Self-contained hot-hollow cathode gun source assembly

DOEpatents

Zeren, J.D.

1984-08-01

A self-contained hot-hollow cathode gun source assembly for use in a vacuum chamber includes a crucible block having a hot-hollow cathode gun mounted underneath and providing a hole for the magnetic deflection of the ion/electron beam into a crucible on top the block.

Cathodal transcranial direct current stimulation in children with dystonia: a sham-controlled study.

PubMed

Young, Scott J; Bertucco, Matteo; Sanger, Terence D

2014-02-01

Increased motor cortex excitability is a common finding in dystonia, and transcranial direct current stimulation can reduce motor cortex excitability. In an earlier study, we found that cathodal direct-current stimulation decreased motor overflow for some children with dystonia. To investigate this observation further, we performed a sham-controlled, double-blind, crossover study of 14 children with dystonia. We found a significant reduction in overflow following real stimulation, when participants performed the experimental task with the hand contralateral to the cathode. While these results suggest that cathodal stimulation may help some children to reduce involuntary overflow, the size of the effect is small. Further research will need to investigate ways to increase the magnitude of the effect of cathodal transcranial direct current stimulation.

Hot hollow cathode gun assembly

DOEpatents

Zeren, J.D.

1983-11-22

A hot hollow cathode deposition gun assembly includes a hollow body having a cylindrical outer surface and an end plate for holding an adjustable heat sink, the hot hollow cathode gun, two magnets for steering the plasma from the gun into a crucible on the heat sink, and a shutter for selectively covering and uncovering the crucible.

The recovery of zinc from hot galvanizing slag in an anion-exchange membrane electrolysis reactor.

PubMed

Ren, Xiulian; Wei, Qifeng; Hu, Surong; Wei, Sijie

2010-09-15

This paper reports the optimization of the process parameters for recovery of zinc from hot galvanizing slag in an anion-exchange membrane electrolysis reactor. The experiments were carried out in an ammoniacal ammonium chloride system. The influence of composition of electrolytes, pH, stirring rate, current density and temperature, on cathodic current efficiency, specific power consumption and anodic dissolution of Zn were investigated. The results indicate that the cathode current efficiency increases and the hydrogen evolution decreased with increasing the cathode current density. The partial current for electrodeposition of Zn has liner relationship with omega(1/2) (omega: rotation rate). The highest current efficiency for dissolving zinc was obtained when NH(4)Cl concentration was 53.46 g L(-1) and the anodic dissolution of zinc was determined by mass transfer rate at stirring rate 0-300 r min(-1). Increase in temperature benefits to improve CE and dissolution of Zn, and reduce cell voltage. Initial pH of electrolytes plays an important role in the deposition and anodic dissolution of Zn. The results of single factor experiment show that about 50% energy consumption was saved for electrodeposition of Zn in the anion-exchange membrane electrolysis reactor. Copyright 2010 Elsevier B.V. All rights reserved.

Improved Cathode Structure for a Direct Methanol Fuel Cell

NASA Technical Reports Server (NTRS)

Valdez, Thomas; Narayanan, Sekharipuram

2005-01-01

An improved cathode structure on a membrane/electrode assembly has been developed for a direct methanol fuel cell, in a continuing effort to realize practical power systems containing such fuel cells. This cathode structure is intended particularly to afford better cell performance at a low airflow rate. A membrane/electrode assembly of the type for which the improved cathode structure was developed (see Figure 1) is fabricated in a process that includes brush painting and spray coating of catalyst layers onto a polymer-electrolyte membrane and onto gas-diffusion backings that also act as current collectors. The aforementioned layers are then dried and hot-pressed together. When completed, the membrane/electrode assembly contains (1) an anode containing a fine metal black of Pt/Ru alloy, (2) a membrane made of Nafion 117 or equivalent (a perfluorosulfonic acid-based hydrophilic, proton-conducting ion-exchange polymer), (3) a cathode structure (in the present case, the improved cathode structure described below), and (4) the electrically conductive gas-diffusion backing layers, which are made of Toray 060(TradeMark)(or equivalent) carbon paper containing between 5 and 6 weight percent of poly(tetrafluoroethylene). The need for an improved cathode structure arises for the following reasons: In the design and operation of a fuel-cell power system, the airflow rate is a critical parameter that determines the overall efficiency, cell voltage, and power density. It is desirable to operate at a low airflow rate in order to obtain thermal and water balance and to minimize the size and mass of the system. The performances of membrane/electrode assemblies of prior design are limited at low airflow rates. Methanol crossover increases the required airflow rate. Hence, one way to reduce the required airflow rate is to reduce the effect of methanol crossover. Improvement of the cathode structure - in particular, addition of hydrophobic particles to the cathode - has been demonstrated to mitigate the effects of crossover and decrease the airflow required.

Indirect-fired gas turbine bottomed with fuel cell

DOEpatents

Micheli, P.L.; Williams, M.C.; Parsons, E.L.

1995-09-12

An indirect-heated gas turbine cycle is bottomed with a fuel cell cycle with the heated air discharged from the gas turbine being directly utilized at the cathode of the fuel cell for the electricity-producing electrochemical reaction occurring within the fuel cell. The hot cathode recycle gases provide a substantial portion of the heat required for the indirect heating of the compressed air used in the gas turbine cycle. A separate combustor provides the balance of the heat needed for the indirect heating of the compressed air used in the gas turbine cycle. Hot gases from the fuel cell are used in the combustor to reduce both the fuel requirements of the combustor and the NOx emissions therefrom. Residual heat remaining in the air-heating gases after completing the heating thereof is used in a steam turbine cycle or in an absorption refrigeration cycle. Some of the hot gases from the cathode can be diverted from the air-heating function and used in the absorption refrigeration cycle or in the steam cycle for steam generating purposes. 1 fig.

Indirect-fired gas turbine bottomed with fuel cell

DOEpatents

Micheli, Paul L.; Williams, Mark C.; Parsons, Edward L.

1995-01-01

An indirect-heated gas turbine cycle is bottomed with a fuel cell cycle with the heated air discharged from the gas turbine being directly utilized at the cathode of the fuel cell for the electricity-producing electrochemical reaction occurring within the fuel cell. The hot cathode recycle gases provide a substantial portion of the heat required for the indirect heating of the compressed air used in the gas turbine cycle. A separate combustor provides the balance of the heat needed for the indirect heating of the compressed air used in the gas turbine cycle. Hot gases from the fuel cell are used in the combustor to reduce both the fuel requirements of the combustor and the NOx emissions therefrom. Residual heat remaining in the air-heating gases after completing the heating thereof is used in a steam turbine cycle or in an absorption refrigeration cycle. Some of the hot gases from the cathode can be diverted from the air-heating function and used in the absorption refrigeration cycle or in the steam cycle for steam generating purposes.

The study of lead vapor ionization in discharge with a hot cathode and efficiency of its deposition on the substrates applied for plasma separation method

NASA Astrophysics Data System (ADS)

Antonov, N. N.; Samokhin, A. A.; Zhabin, S. N.; Gavrikov, A. V.; Smirnov, V. P.

2016-11-01

Spent nuclear fuel plasma separation method approbation implies the use of model substances. Thus it is necessary to solve the problem of material conversion into a cold plasma flow, as well as the problem of deposition on collectors. For this purpose, we carried out a kinetic and hydrodynamic simulation of the discharge with hot cathode in the lead vapor (lead vapor was injected into the interelectrode gap). Dependencies of the ionization efficiency, electrostatic potential distribution, density distribution of ions and electrons in the discharge gap on the discharge current density and the model substance vapor concentration were obtained. The simulation results show that at discharge current density of about 3.5 A/cm2 and the lead vapor concentration of 2 × 1012 cm-3, the ionization efficiency is close to 60%. Experimental research of the discharge with a hot cathode in the lead vapor was carried out. We also carried out the research of the Pb condensation coefficients on various substrates. For experimental data analysis the numerical model based on Monte Carlo method was used. The research results show that deposition coefficients at medium temperatures of substrates near 70 °C do not drop lower than 75%.

Field free, directly heated lanthanum boride cathode

DOEpatents

Leung, Ka-Ngo; Moussa, D.; Wilde, S.B.

1987-02-02

A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic field which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

Studies of a plasma with a hot dense core in LAPD

NASA Astrophysics Data System (ADS)

van Compernolle, Bart; Gekelman, Walter; Pribyl, Patrick; Cooper, Chris

2009-11-01

Recently, considerable effort in the LArge Plasma Device at UCLA (LAPD) has gone into the study of large cathodes which would enable higher discharge currents and higher densities. The new cathode is made out of Lanthanum HexaBoride (LaB6). LaB6 has a low work function and has higher emissivity than Barium oxide coated cathodes. The operating temperature of LaB6 cathodes lies above 1600 degrees Celsius. Tests of this cathode in the Enormous Toroidal Plasma Device (ETPD) showed that densities in excess of 2 10^13 cm-3 and electron temperatures of 12 eV are feasible. Small LaB6 cathodes (3mm - 2cm) have been used before in LAPD in several experiments on heat transport and on magnetized flux ropes. The cathode presented in this paper has a 8 cm diameter, and can be positioned at different radial locations. The cathode will be pulsed into the standard background plasma (ne= 2 10^12 cm-3, .25 <=Te<=6 eV, dia = 60 cm, L = 18 m) creating a plasma with a hot dense core. We present the characterization of the core plasma at different conditions. Studies of the heat transport and density spreading at the interface between the core plasma and background plasma will be done by use of a variety of probes (Langmuir, magnetic, Mach, emissive) as well as fast photography.

Arc initiation in cathodic arc plasma sources

DOEpatents

Anders, Andre

2002-01-01

A "triggerless" arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-1 kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation. A conductive surface layer, such as graphite or the material being deposited, is formed on the surface of the insulator which separates the cathode from the anode. The mechanism of plasma production (and arc initiation) is based on explosive destruction of the layer-cathode interface caused by joule heating. The current flow between the thin insulator coating and cathode occurs at only a few contact points so the current density is high.

Neuroprotective effect of cathodal transcranial direct current stimulation in a rat stroke model.

PubMed

Notturno, Francesca; Pace, Marta; Zappasodi, Filippo; Cam, Etrugul; Bassetti, Claudio L; Uncini, Antonino

2014-07-15

Experimental focal brain ischemia generates in the penumbra recurrent depolarizations which spread across the injured cortex inducing infarct growth. Transcranial direct current stimulation can induce a lasting, polarity-specific, modulation of cortical excitability. To verify whether cathodal transcranial direct current stimulation could reduce the infarct size and the number of depolarizations, focal ischemia was induced in the rat by the 3 vessels occlusion technique. In the first experiment 12 ischemic rats received cathodal stimulation (alternating 15 min on and 15 min off) starting 45 min after middle cerebral artery occlusion and lasting 4 h. In the second experiment 12 ischemic rats received cathodal transcranial direct current stimulation with the same protocol but starting soon after middle cerebral artery occlusion and lasting 6 h. In both experiments controls were 12 ischemic rats not receiving stimulation. Cathodal stimulation reduced the infarct volume in the first experiment by 20% (p=0.002) and in the second by 30% (p=0.003). The area of cerebral infarction was smaller in animals receiving cathodal stimulation in both experiments (p=0.005). Cathodal stimulation reduced the number of depolarizations (p=0.023) and infarct volume correlated with the number of depolarizations (p=0.048). Our findings indicate that cathodal transcranial direct current stimulation exert a neuroprotective effect in the acute phase of stroke possibly decreasing the number of spreading depolarizations. These findings may have translational relevance and open a new avenue in neuroprotection of stroke in humans. Copyright © 2014. Published by Elsevier B.V.

Combined effects of cerebellar transcranial direct current stimulation and transcutaneous spinal direct current stimulation on robot-assisted gait training in patients with chronic brain stroke: A pilot, single blind, randomized controlled trial.

PubMed

Picelli, Alessandro; Chemello, Elena; Castellazzi, Paola; Filippetti, Mirko; Brugnera, Annalisa; Gandolfi, Marialuisa; Waldner, Andreas; Saltuari, Leopold; Smania, Nicola

2018-01-01

Preliminary evidence showed additional effects of anodal transcranial direct current stimulation over the damaged cerebral hemisphere combined with cathodal transcutaneous spinal direct current stimulation during robot-assisted gait training in chronic stroke patients. This is consistent with the neural organization of locomotion involving cortical and spinal control. The cerebellum is crucial for locomotor control, in particular for avoidance of obstacles, and adaptation to novel conditions during walking. Despite its key role in gait control, to date the effects of transcranial direct current stimulation of the cerebellum have not been investigated on brain stroke patients treated with robot-assisted gait training. To evaluate the effects of cerebellar transcranial direct current stimulation combined with transcutaneous spinal direct current stimulation on robot-assisted gait training in patients with chronic brain stroke. After balanced randomization, 20 chronic stroke patients received ten, 20-minute robot-assisted gait training sessions (five days a week, for two consecutive weeks) combined with central nervous system stimulation. Group 1 underwent on-line cathodal transcranial direct current stimulation over the contralesional cerebellar hemisphere + cathodal transcutaneous spinal direct current stimulation. Group 2 received on-line anodal transcranial direct current stimulation over the damaged cerebral hemisphere + cathodal transcutaneous spinal direct current stimulation. The primary outcome was the 6-minute walk test performed before, after, and at follow-up at 2 and 4 weeks post-treatment. The significant differences in the 6-minute walk test noted between groups at the first post-treatment evaluation (p = 0.041) were not maintained at either the 2-week (P = 0.650) or the 4-week (P = 0.545) follow-up evaluations. Our preliminary findings support the hypothesis that cathodal transcranial direct current stimulation over the contralesional cerebellar hemisphere in combination with cathodal transcutaneous spinal direct current stimulation might be useful to boost the effects of robot-assisted gait training in chronic brain stroke patients with walking impairment.

Photon enhanced thermionic emission

DOEpatents

Schwede, Jared; Melosh, Nicholas; Shen, Zhixun

2014-10-07

Photon Enhanced Thermionic Emission (PETE) is exploited to provide improved efficiency for radiant energy conversion. A hot (greater than 200.degree. C.) semiconductor cathode is illuminated such that it emits electrons. Because the cathode is hot, significantly more electrons are emitted than would be emitted from a room temperature (or colder) cathode under the same illumination conditions. As a result of this increased electron emission, the energy conversion efficiency can be significantly increased relative to a conventional photovoltaic device. In PETE, the cathode electrons can be (and typically are) thermalized with respect to the cathode. As a result, PETE does not rely on emission of non-thermalized electrons, and is significantly easier to implement than hot-carrier emission approaches.

Non-Aqueous Primary Li-Air Flow Battery and Optimization of its Cathode through Experiment and Modeling.

PubMed

Kim, Byoungsu; Takechi, Kensuke; Ma, Sichao; Verma, Sumit; Fu, Shiqi; Desai, Amit; Pawate, Ashtamurthy S; Mizuno, Fuminori; Kenis, Paul J A

2017-09-22

A primary Li-air battery has been developed with a flowing Li-ion free ionic liquid as the recyclable electrolyte, boosting power capability by promoting superoxide diffusion and enhancing discharge capacity through separately stored discharge products. Experimental and computational tools are used to analyze the cathode properties, leading to a set of parameters that improve the discharge current density of the non-aqueous Li-air flow battery. The structure and configuration of the cathode gas diffusion layers (GDLs) are systematically modified by using different levels of hot pressing and the presence or absence of a microporous layer (MPL). These experiments reveal that the use of thinner but denser MPLs is key for performance optimization; indeed, this leads to an improvement in discharge current density. Also, computational results indicate that the extent of electrolyte immersion and porosity of the cathode can be optimized to achieve higher current density. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transcranial direct current stimulation (tDCS) neuromodulatory effects on mechanical hyperalgesia and cortical BDNF levels in ovariectomized rats.

PubMed

da Silva Moreira, Sônia Fátima; Medeiros, Liciane Fernandes; de Souza, Andressa; de Oliveira, Carla; Scarabelot, Vanessa Leal; Fregni, Felipe; Caumo, Wolnei; Torres, Iraci L S

2016-01-15

Epidemiological studies show that painful disorders are more prevalent in women than in men, and the transcranial direct current stimulation (tDCS) technique has been tested in chronic pain states. We explored the effect of tDCS on pain behavior and brain-derived neurotrophic factor (BDNF) levels in ovariectomized rats. Forty-five female Wistar adult rats were distributed into five groups: control (CT), ovariectomy + tDCS (OT), ovariectomy + sham tDCS (OS), sham ovariectomy + tDCS (ST), and sham ovariectomy+shamtDCS (SS). The rats were subjected to cathodal tDCS. The vaginal cytology and the estradiol levels confirmed the hormonal status. In addition, nociceptive behavior was evaluated using the tail-flick, von Frey, and hot-plate tests, as well as the BDNF levels in the serum, hypothalamus, hippocampus, spinal cord, and cerebral cortex. One-way analysis of variance (ANOVA) or two-way ANOVA was used for statistical analysis, followed by the Bonferroni, and P-value b 0.05 was considered significant. The ovariectomized animals presented a hypersensitivity response in the hot-plate (P b 0.01) and von Frey (P b 0.05) tests, as well as increased serum BDNF (P b 0.05) and decreased hypothalamic BDNF (P b 0.01) levels. The OT, OS, ST, and SS groups showed decreased hippocampal BDNF levels as compared with the control group (P b 0.001). The interaction between tDCS and ovariectomy on the cortical BDNF levels (P b 0.01) was observed. The ovariectomy induced nociceptive hypersensitivity and altered serum and hypothalamic BDNF levels. The cathodal tDCS partially reversed nociceptive hypersensitivity.

Simplifying microbial electrosynthesis reactor design.

PubMed

Giddings, Cloelle G S; Nevin, Kelly P; Woodward, Trevor; Lovley, Derek R; Butler, Caitlyn S

2015-01-01

Microbial electrosynthesis, an artificial form of photosynthesis, can efficiently convert carbon dioxide into organic commodities; however, this process has only previously been demonstrated in reactors that have features likely to be a barrier to scale-up. Therefore, the possibility of simplifying reactor design by both eliminating potentiostatic control of the cathode and removing the membrane separating the anode and cathode was investigated with biofilms of Sporomusa ovata. S. ovata reduces carbon dioxide to acetate and acts as the microbial catalyst for plain graphite stick cathodes as the electron donor. In traditional 'H-cell' reactors, where the anode and cathode chambers were separated with a proton-selective membrane, the rates and columbic efficiencies of microbial electrosynthesis remained high when electron delivery at the cathode was powered with a direct current power source rather than with a potentiostat-poised cathode utilized in previous studies. A membrane-less reactor with a direct-current power source with the cathode and anode positioned to avoid oxygen exposure at the cathode, retained high rates of acetate production as well as high columbic and energetic efficiencies. The finding that microbial electrosynthesis is feasible without a membrane separating the anode from the cathode, coupled with a direct current power source supplying the energy for electron delivery, is expected to greatly simplify future reactor design and lower construction costs.

Evaluation of Cathode Air Flow Transients in a SOFC/GT Hybrid System Using Hardware in the Loop Simulation.

