Synergistic effects of lead thiocyanate additive and solvent annealing on the performance of wide-bandgap perovskite solar cells

DOE PAGES

Yu, Yue; Wang, Changlei; Grice, Corey R.; ...

2017-04-26

Here, we show that the cooperation of lead thiocyanate additive and a solvent annealing process can effectively increase the grain size of mixed-cation lead mixed-halide perovskite thin films while avoiding excess lead iodide formation. As a result, the average grain size of the wide-bandgap mixed-cation lead perovskite thin films increases from 66 ± 24 to 1036 ± 111 nm, and the mean carrier lifetime shows a more than 3-fold increase, from 330 ns to over 1000 ns. Consequently, the average open-circuit voltage of wide-bandgap perovskite solar cells increases by 80 (70) mV, and the average power conversion efficiency (PCE) increasesmore » from 13.44 ± 0.48 (11.75 ± 0.34) to 17.68 ± 0.36 (15.58 ± 0.55)% when measured under reverse (forward) voltage scans. The best-performing wide-bandgap perovskite solar cell, with a bandgap of 1.75 eV, achieves a stabilized PCE of 17.18%.« less

Evaluation program for secondary spacecraft cells: Initial evaluation tests of General Electric Company 40.0 ampere hour nickel cadmium spacecraft cells for the tracking data relay satellite system

NASA Technical Reports Server (NTRS)

Hall, S. W.

1980-01-01

Average end of charge voltages and pressures, and capacity output in ampere hours are presented. Test limits specify those values at which a cell is to be terminated from charge or discharge. Requirements are based on past cell performance data. The requirement does not constitute a limit for discontinuance from testing. The nickel cadmium batteries were screened for internal shorts, low capacity, electrolyte leakage, or inability of any cell to recover its open circuit voltage above 1.150 volts during the internal short test.

Unexpected Voltage Fade in LMR-NMC Oxides Cycled below the “Activation” Plateau

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yan; Bareno, Javier; Bettge, Martin

2015-01-01

A common feature of lithium-excess layered oxides, nominally of composition xLi 2MnO 3•(1-x)LiMO 2 (M = transition metal) is a high-voltage plateau (~4.5 V vs. Li/Li +) in their capacity-voltage profile during the first delithiation cycle. This plateau is believed to result from activation of the Li 2MnO 3 component, which makes additional lithium available for electrochemical cycling. However, oxides cycled beyond this activation plateau are known to display voltage fade which is a continuous reduction in their equilibrium potential. In this article we show that these oxides display gradual voltage fade even on electrochemical cycling in voltage ranges wellmore » below the activation plateau. The average fade is ~0.08 mV-cycle-1 for Li 1.2Ni 0.15Mn 0.55Co 0.1O 2 vs. Li cells after 20 cycles in the 2–4.1 V range at 55°C; a ~54 mV voltage hysteresis, expressed as the difference in average cell voltage between charge and discharge cycles, is also observed. The voltage fade results from a gradual accumulation of local spinel environments in the crystal structure. Some of these spinel sites result from lithium deficiencies during oxide synthesis and are likely to be at the particle surfaces; other sites result from the migration of transition metal atoms in the partially-delithiated LiMO 2 component into the lithium planes during electrochemical cycling. The observed rate of voltage fade depends on a combination of factors that includes the phase equilibrium between the layered and spinel components and the kinetics of transition metal migration.« less

Relationship between open-circuit voltage in Cu(In,Ga)Se{sub 2} solar cell and peak position of (220/204) preferred orientation near its absorber surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chantana, J., E-mail: jakapan@fc.ritsumei.ac.jp; Minemoto, T.; Watanabe, T.

2013-11-25

Cu(In,Ga)Se{sub 2} (CIGS) absorbers with various Ga/III, Ga/(In+Ga), profiles are prepared by the so-called “multi-layer precursor method” using multi-layer co-evaporation of material sources. It is revealed that open-circuit voltage (V{sub OC}) of CIGS solar cell is primarily dependent on averaged Ga/III near the surface of its absorber. This averaged Ga/III is well predicted by peak position of (220/204) preferred orientation of CIGS film near its surface investigated by glancing-incidence X-ray diffraction with 0.1° incident angle. Finally, the peak position of (220/204) preferred orientation is proposed as a measure of V{sub OC} before solar cell fabrication.

Three-dimensional computational fluid dynamics modelling and experimental validation of the Jülich Mark-F solid oxide fuel cell stack

NASA Astrophysics Data System (ADS)

Nishida, R. T.; Beale, S. B.; Pharoah, J. G.; de Haart, L. G. J.; Blum, L.

2018-01-01

This work is among the first where the results of an extensive experimental research programme are compared to performance calculations of a comprehensive computational fluid dynamics model for a solid oxide fuel cell stack. The model, which combines electrochemical reactions with momentum, heat, and mass transport, is used to obtain results for an established industrial-scale fuel cell stack design with complex manifolds. To validate the model, comparisons with experimentally gathered voltage and temperature data are made for the Jülich Mark-F, 18-cell stack operating in a test furnace. Good agreement is obtained between the model and experiment results for cell voltages and temperature distributions, confirming the validity of the computational methodology for stack design. The transient effects during ramp up of current in the experiment may explain a lower average voltage than model predictions for the power curve.

A magnesium–sodium hybrid battery with high operating voltage

DOE PAGES

Dong, Hui; Li, Yifei; Liang, Yanliang; ...

2016-06-10

Here, we report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mA h g –1. We also demonstrate the cell with an energy density of 135 W h kg –1 and a high power density of up to 1.67 kW kg –1.

Process Research on Polycrystalline Silicon Material (PROPSM)

NASA Technical Reports Server (NTRS)

Culik, J. S.

1983-01-01

The performance limiting mechanisms in large grain (greater than 1-2 mm in diameter) polycrystalline silicon was investigated by measuring the illuminated current voltage (I-V) characteristics of the minicell wafer set. The average short circuit current on different wafers is 3 to 14 percent lower than that of single crystal Czochralski silicon. The scatter was typically less than 3 percent. The average open circuit voltage is 20 to 60 mV less than that of single crystal silicon. The scatter in the open circuit voltage of most of the polycrystalline silicon wafers was 15 to 20 mV, although two wafers had significantly greater scatter than this value. The fill factor of both polycrystalline and single crystal silicon cells was typically in the range of 60 to 70 percent; however several polycrystalline silicon wafers have fill factor averages which are somewhat lower and have a significantly larger degree of scatter.

Reduced distribution of threshold voltage shift in double layer NiSi2 nanocrystals for nano-floating gate memory applications.

PubMed

Choi, Sungjin; Lee, Junhyuk; Kim, Donghyoun; Oh, Seulki; Song, Wangyu; Choi, Seonjun; Choi, Eunsuk; Lee, Seung-Beck

2011-12-01

We report on the fabrication and capacitance-voltage characteristics of double layer nickel-silicide nanocrystals with Si3N4 interlayer tunnel barrier for nano-floating gate memory applications. Compared with devices using SiO2 interlayer, the use of Si3N4 interlayer separation reduced the average size (4 nm) and distribution (+/- 2.5 nm) of NiSi2 nanocrystal (NC) charge traps by more than 50% and giving a two fold increase in NC density to 2.3 x 10(12) cm(-2). The increased density and reduced NC size distribution resulted in a significantly decrease in the distribution of the device C-V characteristics. For each program voltage, the distribution of the shift in the threshold voltage was reduced by more than 50% on average to less than 0.7 V demonstrating possible multi-level-cell operation.

Minimized open-circuit voltage reduction in GaAs/InGaAs quantum well solar cells with bandgap-engineered graded quantum well depths

NASA Astrophysics Data System (ADS)

Li, Xiaohan; Dasika, Vaishno D.; Li, Ping-Chun; Ji, Li; Bank, Seth R.; Yu, Edward T.

2014-09-01

The use of InGaAs quantum wells with composition graded across the intrinsic region to increase open-circuit voltage in p-i-n GaAs/InGaAs quantum well solar cells is demonstrated and analyzed. By engineering the band-edge energy profile to reduce photo-generated carrier concentration in the quantum wells at high forward bias, simultaneous increases in both open-circuit voltage and short-circuit current density are achieved, compared to those for a structure with the same average In concentration, but constant rather than graded quantum well composition across the intrinsic region. This approach is combined with light trapping to further increase short-circuit current density.

Performance and Safety Testing of Varta Li-Ion Polymer Cells

NASA Technical Reports Server (NTRS)

Patel, Pranav; Jeevarajan, Judith

2009-01-01

Varta Cell Characteristics: Voltage : 3.7 V Capacity : 1.21 Ah Dimensions : 5mm X 37mm X 38.5 mm MOSFET switches for Overvoltage and Undervoltage. Initial Screening Results 29 Cells delivered: Statistics on Ph ysical Screening: Thickness (mm): Average- 5.08; Weight(g)- 22.8938; OCV (V)- 3.787; CCV (V)- 3.491.

Progress of Ongoing NASA Lithium-Ion Cell Verification Testing for Aerospace Applications

NASA Technical Reports Server (NTRS)

McKissock, Barbara I.; Manzo, Michelle A.; Miller, Thomas B.; Reid, Concha M.; Bennett, William R.; Gemeiner, Russel

2008-01-01

A Lithium-ion Verification and Validation Program with the purpose to assess the capabilities of current aerospace lithium-ion (Li-ion) battery cells to perform in a low-earth-orbit (LEO) regime was initiated in 2002. This program involves extensive characterization and LEO life testing at ten different combinations of depth-of-discharge, temperature, and end-of-charge voltage. The test conditions selected for the life tests are defined as part of a statistically designed test matrix developed to determine the effects of operating conditions on performance and life of Li-ion cells. Results will be used to model and predict cell performance and degradation as a function of test operating conditions. Testing is being performed at the Naval Surface Warfare Center/Crane Division in Crane, Indiana. Testing was initiated in September 2004 with 40 Ah cells from Saft and 30 Ah cells from Lithion. The test program has been expanded with the addition of modules composed of 18650 cells from ABSL Power Solutions in April 2006 and the addition of 50 Ah cells from Mine Safety Appliances Co. (MSA) in June 2006. Preliminary results showing the average voltage and average available discharge capacity for the Saft and Lithion packs at the test conditions versus cycles are presented.

Sinusoidal voltage protocols for rapid characterisation of ion channel kinetics.

PubMed

Beattie, Kylie A; Hill, Adam P; Bardenet, Rémi; Cui, Yi; Vandenberg, Jamie I; Gavaghan, David J; de Boer, Teun P; Mirams, Gary R

2018-03-24

Ion current kinetics are commonly represented by current-voltage relationships, time constant-voltage relationships and subsequently mathematical models fitted to these. These experiments take substantial time, which means they are rarely performed in the same cell. Rather than traditional square-wave voltage clamps, we fitted a model to the current evoked by a novel sum-of-sinusoids voltage clamp that was only 8 s long. Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions. The new model predicts the current under traditional square-wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically relevant series of action potential clamps is predicted extremely well. The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell-cell variability in current kinetics for the first time. Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics - the voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fitted a mathematical model to currents evoked by a novel 8 second sinusoidal voltage clamp in CHO cells overexpressing hERG1a. The model was then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step voltage clamps, and also a novel voltage clamp comprising a collection of physiologically relevant action potentials. We demonstrate that we can make predictive cell-specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell-cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches. © 2018 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Unexpected Voltage Fade in LMR-NMC Oxides Cycled below the "Activation" Plateau

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Y.; Bareno, J.; Bettge, M.

A common feature of lithium-excess layered oxides, nominally of composition xLi(2)MnO(3)center dot(1-x)LiMO2 (M = transition metal) is a high-voltage plateau (similar to 4.5 V vs. Li/Li+) in their capacity-voltage profile during the first delithiation cycle. This plateau is believed to result from activation of the Li2MnO3 component, which makes additional lithium available for electrochemical cycling. However, oxides cycled beyond this activation plateau are known to display voltage fade which is a continuous reduction in their equilibrium potential. In this article we show that these oxides display gradual voltage fade even on electrochemical cycling in voltage ranges well below the activationmore » plateau. The average fade is similar to 0.08 mV-cycle(-1) for Li(1.2)Ni(0.1)5Mn(0.5)5Co(0.1)O(2) vs. Li cells after 20 cycles in the 2-4.1 V range at 55 degrees C; a similar to 54 mV voltage hysteresis, expressed as the difference in average cell voltage between charge and discharge cycles, is also observed. The voltage fade results from a gradual accumulation of local spinel environments in the crystal structure. Some of these spinel sites result from lithium deficiencies during oxide synthesis and are likely to be at the particle surfaces; other sites result from the migration of transition metal atoms in the partially-delithiated LiMO2 component into the lithium planes during electrochemical cycling. The observed rate of voltage fade depends on a combination of factors that includes the phase equilibrium between the layered and spinel components and the kinetics of transition metal migration. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.« less

Self similarities in desalination dynamics and performance using capacitive deionization.

PubMed

Ramachandran, Ashwin; Hemmatifar, Ali; Hawks, Steven A; Stadermann, Michael; Santiago, Juan G

2018-09-01

Charge transfer and mass transport are two underlying mechanisms which are coupled in desalination dynamics using capacitive deionization (CDI). We developed simple reduced-order models based on a mixed reactor volume principle which capture the coupled dynamics of CDI operation using closed-form semi-analytical and analytical solutions. We use the models to identify and explore self-similarities in the dynamics among flow rate, current, and voltage for CDI cell operation including both charging and discharging cycles. The similarity approach identifies the specific combination of cell (e.g. capacitance, resistance) and operational parameters (e.g. flow rate, current) which determine a unique effluent dynamic response. We here demonstrate self-similarity using a conventional flow between CDI (fbCDI) architecture, and we hypothesize that our similarity approach has potential application to a wide range of designs. We performed an experimental study of these dynamics and used well-controlled experiments of CDI cell operation to validate and explore limits of the model. For experiments, we used a CDI cell with five electrode pairs and a standard flow between (electrodes) architecture. Guided by the model, we performed a series of experiments that demonstrate natural response of the CDI system. We also identify cell parameters and operation conditions which lead to self-similar dynamics under a constant current forcing function and perform a series of experiments by varying flowrate, currents, and voltage thresholds to demonstrate self-similarity. Based on this study, we hypothesize that the average differential electric double layer (EDL) efficiency (a measure of ion adsorption rate to EDL charging rate) is mainly dependent on user-defined voltage thresholds, whereas flow efficiency (measure of how well desalinated water is recovered from inside the cell) depends on cell volumes flowed during charging, which is determined by flowrate, current and voltage thresholds. Results of experiments strongly support this hypothesis. Results show that cycle efficiency and salt removal for a given flowrate and current are maximum when average EDL and flow efficiencies are approximately equal. We further explored a range of CC operations with varying flowrates, currents, and voltage thresholds using our similarity variables to highlight trade-offs among salt removal, energy, and throughput performance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Device characterization and optimization of small molecule organic solar cells assisted by modelling simulation of the current-voltage characteristics.

PubMed

Zuo, Yi; Wan, Xiangjian; Long, Guankui; Kan, Bin; Ni, Wang; Zhang, Hongtao; Chen, Yongsheng

2015-07-15

In order to understand the photovoltaic performance differences between the recently reported DR3TBTT-HD and DR3TBDT2T based solar cells, a modified two-diode model with Hecht equation was built to simulate the corresponding current-voltage characteristics. The simulation results reveal that the poor device performance of the DR3TBDTT-HD based device mainly originated from its insufficient charge transport ability, where an average current of 5.79 mA cm(-2) was lost through this pathway at the maximum power point for the DR3TBDTT-HD device, nearly three times as large as that of the DR3TBDT2T based device under the same device fabrication conditions. The morphology studies support these simulation results, in which both Raman and 2D-GIXD data reveal that DR3TBTT-HD based blend films exhibit lower crystallinity. Spin coating at low temperature was used to increase the crystallinity of DR3TBDTT-HD based blend films, and the average current loss through insufficient charge transport at maximum power point was suppressed to 2.08 mA cm(-2). As a result, the average experimental power conversion efficiency of DR3TBDTT-HD based solar cells increased by over 40%.

A single-cell technique for the measurement of membrane potential, membrane conductance, and the efflux of rapidly penetrating solutes in Amphiuma erythrocytes.

PubMed

Stoner, L C; Kregenow, F M

1980-10-01

We describe a single-cell technique for measuring membrane potential, membrane resistance, and the efflux of rapidly penetrating solutes such as Cl and H2O. Erythrocytes from Amphiuma means were aspirated into a Sylgard (Dow Corning Corp.)-coated capillary. The aspirated cell separated a solution within the capillary from a solution in the bath. Each of these two solutions was contiguous with approximately 5% of the total membrane surface. Microelectrodes placed concentrically within the capillary permit the measurement of intracellular voltage, specific membrane resistance, and the electrical seal between the two solutions. The intracellular voltage averaged -17.7 mV (pH 7.6) and changed as either intra- or extracellular chloride was varied. The average specific membrane resistance measured by passing current across the exposed membrane surface was 110 ohm-cm2. 36Cl and tritiated H2O fluxes (0.84 +/- 0.05 x 10(-6) M . cm-2 . min-1 and 6.4 +/- 1.5 x 10(-3) M . cm-2 . min-1, respectively) were determined by noting the rate at which isotope leaves the cell and crosses the membrane exposed to the bath. Our measured values for the flux of 36Cl and tritiated H2O approximate reported values for free-floating cells. 36Cl efflux, in addition, is inhibited by 4-acetamido-4'-isothiocyano-stilbene 2,2'-disulfonic acid (SITS) and furosemide, known inhibitors of the anion exchange mechanism responsible for the rapid anion fluxes of red blood cells. One can also demonstrate directly that > 89% of 36Cl efflux is "electrically silent" by analyzing the flux in the presence of an imposed transcellular voltage.

Effects of fluctuations on electrical properties of gap-junction connected cells in the turtle retina.

PubMed

Louis, E; Degli Esposti Boschi, C; Ortega, G; Andreu, E; Fernández, E; Sánchez-Andrés, J V

2002-04-19

Electrical properties of gap-junction connected cells (input voltage and length constant) are shown to depend strongly on fluctuations in membrane and contact conductances. This opens new possibilities and incorporates a further difficulty to the analysis of electrophysiological data, since four, instead of two, parameters (the average values and the magnitude of fluctuations of the two conductances) have to be used in fitting the experimental data. The discussion is illustrated by investigating the effects of dopamine on signal spreading in horizontal cells of turtle retina, assuming a linear cell arrangement. It is shown that while a standard fitting with the average values of the two conductances leads to the conclusion that both are equally affected by dopamine, including fluctuations allows fitting the data by varying just the average contact conductance plus the magnitude of fluctuations.

Development of lithium doped radiation resistent solar cells

NASA Technical Reports Server (NTRS)

Berman, P. A.

1972-01-01

Lithium-doped solar cells have been fabricated with initial lot efficiencies averaging 11.9 percent in an air mass zero (AMO) solar simulator and a maximum observed efficiency of 12.8 percent. The best lithium-doped solar cells are approximately 15 percent higher in maximum power than state-of-the-art n-p cells after moderate to high fluences of 1-MeV electrons and after 6-7 months exposure to low flux irradiation by a Sr-90 beta source, which approximates the electron spectrum and flux associated with near Earth space. Furthermore, lithium-doped cells were found to degrade at a rate only one tenth that of state-of-the-art n-p cells under 28-MeV electron irradiation. Excellent progress has been made in quantitative predictions of post-irradiation current-voltage characteristics as a function of cell design by means of capacitance-voltage measurements, and this information has been used to achieve further improvements in lithium-doped cell design.

A dual V t disturb-free subthreshold SRAM with write-assist and read isolation

NASA Astrophysics Data System (ADS)

Bhatnagar, Vipul; Kumar, Pradeep; Pandey, Neeta; Pandey, Sujata

2018-02-01

This paper presents a new dual V t 8T SRAM cell having single bit-line read and write, in addition to Write Assist and Read Isolation (WARI). Also a faster write back scheme is proposed for the half selected cells. A high V t device is used for interrupting the supply to one of the inverters for weakening the feedback loop for assisted write. The proposed cell provides an improved read static noise margin (RSNM) due to the bit-line isolation during the read. Static noise margins for data read (RSNM), write (WSNM), read delay, write delay, data retention voltage (DRV), leakage and average powers have been calculated. The proposed cell was found to operate properly at a supply voltage as small as 0.41 V. A new write back scheme has been suggested for half-selected cells, which uses a single NMOS access device and provides reduced delay, pulse timing hardware requirements and power consumption. The proposed new WARI 8T cell shows better performance in terms of easier write, improved read noise margin, reduced leakage power, and less delay as compared to the existing schemes that have been available so far. It was also observed that with proper adjustment of the cell ratio the supply voltage can further be reduced to 0.2 V.

External pH effects on the depolarization-activated K channels in guard cell protoplasts of Vicia faba

PubMed Central

1994-01-01

Previous studies reveal that the pH of the apoplastic solution in the guard cell walls may vary between 7.2 and 5.1 in closed and open stomata, respectively. During these aperture and pH changes, massive K+ fluxes cross the cellular plasma membrane driving the osmotic turgor and volume changes of guard cells. Therefore, we examined the effect of extracellular pH on the depolarization-activated K channels (KD channels), which constitute the K+ efflux pathway, in the plasma membrane of Vicia faba guard cell protoplasts. We used patch clamp, both in whole cells as well as in excised outside-out membrane patches. Approximately 500 KD channels, at least, could be activated by depolarization in one protoplast (density: approximately 0.6 micron-2). Acidification from ph 8.1 to 4.4 decreased markedly the whole-cell conductance, GK, of the KD channels, shifted its voltage dependence, GK- EM, to the right on the voltage axis, slowed the rate of activation and increased the rate of deactivation, whereas the single channel conductance was not affected significantly. Based on the GK-EM shifts, the estimated average negative surface charge spacing near the KD channel is 39 A. To quantify the effects of protons on the rates of transitions between the hypothesized conformational states of the channels, we fitted the experimental macroscopic steady state conductance-voltage relationship and the voltage dependence of time constants of activation and deactivation, simultaneously, with a sequential three-state model CCO. In terms of this model, protonation affects the voltage-dependent properties via a decrease in localized, rather than homogeneous, surface charge sensed by the gating moieties. In terms of either the CO or CCO model, the protonation of a site with a pKa of 4.8 decreases the voltage-independent number of channels, N, that are available for activation by depolarization. PMID:8035163

Energy breakdown in capacitive deionization.

PubMed

Hemmatifar, Ali; Palko, James W; Stadermann, Michael; Santiago, Juan G

2016-11-01

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Energy breakdown in capacitive deionization

DOE PAGES

Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; ...

2016-08-12

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages.more » We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.« less

Fabrication of efficient low-bandgap perovskite solar cells by combining formamidinium tin iodide with methylammonium lead iodide

DOE PAGES

Liao, Weiqiang; Zhao, Dewei; Yu, Yue; ...

2016-09-13

Mixed tin (Sn)-lead (Pb) perovskites with high Sn content exhibit low bandgaps suitable for fabricating the bottom cell of perovskite-based tandem solar cells. In this work, we report on the fabrication of efficient mixed Sn-Pb perovskite solar cells using precursors combining formamidinium tin iodide (FASnI 3) and methylammonium lead iodide (MAPbI 3). The best-performing cell fabricated using a (FASnI 3) 0.6(MAPbI 3) 0.4 absorber with an absorption edge of ~1.2 eV achieved a power conversion efficiency (PCE) of 15.08 (15.00)% with an open-circuit voltage of 0.795 (0.799) V, a short-circuit current density of 26.86(26.82) mA/cm 2, and a fill factormore » of 70.6(70.0)% when measured under forward (reverse) voltage scan. In conclusion, the average PCE of 50 cells we have fabricated is 14.39 ± 0.33%, indicating good reproducibility.« less

Process Research On Polycrystalline Silicon Material (PROPSM). [flat plate solar array project

NASA Technical Reports Server (NTRS)

Culik, J. S.

1983-01-01

The performance-limiting mechanisms in large-grain (greater than 1 to 2 mm in diameter) polycrystalline silicon solar cells were investigated by fabricating a matrix of 4 sq cm solar cells of various thickness from 10 cm x 10 cm polycrystalline silicon wafers of several bulk resistivities. Analysis of the illuminated I-V characteristics of these cells suggests that bulk recombination is the dominant factor limiting the short-circuit current. The average open-circuit voltage of the polycrystalline solar cells is 30 to 70 mV lower than that of co-processed single-crystal cells; the fill-factor is comparable. Both open-circuit voltage and fill-factor of the polycrystalline cells have substantial scatter that is not related to either thickness or resistivity. This implies that these characteristics are sensitive to an additional mechanism that is probably spatial in nature. A damage-gettering heat-treatment improved the minority-carrier diffusion length in low lifetime polycrystalline silicon, however, extended high temperature heat-treatment degraded the lifetime.

NiH2 Battery Reconditioning for LEO Applications

NASA Technical Reports Server (NTRS)

Armantrout, J. D.; Hafen, D. P.

1997-01-01

This paper summarizes reasons for and benefits of reconditioning nickel-hydrogen (NiH2) batteries used for Low Earth Orbit (LEO) applications. NiH2 battery cells do not have the classic discharge voltage problems more commonly associated with nickel-cadmium (NiCd) cells. This is due, in part, to use of hydrogen electrodes in place of cadmium electrodes. The nickel electrode, however, does have a similar discharge voltage signature for both cell designs. This can have an impact on LEO applications where peak loads at higher relative depths of discharge can impact operations. Periodic reconditioning provides information which can be used for analyzing long term performance trends to predict usable capacity to a specified voltage level. The reconditioning process described herein involves discharging NiH2 batteries at C/20 rates or less, to an average cell voltage of 1.0 volts or less. Recharge is performed at nominal C/5 rates to specified voltage/temperature (V/T) charge levels selected to restore required capacity with minimal overcharge. Reconditioning is a process of restoring reserve capacity lost on cycling, which is commonly called the memory effect in NiCd cells. This effect is characterized by decreases in the discharge voltage curve with operational life and cycling. The end effect of reconditioning NiH2 cells may be hidden in the versatility, of that design over the NiCd cell design and its associated negative electrode fading problem. The process of deep discharge at lower rates by way of reconditioning tends to redistribute electrolyte and water in the NiH2 cell electrode stack, while improving utilization and charge efficiency. NiH2 battery reconditioning effects on life are considered beneficial and may, in fact. extend life based on NiCd experience. In any case, usable capacity data obtained from reconditioning is required for performance evaluation and trend analysis. Characterization and life tests have provided the historical data base used to determine the need for reconditioning in most battery applications. The following sections briefly describe the background of NiH2 battery reconditioning and testing at Lockheed Martin Missiles & Space (LMMS) and other aerospace companies.

Device for monitoring cell voltage

DOEpatents

Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

2012-08-21

A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

Hawaii Energy and Environmental Technologies (HEET) Initiative

DTIC Science & Technology

2009-05-01

current density measured in a PEM fuel cell ( PEMFC ) represents the average of the local reaction rates. Depending on cell design and operating...loss mechanisms determine the spatial and overall performance of a PEMFC : activation, concentration, ohmic, and mass transfer losses. Activation losses...distribution of these various losses in a PEMFC using a six-channel serpentine flow-field. Voltage losses were attributed to each of the mechanisms at each

A Dihydropyridine-sensitive Voltage-dependent Calcium Channel in the Sarcolemmal Membrane of Crustacean Muscle

PubMed Central

Erxleben, Christian; Rathmayer, Werner

1997-01-01

Single-channel currents through calcium channels in muscle of a marine crustacean, the isopod Idotea baltica, were investigated in cell-attached patches. Inward barium currents were strongly voltage-dependent, and the channels were closed at the cell's resting membrane potential. The open probability (Po) increased e-fold for an 8.2 mV (±2.4, n = 13) depolarization. Channel openings were mainly brief (<0.3 ms) and evenly distributed throughout 100-ms pulses. Averaged, quasimacroscopic currents showed fast activation and deactivation and did not inactivate during 100-ms test pulses. Similarly, channel activity persisted at steadily depolarized holding potentials. With 200 mM Ba2+ as charge carrier, the average slope conductance from the unitary currents between +30 and +80 mV, was 20 pS (±2.6, n = 12). The proportion of long openings, which were very infrequent under control conditions, was greatly increased by preincubation of the muscle fibers with the calcium channel agonist, the dihydropyridine Bay K8644 (10–100 μM). Properties of these currents resemble those through the L-type calcium channels of mammalian nerve, smooth muscle, and cardiac muscle cells. PMID:9089439

Japanese photovoltaic power generation for space application

NASA Technical Reports Server (NTRS)

Saga, T.; Kiyota, Y.; Matsutani, T.; Suzuki, A.; Kawasaki, O.; Hisamatsu, T.; Matsuda, S.

1996-01-01

This paper describes Japanese activities on mainly silicon solar cell research development and applications. The high efficiency thin silicon solar cells and the same kinds of solar cells with integrated bypass function (IBF cells) were developed and qualified for space applications. The most efficient cells (NRS/LBSF cells) showed average 18% at AMO and 28 C conditions. After electron irradiation, NRS/BSF cells showed higher efficiency than NRS/LBSF cells. The IBF cells do not suffer high reverse voltage and can survive from shadowing. The designs and characteristics of these solar cells are presented. In the last section, our future plan for the solar cell calibration is presented.

Serial Charging Test on High Capacity Li-Ion Cells for the Orbiter Advanced Hydraulic Power System

NASA Technical Reports Server (NTRS)

Jeevarajan, Judith A.; Irlbeck, Brad

2006-01-01

Although it looks like module level voltage drives the cutoff for charge, the actual cutoff is due to unbalanced cell voltages that drive the module voltage up. Individual cell voltage drives the cutoff for discharge Low resistance cells are the first to reach the low-voltage cutoff Cell-to-Cell voltage differences are generally small and show similar trends for each cycle Increase for a distinct window during charge and at the end of discharge Increase in max to min cell voltage difference with time/cycles Decrease in max to min cell voltage difference during high current pulses with time/cycles Individual cell voltage trends (with respect to other cells) are very repeatable from cycle to cycle, although voltage slowly degrades with time/cycles (resistance growth) Much more difference observed near end of discharge Little change in order of cell voltage (cell with highest voltage to cell with lowest voltage) Temp sensor on the side of cell (between 2 cells) shows much greater rise during discharge than for single cell tests (18 C vs 5 C) Conclusion: Serial Charging of this string of cells is feasible as it has only a minor impact on useful capacity

Energy transduction and signal averaging of fluctuating electric fields by a single protein ion channel.

PubMed

Verdia-Baguena, C; Gomez, V; Cervera, J; Ramirez, P; Mafe, S

2016-12-21

We demonstrate the electrical rectification and signal averaging of fluctuating signals using a biological nanostructure in aqueous solution: a single protein ion channel inserted in the lipid bilayer characteristic of cell membranes. The conversion of oscillating, zero time-average potentials into directional currents permits charging of a load capacitor to significant steady-state voltages within a few minutes in the case of the outer membrane porin F (OmpF) protein, a bacterial channel of Escherichia coli. The experiments and simulations show signal averaging effects at a more fundamental level than the traditional cell and tissue scales, which are characterized by ensembles of many ion channels operating simultaneously. The results also suggest signal transduction schemes with bio-electronic interfaces and ionic circuits where soft matter nanodiodes can be coupled to conventional electronic elements.

Nanographite-TiO2 photoanode for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Sharma, S. S.; Sharma, Khushboo; Sharma, Vinay

2016-05-01

Nanographite-TiO2 (NG-TiO2) composite was successfully synthesized by the hydrothermal method and its performance as the photoanode for dye-sensitized solar cells (DSSCs) was investigated. Environmental Scanning electron microscope (E-SEM) micrographs show the uniform distribution of TiO2 nanoflowers deposited over nanographite sheets. The average performance characteristics of the assembled cell in terms of short-ciruit current density (JSC), open circuit voltage (VOC), fill factor (FF) and photoelectric conversion efficiency (η) were measured.

A decay of gap junctions associated with ganglion cell differentiation during retinal regeneration of the adult newt.

PubMed

Oi, Hanako; Chiba, Chikafumi; Saito, Takehiko

2003-12-01

Changes in the gap junctional coupling and maturation of voltage-activated Na(+) currents during regeneration of newt retinas were examined by whole-cell patch-clamping in slice preparations. Progenitor cells in regenerating retinas did not exhibit Na(+) currents but showed prominent electrical and tracer couplings. Cells identified by LY-fills were typically slender. Na(+) currents were detected in premature ganglion cells with round somata in the 'intermediate-II' regenerating retina. No electrical and tracer couplings were observed between these cells. Mature ganglion cells did not exhibit electrical coupling, but showed tracer coupling. On average, the maximum Na(+) current amplitude recorded from premature ganglion cells was roughly 2.5-fold smaller than that of mature ganglion cells. In addition, the activation threshold of the Na(+) current was nearly 11 mV more positive than that of mature cells. We provide morphological and physiological evidence showing that loss of gap junctions between progenitor cells is associated with ganglion cell differentiation during retinal regeneration and that new gap junctions are recreated between mature ganglion cells. Also we provide evidence suggesting that the loss of gap junctions correlates with the appearance of voltage-activated Na(+) currents in ganglion cells.

Formation of Platinum Catalyst on Carbon Black Using an In-Liquid Plasma Method for Fuel Cells.

PubMed

Show, Yoshiyuki; Ueno, Yutaro

2017-01-31

Platinum (Pt) catalyst was formed on the surface of carbon black using an in-liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC showed an open voltage of 0.85 V and a maximum output power density of 216 mW/cm2.

Formation of Platinum Catalyst on Carbon Black Using an In-Liquid Plasma Method for Fuel Cells

PubMed Central

Show, Yoshiyuki; Ueno, Yutaro

2017-01-01

Platinum (Pt) catalyst was formed on the surface of carbon black using an in-liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC showed an open voltage of 0.85 V and a maximum output power density of 216 mW/cm2. PMID:28336864

Pulsed Laser Illumination of Photovoltaic Cells

NASA Technical Reports Server (NTRS)

Yater, Jane A.; Lowe, Roland; Jenkins, Philip; Landis, Geoffrey A.

1994-01-01

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. The induction FEL and the radio-frequency (RF) FEL both produce pulsed rather than continuous output. In this work, we investigate cell response to pulsed laser light which simulates the RF FEL format, producing 50 ps pulses at a frequency of 78 MHz. A variety of Si, GaAs, CaSb and CdInSe2 (CIS) solar cells are tested at average incident powers between 4 mW/sq cm and 425 mW/sq cm. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced by using a pulsed laser source compared to constant illumination at the same wavelength. Because the pulse separation is less than or approximately equal to the minority carrier lifetime, the illumination conditions are effectively those of a continuous wave laser. The time dependence of the voltage and current response of the cells are also measured using a sampling oscilloscope equipped with a high frequency voltage probe and current transformer. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments shows that the RF FEL pulse format yields much more efficient photovoltaic conversion of light than does an induction FEL pulse format.

High saturation solar light beam induced current scanning of solar cells.

PubMed

Vorster, F J; van Dyk, E E

2007-01-01

The response of the electrical parameters of photovoltaic cells under concentrated solar irradiance has been the subject of many studies performed in recent times. The high saturation conditions typically found in solar cells that are subjected to highly concentrated solar radiation may cause electrically active cell features to behave differently than under monochromatic laser illumination, normally used in light beam induced current (LBIC) investigations. A high concentration solar LBIC (S-LBIC) measurement system has been developed to perform localized cell characterization. The responses of silicon solar cells that were measured qualitatively include externally biased induced cell current at specific cell voltages, I(V), open circuit voltage, V(oc), and the average rate of change of the cell bias with the induced current, DeltaV/DeltaI(V), close to the zero bias region. These images show the relative scale of the parameters of a cell up to the penetration depth of the solar beam and can be obtained with relative ease, qualifying important electrical response features of the solar cell. The S-LBIC maps were also compared with maps that were similarly obtained using a high intensity He-Ne laser beam probe. This article reports on the techniques employed and initial results obtained.

Octanol reduces end-plate channel lifetime

PubMed Central

Gage, Peter W.; McBurney, Robert N.; Van Helden, Dirk

1978-01-01

1. Post-synaptic effects of n-octanol at concentrations of 0·1-1 mM were examined in toad sartorius muscles by use of extracellular and voltage-clamp techniques. 2. Octanol depressed the amplitude and duration of miniature end-plate currents and hence depressed neuromuscular transmission. 3. The decay of miniature end-plate currents remained exponential in octanol solutions even when the time constant of decay (τD) was decreased by 80-90%. 4. The lifetime of end-plate channels, obtained by analysis of acetylcholine noise, was also decreased by octanol. The average lifetime measured from noise spectra agreed reasonably well with the time constant of decay of miniature end-plate currents, both in control solution and in octanol solutions. 5. Octanol caused a reduction in the conductance of end-plate channels. Single channel conductance was on average about 25 pS in control solution and 20 pS in octanol. 6. In most cells the normal voltage sensitivity of the decay of miniature end-plate currents was retained in octanol solutions. The lifetime of end-plate channels measured from acetylcholine noise also remained voltage-sensitive in octanol solutions. In some experiments in which channel lifetime was exceptionally reduced the voltage sensitivity was less than normal. 7. In octanol solutions, τD was still very sensitive to temperature changes in most cells although in some the temperature sensitivity of τD was clearly reduced. Changes in τD with temperature could generally be fitted by the Arrhenius equation suggesting that a single step reaction controlled the decay of currents both in control and in octanol solutions. In some cells in which τD became less than 0·3 ms, the relationship between τD and temperature became inconsistent with the Arrhenius equation. 8. As the decay of end-plate currents in octanol solutions remains exponential, and the voltage and temperature sensitivity can be unchanged even when τD is significantly reduced, it seems likely that octanol decreases τD by increasing the rate of the reaction which normally controls the lifetime of end-plate channels. PMID:203674

The efficiency of photovoltaic cells exposed to pulsed laser light

NASA Technical Reports Server (NTRS)

Lowe, R. A.; Landis, G. A.; Jenkins, P.

1993-01-01

Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe2, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current vs bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC 'ringing', and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components.

a-Si:H/SiNW shell/core for SiNW solar cell applications

PubMed Central

2013-01-01

Vertically aligned silicon nanowires have been synthesized by the chemical etching of silicon wafers. The influence of a hydrogenated amorphous silicon (a-Si:H) layer (shell) on top of a silicon nanowire (SiNW) solar cell has been investigated. The optical properties of a-Si:H/SiNWs and SiNWs are examined in terms of optical reflection and absorption properties. In the presence of the a-Si:H shell, 5.2% reflection ratio in the spectral range (250 to 1,000 nm) is achieved with a superior absorption property with an average over 87% of the incident light. In addition, the characteristics of the solar cell have been significantly improved, which exhibits higher open-circuit voltage, short-circuit current, and efficiency by more than 15%, 12%, and 37%, respectively, compared with planar SiNW solar cells. Based on the current–voltage measurements and morphology results, we show that the a-Si:H shell can passivate the defects generated by wet etching processes. PMID:24195734

Kinetics of Inhibitory Feedback from Horizontal Cells to Photoreceptors: Implications for an Ephaptic Mechanism

PubMed Central

Warren, Ted J.; Van Hook, Matthew J.; Tranchina, Daniel

2016-01-01

Inhibitory feedback from horizontal cells (HCs) to cones generates center-surround receptive fields and color opponency in the retina. Mechanisms of HC feedback remain unsettled, but one hypothesis proposes that an ephaptic mechanism may alter the extracellular electrical field surrounding photoreceptor synaptic terminals, thereby altering Ca2+ channel activity and photoreceptor output. An ephaptic voltage change produced by current flowing through open channels in the HC membrane should occur with no delay. To test for this mechanism, we measured kinetics of inhibitory feedback currents in Ambystoma tigrinum cones and rods evoked by hyperpolarizing steps applied to synaptically coupled HCs. Hyperpolarizing HCs stimulated inward feedback currents in cones that averaged 8–9 pA and exhibited a biexponential time course with time constants averaging 14–17 ms and 120–220 ms. Measurement of feedback-current kinetics was limited by three factors: (1) HC voltage-clamp speed, (2) cone voltage-clamp speed, and (3) kinetics of Ca2+ channel activation or deactivation in the photoreceptor terminal. These factors totaled ∼4–5 ms in cones meaning that the true fast time constants for HC-to-cone feedback currents were 9–13 ms, slower than expected for ephaptic voltage changes. We also compared speed of feedback to feedforward glutamate release measured at the same cone/HC synapses and found a latency for feedback of 11–14 ms. Inhibitory feedback from HCs to rods was also significantly slower than either measurement kinetics or feedforward release. The finding that inhibitory feedback from HCs to photoreceptors involves a significant delay indicates that it is not due to previously proposed ephaptic mechanisms. SIGNIFICANCE STATEMENT Lateral inhibitory feedback from horizontal cells (HCs) to photoreceptors creates center-surround receptive fields and color-opponent interactions. Although underlying mechanisms remain unsettled, a longstanding hypothesis proposes that feedback is due to ephaptic voltage changes that regulate photoreceptor synaptic output by altering Ca2+ channel activity. Ephaptic processes should occur with no delay. We measured kinetics of inhibitory feedback currents evoked in photoreceptors with voltage steps applied to synaptically coupled HCs and found that feedback is too slow to be explained by ephaptic voltage changes generated by current flowing through continuously open channels in HC membranes. By eliminating the proposed ephaptic mechanism for HC feedback regulation of photoreceptor Ca2+ channels, our data support earlier proposals that synaptic cleft pH changes are more likely responsible. PMID:27683904

Testing of typical spacecraft materials in a simulated substorm environment

NASA Technical Reports Server (NTRS)

Stevens, N. J.; Berkopec, F. D.; Staskus, J. V.; Blech, R. A.; Narciso, S. J.

1977-01-01

The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed.

Voltage effects on cells cultured on metallic biomedical implants

NASA Astrophysics Data System (ADS)

Haerihosseini, Seyed Morteza

Electrochemical voltage shifts in metallic biomedical implants occur in-vivo due to a number of processes including mechanically assisted corrosion. Surface potential of biomedical implants and excursions from resting open circuit potential (OCP), which is the voltage they attain while in contact with an electrolyte, can significantly change the interfacial properties of the metallic surfaces and alter the behavior of the surrounding cells, compromising the biocompatibility of metallic implants. Voltages can also be controlled to modulate cell function and fate. To date, the details of the physico-chemical phenomena and the role of different biomaterial parameters involved in the interaction between cells and metallic surfaces under cathodic bias have not been fully elucidated. In this work, changes in the interfacial properties of a CoCrMo biomedical alloy (ASTM F-1537) in phosphate-buffered saline (PBS) (pH 7.4) at different voltages was studied. Step polarization impedance spectroscopy technique was used to apply 50 mV voltage steps to samples, and the time-based current transients were recorded. A new equation was derived based on capacitive discharge through a Tafel element and generalized to deal with non-ideal impedance behavior. The new function compared to the KWW-Randles function, better matched the time-transient response. The results also showed a voltage dependent oxide resistance and capacitance behavior. Additionally, the in-vitro effect of static voltages on the behavior of MC3T3-E1 pre-osteoblasts cultured on CoCrMo alloy (ASTM-1537) was studied to determine the range of cell viability and mode of cell death beyond the viable range. Cell viability and morphology, changes in actin cytoskeleton, adhesion complexes and nucleus, and mode of cell death (necrosis, or intrinsic or extrinsic apoptosis) were characterized at different voltages ranging from -1000 to +500 mV (Ag/AgCl). Moreover, electrochemical currents and metal ion concentrations at each voltage were measured and related to the observed responses. Results show that cathodic and anodic voltages outside the voltage viability range (-400 < V < +500) lead to primarily intrinsic apoptotic and necrotic cell death, respectively. Cell death is associated with cathodic current densities of 0.1 uAcm-2 and anodic current densities of 10 uAcm-2. Significant increase in metallic ions (Co, Cr, Ni, Mo) was seen at +500 mV, and -1000 mV (Cr only) compared to open circuit potential. The number and total projected area of adhesion complexes was also lower on the polarized alloy (p < 0.05). These results show that reduction reactions on CoCrMo alloys leads to apoptosis of cells on the surface and may be a relevant mode of cell death for metallic implants in-vivo. . On the other hand, we studied how surface oxide thickness of Ti affects its voltage viability range and cellular response and whether anodic oxidation can serve as a means to extend this range. Cellular behavior (cell viability, cytoskeletal organization, and cellular adhesion) on bare and anodized Ti samples, potentiostatically held at voltages at the cathodic edge of the viability range, were assessed. Surfaces were characterized using contact angle (CA) measurement technique and atomic force microscopy (AFM), and the observed cellular response was related to the changes in the electrochemical properties (electrochemical currents, open circuit potential, and impedance spectra) of the samples. Results show that anodization at a low voltage (9 V) in phosphate buffer saline (PBS) generates a compact surface oxide with comparable surface roughness and energy to the starting native oxide on the bare surface. The anodized surface extends the viability range at 24 hours by about a 100 mV in the cathodic region, and preserved the cytoskeletal integrity and cell adhesion. Broadening of the viability range corresponds to an increase in impedance of the anodized surface at -400 mV(Ag/AgCl) and the resulting low average currents (below 0.1 uAcm-2) at the interface, which diminish the harmful cathodic reactions. Finally, cellular dynamics (size, polarity, movement) and temporal changes in the number and total area of focal adhesions in transiently transfected MC3T3-E1 pre-osteoblasts cultured on a CoCrMo alloy polarized at the cathodic and anodic edges of its voltage viability range (-400 and +500 mV(Ag/AgCl) respectively) were studied. Nucleus dynamics (size, circularity, movement) and the release of reactive oxygen species (ROS) was also studied on the polarized metal at -1000, -400, and +500 mV(Ag/AgCl). The results show that at -400 mV(Ag/AgCl) a gradual loss of adhesion occurs over 24 hours while cells shrink in size during this time. At +500 mV, cells become non-viable after 5 hours without showing any significant changes in adhesion behavior right before cell death. Nucleus size of cells at -1000 mV decreased sharply within 15 minutes after electrochemical polarization, which rendered the cells completely non-viable. No significant amount of ROS was released by cells on the polarized CoCrMo at any of these voltages.

Electrical performance comparison BSFR-/bifacial solar cell array

NASA Astrophysics Data System (ADS)

Hoffmann, U.; Reissmann, F.

1986-11-01

Conventional and bifacial solar arrays were compared on subsystem level using the Space Telescope-solar array mission as reference. Calculations show that the bifacial solar cell has a performance advantage of 18 to 21 percent. This is due to a 5 C average lower temperature of the bifacial cell at the same orbit conditions; the rearside albedo irradiation of 86 to 170 W/sqm (average of 180 deg and 0 deg orbit orientation respectively); and the fact that the temperature difference between the hot case (satellite between Earth and Sun) and the cold case (before eclipse) is lower for the bifacial cell than for the BSFR cell. This lower difference has the advantage that the operation point for the bifacial cells is closer to maximum voltage point over the orbit. Resistivity of the bifacial solar cells against particle radiation, and absorptivity of front and rearside of the bifacial cell for infrared radiation must be verified. Statistical deviations of the albedo intensity and spectrum are not known.

Battery Cell By-Pass Circuit

NASA Technical Reports Server (NTRS)

Mumaw, Susan J. (Inventor); Evers, Jeffrey (Inventor); Craig, Calvin L., Jr. (Inventor); Walker, Stuart D. (Inventor)

2001-01-01

The invention is a circuit and method of limiting the charging current voltage from a power supply net work applied to an individual cell of a plurality of cells making up a battery being charged in series. It is particularly designed for use with batteries that can be damaged by overcharging, such as Lithium-ion type batteries. In detail. the method includes the following steps: 1) sensing the actual voltage level of the individual cell; 2) comparing the actual voltage level of the individual cell with a reference value and providing an error signal representative thereof; and 3) by-passing the charging current around individual cell necessary to keep the individual cell voltage level generally equal a specific voltage level while continuing to charge the remaining cells. Preferably this is accomplished by by-passing the charging current around the individual cell if said actual voltage level is above the specific voltage level and allowing the charging current to the individual cell if the actual voltage level is equal or less than the specific voltage level. In the step of bypassing the charging current, the by-passed current is transferred at a proper voltage level to the power supply. The by-pass circuit a voltage comparison circuit is used to compare the actual voltage level of the individual cell with a reference value and to provide an error signal representative thereof. A third circuit, designed to be responsive to the error signal, is provided for maintaining the individual cell voltage level generally equal to the specific voltage level. Circuitry is provided in the third circuit for bypassing charging current around the individual cell if the actual voltage level is above the specific voltage level and transfers the excess charging current to the power supply net work. The circuitry also allows charging of the individual cell if the actual voltage level is equal or less than the specific voltage level.

Numerical investigation and thermodynamic analysis of the effect of electrolyte flow rate on performance of all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Khazaeli, Ali; Vatani, Ali; Tahouni, Nassim; Panjeshahi, Mohammad Hassan

2015-10-01

In flow batteries, electrolyte flow rate plays a crucial role on the minimizing mass transfer polarization which is at the compensation of higher pressure drop. In this work, a two-dimensional numerical method is applied to investigate the effect of electrolyte flow rate on cell voltage, maximum depth of discharge and pressure drop a six-cell stack of VRFB. The results show that during the discharge process, increasing electrolyte flow rate can raise the voltage of each cell up to 50 mV on average. Moreover, the maximum depth of discharge dramatically increases with electrolyte flow rate. On the other hand, the pressure drop also positively correlates with electrolyte flow rate. In order to investigate all these effects simultaneously, average energy and exergy efficiencies are introduced in this study for the transient process of VRFB. These efficiencies give insight into choosing an appropriate strategy for the electrolyte flow rate. Finally, the energy efficiency of electricity storage using VRFB is investigated and compared with other energy storage systems. The results illustrate that this kind of battery has at least 61% storage efficiency based on the second law of thermodynamics, which is considerably higher than that of their counterparts.

Device and Method for Continuously Equalizing the Charge State of Lithium Ion Battery Cells

NASA Technical Reports Server (NTRS)

Schwartz, Paul D. (Inventor); Roufberg, Lewis M. (Inventor); Martin, Mark N. (Inventor)

2015-01-01

A method of equalizing charge states of individual cells in a battery includes measuring a previous cell voltage for each cell, measuring a previous shunt current for each cell, calculating, based on the previous cell voltage and the previous shunt current, an adjusted cell voltage for each cell, determining a lowest adjusted cell voltage from among the calculated adjusted cell voltages, and calculating a new shunt current for each cell.

Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells

NASA Astrophysics Data System (ADS)

Pankratov, Dmitry; Sundberg, Richard; Sotres, Javier; Maximov, Ivan; Graczyk, Mariusz; Suyatin, Dmitry B.; González-Arribas, Elena; Lipkin, Aleksey; Montelius, Lars; Shleev, Sergey

2015-10-01

Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 μW cm-2 maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 μW cm-2 after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses.

Azo dyes wastewater treatment and simultaneous electricity generation in a novel process of electrolysis cell combined with microbial fuel cell.

PubMed

Zou, Haiming; Wang, Yan

2017-07-01

A new process of electrolysis cell (EC) coupled with microbial fuel cell (MFC) was developed here and its feasibility in methyl red (MR) wastewater treatment and simultaneous electricity generation was assessed. Results indicate that an excellent MR removal and electricity production performance was achieved, where the decolorization and COD removal efficiencies were 100% and 89.3%, respectively and a 0.56V of cell voltage output was generated. Electrolysis voltage showed a positive influence on decolorization rate (DR) but also cause a rapid decrease in current efficiency (CE). Although a low COD removal rate of 38.5% was found in EC system, biodegradability of MR solution was significantly enhanced, where the averaged DR was 85.6%. Importantly, COD removal rate in EC-MFC integrated process had a 50.8% improvement compared with the single EC system. The results obtained here would be beneficial to provide a prospective alternative for azo dyes wastewater treatment and power production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Open-circuit voltage improvements in low-resistivity solar cells

NASA Technical Reports Server (NTRS)

Godlewski, M. P.; Klucher, T. M.; Mazaris, G. A.; Weizer, V. G.

1979-01-01

Mechanisms limiting the open-circuit voltage in 0.1 ohm-cm solar cells were investigated. It was found that a rather complicated multistep diffusion process could produce cells with significantly improved voltages. The voltage capabilities of various laboratory cells were compared independent of their absorption and collection efficiencies. This was accomplished by comparing the cells on the basis of their saturation currents or, equivalently, comparing their voltage outputs at a constant current-density level. The results show that for both the Lewis diffused emitter cell and the Spire ion-implanted emitter cell the base component of the saturation current is voltage controlling. The evidence for the University of Florida cells, although not very conclusive, suggests emitter control of the voltage in this device. The data suggest further that the critical voltage-limiting parameter for the Lewis cell is the electron mobility in the cell base.

Electronic circuit for measuring series connected electrochemical cell voltages

DOEpatents

Ashtiani, Cyrus N.; Stuart, Thomas A.

2000-01-01

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.

Automatic voltage imbalance detector

DOEpatents

Bobbett, Ronald E.; McCormick, J. Byron; Kerwin, William J.

1984-01-01

A device for indicating and preventing damage to voltage cells such as galvanic cells and fuel cells connected in series by detecting sequential voltages and comparing these voltages to adjacent voltage cells. The device is implemented by using operational amplifiers and switching circuitry is provided by transistors. The device can be utilized in battery powered electric vehicles to prevent galvanic cell damage and also in series connected fuel cells to prevent fuel cell damage.

Hydrogen-oxygen proton-exchange membrane fuel cells and electrolyzers

NASA Technical Reports Server (NTRS)

Baldwin, R.; Pham, M.; Leonida, A.; Mcelroy, J.; Nalette, T.

1989-01-01

Hydrogen-oxygen solid polymer electrolyte (SPE) fuel cells and SPE electrolyzers (products of Hamilton Standard) both use a Proton-Exchange Membrane (PEM) as the sole electrolyte. These solid electrolyte devices have been under continuous development for over 30 years. This experience has resulted in a demonstrated ten-year SPE cell life capability under load conditions. Ultimate life of PEM fuel cells and electrolyzers is primarily related to the chemical stability of the membrane. For perfluorocarbon proton exchange membranes an accurate measure of the membrane stability is the fluoride loss rate. Millions of cell hours have contributed to establishing a relationship between fluoride loss rates and average expected ultimate cell life. This relationship is shown. Several features have been introduced into SPE fuel cells and SPE electrolyzers such that applications requiring greater than or equal to 100,000 hours of life can be considered. Equally important as the ultimate life is the voltage stability of hydrogen-oxygen fuel cells and electrolyzers. Here again the features of SPE fuel cells and SPE electrolyzers have shown a cell voltage stability in the order of 1 microvolt per hour. That level of stability has been demonstrated for tens of thousands of hours in SPE fuel cells at up to 500 amps per square foot (ASF) current density.

Investigation of an Aberrant Cell Voltage During the Filling of a Large Lithium Thionyl Chloride Cell

NASA Technical Reports Server (NTRS)

Thaller, Lawrence H.; Quinzio, Michael V.

1997-01-01

The investigation of an aberrant cell voltage during the filling of a large lithium thionyl chloride cell summary is at: an aberrant voltage trace was noted during the review of cell filling data; incident was traced to an interruption during filling; experimentation suggested oxidizable sites within the carbon electrode were responsible for the drop in voltage; the voltage anomaly could be reproduced by interrupting the filling of similar cells; and anomalous voltage dip was not due to a short.

Investigation of Methods to Eliminate Voltage Delay in Li/SOCl2 Cells.

DTIC Science & Technology

1980-05-01

of storage at 550C the surface was completely covered with cubic crystals averaging about 8 pim on an edge (Figure 24). The lithium surface stored at...completely covered with cubic crystals, showing no smooth undercoating at all (Figure 25). The average crystal diameter was approximately 3.3 pim , with a...used. ithi timl acgu ire0d A Ci yst al I me surt ace, oil dr n torage at elevated temlper aI Ite t. T[he out lace, showed ch[ ott ine by EPAC except

An investigation on the effects of air on electron energy in atmospheric pressure helium plasma jets

NASA Astrophysics Data System (ADS)

Liu, Yadi; Tan, Zhenyu; Chen, Xinxian; Li, Xiaotong; Zhang, Huimin; Pan, Jie; Wang, Xiaolong

2018-03-01

In this work, the effects of air on electron energy in the atmospheric pressure helium plasma jet produced by a needle-plane discharge system have been investigated by means of the numerical simulation based on a two-dimensional fluid model, and the air concentration dependences of the reactive species densities have also been calculated. In addition, the synergistic effects of the applied voltage and air concentration on electron energy have been explored. The present work gives the following significant results. For a fixed applied voltage, the averaged electron energy is basically a constant at air concentrations below about 0.5%, but it evidently decreases above the concentration of 0.5%. Furthermore, the averaged densities of four main reactive species O, O(1D), O2(1Δg), and N2(A3Σu+) increase with the increasing air concentration, but the increase becomes slow at air concentrations above 0.5%. The air concentration dependences of the averaged electron energy under different voltage amplitudes are similar, and for a given air concentration, the averaged electron energy increases with the increase in the voltage amplitude. For the four reactive species, the effects of the air concentration on their averaged densities are similar for a given voltage amplitude. In addition, the averaged densities of the four reactive species increase with increasing voltage amplitude for a fixed air concentration. The present work suggests that a combination of high voltage amplitude and the characteristic air concentration, 0.5% in the present discharge system, allows an expected electron energy and also generates abundant reactive species.

Strongly nonlinear dynamics of electrolytes in large ac voltages.

PubMed

Højgaard Olesen, Laurits; Bazant, Martin Z; Bruus, Henrik

2010-07-01

We study the response of a model microelectrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two features--significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasiequilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination" since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and collapse of space-charge layers, even in the absence of any net Faradaic current through the cell. We also predict that steric effects of finite ion sizes (going beyond dilute-solution theory) act to suppress the strongly nonlinear regime in the limit of concentrated electrolytes, ionic liquids, and molten salts. Beyond the model problem, our reduced equations for thin double layers, based on uniformly valid matched asymptotic expansions, provide a useful mathematical framework to describe additional nonlinear responses to large ac voltages, such as Faradaic reactions, electro-osmotic instabilities, and induced-charge electrokinetic phenomena.

Simple Cell Balance Circuit

NASA Technical Reports Server (NTRS)

Johnson, Steven D.; Byers, Jerry W.; Martin, James A.

2012-01-01

A method has been developed for continuous cell voltage balancing for rechargeable batteries (e.g. lithium ion batteries). A resistor divider chain is provided that generates a set of voltages representing the ideal cell voltage (the voltage of each cell should be as if the cells were perfectly balanced). An operational amplifier circuit with an added current buffer stage generates the ideal voltage with a very high degree of accuracy, using the concept of negative feedback. The ideal voltages are each connected to the corresponding cell through a current- limiting resistance. Over time, having the cell connected to the ideal voltage provides a balancing current that moves the cell voltage very close to that ideal level. In effect, it adjusts the current of each cell during charging, discharging, and standby periods to force the cell voltages to be equal to the ideal voltages generated by the resistor divider. The device also includes solid-state switches that disconnect the circuit from the battery so that it will not discharge the battery during storage. This solution requires relatively few parts and is, therefore, of lower cost and of increased reliability due to the fewer failure modes. Additionally, this design uses very little power. A preliminary model predicts a power usage of 0.18 W for an 8-cell battery. This approach is applicable to a wide range of battery capacities and voltages.

Polychiral semiconducting carbon nanotube-fullerene solar cells.

PubMed

Gong, Maogang; Shastry, Tejas A; Xie, Yu; Bernardi, Marco; Jasion, Daniel; Luck, Kyle A; Marks, Tobin J; Grossman, Jeffrey C; Ren, Shenqiang; Hersam, Mark C

2014-09-10

Single-walled carbon nanotubes (SWCNTs) have highly desirable attributes for solution-processable thin-film photovoltaics (TFPVs), such as broadband absorption, high carrier mobility, and environmental stability. However, previous TFPVs incorporating photoactive SWCNTs have utilized architectures that have limited current, voltage, and ultimately power conversion efficiency (PCE). Here, we report a solar cell geometry that maximizes photocurrent using polychiral SWCNTs while retaining high photovoltage, leading to record-high efficiency SWCNT-fullerene solar cells with average NREL certified and champion PCEs of 2.5% and 3.1%, respectively. Moreover, these cells show significant absorption in the near-infrared portion of the solar spectrum that is currently inaccessible by many leading TFPV technologies.

Direct glycerol fuel cell with polytetrafluoroethylene (PTFE) thin film separator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benipal, Neeva; Qi, Ji; Dalian Univ. of Technology, Dalian

Here, anion-exchange membrane-based direct glycerol fuel cells (AEM-DGFCs) can yield high power density, however challenges exist in developing chemically stable AEMs. Here, we demonstrate a porous PTFE thin film, a well-known chemical, electro-chemical, and thermal robust material that can serve as a separator between anode and cathode, thus achieving high DGFC’s performance. A simple aqueous-phase reduction method was used to prepare carbon nanotube supported PdAg nanoparticles (PdAg/CNT) with an average particle size of 2.9 nm. A DGFC using a PTFE thin film without any further modification with PdAg/CNT anode catalyst exhibits a peak power density of 214.7 mW cm –2more » at 80 °C, about 22.6% lower than a DGFC using a state-of-the-art AEM. We report a 5.8% decrease and 11.1% decrease in cell voltage for a PTFE thin film and AEM; similarly, the cell voltage degradation rate decreases from 1.2 to 0.8 mV h –1 for PTFE thin film, while for AEM, it decreases from 9.6 to 3.0 mV h –1 over an 80 h durability test period. Transmission electron microscopy results indicate that the average particle size of PdAg/CNT increases from 2.9 to 3.7 nm after 80 h discharge; this suggests that PdAg particle growth may be the main reason for the performance drop.« less

Direct glycerol fuel cell with polytetrafluoroethylene (PTFE) thin film separator

DOE PAGES

Benipal, Neeva; Qi, Ji; Dalian Univ. of Technology, Dalian; ...

2017-01-04

Here, anion-exchange membrane-based direct glycerol fuel cells (AEM-DGFCs) can yield high power density, however challenges exist in developing chemically stable AEMs. Here, we demonstrate a porous PTFE thin film, a well-known chemical, electro-chemical, and thermal robust material that can serve as a separator between anode and cathode, thus achieving high DGFC’s performance. A simple aqueous-phase reduction method was used to prepare carbon nanotube supported PdAg nanoparticles (PdAg/CNT) with an average particle size of 2.9 nm. A DGFC using a PTFE thin film without any further modification with PdAg/CNT anode catalyst exhibits a peak power density of 214.7 mW cm –2more » at 80 °C, about 22.6% lower than a DGFC using a state-of-the-art AEM. We report a 5.8% decrease and 11.1% decrease in cell voltage for a PTFE thin film and AEM; similarly, the cell voltage degradation rate decreases from 1.2 to 0.8 mV h –1 for PTFE thin film, while for AEM, it decreases from 9.6 to 3.0 mV h –1 over an 80 h durability test period. Transmission electron microscopy results indicate that the average particle size of PdAg/CNT increases from 2.9 to 3.7 nm after 80 h discharge; this suggests that PdAg particle growth may be the main reason for the performance drop.« less

Digital ac monitor

DOEpatents

Hart, George W.; Kern, Jr., Edward C.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

Digital ac monitor

DOEpatents

Hart, G.W.; Kern, E.C. Jr.

1987-06-09

An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

System and method for charging electrochemical cells in series

DOEpatents

DeLuca, William H.; Hornstra, Jr, Fred; Gelb, George H.; Berman, Baruch; Moede, Larry W.

1980-01-01

A battery charging system capable of equalizing the charge of each individual cell at a selected full charge voltage includes means for regulating charger current to first increase current at a constant rate until a bulk charging level is achieved or until any cell reaches a safe reference voltage. A system controller then begins to decrease the charging rate as long as any cell exceeds the reference voltage until an equalization current level is reached. At this point, the system controller activates a plurality of shunt modules to permit shunting of current around any cell having a voltage exceeding the reference voltage. Leads extending between the battery of cells and shunt modules are time shared to permit alternate shunting of current and voltage monitoring without the voltage drop caused by the shunt current. After each cell has at one time exceeded the reference voltage, the charging current is terminated.

Maximum time-dependent space-charge limited diode currents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griswold, M. E.; Fisch, N. J.

