMS device using binary electrodes and voltage modulation  

DOEpatents

A micromechanical device comprising one or more electronically movable structure sets comprising for each set a first electrode supported on a substrate and a second electrode supported substantially parallel from said first electrode. Said second electrode is movable with respect to said first electrode whereby an electric potential applied between said first and second electrodes causing said second electrode to move relative to said first electrode a distance X, (X), where X is a nonlinear function of said potential, (V). Means are provided for linearizing the relationship between V and X.

Horenstein, Mark N. (West Roxbury, MA) [West Roxbury, MA

2008-06-10

68

Measuring Helical FCG Voltage with an Electric Field Antenna  

SciTech Connect

A method of measuring the voltage produced by a helical explosive flux compression generator using a remote electric field antenna is described in detail. The diagnostic has been successfully implemented on several experiments. Measured data from the diagnostic compare favorably with voltages predicted using the code CAGEN, validating our predictive modeling tools. The measured data is important to understanding generator performance, and is measured with a low-risk, minimally intrusive approach.

White, A D; Anderson, R A; Javedani, J B; Reisman, D B; Goerz, D A; Ferriera, A J; Speer, R D

2011-08-01

69

Ge2Sb2Te5 Phase Change Memory Cell Featuring Platinum Tapered Heating Electrode For Low-Voltage Operation  

NASA Astrophysics Data System (ADS)

Phase change random access memory (PC-RAM) with a Pt tapered heating electrode (Pt-THE), which was fabricated using a focus ion beam (FIB), was investigated. Compared with the tungsten electrode, the Pt-THE facilitates the temperature rise in phase change material, which causes the decrease of reset voltage from 3.5 to 2.4 V. The programming region of the cell with Pt-THE is smaller than that of the cell with a cylindrical tungsten heating electrode. The improved performance of the PC-RAM with a Pt-THE is attributed to the higher resistivity and lower thermal conductivity of the Pt electrode, and the reduction of the programming region, which is also verified by thermal simulation.

Lv, Shilong; Song, Zhitang; Liu, Yan; Feng, Songlin

2010-02-01

70

Traveling electric field probed by a fine particle above voltage-modulated strips in a striped electrode device  

SciTech Connect

It is described that the distribution of the horizontal electric field above a striped electrode can be inferred from the trajectory of a single fine particle with known mass and diameter. The striped electrode consists of 100 segmented stainless steel strips, each electrically insulated. A traveling periodic potential profile is produced above the striped electrode by modulating the voltage signals on the strips. When the voltage modulation is on, the fine particle, which is originally levitated in the sheath region above the striped electrode, experiences a periodic oscillation along both the vertical and the horizontal directions because of the periodic electric force arising from the modulation voltages. Tracking the motion of the fine particles, the electric force is obtained from the momentum equation including the gravity and the neutral gas friction. With the particle charge estimated by the vertical oscillation method, the electric field can be derived. The horizontal electric field obtained by this method is in agreement with the result predicted by a collisional particle-in-cell simulation.

Li Yangfang; Jiang Ke; Thomas, H. M.; Morfill, G. E. [Max-Planck-Institute for Extraterrestrial Physics, Garching 85748 (Germany); Zhang Wengui; Ma, J. X. [Department of Modern Physics, CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2010-03-15

71

Improved electrode paste provides reliable measurement of galvanic skin response  

NASA Technical Reports Server (NTRS)

High-conductivity electrode paste is used in obtaining accurate skin resistance or skin potential measurements. The paste is isotonic to perspiration, is nonirritating and nonsensitizing, and has an extended shelf life.

Day, J. L.

1966-01-01

72

Accuracy of plantar electrodes compared with hand and foot electrodes in fat-free-mass measurement.  

PubMed

This paper investigates the measurement of fat-free mass (FFM) by bioimpedance using foot-to-foot impedancemeters (FFI) with plantar electrodes measuring the foot-to-foot resistance R34 and hand-to-foot medical impedancemeters. FFM measurements were compared with corresponding data using Dual X-ray absorptiometry (DXA). Equations giving FFM were established using linear multiple regression on DXA data in a first group of 170 subjects. For validation, these equations were used on a second group of 86 subjects, and FFM were compared with DXA data; no significant difference was observed. The same protocol was repeated, but using electrodes on the right hand and foot in standing position to measure the hand to-foot resistance R13. Mean differences with DXA were higher for R13 than for R34. Effect of electrode size and feet position on resistance was also investigated. R34 decreased when electrode area increased or if feet were moved forward. It decreased if feet were moved backward. A proper configuration of contact electrodes can improve measurement accuracy and reproducibility of FFI. PMID:24918180

Jaffrin, Michel Y; Bousbiat, Sana

2014-01-01

73

Measuring the displacement of the movable guard electrode in the new vertical calculable capacitor at NIM  

NASA Astrophysics Data System (ADS)

A new type vertical calculable capacitor has been built at National Institute of Metrology (NIM) cooperated with National Measurement Institute of Australia (NMIA). The calculable capacitor is the highest accuracy equipment apparatus except the quantum voltage and the quantum resistance in the electromagnetic metrological field. In order to measure the capacitance precisely, the accurate displacement measurement among the two guard electrodes in the calculable capacitor is a pivotal part. This paper describes a method of measuring the displacement of a Fabry-Perot interferometer, and this interferometer is component of two mirrors in two guard electrodes of the calculable capacitor at NIM. One concave reflective mirror, with 5 m radius and 70% reflectivity, is on the top of the bottom fixed guards electrodes. The other planar mirror is placed at the end of the moveable guard electrodes. This Fabry-Perot interferometer employs a home-made lamb-dip stabilization He-Ne laser at 633 nm to measure the displacement of the movable guard electrode. The internal modulation, which is used for laser stabilization, is also employed for locking the Fabry-Perot interferometer. The displacement of the movable guard electrode could be measured, when the Fabry-Perot interferometer is locked to the stabilization laser at two positions respectively. An iodine stabilization He-Ne laser at 633 nm is employed to simultaneously calibrate the wavelength of lamb-dip working laser. A reproducibility of 1.43×10-8(k=3) for the range of 205 mm can be obtained at present, and that is estimated from the experimental results of calculable capacitor.

Wang, Jianbo; Qian, Jin; Liu, Zhongyou; Liu, Xiuying; Lu, Zhuliang; Huang, Lu; Yin, Cong; Li, Tongbao

2014-11-01

74

Measurements of Electrode Skin Impedances using Carbon Rubber Electrodes - First Results  

NASA Astrophysics Data System (ADS)

Non-invasive bioimpedance measurement as a tool in biomedical engineering and life sciences allows conclusions about condition and composition of living tissue. For interfacing the electronic conduction of the instrumentation and the ionic conduction of the tissue, electrodes are needed. A crucial point is the uncertainty arising from the unknown, time-varying and current density depend Electrode Skin Impedance (ESI). This work presents ESI measurements using carbon rubber electrodes on different human test subjects. The measurements for this work are carried out by employing a high accuracy Bioimpedance Measurement System (BMS) developed by the authors group, which is based on a Field Programmable Gate Array (FPGA) System on Chip (SoC). The system is able to measure magnitude and phase of complex impedances using a two- or four-electrode setup, with excitation currents from 60 ?A to 5 mA in a frequency range from about 10 kHz to 300 kHz. Achieved overall measurement uncertainties are below 1%.

Kaufmann, Steffen; Ardelt, Gunther; Ryschka, Martin

2013-04-01

75

Automated Evaluation of Dynamic Performance of Impulse Voltage Measurement Systems  

NASA Astrophysics Data System (ADS)

This manuscript presents and describes an automated system for the evaluation of the dynamic performance of high-voltage measurement systems, according to the requirements of the standard IEC 60060-2/2010. The system was developed in LabVIEW and controls the acquisition, measurement and analysis of step response tests of measurement systems, automatically calculating the relevant amplitude and time parameters.

Faria, L. C.; Silva, E. C.; Silva, M. T.; Barbosa, C. R. H.; Azevedo, L. C.

2015-01-01

76

Microfabricated Patch Clamp Electrodes for Improved Ion Channel Protein Measurements  

NASA Astrophysics Data System (ADS)

Ion channels are trans-membrane proteins that underlie many cell functions including hormone and neurotransmitter release, muscle contraction and cell signaling cascades. Ion channel proteins are commonly characterized via the patch clamp method in which an extruded glass tube containing ionic solution, manipulated by an expert technician, is brought into contact with a living cell to record ionic current through the cell membrane. Microfabricated planar patch electrodes, micromolded in the silicone elastomer poly-dimethylsiloxane (PDMS) from microlithographically patterned structures, have been developed that improve on this method. Microfabrication techniques allow arrays of patch electrodes to be fabricated, increasing the throughput of the measurement technique. Planar patch electrodes readily allow the automation of cell sealing, further increasing throughput. Microfabricated electrode arrays may be readily integrated with microfluidic structures to allow fast, in situ solution exchange. Miniaturization of the electrode geometry should increase both the signal to noise and the bandwidth of the measurement. Microfabricated patch electrode arrays have been fabricated and measurements have been taken.

Klemic, James; Klemic, Kathryn; Reed, Mark; Sigworth, Frederick

2002-03-01

77

Loss measurement in high voltage thyristor valves  

Microsoft Academic Search

No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter stations and Static VAR controllers. This paper presents a measuring method to be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to

M. Cepek; J. Douville; G. Fecteau; R. Malewski

1994-01-01

78

A simple arc column model that accounts for the relationship between voltage, current and electrode gap during VAR  

SciTech Connect

Mean arc voltage is a process parameter commonly used in vacuum arc remelting (VAR) control schemes. The response of this parameter to changes in melting current (I) and electrode gap (g{sub e}) at constant pressure may be accurately described by an equation of the form V = V{sub 0} + c{sub 1}g{sub e}I + c{sub 2}g{sub e}{sup 2} + c{sub 3}I{sup 2}, where c{sub 1}, c{sub 2} and c{sub 3} are constants, and where the non-linear terms generally constitute a relatively small correction. If the non-linear terms are ignored, the equation has the form of Ohm`s law with a constant offset (V{sub 0}), c{sub 1}g{sub e} playing the role of resistance. This implies that the arc column may be treated approximately as a simple resistor during constant current VAR, the resistance changing linearly with g{sub e}. The VAR furnace arc is known to originate from multiple cathode spot clusters situated randomly on the electrode tip surface. Each cluster marks a point of exist for conduction electrons leaving the cathode surface and entering the electrode gap. Because the spot clusters re highly localized on the cathode surface, each gives rise to an arc column that may be considered to operate independently of other local arc columns. This approximation is used to develop a model that accounts for the observed arc voltage dependence on electrode gap at constant current. Local arc column resistivity is estimated from elementary plasma physics and used to test the model for consistency by using it to predict local column heavy particle density. Furthermore, it is shown that the local arc column resistance increases as particle density increases. This is used to account for the common observation that the arc stiffens with increasing current, i.e. the arc voltage becomes more sensitive to changes in electrode gap as the melting current is increased. This explains why arc voltage is an accurate electrode gap indicator for high current VAR processes but not low current VAR processes.

Williamson, R.L. [Sandia National Labs., Albuquerque, NM (United States). Liquid Metal Processing Lab.

1997-02-01

79

Means to remove electrode contamination effect of Langmuir probe measurement in space  

SciTech Connect

Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

Oyama, K.-I.; Lee, C. H.; Fang, H. K.; Cheng, C. Z. [Plasma and Space Science Center, National Cheng Kung University, No.1 Ta-Hsueh Rd., Tainan 70101, Taiwan (China)

2012-05-15

80

Means to remove electrode contamination effect of Langmuir probe measurement in space.  

PubMed

Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment. PMID:22667663

Oyama, K-I; Lee, C H; Fang, H K; Cheng, C Z

2012-05-01

81

Spark gap with low breakdown voltage jitter  

DOEpatents

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.

Rohwein, Gerald J. (Albuquerque, NM); Roose, Lars D. (Albuquerque, NM)

1996-01-01

82

Spark gap with low breakdown voltage jitter  

DOEpatents

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed. 13 figs.

Rohwein, G.J.; Roose, L.D.

1996-04-23

83

Two electrode well logging system for measuring resistivity of subsurface formations  

SciTech Connect

This patent describes an apparatus for obtaining indications of the electrical resistivity of relatively thin layers of earth formations traversed by a borehole containing relatively conductive liquids, including a two electrode array to be lowered into a borehole. It consists of: an elongated, tubular instrument body member, the entire instrument body member forms an elongated guard electrode member; a measure electrode mounted within and electrically insulated from the guard electrode member. The measure electrode is for emitting a survey current into the earth formations; means for decentralizing within the borehole the entire guard electrode member and for urging the guard electrode member into contact with the wall of the borehole; and a pair of elongated auxiliary guard electrodes mechanically mounted on the guard electrode. The auxiliary guard electrodes are mounted parallel to the longitudinal axis of the guard electrode and the auxiliary guard electrodes are in electrical contact with the guard electrode member.

Marquis, G.L.

1987-09-29

84

Characterization of a capacitance-coupled contactless conductivity detection system with sidewall electrodes on a low-voltage-driven electrophoresis microchip.  

PubMed

A new type of capacitance-coupled contactless conductivity detection (C(4)D) system with sidewall electrodes was proposed for integration on a silicon-on-isolator-poly(dimethylsiloxane) (SOI-PDMS) hybrid low-voltage-driven electrophoresis microchip. By a microelectromechanical system process, the sidewall electrodes were fabricated precisely at either side of the separation channel. The area of the capacitor electrodes was the maximum value to improve the detection sensitivity with an enhanced capacitance effect. According to the simulation results, the structural parameters of the sidewall electrodes were determined as 550-microm length, 15-microm width, 80-microm separation distance, and 1-microm isolator thickness. The integrated microdevice with the SOI-PDMS hybrid electrophoresis microchip was very compact and the size was only 15 cm x 15 cm x 10 cm (width x length x height), which permitted miniaturization and portability. The detector performance was evaluated by K(+) testing. The detection limit of the conductivity detector was determined to be 10(-9) and 10(-6) M for K(+) in the static and electric-driven modes, respectively. Finally, the C(4)D was applied to low-voltage-driven electrophoresis on a microchip to carry out real-time measurement of the separation of amino acids. The separations of 10(-4) M lysine and phenylalanine in the low-voltage-driven electrophoresis mode were performed with an electric field of 300 V/cm and were completed in less than 15 min with a resolution of 1.3. The separation efficiency was found to be 1.3 x 10(3) and 2.8 x 10(3) plates for lysine and phenylalanine, respectively, with a migration time reproducibility of 2.7 and 3.2%. The conductivity detection limit of amino acids achieved was 10(-6) M. The proposed method for the construction of a novel C(4)D integrated on an SOI-PDMS hybrid low-voltage-driven electrophoresis microchip showed the most extensive integration and miniaturization of a microdevice, which is a further crucial step toward the realization of the "lab-on-a-chip" concept. PMID:20386887

Xu, Yi; Liang, Jing; Liu, Haitao; Hu, Xiaoguo; Wen, Zhiyu; Wu, Yongjie; Cao, Mingxia

2010-06-01

85

Electronic transport in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality  

SciTech Connect

We have investigated, by means of a nonequilibrium Green's function method coupled to density functional theory, the electronic transport properties of molecular junctions composed of oligo-para-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, V{sub min}, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent transport model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that V{sub min} corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that V{sub min} corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent transport model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of V{sub min} if compared to the case of molecular junctions with nonorganic contacts treated so far.

Brito Silva, C. A. Jr. [Pos-Graduacao em Engenharia Eletrica, Universidade Federal do Para, 66075-900, Belem, PA (Brazil); Faculdade de Ciencias Naturais, Universidade Federal do Para, 68800-000, Breves, PA (Brazil); Silva, S. J. S. da; Leal, J. F. P. [Pos-Graduacao em Fisica, Universidade Federal do Para, 66075-110, Belem, PA (Brazil); Pinheiro, F. A. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, RJ (Brazil); Del Nero, J. [Departamento de Fisica, Universidade Federal do Para, 66075-110, Belem, PA (Brazil); Departement de Physique, Ecole Normale Superieure, F-75231, Paris (France)

2011-06-15

86

Evaluation of different stimulation and measurement patterns based on internal electrode: application in cardiac impedance tomography.  

PubMed

The conductivity distribution around the thorax is altered during the cardiac cycle due to the blood perfusion, heart contraction and lung inflation. Previous studies showed that these bio-impedance changes are appropriate for non-invasive cardiac function imaging using Electrical Impedance Tomography (EIT) techniques. However, the spatial resolution is presently low. One of the main obstacles in cardiac imaging at the heart location is the large impedance variation of the lungs by respiration and muscles on the dorsal and posterior side of the body. In critical care units there is a potential to insert an internal electrode inside the esophagus directly behind the heart in the same plane of the external electrodes. The aim of the present study is to evaluate different current stimulation and measurement patterns with both external and internal electrodes. Analysis is performed with planar arrangement of 16 electrodes for a simulated 3D cylindrical tank and pig thorax model. In our study we evaluated current injection patterns consisting of adjacent, diagonal, trigonometric, and radial to the internal electrode. The performance of these arrangements was assessed using quantitative methods based on distinguishability, sensitivity and GREIT (Graz consensus Reconstruction algorithm for Electrical Impedance Tomography). Our evaluation shows that an internal electrode configuration based on the trigonometric injection patterns has better performance and improves pixel intensity of the small conductivity changes related to heart near 1.7 times in reconstructed images and also shows more stability with different levels of added noise. For the internal electrode, when we combined radial or adjacent injection with trigonometric injection pattern, we found an improvement in amplitude response. However, the combination of diagonal with trigonometric injection pattern deteriorated the shape deformation (correlation coefficient r=0.344) more than combination of radial and trigonometric injection (correlation coefficient r=0.836) for the perturbations in the area close to the center of the cylinder. We also find that trigonometric stimulation pattern performance is degraded in a realistic thorax model with anatomical asymmetry. For that reason we recommend using internal electrodes only for voltage measurements and as a reference electrode during trigonometric stimulation patterns in practical measurements. PMID:23017828

Nasehi Tehrani, J; Oh, T I; Jin, C; Thiagalingam, A; McEwan, A

2012-11-01

87

Advantages of NiO{sub x} electrode over Au in low-voltage tetracene-based phototransistors  

SciTech Connect

We report on the tetracene-based photo-thin-film transistors (photo-TFTs) which adopt thin poly-4-vinylphenol (PVP)/aluminum oxide (AlO{sub x}) bilayer for a gate dielectric and two different source/drain (S/D) electrodes: semitransparent NiO{sub x} and Au. Our tetracene-based TFT with NiO{sub x} S/D electrode exhibited quite good field effect mobility ({mu}={approx}0.23 cm{sup 2}/V s), high on/off current ratio (I{sub on}/I{sub off}) of {approx}10{sup 5}, and good photo-to-dark current ratio (I{sub ph}/I{sub dark}={approx}10{sup 4}) under an ultraviolet (364 nm) illumination while that with Au S/D electrodes showed much lower device performance ({mu}={approx}0.08 cm{sup 2}/V s, I{sub on}/I{sub off}={approx}10{sup 4}, and I{sub ph}/I{sub dark}={approx}20), although the both TFTs operated at a low voltage of -8 V. With the hole-injection and light-reception advantages of NiO{sub x} electrode, our tetracene photo-TFT demonstrated good dynamic optical gating.

Choi, Jeong-M.; Lee, Kimoon; Hwang, D. K.; Kim, Jae Hoon; Im, Seongil; Park, Ji Hoon; Kim, Eugene [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Department of Information Display Engineering, Hongik University, Seoul 121-791 (Korea, Republic of)

2006-12-01

88

Measuring voltage and current in a DC circuit  

NSDL National Science Digital Library

These exercises target student misconceptions about how to properly measure voltage and current in simple DC circuits by letting them investigate different meter arrangements without fear of damaging equipment. These activities also are designed to lead to other investigations about simple DC circuits.

Ramlo, Susan

89

Measured Breakdown Voltage and Leakage Current of Line Worker Boots  

Microsoft Academic Search

Sixty-hertz breakdown voltage and leakage current for 48 pairs of used line worker boots were measured under dry and wet conditions. Line workers wear conventional work boots, hiking boots, or traditional lineman boots. The outer soles of work and hiking boots are predominantly a single molded piece, called a unisole; lineman boots generally have a separate heel nailed to the

T. Dan Bracken; Glenn S. Sias; Robert M. Patterson

2010-01-01

90

Primary measurement of total ultrasonic power with improved accuracy in rf voltage measurement.  

PubMed

Out of the various existing ultrasonic power measurement techniques, the radiation force balance method using microbalance is most widely used in low power (below 1 W) regime. The major source of uncertainty associated with this technique is the error in ac voltage measurement applied to the transducer for the generation of ultrasonic waves. The sources that deteriorate the ac voltage measurement accuracy include cable length and impedance mismatch. We introduce a new differential peak to peak measurement approach to reduce the ac voltage measurement error. The method holds the average peak amplitude of each polarity. Ultralow offset difference amplifier is used to measure peak to peak voltage. The method is insensitive to the variations in the dc offset of the source. The functionality of this method has been tested and compared with the conventional rf voltage measurement method. The output of this proposed technique is dc, which can be measured with an error of less than 0.1%. PMID:21034111

Dubey, P K; Kumar, Ashok; Kumar, Yudhisther; Gupta, Reeta; Joshi, Deepa

2010-10-01

91

Measurement of pseudoephedrine hydrochloride dissolution using chloride-ion electrode.  

PubMed

Experiments were performed to determine the suitability of using a chloride-ion electrode for the measurement of pseudoephedrine hydrochloride dissolution from commercially available compressed tablets. Dissolution experiments were carried out in 500 ml of distilled water using the USP paddle method at 100 rpm. Both chloride ion and pseudoephedrine (UV spectrophotometry) were measured at six different sampling times. Percent dissolved versus time values were linearized on a log-normal probability basis. The slopes of individual lines obtained from the chloride and pseudoephedrine measurements were compared using a Student t test and did not differ significantly (t = 0.415, df = 5, p greater than 0.05). In addition to providing an efficient, inexpensive, and simple method for measuring pseudoephedrine hydrochloride dissolution rates, the chloride-ion electrode could be used in the measurement of dissolution rates for a wide variety of drugs available as hydrochloride salts. PMID:7299681

Chen, S T; Thompson, R C; Poust, R I

1981-11-01

92

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

93

Effect of applied voltage, initial concentration and natural organic matter on sequential reduction/oxidation of nitrobenzene by graphite electrodes  

PubMed Central

Carbon electrodes are proposed in reactive sediment caps for in situ treatment of contaminants. The electrodes produce reducing conditions and H2 at the cathode and oxidizing conditions and O2 at the anode. Emplaced perpendicular to seepage flow, the electrodes provide the opportunity for sequential reduction and oxidation of contaminants. The objectives of this study are to demonstrate degradation of nitrobenzene (NB) as a probe compound for sequential electrochemical reduction and oxidation, and to determine the effect of applied voltage, initial concentration and natural organic matter on the degradation rate. In H-cell reactors with graphite electrodes and buffer solution, NB was reduced stoichiometrically to aniline (AN) at the cathode with nitrosobenzene (NSB) as the intermediate. AN was then removed at the anode, faster than the reduction step. No common AN oxidation intermediate was detected in the system. Both the first order reduction rate constants of NB (kNB) and NSB (kNSB) increased with applied voltage between 2V and 3.5 V (when the initial NB concentration was 100 µM, kNB=0.3 d?1 and kNSB=0.04 d?1at 2V; kNB=1.6 d?1 and kNSB=0.64 d?1at 3.5 V) but stopped increasing beyond the threshold of 3.5V. When initial NB concentration decreased from 100 to 5 µM, kNB and kNSB became 9 and 5 times faster, respectively, suggesting that competition for active sites on the electrode surface is an important factor in NB degradation. Presence of natural organic matter (in forms of either humic acid or Anacostia River sediment porewater) decreased kNB while slightly increased kNSB, but only to a limited extent (~factor of 3) for dissolved organic carbon content up to 100 mg/l. These findings suggest that electrode-based reactive sediment capping via sequential reduction/oxidation is a potentially robust and tunable technology for in situ contaminants degradation. PMID:22571797

Sun, Mei; Reible, Danny D.; Lowry, Gregory V.; Gregory, Kelvin B.

2012-01-01

94

Measurement of wire electrode temperature in WEDM  

Microsoft Academic Search

Wire temperature is an important parameter in the wire electro-discharge machining (WEDM) process because overheating of the\\u000a wire can cause the wire to break. It is difficult, however, to measure the wire temperature directly under the condition that\\u000a the wire is emerged in water and surrounded by the workpiece. Only mathematical analyses by now have been reported to determine\\u000a such

Fuzhu Han; Gang Cheng; Zhijing Feng; Isago Soichiro

2009-01-01

95

Simultaneous measurement of changes in current and tracer flux in voltage-clamped squid giant axon.  

PubMed Central

A method is described for the simultaneous measurement of changes in membrane current and unidirectional radiotracer flux in internally dialyzed voltage-clamped squid giant axons. The small currents that are produced by electrogenic transport processes or steady-state ionic currents can be resolved using this method. Because the use of grounded guard electrodes in the end pools is not, by itself, an adequate means of eliminating end-effects, two ancillary end pool clamp circuits are described to eliminate extraneous current flow from the ends of the axon. The end pool voltage-clamp circuits serve to minimize net current flow between the end pools and center pool, and employ stable, low-impedance calomel electrodes to monitor the potentials of the end and center pools. The adequacy of the method is demonstrated by experiments in which unidirectional 22Na efflux and current, flowing through tetrodotoxin (TTX)-sensitive Na channels into Na-free seawater, under K-free conditions, are shown to be equal. The equality of unidirectional TTX-sensitive flux and current is maintained over the entire range of membrane potentials examined (-60 to +20 mV). The method has been applied to a series of experiments in which the voltage dependence and stoichiometry of the Na/K pump have been measured (Rakowski et al., 1989), and can be applied in general to the simultaneous measurement of changes in current and flux of other electrogenic transport processes, and of currents through ionic channels that open under steady-state conditions. PMID:2720065

Rakowski, R F

1989-01-01

96

Unraveling the voltage fade mechanism in layer Li-Mn-rich electrode: formation of the tetrahedral cations for spinel conversion  

SciTech Connect

Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.

Mohanty, Debasish [ORNL; Li, Jianlin [ORNL; Abraham, Daniel P [Argonne National Laboratory (ANL); Huq, Ashfia [ORNL; Payzant, E Andrew [ORNL; Wood III, David L [ORNL; Daniel, Claus [ORNL

2014-01-01

97

Optically-initiated silicon carbide high voltage switch with contoured-profile electrode interfaces  

DOEpatents

An improved photoconductive switch having a SiC or other wide band gap substrate material with opposing contoured profile cavities which have a contoured profile selected from one of Rogowski, Bruce, Chang, Harrison, and Ernst profiles, and two electrodes with matching contoured-profile convex interface surfaces.

Sullivan, James S.; Hawkins, Steven A.

2012-09-04

98

Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes  

NASA Astrophysics Data System (ADS)

In this work we numerically calculate the electric current through three kinds of DNA sequences (telomeric, ?-DNA, and p53-DNA) described by different heuristic models. A bias voltage is applied between two zig-zag edged graphene contacts attached to the DNA segments, while a gate terminal modulates the conductance of the molecule. The calculation of current is performed by integrating the transmission function (calculated using the lattice Green's function) over the range of energies allowed by the chemical potentials. We show that a telomeric DNA sequence, when treated as a quantum wire in the fully coherent low-temperature regime, works as an excellent semiconductor. Clear steps are apparent in the current-voltage curves of telomeric sequences and are present independent of lengths and sequence initialisation at the contacts. The current-voltage curves suggest the existence of stepped structures independent of length and sequencing initialisation at the contacts. We also find that the molecule-electrode coupling can drastically influence the magnitude of the current. The difference between telomeric DNA and other DNA, such as ?-DNA and DNA for the tumour suppressor p53, is particularly visible in the length dependence of the current.

Paez, Carlos; Schulz, Peter; Roemer, Rudolf; Wilson, Neil

2013-03-01

99

Technical Development on Partial Discharge Measurement and Electrical Insulation Techniques for Low Voltage Motors Driven by Voltage Inverters  

Microsoft Academic Search

This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization

Hitoshi Okubo; Naoki Hayakawa; Gian Carlo Montanari

2007-01-01

100

Electrocardiogram measurement during sleep with wearing clothes using capacitively-coupled electrodes.  

PubMed

The electrocardiogram (ECG) was measured by non-contact, non-restraint and unconscious method using capacitively-coupled electrodes made of electro-conductive cloth while subjects lay on bed wearing their clothes. These electrodes are very sensitive so measure not only signals but noise. The seat grounded, which arranged under the electrode could suppress noise. Two types of electrode different in length were used, that is long type and short type. Results showed that both electrodes could sense ECG. Noise generated from e.g. commercial power source was almost the same for both electrodes though the length of electrode was longer than the subject for the long type electrode. Setting position was rather serious and noise component changed greatly by the part of body that touches the electrode. Next, ECG was measured on these condition participants lay with supine position, prone position, right lateral position and left lateral position. The ECG was measured on each condition. PMID:18002539

Ishida, Shuhei; Shiozawa, Naruhiro; Fujiwara, Yoshihisa; Makikawa, Masaaki

2007-01-01

101

Determination of the diagnostic x-ray tube practical peak voltage (PPV) from average or average peak voltage measurements.  

PubMed

The practical peak voltage (PPV) has been adopted as the reference measuring quantity for the x-ray tube voltage. However, the majority of commercial kV-meter models measure the average peak, ?(P), the average, ?, the effective, U(eff) or the maximum peak, U(P) tube voltage. This work proposed a method for determination of the PPV from measurements with a kV-meter that measures the average ? or the average peak, ?(p) voltage. The kV-meter reading can be converted to the PPV by applying appropriate calibration coefficients and conversion factors. The average peak k(PPV,kVp) and the average k(PPV,Uav) conversion factors were calculated from virtual voltage waveforms for conventional diagnostic radiology (50-150 kV) and mammography (22-35 kV) tube voltages and for voltage ripples from 0% to 100%. Regression equation and coefficients provide the appropriate conversion factors at any given tube voltage and ripple. The influence of voltage waveform irregularities, like 'spikes' and pulse amplitude variations, on the conversion factors was investigated and discussed. The proposed method and the conversion factors were tested using six commercial kV-meters at several x-ray units. The deviations between the reference and the calculated-according to the proposed method-PPV values were less than 2%. Practical aspects on the voltage ripple measurement were addressed and discussed. The proposed method provides a rigorous base to determine the PPV with kV-meters from ?(p) and ? measurement. Users can benefit, since all kV-meters, irrespective of their measuring quantity, can be used to determine the PPV, complying with the IEC standard requirements. PMID:21403184

Hourdakis, C J

2011-04-01

102

Prediction of partial discharge and breakdown voltages in CF4 for arbitrary electrode geometries  

NASA Astrophysics Data System (ADS)

In literature a model was described for the simulation of the breakdown behaviour of SF6. As input parameters, results from swarm experiments—the critical field strength and the effective ionization coefficient—and thermodynamic properties are sufficient. Recently it was shown that it is possible to transfer this model to another strongly attaching gas. In this contribution the model is applied to tetrafluoromethane (CF4), which has a smaller critical field strength and is less attaching than SF6. Furthermore, the breakdown field strengths of alternating and lightning impulse voltages of different field configurations—from homogeneous to inhomogeneous fields—are predicted for CF4. A comparison to experimental results from the literature shows good agreement. Thus, the model is applicable not only to predict partial discharges and breakdown voltages in strongly attaching gases but also to gases less attaching than SF6.

Koch, M.; Franck, C. M.

2015-02-01

103

Voltage Divider  

NSDL National Science Digital Library

This voltage divider produces an output voltage, Vo, that is proportional to the input voltage, Vs. The output voltage is measured using a voltmeter. The input voltage is the voltage of the voltage source. The constant of proportionality is called the gain of the voltage divider. The value of the gain of the voltage divider is determined by the resistances, R1 and R2, of the two resistors that comprise the voltage divider.

104

Motion Artifacts in Capacitive ECG Measurements: Reducing the Combined Effect of DC Voltages and Capacitance Changes Using an Injection Signal.  

PubMed

Capacitive electrodes are a promising alternative to the conventional adhesive electrodes for ECG measurements. They provide more comfort to the patient when integrated in everyday objects (e.g., beds or seats) for long-term monitoring. However, the application of capacitive sensors is limited by their high sensitivity to motion artifacts. For example, motion at the body-electrode interface causes variations of the coupling capacitance which, in the presence of a dc voltage across the coupling capacitor, create strong artifacts in the measurements. The origin, relevance, and reduction of this specific and important type of artifacts are studied here. An injection signal is exploited to track the variations of the coupling capacitance in real time. This information is then used by an identification scheme to estimate the artifacts and subtract them from the measurements. The method was evaluated in simulations, lab environments, and in a real-life recording on an adult's chest. For the type of artifact under study, a strong artifact reduction ranging from 40 dB for simulated data to 9 dB for a given real-life recording was achieved. The proposed method is automated, does not require any knowledge about the measurement system parameters, and provides an online estimate for the dc voltage across the coupling capacitor. PMID:25137720

Serteyn, A; Vullings, R; Meftah, M; Bergmans, J W M

2015-01-01

105

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

106

Capacitance-Voltage Measurement of Transporting Function at Cell Membrane  

NASA Astrophysics Data System (ADS)

In this paper, we report the detection of transporting function at cell membrane using capacitance-voltage (CV) measurement. The detection principle of our devices is based on the field-effect of electrostatic interaction between charged species at cell membrane in solution and surface electrons in silicon crystal through the gate insulator of Si3N4/SiO2 thin double-layer. We designed an oocyte-based field-effect capacitor, on which a Xenopus laevis oocyte was fixed. The transporter of human organic anion transporting peptide C (hOATP-C) was expressed at oocyte membrane by induction of cRNA. The electrical phenomena such as ion or molecular charge flux at the interface between cell membrane and gate surface could be detected as the change of flat band voltage in CV characteristics. The flat band voltage shift decreased with incubation time after introduction of substrate into the oocyte-based field-effect capacitor. The electrical signal is due to the change of charge flux from the oocyte at the gate surface inspired by transporter-substrate binding. The platform based on the oocyte-based field-effect capacitor is suitable for a simple and non-invasive detection system in order to analyze function of transporters related to drug efficacy.

Sakata, Toshiya; Miyahara, Yuji

107

Effect study of bridge voltage on measurement of thermal conductivities of liquids by thermal probe method  

Microsoft Academic Search

The thermal probe method can be conveniently and rapidly used to measure the thermal conductivities of liquids. But the bridge voltages chosen differently would have large effect on output electric voltage signal ?V which would directly influence the results of experiments. To obtain the best value of voltage, the effects of different bridge voltages on thermal conductivities of samples were

Min Zhang; Jiahua Lu; Jianhua Chen; Zhenhua Che; Le Yang; Zhiyou Zhong; Huizhong Zhao

2010-01-01

108

Robust signatures in the current-voltage characteristics of DNA molecules oriented between two graphene nanoribbon electrodes  

NASA Astrophysics Data System (ADS)

In this work, we numerically calculate the electric current through three kinds of DNA sequences (telomeric, ?-DNA and p53-DNA) described by different heuristic models. A bias voltage is applied between two zigzag edged graphene contacts attached to the DNA segments, while a gate terminal modulates the conductance of the molecule. Calculation of the current is performed by integrating the transmission function (calculated using the lattice Green's function) over the range of energies allowed by the chemical potentials. We show that a telomeric DNA sequence, when treated as a quantum wire in the fully coherent low-temperature regime, works as an excellent semiconductor. Clear steps are apparent in the current-voltage curves of telomeric sequences and are present independent of length and sequence initialization at the contacts. We also find that the molecule-electrode coupling can drastically influence the magnitude of the current. The difference between telomeric DNA and other DNAs, such as ?-DNA and DNA for the tumour suppressor p53, is particularly visible in the length dependence of the current.

Páez, Carlos J.; Schulz, Peter A.; Wilson, Neil R.; Römer, Rudolf A.

2012-09-01

109

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

PubMed

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

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

2014-01-01

110

Low Consistency of Four Brain Connectivity Measures Derived from Intracranial Electrode Measurements  

PubMed Central

Measures of brain connectivity are currently subject to intense scientific and clinical interest. Multiple measures are available, each with advantages and disadvantages. Here, we study epilepsy patients with intracranial electrodes, and compare four different measures of connectivity. Perhaps the most direct measure derives from intracranial electrodes; however, this is invasive and spatial coverage is incomplete. These electrodes can be actively stimulated to trigger electrophysical responses to provide the first measure of connectivity. A second measure is the recent development of simultaneous BOLD fMRI and intracranial electrode stimulation. The resulting BOLD maps form a measure of effective connectivity. A third measure uses low frequency BOLD fluctuations measured by MRI, with functional connectivity defined as the temporal correlation coefficient between their BOLD waveforms. A fourth measure is structural, derived from diffusion MRI, with connectivity defined as an integrated diffusivity measure along a connecting pathway. This method addresses the difficult requirement to measure connectivity between any two points in the brain, reflecting the relatively arbitrary location of the surgical placement of intracranial electrodes. Using a group of eight epilepsy patients with intracranial electrodes, the connectivity from one method is compared to another method using all paired data points that are in common, yielding an overall correlation coefficient. This method is performed for all six paired-comparisons between the four methods. While these show statistically significant correlations, the magnitudes of the correlation are relatively modest (r2 between 0.20 and 0.001). In summary, there are many pairs of points in the brain that correlate well using one measure yet correlate poorly using another measure. These experimental findings present a complicated picture regarding the measure or meaning of brain connectivity. PMID:25566178

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

2014-01-01

111

Measurement of Thermopower and Current-Voltage Characteristics of Molecular Junctions to Identify Orbital Alignment  

SciTech Connect

We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodes’ Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9±1.4) ?V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be ? 0.69?eV with respect to the Fermi level.