PubMed

Zhou, Nana; Yang, Chen; Tucker, David

2015-02-01

Thermal management in the fuel cell component of a direct fired solid oxide fuel cell gas turbine (SOFC/GT) hybrid power system can be improved by effective management and control of the cathode airflow. The disturbances of the cathode airflow were accomplished by diverting air around the fuel cell system through the manipulation of a hot-air bypass valve in open loop experiments, using a hardware-based simulation facility designed and built by the U.S. Department of Energy, National Energy Technology Laboratory (NETL). The dynamic responses of the fuel cell component and hardware component of the hybrid system were studied in this paper.

Effect of energetic electrons on dust charging in hot cathode filament discharge

NASA Astrophysics Data System (ADS)

Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhyay, M.

2011-03-01

The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.

An ionization gauge for ultrahigh vacuum measurement based on a carbon nanotube cathode

NASA Astrophysics Data System (ADS)

Zhang, Huzhong; Cheng, Yongjun; Sun, Jian; Wang, Yongjun; Xi, Zhenhua; Dong, Meng; Li, Detian

2017-10-01

This work reports on the complete design and the properties of an ionization gauge based on a carbon nanotube cathode, which can measure ultrahigh vacuum without thermal effects. The gauge is composed of a pressure sensor and an electronic controller. This pressure sensor is constructed based on a hot-cathode ionization gauge, where the traditional hot filament is replaced by an electron source prepared with multi-wall nanotubes. Besides, an electronic controller was developed for bias voltage supply, low current detection, and pressure indication. The gauge was calibrated in the pressure range of 10-8 to 10-4 Pa in a XHV/UHV calibration apparatus. The gauge shows good linear characteristics in different gases. The calibrated sensitivity is 0.035 Pa-1 in N2, and the standard deviation of the sensitivity is about 1.1%. In addition, the stability of the sensitivity was learned in a long period. The standard deviation of the sensitivity factor "S" during one year is 2.0% for Ar and 1.6% for N2.

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation: A functional MRI study.

PubMed

Kwon, Yong Hyun; Jang, Sung Ho

2012-08-25

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation

PubMed Central

Kwon, Yong Hyun; Jang, Sung Ho

2012-01-01

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation. PMID:25624815

Electrical characteristics of a free-burning direct-current argon arc operating between 90 and 563 kilowatts with two types of cathodes

NASA Technical Reports Server (NTRS)

Curtis, H. B.; Decker, A. J.

1975-01-01

The electrical characteristics of a high-power, long-lived, free-burning dc argon arc are presented. Empirical formulas relating voltage to current, electrode separation, and operating pressure are given for two types of cathodes: a typical point tip cathode and a cathode with a 1.27-cm-(0.5-in.-) diameter crater in the tip. Power was varied from 90 to 563 kW. A discussion of the cathode with the crater tip is given.

Combined Effect of Alternating Current Interference and Cathodic Protection on Pitting Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in Near-Neutral pH Environment.

PubMed

Wang, Liwei; Cheng, Lianjun; Li, Junru; Zhu, Zhifu; Bai, Shuowei; Cui, Zhongyu

2018-03-22

Influence of alternating current (AC) on pitting corrosion and stress corrosion cracking (SCC) behavior of X70 pipeline steel in the near-neutral pH environment under cathodic protection (CP) was investigated. Both corrosion and SCC are inhibited by -0.775 V SCE CP without AC interference. With the superimposition of AC current (1-10 mA/cm²), the direct current (DC) potential shifts negatively under the CP of -0.775 V SCE and the cathodic DC current decreases and shifts to the anodic direction. Under the CP potential of -0.95 V SCE and -1.2 V SCE , the applied AC current promotes the cathodic reaction and leads to the positive shift of DC potential and increase of cathodic current. Local anodic dissolution occurs attributing to the generated anodic current transients in the positive half-cycle of the AC current, resulting in the initiation of corrosion pits (0.6-2 μm in diameter). AC enhances the SCC susceptibility of X70 steel under -0.775 V SCE CP, attributing to the promotion of anodic dissolution and hydrogen evolution. Even an AC current as low as 1 mA/cm² can enhance the SCC susceptibility.

A pre-lithiation method for sulfur cathode used for future lithium metal free full battery

NASA Astrophysics Data System (ADS)

Wu, Yunwen; Yokoshima, Tokihiko; Nara, Hiroki; Momma, Toshiyuki; Osaka, Tetsuya

2017-02-01

Lithium metal free sulfur battery paired by lithium sulfide (Li2S) is a hot point in recent years because of its potential for relatively high capacity and its safety advantage. Due to the insulating nature and high sensitivity to moisture of Li2S, it calls for new way to introduce Li ion into S cathode besides the method of directly using the Li2S powder for the battery pre-lithiation. Herein, we proposed a pre-lithiation method to lithiate the polypyrrole (PPy)/S/Ketjenblack (KB) electrode into PPy/Li2S/KB cathode at room temperature. By this process, the fully lithiated PPy/Li2S/KB cathode showed facilitated charge transfer than the original PPy/S/KB cathode, leading to better cycling performance at high C-rates and disappearance of over potential phenomenon. In this work, the ion-selective PPy layer has been introduced on the cathode surface by an electrodeposition method, which can suppress the polysulfide dissolution from the cathode source. The lithium metal free full battery coupled by the prepared Li2S/KB cathode and graphite anode exhibited excellent cycling performance. Hence, we believe this comprehensive fabrication approach of Li2S cathode will pave a way for the application of new type lithium metal free secondary battery.

Thermal and electrochemical properties of PEO-LiTFSI-Pyr14TFSI-based composite cathodes, incorporating 4 V-class cathode active materials

NASA Astrophysics Data System (ADS)

Wetjen, Morten; Kim, Guk-Tae; Joost, Mario; Appetecchi, Giovanni B.; Winter, Martin; Passerini, Stefano

2014-01-01

Poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PEO-LiTFSI-Pyr14TFSI)-based 4 V-class composite cathodes, incorporating either Li(Ni1/3Co1/3Mn1/3)O2 or Li(Ni0.8Co0.15Al0.05)O2 were prepared by a hot-pressing process and successively investigated in terms of their morphological, thermal, and electrochemical properties. Thereby, excellent mechanical and thermal properties could be demonstrated for all composite cathodes. The electrochemical performance of truly dry all-solid-state Li/P(EO)10LiTFSI-(Pyr14TFSI)2/composite cathode batteries at temperatures as low as 40 °C revealed high delivered capacities. However, in comparison with LiFePO4, the 4 V-class composite cathodes also indicated much lower capacity retention. In-depth investigations on the interfacial properties of Li(Ni0.8Co0.15Al0.05)O2 composite cathodes revealed a strong dependence on the anodic cut-off potential and the presence of current flow through the cell, whereby different degradation mechanisms could be characterized upon cycling, according to which the finite growth of a surface films at both electrode/polymer electrolyte interfaces inhibited continuous decomposition of the polymer electrolyte even at potentials as high as 4.3 V. Moreover, the presence of Pyr14TFSI in the 4 V-class composite cathodes sustainably reduced the cathode interfacial resistance and presumably diminished the corrosion of the aluminum current collector.

METHOD OF PRODUCING AND ACCELERATING AN ION BEAM

NASA Technical Reports Server (NTRS)

Foster, John E. (Inventor)

2005-01-01

A method of producing and accelerating an ion beam comprising the steps of providing a magnetic field with a cusp that opens in an outward direction along a centerline that passes through a vertex of the cusp: providing an ionizing gas that sprays outward through at least one capillary-like orifice in a plenum that is positioned such that the orifice is on the centerline in the cusp, outward of the vortex of the cusp; providing a cathode electron source, and positioning it outward of the orifice and off of the centerline; and positively charging the plenum relative to the cathode electron source such that the plenum functions as m anode. A hot filament may be used as the cathode electron source, and permanent magnets may be used to provide the magnetic field.

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

Wang, Lijun; Deng, Jie; Zhou, Xin

In this paper, cathode spot plasma jet (CSPJ) rotation and cathode spots behavior subjected to two kinds of large diameter axial magnetic field (AMF) electrode (cup-shaped and coil-shaped) are studied and analyzed based on experiments. The influence of gap distances on the CSPJ rotational behavior is analyzed. Experimental results show that CSPJ rotational phenomena extensively exist in the vacuum interrupters, and CSPJ rotational direction is along the direction of composite magnetic field (mainly the combination of the axial and azimuthal components). For coil-shaped and cup-shaped AMF electrodes, the rotational or inclination phenomena before the current peak value are much moremore » significant than that after current peak value (for the same arc current), which is related to the larger ratio of azimuthal magnetic field B{sub t} and AMF B{sub z} (B{sub t}/B{sub z}). With the increase of the gap distance, the AMF strength decreases, when the arc current is kept as constant, the azimuthal magnetic field is kept invariable, the ratio between azimuthal magnetic field and AMF is increased, which results in the increase of rotational effect. For cathode spots motion, compared with cup-shaped electrode, coil-shaped electrode has the inverse AMF direction. The Robson drift direction of cathode spots of coil-shaped electrode is opposite to that of cup-shaped electrode. With the increase of gap distance, the Robson angle is decreased, which is associated with the reduced AMF strength. Erosion imprints of anode and cathode are also related to the CSPJ rotational phenomena and cathode spots behavior. The noise of arc voltage in the initial arcing stage is related to the weaker AMF.« less

Direct current microhollow cathode discharges on silicon devices operating in argon and helium

NASA Astrophysics Data System (ADS)

Michaud, R.; Felix, V.; Stolz, A.; Aubry, O.; Lefaucheux, P.; Dzikowski, S.; Schulz-von der Gathen, V.; Overzet, L. J.; Dussart, R.

2018-02-01

Microhollow cathode discharges have been produced on silicon platforms using processes usually used for MEMS fabrication. Microreactors consist of 100 or 150 μm-diameter cavities made from Ni and SiO2 film layers deposited on a silicon substrate. They were studied in the direct current operating mode in two different geometries: planar and cavity configuration. Currents in the order of 1 mA could be injected in microdischarges operating in different gases such as argon and helium at a working pressure between 130 and 1000 mbar. When silicon was used as a cathode, the microdischarge operation was very unstable in both geometry configurations. Strong current spikes were produced and the microreactor lifetime was quite short. We evidenced the fast formation of blisters at the silicon surface which are responsible for the production of these high current pulses. EDX analysis showed that these blisters are filled with argon and indicate that an implantation mechanism is at the origin of this surface modification. Reversing the polarity of the microdischarge makes the discharge operate stably without current spikes, but the discharge appearance is quite different from the one obtained in direct polarity with the silicon cathode. By coating the silicon cathode with a 500 nm-thick nickel layer, the microdischarge becomes very stable with a much longer lifetime. No current spikes are observed and the cathode surface remains quite smooth compared to the one obtained without coating. Finally, arrays of 76 and 576 microdischarges were successfully ignited and studied in argon. At a working pressure of 130 mbar, all microdischarges are simultaneously ignited whereas they ignite one by one at higher pressure.

A flexible curvilinear electromagnetic filter for direct current cathodic arc source.

PubMed

Dai, Hua; Shen, Yao; Li, Liuhe; Li, Xiaoling; Cai, Xun; Chu, Paul K

2007-09-01

Widespread applications of direct current (dc) cathodic arc deposition are hampered by macroparticle (MP) contamination, although a cathodic arc offers many unique merits such as high ionization rate, high deposition rate, etc. In this work, a flexible curvilinear electromagnetic filter is described to eliminate MPs from a dc cathodic arc source. The filter which has a relatively large size with a minor radius of about 85 mm is suitable for large cathodes. The filter is open and so the MPs do not rebound inside the filter. The flexible design allows the ions to be transported from the cathode to the sample surface optimally. Our measurements with a saturated ion current probe show that the efficiency of this flexible filter reaches about 2.0% (aluminum cathode) when the filter current is about 250 A. The MP density measured from TiN films deposited using this filter is two to three orders of magnitude less than that from films deposited with a 90 degrees duct magnetic filter and three to four orders of magnitude smaller than those deposited without a filter. Furthermore, our experiments reveal that the potential of the filter coil and the magnetic field on the surface of the cathode are two important factors affecting the efficacy of the filter. Different biasing potentials can enhance the efficiency to up to 12-fold, and a magnetic field at about 4.0 mT can improve it by a factor of 2 compared to 5.4 mT.

High-Performance Direct Methanol Fuel Cells with Precious-Metal-Free Cathode.

PubMed

Li, Qing; Wang, Tanyuan; Havas, Dana; Zhang, Hanguang; Xu, Ping; Han, Jiantao; Cho, Jaephil; Wu, Gang

2016-11-01

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable. The newly developed reduced graphene oxide (rGO)-based Fe-N-C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. While the morphology of 2D rGO is largely preserved, the resulting Fe-N-rGO catalyst provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe-N-rGO catalyst. At feed concentrations greater than 2.0 m, the obtained DMFC performance from the Fe-N-rGO cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use nonprecious metal cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.

Cathodal transcranial direct current stimulation in children with dystonia: a pilot open-label trial.

PubMed

Young, Scott J; Bertucco, Matteo; Sheehan-Stross, Rebecca; Sanger, Terence D

2013-10-01

Studies suggest that dystonia is associated with increased motor cortex excitability. Cathodal transcranial direct current stimulation can temporarily reduce motor cortex excitability. To test whether stimulation of the motor cortex can reduce dystonic symptoms in children, we measured tracking performance and muscle overflow using an electromyogram tracking task before and after stimulation. Of 10 participants, 3 showed a significant reduction in overflow, and a fourth showed a significant reduction in tracking error. Overflow decreased more when the hand contralateral to the cathode performed the task than when the hand ipsilateral to the cathode performed the task. Averaged over all participants, the results did not reach statistical significance. These results suggest that cathodal stimulation may allow a subset of children to control muscles or reduce involuntary overflow activity. Further testing is needed to confirm these results in a blinded trial and identify the subset of children who are likely to respond.

Characterization of Boron Contamination in Fluorine Implantation using Boron Trifluoride as a Source Material

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

Schmeide, Matthias; Kondratenko, Serguei

2011-01-07

Fluorine implantation process purity was considered on different types of high current implanters. It was found that implanters equipped with an indirectly heated cathode ion source show an enhanced deep boron contamination compared to a high current implanter using a cold RF-driven multicusp ion source when boron trifluoride is used for fluorine implantations. This contamination is directly related to the source technology and thus, should be considered potentially for any implanter design using hot cathode/hot filament ion source, independently of the manufacturer.The boron contamination results from the generation of double charged boron ions in the arc chamber and the subsequentmore » charge exchange reaction to single charged boron ions taking place between the arc chamber and the extraction electrode. The generation of the double charged boron ions depends mostly on the source parameters, whereas the pressure in the region between the arc chamber and the extraction electrode is mostly responsible for the charge exchange from double charged to single charged ions. The apparent mass covers a wide range, starting at mass 11. A portion of boron ions with energies of (19/11) times higher than fluorine energy has the same magnetic rigidity as fluorine beam and cannot be separated by the analyzer magnet. The earlier described charge exchange effects between the extraction electrode and the entrance to the analyzer magnet, however, generates boron beam with a higher magnetic rigidity compared to fluorine beam and cannot cause boron contamination after mass-separation.The energetic boron contamination was studied as a function of the ion source parameters, such as gas flow, arc voltage, and source magnet settings, as well as analyzing magnet aperture resolution. This allows process optimization reducing boron contamination to the level acceptable for device performance.« less

Investigation of a Mercury-Argon Hot Cathode Discharge

NASA Astrophysics Data System (ADS)

Wamsley, Robert Charles

Classical absorption and laser induced fluorescence (LIF) experiments are used to investigate processes in the cathode region of a Hg-Ar hot cathode discharge. The absorption and LIF measurements are used to test the qualitative understanding and develop a quantitative model of a hot cathode discharge. The main contribution of this thesis is a model of the negative glow region that demonstrates the importance of Penning ionization to the ionization balance in the negative glow. We modeled the excited argon balance equation using a Monte Carlo simulation. In this simulation we used the trapped radiative decay rate of the resonance levels and the Penning ionization rate as the dominant loss terms in the balance equation. The simulated data is compared to and found to agree with absolute excited argon densities measured in a classical absorption experiment. We found the primary production rate per unit volume of excited Ar atoms in the simulation is sharply peaked near the cathode hot spot. We used the ion production rate from this simulation and a Green's function solution to the ambipolar diffusion equation to calculate the contribution of Penning ionization to the total ion density. We compared the results of this calculation to our experimental values of the Hg ^+ densities in the negative glow. We found that Penning ionization is an important and possibly the dominant ionization process in the negative glow.

Sensitivity of hot-cathode ionization vacuum gages in several gases

NASA Technical Reports Server (NTRS)

Holanda, R.

1972-01-01

Four hot-cathode ionization vacuum gages were calibrated in 12 gases. The relative sensitivities of these gages were compared to several gas properties. Ionization cross section was the physical property which correlated best with gage sensitivity. The effects of gage accelerating voltage and ionization-cross-section energy level were analyzed. Recommendations for predicting gage sensitivity according to gage type were made.

Bohm velocity in the presence of a hot cathode

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

Palacio Mizrahi, J. H.; Krasik, Ya. E.

2013-08-15

The spatial distribution of the plasma and beam electrons in a region whose extension from a hot cathode is larger than the Debye length, but smaller than the electron mean free path, is analyzed. In addition, the influence of electrons thermionically emitted from a hot cathode and the ratio of electron-to-ion mass on the Bohm velocity and on the ion and electron densities at the plasma-sheath boundary in a gas discharge are studied. It is shown that thermionic emission has the effect of increasing the Bohm velocity, and this effect is more pronounced for lighter ions. In addition, it ismore » shown that the Bohm velocity cannot be increased to more than 24% above its value when there is no electron emission.« less

Ferrosilicon smelting in a direct current furnace

DOEpatents

Dosaj, Vishu D.; May, James B.

1992-12-29

The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode.

Conductor of high electrical current at high temperature in oxygen and liquid metal environment

DOEpatents

Powell, IV, Adam Clayton; Pati, Soobhankar; Derezinski, Stephen Joseph; Lau, Garrett; Pal, Uday B.; Guan, Xiaofei; Gopalan, Srikanth

2016-01-12

In one aspect, the present invention is directed to apparatuses for and methods of conducting electrical current in an oxygen and liquid metal environment. In another aspect, the invention relates to methods for production of metals from their oxides comprising providing a cathode in electrical contact with a molten electrolyte, providing a liquid metal anode separated from the cathode and the molten electrolyte by a solid oxygen ion conducting membrane, providing a current collector at the anode, and establishing a potential between the cathode and the anode.

Adaptive threshold hunting for the effects of transcranial direct current stimulation on primary motor cortex inhibition.