Recent papers claim that a one dimensional (1D) diode with a time-varying voltage drop can transmit current densities that exceed the Child-Langmuir (CL) limit on average, apparently contradicting a previous conjecture that there is a hard limit on the average current density across any 1D diode, as t → ∞, that is equal to the CL limit. However, these claims rest on a different definition of the CL limit, namely, a comparison between the time-averaged diode current and the adiabatic average of the expression for the stationary CL limit. If the current were considered as a function of the maximummore » applied voltage, rather than the average applied voltage, then the original conjecture would not have been refuted.« less

Sodium and calcium currents in neuroblastoma x glioma hybrid cells before and after morphological differentiation by dibutyryl cyclic AMP.

PubMed

Bodewei, R; Hering, S; Schubert, B; Wollenberger, A

1985-04-01

Sodium and calcium inward currents (INa and ICa) were measured in neuroblastoma X glioma hybrid cells of clones 108CC5 and 108CC15 by a single suction pipette method for internal perfusion and voltage clamp. Morphologically undifferentiated, exponentially growing cells were compared with cells differentiated by cultivation with 1 mmol/l dibutyryl cyclic AMP. Outward currents were eliminated by perfusing the cells with a K+-free solution. Voltage dependence and ion selectivity as well as steady state inactivation characteristics of INa and ICa resembled those of differentiated mouse neuroblastoma cells, clone N1E-115 (Moolenaar and Spector 1978, 1979). These parameters were identical in undifferentiated and differentiated cells of both clones. After differentiation the average density of the peak sodium and calcium currents was increased two and four-fold, respectively, in both cell lines. Our data indicate that exponentially growing, morphologically undifferentiated 108CC5 and 108CC15 neuroblastoma X glioma hybrid cells possess functional Na+ and Ca2+ channels undistinguishable from those of non-proliferating cells of these clones differentiated morphologically by treatment with dibutyryl cyclic AMP. That Na+ and Ca2+ spikes were not detected by other authors in these cells prior to morphological differentiation by dibutyryl cyclic AMP may be attributed to the fact that at the low resting membrane potential measured the Na+ and Ca2+ channels are inactivated.

Dynamic, nonlinear feedback regulation of slow pacemaking by A-type potassium current in ventral tegmental area neurons.

PubMed

Khaliq, Zayd M; Bean, Bruce P

2008-10-22

We analyzed ionic currents that regulate pacemaking in dopaminergic neurons of the mouse ventral tegmental area by comparing voltage trajectories during spontaneous firing with ramp-evoked currents in voltage clamp. Most recordings were made in brain slice, with key experiments repeated using acutely dissociated neurons, which gave identical results. During spontaneous firing, net ionic current flowing between spikes was calculated from the time derivative of voltage multiplied by cell capacitance, signal-averaged over many firing cycles to enhance resolution. Net inward interspike current had a distinctive nonmonotonic shape, reaching a minimum (generally <1 pA) between -60 and -55 mV. Under voltage clamp, ramps over subthreshold voltages elicited a time- and voltage-dependent outward current that peaked near -55 mV. This current was undetectable with 5 mV/s ramps and increased steeply with depolarization rate over the range (10-50 mV/s) typical of natural pacemaking. Ramp-evoked subthreshold current was resistant to alpha-dendrotoxin, paxilline, apamin, and tetraethylammonium but sensitive to 4-aminopyridine and 0.5 mM Ba2+, consistent with A-type potassium current (I(A)). Same-cell comparison of currents elicited by various ramp speeds with natural spontaneous depolarization showed how the steep dependence of I(A) on depolarization rate results in small net inward currents during pacemaking. These results reveal a mechanism in which subthreshold I(A) is near zero at steady state, but is engaged at depolarization rates >10 mV/s to act as a powerful, supralinear feedback element. This feedback mechanism explains how net ionic current can be constrained to <1-2 pA but reliably inward, thus enabling slow, regular firing.

Development of a static feed water electrolysis system

NASA Technical Reports Server (NTRS)

Schubert, F. H.; Lantz, J. B.; Hallick, T. M.

1982-01-01

A one person level oxygen generation subsystem was developed and production of the one person oxygen metabolic requirements, 0.82 kg, per day was demonstrated without the need for condenser/separators or electrolyte pumps. During 650 hours of shakedown, design verification, and endurance testing, cell voltages averaged 1.62 V at 206 mA/sq cm and at average operating temperature as low as 326 K, virtually corresponding to the state of the art performance previously established for single cells. This high efficiency and low waste heat generation prevented maintenance of the 339 K design temperature without supplemental heating. Improved water electrolysis cell frames were designed, new injection molds were fabricated, and a series of frames was molded. A modified three fluid pressure controller was developed and a static feed water electrolysis that requires no electrolyte in the static feed compartment was developed and successfully evaluated.

The effect of adding selective mixed culture of alternative electricity production based on tempe wastewater on tubular microbial fuel cell

NASA Astrophysics Data System (ADS)

Mariana, Elisabeth, Utami, Tania Surya; Arbianti, Rita; Hermansyah, Heri

2017-05-01

Bacteria has long been known could produce electricity. MFC (Microbial Fuel Cell) is a technology that uses bacteria. MFC is potential as producer of alternative renewable energy through the conversion of waste by bacteria into electrical energy. However, this technology cannot reach the target value of the minimum voltage. This research is focused on reviewing the effect of the addition of gram positive and negative bacteria (selective mixed culture) contained in tempe wastewater as well as the optimal volume additions gram using a tubular single chamber membranless reactor. The result shows that the addition of selective mixed culture can increase voltage of MFC. Gram negative bacteria dominate tempe wastewater and has better ability to transfer electrons than gram-positive. The voltage increases with increasing amount of bacteria up to a certain maximum point. Addition of 1 mL gram-negative bacteria improve electrical output and provide the most optimal results of 0.0697 mW/m2 mV or 92.14% excalation against the initial control experiment with the average power density of 0.0702 mW1m2. Additions of most optimum variation also give good results on the use of industrial waste, with electrical voltage and power density high of 8.90 mV and 0.02 mW/m2.

Voltage Oscillations in a Polymer Electrolyte Membrane Fuel Cell with Pd-Pt/C and Pd/C Anodes.

PubMed

Nogueira, Jéssica Alves; Varela, Hamilton

2017-10-01

Polymer electrolyte membrane fuel cells (PEMFC) fed with H 2 contaminated with CO may exhibit oscillatory behavior when operated galvanostatically. The self-organization of the anodic overpotential is interesting because it can be accompanied by an increase in the average performance. Herein we report experimental studies of voltage oscillations that emerge in a PEMFC equipped with a Pd/C or PdPt/C anode and fed with H 2 contaminated with CO (100 ppm). We used on-line mass spectrometry to investigate how the mass fragments associated with CO 2 and CO ( m / z 44 and 28, respectively) varied with the voltage oscillations. Overall, we observed that oscillations in the anodic overpotential are in phase with that of the CO and CO 2 signals. This fact is consistent with an autonomous adsorption-oxidation cyclic process. For both anodes, it has been observed that, in general, an increase in current density implies an increase in oscillatory frequency. By using CO stripping, we also discuss how the onset of CO oxidation is related to the maximum overpotential reached during a cycle, whereas the minimum overpotential can be associated with the catalytic activity of the electrode for H 2 oxidation.

Electropolar effects on anaerobic fermentation of lignocellulosic materials in novel single-electrode cells.

PubMed

Qu, Guangfei; Qiu, Weixia; Liu, Yuhuan; Zhong, Dongwei; Ning, Ping

2014-05-01

As a promising renewable energy technology, anaerobic fermentation is consistently limited by low production and calorific value of biogas, along with the difficulty of lignocellulose degradation. The effects of polarity and micro-voltage on anaerobic fermentation from lignocellulosic materials were investigated in single-electrode fermenter to explore cost-efficient technology. The results illustrated that the biogas production and quality were significantly affected by electric polarity. And cathode-assisted fermentation led to more positive effects than anode-assisted. Compared with results in control group without electrode, the average biogas and methane yield under cathodic micro-voltage (-250 mV) were astonishingly improved by 2.82 and 2.44 mL g(-1)d(-1) respectively. Meanwhile, the degradation ratios of lignin and cellulose were also improved by 23.11% and 19.46%. It demonstrated that single micro-voltage can not only promote lignocellulose degradation but biogas production and calorific value. These micro-voltage effects on fermentation process also provided great opportunity to breakthrough the present limitation of lignocellulosic materials fermentation. Copyright © 2014 Elsevier Ltd. All rights reserved.

PIC-MCC analysis of electron multiplication in a cold-cathode Penning ion generator and its application to identify ignition voltage

NASA Astrophysics Data System (ADS)

Noori, H.; Ranjbar, A. H.; Mahjour-Shafiei, M.

2017-11-01

A cold-cathode Penning ion generator (PIG) has been developed in our laboratory to study the interaction of charged particles with matter. The ignition voltage was measured in the presence of the axial magnetic field in the range of 460-580 G. The performed measurements with stainless steel cathodes were in argon gas at pressure of 4 × 10-2 mbar. A PIC-MCC (particle-in-cell, Monte Carlo collision) technique has been used to calculate the electron multiplication coefficient M for various strength of axial magnetic field and applied voltage. An approach based on the coefficient M and the experimental values of the secondary electron emission coefficient γ, was proposed to determine the ignition voltages, theoretically. Applying the values of secondary coefficient γ leads to the average value of γM(V, B) to be = 1.05 ± 0.03 at the ignition of the PIG which satisfies the proposed ignition criterion. Thus, the ion-induced secondary electrons emitted from the cathode have dominant contribution to self-sustaining of the discharge process in a PIG.

Physiological and molecular characterization of an IRK-type inward rectifier K+ channel in a tumour mast cell line.

PubMed

Wischmeyer, E; Lentes, K U; Karschin, A

1995-04-01

The basophilic leucaemia cell line RBL-2H3 exhibits a robust inwardly rectifying potassium current, IKIR, which is likely to be modulated by G proteins. We examined the physiological and molecular properties of this KIR conductance to define the nature of the underlying channel species. The macroscopic conductance revealed characteristics typical of classical K+ inward rectifiers of the IRK type. Channel gating was rapid, first order (tau approximately 1 ms at -100 mV) and steeply voltage dependent. Both activation potential and slope conductance were dependent on extracellular K+ concentration ([K+]o) and inward rectification persisted in the absence of internal Mg2+. The current was susceptible to a concentration- and voltage-dependent block by extracellular Na+, Cs+ and Ba2+. Initial IKIR whole-cell amplitudes as well as current rundown were dependent on the presence of 1 mM internal ATP. Perfusion of intracellular guanosine 5'-Q-(3-thiotriphosphate) (GTP[gamma S]) suppressed IKIR with an average half-time of decline of approximately 400 s. It was demonstrated that the dominant IRK-type 25 pS conductance channel was indeed suppressed by 100 microM preloaded GTP[gamma S]. Reverse transcriptase-polymerase chain reactions (RT-PCR) with RBL cell poly(A)+ RNA identified a full length K+ inward rectifier with 94% base pair homology to the recently cloned mouse IRK1 channel. It is concluded that RBL cells express a classical voltage-dependent IRK-type K+ inward rectifier RBL-IRK1 which is negatively controlled by G proteins.

Multijunction high-voltage solar cell

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr.; Goradia, C.; Chai, A. T.

1981-01-01

Multijunction cell allows for fabrication of high-voltage solar cell on single semiconductor wafer. Photovoltaic energy source using cell is combined on wafer with circuit it is to power. Cell consists of many voltage-generating regions internally or externally interconnected to give desired voltage and current combination. For computer applications, module is built on silicon wafer with energy for internal information processing and readouts derived from external light source.

Fuel cell stack monitoring and system control

DOEpatents

Keskula, Donald H.; Doan, Tien M.; Clingerman, Bruce J.

2004-02-17

A control method for monitoring a fuel cell stack in a fuel cell system in which the actual voltage and actual current from the fuel cell stack are monitored. A preestablished relationship between voltage and current over the operating range of the fuel cell is established. A variance value between the actual measured voltage and the expected voltage magnitude for a given actual measured current is calculated and compared with a predetermined allowable variance. An output is generated if the calculated variance value exceeds the predetermined variance. The predetermined voltage-current for the fuel cell is symbolized as a polarization curve at given operating conditions of the fuel cell.

A High Voltage Ratio and Low Ripple Interleaved DC-DC Converter for Fuel Cell Applications

PubMed Central

Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

2012-01-01

This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters. PMID:23365536

A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

PubMed

Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

2012-01-01

This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

On-line and real-time diagnosis method for proton membrane fuel cell (PEMFC) stack by the superposition principle

NASA Astrophysics Data System (ADS)

Lee, Young-Hyun; Kim, Jonghyeon; Yoo, Seungyeol

2016-09-01

The critical cell voltage drop in a stack can be followed by stack defect. A method of detecting defective cell is the cell voltage monitoring. The other methods are based on the nonlinear frequency response. In this paper, the superposition principle for the diagnosis of PEMFC stack is introduced. If critical cell voltage drops exist, the stack behaves as a nonlinear system. This nonlinearity can explicitly appear in the ohmic overpotential region of a voltage-current curve. To detect the critical cell voltage drop, a stack is excited by two input direct test-currents which have smaller amplitude than an operating stack current and have an equal distance value from the operating current. If the difference between one voltage excited by a test current and the voltage excited by a load current is not equal to the difference between the other voltage response and the voltage excited by the load current, the stack system acts as a nonlinear system. This means that there is a critical cell voltage drop. The deviation from the value zero of the difference reflects the grade of the system nonlinearity. A simulation model for the stack diagnosis is developed based on the SPP, and experimentally validated.

Molecular Materials for Nonaqueous Flow Batteries with a High Coulombic Efficiency and Stable Cycling.

PubMed

Milton, Margarita; Cheng, Qian; Yang, Yuan; Nuckolls, Colin; Hernández Sánchez, Raúl; Sisto, Thomas J

2017-12-13

This manuscript presents a working redox battery in organic media that possesses remarkable cycling stability. The redox molecules have a solubility over 1 mol electrons/liter, and a cell with 0.4 M electron concentration is demonstrated with steady performance >450 cycles (>74 days). Such a concentration is among the highest values reported in redox flow batteries with organic electrolytes. The average Coulombic efficiency of this cell during cycling is 99.868%. The stability of the cell approaches the level necessary for a long lifetime nonaqueous redox flow battery. For the membrane, we employ a low cost size exclusion cellulose membrane. With this membrane, we couple the preparation of nanoscale macromolecular electrolytes to successfully avoid active material crossover. We show that this cellulose-based membrane can support high voltages in excess of 3 V and extreme temperatures (-20 to 110 °C). These extremes in temperature and voltage are not possible with aqueous systems. Most importantly, the nanoscale macromolecular platforms we present here for our electrolytes can be readily tuned through derivatization to realize the promise of organic redox flow batteries.

Modular Battery Charge Controller

NASA Technical Reports Server (NTRS)

Button, Robert; Gonzalez, Marcelo

2009-01-01

A new approach to masterless, distributed, digital-charge control for batteries requiring charge control has been developed and implemented. This approach is required in battery chemistries that need cell-level charge control for safety and is characterized by the use of one controller per cell, resulting in redundant sensors for critical components, such as voltage, temperature, and current. The charge controllers in a given battery interact in a masterless fashion for the purpose of cell balancing, charge control, and state-of-charge estimation. This makes the battery system invariably fault-tolerant. The solution to the single-fault failure, due to the use of a single charge controller (CC), was solved by implementing one CC per cell and linking them via an isolated communication bus [e.g., controller area network (CAN)] in a masterless fashion so that the failure of one or more CCs will not impact the remaining functional CCs. Each micro-controller-based CC digitizes the cell voltage (V(sub cell)), two cell temperatures, and the voltage across the switch (V); the latter variable is used in conjunction with V(sub cell) to estimate the bypass current for a given bypass resistor. Furthermore, CC1 digitizes the battery current (I1) and battery voltage (V(sub batt) and CC5 digitizes a second battery current (I2). As a result, redundant readings are taken for temperature, battery current, and battery voltage through the summation of the individual cell voltages given that each CC knows the voltage of the other cells. For the purpose of cell balancing, each CC periodically and independently transmits its cell voltage and stores the received cell voltage of the other cells in an array. The position in the array depends on the identifier (ID) of the transmitting CC. After eight cell voltage receptions, the array is checked to see if one or more cells did not transmit. If one or more transmissions are missing, the missing cell(s) is (are) eliminated from cell-balancing calculations. The cell-balancing algorithm is based on the error between the cell s voltage and the other cells and is categorized into four zones of operation. The algorithm is executed every second and, if cell balancing is activated, the error variable is set to a negative low value. The largest error between the cell and the other cells is found and the zone of operation determined. If the error is zero or negative, then the cell is at the lowest voltage and no balancing action is needed. If the error is less than a predetermined negative value, a Cell Bad Flag is set. If the error is positive, then cell balancing is needed, but a hysteretic zone is added to prevent the bypass circuit from triggering repeatedly near zero error. This approach keeps the cells within a predetermined voltage range.

Quantum dynamics of a Josephson junction driven cavity mode system in the presence of voltage bias noise

NASA Astrophysics Data System (ADS)

Wang, Hui; Blencowe, M. P.; Armour, A. D.; Rimberg, A. J.

2017-09-01

We give a semiclassical analysis of the average photon number as well as photon number variance (Fano factor F ) for a Josephson junction (JJ) embedded microwave cavity system, where the JJ is subject to a fluctuating (i.e., noisy) bias voltage with finite dc average. Through the ac Josephson effect, the dc voltage bias drives the effectively nonlinear microwave cavity mode into an amplitude squeezed state (F <1 ), as has been established previously [Armour et al., Phys. Rev. Lett. 111, 247001 (2013), 10.1103/PhysRevLett.111.247001], but bias noise acts to degrade this squeezing. We find that the sensitivity of the Fano factor to bias voltage noise depends qualitatively on which stable fixed point regime the system is in for the corresponding classical nonlinear steady-state dynamics. Furthermore, we show that the impact of voltage bias noise is most significant when the cavity is excited to states with large average photon number.

Hot-spot heating in central-station arrays

NASA Technical Reports Server (NTRS)

Gonzalez, C. C.

1983-01-01

Hot spot tests performed on the Sacramento Municipal Utility District (SMUD) verificaton array show that current imbalance occurs, resulting in significant hot spot heating. One cause of current imbalance is differences in the average shunt resistances of parallel cell strings due to cell shunt resistance variations. In depth hot spot tests are performed on the verification array with bypass diodes. The tests had several objectives: (1) a comparison of hot spot temperatures achieved under field conditions with those obtained with the present laboratory hot spot test using similar modules; (2) an assessment of current imbalance versus cross tie frequency; and (3) an assessment of different shadow patterns and shadow densities. Instrumented modules are used to vary the number of cross ties and to measure the test-cell current and back-bias voltage. The widths, lengths, and densities of the shadows are varied to maximize the back bias voltage at maximum power current. An infrared camera is used to indicate the existence of hot spots and estimate temperature increases in conjunction with thermocouples. The results of these hot spot tests indicate a sensitivity of back bias heating to the shadow size (amount of cell coverage) and density.

Performance of Li-Ion Cells Under Battery Voltage Charge Control

NASA Technical Reports Server (NTRS)

Rao, Gopalakrishna M.; Vaidyanathan, Hari; Day, John H. (Technical Monitor)

2001-01-01

A study consisting of electrochemical characterization and Low-Earth-Orbit (LEO) cycling of Li-Ion cells from three vendors was initiated in 1999 to determine the cycling performance and to infuse the new technology in the future NASA missions. The 8-cell batteries included in this evaluation are prismatic cells manufactured by Mine Safety Appliances Company (MSA), cylindrical cells manufactured by SAFT and prismatic cells manufactured by Yardney Technical Products, Inc. (YTP). The three batteries were cycle tested in the LEO regime at 40% depth of discharge, and under a charge control technique that consists of battery voltage clamp with a current taper. The initial testing was conducted at 20 C; however, the batteries were cycled also intermittently at low temperatures. YTP 20 Ah cells consisted of mixed-oxide (Co and Ni) positive, graphitic carbon negative, LIPF6 salt mixed with organic carbonate solvents. The battery voltage clamp was 32 V. The low temperature cycling tests started after 4575 cycles at 20 C. The cells were not capable of cycling. at low temperature since the charge acceptance at battery level was poor. There was a cell in the battery that showed too high an end-of-charge (EOC) voltage thereby limiting the ability to charge the rest of the cells in the battery. The battery has completed 6714 cycles. SAFT 12 Ah cells consisted of mixed-oxide (Co and NO positive, graphitic carbon negative, LiPF6 salt mixed with organic carbonate solvents. The battery voltage clamp was for 30.8 V. The low temperature cycling tests started after 4594 cycles at 20 C. A cell that showed low end of discharge (EOD) and EOC voltages and three other cells that showed higher EOC voltages limited the charge acceptance at the selected voltage limit during charge. The cells were capable of cycling at 10 C and 0 C but the charge voltage limit had to be increased to 34.3 V (4.3 V per cell). The low temperature cycling may have induced poor chargeability since the voltage had to be increased to achieve the required charge input. The battery has completed 6226 cycles. MSA 10 Ah cells consisted of Co oxide positive, graphitic carbon negative, LiPF6 salt mixed with organic carbonate solvents. The battery voltage clamp was 30.8 V. The low temperature cycling tests were started after 2182 cycles at 20 C. The cells were capable of cycling at 10 C and 0 C. Like SAFT, the voltage limit on charge had to be increased to 36 V (4.5 V per cell). There was a cell (cell S/N 13) in the battery that showed poor performance features such as low EOD voltage and high EOC voltage. The battery has completed 3441 cycles. A reconditioning procedure that consisted of C15 charge to a taper current of C/100 and C/20 discharge improved the voltage behavior of SAFT and MSA cells with no significant effect on YTP cells. We have demonstrated that the charge operation with VT clamp at battery rather than at cell level is feasible for onboard Li-Ion battery operation.

High-Voltage Characterization for the Prototype Induction Cells

NASA Astrophysics Data System (ADS)

Huacen, Wang; Kaizhi, Zhang; Long, Wen; Qinggui, Lai; Linwen, Zhang; Jianjun, Deng

2002-12-01

Two linear induction prototype cells expected to work at 250kV, 3kA,with accelerating voltage flattop (±1%) ⩾ 70ns, have been tested to determine their high-voltage characteristics. Each cell is composed of a ferrite core immersed in oil, a gap with curved stainless steel electrodes, a solenoid magnet, and a insulator. The experiments were carried out with full-scale cells. The high voltage pulses were applied to two cells using a 100ns, 12Ω pulse Blumlein. The tests were performed at various high-voltage levels ranging from -250kV to -350kV. No breakdown was observed during the test at vacuum level (7-10) ṡ10-4 Pa. The cell schematic, the experimental set up, and the measured voltage waveforms are presented in this paper.

Characterization of three types of silicon solar cells for SEPS Deep Space Mission. Volume 3: Current-voltage characteristics of spectrolab sculptured BSR/P+ (K7), BSR/P+ (K6.5) and BSR (K4.5) cells as a function of temperature and intensity

NASA Technical Reports Server (NTRS)

Whitaker, A. F.; Little, S. A.; Wooden, V. A.; Carter, D. E.; Cothren, B. E.; Torstenson, C. A.

1980-01-01

Three types of high performance silicon solar cells, sculptured BSR/P+(K7), BSR/P+(K6.5) and BSR(K4.5) manufactured by Spectrolab were evaluated for their low temperature and low intensity performance. Sixteen cells of each type were subjected to 11 temperatures and 9 intensities. The sculptured BSR/P+(K7) cells provided the greatest maximum power output both at 1 AU and at LTLI conditions. The average efficiencies of this cell were 14.4 percent at 1 SC/+25 deg C and 18.5 percent at 0.086 SC/-100 deg C.

Characterization of three types of silicon solar cells for SEPS deep-space missions. Volume 2: Current voltage characteristics of Solarex textured P(+)8 to 10 mil, planar P(+)8 to 10 mil and planar P(+)2 mil cells as a function of temperature and intensity

NASA Technical Reports Server (NTRS)

Whitaker, A. F.; Little, S. A.; Wooden, V. A.

1980-01-01

Three types of high performance silicon solar cells, textured P(+)8 to 10 mil, planar P(+)8 to 10 mil and planar P(+)2 mil were evaluated for their low temperature and low intensity (LTLI) performance. Sixteen cells of each type were subjected to 11 temperatures and 9 intensities. The textured P(+)8 to 10 mil cells provided the best performance both at 1 astronomical unit and at LTLI conditions. The average efficiencies of this cell were 14.5 percent at 1 solar constant/+25 C and 18.7 percent at 0.086 solar constant/-100 C.

Improved performance of mesoscopic perovskite solar cell using an accelerated crystalline formation method

NASA Astrophysics Data System (ADS)

Sidhik, Siraj; Esparza, Diego; Martínez-Benítez, Alejandro; López-Luke, Tzarara; Carriles, Ramón; De la Rosa, Elder

2017-10-01

Highly smooth organo-lead halide perovskite (OHP) films with less intra-granular defects are necessary to minimize the non-radiative carrier recombination in photovoltaic devices. Herein, a simple air-extraction anti-solvent deposition (AAD) technique is proposed to improve the quality of perovskite films. An air extraction process accompanied by anti-solvent washing helps to improve the morphology of perovskite, leading to smooth, homogeneous, compact, pin-hole free and densely packed films. Perovskite films with an average roughness of 5.01 nm, which is the smoothest morphology in mesoscopic-perovskite solar cell to the extent of our knowledge, high crystallinity, and a crystallite size in the range of ∼500 nm to 1 μm have been achieved. Average power conversion efficiency (PCE) of 16.99% for 15 cells and a best PCE of 17.70% with a high open circuit voltage of 1.075 and fill factor of 74.22% were achieved using the AAD approach without a glove box. The cells exhibit virtually no hysteresis. These efficiency values are approximately 37.68% higher than the cells fabricated using anti-solvent process without air-extraction, where an average efficiency of 12.34% was measured. This method demonstrates high reproducibility and can be employed for the large scale production of PSC at reduced cost.

Charging a capacitor from an external fluctuating potential using a single conical nanopore.

PubMed

Gomez, Vicente; Ramirez, Patricio; Cervera, Javier; Nasir, Saima; Ali, Mubarak; Ensinger, Wolfgang; Mafe, Salvador

2015-04-01

We explore the electrical rectification of large amplitude fluctuating signals by an asymmetric nanostructure operating in aqueous solution. We show experimentally and theoretically that a load capacitor can be charged to voltages close to 1 V within a few minutes by converting zero time-average potentials of amplitudes in the range 0.5-3 V into average net currents using a single conical nanopore. This process suggests that significant energy conversion and storage from an electrically fluctuating environment is feasible with a nanoscale pore immersed in a liquid electrolyte solution, a system characteristic of bioelectronics interfaces, electrochemical cells, and nanoporous membranes.

Charging a Capacitor from an External Fluctuating Potential using a Single Conical Nanopore

PubMed Central

Gomez, Vicente; Ramirez, Patricio; Cervera, Javier; Nasir, Saima; Ali, Mubarak; Ensinger, Wolfgang; Mafe, Salvador

2015-01-01

We explore the electrical rectification of large amplitude fluctuating signals by an asymmetric nanostructure operating in aqueous solution. We show experimentally and theoretically that a load capacitor can be charged to voltages close to 1 V within a few minutes by converting zero time-average potentials of amplitudes in the range 0.5–3 V into average net currents using a single conical nanopore. This process suggests that significant energy conversion and storage from an electrically fluctuating environment is feasible with a nanoscale pore immersed in a liquid electrolyte solution, a system characteristic of bioelectronics interfaces, electrochemical cells, and nanoporous membranes. PMID:25830563

Fuel Cell/Electrochemical Cell Voltage Monitor

NASA Technical Reports Server (NTRS)

Vasquez, Arturo

2012-01-01

A concept has been developed for a new fuel cell individual-cell-voltage monitor that can be directly connected to a multi-cell fuel cell stack for direct substack power provisioning. It can also provide voltage isolation for applications in high-voltage fuel cell stacks. The technology consists of basic modules, each with an 8- to 16-cell input electrical measurement connection port. For each basic module, a power input connection would be provided for direct connection to a sub-stack of fuel cells in series within the larger stack. This power connection would allow for module power to be available in the range of 9-15 volts DC. The relatively low voltage differences that the module would encounter from the input electrical measurement connection port, coupled with the fact that the module's operating power is supplied by the same substack voltage input (and so will be at similar voltage), provides for elimination of high-commonmode voltage issues within each module. Within each module, there would be options for analog-to-digital conversion and data transfer schemes. Each module would also include a data-output/communication port. Each of these ports would be required to be either non-electrical (e.g., optically isolated) or electrically isolated. This is necessary to account for the fact that the plurality of modules attached to the stack will normally be at a range of voltages approaching the full range of the fuel cell stack operating voltages. A communications/ data bus could interface with the several basic modules. Options have been identified for command inputs from the spacecraft vehicle controller, and for output-status/data feeds to the vehicle.

Voltage-Gated Calcium Influx Modifies Cholinergic Inhibition of Inner Hair Cells in the Immature Rat Cochlea.

PubMed

Zachary, Stephen; Nowak, Nathaniel; Vyas, Pankhuri; Bonanni, Luke; Fuchs, Paul Albert

2018-06-20

Until postnatal day (P) 12, inner hair cells of the rat cochlea are invested with both afferent and efferent synaptic connections. With the onset of hearing at P12, the efferent synapses disappear, and afferent (ribbon) synapses operate with greater efficiency. This change coincides with increased expression of voltage-gated potassium channels, the loss of calcium-dependent electrogenesis, and the onset of graded receptor potentials driven by sound. The transient efferent synapses include near-membrane postsynaptic cisterns thought to regulate calcium influx through the hair cell's α9-containing and α10-containing nicotinic acetylcholine receptors. This influx activates small-conductance Ca 2+ -activated K + (SK) channels. Serial-section electron microscopy of inner hair cells from two 9-d-old (male) rat pups revealed many postsynaptic efferent cisterns and presynaptic afferent ribbons whose average minimal separation in five cells ranged from 1.1 to 1.7 μm. Efferent synaptic function was studied in rat pups (age, 7-9 d) of either sex. The duration of these SK channel-mediated IPSCs was increased by enhanced calcium influx through L-type voltage-gated channels, combined with ryanodine-sensitive release from internal stores-presumably the near-membrane postsynaptic cistern. These data support the possibility that inner hair cell calcium electrogenesis modulates the efficacy of efferent inhibition during the maturation of inner hair cell synapses. SIGNIFICANCE STATEMENT Strict calcium buffering is essential for cellular function. This problem is especially acute for compact hair cells where increasing cytoplasmic calcium promotes the opposing functions of closely adjoining afferent and efferent synapses. The near-membrane postsynaptic cistern at efferent synapses segregates synaptic calcium signals by acting as a dynamic calcium store. The hair cell serves as an informative model for synapses with postsynaptic cisterns (C synapses) found in central neurons. Copyright © 2018 the authors 0270-6474/18/385677-11$15.00/0.

Combinatorial approach toward high-throughput analysis of direct methanol fuel cells.

PubMed

Jiang, Rongzhong; Rong, Charles; Chu, Deryn

2005-01-01

A 40-member array of direct methanol fuel cells (with stationary fuel and convective air supplies) was generated by electrically connecting the fuel cells in series. High-throughput analysis of these fuel cells was realized by fast screening of voltages between the two terminals of a fuel cell at constant current discharge. A large number of voltage-current curves (200) were obtained by screening the voltages through multiple small-current steps. Gaussian distribution was used to statistically analyze the large number of experimental data. The standard deviation (sigma) of voltages of these fuel cells increased linearly with discharge current. The voltage-current curves at various fuel concentrations were simulated with an empirical equation of voltage versus current and a linear equation of sigma versus current. The simulated voltage-current curves fitted the experimental data well. With increasing methanol concentration from 0.5 to 4.0 M, the Tafel slope of the voltage-current curves (at sigma=0.0), changed from 28 to 91 mV.dec-1, the cell resistance from 2.91 to 0.18 Omega, and the power output from 3 to 18 mW.cm-2.

Fuel cell stack monitoring and system control

DOEpatents

Keskula, Donald H.; Doan, Tien M.; Clingerman, Bruce J.

2005-01-25

A control method for monitoring a fuel cell stack in a fuel cell system in which the actual voltage and actual current from the fuel cell stack are monitored. A preestablished relationship between voltage and current over the operating range of the fuel cell is established. A variance value between the actual measured voltage and the expected voltage magnitude for a given actual measured current is calculated and compared with a predetermined allowable variance. An output is generated if the calculated variance value exceeds the predetermined variance. The predetermined voltage-current for the fuel cell is symbolized as a polarization curve at given operating conditions of the fuel cell. Other polarization curves may be generated and used for fuel cell stack monitoring based on different operating pressures, temperatures, hydrogen quantities.

An non-uniformity voltage model for proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Li, Kelei; Li, Yankun; Liu, Jiawei; Guo, Ai

2017-01-01

The fuel cell used in transportation has environmental protection, high efficiency and no line traction power system which can greatly reduce line construction investment. That makes it a huge potential. The voltage uniformity is one of the most important factors affecting the operation life of proton exchange membrane fuel cell (PEMFC). On the basis of principle and classical model of the PEMFC, single cell voltage is calculated and the location coefficients are introduced so as to establish a non-uniformity voltage model. These coefficients are estimated with the experimental datum at stack current 50 A. The model is validated respectively with datum at 60 A and 100 A. The results show that the model reflects the basic characteristics of voltage non-uniformity and provides the beneficial reference for fuel cell control and single cell voltage detection.

Multijunction high voltage concentrator solar cells

NASA Technical Reports Server (NTRS)

Valco, G. J.; Kapoor, V. J.; Evans, J. C.; Chai, A.-T.

1981-01-01

The standard integrated circuit technology has been developed to design and fabricate new innovative planar multi-junction solar cell chips for concentrated sunlight applications. This 1 cm x 1 cm cell consisted of several voltage generating regions called unit cells which were internally connected in series within a single chip resulting in high open circuit voltages. Typical open-circuit voltages of 3.6 V and short-circuit currents of 90 ma were obtained at 80 AM1 suns. A dramatic increase in both short circuit current and open circuit voltage with increased light levels was observed.

Stochastic spectral projection of electrochemical thermal model for lithium-ion cell state estimation

NASA Astrophysics Data System (ADS)

Tagade, Piyush; Hariharan, Krishnan S.; Kolake, Subramanya Mayya; Song, Taewon; Oh, Dukjin

2017-03-01

A novel approach for integrating a pseudo-two dimensional electrochemical thermal (P2D-ECT) model and data assimilation algorithm is presented for lithium-ion cell state estimation. This approach refrains from making any simplifications in the P2D-ECT model while making it amenable for online state estimation. Though deterministic, uncertainty in the initial states induces stochasticity in the P2D-ECT model. This stochasticity is resolved by spectrally projecting the stochastic P2D-ECT model on a set of orthogonal multivariate Hermite polynomials. Volume averaging in the stochastic dimensions is proposed for efficient numerical solution of the resultant model. A state estimation framework is developed using a transformation of the orthogonal basis to assimilate the measurables with this system of equations. Effectiveness of the proposed method is first demonstrated by assimilating the cell voltage and temperature data generated using a synthetic test bed. This validated method is used with the experimentally observed cell voltage and temperature data for state estimation at different operating conditions and drive cycle protocols. The results show increased prediction accuracy when the data is assimilated every 30s. High accuracy of the estimated states is exploited to infer temperature dependent behavior of the lithium-ion cell.

Spontaneous activity of isolated dopaminergic periglomerular cells of the main olfactory bulb.

PubMed

Puopolo, Michelino; Bean, Bruce P; Raviola, Elio

2005-11-01

We examined the electrophysiological properties of a population of identified dopaminergic periglomerular cells of the main olfactory bulb using transgenic mice in which catecholaminergic neurons expressed human placental alkaline phosphatase (PLAP) on the outer surface of the plasma membrane. After acute dissociation, living dopaminergic periglomerular cells were identified by a fluorescently labeled monoclonal antibody to PLAP. In current-clamp mode, dopaminergic periglomerular cells spontaneously generated action potentials in a rhythmic fashion with an average frequency of 8 Hz. The hyperpolarization-activated cation current (Ih) did not seem important for pacemaking because blocking the current with ZD 7288 or Cs+ had little effect on spontaneous firing. To investigate what ionic currents do drive pacemaking, we performed action-potential-clamp experiments using records of pacemaking as voltage command in voltage-clamp experiments. We found that substantial TTX-sensitive Na+ current flows during the interspike depolarization. In addition, substantial Ca2+ current flowed during the interspike interval, and blocking Ca2+ current hyperpolarized the neurons and stopped spontaneous firing. These results show that dopaminergic periglomerular cells have intrinsic pacemaking activity, supporting the possibility that they can maintain a tonic release of dopamine to modulate the sensitivity of the olfactory system during odor detection. Calcium entry into these neurons provides electrical drive for pacemaking as well as triggering transmitter release.

Performance characteristics of lithium primary cells after controlled storage. [on-orbit for energy power supply

NASA Technical Reports Server (NTRS)

Deligiannis, F.; Shen, D. H.; Halpert, G.; Ang, V.; Donley, S.

1991-01-01

A program was initiated to investigate the effects of storage on the performance of lithium primary cells. Two types of liquid cathode cells were chosen to investigate these effects. The cell types included Li-SOCl2/BCX cells, Li-SO2 cells from two different manufacturers, and a small sample size of 8-year-old Li-SO2 cells. The following measurements are performed at each test interval: open circuit voltage, resistance and weight, microcalorimetry, ac impedance, capacity, and voltage delay. The authors examine the performance characteristics of these cells after one year of controlled storage at two temperatures (10 and 30 C). The Li-SO2 cells experienced little to no voltage and capacity degradation after one year storage. The Li-SOCl2/BCX cells exhibited significant voltage and capacity degradation after 30 C storage. Predischarging shortly prior to use appears to be an effective method of reducing the initial voltage drop. Studies are in progress to correlate ac impedance and microcalorimetry measurements with capacity losses and voltage delay.

Voltage Oscillations in a Polymer Electrolyte Membrane Fuel Cell with Pd‐Pt/C and Pd/C Anodes

PubMed Central

Nogueira, Jéssica Alves

2017-01-01

Abstract Polymer electrolyte membrane fuel cells (PEMFC) fed with H2 contaminated with CO may exhibit oscillatory behavior when operated galvanostatically. The self‐organization of the anodic overpotential is interesting because it can be accompanied by an increase in the average performance. Herein we report experimental studies of voltage oscillations that emerge in a PEMFC equipped with a Pd/C or PdPt/C anode and fed with H2 contaminated with CO (100 ppm). We used on‐line mass spectrometry to investigate how the mass fragments associated with CO2 and CO (m/z 44 and 28, respectively) varied with the voltage oscillations. Overall, we observed that oscillations in the anodic overpotential are in phase with that of the CO and CO2 signals. This fact is consistent with an autonomous adsorption–oxidation cyclic process. For both anodes, it has been observed that, in general, an increase in current density implies an increase in oscillatory frequency. By using CO stripping, we also discuss how the onset of CO oxidation is related to the maximum overpotential reached during a cycle, whereas the minimum overpotential can be associated with the catalytic activity of the electrode for H2 oxidation. PMID:29046857

How Cells Can Control Their Size by Pumping Ions.

PubMed

Kay, Alan R

2017-01-01

The ability of all cells to set and regulate their size is a fundamental aspect of cellular physiology. It has been known for sometime but not widely so, that size stability in animal cells is dependent upon the operation of the sodium pump, through the so-called pump-leak mechanism (Tosteson and Hoffman, 1960). Impermeant molecules in cells establish an unstable osmotic condition, the Donnan effect, which is counteracted by the operation of the sodium pump, creating an asymmetry in the distribution of Na + and K + staving off water inundation. In this paper, which is in part a tutorial, I show how to model quantitatively the ion and water fluxes in a cell that determine the cell volume and membrane potential. The movement of water and ions is constrained by both osmotic and charge balance, and is driven by ion and voltage gradients and active ion transport. Transforming these constraints and forces into a set of coupled differential equations allows us to model how the ion distributions, volume and voltage change with time. I introduce an analytical solution to these equations that clarifies the influence of ion conductances, pump rates and water permeability in this multidimensional system. I show that the number of impermeant ions ( x ) and their average charge have a powerful influence on the distribution of ions and voltage in a cell. Moreover, I demonstrate that in a cell where the operation of active ion transport eliminates an osmotic gradient, the size of the cell is directly proportional to x . In addition, I use graphics to reveal how the physico-chemical constraints and chemical forces interact with one another in apportioning ions inside the cell. The form of model used here is applicable to all membrane systems, including mitochondria and bacteria, and I show how pumps other than the sodium pump can be used to stabilize cells. Cell biologists may think of electrophysiology as the exclusive domain of neuroscience, however the electrical effects of ion fluxes need to become an intimate part of cell biology if we are to understand a fundamental process like cell size regulation.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage.

PubMed

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-08-10

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage

PubMed Central

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-01-01

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively. PMID:28773801

Membrane properties and cell ultrastructure of taste receptor cells in Necturus lingual slices.

PubMed

Bigiani, A; Kim, D J; Roper, S D

1996-05-01

1. Whole cell patch-clamp recordings and electron micrographs were obtained from cells in Necturus taste buds in lingual slices to study their membrane properties and to correlate these properties with cell ultrastructure. 2. Two different populations of taste receptor cells could be identified: one type possessed voltage-gated Na+ and K+ (noninactivating) currents (group 1 cells); the other type possessed only K+ (inactivating) currents (group 2 cells). 3. The zero-current ("resting") potential (Vo) and whole cell resistance (Ro) of these two types of taste cells differed significantly. For group 1 cells, on average, Vo = -75 mV and Ro = 24.6 G omega, and for group 2 cells, Vo = -49 mV and Ro = 48.9 G omega. The difference in Ro was not explained completely by differences in cell sizes, suggesting that intrinsic membrane properties differed between the populations. 4. Cells injected with biocytin were the electron microscope after tissues were reacted with majority (14 of 16) of cells with voltage-gated Na+ and K+ currents (group 1 cells) were characterized by abundant rough endoplasmic reticulum and dense granular packets in the apical process. These are features of dark cells. All the cells that only possessed K+ currents (group 2 cells) were characterize by well-developed smooth endoplasmic reticulum and an absence granular packets. These features characterize light cells. 5. These findings indicate that there is a good, although not exact, correlation between electrophysiological properties and cell morphotype in Necturus taste bud cells. All dark cells possessed Na+ and K+ currents and thus would be expected to be capable of generating action potentials. Most light cells only possessed outward K+ currents and thus would be incapable of generating action potentials.

Study of the effect of electromagnetic fields on indoor and outdoor radon concentrations

NASA Astrophysics Data System (ADS)

Haider, Lina M.; Shareef, N. R.; Darwoysh, H. H.; Mansour, H. L.

2018-05-01

In the present work, the effect of electromagnetic fields produced by high voltage power lines(132kV) and indoor equipments on the indoor and outdoor average radon concentrations in Al-Kazaliya and Hay Al-Adil regions in Baghdad city were studied using CR-39 track detectors and a gauss-meter.Results of measurements of the present study, have shown that the highest value for the indoor average radon concentration (76.56± 8.44 Bq / m3) was recorded for sample A1(Hay Al-Adel) at a distance of (20 m) from the high voltage power lines, while the lowest value for the indoor average radon concentration (30.46 ± 8.44 Bq / m3) was recorded for sample A3 (Hay Al-Adil) at a distance of (50 m) from the high voltage power lines. The indoor gaussmeter measurements were found to be ranged from (30.2 mG) to (38.5 mG). The higest value for outdoor average radon concentration and the highest gaussmeter measurements were found for sample (1), with values (92.63 ±11.2 Bq / m3) and (87.24 ± 2.85 mG), directly under the high voltage power lines respectively, while the lowest outdoor average radon concentration and the lowest gaussmeter measurements were found in sample (4),with values (34.19 ± 6.33 Bq / m3) and (1.16 ± 0.14 Bq / m3),), at a distance of (120 m) from the high voltage power lines respectively. The results of the present work have shown that there might be an influence of the electromagnetic field on radon concentrations in areas which were close to high voltage power lines and houses which have used many electric equipment for a long period of time.

Dithienogermole as a fused electron donor in bulk heterojunction solar cells.

PubMed

Amb, Chad M; Chen, Song; Graham, Kenneth R; Subbiah, Jegadesan; Small, Cephas E; So, Franky; Reynolds, John R

2011-07-06

We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.

Laser beam apparatus and method for analyzing solar cells

DOEpatents

Staebler, David L.

1980-01-01

A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.

An efficient current-based logic cell model for crosstalk delay analysis

NASA Astrophysics Data System (ADS)

Nazarian, Shahin; Das, Debasish

2013-04-01

Logic cell modelling is an important component in the analysis and design of CMOS integrated circuits, mostly due to nonlinear behaviour of CMOS cells with respect to the voltage signal at their input and output pins. A current-based model for CMOS logic cells is presented, which can be used for effective crosstalk noise and delta delay analysis in CMOS VLSI circuits. Existing current source models are expensive and need a new set of Spice-based characterisation, which is not compatible with typical EDA tools. In this article we present Imodel, a simple nonlinear logic cell model that can be derived from the typical cell libraries such as NLDM, with accuracy much higher than NLDM-based cell delay models. In fact, our experiments show an average error of 3% compared to Spice. This level of accuracy comes with a maximum runtime penalty of 19% compared to NLDM-based cell delay models on medium-sized industrial designs.

Giga-seal formation alters properties of sodium channels of human myoballs.

PubMed

Fahlke, C; Rüdel, R

1992-03-01

The influence of giga-seal formation on the properties of the Na+ channels within the covered membrane patch was investigated with a whole-cell pipette and a patch pipette applied to the same cell. Current kinetics, current/voltage relation and channel densities were determined in three combinations: (i) voltage-clamping and current recording with the whole-cell pipette, (ii) voltage-clamping with the whole-cell pipette and current recording with the patch pipette and, (iii) voltage-clamping and current recording with the patch pipette. The Hodgkin-Huxley (1952) parameters tau m and tau h were smaller for the patch currents than for the whole cell, and the h infinity curve was shifted in the negative direction. The channel density was of the order of 10 times smaller. All effects were independent of the extracellular Ca2+ concentration. The capacitive current generated in the patch by the whole-cell Na+ current and its effect on the transmembrane voltage of the patch were evaluated. The kinetic parameters of the Na+ channels in the patch did not depend on whether the voltage was clamped with the whole-cell pipette or the patch pipette. Thus, the results are not due to spurious voltage.

Prevention of Ca(2+)-mediated action potentials in GABAergic local circuit neurones of rat thalamus by a transient K+ current.

PubMed Central

Pape, H C; Budde, T; Mager, R; Kisvárday, Z F

1994-01-01

1. Neurones enzymatically dissociated from the rat dorsal lateral geniculate nucleus (LGN) were identified as GABAergic local circuit interneurones and geniculocortical relay cells, based upon quantitative analysis of soma profiles, immunohistochemical detection of GABA or glutamic acid decarboxylase, and basic electrogenic behaviour. 2. During whole-cell current-clamp recording, isolated LGN neurones generated firing patterns resembling those in intact tissue, with the most striking difference relating to the presence in relay cells of a Ca2+ action potential with a low threshold of activation, capable of triggering fast spikes, and the absence of a regenerative Ca2+ response with a low threshold of activation in local circuit cells. 3. Whole-cell voltage-clamp experiments demonstrated that both classes of LGN neurones possess at least two voltage-dependent membrane currents which operate in a range of membrane potentials negative to the threshold for generation of Na(+)-K(+)-mediated spikes: the T-type Ca2+ current (IT) and an A-type K+ current (IA). Taking into account the differences in membrane surface area, the average size of IT was similar in the two types of neurones, and interneurones possessed a slightly larger A-conductance. 4. In local circuit neurones, the ranges of steady-state inactivation and activation of IT and IA were largely overlapping (VH = 81.1 vs. -82.8 mV), both currents activated at around -70 mV, and they rapidly increased in amplitude with further depolarization. In relay cells, the inactivation curve of IT was negatively shifted along the voltage axis by about 20 mV compared with that of IA (Vh = -86.1 vs. -69.2 mV), and the activation threshold for IT (at -80 mV) was 20 mV more negative than that for IA. In interneurones, the activation range of IT was shifted to values more positive than that in relay cells (Vh = -54.9 vs. -64.5 mV), whereas the activation range of IA was more negative (Vh = -25.2 vs. -14.5 mV). 5. Under whole-cell voltage-clamp conditions that allowed the combined activation of Ca2+ and K+ currents, depolarizing voltage steps from -110 mV evoked inward currents resembling IT in relay cells and small outward currents indicative of IA in local circuit neurones. After blockade of IA with 4-aminopyridine (4-AP), the same pulse protocol produced IT in both types of neurones. Under current clamp, 4-AP unmasked a regenerative membrane depolarization with a low threshold of activation capable of triggering fast spikes in local circuit neurones.(ABSTRACT TRUNCATED AT 400 WORDS) Images Figure 1 PMID:7965855

A mathematical approach for evaluating nickel-hydrogen cells

NASA Technical Reports Server (NTRS)

Leibecki, H. F.

1986-01-01

A mathematical equation is presented which gives a quantitative relationship between time-voltage discharge curves, when a cell's ampere-hour capacity is determined at a constant discharge current. In particular the equation quantifies the initial exponential voltage decay; the rate of voltage decay; the overall voltage shift of the curve and the total capacity of the cell at the given discharge current. The results of 12 nickel-hydrogen boiler plate cells cycled to 80 percent depth-of-discharge (DOD) are discussed in association with these equations.

Screening Fluorescent Voltage Indicators with Spontaneously Spiking HEK Cells

PubMed Central

Venkatachalam, Veena; Kralj, Joel M.; Dib-Hajj, Sulayman D.; Waxman, Stephen G.; Cohen, Adam E.

2013-01-01

Development of improved fluorescent voltage indicators is a key challenge in neuroscience, but progress has been hampered by the low throughput of patch-clamp characterization. We introduce a line of non-fluorescent HEK cells that stably express NaV 1.3 and KIR 2.1 and generate spontaneous electrical action potentials. These cells enable rapid, electrode-free screening of speed and sensitivity of voltage sensitive dyes or fluorescent proteins on a standard fluorescence microscope. We screened a small library of mutants of archaerhodopsin 3 (Arch) in spiking HEK cells and identified two mutants with greater voltage-sensitivity than found in previously published Arch voltage indicators. PMID:24391999

Circuits and methods for impedance determination using active measurement cancelation

DOEpatents

Jamison, David K.

2016-12-13

A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.

Characterization of a novel, highly integrated tubular solid oxide fuel cell system using high-fidelity simulation tools

NASA Astrophysics Data System (ADS)

Kattke, K. J.; Braun, R. J.

2011-08-01

A novel, highly integrated tubular SOFC system intended for small-scale power is characterized through a series of sensitivity analyses and parametric studies using a previously developed high-fidelity simulation tool. The high-fidelity tubular SOFC system modeling tool is utilized to simulate system-wide performance and capture the thermofluidic coupling between system components. Stack performance prediction is based on 66 anode-supported tubular cells individually evaluated with a 1-D electrochemical cell model coupled to a 3-D computational fluid dynamics model of the cell surroundings. Radiation is the dominate stack cooling mechanism accounting for 66-92% of total heat loss at the outer surface of all cells at baseline conditions. An average temperature difference of nearly 125 °C provides a large driving force for radiation heat transfer from the stack to the cylindrical enclosure surrounding the tube bundle. Consequently, cell power and voltage disparities within the stack are largely a function of the radiation view factor from an individual tube to the surrounding stack can wall. The cells which are connected in electrical series, vary in power from 7.6 to 10.8 W (with a standard deviation, σ = 1.2 W) and cell voltage varies from 0.52 to 0.73 V (with σ = 81 mV) at the simulation baseline conditions. It is observed that high cell voltage and power outputs directly correspond to tubular cells with the smallest radiation view factor to the enclosure wall, and vice versa for tubes exhibiting low performance. Results also reveal effective control variables and operating strategies along with an improved understanding of the effect that design modifications have on system performance. By decreasing the air flowrate into the system by 10%, the stack can wall temperature increases by about 6% which increases the minimum cell voltage to 0.62 V and reduces deviations in cell power and voltage by 31%. A low baseline fuel utilization is increased by decreasing the fuel flowrate and by increasing the stack current demand. Simulation results reveal fuel flow as a poor control variable because excessive tail-gas combustor temperatures limit fuel flow to below 110% of the baseline flowrate. Additionally, system efficiency becomes inversely proportional to fuel utilization over the practical fuel flow range. Stack current is found to be an effective control variable in this type of system because system efficiency becomes directly proportional to fuel utilization. Further, the integrated system acts to dampen temperature spikes when fuel utilization is altered by varying current demand. Radiation remains the dominate heat transfer mechanism within the stack even if stack surfaces are polished lowering emissivities to 0.2. Furthermore, the sensitivity studies point to an optimal system insulation thickness that balances the overall system volume and total conductive heat loss.

Polymer solar cells with enhanced open-circuit voltage and efficiency

NASA Astrophysics Data System (ADS)

Chen, Hsiang-Yu; Hou, Jianhui; Zhang, Shaoqing; Liang, Yongye; Yang, Guanwen; Yang, Yang; Yu, Luping; Wu, Yue; Li, Gang

2009-11-01

Following the development of the bulk heterojunction structure, recent years have seen a dramatic improvement in the efficiency of polymer solar cells. Maximizing the open-circuit voltage in a low-bandgap polymer is one of the critical factors towards enabling high-efficiency solar cells. Study of the relation between open-circuit voltage and the energy levels of the donor/acceptor in bulk heterojunction polymer solar cells has stimulated interest in modifying the open-circuit voltage by tuning the energy levels of polymers. Here, we show that the open-circuit voltage of polymer solar cells constructed based on the structure of a low-bandgap polymer, PBDTTT, can be tuned, step by step, using different functional groups, to achieve values as high as 0.76 V. This increased open-circuit voltage combined with a high short-circuit current density results in a polymer solar cell with a power conversion efficiency as high as 6.77%, as certified by the National Renewable Energy Laboratory.

Life cycle test results of a bipolar nickel hydrogen battery

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1985-01-01

A history is given of low Earth orbit (LEO) laboratory test data on a 6.5 ampere-hour bipolar nickel hydrogen battery designed and built at the NASA Lewis Research Center. The bipolar concept is a means of achieving the goal of producing an acceptable battery, of higher energy density, able to withstand the demands of low-Earth-orbit regimes. Over 4100 LEO cycles were established on a ten cell battery. It seems that any perturbation on normal cycling effects the cells performance. Explanations and theories of the battery's behavior are varied and widespread among those closely associated with it. Deep discharging does provide a reconditioning effect and further experimentation is planned in this area. The battery watt-hour efficiency is about 75 percent and the time averaged, discharge voltage is about 1.26 volts for all cells at both the C/4 and LEO rate. Since a significant portion of the electrode capacity has degraded, the LEO cycle discharges are approaching depths of 90 to 100 percent of the high rate capacity. Therefore, the low end-of-discharge voltages occur precipitously after the knee of the discharge curve and is more an indication of electrode capacity and is a lesser indicator of overall cell performance.

Solar-rechargeable battery based on photoelectrochemical water oxidation: Solar water battery

PubMed Central

Kim, Gonu; Oh, Misol; Park, Yiseul

2016-01-01

As an alternative to the photoelectrochemical water splitting for use in the fuel cells used to generate electrical power, this study set out to develop a solar energy rechargeable battery system based on photoelectrochemical water oxidation. We refer to this design as a “solar water battery”. The solar water battery integrates a photoelectrochemical cell and battery into a single device. It uses a water oxidation reaction to simultaneously convert and store solar energy. With the solar water battery, light striking the photoelectrode causes the water to be photo-oxidized, thus charging the battery. During the discharge process, the solar water battery reduces oxygen to water with a high coulombic efficiency (>90%) and a high average output voltage (0.6 V). Because the reduction potential of oxygen is more positive [E0 (O2/H2O) = 1.23 V vs. NHE] than common catholytes (e.g., iodide, sulfur), a high discharge voltage is produced. The solar water battery also exhibits a superior storage ability, maintaining 99% of its specific discharge capacitance after 10 h of storage, without any evidence of self-discharge. The optimization of the cell design and configuration, taking the presence of oxygen in the cell into account, was critical to achieving an efficient photocharge/discharge. PMID:27629362

Solar-rechargeable battery based on photoelectrochemical water oxidation: Solar water battery.

PubMed

Kim, Gonu; Oh, Misol; Park, Yiseul

2016-09-15

As an alternative to the photoelectrochemical water splitting for use in the fuel cells used to generate electrical power, this study set out to develop a solar energy rechargeable battery system based on photoelectrochemical water oxidation. We refer to this design as a "solar water battery". The solar water battery integrates a photoelectrochemical cell and battery into a single device. It uses a water oxidation reaction to simultaneously convert and store solar energy. With the solar water battery, light striking the photoelectrode causes the water to be photo-oxidized, thus charging the battery. During the discharge process, the solar water battery reduces oxygen to water with a high coulombic efficiency (>90%) and a high average output voltage (0.6 V). Because the reduction potential of oxygen is more positive [E(0) (O2/H2O) = 1.23 V vs. NHE] than common catholytes (e.g., iodide, sulfur), a high discharge voltage is produced. The solar water battery also exhibits a superior storage ability, maintaining 99% of its specific discharge capacitance after 10 h of storage, without any evidence of self-discharge. The optimization of the cell design and configuration, taking the presence of oxygen in the cell into account, was critical to achieving an efficient photocharge/discharge.

Use of multi-functional flexible micro-sensors for in situ measurement of temperature, voltage and fuel flow in a proton exchange membrane fuel cell.

PubMed

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased.

Mitigation of chemical membrane degradation in fuel cells: understanding the effect of cell voltage and iron ion redox cycle.

PubMed

Wong, Ka Hung; Kjeang, Erik

2015-03-01

Chemical membrane degradation through the Fenton's reaction is one of the main lifetime-limiting factors for polymer-electrolyte fuel cells. In this work, a comprehensive, transient membrane degradation model is developed to capture and elucidate the complex in situ degradation mechanism. A redox cycle of iron ions is discovered within the membrane electrolyte assembly, which sustains the Fe(II) concentration and results in the most severe chemical degradation at open circuit voltage. The cycle strength is critically reduced at lower cell voltages, which leads to an exponential decrease in Fe(II) concentration and associated membrane degradation rate. When the cell voltage is held below 0.7 V, a tenfold reduction in cumulative fluoride release is achieved, which suggests that intermediate cell voltage operation would efficiently mitigate chemical membrane degradation and extend the fuel cell lifetime. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fuel cell system

DOEpatents

Early, Jack; Kaufman, Arthur; Stawsky, Alfred

1982-01-01

A fuel cell system is comprised of a fuel cell module including sub-stacks of series-connected fuel cells, the sub-stacks being held together in a stacked arrangement with cold plates of a cooling means located between the sub-stacks to function as electrical terminals. The anode and cathode terminals of the sub-stacks are connected in parallel by means of the coolant manifolds which electrically connect selected cold plates. The system may comprise a plurality of the fuel cell modules connected in series. The sub-stacks are designed to provide a voltage output equivalent to the desired voltage demand of a low voltage, high current DC load such as an electrolytic cell to be driven by the fuel cell system. This arrangement in conjunction with switching means can be used to drive a DC electrical load with a total voltage output selected to match that of the load being driven. This arrangement eliminates the need for expensive voltage regulation equipment.

Carbon nanotubes for voltage reduction and throughput enhancement of electrical cell lysis on a lab-on-a-chip.

PubMed

Shahini, Mehdi; Yeow, John T W

2011-08-12

We report on the enhancement of electrical cell lysis using carbon nanotubes (CNTs). Electrical cell lysis systems are widely utilized in microchips as they are well suited to integration into lab-on-a-chip devices. However, cell lysis based on electrical mechanisms has high voltage requirements. Here, we demonstrate that by incorporating CNTs into microfluidic electrolysis systems, the required voltage for lysis is reduced by half and the lysis throughput at low voltages is improved by ten times, compared to non-CNT microchips. In our experiment, E. coli cells are lysed while passing through an electric field in a microchannel. Based on the lightning rod effect, the electric field strengthened at the tip of the CNTs enhances cell lysis at lower voltage and higher throughput. This approach enables easy integration of cell lysis with other on-chip high-throughput sample-preparation processes.

Cadmium telluride solar cells: Record-breaking voltages

DOE PAGES

Poplawsky, Jonathan D.

2016-01-01

Here, the performance of CdTe solar cells — cheaper alternatives to silicon photovoltaics — is hampered by their low output voltages, which are normally well below the theoretical limit. Now, record voltages of over 1 V have been reported in single-crystal CdTe heterostructure solar cells, which are close to those of benchmark GaAs cells.

Low-Voltage Bypass Device

NASA Technical Reports Server (NTRS)

Wilson, J. P.

1994-01-01

Improved bypass device provides low-resistance current shunt around low-voltage power cell when cell fails in open-circuit condition during operation. In comparison with older bypass devices for same application, this one weighs less, generates less heat, and has lower voltage drop (less resistance). Bypass device connected in parallel with power cell. Draws very little current during normal operation of cell.

Beam-energy-spread minimization using cell-timing optimization

NASA Astrophysics Data System (ADS)

Rose, C. R.; Ekdahl, C.; Schulze, M.

2012-04-01

Beam energy spread, and related beam motion, increase the difficulty in tuning for multipulse radiographic experiments at the dual-axis radiographic hydrodynamic test facility’s axis-II linear induction accelerator (LIA). In this article, we describe an optimization method to reduce the energy spread by adjusting the timing of the cell voltages (both unloaded and loaded), either advancing or retarding, such that the injector voltage and summed cell voltages in the LIA result in a flatter energy profile. We developed a nonlinear optimization routine which accepts as inputs the 74 cell-voltage, injector voltage, and beam current waveforms. It optimizes cell timing per user-selected groups of cells and outputs timing adjustments, one for each of the selected groups. To verify the theory, we acquired and present data for both unloaded and loaded cell-timing optimizations. For the unloaded cells, the preoptimization baseline energy spread was reduced by 34% and 31% for two shots as compared to baseline. For the loaded-cell case, the measured energy spread was reduced by 49% compared to baseline.

Applications technology satellites battery and power system design

NASA Technical Reports Server (NTRS)

Ford, F. E.; Bemis, B.

1977-01-01

A summary of the ATS battery design which is onboard the Applications Technology Satellite (ATS) is provided. The 15 ampere hour nickel cadmium cells were manufactured by Gulton, 19 series connected cells per battery, and there are two batteries in each spacecraft. The operating design life was two years in a synchronous orbit, and a maximum depth of discharge of 50 percent. The design temperature for the batteries in the spacecraft was 0 to 25 C, and the charge control consisted of 1 volt versus temperature on a constant percentage voltage. Also, C/10 current limit, and a commandable trickle charge rate, using C/20 or C/60. The undervoltage was sent across a 9 cell and a 10 cell group, and it was set at one volt average per group on either group.

Breakdown voltage mapping through voltage dependent ReBEL intensity imaging of multi-crystalline Si solar cells

NASA Astrophysics Data System (ADS)

Dix-Peek, RM.; van Dyk, EE.; Vorster, FJ.; Pretorius, CJ.

2018-04-01

Device material quality affects both the efficiency and the longevity of photovoltaic (PV) cells. Therefore, identifying these defects can be beneficial in the development of more efficient and longer lasting PV cells. In this study, a combination of spatially-resolved, electroluminescence (EL), and light beam induced current (LBIC) measurements, were used to identify specific defects and features of a multi-crystalline Si PV cells. In this study, a novel approach is used to map the breakdown voltage of a PV cell through voltage dependent Reverse Bias EL (ReBEL) intensity imaging.