Tan, Aaron; Sadat, Seid; Reddy, Pramod

2010-01-01

112

Design of a micro-interdigitated electrode for impedance measurement performance in a biochemical assay  

E-print Network

The performance of interdigitated electrodes for impedance measurements is dependent upon the geometric design of the electrode pattern and can be significantly impacted by manufactured variability or defects. For processes ...

Donoghue, Linda (Linda Marie)

2011-01-01

113

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.

114

Laser interferometric measurement of ion electrode shape and charge exchange erosion  

NASA Technical Reports Server (NTRS)

A novel projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thruster. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid nondestructive digital data acquisition coupled with automated computer data-processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes.

Macrae, Gregory S.; Mercer, Carolyn R.

1991-01-01

115

Laser interferometric measurement of ion electrode shape and charge exchange erosion  

NASA Technical Reports Server (NTRS)

A projected fringe profilometry system was applied to surface contour measurements of an accelerator electrode from an ion thrustor. The system permitted noncontact, nondestructive evaluation of the fine and gross structure of the electrode. A 3-D surface map of a dished electrode was generated without altering the electrode surface. The same system was used to examine charge exchange erosion pits near the periphery of the electrode to determine the depth, location, and volume of material lost. This electro-optical measurement system allowed rapid, nondestructive, digital data acquisition coupled with automated computer data processing. In addition, variable sensitivity allowed both coarse and fine measurements of objects having various surface finishes.

Macrae, Gregory S.; Mercer, Carolyn R.

1991-01-01

116

Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers  

NASA Astrophysics Data System (ADS)

Single gap (gas gap = 2 mm) bakelite Resistive Plate Chamber (RPC) modules of various sizes from 10 cm × 10 cm to 1 m × 1 m have been fabricated, characterized and optimized for efficiency and time resolution. Thin layers of different grades of silicone compound are applied to the inner electrode surfaces to make them smooth and also to reduce the surface resistivity. In the silicone coated RPCs an efficiency ~ 96% and time resolution ~ 2 ns (FWHM) have been obtained for both the streamer and the avalanche modes of operation. Before fabrication of detectors the electrical properties such as bulk resistivity and surface resistivity of the electrode materials are measured carefully. Effectiveness of different silicone coating in modifying the surface resistivity was evaluated by an instrument developed for monitoring the I-V curve of a high resistive surface. The results indicate definite correlation of the detector efficiency for the atmospheric muons and the RPC noise rates with the surface resistivity and its variation with the applied bias voltage. It was also found that the surface resistivity varies for different grades of silicone material applied as coating, and the results are found to be consistent with the detector efficiency and noise rate measurements done with these RPCs.

Meghna, K. K.; Banerjee, A.; Biswas, S.; Bhattacharya, S.; Bose, S.; Chattopadhyay, S.; Das, G.; Marick, C.; Saha, S.; Viyogi, Y. P.

2012-10-01

117

Numerical electromagnetic field analysis of unit step response characteristics of impulse voltage measuring systems  

Microsoft Academic Search

Unit step response characteristics of impulse voltage measuring systems are studied with the help of numerical electromagnetics code (NEC-2). Prior to this analysis, the accuracy of a transient analysis by this method is investigated for a simple structure. An impulse voltage measuring system, under application of step voltage, behaves like an antenna until a traveling wave makes several roundtrips in

Yoshihiro Baba; Masaru Ishii

2004-01-01

118

Measuring Vitamin C Content of Commercial Orange Juice Using a Pencil Lead Electrode  

ERIC Educational Resources Information Center

A pencil lead successfully served as an electrode for the determination of ascorbic acid in commercial orange juice. Cyclic voltammetry was used as an electrochemical probe to measure the current produced from the oxidation of ascorbic acid with a variety of electrodes. The data demonstrate that the less expensive pencil lead electrode gives…

King, David; Friend, Jeffrey; Kariuki, James

2010-01-01

119

Nonlinear Impedance of Whole Cells Near an Electrode as a Probe of Mitochondrial Activity  

PubMed Central

By simultaneously measuring the bulk media and electrode interface voltages of a yeast (Saccharomyces cerevisiae) suspension subjected to an AC voltage, a yeast-dependent nonlinear response was found only near the current injection electrodes. Computer simulation of yeast near a current injection electrode found an enhanced voltage drop across the yeast near the electrode due to slowed charging of the electrode interfacial capacitance. This voltage drop is sufficient to induce conformation change in membrane proteins. Disruption of the mitochondrial electron transport chain is found to significantly change the measured nonlinear current response, suggesting nonlinear impedance can be used as a non-invasive probe of cellular metabolic activity.

Palanisami, Akilan; Mercier, George T.; Fang, Jie; Miller, John H.

2011-01-01

120

Ionization detector, electrode configuration and single polarity charge detection method  

DOEpatents

An ionization detector, an electrode configuration and a single polarity charge detection method each utilize a boundary electrode which symmetrically surrounds first and second central interlaced and symmetrical electrodes. All of the electrodes are held at a voltage potential of a first polarity type. The first central electrode is held at a higher potential than the second central or boundary electrodes. By forming the first and second central electrodes in a substantially interlaced and symmetrical pattern and forming the boundary electrode symmetrically about the first and second central electrodes, signals generated by charge carriers are substantially of equal strength with respect to both of the central electrodes. The only significant difference in measured signal strength occurs when the charge carriers move to within close proximity of the first central electrode and are received at the first central electrode. The measured signals are then subtracted and compared to quantitatively measure the magnitude of the charge.

He, Zhong (Ann Arbor, MI)

1998-01-01

121

Ionization detector, electrode configuration and single polarity charge detection method  

DOEpatents

An ionization detector, an electrode configuration and a single polarity charge detection method each utilize a boundary electrode which symmetrically surrounds first and second central interlaced and symmetrical electrodes. All of the electrodes are held at a voltage potential of a first polarity type. The first central electrode is held at a higher potential than the second central or boundary electrodes. By forming the first and second central electrodes in a substantially interlaced and symmetrical pattern and forming the boundary electrode symmetrically about the first and second central electrodes, signals generated by charge carriers are substantially of equal strength with respect to both of the central electrodes. The only significant difference in measured signal strength occurs when the charge carriers move to within close proximity of the first central electrode and are received at the first central electrode. The measured signals are then subtracted and compared to quantitatively measure the magnitude of the charge. 10 figs.

He, Z.

1998-07-07

122

System for improving measurement accuracy of transducer by measuring transducer temperature and resistance change using thermoelectric voltages  

NASA Technical Reports Server (NTRS)

A constant current loop measuring system measures a property including the temperature of a sensor responsive to an external condition being measured. The measuring system includes thermocouple conductors connected to the sensor, sensing first and second induced voltages responsive to the external condition. In addition, the measuring system includes a current generator and reverser generating a constant current, and supplying the constant current to the thermocouple conductors in forward and reverse directions generating first and second measured voltages, and a determining unit receiving the first and second measured voltages from the current generator and reverser, and determining the temperature of the sensor responsive to the first and second measured voltages.

Anderson, Karl F. (inventor); Parker, Allen R., Jr. (inventor)

1993-01-01

123

Membrane reference electrode  

DOEpatents

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

Redey, L.; Bloom, I.D.

1988-01-21

124

Membrane reference electrode  

DOEpatents

A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured with high spatial resolution.

Redey, Laszlo (Downers Grove, IL); Bloom, Ira D. (Bolingbrook, IL)

1989-01-01

125

Reliability study of micromechanical actuators for electrostatic RMS voltage measurements using bulk-silicon technology  

Microsoft Academic Search

Micro-electromechanical sensors have been developed for high-frequency voltage metrology applications. They should ultimately allow RF to DC voltage transfer. The conventional measurement principle is based on RF power dissipation by ohmic resistances allowing RMS voltage conversion by the square power law. The principle of electrostatic force, which has already been demonstrated to work from DC to gigahertz frequencies, is a

Jan Dittmer; Rolf Judaschke; Stephanus Büttgenbach

2009-01-01

126

Plane multiwire-electrode ionization chamber for measurements of radon concentration in air  

Microsoft Academic Search

A continuous measuring system has been developed, which uses a plane multiwire-electrode ionization chamber and obtains radon concentrations by measuring insitu alpha energy spectra due to alpha-active nuclei in the air. The chamber has three rigid plane multiwire electrodes in a box of aluminum plates which have holes for the air to flow freely through them. The concentration measurements do

Akira Katase; Yuzuru Matsumoto; Yasunori Nagao; Takeji Sakae; Kenichi Tanabe; Kenji Ishibashi

1986-01-01

127

Measurement of the direct-current (Faradic) resistance of the electrode-electrolyte interface for commonly used electrode materials.  

PubMed

The direct-current (Faradic) resistance is important because it is the highest impedance that an electrode-electrolyte interface can attain. In this study, the Faradic resistance (Rf) of identical pairs of 0.5 cm2 electrodes of bare and chlorided silver, tin and chlorided tin, nickel-silver, copper, and carbon was measured in contact with 0.9% saline at room temperature. It was found that for positive and negative current flow, the data fit the expression Rf=Rf0 e(-alpha i) (with a high coefficient of determination), where Rf0 is the zero-current Faradic resistance and alpha is a constant that describes the manner in which Rf decreases with increasing current (i). It was found that chlorided silver exhibited the lowest Rf0; removing the chloride deposit increased Rf0 by more than sixfold. Likewise, chloriding tin reduced Rf0 by a factor of about 2. Electrolytically cleaning an electrode reduced Rf0. The highest value for Rf0 was for carbon. This paper concludes with a summary of the data for Rf0 scaled to 1 cm2 electrode area for the electrode materials measured in the present study and data from the published literature. PMID:11284673

Geddes, L A; Roeder, R

2001-02-01

128

Origin of Different Dependences of Open-Circuit Voltage on the Electrodes in Layered and Bulk Heterojunction Organic Photovoltaic Cells  

Microsoft Academic Search

Experimental results show that the V OC of layered heterojunction (HJ) organic photovoltaic (PV) cells behaves with a very weak dependence on the electrodes. However, the V OC of bulk HJ PV cells behaves with a strong dependence on the electrodes. In this paper, an explanation for the different behaviors of V OC on the electrodes is proposed. It is

Chunfu Zhang; Shi-Wun Tong; Chang-Yun Jiang; En-Tang Kang; Daniel S. H. Chan; Chunxiang Zhu

2010-01-01

129

The use of virtual ground to control transmembrane voltages and measure bilayer currents in serial arrays of droplet interface bilayers  

NASA Astrophysics Data System (ADS)

The droplet interface bilayer (DIB) is a simple technique for constructing a stable lipid bilayer at the interface of two lipid-encased water droplets submerged in oil. Networks of DIBs formed by connecting more than two droplets constitute a new form of modular biomolecular smart material, where the transduction properties of a single lipid bilayer can affect the actions performed at other interface bilayers in the network via diffusion through the aqueous environments of shared droplet connections. The passive electrical properties of a lipid bilayer and the arrangement of droplets that determine the paths for transport in the network require specific electrical control to stimulate and interrogate each bilayer. Here, we explore the use of virtual ground for electrodes inserted into specific droplets in the network and employ a multichannel patch clamp amplifier to characterize bilayer formation and ion-channel activity in a serial DIB array. Analysis of serial connections of DIBs is discussed to understand how assigning electrode connections to the measurement device can be used to measure activity across all lipid membranes within a network. Serial arrays of DIBs are assembled using the regulated attachment method within a multi-compartment flexible substrate, and wire-type electrodes inserted into each droplet compartment of the substrate enable the application of voltage and measurement of current in each droplet in the array.

Sarles, Stephen A.

2013-09-01

130

Single cell measurement of dopamine release with simultaneous voltage-clamp and amperometry.  

PubMed

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets(1). The dopamine signal is terminated by diffusion(2-3), extracellular enzymes(4), and membrane transporters(5). The dopamine transporter, located in the peri-synaptic cleft of dopamine neurons clears the released amines through an inward dopamine flux (uptake). The dopamine transporter can also work in reverse direction to release amines from inside to outside in a process called outward transport or efflux of dopamine(5). More than 20 years ago Sulzer et al. reported the dopamine transporter can operate in two modes of activity: forward (uptake) and reverse (efflux)(5). The neurotransmitter released via efflux through the transporter can move a large amount of dopamine to the extracellular space, and has been shown to play a major regulatory role in extracellular dopamine homeostasis(6). Here we describe how simultaneous patch clamp and amperometry recording can be used to measure released dopamine via the efflux mechanism with millisecond time resolution when the membrane potential is controlled. For this, whole-cell current and oxidative (amperometric) signals are measured simultaneously using an Axopatch 200B amplifier (Molecular Devices, with a low-pass Bessel filter set at 1,000 Hz for whole-cell current recording). For amperometry recording a carbon fiber electrode is connected to a second amplifier (Axopatch 200B) and is placed adjacent to the plasma membrane and held at +700 mV. The whole-cell and oxidative (amperometric) currents can be recorded and the current-voltage relationship can be generated using a voltage step protocol. Unlike the usual amperometric calibration, which requires conversion to concentration, the current is reported directly without considering the effective volume(7). Thus, the resulting data represent a lower limit to dopamine efflux because some transmitter is lost to the bulk solution. PMID:23207721

Saha, Kaustuv; Swant, Jarod; Khoshbouei, Habibeh

2012-01-01

131

Single Cell Measurement of Dopamine Release with Simultaneous Voltage-clamp and Amperometry  

PubMed Central

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is terminated by diffusion2-3, extracellular enzymes4, and membrane transporters5. The dopamine transporter, located in the peri-synaptic cleft of dopamine neurons clears the released amines through an inward dopamine flux (uptake). The dopamine transporter can also work in reverse direction to release amines from inside to outside in a process called outward transport or efflux of dopamine5. More than 20 years ago Sulzer et al. reported the dopamine transporter can operate in two modes of activity: forward (uptake) and reverse (efflux)5. The neurotransmitter released via efflux through the transporter can move a large amount of dopamine to the extracellular space, and has been shown to play a major regulatory role in extracellular dopamine homeostasis6. Here we describe how simultaneous patch clamp and amperometry recording can be used to measure released dopamine via the efflux mechanism with millisecond time resolution when the membrane potential is controlled. For this, whole-cell current and oxidative (amperometric) signals are measured simultaneously using an Axopatch 200B amplifier (Molecular Devices, with a low-pass Bessel filter set at 1,000 Hz for whole-cell current recording). For amperometry recording a carbon fiber electrode is connected to a second amplifier (Axopatch 200B) and is placed adjacent to the plasma membrane and held at +700 mV. The whole-cell and oxidative (amperometric) currents can be recorded and the current-voltage relationship can be generated using a voltage step protocol. Unlike the usual amperometric calibration, which requires conversion to concentration, the current is reported directly without considering the effective volume7. Thus, the resulting data represent a lower limit to dopamine efflux because some transmitter is lost to the bulk solution. PMID:23207721

Saha, Kaustuv; Swant, Jarod; Khoshbouei, Habibeh

2012-01-01

132

Finite element modeling of electrode-skin contact impedance in electrical impedance tomography  

Microsoft Academic Search

In electrical impedance tomography (EIT), the measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through it are both high. Large electrodes were used to provide a more uniform current distribution and reduce the contact impedance. A large electrode differs from a point electrode in that it has shunting and edge effects that

Ping Hua; E. J. Woo; J. G. Webster; W. J. Tompkins

1993-01-01

133

Electrochemical measurements on lightweight composite nickel-graphite battery electrodes  

Microsoft Academic Search

Lightweight batteries are being developed using a composite material of graphite mat fibers and nickel metal. Electrochemical\\u000a properties of the composite indicates that the composite electrode is superior to sintered carbonyl-nickel powder electrodes\\u000a in nickel-cadmium cells. Nickel-cadmium cells in which the nickel plate was replaced with the composite plate show that the\\u000a watt-h\\/kg obtained from the composite plate was 47

R. A. Sutula; C. R. Crowe

1980-01-01

134

3D visualization of subdural electrode shift as measured at craniotomy reopening  

PubMed Central

Summary Purpose Subdural electrodes are implanted for recording intracranial EEG (iEEG) in cases of medically refractory epilepsy as a means to locate cortical regions of seizure onset amenable to surgical resection. Without the aid of imaging-derived 3D electrode models for surgical planning, surgeons have relied on electrodes remaining stationary from the time between placement and follow-up resection. This study quantifies electrode shift with respect to the cortical surface occurring between electrode placement and subsequent reopening. Methods CT and structural MRI data were gathered following electrode placement on 10 patients undergoing surgical epilepsy treatment. MRI data were used to create patient specific post-grid 3D reconstructions of cortex, while CT data were co-registered to the MRI and thresholded to reveal electrodes only. At the time of resective surgery, the craniotomy was reopened and electrode positions were determined using intraoperative navigational equipment. Changes in position were then calculated between CT coordinates and intraoperative electrode coordinates. Results Five out of ten patients showed statistically significant overall magnitude differences in electrode positions (mean: 7.2 mm), while 4 exhibited significant decompression based shift (mean: 4.7 mm), and 3 showed significant shear displacement along the surface of the brain (mean: 7.1 mm). Discussion Shift in electrode position with respect to the cortical surface has never been precisely measured. We show that in 50% of our cases statistically significant shift occurred. These observations demonstrate the potential utility of complimenting electrode position measures at the reopening of the craniotomy with 3D electrode and brain surface models derived from post-implantation CT and MR imaging for better definition of surgical boundaries. PMID:21334178

LaViolette, Peter S.; Rand, Scott D.; Ellingson, Benjamin M.; Raghavan, Manoj; Lewd, Sean M.; Schmaindaa, Kathleen M.; Muellerd, Wade

2015-01-01

135

Measuring surfactant concentration in plating solutions  

DOEpatents

An arrangement for measuring the concentration of surfactants in a electrolyte containing metal ions includes applying a DC bias voltage and a modulated voltage to a counter electrode. The phase angle between the modulated voltage and the current response to the modulated voltage at a working electrode is correlated to the surfactant concentration.

Bonivert, William D. (Livermore, CA); Farmer, Joseph C. (Livermore, CA); Hachman, John T. (Stockton, CA)

1989-01-01

136

Module Four: Measuring Current and Voltage in Series Circuits; Basic Electricity and Electronics Individualized Learning System.  

ERIC Educational Resources Information Center

The module covers the characteristics of series circuits, how to use the multimeter as an ammeter and voltmeter, and how to make current and voltage measurements in series circuits. This module is divided into three lessons: measuring current in a series circuit, voltage in a series circuit, and using the multimeter as a voltmeter. Each lesson…

Bureau of Naval Personnel, Washington, DC.

137

Microwave and Light-Wave Measurements for Nematic-Liquid-Crystal-Loaded Phase Shifter Using Coplanar Waveguide with Floating Electrode  

NASA Astrophysics Data System (ADS)

We fabricated an experimental liquid-crystal-loaded coplanar waveguide with a floating electrode (CPW-FE) phase shifter with a straight-line structure and investigated its response time and phase characteristics by performing microwave measurements while varying structural parameters. We also constructed a liquid crystal optical cell using indium-tin-oxide (ITO) glass to simulate the CPW-FE structure and obtained measurements by capturing moving pictures using a polarized microscope. By comparing successive frames of this video and measuring response times to a steady state, we examined the behavior of liquid crystal molecules upon the application of a voltage to the liquid crystal layer. These observations enabled a qualitative physical interpretation of the results obtained by the above microwave measurements.

Kamei, Toshihisa; Moritake, Hiroshi; Utsumi, Yozo

2010-01-01

138

Novel active comb-shaped dry electrode for EEG measurement in hairy site.  

PubMed

Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode. PMID:25137719

Huang, Yan-Jun; Wu, Chung-Yu; Wong, Alice May-Kuen; Lin, Bor-Shyh

2015-01-01

139

A Cylindrical Capacitance Sensor with Three Electrodes for Liquid-Level Measurement in Two Different Conditions  

Microsoft Academic Search

In this paper, a practical sensing approach for monitoring the liquid-level in a container is presented. In this research we have developed a new structure sensor with three electrodes. When the container becomes inclined from vertical condition during measuring process, the liquid-level in the liquid container is determined correctly by detecting the change in capacitance between every two electrodes. In

Guirong Lu; Katsunori Shida

2004-01-01

140

Comparison of dry-textile electrodes for electrical bioimpedance spectroscopy measurements  

NASA Astrophysics Data System (ADS)

Textile Electrodes have been widely studied for biopotentials recordings, specially for monitoring the cardiac activity. Commercially available applications, such as Adistar T-shirt and Textronics Cardioshirt, have proved a good performance for heart rate monitoring and are available worldwide. Textile technology can also be used for Electrical Bioimpedance Spectroscopy measurements enabling home and personalized health monitoring applications however solid ground research about the measurement performance of the electrodes must be done prior to the development of any textile-enabled EBI application. In this work a comparison of the measurement performance of two different types of dry-textile electrodes and manufacturers has been performed against standardized RedDot 3M Ag/AgCl electrolytic electrodes. 4-Electrode, whole body, Ankle-to-Wrist EBI measurements have been taken with the Impedimed spectrometer SFB7 from healthy subjects in the frequency range of 3kHz to 500kHz. Measurements have been taken with dry electrodes at different times to study the influence of the interaction skin-electrode interface on the EBI measurements. The analysis of the obtained complex EBI spectra shows that the measurements performed with textile electrodes produce constant and reliable EBI spectra. Certain deviation can be observed at higher frequencies and the measurements obtained with Textronics and Ag/AgCl electrodes present a better resemblance. Textile technology, if successfully integrated it, may enable the performance of EBI measurements in new scenarios allowing the rising of novel wearable monitoring applications for home and personal care as well as car safety.

Márquez, J. C.; Seoane, F.; Välimäki, E.; Lindecrantz, K.

2010-04-01

141

Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps  

SciTech Connect

The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1??m and 100??m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100??m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.

Klas, M.; Matej?ik, Š. [Department of Experimental Physics, Comenius University, Mlynskadolina F2, 84248 Bratislava (Slovakia); Radjenovi?, B.; Radmilovi?-Radjenovi?, M. [Institute of Physics, University of Belgrade, P.O. Box 57, 11080 Belgrade (Serbia)

2014-10-15

142

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

SciTech Connect

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18?×?15?×?15?cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Liu, Lun; Liu, Minghai [State Key Laboratory of AEET, School of Electric and Electronic Engineering, HuaZhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-10-15

143

Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses  

NASA Astrophysics Data System (ADS)

This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

2014-10-01

144

Convenient Fabrication of Fine Electrodes for Electric Measurement of Nanofibers by Nanoimprint Lithography  

NASA Astrophysics Data System (ADS)

We fabricated fine electrodes conventionally by nanoimprint lithography (NIL) to measure the electric properties of nanofibers and showed the performance of fine electrodes by the field-effect transistor (FET) measurement of a semiconducting polymer nanofiber. Furthermore, we performed the FET measurement of regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT) nanofibers using fabricated fine electrodes. As a result, the mobility was estimated to be 1.32×10-3 cm2 V-1 s-1, which was on the same order as that reported previously. The fabrication method was clarified to be effective for molecular electronics.

Iwai, Hisanao; Yoshida, Ken-ich; Heike, Seiji; Hashizume, Tomihiro; Shimomura, Takeshi

2012-03-01

145

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

146

Quantitative Evaluation of Voltage-Induced Magnetic Anisotropy Change by Magnetoresistance Measurement  

NASA Astrophysics Data System (ADS)

We investigated the voltage-induced perpendicular magnetic anisotropy change in an epitaxial magnetic tunnel junction (MTJ) with an ultrathin FeCo layer. Tunneling magnetoresistance (TMR) curves were measured under various bias voltage applications for different FeCo thicknesses. Clear changes in the shape of TMR curves were observed depending on the voltage-controlled perpendicular magnetic anisotropy. By evaluating the relative angle of two ferromagnetic layers, we could estimate the anisotropy energy change quantitatively. The realization of voltage-induced anisotropy change in the MTJ structure makes it possible to control the magnetization dynamics, leading to a new area of electric-field-based spintronics devices.

Shiota, Yoichi; Murakami, Shinichi; Bonell, Frédéric; Nozaki, Takayuki; Shinjo, Teruya; Suzuki, Yoshishige

2011-04-01

147

Time-resolved voltage measurements of Z-pinch radiation sources with a vacuum voltmeter  

SciTech Connect

A vacuum-voltmeter (VVM) was fielded on the Saturn pulsed power generator during a series of argon gas-puff Z-pinch shots. Time-resolved voltage and separately measured load current are used to determine several dynamic properties as the load implodes, namely, the inductance, L(t), net energy coupled to the load, E{sub coupled}(t), and the load radius, r(t). The VVM is a two-stage voltage divider, designed to operate at voltages up to 2 MV. The VVM is presently being modified to operate at voltages up to 6 MV for eventual use on the Z generator.

Murphy, D. P.; Allen, R. J.; Weber, B. V.; Commisso, R. J.; Apruzese, J. P. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Code 6770 Washington, DC 20375 (United States); Phipps, D. G.; Mosher, D. [L3 Communications/Titan Group, Reston, Virginia 20910 (United States)

2008-10-15

148

Measurement of bias voltage dependence of local barrier height at constant tip-sample separation  

Microsoft Academic Search

We measured the bias voltage dependence of the apparent local barrier height (LBH) by STM on an Au (111) surface with an Au tip. The results under two different conditions, a constant tip-sample separation and a constant current, were compared in the low bias voltage range (?30 to ?5 mV). Under constant separation, the LBH does not change with the

Shinjiro Yagyu; Michiko Yoshitake

2003-01-01

149

Electrode-Skin contact impedance: In vivo measurements on an ovine model  

NASA Astrophysics Data System (ADS)

The problem of electrical impedance between the skin and the electrode is an on-going challenge in bio-electronics. This is particularly true in the case of Electrical Impedance Tomography (EIT), which uses a large number of skin-contact electrodes and is very sensitive to noise. In the present article, contact impedance is measured and compared for a range of electrodes placed on the thorax of an ovine model. The study has been approved by the Westmead Hospital Animal Ethics Committee. The electrode models that were employed in the research are Ag/AgCl electrodes (E1), commonly used for ECG and EIT measurements in both humans and animal models, stainless steel crocodile clips (E2), typically used on animal models, and novel multi-point dry electrodes in two modifications: bronze plated (E3) and nickel plated (E4). Further, since the contact impedance is mostly attributed to the acellular outer layer of the skin, in our experiment, we attempted to study the effect of this layer by comparing the results when the skin is intact and when electrodes are introduced underneath the skin through small cuts. This boundary effect was assessed by comparison of measurements obtained during E2 skin surface contact, and sub-cutaneous contact (E5). Twelve gauge intradermal needles were also tested as an electrode (E6). The full impedance spectrum, from 500 Hz to 300 kHz, was recorded, analysed and compared. As expected, the contact impedance in the more invasive cases, i.e the electrodes under the skin, is significantly lower than in the non-invasive cases. At the frequency of 50 kHz which is commonly used in lung EIT acquisition, electrodes E3, E4 and E6 demonstrated contact impedance of less than 200 ?, compared to more than 400 ? measured for electrodes E1, E2 and E5. In conclusion, the novel multipoint electrodes proved to be best suited for EIT purposes, because they are non-invasive and have lower contact impedance than Ag/AgCl and crocodile clips, in both invasive and non-invasive cases. This further prompted us to design a flexible electrode belt using the novel multi-point electrodes for lung EIT on animal models.

Nguyen, D. T.; Kosobrodov, R.; Barry, M. A.; Chik, W.; Jin, C.; Oh, T. I.; Thiagalingam, A.; McEwan, A.

2013-04-01

150

A new measurement method for electrode gain in an orthogonally symmetric beam position monitor  

NASA Astrophysics Data System (ADS)

The new beam position monitor (BPM) system of the injector at the upgrade project of the Hefei Light Source (HLS II) has 19 stripline beam position monitors. Most consist of four orthogonally symmetric stripline electrodes. Differences in electronic gain and mismachining tolerance can cause changes in the beam response of the BPM electrodes. This variation will couple the two measured horizontal positions, resulting in measuring error. To alleviate this effect, a new technique to measure the relative response of the four electrodes has been developed. It is independent of the beam charge, and the related coefficient can be calculated theoretically. The effect of electrode coupling on this technique is analyzed. The calibration data is used to fit the gain for all 19 injector beam position monitors. The results show the standard deviation of the distribution of measured gains is about 5%.

Zou, Jun-Ying; Wu, Fang-Fang; Yang, Yong-Liang; Sun, Bao-Gen; Zhou, Ze-Ran; Luo, Qing; Lu, Ping; Xu, Hong-Liang

2014-12-01

151

Stark broadening measurement of the electron density in an atmospheric pressure argon plasma jet with double-power electrodes  

SciTech Connect

Characteristics of a double-power electrode dielectric barrier discharge of an argon plasma jet generated at the atmospheric pressure are investigated in this paper. Time-averaged optical emission spectroscopy is used to measure the plasma parameters, of which the excitation electron temperature is determined by the Boltzmann's plot method whereas the gas temperature is estimated using a fiber thermometer. Furthermore, the Stark broadening of the hydrogen Balmer H{sub {beta}} line is applied to measure the electron density, and the simultaneous presence of comparable Doppler, van der Waals, and instrumental broadenings is discussed. Besides, properties of the jet discharge are also studied by electrical diagnosis. It has been found that the electron densities in this argon plasma jet are on the order of 10{sup 14} cm{sup -3}, and the excitation temperature, gas temperature, and electron density increase with the applied voltage. On the other hand, these parameters are inversely proportional to the argon gas flow rate.

Qian Muyang; Ren Chunsheng; Wang Dezhen; Zhang Jialiang; Wei Guodong [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2010-03-15

152

Measuring quaternary ammonium cleaning agents with ion selective electrodes  

Microsoft Academic Search

Data for coated-wire, ion selective electrodes (ISEs) are presented for cationic surfactant ions found in common cleaners including benzyldimethyltetradecylammonium, benzyldimethyldodecylammonium, and benzyldimethylhexadecylammonium. The ion exchangers dinonylnaphthalene sulfonic acid, tetraphenyborate, and tetrakis(4-chlorophenyl)borate are examined, showing dinonylnaphthalene sulfonic acid to be the favored species. The ISEs exhibit approximately Nernstian behavior down to the 10?6M limit of detection with lifetimes in excess of

Michael A. Plesha; Bernard J. Van Wie; James M. Mullin; David A. Kidwell

2006-01-01

153

Evaluating the reliability and sensitivity of the Kerr electro-optic field mapping measurements with high-voltage pulsed transformer oil  

NASA Astrophysics Data System (ADS)

Transformer oil is the most widely used dielectric liquid for high voltage insulation. Measurements of the electric field distribution in high voltage pulsed transformer oil are of both practical and theoretical interests. Due to its low Kerr constant, previous electro-optic measurements with transformer oil rely on a technique called ac modulation, which works only for dc steady-state electric field mapping. With the help of a high-sensitivity charge-coupled device, we directly measure the Kerr electro-optic effect between parallel electrodes in transformer oil stressed by high voltage pulses. This work aims at demonstrating the reliability and evaluating the sensitivity of the measurements for three cases with identical electrodes: space-charge free, uniform electric field in the mid-region of the gap; space-charge free, non-uniform fringing electric field; and space charge distorted electric field in the mid-region of the gap. Future directions to improve accuracy by identifying and handling various sources of error and noise are suggested.

Zhang, X.; Nowocin, J. K.; Zahn, M.

2013-08-01

154

Improvement of a proposed model for heat conduction in an electrode submitted to an electric discharge: Application to the indirect determination of the anodic and cathodic voltage drops  

NASA Astrophysics Data System (ADS)

We present an improved version of a heat-conduction model which leads to better-computed values of the anodic voltage drops for electric discharges in a liquid dielectric, with a short interelectrode gap (about 50 ?m) and short duration (10-1000 ?s). The results obtained show monotonic variations according to the duration of the discharge and peak current, and correspond to the measured value of the total interelectrode voltage drop.

Benzerga, L.; Lhiaubet, C.; Meyer, R. M.

1985-07-01

155

Cavitation in the vicinity of the high-voltage electrode as a key step of nanosecond breakdown in liquids  

NASA Astrophysics Data System (ADS)

Fast shadowgraphy of nanosecond discharge in liquids with different dielectric permittivity, namely in water, ethanol and n-pentane, has been performed. Formation of a gas cavity at a nanosecond time scale was observed as a pre-breakdown phenomenon at amplitudes of the high-voltage pulse close to the breakdown threshold. This phenomenon is considered as a possible key step of high-voltage breakdown in polar liquids.

Marinov, I.; Guaitella, O.; Rousseau, A.; Starikovskaia, S. M.

2013-08-01

156

Direct extraction of carrier mobility in graphene field-effect transistor using current-voltage and capacitance-voltage measurements  

NASA Astrophysics Data System (ADS)

Top gated graphene field-effect transistors were fabricated using yttrium oxide film as high-? gate dielectric, and the gate voltage dependent drain current and gate capacitance characteristics were both measured on one graphene device. Based on the two kinds of data sets, we developed a method to extract the carrier mobility of graphene field-effect transistors, along with some other parameters, such as series resistance and residual carrier density. Prior to previous method, this method could well fit the transfer curve of graphene field-effect transistor with high gate oxide capacitance since its carrier concentration is directly obtained from the experimental data rather than from analytic equation.

Zhang, Zhiyong; Xu, Huilong; Zhong, Hua; Peng, Lian-Mao

2012-11-01

157

A measurement of the gate-emitter voltage waveform of IGBT in a motor driver circuit  

Microsoft Academic Search

A fiber optic isolation system is introduced for the measurement of active gate-emitter voltage waveform of IGBT(Insulated Gate Bipolar Transistor) in a motor driver circuit. The system is designed for this kind of floating measurement which requires large common-mode rejection ratio(CMRR) at high frequency and common-mode slew-rate(dV\\/dt). The required performance is analysed by the convolution of the emitter voltage waveform

A. Nara

1994-01-01

158

Method of glass melter electrode length measurement using time domain reflectometry (TDR)  

SciTech Connect

The present invention overcomes the drawbacks inherent in the prior art and solves the problems inherent in conventional Joule-heated vitrification melters, where the melter preferably comprises a vessel having a refractory liner and an opening for receiving material which is converted into molten vitreous material in the vessel. The vessel has an outlet port for removing molten vitreous material from the vessel. A plurality of electrodes is disposed in the vessel and electrical energy is passed between electrode pairs through feed material and molten vitreous material in the vessel. Typically, the electrodes erode and wear in time, and this invention seeks to monitor and evaluate the length and condition of the electrodes. The present invention uses time domain reflectometry (TDR) methods to accurately measure the length of an electrode that is subject to wear and electrolytic decomposition due to the extreme conditions in which the electrode is required to operate. Specifically, TDR would be used to measure the length and effects of erosion of molybdenum electrodes used in Joule-heated vitrification melter. Of course, the inventive concept should not be limited to this preferred environment.

Tarpley, James M.; Zamecnik, John R.

2000-02-28

159

Potentiometric measurement of polymer-membrane electrodes based on lanthanum  

SciTech Connect

Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm{sup ?1}, 1031 cm{sup ?1} and 794.7 cm{sup ?1} for P=O stretching and stretching POC from group ?OP =O. The result showed shift wave number for P =O stretching of the cluster (?OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm{sup ?1} indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R{sub 3}P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10{sup ?3} M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10{sup ?5} and 10{sup ?1} M.

Saefurohman, Asep, E-mail: saefurohman.asep78@Gmail.com; Buchari,, E-mail: saefurohman.asep78@Gmail.com; Noviandri, Indra, E-mail: saefurohman.asep78@Gmail.com [Department of Chemistry, Bandung Institute of Technology (Indonesia); Syoni [Department of Metallurgy Engineering, Bandung Institute of Technology (Indonesia)

2014-03-24

160

Selection of the Optimum Electrospray Voltage for Gradient Elution LC-MS Measurements  

PubMed Central

Changes in liquid composition during gradient elution liquid chromatography (LC) coupled to mass spectrometry (MS) analyses affect the electrospray operation. To establish methodologies for judicious selection of the electrospray voltage, we monitored in real-time the effect of the LC gradient on the spray current. The optimum range of the electrospray voltage decreased as the concentration of organic solvent in the eluent increased during reversed-phase LC analyses. These results provided the means to rationally select the voltage so as to ensure effective electrospray operation throughout gradient-elution LC separations. For analyses in which the electrospray was operated at constant voltage, a small run-to-run variation in the spray current was observed, indicating a changing electric field due to fouling or degradation of the emitter. Algorithms using feedback from spray current measurements to maintain the electrospray voltage within the optimum operating range throughout gradient elution LC-MS were evaluated. The electrospray operation with voltage regulation and at a constant, judiciously selected voltage during gradient elution LC-MS measurements produced data with similar reproducibility. SYNOPSIS Electrospray current measurements during gradient elution liquid chromatography analyses provide reliable feedback for monitoring, understanding, and improving performance. PMID:19196520

Marginean, Ioan; Kelly, Ryan T.; Moore, Ronald J.; Prior, David C.; LaMarche, Brian L.; Tang, Keqi; Smith, Richard D.