PubMed

Mooney, Ronan A; Cirillo, John; Byblow, Winston D

2018-06-01

Primary motor cortex excitability can be modulated by anodal and cathodal transcranial direct current stimulation (tDCS). These neuromodulatory effects may, in part, be dependent on modulation within gamma-aminobutyric acid (GABA)-mediated inhibitory networks. GABAergic function can be quantified non-invasively using adaptive threshold hunting paired-pulse transcranial magnetic stimulation (TMS). The previous studies have used TMS with posterior-anterior (PA) induced current to assess tDCS effects on inhibition. However, TMS with anterior-posterior (AP) induced current in the brain provides a more robust measure of GABA-mediated inhibition. The aim of the present study was to assess the modulation of corticomotor excitability and inhibition after anodal and cathodal tDCS using TMS with PA- and AP-induced current. In 16 young adults (26 ± 1 years), we investigated the response to anodal, cathodal, and sham tDCS in a repeated-measures double-blinded crossover design. Adaptive threshold hunting paired-pulse TMS with PA- and AP-induced current was used to examine separate interneuronal populations within M1 and their influence on corticomotor excitability and short- and long-interval inhibition (SICI and LICI) for up to 60 min after tDCS. Unexpectedly, cathodal tDCS increased corticomotor excitability assessed with AP (P = 0.047) but not PA stimulation (P = 0.74). SICI AP was reduced after anodal tDCS compared with sham (P = 0.040). Pearson's correlations indicated that SICI AP and LICI AP modulation was associated with corticomotor excitability after anodal (P = 0.027) and cathodal tDCS (P = 0.042). The after-effects of tDCS on corticomotor excitability may depend on the direction of the TMS-induced current used to make assessments, and on modulation within GABA-mediated inhibitory circuits.

Methods of Measurement of High Air Velocities by the Hot Wire Method

DTIC Science & Technology

1943-02-01

to that of the heating current, as indicated by the minus sign. The cathode bias of the linearizing stage 1» then adjusted to obtain readings that...and tungsten wire. ! MM Taobaloai lot* lo. tifx» 3.- Heating aunnt of a bot «in at ooutaat-railitaae* operation. ? a UM tMMlMl nta Fe. IN nca . 4

Ferrosilicon smelting in a direct current furnace

DOEpatents

Dosaj, V.D.; May, J.B.

1992-12-29

The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode. 1 figure.

Measurements of hot electrons in the Extrap T1 reversed-field pinch

NASA Astrophysics Data System (ADS)

Welander, A.; Bergsåker, H.

1998-02-01

The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred 0741-3335/40/2/011/img1. To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a 0741-3335/40/2/011/img2 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local 0741-3335/40/2/011/img3 measurements and radial dependences, are presented.

Improvement of water management in a vapor feed direct methanol fuel cell

NASA Astrophysics Data System (ADS)

Masdar, M. Shahbudin; Tsujiguchi, Takuya; Nakagawa, Nobuyoshi

Water transport in a vapor feed direct methanol fuel cell was improved by fixing a hydrophobic air filter (HAF) at the cathode. Effects of the HAF properties and the fixed positions, i.e., just on the cathode surface or by providing a certain space from the surface, of the HAF on the water transport as well as the power generation performance were investigated. The water transport was evaluated by measuring the partial pressure of water, PH2O , and methanol, PCH3OH , at the anode gas layer using in situ mass spectrometry with a capillary probe and also the water and methanol fluxes across the electrode structure using a conventional method. The HAF with the highest hydrophobicity and the highest flow resistance had the strongest effect on increasing the water back diffusion from the cathode to the anode through the membrane and increasing the current density. It was noted that the HAF fixation by providing a space from the cathode surface was more effective in increasing JWCO and the current density than that of the direct placement on the cathode surface. There was an optimum distance for the HAF placement depending on the humidity of the outside air.

System for phase-contrast x-ray radiography using X pinch radiation and a method thereof

DOEpatents

Chandler, Katherine; Chelkovenko, Tatiana; Hammer, David; Pikuz, Sergei; Sinars, Daniel; Song, Byungmoo

2007-11-06

A radiograph system with an anode plate, a cathode plate, and a power source coupled to said anode plate and the cathode plate. At least two wires coupled between the anode plate and the cathode plate provide a configuration to form an X-pinch having a photon source size of less than five microns at energies above 2.5 keV. Material at the configuration forming the X-pinch vaporizes upon application of a suitable current to the wires forming a dense hot plasma and emitting a single x-ray pulse with sufficient photons having energies in the range of from about 2.5 keV to about 20 keV to provide a phase contrast image of an object in the path of the photons. Multiple simultaneous images may be formed of a plurality of objects. Suitable filters and x-ray detectors are provided.

An electrolytic process for ultra fine beryllium

NASA Technical Reports Server (NTRS)

Lidman, W. G.; Griffiths, V.

1972-01-01

Studies were made on the electrolysis of a molten BeCl2-NaCl bath using a mercury cathode and beryllium anode. A quasi-amalgam was obtained. The beryllium was consolidated by direct hot pressing of the amalgam at temperatures in the range of 800 C and using pressures of 5,000, 10,000 and 20,000 psi. The work confirms the ability to produce ultrafine beryllium particles by electrolysis.

Miniature x-ray source

DOEpatents

Trebes, James E.; Bell, Perry M.; Robinson, Ronald B.

2000-01-01

A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode, a getter for maintaining high vacuum, a connector for initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is fabricated from highly x-ray transparent materials, such as sapphire, diamond, or boron nitride.

Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

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

Venkattraman, Ayyaswamy

2013-11-15

The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential andmore » the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.« less

Transcranial Direct Current Stimulation Improves Executive Dysfunctions in ADHD: Implications for Inhibitory Control, Interference Control, Working Memory, and Cognitive Flexibility.

PubMed

Nejati, Vahid; Salehinejad, Mohammad Ali; Nitsche, Michael A; Najian, Asal; Javadi, Amir-Homayoun

2017-09-01

This study examined effects of transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) on major executive functions (EFs), including response inhibition, executive control, working memory (WM), and cognitive flexibility/task switching in ADHD. ADHD children received (a) left anodal/right cathodal DLPFC tDCS and (b) sham stimulation in Experiment 1 and (a) left anodal DLPFC/right cathodal OFC tDCS, (b) left cathodal DLPFC/right anodal OFC tDCS, and (c) sham stimulation in Experiment 2. The current intensity was 1 mA for 15 min with a 72-hr interval between sessions. Participants underwent Go/No-Go task, N-back test, Wisconsin Card Sorting Test (WCST), and Stroop task after each tDCS condition. Anodal left DLPFC tDCS most clearly affected executive control functions (e.g., WM, interference inhibition), while cathodal left DLPFC tDCS improved inhibitory control. Cognitive flexibility/task switching benefited from combined DLPFC-OFC, but not DLPFC stimulation alone. Task-specific stimulation protocols can improve EFs in ADHD.

Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

1996-01-01

A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

1997-01-01

A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

Pulsed plasma thruster by applied a high current hollow cathode discharge

NASA Astrophysics Data System (ADS)

Watanabe, Masayuki; N. Nogera Team; T. Kamada Team

2013-09-01

The pulsed plasma thruster applied by a high current hollow cathode discharge has been investigated. In this research, the pseudo-spark discharge (PSD), which is a one of a pulsed high current hollow cathode discharge, is applied to the plasma thruster. In PSD, the opposite surfaces of the anode and cathode have a small circular hole and the cathode has a cylindrical cavity behind the circular hole. To generate the high speed plasma flow, the diameter of the anode hole is enlarged as compared with that of the cathode hole. As a result, the plasma is accelerated by a combination of an electro-magnetic force and a thermo-dynamic force inside a cathode cavity. For the improvement of the plasma jet characteristic, the magnetic field is also applied to the plasma jet. To magnetize the plasma jet, the external magnetic field is directly induced nearby the electrode holes. Consequently, the plasma jet is accelerated with the self-azimuthal magnetic field. With the magnetic field, the temperature and the density of the plasma jet were around 5 eV and in the order of 10 19 m-3. The density increased several times as compared with that without the magnetic field.

Effect of breathing-hole size on the electrochemical species in a free-breathing cathode of a DMFC

NASA Astrophysics Data System (ADS)

Hwang, J. J.; Wu, S. D.; Lai, L. K.; Chen, C. K.; Lai, D. Y.

A three-dimensional numerical model is developed to study the electrochemical species characteristics in a free-breathing cathode of a direct methanol fuel cell (DMFC). A perforated current collector is attached to the porous cathode that breathes the fresh air through an array of orifices. The radius of the orifice is varied to examine its effect on the electrochemical performance. Gas flow in the porous cathode is governed by the Darcy equation with constant porosity and permeability. The multi-species diffusive transports in the porous cathode are described using the Stefan-Maxwell equation. Electrochemical reaction on the surfaces of the porous matrices is depicted via the Butler-Volmer equation. The charge transports in the porous matrices are dealt with by Ohm's law. The coupled equations are solved by a finite-element-based CFD technique. Detailed distributions of electrochemical species characteristics such as flow velocities, species mass fractions, species fluxes, and current densities are presented. The optimal breathing-hole radius is derived from the current drawn out of the porous cathode under a fixed overpotential.

Negative hydrogen ion sources for accelerators

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

Moehs, D.P.; /Fermilab; Peters, J.

2005-08-01

A variety of H{sup -} ion sources are in use at accelerator laboratories around the world. A list of these ion sources includes surface plasma sources with magnetron, Penning and surface converter geometries as well as magnetic-multipole volume sources with and without cesium. Just as varied is the means of igniting and maintaining magnetically confined plasmas. Hot and cold cathodes, radio frequency, and microwave power are all in use, as well as electron tandem source ignition. The extraction systems of accelerator H{sup -} ion sources are highly specialized utilizing magnetic and electric fields in their low energy beam transport systemsmore » to produce direct current, as well as pulsed and/or chopped beams with a variety of time structures. Within this paper, specific ion sources utilized at accelerator laboratories shall be reviewed along with the physics of surface and volume H{sup -} production in regard to source emittance. Current research trends including aperture modeling, thermal modeling, surface conditioning, and laser diagnostics will also be discussed.« less

Both anodal and cathodal transcranial direct current stimulation improves semantic processing.

PubMed

Brückner, Sabrina; Kammer, Thomas

2017-02-20

Transcranial direct current stimulation (tDCS) is a common method to modulate cortical activity. Anodal tDCS is usually associated with an enhancement of the stimulated brain area, whereas cathodal tDCS is often described as inhibitory brain stimulation method. Our aim was to investigate whether this canonical assumption derived from the motor system could be transferred to the semantic system. Three groups with 20 healthy subjects each were stimulated at Wernicke's area with either anodal, cathodal or sham tDCS. Subsequently, they performed a simple lexical decision task for a duration of about 25min. Subjects receiving anodal tDCS revealed faster reaction times (RTs) compared to the sham group, although not reaching statistical significance. Surprisingly, in the cathodal group RTs were decreased significantly. All subjects were faster in the second half of the task, but the tDCS-induced improvement lasted for the entire duration of the task. Error rates were not influenced by tDCS, neither were RTs in a choice reaction time task. Thus, both anodal and cathodal tDCS applied to Wernicke's area improved semantic processing. Recently, a meta-analysis revealed that the canonical anodal excitation and cathodal inhibition assumption is observed rarely in cognitive studies. In particular, an inhibitory effect of cathodal tDCS on cognition is rare. Our findings thus support the speculation, that especially language functions could be somewhat 'immune' to cathodal inhibition. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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

Beilis, I. I.

A model was developed of vacuum arc cathode spot motion in a magnetic field that obliquely intercepts the cathode surface. The model takes into account a force under an electric field caused by retrograde spot motion across the normal component of the magnetic field, producing a drift velocity component in the direction of the acute angle between the magnetic field and the cathode surface. The relationship between velocity of the retrograde direction and drift velocity of the cathode spot motion to the acute angle was developed. The dependencies of the drift angle θ on the acute angle φ, magnetic fieldmore » strength B, and arc current I were calculated. It was found that the calculated θ increased with φ, B, and I in accordance with Robson's measurements.« less

Effects of direct current on dog liver: Possible mechanisms for tumor electrochemical treatment

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

Li, K.H.; Gu, Y.N.; Xu, B.I.

1997-03-01

Mechanisms of tumor electrochemical treatment (ECT) were studied using normal dog liver. Five physical and chemical methods were used. Two platinum electrodes were inserted into an anesthetized dog`s liver at 3 cm separation. A voltage of 8.5 V direct current (DC) at an average current of 30 mA was applied for 69 min; total charge was 124 coulombs. Concentrations of selected ions near the anode and cathode were measured. The concentrations of Na{sup +} and K{sup +} ions were higher around the cathode, whereas the concentration of Cl{sup {minus}} ions was higher around the anode. Water contents and pH weremore » determined near the anode and the cathode at the midpoint between the two electrodes and in an untreated area away from the electrodes. Hydration occurred around the cathode, and dehydration occurred around the anode. The pH values were 2.1 near the anode and 12.9 near the cathode. Spectrophotometric scans of the liver sample extract were obtained, and the released gases were identified by gas chromatography as chlorine at the anode and hydrogen at the cathode. These results indicate that a series of electrochemical reactions take place during ECT. The cell metabolism and its environment are severely disturbed. Both normal and tumor cells are rapidly and completely destroyed in this altered environment. The authors believe that the above reactions are the ECT mechanisms for treating tumors.« less

Treatment with direct-current stimulation against cingulate seizure-like activity induced by 4-aminopyridine and bicuculline in an in vitro mouse model.

PubMed

Chang, Wei-Pang; Lu, Hsiang-Chin; Shyu, Bai-Chuang

2015-03-01

Clinical studies have shown that cathodal transcranial direct-current stimulation (tDCS) application can produce long-term suppressive effects on drug-resistant seizures. Whether this long-term effect produced by cathodal tDCS can counterbalance the enhancement of synaptic transmission during seizures requires further investigation. Our hypothesis was that the long-term effects of DCS on seizure suppression by the application of cathodal DCS occur through a long-term depression (LTD)-like mechanism. We used a thalamocingulate brain slice preparation combined with a multielectrode array and patch recording to investigate the underlying mechanism of the suppressive effect of DCS on anterior cingulate cortex (ACC) seizures. Patch-clamp recordings showed that cathodal DCS significantly decreased spontaneous excitatory postsynaptic currents (EPSCs) and epileptic EPSCs caused by the 4-aminopyridine. Fifteen minutes of DCS application reliably induced LTD, and the synaptic activation frequency was an important factor in LTD formation. The application of DCS alone without continuous synaptic activation did not induce LTD. Direct-current stimulation-induced LTD appeared to be N-methyl-d-aspartate (NMDA)-dependent, in which the application of the NMDA receptor antagonist D-1-2-amino-5-phosphonopentanoic acid (APV) abolished DCS-induced LTD, and the immediate effect remained. Direct-current stimulation-induced LTD and the long-term effects of DCS on seizure-like activities were also abolished by okadaic acid, a protein phosphatase 1 inhibitor. The long-term effects of DCS on seizures were not influenced by the depotentiation blocker FK-506. Therefore, we conclude that the long-term effects of DCS on seizure-like activities in brain slice occur through an LTD-like mechanism. Copyright © 2015 Elsevier Inc. All rights reserved.

Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source

NASA Astrophysics Data System (ADS)

Christy, Larry

Field emission (FE) properties of carbon nanotube (CNT) fibers from Rice University and the University of Cambridge have been studied for use within a high current electron source for a directed energy weapon. Upon reviewing the performance of these two prevalent CNT fibers, cathodes were designed with CNT fibers from the University of Cincinnati Nanoworld Laboratory. Cathodes composed of a single CNT fiber, an array of three CNT fibers, and a nonwoven CNT sheet were investigated for FE properties; the goal was to design a cathode with emission current in excess of 10 mA. Once the design phase was complete, the cathode samples were fabricated, characterized, and then analyzed to determine FE properties. Electrical conductivity of the CNT fibers was characterized with a 4-probe technique. FE characteristics were measured in an ultra-high vacuum chamber at Wright-Patterson Air Force Base. The arrayed CNT fiber and the enhanced nonwoven CNT sheet emitter design demonstrated the most promising FE properties. Future work will include further analysis and cathode design using this nonwoven CNT sheet material to increase peak current performance during electron emission.

The effect of plasma density and emitter geometry on space charge limits for field emitter array electron charge emission into a space plasma

NASA Astrophysics Data System (ADS)

Morris, Dave; Gilchrist, Brian; Gallimore, Alec

2001-02-01

Field Emitter Array Cathodes (FEACs) are a new technology being developed for several potential spacecraft electron emission and charge control applications. Instead of a single hot (i.e., high powered) emitter, or a gas dependant plasma contactor, FEAC systems consist of many (hundreds or thousands) of small (micron level) cathode/gate pairs printed on a semiconductor wafer that effect cold field emission at relatively low voltages. Each individual cathode emits only micro-amp level currents, but a functional array is capable of amp/cm2 current densities. It is hoped that thus FEAC offers the possibility of a relatively low-power, simple to integrate, and inexpensive technique for the high level of current emissions that are required for an electrodynamic tether (EDT) propulsion mission. Space charge limits are a significant concern for the EDT application. Vacuum chamber tests and PIC simulations are being performed at the University of Michigan Plasmadynamics and Electric Propulsion Laboratory and Space Physics Research Laboratory to determine the effect of plasma density and emitter geometry on space charge limitations. The results of this work and conclusions to date of how to best mitigate space charge limits will be presented. .

Oxygen-reducing biocathodes operating with passive oxygen transfer in microbial fuel cells.

PubMed

Xia, Xue; Tokash, Justin C; Zhang, Fang; Liang, Peng; Huang, Xia; Logan, Bruce E

2013-02-19

Oxygen-reducing biocathodes previously developed for microbial fuel cells (MFCs) have required energy-intensive aeration of the catholyte. To avoid the need for aeration, the ability of biocathodes to function with passive oxygen transfer was examined here using air cathode MFCs. Two-chamber, air cathode MFCs with biocathodes produced a maximum power density of 554 ± 0 mW/m(2), which was comparable to that obtained with a Pt cathode (576 ± 16 mW/m(2)), and 38 times higher than that produced without a catalyst (14 ± 3 mW/m(2)). The maximum current density with biocathodes in this air-cathode MFC was 1.0 A/m(2), compared to 0.49 A/m(2) originally produced in a two-chamber MFC with an aqueous cathode (with cathode chamber aeration). Single-chamber, air-cathode MFCs with the same biocathodes initially produced higher voltages than those with Pt cathodes, but after several cycles the catalytic activity of the biocathodes was lost. This change in cathode performance resulted from direct exposure of the cathodes to solutions containing high concentrations of organic matter in the single-chamber configuration. Biocathode performance was not impaired in two-chamber designs where the cathode was kept separated from the anode solution. These results demonstrate that direct-air biocathodes can work very well, but only under conditions that minimize heterotrophic growth of microorganisms on the cathodes.

Gas ion laser construction for electrically isolating the pressure gauge thereof

NASA Technical Reports Server (NTRS)

Wood, C. E.; Witte, R. S. (Inventor)

1975-01-01

The valve and the pressure gauge of a gas ion laser were electrically insulated from the laser discharge path by connecting them in series with the cathode of the laser. The laser cathode can be grounded and preferably is a cold cathode although a hot cathode may be used instead. The cold cathode was provided with a central aperture to which was connected both the pressure gauge and the gas pressure reservoir through the valve. This will effectively prevent electric discharges from passing either to the pressure gauge or the valve which would otherwise destroy the pressure gauge.