Characterization of Hamamatsu 64-channel TSV SiPMs

NASA Astrophysics Data System (ADS)

Renschler, Max; Painter, William; Bisconti, Francesca; Haungs, Andreas; Huber, Thomas; Karus, Michael; Schieler, Harald; Weindl, Andreas

2018-04-01

The Hamamatsu UV-light enhanced 64-channel SiPM array of the newest generation (S13361-3050AS-08) has been examined for the purpose of being used for the Silicon Elementary Cell Add-on (SiECA) of the EUSO-SPB balloon experiment. At a room temperature of 19 . 5 °C, the average measured breakdown voltage of the array is (51 . 65 ± 0 . 11) V, the average gain is measured to (2 . 10 ± 0 . 07) ṡ 106 and the average photon detection efficiency results to (44 . 58 ± 1 . 80) % at a wavelength of (423 ± 8) nm and a bias voltage of 55 . 2V. The average dark-count rate is (0 . 69 ± 0 . 12) MHz, equivalent to a dark count rate per SiPM area of (57 ± 12) kHz /mm2, and the crosstalk probability is measured to (3 . 96 ± 0 . 64) %. These results confirm the information given by the manufacturer. Measurements performed with the newly installed Single Photon Calibration Stand at KIT (SPOCK) show the improved sensitivity to photons with wavelengths lower than 400 nm compared to the SiPM array S12642-0808PA-50, which was also investigated for comparison. Additional measurements confirm the strong temperature dependence of the SiPM characteristics as given in the data sheet. All the characterized parameters appear to be sufficiently uniform to build up a focal surface of SiPM arrays fulfilling the requirements for a telescope detecting photons in the UV range.

High Voltage Magnesium-ion Battery Enabled by Nanocluster Mg3Bi2 Alloy Anode in Noncorrosive Electrolyte.

PubMed

Tan, Yi-Hong; Yao, Wei-Tang; Zhang, Tianwen; Ma, Tao; Lu, Lei-Lei; Zhou, Fei; Yao, Hong-Bin; Yu, Shu-Hong

2018-05-03

Currently, developing high voltage (beyond 2 V) rechargeable Mg-ion batteries still remains a great challenge owing to the limit of corrosive electrolyte and low compatibility of anode material. Here we report a facile one step solid state alloying route to synthesize nanoclustered Mg 3 Bi 2 alloy as a high-performance anode to build up a 2 V Mg-ion battery using noncorrosive electrolyte. The fabricated nanoclustered Mg 3 Bi 2 anode delivers a high reversible specific capacity (360 mAh g -1 ) with excellent stability (90.7% capacity retention over 200 cycles) and high Coulombic efficiency (average 98%) at 0.1 A g -1 . The good performance is attributed to the stable nanostructures, which effectively accommodate the reversible Mg 2+ ion insertion/deinsertion without losing electric contact among clusters. Significantly, the nanoclustered Mg 3 Bi 2 anode can be coupled with high voltage cathode Prussian Blue to assemble a full cell using noncorrosive electrolyte, showing a stable cycling (88% capacity retention over 200 cycles at 0.2 A g -1 ) and good rate capability (103 mAh g -1 at 0.1 A g -1 and 58 mAh g -1 at 2 A g -1 ). The energy and power density of the as-fabricated full cell can reach up to 81 Wh kg -1 and 2850 W kg -1 , respectively, which are both the highest values among the reported Mg-ion batteries using noncorrosive electrolytes. This study demonstrates a cost-effective route to fabricate stable and high voltage rechargeable Mg-ion battery potentially for grid-scale energy storage.

Experimental evaluation of battery cells for space-based radar application

NASA Technical Reports Server (NTRS)

Maskell, Craig A.; Metcalfe, John R.

1994-01-01

A test program was conducted to characterize five space-quality nickel-hydrogen (NiH2) battery cells. A subset of those tests was also done on five commercial nickel-cadmium (NiCd) cells, for correlation to the characteristics of an Energy Storage Unit Simulator. The test program implemented the recommendations of a 1991 study, as reported to IECEC-92. The findings of the tests are summarized, and expected impacts on the performance of the electrical power system (EPS) of a large space-based radar (SBR) surveillance satellite are derived. The main characteristics examined and compared were terminal voltage (average and transient) and capacity through discharge, equivalent series resistance, derived inductance and capacitance, charge return efficiency, and inter-pulse charge effectiveness.

Potential role of voltage-sensing phosphatases in regulation of cell structure through the production of PI(3,4)P2.

PubMed

Yamaguchi, Shinji; Kurokawa, Tatsuki; Taira, Ikuko; Aoki, Naoya; Sakata, Souhei; Okamura, Yasushi; Homma, Koichi J

2014-04-01

Voltage-sensing phosphatase, VSP, consists of the transmembrane domain, operating as the voltage sensor, and the cytoplasmic domain with phosphoinositide-phosphatase activities. The voltage sensor tightly couples with the cytoplasmic phosphatase and membrane depolarization induces dephosphorylation of several species of phosphoinositides. VSP gene is conserved from urochordate to human. There are some diversities among VSP ortholog proteins; range of voltage of voltage sensor motions as well as substrate selectivity. In contrast with recent understandings of biophysical mechanisms of VSPs, little is known about its physiological roles. Here we report that chick ortholog of VSP (designated as Gg-VSP) induces morphological feature of cell process outgrowths with round cell body in DF-1 fibroblasts upon its forced expression. Expression of the voltage sensor mutant, Gg-VSPR153Q with shifted voltage dependence to a lower voltage led to more frequent changes of cell morphology than the wild-type protein. Coexpression of PTEN that dephosphorylates PI(3,4)P2 suppressed this effect by Gg-VSP, indicating that the increase of PI(3,4)P2 leads to changes of cell shape. In addition, visualization of PI(3,4)P2 with the fluorescent protein fused with the TAPP1-derived pleckstrin homology (PH) domain suggested that Gg-VSP influenced the distribution of PI(3,4)P2 . These findings raise a possibility that one of the VSP's functions could be to regulate cell morphology through voltage-sensitive tuning of phosphoinositide profile. © 2013 Wiley Periodicals, Inc.

Beyond voltage-gated ion channels: Voltage-operated membrane proteins and cellular processes.

PubMed

Zhang, Jianping; Chen, Xingjuan; Xue, Yucong; Gamper, Nikita; Zhang, Xuan

2018-04-18

Voltage-gated ion channels were believed to be the only voltage-sensitive proteins in excitable (and some non-excitable) cells for a long time. Emerging evidence indicates that the voltage-operated model is shared by some other transmembrane proteins expressed in both excitable and non-excitable cells. In this review, we summarize current knowledge about voltage-operated proteins, which are not classic voltage-gated ion channels as well as the voltage-dependent processes in cells for which single voltage-sensitive proteins have yet to be identified. Particularly, we will focus on the following. (1) Voltage-sensitive phosphoinositide phosphatases (VSP) with four transmembrane segments homologous to the voltage sensor domain (VSD) of voltage-gated ion channels; VSPs are the first family of proteins, other than the voltage-gated ion channels, for which there is sufficient evidence for the existence of the VSD domain; (2) Voltage-gated proton channels comprising of a single voltage-sensing domain and lacking an identified pore domain; (3) G protein coupled receptors (GPCRs) that mediate the depolarization-evoked potentiation of Ca 2+ mobilization; (4) Plasma membrane (PM) depolarization-induced but Ca 2+ -independent exocytosis in neurons. (5) Voltage-dependent metabolism of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P 2 , PIP 2 ) in the PM. These recent discoveries expand our understanding of voltage-operated processes within cellular membranes. © 2018 Wiley Periodicals, Inc.

Design of a high voltage input - output ratio dc-dc converter dedicated to small power fuel cell systems

NASA Astrophysics Data System (ADS)

Béthoux, O.; Cathelin, J.

2010-12-01

Consuming chemical energy, fuel cells produce simultaneously heat, water and useful electrical power [J.M. Andújar, F. Segura, Renew. Sust. Energy Rev. 13, 2309 (2009)], [J. Larminie, A. Dicks, Fuel Cell Systems Explained, 2nd edn. (John Wiley & Sons, 2003)]. As a matter of fact, the voltage generated by a fuel cell strongly depends on both the load power demand and the operating conditions. Besides, as a result of many design aspects, fuel cells are low voltage and high current electric generators. On the contrary, electric loads are commonly designed for small voltage swing and a high V/I ratio in order to minimize Joule losses. Therefore, electric loads supplied by fuel cells are typically fed by means of an intermediate power voltage regulator. The specifications of such a power converter are to be able to step up the input voltage with a high ratio (a ratio of 10 is a classic situation) and also to work with an excellent efficiency (in order to minimize its size, its weight and its losses) [A. Shahin, B. Huang, J.P. Martin, S. Pierfederici, B. Davat, Energy Conv. Manag. 51, 56 (2010)]. This paper deals with the design of this essential ancillary device. It intends to bring out the best structure for fulfilling this function. Several dc-dc converters with large voltage step-up ratios are introduced. A topology based on a coupled inductor or tapped inductor is closely studied. A detailed modelling is performed with the purpose of providing designing rules. This model is validated with both simulation and implementation. The experimental prototype is based on the following specifications: the fuel cell output voltage ranges from a 50 V open-voltage to a 25 V rated voltage while the load requires a constant 250 V voltage. The studied coupled inductor converter is compared with a classic boost converter commonly used in this voltage elevating application. Even though the voltage regulator faces severe FC specifications, the measured efficiency reaches 96% at the rated power whereas conventional boost efficiency barely achieves 91.5% in the same operating conditions.

Radio-frequency powered glow discharge device and method with high voltage interface

DOEpatents

Duckworth, D.C.; Marcus, R.K.; Donohue, D.L.; Lewis, T.A.

1994-06-28

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components. 11 figures.

Radio-frequency powered glow discharge device and method with high voltage interface

DOEpatents

Duckworth, Douglas C.; Marcus, R. Kenneth; Donohue, David L.; Lewis, Trousdale A.

1994-01-01

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components.

Hydrogen-oxygen proton-exchange membrane fuel cells and electrolyzers

NASA Technical Reports Server (NTRS)

Baldwin, R.; Pham, M.; Leonida, A.; Mcelroy, J.; Nalette, T.

1989-01-01

Hydrogen-oxygen SPE fuel cells and SPE electrolyzers (products of Hamilton Standard) both use a Proton-Exchange Membrane (PEM) as the sole electrolyte. The SPE cells have demonstrated a ten year life capability under load conditions. Ultimate life of PEM fuel cells and electrolyzers is primarily related to the chemical stability of the membrane. For perfluorocarbon proton-exchange membranes an accurate measure of the membrane stability is the fluoride loss rate. Millions of cell hours have contributed to establishing a relationship between fluroride loss rates and average expected ultimate cell life. Several features were introduced into SPE fuel cells and SPE electrolyzers such that applications requiring greater than or equal to 100,000 hours of life can be considered. Equally important as the ultimate life is the voltage stability of hydrogen-oxygen fuel cells and electrolyzers. Here again the features of SPE fuel cells and SPE electrolyzers have shown a cell voltage stability in the order of 1 microvolt per hour. That level of stability were demonstrated for tens of thousands of hours in SPE fuel cells at up to 500 amps per square foot (ASF) current density. The SPE electrolyzers have demonstrated the same at 1000 ASF. Many future extraterrestrial applications for fuel cells require that they be self recharged. To translate the proven SPE cell life and stability into a highly reliable extraterrestrial electrical energy storage system, a simplification of supporting equipment is required. Static phase separation, static fluid transport and static thermal control will be most useful in producting required system reliability. Although some 200,000 SPE fuel cell hours were recorded in earth orbit with static fluid phase separation, no SPE electrolyzer has, as yet, operated in space.

Use of Multi-Functional Flexible Micro-Sensors for in situ Measurement of Temperature, Voltage and Fuel Flow in a Proton Exchange Membrane Fuel Cell

PubMed Central

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased. PMID:22163545

Charging system and method for multicell storage batteries

DOEpatents

Cox, Jay A.

1978-01-01

A battery-charging system includes a first charging circuit connected in series with a plurality of battery cells for controlled current charging. A second charging circuit applies a controlled voltage across each individual cell for equalization of the cells to the fully charged condition. This controlled voltage is determined at a level above the fully charged open-circuit voltage but at a sufficiently low level to prevent corrosion of cell components by electrochemical reaction. In this second circuit for cell equalization, a transformer primary receives closely regulated, square-wave voltage which is coupled to a plurality of equal secondary coil windings. Each secondary winding is connected in parallel to each cell of a series-connected pair of cells through half-wave rectifiers and a shared, intermediate conductor.

Radiative efficiency of lead iodide based perovskite solar cells

PubMed Central

Tvingstedt, Kristofer; Malinkiewicz, Olga; Baumann, Andreas; Deibel, Carsten; Snaith, Henry J.; Dyakonov, Vladimir; Bolink, Henk J.

2014-01-01

The maximum efficiency of any solar cell can be evaluated in terms of its corresponding ability to emit light. We herein determine the important figure of merit of radiative efficiency for Methylammonium Lead Iodide perovskite solar cells and, to put in context, relate it to an organic photovoltaic (OPV) model device. We evaluate the reciprocity relation between electroluminescence and photovoltaic quantum efficiency and conclude that the emission from the perovskite devices is dominated by a sharp band-to-band transition that has a radiative efficiency much higher than that of an average OPV device. As a consequence, the perovskite have the benefit of retaining an open circuit voltage ~0.14 V closer to its radiative limit than the OPV cell. Additionally, and in contrast to OPVs, we show that the photoluminescence of the perovskite solar cell is substantially quenched under short circuit conditions in accordance with how an ideal photovoltaic cell should operate. PMID:25317958

Image sensor system with bio-inspired efficient coding and adaptation.

PubMed

Okuno, Hirotsugu; Yagi, Tetsuya

2012-08-01

We designed and implemented an image sensor system equipped with three bio-inspired coding and adaptation strategies: logarithmic transform, local average subtraction, and feedback gain control. The system comprises a field-programmable gate array (FPGA), a resistive network, and active pixel sensors (APS), whose light intensity-voltage characteristics are controllable. The system employs multiple time-varying reset voltage signals for APS in order to realize multiple logarithmic intensity-voltage characteristics, which are controlled so that the entropy of the output image is maximized. The system also employs local average subtraction and gain control in order to obtain images with an appropriate contrast. The local average is calculated by the resistive network instantaneously. The designed system was successfully used to obtain appropriate images of objects that were subjected to large changes in illumination.

Child-Langmuir flow with periodically varying anode voltage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rokhlenko, A.

Using the Lagrangian technique, we study settled Child-Langmuir flows in a one dimensional planar diodes whose anode voltages periodically vary around given positive values. Our goal is to find analytically if the average currents in these systems can exceed the famous Child-Langmuir limit found for the stationary current a long time ago. The main result of our study is that in a periodic quasi-stationary regime the average current can be larger than the Child-Langmuir maximum even by 50% compared with its adiabatic average value. The cathode current in this case has the form of rectangular pulses which are formed bymore » a very special triangular voltage modulation. This regime, i.e., periodicity, shape of pulses, and their amplitude, needs to be carefully chosen for the best performance.« less

Planar multijunction high voltage solar cells

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr.; Chai, A. T.; Goradia, C.

1980-01-01

Technical considerations, preliminary results, and fabrication details are discussed for a family of high-voltage planar multi-junction (PMJ) solar cells which combine the attractive features of planar cells with conventional or interdigitated back contacts and the vertical multijunction (VMJ) solar cell. The PMJ solar cell is internally divided into many voltage-generating regions, called unit cells, which are internally connected in series. The key to obtaining reasonable performance from this device was the separation of top surface field regions over each active unit cell. Using existing solar cell fabricating methods, output voltages in excess of 20 volts per linear centimeter are possible. Analysis of the new device is complex, and numerous geometries are being studied which should provide substantial benefits in both normal sunlight usage as well as with concentrators.

Correspondence between visual and electrical input filters of ON and OFF mouse retinal ganglion cells

NASA Astrophysics Data System (ADS)

Sekhar, S.; Jalligampala, A.; Zrenner, E.; Rathbun, D. L.

2017-08-01

Objective. Over the past two decades retinal prostheses have made major strides in restoring functional vision to patients blinded by diseases such as retinitis pigmentosa. Presently, implants use single pulses to activate the retina. Though this stimulation paradigm has proved beneficial to patients, an unresolved problem is the inability to selectively stimulate the on and off visual pathways. To this end our goal was to test, using white noise, voltage-controlled, cathodic, monophasic pulse stimulation, whether different retinal ganglion cell (RGC) types in the wild type retina have different electrical input filters. This is an important precursor to addressing pathway-selective stimulation. Approach. Using full-field visual flash and electrical and visual Gaussian noise stimulation, combined with the technique of spike-triggered averaging (STA), we calculate the electrical and visual input filters for different types of RGCs (classified as on, off or on-off based on their response to the flash stimuli). Main results. Examining the STAs, we found that the spiking activity of on cells during electrical stimulation correlates with a decrease in the voltage magnitude preceding a spike, while the spiking activity of off cells correlates with an increase in the voltage preceding a spike. No electrical preference was found for on-off cells. Comparing STAs of wild type and rd10 mice revealed narrower electrical STA deflections with shorter latencies in rd10. Significance. This study is the first comparison of visual cell types and their corresponding temporal electrical input filters in the retina. The altered input filters in degenerated rd10 retinas are consistent with photoreceptor stimulation underlying visual type-specific electrical STA shapes in wild type retina. It is therefore conceivable that existing implants could target partially degenerated photoreceptors that have only lost their outer segments, but not somas, to selectively activate the on and off visual pathways.

Employing Si solar cell technology to increase efficiency of ultra-thin Cu(In,Ga)Se2 solar cells.

PubMed

Vermang, Bart; Wätjen, Jörn Timo; Fjällström, Viktor; Rostvall, Fredrik; Edoff, Marika; Kotipalli, Ratan; Henry, Frederic; Flandre, Denis

2014-10-01

Reducing absorber layer thickness below 500 nm in regular Cu(In,Ga)Se 2 (CIGS) solar cells decreases cell efficiency considerably, as both short-circuit current and open-circuit voltage are reduced because of incomplete absorption and high Mo/CIGS rear interface recombination. In this work, an innovative rear cell design is developed to avoid both effects: a highly reflective rear surface passivation layer with nano-sized local point contact openings is employed to enhance rear internal reflection and decrease the rear surface recombination velocity significantly, as compared with a standard Mo/CIGS rear interface. The formation of nano-sphere shaped precipitates in chemical bath deposition of CdS is used to generate nano-sized point contact openings. Evaporation of MgF 2 coated with a thin atomic layer deposited Al 2 O 3 layer, or direct current magnetron sputtering of Al 2 O 3 are used as rear surface passivation layers. Rear internal reflection is enhanced substantially by the increased thickness of the passivation layer, and also the rear surface recombination velocity is reduced at the Al 2 O 3 /CIGS rear interface. (MgF 2 /)Al 2 O 3 rear surface passivated ultra-thin CIGS solar cells are fabricated, showing an increase in short circuit current and open circuit voltage compared to unpassivated reference cells with equivalent CIGS thickness. Accordingly, average solar cell efficiencies of 13.5% are realized for 385 nm thick CIGS absorber layers, compared with 9.1% efficiency for the corresponding unpassivated reference cells.

Employing Si solar cell technology to increase efficiency of ultra-thin Cu(In,Ga)Se2 solar cells

PubMed Central

Vermang, Bart; Wätjen, Jörn Timo; Fjällström, Viktor; Rostvall, Fredrik; Edoff, Marika; Kotipalli, Ratan; Henry, Frederic; Flandre, Denis

2014-01-01

Reducing absorber layer thickness below 500 nm in regular Cu(In,Ga)Se2 (CIGS) solar cells decreases cell efficiency considerably, as both short-circuit current and open-circuit voltage are reduced because of incomplete absorption and high Mo/CIGS rear interface recombination. In this work, an innovative rear cell design is developed to avoid both effects: a highly reflective rear surface passivation layer with nano-sized local point contact openings is employed to enhance rear internal reflection and decrease the rear surface recombination velocity significantly, as compared with a standard Mo/CIGS rear interface. The formation of nano-sphere shaped precipitates in chemical bath deposition of CdS is used to generate nano-sized point contact openings. Evaporation of MgF2 coated with a thin atomic layer deposited Al2O3 layer, or direct current magnetron sputtering of Al2O3 are used as rear surface passivation layers. Rear internal reflection is enhanced substantially by the increased thickness of the passivation layer, and also the rear surface recombination velocity is reduced at the Al2O3/CIGS rear interface. (MgF2/)Al2O3 rear surface passivated ultra-thin CIGS solar cells are fabricated, showing an increase in short circuit current and open circuit voltage compared to unpassivated reference cells with equivalent CIGS thickness. Accordingly, average solar cell efficiencies of 13.5% are realized for 385 nm thick CIGS absorber layers, compared with 9.1% efficiency for the corresponding unpassivated reference cells. PMID:26300619

Characterization of slowly inactivating KV{alpha} current in rabbit pulmonary neuroepithelial bodies: effects of hypoxia and nicotine.

PubMed

Fu, Xiao Wen; Nurse, Colin; Cutz, Ernest

2007-10-01

Pulmonary neuroepithelial bodies (NEB) form innervated cell clusters that express voltage-activated currents and function as airway O(2) sensors. We investigated A-type K(+) currents in NEB cells using neonatal rabbit lung slice preparation. The whole cell K(+) current was slowly inactivating with activation threshold of approximately -30 mV. This current was blocked approximately 27% by blood-depressing substance I (BDS-I; 3 microM), a selective blocker of Kv3.4 subunit, and reduced approximately 20% by tetraethylammonium (TEA; 100 microM). The BDS-I-sensitive component had an average peak value of 189 +/- 14 pA and showed fast inactivation kinetics that could be fitted by one-component exponential function with a time constant of (tau1) 77 +/- 10 ms. This Kv slowly inactivating current was also blocked by heteropodatoxin-2 (HpTx-2; 0.2 microM), a blocker of Kv4 subunit. The HpTx-2-sensitive current had an average peak value of 234 +/- 23 pA with a time constant (tau) 82 +/- 11 ms. Hypoxia (Po(2) = 15-20 mmHg) inhibited the slowly inactivating K(+) current by approximately 47%, during voltage steps from -30 to +30 mV, and no further inhibition occurred when TEA was combined with hypoxia. Nicotine at concentrations of 50 and 100 microM suppressed the slowly inactivating K(+) current by approximately 24 and approximately 40%, respectively. This suppression was not reversed by mecamylamine suggesting a direct effect of nicotine on these K(+) channels. In situ hybridization experiments detected expression of mRNAs for Kv3.4 and Kv4.3 subunits, while double-label immunofluorescence confirmed membrane localization of respective channel proteins in NEB cells. These studies suggest that the hypoxia-sensitive current in NEB cells is carried by slowly inactivating A-type K(+) channels, which underlie their oxygen-sensitive potassium currents, and that exposure to nicotine may directly affect their function, contributing to smoking-related lung disease.

Method and Apparatus for In-Situ Health Monitoring of Solar Cells in Space

NASA Technical Reports Server (NTRS)

Krasowski, Michael J. (Inventor); Prokop, Norman F. (Inventor)

2012-01-01

Some embodiments of the present invention describe an apparatus that includes an oscillator, a ramp generator, and an inverter. The apparatus includes an oscillator, an inverter, and a ramp generator. The oscillator is configured to generate a waveform comprising a low time and a high time. The inverter is configured to receive the waveform generated by the oscillator, and invert the waveform. The ramp generator configured to increase a gate control voltage of a transistor connected to a solar cell, and rapidly decrease the gate control voltage of the transistor. During the low time of the waveform, a measurement of a current and a voltage of the solar cell is performed as the current and voltage of the solar cell are transmitted through a first channel and to a second channel. During the high time of the waveform, a measurement of a current of a shorted cell and a voltage reference is performed as the current of the shorted cell and the voltage reference are transmitted through the first channel and the second channel.

Enhancement of Open-Circuit Voltage by Using the 58-π Silylmethyl Fullerenes in Small-Molecule Organic Solar Cells.

PubMed

Jeon, Il; Delacou, Clément; Nakagawa, Takafumi; Matsuo, Yutaka

2016-04-20

The application of 58-π-1,4-bis(silylmethyl)[60]fullerenes, C60 (CH2 SiMe2 Ph)(CH2 SiMe2 Ar) (Ar=Ph and 2-methoxylphenyl for SIMEF-1 and SIMEF-2, respectively), in small-molecule organic solar cells with a diketopyrrolopyrrole donor (3,6-bis[5-(benzofuran-2-yl)thiophen-2-yl]-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(TBFu)2 )) is demonstrated. With the 58-π-silylmethyl fullerene acceptor, SIMEF-1, the devices showed the highest efficiency of 4.57 % with an average of 4.10 %. They manifested an improved open-circuit voltage (1.03 V) owing to the high-lying LUMO level of SIMEF-1, while maintaining a high short-circuit density (9.91 mA cm(-2) ) through controlling the crystallinity of DPP by thermal treatment. On the other hand, despite even higher open-circuit voltage (1.05 V), SIMEF-2-based devices showed lower performances of 3.53 %, owing to a low short-circuit current density (8.33 mA cm(-2) ) and fill factor (0.40) arising from the asymmetric structure, which results in a lower mobility and immiscibility. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photovoltaic Properties of Selenized CuGa/In Films with Varied Compositions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzillo, Christopher P.; Mansfield, Lorelle M.; Ramanathan, Kannan

2016-11-21

Thin CuGa/In films with varied compositions were deposited by co-evaporation and then selenized in situ with evaporated selenium. The selenized Cu(In, Ga)Se2 absorbers were used to fabricate 390 solar cells. Cu/(Ga+In) and Ga/(Ga+In) (Cu/III and Ga/III) were independently varied, and photovoltaic performance was optimal at Cu/III of 77-92% for all Ga/III compositions studied (Ga/III ~ 30, 50, and 70%). The best absorbers at each Ga/III composition were characterized with time-resolved photoluminescence, scanning electron microscopy, and secondary ion mass spectrometry, and devices were studied with temperature-dependent current density-voltage, light and electrical biased quantum efficiency, and capacitance-voltage. The best cells with Ga/IIImore » ~ 30, 50, and 70% had efficiencies of 14.5, 14.4, and 12.2% and maximum power temperature coefficients of -0.496, -0.452, and -0.413%/degrees C, respectively. This resulted in the Ga/III ~ 50% champion having the highest efficiency at temperatures greater than 40 degrees C, making it the optimal composition for practical purposes. This optimum is understood as a result of the absorber's band gap grading- where minimum band gap dominates short-circuit current density, maximum space charge region band gap dominates open-circuit voltage, and average absorber band gap dominates maximum power temperature coefficient.« less

High Efficiency MAPbI3 Perovskite Solar Cell Using a Pure Thin Film of Polyoxometalate as Scaffold Layer.

PubMed

Sardashti, Mohammad Khaledi; Zendehdel, Mahmoud; Nia, Narges Yaghoobi; Karimian, Davud; Sheikhi, Mohammad

2017-10-09

Here, we successfully used a pure layer of [SiW 11 O 39 ] 8- polyoxomethalate (POM) structure as a thin-film scaffold layer for CH 3 NH 3 PbI 3 -based perovskite solar cells (PSCs). A smooth nanoporous surface of POM causes outstanding improvement of the photocurrent density, external quantum efficiency (EQE), and overall efficiency of the PSCs compared to mesoporous TiO 2 (mp-TiO 2 ) as scaffold layer. Average power conversion efficiency (PCE) values of 15.5 % with the champion device showing 16.3 % could be achieved by using POM and a sequential deposition method with the perovskite layer. Furthermore, modified and defect-free POM/perovskite interface led to elimination of the anomalous hysteresis in the current-voltage curves. The open-circuit voltage decay study shows promising decrease of the electron recombination in the POM-based PSCs, which is also related to the modification of the POM/ perovskite interface and higher electron transport inside the POM layer. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

2D Electrides as Promising Anode Materials for Na-Ion Batteries from First-Principles Study.

PubMed

Hu, Junping; Xu, Bo; Yang, Shengyuan A; Guan, Shan; Ouyang, Chuying; Yao, Yugui

2015-11-04

Searching for suitable anodes with good performance is a key challenge for rechargeable Na-ion batteries (NIBs). Using the first-principles method, we predict that 2D nitrogen electride materials can be served as anode materials for NIBs. Particularly, we show that Ca2N meets almost all the requirements of a good NIB anode. Each formula unit of a monolayer Ca2N sheet can absorb up to four Na atoms, corresponding to a theoretical specific capacity of 1138 mAh·g(-1). The metallic character for both pristine Ca2N and its Na intercalated state NaxCa2N ensures good electronic conduction. Na diffusion along the 2D monolayer plane can be very fast even at room temperature, with a Na migration energy barrier as small as 0.084 eV. These properties are key to the excellent rate performance of an anode material. The average open-circuit voltage is calculated to be 0.18 V vs Na/Na(+) for the chemical stoichiometry of Na2Ca2N and 0.09 V for Na4Ca2N. The relatively low average open-circuit voltage is beneficial to the overall voltage of the cell. In addition, the 2D monolayers have very small lattice change upon Na intercalation, which ensures a good cycling stability. All these results demonstrate that the Ca2N monolayer could be an excellent anode material for NIBs.

Measurement and analysis of solar cell current-voltage characteristics

NASA Technical Reports Server (NTRS)

Olsen, Larry C.; Addis, F. William; Doyle, Dan H.; Miller, Wesley A.

1985-01-01

Approaches to measurement and analysis of solar cell current-voltage characteristics under dark and illuminated conditions are discussed. Measurements are taken with a computer based data acquisition system for temperatures in the range of -100 to +100 C. In the fitting procedure, the various I(oi) and C(i) as well as R(S) and R(SH) are determined. Application to current-voltage analyses of high efficiency silicon cells and Boeing CdS/CuInSe2 are discussed. In silicon MINP cells, it is found that at low voltages a tunneling mechanism is dominant, while at larger voltages the I-V characteristics are usually dominated by emitter recombination. In the case of Boeing cells, a current transport model based on a tunneling mechanism and interface recombination acting in series has been developed as a result of I-V analyses.

Power management circuits for self-powered systems based on micro-scale solar energy harvesting

NASA Astrophysics Data System (ADS)

Yoon, Eun-Jung; Yu, Chong-Gun

2016-03-01

In this paper, two types of power management circuits for self-powered systems based on micro-scale solar energy harvesting are proposed. First, if a solar cell outputs a very low voltage, less than 0.5 V, as in miniature solar cells or monolithic integrated solar cells, such that it cannot directly power the load, a voltage booster is employed to step up the solar cell's output voltage, and then a power management unit (PMU) delivers the boosted voltage to the load. Second, if the output voltage of a solar cell is enough to drive the load, the PMU directly supplies the load with solar energy. The proposed power management systems are designed and fabricated in a 0.18-μm complementary metal-oxide-semiconductor process, and their performances are compared and analysed through measurements.

X-ray tube voltage and image quality in adult and pediatric CT

NASA Astrophysics Data System (ADS)

Huda, W.; Ogden, K. M.; Scalzetti, E. M.; Lavallee, R. L.; Samei, E.

2006-03-01

The purpose of this study was to investigate how tissue x-ray attenuation coefficients, and their uncertainties, vary with x-ray tube voltage in different sized patients. Anthropomorphic phantoms (newborn, 10 year old, adult) were scanned a GE LightSpeed scanner at four x-ray tube voltages. Measurements were made of tissue attenuation in the head, chest and abdomen regions, as well as the corresponding noise values. Tissue signal to noise ratios (SNR) were obtained by dividing the average attenuation coefficient by the corresponding standard deviation. Soft tissue attenuation coefficients, relative to water, showed little variation with patient location or x-ray voltage (< 0.5%), but increasing the x-ray tube voltage from 80 to 140 kV reduced bone x-ray attenuation by ~14%. All tissues except adult bone showed a reduction of noise with increasing x-ray tube voltage (kV); the noise was found to be proportional to kV n and the average value of n for all tissues was -1.19 +/- 0.57. In pediatric patients at a constant x-ray tube voltage, SNR values were approximately independent of the body region, but the adult abdomen soft tissue SNR values were ~40% lower than the adult head. SNR values in the newborn were more than double the corresponding SNR soft tissue values in adults. SNR values for lung and bone were generally lower than those for soft tissues. For soft tissues, increasing the x-ray tube voltage from 80 to 140 kV increased the SNR by an average of ~90%. Data in this paper can be used to help design CT imaging protocols that take into account patient size and diagnostic imaging task.

Large area, low cost space solar cells with optional wraparound contacts

NASA Technical Reports Server (NTRS)

Michaels, D.; Mendoza, N.; Williams, R.

1981-01-01

Design parameters for two large area, low cost solar cells are presented, and electron irradiation testing, thermal alpha testing, and cell processing are discussed. The devices are a 2 ohm-cm base resistivity silicon cell with an evaporated aluminum reflector produced in a dielectric wraparound cell, and a 10 ohm-cm silicon cell with the BSF/BSR combination and a conventional contact system. Both cells are 5.9 x 5.9 cm and require 200 micron thick silicon material due to mission weight constraints. Normalized values for open circuit voltage, short circuit current, and maximum power calculations derived from electron radiation testing are given. In addition, thermal alpha testing values of absorptivity and emittance are included. A pilot cell processing run produced cells averaging 14.4% efficiencies at AMO 28 C. Manufacturing for such cells will be on a mechanized process line, and the area of coverslide application technology must be considered in order to achieve cost effective production.

The Use of Ratiometric Fluorescence Measurements of the Voltage Sensitive Dye Di-4-ANEPPS to Examine Action Potential Characteristics and Drug Effects on Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

PubMed

Hortigon-Vinagre, M P; Zamora, V; Burton, F L; Green, J; Gintant, G A; Smith, G L

2016-12-01

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and higher throughput platforms have emerged as potential tools to advance cardiac drug safety screening. This study evaluated the use of high bandwidth photometry applied to voltage-sensitive fluorescent dyes (VSDs) to assess drug-induced changes in action potential characteristics of spontaneously active hiPSC-CM. Human iPSC-CM from 2 commercial sources (Cor.4U and iCell Cardiomyocytes) were stained with the VSD di-4-ANEPPS and placed in a specialized photometry system that simultaneously monitors 2 wavebands of emitted fluorescence, allowing ratiometric measurement of membrane voltage. Signals were acquired at 10 kHz and analyzed using custom software. Action potential duration (APD) values were normally distributed in cardiomyocytes (CMC) from both sources though the mean and variance differed significantly (APD 90 : 229 ± 15 ms vs 427 ± 49 ms [mean ± SD, P < 0.01]; average spontaneous cycle length: 0.99 ± 0.02 s vs 1.47 ± 0.35 s [mean ± SD, P < 0.01], Cor.4U vs iCell CMC, respectively). The 10-90% rise time of the AP (T rise ) was ∼6 ms and was normally distributed when expressed as 1/[Formula: see text] in both cell preparations. Both cell types showed a rate dependence analogous to that of adult human cardiac cells. Furthermore, nifedipine, ranolazine, and E4031 had similar effects on cardiomyocyte electrophysiology in both cell types. However, ranolazine and E4031 induced early after depolarization-like events and high intrinsic firing rates at lower concentrations in iCell CMC. These data show that VSDs provide a minimally invasive, quantitative, and accurate method to assess hiPSC-CM electrophysiology and detect subtle drug-induced effects for drug safety screening while highlighting a need to standardize experimental protocols across preparations. © The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology.

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

NASA Technical Reports Server (NTRS)

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

1977-01-01

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.

Overcharge and overdischarge protection of ambient temperature secondary lithium cells

NASA Technical Reports Server (NTRS)

Huang, Chen-Kuo (Inventor); Surampudi, Subbarao (Inventor); Attia, Alan I. (Inventor); Halpert, Gerald (Inventor)

1994-01-01

A cathode additive is provided for protecting an ambient temperature secondary lithium cell from overcharging or overdischarging. The cathode additive is chosen to create an upper voltage plateau which is slightly higher than a characteristic charge cutoff voltage of the cathode of the cell. The cathode additive additionally creates a lower voltage plateau which is slightly lower than the characteristic discharge cutoff voltage of the cell. Preferably, the cathode additive is a transition metal oxide or a sulfide and may, for example, include a mixture of Li2Mn2O4 and Li(0.1)MoO2.

Performance of a dual anode nickel-hydrogen cell

NASA Technical Reports Server (NTRS)

Gahn, Randall F.

1991-01-01

An experimental study was conducted to characterize the voltage performance of a nickel hydrogen cell containing a hydrogen electrode on both sides of the nickel electrode. The dual anode cell was compared with a convenient single anode cell using the same nickel electrode. Higher discharge voltages and lower charge voltages were obtained with the dual anode cell during constant current discharges to 10C, pulse discharges to 8C, and polarization measurements at 50 percent of charge.

High-voltage solar-cell chip

NASA Technical Reports Server (NTRS)

Kapoor, V. J.; Valco, G. J.; Skebe, G. G.; Evans, J. C., Jr.

1985-01-01

Integrated circuit technology has been successfully applied to the design and fabrication of 0.5 x 0.5-cm planar multijunction solar-cell chips. Each of these solar cells consisted of six voltage-generating unit cells monolithically connected in series and fabricated on a 75-micron-thick, p-type, single crystal, silicon substrate. A contact photolithic process employing five photomask levels together with a standard microelectronics batch-processing technique were used to construct the solar-cell chip. The open-circuit voltage increased rapidly with increasing illumination up to 5 AM1 suns where it began to saturate at the sum of the individual unit-cell voltages at a maximum of 3.0 V. A short-circuit current density per unit cell of 240 mA/sq cm was observed at 10 AM1 suns.

Bio-wave change photo-voltages of the solar cells at same changed rate by probability effect of spacetime structure

NASA Astrophysics Data System (ADS)

Cao, Dayong

In our experiment, when light (of ``lamp LED'' 3W, 20cm away from the solar cells) simultaneous radiated on four solar cells, they would produce their photo-voltages which are called as background photo-voltages. And then, the author used thought wave to remotely (wireless) act on the four solar cells and increase four background photo-voltages at the same rates which is about 64%. After that, Adding the other light (of ``lamp CFL'') to simultaneous radiate on the four solar cells to changed their background photo-voltages. But there are different changed rates which will appear in the general experiments because the luminous sensitivities of the solar cell are different and the photo-voltages is a nonlinear function. The probability effects of the spacetime structure (of Confined Structural non-Newtonian Fluids) of brain wave (because the wave is spacetime) to change a balance structure between Electron Clouds and electron holes of P-N Junction, and change the background photo-voltages of the solar cells. In the experiments, the consciousness effect, and the relationship between brain wave and consciousness effect will be considered. After the decade of the brain research and the ``BRAIN'' Initiative, a decade of the consciousness need be taken. http://meetings.aps.org/Meeting/APR16/Session/M13.8 AEEA.

Improved High/Low Junction Silicon Solar Cell

NASA Technical Reports Server (NTRS)

Neugroschel, A.; Pao, S. C.; Lindholm, F. A.; Fossum, J. G.

1986-01-01

Method developed to raise value of open-circuit voltage in silicon solar cells by incorporating high/low junction in cell emitter. Power-conversion efficiency of low-resistivity silicon solar cell considerably less than maximum theoretical value mainly because open-circuit voltage is smaller than simple p/n junction theory predicts. With this method, air-mass-zero opencircuit voltage increased from 600 mV level to approximately 650 mV.

The Voltage Boost Enabled by Luminescence Extraction in Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganapati, Vidya; Steiner, Myles A.; Yablonovitch, Eli

A new physical principle has emerged to produce record voltages and efficiencies in photovoltaic cells, 'luminescence extraction.' This is exemplified by the mantra 'a good solar cell should also be a good LED.' Luminescence extraction is the escape of internal photons out of the front surface of a solar cell. Basic thermodynamics says that the voltage boost should be related to concentration ratio, C, of a resource by ..delta..V=(kT/q)ln{C}. In light trapping, (i.e. when the solar cell is textured and has a perfect back mirror) the concentration ratio of photons C={4n2}, so one would expect a voltage boost of ..delta..V=kTmore » ln{4n2} over a solar cell with no texture and zero back reflectivity, where n is the refractive index. Nevertheless, there has been ambiguity over the voltage benefit to be expected from perfect luminescence extraction. Do we gain an open circuit voltage boost of ..delta..V=(kT/q)ln{n2}, ..delta..V=(kT/q)ln{2n2}, or ..delta..V=(kT/q)ln{4n2}? What is responsible for this voltage ambiguity ..delta..V=(kT/q)ln{4}=36mVolts? We show that different results come about, depending on whether the photovoltaic cell is optically thin or thick to its internal luminescence. In realistic intermediate cases of optical thickness the voltage boost falls in between; ln{n2}q..delta..V/kT)<;ln{4n2}.« less

Nonlinear empirical model of gas humidity-related voltage dynamics of a polymer-electrolyte-membrane fuel cell stack

NASA Astrophysics Data System (ADS)

Meiler, M.; Andre, D.; Schmid, O.; Hofer, E. P.

Intelligent energy management is a cost-effective key path to realize efficient automotive drive trains [R. O'Hayre, S.W. Cha, W. Colella, F.B. Prinz. Fuel Cell Fundamentals, John Wiley & Sons, Hoboken, 2006]. To develop operating strategy in fuel cell drive trains, precise and computational efficient models of all system components, especially the fuel cell stack, are needed. Should these models further be used in diagnostic or control applications, then some major requirements must be fulfilled. First, the model must predict the mean fuel cell voltage very precisely in all possible operating conditions, even during transients. The model output should be as smooth as possible to support best efficient optimization strategies of the complete system. At least, the model must be computational efficient. For most applications, a difference between real fuel cell voltage and model output of less than 10 mV and 1000 calculations per second will be sufficient. In general, empirical models based on system identification offer a better accuracy and consume less calculation resources than detailed models derived from theoretical considerations [J. Larminie, A. Dicks. Fuel Cell Systems Explained, John Wiley & Sons, West Sussex, 2003]. In this contribution, the dynamic behaviour of the mean cell voltage of a polymer-electrolyte-membrane fuel cell (PEMFC) stack due to variations in humidity of cell's reactant gases is investigated. The validity of the overall model structure, a so-called general Hammerstein model (or Uryson model), was introduced recently in [M. Meiler, O. Schmid, M. Schudy, E.P. Hofer. Dynamic fuel cell stack model for real-time simulation based on system identification, J. Power Sources 176 (2007) 523-528]. Fuel cell mean voltage is calculated as the sum of a stationary and a dynamic voltage component. The stationary component of cell voltage is represented by a lookup-table and the dynamic voltage by a parallel placed, nonlinear transfer function. A suitable experimental setup to apply fast variations of gas humidity is introduced and is used to investigate a 10 cell PEMFC stack under various operation conditions. Using methods like stepwise multiple-regression a good mathematical description with reduced free parameters is achieved.

Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation

PubMed Central

Gryshkov, Oleksandr; Pogozhykh, Denys; Hofmann, Nicola; Pogozhykh, Olena; Mueller, Thomas; Glasmacher, Birgit

2014-01-01

Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×106 cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application. PMID:25259731

Anode reactive bleed and injector shift control strategy

DOEpatents

Cai, Jun [Rochester, NY; Chowdhury, Akbar [Pittsford, NY; Lerner, Seth E [Honeoye Falls, NY; Marley, William S [Rush, NY; Savage, David R [Rochester, NY; Leary, James K [Rochester, NY

2012-01-03

A system and method for correcting a large fuel cell voltage spread for a split sub-stack fuel cell system. The system includes a hydrogen source that provides hydrogen to each split sub-stack and bleed valves for bleeding the anode side of the sub-stacks. The system also includes a voltage measuring device for measuring the voltage of each cell in the split sub-stacks. The system provides two levels for correcting a large stack voltage spread problem. The first level includes sending fresh hydrogen to the weak sub-stack well before a normal reactive bleed would occur, and the second level includes sending fresh hydrogen to the weak sub-stack and opening the bleed valve of the other sub-stack when the cell voltage spread is close to stack failure.

Experimental investigation on On-Off current ratio behavior near onset voltage for a pentacene based organic thin film transistor

NASA Astrophysics Data System (ADS)

Amrani, Aumeur El; Es-saghiri, Abdeljabbar; Boufounas, El-Mahjoub; Lucas, Bruno

2018-06-01

The performance of a pentacene based organic thin film transistor (OTFT) with polymethylmethacrylate as a dielectric insulator and indium tin oxide based electrical gate is investigated. On the one hand, we showed that the threshold voltage increases with gate voltage, and on the other hand that it decreases with drain voltage. Thus, we noticed that the onset voltage shifts toward positive voltage values with the drain voltage increase. In addition, threshold-onset differential voltage (TODV) is proposed as an original approach to estimate an averaged carrier density in pentacene. Indeed, a value of about 4.5 × 1016 cm-3 is reached at relatively high gate voltage of -50 V; this value is in good agreement with that reported in literature with other technique measurements. However, at a low applied gate voltage, the averaged pentacene carrier density remains two orders of magnitude lower; it is of about 2.8 × 1014 cm-3 and remains similar to that obtained from space charge limited current approach for low applied bias voltage of about 2.2 × 1014 cm-3. Furthermore, high IOn/IOff and IOn/IOnset current ratios of 5 × 106 and 7.5 × 107 are reported for lower drain voltage, respectively. The investigated OTFTs also showed good electrical performance including carrier mobility increasing with gate voltage; mobility values of 4.5 × 10-2 cm2 V-1 s-1 and of 4.25 × 10-2 cm2 V-1 s-1 are reached for linear and saturation regimes, respectively. These results remain enough interesting since current modulation ratio exceeds a value of 107 that is a quite important requirement than high mobility for some particular logic gate applications.

Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations

PubMed Central

Fernandez, Fernando R.; Malerba, Paola; White, John A.

2015-01-01

The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances. PMID:25909971

Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations.

PubMed

Fernandez, Fernando R; Malerba, Paola; White, John A

2015-04-01

The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances.

Voltage Profiles for the Lead-Acid Cell: Experiment and Theory

NASA Astrophysics Data System (ADS)

Haaser, Robert; Ross, Joseph H.; Saslow, Wayne M.

1999-10-01

Using platinum electrodes we have measured the voltage profile in space across a lead-acid cell, for slow, steady processes. Once in the slow, steady charge or discharge regime, the experimental voltage profile is quadratic, as predicted by recent theory.^1 However, even without current flow, in the slow, steady regime the voltage profile also is quadratic, rather than a straight line with zero slope. This other quadratic voltage profile is due to nonfaradaic chemical reactions at the working electrodes, which slowly discharge the cell without drawing any current. Such a quadratic voltage profile follows from theory. The voltage jump profiles (change in voltage profile on sudden change in current) on starting or ending a charge or discharge, are linear in space, with slope consistent with the measured resistivity of battery acid. This is as expected if charge on the electrodes, but not in the electrolyte, has time to move. 1. W.M.Saslow, Phys.Rev.Lett.76, 4849 (1996).

Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Williamson, James M.; Trump, Darryl D.; Bletzinger, Peter; Ganguly, Biswa N.

2006-10-01

A surface dielectric barrier discharge (DBD) in atmospheric pressure air was excited either by low frequency (0.3-2 kHz) high-voltage ac or by short, high-voltage pulses at repetition rates from 50 to 600 pulses s-1. The short-pulse excited discharge was more diffuse and did not have the pronounced bright multiple cathode spots observed in the ac excited discharge. The discharge voltage, current and average power deposited into the discharge were calculated for both types of excitation. As a measure of plasma-chemical efficiency, the ozone number density was measured by UV absorption as a function of average deposited power. The density of ozone produced by ac excitation did not increase so rapidly as that produced by short-pulse excitation as a function of average power, with a maximum measured density of ~3 × 1015 cm-3 at 25 W. The maximum ozone production achieved by short-pulse excitation was ~8.5 × 1015 cm-3 at 20 W, which was four times greater than that achieved by ac excitation at the same power level.

Magnetopause reconnection rate estimates for Jupiter's magnetosphere based on interplanetary measurements at ~5AU

NASA Astrophysics Data System (ADS)

Nichols, J. D.; Cowley, S. W. H.; McComas, D. J.

2006-03-01

We make the first quantitative estimates of the magnetopause reconnection rate at Jupiter using extended in situ data sets, building on simple order of magnitude estimates made some thirty years ago by Brice and Ionannidis (1970) and Kennel and Coroniti (1975, 1977). The jovian low-latitude magnetopause (open flux production) reconnection voltage is estimated using the Jackman et al. (2004) algorithm, validated at Earth, previously applied to Saturn, and here adapted to Jupiter. The high-latitude (lobe) magnetopause reconnection voltage is similarly calculated using the related Gérard et al. (2005) algorithm, also previously used for Saturn. We employ data from the Ulysses spacecraft obtained during periods when it was located near 5AU and within 5° of the ecliptic plane (January to June 1992, January to August 1998, and April to October 2004), along with data from the Cassini spacecraft obtained during the Jupiter flyby in 2000/2001. We include the effect of magnetospheric compression through dynamic pressure modulation, and also examine the effect of variations in the direction of Jupiter's magnetic axis throughout the jovian day and year. The intervals of data considered represent different phases in the solar cycle, such that we are also able to examine solar cycle dependency. The overall average low-latitude reconnection voltage is estimated to be ~230 kV, such that the average amount of open flux created over one solar rotation is ~500 GWb. We thus estimate the average time to replenish Jupiter's magnetotail, which contains ~300-500 GWb of open flux, to be ~15-25 days, corresponding to a tail length of ~3.8-6.5 AU. The average high-latitude reconnection voltage is estimated to be ~130 kV, associated with lobe "stirring". Within these averages, however, the estimated voltages undergo considerable variation. Generally, the low-latitude reconnection voltage exhibits a "background" of ~100 kV that is punctuated by one or two significant enhancement events during each solar rotation, in which the voltage is elevated to ~1-3 MV. The high-latitude voltages are estimated to be about a half of these values. We note that the peak values of order a few MV are comparable to the potential drop due to sub-corotating plasma flows in the equatorial magnetosphere between ~20 RJ and the magnetopause, such that during these periods magnetopause reconnection may have a significant effect on the otherwise rotationally dominated magnetosphere. Despite such variations during each solar rotation, however, the total amount of open flux produced during each solar rotation varies typically by less than ~30% on either side of the overall average for that epoch. The averages over individual data epochs vary over the solar cycle from ~600 GWb per solar rotation at solar maximum to ~400 GWb at solar minimum. In addition we show that the IMF sector with positive clock angle is favoured for reconnection when the jovian spin axis clock angle is also positive, and vice versa, although this effect represents a first order correction to the voltage, which is primarily modulated by IMF strength and direction.

Report on Contract W911NF-05-1-0339 (Clarkson University)

DTIC Science & Technology

2012-11-30

voltammetry and impedance spectroscopy: voltage dependent parameters of a silicon solar cell under controlled illumination and temperature, Energy...voltammetry for quantitative evaluation of temperature and voltage dependent parameters of a silicon solar cell , Solar Energy, (11 2011): 0. doi: 10.1016...characterization of silicon solar cells in the electro-analytical approach: Combined measurements of temperature and voltage dependent electrical

Understanding capacity fade in silicon based electrodes for lithium-ion batteries using three electrode cells and upper cut-off voltage studies

NASA Astrophysics Data System (ADS)

Beattie, Shane D.; Loveridge, M. J.; Lain, Michael J.; Ferrari, Stefania; Polzin, Bryant J.; Bhagat, Rohit; Dashwood, Richard

2016-01-01

Commercial Li-ion batteries are typically cycled between 3.0 and 4.2 V. These voltages limits are chosen based on the characteristics of the cathode (e.g. lithium cobalt oxide) and anode (e.g. graphite). When alternative anode/cathode chemistries are studied the same cut-off voltages are often, mistakenly, used. Silicon (Si) based anodes are widely studied as a high capacity alternative to graphite for Lithium-ion batteries. When silicon-based anodes are paired with high capacity cathodes (e.g. Lithium Nickel Cobalt Aluminium Oxide; NCA) the cell typically suffers from rapid capacity fade. The purpose of this communication is to understand how the choice of upper cut-off voltage affects cell performance in Si/NCA cells. A careful study of three-electrode cell data will show that capacity fade in Si/NCA cells is due to an ever-evolving silicon voltage profile that pushes the upper voltage at the cathode to >4.4 V (vs. Li/Li+). This behaviour initially improves cycle efficiency, due to liberation of new lithium, but ultimately reduces cycling efficiency, resulting in rapid capacity fade.

Screen printing technology applied to silicon solar cell fabrication

NASA Technical Reports Server (NTRS)

Thornhill, J. W.; Sipperly, W. E.

1980-01-01

The process for producing space qualified solar cells in both the conventional and wraparound configuration using screen printing techniques was investigated. Process modifications were chosen that could be easily automated or mechanized. Work was accomplished to optimize the tradeoffs associated with gridline spacing, gridline definition and junction depth. An extensive search for possible front contact metallization was completed. The back surface field structures along with the screen printed back contacts were optimized to produce open circuit voltages of at least an average of 600 millivolts. After all intended modifications on the process sequence were accomplished, the cells were exhaustively tested. Electrical tests at AMO and 28 C were made before and after boiling water immersion, thermal shock, and storage under conditions of high temperature and high humidity.

COTS Li-Ion Cells in High Voltage Batteries

NASA Technical Reports Server (NTRS)

Davies, Francis; Darcy, Eric; Jeevarajan, Judy; Cowles, Phil

2003-01-01

Testing at NASA JSC and COMDEV shows that Commercial Off the Shelf (COTS) Li Ion cells can not be used in high voltage batteries safely without considering the voltage stresses that may be put on the protective devices in them during failure modes.

Investigation on the energy spectrums of electrons in atmospheric pressure argon plasma jets and their dependences on the applied voltage

NASA Astrophysics Data System (ADS)

Chen, Xinxian; Tan, Zhenyu; Liu, Yadi; Li, Xiaotong; Pan, Jie; Wang, Xiaolong

2017-08-01

This work presents a systematical investigation on the spatiotemporal evolution of the energy spectrum of electrons in atmospheric pressure argon plasma jets and its dependence on the applied voltage. The investigations are carried out by means of the numerical simulation based on a particle-in-cell Monte-Carlo collision model. The characteristics of the spatiotemporal evolution of the energy spectrum of electrons (ESE) in the discharge space have been presented, and especially the mechanisms of inducing these characteristics have also been revealed. The present work shows the following conclusions. In the evolution of ESE, there is a characteristic time under each applied voltage. Before the characteristic time, the peak value of ESE decreases, the peak position shifts toward high energy, and the distribution of ESE becomes wider and wider, but the reverse is true after the characteristic time. The formation of these characteristics can be mainly attributed to the transport of electrons toward a low electric field as well as a balance between the energy gained from the electric field including the effect of space charges and the energy loss due to inelastic collisions in the process of electron transport. The characteristic time decreases with the applied voltage. In addition, the average energy of electrons at the characteristic time can be increased by enhancing the applied voltage. The results presented in this work are of importance for regulating and controlling the energy of electrons in the plasma jets applied to plasma medicine.

Silicon anode for rechargeable aqueous lithium-air batteries

NASA Astrophysics Data System (ADS)

Teranishi, R.; Si, Q.; Mizukoshi, F.; Kawakubo, M.; Matsui, M.; Takeda, Y.; Yamamoto, O.; Imanishi, N.

2015-01-01

A novel aqueous lithium-air rechargeable cell with the configuration of Si/1 M LiClO4 in ethylene carbonate-diethylene carbonate/Li1+x+yAlx(Ti,Ge)2-xP3-ySiyO12/5 M LiCl-1 M LiOH aqueous solution/carbon black, air is proposed. A silicon anode composed of mechanically milled silicon power with an average particle size of ca. 0.5 μm, vapor grown carbon fiber and a polyimide binder was examined. The open-circuit voltage at the charged state was 2.9 V at 25 °C. The discharge capacity of 700 mAh g-silicon-1 was retained for 40 cycles at 0.3 mA cm-2 with cut-off voltages of 3.5 and 1.5 V. Significant capacity fade was observed at deep charge and discharge cycling at 2000 mAh g-silicon-1.

Rectification of Acetylcholine-Elicited Currents in PC12 Pheochromocytoma Cells

NASA Astrophysics Data System (ADS)

Ifune, C. K.; Steinbach, J. H.

1990-06-01

The current-voltage (I-V) relationship for acetylcholine-elicited currents in the rat pheochromocytoma cell line PC12 is nonlinear. Two voltage-dependent processes that could account for the whole-cell current rectification were examined, receptor channel gating and single receptor channel permeation. We found that both factors are involved in the rectification of the whole-cell currents. The voltage dependence of channel gating determines the shape of the I-V curve at negative potentials. The single-channel I-V relationship is inwardly rectifying and largely responsible for the characteristic shape of the whole-cell I-V curve at positive potentials. The rectification of the single-channel currents is produced by the voltage-dependent block of outward currents by intracellular Mg2+ ions.

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

NASA Technical Reports Server (NTRS)

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

1977-01-01

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.

Electrochemistry in a Nutshell: A General Chemistry Experiment.

ERIC Educational Resources Information Center

Baca, Glenn; Lewis, Dennis A.

1978-01-01

This experiment uses a nine-chambered plexiglas unit to facilitate rapid construction of galvanic cells and measurement of cell voltage. Using this procedure, a pair of students can construct and obtain the cell voltages of two precipitation cells, three concentration cells, and six redox cells in 30-40 minutes. (BB)

The Voltage Boost Enabled by Luminescence Extraction in Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganapati, Vidya; Steiner, Myles A.; Yablonovitch, Eli

Over the past few years, the application of the physical principle, i.e., 'luminescence extraction,' has produced record voltages and efficiencies in photovoltaic cells. Luminescence extraction is the use of optical design, such as a back mirror or textured surfaces, to help internal photons escape out of the front surface of a solar cell. The principle of luminescence extraction is exemplified by the mantra 'a good solar cell should also be a good LED.' Basic thermodynamics says that the voltage boost should be related to concentration ratio C of a resource by ΔV = (kT/q) ln{C}. In light trapping (i.e., when the solar cell is textured and has a perfect back mirror), the concentration ratio of photons C = {4n 2}; therefore, one would expect a voltage boost of ΔV = (kT/q) ln{4n 2} over a solar cell with no texture and zero back reflectivity, where n is the refractive index. Nevertheless, there has been ambiguity over the voltage benefit to be expected from perfect luminescence extraction. Do we gain an open-circuit voltage boost of ΔV = (kT/q) ln{n 2}, ΔV = (kT/q) ln{2 n 2}, or ΔV = (kT/q) ln{4 n 2}? What is responsible for this voltage ambiguity ΔV = (kT/q) ln{4}more » $${\\asymp}$$ 36 mV? Finally, we show that different results come about, depending on whether the photovoltaic cell is optically thin or thick to its internal luminescence. In realistic intermediate cases of optical thickness, the voltage boost falls in between: ln{n 2} < (qΔV/kT) < ln{4n 2}.« less

The Voltage Boost Enabled by Luminescence Extraction in Solar Cells

DOE PAGES

Ganapati, Vidya; Steiner, Myles A.; Yablonovitch, Eli

2016-07-01

Over the past few years, the application of the physical principle, i.e., 'luminescence extraction,' has produced record voltages and efficiencies in photovoltaic cells. Luminescence extraction is the use of optical design, such as a back mirror or textured surfaces, to help internal photons escape out of the front surface of a solar cell. The principle of luminescence extraction is exemplified by the mantra 'a good solar cell should also be a good LED.' Basic thermodynamics says that the voltage boost should be related to concentration ratio C of a resource by ΔV = (kT/q) ln{C}. In light trapping (i.e., when the solar cell is textured and has a perfect back mirror), the concentration ratio of photons C = {4n 2}; therefore, one would expect a voltage boost of ΔV = (kT/q) ln{4n 2} over a solar cell with no texture and zero back reflectivity, where n is the refractive index. Nevertheless, there has been ambiguity over the voltage benefit to be expected from perfect luminescence extraction. Do we gain an open-circuit voltage boost of ΔV = (kT/q) ln{n 2}, ΔV = (kT/q) ln{2 n 2}, or ΔV = (kT/q) ln{4 n 2}? What is responsible for this voltage ambiguity ΔV = (kT/q) ln{4}more » $${\\asymp}$$ 36 mV? Finally, we show that different results come about, depending on whether the photovoltaic cell is optically thin or thick to its internal luminescence. In realistic intermediate cases of optical thickness, the voltage boost falls in between: ln{n 2} < (qΔV/kT) < ln{4n 2}.« less

Method for improving fuel cell performance

DOEpatents

Uribe, Francisco A.; Zawodzinski, Thomas

2003-10-21

A method is provided for operating a fuel cell at high voltage for sustained periods of time. The cathode is switched to an output load effective to reduce the cell voltage at a pulse width effective to reverse performance degradation from OH adsorption onto cathode catalyst surfaces. The voltage is stepped to a value of less than about 0.6 V to obtain the improved and sustained performance.

Widely-duration-tunable nanosecond pulse Nd:YVO4 laser based on double Pockels cells

NASA Astrophysics Data System (ADS)

He, Li-Jiao; Liu, Ke; Bo, Yong; Wang, Xiao-Jun; Yang, Jing; Liu, Zhao; Zong, Qing-Shuang; Peng, Qin-Jun; Cui, Da-Fu; Xu, Zu-Yan

2018-05-01

The development of duration-tunable pulse lasers with constant output power is important for scientific research and materials processing. We present a widely-duration-tunable nanosecond (ns) pulse Nd:YVO4 laser based on double Pockels cells (PCs), i.e. inserting an extra PC into a conventional electro-optic Q-switched cavity dumped laser resonator. Under the absorbed pump power of 24.9 W, the pulse duration is adjustable from 31.9 ns to 5.9 ns by changing the amplitude of the high voltage on the inserted PC from 1100 V to 4400 V at the pulse repetition rate of 10 kHz. The corresponding average output power is almost entirely maintained in the range of 3.5–4.1 W. This represents more than three times increase in pulse duration tunable regime and average power compared to previously reported results for duration-tunable ns lasers. The laser beam quality factor was measured to be M 2  <  1.18.

Voltage controlling mechanisms in low resistivity silicon solar cells: A unified approach

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Swartz, C. K.; Hart, R. E.; Godlewski, M. P.

1984-01-01

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

Voltage controlling mechanisms in low resistivity silicon solar cells - A unified approach

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Swartz, C. K.; Hart, R. E.; Godlewski, M. P.

1984-01-01

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

NREL Collaboration Breaks 1-Volt Barrier in CdTe Solar Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

2016-05-01

NREL scientists have worked with Washington State University and the University of Tennessee to improve the maximum voltage available from CdTe solar cells. Changes in dopants, stoichiometry, interface design, and defect chemistry improved the CdTe conductivity and carrier lifetime by orders of magnitude, thus enabling CdTe solar cells with open-circuit voltages exceeding 1 volt for the first time. Values of current density and fill factor for CdTe solar cells are already at high levels, but sub-par voltages has been a barrier to improved efficiencies. With voltages pushed beyond 1 volt, CdTe cells have a path to produce electricity at costsmore » less than fossil fuels.« less

Single-Cell Electric Lysis on an Electroosmotic-Driven Microfluidic Chip with Arrays of Microwells

PubMed Central

Jen, Chun-Ping; Amstislavskaya, Tamara G.; Liu, Ya-Hui; Hsiao, Ju-Hsiu; Chen, Yu-Hung

2012-01-01

Accurate analysis at the single-cell level has become a highly attractive tool for investigating cellular content. An electroosmotic-driven microfluidic chip with arrays of 30-μm-diameter microwells was developed for single-cell electric lysis in the present study. The cellular occupancy in the microwells when the applied voltage was 5 V (82.4%) was slightly higher than that at an applied voltage of 10 V (81.8%). When the applied voltage was increased to 15 V, the cellular occupancy in the microwells dropped to 64.3%. More than 50% of the occupied microwells contain individual cells. The results of electric lysis experiments at the single-cell level indicate that the cells were gradually lysed as the DC voltage of 30 V was applied; the cell was fully lysed after 25 s. Single-cell electric lysis was demonstrated in the proposed microfluidic chip, which is suitable for high-throughput cell lysis. PMID:22969331

Pattern recognition monitoring of PEM fuel cell

DOEpatents

Meltser, M.A.

1999-08-31

The CO-concentration in the H{sub 2} feed stream to a PEM fuel cell stack is monitored by measuring current and voltage behavior patterns from an auxiliary cell attached to the end of the stack. The auxiliary cell is connected to the same oxygen and hydrogen feed manifolds that supply the stack, and discharges through a constant load. Pattern recognition software compares the current and voltage patterns from the auxiliary cell to current and voltage signature determined from a reference cell similar to the auxiliary cell and operated under controlled conditions over a wide range of CO-concentrations in the H{sub 2} fuel stream. 4 figs.