2009-01-01

161

Improvement of Electrical Stimulation Protocol for Simultaneous Measurement of Extracellular Potential with On-Chip Multi-Electrode Array System  

NASA Astrophysics Data System (ADS)

Cardiotoxicity testing with a multi-electrode array (MEA) system requires the stable beating of cardiomyocytes for the measurement of the field potential duration (FPD), because different spontaneous beating rates cause different responses of FPD prolongation induced by drugs, and the beating rate change effected by drugs complicates the FPD prolongation assessment. We have developed an on-chip MEA system with electrical stimulation for the measurement of the FPD during the stable beating of human embryonic stem (ES) cell-derived cardiomyocyte clusters. Using a conventional bipolar stimulation protocol, we observed such large artifacts in electrical stimulation that we could not estimate the FPD quantitatively. Therefore, we improved the stimulation protocol by using sequential rectangular pulses in which the positive and negative stimulation voltages and number of pulses could be changed flexibly. The balanced voltages and number of pulses for sequential rectangular pulses enabled the recording of small negative artifacts only, which hardly affected the FPD measurement of human-ES-cell-derived cardiomyocyte clusters. These conditions of electrical stimulation are expected to find applications for the control of constant beating for cardiotoxicity testing.

Kaneko, Tomoyuki; Nomura, Fumimasa; Hattori, Akihiro; Yasuda, Kenji

2012-06-01

162

Glass and polymeric membrane electrodes for the measurement of pH in milk and cheese  

Microsoft Academic Search

While there is a considerable interest in the food industry in determining various analytes using ion-selective electrodes (ISEs), only few reports describe their use for direct measurements in food. In this study, the suitability of glass electrodes and ionophore-based solvent polymeric ISEs for the determination of pH in Process cheese, Cheddar cheese and milk was investigated. The liquid junction potential

Praveen Upreti; Lloyd E. Metzger; Philippe Bühlmann

2004-01-01

163

Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO2/Ti Electrode as Catalyst  

NASA Astrophysics Data System (ADS)

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) system is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO2 coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10-4 mol · L-1 · min-1, the oxidation rate using TiO2/Ti electrode prepared by annealing at 500°C in air is 4.5×10-4 mol · L-1 · min-1, an increase with a factor 2.25. The annealing temperature for preparing TiO2/Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO2 photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.

Gong, Jianying; Zhang, Xingwang; Wang, Xiaoping; Lei, Lecheng

2013-12-01

164

Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators  

DOEpatents

A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Kirbie, Hugh C. (Dublin, CA)

1998-01-01

165

Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators  

DOEpatents

A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface. 12 figs.

Caporaso, G.J.; Sampayan, S.E.; Kirbie, H.C.

1998-10-13

166

Electrochemical impedance measurement of prostate cancer cells using carbon nanotube array electrodes in a microfluidic channel  

NASA Astrophysics Data System (ADS)

Highly aligned multi-wall carbon nanotubes were synthesized in the shape of towers and embedded into fluidic channels as electrodes for impedance measurement of LNCaP human prostate cancer cells. Tower electrodes up to 8 mm high were grown and easily peeled off a silicon substrate. The nanotube electrodes were then successfully soldered onto patterned printed circuit boards and cast into epoxy under pressure. After polishing the top of the tower electrodes, RF plasma was used to enhance the electrocatalytic effect by removing excess epoxy and activating the open end of the nanotubes. Electrodeposition of Au particles on the plasma-treated tower electrodes was done at a controlled density. Finally, the nanotube electrodes were embedded into a polydimethylsiloxane (PDMS) channel and electrochemical impedance spectroscopy was carried out with different conditions. Preliminary electrochemical impedance spectroscopy results using deionized water, buffer solution, and LNCaP prostate cancer cells showed that nanotube electrodes can distinguish the different solutions and could be used in future cell-based biosensor development.

Heung Yun, Yeo; Dong, Zhongyun; Shanov, Vesselin N.; Schulz, Mark J.

2007-11-01

167

Time-Varying Magnetic Field Coupled Noise Reduction in Low-Voltage Measurements in Superconductors  

Microsoft Academic Search

Noise generated by time-varying magnetic fields in- terferes in the measurements of low voltages particularly with superconductor materials. The measured values can alter sig- nificantly if it is not compensated appropriately or if suitable protocols are not followed. Measurements on inductive loads, like superconducting wires and coils, considerably generate high magnetic field in the surrounding, which couples electromagnetic noise through

Kalpesh Doshi; Yohan Khristi; Sunil Kedia; Subrata Pradhan

2011-01-01

168

A miniature all-solid-state calcium electrode applied to in situ seawater measurement  

NASA Astrophysics Data System (ADS)

An all-solid-state miniature calcium ion selective electrode (ISE) based on poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT(PSS)) for continuous in situ measurement in seawater was studied. The electrode substrate was a platinum (Pt) wire of 0.5 mm diameter and PEDOT(PSS) was electropolymerized on one end of the Pt wire to act as the solid contact of this calcium ISE. The PEDOT(PSS) layer was covered with a calcium-selective poly(vinyl chloride) membrane, which contained ETH129 as calcium ionophore, potassium tetrakis-(p-chlorophenyl)borate as lipophilic anion and bis(2-ethylhexyl) sebacate as the plasticizer. Experiments using electrochemical impedance spectroscopy and reversed chronopotentiometry illustrated that electropolymerized PEDOT(PSS) decreased the resistance and improved the stability of the electrode. The sensors can work stably in the calcium ion concentration range of 10-6-10-1 mol L-1 with the slope of 27.7 mV/decade. Also Na+, K+ and Mg2+ can hardly interfere with the performance of the electrode. This electrode was applied to measure the calcium ion concentration of seawater samples. The experimental data showed that the electrode can resist the corrosion of seawater and its reproducibility was good (SD < 0.1 mM kg-1). The lifetime of such an electrode was at least six months. Because of the wire-shape and the small size of such a liquid junction free calcium electrode, it is pressure-resistant and easy to package and seal, therefore it is suitable for use in underwater equipment for in situ seawater measurement.

Xu, Hui; Wang, You; Luo, Zhiyuan; Pan, Yiwen

2013-12-01

169

Electrode oxygen-affinity influence on voltage nonlinearities in high-k metal-insulator-metal capacitors  

E-print Network

-insulator-metal capacitors C. Vallée, P. Gonon, C. Jorel, and F. El Kamel Citation: Appl. Phys. Lett. 96, 233504 (2010); doi-insulator-metal capacitors C. Vallée,1,a P. Gonon,1 C. Jorel,1 and F. El Kamel2 1 Microelectronics Technology Laboratory (LTM-insulator-metal capacitors. Several metallic electrodes are tested in order to investigate the role of the metal work

Paris-Sud XI, Université de

170

A new method and instrument for touch and step voltage measurements  

SciTech Connect

This paper describes a new method and instrument for measuring touch and step voltages near a grounding system, for example in and around a substation. The hardware, software, and testing procedures are an extension of the smart ground multimeter, developed under EPRI sponsorship. The instrument injects a transient electric current between the ground under testing and an auxiliary ground, and it measures ground potential differences (GPDs) at up to six locations. The GPD measurements are processed with software which rejects external noise using correlation methods. Subsequently, statistical estimation methods are used to extract the touch or step voltages from the thousands of measurement points normalized with the system short circuit capability. Knowledge of the short circuit capability of the substation allows the quick measurements of the touch and step voltages.

Meliopoulos, A.P.S. (Georgia Inst. of Technology, Atlanta, GA (United States). School of Electrical and Computer Engineering); Patel, S. (Georgia Power Co., Atlanta, GA (United States)); Cokkinides, G.J. (Univ. of South Carolina, Columbia, SC (United States). Dept. of Electrical and Computer Engineering)

1994-10-01

171

Iridium Oxide Nanotube Electrodes for Highly Sensitive and Prolonged Intracellular Measurement of Action Potentials  

PubMed Central

Intracellular recording of action potentials is important to understand electrically-excitable cells. Recently, vertical nanoelectrodes have been developed to achieve highly sensitive, minimally invasive, and large scale intracellular recording. It has been demonstrated that the vertical geometry is crucial for the enhanced signal detection. Here we develop nanoelectrodes made up of nanotubes of iridium oxide. When cardiomyocytes are cultured upon those nanotubes, the cell membrane not only wraps around the vertical tubes but also protrudes deep into the hollow center. We show that this geometry enhances cell-electrode coupling and results in measuring much larger intracellular action potentials. The nanotube electrodes afford much longer intracellular access and are minimally invasive, making it possible to achieve stable recording up to an hour in a single session and more than 8 days of consecutive daily recording. This study suggests that the electrode performance can be significantly improved by optimizing the electrode geometry. PMID:24487777

Lin, Ziliang Carter; Xie, Chong; Osakada, Yasuko; Cui, Yi; Cui, Bianxiao

2014-01-01

172

Advanced Ring-Shaped Microelectrode Assay Combined with Small Rectangular Electrode for Quasi-In vivo Measurement of Cell-to-Cell Conductance in Cardiomyocyte Network  

NASA Astrophysics Data System (ADS)

To predict the risk of fatal arrhythmia induced by cardiotoxicity in the highly complex human heart system, we have developed a novel quasi-in vivo electrophysiological measurement assay, which combines a ring-shaped human cardiomyocyte network and a set of two electrodes that form a large single ring-shaped electrode for the direct measurement of irregular cell-to-cell conductance occurrence in a cardiomyocyte network, and a small rectangular microelectrode for forced pacing of cardiomyocyte beating and for acquiring the field potential waveforms of cardiomyocytes. The advantages of this assay are as follows. The electrophysiological signals of cardiomyocytes in the ring-shaped network are superimposed directly on a single loop-shaped electrode, in which the information of asynchronous behavior of cell-to-cell conductance are included, without requiring a set of huge numbers of microelectrode arrays, a set of fast data conversion circuits, or a complex analysis in a computer. Another advantage is that the small rectangular electrode can control the position and timing of forced beating in a ring-shaped human induced pluripotent stem cell (hiPS)-derived cardiomyocyte network and can also acquire the field potentials of cardiomyocytes. First, we constructed the human iPS-derived cardiomyocyte ring-shaped network on the set of two electrodes, and acquired the field potential signals of particular cardiomyocytes in the ring-shaped cardiomyocyte network during simultaneous acquisition of the superimposed signals of whole-cardiomyocyte networks representing cell-to-cell conduction. Using the small rectangular electrode, we have also evaluated the response of the cell network to electrical stimulation. The mean and SD of the minimum stimulation voltage required for pacing (VMin) at the small rectangular electrode was 166+/-74 mV, which is the same as the magnitude of amplitude for the pacing using the ring-shaped electrode (179+/-33 mV). The results showed that the addition of a small rectangular electrode into the ring-shaped electrode was effective for the simultaneous measurement of whole-cell-network signals and single-cell/small-cluster signals on a local site in the cell network, and for the pacing by electrical stimulation of cardiomyocyte networks.

Nomura, Fumimasa; Kaneko, Tomoyuki; Hamada, Tomoyo; Hattori, Akihiro; Yasuda, Kenji

2013-06-01

173

Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer.  

PubMed

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes. Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1-S6 (ref. 2). The voltage-sensing domain (segments S1-S4) contains charged arginine residues on S4 that move across the membrane electric field, modulating channel open probability. Understanding the physical movements of this voltage sensor is of fundamental importance and is the subject of controversy. Recently, the crystal structure of the KvAP channel motivated an unconventional 'paddle model' of S4 charge movement, indicating that the segments S3b and S4 might move as a unit through the lipid bilayer with a large (15-20-A) transmembrane displacement. Here we show that the voltage-sensor segments do not undergo significant transmembrane translation. We tested the movement of these segments in functional Shaker K+ channels by using luminescence resonance energy transfer to measure distances between the voltage sensors and a pore-bound scorpion toxin. Our results are consistent with a 2-A vertical displacement of S4, not the large excursion predicted by the paddle model. This small movement supports an alternative model in which the protein shapes the electric field profile, focusing it across a narrow region of S4 (ref. 6). PMID:16094368

Posson, David J; Ge, Pinghua; Miller, Christopher; Bezanilla, Francisco; Selvin, Paul R

2005-08-11

174

1 Measurements of the Fracture Energy of Lithiated Silicon Electrodes 2 of Li-Ion Batteries  

E-print Network

demonstrates a unique ability to flow plastically 21 and fracture in a brittle manner. 22 KEYWORDS: Lithium1 Measurements of the Fracture Energy of Lithiated Silicon Electrodes 2 of Li-Ion Batteries 3 Matt University, Cambridge, Massachusetts 02138, United States 5 ABSTRACT: We have measured the fracture energy

175

Catalase activity measured with a micro oxygen electrode in a pressurized reaction vessel. [Mice, rats  

Microsoft Academic Search

The assembly and the use of a simple airtight pressurized reaction vessel are described for the measurement of catalase activity with a micro oxygen electrode in an optically heterogenous medium. The oxygen concentration is expressed as the ratio of observed current to the current in an air-saturated solution. Thus, an individual standard can be obtained for each measurement and the

Halbach

1977-01-01

176

"Analysis of SOFCs using reference electrodes?  

SciTech Connect

Reference electrodes are frequently applied to isolate the performance of one electrode in a solid oxide fuel cell. However, reference electrode simulations raise doubt to veracity of data collected using reference electrodes. The simulations predict that the reported performance for the one electrode will frequently contain performance of both electrodes. Nonetheless, recent reports persistently treat data so collected as ideally isolated. This work confirms the predictions of the reference electrode simulations on two SOFC designs, and to provides a method of validating the data measured in the 3-electrode configuration. Validation is based on the assumption that a change in gas composition to one electrode does not affect the impedance of the other electrode at open circuit voltage. This assumption is supported by a full physics simulation of the SOFC. Three configurations of reference electrode and cell design are experimentally examined using various gas flows and two temperatures. Impedance data are subjected to deconvolution analysis and equivalent circuit fitting and approximate polarization resistances of the cathode and anode are determined. The results demonstrate that the utility of reference electrodes is limited and often wholly inappropriate. Reported impedances and single electrode polarization values must be scrutinized on this basis.

Finklea, Harry; Chen,Xiaoke; Gerdes,Kirk; Pakalapati, Suryanarayana; Celik, Ismail

2013-07-01

177

Complete electrode model in EEG: relationship and differences to the point electrode model  

NASA Astrophysics Data System (ADS)

In electroencephalography (EEG) source analysis, a primary current density generated by the neural activity of the brain is reconstructed from external electrode voltage measurements. This paper focuses on accurate and effective simulations of EEG through the complete electrode model (CEM). The CEM allows for the incorporation of the electrode size, shape and effective contact impedance into the forward simulation. Both neural currents in the brain and shunting currents between the electrodes and the skin can affect the measured voltages in the CEM. The goal of this study was to investigate the CEM by comparing it with the point electrode model (PEM), which is the current standard electrode model for EEG. We used a three-dimensional, realistic and high-resolution finite element head model as the reference computational domain in the comparison. The PEM could be formulated as a limit of the CEM, in which the effective impedance of each electrode goes to infinity and the size tends to zero. Numerical results concerning the forward and inverse errors and electrode voltage strengths with different impedances and electrode sizes are presented. Based on the results obtained, limits for extremely high and low impedance values of the shunting currents are suggested.

Pursiainen, S.; Lucka, F.; Wolters, C. H.

2012-02-01

178

Semi-transparent pentacene thin film transistors with NiO x electrode operating at low voltages  

Microsoft Academic Search

We demonstrate the fabrication of semi-transparent pentacene-based thin-film transistors (TFTs) with thin poly-4-vinylphenol (PVP)\\/high-k yttrium oxide (YOx) double gate dielectric layers and also with thermally-evaporated NiOx source\\/drain (S\\/D) electrodes which show a transmittance of ?30–40% and sheet resistance range of 100–200 ?\\/? (controlled by deposition rate). Our pentacene TFTs with PVP (45 nm)\\/YOx (100 nm) layers operated at less than ?5 V, exhibiting a

D. K. Hwang; Jeong-M. Choi; Kimoon Lee; Ji Hoon Park; Eugene Kim; Seongil Im

2008-01-01

179

Coupling interactions between voltage sensors of the sodium channel as revealed by site-specific measurements.  

PubMed

The voltage-sensing S4 segments in the sodium channel undergo conformational rearrangements in response to changes in the electric field. However, it remains unclear whether these structures move independently or in a coordinated manner. Previously, site-directed fluorescence measurements were shown to track S4 transitions in each of the four domains. Here, using a similar technique, we provide direct evidence of coupling interactions between voltage sensors in the sodium channel. Pairwise interactions between S4s were evaluated by comparing site-specific conformational changes in the presence and absence of a gating perturbation in a distal domain. Reciprocity of effect, a fundamental property of thermodynamically coupled systems, was measured by generating converse mutants. The magnitude of a local gating perturbation induced by a remote S4 mutation depends on the coupling strength and the relative equilibrium positions of the two voltage sensors. In general, our data indicates that the movement of all four voltage sensors in the sodium channel are coupled to a varying extent. Moreover, a gating perturbation in S4-DI has the largest effect on the activation of S4-DIV and vice versa, demonstrating an energetic linkage between S4-DI and S4-DIV. This result suggests a physical mechanism by which the activation and inactivation process may be coupled in voltage-gated sodium channels. In addition, we propose that cooperative interactions between voltage sensors may be the mechanistic basis for the fast activation kinetics of the sodium channel. PMID:14981134

Chanda, Baron; Asamoah, Osei Kwame; Bezanilla, Francisco

2004-03-01

180

Polarization properties of PLZT under applied voltage measured by dual-rotating retarder polarimeter.  

NASA Astrophysics Data System (ADS)

PLZT is a transparent piezoelectric polycrystal usually used for controlling the polarization of a light by an applied voltage. However, PLZT has some disadvantages that it is difficult to obtain polarization properties in detail. The reason for the problem is that when a polarized light induced into PLZT, there are depolarization by scattering in the crystal grain boundary. To evaluate optical properties of PLZT, we have measured its Mueller matrices under applied voltages by using the dual-rotating retarder polarimeter proposed by Azzam. For analysis of detailed polarization properties, we have decomposed its Mueller matrices by the decomposition algorithm given by Chipman. Birefringence and depolarization of PLZT depend on applied voltage. And depolarization ratio rapidly decrease when applied voltage is in the specific range.

Ginya, Makoto; Mizutani, Yasuhiro; Iwata, Tetsuo; Otani, Yukitoshi

181

The Coefficient of the Voltage Induced Frequency Shift Measurement on a Quartz Tuning Fork  

PubMed Central

We have measured the coefficient of the voltage induced frequency shift (VIFS) of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built. PMID:25414971

Hou, Yubin; Lu, Qingyou

2014-01-01

182

Dynamical XPS measurements for probing photoinduced voltage changes  

NASA Astrophysics Data System (ADS)

Photoillumination with 405 nm laser causes shifts in XPS peaks of n-Si(100), and CdS. To distinguish between surface photovoltage (SPV), and charging, dynamical measurements are performed, while sample is subjected to square wave pulses of ± 10.00 V amplitude, and 10 -3-10 5 Hz frequency. For n-Si, Si2p peaks are twinned at + 10.00 and -10.00, yielding always 20.00 eV difference. Photoillumination shifts the twinned peaks to higher energies, but the difference is always 20.00 eV. However, for CdS, the measured binding difference of Cd3d peaks exhibits strong frequency dependence due to charging, which indicates that both fast SPV and slow charging effects are operative.

Sezen, Hikmet; Suzer, Sefik

2010-10-01

183

A method for measuring displacement and deformation of electrodes during resistance spot welding  

NASA Astrophysics Data System (ADS)

A new method for measuring the time-dependent displacement and deformation of electrodes during resistance spot welding (RSW) is described. The method allows assessment of the non-stationary thermal expansion of the electrodes. By measuring the electrode indentation close to the weld-piece surface, the method enables a better estimation of indentation than the present methods that rely on measurement of the displacement of the outside part of the electrodes or their holders. The method is based on using a digital video camera to acquire image sequences of electrode caps in the RSW process. A regular pattern of shallow bores is drilled into the caps to enhance the contrast of the acquired images and facilitate image processing. The distances between the bores are analyzed from the image sequences to determine the temporally and spatially resolved displacement and deformation of the caps. The analysis revealed that the cap deformations in some welding regimes can reach up to 20% of the maximum cap displacements, which are approximately 200 µm. The employed image processing algorithms are presented as well as examples of results that demonstrate the applicability of the method.

Kuš?er, Lovro; Polajnar, Ivan; Diaci, Janez

2011-06-01

184

A portable transfer chamber for electrochemical measurements on electrodes prepared in ultra-high vacuum.  

PubMed

This paper describes a versatile, light weight, and portable chamber dedicated to the transfer of electrodes from ultra-high vacuum (UHV) to atmospheric pressure and the liquid phase. This chamber can be connected to a liquid-phase reaction cell to perform electrochemical measurements and transfer back the electrode to the UHV environment. The experimental set-up can also be turned in order to make the electrode the bottom of the electrochemical cell. The validity and the efficiency of the experimental set-up were tested with a Pt(111) surface that provides unique electrochemical features in acidic sulphate-containing solution. This transfer chamber concept provides the surface science community with a new and versatile tool, complementary to existing systems, which allows fast electrolyte purging or electrochemical measurements under well-controlled mass transport conditions. PMID:23822358

El-Jawad, M; Chemin, J-L; Gilles, B; Maillard, F

2013-06-01

185

Broadband electromagnetic characterization of a 100? traveling-wave electrode by measuring scattering parameters  

NASA Astrophysics Data System (ADS)

The Single Bunch Selector (SBS) will be used on the Spiral2 linear accelerator to reduce the rate of high energy bunches reaching the target with, in principle, no residual particles from the suppressed bunches. For this purpose, a pulsed electromagnetic wave will travel along the 100? microstrip meander line electrode of the SBS. In this work we describe the broadband accurate characterization of the electrode electromagnetic features. The method applied here leads to the analytical determination of complex characteristic impedance, propagation constant, and group velocity from a measurement of the 50? scattering parameters on the meander transmission line. Particular care is given to the de-embedding phase of the transitions required to connect the meander electrode to the measurement device.

Consoli, Fabrizio; Balleyguier, Pascal; Di Giacomo, Marco

2013-07-01

186

Performance of lightweight nickel electrodes  

NASA Technical Reports Server (NTRS)

The NASA Lewis Research Center is currently developing nickel electrodes for nickel-hydrogen (Ni-H2) batteries. These electrodes are lighter in weight and have higher energy densities than the heavier state-of-the-art (SOA) sintered nickel electrodes. In the present approach, lightweight materials or plaques are used as conductive supports for the nickel hydroxide active material. These plaques (fiber and felt, nickel plated plastic and graphite) are commercial products that are fabricated into nickel electrodes by electrochemically impregnating them with active material. Evaluation is performed in half cells structured in the bipolar configuration. Initial performance tests include capacity measurements at five discharge levels, C/2, 1.0C 1.37C, 2.0C and 2.74C. The electrodes that pass the initial tests are life cycle tested in a low Earth orbit regime at 80 percent depth of discharge. Different formulations of nickel fiber materials obtained from several manufacturers are currently being tested as possible candidates for nickel electrodes. One particular lightweight fiber mat electrode has accumulated over 3000 cycles to date, with stable capacity and voltage. Life and performance data of this electrode were investigated and presented. Good dimensional stability and active material adherence have been demonstrated in electrodes made from this lightweight plaque.

Britton, Doris L.

1988-01-01

187

Performance of lightweight nickel electrodes  

NASA Technical Reports Server (NTRS)

The NASA Lewis Research Center is currently developing nickel electrodes for nickel-hydrogen (Ni-H2) batteries. These electrodes are lighter in weight and have higher energy densities than the heavier state-of-the-art (SOA) sintered nickel electrodes. In the present approach, lightweight materials or plaques are used as conductive supports for the nickel hydroxide active material. These plaques (fiber and felt, nickel plated plastic and graphite) are commercial products that are fabricated into nickel electrodes by electrochemically impregnating them with active material. Evaluation is performed in half cells structured in the bipolar configuration. Initial performance tests include capacity measurements at five discharge levels, C/2, 1.0C, 1.37C, 2.0C and 2.74C. The electrodes that pass the initial tests are life cycle tested in a low earth orbit regime at 80 percent depth of discharge. Different formulations of nickel fiber materials obtained from several manufacturers are currently being tested as possible candidates for nickel electrodes. One particular lightweight fiber mat electrode has accumulated over 3000 cycles to date, with stable capacity and voltage. Life and performance data of this electrode were investigated and presented. Good dimensional stability and active material adherence have been demonstrated in electrodes made from this lightweight plaque.

Britton, Doris L.

1988-01-01

188

A test technique for measuring lightning-induced voltages on aircraft electrical circuits  

NASA Technical Reports Server (NTRS)

The development of a test technique used for the measurement of lightning-induced voltages in the electrical circuits of a complete aircraft is described. The resultant technique utilizes a portable device known as a transient analyzer capable of generating unidirectional current impulses similar to lightning current surges, but at a lower current level. A linear relationship between the magnitude of lightning current and the magnitude of induced voltage permitted the scaling up of measured induced values to full threat levels. The test technique was found to be practical when used on a complete aircraft.

Walko, L. C.

1974-01-01

189

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement  

DOEpatents

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet. 4 figs.

Kikta, T.J.; Mitchell, R.D.

1992-11-24

190

Preventive measures reduce exposure to polycyclic aromatic hydrocarbons at a graphite electrode plant  

PubMed Central

OBJECTIVE: This study assessed the efficacy of preventive measures in a graphite electrode plant aimed at reducing occupational exposure to polycyclic aromatic hydrocarbons (PAHs). METHODS: Electrode workers (n = 146) answered a questionnaire and provided an end of shift urine sample. Urinary 1-hydroxypyrene (1-hpur), a biological marker of exposure to PAHs, was measured by high performance liquid chromatography coupled with: (a) fluorescence detection. 1- Hydroxypyrene concentrations were compared with the concentrations measured before implementing the preventive measures; and (b) those of a control group of 54 men not occupationally exposed to PAHs. RESULTS: After implementation of preventive measures, median concentrations 1- hpur were significantly reduced in some groups of workers: by -24%, - 37% and -30% in workers at the green electrode unit, one baking impregnation unit, and the laboratory, respectively. In workers at a second baking impregnation unit, in end product finishing and in the power station 1-hpur concentrations were unchanged. Urinary 1-hp concentrations were still significantly higher in each group of workers than in the control group (p < 0.001 for any comparison). Concentrations in the workers varied with the type of job, the highest values being found in workers engaged in the power station, in the two baking impregnation units and in the green electrode unit. CONCLUSIONS: Implementing preventive measures significantly reduced exposure to PAHs at a graphite electrode plant. The reduction in median and peak concentrations of 1-hpur, which reflects total exposure to, and internal dose of PAHs, was most evident in workers employed in the units where preventive measures had been taken. Despite an overall reduction, further preventive measures are needed to minimise exposure to PAHs and consequently the risk of adverse health effects.   PMID:9764100

dell'Omo, M.; Muzi, G.; Marchionna, G.; Latini, L.; Carrieri, P.; Paolemili, P.; Abbritti, G.

1998-01-01

191

A study about partial discharge measurements performed applying to insulating systems square voltages with different rise times  

Microsoft Academic Search

Partial discharge (PD) measurements output, when non-sinusoidal voltages are applied to insulating systems, can have different meanings, depending on the voltage waveform frequency content and on the PD probe circuit. A PD detection circuit is designed for a low noise-to-signal ratio, thus for suppression of the residual high frequency (HF) voltage. Such a suppression varies with the applied voltage rise

F. Guastavino; G. Coletti; A. Ratto; E. Torello

2005-01-01

192

Determining resistivity of a formation adjacent to a borehole having casing using multiple electrodes and with resistances being defined between the electrodes  

DOEpatents

Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information related to the resistivity of adjacent geological formations from inside the cased well. The multiple electrode apparatus have a minimum of three spaced apart voltage measurement electrodes that electrically engage the interior of the cased well. Measurement information is obtained related to current which is caused to flow from the cased well into the adjacent geological formation. First compensation information is obtained related to a first casing resistance between a first pair of the spaced apart voltage measurement electrodes. Second compensation information is obtained related to a second casing resistance between a second pair of the spaced apart voltage measurement electrodes. The measurement information, and first and second compensation information are used to determine a magnitude related to the adjacent formation resistivity.

Vail, III, William B. (Bothell, WA)

1996-01-01

193

Determining resistivity of a formation adjacent to a borehole having casing using multiple electrodes and with resistances being defined between the electrodes  

DOEpatents

Methods of operation are disclosed for different types of multiple electrode apparatus vertically disposed in a cased well to measure information related to the resistivity of adjacent geological formations from inside the cased well. The multiple electrode apparatus have a minimum of three spaced-apart voltage measurement electrodes that electrically engage the interior of the cased well. Measurement information is obtained related to current which is caused to flow from the cased well into the adjacent geological formation. First compensation information is obtained related to a first casing resistance between a first pair of the spaced-apart voltage measurement electrodes. Second compensation information is obtained related to a second casing resistance between a second pair of the spaced-apart voltage measurement electrodes. The measurement information, and first and second compensation information are used to determine a magnitude related to the adjacent formation resistivity. 13 figs.

Vail, W.B. III

1996-10-29

194

Antenna Characterization for the JOLT Impulsive Radiator via Low-Voltage Measurements  

NASA Astrophysics Data System (ADS)

The JOLT system is a highly directive, impulse-like radiator. The antenna for JOLT is a 10-ft-diameter half-impulse radiating antenna (HIRA). JOLT was one of the first impulse radiating systems to employ a half IRA. For that reason, extensive measurements were made with a prototype, scale model HIRA in order to understand the performance of this class of antenna. In addition, a series of low-voltage antenna subsystem tests were performed with the full JOLT antenna before it was couple to the pulsed power and run at high voltage. The low-voltage measurements proved to be quite valuable, as an important manufacturing defect—a failure to mount the dish perpendicular to the ground plane—was identified and mitigated.

Tyo, J. S.; Schoenberg, J. S. H.; Baum, C. E.; Prather, W. D.; Hackett, R.; Burger, J. W.; Farr, E. G.; Giri, D. V.; McLemore, D. P.

195

Activity coefficients of aqueous sodium chloride from 15?? to 50??C measured with a glass electrode  

USGS Publications Warehouse

Values of the mean activity coefficient of sodium chloride at 15??, 25??, 38?? and 50??C were determined for aqueous NaCl solutions of 0.01 to 1.0 molal from electromotive force measurements on the cell: (sodium-sensitive glass electrode, aqueous sodium chloride, silver chloride-silver).

Truesdell, A.H.

1968-01-01

196

Mapping corrosion kinetics using the wire beam electrode in conjunction with electrochemical noise resistance measurements  

Microsoft Academic Search

A wire beam electrode (WBE) has been used, in conjunction with the electrochemical noise resistance method, to determine the kinetics of nonuniform corrosion of mild steel in a carbon dioxide saturated brine. Local electrochemical parameters including corrosion potential, galvanic current, and electrochemical noise resistance were measured from local areas of a WBE surface. These parameters were used to calculate the

Y. J. Tan; S. Bailey; B. Kinsella; A. Lowe

2000-01-01

197

On-line measurement of ethanol with a gas-sensor-dip-electrode  

Microsoft Academic Search

Summary A simple gas-sensor-dip-electrode (GSDE) for the direct measurement of ethanol in the culture broth is described. The GSDE was used for the online ethanol determination for a period of 2 month during a continuous fermentation with immobilized cells.

K. D. Vorlop; J. W. Becke; J. Klein

1983-01-01

198

Measurements of the Fracture Energy of Lithiated Silicon Electrodes of Li-Ion Batteries  

E-print Network

of the observed cracks appear brittle in nature. By determining the condition for crack initiation, the fracture in a brittle manner. KEYWORDS: Lithium-ion batteries, silicon, fracture energy, fracture toughness LithiumMeasurements of the Fracture Energy of Lithiated Silicon Electrodes of Li-Ion Batteries Matt Pharr

Suo, Zhigang

199

Single-Molecule Electronic Measurements with Metal Electrodes  

ERIC Educational Resources Information Center

A review of concepts like tunneling through a metal-molecule-metal-junction, contrast with electrochemical and optical-charge injection, strong-coupling limit, calculations of tunnel transport, electron transfer through Redox-active molecules is presented. This is followed by a discussion of experimental approaches for single-molecule measurements.

Lindsay, Stuart

2005-01-01

200

Detection of bottom ferromagnetic electrode oxidation in magnetic tunnel junctions by magnetometry measurements  

SciTech Connect

Surface oxidation of the bottom ferromagnetic (FM) electrode, one of the major detrimental factors to the performance of a magnetic tunnel junction (MTJ), is difficult to avoid during the fabrication process of the MTJ's tunnel barrier. Since Co rich alloys are commonly used for the FM electrodes in MTJs, overoxidation of the tunnel barrier results in the formation of a CoO antiferromagnetic (AF) interface layer which couples with the bottom FM electrode to form a typical AF/FM exchange bias (EB) system. In this work, surface oxidation of the CoFe and CoFeB bottom electrodes was detected via magnetometry measurements of EB characterizations including the EB field, training effect, uncompensated spin density, and enhanced coercivity. Variations in these parameters were found to be related to the surface oxidation of the bottom electrode, among them the change in coercivity is most sensitive. Annealed samples show evidence for an oxygen migration back to the MgO tunnel barrier by annealing.

Chen Wei [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Nam, Dao N. H.; Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

2010-12-01

201

Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator  

NASA Astrophysics Data System (ADS)

Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM). Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator's vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator's vacuum-insulator stack (at a radius of 1.6 m) by using standard D -dot and B -dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator's magnetically insulated transmission lines (MITLs) and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z . These results are complementary to previous studies [R. D. McBride et al., Phys. Rev. ST Accel. Beams 13, 120401 (2010)] that showed efficient transmission of large currents through the MITLs on Z . Taken together, the two studies demonstrate the overall efficient delivery of very large electrical powers through the MITLs on Z .

Waisman, E. M.; McBride, R. D.; Cuneo, M. E.; Wenger, D. F.; Fowler, W. E.; Johnson, W. A.; Basilio, L. I.; Coats, R. S.; Jennings, C. A.; Sinars, D. B.; Vesey, R. A.; Jones, B.; Ampleford, D. J.; Lemke, R. W.; Martin, M. R.; Schrafel, P. C.; Lewis, S. A.; Moore, J. K.; Savage, M. E.; Stygar, W. A.

2014-12-01

202

Plane multiwire-electrode ionization chamber for measurements of radon concentration in air  

SciTech Connect

A continuous measuring system has been developed, which uses a plane multiwire-electrode ionization chamber and obtains radon concentrations by measuring in situ alpha energy spectra due to alpha-active nuclei in the air. The chamber has three rigid plane multiwire electrodes in a box of aluminum plates which have holes for the air to flow freely through them. The concentration measurements do not disturb the distribution of radon in the air. Values of concentration are obtained with good statistical errors because of the use of a large volume for the ionization chamber. The slow rise-time pulses of alpha particles from the chamber are analyzed with a specially designed analog-to-digital converter which is controlled with a microcomputer. The energy spectra have been obtained with a FWHM of about 600 keV. Time variations of radon concentrations have been measured in a room in a ferroconcrete building.

Katase, A.; Matsumoto, Y.; Nagao, Y.; Sakae, T.; Tanabe, K.; Ishibashi, K.

1986-05-01

203

Measurement of contact voltage drop and resistance in organic solar cells  

NASA Astrophysics Data System (ADS)

Bulk heterojunction organic solar cells based on poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] and [6,6]-phenyl C71-butyric acid methyl ester are investigated. A prominent kink is observed in the fourth quadrant of the current density-voltage (J-V) response. Annealing the active layer prior to cathode deposition eliminates the kink. The kink is attributed to an extraction barrier. The J-V response in these devices is well described by a power law. This behavior is attributed to an imbalance in charge carrier mobility. An expected photocurrent for the device displaying a kink in the J-V response is determined by fitting to a power law. The difference between the expected and measured photocurrent allows for the determination of a voltage drop within the device. Under simulated 1 sun irradiance, the peak voltage drop and contact resistance at short circuit are 0.14 V and 90 ?, respectively.

Williams, Evan L.; Ooi, Zien; Sonar, Prashant; Dodabalapur, Ananth

2012-12-01

204

A pulse sequencer and transient nanoammeter system for membrane voltage-dependent capacitance measurements  

NASA Astrophysics Data System (ADS)

A highly sensitive system for producing and time-resolving small-signal current transients in bilayer lipid membranes separating two ionic solutions is described. The circuitry can be constructed from inexpensive and readily obtainable electronic components, and may be interfaced with a variety of digital oscilloscopes or data acquisition systems. The system consists of a driver, fast nanoammeter, and timing sequencer. The driver is capable of delivering a stable, very low impedance voltage pulse (-2.0 to +2.0 V) superimposed on a clamping voltage adjustable within the same range. The pulse can be of any width between 500 ?s and 5000 s, and can be delayed with respect to an oscilloscope synchronization trigger, which is also provided. The nanoammeter is accurate between 10 pA and 100 mA and has a time resolution of better than 10 ?s. The driver and nanoammeter were designed specifically to be stable under the conditions of a highly capacitive load with very high dc resistance, as is typical of a bilayer lipid membrane. The system can be used with either reference or blocking electrodes. Ideal and actual membrane transient response curves, along with noise assessment data, are provided for calibration purposes.