NUCLEAR REACTOR AND THERMIONIC FUEL ELEMENT THEREFOR

DOEpatents

Rasor, N.S.; Hirsch, R.L.

1963-12-01

The patent relates to the direct conversion of fission heat to electricity by use of thermionic plasma diodes having fissionable material cathodes, said diodes arranged to form a critical mass in a nuclear reactor. The patent describes a fuel element comprising a plurality of diodes each having a fissionable material cathode, an anode around said cathode, and an ionizable gas therebetween. Provision is made for flowing the gas and current serially through the diodes. (AEC)

Transcranial direct current stimulation for obsessive-compulsive disorder: A randomized, controlled, partial crossover trial.

PubMed

D'Urso, Giordano; Brunoni, Andre R; Mazzaferro, Maria Pia; Anastasia, Annalisa; de Bartolomeis, Andrea; Mantovani, Antonio

2016-12-01

Presupplementary motor area (pre-SMA) hyperactivity has been detected in obsessive-compulsive disorder (OCD) patients. However, it is not understood whether this is a putative primary cause or a compensatory mechanism in OCD pathophysiology. Considering the polarity-dependent effects on cortical excitability of transcranial direct current stimulation (tDCS), we applied cathodal and/or anodal tDCS to the pre-SMA of OCD patients to test which current polarity might better improve symptoms. Twelve OCD patients received initially 10 anodal (n = 6) or cathodal (n = 6) daily consecutive 2 mA/20 min tDCS sessions with the active electrode placed bilaterally on the pre-SMA. In case of improvement or no change in symptoms severity, the subjects were maintained on the same current polarity for 10 more sessions. In case of symptoms worsening after the first 10 sessions they were switched to the other polarity for 10 more sessions to test the hypothesis of a polarity-dependent effect. Therefore, each subject received 20 tDCS sessions. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Sheehan Disability Scale (SDS) were administered biweekly to assess changes in symptoms severity. After 10 sessions, 50% of patients who initially received anodal stimulation were switched to cathodal, while 100% of patients initially assigned to cathodal stimulation continued on the same polarity. At the end of the study, a statistically significant decrease was observed in the mean Y-BOCS scores of those patients who underwent cathodal tDCS. No pre-post difference was found in the scores of patients following anodal tDCS. Cathodal but not anodal tDCS over the pre-SMA significantly improved OCD symptoms. © 2016 Wiley Periodicals, Inc.

Plasma dynamics on current-carrying magnetic flux tubes. II - Low potential simulation

NASA Technical Reports Server (NTRS)

Swift, Daniel W.

1992-01-01

The evolution of plasma in a current-carrying magnetic flux tube of variable cross section is investigated using a one-dimensional numerical simulation. The flux tube is narrow at the two ends and broad in the middle. The middle part of the flux tube is loaded with a hot, magnetically trapped population, and the two ends have a more dense, gravitationally bound population. A potential difference larger than the gravitational potential but less than the energy of the hot population is applied across the domain. The general result is that the potential change becomes distributed along the anode half of the domain, with negligible potential change on the cathode half. The potential is supported by the mirror force of magnetically trapped particles. The simulations show a steady depletion of plasma on the anode side of the flux tube. The current steadily decreases on a time scale of an ion transit time. The results may provide an explanation for the observed plasma depletions on auroral field lines carrying upward currents.

Acute seizure suppression by transcranial direct current stimulation in rats

PubMed Central

Dhamne, Sameer C; Ekstein, Dana; Zhuo, Zhihong; Gersner, Roman; Zurakowski, David; Loddenkemper, Tobias; Pascual-Leone, Alvaro; Jensen, Frances E; Rotenberg, Alexander

2015-01-01

Objective Cathodal transcranial direct current stimulation (tDCS) is a focal neuromodulation technique that suppresses cortical excitability by low-amplitude constant electrical current, and may have an antiepileptic effect. Yet, tDCS has not been tested in status epilepticus (SE). Furthermore, a combined tDCS and pharmacotherapy antiseizure approach is unexplored. We therefore examined in the rat pentylenetetrazol (PTZ) SE model whether cathodal tDCS (1) suppresses seizures, (2) augments lorazepam (LZP) efficacy, and (3) enhances GABAergic cortical inhibition. Methods Experiment 1 aimed to identify an effective cathodal tDCS intensity. Rats received intraperitoneal PTZ followed by tDCS (sham, cathodal 1 mA, or cathodal 0.1 mA; for 20 min), and then a second PTZ challenge. In Experiment 2, two additional animal groups received a subtherapeutic LZP dose after PTZ, and then verum or sham tDCS. Clinical and electroencephalography (EEG) epileptic activity were compared between all groups. In Experiment 3, we measured GABA-mediated paired-pulse inhibition of the motor evoked potential by paired-pulse transcranial magnetic stimulation (ppTMS) in rats that received PTZ or saline, and either verum or sham tDCS. Results Cathodal 1 mA tDCS (1) reduced EEG spike bursts, and suppressed clinical seizures after the second PTZ challenge, (2) in combination with LZP was more effective in seizure suppression and improved the clinical seizure outcomes compared to either tDCS or LZP alone, and (3) prevented the loss of ppTMS motor cortex inhibition that accompanied PTZ injection. Interpretation These results suggest that cathodal 1 mA tDCS alone and in combination with LZP can suppress seizures by augmenting GABAergic cortical inhibition. PMID:26339678

Binder-Free V 2 O 5 Cathode for Greener Rechargeable Aluminum Battery

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

Wang, Huali; Bai, Ying; Chen, Shi

This letter reports on the investigation of a binder-free cathode material to be used in rechargeable aluminum batteries. This cathode is synthesized by directly depositing V2O5 on a Ni foam current collector. Rechargeable aluminum coin cells fabricated using the as-synthesized binder-free cathode delivered an initial discharge capacity of 239 mAh/g, which is much higher than that of batteries fabricated using a cathode composed of V2O5 nanowires and binder. An obvious discharge voltage plateau appeared at 0.6 V in the discharge curves of the Ni–V2O5 cathode, which is slightly higher than that of the V2O5 nanowire cathodes with common binders. Thismore » improvement is attributed to reduced electrochemical polarization.« less

DUHOCAMIS: a dual hollow cathode ion source for metal ion beams.

PubMed

Zhao, W J; Müller, M W O; Janik, J; Liu, K X; Ren, X T

2008-02-01

In this paper we describe a novel ion source named DUHOCAMIS for multiply charged metal ion beams. This ion source is derived from the hot cathode Penning ion gauge ion source (JINR, Dubna, 1957). A notable characteristic is the modified Penning geometry in the form of a hollow sputter electrode, coaxially positioned in a compact bottle-magnetic field along the central magnetic line of force. The interaction of the discharge geometry with the inhomogeneous but symmetrical magnetic field enables this device to be operated as hollow cathode discharge and Penning discharge as well. The main features of the ion source are the very high metal ion efficiency (up to 25%), good operational reproducibility, flexible and efficient operations for low charged as well as highly charged ions, compact setup, and easy maintenance. For light ions, e.g., up to titanium, well-collimated beams in the range of several tens of milliamperes of pulsed ion current (1 ms, 10/s) have been reliably performed in long time runs.

Hollow cathode heater development for the Space Station plasma contactor

NASA Technical Reports Server (NTRS)

Soulas, George C.

1993-01-01

A hollow cathode-based plasma contactor has been selected for use on the Space Station. During the operation of the plasma contactor, the hollow cathode heater will endure approximately 12000 thermal cycles. Since a hollow cathode heater failure would result in a plasma contactor failure, a hollow cathode heater development program was established to produce a reliable heater design. The development program includes the heater design, process documents for both heater fabrication and assembly, and heater testing. The heater design was a modification of a sheathed ion thruster cathode heater. Three heaters have been tested to date using direct current power supplies. Performance testing was conducted to determine input current and power requirements for achieving activation and ignition temperatures, single unit operational repeatability, and unit-to-unit operational repeatability. Comparisons of performance testing data at the ignition input current level for the three heaters show the unit-to-unit repeatability of input power and tube temperature near the cathode tip to be within 3.5 W and 44 degrees C, respectively. Cyclic testing was then conducted to evaluate reliability under thermal cycling. The first heater, although damaged during assembly, completed 5985 ignition cycles before failing. Two additional heaters were subsequently fabricated and have completed 3178 cycles to date in an on-going test.

Cathode degradation and erosion in high pressure arc discharges

NASA Technical Reports Server (NTRS)

Hardy, T. L.; Nakanishi, S.

1984-01-01

The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

Tracking the Effect of Cathodal Transcranial Direct Current Stimulation on Cortical Excitability and Connectivity by Means of TMS-EEG

PubMed Central

Varoli, Erica; Pisoni, Alberto; Mattavelli, Giulia C.; Vergallito, Alessandra; Gallucci, Alessia; Mauro, Lilia D.; Rosanova, Mario; Bolognini, Nadia; Vallar, Giuseppe; Romero Lauro, Leonor J.

2018-01-01

Transcranial direct current stimulation (tDCS) is increasingly used in both research and therapeutic settings, but its precise mechanisms remain largely unknown. At a neuronal level, tDCS modulates cortical excitability by shifting the resting membrane potential in a polarity-dependent way: anodal stimulation increases the spontaneous firing rate, while cathodal decreases it. However, the neurophysiological underpinnings of anodal/cathodal tDCS seem to be different, as well as their behavioral effect, in particular when high order areas are involved, compared to when motor or sensory brain areas are targeted. Previously, we investigated the effect of anodal tDCS on cortical excitability, by means of a combination of Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG). Results showed a diffuse rise of cortical excitability in a bilateral fronto-parietal network. In the present study, we tested, with the same paradigm, the effect of cathodal tDCS. Single pulse TMS was delivered over the left posterior parietal cortex (PPC), before, during, and after 10 min of cathodal or sham tDCS over the right PPC, while recording HD-EEG. Indexes of global and local cortical excitability were obtained both at sensors and cortical sources level. At sensors, global and local mean field power (GMFP and LMFP) were computed for three temporal windows (0–50, 50–100, and 100–150 ms), on all channels (GMFP), and in four different clusters of electrodes (LMFP, left and right, in frontal and parietal regions). After source reconstruction, Significant Current Density was computed at the global level, and for four Broadmann's areas (left/right BA 6 and 7). Both sensors and cortical sources results converge in showing no differences during and after cathodal tDCS compared to pre-stimulation sessions, both at global and local level. The same holds for sham tDCS. These data highlight an asymmetric impact of anodal and cathodal stimulation on cortical excitability, with a diffuse effect of anodal and no effect of cathodal tDCS over the parietal cortex. These results are consistent with the current literature: while anodal-excitatory and cathodal-inhibitory effects are well-established in the sensory and motor domains, both at physiological and behavioral levels, results for cathodal stimulation are more controversial for modulation of exitability of higher order areas. PMID:29867330

Subnanosecond breakdown development in high-voltage pulse discharge: Effect of secondary electron emission

NASA Astrophysics Data System (ADS)

Alexandrov, A. L.; Schweigert, I. V.; Zakrevskiy, Dm. E.; Bokhan, P. A.; Gugin, P.; Lavrukhin, M.

2017-10-01

A subnanosecond breakdown in high-voltage pulse discharge may be a key tool for superfast commutation of high power devices. The breakdown in high-voltage open discharge at mid-high pressure in helium was studied in experiment and in kinetic simulations. The kinetic model of electron avalanche development was constructed, based on PIC-MCC simulations, including dynamics of electrons, ions and fast helium atoms, produced by ions scattering. Special attention was paid to electron emission processes from cathode, such as: photoemission by Doppler-shifted resonant photons, produced in excitation processes involving fast atoms; electron emission by ions and fast atoms bombardment of cathode; the secondary electron emission (SEE) by hot electrons from bulk plasma. The simulations show that the fast atoms accumulation is the main reason of emission growth at the early stage of breakdown, but at the final stage, when the voltage on plasma gap diminishes, namely the SEE is responsible for subnanosecond rate of current growth. It was shown that the characteristic time of the current growth can be controlled by the SEE yield. The influence of SEE yield for three types of cathode material (titanium, SiC, and CuAlMg-alloy) was tested. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified. It is shown that in discharge with SiC and CuAlMg-alloy cathodes (which have enhanced SEE) the current can increase with a subnanosecond characteristic time value as small as τs = 0.4 ns, for the pulse voltage amplitude of 5÷12 kV. An increase of gas pressure from 15 Torr to 30 Torr essentially decreases the time of of current front growth, whereas the pulse voltage variation weakly affects the results.

Situ treatment of contaminated groundwater

DOEpatents

McNab, Jr., Walt W.; Ruiz, Roberto; Pico, Tristan M.

2001-01-01

A system for treating dissolved halogenated organic compounds in groundwater that relies upon electrolytically-generated hydrogen to chemically reduce the halogenated compounds in the presence of a suitable catalyst. A direct current is placed across at least a pair, or an array, of electrodes which are housed within groundwater wells so that hydrogen is generated at the cathode and oxygen at the anode. A pump is located within the well housing in which the cathode(s) is(are) located and draws in groundwater where it is hydrogenated via electrolysis, passes through a well-bore treatment unit, and then transported to the anode well(s) for reinjection into the ground. The well-bore treatment involves a permeable cylinder located in the well bore and containing a packed bed of catalyst material that facilitates the reductive dehalogenation of the halogenated organic compounds by hydrogen into environmentally benign species such as ethane and methane. Also, electro-osmatic transport of contaminants toward the cathode also contributes to contaminant mass removal. The only above ground equipment required are the transfer pipes and a direct circuit power supply for the electrodes. The electrode wells in an array may be used in pairs or one anode well may be used with a plurality of cathode wells. The DC current flow between electrode wells may be periodically reversed which controls the formation of mineral deposits in the alkaline cathode well-bore water, as well as to help rejuvenate the catalysis.

Electrolytic systems and methods for making metal halides and refining metals

DOEpatents

Holland, Justin M.; Cecala, David M.

2015-05-26

Disclosed are electrochemical cells and methods for producing a halide of a non-alkali metal and for electrorefining the halide. The systems typically involve an electrochemical cell having a cathode structure configured for dissolving a hydrogen halide that forms the halide into a molten salt of the halogen and an alkali metal. Typically a direct current voltage is applied across the cathode and an anode that is fabricated with the non-alkali metal such that the halide of the non-alkali metal is formed adjacent the anode. Electrorefining cells and methods involve applying a direct current voltage across the anode where the halide of the non-alkali metal is formed and the cathode where the non-alkali metal is electro-deposited. In a representative embodiment the halogen is chlorine, the alkali metal is lithium and the non-alkali metal is uranium.

Iodine Plasma Species Measurements in a Hall Effect Thruster Plume

DTIC Science & Technology

2013-04-01

direction f = species fraction 0g = gravitational constant at Earth’s surface, 9.81 m/s 2 I = current, subscripts b for beam, c for cathode, d for...Hall effect thruster uses crossed electric and magnetic fields to generate and accelerate ions. The gas in the discharge is partially ionized, although...early 1960s.10 Ions are weakly magnetized and most are accelerated directly out of the channel, forming the ion beam. The bulk of the cathode

Anomalous - viscosity current drive

DOEpatents

Stix, Thomas H.; Ono, Masayuki

1988-01-01

An apparatus and method for maintaining a steady-state current in a toroidal magnetically confined plasma. An electric current is generated in an edge region at or near the outermost good magnetic surface of the toroidal plasma. The edge current is generated in a direction parallel to the flow of current in the main plasma and such that its current density is greater than the average density of the main plasma current. The current flow in the edge region is maintained in a direction parallel to the main current for a period of one or two of its characteristic decay times. Current from the edge region will penetrate radially into the plasma and augment the main plasma current through the mechanism of anomalous viscosity. In another aspect of the invention, current flow driven between a cathode and an anode is used to establish a start-up plasma current. The plasma-current channel is magnetically detached from the electrodes, leaving a plasma magnetically insulated from contact with any material obstructions including the cathode and anode.

Development of reverse biased p-n junction electron emission

NASA Technical Reports Server (NTRS)

Fowler, P.; Muly, E. C.

1971-01-01

A cold cathode emitter of hot electrons for use as a source of electrons in vacuum gauges and mass spectrometers was developed using standard Norton electroluminescent silicon carbide p-n diodes operated under reverse bias conditions. Continued development including variations in the geometry of these emitters was carried out such that emitters with an emission efficiency (emitted current/junction current) as high as 3 x 10-0.00001 were obtained. Pulse measurements of the diode characteristics were made and showed that higher efficiency can be attained under pulse conditions probably due to the resulting lower temperatures resulting from such operation.

Direct measurements of anode/cathode gap plasma in cylindrically imploding loads on the Z machine

NASA Astrophysics Data System (ADS)

Porwitzky, A.; Dolan, D. H.; Martin, M. R.; Laity, G.; Lemke, R. W.; Mattsson, T. R.

2018-06-01

By deploying a photon Doppler velocimetry based plasma diagnostic, we have directly observed low density plasma in the load anode/cathode gap of cylindrically converging pulsed power targets. The arrival of this plasma is temporally correlated with gross current loss and subtle power flow differences between the anode and the cathode. The density is in the range where Hall terms in the electromagnetic equations are relevant, but this physics is lacking in the magnetohydrodynamics codes commonly used to design, analyze, and optimize pulsed power experiments. The present work presents evidence of the importance of physics beyond traditional resistive magnetohydrodynamics for the design of pulsed power targets and drivers.

Fuel Exhaling Fuel Cell.

PubMed

Manzoor Bhat, Zahid; Thimmappa, Ravikumar; Devendrachari, Mruthyunjayachari Chattanahalli; Kottaichamy, Alagar Raja; Shafi, Shahid Pottachola; Varhade, Swapnil; Gautam, Manu; Thotiyl, Musthafa Ottakam

2018-01-18

State-of-the-art proton exchange membrane fuel cells (PEMFCs) anodically inhale H 2 fuel and cathodically expel water molecules. We show an unprecedented fuel cell concept exhibiting cathodic fuel exhalation capability of anodically inhaled fuel, driven by the neutralization energy on decoupling the direct acid-base chemistry. The fuel exhaling fuel cell delivered a peak power density of 70 mW/cm 2 at a peak current density of 160 mA/cm 2 with a cathodic H 2 output of ∼80 mL in 1 h. We illustrate that the energy benefits from the same fuel stream can at least be doubled by directing it through proposed neutralization electrochemical cell prior to PEMFC in a tandem configuration.

Electrically rechargeable REDOX flow cell

NASA Technical Reports Server (NTRS)

Thaller, L. H. (Inventor)

1976-01-01

A bulk energy storage system is designed with an electrically rechargeable reduction-oxidation (REDOX) cell divided into two compartments by a membrane, each compartment containing an electrode. An anode fluid is directed through the first compartment at the same time that a cathode fluid is directed through the second compartment. Means are provided for circulating the anode and cathode fluids, and the electrodes are connected to an intermittent or non-continuous electrical source, which when operating, supplies current to a load as well as to the cell to recharge it. Ancillary circuitry is provided for disconnecting the intermittent source from the cell at prescribed times and for circulating the anode and cathode fluids according to desired parameters and conditions.