Pattern recognition monitoring of PEM fuel cell

DOEpatents

Meltser, Mark Alexander

1999-01-01

The CO-concentration in the H.sub.2 feed stream to a PEM fuel cell stack is monitored by measuring current and voltage behavior patterns from an auxiliary cell attached to the end of the stack. The auxiliary cell is connected to the same oxygen and hydrogen feed manifolds that supply the stack, and discharges through a constant load. Pattern recognition software compares the current and voltage patterns from the auxiliary cell to current and voltage signature determined from a reference cell similar to the auxiliary cell and operated under controlled conditions over a wide range of CO-concentrations in the H.sub.2 fuel stream.

Jitter compensation circuit

DOEpatents

Sullivan, James S.; Ball, Don G.

1997-01-01

The instantaneous V.sub.co signal on a charging capacitor is sampled and the charge voltage on capacitor C.sub.o is captured just prior to its discharge into the first stage of magnetic modulator. The captured signal is applied to an averaging circuit with a long time constant and to the positive input terminal of a differential amplifier. The averaged V.sub. co signal is split between a gain stage (G=0.975) and a feedback stage that determines the slope of the voltage ramp applied to the high speed comparator. The 97.5% portion of the averaged V.sub.co signal is applied to the negative input of a differential amplifier gain stage (G=10). The differential amplifier produces an error signal by subtracting 97.5% of the averaged V.sub.co signal from the instantaneous value of sampled V.sub.co signal and multiplying the difference by ten. The resulting error signal is applied to the positive input of a high speed comparator. The error signal is then compared to a voltage ramp that is proportional to the averaged V.sub.co values squared divided by the total volt-second product of the magnetic compression circuit.

Jitter compensation circuit

DOEpatents

Sullivan, J.S.; Ball, D.G.

1997-09-09

The instantaneous V{sub co} signal on a charging capacitor is sampled and the charge voltage on capacitor C{sub o} is captured just prior to its discharge into the first stage of magnetic modulator. The captured signal is applied to an averaging circuit with a long time constant and to the positive input terminal of a differential amplifier. The averaged V{sub co} signal is split between a gain stage (G = 0.975) and a feedback stage that determines the slope of the voltage ramp applied to the high speed comparator. The 97.5% portion of the averaged V{sub co} signal is applied to the negative input of a differential amplifier gain stage (G = 10). The differential amplifier produces an error signal by subtracting 97.5% of the averaged V{sub co} signal from the instantaneous value of sampled V{sub co} signal and multiplying the difference by ten. The resulting error signal is applied to the positive input of a high speed comparator. The error signal is then compared to a voltage ramp that is proportional to the averaged V{sub co} values squared divided by the total volt-second product of the magnetic compression circuit. 11 figs.

Calcium-dependent inactivation of calcium channels in cochlear hair cells of the chicken.

PubMed

Lee, Seunghwan; Briklin, Olga; Hiel, Hakim; Fuchs, Paul

2007-09-15

Voltage-gated calcium channels support both spontaneous and sound-evoked neurotransmitter release from ribbon synapses of cochlear hair cells. A variety of regulatory mechanisms must cooperate to ensure the appropriate level of activity in the restricted pool of synaptic calcium channels ( approximately 100) available to each synaptic ribbon. One potential feedback mechanism, calcium-dependent inactivation (CDI) of voltage-gated, L-type calcium channels, can be modulated by calmodulin-like calcium-binding proteins. CDI of voltage-gated calcium current was studied in hair cells of the chicken's basilar papilla (analogous to the mammalian cochlea) after blocking the predominant potassium conductances. For inactivating currents produced by 2.5 s steps to the peak of the current-voltage relation (1 mm EGTA internal calcium buffer), single exponential fits yielded an average decay time constant of 1.92 +/- 0.18 s (mean +/- s.e.m., n = 12) at 20-22 degrees C, while recovery occurred with a half-time of approximately 10 s. Inactivation produced no change in reversal potential, arguing that the observed relaxation did not result from alternative processes such as calcium accumulation or activation of residual potassium currents. Substitution of external calcium with barium greatly reduced inactivation, while inhibition of endoplasmic calcium pumps with t-benzohydroquinone (BHQ) or thapsigargin made inactivation occur faster and to a greater extent. Raising external calcium 10-fold (from 2 to 20 mm) increased peak current 3-fold, but did not alter the extent or time course of CDI. However, increasing levels of internal calcium buffer consistently reduced the rate and extent of inactivation. With 1 mm EGTA buffering and in 2 mm external calcium, the available pool of calcium channels was half-inactivated near the resting membrane potential (-50 mV). CDI may be further regulated by calmodulin-like calcium-binding proteins (CaBPs). mRNAs for several CaBPs are expressed in chicken cochlear tissue, and antibodies to CaBP4 label hair cells, but not supporting cells, equivalent to the pattern seen in mammalian cochlea. Thus, molecular mechanisms that underlie CDI appeared to be conserved across vertebrate species, may provide a means to adjust calcium channel open probability, and could serve to maintain the set-point for spontaneous release from the ribbon synapse.

Calcium-dependent inactivation of calcium channels in cochlear hair cells of the chicken

PubMed Central

Lee, Seunghwan; Briklin, Olga; Hiel, Hakim; Fuchs, Paul

2007-01-01

Voltage-gated calcium channels support both spontaneous and sound-evoked neurotransmitter release from ribbon synapses of cochlear hair cells. A variety of regulatory mechanisms must cooperate to ensure the appropriate level of activity in the restricted pool of synaptic calcium channels (∼100) available to each synaptic ribbon. One potential feedback mechanism, calcium-dependent inactivation (CDI) of voltage-gated, L-type calcium channels, can be modulated by calmodulin-like calcium-binding proteins. CDI of voltage-gated calcium current was studied in hair cells of the chicken's basilar papilla (analogous to the mammalian cochlea) after blocking the predominant potassium conductances. For inactivating currents produced by 2.5 s steps to the peak of the current–voltage relation (1 mm EGTA internal calcium buffer), single exponential fits yielded an average decay time constant of 1.92 ± 0.18 s (mean ±s.e.m., n = 12) at 20–22°C, while recovery occurred with a half-time of ∼10 s. Inactivation produced no change in reversal potential, arguing that the observed relaxation did not result from alternative processes such as calcium accumulation or activation of residual potassium currents. Substitution of external calcium with barium greatly reduced inactivation, while inhibition of endoplasmic calcium pumps with t-benzohydroquinone (BHQ) or thapsigargin made inactivation occur faster and to a greater extent. Raising external calcium 10-fold (from 2 to 20 mm) increased peak current 3-fold, but did not alter the extent or time course of CDI. However, increasing levels of internal calcium buffer consistently reduced the rate and extent of inactivation. With 1 mm EGTA buffering and in 2 mm external calcium, the available pool of calcium channels was half-inactivated near the resting membrane potential (−50 mV). CDI may be further regulated by calmodulin-like calcium-binding proteins (CaBPs). mRNAs for several CaBPs are expressed in chicken cochlear tissue, and antibodies to CaBP4 label hair cells, but not supporting cells, equivalent to the pattern seen in mammalian cochlea. Thus, molecular mechanisms that underlie CDI appeared to be conserved across vertebrate species, may provide a means to adjust calcium channel open probability, and could serve to maintain the set-point for spontaneous release from the ribbon synapse. PMID:17656437

Modification of back electrode with WO3 layer and its effect on Cu2ZnSn(S,Se)4-based solar cells

NASA Astrophysics Data System (ADS)

Shi, Kun; Yao, Bin; Li, Yongfeng; Ding, Zhanhui; Deng, Rui; Sui, Yingrui; Zhang, Zhenzhong; Zhao, Haifeng; Zhang, Ligong

2018-01-01

In the present work, we designed and prepared Cu2ZnSn(S,Se)4 (CZTSSe)-based solar cells with a new structure of Al/ITO/ZnO/CdS/CZTSSe/WO3/Mo/SLG (S1-5) by depositing about 5-nm-thick WO3 layer with monoclinic structure on the back electrode Mo/SLG of solar cells with the convention structure of Al/ITO/ZnO/CdS/CZTSSe/Mo/SLG (S2), with the aim of improving the power conversion efficiency (PCE) of CZTSSe-based solar cells. It is found that the average open circuit voltage (Voc) increases from 346.7 mV of the S2 cells to 400.9 mV of the S1-5 cells, the average short circuit current density (Jsc) from 26.4 mA/cm2 to 32.1 mA/cm2 and the filling factor (FF) from 33.8 to 40.0 by addition of the WO3 layer, which results in that the average PCE increases from 3.10% of the S2 cells to 5.14% of the S1-5 cells. The average increasing percent of the PCE is 65.8%. The increase in Voc, Jsc and FF of the S1-5 cells compared to the S2 cells is attributed to that the WO3 layer prevent the Se coming from Se ambient and CZTSSe to react with the Mo to form MoSe2 and other second phases, which makes the shunt resistance (Rsh) of the S1-5 increase and the series resistance (Rs) and reverse saturation current density (J0) decrease compared to the S2 cells. The decreased J0 is main factor of improvement of the PCE. A mechanism of influence of the Rsh, Rs and J0 on the PCE is also revealed. Our result demonstrates that addition of the WO3 layer with a reasonable thickness can be a promising technical route of improving the PCE of the CZTSSe-based solar cell.

Voltage equalization of an ultracapacitor module by cell grouping using number partitioning algorithm

NASA Astrophysics Data System (ADS)

Oyarbide, E.; Bernal, C.; Molina, P.; Jiménez, L. A.; Gálvez, R.; Martínez, A.

2016-01-01

Ultracapacitors are low voltage devices and therefore, for practical applications, they need to be used in modules of series-connected cells. Because of the inherent manufacturing tolerance of the capacitance parameter of each cell, and as the maximum voltage value cannot be exceeded, the module requires inter-cell voltage equalization. If the intended application suffers repeated fast charging/discharging cycles, active equalization circuits must be rated to full power, and thus the module becomes expensive. Previous work shows that a series connection of several sets of paralleled ultracapacitors minimizes the dispersion of equivalent capacitance values, and also the voltage differences between capacitors. Thus the overall life expectancy is improved. This paper proposes a method to distribute ultracapacitors with a number partitioning-based strategy to reduce the dispersion between equivalent submodule capacitances. Thereafter, the total amount of stored energy and/or the life expectancy of the device can be considerably improved.

Performance of a Dual Anode Nickel-Hydrogen Cell

NASA Technical Reports Server (NTRS)

Gahn, Randall F.

1991-01-01

Nickel-hydrogen batteries are presently being used for energy storage on satellites in low Earth orbit and in geosynchronous orbit, and have also been selected for use on the proposed Space Station Freedom. Development continues on the cell technology in order to improve the specific energy and lengthen the cycle life. An experimental study was conducted to compare the voltage performance of a nickel-hydrogen cell containing a dual anode with the standard cell design which uses a single hydrogen electrode. Since the principle voltage loss in a nickel-hydrogen cell is attributed to the mass transport and resistive polarization parameters of the nickel electrode, addition of a hydrogen electrode on the other side of the nickel electrode should reduce the electrochemical polarizations by a factor of two. A 3.5 in. diameter boilerplate cell with a single 30 mils thick nickel electrode was cycled under various current conditions to evaluate its performance with a single anode and then with a double anode. A layered separator consisting of one Zircar cloth separator and one radiation-grafted polyethylene separator were used between the electrodes. The electrolyte was 26% KOH, and the tests were done at room temperature. The discharge voltage characteristics were determined as a function of current and depth-of-discharge. At the 4C discharge rate and 50% DOD, the voltage of the dual anode cell was 100 mV higher than the single anode cell. At 75% DOD the dual anode cell voltage was about 130 mV higher than the standard cell design. Resistances of the two c ell designs obtained from the slope of the mid-discharge voltages plotted against various currents indicated that the dual anode cell resistance was one-half of the state-of-the-art cell.

Enhanced excitability and down-regulated voltage-gated potassium channels in colonic drg neurons from neonatal maternal separation rats.

PubMed

Luo, Jia-Lie; Qin, Hong-Yan; Wong, Chun-Kit; Tsang, Suk-Ying; Huang, Yu; Bian, Zhao-Xiang

2011-05-01

Irritable bowel syndrome (IBS), characterized mainly by abdominal pain, is a functional bowel disorder. The present study aimed to examine changes in the excitability and the activity of the voltage-gated K(+) channel in dorsal root ganglia (DRG) neurons innervating the colon of rats subjected to neonatal maternal separation (NMS). Colonic DRG neurons from NMS rats as identified by FAST DiI™ labeling showed an increased cell size compared with those from nonhandled (NH) rats. Whole cell current-clamp recordings showed that colonic DRG neurons from NMS rats displayed: 1) depolarized resting membrane potential; 2) increased input resistance; 3) a dramatic reduction in rheobase; and 4) a significant increase in the number of action potentials evoked at twice rheobase. Whole cell voltage-clamp recordings revealed that neurons from both groups exhibited transient A-type (I(A)) and delayed rectifier (I(K)) K(+) currents. Compared with NH rat neurons, the averaged density of I(K) was significantly reduced in NMS rat neurons. Furthermore, the Kv1.2 expression was significantly decreased in NMS rat colonic DRG neurons. These results suggest that NMS increases the excitability of colonic DRG neurons mainly by suppressing the I(K) current, which is likely accounted for by the downregulation of the Kv1.2 expression and somal hypertrophy. This study demonstrates the alteration of delayed rectifier K current and Kv1.2 expression in DRG neurons from IBS model rats, representing a molecular mechanism underlying visceral pain and sensitization in IBS, suggesting the potential of Kv1.2 as a therapeutic target for the treatment of IBS. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Imaging Neuronal Seal Resistance on Silicon Chip using Fluorescent Voltage-Sensitive Dye

PubMed Central

Braun, Dieter; Fromherz, Peter

2004-01-01

The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and by imaging the voltage change across the attached cell membrane with a fluorescent voltage-sensitive dye. The phase map of voltage change was fitted with a planar core-coat conductor model using the sheet resistance as a free parameter. For nerve cells from rat brain on polylysine as well as for HEK293 cells and MDCK cells on fibronectin we find a similar sheet resistance of 10 MΩ. Taking into account the independently measured distance of 50 nm between chip and membrane for these cells, we obtain a specific resistance of 50 Ωcm that is indistinguishable from bulk electrolyte. On the other hand, the sheet resistance for erythrocytes on polylysine is far higher, at ∼1.5 GΩ. Considering the distance of 10 nm, the specific resistance in the narrow cleft is enhanced to 1500 Ωcm. We find this novel optical method to be a convenient tool to optimize the interface between cells and chips for bioelectronic devices. PMID:15298937

Imaging neuronal seal resistance on silicon chip using fluorescent voltage-sensitive dye.

PubMed

Braun, Dieter; Fromherz, Peter

2004-08-01

The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and by imaging the voltage change across the attached cell membrane with a fluorescent voltage-sensitive dye. The phase map of voltage change was fitted with a planar core-coat conductor model using the sheet resistance as a free parameter. For nerve cells from rat brain on polylysine as well as for HEK293 cells and MDCK cells on fibronectin we find a similar sheet resistance of 10 MOmega. Taking into account the independently measured distance of 50 nm between chip and membrane for these cells, we obtain a specific resistance of 50 Omegacm that is indistinguishable from bulk electrolyte. On the other hand, the sheet resistance for erythrocytes on polylysine is far higher, at approximately 1.5 GOmega. Considering the distance of 10 nm, the specific resistance in the narrow cleft is enhanced to 1500 Omegacm. We find this novel optical method to be a convenient tool to optimize the interface between cells and chips for bioelectronic devices.

Liquid-Solid Dual-Gate Organic Transistors with Tunable Threshold Voltage for Cell Sensing.

PubMed

Zhang, Yu; Li, Jun; Li, Rui; Sbircea, Dan-Tiberiu; Giovannitti, Alexander; Xu, Junling; Xu, Huihua; Zhou, Guodong; Bian, Liming; McCulloch, Iain; Zhao, Ni

2017-11-08

Liquid electrolyte-gated organic field effect transistors and organic electrochemical transistors have recently emerged as powerful technology platforms for sensing and simulation of living cells and organisms. For such applications, the transistors are operated at a gate voltage around or below 0.3 V because prolonged application of a higher voltage bias can lead to membrane rupturing and cell death. This constraint often prevents the operation of the transistors at their maximum transconductance or most sensitive regime. Here, we exploit a solid-liquid dual-gate organic transistor structure, where the threshold voltage of the liquid-gated conduction channel is controlled by an additional gate that is separated from the channel by a metal-oxide gate dielectric. With this design, the threshold voltage of the "sensing channel" can be linearly tuned in a voltage window exceeding 0.4 V. We have demonstrated that the dual-gate structure enables a much better sensor response to the detachment of human mesenchymal stem cells. In general, the capability of tuning the optimal sensing bias will not only improve the device performance but also broaden the material selection for cell-based organic bioelectronics.

Advanced thermopower wave in novel ZnO nanostructures/fuel composite.

PubMed

Lee, Kang Yeol; Hwang, Hayoung; Choi, Wonjoon

2014-09-10

Thermopower wave is a new concept of energy conversion from chemical to thermal to electrical energy, produced from the chemical reaction in well-designed hybrid structures between nanomaterials and combustible fuels. The enhancement and optimization of energy generation is essential to make it useful for future applications. In this study, we demonstrate that simple solution-based synthesized zinc oxide (ZnO) nanostructures, such as nanorods and nanoparticles are capable of generating high output voltage from thermopower waves. In particular, an astonishing improvement in the output voltage (up to 3 V; average 2.3 V) was achieved in a ZnO nanorods-based composite film with a solid fuel (collodion, 5% nitrocellulose), which generated an exothermic chemical reaction. Detailed analyses of thermopower waves in ZnO nanorods- and cube-like nanoparticles-based hybrid composites have been reported in which nanostructures, output voltage profile, wave propagation velocities, and surface temperature have been characterized. The average combustion velocities for a ZnO nanorods/fuel and a ZnO cube-like nanoparticles/fuel composites were 40.3 and 30.0 mm/s, while the average output voltages for these composites were 2.3 and 1.73 V. The high output voltage was attributed to the amplified temperature in intermixed composite of ZnO nanostructures and fuel due to the confined diffusive heat transfer in nanostructures. Moreover, the extended interfacial areas between ZnO nanorods and fuel induced large amplification in the dynamic change of the chemical potential, and it resulted in the enhanced output voltage. The differences of reaction velocity and the output voltage between ZnO nanorods- and ZnO cube-like nanoparticles-based composites were attributed to variations in electron mobility and grain boundary, as well as thermal conductivities of ZnO nanorods and particles. Understanding this astonishing increase and the variation of the output voltage and reaction velocity, precise ZnO nanostructures, will help in formulating specific strategies for obtaining enhanced energy generation from thermopower waves.

Gap junctions in Malpighian tubules of Aedes aegypti.

PubMed

Weng, Xing-He; Piermarini, Peter M; Yamahiro, Atsuko; Yu, Ming-Jiun; Aneshansley, Daniel J; Beyenbach, Klaus W

2008-02-01

We present electrical, physiological and molecular evidence for substantial electrical coupling of epithelial cells in Malpighian tubules via gap junctions. Current was injected into one principal cell of the isolated Malpighian tubule and membrane voltage deflections were measured in that cell and in two neighboring principal cells. By short-circuiting the transepithelial voltage with the diuretic peptide leucokinin-VIII we largely eliminated electrical coupling of principal cells through the tubule lumen, thereby allowing coupling through gap junctions to be analyzed. The analysis of an equivalent electrical circuit of the tubule yielded an average gap-junction resistance (R(gj)) of 431 kOmega between two cells. This resistance would stem from 6190 open gap-junctional channels, assuming the high single gap-junction conductance of 375 pS found in vertebrate tissues. The addition of the calcium ionophore A23187 (2 micromol l(-1)) to the peritubular Ringer bath containing 1.7 mmol l(-1) Ca(2+) did not affect the gap-junction resistance, but metabolic inhibition of the tubule with dinitrophenol (0.5 mmol l(-1)) increased the gap-junction resistance 66-fold, suggesting the regulation of gap junctions by ATP. Lucifer Yellow injected into a principal cell did not appear in neighboring principal cells. Thus, gap junctions allow the passage of current but not Lucifer Yellow. Using RT-PCR we found evidence for the expression of innexins 1, 2, 3 and 7 (named after their homologues in Drosophila) in Malpighian tubules. The physiological demonstration of gap junctions and the molecular evidence for innexin in Malpighian tubules of Aedes aegypti call for the double cable model of the tubule, which will improve the measurement and the interpretation of electrophysiological data collected from Malpighian tubules.

Cell buffer with built-in test

NASA Technical Reports Server (NTRS)

Ott, William E. (Inventor)

2004-01-01

A cell buffer with built-in testing mechanism is provided. The cell buffer provides the ability to measure voltage provided by a power cell. The testing mechanism provides the ability to test whether the cell buffer is functioning properly and thus providing an accurate voltage measurement. The testing mechanism includes a test signal-provider to provide a test signal to the cell buffer. During normal operation, the test signal is disabled and the cell buffer operates normally. During testing, the test signal is enabled and changes the output of the cell buffer in a defined way. The change in the cell buffer output can then be monitored to determine if the cell buffer is functioning correctly. Specifically, if the voltage output of the cell buffer changes in a way that corresponds to the provided test signal, then the functioning of the cell buffer is confirmed. If the voltage output of the cell buffer does not change correctly, then the cell buffer is known not to be operating correctly. Thus, the built in testing mechanism provides the ability to quickly and accurately determine if the cell buffer is operating correctly. Furthermore, the testing mechanism provides this functionality without requiring excessive device size and complexity.

Controlling hazardous reactions during voltage reversal of high energy lithium cells

NASA Technical Reports Server (NTRS)

Domeniconi, M.

1983-01-01

The roll of general cell design characteristics in preventing hazardous reactions during voltage reversal of lithium cells is discussed. Anode limited versus cathode limited design and case positive versus case negative design are addressed.

In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

PubMed Central

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse. PMID:22163556

In-situ monitoring of internal local temperature and voltage of proton exchange membrane fuel cells.

PubMed

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm(2), and that with a sensor is 426 mW/cm(2). Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

Insulin increases excitability via a dose-dependent dual inhibition of voltage-activated K+ currents in differentiated N1E-115 neuroblastoma cells.

PubMed

Lima, Pedro A; Vicente, M Inês; Alves, Frederico M; Dionísio, José C; Costa, Pedro F

2008-04-01

A role in the control of excitability has been attributed to insulin via modulation of potassium (K(+)) currents. To investigate insulin modulatory effects on voltage-activated potassium currents in a neuronal cell line with origin in the sympathetic system, we performed whole-cell voltage-clamp recordings in differentiated N1E-115 neuroblastoma cells. Two main voltage-activated K(+) currents were identified: (a) a relatively fast inactivating current (I(fast) - time constant 50-300 ms); (b) a slow delayed rectifying K(+) current (I(slow) - time constant 1-4 s). The kinetics of inactivation of I(fast), rather than I(slow), showed clear voltage dependence. I(fast) and I(slow) exhibited different activation and inactivation dependence for voltage, and have different but nevertheless high sensitivities to tetraethylammonium, 4-aminopyridine and quinidine. In differentiated cells - rather than in non-differentiated cells - application of up to 300 nm insulin reduced I(slow) only (IC(50) = 6.7 nm), whereas at higher concentrations I(fast) was also affected (IC(50) = 7.7 microm). The insulin inhibitory effect is not due to a change in the activation or inactivation current-voltage profiles, and the time-dependent inactivation is also not altered; this is not likely to be a result of activation of the insulin-growth-factor-1 (IGF1) receptors, as application of IGF1 did not result in significant current alteration. Results suggest that the current sensitive to low concentrations of insulin is mediated by erg-like channels. Similar observations concerning the insulin inhibitory effect on slow voltage-activated K(+) currents were also made in isolated rat hippocampal pyramidal neurons, suggesting a widespread neuromodulator role of insulin on K(+) channels.

Monitoring electrolyte concentrations in redox flow battery systems

DOEpatents

Chang, On Kok; Sopchak, David Andrew; Pham, Ai Quoc; Kinoshita, Kimio

2015-03-17

Methods, systems and structures for monitoring, managing electrolyte concentrations in redox flow batteries are provided by introducing a first quantity of a liquid electrolyte into a first chamber of a test cell and introducing a second quantity of the liquid electrolyte into a second chamber of the test cell. The method further provides for measuring a voltage of the test cell, measuring an elapsed time from the test cell reaching a first voltage until the test cell reaches a second voltage; and determining a degree of imbalance of the liquid electrolyte based on the elapsed time.

Safety Performance of Small Lithium-Ion Cells in High Voltage Batteries

NASA Technical Reports Server (NTRS)

Cowles, Philip R.; Darcy, Eric C.; Davies, Frank J.; Jeevarajan, Judith A.; Spurrett, Robert P.

2003-01-01

Topics covered include: Small-cell EAPU work done by NASA-JSC & COM DEV; Looking at safety features (short circuit protection - PTCs); Early tests showed that long strings do not withstand short circuit; a) Some PTCs experience large negative voltages; b) Destructive results. Solution: group cells into shorter substrings, with bypass diodes Work included: a) Tests with single cells shorted; b) Tests with single cells with imposed-negative voltages; c) 6s, 7s and 8s string shorts; and d) Tests with protection scheme in place, on 12s and 41s x 5p.

Zero-voltage DC/DC converter with asymmetric pulse-width modulation for DC micro-grid system

NASA Astrophysics Data System (ADS)

Lin, Bor-Ren

2018-04-01

This paper presents a zero-voltage switching DC/DC converter for DC micro-grid system applications. The proposed circuit includes three half-bridge circuit cells connected in primary-series and secondary-parallel in order to lessen the voltage rating of power switches and current rating of rectifier diodes. Thus, low voltage stress of power MOSFETs can be adopted for high-voltage input applications with high switching frequency operation. In order to achieve low switching losses and high circuit efficiency, asymmetric pulse-width modulation is used to turn on power switches at zero voltage. Flying capacitors are used between each circuit cell to automatically balance input split voltages. Therefore, the voltage stress of each power switch is limited at Vin/3. Finally, a prototype is constructed and experiments are provided to demonstrate the circuit performance.

The planar multijunction cell - A new solar cell for earth and space

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr.; Chai, A.-T.; Goradia, C.

1980-01-01

A new family of high-voltage solar cells, called the planar multijunction (PMJ) cell is being developed. The new cells combine the attractive features of planar cells with conventional or interdigitated back contacts and the vertical multijunction (VMJ) solar cell. The PMJ solar cell is internally divided into many voltage-generating regions, called unit cells, which are internally connected in series. The key to obtaining reasonable performance from this device was the separation of top surface field regions over each active unit cell area. Using existing solar cell fabricating methods, output voltages in excess of 20 volts per linear centimeter are possible. Analysis of the new device is complex, and numerous geometries are being studied which should provide substantial benefits in both normal sunlight usage as well as with concentrators.

Voltage-gated calcium flux mediates Escherichia coli mechanosensation.

PubMed

Bruni, Giancarlo N; Weekley, R Andrew; Dodd, Benjamin J T; Kralj, Joel M

2017-08-29

Electrically excitable cells harness voltage-coupled calcium influx to transmit intracellular signals, typically studied in neurons and cardiomyocytes. Despite intense study in higher organisms, investigations of voltage and calcium signaling in bacteria have lagged due to their small size and a lack of sensitive tools. Only recently were bacteria shown to modulate their membrane potential on the timescale of seconds, and little is known about the downstream effects from this modulation. In this paper, we report on the effects of electrophysiology in individual bacteria. A genetically encoded calcium sensor expressed in Escherichia coli revealed calcium transients in single cells. A fusion sensor that simultaneously reports voltage and calcium indicated that calcium influx is induced by voltage depolarizations, similar to metazoan action potentials. Cytoplasmic calcium levels and transients increased upon mechanical stimulation with a hydrogel, and single cells altered protein concentrations dependent on the mechanical environment. Blocking voltage and calcium flux altered mechanically induced changes in protein concentration, while inducing calcium flux reproduced these changes. Thus, voltage and calcium relay a bacterial sense of touch and alter cellular lifestyle. Although the calcium effectors remain unknown, these data open a host of new questions about E. coli , including the identity of the underlying molecular players, as well as other signals conveyed by voltage and calcium. These data also provide evidence that dynamic voltage and calcium exists as a signaling modality in the oldest domain of life, and therefore studying electrophysiology beyond canonical electrically excitable cells could yield exciting new findings.

Voltage-gated calcium flux mediates Escherichia coli mechanosensation

PubMed Central

Weekley, R. Andrew; Dodd, Benjamin J. T.

2017-01-01

Electrically excitable cells harness voltage-coupled calcium influx to transmit intracellular signals, typically studied in neurons and cardiomyocytes. Despite intense study in higher organisms, investigations of voltage and calcium signaling in bacteria have lagged due to their small size and a lack of sensitive tools. Only recently were bacteria shown to modulate their membrane potential on the timescale of seconds, and little is known about the downstream effects from this modulation. In this paper, we report on the effects of electrophysiology in individual bacteria. A genetically encoded calcium sensor expressed in Escherichia coli revealed calcium transients in single cells. A fusion sensor that simultaneously reports voltage and calcium indicated that calcium influx is induced by voltage depolarizations, similar to metazoan action potentials. Cytoplasmic calcium levels and transients increased upon mechanical stimulation with a hydrogel, and single cells altered protein concentrations dependent on the mechanical environment. Blocking voltage and calcium flux altered mechanically induced changes in protein concentration, while inducing calcium flux reproduced these changes. Thus, voltage and calcium relay a bacterial sense of touch and alter cellular lifestyle. Although the calcium effectors remain unknown, these data open a host of new questions about E. coli, including the identity of the underlying molecular players, as well as other signals conveyed by voltage and calcium. These data also provide evidence that dynamic voltage and calcium exists as a signaling modality in the oldest domain of life, and therefore studying electrophysiology beyond canonical electrically excitable cells could yield exciting new findings. PMID:28808010

Method and Apparatus for In-Situ Health Monitoring of Solar Cells in Space

NASA Technical Reports Server (NTRS)

Prokop, Norman F. (Inventor); Krasowski, Michael J. (Inventor)

2016-01-01

Embodiments of the present invention describe an apparatus including an oscillator, a ramp generator, and an inverter. The oscillator is configured to generate a waveform comprising a low time and a high time. The inverter is configured to receive the waveform generated by the oscillator, and invert the waveform. The ramp generator is configured to increase a gate control voltage of a transistor connected to a solar cell, and rapidly decrease the gate control voltage of the transistor. During the low time, a measurement of a current and a voltage of the solar cell is performed. During the high time, a measurement of a current of a shorted cell and a voltage reference is performed.

Study to define low voltage and low temperature operating limits of the Pioneer 10/11 Meteoroid Detection Equipment (MDE) system

NASA Technical Reports Server (NTRS)

Parker, C. D.

1975-01-01

The Pioneer 10/11 meteoroid detection equipment (MDE) pressure cells were tested at liquid nitrogen (LN2) and liquid helium (LHe) temperatures with the excitation voltage controlled as a parameter. The cells failed by firing because of pressurizing gas condensation as the temperature was lowered from LN2 to LHe temperature and when raised from LHe temperature. A study was conducted to determine cell pressure as a function of temperature, and cell failure was estimated as a function of temperature and excitation voltage. The electronic system was also studied, and a profile of primary spacecraft voltage (nominally 28 Vdc) and temperature corresponding to electronic system failure was determined experimentally.

NASA/GSFC Testing of Li-Ion Cells: Update

NASA Technical Reports Server (NTRS)

Vaidyanathan, Hari; Rao, Gopalakrishna M.

2001-01-01

This viewgraph paper presents a report on the ongoing testing of Lithium Ion (Li-Ion) cells. Characterizes cells according to capacity, self-discharge, and mid-discharge voltage. Determines the cycling performance of Li-Ion cells as batteries according to number of cycles, charge voltage, and temperature.

The Design and Development of the SMEX-Lite Power System

NASA Technical Reports Server (NTRS)

Rakow, Glenn P.; Schnurr, Richard G., Jr.; Solly, Michael A.

1998-01-01

This paper describes the design and development of a 250W orbit average electrical power system electronic Power Node and software for use in Low Earth Orbit missions. The mass of the Power Node is 3.6 Kg (8 lb.). The dimensions of the Power Node are 30cm x 26cm x 7.9cm (11 in. x 10.25 in x 3.1 in.) The design was realized using software, Field Programmable Gate Array (FPGA) digital logic and surface mount technology. The design is generic enough to reduce the non-recurring engineering for different mission configurations. The Power Node charges one to five, low cost, 22-cell 4 AH D-cell battery packs independently. The battery charging algorithms are executed in the power software to reduce the mass and size of the power electronic. The Power Node implements a peak-power tracking algorithm using an innovative hardware/software approach. The power software task is hosted on the spacecraft processor. The power software task generates a MIL-STD-1553 command packet to update the Power Node control settings. The settings for the battery voltage and current limits, as well as minimum solar array voltage used to implement peak power tracking are contained in this packet. Several advanced topologies are used in the Power Node. These include synchronous rectification in the bus regulators, average current control in the battery chargers and quasi-resonant converters for the Field Effect Transistor (FET) transistor drive electronics. Lastly, the main bus regulator uses a feed-forward topology with the PWM implemented in an FPGA.

Consciousness can reduce the voltage of the output signal of solar cell

NASA Astrophysics Data System (ADS)

Cao, Dayong

2011-03-01

When the sun's light radiate on the solar cell, it can produce the output signal as the pho- tocurrent. We use the Data Acquisition Modules to record the voltage of the output signals. The v1 is voltage of the photocurrent of solar cell1; The v2 is the one of solar cell2. And these two solar cells stay side by side. When we record the voltages from the morning to the noon, the voltages will go up, and the v1 is bigger than the v2 during this time. But in other experi- menter, not only sun's light ratiade on two solar cells, but also consciousness act on two solar cells. Not only I can use consciousness to reduce the growth voltage of the output signals, but also can change the v1 to be littler than the v2. The experiment was conducted on Sep. 2010. When light of lamp radiate on two solar cells, I can reduce v1, at the same time, can augment v2. These experiments had been finished in Los Angeles, Oct. 26th. And the experiment show that the consciousness active function differ from the passive function of conditioned reflex (of Pavlov). There is the physical system of the mass, energy, space and time-MEST; There is the spirited system of the mind, consciousness, emotion and desire-MECD; the information system is the code system. We can use the consciousness change the electron-structure of solar cell by the interaction of the information.

Water-activated graphite felt as a high-performance electrode for vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Kabtamu, Daniel Manaye; Chen, Jian-Yu; Chang, Yu-Chung; Wang, Chen-Hao

2017-02-01

A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as sbnd OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge-discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm-2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.

A Highly Active Low Voltage Redox Mediator for Enhanced Rechargeability of Lithium-Oxygen Batteries.

PubMed

Kundu, Dipan; Black, Robert; Adams, Brian; Nazar, Linda F

2015-12-23

Owing to its high theoretical specific energy, the Li-oxygen battery is one of the fundamentally most promising energy storage systems, but also one of the most challenging. Poor rechargeability, involving the oxidation of insoluble and insulating lithium peroxide (Li2O2), has remained the "Achilles' heel" of this electrochemical energy storage system. We report here on a new redox mediator tris[4-(diethylamino)phenyl]amine (TDPA), that-at 3.1 V-exhibits the lowest and closest potential redox couple compared to the equilibrium voltage of the Li-oxygen cell of those reported to date, with a second couple also at a low potential of 3.5 V. We show it is a soluble "catalyst" capable of lowering the Li2O2 charging potential by >0.8 V without requiring direct electrical contact of the peroxide and that it also facilitates high discharge capacities. Its chemical and electrochemical stability, fast diffusion kinetics, and two dynamic redox potentials represent a significant advance in oxygen-evolution catalysis. It enables Li-O2 cells that can be recharged more than 100 cycles with average round-trip efficiencies >80%, opening a new avenue for practical Li-oxygen batteries.

Long-term durability of HT-PEM fuel cells based on thermally cross-linked polybenzimidazole

NASA Astrophysics Data System (ADS)

Søndergaard, Tonny; Cleemann, Lars Nilausen; Becker, Hans; Aili, David; Steenberg, Thomas; Hjuler, Hans Aage; Seerup, Larisa; Li, Qingfeng; Jensen, Jens Oluf

2017-02-01

Long-term durability of high temperature polymer electrolyte membrane fuel cells based on thermally cross-linked polybenzimidazole membranes was studied and compared with reference membranes based on linear polybenzimidazole. The test was conducted at 160 °C under constant load currents of 200 mA cm-2 for periods of 1000, 4400, and 13,000 h. Extensive beginning-of-life (BoL) and end-of-test (EoT) characterisation was carried out, and disturbance of the steady state operated cells was minimised by limiting in-line diagnostics to the low-invasive technique of electrochemical impedance spectroscopy (EIS). Up until the operating time of 9200 h, the cell equipped with the cross-linked membrane showed an average degradation rate of 0.5 μV h-1, compared to 2.6 μV h-1 for the reference membrane, though parallel tests for a shorter period of time showed deviations, likely due to malfunctioning contact between layers or cell components. For the full test period of 13,000 h, the average voltage decay rate was about 1.4 and 4.6 μV h-1 for cells equipped with cross-linked and linear polybenzimidazole membranes, respectively. EIS and post-test analysis revealed that the cross-linked membrane showed better stability in terms of area specific resistance due to improved acid retention characteristics.

Review of the U.S. Department of Energy's "Deep Dive" Effort to Understand Voltage Fade in Li- and Mn-rich Cathodes

DOE PAGES

Croy, Jason R.; Balasubramanian, Mahalingam; Gallagher, Kevin G.; ...

2015-11-01

With roughly two-thirds of daily oil consumption in the United States allotted for transportation, the possibility of efficient and affordable electric vehicles suggests a way to substantially alleviate the Country’s dependence on oil and mitigate the rise of greenhouse gases. Although commercialized Li-ion batteries do not currently meet the stringent demands of a would-be, economically competitive, electrified vehicle fleet, significant efforts are being focused on promising new materials for the next generation of Li-ion batteries. The leading class of materials most suitable for the challenge is the Li- and manganese-rich class of oxides. Denoted as LMR-NMC (Li-manganese-rich, nickel, manganese, cobalt),more » these materials could significantly improve energy densities, cost, and safety, relative to state-of-the-art Ni- and Co-rich Li-ion cells, if successfully developed.1 The success or failure of such a development relies heavily on understanding two defining characteristics of LMR-NMC cathodes. The first is a mechanism whereby the average voltage of cells continuously decreases with each successive charge and discharge cycle. This phenomenon, known as voltage fade, decreases the energy output of cells to unacceptable levels too early in cycling. The second characteristic is a pronounced hysteresis, or voltage difference, between charge and discharge cycles. The hysteresis represents not only an energy inefficiency (i.e., energy in vs energy out) but may also complicate the state of charge/depth of discharge management of larger systems, especially when accompanied by voltage fade. n 2012, the United States Department of Energy’s Office of Vehicle Technologies, well aware of the inherent potential of LMR-NMC materials for improving the energy density of automotive energy storage systems, tasked a team of scientists across the National Laboratory Complex to investigate the phenomenon of voltage fade. Unique studies using synchrotron X-ray absorption (XAS) and high-resolution diffraction (HR-XRD) were coupled with nuclear magnetic resonance spectroscopy (NMR), neutron diffraction, high-resolution transmission electron microscopy (HR-TEM), first-principles calculations, molecular dynamics simulations, and detailed electrochemical analyses. These studies demonstrated for the first time the atomic-scale, structure–property relationships that exist between nanoscale inhomogeneities and defects, and the macroscale, electrochemical performance of these layered oxides. These inhomogeneities and defects have been directly correlated with voltage fade and hysteresis, and a model describing these mechanisms has been proposed. This Account gives a brief summary of the findings of this recently concluded, approximately three-year investigation. Lastly, the interested reader is directed to the extensive body of work cited in the given references for a more comprehensive review of the subject.« less

Electrolyte for high voltage Li/LiMn 1.9Co 0.1O 4 cells

NASA Astrophysics Data System (ADS)

Hayashi, Katsuya; Nemoto, Yasue; Tobishima, Shin-ichi; Yamaki, Jun-ichi

An electrolyte for high voltage lithium metal anode cells must simultaneously satisfy at least the following requirements; (i) high cycling efficiency on the lithium metal anode; (ii) higher oxidation potential than the charging voltage, and (iii) high specific conductivity. We have examined various electrolytes for lithium metal anode cells using a high voltage cathode, LiMn 1.9Co 0.1O 4. Of the electrolytes resistant to high voltage that we used, a system containing 60 to 90 vol.% of dimethyl carbonate (DMC) mixed with ethylene carbonate (EC) and 1.0 M lithium hexafluorophosphate (LiPF 6) provided the best cycling efficiency on a lithium metal anode, as well as a high specific conductivity around 10 mS cm -1 at 20 °C.

Silicon Photomultiplier charaterization

NASA Astrophysics Data System (ADS)

Munoz, Leonel; Osornio, Leo; Para, Adam

2014-03-01

Silicon Photo Multiples (SiPM's) are relatively new photon detectors. They offer many advantages compared to photo multiplier tubes (PMT's) such as insensitivity to magnetic field, robustness at varying lighting levels, and low cost. The SiPM output wave forms are poorly understood. The experiment conducted collected waveforms of responses of Hamamatsu SiPM to incident laser pulse at varying temperatures and bias voltages. Ambient noise was characterized at all temperatures and bias voltages by averaging the waveforms. Pulse shape of the SiPM response was determined under different operating conditions: the pulse shape is nearly independent of the bias voltage but exhibits strong variation with temperature, consistent with the temperature variation of the quenching resistor. Amplitude of responses of the SiPM to low intensity laser light shows many peaks corresponding to the detection of 1,2,3 etc. photons. Amplitude of these pulses depends linearly on the bias voltage, enabling determination of the breakdown voltage at each temperature. Poisson statistics has been used to determine the average number of detected photons at each operating conditions. Department of Education Grant No. P0315090007 and the Department of Energy/ Fermi National Accelerator Laboratory.

Design of high breakdown voltage GaN vertical HFETs with p-GaN buried buffer layers for power switching applications

NASA Astrophysics Data System (ADS)

Du, Jiangfeng; Liu, Dong; Zhao, Ziqi; Bai, Zhiyuan; Li, Liang; Mo, Jianghui; Yu, Qi

2015-07-01

To achieve a high breakdown voltage, a GaN vertical heterostructure field effect transistor with p-GaN buried layers (PBL-VHFET) is proposed in this paper. The breakdown voltage of this GaN-based PBL-VHFET could be improved significantly by the optimizing thickness of p-GaN buried layers and doping concentration in PBL. When the GaN buffer layer thickness is 15 μm, the thickness, length and p-doping concentration of PBL are 0.3 μm, 2.7 μm, and 3 × 1017 cm-3, respectively. Simulation results show that the breakdown voltage and on-resistance of the device with two p-GaN buried layers are 3022 V and 3.13 mΩ cm2, respectively. The average breakdown electric field would reach as high as 201.5 V/μm. Compared with the typical GaN vertical heterostructure FETs without PBL, both of breakdown voltage and average breakdown electric field of device are increased more than 50%.

Quantitative Analysis Method of Output Loss due to Restriction for Grid-connected PV Systems

NASA Astrophysics Data System (ADS)

Ueda, Yuzuru; Oozeki, Takashi; Kurokawa, Kosuke; Itou, Takamitsu; Kitamura, Kiyoyuki; Miyamoto, Yusuke; Yokota, Masaharu; Sugihara, Hiroyuki

Voltage of power distribution line will be increased due to reverse power flow from grid-connected PV systems. In the case of high density grid connection, amount of voltage increasing will be higher than the stand-alone grid connection system. To prevent the over voltage of power distribution line, PV system's output will be restricted if the voltage of power distribution line is close to the upper limit of the control range. Because of this interaction, amount of output loss will be larger in high density case. This research developed a quantitative analysis method for PV systems output and losses to clarify the behavior of grid connected PV systems. All the measured data are classified into the loss factors using 1 minute average of 1 second data instead of typical 1 hour average. Operation point on the I-V curve is estimated to quantify the loss due to the output restriction using module temperature, array output voltage, array output current and solar irradiance. As a result, loss due to output restriction is successfully quantified and behavior of output restriction is clarified.

Lithium-tellurium bimetallic cell has increased voltage

NASA Technical Reports Server (NTRS)

Cairns, E. J.; Rogers, G. L.; Shimotake, H.

1968-01-01

Lithium-tellurium secondary cell with a fused lithium halide electrolyte, tested in the temperature range 467 degrees to 500 degrees C, showed improvement over the sodium bismuth cell. The voltage of this bimetallic cell was increased by using the more electropositive anode material, lithium, and the more electronegative cathode material, tellurium.

Method for reducing fuel cell output voltage to permit low power operation

DOEpatents

Reiser, Carl A.; Landau, Michael B.

1980-01-01

Fuel cell performance is degraded by recycling a portion of the cathode exhaust through the cells and, if necessary, also reducing the total air flow to the cells for the purpose of permitting operation below a power level which would otherwise result in excessive voltage.

Continuous-flow multi-pulse electroporation at low DC voltages by microfluidic flipping of the voltage space topology

NASA Astrophysics Data System (ADS)

Bhattacharjee, N.; Horowitz, L. F.; Folch, A.

2016-10-01

Concerns over biosafety, cost, and carrying capacity of viral vectors have accelerated research into physical techniques for gene delivery such as electroporation and mechanoporation. Advances in microfabrication have made it possible to create high electric fields over microscales, resulting in more efficient DNA delivery and higher cell viability. Continuous-flow microfluidic methods are typically more suitable for cellular therapies where a large number of cells need to be transfected under sterile conditions. However, the existing continuous-flow designs used to generate multiple pulses either require expensive peripherals such as high-voltage (>400 V) sources or function generators, or result in reduced cell viability due to the proximity of the cells to the electrodes. In this paper, we report a continuous-flow microfluidic device whose channel geometry reduces instrumentation demands and minimizes cellular toxicity. Our design can generate multiple pulses of high DC electric field strength using significantly lower voltages (15-60 V) than previous designs. The cells flow along a serpentine channel that repeatedly flips the cells between a cathode and an anode at high throughput. The cells must flow through a constriction each time they pass from an anode to a cathode, exposing them to high electric field strength for short durations of time (the "pulse-width"). A conductive biocompatible poly-aniline hydrogel network formed in situ is used to apply the DC voltage without bringing the metal electrodes close to the cells, further sheltering cells from the already low voltage electrodes. The device was used to electroporate multiple cell lines using electric field strengths between 700 and 800 V/cm with transfection efficiencies superior than previous flow-through designs.

Continuous-flow multi-pulse electroporation at low DC voltages by microfluidic flipping of the voltage space topology.

PubMed

Bhattacharjee, N; Horowitz, L F; Folch, A

2016-10-17

Concerns over biosafety, cost, and carrying capacity of viral vectors have accelerated research into physical techniques for gene delivery such as electroporation and mechanoporation. Advances in microfabrication have made it possible to create high electric fields over microscales, resulting in more efficient DNA delivery and higher cell viability. Continuous-flow microfluidic methods are typically more suitable for cellular therapies where a large number of cells need to be transfected under sterile conditions. However, the existing continuous-flow designs used to generate multiple pulses either require expensive peripherals such as high-voltage (>400 V) sources or function generators, or result in reduced cell viability due to the proximity of the cells to the electrodes. In this paper, we report a continuous-flow microfluidic device whose channel geometry reduces instrumentation demands and minimizes cellular toxicity. Our design can generate multiple pulses of high DC electric field strength using significantly lower voltages (15-60 V) than previous designs. The cells flow along a serpentine channel that repeatedly flips the cells between a cathode and an anode at high throughput. The cells must flow through a constriction each time they pass from an anode to a cathode, exposing them to high electric field strength for short durations of time (the "pulse-width"). A conductive biocompatible poly-aniline hydrogel network formed in situ is used to apply the DC voltage without bringing the metal electrodes close to the cells, further sheltering cells from the already low voltage electrodes. The device was used to electroporate multiple cell lines using electric field strengths between 700 and 800 V/cm with transfection efficiencies superior than previous flow-through designs.

Alteration of the fast excitatory postsynaptic current by barium in voltage-clamped amphibian sympathetic ganglion cells.

PubMed Central

Connor, E. A.; Parsons, R. L.

1984-01-01

Barium-induced alterations in fast excitatory postsynaptic currents (e.p.s.cs) have been studied in voltage-clamped bullfrog sympathetic ganglion B cells. In the presence of 2-8 mM barium, e.p.s.c. decay was prolonged and in many cells the e.p.s.c. decay phase deviated from a single exponential function. The decay phase in these cases was more accurately described as the sum of two exponential functions. The frequency of occurrence of a complex decay increased both with increasing barium concentration and with hyperpolarization. Miniature e.p.s.c. decay also was prolonged in barium-treated cells. E.p.s.c. amplitude was not markedly affected by barium (2-8 mM) in cells voltage-clamped to -50 mV whereas at -90 mV there was a progressive increase in peak size with increasing barium concentration. In control cells the e.p.s.c.-voltage relationship was linear between -20 and -100 mV; however, this relationship became progressively non-linear with membrane hyperpolarization in barium-treated cells. The e.p.s.c. reversal potential was shifted to a more negative value in the presence of barium. There was a voltage-dependent increase in charge movement during the e.p.s.c. in barium-treated cells which was not present in control cells. We conclude that the voltage-dependent alteration in e.p.s.c. decay time course, peak amplitude and charge movement in barium-treated cells is due to a direct postsynaptic action of barium on the kinetics of receptor-channel gating in postganglionic sympathetic neurones. PMID:6333261

Spontaneous voltage and current fluctuations in tissue cultured mouse dorsal root ganglion cells.

PubMed

Mathers, D A; Barker, J L

1984-02-13

Fetal mouse dorsal root ganglion (DRG) neurons were maintained in primary dissociated cell culture for periods of 7 days to 3 months. Intracellular recordings from these cells revealed the presence of spontaneous subthreshold potentials in 101/177 neurons studied. When measured at the resting membrane potential, these spontaneous voltage events took two forms: (a) high frequency potential fluctuations several millivolts in peak-to-peak amplitude and (b) small, discrete hyperpolarizations. Neurons exhibiting either type of event were designated as 'active' DRG cells. No spontaneous potentials were seen in DRG cells hyperpolarized to membrane voltages more negative than -64 +/- 11.5 mV (n = 5 cells). Under voltage-clamp conditions, the subthreshold potentials of active DRG cells were replaced by fluctuations in outward current. The power spectral density, S(f) of these current fluctuations was approximated by an equation of the form S(f) = (S(o)/[1 + (f/fc) alpha] where 2 less than or equal to a less than or equal to 3 and the half-power frequency fc = 11.3 +/- 3.1 Hz at 23 degrees C (n = 17 cells). The spontaneous voltage fluctuations of active DRG cells were abolished in Ca2+-free saline, and of the divalent metal cations Sr2+, Mg2+, Ba2+, Co2+ and Mn2+, only Sr2+ could substitute for Ca2+ in the maintenance of this activity. Tetraethylammonium ions (1-10 mM) reversibly blocked the spontaneous potentials, while caffeine (10 mM) increased the frequency of these events. The spontaneous voltage fluctuations were not dependent on the presence of spinal cord neurons in the culture plate, and they were also observed in cultured DRG cells derived from adult mice.

Voltage controlled nano-injection system for single-cell surgery

PubMed Central

Seger, R. Adam; Actis, Paolo; Penfold, Catherine; Maalouf, Michelle; Vilozny, Boaz; Pourmand, Nader

2015-01-01

Manipulation and analysis of single cells is the next frontier in understanding processes that control the function and fate of cells. Herein we describe a single-cell injection platform based on nanopipettes. The system uses scanning microscopy techniques to detect cell surfaces, and voltage pulses to deliver molecules into individual cells. As a proof of concept, we injected adherent mammalian cells with fluorescent dyes. PMID:22899383

Voltage controlled nano-injection system for single-cell surgery.

PubMed

Adam Seger, R; Actis, Paolo; Penfold, Catherine; Maalouf, Michelle; Vilozny, Boaz; Pourmand, Nader

2012-09-28

Manipulation and analysis of single cells is the next frontier in understanding processes that control the function and fate of cells. Herein we describe a single-cell injection platform based on nanopipettes. The system uses scanning microscopy techniques to detect cell surfaces, and voltage pulses to deliver molecules into individual cells. As a proof of concept, we injected adherent mammalian cells with fluorescent dyes.

State-of-the-Art Fuel Cell Voltage Durability and Cost Status: 2018 Composite Data Products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saur, Genevieve; Kurtz, Jennifer M; Dinh, Huyen N

This publication includes 18 composite data products (CDPs) for fuel cell technology status, focusing on state-of-the-art fuel cell voltage durability and cost with data through the fourth quarter of 2017.

A theoretical analysis of the current-voltage characteristics of solar cells

NASA Technical Reports Server (NTRS)

Fang, R. C. Y.; Hauser, J. R.

1977-01-01

The correlation of theoretical and experimental data is discussed along with the development of a complete solar cell analysis. The dark current-voltage characteristics, and the parameters for solar cells are analyzed. The series resistance, and impurity gradient effects on solar cells were studied, the effects of nonuniformities on solar cell performance were analyzed.

Battery Charge Equalizer with Transformer Array

NASA Technical Reports Server (NTRS)

Davies, Francis

2013-01-01

High-power batteries generally consist of a series connection of many cells or cell banks. In order to maintain high performance over battery life, it is desirable to keep the state of charge of all the cell banks equal. A method provides individual charging for battery cells in a large, high-voltage battery array with a minimum number of transformers while maintaining reasonable efficiency. This is designed to augment a simple highcurrent charger that supplies the main charge energy. The innovation will form part of a larger battery charge system. It consists of a transformer array connected to the battery array through rectification and filtering circuits. The transformer array is connected to a drive circuit and a timing and control circuit that allow individual battery cells or cell banks to be charged. The timing circuit and control circuit connect to a charge controller that uses battery instrumentation to determine which battery bank to charge. It is important to note that the innovation can charge an individual cell bank at the same time that the main battery charger is charging the high-voltage battery. The fact that the battery cell banks are at a non-zero voltage, and that they are all at similar voltages, can be used to allow charging of individual cell banks. A set of transformers can be connected with secondary windings in series to make weighted sums of the voltages on the primaries.

Temporal Dynamics of Microbial Rhodopsin Fluorescence Reports Absolute Membrane Voltage

PubMed Central

Hou, Jennifer H.; Venkatachalam, Veena; Cohen, Adam E.

2014-01-01

Plasma membrane voltage is a fundamentally important property of a living cell; its value is tightly coupled to membrane transport, the dynamics of transmembrane proteins, and to intercellular communication. Accurate measurement of the membrane voltage could elucidate subtle changes in cellular physiology, but existing genetically encoded fluorescent voltage reporters are better at reporting relative changes than absolute numbers. We developed an Archaerhodopsin-based fluorescent voltage sensor whose time-domain response to a stepwise change in illumination encodes the absolute membrane voltage. We validated this sensor in human embryonic kidney cells. Measurements were robust to variation in imaging parameters and in gene expression levels, and reported voltage with an absolute accuracy of 10 mV. With further improvements in membrane trafficking and signal amplitude, time-domain encoding of absolute voltage could be applied to investigate many important and previously intractable bioelectric phenomena. PMID:24507604

Lithium-Ion Batteries Being Evaluated for Low-Earth-Orbit Applications

NASA Technical Reports Server (NTRS)

McKissock, Barbara I.

2005-01-01

The performance characteristics and long-term cycle life of aerospace lithium-ion (Li-ion) batteries in low-Earth-orbit applications are being investigated. A statistically designed test using Li-ion cells from various manufacturers began in September 2004 to study the effects of temperature, end-of-charge voltage, and depth-of-discharge operating conditions on the cycle life and performance of these cells. Performance degradation with cycling is being evaluated, and performance characteristics and failure modes are being modeled statistically. As technology improvements are incorporated into aerospace Li-ion cells, these new designs can be added to the test to evaluate the effect of the design changes on performance and life. Cells from Lithion and Saft have achieved over 2000 cycles under 10 different test condition combinations and are being evaluated. Cells from Mine Safety Appliances (MSA) and modules made up of commercial-off-the-shelf 18650 Li-ion cells connected in series/parallel combinations are scheduled to be added in the summer of 2005. The test conditions include temperatures of 10, 20, and 30 C, end-of-charge voltages of 3.85, 3.95, and 4.05 V, and depth-of-discharges from 20 to 40 percent. The low-Earth-orbit regime consists of a 55 min charge, at a constant-current rate that is 110 percent of the current required to fully recharge the cells in 55 min until the charge voltage limit is reached, and then at a constant voltage for the remaining charge time. Cells are discharged for 35 min at the current required for their particular depth-of-discharge condition. Cells are being evaluated in four-cell series strings with charge voltage limits being applied to individual cells by the use of charge-control units designed and produced at the NASA Glenn Research Center. These charge-control units clamp the individual cell voltages as each cell reaches its end-of-charge voltage limit, and they bypass the excess current from that cell, while allowing the full current flow to the remaining cells in the pack. The goal of this evaluation is to identify conditions and cell designs for Li-ion technology that can achieve more than 30,000 low-Earth-orbit cycles. Testing is being performed at the Naval Surface Warfare Center, Crane Division, in Crane, Indiana.

Superstrate sub-cell voltage-matched multijunction solar cells

DOEpatents

Mascarenhas, Angelo; Alberi, Kirstin

2016-03-15

Voltage-matched thin film multijunction solar cell and methods of producing cells having upper CdTe pn junction layers formed on a transparent substrate which in the completed device is operatively positioned in a superstate configuration. The solar cell also includes a lower pn junction formed independently of the CdTe pn junction and an insulating layer between CdTe and lower pn junctions. The voltage-matched thin film multijunction solar cells further include a parallel connection between the CdTe pn junction and lower pn junctions to form a two-terminal photonic device. Methods of fabricating devices from independently produced upper CdTe junction layers and lower junction layers are also disclosed.

Lithium-cupric sulfide cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuesta, A.J.; Bump, D.D.

1980-01-01

Lithium cells have become the primary power source for cardiac pacemakers due to their reliability and longevity at low current drain rates. A lithium-cupric sulfide cell was developed which makes maximum use of the shape of a pacemaker's battery compartment. The cell has a stable voltage throughout 90% of its lifetime. It then drops to a second stable voltage before depletion. The voltage drop creates a small decrease in pacemaker rate, which alerts the physician to replace the pacemaker. No loss of capacity due to self-discharge as been seen to date, and cells have proven to be safe under extrememore » conditions. 2 refs.« less

A study of short test and charge retention test methods for nickel-cadmium spacecraft cells

NASA Technical Reports Server (NTRS)

Scott, W. R.

1975-01-01

Methods for testing nickel-cadmium cells for internal shorts and charge retention were studied. Included were (a) open circuit voltage decay after a brief charge, (b) open circuit voltage recovery after shorting, and (c) open circuit voltage decay and capacity loss after a full charge. The investigation included consideration of the effects of prior history, of conditioning cells prior to testing, and of various test method variables on the results of the tests. Sensitivity of the tests was calibrated in terms of equivalent external resistance. The results were correlated. It was shown that a large number of variables may affect the results of these tests. It is concluded that the voltage decay after a brief charge and the voltage recovery methods are more sensitive than the charged stand method, and can detect an internal short equivalent to a resistance of about (10,000/C)ohms where "C' is the numerical value of the capacity of the cell in ampere hours.

Harnessing Solar Energy Using Photosynthetic and Organic Pigments

NASA Astrophysics Data System (ADS)

Fitzsimons, Toby Ryan

Fossil fuels are a finite energy resource that must be supplemented or replaced by more stable forms of electrical energy. Solar technology research strives to supplement and provide eventual replacement for fossil fuel technology. This experiment focused on the use of natural pigments as photo-sensitizers in the current generation of solar cells called dye sensitized solar cells (DSSCs). Pigments from purified chlorophyll a, chlorophyll b, chlorophyll a/b, crude spinach (Spinacia oleracea) extract, phycocyanin, and chlorophyllin were used to construct DSSCs and evaluated, along with a control containing no pigment, for solar energy conversion. The anode of the solar cells consisted of titanium dioxide (TiO2) plates soaked in pigment solutions for twenty-four hours. The plates were assembled, along with an electrolyte sandwiched between cells, and a platinum-coated counter plate that functioned as the cathode. A gasket seal was placed between the plates and held together with rubber bands. The DSSCs were each tested for a maximum power (Pmax) point and a resistor was selected that corresponded to the resistance at that point. The cells were randomly placed into a power block assembly located in an environmental chamber with lighting that provided an average of 27,590 lumens at the surface of DSSCs. With appropriate resistors in place, the cells were subjected to twelve-hour days and twelve-hour nights for ten days, and measurements were recorded every ten minutes. Data were collected to obtain values for voltage in millivolts (mV), current in microamps (microA), and power in microwatts (microW), as well as beginning and ending efficiencies in converting light to usable energy. Voltages were substantially higher during the day than at night for all pigments, except for the control, indicating that the pigments functioned as DSSCs. Hence, only daytime values were used for data analysis. Voltage during the ten-day experiment ranged from 3.99 to 274 mV; current ranged from 0.0180 to 41.9 microA, and power ranged from 0.00 to 11.3 microW. Chlorophyllin had the highest peak and least voltage (274 and 161 mV), highest peak and least current (41.9 and 21.8 microA), and highest peak and least power (11.3 and 4.84 microW). The ranking of the pigments for peak voltage was: Chlorophyllin = Crude Extract ≥ Chlorophyll a = Chlorophyll a/b ≥ Phycocyanin = Chlorophyll b > Control. The ranking for least voltage was: Chlorophyllin > Phycocyanin ≥ Chlorophyll a/b ≥ Crude Extract ≥ Chlorophyll b ≥ Chlorophyll a ≥ Control. Ranking for peak and least values were similar for current and power. Solar energy conversion (efficiency in converting light energy to usable energy in watts per square meter) for all treatments ranged from 0.000595 to 0.0217% at the beginning of the experiment, and was highest in cells constructed with chlorophyllin. Based on rankings from peak and ending voltage values, as well as other measurements, it was concluded that DSSCs constructed with chlorophyllin performed the best and lasted the longest as photo-sensitizers, compared to other pigments used in this investigation. The DSSCs constructed with crude extract performed almost as well as those constructed with chlorophyllin at the beginning of the experiment, but degradation of this naturally-made pigment may have prevented these cells from sustaining solar energy conversion for more than a few days. Other pigments demonstrated conversion values higher than those of control DSSCs which contained no pigments. The results from this project provide evidence that DSSCs can produce useable energy. More research is needed to enhance and prolong the efficiency of DSSCs in solar energy conversion.

Biphasic voltage-dependent inactivation of human NaV 1.3, 1.6 and 1.7 Na+ channels expressed in rodent insulin-secreting cells.

PubMed

Godazgar, Mahdieh; Zhang, Quan; Chibalina, Margarita V; Rorsman, Patrik

2018-05-01

Na + current inactivation is biphasic in insulin-secreting cells, proceeding with two voltage dependences that are half-maximal at ∼-100 mV and -60 mV. Inactivation of voltage-gated Na + (Na V ) channels occurs at ∼30 mV more negative voltages in insulin-secreting Ins1 and primary β-cells than in HEK, CHO or glucagon-secreting αTC1-6 cells. The difference in inactivation between Ins1 and non-β-cells persists in the inside-out patch configuration, discounting an involvement of a diffusible factor. In Ins1 cells and primary β-cells, but not in HEK cells, inactivation of a single Na V subtype is biphasic and follows two voltage dependences separated by 30-40 mV. We propose that Na V channels adopt different inactivation behaviours depending on the local membrane environment. Pancreatic β-cells are equipped with voltage-gated Na + channels that undergo biphasic voltage-dependent steady-state inactivation. A small Na + current component (10-15%) inactivates over physiological membrane potentials and contributes to action potential firing. However, the major Na + channel component is completely inactivated at -90 to -80 mV and is therefore inactive in the β-cell. It has been proposed that the biphasic inactivation reflects the contribution of different Na V α-subunits. We tested this possibility by expression of TTX-resistant variants of the Na V subunits found in β-cells (Na V 1.3, Na V 1.6 and Na V 1.7) in insulin-secreting Ins1 cells and in non-β-cells (including HEK and CHO cells). We found that all Na V subunits inactivated at 20-30 mV more negative membrane potentials in Ins1 cells than in HEK or CHO cells. The more negative inactivation in Ins1 cells does not involve a diffusible intracellular factor because the difference between Ins1 and CHO persisted after excision of the membrane. Na V 1.7 inactivated at 15--20 mV more negative membrane potentials than Na V 1.3 and Na V 1.6 in Ins1 cells but this small difference is insufficient to solely explain the biphasic inactivation in Ins1 cells. In Ins1 cells, but never in the other cell types, widely different components of Na V inactivation (separated by 30 mV) were also observed following expression of a single type of Na V α-subunit. The more positive component exhibited a voltage dependence of inactivation similar to that found in HEK and CHO cells. We propose that biphasic Na V inactivation in insulin-secreting cells reflects insertion of channels in membrane domains that differ with regard to lipid and/or membrane protein composition. © 2018 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Four-cell solar tracker

NASA Technical Reports Server (NTRS)

Berdahl, C. M.