Fielder, Scott S.; Noglik, Horst; Pietro, William J.

1994-03-01

205

Measurement of transmembrane potential and current in cardiac muscle: a new voltage clamp method.  

PubMed Central

1. A single sucrose gap voltage clamp technique was developed to correct for artifacts of 'leakage' corrent and extracellular resistance making possible improved measurement of membrane current and membrane potential in cardiac muscle. 2. A fourth compartment termed 'guard gap' was added to the sucrose gap. The guard gap is maintained at the same potential as the Reinger pool, so that no extracellular leakage current can flow into the Ringer pool. Comparison of experimental results with the predictions of an idealized cable model indicates that the guard gap is effective in trapping leakage current. 3. The slow charging of membrane capacitance due to extracellular series resistance was accelerated by applying a 'pre-pulse' of the command potential past the final voltage clamp value. 4. A second technique, termed 'chopped current pulse clamp', was used to compensate for the extracellular resistance throughout the voltage clamp step. The applied current was turned on and off at a frequency of 0-5-2 kHz. The membrane potential sampled during the zero current phase was fed back through the clamp loop. 5. With either of these compensation techniques, the voltage and current traces settle to effectively constant values within 2-4 msec after initiation of a hyperpolarizing voltage clamp step from rest. 6. The membrane conductance measured by the prepulse and chopped current-pulse technique are equal and confirm a higher conductance at rest than during the plateau of the action potential. 7. The 'instantaneous' current-voltage relation of the membrane is linear during the plateau of the frog ventricular action potential. PMID:301933

Goldman, Y; Morad, M

1977-01-01

206

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

207

A Fluorometric Approach to Local Electric Field Measurements in a Voltage-Gated Ion Channel  

Microsoft Academic Search

Site-specific electrostatic measurements have been limited to soluble proteins purified for in vitro spectroscopic characterization or proteins of known structure; however, comparable measurements have not been made for functional membrane bound proteins. Here, using an electrochromic fluorophore, we describe a method to monitor localized electric field changes in a voltage-gated potassium channel. By coupling the novel probe Di-1-ANEPIA to cysteines

Osei Kwame Asamoah; Joseph P. Wuskell; Leslie M. Loew; Francisco Bezanilla

2003-01-01

208

Voltage biasing, cyclic voltammetry, & electrical impedance spectroscopy for neural interfaces.  

PubMed

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays. PMID:22395095

Wilks, Seth J; Richner, Tom J; Brodnick, Sarah K; Kipke, Daryl R; Williams, Justin C; Otto, Kevin J

2012-01-01

209

Electrolyte measurement device and measurement procedure  

DOEpatents

A method and apparatus for measuring the through-thickness resistance or conductance of a thin electrolyte is provided. The method and apparatus includes positioning a first source electrode on a first side of an electrolyte to be tested, positioning a second source electrode on a second side of the electrolyte, positioning a first sense electrode on the second side of the electrolyte, and positioning a second sense electrode on the first side of the electrolyte. current is then passed between the first and second source electrodes and the voltage between the first and second sense electrodes is measured.

Cooper, Kevin R. (Southern Pines, NC); Scribner, Louie L. (Southern Pines, NC)

2010-01-26

210

Wavelength stabilisation of a DFB laser diode using measurement of junction voltage  

NASA Astrophysics Data System (ADS)

Laser diode wavelength stability is vital for applications such as spectroscopy and data communication, and the emitted wavelength is a function of temperature. In a conventional system, the laser diode temperature is controlled using a Peltier element with a temperature-sensing thermistor, the latter placed at a short distance from the laser diode chip. Despite the use of good thermal design and a case, a change in ambient temperature may cause a change to internal thermal gradients, resulting in a systematic error in the laser diode wavelength. In this paper we describe a novel system to measure the temperature of the laser diode junction via measurement of the junction voltage. The method has been applied to a 1651 nm DFB laser diode for use in tunable diode laser spectroscopy (TDLS) of methane. The wavelength stability of both thermistor- and voltage- control systems are compared over a period of 30 minutes and with different ambient temperatures. Over 30 min at constant ambient temperature, thermistor control provided a precision of +/- 0.4 pm (40 MHz) and junction voltage control gave a similar +/- 0.6 pm (70 MHz). For an ambient temperature change of 20°C, conventional thermistor control suffered a wavelength change of 76 pm (8.4 GHz), whereas junction voltage control reduced this to 0.6 pm (70 MHz), at or below the level of long-term wavelength precision.

Asmari, A.; Hodgkinson, J.; Chehura, E.; Staines, S. E.; Tatam, R. P.

2014-05-01

211

Forward voltage short-pulse technique for measuring high power laser array junction temperature  

NASA Technical Reports Server (NTRS)

The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)

2012-01-01

212

Capacitive effects in quasi-steady-state voltage and lifetime measurements of silicon devices  

NASA Astrophysics Data System (ADS)

When measuring I-V characteristics and carrier lifetimes in quasi-steady-state (QSS) conditions, it is important to consider the time dependence of the charge due to excess carriers within the device. This paper shows that the space-charge region present in pn-junction devices and in many lifetime test structures can produce a significant capacitive effect when measuring the low voltage and low carrier density range of QSS I-V curves. Both computer modeling and experiments show that the junction capacitance is particularly significant in the case of low-resistivity silicon wafers, but it can also be noticeable in intermediate and high-resistivity samples. The paper demonstrates that the static I-V characteristics can be accurately reconstructed using a simple analytical model for the space-charge region. It thus fills a gap in the understanding of the low injection range of QSS voltage and lifetime measurements.

Cuevas, A.; Recart, F.

2005-10-01

213

The isolated anterior stomach of larval mosquitoes (Aedes aegypti): voltage-clamp measurements with a tubular epithelium.  

PubMed

The anterior stomach of larval Aedes aegypti was isolated and perfused via two pipettes. For transepithelial voltage (V(te)) measurement, the inflow pipette and the bath were connected via agar bridges to calomel electrodes. For voltage-clamping, the lumen of the tissue contained an Ag/AgCl wire held by the outflow pipette, and the preparation was placed in a bath within a spiral of Ag/AgCl wire. After equilibrating the tissue in mosquito saline on both sides, a V(te) of -8+/-1 mV was measured (+/-S.E.M., N=32). Current-voltage curves (+/-100 mV) demonstrated ohmic behaviour of the epithelium. Short-circuiting resulted in a current (I(sc)) of 103+/-16 microA cm(-2) and a mean transepithelial conductance (G(te)) of 11.8+/-1.3 mS cm(-2) (+/-S.E.M., N=32). A Yonath-Civan plot of G(te) of individual preparations over the corresponding I(sc) resulted in a straight line (r(2)=0.8422), indicating that the difference in I(sc) of individual preparations is mainly based on different transcellular conductances (G(c)). This analysis allowed to estimate the mean leak conductance (G(l) approximately 3.9 mS cm(-2)) and the mean transcellular electromotive force (E(c) approximately 13 mV). After administering 0.2 micromol L(-1) serotonin, I(sc) and G(te) significantly increased, to 457+/-49 microA cm(-2) and to 21.3+/-2.3 mS cm(-2) (+/-S.E.M., N=31, P<0.05), respectively. The Yonath-Civan plot after serotonin resulted again in a straight line (r(2)=0.8219), indicating a mean G(l) of about 1 mS cm(-2) and a mean E(c) of about 22 mV. Dinitrophenol (2.5 mmol L(-1)) almost abolished I(sc) and significantly reduced G(te) (N=6). Concanamycin A (100 micromol L(-1)) reduced I(sc) by more than 90% without significantly affecting G(te). PMID:16310390

Onken, Horst; Moffett, Stacia B; Moffett, David F

2006-01-01

214

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage-gated ion channels  

E-print Network

in the lipid bilayer Distance measurements reveal a common topology of prokaryotic voltage.pnas.org/misc/reprints.shtml To order reprints, see: Notes: #12;Distance measurements reveal a common topology of prokaryotic voltage conformations in a mem- brane environment. The validity of the crystal structure for the prokaryotic K channel

Bezanilla, Francisco

215

Measurement of Component Cell Current-Voltage Characteristics in a Tandem-JunctionTwo-Terminal Solar Cell  

E-print Network

Measurement of Component Cell Current-Voltage Characteristics in a Tandem- JunctionTwo-Terminal Solar Cell Chandan Das, Xianbi Xiang and Xunming Deng Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 Abstract A new method for measuring component cell current-voltage (I

Deng, Xunming

216

Thoracic impedance measures tissue characteristics in the vicinity of the electrodes, not intervening lung water: implications for heart failure monitoring.  

PubMed

The rationale for intrathoracic impedance (Z) detection of worsening heart failure (HF) presupposes that changes in Z reflect changes in pulmonary congestion, but is confounded by poor specificity in clinical trials. We therefore tested the hypothesis that Z is primarily affected by tissue/water content in proximity to electrodes rather than by lung water distribution between electrodes through the use of a new computational model for deriving the near-field impedance contributions from the various electrodes. Six sheep were implanted with a left atrial pressure (LAP) monitor and a cardiac resynchronization therapy device which measured Z from six vectors comprising of five electrodes. The vector-based Z was modelled as the summation of the near-field impedances of the two electrodes forming the vector. During volume expansion an acute increase in LAP resulted in simultaneous reductions in the near-field impedances of the intra-cardiac electrodes, while the subcutaneous electrode showed several hours of lag (all p < 0.001). In contrast, during the simulated formation of device-pocket edema (induced by fluid injection) the near-field impedance of the subcutaneous electrode had an instantaneous response, while the intra-cardiac electrodes had a minimal inconsistent response. This study suggests that the primary contribution to the vector based Z is from the tissue/water in proximity to the individual electrodes. This novel finding may help explain the limited utility of Z for detecting worsening HF. PMID:24619657

Charles, Christopher J; Rademaker, Miriam T; Melton, Iain C; Gutfinger, Dan; Eigler, Neal L; Qu, Fujian; Troughton, Richard W

2015-02-01

217

A lithography-independent and fully confined fabrication process of phase-change materials in metal electrode nanogap with 16-?A threshold current and 80-mV SET voltage  

NASA Astrophysics Data System (ADS)

In this paper,we fabricate a lateral phase change memory device composed of a Ge2Sb2Te5 nanowire (GST NW) fully confined in a tungsten electrode nanogap. A SiNx spacer is used not only as etch mask for the fabrication of the GST NW, but also as sacrificial layer for the lift-off process, which makes it feasible to fully confine the GST NW in the metal electrode nanogap. Electrical characterization shows that the device has unprecedentedly low threshold current and SET voltage of only 16 ?A and 80 mV, respectively.

Fu, Yingchun; Wang, Xiaofeng; Zhang, Jiayong; Wang, Xiaodong; Chang, Chun; Ma, Huili; Cheng, Kaifang; Chen, Xiaogang; Song, Zhitang; Feng, Songlin; Ji, An; Yang, Fuhua

2013-01-01

218

Note: Adhesive stamp electrodes using spider silk masks for electronic transport measurements of supra-micron sized samples  

NASA Astrophysics Data System (ADS)

A procedure for fabricating adhesive stamp electrodes based on gold coated adhesive tape used to measure electronic transport properties of supra-micron samples in the lateral range 10-100 ?m and thickness >1 ?m is described. The electrodes can be patterned with a ˜4 ?m separation by metal deposition through a mask using Nephila clavipes spider dragline silk fibers. Ohmic contact is made by adhesive lamination of a sample onto the patterned electrodes. The performance of the electrodes with temperature and magnetic field is demonstrated for the quasi-one-dimensional organic conductor (TMTSF)2PF6 and single crystal graphite, respectively.

Steven, E.; Jobiliong, E.; Eugenio, P. M.; Brooks, J. S.

2012-04-01

219

Single-molecule conductance of dipyridines binding to Ag electrodes measured by electrochemical scanning tunneling microscopy break junction  

NASA Astrophysics Data System (ADS)

We have measured the conductance of three pyridyl-terminated molecules binding to Ag electrodes by using electrochemical jump-to-contact scanning tunneling microscopy break junction approach (ECSTM-BJ). Three molecules, including 4,4'-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA), contacting with Ag electrodes show three sets of conductance values, which follow the order of BPY > BPY-EE > BPY-EA. These values are smaller than those of molecules with Au electrodes, but larger than those of molecules with Cu electrodes. The difference may attribute to the different electronic coupling efficiencies between the molecules and electrodes. Moreover, the influence of the electrochemical potential on the Fermi level of electrodes is also discussed.

Zhou, Xiao-Yi; Wang, Ya-Hao; Qi, Han-Mei; Zheng, Ju-Fang; Niu, Zhen-Jiang; Zhou, Xiao-Shun

2014-02-01

220

Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic…

Ito, Takashi; Perera, D. M. Neluni T.; Nagasaka, Shinobu

2008-01-01

221

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

222

Investigation of pulse voltage shape effects on electrohydrodynamic jets using a vision measurement technique  

NASA Astrophysics Data System (ADS)

In this paper, we present a vision measurement technique to evaluate electrohydrodynamic (EHD) inkjet behavior, and discuss the effects of the pulse voltage shape on the EHD jets for drop-on-demand printing, including the falling and rising time in the pulse voltage. Sequential images acquired by a charge-coupled device (CCD) camera with a strobe light-emitting diode (LED) were used to visualize EHD jet behavior with respect to time. A vision algorithm was implemented in an EHD jet system to enable in situ measurement and analysis of EHD jets. A guideline for selecting pulse shape parameters is also presented, to enable the achievement of high-frequency reliable jets for drop-on-demand printing. Printing results are presented to demonstrate the drop consistency of jets.

Kwon, Kye-Si; Lee, Dae-Yong

2013-06-01

223

Coupling Interactions between Voltage Sensors of the Sodium Channel as Revealed by Site-specific Measurements  

Microsoft Academic Search

The voltage-sensing S4 segments in the sodium channel undergo conformational rearrangements in response to changes in the electric field. However, it remains unclear whether these structures move indepen- dently or in a coordinated manner. Previously, site-directed fluorescence measurements were shown to track S4 transitions in each of the four domains (Chanda, B., and F. Bezanilla. 2002. J. Gen. Physiol. 120:629-645).

Baron Chanda; Osei Kwame Asamoah; Francisco Bezanilla

2004-01-01

224

Measured voltages and currents internal to closed metal cylinders due to diffusion of simulated lightning currents  

SciTech Connect

One mechanism for the penetration of lightning energy into the interior of a weapon is by current diffusion through the exterior metal case. Tests were conducted in which simulated lightning currents were driven over the exteriors of similar aluminum and ferrous steel cylinders of 0.125-in wall thickness. Under conditions in which the test currents were driven asymmetrically over the exteriors of the cylinders, voltages were measured between various test points in the interior as functions of the amplitude and duration of the applied current. The maximum recorded open-circuit voltage, which occurred in the steel cylinder, was 1.7 V. On separate shots, currents flowing on a low impedance shorting conductor between the same set of test points were also measured, yielding a maximum current of 630 A, again occurring across the interior of the steel cylinder. Under symmetrical exterior drive current conditions, a maximum end-to-end internal voltage of 4.1 V was obtained, also in the steel cylinder, with a corresponding current of 480 A measured on a coaxial conductor connected between the two end plates of the cylinder. Data were acquired over a range of input current amplitudes between about 40 and 100 kA. These data provide the experimental basis for validating models that can subsequently be applied to real weapons and other objects of interest.

Schnetzer, G.H.; Fisher, R.J.

1994-08-01

225

Measuring Ca(2+) binding to short chain fatty acids and gluconate with a Ca(2+) electrode: role of the reference electrode.  

PubMed

Many organic anions bind free Ca(2+), the total concentration of which must be adjusted in experimental solutions. Because published values for the apparent dissociation constant (Kapp) describing the Ca(2+) affinity of short chain fatty acids (SCFAs) and gluconate are highly variable, Ca(2+) electrodes coupled to either a 3M KCl or a Na(+) selective electrode were used to redetermine Kapp. All solutions contained 130mM Na(+), whereas the concentration of the studied anion was varied from 15 to 120mM, replacing Cl(-) that was decreased concomitantly to maintain osmolarity. This induces changes in the liquid junction potential (LJP) at the 3M KCl reference electrode, leading to a systematic underestimation of Kapp if left uncorrected. Because the Na(+) concentration in all solutions was constant, a Na(+) electrode was used to directly measure the changes in the LJP at the 3 M KCl reference, which were under 5mV but twice those predicted by the Henderson equation. Determination of Kapp either after correction for these LJP changes or via direct reference to a Na(+) electrode showed that SCFAs do not bind Ca(2+) and that the Kapp for the binding of Ca(2+) to gluconate at pH 7.4, ionic strength 0.15M, and 23°C was 52.7mM. PMID:24835426

Stumpff, Friederike; McGuigan, John A S

2014-08-15

226

High performance cermet electrodes  

DOEpatents

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

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

1986-01-01

227

Teaching pH Measurements with a Student-Assembled Combination Quinhydrone Electrode  

ERIC Educational Resources Information Center

A simple combination pH electrode consisting of a solid-state quinhydrone sensor and a solid-state quinhydrone reference electrode is described. Both electrodes are essentially rubber stoppers that are inserted into a special doublewalled holder.

Scholz, Fritz; Steinhardt, Tim; Kahlert, Heike; Porksen, Jens R.; Behnert, Jurgen

2005-01-01

228

Nondestructive and repeatable capacitance-voltage and current-voltage measurements across the oxide/electrolyte interface by UHV-electrochemistry approach  

NASA Astrophysics Data System (ADS)

We attempt measurements of nondestructive and repeatable current-voltage (I-V) and capacitance-voltage (C-V) characteristics across the oxide/electrolyte interface for single-crystal SrTiO3 (STO) and its homoepitaxial films as a model system by the ultrahigh-vacuum (UHV)-electrochemistry approach. Direct comparisons of these characteristics before and after the growth of films and/or chemical treatments allow us to more reliably obtain some insights on the interface and bulk crystal quality of STO, in terms of which the irreversible surface reforming process as well as the frequency dependence of C will be discussed in this paper.

Miura, Yoshihiro; Takata, Shintaro; Matsumoto, Yuji

2014-09-01

229

Fault Location for Transmission Lines with Voltage and Current Measurements at One Bus  

NASA Astrophysics Data System (ADS)

This paper presents a novel fault location method for transmission lines. The proposed method extends an existing method to locate faults by employing voltage and current measurements at one bus, which can be the bus of the faulted line or be far away from the faulted line. The method is applicable if a loop exists that encloses the faulted line, and the bus, of which the voltage is used, and the branch, of which the current is used. The during-fault positive-sequence bus impedance matrix is derived. Then superimposed voltages and currents due to the fault are expressed as a function of fault location and related transfer and driving point impedances. Consequently, the fault location can be evaluated using the obtained measurements. The distributed parameter line model is adopted to consider the shunt capacitances of the line. The proposed method is independent of fault resistance and fault type. Simulation studies have been carried out based on a 27-bus power system, and promising results have been achieved.

Xiu, Wanjing; Liao, Yuan

2014-10-01

230

New frequency/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance  

SciTech Connect

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup.

Gabrielli, C.; Perrot, H.; Rose, D.; Rubin, A.; Toque, J. P.; Pham, M. C.; Piro, B. [LISE--UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05, France and ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France)

2007-07-15

231

An unattended device for high-voltage sampling and passive measurement of thoron decay products  

SciTech Connect

An integrating measurement device for the concentration of airborne thoron decay products was designed and calibrated. It is suitable for unattended use over up to several months also in inhabited dwellings. The device consists of a hemispheric capacitor with a wire mesh as the outer electrode on ground potential and the sampling substrates as the inner electrode on +7.0 kV. Negatively charged and neutral thoron decay products are accelerated to and deposited on the sampling substrates. As sampling substrates, CR39 solid-state nuclear track detectors are used in order to record the alpha decay of the sampled decay products. Nuclide discrimination is achieved by covering the detectors with aluminum foil of different thickness, which are penetrated only by alpha particles with sufficient energy. Devices of this type were calibrated against working level monitors in a thoron experimental house. The sensitivity was measured as 9.2 tracks per Bq/m{sup 3} × d of thoron decay products. The devices were used over 8 weeks in several houses built of earthen material in southern Germany, where equilibrium equivalent concentrations of 1.4–9.9 Bq/m{sup 3} of thoron decay products were measured.

Gierl, Stefanie; Meisenberg, Oliver, E-mail: oliver.meisenberg@helmholtz-muenchen.de; Wielunski, Marek; Tschiersch, Jochen [Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg (Germany)] [Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg (Germany); Haninger, Thomas [Helmholtz Zentrum München, German Research Center for Environmental Health, Auswertungsstelle für Strahlendosimeter, Otto-Hahn-Ring 6, 81739 München (Germany)] [Helmholtz Zentrum München, German Research Center for Environmental Health, Auswertungsstelle für Strahlendosimeter, Otto-Hahn-Ring 6, 81739 München (Germany)

2014-02-15

232

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements  

NASA Astrophysics Data System (ADS)

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level.

Scandurra, Graziella; Giusi, Gino; Ciofi, Carmine

2014-04-01

233

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. 4 figs.

Kronberg, J.W.

1994-05-31

234

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

235

Rapid pH change due to bacteriorhodopsin measured with a tin-oxide electrode.  

PubMed Central

The photocurrent transient generated by bacteriorhodopsin (bR) on a tin-oxide electrode is due to pH change and not to charge displacement as previously assumed. Films of either randomly oriented or highly oriented purple membranes were deposited on transparent electrodes made of tin-oxide-coated glass. The membranes contained either wild-type or D96N-mutant bR. When excited with yellow light through the glass, the bR pumps protons across the membrane. The result is a rapid local pH change as well as a charge displacement. Experiments with these films show that it is the pH change rather than the displacement that produces the current transient. The calibration for the transient pH measurement is given. The sensitivity of a tin-oxide electrode to a transient pH change is very much larger than its sensitivity to a steady-state pH change. PMID:7787036

Robertson, B; Lukashev, E P

1995-01-01

236

Catalytic adsorptive stripping voltammetric measurements of trace vanadium at bismuth film electrodes.  

PubMed

Bismuth-coated glassy carbon electrodes have been successfully applied for catalytic adsorptive stripping voltammetric measurements of low levels of vanadium(V) in the presence of chloranilic acid (CAA) and bromate ion. The new protocol is based on the accumulation of the vanadium-chloranilic acid complex from an acetate buffer (pH 5.5) solution at a preplated bismuth film electrode held at -0.35V (versus Ag/AgCl), followed by a square-wave voltammetric scan. Factors influencing the adsorptive stripping performance, including the CAA and bromate concentrations, solution pH, and accumulation potential or time have been optimized. The response compares favorably with that observed at mercury film electrodes. A linear response is observed over the 5-25mug/L concentration range (2min accumulation), along with a detection limit of 0.20mug/L vanadium (10min accumulation). High stability is indicated from the reproducible response of a 50mug/L vanadium solution (n=25; R.S.D.=3.1%). Applicability to a groundwater sample is illustrated. PMID:18970657

Wang, Joseph; Lu, Donglai; Thongngamdee, Sompong; Lin, Yuehe; Sadik, Omowunmi A

2006-06-15

237

Measurements of voltage current characteristics of a plasma needle and its effect on plant cells  

NASA Astrophysics Data System (ADS)

In this paper we present voltage-current-power characteristics of a plasma needle operating in the flow of helium at atmospheric pressure. In addition, we show some examples of how such a plasma affects plant tissues. In the characterization of the plasma needle, current and voltage waveforms were recorded by two derivative probes. These two probes are similar to the probes previously used by Puac et al for measuring transmitted power in low pressure CCP rf discharge. The instantaneous power was calculated from current and voltage waveforms and U-I characteristics of the discharge were determined. Regimes of operation with and without the grounding ring at the tip of the needle were considered. We have chosen two model systems to study the effect of the plasma needle on plant cells and tissues: sweet fern gametophyte (prothallus) and calli produced in vitro. Since the prothallus consists of a single layer of cells, the cytological effects could be easily examined. In addition, calli and prothallus are easy to manipulate and in vitro culture provides a possibility to work under constant and controlled conditions.

Puac, N.; Petrovic, Z. Lj; Malovic, G.; Dordevic, A.; Zivkovic, S.; Giba, Z.; Grubisic, D.

2006-08-01

238

Focused ion beam processing to fabricate ohmic contact electrodes on a bismuth nanowire for Hall measurements  

PubMed Central

Ohmic contact electrodes for four-wire resistance and Hall measurements were fabricated on an individual single-crystal bismuth nanowire encapsulated in a cylindrical quartz template. Focused ion beam processing was utilized to expose the side surfaces of the bismuth nanowire in the template, and carbon and tungsten electrodes were deposited on the bismuth nanowire in situ to achieve electrical contacts. The temperature dependence of the four-wire resistance was successfully measured for the bismuth nanowire, and a difference between the resistivities of the two-wire and four-wire methods was observed. It was concluded that the two-wire method was unsuitable for estimation of the resistivity due to the influence of contact resistance, even if the magnitude of the bismuth nanowire resistance was greater than the kilo-ohm order. Furthermore, Hall measurement of a 4-?m-diameter bismuth microwire was also performed as a trial, and the evaluated temperature dependence of the carrier mobility was in agreement with that for bulk bismuth, which indicates that the carrier mobility was successfully measured using this technique. PACS 81.07.Gf PMID:24070421

2013-01-01

239

Focused ion beam processing to fabricate ohmic contact electrodes on a bismuth nanowire for Hall measurements.  

PubMed

Ohmic contact electrodes for four-wire resistance and Hall measurements were fabricated on an individual single-crystal bismuth nanowire encapsulated in a cylindrical quartz template. Focused ion beam processing was utilized to expose the side surfaces of the bismuth nanowire in the template, and carbon and tungsten electrodes were deposited on the bismuth nanowire in situ to achieve electrical contacts. The temperature dependence of the four-wire resistance was successfully measured for the bismuth nanowire, and a difference between the resistivities of the two-wire and four-wire methods was observed. It was concluded that the two-wire method was unsuitable for estimation of the resistivity due to the influence of contact resistance, even if the magnitude of the bismuth nanowire resistance was greater than the kilo-ohm order. Furthermore, Hall measurement of a 4-?m-diameter bismuth microwire was also performed as a trial, and the evaluated temperature dependence of the carrier mobility was in agreement with that for bulk bismuth, which indicates that the carrier mobility was successfully measured using this technique. PACS: 81.07.Gf. PMID:24070421

Murata, Masayuki; Hasegawa, Yasuhiro

2013-01-01

240

High-voltage space-plasma interactions measured on the PASP Plus test arrays  

NASA Astrophysics Data System (ADS)

The Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) experiment was developed by the Air Force's Phillips Laboratory with support from NASA's Lewis Research Center. It was launched on the Advanced Photovoltaic and Electronics EXperiments (APEX) satellite on August 3, 1994 into a 70 degree inclination, 363 km by 2550 km elliptical orbit. This orbit allows the investigation of space plasma effects on high-voltage operation (leakage current at positive voltages and arcing at negative voltages) in the perigee region. PASP Plus is testing twelve solar arrays. There are four planar Si arrays: an old standard type (used as a reference), the large-cell Space Station Freedom (SSF) array, a thin 'APSA' array, and an amorphous Si array. Next are three GaAs on Ge planar arrays and three new material planar arrays, including InP and two multijunction types. Finally, there are two concentrator arrays: a reflective-focusing Mini-Cassegrainian and a Fresnel-lens focusing Mini-Dome. PASP Plus's diagnostic sensors include: Langmuir probe to measure plasma density, an electrostatic analyzer (ESA) to measure the 30 eV to 30 KeV electron/ion spectra and determine vehicle negative potential during positive biasing, and a transient pulse monitor (TPM) to characterize the arcs that occur during the negative biasing. Through positive biasing of its test arrays, PASP Plus investigated the snapover phenomenon, which took place over the range of +100 to +300 V. It was found that array configurations where the interconnects are shielded from the space plasma (i.e., the concentrators or arrays with 'wrap-through' connectors) have lower leakage current. The concentrators exhibited negligible leakage current over the whole range up to +500 V. In the case of two similar GaAs on Ge arrays, the one with 'wrap-through' connectors had lower leakage current than the one with conventional interconnects. Through negative biasing, PASP Plus investigated the arcing rates of its test arrays. The standard Si array, with its old construction (exposed rough-surface interconnects), arced significantly over a wide voltage and plasma-density range. The other arrays arced at very low rates, mostly at voltages greater than -350 V and plasma densities near or greater than 10(exp 5)/cm(exp -3). AS expected according to theory, arcing was more prevalent when array temperatures were cold (based on biasing in eclipse).

Guidice, Donald A.

1995-10-01

241

In vivo impedance spectroscopy of deep brain stimulation electrodes  

PubMed Central

Deep brain stimulation (DBS) represents a powerful clinical technology, but a systematic characterization of the electrical interactions between the electrode and the brain are lacking. The goal of this study was to examine the in vivo changes in DBS electrode impedance that occur after implantation and during clinically-relevant stimulation. Clinical DBS devices typically apply high-frequency voltage-controlled stimulation, and as a result the injected current is directly regulated by the impedance of the electrode-tissue interface. We monitored the impedance of scaled-down clinical DBS electrodes implanted in the thalamus and subthalamic nucleus of a rhesus macaque using electrode impedance spectroscopy (EIS) measurements ranging from 0.5 Hz to 10 kHz. To further characterize our measurements, equivalent circuit models of the electrode-tissue interface were used to quantify the role of various interface components in producing the observed electrode impedance. Following implantation, DBS electrode impedance increased and a semicircular arc was observed in the high frequency range of the EIS measurements, commonly referred to as the tissue component of the impedance. Clinically-relevant stimulation produced a rapid decrease in electrode impedance with extensive changes in the tissue component. These post-operative and stimulation-induced changes in impedance could play an important role in the observed functional effects of voltage-controlled DBS and should be considered during clinical stimulation parameter selection and chronic animal research studies. PMID:19494421

Lempka, Scott F.; Miocinovic, Svjetlana; Johnson, Matthew D.; Vitek, Jerrold L.; McIntyre, Cameron C.

2010-01-01

242

Normalization of Voltage-Sensitive Dye Signal with Functional Activity Measures  

PubMed Central

In general, signal amplitude in optical imaging is normalized using the well-established ?F/F method, where functional activity is divided by the total fluorescent light flux. This measure is used both directly, as a measure of population activity, and indirectly, to quantify spatial and spatiotemporal activity patterns. Despite its ubiquitous use, the stability and accuracy of this measure has not been validated for voltage-sensitive dye imaging of mammalian neocortex in vivo. In this report, we find that this normalization can introduce dynamic biases. In particular, the ?F/F is influenced by dye staining quality, and the ratio is also unstable over the course of experiments. As methods to record and analyze optical imaging signals become more precise, such biases can have an increasingly pernicious impact on the accuracy of findings, especially in the comparison of cytoarchitechtonic areas, in area-of-activation measurements, and in plasticity or developmental experiments. These dynamic biases of the ?F/F method may, to an extent, be mitigated by a novel method of normalization, ?F/?Fepileptiform. This normalization uses as a reference the measured activity of epileptiform spikes elicited by global disinhibition with bicuculline methiodide. Since this normalization is based on a functional measure, i.e. the signal amplitude of “hypersynchronized” bursts of activity in the cortical network, it is less influenced by staining of non-functional elements. We demonstrate that such a functional measure can better represent the amplitude of population mass action, and discuss alternative functional normalizations based on the amplitude of synchronized spontaneous sleep-like activity. These findings demonstrate that the traditional ?F/F normalization of voltage-sensitive dye signals can introduce pernicious inaccuracies in the quantification of neural population activity. They further suggest that normalization-independent metrics such as waveform propagation patterns, oscillations in single detectors, and phase relationships between detector pairs may better capture the biological information which is obtained by high-sensitivity imaging. PMID:19116673

Dann, Benjamin; Wanger, Tim; Ohl, Frank W.

2008-01-01

243

Multiple Input Electrode Gap Control During Vacuum Arc Remelting  

SciTech Connect

Accurate control of the electrode gap in a vacuum arc remelting (VAR) furnace has been a goal of melters for many years. The size of the electrode gap has a direct influence on ingot solidification structure. At the high melting currents (30 to 40 kA) typically used for VAR of segregation insensitive Ti and Zr alloys, process voltage is used as an indicator of electrode gap, whereas drip-short frequency (or period) is usually used at the lower currents (5 to 8 kA) employed during VAR of superalloys. Modem controllers adjust electrode position or drive velocity to maintain a voltage or drip-short frequency (or period) set-point. Because these responses are non-linear functions of electrode gap and melting current, these controllers have a limited range for which the feedback gains are valid. Models are available that relate process voltage and drip-short frequency to electrode gap. These relationships may be used to linearize the controller feedback signal. An estimate of electrode gap may then be obtained by forming a weighted sum of the independent gap estimates obtained from the voltage and drip-short signals. By using multiple independent measures to estimate the gap, a controller that is less susceptible to process disturbances can be developed. Such a controller was designed, built and tested. The tests were carried out at Allvac Corporation during VAR of 12Cr steel at intermediate current levels.

Beaman, J.J.; Hysinger, C.L.; Melgaard, D.K.; Williamson, R.L.

1999-01-14

244

High Voltage Breakdown Limits of Molybdenum and Carbon-based Grids for Ion Thrusters  

Microsoft Academic Search

An investigation of the high voltage breakdown thresholds for molybdenum and carbon- based electrodes used in ion thruster accelerator grids has been undertaken. The maximum electric field for the onset of field emission, and the threshold for arc initiation, has been measured for molybdenum, graphite, carbon-carbon composite, pyrolytic graphite with different surface treatments. Modification of the electrode surfaces due to

Dan M. Goebel

2005-01-01

245

A fluorometric approach to local electric field measurements in a voltage-gated ion channel.  

PubMed

Site-specific electrostatic measurements have been limited to soluble proteins purified for in vitro spectroscopic characterization or proteins of known structure; however, comparable measurements have not been made for functional membrane bound proteins. Here, using an electrochromic fluorophore, we describe a method to monitor localized electric field changes in a voltage-gated potassium channel. By coupling the novel probe Di-1-ANEPIA to cysteines in Shaker and tracking field-induced optical changes, in vivo electrostatic measurements were recorded with submillisecond resolution. This technique reports dynamic changes in the electric field during the gating process and elucidates the electric field profile within Shaker. The extension of this method to other membrane bound proteins, including transporters, will yield insight into the role of electrical forces on protein function. PMID:12526775

Asamoah, Osei Kwame; Wuskell, Joseph P; Loew, Leslie M; Bezanilla, Francisco

2003-01-01

246

Access resistance of stimulation electrodes as a function of electrode proximity to the retina  

NASA Astrophysics Data System (ADS)

Objective. Epiretinal prostheses seek to effectively stimulate the retina by positioning electrode arrays close to its surface so current pulses generate narrow retinal electric fields. Our objective was to evaluate the use of the electrical impedance of insulated platinum electrodes as a measure of the proximity of insulated platinum electrodes to the inner surface of the retina. Approach. We examined the impedance of platinum disk electrodes, 0.25 mm in diameter, insulated with two widths (0.8 and 1.6 mm outer diameter) of transparent fluoropolymer in a rabbit retinal eyecup preparation. Optical coherence tomography measured the electrode’s proximity to the retinal surface which was correlated with changes in the voltage waveform at the electrode. Electrode impedance changes during retinal deformation were also studied. Main results. When the 1.6 mm diameter insulated electrodes advanced towards the retinal surface from 1000 ?m, their voltage step at current pulse onset increased, reflecting an access resistance increase of 3880 ± 630 ?, with the 50% midpoint averaging 30 ?m, while thin 0.8 mm insulated electrode advancement showed an access resistance increase 50% midpoint averaging 16 ?m. Using impedance spectroscopy, electrode–retina proximity differences were seen in the 1.6 mm insulated electrode impedance modulus between 1 and 100 kHz and the waveform phase angle at 0.3–10 kHz, while thin 0.8 mm insulated electrode advancement produced smaller impedance modulus changes with retinal proximity between 3 and 100 kHz. These impedance changes with retinal proximity may reflect different sized zones of eye wall being coupled in series with the insulated platinum electrode. Significance. The proximity of stimulus electrodes to neural tissue in fluid-filled spaces can be estimated from access resistance changes in the stimulus pulse waveform. Because many prosthetic devices allow back telemetry communication of the stimulus electrode waveform, it is possible these series resistance increases observed with retinal proximity could be used as a metric of stimulus electrode placement.

Majdi, Joseph A.; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D.

2015-02-01

247

Spatiotemporal electrochemical measurements across an electric double layer capacitor electrode with application to aqueous sodium hybrid batteries  

NASA Astrophysics Data System (ADS)

This paper presents in-situ spatiotemporal measurements of the electrolyte phase potential within an electric double layer capacitor (EDLC) negative electrode as envisaged for use in an aqueous hybrid battery for grid-scale energy storage. The ultra-thick electrodes used in these batteries to reduce non-functional material costs require sufficiently fast through-plane mass and charge transport to attain suitable charging and discharging rates. To better evaluate the through-plane transport, we have developed an electrode scaffold (ES) for making in situ electrolyte potential distribution measurements at discrete known distances across the thickness of an uninterrupted EDLC negative electrode. Using finite difference methods, we calculate local current, volumetric charging current and charge storage distributions from the spatiotemporal electrolyte potential measurements. These potential distributions provide insight into complex phenomena that cannot be directly observed using other existing methods. Herein, we use the distributions to identify areas of the electrode that are underutilized, assess the effects of various parameters on the cumulative charge storage distribution, and evaluate an effectiveness factor for charge storage in EDLC electrodes.