Cathodal Transcranial Direct Current Stimulation Over Left Dorsolateral Prefrontal Cortex Area Promotes Implicit Motor Learning in a Golf Putting Task.

PubMed

Zhu, Frank F; Yeung, Andrew Y; Poolton, Jamie M; Lee, Tatia M C; Leung, Gilberto K K; Masters, Rich S W

2015-01-01

Implicit motor learning is characterized by low dependence on working memory and stable performance despite stress, fatigue, or multi-tasking. However, current paradigms for implicit motor learning are based on behavioral interventions that are often task-specific and limited when applied in practice. To investigate whether cathodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) area during motor learning suppressed working memory activity and reduced explicit verbal-analytical involvement in movement control, thereby promoting implicit motor learning. Twenty-seven healthy individuals practiced a golf putting task during a Training Phase while receiving either real cathodal tDCS stimulation over the left DLPFC area or sham stimulation. Their performance was assessed during a Test phase on another day. Verbal working memory capacity was assessed before and after the Training Phase, and before the Test Phase. Compared to sham stimulation, real stimulation suppressed verbal working memory activity after the Training Phase, but enhanced golf putting performance during the Training Phase and the Test Phase, especially when participants were required to multi-task. Cathodal tDCS over the left DLPFC may foster implicit motor learning and performance in complex real-life motor tasks that occur during sports, surgery or motor rehabilitation. Copyright © 2015 Elsevier Inc. All rights reserved.

A centre-triggered magnesium fuelled cathodic arc thruster uses sublimation to deliver a record high specific impulse

NASA Astrophysics Data System (ADS)

Neumann, Patrick R. C.; Bilek, Marcela; McKenzie, David R.

2016-08-01

The cathodic arc is a high current, low voltage discharge that operates in vacuum and provides a stream of highly ionised plasma from a solid conducting cathode. The high ion velocities, together with the high ionisation fraction and the quasineutrality of the exhaust stream, make the cathodic arc an attractive plasma source for spacecraft propulsion applications. The specific impulse of the cathodic arc thruster is substantially increased when the emission of neutral species is reduced. Here, we demonstrate a reduction of neutral emission by exploiting sublimation in cathode spots and enhanced ionisation of the plasma in short, high-current pulses. This, combined with the enhanced directionality due to the efficient erosion profiles created by centre-triggering, substantially increases the specific impulse. We present experimentally measured specific impulses and jet power efficiencies for titanium and magnesium fuels. Our Mg fuelled source provides the highest reported specific impulse for a gridless ion thruster and is competitive with all flight rated ion thrusters. We present a model based on cathode sublimation and melting at the cathodic arc spot explaining the outstanding performance of the Mg fuelled source. A further significant advantage of an Mg-fuelled thruster is the abundance of Mg in asteroidal material and in space junk, providing an opportunity for utilising these resources in space.

Observation of Repetition-Rate Dependent Emission From an Un-Gated Thermionic Cathode Rf Gun

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

Edelen, J. P.; Sun, Y.; Harris, J.R.

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an ungated thermionicmore » cathode RF gun to high average current.« less

Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

DOEpatents

Rau, Gregory Hudson

2014-07-01

A system for forming metal hydroxide from a metal carbonate utilizes a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide.

Methods of conditioning direct methanol fuel cells

DOEpatents

Rice, Cynthia; Ren, Xiaoming; Gottesfeld, Shimshon

2005-11-08

Methods for conditioning the membrane electrode assembly of a direct methanol fuel cell ("DMFC") are disclosed. In a first method, an electrical current of polarity opposite to that used in a functioning direct methanol fuel cell is passed through the anode surface of the membrane electrode assembly. In a second method, methanol is supplied to an anode surface of the membrane electrode assembly, allowed to cross over the polymer electrolyte membrane of the membrane electrode assembly to a cathode surface of the membrane electrode assembly, and an electrical current of polarity opposite to that in a functioning direct methanol fuel cell is drawn through the membrane electrode assembly, wherein methanol is oxidized at the cathode surface of the membrane electrode assembly while the catalyst on the anode surface is reduced. Surface oxides on the direct methanol fuel cell anode catalyst of the membrane electrode assembly are thereby reduced.

Polymer membrane based electrolytic cell and process for the direct generation of hydrogen peroxide in liquid streams

NASA Technical Reports Server (NTRS)

White, James H. (Inventor); Schwartz, Michael (Inventor); Sammells, Anthony F. (Inventor)

1997-01-01

An electrolytic cell for generating hydrogen peroxide is provided including a cathode containing a catalyst for the reduction of oxygen, and an anode containing a catalyst for the oxidation of water. A polymer membrane, semipermeable to either protons or hydroxide ions is also included and has a first face interfacing to the cathode and a second face interfacing to the anode so that when a stream of water containing dissolved oxygen or oxygen bubbles is passed over the cathode and a stream of water is passed over the anode, and an electric current is passed between the anode and the cathode, hydrogen peroxide is generated at the cathode and oxygen is generated at the anode.

Plasma Source Development for LAPD

NASA Astrophysics Data System (ADS)

Pribyl, P.; Gekelman, W.; Drandell, M.; Grunspen, S.; Nakamoto, M.; McBarron, A.

2003-10-01

The Large Plasma Device (LAPD) relies on an indirectly heated Barium Oxide (BaO) cathode to generate an extremely repeatable low-noise plasma. However there are two defects of this system: one is that the cathode is subject to oxygen poisoning in the event of accidental air leaks, requiring a lengthy recoating and regeneration process. Second, the indirect radiative heating is only about 50 % efficient, leading to a series of reliability issues. Alternate plasma sources are being investigated, including two types of directly heated BaO cathode and several configurations of inductively coupled RF plasmas. Direct heating for a cathode can be achieved either by embedding heaters within the nickel substrate, or by using inductive heating techniques to drive currents within the nickel itself. In both cases, the BaO coating still serves to emit the electrons and thus generate the plasma arc. An improved system would generate the plasma without the use of a "cathode" e.g. by inductively coupling energy directly into the plasma discharge. This technique is being investigated from the point of view of whether a) the bulk of the plasma column can be made sufficiently low-noise to be of experimental value and b) sufficiently dense plasmas can be formed.

Apollo/Saturn C00.00.19.3 operations and maintenance. Cathodic protection of communication cables

NASA Technical Reports Server (NTRS)

1972-01-01

Operating and maintenance instructions for cathodic protection of communication cables at the Cape Kennedy Launch Complex are presented. The system is designed to prevent or arrest corrosion of communication cables buried in soil or submerged in water by impressing sufficient direct current from the rectifier through the anodes to the cable. This process neutralizes or counteracts current flowing from the cable into the soil or water, thus preventing or arresting corrosion of the cable sheath material.

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

NASA Astrophysics Data System (ADS)

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.; Khodak, A.

2018-01-01

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on the current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. The results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

DOE PAGES

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.; ...

2018-01-22

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on themore » current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. Here, the results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.« less

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

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

Khrabry, A.; Kaganovich, I. D.; Nemchinsky, V.

The atmospheric pressure arcs have recently found application in the production of nanoparticles. The distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed a one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play an important role in the operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable to the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on themore » current density. The model was extensively verified and validated against previous simulation results and experimental data. The Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In the case of strong anode cooling (water-cooled anode) when the anode is cold, temperature and plasma density gradients increase with current density, resulting in a decrease of the anode voltage (the absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with the current density, leading to a drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission, and the opposite trend in the VAC is observed. Here, the results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.« less

High performance direct methanol fuel cell with thin electrolyte membrane

NASA Astrophysics Data System (ADS)

Wan, Nianfang

2017-06-01

A high performance direct methanol fuel cell is achieved with thin electrolyte membrane. 320 mW cm-2 of peak power density and over 260 mW cm-2 at 0.4 V are obtained when working at 90 °C with normal pressure air supply. It is revealed that the increased anode half-cell performance with temperature contributes primarily to the enhanced performance at elevated temperature. From the comparison of iR-compensated cathode potential of methanol/air with that of H2/air fuel cell, the impact of methanol crossover on cathode performance decreases with current density and becomes negligible at high current density. Current density is found to influence fuel efficiency and methanol crossover significantly from the measurement of fuel efficiency at different current density. At high current density, high fuel efficiency can be achieved even at high temperature, indicating decreased methanol crossover.

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C.; Booten, Charles W.; Martin, Jerry L.

2012-11-06

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C; Booten, Charles W; Martin, Jerry L

2013-12-24

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Solid oxide fuel cell systems with hot zones having improved reactant distribution

DOEpatents

Poshusta, Joseph C.; Booten, Charles W.; Martin, Jerry L.

2016-05-17

A Solid Oxide Fuel Cell (SOFC) system having a hot zone with a center cathode air feed tube for improved reactant distribution, a CPOX reactor attached at the anode feed end of the hot zone with a tail gas combustor at the opposing end for more uniform heat distribution, and a counter-flow heat exchanger for efficient heat retention.

Arrays of Bundles of Carbon Nanotubes as Field Emitters

NASA Technical Reports Server (NTRS)

Manohara, Harish; Bronkowski, Michael

2007-01-01

Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

Transcranial direct current stimulation improves seizure control in patients with Rasmussen encephalitis.

PubMed

Tekturk, Pinar; Erdogan, Ezgi Tuna; Kurt, Adnan; Kocagoncu, Ece; Kucuk, Zeynep; Kinay, Demet; Yapici, Zuhal; Aksu, Serkan; Baykan, Betul; Karamursel, Sacit

2016-03-01

Rasmussen encephalitis is associated with severe seizures that are unresponsive to antiepileptic drugs, as well as immunosuppressants. Transcranial direct current stimulation (t-DCS) is a non-invasive and safe method tried mostly for focal epilepsies with different aetiologies. To date, there is only one published study with two case reports describing the effect of t-DCS in Rasmussen encephalitis. Our aim was to investigate the effect of t-DCS on seizures in Rasmussen encephalitis and to clarify its safety. Five patients (mean age: 19; three females), diagnosed with Rasmussen encephalitis were included in this study. Patients received first cathodal, then anodal (2 mA for 30 minutes on three consecutive days for non-sham stimulations), and finally sham stimulation with two-month intervals, respectively. Three patients received classic (DC) cathodal t-DCS whereas two patients received cathodal stimulation with amplitude modulation at 12 Hz. Afterwards, all patients received anodal stimulation with amplitude modulation at 12 Hz. In the last part of the trial, sham stimulation (a 60-second stimulation with gradually decreasing amplitude to zero in the last 15 seconds) was applied to three patients. Maximum current density was 571 mA/m2 using 70 mm x 50 mm wet sponge electrodes with 2-mA maximum, current controlled stimulator, and maximum charge density was 1028 C/m2 for a 30-minute stimulation period. After cathodal stimulation, all but one patient had a greater than 50% decrease in seizure frequency. Two patients who received modulated cathodal t-DCS had better results. The longest positive effect lasted for one month. A second trial with modulated anodal stimulation and a third with sham stimulation were not effective. No adverse effect was reported with all types of stimulations. Both classic and modulated cathodal t-DCS may be suitable alternative methods for improving seizure outcome in Rasmussen encephalitis patients.

Effect of sorbed methanol, current, and temperature on multicomponent transport in nafion-based direct methanol fuel cells.

PubMed

Rivera, Harry; Lawton, Jamie S; Budil, David E; Smotkin, Eugene S

2008-07-24

The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources: methanol diffuses through the membrane electrode assembly (MEA) to the cathode where it is catalytically oxidized to CO2; additionally, a portion of the CO2 produced at the anode diffuses through the MEA to the cathode. The potential-dependent CO2 exhaust from the cathode was monitored by online electrochemical mass spectrometry (ECMS) with air and with H2 at the cathode. The precise determination of the crossover rates of methanol and CO2, enabled by the subtractive normalization of the methanol/air to the methanol/H2 ECMS data, shows that methanol decreases the membrane viscosity and thus increases the diffusion coefficients of sorbed membrane components. The crossover of CO2 initially increases linearly with the Faradaic oxidation of methanol, reaches a temperature-dependent maximum, and then decreases. The membrane viscosity progressively increases as methanol is electrochemically depleted from the anode/electrolyte interface. The crossover maximum occurs when the current dependence of the diffusion coefficients and membrane CO2 solubility dominate over the Faradaic production of CO2. The plasticizing effect of methanol is corroborated by measurements of the rotational diffusion of TEMPONE (2,2,6,6-tetramethyl-4-piperidone N-oxide) spin probe by electron spin resonance spectroscopy. A linear inverse relationship between the methanol crossover rate and current density confirms the absence of methanol electro-osmotic drag at concentrations relevant to operating DMFCs. The purely diffusive transport of methanol is explained in terms of current proton solvation and methanol-water incomplete mixing theories.

Assessment of anodal and cathodal transcranial direct current stimulation (tDCS) on MMN-indexed auditory sensory processing.

PubMed

Impey, Danielle; de la Salle, Sara; Knott, Verner

2016-06-01

Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a very weak constant current to temporarily excite (anodal stimulation) or inhibit (cathodal stimulation) activity in the brain area of interest via small electrodes placed on the scalp. Currently, tDCS of the frontal cortex is being used as a tool to investigate cognition in healthy controls and to improve symptoms in neurological and psychiatric patients. tDCS has been found to facilitate cognitive performance on measures of attention, memory, and frontal-executive functions. Recently, a short session of anodal tDCS over the temporal lobe has been shown to increase auditory sensory processing as indexed by the Mismatch Negativity (MMN) event-related potential (ERP). This preliminary pilot study examined the separate and interacting effects of both anodal and cathodal tDCS on MMN-indexed auditory pitch discrimination. In a randomized, double blind design, the MMN was assessed before (baseline) and after tDCS (2mA, 20min) in 2 separate sessions, one involving 'sham' stimulation (the device is turned off), followed by anodal stimulation (to temporarily excite cortical activity locally), and one involving cathodal stimulation (to temporarily decrease cortical activity locally), followed by anodal stimulation. Results demonstrated that anodal tDCS over the temporal cortex increased MMN-indexed auditory detection of pitch deviance, and while cathodal tDCS decreased auditory discrimination in baseline-stratified groups, subsequent anodal stimulation did not significantly alter MMN amplitudes. These findings strengthen the position that tDCS effects on cognition extend to the neural processing of sensory input and raise the possibility that this neuromodulatory technique may be useful for investigating sensory processing deficits in clinical populations. Copyright © 2016 Elsevier Inc. All rights reserved.

A Robust High Current Density Electron Gun

NASA Astrophysics Data System (ADS)

Mako, F.; Peter, W.; Shiloh, J.; Len, L. K.

1996-11-01

Proof-of-principle experiments are proposed to validate a new concept for a robust, high-current density Pierce electron gun (RPG) for use in klystrons and high brightness electron sources for accelerators. This rugged, long-life electron gun avoids the difficulties associated with plasma cathodes, thermionic emitters, and field emission cathodes. The RPG concept employs the emission of secondary electrons in a transmission mode as opposed to the conventional mode of reflection, i.e., electrons exit from the back face of a thin negative electron affinity (NEA) material, and in the same direction as the incident beam. Current amplification through one stage of a NEA material could be over 50 times. The amplification is accomplished in one or more stages consisting of one primary emitter and one or more secondary emitters. The primary emitter is a low current density robust emitter (e.g., thoriated tungsten). The secondary emitters are thin NEA electrodes which emit secondary electrons in the same direction as the incident beam. Specific application is targeted for a klystron gun to be used by SLAC with a cold cathode at 30-40 amps/cm^2 output from the secondary emission stage, a ~2 μs pulse length, and ~200 pulses/second.

The theory of an auto-resonant field emission cathode relativistic electron accelerator for high efficiency microwave to direct current power conversion

NASA Technical Reports Server (NTRS)

Manning, Robert M.

1990-01-01

A novel method of microwave power conversion to direct current is discussed that relies on a modification of well known resonant linear relativistic electron accelerator techniques. An analysis is presented that shows how, by establishing a 'slow' electromagnetic field in a waveguide, electrons liberated from an array of field emission cathodes, are resonantly accelerated to several times their rest energy, thus establishing an electric current over a large potential difference. Such an approach is not limited to the relatively low frequencies that characterize the operation of rectennas, and can, with appropriate waveguide and slow wave structure design, be employed in the 300 to 600 GHz range where much smaller transmitting and receiving antennas are needed.

Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

NASA Astrophysics Data System (ADS)

Chau, S. W.; Hsu, K. L.; Lin, D. L.; Tzeng, C. C.

2007-04-01

The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter to operate the straight-polarity WTC plasma torch at high output power with a limited cathode erosion rate. This emphasizes the importance of an external magnetic field on a WTC torch system for reducing the erosion at the cathode.

GALVANOTAXIS OF SLIME MOLD

PubMed Central

Anderson, John D.

1951-01-01

The plasmodium of Physarum polycephalum reacts to direct current by migration toward the cathode. Cathodal migration was obtained upon a variety of substrata such as baked clay, paper, cellophane, and agar with a current density in the substratum of 1.0 µa./mm.2 Injury was produced by current densities of 8.0 to 12.0 µa./mm.2 The negative galvanotactic response was not due to electrode products. Attempts to demonstrate that the response was due to gradients or orientation in the substratum, pH changes in the mold, cataphoresis, electroosmosis, or endosmosis were not successful. The addition of salts (CaCl2, LiCl, NaCl, Na2SO4, NaHCO3, KCl, MgSO4, sodium citrate, and sea water) to agar indicated that change of cations had more effect than anions upon galvanotaxis and that the effect was upon threshold values. K ion (0.01 M KCl) increased the lower threshold value to 8.0 µa./mm.2 and the upper threshold value to 32.0 µa./mm.2, whereas the Li ion (0.01 M LiCl) increased the lower threshold to only 4.0 µa./mm.2 and the upper threshold to only 16.0 µa./mm.2 The passage of electric current produced no increase in the rate of cathodal migration; neither was there a decrease until injurious current densities were reached. With increase of subthreshold current densities there was a progressive decrease in rate of migration toward the anode until complete anodal inhibition occurred. There was orientation at right angles to the electrodes in alternating current (60 cycle) with current density of 4.0 µa./mm.2 and in direct current of 5.0 µa./mm.2 when polarity of current was reversed every minute. It is concluded that the negative galvanotactic response of P. polycephalum is due to inhibition of migration on the anodal side of the plasmodium and that this inhibition results in the limitation of the normal migration of the mold to a cathodal direction. The mechanism of the anodal inhibition has not been elucidated. PMID:14873916

Arc discharge regulation of a megawatt hot cathode bucket ion source for the experimental advanced superconducting tokamak neutral beam injector

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

Xie Yahong; Hu Chundong; Liu Sheng

2012-01-15

Arc discharge of a hot cathode bucket ion source tends to be unstable what attributes to the filament self-heating and energetic electrons backstreaming from the accelerator. A regulation method, which based on the ion density measurement by a Langmuir probe, is employed for stable arc discharge operation and long pulse ion beam generation. Long pulse arc discharge of 100 s is obtained based on this regulation method of arc power. It establishes a foundation for the long pulse arc discharge of a megawatt ion source, which will be utilized a high power neutral beam injection device.