1981-01-01

Forty cm Sun tracker, consisting of optical telescope and four solar cells, stays pointed at Sun throughout day for maximum energy collection. Each solar cell generates voltage proportional to part of solar image it receives; voltages drive servomotors that keep image centered. Mirrored portion of cylinder extends acquisition angle of device by reflecting Sun image back onto solar cells.

Photo-sensitization of ZnS nanoparticles with renowned ruthenium dyes N3, N719 and Z907 for application in solid state dye sensitized solar cells: A comparative study.

PubMed

Nosheen, Erum; Shah, Syed Mujtaba; Hussain, Hazrat; Murtaza, Ghulam

2016-09-01

This article presents a comprehensive relative report on the grafting of ZnS with renowned ruthenium ((Ru) dyes i.e. N3, N719 and Z907) and gives insight into their charge transfer interaction and sensitization mechanism for boosting solar cell efficiency. Influence of dye concentration on cell performance is also reported here. ZnS nanoparticles synthesized by a simple coprecipitation method with an average particle size of 15±2nm were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Elemental dispersive X-ray analysis (EDAX), tunneling electron microscopy (TEM) and UV-Visible (UV-Vis) spectroscopy. UV-Vis, photoluminescence (PL) and Fourier transform infra-red (FT-IR) spectroscopy confirms the successful grafting of these dyes over ZnS nanoparticles surface. Low-energy metal-to-ligand charge-transfer transition (MLCT) bands of dyes are mainly affected on grafting over the nanoparticle surface. Moreover their current voltage (I-V) results confirm the efficiency enhancement in ZnS solid state dye sensitized solar cells (SSDSSCs) owing to effective sensitization of this material with Ru dyes and helps in finding the optimum dye concentration for nanoparticles sensitization. Highest rise in overall solar cell efficiency i.e. 64% of the reference device has been observed for 0.3mM N719-ZnS sample owing to increased open circuit voltage (Voc) and fill factor (FF). Experimental and proposed results were found in good agreement with each other. Copyright © 2016 Elsevier B.V. All rights reserved.

Repeatable, accurate, and high speed multi-level programming of memristor 1T1R arrays for power efficient analog computing applications.

PubMed

Merced-Grafals, Emmanuelle J; Dávila, Noraica; Ge, Ning; Williams, R Stanley; Strachan, John Paul

2016-09-09

Beyond use as high density non-volatile memories, memristors have potential as synaptic components of neuromorphic systems. We investigated the suitability of tantalum oxide (TaOx) transistor-memristor (1T1R) arrays for such applications, particularly the ability to accurately, repeatedly, and rapidly reach arbitrary conductance states. Programming is performed by applying an adaptive pulsed algorithm that utilizes the transistor gate voltage to control the SET switching operation and increase programming speed of the 1T1R cells. We show the capability of programming 64 conductance levels with <0.5% average accuracy using 100 ns pulses and studied the trade-offs between programming speed and programming error. The algorithm is also utilized to program 16 conductance levels on a population of cells in the 1T1R array showing robustness to cell-to-cell variability. In general, the proposed algorithm results in approximately 10× improvement in programming speed over standard algorithms that do not use the transistor gate to control memristor switching. In addition, after only two programming pulses (an initialization pulse followed by a programming pulse), the resulting conductance values are within 12% of the target values in all cases. Finally, endurance of more than 10(6) cycles is shown through open-loop (single pulses) programming across multiple conductance levels using the optimized gate voltage of the transistor. These results are relevant for applications that require high speed, accurate, and repeatable programming of the cells such as in neural networks and analog data processing.

Role of Copper in the Performance of CdS/CdTe Solar Cells (Poster)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demtsu, S.; Albin, D.; Sites, J.

2006-05-01

The performance of CdS/CdTe solar cells made with evaporated Cu as a primary back contact was studied through current-voltage (JV) at different intensities, quantum efficiency (QE) under light and voltage bias, capacitance-voltage (CV), and drive-level capacitance profiling (DLCP) measurements. The results show that while modest amounts of Cu enhance cell performance, excessive amounts degrade device quality and reduce performance. The analysis is supported with numerical simulations to reproduce and explain some of the experimental results.

SONOS Nonvolatile Memory Cell Programming Characteristics

NASA Technical Reports Server (NTRS)

MacLeod, Todd C.; Phillips, Thomas A.; Ho, Fat D.

2010-01-01

Silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory is gaining favor over conventional EEPROM FLASH memory technology. This paper characterizes the SONOS write operation using a nonquasi-static MOSFET model. This includes floating gate charge and voltage characteristics as well as tunneling current, voltage threshold and drain current characterization. The characterization of the SONOS memory cell predicted by the model closely agrees with experimental data obtained from actual SONOS memory cells. The tunnel current, drain current, threshold voltage and read drain current all closely agreed with empirical data.

Multilevel DC link inverter

DOEpatents

Su, Gui-Jia

2003-06-10

A multilevel DC link inverter and method for improving torque response and current regulation in permanent magnet motors and switched reluctance motors having a low inductance includes a plurality of voltage controlled cells connected in series for applying a resulting dc voltage comprised of one or more incremental dc voltages. The cells are provided with switches for increasing the resulting applied dc voltage as speed and back EMF increase, while limiting the voltage that is applied to the commutation switches to perform PWM or dc voltage stepping functions, so as to limit current ripple in the stator windings below an acceptable level, typically 5%. Several embodiments are disclosed including inverters using IGBT's, inverters using thyristors. All of the inverters are operable in both motoring and regenerating modes.

Structure control of tungsten nanocontacts through pulsed-voltage application

NASA Astrophysics Data System (ADS)

Suzuki, Yasuchika; Kizuka, Tokushi

2018-05-01

The structural variation in tungsten nanocontacts (NCs) during a pulsed-voltage application was observed in situ by high-resolution transmission electron microscopy. The direction of electromigration in the NCs changed from the well-known direction to the opposite direction at a critical voltage of 0.9 V. Upon applying a higher pulsed voltage of 2.5 V, the NC structure changed to amorphous, with an average conductance density decreased to 82% of that of the crystalline NCs. We demonstrated that the external shape and texture of tungsten NCs can be controlled with an atomic precision through electromigration and amorphization by a pulsed-voltage application.

A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators

NASA Astrophysics Data System (ADS)

Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

2016-01-01

It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180-400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.

A theoretical analysis of the current-voltage characteristics of solar cells

NASA Technical Reports Server (NTRS)

Fang, R. C. Y.; Hauser, J. R.

1979-01-01

The following topics are discussed: (1) dark current-voltage characteristics of solar cells; (2) high efficiency silicon solar cells; (3) short circuit current density as a function of temperature and the radiation intensity; (4) Keldysh-Franz effects and silicon solar cells; (5) thin silicon solar cells; (6) optimum solar cell designs for concentrated sunlight; (7) nonuniform illumination effects of a solar cell; and (8) high-low junction emitter solar cells.

The Calibration of dc Voltage Standards at NIST

PubMed Central

Field, Bruce F.

1990-01-01

This document describes the procedures used at NIST to calibrate dc voltage standards in terms of the NIST volt. Three calibration services are offered by the Electricity Division: Regular Calibration Service (RCS) of client standard cells at NIST; the Volt Transfer Program (VTP) a process to determine the difference between the NIST volt and the volt as maintained by a group of standard cells in a client laboratory; and the calibration of client solid-state dc voltage standards at NIST. The operational procedures used to compare these voltage standards to NIST voltage standards and to maintain the NIST volt via the ac Josephson effect are discussed. PMID:28179777

False Operation of Static Random Access Memory Cells under Alternating Current Power Supply Voltage Variation

NASA Astrophysics Data System (ADS)

Sawada, Takuya; Takata, Hidehiro; Nii, Koji; Nagata, Makoto

2013-04-01

Static random access memory (SRAM) cores exhibit susceptibility against power supply voltage variation. False operation is investigated among SRAM cells under sinusoidal voltage variation on power lines introduced by direct RF power injection. A standard SRAM core of 16 kbyte in a 90 nm 1.5 V technology is diagnosed with built-in self test and on-die noise monitor techniques. The sensitivity of bit error rate is shown to be high against the frequency of injected voltage variation, while it is not greatly influenced by the difference in frequency and phase against SRAM clocking. It is also observed that the distribution of false bits is substantially random in a cell array.

Increased voltage photovoltaic cell

NASA Technical Reports Server (NTRS)

Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

1985-01-01

A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

Active Mechanisms of Vibration Encoding and Frequency Filtering in Central Mechanosensory Neurons.

PubMed

Azevedo, Anthony W; Wilson, Rachel I

2017-10-11

To better understand biophysical mechanisms of mechanosensory processing, we investigated two cell types in the Drosophila brain (A2 and B1 cells) that are postsynaptic to antennal vibration receptors. A2 cells receive excitatory synaptic currents in response to both directions of movement: thus, twice per vibration cycle. The membrane acts as a low-pass filter, so that voltage and spiking mainly track the vibration envelope rather than individual cycles. By contrast, B1 cells are excited by only forward or backward movement, meaning they are sensitive to vibration phase. They receive oscillatory synaptic currents at the stimulus frequency, and they bandpass filter these inputs to favor specific frequencies. Different cells prefer different frequencies, due to differences in their voltage-gated conductances. Both Na + and K + conductances suppress low-frequency synaptic inputs, so cells with larger voltage-gated conductances prefer higher frequencies. These results illustrate how membrane properties and voltage-gated conductances can extract distinct stimulus features into parallel channels. Copyright © 2017 Elsevier Inc. All rights reserved.

Benzonatate inhibition of voltage-gated sodium currents.

PubMed

Evans, M Steven; Maglinger, G Benton; Fletcher, Anita M; Johnson, Stephen R

2016-02-01

Benzonatate was FDA-approved in 1958 as an antitussive. Its mechanism of action is thought to be anesthesia of vagal sensory nerve fibers that mediate cough. Vagal sensory neurons highly express the Nav1.7 subtype of voltage-gated sodium channels, and inhibition of this channel inhibits the cough reflex. Local anesthetics inhibit voltage-gated sodium channels, but there are no reports of whether benzonatate affects these channels. Our hypothesis is that benzonatate inhibits Nav1.7 voltage-gated sodium channels. We used whole cell voltage clamp recording to test the effects of benzonatate on voltage-gated sodium (Na(+)) currents in two murine cell lines, catecholamine A differentiated (CAD) cells, which express primarily Nav1.7, and N1E-115, which express primarily Nav1.3. We found that, like local anesthetics, benzonatate strongly and reversibly inhibits voltage-gated Na(+) channels. Benzonatate causes both tonic and phasic inhibition. It has greater effects on channel inactivation than on activation, and its potency is much greater at depolarized potentials, indicating inactivated-state-specific effects. Na(+) currents in CAD cells and N1E-115 cells are similarly affected, indicating that benzonatate is not Na(+) channel subtype-specific. Benzonatate is a mixture of polyethoxy esters of 4-(butylamino) benzoic acid having varying degrees of hydrophobicity. We found that Na(+) currents are inhibited most potently by a benzonatate fraction containing the 9-ethoxy component. Detectable effects of benzonatate occur at concentrations as low as 0.3 μM, which has been reported in humans. We conclude that benzonatate has local anesthetic-like effects on voltage-gated sodium channels, including Nav1.7, which is a possible mechanism for cough suppression by the drug. Copyright © 2015 Elsevier Ltd. All rights reserved.

Radiation damage in high voltage silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Brandhorst, H., Jr.; Swartz, C. K.; Weizer, V. G.

1980-01-01

Three high open-circuit voltage cell designs based on 0.1 ohm-cm p-type silicon were irradiated with 1 MeV electrons and their performance determined to fluences as high as 10 to the 15th power/sq cm. Of the three cell designs, radiation induced degradation was greatest in the high-low emitter (HLE cell). The diffused and ion implanted cells degraded approximately equally but less than the HLE cell. Degradation was greatest in an HLE cell exposed to X-rays before electron irradiation. The cell regions controlling both short-circuit current and open-circuit voltage degradation were defined in all three cell types. An increase in front surface recombination velocity accompanied time dependent degradation of an HLE cell after X-irradiation. It was speculated that this was indirectly due to a decrease in positive charge at the silicon-oxide interface. Modifications aimed at reducing radiation induced degradation are proposed for all three cell types.

Battery Cell Voltage Sensing and Balancing Using Addressable Transformers

NASA Technical Reports Server (NTRS)

Davies, Francis

2009-01-01

A document discusses the use of saturating transformers in a matrix arrangement to address individual cells in a high voltage battery. This arrangement is able to monitor and charge individual cells while limiting the complexity of circuitry in the battery. The arrangement has inherent galvanic isolation, low cell leakage currents, and allows a single bad cell in a battery of several hundred cells to be easily spotted.

Why Batteries Deliver a Fairly Constant Voltage until Dead

ERIC Educational Resources Information Center

Smith, Garon C.; Hossain, Md. Mainul; MacCarthy, Patrick

2012-01-01

Two characteristics of batteries, their delivery of nearly constant voltage and their rapid failure, are explained through a visual examination of the Nernst equation. Two Galvanic cells are described in detail: (1) a wet cell involving iron and copper salts and (2) a mercury oxide dry cell. A complete description of the wet cell requires a…

A battery simulator

NASA Technical Reports Server (NTRS)

Ferrell, S., Jr.; Lahr, N.

1970-01-01

Simulator verifies proper operation of a battery cell voltage-monitoring device. It also contains variable ac voltage to ascertain that a battery scanner will perform its function at all possible ac voltages.

Subthreshold voltage noise of rat neocortical pyramidal neurones

PubMed Central

Jacobson, Gilad A; Diba, Kamran; Yaron-Jakoubovitch, Anat; Oz, Yasmin; Koch, Christof; Segev, Idan; Yarom, Yosef

2005-01-01

Neurones are noisy elements. Noise arises from both intrinsic and extrinsic sources, and manifests itself as fluctuations in the membrane potential. These fluctuations limit the accuracy of a neurone's output but have also been suggested to play a computational role. We present a detailed study of the amplitude and spectrum of voltage noise recorded at the soma of layer IV–V pyramidal neurones in slices taken from rat neocortex. The dependence of the noise on holding potential, synaptic activity and Na+ conductance is systematically analysed. We demonstrate that voltage noise increases non-linearly as the cell depolarizes (from a standard deviation (s.d.) of 0.19 mV at −75 mV to an s.d. of 0.54 mV at −55 mV). The increase in voltage noise is accompanied by an increase in the cell impedance, due to voltage dependence of Na+ conductance. The impedance increase accounts for the majority (70%) of the voltage noise increase. The increase in voltage noise and impedance is restricted to the low-frequency range (0.2–2 Hz). At the high frequency range (5–100 Hz) the voltage noise is dominated by synaptic activity. In our slice preparation, synaptic noise has little effect on the cell impedance. A minimal model reproduces qualitatively these data. Our results imply that ion channel noise contributes significantly to membrane voltage fluctuations at the subthreshold voltage range, and that Na+ conductance plays a key role in determining the amplitude of this noise by acting as a voltage-dependent amplifier of low-frequency transients. PMID:15695244

Improved Short-Circuit Protection for Power Cells in Series

NASA Technical Reports Server (NTRS)

Davies, Francis

2008-01-01

A scheme for protection against short circuits has been devised for series strings of lithium electrochemical cells that contain built-in short-circuit protection devices, which go into a high-resistance, current-limiting state when heated by excessive current. If cells are simply connected in a long series string to obtain a high voltage and a short circuit occurs, whichever short-circuit protection device trips first is exposed to nearly the full string voltage, which, typically, is large enough to damage the device. Depending on the specific cell design, the damage can defeat the protective function, cause a dangerous internal short circuit in the affected cell, and/or cascade to other cells. In the present scheme, reverse diodes rated at a suitably high current are connected across short series sub-strings, the lengths of which are chosen so that when a short-circuit protection device is tripped, the voltage across it does not exceed its rated voltage. This scheme preserves the resetting properties of the protective devices. It provides for bypassing of cells that fail open and limits cell reversal, though not as well as does the more-expensive scheme of connecting a diode across every cell.

Investigation of the open-circuit voltage in wide-bandgap InGaP-host InP quantum dot intermediate-band solar cells

NASA Astrophysics Data System (ADS)

Aihara, Taketo; Tayagaki, Takeshi; Nagato, Yuki; Okano, Yoshinobu; Sugaya, Takeyoshi

2018-04-01

To analyze the open-circuit voltage (V oc) in intermediate-band solar cells, we investigated the current-voltage characteristics in wide-bandgap InGaP-based InP quantum dot (QD) solar cells. From the temperature dependence of the current-voltage curves, we show that the V oc in InP QD solar cells increases with decreasing temperature. We use a simple diode model to extract V oc at the zero-temperature limit, V 0, and the temperature coefficient C of the solar cells. Our results show that, while the C of InP QD solar cells is slightly larger than that of the reference InGaP solar cells, V 0 significantly decreases and coincides with the bandgap energy of the InP QDs rather than that of the InGaP host. This V 0 indicates that the V oc reduction in the InP QD solar cells is primarily caused by the breaking of the Fermi energy separation between the QDs and the host semiconductor in intermediate-band solar cells, rather than by enhanced carrier recombination.

Developments toward an 18% efficient silicon solar cell

NASA Technical Reports Server (NTRS)

Meulenberg, A., Jr.

1983-01-01

Limitations to increased open-circuit voltage were identified and experimentally verified for 0.1 ohm-cm solar cells with heavily doped emitters. After major reduction in the dark current contribution from the metal-silicon interface of the grid contacts, the surface recombination velocity of the oxide-silicon interface of shallow junction solar cells is the limiting factor. In deep junction solar cells, where the junction field does not aid surface collection, the emitter bulk is the limiting factor. Singly-diffused, shallow junction cells have been fabricated with open circuit voltages in excess of 645 mV. Double-diffusion shallow and deep junctions cells have displayed voltages above 650 mV. MIS solar cells formed on 0.1 ohm-cm substrates have exibited the lowest dark currents produced in the course of the contract work.

Molecular basis of ancestral vertebrate electroreception

PubMed Central

Bellono, Nicholas W.; Leitch, Duncan B.; Julius, David

2017-01-01

Elasmobranch fishes, including sharks, rays, and skates, use specialized electrosensory organs called Ampullae of Lorenzini to detect extremely small changes in environmental electric fields. Electrosensory cells within these ampullae are able to discriminate and respond to minute changes in environmental voltage gradients through an as-yet unknown mechanism. Here we show that the voltage-gated calcium channel CaV1.3 and big conductance calcium-activated potassium (BK) channel are preferentially expressed by electrosensory cells in little skate (Leucoraja erinacea) and functionally couple to mediate electrosensory cell membrane voltage oscillations, which are important in the detection of specific, weak electrical signals. Both channels exhibit unique properties compared with their mammalian orthologues to support electrosensory functions: structural adaptations in CaV1.3 mediate a low voltage threshold for activation, while alterations in BK support specifically tuned voltage oscillations. These findings reveal a molecular basis of electroreception and demonstrate how discrete evolutionary changes in ion channel structure facilitate sensory adaptation. PMID:28264196

Coronary sinus signal amplitude predicts left atrial scarring.

PubMed

Attanasio, Philipp; Qaiyumi, Daniel; Röhle, Robert; Wutzler, Alexander; Safak, Erdal; Muntean, Bogdan; Boldt, Leif-Hendrik; Pieske, Burkert; Haverkamp, Wilhelm; Huemer, Martin

2017-12-22

Left atrial scarring is recognised as a critical component in the maintenance of atrial fibrillation and is associated with the failure of interventional treatment. Diminished bipolar voltage (LV) has been proposed as a useful tool for left atrial scar quantification. We hypothesised that, due to its anatomic location, signals on the coronary sinus catheter might be used to predict the amount of left atrial low voltage. A total of 124 patients (42% women, average age 66 ± 9 years) were included. Forty-one with paroxysmal and 83 with persistent atrial fibrillation. Left atrial low-voltage (<0.5 mV, measured during sinus rhythm) area size and distribution varied considerably among the included patients (mean: 34.9%; maximum: 94.6%; minimum: 0.4%). Spearman correlation revealed a strong negative correlation between bipolar voltage of the signals on the coronary sinus catheter and the amount of left atrial scarring (R = -0.778, p < .0001). The optimal CS voltage cut off for prediction of left atrial low-voltage size of ≥50% was 1.9 mV with an area-under-the receiver-operating-characteristic (ROC) curve of 0.982, a sensitivity of 97% and a specificity of 98%. There is a strong negative correlation between the size of left atrial low-voltage areas (LVA) and coronary sinus signal amplitude. With increasing left atrial LVA size, CS signal amplitudes decrease, and vice versa. On the basis of these findings, average CS signal amplitudes of ≤1.9 mV can be used as a predictor for a left atrial low-voltage size of ≥50%.

Faster voltage-dependent activation of Na+ channels in growth cones versus somata of neuroblastoma N1E-115 cells.

PubMed Central

Zhang, J; Loew, L M; Davidson, R M

1996-01-01

Kinetics of voltage-gated ionic channels fundamentally reflect the response of the channels to local electric fields. In this report cell-attached patch-clamp studies reveal that the voltage-dependent activation rate of sodium channels residing in the growth cone membrane differs from that of soma sodium channels in differentiating N1E-115 neuroblastoma cells. Because other electrophysiological properties of these channels do not differ, this finding may be a reflection of the difference in intramembrane electric field in these two regions of the cell. This represents a new mechanism for channels to attain a range of activities both within and between cells. PMID:8913589

Faster voltage-dependent activation of Na+ channels in growth cones versus somata of neuroblastoma N1E-115 cells.

PubMed

Zhang, J; Loew, L M; Davidson, R M

1996-11-01

Kinetics of voltage-gated ionic channels fundamentally reflect the response of the channels to local electric fields. In this report cell-attached patch-clamp studies reveal that the voltage-dependent activation rate of sodium channels residing in the growth cone membrane differs from that of soma sodium channels in differentiating N1E-115 neuroblastoma cells. Because other electrophysiological properties of these channels do not differ, this finding may be a reflection of the difference in intramembrane electric field in these two regions of the cell. This represents a new mechanism for channels to attain a range of activities both within and between cells.

Radiation tolerance of low resistivity, high voltage silicon solar cells

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Weinberg, I.; Swartz, C. K.

1984-01-01

The radiation tolerance of the following three low resistivity, high voltage silicon solar cells was investigated: (1) the COMSAT MSD (multi-step diffused) cell, (2) the MinMIS cell, and (3) the MIND cell. A description of these solar cells is given along with drawings of their configurations. The diffusion length damage coefficients for the cells were calculated and presented. Solar cell spectral response was also discussed. Cells of the MinMIS type were judged to be unsuitable for use in the space radiation environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poplawsky, Jonathan D.

Here, the performance of CdTe solar cells — cheaper alternatives to silicon photovoltaics — is hampered by their low output voltages, which are normally well below the theoretical limit. Now, record voltages of over 1 V have been reported in single-crystal CdTe heterostructure solar cells, which are close to those of benchmark GaAs cells.

Development of a High Average Current Thermionic Injector for Free-Electron Lasers

DTIC Science & Technology

2013-02-11

high   average   power   FEL   should   produce   high ...The  cathode  heater   is   powered  by  a  60  Hz  AC   feed  that  floats  on  the   high  voltage  pulse... high -­‐voltage   power  supply  for  the  IOT  gun  is  a  70  kV  Rockwell  hard  tube   modulator   with  

In-situ diagnostic tools for hydrogen transfer leak characterization in PEM fuel cell stacks part II: Operational applications

NASA Astrophysics Data System (ADS)

Niroumand, Amir M.; Homayouni, Hooman; DeVaal, Jake; Golnaraghi, Farid; Kjeang, Erik

2016-08-01

This paper describes a diagnostic tool for in-situ characterization of the rate and distribution of hydrogen transfer leaks in Polymer Electrolyte Membrane (PEM) fuel cell stacks. The method is based on reducing the air flow rate from a high to low value at a fixed current, while maintaining an anode overpressure. At high air flow rates, the reduction in air flow results in lower oxygen concentration in the cathode and therefore reduction in cell voltages. Once the air flow rate in each cell reaches a low value at which the cell oxygen-starves, the voltage of the corresponding cell drops to zero. However, oxygen starvation results from two processes: 1) the electrochemical oxygen reduction reaction which produces current; and 2) the chemical reaction between oxygen and the crossed over hydrogen. In this work, a diagnostic technique has been developed that accounts for the effect of the electrochemical reaction on cell voltage to identify the hydrogen leak rate and number of leaky cells in a fuel cell stack. This technique is suitable for leak characterization during fuel cell operation, as it only requires stack air flow and voltage measurements, which are readily available in an operational fuel cell system.

Layered oxide, graphite and silicon-graphite electrodes for Lithium-ion cells: Effect of electrolyte composition and cycling windows

DOE PAGES

Klett, Matilda; Gilbert, James A.; Pupek, Krzysztof Z.; ...

2016-10-14

The electrochemical performance of cells with a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2 (NCM523) positive electrode and a blended silicon-graphite (Si-Gr) negative electrode are investigated using various electrolyte compositions and voltage cycling windows. Voltage profiles of the blended Si-Gr electrode show a superposition of graphite potential plateaus on a sloped Si profile with a large potential hysteresis. The effect of this hysteresis is seen in the cell impedance versus voltage data, which are distinctly different for the charge and discharge cycles. We confirm that the addition of compounds, such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to themore » baseline 1.2 M LiPF 6 in ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7 w/w) electrolyte, improves cell capacity retention with higher retention seen at higher additive contents. We show that reducing the lower cutoff voltage (LCV) of full cells to 2.5 V increases the Si-Gr electrode potential to 1.12 V vs. Li/Li +; this relatively-high delithiation potential correlates with the lower capacity retention displayed by the cell. Hence, we show that raising the upper cutoff voltage (UCV) can increase cell energy density without significantly altering capacity retention over 100 charge discharge cycles.« less

Layered oxide, graphite and silicon-graphite electrodes for Lithium-ion cells: Effect of electrolyte composition and cycling windows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klett, Matilda; Gilbert, James A.; Pupek, Krzysztof Z.

The electrochemical performance of cells with a Li 1.03(Ni 0.5Co 0.2Mn 0.3) 0.97O 2 (NCM523) positive electrode and a blended silicon-graphite (Si-Gr) negative electrode are investigated using various electrolyte compositions and voltage cycling windows. Voltage profiles of the blended Si-Gr electrode show a superposition of graphite potential plateaus on a sloped Si profile with a large potential hysteresis. The effect of this hysteresis is seen in the cell impedance versus voltage data, which are distinctly different for the charge and discharge cycles. We confirm that the addition of compounds, such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) to themore » baseline 1.2 M LiPF 6 in ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7 w/w) electrolyte, improves cell capacity retention with higher retention seen at higher additive contents. We show that reducing the lower cutoff voltage (LCV) of full cells to 2.5 V increases the Si-Gr electrode potential to 1.12 V vs. Li/Li +; this relatively-high delithiation potential correlates with the lower capacity retention displayed by the cell. Hence, we show that raising the upper cutoff voltage (UCV) can increase cell energy density without significantly altering capacity retention over 100 charge discharge cycles.« less

Temperature gradient measurements by using thermoelectric effect in CNTs-silicone adhesive composite.

PubMed

Chani, Muhammad Tariq Saeed; Karimov, Kh S; Asiri, Abdullah M; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1∶1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results.

Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite

PubMed Central

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1∶1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375

Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels.

PubMed

Kargol, Armin; Malkinski, Leszek; Eskandari, Rahmatollah; Carter, Maya; Livingston, Daniel

2015-09-01

We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus.

Internal voltage control of hydrogen-oxygen fuel cells: Feasibility study

NASA Technical Reports Server (NTRS)

Prokopius, P. R.

1975-01-01

An experimental study was conducted to assess the feasibility of internal voltage regulation of fuel cell systems. Two methods were tested. In one, reactant partial pressure was used as the voltage control parameter and in the other reactant total pressure was used for control. Both techniques were breadboarded and tested on a single alkaline-electrolyte fuel cell. Both methods were found to be possible forms of regulation, however, of the two the total pressure technique would be more efficient, simpler to apply and would provide better transient characteristics.

A concise way to estimate the average density of interface states in an ITO-SiOx/n-Si heterojunction solar cell

NASA Astrophysics Data System (ADS)

Li, Y.; Han, B. C.; Gao, M.; Wan, Y. Z.; Yang, J.; Du, H. W.; Ma, Z. Q.

2017-09-01

On the basis of a photon-assisted high frequency capacitance-voltage (C-V) method (1 MHz C-V), an effective approach is developed to evaluate the average interface state density (Dit) of an ITO-SiOx/n-Si heterojunction structure. Tin-doped indium oxide (ITO) films with different thicknesses were directly deposited on (100) n-type crystalline silicon by magnetron sputtering to fabricate semiconductor-insulator-semiconductor (SIS) hetero-interface regions where an ultra-thin SiOx passivation layer was naturally created. The morphology of the SiOx layer was confirmed by X-ray photoelectron spectroscopy depth profiling and transmission electron microscope analysis. The thinness of this SiOx layer was the main reason for the SIS interface state density being more difficult to detect than that of a typical metal-oxide-semiconductor structure. A light was used for photon injection while measuring the C-V of the device, thus enabling the photon-assisted C-V measurement of the Dit. By quantifying decreases of the light-induced-voltage as a variation of the capacitance caused by parasitic charge at interface states the passivation quality within the interface of ITO-SiOx/n-Si could be reasonably evaluated. The average interface state density of these SIS devices was measured as 1.2-1.7 × 1011 eV-1 cm-2 and declined as the passivation layer was made thicker. The lifetime of the minority carriers, dark leakage current, and the other photovoltaic parameters of the devices were also used to determine the passivation.

Nanosecond pulsed electric fields (nsPEFs) low cost generator design using power MOSFET and Cockcroft-Walton multiplier circuit as high voltage DC source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulaeman, M. Y.; Widita, R.

2014-09-30

Purpose: Non-ionizing radiation therapy for cancer using pulsed electric field with high intensity field has become an interesting field new research topic. A new method using nanosecond pulsed electric fields (nsPEFs) offers a novel means to treat cancer. Not like the conventional electroporation, nsPEFs able to create nanopores in all membranes of the cell, including membrane in cell organelles, like mitochondria and nucleus. NsPEFs will promote cell death in several cell types, including cancer cell by apoptosis mechanism. NsPEFs will use pulse with intensity of electric field higher than conventional electroporation, between 20–100 kV/cm and with shorter duration of pulsemore » than conventional electroporation. NsPEFs requires a generator to produce high voltage pulse and to achieve high intensity electric field with proper pulse width. However, manufacturing cost for creating generator that generates a high voltage with short duration for nsPEFs purposes is highly expensive. Hence, the aim of this research is to obtain the low cost generator design that is able to produce a high voltage pulse with nanosecond width and will be used for nsPEFs purposes. Method: Cockcroft-Walton multiplier circuit will boost the input of 220 volt AC into high voltage DC around 1500 volt and it will be combined by a series of power MOSFET as a fast switch to obtain a high voltage with nanosecond pulse width. The motivation using Cockcroft-Walton multiplier is to acquire a low-cost high voltage DC generator; it will use capacitors and diodes arranged like a step. Power MOSFET connected in series is used as voltage divider to share the high voltage in order not to damage them. Results: This design is expected to acquire a low-cost generator that can achieve the high voltage pulse in amount of −1.5 kV with falltime 3 ns and risetime 15 ns into a 50Ω load that will be used for nsPEFs purposes. Further detailed on the circuit design will be explained at presentation.« less

Imaging Voltage in Genetically Defined Neuronal Subpopulations with a Cre Recombinase-Targeted Hybrid Voltage Sensor.

PubMed

Bayguinov, Peter O; Ma, Yihe; Gao, Yu; Zhao, Xinyu; Jackson, Meyer B

2017-09-20

Genetically encoded voltage indicators create an opportunity to monitor electrical activity in defined sets of neurons as they participate in the complex patterns of coordinated electrical activity that underlie nervous system function. Taking full advantage of genetically encoded voltage indicators requires a generalized strategy for targeting the probe to genetically defined populations of cells. To this end, we have generated a mouse line with an optimized hybrid voltage sensor (hVOS) probe within a locus designed for efficient Cre recombinase-dependent expression. Crossing this mouse with Cre drivers generated double transgenics expressing hVOS probe in GABAergic, parvalbumin, and calretinin interneurons, as well as hilar mossy cells, new adult-born neurons, and recently active neurons. In each case, imaging in brain slices from male or female animals revealed electrically evoked optical signals from multiple individual neurons in single trials. These imaging experiments revealed action potentials, dynamic aspects of dendritic integration, and trial-to-trial fluctuations in response latency. The rapid time response of hVOS imaging revealed action potentials with high temporal fidelity, and enabled accurate measurements of spike half-widths characteristic of each cell type. Simultaneous recording of rapid voltage changes in multiple neurons with a common genetic signature offers a powerful approach to the study of neural circuit function and the investigation of how neural networks encode, process, and store information. SIGNIFICANCE STATEMENT Genetically encoded voltage indicators hold great promise in the study of neural circuitry, but realizing their full potential depends on targeting the sensor to distinct cell types. Here we present a new mouse line that expresses a hybrid optical voltage sensor under the control of Cre recombinase. Crossing this line with Cre drivers generated double-transgenic mice, which express this sensor in targeted cell types. In brain slices from these animals, single-trial hybrid optical voltage sensor recordings revealed voltage changes with submillisecond resolution in multiple neurons simultaneously. This imaging tool will allow for the study of the emergent properties of neural circuits and permit experimental tests of the roles of specific types of neurons in complex circuit activity. Copyright © 2017 the authors 0270-6474/17/379305-15$15.00/0.

Zn/gelled 6 M KOH/O 2 zinc-air battery

NASA Astrophysics Data System (ADS)

Mohamad, A. A.

The gel electrolyte for the zinc-air cell was prepared by mixing hydroponics gel with a 6 M potassium hydroxide aqueous solution. The self-discharge of cells was characterized by measuring the open-circuit voltage. The effect of a discharge rate of 50 mA constant current on cell voltage and plateau hour, as well as the voltage-current and current density-power density were measured and analysed. The electrode degradation after discharge cycling was characterized by structural and surface methods. The oxidation of the electrode surface further blocked the utilization of the Zn anode and was identified as a cause for the failure of the cell.

The voltage threshold for arcing for solar cells in Leo - Flight and ground test results

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.

1986-01-01

Ground and flight results of solar cell arcing in low earth orbit (LEO) conditions are compared and interpreted. It is shown that an apparent voltage threshold for arcing may be produced by a storage power law dependence of arc rate on voltage, combined with a limited observation time. The change in this apparent threshold with plasma density is a reflection of the density dependence of the arc rate. A nearly linear dependence of arc rate on density is inferred from the data. A real voltage threshold for arcing for 2 by 2 cm solar cells may exist however, independent of plasma density, near -230 V relative to the plasma. Here, arc rates may change by more than an order of magnitude for a change of only 30 V in array potential. For 5.9 by 5.9 solar cells, the voltage dependence of the arc rate is steeper, and the data are insufficient to indicate the existence of an arcing increased by an atomic oxygen plasma, as is found in LEO, and by arcing from the backs of welded-through substrates.

The voltage threshold for arcing for solar cells in LEO: Flight and ground test results

NASA Technical Reports Server (NTRS)

Ferguson, D. C.

1986-01-01

Ground and flight results of solar cell arcing in low Earth orbit (LEO) conditions are compared and interpreted. It is shown that an apparent voltage threshold for arcing may be produced by a strong power law dependence of arc rate on voltage, combined with a limited observation time. The change in this apparent threshold with plasma density is a reflection of the density dependence of the arc rate. A nearly linear dependence of arc rate on density is inferred from the data. A real voltage threshold for arcing for 2 by 2 cm solar cells may exist however, independent of plasma density, near -230 V relative to the plasma. Here, arc rates may change by more than an order of magnitude for a change of only 30 V in array potential. For 5.9 by 5.9 solar cells, the voltage dependence of the arc rate is steeper, and the data are insufficient to indicate the existence of an arcing increased by an atomic oxygen plasma, as is found in LEO, and by arcing from the backs of welded-through substrates.

Modulation of voltage-gated conductances of retinal horizontal cells by UV-excited TiO2 nanoparticles.

PubMed

Meshik, Xenia; Choi, Min; Baker, Adam; Malchow, R Paul; Covnot, Leigha; Doan, Samuel; Mukherjee, Souvik; Farid, Sidra; Dutta, Mitra; Stroscio, Michael A

2017-04-01

This study examines the ability of optically-excited titanium dioxide nanoparticles to influence voltage-gated ion channels in retinal horizontal cells. Voltage clamp recordings were obtained in the presence and absence of TiO 2 and ultraviolet laser excitation. Significant current changes were observed in response to UV light, particularly in the -40 mV to +40 mV region where voltage-gated Na + and K + channels have the highest conductance. Cells in proximity to UV-excited TiO 2 exhibited a left-shift in the current-voltage relation of around 10 mV in the activation of Na + currents. These trends were not observed in control experiments where cells were excited with UV light without being exposed to TiO 2 . Electrostatic force microscopy confirmed that electric fields can be induced in TiO 2 with UV light. Simulations using the Hodgkin-Huxley model yielded results which agreed with the experimental data and showed the I-V characteristics of individual ion channels in the presence of UV-excited TiO 2 . Copyright © 2016 Elsevier Inc. All rights reserved.

Monolithically interconnected GaAs solar cells: A new interconnection technology for high voltage solar cell output

NASA Astrophysics Data System (ADS)

Dinetta, L. C.; Hannon, M. H.

1995-10-01

Photovoltaic linear concentrator arrays can benefit from high performance solar cell technologies being developed at AstroPower. Specifically, these are the integration of thin GaAs solar cell and epitaxial lateral overgrowth technologies with the application of monolithically interconnected solar cell (MISC) techniques. This MISC array has several advantages which make it ideal for space concentrator systems. These are high system voltage, reliable low cost monolithically formed interconnections, design flexibility, costs that are independent of array voltage, and low power loss from shorts, opens, and impact damage. This concentrator solar cell will incorporate the benefits of light trapping by growing the device active layers over a low-cost, simple, PECVD deposited silicon/silicon dioxide Bragg reflector. The high voltage-low current output results in minimal 12R losses while properly designing the device allows for minimal shading and resistance losses. It is possible to obtain open circuit voltages as high as 67 volts/cm of solar cell length with existing technology. The projected power density for the high performance device is 5 kW/m for an AMO efficiency of 26% at 1 5X. Concentrator solar cell arrays are necessary to meet the power requirements of specific mission platforms and can supply high voltage power for electric propulsion systems. It is anticipated that the high efficiency, GaAs monolithically interconnected linear concentrator solar cell array will enjoy widespread application for space based solar power needs. Additional applications include remote man-portable or ultra-light unmanned air vehicle (UAV) power supplies where high power per area, high radiation hardness and a high bus voltage or low bus current are important. The monolithic approach has a number of inherent advantages, including reduced cost per interconnect and increased reliability of array connections. There is also a high potential for a large number of consumer products. Dual-use applications can include battery chargers and remote power supplies for consumer electronics products such as portable telephones/beepers, portable radios, CD players, dashboard radar detectors, remote walkway lighting, etc.

Monolithically interconnected GaAs solar cells: A new interconnection technology for high voltage solar cell output

NASA Technical Reports Server (NTRS)

Dinetta, L. C.; Hannon, M. H.

1995-01-01

Photovoltaic linear concentrator arrays can benefit from high performance solar cell technologies being developed at AstroPower. Specifically, these are the integration of thin GaAs solar cell and epitaxial lateral overgrowth technologies with the application of monolithically interconnected solar cell (MISC) techniques. This MISC array has several advantages which make it ideal for space concentrator systems. These are high system voltage, reliable low cost monolithically formed interconnections, design flexibility, costs that are independent of array voltage, and low power loss from shorts, opens, and impact damage. This concentrator solar cell will incorporate the benefits of light trapping by growing the device active layers over a low-cost, simple, PECVD deposited silicon/silicon dioxide Bragg reflector. The high voltage-low current output results in minimal 12R losses while properly designing the device allows for minimal shading and resistance losses. It is possible to obtain open circuit voltages as high as 67 volts/cm of solar cell length with existing technology. The projected power density for the high performance device is 5 kW/m for an AMO efficiency of 26% at 1 5X. Concentrator solar cell arrays are necessary to meet the power requirements of specific mission platforms and can supply high voltage power for electric propulsion systems. It is anticipated that the high efficiency, GaAs monolithically interconnected linear concentrator solar cell array will enjoy widespread application for space based solar power needs. Additional applications include remote man-portable or ultra-light unmanned air vehicle (UAV) power supplies where high power per area, high radiation hardness and a high bus voltage or low bus current are important. The monolithic approach has a number of inherent advantages, including reduced cost per interconnect and increased reliability of array connections. There is also a high potential for a large number of consumer products. Dual-use applications can include battery chargers and remote power supplies for consumer electronics products such as portable telephones/beepers, portable radios, CD players, dashboard radar detectors, remote walkway lighting, etc.

Comparison of ``AA`` nickel metal hydride cells with ``AA`` Ni-Cd cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alminauskas, V.; Johnson, W.

1996-12-31

This paper compares ``AA`` size nickel metal hydride (Ni-HM) cells with comparable ``AA;; nickel cadmium (Ni-Cd) cells both of which were obtained in 1993. The Ni-MH cells were found to be a suitable substitute for conventional Ni-Cd cells. Both these cell types have similar voltages and discharge characteristics. The Ni-MH cells, though had nearly twice the capacity as comparable Ni-Cd cells. There was no significant difference in self discharge between the two types of cells. The Ni-MH cells also performed as well as Ni-Cd cells at rates lower than 5 amperes and at temperatures higher than 0 C (32 F).more » The most interesting finding is that the Ni-MH cells showed an irreversible decay of the discharge voltage with each cycle which was more noticeable during pulses. Eventually the Ni-MH packs fail, not because of loss of capacity, but because of low voltage during the pulse.« less

High power thyristors with 5 kV blocking voltage. Volume 1: Development of high-voltage-thyristors (4.5 kV) with good dynamic properties

NASA Technical Reports Server (NTRS)

Lock, K.; Patalong, H.; Platzoeder, K.

1979-01-01

Using neutron irradiated silicon with considerably lower spread in resistivity as compared to conventionally doped silicon it was possible to produce power thyristors with breakdown voltages between 3.5 kV and 5.5 kV. The thyristor pellets have a diameter of 50 mm. Maximum average on-state currents of 600 to 800 A can be reached with these elements. The dynamic properties of the thryistors could be improved to allow standard applications up to maximum repetitive voltages of 4.5 kV.

Impact of charge transport on current–voltage characteristics and power-conversion efficiency of organic solar cells

PubMed Central

Würfel, Uli; Neher, Dieter; Spies, Annika; Albrecht, Steve

2015-01-01

This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current–voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells. PMID:25907581

Recombination in polymer-fullerene bulk heterojunction solar cells

NASA Astrophysics Data System (ADS)

Cowan, Sarah R.; Roy, Anshuman; Heeger, Alan J.

2010-12-01

Recombination of photogenerated charge carriers in polymer bulk heterojunction (BHJ) solar cells reduces the short circuit current (Jsc) and the fill factor (FF). Identifying the mechanism of recombination is, therefore, fundamentally important for increasing the power conversion efficiency. Light intensity and temperature-dependent current-voltage measurements on polymer BHJ cells made from a variety of different semiconducting polymers and fullerenes show that the recombination kinetics are voltage dependent and evolve from first-order recombination at short circuit to bimolecular recombination at open circuit as a result of increasing the voltage-dependent charge carrier density in the cell. The “missing 0.3 V” inferred from comparison of the band gaps of the bulk heterojunction materials and the measured open-circuit voltage at room-temperature results from the temperature dependence of the quasi-Fermi levels in the polymer and fullerene domains—a conclusion based on the fundamental statistics of fermions.

Properties of voltage-activated Na+ and K+ currents in mouse hippocampal glial cells in situ and after acute isolation from tissue slices.

PubMed

Steinhäuser, C; Kressin, K; Kuprijanova, E; Weber, M; Seifert, G

1994-10-01

In the present study, we were interested in a quantitative analysis of voltage-activated channels in a subpopulation of hippocampal glial cells, termed "complex" cells. The patch-clamp technique in the whole-cell mode was applied to identified cells in situ and to glial cells acutely isolated from tissue slices. The outward current was composed of two components: a sustained and a transient current. The transient K+ channel had electrophysiological and pharmacological properties resembling those of the channel through which the A-currents pass. In addition, this glial A-type current possessed a significant Ca2+ dependence. The current parameters determined in situ or in isolated cells corresponded well. Due to space clamp problems in situ, properties of voltage-dependent Na+ currents were only analysed in suspended glial cells. The tetrodotoxin (TTX) sensitivity and the stationary and kinetic characteristics of this current were similar to corresponding properties of hippocampal neurons. These quantitative data demonstrate that at an early postnatal stage of central nervous system maturation, glial cells in situ express a complex pattern of voltage-gated ion channels. The results are compared to findings in other preparations and the possible consequences of transmitter-mediated channel modulation in glial cells are discussed.

Layered oxides-LiNi1/3Co1/3Mn1/3O2 as anode electrode for symmetric rechargeable lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Yuesheng; Feng, Zimin; Yang, Shi-Ze; Gagnon, Catherine; Gariépy, Vincent; Laul, Dharminder; Zhu, Wen; Veillette, René; Trudeau, Michel L.; Guerfi, Abdelbast; Zaghib, Karim

2018-02-01

High-performance and long-cycling rechargeable lithium-ion batteries have been in steadily increasing demand for the past decades. Nevertheless, the two dominant anodes at the moment, graphite and L4T5O12, suffer from a safety issue of lithium plating (operating voltage at ∼ 0.1 V vs. Li+/Li) and low capacity (175 mAh/g), respectively. Here, we report LiNi1/3Co1/3Mn1/3O2 as an alternative anode material which has a working voltage of ∼1.1 V and a capacity as high as 330 mAh/g at the current rate of C/15. Symmetric cells with both electrodes containing LiNi1/3Co1/3Mn1/3O2 can deliver average discharge voltage of 2.2 V. In-situ XRD, HRTEM and first principles calculations indicate that the reaction mechanism of a LiNi1/3Co1/3Mn1/3O2 anode is comprised mainly of conversion. Both the fundamental understanding and practical demonstrations suggest that LiNi1/3Co1/3Mn1/3O2 is a promising negative electrode material for lithium-ion batteries.

Influence of process conditions during impulsed electrostatic droplet formation on size distribution of hydrogel beads.

PubMed

Lewińska, Dorota; Rosiński, Stefan; Weryński, Andrzej

2004-02-01

In the medical applications of microencapsulation of living cells there are strict requirements concerning the high size uniformity and the optimal diameter, the latter dependent on the kind of therapeutic application, of manufactured gel beads. The possibility of manufacturing small size gel bead samples (diameter 300 microm and below) with a low size dispersion (less than 10%), using an impulsed voltage droplet generator, was examined in this work. The main topic was the investigation of the influence of values of electric parameters (voltage U, impulse time tau and impulse frequency f) on the quality of obtained droplets. It was concluded that, owing to the implementation of the impulse mode and regulation of tau and f values, it is possible to work in a controlled manner in the jet flow regime (U> critical voltage UC). It is also possible to obtain uniform bead samples with the average diameter, deff, significantly lower than the nozzle inner diameter dI (bead diameters 0.12-0.25 mm by dI equal to 0.3 mm, size dispersion 5-7%). Alterations of the physical parameters of the process (polymer solution physico-chemical properties, flow rate, distance between nozzle and gellifying bath) enable one to manufacture uniform gel beads in the wide range of diameters using a single nozzle.

Voltage Preconditioning Allows Modulated Gene Expression in Neurons Using PEI-complexed siRNA

PubMed Central

Sridharan, Arati; Patel, Chetan; Muthuswamy, Jit

2013-01-01

We present here a high efficiency, high viability siRNA-delivery method using a voltage-controlled chemical transfection strategy to achieve modulated delivery of polyethylenimine (PEI) complexed with siRNA in an in vitro culture of neuro2A cells and neurons. Low voltage pulses were applied to adherent cells before the administration of PEI-siRNA complexes. Live assays of neuro2a cells transfected with fluorescently tagged siRNA showed an increase in transfection efficiency from 62 ± 14% to 98 ± 3.8% (after −1 V). In primary hippocampal neurons, transfection efficiencies were increased from 30 ± 18% to 76 ± 18% (after −1 V). Negligible or low-level transfection was observed after preconditioning at higher voltages, suggesting an inverse relationship with applied voltage. Experiments with propidium iodide ruled out the role of electroporation in the transfection of siRNAs suggesting an alternate electro-endocytotic mechanism. In addition, image analysis of preconditioned and transfected cells demonstrates siRNA uptake and loading that is tuned to preconditioning voltage levels. There is approximately a fourfold increase in siRNA loading after preconditioning at −1 V compared with the same at ±2–3 V. Modulated gene expression is demonstrated in a functional knockdown of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in neuro2A cells using siRNA. Cell density and dendritic morphological changes are also demonstrated in modulated knockdown of brain derived neurotrophic factor (BDNF) in primary hippocampal neurons. The method reported here has potential applications in the development of high-throughput screening systems for large libraries of siRNA molecules involving difficult-to-transfect cells like neurons. PMID:23531602

Voltage Preconditioning Allows Modulated Gene Expression in Neurons Using PEI-complexed siRNA.

PubMed

Sridharan, Arati; Patel, Chetan; Muthuswamy, Jit

2013-03-26

We present here a high efficiency, high viability siRNA-delivery method using a voltage-controlled chemical transfection strategy to achieve modulated delivery of polyethylenimine (PEI) complexed with siRNA in an in vitro culture of neuro2A cells and neurons. Low voltage pulses were applied to adherent cells before the administration of PEI-siRNA complexes. Live assays of neuro2a cells transfected with fluorescently tagged siRNA showed an increase in transfection efficiency from 62 ± 14% to 98 ± 3.8% (after -1 V). In primary hippocampal neurons, transfection efficiencies were increased from 30 ± 18% to 76 ± 18% (after -1 V). Negligible or low-level transfection was observed after preconditioning at higher voltages, suggesting an inverse relationship with applied voltage. Experiments with propidium iodide ruled out the role of electroporation in the transfection of siRNAs suggesting an alternate electro-endocytotic mechanism. In addition, image analysis of preconditioned and transfected cells demonstrates siRNA uptake and loading that is tuned to preconditioning voltage levels. There is approximately a fourfold increase in siRNA loading after preconditioning at -1 V compared with the same at ±2-3 V. Modulated gene expression is demonstrated in a functional knockdown of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in neuro2A cells using siRNA. Cell density and dendritic morphological changes are also demonstrated in modulated knockdown of brain derived neurotrophic factor (BDNF) in primary hippocampal neurons. The method reported here has potential applications in the development of high-throughput screening systems for large libraries of siRNA molecules involving difficult-to-transfect cells like neurons.Molecular Therapy-Nucleic Acids (2013) 2, e82; doi:10.1038/mtna.2013.10; published online 26 March 2013.

User handbook for block IV silicon solar cell modules

NASA Technical Reports Server (NTRS)

Smokler, M. I.

1982-01-01

The essential electrical and mechanical characteristics of block 4 photovoltaic solar cell modules are described. Such module characteristics as power output, nominal operating voltage, current-voltage characteristics, nominal operating cell temperature, and dimensions are tabulated. The limits of the environmental and other stress tests to which the modules are subjected are briefly described.

Recent progress in high-output-voltage silicon solar cells

NASA Technical Reports Server (NTRS)

Muelenberg, A.; Arndt, R. A.; Allison, J. F.; Weizer, V.

1980-01-01

The status of the technology associated with the development of high output voltage silicon solar cells is reported. The energy conversion efficiency of a double diffusion process is compared to that of a single diffusion process. The efficiency of a 0.1 ohm/cm solar cell is characterized both before and after covering.

Fabrication of multijunction high voltage concentrator solar cells by integrated circuit technology

NASA Technical Reports Server (NTRS)

Valco, G. J.; Kapoor, V. J.; Evans, J. C., Jr.; Chai, A.-T.

1981-01-01

Standard integrated circuit technology has been developed for the design and fabrication of planar multijunction (PMJ) solar cell chips. Each 1 cm x 1 cm solar chip consisted of six n(+)/p, back contacted, internally series interconnected unit cells. These high open circuit voltage solar cells were fabricated on 2 ohm-cm, p-type 75 microns thick, silicon substrates. A five photomask level process employing contact photolithography was used to pattern for boron diffusions, phorphorus diffusions, and contact metallization. Fabricated devices demonstrated an open circuit voltage of 3.6 volts and a short circuit current of 90 mA at 80 AMl suns. An equivalent circuit model of the planar multi-junction solar cell was developed.

Transfer characteristics of the hair cell's afferent synapse

NASA Astrophysics Data System (ADS)

Keen, Erica C.; Hudspeth, A. J.

2006-04-01

The sense of hearing depends on fast, finely graded neurotransmission at the ribbon synapses connecting hair cells to afferent nerve fibers. The processing that occurs at this first chemical synapse in the auditory pathway determines the quality and extent of the information conveyed to the central nervous system. Knowledge of the synapse's input-output function is therefore essential for understanding how auditory stimuli are encoded. To investigate the transfer function at the hair cell's synapse, we developed a preparation of the bullfrog's amphibian papilla. In the portion of this receptor organ representing stimuli of 400-800 Hz, each afferent nerve fiber forms several synaptic terminals onto one to three hair cells. By performing simultaneous voltage-clamp recordings from presynaptic hair cells and postsynaptic afferent fibers, we established that the rate of evoked vesicle release, as determined from the average postsynaptic current, depends linearly on the amplitude of the presynaptic Ca2+ current. This result implies that, for receptor potentials in the physiological range, the hair cell's synapse transmits information with high fidelity. auditory system | exocytosis | glutamate | ribbon synapse | synaptic vesicle

Mechanisms limiting the performance of large grain polycrystalline silicon solar cells

NASA Technical Reports Server (NTRS)

Culik, J. S.; Alexander, P.; Dumas, K. A.; Wohlgemuth, J. W.

1984-01-01

The open-circuit voltage and short-circuit current of large-grain (1 to 10 mm grain diameter) polycrystalline silicon solar cells is determined by the minority-carrier diffusion length within the bulk of the grains. This was demonstrated by irradiating polycrystalline and single-crystal (Czochralski) silicon solar cells with 1 MeV electrons to reduce their bulk lifetime. The variation of short-circuit current with minority-carrier diffusion length for the polycrystalline solar cells is identical to that of the single-crystal solar cells. The open-circuit voltage versus short-circuit current characteristic of the polycrystalline solar cells for reduced diffusion lengths is also identical to that of the single-crystal solar cells. The open-circuit voltage of the polycrystalline solar cells is a strong function of quasi-neutral (bulk) recombination, and is reduced only slightly, if at all, by grain-boundary recombination.

Electromagnetic Radiation in the Plasma Environment Around the Shuttle

NASA Technical Reports Server (NTRS)

Vayner, Boris V.; Ferguson, Dale C.

1995-01-01

As part of the SAMPIE (The Solar Array Module Plasma Interaction Experiment) program, the Langmuir probe (LP) was employed to measure plasma characteristics during the flight STS-62. The whole set of data could be divided into two parts: (1) low frequency sweeps to determine voltage-current characteristics and to find electron temperature and number density; (2) high frequency turbulence (HFT dwells) data caused by electromagnetic noise around the shuttle. The broadband noise was observed at frequencies 250-20,000 Hz. Measurements were performed in ram conditions; thus, it seems reasonable to believe that the influence of spacecraft operations on plasma parameters was minimized. The average spectrum of fluctuations is in agreement with theoretical predictions. According to purposes of SAMPIE, the samples of solar cells were placed in the cargo bay of the shuttle, and high negative bias voltages were applied to them to initiate arcing between these cells and surrounding plasma. The arcing onset was registered by special counters, and data were obtained that included the amplitudes of current, duration of each arc, and the number of arcs per one experiment. The LP data were analyzed for two different situations: with arcing and without arcing. Electrostatic noise spectra for both situations and theoretical explanation of the observed features are presented in this report.

High speed municipal sewage treatment in microbial fuel cell integrated with anaerobic membrane filtration system.

PubMed

Lee, Y; Oa, S W

2014-01-01

A cylindrical two chambered microbial fuel cell (MFC) integrated with an anaerobic membrane filter was designed and constructed to evaluate bioelectricity generation and removal efficiency of organic substrate (glucose or domestic wastewater) depending on organic loading rates (OLRs). The MFC was continuously operated with OLRs 3.75, 5.0, 6.25, and 9.38 kg chemical oxygen demand (COD)/(m(3)·d) using glucose as a substrate, and the cathode chamber was maintained at 5-7 mg/L of dissolved oxygen. The optimal OLR was found to be 6.25 kgCOD/(m(3)·d) (hydraulic retention time (HRT) 1.9 h), and the corresponding voltage and power density averaged during the operation were 0.15 V and 13.6 mW/m(3). With OLR 6.25 kgCOD/(m(3)·d) using domestic wastewater as a substrate, the voltage and power reached to 0.13 V and 91 mW/m(3) in the air cathode system. Even though a relatively short HRT of 1.9 h was applied, stable effluent could be obtained by the membrane filtration system and the following air purging. In addition, the short HRT would provide economic benefit in terms of reduction of construction and operating costs compared with a conventional aerobic treatment process.

Preparation of AgInS2 nanoparticles by a facile microwave heating technique; study of effective parameters, optical and photovoltaic characteristics

NASA Astrophysics Data System (ADS)

Tadjarodi, Azadeh; Cheshmekhavar, Amir Hossein; Imani, Mina

2012-12-01

In this work, AgInS2 (AIS) semiconductor nanoparticles were synthesized by an efficient and facile microwave heating technique using several sulfur sources and solvents in the different reaction times. The SEM images presented the particle morphology for all of the obtained products in the arranged reaction conditions. The particle size of 70 nm was obtained using thioacetamide (TAA), ethylene glycol (EG) as the sulfur source and solvent, respectively at the reaction time of 5 min. It was found that the change of the mentioned parameters lead to alter on the particle size of the resulting products. The average particle size was estimated using a microstructure measurement program and Minitab statistical software. The optical band gap energy of 1.96 eV for the synthesized AIS nanoparticles was determined by the diffuse reflectance spectroscopy (DRS). AgInS2/CdS/CuInSe2 heterojunction solar cell was constructed and photovoltaic parameters, i.e., open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) were estimated by photocurrent-voltage (I-V) curve. The calculated fill factor of 30% and energy conversion efficiency of 1.58% revealed the capability of AIS nanoparticles to use in the solar cell devices.

Electrical insulation design requirements and reliability goals

NASA Astrophysics Data System (ADS)

Ross, R. G., Jr.

1983-11-01

The solar cells in a photovoltaic module which must be electrically isolated from module exterior surfaces to satisfy a variety of safety and operating considerations are discussed. The performance and reliability of the insulation system are examined. Technical requirements involve the capability of withstanding the differential voltage from the solar cells to the module frame. The maximum system voltage includes consideration of maximum open circuit array voltages achieved under low-temperature, high-irradiance conditions, and transient overvoltages due to system feedback of lightning transients. The latter is bounded by the characteristics of incorporated voltage limiting devices such as MOVs.

Performance of a 14.9-kW laminated-frame dc series motor with chopper controller

NASA Technical Reports Server (NTRS)

Schwab, J. R.

1979-01-01

Traction motor using two types of excitation: ripple free dc from a motor generator set for baseline data and chopped dc as supplied by a battery and chopper controller was tested. For the same average values of input voltage and current, the power output was independent of the type of excitation. At the same speeds, motor efficiency at low power output (corresponding to low duty cycle of the controller) was 5 to 10 percentage points less on chopped dc than on ripple-free dc. This illustrates that for chopped waveforms, it is incorrect to calculate input power as the product of average voltage and average current. Locked-rotor torque, no load losses, and magnetic saturation data were so determined.

Some properties of NiH2 cells

NASA Astrophysics Data System (ADS)

Rogers, H. H.

1982-03-01

Different tests on a flight type cell are discussed. The temperature was measured at the cell flange. The cell was charged to rollover at .75 C rate at 40 degrees C for the first temperature. At that point a voltage reading was taken. Charging was done for an arbitrary ten seconds at .75 C, 30 C, 20 C, 10 C and zero C to obtain momentarily stable voltages.

Enhancement of reverse transfection efficiency by combining stimulated DNA surface desorption and electroporation

NASA Astrophysics Data System (ADS)

Creasey, Rhiannon; Hook, Andrew; Thissen, Helmut; Voelcker, Nicolas H.

2007-12-01

Transfection cell microarrays (TCMs) are a high-throughput, miniaturised cell-culture system utilising reverse transfection, in which cells are seeded onto a DNA array resulting in localised regions of transfected cells. TCMs are useful for the analysis of gene expression, and can be used to identify genes involved in many cellular processes. This is of significant interest in fields such as tissue engineering, diagnostic screening, and drug testing [1, 2]. Low transfection efficiency has so far limited the application and utility of this technique. Recently, the transfection efficiency of TCMs was improved by an application of a high voltage for a short period of time to the DNA array resulting in the electroporation of cells attached to the surface [3, 4]. Furthermore, application of a low voltage for a longer period of time to the DNA array was shown to improve the transfection efficiency by stimulating the desorption of attached DNA, increasing the concentration of DNA available for cellular uptake [5]. In the present study, the optimisation of the uptake of adsorbed DNA vectors by adherent cells, utilising a voltage bias without compromising cell viability was investigated. This was achieved by depositing negatively charged DNA plasmids onto a positively charged allylamine plasma polymer (ALAPP) layer deposited on highly doped p-type silicon wafers either using a pipettor or a microarray contact printer. Surface-dependant human embryonic kidney (HEK 293 line) cells were cultured onto the DNA vector loaded ALAPP spots and the plasmid transfection events were detected by fluorescence microscopy. Cell viability assays, including fluorescein diacetate (FDA) / Hoechst DNA labelling, were carried out to determine the number of live adherent cells before and after application of a voltage. A protocol was developed to screen for voltage biases and exposure times in order to optimise transfection efficiency and cell viability. Cross-contamination between the microarray spots carrying different DNA vectors was also investigated. By application of a voltage of 286 V/cm for 10 ms, transfection efficiency was doubled compared to using only transfection reagent, whilst maintaining a cell viability of 60-70% of the positive control.

Activation of cannabinoid CB1 receptors modulates evoked action potentials in rat retinal ganglion cells.