Tully, Katherine C.; Whitacre, Jay F.; Litster, Shawn

2014-02-01

248

Electrostatic curved electrode actuators  

Microsoft Academic Search

In this paper, the design, fabrication, and first experimental results of electrostatic curved electrode actuators are addressed. The actuator design is based upon the deformation of a movable micromechanical structure by electrostatic forces using a fixed curved electrode. When a voltage is applied, an electrostatic force is created that will deform the free structure along the outline of the fixed

Rob Legtenberg; Erwin Berenschot; Miko Elwenspoek; J. H. J. Fluitman

1995-01-01

249

Liquid electrode  

DOEpatents

A dropping electrolyte electrode is described for use in electrochemical analysis of non-polar sample solutions, such as benzene or cyclohexane. The liquid electrode, preferably an aqueous salt solution immiscible in the sample solution, is introduced into the solution in dropwise fashion from a capillary. The electrolyte is introduced at a known rate, thus, the droplets each have the same volume and surface area. The electrode is used in making standard electrochemical measurements in order to determine properties of non-polar sample solutions. 2 figures.

Ekechukwu, A.A.

1994-07-05

250

Small vertical movement of a K+ channel voltage sensor measured with luminescence energy transfer  

Microsoft Academic Search

Voltage-gated ion channels open and close in response to voltage changes across electrically excitable cell membranes. Voltage-gated potassium (Kv) channels are homotetramers with each subunit constructed from six transmembrane segments, S1-S6 (ref. 2). The voltage-sensing domain (segments S1-S4) contains charged arginine residues on S4 that move across the membrane electric field, modulating channel open probability. Understanding the physical movements of

David J. Posson; Pinghua Ge; Christopher Miller; Francisco Bezanilla; Paul R. Selvin

2005-01-01

251

The impact of electrode area, contact impedance and boundary shape on EIT images.  

PubMed

Electrical impedance tomography (EIT) measures the conductivity distribution within an object based on the current applied and voltage measured at surface electrodes. Thus, EIT images are sensitive to electrode properties (i.e. contact impedance, electrode area and boundary shape under the electrode). While some of these electrode properties have been investigated individually, this paper investigates these properties and their interaction using finite element method simulations and the complete electrode model (CEM). The effect of conformal deformations on image reconstruction when using the CEM was of specific interest. Observed artefacts were quantified using a measure that compared an ideal image to the reconstructed image, in this case a no-noise reconstruction that isolated the electrodes' effects. For electrode contact impedance and electrode area, uniform reductions to all electrodes resulted in ringing artefacts in the reconstructed images when the CEM was used, while parameter variations that were not correlated amongst electrodes resulted in artefacts distributed throughout the image. When the boundary shape changed under the electrode, as with non-symmetric conformal deformations, using the CEM resulted in structured distortions within the reconstructed image. Mean electrode contact impedance increases, independent of inter-electrode variation, did not result in artefacts in the reconstructed image. PMID:21646710

Boyle, Alistair; Adler, Andy

2011-07-01

252

Access resistance of stimulation electrodes as a function of electrode proximity to the retina.  

PubMed

Objective. Epiretinal prostheses seek to effectively stimulate the retina by positioning electrode arrays close to its surface so current pulses generate narrow retinal electric fields. Our objective was to evaluate the use of the electrical impedance of insulated platinum electrodes as a measure of the proximity of insulated platinum electrodes to the inner surface of the retina. Approach. We examined the impedance of platinum disk electrodes, 0.25 mm in diameter, insulated with two widths (0.8 and 1.6 mm outer diameter) of transparent fluoropolymer in a rabbit retinal eyecup preparation. Optical coherence tomography measured the electrode's proximity to the retinal surface which was correlated with changes in the voltage waveform at the electrode. Electrode impedance changes during retinal deformation were also studied. Main results. When the 1.6 mm diameter insulated electrodes advanced towards the retinal surface from 1000 ?m, their voltage step at current pulse onset increased, reflecting an access resistance increase of 3880 ± 630 ?, with the 50% midpoint averaging 30 ?m, while thin 0.8 mm insulated electrode advancement showed an access resistance increase 50% midpoint averaging 16 ?m. Using impedance spectroscopy, electrode-retina proximity differences were seen in the 1.6 mm insulated electrode impedance modulus between 1 and 100 kHz and the waveform phase angle at 0.3-10 kHz, while thin 0.8 mm insulated electrode advancement produced smaller impedance modulus changes with retinal proximity between 3 and 100 kHz. These impedance changes with retinal proximity may reflect different sized zones of eye wall being coupled in series with the insulated platinum electrode. Significance. The proximity of stimulus electrodes to neural tissue in fluid-filled spaces can be estimated from access resistance changes in the stimulus pulse waveform. Because many prosthetic devices allow back telemetry communication of the stimulus electrode waveform, it is possible these series resistance increases observed with retinal proximity could be used as a metric of stimulus electrode placement. PMID:25474329

Majdi, Joseph A; Minnikanti, Saugandhika; Peixoto, Nathalia; Agrawal, Anant; Cohen, Ethan D

2015-02-01

253

Effect of electrode polarity on wire explosion in vacuum  

SciTech Connect

This paper presents experimental results on electrical explosions of thin tungsten wires at wire currents of 0.04-0.4 kA and current rise times of several tens of nanoseconds. The experiment was performed for both negative and positive polarity of the high-voltage electrode. In addition to conventional current and voltage measurements, the current to a grounded cylindrical collector placed between the exploded wire and the return conductor was measured. The collector current was observed only for a 6 {mu}m wire exploded with the high-voltage electrode being at a negative potential. In all other test modes (a 6 {mu}m wire exploded with electrode positive polarity, 6 {mu}m wire exploded with electrodes enclosed in ceramic tubes, 30 {mu}m wires exploded with electrode negative and positive polarities) no collector current was detected. A model of the discharge initiation during a wire explosion (WE) in vacuum has been proposed which is based on the supposition that a surface discharge develops over the electrodes. The presence of plasma-emitted electrons at the cathode surface makes it possible to interpret the experimental results on WEs at different electrode polarities reported both in this paper and in previous publications.

Rousskikh, A. G.; Pil'tikhina, D [Institute of High Current Electronics, RAS, 634055, Tomsk (Russian Federation); Baksht, R. B.; Beilis, I. I. [Tel Aviv University, 69978, Tel Aviv (Israel); Chaikovsky, S. A. [P. N. Lebedev Physics Institute, 117924, Moscow (Russian Federation)

2008-07-01

254

A new possible mechanism of lithium insertion and extraction in low-temperature pyrolytic carbon electrode  

Microsoft Academic Search

Lithium\\/carbon (Li\\/C) cells have been assembled with phenolic resin, pyrolyzed at 650°C for 2 h, as the working electrodes. By measuring the Raman spectra of the carbon electrodes discharged and charged to various equilibrium voltages and the discharge\\/charge curves of the Li\\/C cell, it is found that the intensity of the G-band of the discharged\\/charged pyrolytic carbon electrode in the

Zhaoxiang Wang; Xuejie Huang; Rongjian Xue; Liquan Chen

1999-01-01

255

Measurements of power loss distribution in a typical stator core under PWM voltage excitation  

NASA Astrophysics Data System (ADS)

The pulse width modulated (PWM) inverter is widely used to feed small induction motors for variable speed and torque control. When a laminated stator core is energised in this way additional iron losses occur due to localised distorted flux. Flux density and power loss distribution under PWM and sinusoidal voltage excitations were measured in a typical induction motor stator core lamination at 1.3 T, 50 Hz by using a computer-aided magnetising system to set up flux distribution as would occur in a practical three-phase stator core. The iron loss increased 15-20% under PWM excitation. The loss increase under PWM excitation in the stator core laminations was 3% lower than in Epstein strips of the same electrical steel under the same conditions showing an effect of the magnetic circuit geometry.

Tutkun, N.; Moses, A. J.

2003-06-01

256

A timing detector with pulsed high-voltage power supply for mass measurements at CSRe  

NASA Astrophysics Data System (ADS)

Accuracy of nuclear mass measurements in storage rings depends critically on the accuracy with which the revolution times of stored ions can be obtained. In such experiments, micro-channel plates (MCP) are used as timing detectors. Due to large phase space of injected secondary beams, a large number of ions cannot be stored in the ring and is lost within the first few revolutions. However, these ions interact with the detector and can saturate the MCP and thus deteriorate its performance. In order to eliminate such effects, a fast, pulsed high-voltage power supply (PHVPS) has been employed which keeps the detector switched-off during the first few revolutions. The new detector setup was taken into operation at the Experimental Cooler-Storage-Ring CSRe in Lanzhou and resulted in a significant improvement of the detector amplitude and efficiency characteristics.

Zhang, W.; Tu, X. L.; Wang, M.; Zhang, Y. H.; Xu, H. S.; Litvinov, Yu. A.; Blaum, K.; Chen, X. C.; Hu, Z. G.; Huang, W. J.; Ma, X. W.; Mao, R. S.; Mei, B.; Shuai, P.; Sun, B. H.; Yamaguchi, T.; Xia, J. W.; Xiao, G. Q.; Xu, X.; Yan, X. L.; Yang, J. C.; Yuan, Y. J.; Zhou, X. H.; Zhao, H. W.; Zhao, T. C.

2014-08-01

257

Effect of current compliance and voltage sweep rate on the resistive switching of HfO{sub 2}/ITO/Invar structure as measured by conductive atomic force microscopy  

SciTech Connect

The electrical characterization of HfO{sub 2}/ITO/Invar resistive switching memory structure was studied using conductive atomic force microscopy (AFM) with a semiconductor parameter analyzer, Agilent 4156C. The metal alloy Invar was used as the metal substrate to ensure good ohmic contact with the substrate holder of the AFM. A conductive Pt/Ir AFM tip was placed in direct contact with the HfO{sub 2} surface, such that it acted as the top electrode. Nanoscale current-voltage (I-V) characteristics of the HfO{sub 2}/ITO/Invar structure were measured by applying a ramp voltage through the conductive AFM tip at various current compliances and ramp voltage sweep rates. It was found that the resistance of the low resistance state (RLRS) decreased with increasing current compliance value, but resistance of high resistance state (RHRS) barely changed. However, both the RHRS and RLRS decreased as the voltage sweep rate increased. The reasons for this dependency on current compliance and voltage sweep rate are discussed.

Wu, You-Lin, E-mail: ylwu@ncnu.edu.tw; Liao, Chun-Wei [Department of Electrical Engineering, National Chi Nan University, Puli, Nantou, Taiwan (China); Ling, Jing-Jenn [Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Puli, Nantou, Taiwan (China)

2014-06-16

258

Preparation of a highly sensitive enzyme electrode using gold nanoparticles for measurement of pesticides at the ppt level.  

PubMed

A highly sensitive enzyme electrode was prepared based on gold nanoparticles for measurement of pesticides. Gold nanoparticles of 25-30 nm were synthesized on a glassy carbon electrode by double-pulse technique while the coverage was controlled by applied potential and time. The gold nanoparticles were modified to form a self-assembled monolayer, followed by covalent binding of tyrosinase. The TYR-AuNP-GC electrode was compared with bare GC, AuNP-GC, and modified AuNP-GC and TYR-Au (plate type) electrodes in terms of cyclic voltammetry. The voltammograms well represent the sensitivity of enzymatic oxidation of catechol, substrates for the enzyme activity. The prepared electrode integrated into a continuous flow system and was tested to detect pesticides, such as 2,4-D, atrazine, and ziram. Under the optimized conditions of the flow system, the electrode performed reasonably according to the inhibition mechanism in the concentration range of 0.001-0.5 ng mL(-1). The enhanced performance was attributed to the favored microenvironment for the enzyme activity provided by SAM on gold nanoparticles. PMID:18449400

Kim, Gha-Young; Shim, Joonmok; Kang, Min-Su; Moon, Seung-Hyeon

2008-05-01

259

Proton conductivity of Nafion 117 as measured by a four-electrode AC impedance method  

SciTech Connect

Nafion 117{reg_sign} is a proton conducting ion-exchange membrane which is now receiving much attention due to its use as an electrolyte in the polymer-electrolyte-membrane fuel cell (PEMFC), which is of great interest for electric vehicle propulsion. The proton conductivity of Nafion 117 was measured under various conditions of humidity and temperature using a four-electrode ac impedance method. The conductivity of this membrane without heat-treatment was ca. 7.8 {times} 10{sup {minus}2} S/cm at ambient temperature and 100% relative humidity; it varied strongly with the humidity and heat-treatment of the membrane. After heat-treatment, the membrane showed a slight dependence of conductivity on temperature. From 21 to 45 C, its conductivity at a given relative humidity decreased with increasing temperature, while from 45 to 80 C it increased with temperature.

Sone, Y.; Ekdunge, P.; Simonsson, D. [Royal Inst. of Tech., Stockholm (Sweden)

1996-04-01

260

A Simple Hydrogen Electrode  

ERIC Educational Resources Information Center

This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements

Eggen, Per-Odd

2009-01-01

261

A Comparison of Two Sensors Used to Measure High-Voltage, Fast-Risetime Signals in Coaxial Cable  

Microsoft Academic Search

We consider here two sensors that are commonly used to measure high-voltage fast- risetime signals in coaxial cable. One sensor measures the current in the cable, and is called a Current-Viewing Resistor, or CVR. In this design, the cable jacket is cut, a portion of the cable jacket is removed, and a number of resistors are inserted in parallel across

Everett G. Farr; M. Atchley; Donald E. Ellibee; William J. Carey; Larry L. Altgilbers

262

The ve percent electrode system for high-resolution EEG and ERP measurements  

E-print Network

that a standard method of placement of electrodes used in electroencephalography (EEG) was needed. Possible- national Federation of Societies for Electroencephalography and Clinical Neurophysiology (Nuwer et al

Daunizeau, Jean

263

AC voltage endurance of polyimide insulated magnet wire  

Microsoft Academic Search

This paper presents results from accelerated ageing of magnet wire insulated with a 43 ¿m thick layer of polyimide. Tests were performed using samples of twisted wires and single wires covered with a silver painted grounded electrode. Comparable endurance measurements were done at different voltage and temperatures from 23°C to 215°C. The result showed that the time to failure can

Erling Ildstad; Sajal Raj Chalise

2009-01-01

264

A high current engineers approach to a high voltage impulse measurement problem  

Microsoft Academic Search

It is conventional to use power utility high-voltage test laboratories to perform lightning puncture strength tests on aircraft components such as radomes. When impulse testing power utility items, there is no interest in the voltage across or current through the item under test after failure. When testing aircraft radomes however, as the air breaks down long streamers are formed and

R. E. Baldwin

1997-01-01

265

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

SciTech Connect

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan [Variable Energy Cyclotron Centre, Kolkata (India)

2013-02-15

266

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.  

PubMed

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result. PMID:23464200

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

267

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata  

NASA Astrophysics Data System (ADS)

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

2013-02-01

268

Nonwoven Fabric Active Electrodes for Biopotential Measurement During Normal Daily Activity  

Microsoft Academic Search

Body movement is responsible for most of the interference during physiological data acquisition during normal daily activities. In this paper, we introduce nonwoven fabric active electrodes that provide the comfort required for clothing while robustly recording physiological data in the presence of body movement. The nonwoven fabric active electrodes were designed and fabricated using both hand- and screen-printing thick-film techniques.

Tae-Ho Kang; Carey R. Merritt; Edward Grant; Behnam Pourdeyhimi; H. Troy Nagle

2008-01-01

269

Development of Reliable Three-Electrode Impedance Measurements in Plastic Li-Ion Batteries  

Microsoft Academic Search

The electrochemical impedance spectroscopy ~EIS! is a well- developed technique used to predict the behavior of batteries, and to determine the factors limiting the performance of an electrode, in- cluding its conductivity, charge-transfer properties, properties of the passivation layer, etc. Numerous recent studies have been published on various aspects of the insertion electrodes used in lithium-ion cells as researchers attempt

Mickae?l Dolle?; Franc?ois Orsini; Antoni S. Gozdz; Jean-Marie Tarascona

2001-01-01

270

ELECTRODE MEASUREMENT OF REDOX POTENTIAL IN ANAEROBIC FERRIC/FERROUS CHLORIDE SYSTEMS  

EPA Science Inventory

The behavior of two inert redox electrodes (Pt and wax-impregnated graphite) was investigated in anaerobic ferrous and ferric chloride solutions in order to establish if these electrodes respond to the FE3/Fe2+ couple in a Nernstian nanner. ew method for determining dissolved fer...

271

ELECTRODE MEASUREMENT OF REDOX POTENTIAL IN ANAEROBIC FERRIC/FERROUS CHLORIDE SYSTEMS  

EPA Science Inventory

The behaviour of two inert redox electrodes (Pt and wax-impregnated graphite) was investigated in anaerobic ferrous and ferric chloride solutions in order to establish if these electrodes respond to the Fe3+/Fe2+ couple in a Nernstian manner. A new method fo...

272

X-ray spectroscopy in mammography with a silicon PIN photodiode with application to the measurement of tube voltage.  

PubMed

In this work a silicon PIN photodiode was employed in mammographic x-ray spectroscopy under clinical and nonclinical conditions. Measurements have been performed at a constant potential tungsten anode tube, adapted in this work with molybdenum filters to produce a beam like that used in mammography, and at a clinical equipment with a molybdenum anode tube by using an additional aluminum filtration. The corrected x-ray spectra were in full agreement with those generated by theoretical models published in the literature and agree well with those measured with a CdZnTe detector for tube voltages less than 30 kV. The half value layer and the relative exposure values calculated from the corrected silicon PIN photodiode spectra were in agreement with those measured with an ionization chamber. These results indicate that a silicon PIN photodiode are very suitable for mammographic x-ray spectroscopy. As an application, the voltage (kV) applied to mammographic x-ray equipment has been measured through the evaluation of the spectra high energy cut off. Uncertainties evaluated for the voltage values calculated from the measured spectra are less than 0.13% for voltages in the range 20-35 kV. The low uncertainties associated with the obtained results in this work point out that the method employed can be accurately used for calibration of noninvasive mammographic kVp meters. PMID:15587652

Künzel, Roseli; Herdade, Silvio Bruni; Terini, Ricardo Andrade; Costa, Paulo Roberto

2004-11-01

273

Multimegavolt voltage measurements in a PBFA II prototype water line using the electro-optic Kerr effect  

SciTech Connect

We have developed a highly accurate, non-perturbing, non-invasive voltage monitor for multimegavolt measurements in water using the electro-optic Kerr effect. Measurements have been made in various geometries at approx.2.5 MV in the water transmission line of the DEMON (PBFA-II demonstration) accelerator at Sandia. In each geometry, including flat parallel plates, tapered flat plates, coaxial line, and intermediate store capacitor, the Kerr voltage measurements are compared with those of standard V-dot probes. The accuracy of the Kerr measurements is approx.+-4%, improvable to < +-2%. The technique can be used to calibrate V-dot probes under full-voltage operating conditions. Moreover, in the presence of streamers or voltage nonuniformities (induced by switching feeds, e.g.), the Kerr measurements are more reliable and accurate than probes. In order to replace V-dot probes in a routine, multi-channel application, we are implementing the Kerr monitor on the streak-camera-based High Speed Multichannel Data Recorder.

Allen, G.R.; Davis, H.P.; Turman, B.N.; Bloomquist, D.D.; Chang, J.; Neyer, B.T.; Hebner, R.E.

1985-01-01

274

Electronic transport, transition-voltage spectroscopy, and the Fano effect in single molecule junctions composed of a biphenyl molecule attached to metallic and semiconducting carbon nanotube electrodes.  

PubMed

We have investigated electronic transport in a single-molecule junction composed of a biphenyl molecule attached to a p-doped semiconductor and metallic carbon nanotube leads. We find that the current-voltage characteristics are asymmetric as a result of the different electronic natures of the right and left leads, which are metallic and semiconducting, respectively. We provide an analysis of transition voltage spectroscopy in such a system by means of both Fowler-Nordheim and Lauritsen-Millikan plots; this analysis allows one to identify the positions of resonances and the regions where the negative differential conductance occurs. We show that transmittance curves are well described by the Fano lineshape, for both direct and reverse bias, demonstrating that the frontier molecular orbitals are effectively involved in the transport process. This result gives support to the interpretation of transition voltage spectroscopy based on the coherent transport model. PMID:25109887

Brito da Silva Júnior, Carlos Alberto; Leal, José Fernando Pereira; Aleixo, Vicente Ferrer Pureza; Pinheiro, Felipe A; Del Nero, Jordan

2014-09-28

275

Charge-pump voltage converter  

DOEpatents

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2009-11-03

276

Design of an Integrated Thermoelectric Generator Power Converter for Ultra-Low Power and Low Voltage Body Energy Harvesters aimed at EEG/ECG Active Electrodes  

NASA Astrophysics Data System (ADS)

This paper describes a design procedure for an efficient body thermal energy harvesting integrated power converter. This procedure is based on loss examination for a selfpowered medical device. All optimum system parameters are calculated respecting the transducer constraints and the application form factor. It is found that it is possible to optimize converter's working frequency with proper design of its pulse generator circuit. At selected frequency, it has been demonstrated that wide area voltage doubler can be eliminated at the expense of wider switches. With this method, more than 60% efficiency is achieved in simulation for just 20mV transducer output voltage and 30% of entire chip area is saved.

Ataei, Milad; Robert, Christian; Boegli, Alexis; Farine, Pierre-André

2014-11-01

277

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

278

Measurement of total calcium by flash chronopotentiometry at polymer membrane ion-selective electrodes.  

PubMed

Ionophore-based ion-selective electrodes are widely used for potentiometric electrolyte measurements, in which case they are known to detect the free ion activity. Total ion concentrations cannot be directly assessed by this methodology if the ion is predominantly present in a complexed form. We present here the direct measurement of total calcium using a calcium ion-selective electrode interrogated in a flash chronopotentiometric transduction mode. A high magnitude of cathodic current pulse is applied across a calcium ion-selective membrane containing the ionophore ETH 5234 but void of ion-exchanger to prevent spontaneous extraction. This induces a defined flux of calcium ions from the sample side to the membrane and results in the release of labile bound calcium and a concomitant depletion at the membrane surface at a critical current or time. This is observed as an inflection point on the potential-time curve and the square root of the transition time is linearly related to the total concentration in the sample. It is shown that the responses to solutions of labile calcium complexes of nitrilotriacetic acid (NTA) are in a good agreement with that of the same concentration of calcium chloride in saline solution with this protocol. Initial applications are aimed towards assaying extracellular calcium. Calcium binding to albumin is shown to be inconsequential with sample dilutions typical for clinical assays. Calcium calibration curves in real and artificial dilute serum are finally shown to correspond to that of calcium chloride, suggesting that the methodology is indeed capable of detecting total calcium under these conditions. The present membrane materials allow detection of up to over 0.5mM total calcium in serum, currently requiring such samples to be diluted about 5-fold. The slopes of the square root of time-concentration dependence for the calibrations of free calcium in a background of NaCl and total serum calcium were found to be 3.857 and 3.717 s(1/2)mM(-1), respectively, deviating by just 3.6%. The lower detection limit (3x SD) was calculated as 12 microM. PMID:19646590

Gemene, Kebede L; Bakker, Eric

2009-08-26

279

Use of vacuum tubes in test instrumentation for measuring characteristics of fast high-voltage semiconductor devices  

NASA Technical Reports Server (NTRS)

Circuits are described that permit measurement of fast events occurring in power semiconductors. These circuits were developed for the dynamic characterization of transistors used in inductive-load switching applications. Fast voltage clamping using vacuum diodes is discussed, and reference is made to a unique circuit that was built for performing nondestructive, reverse-bias, second-breakdown tests on transistors.

Berning, D.

1981-01-01

280

Electrical measurements of voltage stressed Al2O3/GaAs MOSFET , P.D. Ye b  

E-print Network

Electrical measurements of voltage stressed Al2O3/GaAs MOSFET Z. Tang a , P.D. Ye b , D. Lee a , C layer deposition deposited Al2O3 gate dielectric have been investigated. The IV characteristics were charges may be first removed from the Al2O3 layer during the initial CVS, while the trapping of electrons

Ye, Peide "Peter"

281

Feasibility of using respiratory correlated mega voltage cone beam computed tomography to measure tumor motion.  

PubMed

The purpose of this study was to test the feasibility of using respiratory correlated mega voltage cone-beam computed tomography (MVCBCT), taken during patient localization, to quantify the size and motion of lung tumors. An imaging phantom was constructed of a basswood frame embedded with six different-sized spherical pieces of paraffin wax. The Quasar respiratory motion phantom was programmed to move the imaging phantom using typical respiratory motion. The moving imaging phantom was scanned using various MVCBCT imaging parameters, including two beam line types, two protocols with different ranges of rotation and different imaging doses. A static phantom was also imaged as a control. For all the 3D volumetric images, the contours of the six spherical inserts were measured manually. Compared with the nominal sphere diameter, the average relative error in the size of the respiratory correlated MVCBCT spheres ranged from 5.3% to 12.6% for the four largest spheres, ranging in size from 3.6 cc to 29 cc. Larger errors were recorded for the two smallest inserts. The average relative error in motion was 5.1% smaller than the programmed amplitude of 3.0 cm. We are able to conclude that it is feasible to use respiratory correlated MVCBCT to quantify tumor motion for lung cancer patients. PMID:21587196

Chen, Mingqing; Siochi, R Alfredo

2011-01-01

282

Impedances of Nickel Electrodes Cycled in Various KOH Concentrations  

NASA Technical Reports Server (NTRS)

Impedances were measured of electrodes from boiler-plate cells cycled i n KOH concentrations from 21% to 36%. These cells under accelerated conditions at 80% DOD to failure, defined discharge voltage. Cell life ranged from about 1,000 t o 40 impedances were measured at five voltages corresponding to charge. The results were analyzed using a standard circuit model including a Warburg impedance term. The kinetic resistances and Warburg slopes were greater for those electrodes which had failed earliest. Other circuit models have also been examined. The results are considered indicative but not conclusive, since the cells had been stored after failure for varying lengths of time which is known to affect the impedance. In order to minimize the effects of storage, the electrodes were cycled 10 times before the impedance measurements were taken.

Reid, Margaret A.; Loyselle, Patricia L.

1991-01-01

283

A new electro-optic hybrid current-sensing scheme for current measurement at high voltage  

NASA Astrophysics Data System (ADS)

A new electro-optic hybrid current sensor is presented here. The sensor consists of three parts: first is a Rogowski coil and integrator whose output voltage is proportional to the current flowing in the power line. Second is a combination voltage to frequency converter and electro-optic converter. The combination converter transforms the integrated Rogowski coil voltage into a FM optical signal. The optical signal can then be transmitted to a low voltage region via an optical fiber for subsequent demodulation processing. Third is an intrinsic power supply in which a small conventional current transformer is used to draw power from the power line. A current sensor based on this design was developed, having a diameter of 15 cm, length of 30 cm, and weight of 2 kg, and has been working well at a 110 kV substation for two years. This sensor features small size, light weight, high accuracy, low cost, and reduced hazard.

Zhang, Gang; Li, Shaohui; Qin, Yi; Zhang, Zhipeng

1999-09-01

284

Polarographic Electrode Measures of Cerebral Tissue Oxygenation: Implications for Functional Brain Imaging  

PubMed Central

The changes in blood flow, blood volume and oxygenation that accompany focal increases in neural activity are collectively referred to as the hemodynamic response and form the basis of non-invasive neuroimaging techniques such as blood oxygen level dependent (BOLD) functional magnetic resonance imaging. A principle factor influencing blood oxygenation, the cerebral metabolic rate of oxygen consumption is poorly understood and as such, data from imaging techniques are difficult to interpret in terms of the underlying neural activity. In particular how neurometabolic changes vary temporally, spatially and in magnitude remains uncertain. Furthermore knowledge of which aspects of neural activity are closely reflected by metabolic changes is essential for the correct interpretation of cognitive neuroscience studies in terms of information processing. Polarographic electrode measurements of cerebral tissue oxygenation in animal models following presentation of sensory stimuli have started to address these issues. Early studies demonstrated both increases and decreases in tissue oxygenation following neural activation. However a recent series of elegant studies in the cat visual system demonstrated a tight spatial and temporal coupling between evoked peri-synaptic activity and oxygen consumption following presentation of visual stimuli.

Bartlett, Kate; Saka, Mohamad; Jones, Myles

2008-01-01

285

Spark breakdown of liquid hydrocarbons. I. Fast current and voltage measurements of the spark breakdown in liquid n-hexane  

NASA Astrophysics Data System (ADS)

A fast coaxial discharge line for the study of the electric breakdown of liquid hydrocarbons is described. It allows the simultaneous measurement of discharge current (up to 5 kA) and voltage (up to 50 kV) with nanosecond time resolution. The spark gap is of tip-plane geometry. A detailed frequency analysis of the discharge and measurement circuits has been performed. Examples for the spark breakdown of n-hexane under a variety of conditions are presented.

Fuhr, Jitka; Schmidt, Werner F.; Sato, Shuji

1986-06-01

286

A Comparison of Two Sensors Used to Measure High-Voltage, Fast-Risetime Signals in Coaxial Cable  

Microsoft Academic Search

We consider here two sensors that are commonly used to measure high-voltage fast-risetime signals in coaxial cable. One sensor measures the current in the cable, and is called a Current-Viewing Resistor, or CVR. In this design, the cable jacket is cut, a portion of the cable jacket is removed, and a number of resistors are inserted in parallel across the

Everett G. Farr; Lanney M. Atchley; Donald E. Ellibee; William J. Carey; Larry L. Altgilbers

2007-01-01

287

In situ measurements of electrode work functions in free-burning arcs during operation at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A method of in situ measurement of electrode work functions in free-burning argon arcs during operation is presented. This technique is based on the photoelectric effect ocurring at the surface of a tungsten cathode with the use of a pulse laser system consisting of a Nd-YAG laser and a dye laser. Three types of tungsten electrode, namely, pure W, W-2% ThO2 and W-2% La2O3 are used in this work. Free-burning arcs are operated in argon at atmospheric pressure at currents of 100 A and 200 A. The effective work functions of pure W, W-2% ThO2 and W-2% La2O3 electrodes during operation at a current of 200 A are found to be, respectively, 4.6, 2.8 and 3.0 eV from in situ measurements. These results are very close to the work functions of pure W, ThO2 and La2O3 obtained from the literature. The in situ measurements, however, show that the effective work functions of pure W, W-2% ThO2 and W-2% La2O3 electrodes for an 100 A arc are, respectively, 2.9 eV, 2.6 eV and 2.0 eV. It is shown that each effective work function for an 100 A arc clearly becomes lower than that for a 200 A arc for all types of tungsten electrodes.

Tanaka, Manabu; Ushio, Masao; Ikeuchi, Mitsuru; Kagebayashi, Yoshiro

2005-01-01

288

Dynamic Analysis of Mcfc Porous Electrode  

NASA Astrophysics Data System (ADS)

The intent of this work is to develop AC impedance measurements, in combination with other methods, as a tool to determine the relative importance of various resistance sources in the multi-step process occurring at a gas-diffusion porous electrode. In particular, the case of a MCFC cathode is studied. The goals of this study are: (1) elucidation of electrode mechanism; (2) analysis of the porous electrode performance for the purpose of optimizing design; and (3) developing the capabilities of AC impedance as an index of long-term cell performance decay. The oxygen reduction reaction of molten carbonate fuel cell and the corresponding kinetic as well as transport parameters were tried to be estimated by using impedance techniques combining with other electrochemical methods from flag, wire and rotating disk electrodes in pot cell as well as porous electrode in lab cell. The dominant pathway for oxygen reduction in 62%Li _2CO_3/38%K _2CO_3 melt at 650^circC is via superoxide ions. This follows from flag electrode impedance results indicating that O_sp{2}{ -}/CO_2 mixed diffusion is the dominant source of resistance. The polarization behavior of gas-diffusion porous electrodes has been analyzed in terms of individual voltage loss and overall voltage loss. In most cases, the optimal electrolyte filling will be obtained when the dominant source of voltage loss switches from ohmic or mass transfer resistances to kinetic activation resistance, and similar behavior for optimal electrode thickness. Pressurized operation is favorable for performance if the reaction mechanism follows the superoxide mechanism, but not if the peroxide path dominates. A distributed-network approach has been developed and it is concluded that a digital simulation of AC-superimposed -on-DC impedance of a porous electrode is possible and helpful. Kinetic activation and mass transfer resistances are extracted separate and conclude that both peroxide and superoxide contribute the oxygen reduction around rest potential, but the superoxide will be the dominant reduction species under current load. CO_2 can somewhat reacts with (O)^- to form CO _sp{3}{=}, this leads CO_2 has a near zero reaction order for porous electrode. The capabilities of using AC impedance techniques for monitoring the long term cell performance is promising but needs further development.

Lee, Gwo-Lin Kevin

1992-01-01

289

Absolute Standard Hydrogen Electrode Potential Measured by Reduction of Aqueous Nanodrops in the Gas Phase  

PubMed Central

In solution, half-cell potentials are measured relative to those of other half cells, thereby establishing a ladder of thermochemical values that are referenced to the standard hydrogen electrode (SHE), which is arbitrarily assigned a value of exactly 0 V. Although there has been considerable interest in, and efforts toward, establishing an absolute electrochemical half-cell potential in solution, there is no general consensus regarding the best approach to obtain this value. Here, ion-electron recombination energies resulting from electron capture by gas-phase nanodrops containing individual [M(NH3)6]3+, M = Ru, Co, Os, Cr, and Ir, and Cu2+ ions are obtained from the number of water molecules that are lost from the reduced precursors. These experimental data combined with nanodrop solvation energies estimated from Born theory and solution-phase entropies estimated from limited experimental data provide absolute reduction energies for these redox couples in bulk aqueous solution. A key advantage of this approach is that solvent effects well past two solvent shells, that are difficult to model accurately, are included in these experimental measurements. By evaluating these data relative to known solution-phase reduction potentials, an absolute value for the SHE of 4.2 ± 0.4 V versus a free electron is obtained. Although not achieved here, the uncertainty of this method could potentially be reduced to below 0.1 V, making this an attractive method for establishing an absolute electrochemical scale that bridges solution and gas-phase redox chemistry. PMID:18288835

Donald, William A.; Leib, Ryan D.; O'Brien, Jeremy T.; Bush, Matthew F.; Williams, Evan R.

2008-01-01

290

Carrier transport and collection in fully depleted semiconductors by a combined action of the space charge field and the field due to electrode voltages  

DOEpatents

A semiconductor charge transport device and method for making same, characterized by providing a thin semiconductor wafer having rectifying junctions on its opposing major surfaces and including a small capacitance ohmic contact, in combination with bias voltage means and associated circuit means for applying a predetermined voltage to effectively deplete the wafer in regions thereof between the rectifying junctions and the ohmic contact. A charge transport device of the invention is usable as a drift chamber, a low capacitance detector, or a charge coupled device each constructed according to the methods of the invention for making such devices. Detectors constructed according to the principles of the invention are characterized by having significantly higher particle position indicating resolution than is attainable with prior art detectors, while at the same time requiring substantially fewer readout channels to realize such high resolution.

Rehak, Pavel (Patchogue, NY); Gatti, Emilio (Lesmo, IT)

1987-01-01

291

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

292

Influence of Humidity on the Electrical Conductivity of Synthesized DNA Film on Nanogap Electrode  

Microsoft Academic Search

We have studied the electrical conductivity of DNA film using nanogap electrodes. Current-voltage measurements and alternating current measurements were performed for analysis of conductivity. The electrical conductivity of the DNA films of poly(dG)\\\\cdotpoly(dC) are found to depend strongly on the humidity. The resistance of poly(dG)\\\\cdotpoly(dC) decreases dramatically with increasing relative humidity. The contact resistance between DNA film and Au electrodes

Yoichi Otsuka; Hea-yeon Lee; Jian-hua Gu; Jeong-O Lee; Kyung-Hwa Yoo; Hidekazu Tanaka; Hitoshi Tabata; Tomoji Kawai

2002-01-01

293

Spatially resolved in situ measurements of the ion distribution near the surface of electrode in a steady-state diffusion in an electrolytic tank with confocal micro X-ray fluorescence.  