Arc discharge regulation of a megawatt hot cathode bucket ion source for the experimental advanced superconducting tokamak neutral beam injector.

PubMed

Xie, Yahong; Hu, Chundong; Liu, Sheng; Jiang, Caichao; Li, Jun; Liang, Lizhen

2012-01-01

Arc discharge of a hot cathode bucket ion source tends to be unstable what attributes to the filament self-heating and energetic electrons backstreaming from the accelerator. A regulation method, which based on the ion density measurement by a Langmuir probe, is employed for stable arc discharge operation and long pulse ion beam generation. Long pulse arc discharge of 100 s is obtained based on this regulation method of arc power. It establishes a foundation for the long pulse arc discharge of a megawatt ion source, which will be utilized a high power neutral beam injection device.

Transcranial direct-current stimulation increases extracellular dopamine levels in the rat striatum

PubMed Central

Tanaka, Tomoko; Takano, Yuji; Tanaka, Satoshi; Hironaka, Naoyuki; Kobayashi, Kazuto; Hanakawa, Takashi; Watanabe, Katsumi; Honda, Manabu

2013-01-01

Background: Transcranial direct-current stimulation (tDCS) is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo. Objective/Hypothesis: To investigate whether the application of cathodal or anodal tDCS affects extracellular dopamine and serotonin levels in the rat striatum. Methods: Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal tDCS was applied continuously for 10 min with a current intensity of 800 μA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation. Results: Following the application of cathodal, but not anodal, tDCS for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels. Conclusion: These findings suggest that tDCS has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia. PMID:23596399

Operation of Direct Drive Systems: Experiments in Peak Power Tracking and Multi-Thruster Control

NASA Technical Reports Server (NTRS)

Snyder, John Steven; Brophy, John R.

2013-01-01

Direct-drive power and propulsion systems have the potential to significantly reduce the mass of high-power solar electric propulsion spacecraft, among other advantages. Recent experimental direct-drive work has significantly mitigated or retired the technical risks associated with single-thruster operation, so attention is now moving toward systems-level areas of interest. One of those areas is the use of a Hall thruster system as a peak power tracker to fully use the available power from a solar array. A simple and elegant control based on the incremental conductance method, enhanced by combining it with the unique properties of Hall thruster systems, is derived here and it is shown to track peak solar array power very well. Another area of interest is multi-thruster operation and control. Dualthruster operation was investigated in a parallel electrical configuration, with both thrusters operating from discharge power provided by a single solar array. Startup and shutdown sequences are discussed, and it is shown that multi-thruster operation and control is as simple as for a single thruster. Some system architectures require operation of multiple cathodes while they are electrically connected together. Four different methods to control the discharge current emitted by individual cathodes in this configuration are investigated, with cathode flow rate control appearing to be advantageous. Dual-parallel thruster operation with equal cathode current sharing at total powers up to 10 kW is presented.

OBSERVATION OF REPETITION-RATE DEPENDANT EMISSION FROM AN UN-GATED THERMIONIC CATHODE RF GUN

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

Edelen, J. P.; Sun, Y.; Harris, J. R.

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an ungated thermionicmore » cathode RF gun to high average current machines.« less

Status of Hollow Cathode Heater Development for the Space Station Plasma Contactor

NASA Technical Reports Server (NTRS)

Soulas, George C.

1994-01-01

A hollow cathode-based plasma contactor has been selected for use on the Space Station. During the operation of the plasma contactor, the hollow cathode heater will endure approximately 12000 thermal cycles. Since a hollow cathode heater failure would result in a plasma contactor failure, a hollow cathode heater development program was established to produce a reliable heater. The development program includes the heater design, process documents for both heater fabrication and assembly, and heater testing. The heater design was a modification of a sheathed ion thruster cathode heater. Heater tests included testing of the heater unit alone and plasma contactor and ion thruster testing. To date, eight heaters have been or are being processed through heater unit testing, two through plasma contactor testing and three through ion thruster testing, all using direct current power supplies. Comparisons of data from heater unit performance tests before cyclic testing, plasma contactor tests, and ion thruster tests at the ignition input current level show the average deviation of input power and tube temperature near the cathode tip to be +/-0.9 W and +/- 21 C, respectively. Heater unit testing included cyclic testing to evaluate reliability under thermal cycling. The first heater, although damaged during assembly, completed 5985 ignition cycles before failing. Four additional heaters successfully completed 6300, 6300, 700, and 700 cycles. Heater unit testing is currently ongoing for three heaters which have to date accumulated greater than 7250, greater than 5500, and greater than 5500 cycles, respectively.

Study on the water flooding in the cathode of direct methanol fuel cells.

PubMed

Im, Hun Suk; Kim, Sang-Kyung; Lim, Seongyop; Peck, Dong-Hyun; Jung, Doohwan; Hong, Won Hi

2011-07-01

Water flooding phenomena in the cathode of direct methanol fuel cells were analyzed by using electrochemical impedance spectroscopy. Two kinds of commercial gas diffusion layers with different PTFE contents of 5 wt% (GDL A5) and 20 wt% (GDL B20) were used to investigate the water flooding under various operating conditions. Water flooding was divided into two types: catalyst flooding and backing flooding. The cathode impedance spectra of each gas diffusion layer was obtained and compared under the same conditions. The diameter of the capacitive semicircle became larger with increasing current density for both, and this increase was greater for GDL B20 than GDL A5. Catalyst flooding is dominant and backing flooding is negligible when the air flow rate is high and current density is low. An equivalent model was suggested and fitted to the experimental data. Parameters for catalyst flooding and backing flooding were individually obtained. The capacitance of the catalyst layer decreases as the air flow rate decreases when the catalyst flooding is dominant.

Modulating risky decision-making in Parkinson's disease by transcranial direct current stimulation.

PubMed

Benussi, A; Alberici, A; Cantoni, V; Manenti, R; Brambilla, M; Dell'Era, V; Gazzina, S; Manes, M; Cristillo, V; Padovani, A; Cotelli, M; Borroni, B

2017-05-01

Performance on gambling tasks in Parkinson's disease (PD) is of particular interest, as pathological gambling is often associated with dopamine replacement therapy in these patients. We aimed to evaluate the effects of transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (DLPFC) in modulating gambling behaviour in PD. We assessed the effects of cathodal tDCS over the right DLPFC during the Iowa Gambling Task in 20 patients with PD, compared with sham stimulation. We then conducted a second experimental design, assessing the effects of anodal tDCS over the right DLPFC. We observed that cathodal tDCS over the right DLPFC increased Iowa Gambling Task scores compared with sham stimulation. In the second experimental design, we did not find significant differences between anodal and sham tDCS. Cathodal tDCS over the right DLPFC possibly reduces the pathological overdrive in frontostriatal networks in patients with PD on dopaminergic medication, thus modulating impulsive and risky decision-making. © 2017 EAN.

Emission current control system for multiple hollow cathode devices

NASA Technical Reports Server (NTRS)

Beattie, John R. (Inventor); Hancock, Donald J. (Inventor)

1988-01-01

An emission current control system for balancing the individual emission currents from an array of hollow cathodes has current sensors for determining the current drawn by each cathode from a power supply. Each current sensor has an output signal which has a magnitude proportional to the current. The current sensor output signals are averaged, the average value so obtained being applied to a respective controller for controlling the flow of an ion source material through each cathode. Also applied to each controller are the respective sensor output signals for each cathode and a common reference signal. The flow of source material through each hollow cathode is thereby made proportional to the current drawn by that cathode, the average current drawn by all of the cathodes, and the reference signal. Thus, the emission current of each cathode is controlled such that each is made substantially equal to the emission current of each of the other cathodes. When utilized as a component of a multiple hollow cathode ion propulsion motor, the emission current control system of the invention provides for balancing the thrust of the motor about the thrust axis and also for preventing premature failure of a hollow cathode source due to operation above a maximum rated emission current.

Transspinal direct current stimulation modulates migration and proliferation of adult newly born spinal cells in mice.

PubMed

Samaddar, Sreyashi; Vazquez, Kizzy; Ponkia, Dipen; Toruno, Pedro; Sahbani, Karim; Begum, Sultana; Abouelela, Ahmed; Mekhael, Wagdy; Ahmed, Zaghloul

2017-02-01

Direct current electrical fields have been shown to be a major factor in the regulation of cell proliferation, differentiation, migration, and survival, as well as in the maturation of dividing cells during development. During adulthood, spinal cord cells are continuously produced in both animals and humans, and they hold great potential for neural restoration following spinal cord injury. While the effects of direct current electrical fields on adult-born spinal cells cultured ex vivo have recently been reported, the effects of direct current electrical fields on adult-born spinal cells in vivo have not been characterized. Here, we provide convincing findings that a therapeutic form of transspinal direct current stimulation (tsDCS) affects the migration and proliferation of adult-born spinal cells in mice. Specifically, cathodal tsDCS attracted the adult-born spinal cells, while anodal tsDCS repulsed them. In addition, both tsDCS polarities caused a significant increase in cell number. Regarding the potential mechanisms involved, both cathodal and anodal tsDCS caused significant increases in expression of brain-derived neurotrophic factor, while expression of nerve growth factor increased and decreased, respectively. In the spinal cord, both anodal and cathodal tsDCS increased blood flow. Since blood flow and angiogenesis are associated with the proliferation of neural stem cells, increased blood flow may represent a major factor in the modulation of newly born spinal cells by tsDCS. Consequently, we propose that the method and novel findings presented in the current study have the potential to facilitate cellular, molecular, and/or bioengineering strategies to repair injured spinal cords. NEW & NOTEWORTHY Our results indicate that transspinal direct current stimulation (tsDCS) affects the migratory pattern and proliferation of adult newly born spinal cells, a cell population which has been implicated in learning and memory. In addition, our results suggest a potential mechanism of action regarding the functional effects of applying direct current. Thus tsDCS may represent a novel method by which to manipulate the migration and cell number of adult newly born cells and restore functions following brain or spinal cord injury. Copyright © 2017 the American Physiological Society.

Cu--Ni--Fe anode for use in aluminum producing electrolytic cell

DOEpatents

Bergsma, S. Craig; Brown, Craig W.; Bradford, Donald R; Barnett, Robert J.; Mezner, Michael B.

2006-07-18

A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising the steps of providing a molten salt electrolyte at a temperature of less than 900.degree. C. having alumina dissolved therein in an electrolytic cell having a liner for containing the electrolyte, the liner having a bottom and walls extending upwardly from said bottom. A plurality of non-consumable Cu--Ni--Fe anodes and cathodes are disposed in a vertical direction in the electrolyte, the cathodes having a plate configuration and the anodes having a flat configuration to compliment the cathodes. The anodes contain apertures therethrough to permit flow of electrolyte through the apertures to provide alumina-enriched electrolyte between the anodes and the cathodes. Electrical current is passed through the anodes and through the electrolyte to the cathodes, depositing aluminum at the cathodes and producing gas at the anodes.

Pulsed electromagnetic gas accelleration. [incorporation of hollow cathode in plasma discharge and suitability determination of MPD discharge as plasmadynamic laser source

NASA Technical Reports Server (NTRS)

Jahn, R. G.

1973-01-01

Direct measurement with thermocouples of the power deposited in the anode of a multi-megawatt magnetoplasmadynamic discharge has shown the fractional anode power to decrease from 50% at 200 kW to 10% at 20 MW. Using local measurements of current density, electric potential, and electron temperature, the traditional model for heat conduction to the anode is found to be inadequate. Other experiments in which the voltage-current characteristics and exhaust velocities of MPD arcs using Plexiglas and boron nitride chamber insulators and various mass injection configurations show that ablation can affect nominal accelerator operation in several distinct ways. The incorporation of a hollow cathode in a 7 kA plasma discharge has shown that a stable current attachment can be realized in the cavity without the aid of cathode heaters, keeper electrodes, or emissive coatings.

Empirical Observations on the Sensitivity of Hot Cathode Ionization Type Vacuum Gages

NASA Technical Reports Server (NTRS)

Summers, R. L.

1969-01-01

A study of empirical methods of predicting tile relative sensitivities of hot cathode ionization gages is presented. Using previously published gage sensitivities, several rules for predicting relative sensitivity are tested. The relative sensitivity to different gases is shown to be invariant with gage type, in the linear range of gage operation. The total ionization cross section, molecular and molar polarizability, and refractive index are demonstrated to be useful parameters for predicting relative gage sensitivity. Using data from the literature, the probable error of predictions of relative gage sensitivity based on these molecular properties is found to be about 10 percent. A comprehensive table of predicted relative sensitivities, based on empirical methods, is presented.

Numerical study of the generation of runaway electrons in a gas diode with a hot channel

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

Lisenkov, V. V., E-mail: lisenkov@iep.uran.ru; Ural Federal University, 19 Mira St., Ekaterinburg 620002; Shklyaev, V. A., E-mail: shklyaev@to.hcei.tsc.ru

2015-11-15

A new method for increasing the efficiency of runaway electron beam generation in atmospheric pressure gas media has been suggested and theoretically proved. The method consists of creating a hot region (e.g., a spark channel or a laser plume) with a decreased numerical density of gas molecules (N) near the cathode. In this method, the ratio E/N (E—electric field strength) is increased by decreasing N instead of increasing E, as has been done in the past. The numerical model that is used allows the simultaneous calculation of the formation of a subnanosecond gas discharge and the generation of runaway electronsmore » in gas media. The calculations have demonstrated the possibility of obtaining current pulses of runaway electrons with amplitudes of hundred of amperes and durations of more than 100 ps. The influence of the hot channel geometry on the parameters of the generated beam has been investigated.« less

Influence of Concurrent Finger Movements on Transcranial Direct Current Stimulation (tDCS)-Induced Aftereffects.

PubMed

Shirota, Yuichiro; Terney, Daniella; Antal, Andrea; Paulus, Walter

2017-01-01

Transcranial direct current stimulation (tDCS) has been reported to have bidirectional influence on the amplitude of motor-evoked potentials (MEPs) in resting participants in a polarity-specific manner: anodal tDCS increased and cathodal tDCS decreased them. More recently, the effects of tDCS have been shown to depend on a number of additional factors. We investigated whether a small variety of movements involving target and non-target muscles could differentially modify the efficacy of tDCS. MEPs were elicited from the right first dorsal interosseous muscle, defined as the target muscle, by single pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1). During M1 tDCS, which lasted for 10 min applying anodal, cathodal, or sham condition, the participants were instructed to squeeze a ball with their right hand (Task 1), to move their right index finger only in the medial (Task 2), in the lateral direction (Task 3), or in medial and lateral direction alternatively (Task 4). Anodal tDCS reduced MEP amplitudes measured in Task 1 and Task 2, but to a lesser extent in the latter. In Task 3, anodal tDCS led to greater MEP amplitudes than cathodal stimulation. Alternating movements resulted in no effect of tDCS on MEP amplitude (Task 4). The results are congruent with the current notion that the aftereffects of tDCS are highly variable relying on a number of factors including the type of movements executed during stimulation.

High current density cathode for electrorefining in molten electrolyte

DOEpatents

Li, Shelly X.

2010-06-29

A high current density cathode for electrorefining in a molten electrolyte for the continuous production and collection of loose dendritic or powdery deposits. The high current density cathode eliminates the requirement for mechanical scraping and electrochemical stripping of the deposits from the cathode in an anode/cathode module. The high current density cathode comprises a perforated electrical insulated material coating such that the current density is up to 3 A/cm.sup.2.

Effects of Transcranial Direct Current Stimulation (tDCS) on Pain Distress Tolerance: A Preliminary Study.

PubMed

Mariano, Timothy Y; van't Wout, Mascha; Jacobson, Benjamin L; Garnaat, Sarah L; Kirschner, Jason L; Rasmussen, Steven A; Greenberg, Benjamin D

2015-08-01

Pain remains a critical medical challenge. Current treatments target nociception without addressing affective symptoms. Medically intractable pain is sometimes treated with cingulotomy or deep brain stimulation to increase tolerance of pain-related distress. Transcranial direct current stimulation (tDCS) may noninvasively modulate cortical areas related to sensation and pain representations. The present study aimed to test the hypothesis that cathodal ("inhibitory") stimulation targeting left dorsal anterior cingulate cortex (dACC) would increase tolerance to distress from acute painful stimuli vs anodal stimulation. Forty healthy volunteers received both anodal and cathodal stimulation. During stimulation, we measured pain distress tolerance with three tasks: pressure algometer, cold pressor, and breath holding. We measured pain intensity with a visual-analog scale before and after each task. Mixed ANOVA revealed that mean cold pressor tolerance tended to be higher with cathodal vs anodal stimulation (P = 0.055) for participants self-completing the task. Pressure algometer (P = 0.81) and breath holding tolerance (P = 0.19) did not significantly differ. The pressure algometer exhibited a statistically significant order effect irrespective of stimulation polarity (all P < 0.008). Pain intensity ratings increased acutely after cold pressor and pressure algometer tasks (both P < 0.01), but not after breath holding (P = 0.099). Cold pressor pain ratings tended to rise less after cathodal vs anodal tDCS (P = 0.072). Although our primary results were nonsignificant, there is a preliminary suggestion that cathodal tDCS targeting left dACC may increase pain distress tolerance to cold pressor. Pressure algometer results are consistent with task-related sensitization. Future studies are needed to refine this novel approach for pain neuromodulation. Wiley Periodicals, Inc.

Simulations of Field-Emission Electron Beams from CNT Cathodes in RF Photoinjectors

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

Mihalcea, Daniel; Faillace, Luigi; Panuganti, Harsha

2015-06-01

Average field emission currents of up to 700 mA were produced by Carbon Nano Tube (CNT) cathodes in a 1.3 GHz RF gun at Fermilab High Brightness Electron Source Lab. (HBESL). The CNT cathodes were manufactured at Xintek and tested under DC conditions at RadiaBeam. The electron beam intensity as well as the other beam properties are directly related to the time-dependent electric field at the cathode and the geometry of the RF gun. This report focuses on simulations of the electron beam generated through field-emission and the results are compared with experimental measurements. These simulations were performed with themore » time-dependent Particle In Cell (PIC) code WARP.« less

Polarity-dependent improvement of maximal-effort sprint cycling performance by direct current stimulation of the central nervous system.

PubMed

Sasada, Syusaku; Endoh, Takashi; Ishii, Tomoya; Komiyama, Tomoyoshi

2017-09-14

Sprint motor performance, such as in short-distance running or cycling, gradually decreases after reaching a maximum speed or cadence. This may be attributed to the central nervous system. Brain stimulation studies have recently revealed the plastic nature of the human brain and spinal cord, but it is unclear how direct current stimulation (DCS) affects sprint motor performance. To address this issue, we investigated DCS's effect on healthy volunteers' sprint cycling performance. DCS was applied to the lumbar spinal cord (3mA) or the leg area of the motor cortex (2mA) for 15min with 3 different polarities: anodal, cathodal, and sham. After DCS, the subjects performed maximal-effort sprint cycling for 30s under a constant load. Pooled mean power during the 30s was significantly greater after cathodal transcutaneous spinal DCS to the lumbar spinal cord (tsDCS) than anodal or sham tsDCS. The improvement with cathodal stimulation was notable both 0-5 and 20-25s after the performance onset. There were no significant inter-conditional differences in peak power. Pooled mean power was significantly greater after anodal transcranial DCS to the motor cortex (tDCS) than after cathodal tDCS, although mean powers of anodal and sham tDCS were not significantly different. The increase in mean power after cathodal tsDCS could result from a reduction in central fatigue. This stimulus method might improve sprint performance. Copyright © 2017 Elsevier B.V. All rights reserved.