PubMed

Jiang, Shu-Xia; Li, Qian; Wang, Xiao-Han; Li, Fang; Wang, Zhong-Feng

2013-08-25

Activation of cannabinoid CB1 receptors (CB1Rs) regulates a variety of physiological functions in the vertebrate retina through modulating various types of ion channels. The aim of the present study was to investigate the effects of this receptor on cell excitability of rat retinal ganglion cells (RGCs) in retinal slices using whole-cell patch-clamp techniques. The results showed that under current-clamped condition perfusing WIN55212-2 (WIN, 5 μmol/L), a CB1R agonist, did not significantly change the spontaneous firing frequency and resting membrane potential of RGCs. In the presence of cocktail synaptic blockers, including excitatory postsynaptic receptor blockers CNQX and D-APV, and inhibitory receptor blockers bicuculline and strychnine, perfusion of WIN (5 μmol/L) hardly changed the frequencies of evoked action potentials by a series of positive current injection (from +10 to +100 pA). Phase-plane plot analysis showed that both average threshold voltage for triggering action potential and delay time to reach threshold voltage were not affected by WIN. However, WIN significantly decreased +dV/dtmax and -dV/dtmax of action potentials, suggestive of reduced rising and descending velocities of action potentials. The effects of WIN were reversed by co-application of SR141716, a CB1R selective antagonist. Moreover, WIN did not influence resting membrane potential of RGCs with synaptic inputs being blocked. These results suggest that activation of CB1Rs may regulate intrinsic excitability of rat RGCs through modulating evoked action potentials.

Voltage-gated sodium channel expression and action potential generation in differentiated NG108-15 cells.

PubMed

Liu, Jinxu; Tu, Huiyin; Zhang, Dongze; Zheng, Hong; Li, Yu-Long

2012-10-25

The generation of action potential is required for stimulus-evoked neurotransmitter release in most neurons. Although various voltage-gated ion channels are involved in action potential production, the initiation of the action potential is mainly mediated by voltage-gated Na+ channels. In the present study, differentiation-induced changes of mRNA and protein expression of Na+ channels, Na+ currents, and cell membrane excitability were investigated in NG108-15 cells. Whole-cell patch-clamp results showed that differentiation (9 days) didn't change cell membrane excitability, compared to undifferentiated state. But differentiation (21 days) induced the action potential generation in 45.5% of NG108-15 cells (25/55 cells). In 9-day-differentiated cells, Na+ currents were mildly increased, which was also found in 21-day differentiated cells without action potential. In 21-day differentiated cells with action potential, Na+ currents were significantly enhanced. Western blot data showed that the expression of Na+ channels was increased with differentiated-time dependent manner. Single-cell real-time PCR data demonstrated that the expression of Na+ channel mRNA was increased by 21 days of differentiation in NG108-15 cells. More importantly, the mRNA level of Na+ channels in cells with action potential was higher than that in cells without action potential. Differentiation induces expression of voltage-gated Na+ channels and action potential generation in NG108-15 cells. A high level of the Na+ channel density is required for differentiation-triggered action potential generation.

High voltage series connected tandem junction solar battery

DOEpatents

Hanak, Joseph J.

1982-01-01

A high voltage series connected tandem junction solar battery which comprises a plurality of strips of tandem junction solar cells of hydrogenated amorphous silicon having one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon, arranged in a tandem configuration, can have the same bandgap or differing bandgaps. The tandem junction strip solar cells are series connected to produce a solar battery of any desired voltage.

FLASH X-RAY (FXR) LINEAR INDUCTION ACCELERATOR (LIA) OPTIMIZATION Sensor Delay Correction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ong, M M; Houck, T L; Kreitzer, B R

2006-05-01

The radiographic goal of the FXR Optimization Project is to generate an x-ray pulse with peak energy of 19 MeV, spot-size of 1.5 mm, a dose of 500 rad, and duration of 60 ns. The electrical objectives are to generate a 3 kA electron-beam and refine our 16 MV accelerator so that the voltage does not vary more than 1%-rms. In a multi-cell linear induction accelerator, like FXR, the timing of the acceleration pulses relative to the beam is critical. The pulses must be timed optimally so that a cell is at full voltage before the beam arrives and doesmore » not drop until the beam passes. In order to stay within the energy-variation budget, the synchronization between the cells and beam arrival must be controlled to a couple of nanoseconds. Therefore, temporal measurements must be accurate to a fraction of a nanosecond. FXR Optimization Project developed a one-giga-sample per second (gs/s) data acquisition system to record beam sensor data. Signal processing algorithms were written to determine cell timing with an uncertainty of a fraction of a nanosecond. However, the uncertainty in the sensor delay was still a few nanoseconds. This error had to be reduced if we are to improve the quality of the electron beam. Two types of sensors are used to align the cell voltage pulse against the beam current. The beam current is measured with resistive-wall sensors. The cell voltages are read with capacitive voltage monitors. Sensor delays can be traced to two mechanisms: (1) the sensors are not co-located at the beam and cell interaction points, and (2) the sensors have different length jumper cables and other components that connect them to the standard-length coaxial cables of the data acquisition system. Using the physical locations and dimensions of the sensor components, and the dielectric constant of the materials, delay times were computed. Relative to the cell voltage, the beam current was theoretically reporting late by 7.7 ns. Two experiments were performed to verify and refine the sensor delay correction. In the first experiment, the beam was allowed to drift through a cell that was not pulsed. The beam induces a potential into the cell that is read by the voltage monitor. Analysis of the data indicated that the beam sensor signal was likely 7.1 ns late. In the second experiment, the beam current is calculated from the injector diode voltage that is the sum of the cell voltages. A 7 ns correction produced a very good match between the signals from the two types of sensors. For simplicity, we selected a correction factor that advanced the current signals by 7 ns. This should reduce the uncertainty in the temporal measurements to less than 1 ns.« less

Imaging of Brain Slices with a Genetically Encoded Voltage Indicator.

PubMed

Quicke, Peter; Barnes, Samuel J; Knöpfel, Thomas

2017-01-01

Functional fluorescence microscopy of brain slices using voltage sensitive fluorescent proteins (VSFPs) allows large scale electrophysiological monitoring of neuronal excitation and inhibition. We describe the equipment and techniques needed to successfully record functional responses optical voltage signals from cells expressing a voltage indicator such as VSFP Butterfly 1.2. We also discuss the advantages of voltage imaging and the challenges it presents.

Performance and Safety Tests of Lithium-Ion Cells Arranged in a Matrix Design Configuration

NASA Technical Reports Server (NTRS)

Jeevarajan, Judith; Tracinski, Walt

2010-01-01

Matrix Packs display large variations in cell bank voltages at the charge and discharge current (C/2) used in this test program. The voltage difference is larger at the end of discharge than at the end of charge under the conditions studied. Disconnection of a cell from the pack leads to a larger voltage difference during discharge (greater than 2.0 V) between the bank that has one less cell and the other banks. Thermal profile does not show any significant changes or increase in temperature after one cell was disconnected from the bank in spite of falling to very low voltages at the end of discharge. All tests on the matrix pack with the HAM displayed lower max in general due to the placement of thermocouple on the outside of the HAM rather than on the cells. Disconnection of cells has almost no influence on the performance of the packs and does not show any abnormal thermal changes for the 100 cycles obtained in this test program. Longer cycle life may influence the performance especially if the low voltage cell goes into reversal. Overcharge leads to CID activation of cells. If the matrix configuration has a larger number of cells in series, (more than 5 S configuration), the limitations of protective devices may manifest itself irrespective of it being in a matrix configuration. External short circuit causes a fire with expulsion of content from some cells. The fire does not propagate itself laterally, but if there was cell module stacking, then the fire would cause the cells above it to also go into flames/thermal runaway. Limitations of protective devices are observed in this case as the PTCs in the cells did not protect under this abusive condition. Matrix configurations seem to provide protection against lateral propagation of fire and flame. Matrix pack configuration seems to provide good performance in spite of losing cell connections; at least for the configuration tested under this program.

Spontaneous oscillations of cell voltage, power density, and anode exit CO concentration in a PEM fuel cell.

PubMed

Lu, Hui; Rihko-Struckmann, Liisa; Sundmacher, Kai

2011-10-28

The spontaneous oscillations of the cell voltage and output power density of a PEMFC (with PtRu/C anode) using CO-containing H(2) streams as anodic fuels have been observed during galvanostatic operating. It is ascribed to the dynamic coupling of the CO adsorption (poisoning) and the electrochemical CO oxidation (reactivating) processes in the anode chamber of the single PEMFC. Accompanying the cell voltage and power density oscillations, the discrete CO concentration oscillations at the anode outlet of the PEMFC were also detected, which directly confirms the electrochemical CO oxidation taking place in the anode chamber during galvanostatic operating. This journal is © the Owner Societies 2011

Li-Ion polymer cells thermal property changes as a function of cycle-life

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maleki, Hossein; Wang, Hsin; Porter, Wallace D

2014-01-01

The impact of elevated temperature chargeedischarge cycling on thermal conductivity (K-value) of Lithium Ion Polymer (LIP) cells of various chemistries from three different manufacturers was investigated. These included high voltage (Graphite/LiCoO2:3.0e4.35 V), wide voltage (Si:C/LiCoO2:2.7e4.35 V) and conventional (Graphite/LiCoO2:3.0e4.2 V) chemistries. Investigation results show limited variability within the in-plane and through-plane K-values for the fresh cells with graphite-based anodes from all three suppliers. After 500 cycles at 45 C, in-plane and through-plane K-values of the high voltage cells reduced less vs. those for the wide voltage cells. Such results suggest that high temperature cycling could have a greater impact onmore » thermal properties of Si:C cells than on the LIP cells with graphite (Gr) anode cells we tested. This difference is due to the excess swelling of Si:C-anode based cells vs. Gr-anode cells during cycling, especially at elevated temperatures. Thermal modeling is used to evaluate the impact of K-value changes, due to cycles at 45 C, on the cells internal heat propagation under internal short circuit condition that leads to localized meltdown of the separator.« less

Fuel cell serves as oxygen level detector

NASA Technical Reports Server (NTRS)

1965-01-01

Monitoring the oxygen level in the air is accomplished by a fuel cell detector whose voltage output is proportional to the partial pressure of oxygen in the sampled gas. The relationship between output voltage and partial pressure of oxygen can be calibrated.

Solar array experiments on the SPHINX satellite. [Space Plasma High voltage INteraction eXperiment satellite

NASA Technical Reports Server (NTRS)

Stevens, N. J.

1974-01-01

The Space Plasma, High Voltage Interaction Experiment (SPHINX) is the name given to an auxiliary payload satellite scheduled to be launched in January 1974. The principal experiments carried on this satellite are specifically designed to obtain the engineering data on the interaction of high voltage systems with the space plasma. The classes of experiments are solar array segments, insulators, insulators with pin holes and conductors. The satellite is also carrying experiments to obtain flight data on three new solar array configurations: the edge illuminated-multijunction cells, the teflon encased cells, and the violet cells.

Simulator of Non-homogenous Alumina and Current Distribution in an Aluminum Electrolysis Cell to Predict Low-Voltage Anode Effects

NASA Astrophysics Data System (ADS)

Dion, Lukas; Kiss, László I.; Poncsák, Sándor; Lagacé, Charles-Luc

2018-04-01

Perfluorocarbons are important contributors to aluminum production greenhouse gas inventories. Tetrafluoromethane and hexafluoroethane are produced in the electrolysis process when a harmful event called anode effect occurs in the cell. This incident is strongly related to the lack of alumina and the current distribution in the cell and can be classified into two categories: high-voltage and low-voltage anode effects. The latter is hard to detect during the normal electrolysis process and, therefore, new tools are necessary to predict this event and minimize its occurrence. This paper discusses a new approach to model the alumina distribution behavior in an electrolysis cell by dividing the electrolytic bath into non-homogenous concentration zones using discrete elements. The different mechanisms related to the alumina distribution are discussed in detail. Moreover, with a detailed electrical model, it is possible to calculate the current distribution among the different anodic assemblies. With this information, the model can evaluate if low-voltage emissions are likely to be present under the simulated conditions. Using the simulator will help the understanding of the role of the alumina distribution which, in turn, will improve the cell energy consumption and stability while reducing the occurrence of high- and low-voltage anode effects.

Low-voltage-operated organic one-time programmable memory using printed organic thin-film transistors and antifuse capacitors.

PubMed

Jung, Soon-Won; Na, Bock Soon; Park, Chan Woo; Koo, Jae Bon

2014-11-01

We demonstrate an organic one-time programmable memory cell formed entirely at plastic-compatible temperatures. All the processes are performed at below 130 degrees C. Our memory cell consists of a printed organic transistor and an organic capacitor. Inkjet-printed organic transistors are fabricated by using high-k polymer dielectric blends comprising poly(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)] and poly(methyl methacrylate) (PMMA) for low-voltage operation. P(NDI2OD-T2) transistors have a high field-effect mobility of 0.2 cm2/Vs and a low operation gate voltage of less than 10 V. The operation voltage effectively decreases owing to the high permittivity of the P(VDF-TrFE):PMMA blended film. The data in the memory cell are programmed by electrically breaking the organic capacitor. The organic capacitor acts like an antifuse capacitor, because it is initially open, and it becomes permanently short-circuited by applying a high voltage. The organic memory cells are programmed with 4 V, and they are read out with 2 V. The memory data are read out by sensing the current in the memory cell. The printed organic one-time programmable memory is suitable for applications storing small amount of data, such as low-cost radio-frequency identification (RFID) tag.

Probe Measurements of Parameters of Streamers of Nanosecond Frequency Crown Discharge

NASA Astrophysics Data System (ADS)

Ponizovskiy, A. Z.; Gosteev, S. G.

2017-12-01

Investigations of the parameters of single streamers of nanosecond frequency corona discharge, creating a voluminous low-temperature plasma in extended coaxial electrode systems, are performed. Measurements of the parameters of streamers were made by an isolated probe situated on the outer grounded electrode. Streamers were generated under the action of voltage pulses with a front of 50-300 ns, duration of 100-600 ns, and amplitude up to 100 kV at the frequency of 50-1000 Hz. The pulse voltage, the total current of the corona, current per probe, and glow in the discharge gap were recorded in the experiments. It was established that, at these parameters of pulse voltage, streamers propagate at an average strength of the electric field of 4-10 kV/cm. Increasing the pulse amplitude leads to an increase in the number of streamers hitting the probe, an increase in the average charge of the head of a streamer, and, as a consequence, an increase in the total streamer current and the energy introduced into the gas. In the intervals up to 3 cm, streamer breakdown at an average field strength of 5-10 kV/cm is possible. In longer intervals, during the buildup of voltage after generation of the main pulse, RF breakdown is observed at E av ≈ 4 kV/cm.

Statistical and clustering analysis for disturbances: A case study of voltage dips in wind farms

DOE PAGES

Garcia-Sanchez, Tania; Gomez-Lazaro, Emilio; Muljadi, Eduard; ...

2016-01-28

This study proposes and evaluates an alternative statistical methodology to analyze a large number of voltage dips. For a given voltage dip, a set of lengths is first identified to characterize the root mean square (rms) voltage evolution along the disturbance, deduced from partial linearized time intervals and trajectories. Principal component analysis and K-means clustering processes are then applied to identify rms-voltage patterns and propose a reduced number of representative rms-voltage profiles from the linearized trajectories. This reduced group of averaged rms-voltage profiles enables the representation of a large amount of disturbances, which offers a visual and graphical representation ofmore » their evolution along the events, aspects that were not previously considered in other contributions. The complete process is evaluated on real voltage dips collected in intense field-measurement campaigns carried out in a wind farm in Spain among different years. The results are included in this paper.« less

[Study of microorganism sterilization by instant microwave and electromagnetic pulse].

PubMed

Lu, Zhiyuan; Shi, Pinpin; Zhu, Manzuo; Sun, Wenquan; Ding, Hua; Hou, Jianqiang

2008-08-01

The sterilization effects of constant electromagnetic wave and instant pulse on foods and traditional Chinese medical pills are introduced in this paper. From the velum's voltage variation caused by the outward electric filed,the dielectric properties of membranaceous ion and the pass rate of the membranaceous ion, we could analyze the biological heating effect and the biological non-heating effect. The sterilization effect of constant electromagnetic wave is based on the biological heating effect, while the instant electromagnetic pulse is based on the biological non-heating effect. With the applied electronic field, the voltage of membrane could increase, which results in the gates of K+ open, and the flowing out of K+. And the variation of the membranaceous voltage makes the gates of Ca2+ open. The Ca2+ of large consistency could come into the cell by the gradient of voltage. It could induce the death of the cells. The greater the variation of membranaceous voltage becomes, the higher will be the death rate of the cells.

Accurate reconstruction of the jV-characteristic of organic solar cells from measurements of the external quantum efficiency

NASA Astrophysics Data System (ADS)

Meyer, Toni; Körner, Christian; Vandewal, Koen; Leo, Karl

2018-04-01

In two terminal tandem solar cells, the current density - voltage (jV) characteristic of the individual subcells is typically not directly measurable, but often required for a rigorous device characterization. In this work, we reconstruct the jV-characteristic of organic solar cells from measurements of the external quantum efficiency under applied bias voltages and illumination. We show that it is necessary to perform a bias irradiance variation at each voltage and subsequently conduct a mathematical correction of the differential to the absolute external quantum efficiency to obtain an accurate jV-characteristic. Furthermore, we show that measuring the external quantum efficiency as a function of voltage for a single bias irradiance of 0.36 AM1.5g equivalent sun provides a good approximation of the photocurrent density over voltage curve. The method is tested on a selection of efficient, common single-junctions. The obtained conclusions can easily be transferred to multi-junction devices with serially connected subcells.

Intermediate photovoltaic system application experiment operational performance report: Volume 5, for Beverly High School, Beverly, Mass.

NASA Astrophysics Data System (ADS)

1982-02-01

Performance data for the month of January, 1982 for a grid connected photovoltaic power supply in Massachusetts are presented. Data include: monthly and daily electrical energy produced; monthly and daily solar energy incident on the array; monthly and daily array efficiency; plots of energy produced as a function of power level, voltage, cell temperature and time of day; power conditioner input, output and efficiency for each of two individual units and for the total power conditioning system; photovoltaic system efficiency; capacity factor; PV system to load and grid to load energies and corresponding dollar values; daily energy supplies to the load by the PV system; daily PV system availability; monthly and hourly insolation; monthly and hourly temperature average; monthly and hourly wind speed; wind direction distribution; average heating and cooling degree days; number of freeze/thaw cycles; and the data acquisition mode and recording interval plot.

Lithium Cell Reactions.

DTIC Science & Technology

1983-12-01

Li/SOCL, cells in- dicate that up to PPM water can be added to the electrolyte without detrimental effects. At water levels ab 100 PPM voltage delay...48 2.3 THE EFFECT OF WATER AND HYDROLYSIS PRODUCTS ON PERFORMANCE ........ 51 2.4 THE...Li/SOCI, Cells with 0, 20 and 100 PPM Water added to the Electrolyte.* ..................................................... 52 51. Voltage Delay for

Performance and Safety of Lithium Ion Cells

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Smart, M. C.; Whitcanack, L.; Surampudi, S.; Marsh, R.

2001-01-01

This report evaluates the performance and safety of Lithium Ion (Li-Ion) cells when used in batteries. Issues discussed include the cycle life, energy efficiency, tolerance to higher charge voltage, tolerance to extended tapered charge voltage, charge on cycling, specific energy, low temperature discharge, low temperature charge, various charge characteristics, storage characteristics, and more of Li-Ion cells.

30 CFR 90.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... pack multiplied by 1.25. The voltage for other than nickel cadmium cell batteries shall not be lower than the product of the number of cells in the battery pack multiplied by the manufacturer's nominal voltage per cell value; (2) Examination of all components of the cyclone to assure that they are clean and...

Deviation Value for Conventional X-ray in Hospitals in South Sulawesi Province from 2014 to 2016

NASA Astrophysics Data System (ADS)

Bachtiar, Ilham; Abdullah, Bualkar; Tahir, Dahlan

2018-03-01

This paper describes the conventional X-ray machine parameters tested in the region of South Sulawesi from 2014 to 2016. The objective of this research is to know deviation of every parameter of conventional X-ray machine. The testing parameters were analyzed by using quantitative methods with participatory observational approach. Data collection was performed by testing the output of conventional X-ray plane using non-invasive x-ray multimeter. The test parameters include tube voltage (kV) accuracy, radiation output linearity, reproducibility and radiation beam value (HVL) quality. The results of the analysis show four conventional X-ray test parameters have varying deviation spans, where the tube voltage (kV) accuracy has an average value of 4.12%, the average radiation output linearity is 4.47% of the average reproducibility of 0.62% and the averaged of the radiation beam (HVL) is 3.00 mm.

The high voltage homopolar generator

NASA Astrophysics Data System (ADS)

Price, J. H.; Gully, J. H.; Driga, M. D.

1986-11-01

System and component design features of proposed high voltage homopolar generator (HVHPG) are described. The system is to have an open circuit voltage of 500 V, a peak output current of 500 kA, 3.25 MJ of stored inertial energy and possess an average magnetic-flux density of 5 T. Stator assembly components are discussed, including the stator, mount structure, hydrostatic bearings, main and motoring brushgears and rotor. Planned operational procedures such as monitoring the rotor to full speed and operation with a superconducting field coil are delineated.

Improved detection of electrical activity with a voltage probe based on a voltage-sensing phosphatase.

PubMed

Tsutsui, Hidekazu; Jinno, Yuka; Tomita, Akiko; Niino, Yusuke; Yamada, Yoshiyuki; Mikoshiba, Katsuhiko; Miyawaki, Atsushi; Okamura, Yasushi

2013-09-15

  One of the most awaited techniques in modern physiology is the sensitive detection of spatiotemporal electrical activity in a complex network of excitable cells. The use of genetically encoded voltage probes has been expected to enable such analysis. However, in spite of recent progress, existing probes still suffer from low signal amplitude and/or kinetics too slow to detect fast electrical activity. Here, we have developed an improved voltage probe named Mermaid2, which is based on the voltage-sensor domain of the voltage-sensing phosphatase from Ciona intestinalis and Förster energy transfer between a pair of fluorescent proteins. In mammalian cells, Mermaid2 permits ratiometric readouts of fractional changes of more than 50% over a physiologically relevant voltage range with fast kinetics, and it was used to follow a train of action potentials at frequencies of up to 150 Hz. Mermaid2 was also able to detect single action potentials and subthreshold voltage responses in hippocampal neurons in vitro, in addition to cortical electrical activity evoked by sound stimuli in single trials in living mice.

Averaging peak-to-peak voltage detector for absolute mass determination of single particles with quadrupole ion traps

NASA Astrophysics Data System (ADS)

Peng, Wen-Ping; Lee, Yuan T.; Ting, Joseph W.; Chang, Huan-Cheng

2005-02-01

A sine wave that controls a quadrupole ion trap is generated from a low voltage source, boosted to high voltage through a transformer. Since not even the best transformers can keep a flat amplitude response with respect to frequency, knowing the accurate peak-to-peak value of the sine wave is paramount when the frequency is varied. We have developed an averaging peak-to-peak voltage detector for such measurements and demonstrated that the device is an essential tool to make possible high-precision mass determination of single charged microparticles with masses greater than 1×1011u. Tests of the detector with sine waves from a FLUKE 5720A standard source in the neighborhood of 1400Vpp and frequencies ranging from 100to700Hz showed a measurement accuracy better than 10ppm. The detector settled within 5s after each reset to 5 digits of DVM rock-steady reading, and the calibration against the same source after 3weeks of continuous use of the circuit produced a mere overall 1ppm difference.

Voltage-gated sodium channels in taste bud cells.

PubMed

Gao, Na; Lu, Min; Echeverri, Fernando; Laita, Bianca; Kalabat, Dalia; Williams, Mark E; Hevezi, Peter; Zlotnik, Albert; Moyer, Bryan D

2009-03-12

Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

A boosted negative bit-line SRAM with write-assisted cell in 45 nm CMOS technology

NASA Astrophysics Data System (ADS)

Bhatnagar, Vipul; Kumar, Pradeep; Pandey, Neeta; Pandey, Sujata

2018-02-01

A new 11 T SRAM cell with write-assist is proposed to improve operation at low supply voltage. In this technique, a negative bit-line voltage is applied to one of the write bit-lines, while a boosted voltage is applied to the other write bit-line where transmission gate access is used in proposed 11 T cell. Supply voltage to one of the inverters is interrupted to weaken the feedback. Improved write feature is attributed to strengthened write access devices and weakened feedback loop of cell at the same time. Amount of boosting required for write performance improvement is also reduced due to feedback weakening, solving the persistent problem of half-selected cells and reliability reduction of access devices with the other suggested boosted and negative bit-line techniques. The proposed design improves write time by 79%, 63% and slower by 52% with respect to LP 10 T, WRE 8 T and 6 T cells respectively. It is found that write margin for the proposed cell is improved by about 4×, 2.4× and 5.37× compared to WRE8 T, LP10 T and 6 T respectively. The proposed cell with boosted negative bit line (BNBL) provides 47%, 31%, and 68.4% improvement in write margin with respect to no write-assist, negative bit line (NBL) and boosted bit line (BBL) write-assist respectively. Also, new sensing circuit with replica bit-line is proposed to give a more precise timing of applying boosted voltages for improved results. All simulations are done on TSMC 45 nm CMOS technology.

High throughput ion-channel pharmacology: planar-array-based voltage clamp.

PubMed

Kiss, Laszlo; Bennett, Paul B; Uebele, Victor N; Koblan, Kenneth S; Kane, Stefanie A; Neagle, Brad; Schroeder, Kirk

2003-02-01

Technological advances often drive major breakthroughs in biology. Examples include PCR, automated DNA sequencing, confocal/single photon microscopy, AFM, and voltage/patch-clamp methods. The patch-clamp method, first described nearly 30 years ago, was a major technical achievement that permitted voltage-clamp analysis (membrane potential control) of ion channels in most cells and revealed a role for channels in unimagined areas. Because of the high information content, voltage clamp is the best way to study ion-channel function; however, throughput is too low for drug screening. Here we describe a novel breakthrough planar-array-based HT patch-clamp technology developed by Essen Instruments capable of voltage-clamping thousands of cells per day. This technology provides greater than two orders of magnitude increase in throughput compared with the traditional voltage-clamp techniques. We have applied this method to study the hERG K(+) channel and to determine the pharmacological profile of QT prolonging drugs.

Simulation and resolution of voltage reversal in microbial fuel cell stack.

PubMed

Sugnaux, Marc; Savy, Cyrille; Cachelin, Christian Pierre; Hugenin, Gérald; Fischer, Fabian

2017-08-01

To understand the biotic and non-biotic contributions of voltage reversals in microbial fuel cell stacks (MFC) they were simulated with an electronic MFC-Stack mimic. The simulation was then compared with results from a real 3L triple MFC-Stack with shared anolyte. It showed that voltage reversals originate from the variability of biofilms, but also the external load plays a role. When similar biofilm properties were created on all anodes the likelihood of voltage reversals was largely reduced. Homogenous biofilms on all anodes were created by electrical circuit alternation and electrostimulation. Conversely, anolyte recirculation, or increased nutriment supply, postponed reversals and unfavourable voltage asymmetries on anodes persisted. In conclusion, voltage reversals are often a negative event but occur also in close to best MFC-Stack performance. They were manageable and this with a simplified MFC architecture in which multiple anodes share the same anolyte. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gene delivery by microfluidic flow-through electroporation based on constant DC and AC field.

PubMed

Geng, Tao; Zhan, Yihong; Lu, Chang

2012-01-01

Electroporation is one of the most widely used physical methods to deliver exogenous nucleic acids into cells with high efficiency and low toxicity. Conventional electroporation systems typically require expensive pulse generators to provide short electrical pulses at high voltage. In this work, we demonstrate a flow-through electroporation method for continuous transfection of cells based on disposable chips, a syringe pump, and a low-cost power supply that provides a constant voltage. We successfully transfect cells using either DC or AC voltage with high flow rates (ranging from 40 µl/min to 20 ml/min) and high efficiency (up to 75%). We also enable the entire cell membrane to be uniformly permeabilized and dramatically improve gene delivery by inducing complex migrations of cells during the flow.

New experimental techniques for solar cells

NASA Technical Reports Server (NTRS)

Lenk, R.

1993-01-01

Solar cell capacitance has special importance for an array controlled by shunting. Experimental measurements of solar cell capacitance in the past have shown disagreements of orders of magnitude. Correct measurement technique depends on maintaining the excitation voltage less than the thermal voltage. Two different experimental methods are shown to match theory well, and two effective capacitances are defined for quantifying the effect of the solar cell capacitance on the shunting system.

Analysis of electrical noise in turtle cones

PubMed Central

Lamb, T. D.; Simon, E. J.

1977-01-01

1. Properties of the light-sensitive voltage noise in cones in the retina of the turtle, Pseudemys scripta elegans, have been studied by intracellular recording. 2. Suppression of the noise by light was a function of the hyperpolarizing response of a cone but not of the size or pattern of illumination. 3. Power density spectra of the noise were fitted in many cones by the product of two Lorentzians with characteristic time constants τ1 and τ2 averaging 40 and 7 msec respectively. The spectra of some cells were peaked and could be fitted by a resonance curve. 4. Spectra in dim light exhibited decreased low frequency power. They could often be fitted by a product of two Lorentzians using the same value of τ2 as used in darkness but decreasing τ1 and the zero frequency asymptote. An e-fold reduction in τ1 occurred with lights which hyperpolarized by 4-7 mV. 5. Injection of hyperpolarizing currents of about 0·1-0·2 nA into weakly coupled cones reduced the noise, and also reduced the sensitivity to dim flashes. 6. The variance-voltage relation during steady illumination of different intensities differed from cone to cone. Dim lights increased the noise in some cells and decreased it in others, but moderately bright lights which gave steady responses of more than about one third maximal reduced the noise in all cells. 7. When the cell was transiently depolarized during the differentiated component following steady illumination, the noise was less than it was after prolonged darkness. 8. In the after-effect of bright light, the time course of recovery of noise was the same as that of flash sensitivity and voltage. The noise was reduced e-fold for hyperpolarizations averaging 3 mV while for sensitivity this reduction occurred for 1·3 mV. For a given hyperpolarization the noise was lower during the after-effect than during steady dim illumination. 9. When a series of dim flashes was delivered to a cone, no significant increase in variance over the dark noise was detected during the photo-response. This implies that each photoisomerization evokes no more than about 1·5 μV at the peak of the response in a coupled cone, corresponding to about 50 μV in an isolated cone. 10. The elementary shot events underlying the noise are about 100 μV in amplitude in an isolated cone, have a characteristic time constant of 16-60 msec and reflect unit conductance fluctuations of about 16 pS (S, Siemen ≡ Ω-1). 11. It is concluded that the noise source is internal to the cones. We postulate that the noise arises from opening and closing of the light-sensitive ionic channels in the outer segment, and that in darkness there is a residual concentration of the blocking substance which on average closes up to about one third of the channels. It seems likely that the unit event involves a considerable number of blocking molecules and ionic channels. PMID:592199

Chloromethyl chlorosulfate as a voltage delay inhibitor in lithium cells

DOEpatents

Delnick, F.M.

1993-04-13

Chloromethyl chlorosulfate (CMCS) is used as a passive film growth inhibitor in electrochemical cells to minimize voltage delay and low-voltage discharge. Film growth on lithium anodes is significantly diminished when CMCS is added to SOCl[sub 2] and SO[sub 2]Cl[sub 2] electrolytes of lithium batteries. The CMCS also has the effect of extending the shelf-life of Li/SOCl[sub 2] and Li/SO[sub 2]Cl[sub 2] batteries.

Chloromethyl chlorosulfate as a voltage delay inhibitor in lithium cells

DOEpatents

Delnick, Frank M.

1993-01-01

Chloromethyl chlorosulfate (CMCS) is used as a passive film growth inhibitor in electrochemical cells to minimize voltage delay and low-voltage discharge. Film growth on lithium anodes is significantly diminished when CMCS is added to SOCl.sub.2 and SO.sub.2 Cl.sub.2 electrolytes of lithium batteries. The CMCS also has the effect of extending the shelf-life of Li/SOCl.sub.2 and Li/SO.sub.2 Cl.sub.2 batteries.

Intelligent energy harvesting scheme for microbial fuel cells: Maximum power point tracking and voltage overshoot avoidance

NASA Astrophysics Data System (ADS)

Alaraj, Muhannad; Radenkovic, Miloje; Park, Jae-Do

2017-02-01

Microbial fuel cells (MFCs) are renewable and sustainable energy sources that can be used for various applications. The MFC output power depends on its biochemical conditions as well as the terminal operating points in terms of output voltage and current. There exists one operating point that gives the maximum possible power from the MFC, maximum power point (MPP), for a given operating condition. However, this MPP may vary and needs to be tracked in order to maintain the maximum power extraction from the MFC. Furthermore, MFC reactors often develop voltage overshoots that cause drastic drops in the terminal voltage, current, and the output power. When the voltage overshoot happens, an additional control measure is necessary as conventional MPPT algorithms will fail because of the change in the voltage-current relationship. In this paper, the extremum seeking (ES) algorithm was used to track the varying MPP and a voltage overshoot avoidance (VOA) algorithm is developed to manage the voltage overshoot conditions. The proposed ES-MPPT with VOA algorithm was able to extract 197.2 mJ during 10-min operation avoiding voltage overshoot, while the ES MPPT-only scheme stopped harvesting after only 18.75 mJ because of the voltage overshoot happened at 0.4 min.

C-terminus-mediated voltage gating of Arabidopsis guard cell anion channel QUAC1.

PubMed

Mumm, Patrick; Imes, Dennis; Martinoia, Enrico; Al-Rasheid, Khaled A S; Geiger, Dietmar; Marten, Irene; Hedrich, Rainer

2013-09-01

Anion transporters in plants play a fundamental role in volume regulation and signaling. Currently, two plasma membrane-located anion channel families—SLAC/SLAH and ALMT—are known. Among the ALMT family, the root-expressed ALuminium-activated Malate Transporter 1 was identified by comparison of aluminum-tolerant and Al(3+)-sensitive wheat cultivars and was subsequently shown to mediate voltage-independent malate currents. In contrast, ALMT12/QUAC1 (QUickly activating Anion Channel1) is expressed in guard cells transporting malate in an Al(3+)-insensitive and highly voltage-dependent manner. So far, no information is available about the structure and mechanism of voltage-dependent gating with the QUAC1 channel protein. Here, we analyzed gating of QUAC1-type currents in the plasma membrane of guard cells and QUAC1-expressing oocytes revealing similar voltage dependencies and activation–deactivation kinetics. In the heterologous expression system, QUAC1 was electrophysiologically characterized at increasing extra- and intracellular malate concentrations. Thereby, malate additively stimulated the voltage-dependent QUAC1 activity. In search of structural determinants of the gating process, we could not identify transmembrane domains common for voltage-sensitive channels. However, site-directed mutations and deletions at the C-terminus of QUAC1 resulted in altered voltage-dependent channel activity. Interestingly, the replacement of a single glutamate residue, which is conserved in ALMT channels from different clades, by an alanine disrupted QUAC1 activity. Together with C- and N-terminal tagging, these results indicate that the cytosolic C-terminus is involved in the voltage-dependent gating mechanism of QUAC1.

Laboratory instrumentation and techniques for characterizing multi-junction solar cells for space applications

NASA Technical Reports Server (NTRS)

Woodyard, James R.

1995-01-01

Multi-junction solar cells are attractive for space applications because they can be designed to convert a larger fraction of AMO into electrical power at a lower cost than single-junction cells. The performance of multi-junction cells is much more sensitive to the spectral irradiance of the illuminating source than single-junction cells. The design of high efficiency multi-junction cells for space applications requires matching the optoelectronic properties of the junctions to AMO spectral irradiance. Unlike single-junction cells, it is not possible to carry out quantum efficiency measurements using only a monochromatic probe beam and determining the cell short-circuit current assuming linearity of the quantum efficiency. Additionally, current-voltage characteristics can not be calculated from measurements under non-AMO light sources using spectral-correction methods. There are reports in the literature on characterizing the performance of multi junction cells by measuring and convoluting the quantum efficiency of each junction with the spectral irradiance; the technique is of limited value for the characterization of cell performance under AMO power-generating conditions. We report the results of research to develop instrumentation and techniques for characterizing multi junction solar cells for space . An integrated system is described which consists of a standard lamp, spectral radiometer, dual-source solar simulator, and personal computer based current-voltage and quantum efficiency equipment. The spectral radiometer is calibrated regularly using the tungsten-halogen standard lamp which has a calibration based on NIST scales. The solar simulator produces the light bias beam for current-voltage and cell quantum efficiency measurements. The calibrated spectral radiometer is used to 'fit' the spectral irradiance of the dual-source solar simulator to WRL AMO data. The quantum efficiency apparatus includes a monochromatic probe beam for measuring the absolute cell quantum efficiency at various voltage biases, including the voltage bias corresponding to the maximum-power point under AMO light bias. The details of the procedures to 'fit' the spectral irradiance to AMO will be discussed. An assessment of the role of the accuracy of the 'fit' of the spectral irradiance and probe beam intensity on measured cell characteristics will be presented. quantum efficiencies were measured with both spectral light bias and AMO light bias; the measurements show striking differences. Spectral irradiances were convoluted with cell quantum efficiencies to calculate cell currents as function of voltage. The calculated currents compare with measured currents at the 1% level. Measurements on a variety of multi-junction cells will be presented. The dependence of defects in junctions on cell quantum efficiencies measured under light and voltage bias conditions will be presented. Comments will be made on issues related to standards for calibration, and limitations of the instrumentation and techniques. Expeditious development of multi-junction solar cell technology for space presents challenges for cell characterization in the laboratory.

Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells

PubMed Central

Saung, Wint Thu; Foskett, J. Kevin

2017-01-01

Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na+ currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials. NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na+ and K+ channels but contributed modestly to the kinetics of action potentials. PMID:28202574

Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells.

PubMed

Ma, Zhongming; Saung, Wint Thu; Foskett, J Kevin

2017-05-01

Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na + currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials. NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na + and K + channels but contributed modestly to the kinetics of action potentials. Copyright © 2017 the American Physiological Society.

Thin-film silicon for flexible metal-air batteries.

PubMed

Garamoun, Ahmed; Schubert, Markus B; Werner, Jürgen H

2014-12-01

Due to its high energy density, theoretical studies propose silicon as a promising candidate material for metal-air batteries. Herein, for the first time, experimental results detail the use of n-type doped amorphous silicon and silicon carbide as fuel in Si-air batteries. Thin-film silicon is particularly interesting for flexible and rolled batteries with high specific energies. Our Si-air batteries exhibit a specific capacity of 269 Ah kg(-1) and an average cell voltage of 0.85 V at a discharge current density of 7.9 μA cm(-2) , corresponding to a specific energy of 229 Wh kg(-1) . Favorably in terms of safety, low concentrated alkaline solution serves as electrolyte. Discharging of the Si-air cells continues as long as there is silicon available for oxidation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of perovskite solar cells: Towards a reliable measurement protocol

NASA Astrophysics Data System (ADS)

Zimmermann, Eugen; Wong, Ka Kan; Müller, Michael; Hu, Hao; Ehrenreich, Philipp; Kohlstädt, Markus; Würfel, Uli; Mastroianni, Simone; Mathiazhagan, Gayathri; Hinsch, Andreas; Gujar, Tanaji P.; Thelakkat, Mukundan; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Lead halide perovskite solar cells have shown a tremendous rise in power conversion efficiency with reported record efficiencies of over 20% making this material very promising as a low cost alternative to conventional inorganic solar cells. However, due to a differently severe "hysteretic" behaviour during current density-voltage measurements, which strongly depends on scan rate, device and measurement history, preparation method, device architecture, etc., commonly used solar cell measurements do not give reliable or even reproducible results. For the aspect of commercialization and the possibility to compare results of different devices among different laboratories, it is necessary to establish a measurement protocol which gives reproducible results. Therefore, we compare device characteristics derived from standard current density-voltage measurements with stabilized values obtained from an adaptive tracking of the maximum power point and the open circuit voltage as well as characteristics extracted from time resolved current density-voltage measurements. Our results provide insight into the challenges of a correct determination of device performance and propose a measurement protocol for a reliable characterisation which is easy to implement and has been tested on varying perovskite solar cells fabricated in different laboratories.

Characteristics of single Ca(2+) channel kinetics in feline hypertrophied ventricular myocytes.

PubMed

Yang, Xiangjun; Hui, Jie; Jiang, Tingbo; Song, Jianping; Liu, Zhihua; Jiang, Wenping

2002-04-01

To explore the mechanism underlying the prolongation of action potential and delayed inactivation of the L-type Ca(2+) (I(Ca, L)) current in a feline model of left ventricular system hypertension and concomitant hypertrophy. Single Ca(2+) channel properties in myocytes isolated from normal and pressure overloaded cat left ventricles were studied, using patch-clamp techniques. Left ventricular pressure overload was induced by partial ligation of the ascending aorta for 4 - 6 weeks. The amplitude of single Ca(2+) channel current evoked by depolarizing pulses from -40 mV to 0 mV was 1.02 +/- 0.03 pA in normal cells and 1.05 +/- 0.03 pA in hypertrophied cells, and there was no difference in single channel current-voltage relationships between the groups since slope conductance was 26.2 +/- 1.0 pS in normal and hypertrophied cells, respectively. Peak amplitudes of the ensemble-averaged single Ca(2+) channel currents were not different between the two groups of cells. However, the amplitude of this averaged current at the end of the clamp pulse was significantly larger in hypertrophied cells than in normal cells. Open-time histograms revealed that open-time distribution was fitted by a single exponential function in channels of normal cells and by a two exponential function in channels of hypertrophied cells. The number of long-lasting openings was increased in channels of hypertrophied cells, and therefore the calculated mean open time of the channel was significantly longer compared to normal controls. Kinetic changes in the Ca(2+) channel may underlie both hypertrophy-associated delayed inactivation of the Ca(2+) current and, in part, the pressure overload-induced action potential lengthening in this cat model of ventricular left systolic hypertension and hypertrophy.

Transmembrane potential measurements on plant cells using the voltage-sensitive dye ANNINE-6.

PubMed

Flickinger, Bianca; Berghöfer, Thomas; Hohenberger, Petra; Eing, Christian; Frey, Wolfgang

2010-11-01

The charging of the plasma membrane is a necessary condition for the generation of an electric-field-induced permeability increase of the plasmalemma, which is usually explained by the creation and the growth of aqueous pores. For cells suspended in physiological buffers, the time domain of membrane charging is in the submicrosecond range. Systematic measurements using Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) protoplasts stained with the fast voltage-sensitive fluorescence dye ANNINE-6 have been performed using a pulsed laser fluorescence microscopy setup with a time resolution of 5 ns. A clear saturation of the membrane voltage could be measured, caused by a strong membrane permeability increase, commonly explained by enhanced pore formation, which prevents further membrane charging by external electric field exposure. The field strength dependence of the protoplast's transmembrane potential V (M) shows strong asymmetric saturation characteristics due to the high resting potential of the plants plasmalemma. At the pole of the hyperpolarized hemisphere of the cell, saturation starts at an external field strength of 0.3 kV/cm, resulting in a measured transmembrane voltage shift of ∆V(M) = -150 mV, while on the cathodic (depolarized) cell pole, the threshold for enhanced pore formation is reached at a field strength of approximately 1.0 kV/cm and ∆V(M) = 450 mV, respectively. From this asymmetry of the measured maximum membrane voltage shifts, the resting potential of BY-2 protoplasts at the given experimental conditions can be determined to V(R) = -150 mV. Consequently, a strong membrane permeability increase occurs when the membrane voltage diverges |V(M)| = 300 mV from the resting potential of the protoplast. The largest membrane voltage change at a given external electric field occurs at the cell poles. The azimuthal dependence of the transmembrane potential, measured in angular intervals of 10° along the circumference of the cell, shows a flattening and a slight decrease at higher fields at the pole region due to enhanced pore formation. Additionally, at the hyperpolarized cell pole, a polarization reversal could be observed at an external field range around 1.0 kV/cm. This behavior might be attributed to a fast charge transfer through the membrane at the hyperpolarized pole, e.g., by voltage-gated channels.

Route to genetically targeted optical electrophysiology: development and applications of voltage-sensitive fluorescent proteins

PubMed Central

Akemann, Walther; Song, Chenchen; Mutoh, Hiroki; Knöpfel, Thomas

2015-01-01

Abstract. The invention of membrane voltage protein indicators widens the reach of optical voltage imaging in cell physiology, most notably neurophysiology, by enabling membrane voltage recordings from genetically defined cell types in chronic and life-long preparations. While the last years have seen a dramatic improvement in the technical performance of these indicators, concomitant innovations in optogenetics, optical axon tracing, and high-speed digital microscopy are beginning to fulfill the age-old vision of an all-optical analysis of neuronal circuits, reaching beyond the limits of traditional electrode-based recordings. We will present our personal account of the development of protein voltage indicators from the pioneering days to the present state, including their applications in neurophysiology that has inspired our own work for more than a decade. PMID:26082930

Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes

PubMed Central

Ortiz, Gregorio F.; López, María C.; Li, Yixiao; McDonald, Matthew J.; Cabello, Marta; Tirado, José L.; Yang, Yong

2016-01-01

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO2/Li3PO4/Li2CoPO4F. The Li2CoPO4F cathode and TiO2 anode materials are synthesized by a sol–gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li2CoPO4F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li3PO4-coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO2 and (200) of γ-Li3PO4, as detected by HRTEM. The charge profile of Li2CoPO4F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8–1.9 V). The full cell made with TiO2/Li3PO4/Li2CoPO4F delivered an initial reversible capacity of 150 mA h g−1 at C rate with good cyclic performance at an average potential of 3.1–3.2 V. Thus, the full cell provides an energy density of 472 W h kg−1. This full battery behaves better than TiO2/Li2CoPO4F. The introduction of Li3PO4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport. PMID:26879916

Non-linear amplification of graded voltage signals in the first-order visual interneurons of the butterfly Papilio xuthus.

PubMed

Rusanen, Juha; Frolov, Roman; Weckström, Matti; Kinoshita, Michiyo; Arikawa, Kentaro

2018-04-30

Lamina monopolar cells (LMCs) are the first-order visual interneurons of insects and crustacea, primarily involved in achromatic vision. Here we investigated morphological and electrophysiological properties of LMCs in the butterfly Papilio xuthus Using intracellular recording coupled with dye injection, we found two types of LMCs. Cells with roundish terminals near the distal surface of the medulla demonstrating no or small depolarizing spikes were classified as L1/2. LMCs with elongated terminals deep in the medulla that showed prominent spiking were classified as L3/4. The majority of LMCs of both types had broad spectral sensitivities, peaking between 480 and 570 nm. Depending on the experimental conditions, spikes varied from small to action potential-like events, with their amplitudes and rates decreasing as stimulus brightness increased. When the eye was stimulated with naturalistic contrast-modulated time series, spikes were reliably triggered by high-contrast components of the stimulus. Spike-triggered average functions showed that spikes emphasize rapid membrane depolarizations. Our results suggest that spikes are mediated by voltage-activated Na + channels, which are mainly inactivated at rest. Strong local minima in the coherence functions of spiking LMCs indicate that the depolarizing conductance contributes to the amplification of graded responses even when detectable spikes are not evoked. We propose that the information transfer strategies of spiking LMCs change with light intensity. In dim light, both graded voltage signals and large spikes are used together without mutual interference, due to separate transmission bandwidths. In bright light, signals are non-linearly amplified by the depolarizing conductance in the absence of detectable spikes. © 2018. Published by The Company of Biologists Ltd.

Static Feed Water Electrolysis Subsystem Testing and Component Development

NASA Technical Reports Server (NTRS)

Koszenski, E. P.; Schubert, F. H.; Burke, K. A.

1983-01-01

A program was carried out to develop and test advanced electrochemical cells/modules and critical electromechanical components for a static feed (alkaline electrolyte) water electrolysis oxygen generation subsystem. The accomplishments were refurbishment of a previously developed subsystem and successful demonstration for a total of 2980 hours of normal operation; achievement of sustained one-person level oxygen generation performance with state-of-the-art cell voltages averaging 1.61 V at 191 ASF for an operating temperature of 128F (equivalent to 1.51V when normalized to 180F); endurance testing and demonstration of reliable performance of the three-fluid pressure controller for 8650 hours; design and development of a fluid control assembly for this subsystem and demonstration of its performance; development and demonstration at the single cell and module levels of a unitized core composite cell that provides expanded differential pressure tolerance capability; fabrication and evaluation of a feed water electrolyte elimination five-cell module; and successful demonstration of an electrolysis module pressurization technique that can be used in place of nitrogen gas during the standby mode of operation to maintain system pressure and differential pressures.

High Efficiency Near-Infrared and Semitransparent Non-Fullerene Acceptor Organic Photovoltaic Cells.

PubMed

Li, Yongxi; Lin, Jiu-Dong; Che, Xiaozhou; Qu, Yue; Liu, Feng; Liao, Liang-Sheng; Forrest, Stephen R

2017-11-29

The absence of near-infrared (NIR) solar cells with high open circuit voltage (V oc ) and external quantum efficiency (EQE) has impeded progress toward achieving organic photovoltaic (OPV) power conversion efficiency PCE > 15%. Here we report a small energy gap (1.3 eV), chlorinated nonfullerene acceptor-based solar cell with PCE = 11.2 ± 0.4%, short circuit current of 22.5 ± 0.6 mA cm -2 , V oc = 0.70 ± 0.01 V and fill factor of 0.71 ± 0.02, which is the highest performance reported to date for NIR single junction OPVs. Importantly, the EQE of this NIR solar cell reaches 75%, between 650 and 850 nm while leaving a transparency window between 400 and 600 nm. The semitransparent OPV using an ultrathin (10 nm) Ag cathode shows PCE = 7.1 ± 0.1%, with an average visible transmittance of 43 ± 2%, Commission d'Eclairage chromaticity coordinates of (0.29, 0.32) and a color rendering index of 91 for simulated AM1.5 illumination transmitted through the cell.

A New MPPT Control for Photovoltaic Panels by Instantaneous Maximum Power Point Tracking

NASA Astrophysics Data System (ADS)

Tokushima, Daiki; Uchida, Masato; Kanbei, Satoshi; Ishikawa, Hiroki; Naitoh, Haruo

This paper presents a new maximum power point tracking control for photovoltaic (PV) panels. The control can be categorized into the Perturb and Observe (P & O) method. It utilizes instantaneous voltage ripples at PV panel output terminals caused by the switching of a chopper connected to the panel in order to identify the direction for the maximum power point (MPP). The tracking for the MPP is achieved by a feedback control of the average terminal voltage of the panel. Appropriate use of the instantaneous and the average values of the PV voltage for the separate purposes enables both the quick transient response and the good convergence with almost no ripples simultaneously. The tracking capability is verified experimentally with a 2.8 W PV panel under a controlled experimental setup. A numerical comparison with a conventional P & O confirms that the proposed control extracts much more power from the PV panel.

Influence of the operating parameters of the needle-plate electrostatic precipitator on the size distribution of aerosol particles

NASA Astrophysics Data System (ADS)

Arsenov, P. V.; Efimov, A. A.; Protas, N. V.; Ivanov, V. V.

2018-03-01

The influence of the operating parameters (voltage and aerosol flow rate) of the needle-plate electrostatic precipitator (NP-ESP) on the size distribution of aerosol particles has been studied. The NP-ESP consists of a needle and a plate located in the plastic tube used as aerosol transport duct. Alumina (Al2O3) particles were synthesized by a spark discharge and used as a test aerosol with a size range from 25 to 500 nm. It was found that the average particle size decreases with increasing voltage and aerosol flow rate through the NP-ESP. It was also found that the average particle size can be reduced more than in 2 times in comparison with the initial size distribution at a voltage and aerosol flow rate through the NP-ESP are equal to 16 kV and 250 l/min, respectively.

Electrical transport characterization of PEDOT:PSS/n-Si Schottky diodes and their applications in solar cells.

PubMed

Khurelbaatar, Zagarzusem; Hyung, Jung-Hwan; Kim, Gil-Sung; Park, No-Won; Shim, Kyu-Hwan; Lee, Sang-Kwon

2014-06-01

We demonstrate locally contacted PEDOT:PSS Schottky diodes with excellent rectifying behavior, fabricated on n-type Si substrates using a spin-coating process and a reactive-ion etching process. Electrical transport characterizations of these Schottky diodes were investigated by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. We found that these devices exhibit excellent modulation in the current with an on/off ratio of - 10(6). Schottky junction solar cells composed of PEDOT:PSS and n-Si structures were also examined. From the current density-voltage (J-V) measurement of a solar cell under illumination, the short circuit current (I(sc)), open circuit voltage (V(oc)), and conversion efficiency (eta) were - 19.7 mA/cm2, - 578.5 mV, and - 6.5%, respectively. The simple and low-cost fabrication process of the PEDOT:PSS/n-Si Schottky junctions makes them a promising candidate for further high performance solar cell applications.

Study of flow behavior in all-vanadium redox flow battery using spatially resolved voltage distribution

NASA Astrophysics Data System (ADS)

Bhattarai, Arjun; Wai, Nyunt; Schweiss, Rüdiger; Whitehead, Adam; Scherer, Günther G.; Ghimire, Purna C.; Nguyen, Tam D.; Hng, Huey Hoon

2017-08-01

Uniform flow distribution through the porous electrodes in a flow battery cell is very important for reducing Ohmic and mass transport polarization. A segmented cell approach can be used to obtain in-situ information on flow behaviour, through the local voltage or current mapping. Lateral flow of current within the thick felts in the flow battery can hamper the interpretation of the data. In this study, a new method of segmenting a conventional flow cell is introduced, which for the first time, splits up both the porous felt as well as the current collector. This dual segmentation results in higher resolution and distinct separation of voltages between flow inlet to outlet. To study the flow behavior for an undivided felt, monitoring the OCV is found to be a reliable method, instead of voltage or current mapping during charging and discharging. Our approach to segmentation is simple and applicable to any size of the cell.

Dual patch voltage clamp study of low membrane resistance astrocytes in situ.

PubMed

Ma, Baofeng; Xu, Guangjin; Wang, Wei; Enyeart, John J; Zhou, Min

2014-03-17

Whole-cell patch clamp recording has been successfully used in identifying the voltage-dependent gating and conductance properties of ion channels in a variety of cells. However, this powerful technique is of limited value in studying low membrane resistance cells, such as astrocytes in situ, because of the inability to control or accurately measure the real amplitude of command voltages. To facilitate the study of ionic conductances of astrocytes, we have developed a dual patch recording method which permits membrane current and membrane potential to be simultaneously recorded from astrocytes in spite of their extraordinarily low membrane resistance. The utility of this technique is demonstrated by measuring the voltage-dependent activation of the inwardly rectifying K+ current abundantly expressed in astrocytes and multiple ionic events associated with astrocytic GABAA receptor activation. This protocol can be performed routinely in the study of astrocytes. This method will be valuable for identifying and characterizing the individual ion channels that orchestrate the electrical activity of low membrane resistance cells.

Contribution of Sialic Acid to the Voltage Dependence of Sodium Channel Gating

PubMed Central

Bennett, Eric; Urcan, Mary S.; Tinkle, Sally S.; Koszowski, Adam G.; Levinson, Simon R.

1997-01-01

A potential role for sialic acid in the voltage-dependent gating of rat skeletal muscle sodium channels (rSkM1) was investigated using Chinese hamster ovary (CHO) cells stably transfected with rSkM1. Changes in the voltage dependence of channel gating were observed after enzymatic (neuraminidase) removal of sialic acid from cells expressing rSkM1 and through the expression of rSkM1 in a sialylation-deficient cell line (lec2). The steady-state half-activation voltages (Va) of channels under each condition of reduced sialylation were ∼10 mV more depolarized than control channels. The voltage dependence of the time constants of channel activation and inactivation were also shifted in the same direction and by a similar magnitude. In addition, recombinant deletion of likely glycosylation sites from the rSkM1 sequence resulted in mutant channels that gated at voltages up to 10 mV more positive than wild-type channels. Thus three independent means of reducing channel sialylation show very similar effects on the voltage dependence of channel gating. Finally, steady-state activation voltages for channels subjected to reduced sialylation conditions were much less sensitive to the effects of external calcium than those measured under control conditions, indicating that sialic acid directly contributes to the negative surface potential. These results are consistent with an electrostatic mechanism by which external, negatively charged sialic acid residues on rSkM1 alter the electric field sensed by channel gating elements. PMID:9089440

Multibit Polycristalline Silicon-Oxide-Silicon Nitride-Oxide-Silicon Memory Cells with High Density Designed Utilizing a Separated Control Gate

NASA Astrophysics Data System (ADS)

Rok Kim, Kyeong; You, Joo Hyung; Dal Kwack, Kae; Kim, Tae Whan

2010-10-01

Unique multibit NAND polycrystalline silicon-oxide-silicon nitride-oxide-silicon (SONOS) memory cells utilizing a separated control gate (SCG) were designed to increase memory density. The proposed NAND SONOS memory device based on a SCG structure was operated as two bits, resulting in an increase in the storage density of the NVM devices in comparison with conventional single-bit memories. The electrical properties of the SONOS memory cells with a SCG were investigated to clarify the charging effects in the SONOS memory cells. When the program voltage was supplied to each gate of the NAND SONOS flash memory cells, the electrons were trapped in the nitride region of the oxide-nitride-oxide layer under the gate to supply the program voltage. The electrons were accumulated without affecting the other gate during the programming operation, indicating the absence of cross-talk between two trap charge regions. It is expected that the inference effect will be suppressed by the lower program voltage than the program voltage of the conventional NAND flash memory. The simulation results indicate that the proposed unique NAND SONOS memory cells with a SCG can be used to increase memory density.

Voltage and frequency dependence of prestin-associated charge transfer

PubMed Central

Sun, Sean X.; Farrell, Brenda; Chana, Matthew S.; Oster, George; Brownell, William E.; Spector, Alexander A.

2009-01-01

Membrane protein prestin is a critical component of the motor complex that generates forces and dimensional changes in cells in response to changes in the cell membrane potential. In its native cochlear outer hair cell, prestin is crucial to the amplification and frequency selectivity of the mammalian ear up to frequencies of tens of kHz. Other cells transfected with prestin acquire voltage-dependent properties similar to those of the native cell. The protein performance is critically dependent on chloride ions, and intrinsic protein charges also play a role. We propose an electro-diffusion model to reveal the frequency and voltage dependence of electric charge transfer by prestin. The movement of the combined charge (i.e., anion and protein charges) across the membrane is described with a Fokker-Planck equation coupled to a kinetic equation that describes the binding of chloride ions to prestin. We found a voltage-and frequency-dependent phase shift between the transferred charge and the applied electric field that determines capacitive and resistive components of the transferred charge. The phase shift monotonically decreases from zero to -90 degree as a function of frequency. The capacitive component as a function of voltage is bell-shaped, and decreases with frequency. The resistive component is bell-shaped for both voltage and frequency. The capacitive and resistive components are similar to experimental measurements of charge transfer at high frequencies. The revealed nature of the transferred charge can help reconcile the high-frequency electrical and mechanical observations associated with prestin, and it is important for further analysis of the structure and function of this protein. PMID:19490917

Myosin light chain kinase controls voltage-dependent calcium channels in vascular smooth muscle.

PubMed

Martinsen, A; Schakman, O; Yerna, X; Dessy, C; Morel, N

2014-07-01

The Ca(2+)-dependent kinase myosin light chain kinase (MLCK) is the activator of smooth muscle contraction. In addition, it has been reported to be involved in Ca(2+) channel regulation in cultured cells, and we previously showed that the MLCK inhibitor ML-7 decreases arginine vasopressin (AVP)-induced Ca(2+) influx in rat aorta. This study was designed to investigate whether MLCK is involved in Ca(2+) regulation in resistance artery smooth muscle cell, which plays a major role in the control of blood pressure. As ML compounds were shown to have off-target effects, MLCK was downregulated by transfection with a small interfering RNA targeting MLCK (MLCK-siRNA) in rat small resistance mesenteric artery (RMA) and in the rat embryonic aortic cell line A7r5. Noradrenaline-induced contraction and Ca(2+) signal were significantly depressed in MLCK-siRNA compared to scramble-siRNA-transfected RMA. Contraction and Ca(2+) signal induced by high KCl and voltage-activated Ca(2+) current were also significantly decreased in MLCK-siRNA-transfected RMA, suggesting that MLCK depletion modifies voltage-operated Ca(2+) channels. KCl- and AVP-induced Ca(2+) signals and voltage-activated Ca(2+) current were decreased in MLCK-depleted A7r5 cells. Eventually, real-time quantitative PCR analysis indicated that in A7r5, MLCK controlled mRNA expression of CaV1.2 (L-type) and CaV3.1 (T-type) voltage-dependent Ca(2+) channels. Our results suggest that MLCK controls the transcription of voltage-dependent Ca(2+) channels in vascular smooth muscle cells.

Synaptic Ribbon Active Zones in Cone Photoreceptors Operate Independently from One Another

PubMed Central

Grassmeyer, Justin J.; Thoreson, Wallace B.

2017-01-01

Cone photoreceptors depolarize in darkness to release glutamate-laden synaptic vesicles. Essential to release is the synaptic ribbon, a structure that helps organize active zones by clustering vesicles near proteins that mediate exocytosis, including voltage-gated Ca2+ channels. Cone terminals have many ribbon-style active zones at which second-order neurons receive input. We asked whether there are functionally significant differences in local Ca2+ influx among ribbons in individual cones. We combined confocal Ca2+ imaging to measure Ca2+ influx at individual ribbons and patch clamp recordings to record whole-cell ICa in salamander cones. We found that the voltage for half-maximal activation (V50) of whole cell ICa in cones averaged −38.1 mV ± 3.05 mV (standard deviation [SD]), close to the cone membrane potential in darkness of ca. −40 mV. Ca2+ signals at individual ribbons varied in amplitude from one another and showed greater variability in V50 values than whole-cell ICa, suggesting that Ca2+ signals can differ significantly among ribbons within cones. After accounting for potential sources of technical variability in measurements of Ca2+ signals and for contributions from cone-to-cone differences in ICa, we found that the variability in V50 values for ribbon Ca2+ signals within individual cones showed a SD of 2.5 mV. Simulating local differences in Ca2+ channel activity at two ribbons by shifting the V50 value of ICa by ±2.5 mV (1 SD) about the mean suggests that when the membrane depolarizes to −40 mV, two ribbons could experience differences in Ca2+ influx of >45%. Further evidence that local Ca2+ changes at ribbons can be regulated independently was obtained in experiments showing that activation of inhibitory feedback from horizontal cells (HCs) to cones in paired recordings changed both amplitude and V50 of Ca2+ signals at individual ribbons. By varying the strength of synaptic output, differences in voltage dependence and amplitude of Ca2+ signals at individual ribbons shape the information transmitted from cones to downstream neurons in vision. PMID:28744203

Tetrodotoxin-sensitive, voltage-dependent sodium currents in hair cells from the alligator cochlea.

PubMed

Evans, M G; Fuchs, P A

1987-10-01

We have used whole-cell patch clamp techniques to record from tall hair cells isolated from the apical half of the alligator cochlea. Some of these cells gave action potentials in response to depolarizing current injections. When the same cells were voltage clamped, large transient inward currents followed by smaller outward currents were seen in response to depolarizing steps. We studied the transient inward current after the outward current had been blocked by external tetraethylammonium (20 mM) or by replacing internal potassium with cesium. It was found to be a sodium current because it was abolished by either replacing external sodium with choline or by external application of tetrodotoxin (100 nM). The sodium current showed voltage-dependent activation and inactivation. Most of the spiking hair cells came from the apex of the cochlea, where they would be subject to low-frequency mechanical stimulation in vivo.

Methods for improving solar cell open circuit voltage

DOEpatents

Jordan, John F.; Singh, Vijay P.

1979-01-01

A method for producing a solar cell having an increased open circuit voltage. A layer of cadmium sulfide (CdS) produced by a chemical spray technique and having residual chlorides is exposed to a flow of hydrogen sulfide (H.sub.2 S) heated to a temperature of 400.degree.-600.degree. C. The residual chlorides are reduced and any remaining CdCl.sub.2 is converted to CdS. A heterojunction is formed over the CdS and electrodes are formed. Application of chromium as the positive electrode results in a further increase in the open circuit voltage available from the H.sub.2 S-treated solar cell.

Static charge outside chamber induces dielectric breakdown of solid-state nanopore membranes

NASA Astrophysics Data System (ADS)

Matsui, Kazuma; Goto, Yusuke; Yanagi, Itaru; Yanagawa, Yoshimitsu; Ishige, Yu; Takeda, Ken-ichi

2018-04-01

Reducing device capacitance is effective for decreasing current noise observed in a solid-state nanopore-based DNA sequencer. On the other hand, we have recently found that voltage stress causes pinhole-like defects in such low-capacitance devices. The origin of voltage stress, however, has not been determined. In this research, we identified that a dominant origin is static charge on the outer surface of a flow cell. Even though the outer surface was not in direct contact with electrolytes in the flow cell, the charge induces high voltage stress on a membrane according to the capacitance coupling ratio of the flow cell to the membrane.