PubMed

Confocal micro-X-ray fluorescence (MXRF) technology based on a polycapillary focusing X-ray lens and a polycapillary parallel X-ray lens was used to carry out element-resolved and in situ analysis of ion distribution near the surface of the electrode in a steady-state diffusion in an electrolytic tank. The standard curve of the Cu K? fluorescence intensity corresponding to the concentration of CuCl2 was measured to quantitatively determine the ion distribution near the surface of the electrode in a steady-state diffusion. The distribution of the electrolytic ions around the surface of the electrode in the electrolytic tank was measured in situ, and the effects of the concentration of the electrolyte and the bath voltage on the shape of the layer with a nonuniform distribution of the Cu(2+) ions near the cathode surface in a steady state were analyzed with the confocal MXRF. The confocal MXRF has potential applications in spatially resolved analysis of the liquid mass transfer in electrolytic tanks in situ. PMID:24354283

Peng, Song; Liu, Zhiguo; Sun, Tianxi; Ma, Yongzhong; Ding, Xunliang

2014-01-01

294

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

295

An area-efficient 55 nm 10-bit 1-MS/s SAR ADC for battery voltage measurement  

NASA Astrophysics Data System (ADS)

An area-efficient CMOS 1-MS/s 10-bit charge-redistribution SAR ADC for battery voltage measurement in a SoC chip is proposed. A new DAC architecture presents the benefits of a low power approach without applying the common mode voltage. The threshold inverter quantizer (TIQ)-based CMOS Inverter is used as a comparator in the ADC to avoid static power consumption which is attractive in battery-supply application. Sixteen level-up shifters aim at converting the ultra low core voltage control signals to the higher voltage level analog circuit in a 55 nm CMOS process. The whole ADC power consumption is 2.5 mW with a maximum input capacitance of 12 pF in the sampling mode. The active area of the proposed ADC is 0.0462 mm2 and it achieves the SFDR and ENOB of 65.6917 dB and 9.8726 bits respectively with an input frequency of 200 kHz at 1 MS/s sampling rate.

Hongming, Chen; Yueguo, Hao; Long, Zhao; Yuhua, Cheng

2013-09-01

296

Measurements of stray antenna capacitance in the STEREO\\/WAVES instrument: Comparison of the measured voltage spectrum with an antenna electron shot noise model  

Microsoft Academic Search

One of the most accurate techniques for in situ measuring the electron density and temperature in space plasmas is the quasi-thermal noise spectroscopy, which uses the voltage fluctuation spectrum on an electric antenna. This technique has been used successfully on the WIND and ULYSSES spacecraft; however, on STEREO this technique may only work in high-density filamentary structures, where the Debye

I. Zouganelis; M. Maksimovic; N. Meyer-Vernet; S. D. Bale; J. P. Eastwood; A. Zaslavsky; M. Dekkali; K. Goetz; M. L. Kaiser

2010-01-01

297

Eight electrode optical readout gap  

DOEpatents

A protective device for a plurality of electrical circuits includes a plurality of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

Boettcher, G.E.; Crain, R.W.

1984-01-01

298

Measurement of high-voltage and radiation-damage limitations to advanced solar array performance  

NASA Technical Reports Server (NTRS)

A description is given of the reconfigured Photovoltaic Array Space Power (PASP) Plus experiment: its objectives, solar-array complement, and diagnostic sensors. Results from a successful spaceflight will lead to a better understanding of high-voltage and radiation-damage limitations in the operation of new-technology solar arrays.

Guidice, D. A.; Severance, P. S.; Keinhardt, K. C.

1991-01-01

299

A test and measurement technique for determining possible lightning-induced voltages in aircraft electrical circuits  

NASA Technical Reports Server (NTRS)

Transient analyzer consists of four 0.5 microfarads capacitors chargeable by self-contained solid state 50 KV dc power supply operating from standard 110 Vac line voltage. Unit can circulate unidirectional current impulses of up to 500 amperes through aircraft at waveshapes similar to those of natural lightning strokes.

Plumer, J. A.; Walko, L. C.

1975-01-01

300

An On-Chip NBTI Sensor for Measuring PMOS Threshold Voltage Degradation  

E-print Network

-H bonds at the oxide interface by holes in the PMOS inversion layer. The bond breaking process causes hydrogen species to diffuse into the gate oxide, creating interfacial and bulk traps (Figure 1.a). Those traps is commonly cited as the root or sole cause of the threshold voltage shift, oxide trapped holes

Kim, Chris H.

301

Selection of Electrode Area for Electrochemical Noise Measurements to Monitor Localized CO2 Corrosion  

E-print Network

Corrosion Xiu Jianga,b , Srdjan Nesia* , François Huetc , Brian Kinsellaa , Bruce Browna , David Younga a Institute for Corrosion and Multiphase Technology, Department of Chemical and Biomolecular Engineering, Ohio electrodes were recorded using a ZRA (Zero Resistance Ammeter) to monitor localized CO2 corrosion in CO2

Paris-Sud XI, Université de

302

Automated Targeting of Cells to Electrochemical Electrodes Using a Surface Chemistry Approach for the Measurement of Quantal Exocytosis  

PubMed Central

Here, we describe a method to fabricate a multichannel high-throughput microchip device for the measurement of quantal transmitter release from individual cells. Instead of bringing carbon-fiber electrodes to cells, the device uses a surface chemistry approach to bring cells to an array of electrochemical microelectrodes. The microelectrodes are small and cytophilic in order to promote adhesion of a single cell, whereas all other areas of the chip are covered with a thin cytophobic film to block cell attachement and facilitate the movement of cells to electrodes. This cytophobic film also insulates unused areas of the conductive film; thus, the alignment of cell docking sites to working electrodes is automatic. Amperometric spikes resulting from single-granule fusion events were recorded on the device and had amplitudes and kinetics similar to those measured using carbon-fiber microelectrodes. Use of this device will increase the pace of basic neuroscience research and may also find applications in drug discovery or validation. PMID:21113333

2010-01-01

303

Fully integrated CMOS microsystem for electrochemical measurements on 32 × 32 working electrodes at 90 frames per second.  

PubMed

Microelectrode arrays offer the potential to electrochemically monitor concentrations of molecules at high spatial resolution. However, current systems are limited in the number of sensor sites, signal resolution, and throughput. Here, we present a fully integrated complementary metal oxide semiconductor (CMOS) system with an array of 32 × 32 working electrodes to perform electrochemical measurements like amperometry and voltammetry. The array consists of platinum electrodes with a center-to-center distance of 100 ?m and electrode diameters of 5 to 50 ?m. Currents in the range from 10 ?A down to pA can be measured. The current is digitized by sigma-delta converters at a maximum resolution of 13.3 bits. The integrated noise is 220 fA for a bandwidth of 100 Hz, allowing for detection of pA currents. Currents can be continuously acquired at up to 1 kHz bandwidth, or the whole array can be read out rapidly at a frame rate of up to 90 Hz. The results of the electrical characterization meet the requirements of a wide range of electrochemical methods including cyclic voltammograms and amperometric images of high spatial and temporal resolution. PMID:24941330

Rothe, Joerg; Frey, Olivier; Stettler, Alexander; Chen, Yihui; Hierlemann, Andreas

2014-07-01

304

How well do cochlear implant intraoperative impedance measures predict postoperative electrode function?  

PubMed Central

Objective Objectives were to: 1) evaluate the incidence of abnormal cochlear implant electrode impedance intraoperatively and at the initial activation, 2) identify the percentage of abnormalities that resolve by the initial activation, and 3) determine the incidence of normal intraoperative impedances that present as abnormal at the initial activation. Study Design Retrospective records review of intraoperative and postoperative cochlear implant electrode impedances. Setting Tertiary referral center. Patients Records were examined for 194 devices implanted in 165 pediatric and adult patients. Results Results indicate at least 1 open (OC) or short circuit (SC) in 12.4% (24/194) of devices intraoperatively, decreasing to 8.2% (16/194) postoperatively. OCs were more prevalent than SCs for intraoperative (92% vs. 8%) and postoperative (94% vs. 6%) intervals. Of the 3430 total electrodes, 78 had abnormal impedance intraoperatively. Sixty-four of those (82%) resolved by the postoperative interval (62 OC, 2 SC) while 14/78 (18%) remained abnormal postoperatively (12 OC, 2 SC). Six of 3430 (0.17%) electrodes had normal impedance intraoperatively but were abnormal postoperatively. Conclusions The incidence of SCs in the present study is likely underestimated due to poor sensitivity of monopolar coupling for detecting SCs. Intraoperative OCs have a high probability of resolving by the initial activation, particularly when contiguous electrodes are affected, and suggests limited need for the use of a backup device in these cases. Surgical technique and/or complications such as explant/reimplant or perilymphatic gushers may result in increased incidence of bubbles in the cochlea, and may play a role in abnormal intraoperative impedance results. PMID:23295726

Goehring, Jenny L.; Hughes, Michelle L.; Baudhuin, Jacquelyn L.; Lusk, Rodney P.

2012-01-01

305

Elucidation of a Peculiar Phenomenon of Voltage Measuring at a Substation  

NASA Astrophysics Data System (ADS)

An automatic fault-recorder installed in a substation of Chubu Electric Power Company detected a peculiar phenomenon that bus-bar voltage fell to around 20-30% of the nominal value for a short time (about 8-10 cycles) though electric current didn't change during the period. The phenominon was recorded several times. In this paper, we analyzed the origin of this phenomenon and conducted simulations by EMTP. As a result, we estimated that this phenomenon occurred by the saturation of VT (voltage transformer), and this saturation caused by lightning strokes to the transmission line with line arresters, which have been increasingly installed in recent years. Moreover, we evaluated the influence of the phenomenon to protection relays.

Takafuji, Kouya; Satou, Takashi; Itou, Hisanori; Kouda, Isao; Haba, Toshiaki; Satake, Atushi; Haginomori, Eiichi

306

Design of the Wireless Temperature Measurement Alarming System in the High-Voltage Transformer Substation  

Microsoft Academic Search

Due to electric power overload and equipment aging, fire and explosion occur at transmission circuitry joints in high-voltage\\u000a transformer substation caused by high temperatures accumulated at these spots. This frequently brings huge financial loss.\\u000a Conventional far-infrared temperature detector is inefficient for its limited precision level and real-time temperature detection\\u000a using fibre optic cable system appears to be too costly. This

Qiang Gao; Hongli Wang; Huaxiang Wang

307

Analysis of the photo voltage decay /PVD/ method for measuring minority carrier lifetimes in P-N junction solar cells  

NASA Technical Reports Server (NTRS)

The photo voltage decay (PVD) method for the measurement of minority carrier lifetimes in P-N junction solar cells with cell thickness comparable to or even less than the minority carrier diffusion length is examined. The method involves the generation of free carriers in the quasi-neutral bulk material by flashes of light and the monitoring of the subsequent decay of the induced open-circuit voltages as the carriers recombine, which is dependent on minority carrier recombination lifetime. It is shown that the voltage versus time curve for an ordinary solar cell (N(+)-P junction) is proportional to the inverse minority carrier lifetime plus a factor expressing the ratio of diffusion length to cell thickness. In the case of an ideal back-surface-field cell (N(+)-P-P(+) junction) however, the slope is directly proportional to the inverse minority carrier lifetime. It is noted that since most BSF cells are not ideal, possessing a sizable back surface recombination velocity, the PVD measurements must be treated with caution and supplemented with other nonstationary methods.

Von Roos, O.

1981-01-01

308

Measurement of low radioactivity background in a high voltage cable by high resolution inductively coupled plasma mass spectrometry  

SciTech Connect

The measurement of naturally occurring low level radioactivity background in a high voltage (HV) cable by high resolution inductively coupled plasma mass spectrometry (HR ICP MS) is presented in this work. The measurements were performed at the Chemistry Service of the Gran Sasso National Laboratory. The contributions to the radioactive background coming from the different components of the heterogeneous material were separated. Based on the mass fraction of the cable, the whole contamination was calculated. The HR ICP MS results were cross-checked by gamma ray spectroscopy analysis that was performed at the low background facility STELLA (Sub Terranean Low Level Assay) of the LNGS underground lab using HPGe detectors.

Vacri, M. L. di; Nisi, S.; Balata, M. [Gran Sasso National Laboratory, Chemistry Service, SS 17bis km 18.910, 67100 Assergi (Aq) (Italy)] [Gran Sasso National Laboratory, Chemistry Service, SS 17bis km 18.910, 67100 Assergi (Aq) (Italy)

2013-08-08

309

Measurement of low radioactivity background in a high voltage cable by high resolution inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

The measurement of naturally occurring low level radioactivity background in a high voltage (HV) cable by high resolution inductively coupled plasma mass spectrometry (HR ICP MS) is presented in this work. The measurements were performed at the Chemistry Service of the Gran Sasso National Laboratory. The contributions to the radioactive background coming from the different components of the heterogeneous material were separated. Based on the mass fraction of the cable, the whole contamination was calculated. The HR ICP MS results were cross-checked by gamma ray spectroscopy analysis that was performed at the low background facility STELLA (Sub Terranean Low Level Assay) of the LNGS underground lab using HPGe detectors.

di Vacri, M. L.; Nisi, S.; Balata, M.

2013-08-01

310

[29] It was not possible to measure the adsorption of DMAP stabilized gold nanoparticles onto bare (gold-coated) QCM electrodes, as the gold sur-  

E-print Network

[29] It was not possible to measure the adsorption of DMAP stabilized gold nanoparticles onto bare (gold-coated) QCM electrodes, as the gold sur- face destabilized the nanoparticle solution and caused

311

Making hexagonal electrodes on Nafion for deformable mirrors applications  

NASA Astrophysics Data System (ADS)

In this paper, a fabrication of IPMC (Ionic Polymer Metal Composites) films with hexagonal electrodes for deformable mirrors applications has been described. With the array of hexagonal electrodes on one side of IPMC membrane, we can control the contour of IPMC by driving voltage selectively. Our fabrication process involves ion-exchange, lithography, and electroless plating steps. A positive photoresist in photolithography is used as the mask in the electroless plating process to selectively grow platinum electrodes in IPMC regions. We have measured the surface resistance of the IPMC. The surface resistance of the hexagonal electrodes is about 5?, which is small enough to enable the IPMC to be actuated by low voltage. The other side of the IPMC membrane is smooth and can be used as reflection surface. We have generated deformation on our IPMCs (5 cm X 5 cm) under a low actuation voltage less than 5 volts successfully. The maximum stroke of the IPMC deformable mirror is about 25 um. Due to the low driving voltage of IPMCs, the deformable mirrors made of IPMCs is promising.

Huang, Po-Jung; Su, Guo-Dung J.

2014-09-01

312

A summary of the low angle x-ray atomic scattering factors which have been measured by the critical voltage effect in High Energy Electron Diffraction (HEED)  

SciTech Connect

A tabulated summary of all the accurate (/approximately/0.1%) low-angle x-ray atomic scattering (form) factors which have been determined by the systematic critical voltage technique in HEED is presented. For low atomic number elements (Z/approx lt/40) the low angle form factors can be significantly different to best free atom values, and so the best band structure calculated and/or x-ray measured form factors consistent with the critical voltage measurements are also indicated. At intermediate atomic numbers Zapprox. =40..-->..50 only the very low-angle form factors appear to be different to the best free atom values, and even then only by a small amount. For heavy elements (Z/approx lt/70) the best free atom form factors appear to agree very closely with the critical voltage measured values and so, in this case, critical voltage measurements give very accurate measurements of Debye-Waller factors. 48 refs.

Fox, A.G.; Fisher, R.M.

1987-08-01

313

Characterization of charge carrier injection in organic and hybrid organic/inorganic semiconductor devices by capacitance-voltage measurements  

NASA Astrophysics Data System (ADS)

Organic and hybrid organic / inorganic semiconductor heterostructures offer great potential as key technology for cost-efficient electro-photonic devices. To exploit their full potential, fundamental understanding of charge carrier injection is essential. Therefore we use current-luminance-voltage (I-L-V) and capacitance-voltage (C-V) measurements to analyze the injection characteristics of monochrome OLED test structures and hybrid organic / inorganic (HOI) pentacene / n-GaN and Alq3 / n-GaN heterostructures processed by organic vapor phase deposition (OVPD) and metal organic chemical vapor deposition (MOCVD), respectively. In a first step, we fundamentally analyze the specific C-V characteristics of OLED test structures. The multilayer devices show additional features in the C-V profile as compared to the bilayer OLED investigated by Brütting et al.1,2. We attribute this behavior to the additional organic / organic interfaces and the resulting energetic barriers in multilayer devices. In addition, we compared the C-V measurements of pristine and degraded OLED test structures. Here we conclude that a deterioration of hole injection in degraded devices is dominant, whereas electron injection remains largely unaffected. Furthermore, in pristine and degraded OLED, increased temperatures generally lead to improved charge injection as well as a reduced impact of the additional barriers in multilayer stacks. By analyzing I-V and C-V measurements of HOI heterostructures, we find ambipolar currents in pentacene-based diodes with electrons from n-GaN being injected at lower bias than the onset of hole injection from the gold anode contacts. Generally, I-V measurements of both types of HOI heterostructures show an onset of charge injection at very low bias voltage. Accordingly, n-GaN offers superior electron injection characteristics recommending n-GaN as cathode contact e.g. in fully transparent OLED microdisplays.

Weingarten, M.; Slawinski, M.; Urbain, F.; Fahle, D.; Bertram, D.; Heuken, M.; Kalisch, H.; Vescan, A.

2012-09-01

314

Amplifier for measuring low-level signals in the presence of high common mode voltage  

NASA Technical Reports Server (NTRS)

A high common mode rejection differential amplifier wherein two serially arranged Darlington amplifier stages are employed and any common mode voltage is divided between them by a resistance network. The input to the first Darlington amplifier stage is coupled to a signal input resistor via an amplifier which isolates the input and presents a high impedance across this resistor. The output of the second Darlington stage is transposed in scale via an amplifier stage which has its input a biasing circuit which effects a finite biasing of the two Darlington amplifier stages.

Lukens, F. E. (inventor)

1985-01-01

315

Aquifer and Vadose Zone Pollution Determined From Geoelectrical Measurements With Multi- Electrode Wells and Surface Multi-Profiling  

NASA Astrophysics Data System (ADS)

During the last three years we are developing hydrobiogeological researches to quantitatively describe the underground contamination of a 4.0 km2 area, including two landfill deposits and a tannery industry of Alagoinhas city, Bahia state, Brazil. We used electrical geophysics, geological, geochemical and biological analysis to gain a general understanding of the complex interactions between organic and inorganic pollutants and their environmental impacts. A geological reconnaissance work and a geoelectrical survey using vertical electrical soundings were made around the area to detect and to delineate the extent of the underground contamination plume. The results pointed out the presence of a strong conductive anomaly within the aquifer resulting from invasive fluids both from the landfills and from the surface disposal lagoons from the tannery. Water samples collected at available wells and along the Sauipe river, have shown drastic changes in the total dissolved solids, total chromium, inorganic macro-components, biochemical oxygen demand, chemical oxygen demand, nutrients and bacterial content. As a complimentary work, apparent resistivity and chargeability data were measured as a function of depth along three new multi-electrode wells, and as a function of electrode spacing along five double semi-Schlumberger subsurface profiles. A multi-electrode well is a special monitoring well where we externally install copper electrodes as thin metallic rings spaced by 0.50 m, along its entire filter and casing length. Such electrodes are connected through insulated cables to the ground surface and may be combined into different arrays. Two-side semi-Schlumberger soundings expanded up to 200 m AB/2 spacing and with centers spaced by 50 m along special transverse centered at the plume were inverted using 1D and 2D models. Both techniques were used to detail the groundwater contamination around the Alagoinhas landfills. The electrical measurements performed at the earth surface and within wells, were used both to characterize the plume and to estimate changes in water saturation and water chemistry bellow the water table and throughout the upper vadose section of the Marizal- São Sebastião aquifer system. Well data were acquired during three different campaigns of 2004-2006 years, covering a complete seasonal cycle. The results are quantitativelyinterpreted using the volume conductivity approach described by Lima et al. (2005) extended for condiction of partial water saturation.

de Lima, O. A.; Pereira, P. D.

2007-05-01

316

Fabrication of Two-Layered Channel System with Embedded Electrodes to Measure Resistance Across Epithelial and Endothelial Barriers  

PubMed Central

This manuscript describes a straightforward fabrication process for embedding Ag/AgCl electrodes within a two-layer PDMS microfluidic chip where an upper and a lower channel are separated by a semi-porous membrane. This system allows for the reliable real-time measurement of trans-endothelial and trans-epithelial electrical resistance (TEER), an accepted quantification of cell monolayer integrity, across cells cultured on membranes inside the microchannels using impedance spectroscopy. The technique eliminates the need for costly or specialized microelectrode fabrication, enabling commercially available wire electrodes to easily be incorporated into PDMS microsystems for measuring TEER under microfluidic environments. The capability of measuring impedance across a confluent cell monolayer is confirmed using (i) brain-derived endothelial cells (bEND.3), (ii) Madin Darby Canine Kidney Cells (MDCK-2), and mouse myoblast (C2C12) (all from ATCC, Manassas, VA). TEER values as a function of cell type and cell culture time were measured and both agree with previously published values from macro-scale culture techniques. This system opens new opportunities for conveniently resolving both trans-endothelial and trans-epithelial electrical resistance to monitor cell function in real-time in microfluidic cell cultures. PMID:20178370

Douville, Nicholas J.; Tung, Yi-Chung; Li, Ran; Wang, Jack Dong; El-Sayed, Mohamed E.H.; Takayama, Shuichi

2010-01-01

317

High voltage grounding device for pressurized equipment  

Microsoft Academic Search

A safety device is described for discharging high voltage circuits operated in pressurized containers. The device is positioned in pressurized containers. The device is positioned within an elbow or other protrusion through which passes the high voltage feed-through electrode. In one embodiment the grounding contact is automatically forced against the high voltage contact by the expansion of a bellows upon

J. W. Ogland

1985-01-01

318

Electrochemical performance of platinum electrodes within the multi-electrode spiral nerve cuff.  

PubMed

In this study, the electrochemical performance of platinum electrodes within a multi-electrode spiral cuff to be used for selective nerve stimulation was investigated. The original cuff, simplified into a half-cuff, contained a single row of nine electrodes (0.5 × 2 mm) at a distance of 2 mm from its inner surface. Cyclic voltammetry was used to investigate the electrochemical reactions at the electrode-electrolyte interface, to define a potential window within which the electrode could be safely used in selective nerve stimulation, to calculate the charge injection capacity and cathodal charge storage capacity. Voltage transients retrieved during excitation with quasitrapezoidal biphasic current pulses, tested by selective nerve stimulation of the isolated porcine left cervical vagus nerve segment, were used to determine the maximum polarization across the electrode-electrolyte interface and to calculate cathodic charge injection capacity of the electrode. The results show that the most negative and most positive potentials across the electrode-electrolyte interface reached -0.54 and 0.59 V; these did not exceed the safe potential limits for water electrolysis. Furthermore, the time integral of the cathodic current by cyclic voltammetry measured over the potential range of water electrolysis, actually representing the cathodal charge storage capacity, was approximately -4 mC cm(-2). The charge injection capacity, representing the maximum charge density injected in a current stimulation pulse, using only reversible processes, however, was around 75 µC cm(-2). In conclusion, both, the tested stimulation pulse and electrode are suitable for efficient and safe selective nerve stimulation. PMID:24938675

Rozman, Janez; Pe?lin, Polona; Mehle, Andraž; Šala, Martin

2014-09-01

319

Determining resistivity of a formation adjacent to a borehole having casing with an apparatus having all current conducting electrodes within the cased well  

DOEpatents

Methods of operation of different types of multiple electrode apparatus vertically disposed in a cased well to measure information useful to determine the resistivity of adjacent geological formations from within the cased well are described. The multiple electrode apparatus has a plurality of spaced apart voltage measurement electrodes that electrically engage a portion of the interior of the cased well. During measurements of information useful to determine formation resistivity, current is conducted between a first current conducting electrode in electrical contact with the interior of the cased well to a second current conducting electrode that is also in electrical contact with the interior of the cased well. The first and second current conducting electrodes are separated by a distance sufficient so that at least a portion of the current conducted between the first and second current conducting electrodes is conducted through the geological formation of interest.

Vail, III, William Banning (Bothell, WA)

2001-01-01

320

Impedances of electrochemically impregnated nickel electrodes as functions of potential, KOH concentration, and impregnation method  

NASA Technical Reports Server (NTRS)

Impedances of fifteen electrodes form each of the four U.S. manufactures were measured at 0.200 V vs. the Hg/HgO reference electrode. This corresponds to a voltage of 1.145 for a Ni/H2 cell. Measurements were also made of a representative sample of these at 0.44 V. At the higher voltage, the impedances were small and very similar, but at the lower voltage there were major differences between manufacturers. Electrodes from the same manufacturers showed only small differences. The impedances of electrodes from two manufacturers were considerably different in 26 percent KOH from those in 31 percent KOH. These preliminary results seen to correlate with the limited data from earlier life testing of cells from these manufacturers. The impedances of cells being tested for Space Station Freedom are being followed, and more impendance measurements of electrodes are being performed as functions of manufacturer, voltage, electrolyte concentration, and cycle history in hopes of finding better correlations of impedance with life.

Reid, Margaret A.

1989-01-01

321

Calibration of bridge-, charge- and voltage amplifiers for dynamic measurement applications  

NASA Astrophysics Data System (ADS)

Measuring amplifiers are used for transducer output signal conditioning in many dynamic measurement applications. For a traceable measurement, a calibration of all components of the measuring chain—and therefore of the conditioning amplifiers, too—is mandatory. In this paper methods for a dynamic calibration of different types of conditioning amplifiers are presented. Measurement uncertainties and calibration results for typical amplifiers are discussed.

Klaus, Leonard; Bruns, Thomas; Volkers, Henrik

2015-02-01

322

Impedance measurements of a chalcogenide membrane iron(III)-selective electrode in contact with aqueous electrolytes  

Microsoft Academic Search

The electrochemical characterization of a chalcogenide-based iron(III)-selective electrode [Fe(III) ISE] [i.e., Fe2.5(Se60Ge28Sb12)97.5] was achieved using impedance spectroscopy. The influence of electrolyte composition (i.e., NO3?, Cl?, and pH) on the membrane oxidation reaction has been examined, and a mechanism for its action is proposed. Equivalent circuit analysis was undertaken to determine the interfacial charge transfer resistance and corresponding double layer capacitance

B Pejcic; R De Marco

2004-01-01

323

Development of an opto-electrical probe for measuring impulse high-voltage across thyristors in HVDC valve of three-Gorges project  

Microsoft Academic Search

A high-voltage resistive probe is developed to measure impulse voltage (1.2\\/50?s) distribution along thyristor units in HVDC converter valve with an optoelectronic system to transmit the measured signal. A pulse frequency modulation (PFM) mode is adopted for this transmitting system, owing to its immunity to high-intensity electromagnetic interference. Experimental results indicate that the undefined degree of the scale factor under

Zhongyuan Zhao; Zhengyu Lu; Yilei Gu; Yuchang Qiu

2004-01-01

324

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively. 7 figs.

Droege, T.F.

1989-12-19

325

High voltage DC power supply  

DOEpatents

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively.

Droege, Thomas F. (Batavia, IL)

1989-01-01

326

Process for measuring degradation of sulfur hexafluoride in high voltage systems  

DOEpatents

This invention is a method of detecting the presence of toxic and corrosive by-products in high voltage systems produced by electrically induced degradation of SF/sub 6/ insulating gas in the presence of certain impurities. It is an improvement over previous methods because it is extremely sensitive, detecting by-products present in parts per billion concentrations, and because the device employed is of a simple design and takes advantage of the by-products natural affinity for fluoride ions. The method employs an ion-molecule reaction cell in which negative ions of the by-products are produced by fluorine attachment. These ions are admitted to a negative ion mass spectrometer and identified by their spectra. This spectrometry technique is an improvement over conventional techniques because the negative ion peaks are strong and not obscured by a major ion spectra of the SF/sub 6/ component as is the case in positive ion mass spectrometry.

Sauers, I.

1985-04-23

327

Process for measuring degradation of sulfur hexafluoride in high voltage systems  

DOEpatents

This invention is a method of detecting the presence of toxic and corrosive by-products in high voltage systems produced by electrically induced degradation of SF.sub.6 insulating gas in the presence of certain impurities. It is an improvement over previous methods because it is extremely sensitive, detecting by-products present in parts per billion concentrations, and because the device employed is of a simple design and takes advantage of the by-products natural affinity for fluoride ions. The method employs an ion-molecule reaction cell in which negative ions of the by-products are produced by fluorine attachment. These ions are admitted to a negative ion mass spectrometer and identified by their spectra. This spectrometry technique is an improvement over conventional techniques because the negative ion peaks are strong and not obscured by a major ion spectra of the SF.sub.6 component as is the case in positive ion mass spectrometry.

Sauers, Isidor (Knoxville, TN)

1986-01-01

328

Changes in biphasic electrode impedance with protein adsorption and cell growth  

NASA Astrophysics Data System (ADS)

This study was undertaken to assess the contribution of protein adsorption and cell growth to increases in electrode impedance that occur immediately following implantation of cochlear implant electrodes and other neural stimulation devices. An in vitro model of the electrode-tissue interface was used. Radiolabelled albumin in phosphate buffered saline was added to planar gold electrodes and electrode impedance measured using a charge-balanced biphasic current pulse. The polarization impedance component increased with protein adsorption, while no change to access resistance was observed. The maximum level of protein adsorbed was measured at 0.5 µg cm-2, indicating a tightly packed monolayer of albumin molecules on the gold electrode and resin substrate. Three cell types were grown over the electrodes, macrophage cell line J774, dissociated fibroblasts and epithelial cell line MDCK, all of which created a significant increase in electrode impedance. As cell cover over electrodes increased, there was a corresponding increase in the initial rise in voltage, suggesting that cell cover mainly contributes to the access resistance of the electrodes. Only a small increase in the polarization component of impedance was seen with cell cover.

Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Huang, Christie; Milojevic, Dusan; Shepherd, Robert; Cowan, Robert

2010-10-01

329

Development of PDMS-based flexible dry type SEMG electrodes by micromachining technologies  

NASA Astrophysics Data System (ADS)

The authors developed PDMS (polydimethylsiloxane)-based dry type surface electromyography (SEMG) electrodes for myoelectric prosthetic hands. The SEMG electrodes were strongly recommended to be fabricated on a flexible substrate to be compatible with the surface of skin. In this study, the authors designed a bar-shaped dry-type flexible SEMG electrodes comprised of two input electrodes and a reference electrode on a flexible PDMS substrate to measure EMG signals. The space distance between each electrode with a size of 10 mm × 2 mm was chosen to 18 mm to get optimal result according to the simulation result with taking into consideration the conduction velocity and the median frequency of EMG signals. Raw EMG signals were measured from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles, to drive the application of the myoelectric hand prosthesis. Measured raw EMG signals were transformed to root mean square (RMS) EMG signals using Acqknowledge4.2. The experimental peak voltage values of RMS EMG signals from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles were 2.96 V, 4.45 V, 1.74 V, and 2.62 V, respectively. Values from the dry type flexible SEMG electrodes showed higher peak values than a commercially available wet type Ag-AgCl electrode. The study shows that the PDMS-based flexible electrode devised for measuring myoelectric signals from the surface of skin is more useful for prosthetic hands because of its greater sensitivity and flexibility.

Jung, Jung Mo; Cha, Doo Yeol; Kim, Deok Su; Yang, Hee Jun; Choi, Kyo Sang; Choi, Jong Myoung; Chang, Sung Pil

2014-09-01

330

On the possibility of determining the energy-distribution function of nonlocal penning electrons by measuring the current to wall electrode in afterglow plasma  

NASA Astrophysics Data System (ADS)

The results of numerical simulation of the afterglow plasma of pulsed discharge in a nonlocal regime confirm the possibility of determining the energy-distribution function (EDF) of nonlocal penning electrons by measuring their current to a wall electrode. It is shown that the EDF of nonlocal Penning electrons is proportional to the first derivative of the electron-current density with respect to potential on the wall electrode.

Saifutdinov, A. I.; Kapustin, K. D.; Kudryavtsev, A. A.

2014-11-01

331

Evaluation of the electrode method for measuring H/sub 2/S vapor pressure over alkanolamine solutions  

SciTech Connect

A new electrode method for measuring the equilibrium vapor pressure of H/sub 2/S over any sulfide solution was tested. The method relates the electropotential difference produced between pH and silver/sulfide ion specific electrodes to the H/sub 2/S equilibrium vapor pressure of solution. The experimental technique is simple and time efficient. In this work, H/sub 2/S equilibrium vapor pressures were measured from 10/sup -4/ kPa to 10 kPa at 25/sup 0/C in aqueous solutions of monoethanolamine-MEA (2.5 N), diethanolamine-DEA (2.0N), and methyldiethanolamine-MDEA (1.0 N and 4.28 N). The H/sub 2/S vapor-liquid equilibria (VLE) of 4.28 N MDEA was also examined at 40/sup 0/C. The results indicate that the addition of MEA to a MDEA solution reduces the H/sub 2/S vapor pressure only at low H/sub 2/S loadings.

Austgen, D.M.; Rochelle, G.T.

1987-01-01

332

An approach to the diagnosis of metabolic syndrome by the multi-electrode impedance method  

NASA Astrophysics Data System (ADS)

It is well known that metabolic syndrome can induce myocardial infarction and cerebral infarction. So, it is very important to measure the visceral fat volume. In the electric impedance method, information in the vicinity of the electrodes is strongly reflected. Therefore, we propose a new multi-electrode arrangement method based on the impedance sensitivity theorem to measure the visceral fat volume. This electrode arrangement is designed to enable high impedance sensitivity in the visceral and subcutaneous fat regions. Currents are simultaneously applied to several current electrodes on the body surface, and one voltage electrode pair is arranged on the body surface near the organ of interest to obtain the visceral fat information and another voltage electrode pair is arranged on the body surface near the current electrodes to obtain the subcutaneous fat information. A simulation study indicates that by weighting the impedance sensitivity distribution, as in our method, a high-sensitivity region in the visceral and the subcutaneous fat regions can be formed. In addition, it was confirmed that the visceral fat volume can be estimated by the measured impedance data.

Furuya, N.; Sakamoto, K.; Kanai, H.

2010-04-01

333

Measuring neural coupling from non-Gaussian power spectra of voltage traces taken from awake behaving animals  

NASA Astrophysics Data System (ADS)

Brains consist of complex networks of neurons possessing highly non-linear interactions, suggesting that neural systems will show cooperative dynamics. Previous studies of the non-Gaussian statistics of 1/f noise in spin glasses and amorphous semiconductors have revealed important information concerning interaction kinetics not available through other techniques. Five male Brown-Norway-Cross rats were chronically implanted with arrays of microwire electrodes from which local field potentials (LFPs) were recorded from the dorsocentral striatum as the animals performed complex navigational tasks. The power spectra displayed a frequency dependence significantly different from 1/f. The correlation coefficients of the Fourier transform of the LFPs from striatum showed significant non-zero correlations between frequencies separated by less than three octaves. This novel technique may be useful in measuring functional interactions in neural systems.

Masimore, Beth; Kakalios, James; Redish, A. David

2003-05-01

334

A method for measuring high resistances with negligible leakage effect using one voltage source and one voltmeter  

NASA Astrophysics Data System (ADS)

We present a method for measuring high resistances using one voltage source and one voltmeter. With this method, there exist two techniques. One is to measure a high resistance with a much lower resistance and the other is to cancel the leakage effect effectively using two nominally equal resistances without an auxiliary guarding apparatus. To demonstrate the method's validity, a 1 G? resistance was measured using the two techniques replacing a dummy 1 G? resistance as a leakage resistance; the measurement results agree well with the theoretical results within the measurement uncertainty of 3 × 10-6 (k = 2) level. We used the method to determine 10 M?, 1 G? and 1 T? resistances with an active-guard type and a T-type. The best expanded uncertainties at k = 2 from the results were estimated as 0.3 × 10-6, 0.8 × 10-6 and 20 × 10-6, respectively. We also show that while the expanded uncertainty of 70 × 10-6 is obtained using an 81/2 digit digital multimeter, it is improved to 20 × 10-6 using an electrometer with high-input resistance, low bias current and high resolution when the second technique is used to measure high resistances.

Yu, Kwang Min; Kim, Wan Seop; Lee, Sang Hwa; Han, Kwon Soo; Kang, Jeon Hong

2014-07-01

335

Fabrication of Functionalized Carbon Nanotube Buckypaper Electrodes for Application in Glucose Biosensors  

PubMed Central

A highly sensitive glucose detection method was developed using functionalized carbon nanotube buckypaper as a free standing electrode in an electrochemical biosensor. Glucose oxidase was immobilized onto various buckypaper samples in order to oxidize glucose resulting in a measureable current/voltage signal output of the biosensor. Cyclic voltammetry (CV) and amperometry were utilized to determine the sensitivity of these buckypaper electrodes. Sensors of three different types of buckypaper were prepared and compared. These modified buckypaper electrode-based sensors showed much higher sensitivity to glucose compared to other electrochemical glucose sensors. PMID:25587433

Papa, Henry; Gaillard, Melissa; Gonzalez, Leon; Chatterjee, Jhunu

2014-01-01

336

Tunneling spectroscopy of clean and adsorbate-covered gold surfaces in humid air, measured with fast bias voltage ramps  

NASA Astrophysics Data System (ADS)

The noise level of tunneling spectroscopic data can be significantly reduced by averaging the tunneling current over a large number of short bias voltage ramps, instead of recording over a single slow ramp. This effect is demonstrated for tunneling spectra of Au(111) by averaging over 200 consecutive bias voltage ramps, each 500 ?s long. We attribute the improvement of the data quality to the frequency dependence of the current noise spectral density. Due to mechanical vibrations and tip instabilities the noise density is usually much higher for low frequencies ca. < 1 kHz than for the high frequencies relevant for measuring with fast bias ramps. The high data quality allowed for the routine detection of the Au(111) surface state and the investigation of the influence of steps in humid air, i.e., with a water-covered tunneling gap. For a CN covered Au surface in the presence of water we unexpectedly found additional electronic density of states at positive energies, around 0.6 eV, i.e., for unoccupied states. STS spectra of a (?{ 3} ×?{ 3}) R 30 ° Cu-UPD layer, formed by adsorbed sulfate and Cu species, indicate tunneling via the sulfate electronic density of states.