High-definition transcranial direct current stimulation (HD-tDCS) of left dorsolateral prefrontal cortex affects performance in Balloon Analogue Risk Task (BART).

PubMed

Guo, Heng; Zhang, Zhuoran; Da, Shu; Sheng, Xiaotian; Zhang, Xichao

2018-02-01

Studies on risk preferences have long been of great concern and have examined the neural basis underlying risk-based decision making. However, studies using conventional transcranial direct current stimulation (tDCS) revealed that bilateral stimulation could change risk propensity with limited evidence of precisely focalized unilateral high-definition transcranial direct current stimulation (HD-tDCS). The aim of this experiment was to investigate the effect of HD-tDCS focalizing the left dorsal lateral prefrontal cortex (DLPFC) on risk-taking behavior during the Balloon Analogue Risk Task (BART). This study was designed as a between-subject, single-blind, sham-controlled experiment. University students were randomly assigned to three groups: the anodal group (F3 anode, AF3, F1, F5, FC3 returned), the cathodal group (F3 cathodal, AF3, F1, F5, FC3 returned) and the sham group. Subsequently, 1.5-mA 20-min HD-tDCS was applied during the BART, and the Positive Affect and Negative Affect Scale (PANAS), the Sensation Seeking Scale-5 (SSS-5), and the Behavioral Inhibition System and Behavioral Approach System scale (BIS/BAS) were measured as control variables. The cathodal group earned less total money than the sham group, and no significant difference was observed between the anodal group and the sham group. These results showed that, to some extent, focalized unilateral cathodal HD-tDCS on left DLPFC could change performance during risky tasks and diminish risky decision making. Further studies are needed to investigate the dose effect and electrode distribution of HD-tDCS during risky tasks and examine synchronous brain activity to show the neural basis.

Cross-stacked carbon nanotube film as an additional built-in current collector and adsorption layer for high-performance lithium sulfur batteries.

PubMed

Sun, Li; Kong, Weibang; Li, Mengya; Wu, Hengcai; Jiang, Kaili; Li, Qunqing; Zhang, Yihe; Wang, Jiaping; Fan, Shoushan

2016-02-19

Cross-stacked carbon nanotube (CNT) film is proposed as an additional built-in current collector and adsorption layer in sulfur cathodes for advanced lithium sulfur (Li-S) batteries. On one hand, the CNT film with high conductivity, microstructural rough surface, high flexibility and mechanical durability retains stable and direct electronic contact with the sulfur cathode materials, therefore decreasing internal resistivity and suppressing polarization of the cathode. On the other hand, the highly porous structure and the high surface area of the CNT film provide abundant adsorption points to support and confine sulfur cathode materials, alleviate their aggregation and promote high sulfur utilization. Moreover, the lightweight and compact structure of the CNT film adds no extra weight or volume to the sulfur cathode, benefitting the improvement of energy densities. Based on these characteristics, the sulfur cathode with a 100-layer cross-stacked CNT film presents excellent rate performances with capacities of 986, 922 and 874 mAh g(-1) at cycling rates of 0.2C, 0.5C and 1C for sulfur loading of 60 wt%, corresponding to an improvement of 52%, 109% and 146% compared to that without a CNT film. Promising cycling performances are also demonstrated, offering great potential for scaled-up production of sulfur cathodes for Li-S batteries.

Cathodal Transcranial Direct Current Stimulation of the Right Wernicke's Area Improves Comprehension in Subacute Stroke Patients

ERIC Educational Resources Information Center

You, Dae Sang; Kim, Dae-Yul; Chun, Min Ho; Jung, Seung Eun; Park, Sung Jong

2011-01-01

Previous studies have shown the appearance of right-sided language-related brain activity in right-handed patients after a stroke. Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) have been shown to modulate excitability in the brain. Moreover, rTMS and…

Electric thruster research

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1982-01-01

It has been customary to assume that ions flow nearly equally in all directions from the ion production region within an electron-bombardment discharge chamber. In general, the electron current through a magnetic field can alter the electron density, and hence the ion density, in such a way that ions tend to be directed away from the region bounded by the magnetic field. When this mechanism is understood, it becomes evident that many past discharge chamber designs have operated with a preferentially directed flow of ions. Thermal losses were calculated for an oxide-free hollow cathode. At low electron emissions, the total of the radiation and conduction losses agreed with the total discharge power. At higher emissions, though, the plasma collisions external to the cathode constituted an increasingly greater fraction of the discharge power. Experimental performance of a Hall-current thruster was adversely affected by nonuniformities in the magnetic field, produced by the cathode heating current. The technology of closed-drift thrusters was reviewed. The experimental electron diffusion in the acceleration channel was found to be within about a factor of 3 of the Bohm value for the better thruster designs at most operating conditions. Thruster efficiencies of about 0.5 appear practical for the 1000 to 2000 s range of specific impulse. Lifetime information is limited, but values of several thousands of hours should be possible with anode layer thrusters operated or = to 2000 s.

Long life electrodes for large-area x-ray generators

NASA Technical Reports Server (NTRS)

Rothe, Dietmar E. (Inventor)

1991-01-01

This invention is directed to rugged, reliable, and long-life electrodes for use in large-area, high-current-density electron gun and x-ray generators which are employed as contamination-free preionizers for high-energy pulsed gas lasers. The electron source at the cathode is a corona plasma formed at the interface between a conductor, or semiconductor, and a high-permittivity dielectric. Detailed descriptions are provided of a reliable cold plasma cathode, as well as an efficient liquid-cooled electron beam target (anode) and x-ray generator which concentrates the x-ray flux in the direction of an x-ray window.

Sulfur-carbon nanocomposites and their application as cathode materials in lithium-sulfur batteries

DOEpatents

Liang, Chengdu; Dudney, Nancy J; Howe, Jane Y

2015-05-05

The invention is directed in a first aspect to a sulfur-carbon composite material comprising: (i) a bimodal porous carbon component containing therein a first mode of pores which are mesopores, and a second mode of pores which are micropores; and (ii) elemental sulfur contained in at least a portion of said micropores. The invention is also directed to the aforesaid sulfur-carbon composite as a layer on a current collector material; a lithium ion battery containing the sulfur-carbon composite in a cathode therein; as well as a method for preparing the sulfur-composite material.

Sulfur-carbon nanocomposites and their application as cathode materials in lithium-sulfur batteries

DOEpatents

Liang, Chengdu; Dudney, Nancy J.; Howe, Jane Y.

2017-08-01

The invention is directed in a first aspect to a sulfur-carbon composite material comprising: (i) a bimodal porous carbon component containing therein a first mode of pores which are mesopores, and a second mode of pores which are micropores; and (ii) elemental sulfur contained in at least a portion of said micropores. The invention is also directed to the aforesaid sulfur-carbon composite as a layer on a current collector material; a lithium ion battery containing the sulfur-carbon composite in a cathode therein; as well as a method for preparing the sulfur-composite material.

Electrocatalytic activity of Pd-loaded Ti/TiO2 nanotubes cathode for TCE reduction in groundwater.

PubMed

Xie, Wenjing; Yuan, Songhu; Mao, Xuhui; Hu, Wei; Liao, Peng; Tong, Man; Alshawabkeh, Akram N

2013-07-01

A novel cathode, Pd loaded Ti/TiO2 nanotubes (Pd-Ti/TiO2NTs), is synthesized for the electrocatalytic reduction of trichloroethylene (TCE) in groundwater. Pd nanoparticles are successfully loaded on TiO2 nanotubes which grow on Ti plate via anodization. Using Pd-Ti/TiO2NTs as the cathode in an undivided electrolytic cell, TCE is efficiently and quantitatively transformed to ethane. Under conditions of 100 mA and pH 7, the removal efficiency of TCE (21 mg/L) is up to 91% within 120 min, following pseudo-first-order kinetics with the rate constant of 0.019 min(-1). Reduction rates increase from 0.007 to 0.019 min(-1) with increasing the current from 20 to 100 mA, slightly decrease in the presence of 10 mM chloride or bicarbonate, and decline with increasing the concentrations of sulfite or sulfide. O2 generated at the anode slightly influences TCE reduction. At low currents, TCE is mainly reduced by direct electron transfer on the Pd-Ti/TiO2NT cathode. However, the contribution of Pd-catalytic hydrodechlorination, an indirect reduction mechanism, becomes significant with increasing the current. Compared with other common cathodes, i.e., Ti-based mixed metal oxides, graphite and Pd/Ti, Pd-Ti/TiO2NTs cathode shows superior performance for TCE reduction. Copyright © 2013 Elsevier Ltd. All rights reserved.

Transvertebral direct current stimulation paired with locomotor training in chronic spinal cord injury: A case study.

PubMed

Powell, Elizabeth Salmon; Carrico, Cheryl; Raithatha, Ravi; Salyers, Emily; Ward, Andrea; Sawaki, Lumy

2016-01-01

This double-blind, sham-controlled, crossover case study combined transvertebral direct current stimulation (tvDCS) and locomotor training on a robot-assisted gait orthosis (LT-RGO). Determine whether cathodal tvDCS paired with LT-RGO leads to greater changes in function and neuroplasticity than sham tvDCS paired with LT-RGO. University of Kentucky (UK) HealthCare Stroke and Spinal Cord Neurorehabilitation Research at HealthSouth Cardinal Hill Hospital. A single subject with motor incomplete spinal cord injury (SCI) participated in 24 sessions of sham tvDCS paired with LT-RGO before crossover to 24 sessions of cathodal tvDCS paired with LT-RGO. Functional outcomes were measured with 10 Meter Walk Test (10MWT), 6 Minute Walk Test (6MWT), Spinal Cord Independence Measure-III (SCIM-III) mobility component, lower extremity manual muscle test (MMT), and Berg Balance Scale (BBS). Corticospinal changes were assessed using transcranial magnetic stimulation. Improvement in 10MWT speed, SCIM-III mobility component, and BBS occurred with both conditions. 6MWT worsened after sham tvDCS and improved after cathodal tvDCS. MMT scores for both lower extremities improved following sham tvDCS but decreased following cathodal tvDCS. Corticospinal excitability increased following cathodal tvDCS but not sham tvDCS. These results suggest that combining cathodal tvDCS and LT-RGO may improve functional outcomes, increase corticospinal excitability, and possibly decrease spasticity. Randomized controlled trials are needed to confirm these conclusions. This publication was supported by the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant UL1TR000117, and the HealthSouth Cardinal Hill Stroke and Spinal Cord Endowment (1215375670).

Constance mirror program: Progress and plans

NASA Technical Reports Server (NTRS)

Klinkowstein, R. E.; Mauel, M. E.; Irby, J. H.; Smullin, L. D.; Voldman, S. H.

1981-01-01

The current state of the mechanics of the Constance II experiment, the physics results gathered, the motivation background, and future plans for the Constance II experiment are reviewed. Several improvements have been made and several experimental investigations have been completed. These include the construction/installation/testing of: (1) liquid-nitrogen cooled, Ioffe bars installed, (2) a diverter coil (3) the 100 kW ICRF generator, (4) the data acquisition system, and (5) the optimum hot-iron operation of the machine with Titanium and pulsed-gas plasma guns. Measurements were made of the density, temperature, and radius of the plasma. Ion-cyclotron fluctuations were observed, their bandwidth measured, and data collected demonstrating resonance heating. New X-ray diagnostics were designed and purchased, and progress on the Thomson scattering was made. Finally, a new hot cathode gun was designed and constructed.

An improved alkaline direct formate paper microfluidic fuel cell.

PubMed

Galvan, Vicente; Domalaon, Kryls; Tang, Catherine; Sotez, Samantha; Mendez, Alex; Jalali-Heravi, Mehdi; Purohit, Krutarth; Pham, Linda; Haan, John; Gomez, Frank A

2016-02-01

Paper-based microfluidic fuel cells (MFCs) are a potential replacement for traditional FCs and batteries due to their low cost, portability, and simplicity to operate. In MFCs, separate solutions of fuel and oxidant migrate through paper due to capillary action and laminar flow and, upon contact with each other and catalyst, produce electricity. In the present work, we describe an improved microfluidic paper-based direct formate FC (DFFC) employing formate and hydrogen peroxide as the anode fuel and cathode oxidant, respectively. The dimensions of the lateral column, current collectors, and cathode were optimized. A maximum power density of 2.53 mW/cm(2) was achieved with a DFFC of surface area 3.0 cm(2) , steel mesh as current collector, 5% carbon to paint mass ratio for cathode electrode and, 30% hydrogen peroxide. The longevity of the MFC's detailed herein is greater than eight hours with continuous flow of streams. In a series configuration, the MFCs generate sufficient energy to power light-emitting diodes and a handheld calculator. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transmission Line Modeling Applied to Hot Corrosion of Fe-40at.pctAl in Molten LiCl-KCl

NASA Astrophysics Data System (ADS)

Barraza-Fierro, Jesus Israel; Espinosa-Medina, Marco Antonio; Castaneda, Homero

2015-12-01

The effect of Cu and Li additions to the intermetallic alloy Fe-40at.pctAl on the corrosion performance in an LiCl-55wtpctKCl molten eutectic salt was studied by means of electrochemical impedance spectroscopy, transmission line modeling (TLM), and cathodic polarization. The tests were done at 723 K, 773 K, and 823 K (450 °C, 500 °C, and 550 °C), for 60 and 720 minutes. The element additions could improve the corrosion resistance of Fe-40at.pctAl in molten LiCl-KCl, while TLM could characterize and quantify the interfacial processes in hot corrosion. The polarization curves helped to establish the possible cathodic reactions in the experimental conditions.

Effect of notch depth of modified current collector on internal-short-circuit mitigation for lithium-ion battery

NASA Astrophysics Data System (ADS)

Wang, Meng; Noelle, Daniel J.; Shi, Yang; Le, Anh V.; Qiao, Yu

2018-01-01

Formation of internal short circuit (ISC) may result in catastrophic thermal runaway of lithium-ion battery (LIB). Among LIB cell components, direct contact between cathode and anode current collectors is most critical to the ISC behavior, yet is still relatively uninvestigated. In the current study, we analyze the effect of heterogeneity of current collector on the temperature increase of LIB cells subjected to mechanical abuse. The cathode current collector is modified by surface notches, so that it becomes effectively brittle and the ISC site can be isolated. Results from impact tests on LIB cells with modified current collectors suggest that their temperature increase can be negligible. The critical parameters include the failure strain and the failure work of modified current collector, both of which are related to the notch depth.

Parametrically Optimized Carbon Nanotube-Coated Cold Cathode Spindt Arrays

PubMed Central

Yuan, Xuesong; Cole, Matthew T.; Zhang, Yu; Wu, Jianqiang; Milne, William I.; Yan, Yang

2017-01-01

Here, we investigate, through parametrically optimized macroscale simulations, the field electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum electron devices. The present study builds on empirical data gleaned from our recent experimental findings on the room temperature electron emission from large area CNT electron sources. We determine the field emission current of the present microstructures directly using particle in cell (PIC) software and present a new CNT cold cathode array variant which has been geometrically optimized to provide maximal emission current density, with current densities of up to 11.5 A/cm2 at low operational electric fields of 5.0 V/μm. PMID:28336845

Contralesional Cathodal versus Dual Transcranial Direct Current Stimulation for Decreasing Upper Limb Spasticity in Chronic Stroke Individuals: A Clinical and Neurophysiological Study.

PubMed

Del Felice, Alessandra; Daloli, Verena; Masiero, Stefano; Manganotti, Paolo

2016-12-01

Different transcranial direct current stimulation (tDCS) paradigms have been implemented to treat poststroke spasticity, but discordant results have been reported. This study aimed to determine the efficacy and persistence of dual tDCS (anode over affected motor cortex [M1] and cathode over contralateral M1) compared with cathodal tDCS (cathode over contralateral M1) on upper limb (UL) functional, behavioral, and neurophysiological measures in chronic poststroke individuals. Ten subjects with UL spasticity (7 men; mean 62 years; 8 ischemic stroke; years from event: 2.3 years) were enrolled in a cross-over, double-blinded study. Cathodal and dual tDCS, both preceded by 1 week of sham stimulation 1 month before real stimulation, were applied with 3 months interval. Stimulating paradigm was 20 minutes for five consecutive days in each block. Evaluations were performed before (T1), after real or sham treatment (T2), and after 1 (T3), 4 (T4), and 8 weeks (T5). Functional, behavioral, and neurophysiological tests were performed at each time. Both tDCS paradigms decreased spasticity, increased strength, and ameliorated behavioral scales. Cathodal tDCS was superior to dual tDCS in reducing UL distal spasticity immediately after treatment (T2: cathodal > dual: P = .023) and provided a higher and longer lasting reduction at proximal districts (T3: cathodal > dual: P = .042; T4: cathodal > dual: P = .028; T5: cathodal > dual: P = .05). These findings are supported by an H-reflex modulation (overall time effect P > .002). Cathodal tDCS is slightly more effective than dual tDCS in reducing distal UL spasticity in chronic poststroke subjects. A modulation of spinal inhibitory mechanisms, demonstrated by H-reflex modifications, supports this finding. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Computational Interpretation of the Relation Between Electric Field and the Applied Current for Cathodic Protection Under Different Conductivity Environments

NASA Astrophysics Data System (ADS)

Kim, Yong-Sang; Ko, Sang-Jin; Lee, Sangkyu; Kim, Jung-Gu

2018-03-01

An interpretation of the relation between the electric field and the applied current for cathodic protection is investigated using a boundary element method simulation. Also, a conductivity-difference environment is set for the interface influence. The variation of the potential distribution is increased with the increase of the applied current and the conductivity difference due to the rejection of the current at the interface. In the case of the electric field, the tendencies of the increasing rate and the applied currents are similar, but the interface influence is different according to the directional component and field type (decrease of E z and increases of E x and E y) due to the directional difference between the electric fields. Also, the change tendencies of the electric fields versus the applied current plots are affected by the polarization curve tendency regarding the polarization type (activation and concentration polarizations in the oxygen-reduction and hydrogen-reduction reactions). This study shows that the underwater electric signature is determined by the polarization behavior of the materials.

Cathode power distribution system and method of using the same for power distribution

DOEpatents

Williamson, Mark A; Wiedmeyer, Stanley G; Koehl, Eugene R; Bailey, James L; Willit, James L; Barnes, Laurel A; Blaskovitz, Robert J

2014-11-11

Embodiments include a cathode power distribution system and/or method of using the same for power distribution. The cathode power distribution system includes a plurality of cathode assemblies. Each cathode assembly of the plurality of cathode assemblies includes a plurality of cathode rods. The system also includes a plurality of bus bars configured to distribute current to each of the plurality of cathode assemblies. The plurality of bus bars include a first bus bar configured to distribute the current to first ends of the plurality of cathode assemblies and a second bus bar configured to distribute the current to second ends of the plurality of cathode assemblies.