Modeling the voltage loss mechanisms in lithium-sulfur cells: the importance of electrolyte resistance and precipitation kinetics.

PubMed

Zhang, Teng; Marinescu, Monica; O'Neill, Laura; Wild, Mark; Offer, Gregory

2015-09-21

Understanding of the complex electrochemical, transport, and phase-change phenomena in Li-S cells requires experimental characterization in tandem with mechanistic modeling. However, existing Li-S models currently contradict some key features of experimental findings, particularly the evolution of cell resistance during discharge. We demonstrate that, by introducing a concentration-dependent electrolyte conductivity, the correct trends in voltage drop due to electrolyte resistance and activation overpotentials are retrieved. In addition, we reveal the existence of an often overlooked potential drop mechanism in the low voltage-plateau which originates from the limited rate of Li2S precipitation.

Nonfullerene Tandem Organic Solar Cells with High Open-Circuit Voltage of 1.97 V.

PubMed

Liu, Wenqing; Li, Shuixing; Huang, Jiang; Yang, Shida; Chen, Jiehuan; Zuo, Lijian; Shi, Minmin; Zhan, Xiaowei; Li, Chang-Zhi; Chen, Hongzheng

2016-11-01

Small-molecule nonfullerene-based tandem organic solar cells (OSCs) are fabricated for the first time by utilizing P3HT:SF(DPPB) 4 and PTB7-Th:IEIC bulk heterojunctions as the front and back subcells, respectively. A power conversion efficiency of 8.48% is achieved with an ultrahigh open-circuit voltage of 1.97 V, which is the highest voltage value reported to date among efficient tandem OSCs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Voltage dependence of the rat chorda tympani response to Na+ salts: implications for the functional organization of taste receptor cells.

PubMed

Ye, Q; Heck, G L; DeSimone, J A

1993-07-01

1. Voltage-clamp and current-clamp data were obtained from a circumscribed region of the anterior rat lingual epithelium while simultaneously monitoring the afferent, stimulus-evoked, neural response from the same receptive field. 2. Chorda tympani (CT) responses at constant Na(+)-salt concentration were enhanced by submucosa negative voltage clamp and suppressed by positive voltage clamp. The complete CT response profile, including the time course of adaptation, was not uniquely determined by NaCl concentration alone. The response could be reproduced at different NaCl concentrations by applying a compensating voltage. 3. The form of the concentration and voltage dependence of the CT response indicates that the complete stimulus energy is the Na+ electrochemical potential difference across receptor cell apical membranes, and not Na+ concentration alone. This is the underlying principal behind the equivalence of chemical and electric taste for Na+ salts. 4. CT responses to sodium gluconate (25 and 200 mM) and 25 mM NaCl produced amiloride-insensitive components (AIC) of low magnitude. NaCl at 200 mM produced a significantly larger AIC. The AIC was voltage-clamp independent. The relative magnitude of the AIC was positively correlated with the transepithelial conductance of each salt. This suggests that the large AIC for 200 mM NaCl results from its relatively high permeability through the paracellular pathway. 5. Analysis of the CT response under voltage clamp revealed two anion effects on Na(+)-salt taste, both of which act through the paracellular shunt. 1) Anions modify the transepithelial potential (TP) across tight junctions and thereby modulate the cell receptor potential. This anion effect can be eliminated by voltage clamping the TP. 2) Sufficiently mobile anions facilitate electroneutral diffusion of Na+ salts through tight junctions. This effect is observed especially when Cl- is the anion and when the stimulus concentration favors NaCl influx, allowing Na+ to stimulate receptor cells from the submucosal side. Because the submucosal intercellular spaces are nearly isopotential regions, this effect is insensitive to voltage clamp of the TP. The large AIC associated with this anion effect is due to the low permeability of amiloride.

Entorhinal stellate cells show preferred spike phase-locking to theta inputs that is enhanced by correlations in synaptic activity

PubMed Central

Fernandez, Fernando R.; Malerba, Paola; Bressloff, Paul C.; White, John A.

2013-01-01

In active networks, excitatory and inhibitory synaptic inputs generate membrane voltage fluctuations that drive spike activity in a probabilistic manner. Despite this, some cells in vivo show a strong propensity to precisely lock to the local field potential and maintain a specific spike-phase relationship relative to other cells. In recordings from rat medial entorhinal cortical stellate cells, we measured spike phase-locking in response to sinusoidal “test” inputs in the presence of different forms of background membrane voltage fluctuations, generated via dynamic clamp. We find that stellate cells show strong and robust spike phase-locking to theta (4–12 Hz) inputs. This response occurs under a wide variety of background membrane voltage fluctuation conditions that include a substantial increase in overall membrane conductance. Furthermore, the IH current present in stellate cells is critical to the enhanced spike phase-locking response at theta. Finally, we show that correlations between inhibitory and excitatory conductance fluctuations, which can arise through feed-back and feed-forward inhibition, can substantially enhance the spike phase-locking response. The enhancement in locking is a result of a selective reduction in the size of low frequency membrane voltage fluctuations due to cancelation of inhibitory and excitatory current fluctuations with correlations. Hence, our results demonstrate that stellate cells have a strong preference for spike phase-locking to theta band inputs and that the absolute magnitude of locking to theta can be modulated by the properties of background membrane voltage fluctuations. PMID:23554484

Tandem Solar Cells Using GaAs Nanowires on Si: Design, Fabrication, and Observation of Voltage Addition.

PubMed

Yao, Maoqing; Cong, Sen; Arab, Shermin; Huang, Ningfeng; Povinelli, Michelle L; Cronin, Stephen B; Dapkus, P Daniel; Zhou, Chongwu

2015-11-11

Multijunction solar cells provide us a viable approach to achieve efficiencies higher than the Shockley-Queisser limit. Due to their unique optical, electrical, and crystallographic features, semiconductor nanowires are good candidates to achieve monolithic integration of solar cell materials that are not lattice-matched. Here, we report the first realization of nanowire-on-Si tandem cells with the observation of voltage addition of the GaAs nanowire top cell and the Si bottom cell with an open circuit voltage of 0.956 V and an efficiency of 11.4%. Our simulation showed that the current-matching condition plays an important role in the overall efficiency. Furthermore, we characterized GaAs nanowire arrays grown on lattice-mismatched Si substrates and estimated the carrier density using photoluminescence. A low-resistance connecting junction was obtained using n(+)-GaAs/p(+)-Si heterojunction. Finally, we demonstrated tandem solar cells based on top GaAs nanowire array solar cells grown on bottom planar Si solar cells. The reported nanowire-on-Si tandem cell opens up great opportunities for high-efficiency, low-cost multijunction solar cells.

Lithium battery discharge tests

NASA Technical Reports Server (NTRS)

Johnson, C. J.

1980-01-01

The long term discharge of a variety of lithium cells was characterized and the susceptibility of the cells to chemical variation during the slow discharge was tested. A shunt resistor was set across the terminals to monitor the voltage as a function of time. Failures were identified by premature voltage drops.

Application of the electroosmotic effect for thrust generation

NASA Astrophysics Data System (ADS)

Hansen, Thomas Edward

The present work focuses on demonstrating the capabilities of electroosmotic pumps, (EOP) to generate thrust. An underwater glider was successfully propelled by electroosmosis for the first time published - at 0.85 inches per second. Asymmetric AC voltage pulsing proved to produce higher flow rates then equivalent DC pumps for the same average voltage. Ultra-short pulsing proved 100 nanosecond rise times in EOP are possible, which surpassed published predictions by three orders of magnitude. Theories behind efficiency losses of high power EOP were investigated. Direct measurement of effective voltage at the face of a membrane is the most accurate way to determine voltage drop across the electrolyte of an EOP. Forced convection lowered efficiency of the EOP for low voltages by preventing capacitance charging, but proved to prolong pump life during high power application.

Inhibitory effects of magnolol on voltage-gated Na+ and K+ channels of NG108-15 cells.

PubMed

Gong, Chi-Li; Wong, Kar-Lok; Cheng, Ka-Shun; Kuo, Chang-Shin; Chao, Chia-Chia; Tsai, Min-Fan; Leung, Yuk-Man

2012-05-05

Magnolol, a polyphenolic compound isolated from Houpu, a Chinese herb from the bark of Magnolia officinalis, has been reported to have in vitro and in vivo neuroprotective effects. In spite of these reported beneficial effects, studies on the direct impact of magnolol on neuronal ion channels have been scarce. Whether magnolol affects voltage-gated Na(+) channels (VGSC) and voltage-gated K(+) (Kv) channels is unknown. Using the whole-cell voltage-clamp method, we studied the effects of magnolol on voltage-gated ion channels in neuronal NG108-15 cells. Magnolol inhibited VGSC channels with mild state-dependence (IC(50) of 15 and 30 μM, at holding potentials of -70 and -100 mV, respectively). No frequency-dependence was observed in magnolol block. Magnolol caused a left-shift of 18 mV in the steady-state inactivation curve but did not affect the voltage-dependence of activation. Magnolol inhibited Kv channels with an IC(50) of 21 μM, and it caused a 20-mV left-shift in the steady-state inactivation curve without affecting the voltage-dependence of activation. In conclusion, magnolol is an inhibitor of both VGSC and Kv channels and these inhibitory effects may in part contribute to some of the reported neuroprotective effects of magnolol. Copyright © 2012 Elsevier B.V. All rights reserved.

The effect of applied control strategy on the current-voltage correlation of a solid oxide fuel cell stack during dynamic operation

NASA Astrophysics Data System (ADS)

Szmyd, Janusz S.; Komatsu, Yosuke; Brus, Grzegorz; Ghigliazza, Francesco; Kimijima, Shinji; Ściążko, Anna

2014-09-01

This paper discusses the transient characteristics of the planar type SOFC cell stack, of which the standard output is 300 W. The transient response of the voltage to the manipulation of an electric current was investigated. The effects of the response and of the operating condition determined by the operating temperature of the stack were studied by mapping a current-voltage (I-V) correlation. The current-based fuel control (CBFC) was adopted for keeping the fuel utilization factor at constant while the value of the electric current was ramped at the constant rate. The present experimental study shows that the transient characteristics of the cell voltage are determined by primarily the operating temperature caused by the manipulation of the current. Particularly, the slope of the I-V curve and the overshoot found on the voltage was remarkably influenced by the operating temperature. The different values of the fuel utilization factor influence the height of the settled voltages. The CBFC has significance in determining the slope of the I-V characteristic, but the different values ofthe fuel utilization factor does not affect the slope as the operating temperature does. The CBFC essentially does not alter the amplitude of the overshoot on the voltage response, since this is dominated by the operating temperature and its change is caused by manipulating the current.

An Improved Targeted cAMP Sensor to Study the Regulation of Adenylyl Cyclase 8 by Ca2+ Entry through Voltage-Gated Channels

PubMed Central

Everett, Katy L.; Cooper, Dermot M. F.

2013-01-01

Here we describe an improved sensor with reduced pH sensitivity tethered to adenylyl cyclase (AC) 8. The sensor was used to study cAMP dynamics in the AC8 microdomain of MIN6 cells, a pancreatic β-cell line. In these cells, AC8 was activated by Ca2+ entry through L-type voltage-gated channels following depolarisation. This activation could be reconstituted in HEK293 cells co-expressing AC8 and either the α1C or α1D subunit of L-type voltage-gated Ca2+ channels. The development of this improved sensor opens the door to the study of cAMP microdomains in excitable cells that have previously been challenging due to the sensitivity of fluorescent proteins to pH changes. PMID:24086669

High altitude current-voltage measurement of GaAs/Ge solar cells

NASA Astrophysics Data System (ADS)

Hart, Russell E., Jr.; Brinker, David J.; Emery, Keith A.

Measurements of high-voltage (Voc of 1.2 V) gallium arsenide on germanium tandem junction solar cells at air mass 0.22 showed that the insolation in the red portion of the solar spectrum is insufficient to obtain high fill factor. On the basis of measurements in the LeRC X-25L solar simulator, these cells were believed to be as efficient as 21.68 percent AM0. Solar simulator spectrum errors in the red end allowed the fill factor to be as high as 78.7 percent. When a similar cell's current-voltage characteristic was measured at high altitude in the NASA Lear Jet Facility, a loss of 15 percentage points in fill factor was observed. This decrease was caused by insufficient current in the germanium bottom cell of the tandem stack.

Impact of cation-π interactions on the cell voltage of carbon nanotube-based Li batteries.

PubMed

Gao, Shaohua; Shi, Guosheng; Fang, Haiping

2016-01-21

Carbon nanotube (CNT)-based Li batteries have attracted wide attention because of their high capacity, high cyclability and high energy density and are believed to be one of the most promising electrochemical energy storage systems. In CNT-based Li batteries, the main interaction between the Li(+) ions and the CNT is the cation-π interaction. However, up to now, it is still not clear how this interaction affects the storage characteristics of CNT-based Li batteries. Here, using density functional theory (DFT) calculations, we report a highly favorable impact of cation-π interactions on the cell voltage of CNT-based Li batteries. Considering both Li(+)-π interaction and Li-π interaction, we show that cell voltage enhances with the increase of the CNT diameter. In addition, when the Li(+) ion adsorbs on the external wall, the cell voltage is larger than that when it adsorbs on the internal wall. This suggests that CNTs with a large diameter and a low array density are more advantageous to enhance storage performance of CNT-based Li batteries. Compared with Li(+) ions on the (4,4) CNT internal wall, the cell voltage of Li(+) on the (10,10) CNT external wall is 0.55 V higher, which indicates an improvement of about 38%. These results will be helpful for the design of more efficient CNT-based Li batteries.

Coordinated single-phase control scheme for voltage unbalance reduction in low voltage network.

PubMed

Pullaguram, Deepak; Mishra, Sukumar; Senroy, Nilanjan

2017-08-13

Low voltage (LV) distribution systems are typically unbalanced in nature due to unbalanced loading and unsymmetrical line configuration. This situation is further aggravated by single-phase power injections. A coordinated control scheme is proposed for single-phase sources, to reduce voltage unbalance. A consensus-based coordination is achieved using a multi-agent system, where each agent estimates the averaged global voltage and current magnitudes of individual phases in the LV network. These estimated values are used to modify the reference power of individual single-phase sources, to ensure system-wide balanced voltages and proper power sharing among sources connected to the same phase. Further, the high X / R ratio of the filter, used in the inverter of the single-phase source, enables control of reactive power, to minimize voltage unbalance locally. The proposed scheme is validated by simulating a LV distribution network with multiple single-phase sources subjected to various perturbations.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).

A quick response four decade logarithmic high-voltage stepping supply

NASA Technical Reports Server (NTRS)

Doong, H.

1978-01-01

An improved high-voltage stepping supply, for space instrumentation is described where low power consumption and fast settling time between steps are required. The high-voltage stepping supply, utilizing an average power of 750 milliwatts, delivers a pair of mirror images with 64 level logarithmic outputs. It covers a four decade range of + or - 2500 to + or - 0.29 volts having an output stability of + or - 0.5 percent or + or - 20 millivolts for all line load and temperature variations. The supply provides a typical step setting time of 1 millisecond with 100 microseconds for the lower two decades. The versatile design features of the high-voltage stepping supply provides a quick response staircase generator as described or a fixed voltage with the option to change levels as required over large dynamic ranges without circuit modifications. The concept can be implemented up to + or - 5000 volts. With these design features, the high-voltage stepping supply should find numerous applications where charged particle detection, electro-optical systems, and high voltage scientific instruments are used.

Electrical coupling of single cardiac rat myocytes to field-effect and bipolar transistors.

PubMed

Kind, Thomas; Issing, Matthias; Arnold, Rüdiger; Müller, Bernt

2002-12-01

A novel bipolar transistor for extracellular recording the electrical activity of biological cells is presented, and the electrical behavior compared with the field-effect transistor (FET). Electrical coupling is examined between single cells separated from the heart of adults rats (cardiac myocytes) and both types of transistors. To initiate a local extracellular voltage, the cells are periodically stimulated by a patch pipette in voltage clamp and current clamp mode. The local extracellular voltage is measured by the planar integrated electronic sensors: the bipolar and the FET. The small signal transistor currents correspond to the local extracellular voltage. The two types of sensor transistors used here were developed and manufactured in the laboratory of our institute. The manufacturing process and the interfaces between myocytes and transistors are described. The recordings are interpreted by way of simulation based on the point-contact model and the single cardiac myocyte model.

High Voltage LiNi 0.5 Mn 0.3 Co 0.2 O 2 /Graphite Cell Cycled at 4.6 V with a FEC/HFDEC-Based Electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Meinan; Su, Chi-Cheung; Feng, Zhenxing

2017-04-26

A high voltage LiNi0.5Mn0.3Co0.2O2/graphite cell with a fluorinated electrolyte formulation 1.0 m LiPF6 fluoroethylene carbonate/bis(2,2,2-trifluoroethyl) carbonate is reported and its electrochemical performance is evaluated at cell voltage of 4.6 V. Comparing with its nonfluorinated electrolyte counterpart, the reported fluorinated one shows much improved Coulombic efficiency and capacity retention when a higher cut-off voltage (4.6 V) is applied. Scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy data clearly demonstrate the superior oxidative stability of the new electrolyte. The structural stability of the bulk cathode materials cycled with different electrolytes is extensively studied by X-ray absorption near edge structure andmore » X-ray diffraction.« less

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

PubMed

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

2014-10-01

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. To reach such voltage-clamp recordings, we combine an active electrode compensation algorithm (AEC) with a digital controller (AECVC). 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. 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.

Making Electricity with Fruit.

ERIC Educational Resources Information Center

Dispezio, Michael A.

1992-01-01

Describes how electrochemical cells exploit reduction-oxidation (redox) reactions to produce electric current. Presents an activity using a paper clip, copper wire, an apple, and a voltmeter where students can measure the voltage from an apple cell. Describes variables that can be changed to assess the impact on the voltage produced. (PR)

Electrochemical testing of suspension plasma sprayed solid oxide fuel cell electrolytes

NASA Astrophysics Data System (ADS)

Waldbillig, D.; Kesler, O.

Electrochemical performance of metal-supported plasma sprayed (PS) solid oxide fuel cells (SOFCs) was tested for three nominal electrolyte thicknesses and three electrolyte fabrication conditions to determine the effects of electrolyte thickness and microstructure on open circuit voltage (OCV) and series resistance (R s). The measured OCV values were approximately 90% of the Nernst voltages, and electrolyte area specific resistances below 0.1 Ω cm 2 were obtained at 750 °C for electrolyte thicknesses below 20 μm. Least-squares fitting was used to estimate the contributions to R s of the YSZ bulk material, its microstructure, and the contact resistance between the current collectors and the cells. It was found that the 96% dense electrolyte layers produced from high plasma gas flow rate conditions had the lowest permeation rates, the highest OCV values, and the smallest electrolyte-related voltage losses. Optimal electrolyte thicknesses were determined for each electrolyte microstructure that would result in the lowest combination of OCV loss and voltage loss due to series resistance for operating voltages of 0.8 V and 0.7 V.

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell

NASA Technical Reports Server (NTRS)

Gahn, Randall F.

1987-01-01

An experimental method was developed for evaluating the effect of component compression on the charge and discharge voltage characteristics of a 3 1/2 in. diameter boiler plate cell. A standard boiler plate pressure vessel was modified by the addition of a mechanical feedthrough on the bottom of the vessel which permitted different compressions to be applied to the components without disturbing the integrity of the stack. Compression loadings from 0.94 to 27.4 psi were applied by suspending weights from the feedthrough rod. Cell voltages were measured for 0.96-C, 55-min charge and for 1.37-C, 35-min and 2-C, 24-min discharges. An initial change in voltage performance on both charge and discharge as the loading increased was attributed to seating of the components. Subsequent variation of the compression from 2.97 to 27.4 psi caused only minor changes in either the charge or the discharge voltages. Several one month open-circuit voltage stands and 1100 cycles under LEO conditions at the maximum loading have produced no change in performance.

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell. [Individual Pressure Vessel

NASA Technical Reports Server (NTRS)

Gahn, Randall F.

1987-01-01

An experimental method was developed for evaluating the effect of component compression on the charge and discharge voltage characteristics of a 3 1/2 in. diameter boiler plate cell. A standard boiler plate pressure vessel was modified by the addition of a mechanical feedthrough on the bottom of the vessel which permitted different compressions to be applied to the components without disturbing the integrity of the stack. Compression loadings from 0.94 to 27.4 psi were applied by suspending weights from the feedthrough rod. Cell voltages were measured for 0.96-C, 55-min charge and for 1.37-C, 35-min and 2-C, 24-min discharges. An initial change in voltage performance on both charge and discharge as the loading increased was attributed to seating of the components. Subsequent variation of the compression from 2.97 to 27.4 psi caused only minor changes in either the charge or the discharge voltages. Several one month open-circuit voltage stands and 1100 cycles under LEO conditions at the maximum loading have produced no change in performance.

Separate Cl^- Conductances Activated by cAMP and Ca2+ in Cl^--Secreting Epithelial Cells

NASA Astrophysics Data System (ADS)

Cliff, William H.; Frizzell, Raymond A.

1990-07-01

We studied the cAMP- and Ca2+-activated secretory Cl^- conductances in the Cl^--secreting colonic epithelial cell line T84 using the whole-cell patch-clamp technique. Cl^- and K^+ currents were measured under voltage clamp. Forskolin or cAMP increased Cl^- current 2-15 times with no change in K^+ current. The current-voltage relation for cAMP-activated Cl^- current was linear from -100 to +100 mV and showed no time-dependent changes in current during voltage pulses. Ca2+ ionophores or increased pipette Ca2+ increased both Cl^- and K^+ currents 2-30 times. The Ca2+-activated Cl^- current was outwardly rectified, activated during depolarizing voltage pulses, and inactivated during hyperpolarizing voltage pulses. Addition of ionophore after forskolin further increased Cl^- conductance 1.5-5 times, and the current took on the time-dependent characteristics of that stimulated by Ca2+. Thus, cAMP and Ca2+ activate Cl^- conductances with different properties, implying that these second messengers activate different Cl^- channels or that they induce different conductive and kinetic states in the same Cl^- channel.

Modelling and simulation of fuel cell dynamics for electrical energy usage of Hercules airplanes.

PubMed

Radmanesh, Hamid; Heidari Yazdi, Seyed Saeid; Gharehpetian, G B; Fathi, S H

2014-01-01

Dynamics of proton exchange membrane fuel cells (PEMFC) with hydrogen storage system for generating part of Hercules airplanes electrical energy is presented. Feasibility of using fuel cell (FC) for this airplane is evaluated by means of simulations. Temperature change and dual layer capacity effect are considered in all simulations. Using a three-level 3-phase inverter, FC's output voltage is connected to the essential bus of the airplane. Moreover, it is possible to connect FC's output voltage to airplane DC bus alternatively. PID controller is presented to control flow of hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. FC's output voltage is regulated via an ultracapacitor. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage regulation are acceptable. The proposed system utilizes an electrolyser to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in other applications in airplane.

Modelling and Simulation of Fuel Cell Dynamics for Electrical Energy Usage of Hercules Airplanes

PubMed Central

Radmanesh, Hamid; Heidari Yazdi, Seyed Saeid; Gharehpetian, G. B.; Fathi, S. H.

2014-01-01

Dynamics of proton exchange membrane fuel cells (PEMFC) with hydrogen storage system for generating part of Hercules airplanes electrical energy is presented. Feasibility of using fuel cell (FC) for this airplane is evaluated by means of simulations. Temperature change and dual layer capacity effect are considered in all simulations. Using a three-level 3-phase inverter, FC's output voltage is connected to the essential bus of the airplane. Moreover, it is possible to connect FC's output voltage to airplane DC bus alternatively. PID controller is presented to control flow of hydrogen and oxygen to FC and improve transient and steady state responses of the output voltage to load disturbances. FC's output voltage is regulated via an ultracapacitor. Simulations are carried out via MATLAB/SIMULINK and results show that the load tracking and output voltage regulation are acceptable. The proposed system utilizes an electrolyser to generate hydrogen and a tank for storage. Therefore, there is no need for batteries. Moreover, the generated oxygen could be used in other applications in airplane. PMID:24782664

Intrinsic non-radiative voltage losses in fullerene-based organic solar cells

NASA Astrophysics Data System (ADS)

Benduhn, Johannes; Tvingstedt, Kristofer; Piersimoni, Fortunato; Ullbrich, Sascha; Fan, Yeli; Tropiano, Manuel; McGarry, Kathryn A.; Zeika, Olaf; Riede, Moritz K.; Douglas, Christopher J.; Barlow, Stephen; Marder, Seth R.; Neher, Dieter; Spoltore, Donato; Vandewal, Koen

2017-06-01

Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to 1.45-1.65 eV, that is, 0.2-0.3 eV higher than for technologies with minimized non-radiative voltage losses.

Relaxation of Isolated Ventricular Cardiomyocytes by a Voltage-Dependent Process

NASA Astrophysics Data System (ADS)

Bridge, John H. B.; Spitzer, Kenneth W.; Ershler, Philip R.

1988-08-01

Cell contraction and relaxation were measured in single voltage-clamped guinea pig cardiomyocytes to investigate the contribution of sarcolemmal Na+-Ca2+ exchange to mechanical relaxation. Cells clamped from -80 to 0 millivolts displayed initial phasic and subsequent tonic contractions; caffeine reduced or abolished the phasic and enlarged the tonic contraction. The rate of relaxation from tonic contractions was steeply voltage-dependent and was significantly slowed in the absence of a sarcolemmal Na+ gradient. Tonic contractions elicited in the absence of a Na+ gradient promptly relaxed when external Na+ was applied, reflecting activation of Na+-Ca2+ exchange. It appears that a voltage-dependent Na+-Ca2+ exchange can rapidly mechanically relax mammalian heart muscle.

PQScal (Power Quality Score Calculation for Distribution Systems with DER Integration)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Power Quality is of great importance to evaluate the “health” of a distribution system, especially when the distributed energy resource (DER) penetration becomes more significant. The individual components that make up power quality, such as voltage magnitude and unbalance, can be measured in simulations or in the field, however, a comprehensive method to incorporate all of these values into a single score doesn't exist. As a result, we propose a methodology to quantify the power quality health using the single number value, named as Power Quality Score (PQS). The PQS is dependent on six metrics that are developed based onmore » both components that directly impact power quality and those are often reference in the context of power quality. These six metrics are named as System Average Voltage Magnitude Violation Index (SAVMVI), System Average Voltage Fluctuation Index (SAVFI), System Average Voltage Unbalance Index (SAVUI), System Control Device Operation Index (SCDOI), System Reactive Power Demand Index (SRPDI) and System Energy Loss Index (SELI). This software tool, PQScal, is developed based on this novel PQS methodology. Besides of traditional distribution systems, PQScal can also measure the power quality for distribution systems with various DER penetrations. PQScal has been tested on two utility distribution feeders with distinct model characteristics and its effectiveness has been proved. In sum, PQScal can help utilities or other parties to measure the power quality of distribution systems with DER integration easily and effectively.« less

LEDs based upon AlGaInP heterostructures with multiple quantum wells: comparison of fast neutrons and gamma-quanta irradiation

NASA Astrophysics Data System (ADS)

Gradoboev, A. V.; Orlova, K. N.; Simonova, A. V.

2018-05-01

The paper presents the research results of watt and volt characteristics of LEDs based upon AlGaInP heterostructures with multiple quantum wells in the active region. The research is completed for LEDs (emission wavelengths 624 nm and 590 nm) under irradiation by fast neutron and gamma-quanta in passive powering mode. Watt-voltage characteristics in the average and high electron injection areas are described as a power function of the operating voltage. It has been revealed that the LEDs transition from average electron injection area to high electron injection area occurs by overcoming the transition area. It disappears as it get closer to the limit result of the irradiation LEDs that is low electron injection mode in the entire supply voltage range. It has been established that the gamma radiation facilitates initial defects restructuring only 42% compared to 100% when irradiation is performed by fast neutrons. Ratio between measured on the boundary between low and average electron injection areas current value and the contribution magnitude of the first stage LEDs emissive power reducing is established. It is allows to predict LEDs resistance to irradiation by fast neutrons and gamma rays.

Characterization of physiochemical properties of polymeric and electrochemical materials for aerospace flight

NASA Technical Reports Server (NTRS)

Rock, M.; Kunigahalli, V.; Khan, S.; Mcnair, A.

1984-01-01

Nickel-cadmium rechargeable batteries are a vital and reliable energy storage source for aerospace applications. As the demand for longer life and more reliable space batteries increases, the understanding and solving of cell aging factors and mechanisms become essential. Over the years, many cell designs and manufacturing process changes have been developed and implemented. Cells fabricated with various design features were life cycled in a simulated low-Earth orbit regime. Following the test program, a comprehensive electrochemical analysis of cell components was undertaken to study cell degradation mechanisms. Discharge voltage degradation or voltage plateau has been observed during orbit cycling, but, its cause and explanation have been the subject of much discussion. A Hg/HgO reference electrode was used to monitor the reference versus each electrode potential during the discharge of a cycled cell. The results indicate that the negative electrode was responsible for the voltage plateau. Cell analysis revealed large crystals of cadmium hydroxide on the surface of the negative electrode and throughout the separator.

Nonlinear current-voltage characteristics based on semiconductor nanowire networks enable a new concept in thermoelectric device optimization

NASA Astrophysics Data System (ADS)

Diaz Leon, Juan J.; Norris, Kate J.; Hartnett, Ryan J.; Garrett, Matthew P.; Tompa, Gary S.; Kobayashi, Nobuhiko P.

2016-08-01

Thermoelectric (TE) devices that produce electric power from heat are driven by a temperature gradient (Δ T = T_{{hot}} - T_{{cold}}, T hot: hot side temperature, T cold: cold side temperature) with respect to the average temperature ( T). While the resistance of TE devices changes as Δ T and/or T change, the current-voltage ( I- V) characteristics have consistently been shown to remain linear, which clips generated electric power ( P gen) within the given open-circuit voltage ( V OC) and short-circuit current ( I SC). This P gen clipping is altered when an appropriate nonlinearity is introduced to the I- V characteristics—increasing P gen. By analogy, photovoltaic cells with a large fill factor exhibit nonlinear I- V characteristics. In this paper, the concept of a unique TE device with nonlinear I- V characteristics is proposed and experimentally demonstrated. A single TE device with nonlinear I- V characteristics is fabricated by combining indium phosphide (InP) and silicon (Si) semiconductor nanowire networks. These TE devices show P gen that is more than 25 times larger than those of comparable devices with linear I- V characteristics. The plausible causes of the nonlinear I- V characteristics are discussed. The demonstrated concept suggests that there exists a new pathway to increase P gen of TE devices made of semiconductors.

Review of the U.S. Department of Energy's "deep dive" effort to understand voltage fade in Li- and Mn-rich cathodes.

PubMed

Croy, Jason R; Balasubramanian, Mahalingam; Gallagher, Kevin G; Burrell, Anthony K

2015-11-17

The commercial introduction of the lithium-ion (Li-ion) battery nearly 25 years ago marked a technological turning point. Portable electronics, dependent on energy storage devices, have permeated our world and profoundly affected our daily lives in a way that cannot be understated. Now, at a time when societies and governments alike are acutely aware of the need for advanced energy solutions, the Li-ion battery may again change the way we do business. With roughly two-thirds of daily oil consumption in the United States allotted for transportation, the possibility of efficient and affordable electric vehicles suggests a way to substantially alleviate the Country's dependence on oil and mitigate the rise of greenhouse gases. Although commercialized Li-ion batteries do not currently meet the stringent demands of a would-be, economically competitive, electrified vehicle fleet, significant efforts are being focused on promising new materials for the next generation of Li-ion batteries. The leading class of materials most suitable for the challenge is the Li- and manganese-rich class of oxides. Denoted as LMR-NMC (Li-manganese-rich, nickel, manganese, cobalt), these materials could significantly improve energy densities, cost, and safety, relative to state-of-the-art Ni- and Co-rich Li-ion cells, if successfully developed.1 The success or failure of such a development relies heavily on understanding two defining characteristics of LMR-NMC cathodes. The first is a mechanism whereby the average voltage of cells continuously decreases with each successive charge and discharge cycle. This phenomenon, known as voltage fade, decreases the energy output of cells to unacceptable levels too early in cycling. The second characteristic is a pronounced hysteresis, or voltage difference, between charge and discharge cycles. The hysteresis represents not only an energy inefficiency (i.e., energy in vs energy out) but may also complicate the state of charge/depth of discharge management of larger systems, especially when accompanied by voltage fade. In 2012, the United States Department of Energy's Office of Vehicle Technologies, well aware of the inherent potential of LMR-NMC materials for improving the energy density of automotive energy storage systems, tasked a team of scientists across the National Laboratory Complex to investigate the phenomenon of voltage fade. Unique studies using synchrotron X-ray absorption (XAS) and high-resolution diffraction (HR-XRD) were coupled with nuclear magnetic resonance spectroscopy (NMR), neutron diffraction, high-resolution transmission electron microscopy (HR-TEM), first-principles calculations, molecular dynamics simulations, and detailed electrochemical analyses. These studies demonstrated for the first time the atomic-scale, structure-property relationships that exist between nanoscale inhomogeneities and defects, and the macroscale, electrochemical performance of these layered oxides. These inhomogeneities and defects have been directly correlated with voltage fade and hysteresis, and a model describing these mechanisms has been proposed. This Account gives a brief summary of the findings of this recently concluded, approximately three-year investigation. The interested reader is directed to the extensive body of work cited in the given references for a more comprehensive review of the subject.

Hypervelocity Impact Studies on Solar Cell Modules

NASA Technical Reports Server (NTRS)

Brandhorst, Henry W., Jr.; Best, Stevie R.

2001-01-01

Space environmental effects have caused severe problems as satellites move toward increased power and operating voltage levels. The greatest unknown, however, is the effect of high velocity micrometeoroid impacts on high voltage arrays (>200V). Understanding such impact phenomena is necessary for the design of future reliable, high voltage solar arrays, especially for Space Solar Power applications. Therefore, the objective of this work was to study the effect of hypervelocity impacts on high voltage solar arrays. Initially, state of the art, 18% efficient GaAs solar cell strings were targeted. The maximum bias voltage on a two-cell string was -200 V while the adjacent string was held at -140 V relative to the plasma potential. A hollow cathode device provided the plasma. Soda lime glass particles 40-120 micrometers in diameter were accelerated in the Hypervelocity Impact Facility to velocities as high as 11.6 km/sec. Coordinates and velocity were obtained for each of the approximately 40 particle impact sites on each shot. Arcing did occur, and both discharging and recharging of arcs between the two strings was observed. The recharging phenomena appeared to stop at approximately 66V string differential. No arcing was observed at 400 V on concentrator cell modules for the Stretched Lens Array.

Real-Time Nanoscale Open-Circuit Voltage Dynamics of Perovskite Solar Cells.

PubMed

Garrett, Joseph L; Tennyson, Elizabeth M; Hu, Miao; Huang, Jinsong; Munday, Jeremy N; Leite, Marina S

2017-04-12

Hybrid organic-inorganic perovskites based on methylammonium lead (MAPbI 3 ) are an emerging material with great potential for high-performance and low-cost photovoltaics. However, for perovskites to become a competitive and reliable solar cell technology their instability and spatial variation must be understood and controlled. While the macroscopic characterization of the devices as a function of time is very informative, a nanoscale identification of their real-time local optoelectronic response is still missing. Here, we implement a four-dimensional imaging method through illuminated heterodyne Kelvin probe force microscopy to spatially (<50 nm) and temporally (16 s/scan) resolve the voltage of perovskite solar cells in a low relative humidity environment. Local open-circuit voltage (V oc ) images show nanoscale sites with voltage variation >300 mV under 1-sun illumination. Surprisingly, regions of voltage that relax in seconds and after several minutes consistently coexist. Time-dependent changes of the local V oc are likely due to intragrain ion migration and are reversible at low injection level. These results show for the first time the real-time transient behavior of the V oc in perovskite solar cells at the nanoscale. Understanding and controlling the light-induced electrical changes that affect device performance are critical to the further development of stable perovskite-based solar technologies.

Seed mediated synthesis of nanosized zinc oxide and its electron transporting activity in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Rajkumar, C.; Arulraj, Arunachalam

2018-01-01

A zinc oxide (ZnO) nanoparticle has been synthesized using seed mediated method at a low temperature of 90 °C. To understand its optical, structural and morphological properties of as-synthesized ZnO, it was characterized using various analytical techniques. The obtained result reveals that ZnO nanoparticles possess hexagonal wurtzite crystal structure with an average crystallite size of ˜40 nm. The presence of hydroxyl, amine and alkyl groups was confirmed from Fourier transform infrared analysis. Furthermore, the synthesized ZnO powder has employed as photoanode for the fabrication of dye-sensitized solar cells using Doctor-blade technique. To evaluate its photo-conversion efficiency, the device has been assembled into a cell module and illuminated with the light intensity of 100 mW cm-2. The device exhibits the photo-conversion efficiency of 1.85% with the current density of 4.532 mA cm-2 and voltage of 0.61 V.

How do voltage-gated sodium channels enhance migration and invasiveness in cancer cells?

PubMed

Besson, Pierre; Driffort, Virginie; Bon, Émeline; Gradek, Frédéric; Chevalier, Stéphan; Roger, Sébastien

2015-10-01

Voltage-gated sodium channels are abnormally expressed in tumors, often as neonatal isoforms, while they are not expressed, or only at a low level, in the matching normal tissue. The level of their expression and their activity is related to the aggressiveness of the disease and to the formation of metastases. A vast knowledge on the regulation of their expression and functioning has been accumulated in normal excitable cells. This helped understand their regulation in cancer cells. However, how voltage-gated sodium channels impose a pro-metastatic behavior to cancer cells is much less documented. This aspect will be addressed in the review. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. Copyright © 2015 Elsevier B.V. All rights reserved.

Challenges and approaches for high-voltage spinel lithium-ion batteries.

PubMed

Kim, Jung-Hyun; Pieczonka, Nicholas P W; Yang, Li

2014-07-21

Lithium-ion (Li-ion) batteries have been developed for electric vehicle (EV) applications, owing to their high energy density. Recent research and development efforts have been devoted to finding the next generation of cathode materials for Li-ion batteries to extend the driving distance of EVs and lower their cost. LiNi(0.5)Mn(1.5)O(4) (LNMO) high-voltage spinel is a promising candidate for a next-generation cathode material based on its high operating voltage (4.75 V vs. Li), potentially low material cost, and excellent rate capability. Over the last decade, much research effort has focused on achieving a fundamental understanding of the structure-property relationship in LNMO materials. Recent studies, however, demonstrated that the most critical barrier for the commercialization of high-voltage spinel Li-ion batteries is electrolyte decomposition and concurrent degradative reactions at electrode/electrolyte interfaces, which results in poor cycle life for LNMO/graphite full cells. Despite scattered reports addressing these processes in high-voltage spinel full cells, they have not been consolidated into a systematic review article. With this perspective, emphasis is placed herein on describing the challenges and the various approaches to mitigate electrolyte decomposition and other degradative reactions in high-voltage spinel cathodes in full cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computer-aided control of electrolysis of solid Nb2O5 in molten CaCl2.

PubMed

Wu, Tian; Xiao, Wei; Jin, Xianbo; Liu, Chao; Wang, Dihua; Chen, George Z

2008-04-07

Low energy production of Nb powders via computer-aided control (CAC) of two-electrode electrolysis of porous Nb2O5 pellets (ca. 1.0 g) has been successfully demonstrated in molten CaCl2 at 1123 K. It was observed that potentiostatic electrolysis of the oxide in a three-electrode cell led to a cell voltage, i.e. the potential difference between the working (cathode) and counter (anode) electrodes, that decreased to a low and stable value within 1-2 h of the potential application until the end of the electrolysis (up to 12 h in this work). The cell voltage varied closely according to the current change. The stabilised cell voltage was below 2.5 V when the cathode potential was more positive than that for the reduction of Ca2+, leading to much lower energy consumption than that of constant voltage (>3.0 V) two-electrode electrolysis, as previously reported. Using a computer to program the variation of the cell voltage of two-electrode electrolysis according to that observed in the potentiostatic three-electrode electrolysis (0.05 V vs. Ca/Ca2+), a Nb powder with ca. 3900 ppm oxygen was produced in 12 h, with the energy consumption being 37.4% less than that of constant voltage two-electrode electrolysis at 3.0 V. Transmission electron microscopy revealed thin oxide layers (4-6 nm) on individual nodular particles (1-5 microm) of the obtained Nb powder. The oxide layer was likely formed in post-electrolysis processing operations, including washing in water, and contributed largely to the oxygen content in the obtained Nb powder.

Synaptic calcium regulation in hair cells of the chicken basilar papilla.

PubMed

Im, Gi Jung; Moskowitz, Howard S; Lehar, Mohammed; Hiel, Hakim; Fuchs, Paul Albert

2014-12-10

Cholinergic inhibition of hair cells occurs by activation of calcium-dependent potassium channels. A near-membrane postsynaptic cistern has been proposed to serve as a store from which calcium is released to supplement influx through the ionotropic ACh receptor. However, the time and voltage dependence of acetylcholine (ACh)-evoked potassium currents reveal a more complex relationship between calcium entry and release from stores. The present work uses voltage steps to regulate calcium influx during the application of ACh to hair cells in the chicken basilar papilla. When calcium influx was terminated at positive membrane potential, the ACh-evoked potassium current decayed exponentially over ∼100 ms. However, at negative membrane potentials, this current exhibited a secondary rise in amplitude that could be eliminated by dihydropyridine block of the voltage-gated calcium channels of the hair cell. Calcium entering through voltage-gated channels may transit through the postsynaptic cistern, since ryanodine and sarcoendoplasmic reticulum calcium-ATPase blockers altered the time course and magnitude of this secondary, voltage-dependent contribution to ACh-evoked potassium current. Serial section electron microscopy showed that efferent and afferent synaptic structures are juxtaposed, supporting the possibility that voltage-gated influx at afferent ribbon synapses influences calcium homeostasis during long-lasting cholinergic inhibition. In contrast, spontaneous postsynaptic currents ("minis") resulting from stochastic efferent release of ACh were made briefer by ryanodine, supporting the hypothesis that the synaptic cistern serves primarily as a calcium barrier and sink during low-level synaptic activity. Hypolemmal cisterns such as that at the efferent synapse of the hair cell can play a dynamic role in segregating near-membrane calcium for short-term and long-term signaling. Copyright © 2014 the authors 0270-6474/14/3416688-10$15.00/0.

Synaptic Calcium Regulation in Hair Cells of the Chicken Basilar Papilla

PubMed Central

Im, Gi Jung; Moskowitz, Howard S.; Lehar, Mohammed; Hiel, Hakim

2014-01-01

Cholinergic inhibition of hair cells occurs by activation of calcium-dependent potassium channels. A near-membrane postsynaptic cistern has been proposed to serve as a store from which calcium is released to supplement influx through the ionotropic ACh receptor. However, the time and voltage dependence of acetylcholine (ACh)-evoked potassium currents reveal a more complex relationship between calcium entry and release from stores. The present work uses voltage steps to regulate calcium influx during the application of ACh to hair cells in the chicken basilar papilla. When calcium influx was terminated at positive membrane potential, the ACh-evoked potassium current decayed exponentially over ∼100 ms. However, at negative membrane potentials, this current exhibited a secondary rise in amplitude that could be eliminated by dihydropyridine block of the voltage-gated calcium channels of the hair cell. Calcium entering through voltage-gated channels may transit through the postsynaptic cistern, since ryanodine and sarcoendoplasmic reticulum calcium-ATPase blockers altered the time course and magnitude of this secondary, voltage-dependent contribution to ACh-evoked potassium current. Serial section electron microscopy showed that efferent and afferent synaptic structures are juxtaposed, supporting the possibility that voltage-gated influx at afferent ribbon synapses influences calcium homeostasis during long-lasting cholinergic inhibition. In contrast, spontaneous postsynaptic currents (“minis”) resulting from stochastic efferent release of ACh were made briefer by ryanodine, supporting the hypothesis that the synaptic cistern serves primarily as a calcium barrier and sink during low-level synaptic activity. Hypolemmal cisterns such as that at the efferent synapse of the hair cell can play a dynamic role in segregating near-membrane calcium for short-term and long-term signaling. PMID:25505321

Analysis of each branch current of serial solar cells by using an equivalent circuit model

NASA Astrophysics Data System (ADS)

Yi, Shi-Guang; Zhang, Wan-Hui; Ai, Bin; Song, Jing-Wei; Shen, Hui

2014-02-01

In this paper, based on the equivalent single diode circuit model of the solar cell, an equivalent circuit diagram for two serial solar cells is drawn. Its equations of current and voltage are derived from Kirchhoff's current and voltage law. First, parameters are obtained from the I—V (current—voltage) curves for typical monocrystalline silicon solar cells (125 mm × 125 mm). Then, by regarding photo-generated current, shunt resistance, serial resistance of the first solar cell, and resistance load as the variables. The properties of shunt currents (Ish1 and Ish2), diode currents (ID1 and ID2), and load current (IL) for the whole two serial solar cells are numerically analyzed in these four cases for the first time, and the corresponding physical explanations are made. We find that these parameters have different influences on the internal currents of solar cells. Our results will provide a reference for developing higher efficiency solar cell module and contribute to the better understanding of the reason of efficiency loss of solar cell module.

High voltage photovoltaic power converter

DOEpatents

Haigh, Ronald E.; Wojtczuk, Steve; Jacobson, Gerard F.; Hagans, Karla G.

2001-01-01

An array of independently connected photovoltaic cells on a semi-insulating substrate contains reflective coatings between the cells to enhance efficiency. A uniform, flat top laser beam profile is illuminated upon the array to produce electrical current having high voltage. An essentially wireless system includes a laser energy source being fed through optic fiber and cast upon the photovoltaic cell array to prevent stray electrical signals prior to use of the current from the array. Direct bandgap, single crystal semiconductor materials, such as GaAs, are commonly used in the array. Useful applications of the system include locations where high voltages are provided to confined spaces such as in explosive detonation, accelerators, photo cathodes and medical appliances.

Na-ion batteries based on the inorganic BN nanocluster anodes: DFT studies.

PubMed

Nejati, K; Hosseinian, A; Bekhradnia, A; Vessally, E; Edjlali, L

2017-06-01

It has been recently indicated that the Li-ion batteries may be replaced by Na-ion batteries because of their low safety, high cost, and low-temperature performance, and lack of the Li mineral reserves. Here, using density functional theory calculations, we studied the potential application of B 12 N 12 nanoclusters as anode in Na-ion batteries. Our calculations indicate that the adsorption energy of Na + and Na are about -23.4 and -1.4kcal/mol, respectively, and the pristine BN cage to improve suffers from a low cell voltage (∼0.92V) as an anode in Na-ion batteries. We presented a strategy to increase the cell voltage and performance of Na-ion batteries. We showed that encapsulation of different halides (X=F - , Cl - , or Br - ) into BN cage significantly increases the cell voltage. By increasing the atomic number of X, the Gibbs free energy change of cell becomes more negative and the cell voltage is increased up to 3.93V. The results are discussed based on the structural, energetic, frontier molecular orbital, charge transfer and electronic properties and compared with the performance of other nanostructured anodes. Copyright © 2017 Elsevier Inc. All rights reserved.

In-situ study of discontinuous precipitation in Al-15 at.% Zn

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdou, S.; El-Boragy, M.; Solorzano, G.

1996-05-01

In the present study, attention was focused on in-situ work on discontinuous precipitation in Al-15.0 at.% Zn in a high voltage electron microscope using a hot stage and a video system. The microscope was an AEI instrument with a maximum voltage of 1.25 MV. The voltage used was 500 kV. The scope of the present study was to check if the grain boundary migration in the discontinuous precipitation reaction proceeds in a stop-and-go fashion. From all the observations reported here it can be concluded that the stop-and-go type of grain boundary migration seems to be a very general one. Butmore » in many cases it cannot easily experimentally be proved. In case of discontinuous precipitation in Al-15.0 at.% Zn it has been clearly demonstrated by in-situ observations in a high-voltage electron microscope that the reaction front migration occurs in a stop-and-go fashion. Consequently, there is a drastic difference between the average velocity and the instantaneous velocity. The only quantity, which can be determined in traditional experiments, is the average velocity to which the Petermann-Hornbogen equation is adequate.« less

Phosphoinositide 5- and 3-phosphatase activities of a voltage-sensing phosphatase in living cells show identical voltage dependence

PubMed Central

Keum, Dongil; Kim, Dong-Il; Suh, Byung-Chang

2016-01-01

Voltage-sensing phosphatases (VSPs) are homologs of phosphatase and tensin homolog (PTEN), a phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] 3-phosphatase. However, VSPs have a wider range of substrates, cleaving 3-phosphate from PI(3,4)P2 and probably PI(3,4,5)P3 as well as 5-phosphate from phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and PI(3,4,5)P3 in response to membrane depolarization. Recent proposals say these reactions have differing voltage dependence. Using Förster resonance energy transfer probes specific for different PIs in living cells with zebrafish VSP, we quantitate both voltage-dependent 5- and 3-phosphatase subreactions against endogenous substrates. These activities become apparent with different voltage thresholds, voltage sensitivities, and catalytic rates. As an analytical tool, we refine a kinetic model that includes the endogenous pools of phosphoinositides, endogenous phosphatase and kinase reactions connecting them, and four exogenous voltage-dependent 5- and 3-phosphatase subreactions of VSP. We show that apparent voltage threshold differences for seeing effects of the 5- and 3-phosphatase activities in cells are not due to different intrinsic voltage dependence of these reactions. Rather, the reactions have a common voltage dependence, and apparent differences arise only because each VSP subreaction has a different absolute catalytic rate that begins to surpass the respective endogenous enzyme activities at different voltages. For zebrafish VSP, our modeling revealed that 3-phosphatase activity against PI(3,4,5)P3 is 55-fold slower than 5-phosphatase activity against PI(4,5)P2; thus, PI(4,5)P2 generated more slowly from dephosphorylating PI(3,4,5)P3 might never accumulate. When 5-phosphatase activity was counteracted by coexpression of a phosphatidylinositol 4-phosphate 5-kinase, there was accumulation of PI(4,5)P2 in parallel to PI(3,4,5)P3 dephosphorylation, emphasizing that VSPs can cleave the 3-phosphate of PI(3,4,5)P3. PMID:27222577

Characterization and separation of Cryptosporidium and Giardia cells using on-chip dielectrophoresis.

PubMed

Narayanan Unni, Harikrishnan; Hartono, Deny; Yue Lanry Yung, Lin; Mah-Lee Ng, Mary; Pueh Lee, Heow; Cheong Khoo, Boo; Lim, Kian-Meng

2012-03-01

Dielectrophoresis (DEP) has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping, characterization, and separation of two species of Cryptosporidium (C. parvum and C. muris) and Giardia lambia (G. lambia) using a microfluidic experimental setup. Cryptosporidium oocysts, which are 2-4 μm in size and nearly spherical in shape, are used for the preliminary stage of prototype development and testing. G. lambia cysts are 8-12 μm in size. In order to facilitate effective trapping, simulations were performed to study the effects of buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip. Microscopic experiments were performed using the fabricated device and the real part of Clausius-Mossotti factor of the cells was estimated from critical voltages for particle trapping at the electrodes under steady fluid flow. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the cells. The separation of C. muris and G. lambia is achieved successfully at a frequency of 10 MHz and a voltage of 3 Vpp (peak to peak voltage).

Silicon solar cell process development, fabrication and analysis

NASA Technical Reports Server (NTRS)

Minahan, J. A.

1981-01-01

The fabrication of solar cells from several unconventional silicon materials is described, and cell performance measured and analyzed. Unconventional materials evaluated are edge defined film fed grown (EFG), heat exchanger method (HEM), dendritic web grown, and continuous CZ silicons. Resistivity, current voltage, and spectral sensitivity of the cells were measured. Current voltage was measured under AM0 and AM1 conditions. Maximum conversion efficiencies of cells fabricated from these and other unconventional silicons were compared and test results analyzed. The HEM and continuous CZ silicon were found to be superior to silicon materials considered previously.

Further study of inversion layer MOS solar cells

NASA Technical Reports Server (NTRS)

Ho, Fat Duen

1987-01-01

A group of inversion layer MOS solar cells has been fabricated. The highest value of open-circuit voltage obtained for the cells is 0.568V. One of the cells has produced a short-circuit current of 79.6 mA and an open-circuit voltage of 0.54V. It is estimated that the actual area AMO efficiency of this cell is 6.6 percent with an assumed value of 0.75 for its fill factor. Efforts made for fabricating an IL/MOS cell with reasonable efficiencies are reported. Future work for 4 sq cm IL cells and 25 sq cm IL cells is discussed.

Expression and testing in plants of ArcLight, a genetically-encoded voltage indicator used in neuroscience research.

PubMed

Matzke, Antonius J M; Matzke, Marjori

2015-10-12

It is increasingly appreciated that electrical controls acting at the cellular and supra-cellular levels influence development and initiate rapid responses to environmental cues. An emerging method for non-invasive optical imaging of electrical activity at cell membranes uses genetically-encoded voltage indicators (GEVIs). Developed by neuroscientists to chart neuronal circuits in animals, GEVIs comprise a fluorescent protein that is fused to a voltage-sensing domain. One well-known GEVI, ArcLight, undergoes strong shifts in fluorescence intensity in response to voltage changes in mammalian cells. ArcLight consists of super-ecliptic (SE) pHluorin (pH-sensitive fluorescent protein) with an A227D substitution, which confers voltage sensitivity in neurons, fused to the voltage-sensing domain of the voltage-sensing phosphatase of C iona i ntestinalis (Ci-VSD). In an ongoing effort to adapt tools of optical electrophysiology for plants, we describe here the expression and testing of ArcLight and various derivatives in different membranes of root cells in Arabidopsis thaliana. Transgenic constructs were designed to express ArcLight and various derivatives targeted to the plasma membrane and nuclear membranes of Arabidopsis root cells. In transgenic seedlings, changes in fluorescence intensity of these reporter proteins following extracellular ATP (eATP) application were monitored using a fluorescence microscope equipped with a high speed camera. Coordinate reductions in fluorescence intensity of ArcLight and Ci-VSD-containing derivatives were observed at both the plasma membrane and nuclear membranes following eATP treatments. However, similar responses were observed for derivatives lacking the Ci-VSD. The dispensability of the Ci-VSD suggests that in plants, where H(+) ions contribute substantially to electrical activities, the voltage-sensing ability of ArcLight is subordinate to the pH sensitivity of its SEpHluorin base. The transient reduction of ArcLight fluorescence triggered by eATP most likely reflects changes in pH and not membrane voltage. The pH sensitivity of ArcLight precludes its use as a direct sensor of membrane voltage in plants. Nevertheless, ArcLight and derivatives situated in the plasma membrane and nuclear membranes may offer robust, fluorescence intensity-based pH indicators for monitoring concurrent changes in pH at these discrete membrane systems. Such tools will assist analyses of pH as a signal and/or messenger at the cell surface and the nuclear periphery in living plants.

Enhanced Charge Extraction of Li-Doped TiO₂ for Efficient Thermal-Evaporated Sb₂S₃ Thin Film Solar Cells.

PubMed

Lan, Chunfeng; Luo, Jingting; Lan, Huabin; Fan, Bo; Peng, Huanxin; Zhao, Jun; Sun, Huibin; Zheng, Zhuanghao; Liang, Guangxing; Fan, Ping

2018-02-28

We provided a new method to improve the efficiency of Sb₂S₃ thin film solar cells. The TiO₂ electron transport layers were doped by lithium to improve their charge extraction properties for the thermal-evaporated Sb₂S₃ solar cells. The Mott-Schottky curves suggested a change of energy band and faster charge transport in the Li-doped TiO₂ films. Compared with the undoped TiO₂, Li-doped mesoporous TiO₂ dramatically improved the photo-voltaic performance of the thermal-evaporated Sb₂S₃ thin film solar cells, with the average power conversion efficiency ( PCE ) increasing from 1.79% to 4.03%, as well as the improved open-voltage ( V oc ), short-circuit current ( J sc ) and fill factors. The best device based on Li-doped TiO₂ achieved a power conversion efficiency up to 4.42% as well as a V oc of 0.645 V, which are the highest values among the reported thermal-evaporated Sb₂S₃ solar cells. This study showed that Li-doping on TiO₂ can effectively enhance the charge extraction properties of electron transport layers, offering a new strategy to improve the efficiency of Sb₂S₃-based solar cells.

Hydrophobic Polystyrene Passivation Layer for Simultaneously Improved Efficiency and Stability in Perovskite Solar Cells.

PubMed

Li, Minghua; Yan, Xiaoqin; Kang, Zhuo; Huan, Yahuan; Li, Yong; Zhang, Ruxiao; Zhang, Yue

2018-06-06

The major restraint for the commercialization of the high-performance hybrid metal halide perovskite solar cells is the long-term stability, especially at the infirm interface between the perovskite film and organic charge-transfer layer. Recently, engineering the interface between the perovskite and spiro-OMeTAD becomes an effective strategy to simultaneously improve the efficiency and stability in the perovskite solar cells. In this work, we demonstrated that introducing an interfacial polystyrene layer between the perovskite film and spiro-OMeTAD layer can effectively improve the perovskite solar cells photovoltaic performance. The inserted polystyrene layer can passivate the interface traps and defects effectively and decrease the nonradiative recombination, leading to enhanced photoluminescence intensity and carrier lifetime, without compromising the carrier extraction and transfer. Under the optimized condition, the perovskite solar cells with the polystyrene layer achieve an enhanced average power efficiency of about 19.61% (20.46% of the best efficiency) from about 17.63% with negligible current density-voltage hysteresis. Moreover, the optimized perovskite solar cells with the hydrophobic polystyrene layer can maintain about 85% initial efficiency after 2 months storage in open air conditions without encapsulation.

Combined O2/combustibles solid electrolyte gas monitoring device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hickam, W.M.; Lin, C.; Zomp, J.M.

1980-11-04

A circuit means in combination with a conventional oxygen ion conductive solid electrolyte cell establishes the cell in a voltage mode for the purposes of measuring excess oxygen and developing a voltage signal indicative thereof, and switching the cell to a current mode of operation in response to an excess combustible environment wherein current drawn by the cell to pump oxygen for combustible reaction with the excess combustibles environment is measured as an indication of the combustibles content of the gas.

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Godlewski, M. P.

1984-01-01

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

Perturbed atrial calcium handling in an ovine model of heart failure: Potential roles for reductions in the L-type calcium current

PubMed Central

Clarke, Jessica D.; Caldwell, Jessica L.; Horn, Margaux A.; Bode, Elizabeth F.; Richards, Mark A.; Hall, Mark C.S.; Graham, Helen K.; Briston, Sarah J.; Greensmith, David J.; Eisner, David A.; Dibb, Katharine M.; Trafford, Andrew W.

2015-01-01

Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca2 + and the response to β-adrenergic (β-AR) stimulation in atrial myocytes. HF was induced in sheep by ventricular tachypacing and changes in intracellular Ca2 + concentration studied in single left atrial myocytes under voltage and current clamp conditions. The following were all reduced in HF atrial myocytes; Ca2 + transient amplitude (by 46% in current clamped and 28% in voltage clamped cells), SR dependent rate of Ca2 + removal (kSR, by 32%), L-type Ca2 + current density (by 36%) and action potential duration (APD90 by 22%). However, in HF SR Ca2 + content was increased (by 19%) when measured under voltage-clamp stimulation. Inhibiting the L-type Ca2 + current (ICa-L) in control cells reproduced both the decrease in Ca2 + transient amplitude and increase of SR Ca2 + content observed in voltage-clamped HF cells. During β-AR stimulation Ca2 + transient amplitude was the same in control and HF cells. However, ICa-L remained less in HF than control cells whilst SR Ca2 + content was highest in HF cells during β-AR stimulation. The decrease in ICa-L that occurs in HF atrial myocytes appears to underpin the decreased Ca2 + transient amplitude and increased SR Ca2 + content observed in voltage-clamped cells. PMID:25463272

Important parameters affecting the cell voltage of aqueous electrical double-layer capacitors

NASA Astrophysics Data System (ADS)

Wu, Tzu-Ho; Hsu, Chun-Tsung; Hu, Chi-Chang; Hardwick, Laurence J.

2013-11-01

This study discusses and demonstrates how the open-circuit potential and charges stored in the working potential window on positive and negative electrodes affect the cell voltage of carbon-based electrical double-layer capacitors (EDLCs) in aqueous electrolytes. An EDLC consisting of two activated carbon electrodes is employed as the model system for identifying these key parameters although the potential window of water decomposition can be simply determined by voltammetric methods. First, the capacitive performances of an EDLC with the same charge on positive and negative electrodes are evaluated by cyclic voltammetric, charge-discharge, electrochemical impedance spectroscopic (EIS) analyses, and inductance-capacitance-resistance meter (LCR meter). The principles for obtaining the highest acceptable cell voltage of such symmetric ECs with excellent reversibility and capacitor-like behaviour are proposed. Aqueous charge-balanced EDLCs can be operated as high as 2.0 V with high energy efficiency (about 90%) and only 4% capacitance loss after the 600-cycle stability checking. The necessity of charge balance (but not capacitance balance) for positive and negative electrodes is substantiated from the lower acceptable cell voltage of charge-unbalanced EDLCs.

NO involvement in the inhibition of ghrelin on voltage-dependent potassium currents in rat hippocampal cells.

PubMed

Lu, Yong; Dang, Shaokang; Wang, Xu; Zhang, Junli; Zhang, Lin; Su, Qian; Zhang, Huiping; Lin, Tianwei; Zhang, Xiaoxiao; Zhang, Yurong; Sun, Hongli; Zhu, Zhongliang; Li, Hui

2018-01-01

Ghrelin is a peptide hormone that plays an important role in promoting appetite, regulating distribution and rate of use of energy, cognition, and mood disorders, but the relevant neural mechanisms of these function are still not clear. In this study, we examined the effect of ghrelin on voltage-dependent potassium (K + ) currents in hippocampal cells of 1-3 days SD rats by whole-cell patch-clamp technique, and discussed whether NO was involved in this process. The results showed that ghrelin significantly inhibited the voltage-dependent K + currents in hippocampal cells, and the inhibitory effect was more significant when l-arginine was co-administered. In contrast, N-nitro- l-arginine methyl ester increased the ghrelin inhibited K + currents and attenuated the inhibitory effect of ghrelin. While d-arginine (D-AA) showed no significant impact on the ghrelin-induced decrease in K + current. These results show that ghrelin may play a physiological role by inhibiting hippocampal voltage dependent K + currents, and the NO pathway may be involved in this process. Copyright © 2017 Elsevier B.V. All rights reserved.

Performance analysis of cascaded h-bridge multilevel inverter using mixed switching frequency with various dc-link voltages

NASA Astrophysics Data System (ADS)

Citarsa, I. B. F.; Satiawan, I. N. W.; Wiryajati, I. K.; Supriono

2016-01-01

Multilevel inverters have been widely used in many applications since the technology is advantageous to increase the converter capability as well as to improve the output voltage quality. According to the applied switching frequency, multilevel modulations can be subdivided into three classes, i.e: fundamental switching frequency, high switching frequency and mixed switching frequency. This paper investigates the performance of cascaded H-bridge (CHB) multilevel inverter that is modulated using mixed switching frequency (MSF) PWM with various dc-link voltage ratios. The simulation results show the nearly sinusoidal load output voltages are successfully achieved. It is revealed that there is improvement in output voltages quality in terms of THD and low-order harmonics content. The CHB inverter that is modulated using MSF PWM with equal dc-link voltage ratio (½ Vdc: ½ Vdc) produces output voltage with the lowest low-order harmonics (less than 1% of fundamental) while the CHB inverter that is modulated using MSF PWM with un-equal dc-link voltage ratio (2/3 Vdc: 1/3 Vdc) produces a 7-level output voltage with the lowest THD (16.31%) compared to the other PWM methods. Improvement of the output voltage quality here is also in line with improvement of the number of available levels provided in the output voltage. Here only 2 cells H-bridge inverter (contain 8 switches) are needed to produce a 7- level output voltage, while in the conventional CHB inverter at least 3 cells of H-bridge inverter (contain 12 switches) are needed to produce a 7-level output voltage. Hence it is valuable in term of saving number of component.