Rösch, Raphael; Schuster, Rolf

2015-01-01

337

Three-dimensional electrical impedance tomography based on the complete electrode model  

Microsoft Academic Search

In electrical impedance tomography an approximation for the internal resistivity distribution is computed based on the knowledge of the injected currents and measured voltages on the surface of the body. It is often assumed that the injected currents are confined to the two-dimensional (2-D) electrode plane and the reconstruction is based on 2-D assumptions. However, the currents spread out in

P. J. Vauhkonen; Marko Vauhkonen; Tuomo Savolainen; Jari P. Kaipio

1999-01-01

338

Finite-Element and Genetic Algorithm Design of Multi-segmented Electro-optic Sensor for Pulsed High-Voltage Measurement  

Microsoft Academic Search

In the last few years, innovative electro-optic sensors, such as Optical Voltage and Optical Current Transformers, have been developed and used for high-voltage and high-current measurements in power systems. This kind of sensor presents fast transitory response, no susceptibility to electromagnetic interference high signal\\/noise ratio, reduced size and weight, and provides electric isolation. These devices are based on optical modulator.

Angelo Passaro; Jonas Rubini Júnior; Nancy Mieko Abe; Milton Sasaki; Josemir Coelho Santos

339

Building a Low-Cost, Six-Electrode Instrument to Measure Electrical Properties of Self-Assembled Monolayers of Gold Nanoparticles  

ERIC Educational Resources Information Center

The development of a new low-cost, six-electrode instrument for measuring the electrical properties of the self-assembled monolayers of gold particles is being described. The system can also be used to measure conductive liquids, except for those that contain aqua region.

Gerber, Ralph W.; Oliver-Hoyo, Maria

2007-01-01

340

Modeling gating charge and voltage changes in response to charge separation in membrane proteins  

PubMed Central

Measurements of voltage changes in response to charge separation within membrane proteins can offer fundamental information on mechanisms of charge transport and displacement processes. A recent example is provided by studies of cytochrome c oxidase. However, the interpretation of the observed voltage changes in terms of the number of charge equivalents and transfer distances is far from being trivial or unique. Using continuum approaches to describe the voltage generation may involve significant uncertainties and reliable microscopic simulations are not yet available. Here, we attempt to solve this problem by using a coarse-grained model of membrane proteins, which includes an explicit description of the membrane, the electrolytes, and the electrodes. The model evaluates the gating charges and the electrode potentials (c.f. measured voltage) upon charge transfer within the protein. The accuracy of the model is evaluated by a comparison of measured voltage changes associated with electron and proton transfer in bacterial photosynthetic reaction centers to those calculated using our coarse-grained model. The calculations reproduce the experimental observations and thus indicate that the method is of general use. Interestingly, it is found that charge-separation processes with different spatial directions (but the same distance perpendicular to the membrane) can give similar observed voltage changes, which indicates that caution should be exercised when using simplified interpretation of the relationship between charge displacement and voltage changes. PMID:25049404

Kim, Ilsoo; Chakrabarty, Suman; Brzezinski, Peter; Warshel, Arieh

2014-01-01

341

High frequency breakdown voltage  

SciTech Connect

This report contains information about the effect of frequency on the breakdown voltage of an air gap at standard pressure and temperature, 76 mm Hg and O{degrees}C, respectively. The frequencies of interest are 47 MHz and 60 MHz. Additionally, the breakdown in vacuum is briefly considered. The breakdown mechanism is explained on the basis of collision and ionization. The presence of the positive ions produced by ionization enhances the field in the gap, and thus determines the breakdown. When a low-frequency voltage is applied across the gap, the breakdown mechanism is the same as that caused by the DC or static voltage. However, when the frequency exceeds the first critical value f{sub c}, the positive ions are trapped in the gap, increasing the field considerably. This makes the breakdown occur earlier; in other words, the breakdown voltage is lowered. As the frequency increases two decades or more, the second critical frequency, f{sub ce}, is reached. This time the electrons start being trapped in the gap. Those electrons that travel multiple times across the gap before reaching the positive electrode result in an enormous number of electrons and positive ions being present in the gap. The result is a further decrease of the breakdown voltage. However, increasing the frequency does not decrease the breakdown voltage correspondingly. In fact, the associated breakdown field intensity is almost constant (about 29 kV/cm).The reason is that the recombination rate increases and counterbalances the production rate, thus reducing the effect of the positive ions` concentration in the gap. The theory of collision and ionization does not apply to the breakdown in vacuum. It seems that the breakdown in vacuum is primarily determined by the irregularities on the surfaces of the electrodes. Therefore, the effect of frequency on the breakdown, if any, is of secondary importance.

Chu, Thanh Duy

1992-03-01

342

Image processing for non-ratiometric measurement of membrane voltage using fluorescent reporters and pulsed laser illumination.  

PubMed

The measurement of transmembrane voltages induced by pulsed electric field exposure can be achieved by using fluorescent dyes like ANNINE-6. Such approach requires a quantitative determination of the fluorescence intensity along the cell's membrane by image processing. When high temporal resolution is required, the illumination source is frequently a dye-laser which causes high fluctuations in the intensity of illumination which in turn affects the fluorescence intensity and thus the quality of the results. We propose an image processing technique that allows to overcome the fluctuations and to produce quantitative data. It uses the optical background noise as a correcting factor. Standard deviation in the fluctuations is thus efficiently reduced by at least a factor of 2.5. Additionally we draw attention to the fact that the parasitic component of the laser radiation (ASE) can also suppress fluctuations although it deteriorates wavelength precision. PMID:25091458

Silve, Aude; Rocke, Sarah; Frey, Wolfgang

2014-07-23

343

Effects of skin blood flow and temperature on skin--electrode impedance and offset potential: measurements at low alternating current density.  

PubMed

Skin--electrode impedance was determined at 100 Hz and 1 kHz between two disposable electrodes, 5 cm apart, at current densities < 65 microA.cm-2. Measurements were made on the volar skin of the forearm during cooling on cardiopulmonary bypass, and on the dorsum of the foot in the absence of skin blood flow during aortic aneurysm repair. Both the resistive and reactive components of the skin-electrode impedence showed an inverse linear relationship to temperature between 26 and 36 degrees C. The magnitude of the impedance change was different for each patient studied; resistance changes ranged from 0.03 to 23.2 k omega. Degrees C-1 at 100 Hz and from 0.03 to 2.7 k omega. Degrees C-1 at 1 kHz, while reactance changes ranged from 0.4 to 2.1 k omega. Degrees C-1 at 100 Hz and from 0.04 to 0.18 k omega. Degrees C-1 at 1 kHz. Changes in skin-electrode impedance were not due to changes in skin blood flow. There was no consistent change in offset potential with temperature. Although the skin-electrode impedance increases as temperature falls, it is concluded that temperature effects at the skin-electrode interface are not responsible for the observed failure of evoked electromyography during clinical monitoring of neuromuscular function. PMID:1404312

Smith, D C

1992-01-01

344

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

345

Filter-fluorescer measurement of low-voltage simulator x-ray energy spectra  

SciTech Connect

X-ray energy spectra of the Maxwell Laboratories MBS and Physics International Pulserad 737 were measured using an eight-channel filter-fluorescer array. The PHOSCAT computer code was used to calculate channel response functions, and the UFO code to unfold spectrum.

Baldwin, G.T.; Craven, R.E.

1986-01-01

346

Synchronous Machine Operational Impeadances From Low Voltage Measurements at the Stator Terminals  

Microsoft Academic Search

Models of a synchronous machine for use in stability studies have been derived by measurements off-line at standstill. The method involves accurate determination of magnitude and phase of the impedance as seen at the stator terminals, for a range of frequency from 0.005 to 100 Hz. The data obtained pertains particularly to establishment of parameters for equivalent rotor circuits of

W. Watson; G. Manchur

1974-01-01

347

Near-uv photon efficiency in a TiO2 electrode - Application to hydrogen production from solar energy  

NASA Technical Reports Server (NTRS)

An n-type (001) TiO2 electrode irradiated at 365 nm was tested under anodic polarization. A saturation current independent of pH and proportional to light intensity has been observed. Accurate measurements of the incident power lead to a 60 per cent photon efficiency. A photoelectrochemical cell built with such an electrode, operated under solar irradiation without concentration, produced an electrolysis current of 0.7 mA/sq cm without applied voltage.

Desplat, J.-L.

1976-01-01

348

Constant voltage electro-slag remelting control  

DOEpatents

A system for controlling electrode gap in an electro-slag remelt furnace has a constant regulated voltage and an electrode which is fed into the slag pool at a constant rate. The impedance of the circuit through the slag pool is directly proportional to the gap distance. Because of the constant voltage, the system current changes are inversely proportional to changes in gap. This negative feedback causes the gap to remain stable. 1 fig.

Schlienger, M.E.

1996-10-22

349

Micro-structured electrode arrays  

Microsoft Academic Search

Micro-structured electrode (MSE) arrays allow to generate large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. The electrode dimensions in the ?m-range realized by means of modern micro-machining and galvanic techniques are small enough to generate sufficiently high electric field strengths to ignite gas discharges applying only moderate radio frequency (RF, 13.56MHz) voltages (80–390V in Ne,

Lutz Baars-Hibbe; Christian Schrader; Philipp Sichler; Thorben Cordes; Karl-Heinz Gericke; Stephanus Büttgenbach; Siegfried Draeger

2004-01-01

350

Development of a prototype micro-EIT system using three sets of 15×8 array electrodes  

NASA Astrophysics Data System (ADS)

We developed a new microscopic electrical impedance tomography (micro-EIT) system to visualize admittivity distributions within a miniature hexahedral container, where we place small biological samples with a background solution or gel. Each of two facing sides (left and right) of the container is fully covered by a solid metal electrode. We inject current between them, thereby producing a uniform parallel current flow along the longitudinal direction inside the container. Each of three sides at the bottom, front and back is equipped with a 15×8 array of voltage-sensing electrodes. Switching modules are located underneath the container so that we can measure voltage between any neighbouring pair of electrodes. Three switching modules are connected to a 16-channel multi-frequency EIT system to collect induced voltage data from the three sets of 15x8 array electrodes subject to the single fixed current injection. Voltage data set from 360 voltage-sensing electrodes on three sides are utilized to produce cross-sectional images of the admittivity distribution. We describe the design and construction of the new micro-EIT system. Our future work should include development of a customized image reconstruction algorithm for the micro-EIT system and experimental validation.

Liu, Qin; Wi, Hun; In Oh, Tong; Woo, Eung Je; Seo, Jin Keun

2010-04-01

351

Breakdown voltage determination of gaseous and near cryogenic fluids with application to rocket engine ignition  

NASA Astrophysics Data System (ADS)

Liquid rocket engines extensively use spark-initiated torch igniters for ignition. As the focus shifts to longer missions that require multiple starts of the main engines, there exists a need to solve the significant problems associated with using spark-initiated devices. Improving the fundamental understanding of predicting the required breakdown voltage in rocket environments along with reducing electrical noise is necessary to ensure that missions can be completed successfully. To better understand spark ignition systems and add to the fundamental research on spark development in rocket applications, several parameter categories of interest were hypothesized to affect breakdown voltage: (i) fluid, (ii) electrode, and (iii) electrical. The fluid properties varied were pressure, temperature, density and mass flow rate. Electrode materials, insert electrode angle and spark gap distance were the electrode properties varied. Polarity was the electrical property investigated. Testing how breakdown voltage is affected by each parameter was conducted using three different isolated insert electrodes fabricated from copper and nickel. A spark plug commonly used in torch igniters was the other electrode. A continuous output power source connected to a large impedance source and capacitance provided the pulsing potential. Temperature, pressure and high voltage measurements were recorded for the 418 tests that were successfully completed. Nitrogen, being inert and similar to oxygen, a propellant widely used in torch igniters, was used as the fluid for the majority of testing. There were 68 tests completed with oxygen and 45 with helium. A regression of the nitrogen data produced a correction coefficient to Paschen's Law that predicts the breakdown voltage to within 3000 volts, better than 20%, compared to an over prediction on the order of 100,000 volts using Paschen's Law. The correction coefficient is based on the parameters most influencing breakdown voltage: fluid density, spark gap distance, electrode angles, electrode materials and polarity. The research added to the fundamental knowledge of spark development in rocket ignition applications by determining the parameters that most influence breakdown voltage. Some improvements to the research should include better temperature measurements near the spark gap, additional testing with oxygen and testing with fuels of interest such as hydrogen and methane.

Nugent, Nicholas Jeremy

352

Considerations for Estimating Electrode Performance in Li-Ion Cells  

NASA Technical Reports Server (NTRS)

Advanced electrode materials with increased specific capacity and voltage performance are critical to the development of Li-ion batteries with increased specific energy and energy density. Although performance metrics for individual electrodes are critically important, a fundamental understanding of the interactions of electrodes in a full cell is essential to achieving the desired performance, and for establishing meaningful goals for electrode performance. This paper presents practical design considerations for matching positive and negative electrodes in a viable design. Methods for predicting cell-level discharge voltage, based on laboratory data for individual electrodes, are presented and discussed.

Bennett, William R.

2012-01-01

353

Experimental evaluation of actual delivered dose using mega-voltage cone-beam CT and direct point dose measurement  

SciTech Connect

Radiation therapy in patients is planned by using computed tomography (CT) images acquired before start of the treatment course. Here, tumor shrinkage or weight loss or both, which are common during the treatment course for patients with head-and-neck (H and N) cancer, causes unexpected differences from the plan, as well as dose uncertainty with the daily positional error of patients. For accurate clinical evaluation, it is essential to identify these anatomical changes and daily positional errors, as well as consequent dosimetric changes. To evaluate the actual delivered dose, the authors proposed direct dose measurement and dose calculation with mega-voltage cone-beam CT (MVCBCT). The purpose of the present study was to experimentally evaluate dose calculation by MVCBCT. Furthermore, actual delivered dose was evaluated directly with accurate phantom setup. Because MVCBCT has CT-number variation, even when the analyzed object has a uniform density, a specific and simple CT-number correction method was developed and applied for the H and N site of a RANDO phantom. Dose distributions were calculated with the corrected MVCBCT images of a cylindrical polymethyl methacrylate phantom. Treatment processes from planning to beam delivery were performed for the H and N site of the RANDO phantom. The image-guided radiation therapy procedure was utilized for the phantom setup to improve measurement reliability. The calculated dose in the RANDO phantom was compared to the measured dose obtained by metal-oxide-semiconductor field-effect transistor detectors. In the polymethyl methacrylate phantom, the calculated and measured doses agreed within about +3%. In the RANDO phantom, the dose difference was less than +5%. The calculated dose based on simulation-CT agreed with the measured dose within±3%, even in the region with a high dose gradient. The actual delivered dose was successfully determined by dose calculation with MVCBCT, and the point dose measurement with the image-guided radiation therapy procedure.

Matsubara, Kana, E-mail: matsubara-kana@hs.tmu.ac.jp [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan); Kohno, Ryosuke [National Cancer Center Hospital East, Chiba (Japan); National Cancer Center Research Institute, Chiba (Japan); Nishioka, Shie; Shibuya, Toshiyuki; Ariji, Takaki; Akimoto, Tetsuo [National Cancer Center Hospital East, Chiba (Japan); Saitoh, Hidetoshi [Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku Tokyo (Japan)

2013-07-01

354

External electro-optic measuring system with high spatial resolution and high voltage sensitivity by using an electro-optic solid immersion probe  

NASA Astrophysics Data System (ADS)

A GaAs hemisphere has been used for the first time both as a probe and a solid immersion lens in a reflecting external electro-optic measuring system to substantially improve the spatial resolution and the voltage sensitivity of the system. The electric signals propagating on microstrip lines were detected successfully. In contrast with a conventional cubic probe under the same measuring conditions we found that the voltage sensitivity of the measuring system with the hemispherical probe was improved by a factor of nearly 1.7 to 3 mV Hz-1/2, and the spatial resolution was improved by a factor of 4.5 to 0.6 µm. The improvements in the spatial resolution and voltage sensitivity are due to the increased effective number aperture and the total internal reflection in hemispherical GaAs probe, respectively.

Zhanguo, Chen; Gang, Jia; Maobin, Yi

2001-10-01

355

Performance evaluation of the electrode configuration in bioelectrical impedance analysis for visceral fat measurement  

Microsoft Academic Search

Excessive amount of visceral fat is considered as a crucial indicator for the metabolic syndrome (MS). Visceral fat area (VFA) at the umbilicus level measured by CT is adopted as the gold standard, but it has many limitations. Recently, Application of bioelectrical impedance analysis (BIA) for measuring VFA is widely used. However, the correlation between impedance and VFA is highly

Kwangsoo Kim; Mi-hee Lee; Jungchae Kim; Seok Myung Jung; Sun Ha Jee; S. K. Yoo

2009-01-01

356

GRAPHITE ELECTRODE FOR THE MEASUREMENT OF REDOX POTENTIAL AND OXYGEN DIFFUSION RATE IN SOIL  

EPA Science Inventory

The objective of the project was to evaluate control measurements that might be made at land treatment sites to determine the effectiveness of operation in the management of hazardous wastes. Initial studies were on measurement of oxygen concentration and oxygen diffusion rate (O...

357

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

358

Measuring voltage in a Y Ba2 Cu3 O8 superconductor induced by a moving magnet  

NASA Astrophysics Data System (ADS)

This study examined a pair of permanent magnets rotating above a tape-shaped single grain YBa2Cu3O8 (YBCO) superconducting sample (SS) with and without an applied bias current. The root-mean-square voltages (Vrms) induced by the forced movements of the vortices inside the SS were measured. At SS temperatures higher than the critical temperature (Tc) , the induced Vrms was a constant, as expected from Faraday’s law. However, at a temperature in the superconducting transition region, the induced Vrms is a sensitive function of both the motion of the magnet and the bias current applied to the SS. At temperatures below the transition region, the induced Vrms did not drop to zero immediately. Instead, it dropped only to a particular value and then decreased as the temperature decreased. The experimental results obtained at temperatures in the superconducting transition region can be understood by considering the superposition of the two induced voltages. One is induced according to Faraday’s law, and the other one is induced by the flux flow inside the SS, which is caused by the bias current. At temperatures below the transition region, an explanation of how the magnetic field of a moving magnet passes through the superconductor is provided, and is consistent qualitatively with the experimental results. In this explanation, some of the magnetic field is assumed first to fill in and then to be pulled out from all sides of the SS in accordance with Bean’s model as the moving magnet passes through the SS from above.

Chan, W. C.; Lin, C. B.; Chao, H.; Chiang, C. H.

2005-11-01

359

Voltage Drop  

NSDL National Science Digital Library

The first site with information on voltage drop is provided by Power and System Innovations on their Frequently Asked Questions: Voltage Drop (1) page. Visitors can read what voltage drop is, what causes it, what happens as a result of it, and what the maximum recommended voltage drop is. The second site, Basics of Electricity (2), is part of General Electric's Lighting for Business Web site. Through descriptions and illustrations, the site explains what voltage drop is and gives examples of how it is calculated using Ohm's law. The next site is a lab worksheet that is part of a class from the Electrical and Computer Engineering Department of Montana State University called Voltage Drop in Cables (3). The objective of the lesson is to determine the internal resistance of an extension cord and choose the proper wire size for a particular application. Students are given an explanation of the procedure and a number of questions to answer related to the exercise. The Oregon Building Congress offers the Lesson Plans (4) Web site and the downloadable Voltage Drop educational activity. The lesson, which is suggested to be contained within a unit on formulas and solving literal equations, explores the concept of voltage drop that is encountered in basic wiring. The fifth site entitled Explanation of Voltage Drop in a Series Circuit (5) is offered by the Horizons Electronic Lesson Plan Resource. The page describes voltage drop as an electronic concept, gives a formula determining voltage drop, provides a schematic that helps illustrate the concept, and offers a quiz and answer sheet. Next, from electrician.com, is the online Voltage Drop Calculator (6). Users input the type and size of wire being used, the voltage and phase, circuit length, and amp load to calculate voltage drop and several other parameters. The seventh site, entitled The Hazards of Voltage Drop (7), is provided within the Electrical Construction Maintenance Web site. The page describes how electrical equipment can overheat or even power down if it operates below its voltage rating. It also provides a thorough explanation of how to determine the load's operating voltage. The last site, maintained by Williamson Labs (8), is a comprehensive learning site called Elementary Electricity. Visitors will find a wealth of information here, including fun descriptions, graphics, and animations on all aspects of electricity including voltage drop.

360

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

361

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 are described. 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, L.; Vissers, D.R.

1981-12-30

362

Electrocatalytic Measurement Methodology of Oxide Catalysts Using a Thin-Film Rotating Disk Electrode  

E-print Network

Transition-metal oxides can exhibit high electrocatalytic activity for reactions such as the oxygen reduction reaction (ORR) in alkaline media. It is often difficult to measure and compare the activities of oxide catalysts ...

Suntivich, Jin

363

Voltage induced magnetic anisotropy change in ultrathin Fe80Co20/MgO junctions with Brillouin light scattering  

NASA Astrophysics Data System (ADS)

We investigate voltage induced perpendicular magnetic anisotropy (PMA) changes in MgO/Cr/Au/Fe80Co20/MgO/polyimide/ indium tin oxide (ITO). In order to observe the PMA change, spin wave frequency was measured by Brillouin light scattering with finite bias voltages applied between Au and ITO electrodes. The obtained PMA constants from spin wave frequency of Fe80Co20 layer show clear bias voltage dependences, which agree well with the previous polar-Kerr effect measurement results and theoretical study. This study suggests spintronics devices operated by an electric field for next generation devices complying with low-power consumption.

Ha, Seung-Seok; Kim, Nam-Hee; Lee, Sukmock; You, Chun-Yeol; Shiota, Yoichi; Maruyama, Takuto; Nozaki, Takayuki; Suzuki, Yoshishige

2010-04-01

364

Streamer inception in mineral oil under ac voltage  

Microsoft Academic Search

This paper describes an experimental study of streamer inception in mineral oil under ac voltage, with rod and point electrodes. Positive and negative streamer inception frequencies versus voltage are investigated in gaps up to 40 cm with different electrode shapes and different conditioning of the oil (filtered oil, addition of cellulose particles, water). Streamer inception probability increases exponentially versus field,

O. Lesaint; T. V. Top

2011-01-01

365

Combined quartz crystal impedance and electrochemical impedance measurements during adsorption of bovine serum albumin onto bare and cysteine- or thiophenol-modified gold electrodes  

Microsoft Academic Search

Combined piezoelectric quartz crystal (PQC) impedance and electrochemical impedance measurements as a novel technique were reported for monitoring adsorption of bovine serum albumin (BSA) onto bare and cysteine- or thiophenol-modified gold electrodes. Equivalent circuit parameters and resonant frequencies for PQC resonance as well as the electrical double layer capacitance were obtained and discussed. A scheme of two consecutive reactions occurring

Qingji Xie; Youyu Zhang; Mancai Xu; Zelin Li; Yu Yuan; Shouzhuo Yao

1999-01-01

366

Detection of crevice corrosion under an O-ring by polarization resistance measurements using electrodes embedded in the O-ring  

SciTech Connect

An electrochemical sensor which incorporates a counter electrode (CE) and a reference electrode (RE) into an O-ring has been developed for in situ monitoring of crevice corrosion initiation and propagation. It is applicable to crevice corrosion situations where the crevice is created by a gasket or an O-ring and the attack occurs in that crevice. It is shown that polarization resistance (R{sub p}) values calculated from in situ electrochemical impedance measurements correlate with the onset of crevice attack and with its propagation for crevice corrosion of alloy 625 (UNS N06625) in 3.5% NaCl and in 10% FeCl{sub 3} solutions.

Inman, M.; Rawat, A.K.; Taylor, E.J. [Faraday Technology, Inc., Dayton, OH (United States); Moran, P.J. [Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.

1997-12-01

367

Effect of multipactor conditioning on technical electrode surfaces  

NASA Astrophysics Data System (ADS)

Historically, multipactor conditioning has been utilized to remove surface contaminants from rf electrodes by electron-stimulated gas desorption, and such conditioning has been shown to reduce multipactor susceptibility. Multipactor threshold improvements are due to increasing E1, the minimum energy for the secondary electron coefficient, ?>1, such that resonant electrons are incapable of producing discharge-sustaining secondary emission. Using an rf amplitude sweep technique, the evolution of the multipactor threshold is measured as a function of multipactor conditioning time for a series of technical electrode surfaces. Results show over +3 dB of threshold improvement in copper and gold electrodes, while the aluminum threshold actually decreases with conditioning exposure. Additionally, these conditioning results indicate the possible voltage region for transient-mode multipaction (TMM), which can cause significant risk to rf systems such as space satellite components for which in-situ conditioning is generally not possible. Experimental results and supporting Monte Carlo particle tracking simulation results are presented.

Graves, T. P.; Spektor, R.; Stout, P.

2009-11-01

368

Total body composition measurement by using bioelectric impedance analysis and its impact on obesity  

Microsoft Academic Search

We are going to propose a novel total body composition measurement device which is based on Bioelectrical-Impedance Analysis (BIA) which is temperature compensated with the aid of a computer. We are making use of aluminium electrodes for this purpose. Proximal electrodes are used to measure the voltage distant electrodes of right head and foot with an excitation current of 0.8mA

M. K. B. Kishore; V. Sapthagirivasan; Vemula Krishna Manohar; M. Anburajan

2010-01-01

369

Device and method for the measurement of depth of interaction using co-planar electrodes  

DOEpatents

A device and method for measuring a depth of interaction of an ionizing event and improving resolution of a co-planar grid sensor (CPG) are provided. A time-of-occurrence is measured using a comparator to time the leading edge of the event pulse from the non-collecting or collecting grid. A difference signal between the grid signals obtained with a differential amplifier includes a pulse with a leading edge occurring at the time-of-detection, measured with another comparator. A timing difference between comparator outputs corresponds to the depth of interaction, calculated using a processor, which in turn weights the difference grid signal to improve spectral resolution of a CPG sensor. The device, which includes channels for grid inputs, may be integrated into an Application Specific Integrated Circuit. The combination of the device and sensor is included. An improved high-resolution CPG is provided, e.g., a gamma-ray Cadmium Zinc Telluride CPG sensor operating at room temperature.

DeGeronimo, Gianluigi (Syosset, NY)

2007-09-18

370

Performance enhancement of ITO/oxide/semiconductor MOS-structure silicon solar cells with voltage biasing  

PubMed Central

In this study, we demonstrate the photovoltaic performance enhancement of a p-n junction silicon solar cell using a transparent-antireflective ITO/oxide film deposited on the spacing of the front-side finger electrodes and with a DC voltage applied on the ITO-electrode. The depletion width of the p-n junction under the ITO-electrode was induced and extended while the absorbed volume and built-in electric field were also increased when the biasing voltage was increased. The photocurrent and conversion efficiency were increased because more photo-carriers are generated in a larger absorbed volume and because the carriers transported and collected more effectively due to higher biasing voltage effects. Compared to a reference solar cell (which was biased at 0 V), a conversion efficiency enhancement of 26.57% (from 12.42% to 15.72%) and short-circuit current density enhancement of 42.43% (from 29.51 to 42.03 mA/cm2) were obtained as the proposed MOS-structure solar cell biased at 2.5 V. In addition, the capacitance-volt (C-V) measurement was also used to examine the mechanism of photovoltaic performance enhancement due to the depletion width being enlarged by applying a DC voltage on an ITO-electrode.

2014-01-01

371

Electrodeposition of Nanoporous Nickel Layers Using Inductive Voltage Pulses  

NASA Astrophysics Data System (ADS)

We used inductive voltage pulses for electro-deposition of porous nickel thin film onto steel electrode. Short pulses (tp<1 ?s) with variable amplitude (to ensure electro-deposition current density in region 124-224 A/dm2) were applied to electrode and resulting coating were analyzed with electrochemical and microscopic methods. At lower current densities only smooth nickel coatings growth, while at higher current densities the bubbles appear and porous layer was formed. Electrochemical impedance spectra of smooth and porous layers are measured in deionized water and in 1M KOH solution. The capacity in equivalent scheme is proportional to electrode surface, and from impedance spectra it is calculated that porous layer has 20 times larger active surface comparing to smooth layer (in KOH solution). From electrochemical measurements it is estimated that more efficient hydrogen evolution reaction occurs on electrode with porous nickel layer obtained at 223 A/dm2. It is shown in this work that inductive short pulse method can be used to obtain nano-porous nickel coatings on electrodes for efficient electrolysis cell.

Vanags, Martins; Kleperis, Janis; Bajars, Gunars; Nemcevs, Vladimirs

2013-12-01

372

Method of indirect determination of the anodic and cathodic voltage drops in short high-current electric discharges in a dielectric liquid  

NASA Astrophysics Data System (ADS)

The removal of electrode material by electric discharges in a dielectric liquid is usually performed with a short interelectrode gap (about 50 ?m) and short discharge durations (20-2000 ?s). It is therefore virtually impossible to measure the anodic and cathodic voltage drops of such discharges. However, considering that there is a direct relation between the amount of electrode material removed and the electric energy provided in the anodic (or cathodic) region, an indirect determination of those voltage drops is obtained by comparison of experimental results concerning mass loss at the electrodes and the molten volume computed after a linearized heat-conduction model. The results obtained are in agreement with the measured value of the total interelectrode voltage drop.

Lhiaubet, C.; Meyer, R. M.

1981-06-01

373

Dielectric elastomer actuators with elastomeric electrodes  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

374

Ifluence of outer electrode material on ozone production in coaxial negative corona discharge fed by oxygen  

NASA Astrophysics Data System (ADS)

The "electric odour", observed by Van Marum when oxygen was passing trough electric spark in 1785, has been later (1839), identified by Ch. F. Schonbeim as a new chemical compound named ozone (Stolarski 1999). Almost from those times ozone is widely used chemical compound. The effect of outer electrode material on the ozone production in negative corona discharge have been studied. Two electrodes with the same dimensions were used in the experiment. One was made of stainless steel other one of brass. First the outer electrode was mechanically cleaned to remove the layer of oxides. The reactor have been filled by pure oxygen and closed. Then the measurement (1 hour measurement of discharge current at the constant voltage and time dependence of ozone concentration in the reactor) was repeated 5 times without cleaning the surface to see the ageing effects. Especially the influence of electrode oxidation on ozone concentration was studied. The experiments have been carried out at atmospheric pressure and ambient temperature. The ozone concentration was measured by UV spectroscopy method directly in the discharge reactor. As one can expect the brass surface was oxidizing faster. After five measurements the electrode surface was covered by layer of greenish oxides. On the other hand the steel electrode surface had no visible oxides layer. The oxidation of the outer electrode had little systematic effect on the ozone concentration but in case of brass electrode the results were scattered in the range from 8000 ppm to 15000 ppm of ozone. It seems that the more oxides are created on the surface the less ozone is produced or the faster the ozone decomposition processes are (see Fig. 1). On the other hand in case of stainless steel electrode the ozone concentrations were comparable in all 5 measurements. Overall ozone concentration was higher in steel electrode. Figure 1: Time dependence of ozone concentration.

Orszagh, J.; Skalny, J. D.; Mason, N. J.

2008-07-01

375

Switching of a photochromic molecule on gold electrodes: single-molecule measurements  

NASA Astrophysics Data System (ADS)

We have studied the electronic changes caused by light-induced isomerization of a photochromic molecule between an open state (that absorbs in the UV to become closed) and a closed state (that absorbs in the visible to become open). Data obtained using a newly developed repetitive break junction method are interpreted in terms of single-molecule resistances of 526 ± 90 M? in the open form and 4 ± 1 M? in the closed form when the molecule is bound between two gold contacts via dithiol linkages. The corresponding ratio of open to closed resistance is in close agreement with the results of ab initio calculations, though the measured resistances are about half of the calculated values. Optical spectroscopy indicates that the photoisomerization occurs in both directions on small gold particles, evaporated thin gold films, and in the break junction experiments. http://stacks.iop.org/0957-4484/16/695

He, Jin; Chen, Fan; Liddell, Paul A.; Andréasson, Joakim; Straight, Stephen D.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.; Li, Jun; Sankey, Otto F.; Lindsay, Stuart M.

2005-06-01

376

Electrical stimulation and electrode properties. Part 2: pure metal electrodes.  

PubMed

Electrical stimulation can cause significant damage to clinical electrodes as well as patient injury. In this study, the effects of stimulation on pure metal electrodes were investigated without the complexities introduced by the multiple elements that make up the clinical electrode. As with the clinical electrodes, there was significant decomposition of pure stainless steel anodes with no associated significant changes in the cathodes when stimulation employed long pulse durations. Effects of stimulation were greater when the anode and cathode were closer under constant voltage stimulation but were distance independent under constant current stimulation. High ionic content of the solution also increased the degree of damage to the anode as did the presence of chloride in the solution. Electrode composition also influenced the amount damage to the anode. Platinum and platinum-iridium electrodes showed no damage with any stimulus while stainless steel showed the lowest resistance to corrosion for direct current (DC) stimulation. Tungsten electrodes behaved very differently than stainless steel, decomposing with pulse stimulation and resisting decomposition during DC stimulation because of the formation of surface protective layers. Because platinum was able to maintain high levels of current over time, prolonged stimulation produced dramatic increases in the temperature of the solution; however, even short periods of stimulation were sufficient to produce dramatic changes in pH in the neighborhood of the electrode. PMID:21313789

Stevenson, Matthew; Baylor, Kelly; Netherton, Brett L; Stecker, Mark M

2010-12-01

377

Direct measurement of the internal electron quasi-Fermi level in dye sensitized solar cells using a titanium secondary electrode.  

PubMed

The spatial dependence of the electron quasi-Fermi level (QFL) in the interior of dye sensitized nanocrystalline solar cells (DSC) under short circuit conditions can be inferred from calculations based on a diffusive electron transport model. The calculations predict that the difference in the QFL between the electrolyte and contact sides of the TiO(2) layer under short circuit conditions at 1 sun could be as much as 0.5-0.7 eV. The predicted QFL profiles depend on assumptions made about energy positions, electron mobility, and the conduction band density of states. In this work, the position of the QFL at the electrolyte side of the dye sensitized TiO(2) film in a DSC has been measured using a thin passivated titanium contact deposited on top of the nanocrystalline TiO(2) by evaporation. The method allows changes in the electron QFL at all points on the IV characteristic of the cell to be monitored under dark and photostationary conditions. In addition, cells incorporating the titanium electrode can give information about the behavior of the QFL under dynamic conditions. PMID:16913742

Lobato, K; Peter, L M; Würfel, U

2006-08-24

378

Label-free measurement of cell-electrode cleft gap distance with high spatial resolution surface plasmon microscopy.  

PubMed

Understanding the interface between cells or tissues and artificial materials is of critical importance for a broad range of areas. For example, in neurotechnology, the interfaces between neurons and external devices create a link between technical and the nervous systems by stimulating or recording from neural tissue. Here, a more effective interface is required to enhance the electrical characteristics of neuronal recordings and stimulations. Up to now, the lack of a systematic characterization of cell-electrode interaction turns out to be the major bottleneck. In this work, we employed a recently developed surface plasmon microscope (SPM) to monitor in real-time the cell-metal interface and to measure in situ the gap distance of the cleft with the spatial resolution reaching to the optical diffraction limit. The SPM allowed determination of the distance of human embryonic kidney 293 cells cultured on gold surfaces coated with various peptides or proteins without any labeling. This method can dramatically simplify the interaction investigation at metal-living cell interface and should be incorporated into systematic characterization methods. PMID:25423587

Toma, Koji; Kano, Hiroshi; Offenhäusser, Andreas

2014-12-23

379

Measurement of effective blast energy for direct initiation of spherical gaseous detonations from high-voltage spark discharge  

NASA Astrophysics Data System (ADS)

In this study, effective energy from spark discharge for direct blast initiation of spherical gaseous detonations is investigated. In the experiment, direct initiation of detonation is achieved via a spark discharge from a high-voltage and low-inductance capacitor bank and the spark energy is estimated from the analysis of the current output. To determine the blast wave energy from the powerful spark, the time-of-arrival of the blast wave in air is measured at different radii using a piezoelectric pressure transducer. Good agreement is found in the scaled blast trajectories, i.e., scaled time c o· t/ R o where c o is the ambient sound speed, as a function of blast radius R s/ R o between the numerical simulation of a spherical blast wave from a point energy source and the experimental results where the explosion length scale R o is computed using the equivalent spark energy from the first 1/4 current discharge cycle. Alternatively, by fitting the experimental trajectories data, the blast energy estimated from the numerical simulation appears also in good agreement with that obtained experimentally using the 1/4 cycle criterion. Using the 1/4 cycle of spark discharge for the effective energy, direct initiation experiments of spherical gaseous detonations are carried out to determine the critical initiation energy in C2H2-2.5O2 mixtures with 70 and 0% argon dilution. The experimental results obtained from the 1/4 cycle of spark discharge agree well with the prediction from two initiation models, namely, the Lee's surface energy model and a simplified work done model. The main source of discrepancy in the comparison can be explained by the uncertainty of cell size measurement which is needed for both the semi-empirical models.

Zhang, B.; Ng, H. D.; Lee, J. H. S.