Novel 384-well population patch clamp electrophysiology assays for Ca2+-activated K+ channels.

PubMed

John, Victoria H; Dale, Tim J; Hollands, Emma C; Chen, Mao Xiang; Partington, Leanne; Downie, David L; Meadows, Helen J; Trezise, Derek J

2007-02-01

Planar array electrophysiology techniques were applied to assays for modulators of recombinant hIK and hSK3 Ca2+-activated K+ channels. In CHO-hIK-expressing cells, under asymmetric K+ gradients, small-molecule channel activators evoked time- and voltage-independent currents characteristic of those previously described by classical patch clamp electrophysiology methods. In single-hole (cell) experiments, the large cell-to-cell heterogeneity in channel expression rendered it difficult to generate activator concentration-response curves. However, in population patch clamp mode, in which signals are averaged from up to 64 cells, well-to-well variation was substantially reduced such that concentration-response curves could be easily constructed. The absolute EC50 values and rank order of potency for a range of activators, including 1-EBIO and DC-EBIO, corresponded well with conventional patch clamp data. Activator responses of hIK and hSK3 channels could be fully and specifically blocked by the selective inhibitors TRAM-34 and apamin, with IC50 values of 0.31 microM and 3 nM, respectively. To demonstrate assay precision and robustness, a test set of 704 compounds was screened in a 384-well format of the hIK assay. All plates had Z' values greater than 0.6, and the statistical cutoff for activity was 8%. Eleven hits (1.6%) were identified from this set, in addition to the randomly spiked wells with known activators. Overall, our findings demonstrate that population patch clamp is a powerful and enabling method for screening Ca2+-activated K+ channels and provides significant advantages over single-cell electrophysiology (IonWorks(HT)) and other previously published approaches. Moreover, this work demonstrates for the 1st time the utility of population patch clamp for ion channel activator assays and for non-voltage-gated ion channels.

Intermediate photovoltaic system application experiment operational performance report. Volume 6: Beverly High School, Beverly, Mass.

NASA Astrophysics Data System (ADS)

1982-03-01

Performance data are given for the month of February, 1982 for a photovoltaic power supply at a Massachusetts high school. Data given include: monthly and daily electrical energy yield; monthly and daily insolation; monthly and daily array efficiency; energy production as a function of power level, voltage, cell temperature, and hour of day; insolation as a function of hour of the day; input, output and efficiency for each of two power conditioning units and for the total power conditioning system; energy supplied to the load by the photovoltaic system and by the grid; photovoltaic system efficiency; dollar value of the energy supplied by the photovoltaic system; capacity factor; daily photovoltaic energy to load; daily system availability and hours of daylight; heating and cooling degree days; hourly cell temperature, ambient temperature, wind speed, and insolation; average monthly wind speed; wind direction distribution; and daily data acquisition mode and recording interval plot.

Primary zinc-air batteries for space power

NASA Technical Reports Server (NTRS)

Bragg, Bobby J.; Bourland, Deborah S.; Merry, Glenn; Putt, Ron

1992-01-01

Prismatic HR and LC cells and batteries were built and tested, and they performed well with respect to the program goals of high capacity and high rate capability at specific energies. The HR batteries suffered reduced utilizations owing to dryout at the 2 and 3 A rates for the 50 C tests owing to the requirement for forced convection. The LC batteries suffered reduced utilizations under all conditions owing to the chimney effect at 1 G, although this effect would not occur at 0 G. An empirical model was developed which accurately predicted utilizations and average voltages for single cells, although thermal effects encountered during battery testing caused significant deviations, both positive and negative, from the model. Based on the encouraging results of the test program, we believe that the zinc-air primary battery of a flat, stackable configuration can serve as a high performance and safe power source for a range of space applications.

Microbial community structure of different electrode materials in constructed wetland incorporating microbial fuel cell.

PubMed

Wang, Junfeng; Song, Xinshan; Wang, Yuhui; Abayneh, Befkadu; Ding, Yi; Yan, Denghua; Bai, Junhong

2016-12-01

The microbial fuel cell coupled with constructed wetland (CW-MFC) microcosms were operated under fed-batch mode for evaluating the effect of electrode materials on bioelectricity generation and microbial community composition. Experimental results indicated that the bioenergy output in CW-MFC increased with the substrate concentration; maximum average voltage (177mV) was observed in CW-MFC with carbon fiber felt (CFF). In addition, the four different materials resulted in the formation of significantly different microbial community distribution around the anode electrode. The relative abundance of Proteobacteria in CFF and foamed nickel (FN) was significantly higher than that in stainless steel mesh (SSM) and graphite rod (GR) samples. Notably, the findings indicate that CW-MFC utilizing FN anode electrode could apparently improve relative abundance of Dechloromonas, which has been regarded as a denitrifying and phosphate accumulating microorganism. Copyright © 2016 Elsevier Ltd. All rights reserved.

Photovoltaic characteristics of natural light harvesting dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hafez, H. S.; Shenouda, S. S.; Fadel, M.

2018-03-01

In this work of research, anthocyanin as a natural dye obtained from raspberry fruits, was used and tested as a photon harvesting/electron donating dye in titanium dioxide nanoparticle-based DSSCs. A working photoelectrode made from TiO2 nanoparticles with an average particle size (10-40 nm) that is coated on Florine doped tin-oxide substrate, was prepared via a simple and low cost hydrothermal method. A detailed structural and morphological analysis of the TiO2 photoactive electrode was investigated by X-ray diffraction (XRD), diffuse reflectance spectrometer, transmission electron microscope (TEM) and scanning electron microscope (SEM). Complete photovoltaic characteristics including (current, voltage, outpower, and responsivity) of the natural anthocyanin based dye sensitized solar cell have been investigated under different illumination intensity ranging from 10 to 100 mW.cm- 2. The cell responsivity and efficiency of the fabricated solar cell under different illumination intensity were found to be in the range (R = 15.6-23.8 mA.W- 1 and η = 0.13-0.25) at AM = 1.5 conditions. This study is important for enhancing the future applications of the promising DSSC technology.

Analysis of DMFC/battery hybrid power system for portable applications

NASA Astrophysics Data System (ADS)

Lee, Bong-Do; Jung, Doo-Hwan; Ko, Young-Ho

This study was carried out to develop a direct methanol fuel cell (DMFC)/battery hybrid power system used in portable applications. For a portable power system, the DMFC was applied for the main power source at average load and the battery was applied for auxiliary power at overload. Load share characteristics of hybrid power source were analyzed by computational simulation. The connection apparatus between the DMFC and the battery was set and investigated in the real system. Voltages and currents of the load, the battery and the DMFC were measured according to fuel, air and load changes. The relationship between load share characteristic and battery capacity was surveyed. The relationship was also studied in abnormal operation. A DMFC stack was manufactured for this experiment. For the study of the connection characteristics to the fuel cell Pb-acid, Ni-Cd and Ni-MH batteries were tested. The results of this study can be applied to design the interface module of the fuel cell/battery hybrid system and to determine the design requirement in the fuel cell stack for portable applications.

Development of Ca2+ hotspots between Lymnaea neurons during synaptogenesis

PubMed Central

Feng, Zhong-Ping; Grigoriev, Nikita; Munno, David; Lukowiak, Ken; MacVicar, Brian A; Goldberg, Jeffrey I; Syed, Naweed I

2002-01-01

Calcium (Ca2+) channel clustering at specific presynaptic sites is a hallmark of mature synapses. However, the spatial distribution patterns of Ca2+ channels at newly formed synapses have not yet been demonstrated. Similarly, it is unclear whether Ca2+ ‘hotspots’ often observed at the presynaptic sites are indeed target cell contact specific and represent a specialized mechanism by which Ca2+ channels are targeted to select synaptic sites. Utilizing both soma–soma paired (synapsed) and single neurons from the mollusk Lymnaea, we have tested the hypothesis that differential gradients of voltage-dependent Ca2+ signals develop in presynaptic neuron at its contact point with the postsynaptic neuron; and that these Ca2+ hotspots are target cell contact specific. Fura-2 imaging, or two-photon laser scanning microscopy of Calcium Green, was coupled with electrophysiological techniques to demonstrate that voltage-induced Ca2+ gradients (hotspots) develop in the presynaptic cell at its contact point with the postsynaptic neuron, but not in unpaired single cells. The incidence of Ca2+ hotspots coincided with the appearance of synaptic transmission between the paired cells, and these gradients were target cell contact specific. In contrast, the voltage-induced Ca2+ signal in unpaired neurons was uniformly distributed throughout the somata; a similar pattern of Ca2+ gradient was observed in the presynaptic neuron when it was soma–soma paired with a non-synaptic partner cell. Moreover, voltage clamp recording techniques, in conjunction with a fast, optical differential perfusion system, were used to demonstrate that the total whole-cell Ca2+ (or Ba2+) current density in single and paired cells was not significantly different. However, the amplitude of Ba2+ current was significantly higher in the presynaptic cell at its contact side with the postsynaptic neurons, compared with non-contacted regions. In summary, this study demonstrates that voltage-induced Ca2+ hotspots develop in the presynaptic cell, concomitant with the appearance of synaptic transmission between the soma–soma paired cells. The appearance of Ca2+ gradients in presynaptic neurons is target cell contact specific and is probably due to a spatial redistribution of existing channels during synaptogenesis. PMID:11850501

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jing; Camardese, John; Shunmugasundaram, Ramesh

Lithium-rich layered Ni–Mn–Co oxide materials have been intensely studied in the past decade. Mn-rich materials have serious voltage fade issues, and the Ni-rich materials have poor thermal stability and readily oxidize the organic carbonate electrolyte. Core–shell (CS) strategies that use Ni-rich material as the core and Mn-rich materials as the shell can balance the pros and cons of these materials in a hybrid system. The lithium-rich CS materials introduced here show much improved overall electrochemical performance compared to the core-only and shell-only samples. Energy dispersive spectroscopy results show that there was diffusion of transition metals between the core and shellmore » phases after sintering at 900 °C compared to the prepared hydroxide precursors. A Mn-rich shell was still maintained whereas the Co which was only in the shell in the precursor was approximately homogeneous throughout the particles. The CS samples with optimal lithium content showed low irreversible capacity (IRC), as well as high capacity and excellent capacity retention. Sample CS2-3 (the third sample in the 0.67Li 1+x(Ni₀.₆₇Mn₀.₃₃) 1–xO₂·0.33Li 1+y(Ni₀.₄Mn₀.₅Co₀.₁) 1–yO₂ CS2 series) had a reversible capacity of ~218 mAh/g with 12.3% (~30 mAh/g) irreversible capacity (IRC) and 98% capacity retention after 40 cycles to 4.6 V at 30 °C at a rate of ~C/20. Differential capacity versus potential (dQ/dV versus V) analysis confirmed that cells of the CS samples had stable impedance as well as a very stable average voltage. Apparently, the Mn-rich shell can effectively protect the Ni-rich core from reactions with the electrolyte while the Ni-rich core renders a high and stable average voltage.« less

Ionic currents in the guinea-pig taenia coli.

PubMed Central

Inomata, H; Kao, C Y

1976-01-01

Short segments of portions of taenia coli of the guinea-pig averaging 54 mum X 219 mum X ca. 200 mum have been studied by a double sucrose-gap voltage-clamp technique. 2. The average total capacitance was 0-4 muF, corresponding to approximately 10(4) cells, if a specific membrane capacitance of 3 muF/cm2 were assumed. 3. A significant resistance, averaging 11-4omega, was in series with the membrane, and seriously limited the accuracy of the voltage control possible. 4. On depolarization, an early transient inward current was followed by a late maintained outwary current. 5. The late current was carried mainly by K+, because its direction could be reversed if the preparation were first depolarized in isotonic K2SO4 and held back to the original resting potential. 6. After appropriate corrections for residual capacitative and leakage currents, a reversal potential for the late current (Eb) was determined to be 15-20 mV more negative than the natural resting potential. It was not affected by the amplitude or the duration of the activating voltage step, but could be changed by prolonged applications of holding current. 7. At rest, the ratio of PNa:PK was 0-16:1; for Eb it was 0-05:1. 8. The reversal potential for the transient early inward current (Ea) averaged 22 mV in Krebs-bicarbonate solution, but was shifted to about 35 mV when the late current was first suppressed with tetraethylammonium ion. The shift suggested that there was some overlap of the early and late currents. 9. Reduction of [Na+]o to 50% of normal, or replacement of all Na+ with dimethyldiethanol ammonium ion and choline ion, failed to cause any significant shifts in the reversal potential of the early current or reduce the magnitude of the early current. 10. Reduction of [Ca2+]o to 0-25 or 0-1 of the normal caused shifts of the Ea toward the negative and reductions in the early current. These changes can occur without changes in the maximum chord conductance of the early current, such as might happen in ordinary Krebs-bicarbonate solution, or in preparations which had been depolarized by prior treatment with isotonic K2SO4 and then held back to the original membrane voltage. 11. Increase of [Ca2+]o to 5 times normal increased the early inward current, and the maximum chord conductances of the early and late currents, but did not shift the Ea. 12. In preparations pretreated with TEA, increasing [Ca2+]o to 5 times normal shifted Ea toward 45 mV. 13. The various observations are interpreted to mean that the early current in the taenia coli is carried principally by influx of Ca2+, and not by Na+. PMID:1255524

Chemoselective tarantula toxins report voltage activation of wild-type ion channels in live cells

PubMed Central

Tilley, Drew C.; Eum, Kenneth S.; Fletcher-Taylor, Sebastian; Austin, Daniel C.; Dupré, Christophe; Patrón, Lilian A.; Garcia, Rita L.; Lam, Kit; Yarov-Yarovoy, Vladimir; Cohen, Bruce E.; Sack, Jon T.

2014-01-01

Electrically excitable cells, such as neurons, exhibit tremendous diversity in their firing patterns, a consequence of the complex collection of ion channels present in any specific cell. Although numerous methods are capable of measuring cellular electrical signals, understanding which types of ion channels give rise to these signals remains a significant challenge. Here, we describe exogenous probes which use a novel mechanism to report activity of voltage-gated channels. We have synthesized chemoselective derivatives of the tarantula toxin guangxitoxin-1E (GxTX), an inhibitory cystine knot peptide that binds selectively to Kv2-type voltage gated potassium channels. We find that voltage activation of Kv2.1 channels triggers GxTX dissociation, and thus GxTX binding dynamically marks Kv2 activation. We identify GxTX residues that can be replaced by thiol- or alkyne-bearing amino acids, without disrupting toxin folding or activity, and chemoselectively ligate fluorophores or affinity probes to these sites. We find that GxTX–fluorophore conjugates colocalize with Kv2.1 clusters in live cells and are released from channels activated by voltage stimuli. Kv2.1 activation can be detected with concentrations of probe that have a trivial impact on cellular currents. Chemoselective GxTX mutants conjugated to dendrimeric beads likewise bind live cells expressing Kv2.1, and the beads are released by channel activation. These optical sensors of conformational change are prototype probes that can indicate when ion channels contribute to electrical signaling. PMID:25331865

Bupivacaine inhibits large conductance, voltage- and Ca2+- activated K+ channels in human umbilical artery smooth muscle cells

PubMed Central

Martín, Pedro; Enrique, Nicolás; Palomo, Ana R. Roldán; Rebolledo, Alejandro; Milesi, Veronica

2012-01-01

Bupivacaine is a local anesthetic compound belonging to the amino amide group. Its anesthetic effect is commonly related to its inhibitory effect on voltage-gated sodium channels. However, several studies have shown that this drug can also inhibit voltage-operated K+ channels by a different blocking mechanism. This could explain the observed contractile effects of bupivacaine on blood vessels. Up to now, there were no previous reports in the literature about bupivacaine effects on large conductance voltage- and Ca2+-activated K+ channels (BKCa). Using the patch-clamp technique, it is shown that bupivacaine inhibits single-channel and whole-cell K+ currents carried by BKCa channels in smooth muscle cells isolated from human umbilical artery (HUA). At the single-channel level bupivacaine produced, in a concentration- and voltage-dependent manner (IC50 324 µM at +80 mV), a reduction of single-channel current amplitude and induced a flickery mode of the open channel state. Bupivacaine (300 µM) can also block whole-cell K+ currents (~45% blockage) in which, under our working conditions, BKCa is the main component. This study presents a new inhibitory effect of bupivacaine on an ion channel involved in different cell functions. Hence, the inhibitory effect of bupivacaine on BKCa channel activity could affect different physiological functions where these channels are involved. Since bupivacaine is commonly used during labor and delivery, its effects on umbilical arteries, where this channel is highly expressed, should be taken into account. PMID:22688134

Characteristics of arc currents on a negatively biased solar cell array in a plasma

NASA Technical Reports Server (NTRS)

Snyder, D. B.

1984-01-01

The time dependence of the emitted currents during arcing on solar cell arrays is being studied. The arcs are characterized using three parameters: the voltage change of the array during the arc (i.e., the charge lost), the peak current during the arc, and the time constant describing the arc current. This paper reports the dependence of these characteristics on two array parameters, the interconnect bias voltage and the array capacitance to ground. It was found that the voltage change of the array during an arc is nearly equal to the bias voltage. The array capacitance, on the other hand, influences both the peak current and the decay time constant of the arc. Both of these characteristics increase with increasing capacitance.

A membraneless single compartment abiotic glucose fuel cell

NASA Astrophysics Data System (ADS)

Slaughter, Gymama; Sunday, Joshua

2014-09-01

A simple energy harvesting strategy has been developed to selectively catalyze glucose in the presence of oxygen in a glucose/O2 fuel cell. The anode consists of an abiotic catalyst Al/Au/ZnO, in which ZnO seed layer was deposited on the surface of Al/Au substrate using hydrothermal method. The cathode is constructed from a single rod of platinum with an outer diameter of 500 μm. The abiotic glucose fuel cell was studied in phosphate buffer solution (pH 7.4) containing 5 mM glucose at a temperature of 22 °C. The cell is characterized according to its open-circuit voltage, polarization profile, and power density plot. Under these conditions, the abiotic glucose fuel cell possesses an open-circuit voltage of 840 mV and delivered a maximum power density of 16.2 μW cm-2 at a cell voltage of 495 mV. These characteristics are comparable to biofuel cell utilizing a much more complex system design. Such low-cost lightweight abiotic catalyzed glucose fuel cells have a great promise to be optimized, miniaturized to power bio-implantable devices.

Investigation of the double exponential in the current-voltage characteristics of silicon solar cells. [proton irradiation effects on ATS 1 cells

NASA Technical Reports Server (NTRS)

Wolf, M.; Noel, G. T.; Stirn, R. J.

1977-01-01

Difficulties in relating observed current-voltage characteristics of individual silicon solar cells to their physical and material parameters were underscored by the unexpected large changes in the current-voltage characteristics telemetered back from solar cells on the ATS-1 spacecraft during their first year in synchronous orbit. Depletion region recombination was studied in cells exhibiting a clear double-exponential dark characteristic by subjecting the cells to proton irradiation. A significant change in the saturation current, an effect included in the Sah, Noyce, Shockley formulation of diode current resulting from recombination in the depletion region, was caused by the introduction of shallow levels in the depletion region by the proton irradiation. This saturation current is not attributable only to diffusion current from outside the depletion region and only its temperature dependence can clarify its origin. The current associated with the introduction of deep-lying levels did not change significantly in these experiments.

Flow-through electroporation based on constant voltage for large-volume transfection of cells.

PubMed

Geng, Tao; Zhan, Yihong; Wang, Hsiang-Yu; Witting, Scott R; Cornetta, Kenneth G; Lu, Chang

2010-05-21

Genetic modification of cells is a critical step involved in many cell therapy and gene therapy protocols. In these applications, cell samples of large volume (10(8)-10(9)cells) are often processed for transfection. This poses new challenges for current transfection methods and practices. Here we present a novel flow-through electroporation method for delivery of genes into cells at high flow rates (up to approximately 20 mL/min) based on disposable microfluidic chips, a syringe pump, and a low-cost direct current (DC) power supply that provides a constant voltage. By eliminating pulse generators used in conventional electroporation, we dramatically lowered the cost of the apparatus and improved the stability and consistency of the electroporation field for long-time operation. We tested the delivery of pEFGP-C1 plasmids encoding enhanced green fluorescent protein into Chinese hamster ovary (CHO-K1) cells in the devices of various dimensions and geometries. Cells were mixed with plasmids and then flowed through a fluidic channel continuously while a constant voltage was established across the device. Together with the applied voltage, the geometry and dimensions of the fluidic channel determined the electrical parameters of the electroporation. With the optimal design, approximately 75% of the viable CHO cells were transfected after the procedure. We also generalize the guidelines for scaling up these flow-through electroporation devices. We envision that this technique will serve as a generic and low-cost tool for a variety of clinical applications requiring large volume of transfected cells. Copyright 2010 Elsevier B.V. All rights reserved.

If and SR Ca2+ release both contribute to pacemaker activity in canine sinoatrial node cells

PubMed Central

Gao, Zhan; Chen, Biyi; Joiner, Mei-ling A.; Wu, Yuejin; Guan, Xiaoqun; Koval, Olha M.; Chaudhary, Ashok K.; Cunha, Shane R.; Mohler, Peter J.; Martins, James B.; Song, Long-Sheng; Anderson, Mark E.

2010-01-01

Increasing evidence suggests that cardiac pacemaking is the result of two sinoatrial node (SAN) cell mechanisms: a ‘voltage clock’ and a Ca2+ dependent process, or ‘Ca2+ clock.’ The voltage clock initiates action potentials (APs) by SAN cell membrane potential depolarization from inward currents, of which the pacemaker current (If) is thought to be particularly important. A Ca2+ dependent process triggers APs when sarcoplasmic reticulum (SR) Ca2+ release activates inward current carried by the forward mode of the electrogenic Na+/Ca2+ exchanger (NCX). However, these mechanisms have mostly been defined in rodents or rabbits, but are unexplored in single SAN cells from larger animals. Here, we used patch-clamp and confocal microscope techniques to explore the roles of the voltage and Ca2+ clock mechanisms in canine SAN pacemaker cells. We found that ZD7288, a selective If antagonist, significantly reduced basal automaticity and induced irregular, arrhythmia-like activity in canine SAN cells. In addition, ZD7288 impaired but did not eliminate the SAN cell rate acceleration by isoproterenol. In contrast, ryanodine significantly reduced the SAN cell acceleration by isoproterenol, while ryanodine reduction of basal automaticity was modest (∼14%) and did not reach statistical significance. Importantly, pretreatment with ryanodine eliminated SR Ca2+ release, but did not affect basal or isoproterenol-enhanced If. Taken together, these results indicate that voltage and Ca2+ dependent automaticity mechanisms coexist in canine SAN cells, and suggest If and SR Ca2+ release cooperate to determine baseline and catecholamine-dependent automaticity in isolated dog SAN cells. PMID:20380837

In vitro cardiomyocyte-driven biogenerator based on aligned piezoelectric nanofibers

NASA Astrophysics Data System (ADS)

Liu, Xia; Zhao, Hui; Lu, Yingxian; Li, Song; Lin, Liwei; Du, Yanan; Wang, Xiaohong

2016-03-01

Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion.Capturing the body's mechanical energy from the heart, lungs, and diaphragm can probably meet the requirements for in vivo applications of implantable biomedical devices. In this work, we present a novel contractile cardiomyocyte (CM)-driven biogenerator based on piezoelectric nanofibers (NFs) uniaxially aligned on a PDMS thin film. Flexible nanostructures interact with the CMs, as a physical cue to guide the CMs to align in a specific way, and create mechanical interfaces of contractile CMs and piezoelectric NFs. As such, the cellular construct features specific alignment and synchronous contraction, which realizes the maximal resultant force to drive the NFs to bend periodically. Studies on contraction mapping show that neonatal rat CMs self-assemble into a functional bio-bot film with well-defined axes of force generation. Consequently, the biogenerator produces an average voltage of 200 mV and current of 45 nA at the cell concentration of 1.0 million per ml, offering a biocompatible and scalable platform for biological energy conversion. Electronic supplementary information (ESI) available: Includes the ESI methods and figures, and videos of cell contraction and biogenerator bending. See DOI: 10.1039/c5nr08430j

Performance Characteristics of Lithium Ion Prototype Cells for 2003 Mars Sample Return Athena Rover

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Smart, M. C.; Ewell, R.; Surampudi, S.; Marsh, R. A.

2000-01-01

A viewgraph presentation outlines the mission objectives and power subsystem for the Mars Sample Return (MSR) Athena Rover. The NASA-DOD (depth of discharge) Interagency Li Ion program objectives are discussed. Evaluation tests performed at JPL are listed, and test results are shown for the Li-Ion cell initial capacity, charge/discharge capacity, voltage and ratio, specific energy, watt-hour efficiency, and cell voltage at various temperatures.

Method of removing the effects of electrical shorts and shunts created during the fabrication process of a solar cell

DOEpatents

Nostrand, Gerald E.; Hanak, Joseph J.

1979-01-01

A method of removing the effects of electrical shorts and shunts created during the fabrication process and improving the performance of a solar cell with a thick film cermet electrode opposite to the incident surface by applying a reverse bias voltage of sufficient magnitude to burn out the electrical shorts and shunts but less than the break down voltage of the solar cell.

Microchip amplifier for in vitro, in vivo, and automated whole cell patch-clamp recording

PubMed Central

Kolb, Ilya; Kodandaramaiah, Suhasa B.; Chubykin, Alexander A.; Yang, Aimei; Bear, Mark F.; Boyden, Edward S.; Forest, Craig R.

2014-01-01

Patch clamping is a gold-standard electrophysiology technique that has the temporal resolution and signal-to-noise ratio capable of reporting single ion channel currents, as well as electrical activity of excitable single cells. Despite its usefulness and decades of development, the amplifiers required for patch clamping are expensive and bulky. This has limited the scalability and throughput of patch clamping for single-ion channel and single-cell analyses. In this work, we have developed a custom patch-clamp amplifier microchip that can be fabricated using standard commercial silicon processes capable of performing both voltage- and current-clamp measurements. A key innovation is the use of nonlinear feedback elements in the voltage-clamp amplifier circuit to convert measured currents into logarithmically encoded voltages, thereby eliminating the need for large high-valued resistors, a factor that has limited previous attempts at integration. Benchtop characterization of the chip shows low levels of current noise [1.1 pA root mean square (rms) over 5 kHz] during voltage-clamp measurements and low levels of voltage noise (8.2 μV rms over 10 kHz) during current-clamp measurements. We demonstrate the ability of the chip to perform both current- and voltage-clamp measurement in vitro in HEK293FT cells and cultured neurons. We also demonstrate its ability to perform in vivo recordings as part of a robotic patch-clamping system. The performance of the patch-clamp amplifier microchip compares favorably with much larger commercial instrumentation, enabling benchtop commoditization, miniaturization, and scalable patch-clamp instrumentation. PMID:25429119

The most likely voltage path and large deviations approximations for integrate-and-fire neurons.

PubMed

Paninski, Liam

2006-08-01

We develop theory and numerical methods for computing the most likely subthreshold voltage path of a noisy integrate-and-fire (IF) neuron, given observations of the neuron's superthreshold spiking activity. This optimal voltage path satisfies a second-order ordinary differential (Euler-Lagrange) equation which may be solved analytically in a number of special cases, and which may be solved numerically in general via a simple "shooting" algorithm. Our results are applicable for both linear and nonlinear subthreshold dynamics, and in certain cases may be extended to correlated subthreshold noise sources. We also show how this optimal voltage may be used to obtain approximations to (1) the likelihood that an IF cell with a given set of parameters was responsible for the observed spike train; and (2) the instantaneous firing rate and interspike interval distribution of a given noisy IF cell. The latter probability approximations are based on the classical Freidlin-Wentzell theory of large deviations principles for stochastic differential equations. We close by comparing this most likely voltage path to the true observed subthreshold voltage trace in a case when intracellular voltage recordings are available in vitro.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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 μm 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 μm). 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.

Effect of storage and LEO cycling on manufacturing technology IPV nickel-hydrogen cells

NASA Technical Reports Server (NTRS)

Smithrick, John J.

1987-01-01

Yardney Manufacturing Technology (MANTECH) 50 A-hr space weight individual pressure vessel nickel-hydrogen cells were evaluated. This consisted of investigating: the effect of storage and charge/discharge cycling on cell performance. For the storage test the cells were precharged with hydrogen, by the manufacturer, to a pressure of 14.5 psia. After undergoing activation and acceptance tests, the cells were discharged at C/10 rate (5A) to 0.1 V or less. The terminals were then shorted. The cells were shipped to NASA Lewis Research Center where they were stored at room temperature in the shorted condition for 1 year. After storage, the acceptance tests were repeated at NASA Lewis. A comparison of test results indicate no significant degradation in electrical performance due to 1 year storage. For the cycle life test the regime was a 90 minute low earth orbit at deep depths of discharge (80 and 60 percent). At the 80 percent DOD the three cells failed on the average at cycle 741. Failure for this test was defined to occur when the cell voltage degraded to 1 V prior to completion of the 35 min discharge. The DOD was reduced to 60 percent. The cycle life test was continued.

High rate copper and energy recovery in microbial fuel cells

PubMed Central

Rodenas Motos, Pau; ter Heijne, Annemiek; van der Weijden, Renata; Saakes, Michel; Buisman, Cees J. N.; Sleutels, Tom H. J. A.

2015-01-01

Bioelectrochemical systems (BESs) are a novel, promising technology for the recovery of metals. The prerequisite for upscaling from laboratory to industrial size is that high current and high power densities can be produced. In this study we report the recovery of copper from a copper sulfate stream (2 g L-1 Cu2+) using a laboratory scale BES at high rate. To achieve this, we used a novel cell configuration to reduce the internal voltage losses of the system. At the anode, electroactive microorganisms produce electrons at the surface of an electrode, which generates a stable cell voltage of 485 mV when combined with a cathode where copper is reduced. In this system, a maximum current density of 23 A m-2 in combination with a power density of 5.5 W m-2 was produced. XRD analysis confirmed 99% purity in copper of copper deposited onto cathode surface. Analysis of voltage losses showed that at the highest current, most voltage losses occurred at the cathode, and membrane, while anode losses had the lowest contribution to the total voltage loss. These results encourage further development of BESs for bioelectrochemical metal recovery. PMID:26150802

A dc to dc converter

NASA Astrophysics Data System (ADS)

Willis, A. E.; Gould, J. M.; Matheney, J. L.; Garrett, H.

1984-01-01

The object of the invention is to provide an improved converter for converting one direct current voltage to another. A plurality of phased square wave voltages are provided from a ring counter through amplifiers to a like plurality of output transformers. Each of these transformers has two windings, and S(1) winding and an S(2) winding. The S(1) windings are connected in series, then the S(2) windings are connected in series, and finally, the two sets of windings are connected in series. One of six SCRs is connected between each two series connected windings to a positive output terminal and one of diodes is connected between each set of two windings of a zero output terminal. By virtue of this configuration, a quite high average direct current voltage is obtained, which varies between full voltage and two-thirds full voltage rather than from full voltage to zero. Further, its variation, ripple frequency, is reduced to one-sixth of that present in a single phase system. Application to raising battery voltage for an ion propulsion system is mentioned.

Timing and efficacy of Ca2+ channel activation in hippocampal mossy fiber boutons.

PubMed

Bischofberger, Josef; Geiger, Jörg R P; Jonas, Peter

2002-12-15

The presynaptic Ca2+ signal is a key determinant of transmitter release at chemical synapses. In cortical synaptic terminals, however, little is known about the kinetic properties of the presynaptic Ca2+ channels. To investigate the timing and magnitude of the presynaptic Ca2+ inflow, we performed whole-cell patch-clamp recordings from mossy fiber boutons (MFBs) in rat hippocampus. MFBs showed large high-voltage-activated Ca(2+) currents, with a maximal amplitude of approximately 100 pA at a membrane potential of 0 mV. Both activation and deactivation were fast, with time constants in the submillisecond range at a temperature of approximately 23 degrees C. An MFB action potential (AP) applied as a voltage-clamp command evoked a transient Ca2+ current with an average amplitude of approximately 170 pA and a half-duration of 580 microsec. A prepulse to +40 mV had only minimal effects on the AP-evoked Ca2+ current, indicating that presynaptic APs open the voltage-gated Ca2+ channels very effectively. On the basis of the experimental data, we developed a kinetic model with four closed states and one open state, linked by voltage-dependent rate constants. Simulations of the Ca2+ current could reproduce the experimental data, including the large amplitude and rapid time course of the current evoked by MFB APs. Furthermore, the simulations indicate that the shape of the presynaptic AP and the gating kinetics of the Ca2+ channels are tuned to produce a maximal Ca2+ influx during a minimal period of time. The precise timing and high efficacy of Ca2+ channel activation at this cortical glutamatergic synapse may be important for synchronous transmitter release and temporal information processing.

30 CFR 70.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... battery pack multiplied by the manufacturer's nominal voltage per cell value; (2) Examination of all... calibrated at the flowrate of 2.0 liters of air per minute, or at a different flowrate as prescribed by the... than the product of the number of cells in the battery pack multiplied by 1.25. The voltage for other...

Formation of BaSi2 heterojunction solar cells using transparent MoOx hole transport layers

NASA Astrophysics Data System (ADS)

Du, W.; Takabe, R.; Baba, M.; Takeuchi, H.; Hara, K. O.; Toko, K.; Usami, N.; Suemasu, T.

2015-03-01

Heterojunction solar cells that consist of 15 nm thick molybdenum trioxide (MoOx, x < 3) as a hole transport layer and 600 nm thick unpassivated or passivated n-BaSi2 layers were demonstrated. Rectifying current-voltage characteristics were observed when the surface of BaSi2 was exposed to air. When the exposure time was decreased to 1 min, an open circuit voltage of 200 mV and a short circuit current density of 0.5 mA/cm2 were obtained under AM1.5 illumination. The photocurrent density under a reverse bias voltage of -1 V reached 25 mA/cm2, which demonstrates the significant potential of BaSi2 for solar cell applications.

Design and Experimental Verification of a 0.19 V 53 μW 65 nm CMOS Integrated Supply-Sensing Sensor With a Supply-Insensitive Temperature Sensor and an Inductive-Coupling Transmitter for a Self-Powered Bio-sensing System Using a Biofuel Cell.

PubMed

Kobayashi, Atsuki; Ikeda, Kei; Ogawa, Yudai; Kai, Hiroyuki; Nishizawa, Matsuhiko; Nakazato, Kazuo; Niitsu, Kiichi

2017-12-01

In this paper, we present a self-powered bio-sensing system with the capability of proximity inductive-coupling communication for supply sensing and temperature monitoring. The proposed bio-sensing system includes a biofuel cell as a power source and a sensing frontend that is associated with the CMOS integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, a supply-insensitive time-domain temperature sensor, and a current-driven inductive-coupling transmitter and achieves low-voltage operation. The timer converts the output voltage from a biofuel cell to frequency. The temperature sensor provides a pulse width modulation (PWM) output that is not dependent on the supply voltage, and the associated inductive-coupling transmitter enables proximity communication. A test chip was fabricated in 65 nm CMOS technology and consumed 53 μW with a supply voltage of 190 mV. The low-voltage-friendly design satisfied the performance targets of each integrated sensor without any trimming. The chips allowed us to successfully demonstrate proximity communication with an asynchronous receiver, and the measurement results show the potential for self-powered operation using biofuel cells. The analysis and experimental verification of the system confirmed their robustness.

Overexpression of the Large-Conductance, Ca2+-Activated K+ (BK) Channel Shortens Action Potential Duration in HL-1 Cardiomyocytes.

PubMed

Stimers, Joseph R; Song, Li; Rusch, Nancy J; Rhee, Sung W

2015-01-01

Long QT syndrome is characterized by a prolongation of the interval between the Q wave and the T wave on the electrocardiogram. This abnormality reflects a prolongation of the ventricular action potential caused by a number of genetic mutations or a variety of drugs. Since effective treatments are unavailable, we explored the possibility of using cardiac expression of the large-conductance, Ca2+-activated K+ (BK) channel to shorten action potential duration (APD). We hypothesized that expression of the pore-forming α subunit of human BK channels (hBKα) in HL-1 cells would shorten action potential duration in this mouse atrial cell line. Expression of hBKα had minimal effects on expression levels of other ion channels with the exception of a small but significant reduction in Kv11.1. Patch-clamped hBKα expressing HL-1 cells exhibited an outward voltage- and Ca2+-sensitive K+ current, which was inhibited by the BK channel blocker iberiotoxin (100 nM). This BK current phenotype was not detected in untransfected HL-1 cells or in HL-1 null cells sham-transfected with an empty vector. Importantly, APD in hBKα-expressing HL-1 cells averaged 14.3 ± 2.8 ms (n = 10), which represented a 53% reduction in APD compared to HL-1 null cells lacking BKα expression. APD in the latter cells averaged 31.0 ± 5.1 ms (n = 13). The shortened APD in hBKα-expressing cells was restored to normal duration by 100 nM iberiotoxin, suggesting that a repolarizing K+ current attributed to BK channels accounted for action potential shortening. These findings provide initial proof-of-concept that the introduction of hBKα channels into a cardiac cell line can shorten APD, and raise the possibility that gene-based interventions to increase hBKα channels in cardiac cells may hold promise as a therapeutic strategy for long QT syndrome.

Boolean gates on actin filaments

NASA Astrophysics Data System (ADS)

Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

2016-01-01

Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications.

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

NASA Technical Reports Server (NTRS)

Reid, Margaret A.

1989-01-01

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.

A novel method for in-situ monitoring of local voltage, temperature and humidity distributions in fuel cells using flexible multi-functional micro sensors.

PubMed

Lee, Chi-Yuan; Fan, Wei-Yuan; Chang, Chih-Ping

2011-01-01

In this investigation, micro voltage, temperature and humidity sensors were fabricated and integrated for the first time on a stainless steel foil using micro-electro-mechanical systems (MEMS). These flexible multi-functional micro sensors have the advantages of high temperature resistance, flexibility, smallness, high sensitivity and precision of location. They were embedded in a proton exchange membrane fuel cell (PEMFC) and used to simultaneously measure variations in the inner voltage, temperature and humidity. The accuracy and reproducibility of the calibrated results obtained using the proposed micro sensors is excellent. The experimental results indicate that, at high current density and 100%RH or 75%RH, the relative humidity midstream and downstream saturates due to severe flooding. The performance of the PEM fuel cell can be stabilized using home-made flexible multi-functional micro sensors by the in-situ monitoring of local voltage, temperature and humidity distributions within it.

A Novel Method for In-Situ Monitoring of Local Voltage, Temperature and Humidity Distributions in Fuel Cells Using Flexible Multi-Functional Micro Sensors

PubMed Central

Lee, Chi-Yuan; Fan, Wei-Yuan; Chang, Chih-Ping

2011-01-01

In this investigation, micro voltage, temperature and humidity sensors were fabricated and integrated for the first time on a stainless steel foil using micro-electro-mechanical systems (MEMS). These flexible multi-functional micro sensors have the advantages of high temperature resistance, flexibility, smallness, high sensitivity and precision of location. They were embedded in a proton exchange membrane fuel cell (PEMFC) and used to simultaneously measure variations in the inner voltage, temperature and humidity. The accuracy and reproducibility of the calibrated results obtained using the proposed micro sensors is excellent. The experimental results indicate that, at high current density and 100%RH or 75%RH, the relative humidity midstream and downstream saturates due to severe flooding. The performance of the PEM fuel cell can be stabilized using home-made flexible multi-functional micro sensors by the in-situ monitoring of local voltage, temperature and humidity distributions within it. PMID:22319361

Expression of the voltage-sensing phosphatase gene in the chick embryonic tissues and in the adult cerebellum.

PubMed

Yamaguchi, Shinji; Aoki, Naoya; Kitajima, Takaaki; Okamura, Yasushi; Homma, Koichi J

2014-10-01

Voltage-sensing phosphatase (VSP) consists of a transmembrane voltage sensor domain (VSD) and the cytoplasmic domain with phosphoinositide-phosphatase activities. It operates as the voltage sensor and directly translates membrane potential into phosphoinositide turnover by coupling VSD to the cytoplasmic domain. VSPs are evolutionarily conserved from marine invertebrate up to humans. Recently, we demonstrated that ectopic expression of the chick ortholog of VSP, Gg-VSP, in a fibroblast cell line caused characteristic cell process outgrowths. Co-expression of chick PTEN suppressed such morphological change, suggesting that VSP regulates cell shape by increasing PI(3,4)P2. However, the in vivo function of Gg-VSP remains unclear. Here, we showed that in chick embryos Gg-VSP is expressed in the stomach, mesonephros, pharyngeal arch, limb bud, somites, floor plate of neural tube, and notochord. In addition, both Gg-VSP transcripts and the protein were found in the cerebellar Purkinje neurons. These findings provide an insight into the physiological functions of VSP.

Electrically erasable non-volatile memory via electrochemical deposition of multifractal aggregates

NASA Astrophysics Data System (ADS)

West, William Clark

An electrically erasable non-volatile memory system based on the electrochemical deposition of Ag or Cu from a solid electrolyte is presented. This memory system, referred to as Metal Dendrite Memory, is characterized by its simplicity of design and operation, low power consumption, and potentially high cell density. By applying a small DC voltage (2.5-5V) across a Cu or Ag doped As-S amorphous chalcogenide film sandwiched between two metal electrodes, a metal filament can be electrodeposited, shorting the large impedance solid electrolyte ("on" state). Application of smaller amplitude voltage pulses (1-1.5V) across the metal filament ruptures the short, returning the cell to the high impedance state ("off" state). The state of the cell is read by applying very small amplitude voltage pulses (0.25V). These "read" voltage pulses do not disturb the state of the cell even after 10sp7 pulses. Due to difficulties in characterizing this solid electrolyte system via conventional techniques, the MDM cells have been examined using low excitation characterization methods such as Impedance Spectroscopy (IS) and polarization measurements. These studies have yielded a self-consistent equivalent circuit model as well as parameters such as ionic diffusivity and conductivity, double layer and geometric capacitances. In addition to materials characterization, the speed at which the MDM cells operate has been systematically studied using a series of statistically designed experiments, demonstrating the importance of photodoping time and applied voltage on device speed. These results were further examined using IS and Rutherford Backscattering Spectrometry (RBS). The morphology of the growing electrodeposit was studied in several different electrode arrangements and excitation conditions. Under migrationally limited conditions, the electrodeposit grew in multifractal patterns, as measured using lacunarity analysis. If a conducting film was deposited parallel to the growth direction, the electrodeposition could be driven from Diffusion Limited Aggregation (DLA) to Densely Branched Morphology (DBM) modes by changing the voltage applied to the cell. In summary, this study has laid the groundwork for future research and development of MDM memory systems by identifying many important characteristics of the MDM cell. These findings include quantitative measurement of ionic transport values, identification of the electrochemical mechanisms involved in MDM data storage, determination of parameters that are statistically significant in affecting data storage speed, and determination of the effect of cell geometry and bias on electrodeposit morphology.

[Investigation of radiation dose for lower tube voltage CT using automatic exposure control].

PubMed

Takata, Mitsuo; Matsubara, Kousuke; Koshida, Kichirou; Tarohda, Tohru

2015-04-01

The purpose of our study was to investigate radiation dose for lower tube voltage CT using automatic exposure control (AEC). An acrylic body phantom was used, and volume CT dose indices (CTDIvol) for tube voltages of 80, 100, 120, and 135 kV were investigated with combination of AEC. Average absorbed dose in the abdomen for 100 and 120 kV were also measured using thermoluminescence dosimeters. In addition, we examined noise characteristics under the same absorbed doses. As a result, the exposure dose was not decreased even when the tube voltage was lowered, and the organ absorbed dose value became approximately 30% high. And the noise was increased under the radiographic condition to be an equal absorbed dose. Therefore, radiation dose increases when AEC is used for lower tube voltage CT under the same standard deviation (SD) setting with 120 kV, and the optimization of SD setting is crucial.

Treatment of emulsified oils by electrocoagulation: pulsed voltage applications.

PubMed

Genc, Ayten; Bakirci, Busra

2015-01-01

The effect of pulsed voltage application on energy consumption during electrocoagulation was investigated. Three voltage profiles having the same arithmetic average with respect to time were applied to the electrodes. The specific energy consumption for these profiles were evaluated and analyzed together with oil removal efficiencies. The effects of applied voltages, electrode materials, electrode configurations, and pH on oil removal efficiency were determined. Electrocoagulation experiments were performed by using synthetic and real wastewater samples. The pulsed voltages saved energy during the electrocoagulation process. In continuous operation, energy saving was as high as 48%. Aluminum electrodes used for the treatment of emulsified oils resulted in higher oil removal efficiencies in comparison with stainless steel and iron electrodes. When the electrodes gap was less than 1 cm, higher oil removal efficiencies were obtained. The highest oil removal efficiencies were 95% and 35% for the batch and continuous operating modes, respectively.

Integrally regulated solar array demonstration using an Intel 8080 microprocessor

NASA Technical Reports Server (NTRS)

Petrik, E. J.

1977-01-01

A concept for regulating the voltage of a solar array by using a microprocessor to effect discrete voltage changes was demonstrated. Eight shorting switches were employed to regulate a simulated array at set-point voltages between 10,000 and 15,000 volts. The demonstration showed that the microprocessor easily regulated the solar array output voltage independently of whether or not the switched cell groups were binary sized in voltage. In addition, the microprocessor provided logic memory capability to perform additional tasks such as locating and insolating a faulty switch.

Uncertainty quantification of fast sodium current steady-state inactivation for multi-scale models of cardiac electrophysiology.

PubMed

Pathmanathan, Pras; Shotwell, Matthew S; Gavaghan, David J; Cordeiro, Jonathan M; Gray, Richard A

2015-01-01

Perhaps the most mature area of multi-scale systems biology is the modelling of the heart. Current models are grounded in over fifty years of research in the development of biophysically detailed models of the electrophysiology (EP) of cardiac cells, but one aspect which is inadequately addressed is the incorporation of uncertainty and physiological variability. Uncertainty quantification (UQ) is the identification and characterisation of the uncertainty in model parameters derived from experimental data, and the computation of the resultant uncertainty in model outputs. It is a necessary tool for establishing the credibility of computational models, and will likely be expected of EP models for future safety-critical clinical applications. The focus of this paper is formal UQ of one major sub-component of cardiac EP models, the steady-state inactivation of the fast sodium current, INa. To better capture average behaviour and quantify variability across cells, we have applied for the first time an 'individual-based' statistical methodology to assess voltage clamp data. Advantages of this approach over a more traditional 'population-averaged' approach are highlighted. The method was used to characterise variability amongst cells isolated from canine epi and endocardium, and this variability was then 'propagated forward' through a canine model to determine the resultant uncertainty in model predictions at different scales, such as of upstroke velocity and spiral wave dynamics. Statistically significant differences between epi and endocardial cells (greater half-inactivation and less steep slope of steady state inactivation curve for endo) was observed, and the forward propagation revealed a lack of robustness of the model to underlying variability, but also surprising robustness to variability at the tissue scale. Overall, the methodology can be used to: (i) better analyse voltage clamp data; (ii) characterise underlying population variability; (iii) investigate consequences of variability; and (iv) improve the ability to validate a model. To our knowledge this article is the first to quantify population variability in membrane dynamics in this manner, and the first to perform formal UQ for a component of a cardiac model. The approach is likely to find much wider applicability across systems biology as current application domains reach greater levels of maturity. Published by Elsevier Ltd.

Improved performance of the microbial electrolysis desalination and chemical-production cell with enlarged anode and high applied voltages.

PubMed

Ye, Bo; Luo, Haiping; Lu, Yaobin; Liu, Guangli; Zhang, Renduo; Li, Xiao

2017-11-01

The aim of this study was to improve performance of the microbial electrolysis desalination and chemical-production cell (MEDCC) using enlarged anode and high applied voltages. MEDCCs with anode lengths of 9 and 48cm (i.e., the 9cm-anode MEDCC and 48cm-anode MEDCC, respectively) were tested under different voltages (1.2-3.0V). Our results demonstrated for the first time that the MEDCC could maintain high performance even under the applied voltage higher than that for water dissociation (i.e., 1.8V). Under the applied voltage of 2.5V, the maximum current density in the 48cm-anode MEDCC reached 32.8±2.6A/m 2 , which is one of the highest current densities reported so far in the bioelectrochemical system (BES). The relative abundance of Geobacter was changed along the anode length. Our results show the great potential of the BES with enlarged anode and high applied voltages. Copyright © 2017 Elsevier Ltd. All rights reserved.

A read-in IC for infrared scene projectors with voltage drop compensation for improved uniformity of emitter current

NASA Astrophysics Data System (ADS)

Cho, Min Ji; Shin, Uisub; Lee, Hee Chul

2017-05-01

This paper proposes a read-in integrated circuit (RIIC) for infrared scene projectors, which compensates for the voltage drops in ground lines in order to improve the uniformity of the emitter current. A current output digital-to-analog converter is utilized to convert digital scene data into scene data currents. The unit cells in the array receive the scene data current and convert it into data voltage, which simultaneously self-adjusts to account for the voltage drop in the ground line in order to generate the desired emitter current independently of variations in the ground voltage. A 32 × 32 RIIC unit cell array was designed and fabricated using a 0.18-μm CMOS process. The experimental results demonstrate that the proposed RIIC can output a maximum emitter current of 150 μA and compensate for a voltage drop in the ground line of up to 500 mV under a 3.3-V supply. The uniformity of the emitter current is significantly improved compared to that of a conventional RIIC.

Two-photon voltage imaging using a genetically encoded voltage indicator

PubMed Central

Akemann, Walther; Sasaki, Mari; Mutoh, Hiroki; Imamura, Takeshi; Honkura, Naoki; Knöpfel, Thomas

2013-01-01

Voltage-sensitive fluorescent proteins (VSFPs) are a family of genetically-encoded voltage indicators (GEVIs) reporting membrane voltage fluctuation from genetically-targeted cells in cell cultures to whole brains in awake mice as demonstrated earlier using 1-photon (1P) fluorescence excitation imaging. However, in-vivo 1P imaging captures optical signals only from superficial layers and does not optically resolve single neurons. Two-photon excitation (2P) imaging, on the other hand, has not yet been convincingly applied to GEVI experiments. Here we show that 2P imaging of VSFP Butterfly 1.2 expresssing pyramidal neurons in layer 2/3 reports optical membrane voltage in brain slices consistent with 1P imaging but with a 2–3 larger ΔR/R value. 2P imaging of mouse cortex in-vivo achieved cellular resolution throughout layer 2/3. In somatosensory cortex we recorded sensory responses to single whisker deflections in anesthetized mice at full frame video rate. Our results demonstrate the feasibility of GEVI-based functional 2P imaging in mouse cortex. PMID:23868559

Nanostructured cavity devices for extracellular stimulation of HL-1 cells

NASA Astrophysics Data System (ADS)

Czeschik, Anna; Rinklin, Philipp; Derra, Ulrike; Ullmann, Sabrina; Holik, Peter; Steltenkamp, Siegfried; Offenhäusser, Andreas; Wolfrum, Bernhard

2015-05-01

Microelectrode arrays (MEAs) are state-of-the-art devices for extracellular recording and stimulation on biological tissue. Furthermore, they are a relevant tool for the development of biomedical applications like retina, cochlear and motor prostheses, cardiac pacemakers and drug screening. Hence, research on functional cell-sensor interfaces, as well as the development of new surface structures and modifications for improved electrode characteristics, is a vivid and well established field. However, combining single-cell resolution with sufficient signal coupling remains challenging due to poor cell-electrode sealing. Furthermore, electrodes with diameters below 20 µm often suffer from a high electrical impedance affecting the noise during voltage recordings. In this study, we report on a nanocavity sensor array for voltage-controlled stimulation and extracellular action potential recordings on cellular networks. Nanocavity devices combine the advantages of low-impedance electrodes with small cell-chip interfaces, preserving a high spatial resolution for recording and stimulation. A reservoir between opening aperture and electrode is provided, allowing the cell to access the structure for a tight cell-sensor sealing. We present the well-controlled fabrication process and the effect of cavity formation and electrode patterning on the sensor's impedance. Further, we demonstrate reliable voltage-controlled stimulation using nanostructured cavity devices by capturing the pacemaker of an HL-1 cell network.Microelectrode arrays (MEAs) are state-of-the-art devices for extracellular recording and stimulation on biological tissue. Furthermore, they are a relevant tool for the development of biomedical applications like retina, cochlear and motor prostheses, cardiac pacemakers and drug screening. Hence, research on functional cell-sensor interfaces, as well as the development of new surface structures and modifications for improved electrode characteristics, is a vivid and well established field. However, combining single-cell resolution with sufficient signal coupling remains challenging due to poor cell-electrode sealing. Furthermore, electrodes with diameters below 20 µm often suffer from a high electrical impedance affecting the noise during voltage recordings. In this study, we report on a nanocavity sensor array for voltage-controlled stimulation and extracellular action potential recordings on cellular networks. Nanocavity devices combine the advantages of low-impedance electrodes with small cell-chip interfaces, preserving a high spatial resolution for recording and stimulation. A reservoir between opening aperture and electrode is provided, allowing the cell to access the structure for a tight cell-sensor sealing. We present the well-controlled fabrication process and the effect of cavity formation and electrode patterning on the sensor's impedance. Further, we demonstrate reliable voltage-controlled stimulation using nanostructured cavity devices by capturing the pacemaker of an HL-1 cell network. Electronic supplementary information (ESI) available: Comparison of non-filtered and Savitzky-Golay filtered action potential recordings, electrical signals and corresponding optical signals. See DOI: 10.1039/c5nr01690h

Universal Features of Electron Dynamics in Solar Cells with TiO2 Contact: From Dye Solar Cells to Perovskite Solar Cells.

PubMed

Todinova, Anna; Idígoras, Jesús; Salado, Manuel; Kazim, Samrana; Anta, Juan A

2015-10-01

The electron dynamics of solar cells with mesoporous TiO2 contact is studied by electrochemical small-perturbation techniques. The study involved dye solar cells (DSC), solid-state perovskite solar cells (SSPSC), and devices where the perovskite acts as sensitizer in a liquid-junction device. Using a transport-recombination continuity equation we found that mid-frequency time constants are proper lifetimes that determine the current-voltage curve. This is not the case for the SSPSC, where a lifetime of ∼1 μs, 1 order of magnitude longer, is required to reproduce the current-voltage curve. This mismatch is attributed to the dielectric response on the mid-frequency component. Correcting for this effect, lifetimes lie on a common exponential trend with respect to open-circuit voltage. Electron transport times share a common trend line too. This universal behavior of lifetimes and transport times suggests that the main difference between the cells is the power to populate the mesoporous TiO2 contact with electrons.

Oxidatively stable fluorinated sulfone electrolytes for high voltage high energy lithium-ion batteries

DOE PAGES

Su, Chi -Cheung; He, Meinan; Redfern, Paul C.; ...

2017-03-16

New fluorinated sulfones were synthesized and evaluated in high voltage lithium-ion batteries using LiNi 0.5Mn 1.5O 4 (LNMO) cathode. Fluorinated sulfones with an α-trifluoromethyl group exhibit enhanced oxidation stability, reduced viscosity and superior separator wettability as compared to their non-fluorinated counterparts. Finally, the improved performance in high voltage cells makes it a promising high voltage electrolyte for 5-V lithium-ion chemistry.

Network for minimizing current imbalances in a faradaic battery

DOEpatents

Wozniak, Walter; Haskins, Harold J.

1994-01-01

A circuit for connecting a faradaic battery with circuitry for monitoring the condition of the battery includes a plurality of voltage divider networks providing battery voltage monitoring nodes and includes compensating resistors connected with the networks to maintain uniform discharge currents through the cells of the battery. The circuit also provides a reduced common mode voltage requirement for the monitoring circuitry by referencing the divider networks to one-half the battery voltage.

Reversible electron-hole separation in a hot carrier solar cell

NASA Astrophysics Data System (ADS)

Limpert, S.; Bremner, S.; Linke, H.

2015-09-01

Hot-carrier solar cells are envisioned to utilize energy filtering to extract power from photogenerated electron-hole pairs before they thermalize with the lattice, and thus potentially offer higher power conversion efficiency compared to conventional, single absorber solar cells. The efficiency of hot-carrier solar cells can be expected to strongly depend on the details of the energy filtering process, a relationship which to date has not been satisfactorily explored. Here, we establish the conditions under which electron-hole separation in hot-carrier solar cells can occur reversibly, that is, at maximum energy conversion efficiency. We thus focus our analysis on the internal operation of the hot-carrier solar cell itself, and in this work do not consider the photon-mediated coupling to the Sun. After deriving an expression for the voltage of a hot-carrier solar cell valid under conditions of both reversible and irreversible electrical operation, we identify separate contributions to the voltage from the thermoelectric effect and the photovoltaic effect. We find that, under specific conditions, the energy conversion efficiency of a hot-carrier solar cell can exceed the Carnot limit set by the intra-device temperature gradient alone, due to the additional contribution of the quasi-Fermi level splitting in the absorber. We also establish that the open-circuit voltage of a hot-carrier solar cell is not limited by the band gap of the absorber, due to the additional thermoelectric contribution to the voltage. Additionally, we find that a hot-carrier solar cell can be operated in reverse as a thermally driven solid-state light emitter. Our results help explore the fundamental limitations of hot-carrier solar cells, and provide a first step towards providing experimentalists with a guide to the optimal configuration of devices.

A microfluidic flow-through device for high throughput electrical lysis of bacterial cells based on continuous dc voltage.

PubMed

Wang, Hsiang-Yu; Bhunia, Arun K; Lu, Chang

2006-12-15

Interest in electrical lysis of biological cells on a microfludic platform has increased because it allows for the rapid recovery of intracellular contents without introducing lytic agents. In this study we demonstrated a simple microfluidic flow-through device which lysed Escherichia coli cells under a continuous dc voltage. The E. coli cells had previously been modified to express green fluorescent protein (GFP). In our design, the cell lysis only happened in a defined section of a microfluidic channel due to the local field amplification by geometric modification. The geometric modification also effectively decreased the required voltage for lysis by several folds. We found that local field strength of 1000-1500 V/cm was required for nearly 100% cell death. This threshold field strength was considerably lower than the value reported in the literature, possibly due to the longer duration of the field [Lee, S.W., Tai, Y.C., 1999. Sens. Actuators A: Phys. 73, 74-79]. Cell lysis was detected by both plate count and fluorescence spectroscopy. The cell membrane was completely disintegrated in the lysis section of the microfluidic device, when the field strength was higher than 2000 V/cm. The devices were fabricated using low-cost soft lithography with channel widths considerably larger than the cell size to avoid clogging and ensure stable performance. Our tool will be ideal for high throughput processing of bacterial cells for chemical analysis of intracellular contents such as DNA and proteins. The application of continuous dc voltage greatly simplified the instrumentation compared to devices using electrical pulses for similar purposes. In principle, the same approach can also be applied for lysis of mammalian cells and electroporative transfection.

Voltage-dependent calcium-permeable channels in the plasma membrane of a higher plant cell.

PubMed

Thuleau, P; Ward, J M; Ranjeva, R; Schroeder, J I

1994-07-01

Numerous biological assays and pharmacological studies on various higher plant tissues have led to the suggestion that voltage-dependent plasma membrane Ca2+ channels play prominent roles in initiating signal transduction processes during plant growth and development. However, to date no direct evidence has been obtained for the existence of such depolarization-activated Ca2+ channels in the plasma membrane of higher plant cells. Carrot suspension cells (Daucus carota L.) provide a well-suited system to determine whether voltage-dependent Ca2+ channels are present in the plasma membrane of higher plants and to characterize the properties of putative Ca2+ channels. It is known that both depolarization, caused by raising extracellular K+, and exposure to fungal toxins or oligogalacturonides induce Ca2+ influx into carrot cells. By direct application of patch-clamp techniques to isolated carrot protoplasts, we show here that depolarization of the plasma membrane positive to -135 mV activates Ca(2+)-permeable channels. These voltage-dependent ion channels were more permeable to Ca2+ than K+, while displaying large permeabilities to Ba2+ and Mg2+ ions. Ca(2+)-permeable channels showed slow and reversible inactivation. The single-channel conductance was 13 pS in 40 mM CaCl2. These data provide direct evidence for the existence of voltage-dependent Ca2+ channels in the plasma membrane of a higher plant cell and point to physiological mechanisms for plant Ca2+ channel regulation. The depolarization-activated Ca(2+)-permeable channels identified here could constitute a regulated pathway for Ca2+ influx in response to physiologically occurring stimulus-induced depolarizations in higher plant cells.

Effect of regioregularity on recombination dynamics in inverted bulk heterojunction organic solar cells

NASA Astrophysics Data System (ADS)

Chandrasekaran, Naresh; Liu, Amelia C. Y.; Kumar, Anil; McNeill, Christopher R.; Kabra, Dinesh

2018-01-01

The effect of polymer regioregularity on the charge transport properties and bimolecular recombination rates of polymer-based solar cells is studied in detail using transient photovoltaic techniques. We compare organic solar cells fabricated with an ITO/ZnO/PEIE/P3HT:PCBM/MoO3/Ag structure using either 100% regioregular poly(3-hexylthiophene) (DF-P3HT) yielding an average power conversion efficiency (PCE) of 3.8  ±  0.3% or 92% regioregular P3HT (rr-P3HT) that yields an average PCE of 3.28  ±  0.4%. Transient photocurrent measurements reveal the presence of less mobile photoinduced charges in rr-P3HT:PCBM cells when compared to DF-P3HT:PCBM solar cells. Transient photovoltage measurements are used to establish the relationship between regioregularity and bimolecular recombination rate constant (k) finding that under 1 Sun, devices with high regioregularity have a longer τ despite having a higher k. The high value of k for the DF-P3HT:PCBM system as compared to the rr-P3HT:PCBM system is attributed to enhanced mobility and better charge transport of mobile charges in the DF-P3HT:PCBM system, consistent with enhanced fibrillar order in DF-P3HT films observed with transmission electron microscopy. We also note a slight decrease in cell open circuit voltage with increase in polymer regioregularity, which is due to the increase in k. Other recombination mechanisms such as trap-assisted recombination are found to be important in the lower regioregular P3HT device compounded by the reduced mobility and poor inter-chain ordering.

Volume-dependent ATP-conductive large-conductance anion channel as a pathway for swelling-induced ATP release.

PubMed

Sabirov, R Z; Dutta, A K; Okada, Y

2001-09-01

In mouse mammary C127i cells, during whole-cell clamp, osmotic cell swelling activated an anion channel current, when the phloretin-sensitive, volume-activated outwardly rectifying Cl(-) channel was eliminated. This current exhibited time-dependent inactivation at positive and negative voltages greater than around +/-25 mV. The whole-cell current was selective for anions and sensitive to Gd(3)+. In on-cell patches, single-channel events appeared with a lag period of approximately 15 min after a hypotonic challenge. Under isotonic conditions, cell-attached patches were silent, but patch excision led to activation of currents that consisted of multiple large-conductance unitary steps. The current displayed voltage- and time-dependent inactivation similar to that of whole-cell current. Voltage-dependent activation profile was bell-shaped with the maximum open probability at -20 to 0 mV. The channel in inside-out patches had the unitary conductance of approximately 400 pS, a linear current-voltage relationship, and anion selectivity. The outward (but not inward) single-channel conductance was suppressed by extracellular ATP with an IC(50) of 12.3 mM and an electric distance (delta) of 0.47, whereas the inward (but not outward) conductance was inhibited by intracellular ATP with an IC(50) of 12.9 mM and delta of 0.40. Despite the open channel block by ATP, the channel was ATP-conductive with P(ATP)/P(Cl) of 0.09. The single-channel activity was sensitive to Gd(3)+, SITS, and NPPB, but insensitive to phloretin, niflumic acid, and glibenclamide. The same pharmacological pattern was found in swelling-induced ATP release. Thus, it is concluded that the volume- and voltage-dependent ATP-conductive large-conductance anion channel serves as a conductive pathway for the swelling-induced ATP release in C127i cells.

Electronics Reliability Fracture Mechanics, Volume 1. Causes of Failures of Shop Replaceable Units and Hybrid Microcircuits

DTIC Science & Technology

1992-05-01

Plate Figure H-1. Temperature Coefficient Test Circuit The forward voltage was measured at 3 different termperatures. The average TC was calculated to be...AT, rather than the average figure given by the large area Isolation diffusion. The peak temperature , rather than the average temperature , is the...components would cause the temperatures of the components to be nearer the average , particularly those near the minimum and maximum. X-I The largest