2012-01-01

380

Time-resolved photoluminescence measurements for determining voltage-dependent charge-separation efficiencies of subcells in triple-junction solar cells  

NASA Astrophysics Data System (ADS)

Conventional external quantum-efficiency measurement of solar cells provides charge-collection efficiency for approximate short-circuit conditions. Because this differs from actual operating voltages, the optimization of high-quality tandem solar cells is especially complicated. Here, we propose a contactless method, which allows for the determination of the voltage dependence of charge-collection efficiency for each subcell independently. By investigating the power dependence of photoluminescence decays, charge-separation and recombination-loss time constants are obtained. The upper limit of the charge-collection efficiencies at the operating points is then obtained by applying the uniform field model. This technique may complement electrical characterization of the voltage dependence of charge collection, since subcells are directly accessible.

Tex, David M.; Ihara, Toshiyuki; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

2015-01-01

381

FIA-automated system used to electrochemically measure nitrite and its interfering chemicals through a 1-2 DAB / Au electrode: gain of sensitivity at upper potentials  

NASA Astrophysics Data System (ADS)

The measurement of nitrite and its interfering-chemicals (paracetamol, ascorbic acid and uric acid) was performed employing a Flow-injection Analysis (FIA) system, which was automated using solenoid valves and air-pump. It is very important to quantify nitrite from river water, food and biologic fluids due to its antibacterial capacity in moderated concentrations, or its toxicity for human health even at low concentrations (> 20 ?mol L-1 in blood fluids). Electrodes of the electrochemical planar sensor were defined by silk-screen technology. The measuring electrode was made from gold paste covered with 1-2 cis Diaminobenzene (DAB), which allowed good selectivity, linearity, repeatability, stability and optimized gain of sensitivity at 0.5 VAg/AgCl Nafion®117 (6.93 ?A mol-1 L mm-2) compared to 0.3 VAg/AgCl Nafion® 117. The reference electrode was obtained from silver/palladium paste modified with chloride and covered with Nafion® 117. The auxiliary electrode was made from platinum paste. It was noteworthy that nitrite response adds to the response of the studied interfering-chemicals and it is predominant for concentrations lower than 175 ?mol L-1.

Almeida, F. L.; dos Santos Filho, S. G.; Fontes, M. B. A.

2013-03-01

382

Voltage Controlled Voltage Source (VCVS)  

NSDL National Science Digital Library

Hosted by Clarkson University, this applet demonstrates a circuit that contains a voltage controlled voltage source (VCVS). The gain may be modified using the scroll bar. Even though brief, this resource can be used in a variety of different technical education classrooms.

Dorf, Richard C.

383

NREL Develops Technique to Measure Membrane Thickness and Defects in Polymer Electrode Membrane Fuel Cells (Fact Sheet)  

SciTech Connect

This fact sheet describes NREL's accomplishments in fuel cell membrane electrode assembly research and development. Work was performed by the Hydrogen Technologies and Systems Center and the National Center for Photovoltaics.

Not Available

2010-11-01

384

Changes in impedance of Ni electrodes upon standing and cycling  

NASA Technical Reports Server (NTRS)

Impedances of Ni electrodes vary with many factors including voltage, cycling, and manufacturer. However, results from Ni/H2 cells being tested for Space Station Freedom show that consistent results are obtained within a group of cells from the same manufacturer if the cells are cycled and stored in the same manner. Impedance changes with storage and cycling are being investigated. Impedances are low in the fully charged state but rise abruptly by several orders of magnitude at a voltage corresponding to a very low state-of-charge. After standing for several months, this increase occurred at a higher voltage, consistent with an increase in structural order during storage which hinders diffusion of protons and reduces high rate capacity. Early measurements on the effects of cycling on Ni/H2 cells being tested for Space Station Freedom show differences between cells from different manufacturers.

Reid, Margaret A.

1989-01-01

385

A flexible electrode array for muscle impedance measurements in the mouse hind limb: A tool to speed research in neuromuscular disease  

NASA Astrophysics Data System (ADS)

Electrical impedance myography (EIM) is a bioelectrical impedance technique focused on the assessment of neuromuscular diseases using tetrapolar surface arrays. Recently, we have shown that reproducible and sensitive EIM measurements can be made on the gastrocnemius muscle of the mouse hind limb and that these are sensitive to disease alterations. A dedicated array would help speed data acquisition and provide additional sensitivity to disease-induced alterations. A flexible electrode array was developed with electrode sizes of 1mm × 1mm by Parlex, Inc. Tetrapolar electrode sets were arranged both parallel to (longitudinal) and orthogonally to (transverse) the major muscle fiber direction of the gastrocnemius muscle. Measurements were made with a dedicated EIM system. A total of 11 healthy animals and 7 animals with spinal muscular atrophy (a form of motor neuron disease) were evaluated after the fur was completely removed with a depilatory agent from the hind limb. Standard electrophysiologic testing (compound motor action potential amplitude and motor unit number estimation) was also performed. The flexible electrode array demonstrated high repeatability in both the longitudinal and transverse directions in the healthy and diseased animals (with intraclass correlation coefficients of 0.94 and 0.89, respectively, for phase angle measured transversely). In addition, differences between healthy and diseased animals were identifiable. For example, the 50 kHz transverse phase angle was higher in the healthy as compared to the SMA animals (16.8° ± 0.5 vs. 14.3° ± 0.7, respectively) at 21 weeks of age (p = 0.01). Differences in anisotropy were also identifiable. Correlations to several standard neurophysiologic parameters also appeared promising. This novel flexible tetrapolar electrode array can be used on the mouse hind limb and provides multidirectional data that can be used to assess muscle health. This technique has the potential of finding widespread use in the evaluation of drug therapies in neuromuscular animal disease models.

Li, J.; Rutkove, S. B.

2013-04-01

386

Effect of a floating electrode on a plasma jet  

SciTech Connect

Two kinds of floating electrode, floating dielectric barrier covered electrode (FDBCE) and floating pin electrode (FPE), which can enhance the performance of plasma jet are reported. The intense discharge between the floating electrode and power electrode decreased the voltage to trigger the plasma jet substantially. The transition of plasma bullet from ring shape to disk shape in the high helium concentration region happened when the floating electrode was totally inside the powered ring electrode. The enhanced electric field between propagating plasma bullet and ground electrode is the reason for this transition. The double plasma bullets happened when part of the FDBCE was outside the powered ring electrode, which is attributed to the structure and surface charge of FDBCE. As part of the FPE was outside the powered ring electrode, the return stroke resulted in a single intensified plasma channel between FPE and ground electrode.

Hu, J. T.; Wang, J. G.; Liu, X. Y.; Liu, D. W.; Lu, X. P. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China)] [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Shi, J. J. [College of Science, Donghua University, Shanghai 201620 (China)] [College of Science, Donghua University, Shanghai 201620 (China); Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, New South Wales 2070 (Australia)] [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, New South Wales 2070 (Australia)

2013-08-15

387

Electrode measurements of the oxidation-reduction potential in the Gotland Deep using medium-term moored profiling instrumentation  

NASA Astrophysics Data System (ADS)

The variation of in situ redox potential (Eh) was studied in the stratified water column (30 - 185 m) of the central Baltic Sea, for a period of 56 days (November, 2010 - January, 2011) using the Gotland Deep Environmental Sampling Station (GODESS) in order to identify the processes that control Eh. During the deployment of the mooring 170 profiles of hydro-physical parameters were registered, including the oxidation-reduction potential, pH, dissolved oxygen, chlorophyll a fluorescence, turbidity, temperature and conductivity. In general, the measured Eh (with respect to standard hydrogen electrode, SHE) ranged from - 55 to 167 mV. A comparison of the measured Eh with that calculated for the particular redox couples was carried out by applying the Nernst-equation. The standard reduction potentials were corrected for temperature and pH. Furthermore, the concentrations of the most important redox components such as Fe, Mn, N, O, C and S used for comparison were estimated by using empirical functions or were based on measurements of discrete water samples, taken at the time of deployment and recovery of the mooring. The results reveal that the reduction of Fe(III) essentially controls the electrode potential of the redox sensor in most parts of the anoxic waters. Below the redoxcline the reduction of hematite and then ferric oxyhydroxid could be related to the redox potential and somewhat deeper Fe(III)/Fe(II) was found to be the dominant redox couple. Theoretically a mixed potential theory should have been applied because in natural waters a variety of redox pairs is present but Fe couples appear to dominate all the other redox equlibria. This could be explained by the relatively high exchange current of Fe and by the high concentrations (up to 1.5 µM) present at those depths in the study area. However, there are still gaps in our knowledge about the cycling of redox-sensitive elements and long-term moored profiling instrumentations may help to improve our understanding. Thus, we are pursuing the use of in situ analyzers for electro active compounds on moored systems in the future. In this case, analyzer data would be associated with chemical and physical parameters measured with high resolution in time and space, giving information on mixing processes and reaction kinetics. This approach is required to assess the relevance, for instance, of intrusions of oxygenated waters, vertical eddy-diffusion and fluctuations caused by internal waves on the cycle of redox-sensitive elements. This is particularly important as lateral transport appears to play a dominant role along isopycnal surfaces, especially in medium-sized stratified basins and yet have not been investigated extensively in the Baltic Sea with respect to the cycles of the most electro-active compounds.

Meyer, David; Prien, Ralf; Dellwig, Olaf; Schulz-Bull, Detlef

2013-04-01

388

High voltage solar array experiments  

NASA Technical Reports Server (NTRS)

The interaction between the components of a high voltage solar array and a simulated space plasma is studied to obtain data for the design of a high voltage solar array capable of 15kW at 2 to 16kV. Testing was conducted in a vacuum chamber 1.5-m long by 1.5-m diameter having a plasma source which simulated the plasma conditions existing in earth orbit between 400 nautical miles and synchronous altitude. Test samples included solar array segments pinholes in insulation covering high voltage electrodes, and plain dielectric samples. Quantitative data are presented in the areas of plasma power losses, plasma and high voltage induced damage, and dielectric properties. Limitations of the investigation are described.

Kennerud, K. L.

1974-01-01

389

Built-in voltage of organic bulk heterojuction p-i-n solar cells measured by electroabsorption spectroscopy  

SciTech Connect

We investigate the influence of the built-in voltage on the performance of organic bulk heterojuction solar cells that are based on a p-i-n structure. Electrical doping in the hole and the electron transport layer allows to tune their work function and hence to adjust the built-in voltage: Changing the doping concentration from 0.5 to 32 wt% induces a shift of the work function towards the transport levels and increases the built-in voltage. To determine the built-in voltage, we use electroabsorption spectroscopy which is based on an evaluation of the spectra caused by a change in absorption due to an electric field (Stark effect). For a model system with a bulk heterojunction of BF-DPB and C{sub 60}, we show that higher doping concentrations in both the electron and the hole transport layer increase the built-in voltage, leading to an enhanced short circuit current and solar cell performance.

Siebert-Henze, E., E-mail: ellen.siebert@iapp.de; Lyssenko, V. G.; Fischer, J.; Tietze, M.; Brueckner, R.; Schwarze, M.; Vandewal, K.; Ray, D.; Riede, M.; Leo, K. [Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden (Germany)] [Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden (Germany)

2014-04-15

390

Electrooptic polymer voltage sensor and method of manufacture thereof  

NASA Technical Reports Server (NTRS)

An optical voltage sensor utilizing an electrooptic polymer is disclosed for application to electric power distribution systems. The sensor, which can be manufactured at low cost in accordance with a disclosed method, measures voltages across a greater range than prior art sensors. The electrooptic polymer, which replaces the optical crystal used in prior art sensors, is sandwiched directly between two high voltage electrodes. Voltage is measured by fiber optical means, and no voltage division is required. The sample of electrooptic polymer is fabricated in a special mold and later mounted in a sensor housing. Alternatively, mold and sensor housing may be identical. The sensor housing is made out of a machinable polymeric material and is equipped with two opposing optical windows. The optical windows are mounted in the bottom of machined holes in the wall of the mold. These holes provide for mounting of the polarizing optical components and for mounting of the fiber optic connectors. One connecting fiber is equipped with a light emitting diode as a light source. Another connecting fiber is equipped with a photodiode as a detector.

Gottsche, Allan (Inventor); Perry, Joseph W. (Inventor)

1993-01-01

391

Method of making biocompatible electrodes  

DOEpatents

A process of improving the sensing function of biocompatible electrodes and the product so made are disclosed. The process is designed to alter the surfaces of the electrodes at their tips to provide increased surface area and therefore decreased contact resistance at the electrode-tissue interface for increased sensitivity and essentially includes rendering the tips atomically clean by exposing them to bombardment by ions of an inert gas, depositing an adhesion layer on the cleaned tips, forming a hillocked layer on the adhesion layer by increasing the temperature of the tips, and applying a biocompatible coating on the hillocked layer. The resultant biocompatible electrode is characterized by improved sensitivity, minimum voltage requirement for organ stimulation and a longer battery life for the device in which it is employed.

Wollam, John S. (Acton, MA)

1992-01-01

392

Discharge characteristics of an atmospheric-pressure argon plasma column generated with a single-electrode configuration  

NASA Astrophysics Data System (ADS)

An atmospheric-pressure argon discharge plasma column is generated by making use of a single-electrode configuration with the power supply operating at a frequency of 45 kHz. It is observed that corona, glowlike plume, and filamentary discharges evolve individually with increasing applied voltage. It is in the filamentary state with average electron density of order 1012 cm-3 that plasma column grows up in the tube with increasing applied voltage. Its discharge characteristics are determined by measuring electrical parameters (voltage, conduction current, and average absorbed power) and optical emission spectroscopy.

Li, Shou-Zhe; Huang, Wen-Tong; Zhang, Jialiang; Wang, Dezhen

2009-07-01

393

Silver-coated TiO2 electrodes for high performance dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

Silver-coated TiO2 electrodes were prepared by photodeposition with different light durations. Comparing with the dye-sensitized solar cells (DSSCs) using conventional TiO2 electrode, the conversion efficiency of DSSCs fabricated with silver-coated TiO2 electrodes was improved from 5.97% to 6.86%. The Ag layer could reflect incident light and lengthen the optical path in electrodes, and also appropriate Ag particles absorbed on the TiO2 surface slowed down the electron recombination. The recombination mechanisms of DSSCs were analyzed by open circuit voltage decay (OCVD) measurements, which provide evidence that the charge transfer from the surface state was strongly suppressed by the silver coating.

Peng, Wei; Zeng, Yun; Gong, Hao; Leng, Yong-qing; Yan, Yong-hong; Hu, Wei

2013-11-01

394

Carbon nanotube counter electrode for high-efficient fibrous dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

High-efficient fibrous dye-sensitized solar cell with carbon nanotube (CNT) thin films as counter electrodes has been reported. The CNT films were fabricated by coating CNT paste or spraying CNT suspension solution on Ti wires. A fluorine tin oxide-coated CNT underlayer was used to improve the adherence of the CNT layer on Ti substrate for sprayed samples. The charge transfer catalytic behavior of fibrous CNT/Ti counter electrodes to the iodide/triiodide redox pair was carefully studied by electrochemical impedance and current-voltage measurement. The catalytic activity can be enhanced by increasing the amount of CNT loading on substrate. Both the efficiencies of fibrous dye-sensitized solar cells using paste coated and sprayed CNT films as counter electrodes are comparative to that using Pt wires, indicating the feasibility of CNT/Ti wires as fibrous counter electrode for superseding Pt wires.

Huang, Shuqing; Sun, Huicheng; Huang, Xiaoming; Zhang, Quanxin; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

2012-04-01

395

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front there through. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique. 12 figs.

Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

1986-12-09

396

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material  

DOEpatents

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front therethrough. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique.

Lee, David O. (Albuquerque, NM); Montoya, Paul C. (Albuquerque, NM); Wayland, Jr., James R. (Albuquerque, NM)

1986-01-01

397

Subdural Electrodes  

PubMed Central

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

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

2010-01-01

398

Distance measurements reveal a common topology of prokaryotic voltage-gated ion channels in the lipid bilayer.  

PubMed

Voltage-dependent ion channels are fundamental to the physiology of excitable cells because they underlie the generation and propagation of the action potential and excitation-contraction coupling. To understand how ion channels work, it is important to determine their structures in different conformations in a membrane environment. The validity of the crystal structure for the prokaryotic K(+) channel, K(V)AP, has been questioned based on discrepancies with biophysical data from functional eukaryotic channels, underlining the need for independent structural data under native conditions. We investigated the structural organization of two prokaryotic voltage-gated channels, NaChBac and K(V)AP, in liposomes by using luminescence resonance energy transfer. We describe here a transmembrane packing representation of the voltage sensor and pore domains of the prokaryotic Na channel, NaChBac. We find that NaChBac and K(V)AP share a common arrangement in which the structures of the Na and K selective pores and voltage-sensor domains are conserved. The packing arrangement of the voltage-sensing region as determined by luminescence resonance energy transfer differs significantly from that of the K(V)AP crystal structure, but resembles that of the eukaryotic K(V)1.2 crystal structure. However, the voltage-sensor domain in prokaryotic channels is closer to the pore domain than in the K(V)1.2 structure. Our results indicate that prokaryotic and eukaryotic channels that share similar functional properties have similar helix arrangements, with differences arising likely from the later introduction of additional structural elements. PMID:17043236

Richardson, Jessica; Blunck, Rikard; Ge, Pinghua; Selvin, Paul R; Bezanilla, Francisco; Papazian, Diane M; Correa, Ana M

2006-10-24

399

Working Electrodes  

Microsoft Academic Search

\\u000a In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can\\u000a be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution;\\u000a however, solid electrolytes and ionic melts can be used as well. The term “electrode” is also used in a technical sense,

Šebojka Komorsky-Lovri?

400

ac electro-osmotic micropump by asymmetric electrode polarization  

NASA Astrophysics Data System (ADS)

ac electro-osmosis (ACEO) has emerged recently as a promising strategy for fluid transport at microscale. With an array of planar interdigital electrodes immersed in an electrolyte, different charging mechanisms at electrode/electrolyte interface and electrokinetic surface flows can be induced by nonuniform electrical fields. To implement ACEO micropump, asymmetry in an electrode pair is essential to generate net flow, which has been typically achieved through asymmetric electrode geometries. This work proposes asymmetric electrode polarization processes to break the electrode symmetry. A dc bias is superimposed onto ac potentials, so that the two electrodes in a pair undergo capacitive charging or Faradaic charging separately. Applying such signals, pumping action has been demonstrated with only a few volts of applied voltage and a power consumption in the range of milliwatts. Pumping velocity by asymmetric electrode polarization exhibits an exponential dependency on voltage.

Wu, Jie (Jayne)

2008-01-01

401

Electrode contamination effects of retarding potential analyzer.  

PubMed

The electrode contamination in electrostatic analyzers such as Langmuir probes and retarding potential analyzers (RPA) is a serious problem for space measurements. The contamination layer acts as extra capacitance and resistance and leads to distortion in the measured I-V curve, which leads to erroneous measurement results. There are two main effects of the contamination layer: one is the impedance effect and the other is the charge attachment and accumulation due to the capacitance. The impedance effect can be reduced or eliminated by choosing the proper sweeping frequency. However, for RPA the charge accumulation effect becomes serious because the capacitance of the contamination layer is much larger than that of the Langmuir probe of similar dimension. The charge accumulation on the retarding potential grid causes the effective potential, that ions experience, to be changed from the applied voltage. Then, the number of ions that can pass through the retarding potential grid to reach the collector and, thus, the measured ion current are changed. This effect causes the measured ion drift velocity and ion temperature to be changed from the actual values. The error caused by the RPA electrode contamination is expected to be significant for sounding rocket measurements with low rocket velocity (1-2 km/s) and low ion temperature of 200-300 K in the height range of 100-300 km. In this paper we discuss the effects associated with the RPA contaminated electrodes based on theoretical analysis and experiments performed in a space plasma operation chamber. Finally, the development of a contamination-free RPA for sounding rocket missions is presented. PMID:24517809

Fang, H K; Oyama, K-I; Cheng, C Z

2014-01-01

402

Electrode contamination effects of retarding potential analyzer  

NASA Astrophysics Data System (ADS)

The electrode contamination in electrostatic analyzers such as Langmuir probes and retarding potential analyzers (RPA) is a serious problem for space measurements. The contamination layer acts as extra capacitance and resistance and leads to distortion in the measured I-V curve, which leads to erroneous measurement results. There are two main effects of the contamination layer: one is the impedance effect and the other is the charge attachment and accumulation due to the capacitance. The impedance effect can be reduced or eliminated by choosing the proper sweeping frequency. However, for RPA the charge accumulation effect becomes serious because the capacitance of the contamination layer is much larger than that of the Langmuir probe of similar dimension. The charge accumulation on the retarding potential grid causes the effective potential, that ions experience, to be changed from the applied voltage. Then, the number of ions that can pass through the retarding potential grid to reach the collector and, thus, the measured ion current are changed. This effect causes the measured ion drift velocity and ion temperature to be changed from the actual values. The error caused by the RPA electrode contamination is expected to be significant for sounding rocket measurements with low rocket velocity (1-2 km/s) and low ion temperature of 200-300 K in the height range of 100-300 km. In this paper we discuss the effects associated with the RPA contaminated electrodes based on theoretical analysis and experiments performed in a space plasma operation chamber. Finally, the development of a contamination-free RPA for sounding rocket missions is presented.

Fang, H. K.; Oyama, K.-I.; Cheng, C. Z.

2014-01-01

403

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

NASA Astrophysics Data System (ADS)

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan

2014-07-01

404

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

SciTech Connect

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0?cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electric and Electronic Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-07-15

405

Field-enhanced electrodes for additive-injection non-thermal plasma (NTP) processor  

DOEpatents

The present invention comprises a field enhanced electrode package for use in a non-thermal plasma processor. The field enhanced electrode package includes a high voltage electrode and a field-enhancing electrode with a dielectric material layer disposed in-between the high voltage electrode and the field-enhancing electrode. The field-enhancing electrode features at least one raised section that includes at least one injection hole that allows plasma discharge streamers to occur primarily within an injected additive gas.

Rosocha, Louis A. (Los Alamos, NM); Ferreri, Vincent (Westminster, CO); Kim, Yongho (Los Alamos, NM)

2009-04-21

406

Urchin-like nanowire array: a strategy for high-performance ZnO-based electrode utilized in photoelectrochemistry  

NASA Astrophysics Data System (ADS)

The electrodes in photoelectrochemical cells responsible for the generation of hydrogen and oxygen by water splitting have been intensively studied because of their high photon-to-electron conversion efficiency. The morphology of nanostructures with these high-efficiency electrodes was systematically compared with the morphology of ZnO structures with vertically aligned nanorod arrays (NA), hollow hemisphere arrays (HA), urchin-like (UL) nanorod arrays, and thin films (TF). The UV-vis light absorption, photoresponse (current-voltage characteristics in the dark and under light), and photoelectrochemistry of the electrodes were measured. The highest photon-to-electron conversion efficiency of 65% at a specific UV wavelength for an electrode with a ZnO UL structure was derived from the UL morphology of high light-trapping efficiency and carrier collection efficiency. The UL morphology also produced a photon-to-electron conversion efficiency of 4.5% under a solar simulator by CdS-sensitization of the ZnO UL electrode. The value was the highest observed thus far among the ZnO-based electrodes. We demonstrated that photoresponse measurement is a practical and simple technique for the estimation of the photon-to-electron conversion efficiency of an electrode.The electrodes in photoelectrochemical cells responsible for the generation of hydrogen and oxygen by water splitting have been intensively studied because of their high photon-to-electron conversion efficiency. The morphology of nanostructures with these high-efficiency electrodes was systematically compared with the morphology of ZnO structures with vertically aligned nanorod arrays (NA), hollow hemisphere arrays (HA), urchin-like (UL) nanorod arrays, and thin films (TF). The UV-vis light absorption, photoresponse (current-voltage characteristics in the dark and under light), and photoelectrochemistry of the electrodes were measured. The highest photon-to-electron conversion efficiency of 65% at a specific UV wavelength for an electrode with a ZnO UL structure was derived from the UL morphology of high light-trapping efficiency and carrier collection efficiency. The UL morphology also produced a photon-to-electron conversion efficiency of 4.5% under a solar simulator by CdS-sensitization of the ZnO UL electrode. The value was the highest observed thus far among the ZnO-based electrodes. We demonstrated that photoresponse measurement is a practical and simple technique for the estimation of the photon-to-electron conversion efficiency of an electrode. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00889d

Hieu, Hoang Nhat; Dung, Nguyen Quoc; Kim, Jimin; Kim, Dojin

2013-05-01

407

Measurements and Modeling of Noise on 22.9kV Medium-Voltage Underground Power Line for Broadband Power Line Communication  

Microsoft Academic Search

\\u000a This paper proposed the measurements and modeling of noise on the 22.9-kV Medium-Voltage (MV) underground power distribution\\u000a cable for Broadband Power Line Communication (BPLC). The proposed measurement system was composed of inductive coupler and\\u000a Digital Phosphor Oscilloscope (DPO). The measurement noise data was obtained from thirty-two pad mounted transformers in the\\u000a test field located in Choji area of Ansan city.

Seungjoon Lee; Donghwan Shin; Yonghwa Kim; Jaejo Lee; Kihwan Eom

2010-01-01

408

Superposition of borehole-to-surface voltage residuals for Vadose Zone plume delineation.  

PubMed

An injected tracer field experiment was conducted at the University of Idaho Ground Water Field Laboratory to evaluate the application of borehole-to-surface voltage measurements for delineation of the tracer distribution in partially saturated, fractured basalt. A tap water tracer was injected into a fracture-dominated, salt-water plume formed during a previous salt-water injection experiment. The tap water tracer was injected into a central injection well under constant hydraulic head for 34 days. The injection well was surrounded by seven test boreholes. Each borehole contained several copper wire electrodes for borehole-to-surface potential measurements between a surface grid of 224 copper sulfate, porous pot electrodes. Eight pole-pole, borehole-to-surface voltage data sets were acquired during each measurement period by energization of a selected electrode in each of the eight boreholes. Predicted voltages for a uniform earth (homogeneous and isotropic) potential model (finite difference) were subtracted from each data set (for its respective current source location), and the voltage residuals superposed to create new data sets with greater measurement sensitivity and coverage, to aid in interpretation. These data sets were collected over four measurement periods during tap water injection and four measurement periods during the subsequent 64-day drainage phase. The data were interpreted with the use of three-dimensional models and by comparisons with other electrical and hydrological observations. Results indicate that superposition of multiple data sets of voltage residuals significantly improved the lateral resolution of subsurface bulk resistivity changes that occurred over time. PMID:16298016

Osiensky, James L; Belknap, Willard J; Donaldson, Paul R

2006-01-10

409

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into the formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figures.

Vail, W.B. III.

1991-08-27

410

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas present. Lithological characteristics of the formation such as the pressence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

Vail, III, William B. (Bothell, WA)

1991-01-01

411

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figs.

Vail, W.B. III.

1989-11-21

412

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing  

DOEpatents

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

Vail, III, William B. (Bothell, WA)

1989-01-01

413

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

414

Local voltage drop in a single functionalized graphene sheet characterized by Kelvin probe force microscopy.  

PubMed

We studied the local voltage drop in functionalized graphene sheets of sub?m size under external bias conditions by Kelvin probe force microscopy. Using this noninvasive experimental approach, we measured ohmic current-voltage characteristics and an intrinsic conductivity of about 3.7 × 10(5) S/m corresponding to a sheet resistance of 2.7 k?/sq under ambient conditions for graphene produced via thermal reduction of graphite oxide. The contact resistivity between functionalized graphene and metal electrode was found to be <6.3 × 10(-7) ?cm(2). PMID:21848299

Yan, Liang; Punckt, Christian; Aksay, Ilhan A; Mertin, Wolfgang; Bacher, Gerd

2011-09-14

415

Electrical Conductivity of Frozen Shrimp and Flounder at Different Temperatures and Voltage Levels  

Microsoft Academic Search

Electrical conductivity (EC) is an important property during ohmic thawing of seafood. EC of frozen flounder, tiger and white shrimp, and shrimp shells at different voltages and temperatures (T) was measured. The materials were homogenized in a blender. PVC tubes (lengths: 4.1 to 5.6 cm, diameter: 1.5 cm) were filled with the material and fitted with circular stainless steel electrodes

Diego A. Luzuriaga; Murat O. Balaban

1996-01-01

416

Nonlinear antiferroelectric-like capacitance-voltage curves in ferroelectric BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

The ferroelectric capacitance is usually nonlinear against increasing/decreasing voltage in sweeping time longer than 1 s and achieves a maximum value at around a coercive voltage within each loop. With the improved short-pulse measurements, we estimated the differential capacitance of ferroelectric Au/BiFeO3/LaNiO3/SrTiO3 thin-film capacitors from a nanosecond discharging current induced by a delta voltage after a stressing voltage pulse with widths of 500 ns-50 ms. With the shortening of the voltage sweeping time, we clearly observed two capacitance maxima from each branch of a capacitance-voltage (C-V) loop, reminiscent of an antiferroelectric behavior. After transformation of nanosecond domain switching current transients under pulses into polarization-voltage hysteresis loops, we further measured time dependent polarization retention as well as imprint in the range of 100 ns-1 s. Both positive and negative polarizations decay exponentially at characteristic times of 2.25 and 198 ?s, suggesting the coexistence of preferred domains pointing to top and bottom electrodes in most epitaxial films. This exponential time dependence is similar to the dielectric degradation under a dc voltage, and the polarization retention can be improved through long-time opposite voltage stressing. With this improvement, the additional antiferroelectric-like dielectric maximum within each branch of a C-V loop disappears. This experiment provides the strong evidence of the effect of time-dependent charge injection on polarization retention and dielectric degradation.

Jiang, A. Q.; Zhang, D. W.; Tang, T. A.

2013-07-01

417

Memristor-integrated voltage-stabilizing supercapacitor system.  

PubMed

Voltage-stabilized supercapacitors: A single supercapacitor formed with PCBM/Pt/IPS nanorod-array electrodes is designed and delivers enhanced areal capacitance, capacitance retention, and excellent electrical stability under bending, while a significant voltage-decrease is observed during the discharging process. Once integrated with the memristor, the memristor-integrated supercapacitor systems deliver an extremely low voltage-drop, indicating greatly enhanced voltage-stabilizing features. PMID:24805149

Liu, Bin; Liu, Boyang; Wang, Xianfu; Wu, Xinghui; Zhao, Wenning; Xu, Zhimou; Chen, Di; Shen, Guozhen

2014-08-01

418

The influence of a voltage ramp on the measurement of I-V characteristics of a solar cell  

NASA Technical Reports Server (NTRS)

For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.

Von Roos, O.

1980-01-01

419

Glow-to-arc transition events in H2-Ar direct current pulsed plasma: Automated measurement of current and voltage  

NASA Astrophysics Data System (ADS)

The glow-to-arc transition phenomena (arcing) observed in plasma reactors used in materials processing was studied through the arcs characteristic current and voltage waveforms. In order to capture these arcs signals, a LABVIEW™ based automated instrumentation system (ARCVIEW) was developed, including the integration of an oscilloscope equipped with proper current and voltage probes. The system also allows capturing the process parameters at the arc occurrence moments, which were used to map the arcs events conditions. Experiments in H2-Ar DC pulsed plasma returned signals data from 215 arcs events, which were analyzed through software routines. According to the results, an anti-arcing system should react in the time order of few microseconds to prevent most of the damage caused by the undesired arcing phenomena.

Mendes, Luciano A.; Mafra, Márcio; Rodrigues, Jhonatam C.

2012-01-01

420

Cermet electrode  

DOEpatents

Disclosed is a cermet electrode consisting of metal particles of nickel, cobalt, iron, or alloys or mixtures thereof immobilized by zirconia stabilized in cubic form which contains discrete deposits of about 0.1 to about 5% by weight of praseodymium, dysprosium, terbium, or a mixture thereof. The solid oxide electrode can be made by covering a substrate with particles of nickel, cobalt, iron, or mixtures thereof, growing a stabilized zirconia solid oxide skeleton around the particles thereby immobilizing them, contacting the skeleton with a compound of praseodymium, dysprosium, terbium, or a mixture thereof, and heating the skeleton to a temperature of at least 500.degree. C. The electrode can also be made by preparing a slurry of nickel, cobalt, iron, or mixture and a compound of praseodymium, dysprosium, terbium, or a mixture thereof, depositing the slurry on a substrate, heating the slurry to dryness, and growing a stabilized zirconia skeleton around the metal particles.

Maskalick, Nicholas J. (Pittsburgh, PA)

1988-08-30

421

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

422

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

423

Photoelectrochemical electrodes  

NASA Technical Reports Server (NTRS)

The surface of a moderate band gap semiconductor such as p-type molybdenum sulfide is modified to contain an adherent film of charge mediating ionene polymer containing an electroactive unit such as bipyridimium. Electron transport between the electrode and the mediator film is favorable and photocorrosion and recombination processes are suppressed. Incorporation of particles of catalyst such as platinum within the film provides a reduction in overvoltage. The polymer film is readily deposited on the electrode surface and can be rendered stable by ionic or addition crosslinking. Catalyst can be predispersed in the polymer film or a salt can be impregnated into the film and reduced therein.

Williams, R. M.; Rembaum, A. (inventors)

1983-01-01

424

Pure ion current collection in ion sensitive probe measurement with a metal mesh guard electrode for evaluation of ion temperature in magnetized plasma  

SciTech Connect

This paper presents a new design of ion sensitive probe (ISP) that enables collection of pure ion current for accurate measurement of the perpendicular ion temperature in magnetized plasmas. The new type of ISP resolves a longstanding issue widely observed in ISP type measurements, namely, that the current-voltage characteristic is smeared by an unexpected electron current in the standard ISP model. The new ISP is equipped with a fine scale metal mesh on the sensor entrance to prevent electrons from flowing to the sensor, a phenomenon considered to be caused by the space-charge effect. The new ISP successfully measured the ion temperature of electron cyclotron resonance plasmas.

Hsieh, Tung-Yuan; Kawamori, Eiichirou [Institute of Space, Astrophysical and Plasma Sciences, National Cheng Kung University, Taiwan (China); Nishida, Yasushi [Plasma and Space Science Center, National Cheng Kung University, Taiwan (China)

2013-02-15

425

Electrode processes in MPD thrusters  

NASA Technical Reports Server (NTRS)

As a preliminary step in understanding and controlling electrode erosion in a magnetoplasmadynamic arc-jet, a literature survey on electrode processes in high current discharges was conducted and the findings are reported. The cathode erosion rate is delimited and the formation of anode spots, which produce large erosion, is discussed. Needed experimental measurements are suggested.

Harstad, K.

1982-01-01

426

Breast cancer detection using high-density flexible electrode arrays and electrical impedance tomography.  

PubMed

While mammography remains the gold standard for breast cancer screening, additional adjunctive tools for early detection of breast cancer are needed especially for young women, women with dense breast tissue and those at increased risk due to genetic factors. These patient populations, along with those populations for whom mammography is not readily available, require alternative technologies capable of effectively detecting breast cancer. One such adjunctive modality for breast cancer detection is Electrical Impedance Tomography (EIT). It is a non-invasive technique that measures tissue conductivity by injecting a small current through a surface electrode while measuring electrode voltage(s). The surface measurements are then used to reconstruct a conductivity mapping of the tissue. The difference in conductivities between healthy tissue and that of carcinoma enable EIT to detect cancer. Electrical Impedance Tomography does not subject the patient to ionizing radiation, and offers significant potential for detecting very small tumors in early stages of development at a low cost. While prior systems have demonstrated success using EIT for breast cancer detection, the resolution of the reconstructed image was limited by the spatial resolution of the sensing electrode array. Here, we report the use of higher density (3mm spacing) flexible micro-electrode arrays to obtain tissue impedance maps. Accurate EIT reconstruction is highly dependent on the spatial resolution and fidelity of the surface measurements. High-density, flexible arrays that conform to the breast surface can offer great potential in reconstructing higher resolution conductivity maps than have been previously achieved. PMID:25570162

Campisi, Matthew S; Barbre, Curtis; Chola, Aditya; Cunningham, Gisselle; Woods, Virginia; Viventi, Jonathan

2014-08-01

427

Powder processing of hybrid titanium neural electrodes  

NASA Astrophysics Data System (ADS)

A preliminary investigation into the powder production of a novel hybrid titanium neural electrode for EEG is presented. The rheological behavior of titanium powder suspensions using sodium alginate as a dispersant are examined for optimal slip casting conditions. Electrodes were slip cast and sintered at 950°C for 1 hr, 1000°C for 1, 3, and 6 hrs, and 1050°C for 1 hr. Residual porosities from sintering are characterized using Archimedes' technique and image analysis. The pore network is gel impregnated by submerging the electrodes in electrically conductive gel and placing them in a chamber under vacuum. Gel evaporation of the impregnated electrodes is examined. Electrodes are characterized in the dry and gelled states using impedance spectrometry and compared to a standard silver- silver chloride electrode. Power spectral densities for the sensors in the dry and gelled state are also compared. Residual porosities for the sintered specimens were between 50.59% and 44.81%. Gel evaporation tests show most of the impregnated gel evaporating within 20 min of exposure to atmospheric conditions with prolonged evaporation times for electrodes with higher impregnated gel mass. Impedance measurements of the produced electrodes indicate the low impedance of the hybrid electrodes are due to the increased contact area of the porous electrode. Power spectral densities of the titanium electrode behave similar to a standard silver-silver chloride electrode. Tests suggest the powder processed hybrid titanium electrode's performance is better than current dry contact electrodes and comparable to standard gelled silver-silver chloride electrodes.

Lopez, Jose Luis, Jr.