Prefrontal transcranial direct current stimulation improves fundamental vehicle control abilities.

PubMed

Sakai, Hiroyuki; Uchiyama, Yuji; Tanaka, Satoshi; Sugawara, Sho K; Sadato, Norihiro

2014-10-15

Noninvasive brain stimulation techniques have increasingly attracted the attention of neuroscientists because they enable the identification of the causal role of a targeted brain region. However, few studies have applied such techniques to everyday life situations. Here, we investigate the causal role of the dorsolateral prefrontal cortex (DLPFC) in fundamental vehicle control abilities. Thirteen participants underwent a simulated driving task under prefrontal transcranial direct current stimulation (tDCS) on three separate testing days. Each testing day was randomly assigned to either anodal over the right with cathodal over the left DLPFC, cathodal over the right with anodal over the left DLPFC, or sham stimulation. The driving task required the participants to maintain an inter-vehicle distance to a leading car traveling a winding road with a constant speed. Driving performance was quantified using two metrics: the root-mean-square error of inter-vehicle distance as car-following performance, and the standard deviation of lateral position as lane-keeping performance. Results showed that both car-following and lane-keeping performances were significantly greater for right anodal/left cathodal compared with right cathodal/left cathodal and sham stimulation. These results suggest not only the causal involvement of the DLPFC in driving, but also right hemisphere dominance for vehicle control. The findings of this study indicate that tDCS can be a useful tool to examine the causal role of a specific brain region in ecologically valid environments, and also might be a help to drivers with difficulties in vehicle control. Copyright © 2014 Elsevier B.V. All rights reserved.

Titanium is not "the most biocompatible metal" under cathodic potential: The relationship between voltage and MC3T3 preosteoblast behavior on electrically polarized cpTi surfaces.

PubMed

Ehrensberger, Mark T; Sivan, Shiril; Gilbert, Jeremy L

2010-06-15

An electrochemically controlled system has been developed which allows for cell culture directly on electrically polarized metal surfaces with simultaneous control and assessment of the electrochemical current, potential, and impedance of the interface. This system was utilized in this study to assess the interactions between electrochemically polarized commercially pure titanium (cpTi) and MC3T3 preosteoblast cells. Cells were cultured on CpTi for 24 h at static potentials between -1000 mV and +1000 mV vs. Ag/AgCl and cell morphology (SEM and cell area) and viability (MTT and Live-Dead assay) were assessed along with the electrochemical current densities and surface oxide impedance properties. The results indicate that cathodic polarization in the range of -600 mV to -1000 mV markedly reduces the spreading and viability of cells cultured directly on cpTi within 24 h, while anodic polarization (-300 mV to +1000 mV) out to 72 h shows no difference in cell behavior as compared to the OCP condition. Analysis of the relationship between the cell outcomes and the electrochemical current densities and impedance indicated the presence of voltage-dependent electrochemical thresholds (cathodic current density, i(c) > 1.0 microA/cm(2), R(p) < 10(5) Omega cm(2)) which may control the biocompatibility of cpTi. In addition, these outcomes have direct clinical significance for modular orthopedic implants whose potential can shift, via fretting corrosion, down into the range of potentials exhibiting poor cell behavior. (c) 2009 Wiley Periodicals, Inc.

Polarity-dependent effects of transcranial direct current stimulation in obsessive-compulsive disorder.

PubMed

D'Urso, Giordano; Brunoni, Andre Russowsky; Anastasia, Annalisa; Micillo, Marco; de Bartolomeis, Andrea; Mantovani, Antonio

2016-01-01

About one third of patients with obsessive-compulsive disorder (OCD) fail to experience significant clinical benefit from currently available treatments. Hyperactivity of the presupplementary motor area (pre-SMA) has been detected in OCD patients, but it is not clear whether it is the primary cause or a secondary compensatory mechanism in OCD pathophysiology. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique with polarity-dependent effects on motor cortical excitability. A 33-year-old woman with treatment-resistant OCD received 20 daily consecutive 2 mA/20 min tDCS sessions with the active electrode placed on the pre-SMA, according to the 10-20 EEG system, and the reference electrode on the right deltoid. The first 10 sessions were anodal, while the last 10 were cathodal. Symptoms severity was assessed using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) severity score. In the end of anodal stimulation, OCD symptoms had worsened. Subsequent cathodal stimulation induced a dramatic clinical improvement, which led to an overall 30% reduction in baseline symptoms severity score on the Y-BOCS. Our study supports the hypothesis that pre-SMA hyperfunction might be responsible for OCD symptoms and shows that cathodal inhibitory tDCS over this area might be an option when dealing with treatment-resistant OCD.

Modulating Memory Performance in Healthy Subjects with Transcranial Direct Current Stimulation Over the Right Dorsolateral Prefrontal Cortex.

PubMed

Smirni, Daniela; Turriziani, Patrizia; Mangano, Giuseppa Renata; Cipolotti, Lisa; Oliveri, Massimiliano

2015-01-01

The role of the Dorsolateral Prefrontal Cortex (DLPFC) in recognition memory has been well documented in lesion, neuroimaging and repetitive Transcranial Magnetic Stimulation (rTMS) studies. The aim of the present study was to investigate the effects of transcranial Direct Current Stimulation (tDCS) over the left and the right DLPFC during the delay interval of a non-verbal recognition memory task. 36 right-handed young healthy subjects participated in the study. The experimental task was an Italian version of Recognition Memory Test for unknown faces. Study included two experiments: in a first experiment, each subject underwent one session of sham tDCS and one session of left or right cathodal tDCS; in a second experiment each subject underwent one session of sham tDCS and one session of left or right anodal tDCS. Cathodal tDCS over the right DLPFC significantly improved non verbal recognition memory performance, while cathodal tDCS over the left DLPFC had no effect. Anodal tDCS of both the left and right DLPFC did not modify non verbal recognition memory performance. Complementing the majority of previous studies, reporting long term memory facilitations following left prefrontal anodal tDCS, the present findings show that cathodal tDCS of the right DLPFC can also improve recognition memory in healthy subjects.

Modulation of Total Sleep Time by Transcranial Direct Current Stimulation (tDCS).

PubMed

Frase, Lukas; Piosczyk, Hannah; Zittel, Sulamith; Jahn, Friederike; Selhausen, Peter; Krone, Lukas; Feige, Bernd; Mainberger, Florian; Maier, Jonathan G; Kuhn, Marion; Klöppel, Stefan; Normann, Claus; Sterr, Annette; Spiegelhalder, Kai; Riemann, Dieter; Nitsche, Michael A; Nissen, Christoph

2016-09-01

Arousal and sleep are fundamental physiological processes, and their modulation is of high clinical significance. This study tested the hypothesis that total sleep time (TST) in humans can be modulated by the non-invasive brain stimulation technique transcranial direct current stimulation (tDCS) targeting a 'top-down' cortico-thalamic pathway of sleep-wake regulation. Nineteen healthy participants underwent a within-subject, repeated-measures protocol across five nights in the sleep laboratory with polysomnographic monitoring (adaptation, baseline, three experimental nights). tDCS was delivered via bi-frontal target electrodes and bi-parietal return electrodes before sleep (anodal 'activation', cathodal 'deactivation', and sham stimulation). Bi-frontal anodal stimulation significantly decreased TST, compared with cathodal and sham stimulation. This effect was location specific. Bi-frontal cathodal stimulation did not significantly increase TST, potentially due to ceiling effects in good sleepers. Exploratory resting-state EEG analyses before and after the tDCS protocols were consistent with the notion of increased cortical arousal after anodal stimulation and decreased cortical arousal after cathodal stimulation. The study provides proof-of-concept that TST can be decreased by non-invasive bi-frontal anodal tDCS in healthy humans. Further elucidating the 'top-down' pathway of sleep-wake regulation is expected to increase knowledge on the fundamentals of sleep-wake regulation and to contribute to the development of novel treatments for clinical conditions of disturbed arousal and sleep.

Transcranial direct current stimulation over prefrontal cortex diminishes degree of risk aversion.

PubMed

Ye, Hang; Chen, Shu; Huang, Daqiang; Wang, Siqi; Jia, Yongmin; Luo, Jun

2015-06-26

Previous studies have established that transcranial direct current stimulation (tDCS) is a powerful technique for manipulating the activity of the human cerebral cortex. Many studies have found that weighing the risks and benefits in decision-making involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). We studied whether participants change the balance of risky and safe responses after receiving tDCS applied over the right and left prefrontal cortex. A total of 60 healthy volunteers performed a risk task while they received either anodal tDCS over the right prefrontal cortex, with cathodal over the left; anodal tDCS over the left prefrontal cortex, with cathodal over the right; or sham stimulation. The participants tended to choose less risky options after receiving sham stimulation, demonstrating that the task might be highly influenced by the "wealth effect". There was no statistically significant change after either right anodal/left cathodal or left anodal/right cathodal tDCS, indicating that both types of tDCS impact the participants' degrees of risk aversion, and therefore, counteract the wealth effect. We also found gender differences in the participants' choices. These findings extend the notion that DLPFC activity is critical for risk decision-making. Application of tDCS to the right/left DLPFC may impact a person's attitude to taking risks. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Modulation of Total Sleep Time by Transcranial Direct Current Stimulation (tDCS)

PubMed Central

Frase, Lukas; Piosczyk, Hannah; Zittel, Sulamith; Jahn, Friederike; Selhausen, Peter; Krone, Lukas; Feige, Bernd; Mainberger, Florian; Maier, Jonathan G; Kuhn, Marion; Klöppel, Stefan; Normann, Claus; Sterr, Annette; Spiegelhalder, Kai; Riemann, Dieter; Nitsche, Michael A; Nissen, Christoph

2016-01-01

Arousal and sleep are fundamental physiological processes, and their modulation is of high clinical significance. This study tested the hypothesis that total sleep time (TST) in humans can be modulated by the non-invasive brain stimulation technique transcranial direct current stimulation (tDCS) targeting a ‘top-down' cortico-thalamic pathway of sleep-wake regulation. Nineteen healthy participants underwent a within-subject, repeated-measures protocol across five nights in the sleep laboratory with polysomnographic monitoring (adaptation, baseline, three experimental nights). tDCS was delivered via bi-frontal target electrodes and bi-parietal return electrodes before sleep (anodal ‘activation', cathodal ‘deactivation', and sham stimulation). Bi-frontal anodal stimulation significantly decreased TST, compared with cathodal and sham stimulation. This effect was location specific. Bi-frontal cathodal stimulation did not significantly increase TST, potentially due to ceiling effects in good sleepers. Exploratory resting-state EEG analyses before and after the tDCS protocols were consistent with the notion of increased cortical arousal after anodal stimulation and decreased cortical arousal after cathodal stimulation. The study provides proof-of-concept that TST can be decreased by non-invasive bi-frontal anodal tDCS in healthy humans. Further elucidating the ‘top-down' pathway of sleep-wake regulation is expected to increase knowledge on the fundamentals of sleep-wake regulation and to contribute to the development of novel treatments for clinical conditions of disturbed arousal and sleep. PMID:27143601

Enhancing the mirror illusion with transcranial direct current stimulation.

PubMed

Jax, Steven A; Rosa-Leyra, Diana L; Coslett, H Branch

2015-05-01

Visual feedback has a strong impact on upper-extremity movement production. One compelling example of this phenomena is the mirror illusion (MI), which has been used as a treatment for post-stroke movement deficits (mirror therapy). Previous research indicates that the MI increases primary motor cortex excitability, and this change in excitability is strongly correlated with the mirror's effects on behavioral performance of neurologically-intact controls. Based on evidence that primary motor cortex excitability can also be increased using transcranial direct current stimulation (tDCS), we tested whether bilateral tDCS to the primary motor cortices (anode right-cathode left and anode left-cathode right) would modify the MI. We measured the MI using a previously-developed task in which participants make reaching movements with the unseen arm behind a mirror while viewing the reflection of the other arm. When an offset in the positions of the two limbs relative to the mirror is introduced, reaching errors of the unseen arm are biased by the reflected arm's position. We found that active tDCS in the anode right-cathode left montage increased the magnitude of the MI relative to sham tDCS and anode left-cathode right tDCS. We take these data as a promising indication that tDCS could improve the effect of mirror therapy in patients with hemiparesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modulating activity in the prefrontal cortex changes decision-making for risky gains and losses: a transcranial direct current stimulation study.

PubMed

Ye, Hang; Chen, Shu; Huang, Daqiang; Wang, Siqi; Luo, Jun

2015-06-01

When making choices under uncertainty, people usually consider both the risks and benefits of each option. Previous studies have found that weighing of risks and benefits during decision-making involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC), but the causal effect of this network on risk decision-making has remained unclear. This experiment was based on a risk-measurement table designed to provide a direct measure of risk preference, with a weighted value of the choices (denoted as weighted risk aversion, WRA) as an index of the participant's degree of risk aversion. We studied whether bifrontal transcranial direct current stimulation (tDCS) applied over the right and left prefrontal cortex can change the balance of risky vs. safe responses under both gain frame and loss frame. A total of 60 volunteers performed risk tasks while receiving either anodal over the right with cathodal over the left DLPFC, anodal over the left with cathodal over the right DLPFC, or sham stimulation. The participants tended to choose more risky options in the gain frame and more safe options in the loss frame after the right anodal/left cathodal tDCS. We also found that right anodal/left cathodal tDCS significantly decreased the WRA values compared with those associated with sham stimulation. These findings extend the notion that DLPFC activity is critical for risk decision-making, indicating an asymmetric role of the right DLPFC in the gain frame vs. the loss frame of risk decision-making. Copyright © 2015 Elsevier B.V. All rights reserved.

Hollow Cathode and Keeper-region Plasma Measurements Using Ultra-fast Miniature Scanning Probes

NASA Technical Reports Server (NTRS)

Goebel, Dan M.; Jameson, Kristina K.; Watkins, Ron M.; Katz, Ira

2004-01-01

In order to support the development of comprehensive performance and life models for future deep space missions that will utilize ion thrusters, we have undertaken a study of the plasma structure in hollow cathodes using an new pneumatic scanning probe diagnostic. This device is designed to insert a miniature probe directly into the hollow cathode orifice from either the upstream insert region in the interior of the hollow cathode, or from the downstream keeper-plasma region at the exit of the hollow cathode, to provide complete axial profiles of the discharge plasma parameters. Previous attempts to diagnose this region with probes was Limited by the melting of small probes in the intense discharge near the orifice, or caused significant perturbation of the plasma by probes large enough to survive. Our new probe is extremely compact, and when configured as a single Langmuir probe, the ceramic tube insulator is only 0.5mm in diameter and the current collecting conductor has a total area of 0.002 cm2. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage waveform to the probe as it is scanned by the pneumatic actuator into and out of the plasma region, The bellow-sealed pneumatic drive scans the probe 4 cm in the cathode insert region and 10 cm in the anode/keeper plasmas region at average speeds of about 1 mm/msec, and the residence time at the end of the insertion stroke in the densest part of the plasma near the orifice is measured to be only 10 msec. Since the voltage sweep time is fast compared to the motion of the probe, axial profiles of the plasma density, temperature and potential with reasonable spatial resolution are obtained. Measurements of the internal cathode pressures and the axial plasma-parameter profiles for a hollow cathode operating at discharge currents of up to 35 A in xenon will be presented.

Parametric dependence of ion temperature and electron density in the SUMMA hot-ion plasma using laser light scattering and emission spectroscopy

NASA Technical Reports Server (NTRS)

Snyder, A.; Patch, R. W.; Lauver, M. R.

1980-01-01

Hot-ion plasma experiments were conducted in the NASA Lewis SUMMA facility. A steady-state modified Penning discharge was formed by applying a radially inward dc electric field of several kilovolts near the magnetic mirror maxima. Results are reported for a hydrogen plasma covering a wide range in midplane magnetic flux densities from 0.5 to 3.37 T. Input power greater than 45 kW was obtained with water-cooled cathodes. Steady-state plasmas with ion kinetic temperatures from 18 to 830 eV were produced and measured spectroscopically. These ion temperatures were correlated with current, voltage, and magnetic flux density as the independent variables. Electron density measurements were made using an unusually sensitive Thomson scattering apparatus. The measured electron densities range from 2.1 x 10 to the 11th to 6.8 x 10 to the 12th per cu cm.

Space-charge-limited currents for cathodes with electric field enhanced geometry

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

Lai, Dingguo, E-mail: laidingguo@nint.ac.cn; Qiu, Mengtong; Xu, Qifu

This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that themore » space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.« less

Diamond field emitter array cathodes and possibilities of employing additive manufacturing for dielectric laser accelerating structures

NASA Astrophysics Data System (ADS)

Simakov, Evgenya I.; Andrews, Heather L.; Herman, Matthew J.; Hubbard, Kevin M.; Weis, Eric

2017-03-01

Demonstration of a stand-alone practical dielectric laser accelerator (DLA) requires innovation in two major critical components: high-current ultra-low-emittance cathodes and efficient laser accelerator structures. LANL develops two technologies that in our opinion are applicable to the novel DLA architectures: diamond field emitter array (DFEA) cathodes and additive manufacturing of photonic band-gap (PBG) structures. This paper discusses the results of testing of DFEA cathodes in the field-emission regime and the possibilities for their operation in the photoemission regime, and compares their emission characteristics to the specific needs of DLAs. We also describe recent advances in additive manufacturing of dielectric woodpile structures using a Nanoscribe direct laser-writing device capable of maskless lithography and additive manufacturing, and the development of novel infrared dielectric materials compatible with additive manufacturing.

Electrified emotions: Modulatory effects of transcranial direct stimulation on negative emotional reactions to social exclusion.

PubMed

Riva, Paolo; Romero Lauro, Leonor J; Vergallito, Alessandra; DeWall, C Nathan; Bushman, Brad J

2015-01-01

Social exclusion, ostracism, and rejection can be emotionally painful because they thwart the need to belong. Building on studies suggesting that the right ventrolateral prefrontal cortex (rVLPFC) is associated with regulation of negative emotions, the present experiment tests the hypothesis that decreasing the cortical excitability of the rVLPFC may increase negative emotional reactions to social exclusion. Specifically, we applied cathodal transcranial direct current stimulation (tDCS) over the rVLPFC and predicted an increment of negative emotional reactions to social exclusion. In Study 1, participants were either socially excluded or included, while cathodal tDCS or sham stimulation was applied over the rVLPFC. Cathodal stimulation of rVLPFC boosted the typical negative emotional reaction caused by social exclusion. No effects emerged from participants in the inclusion condition. To test the specificity of tDCS effects over rVLPFC, in Study 2, participants were socially excluded and received cathodal tDCS or sham stimulation over a control region (i.e., the right posterior parietal cortex). No effects of tDCS stimulation were found. Our results showed that the rVLPFC is specifically involved in emotion regulation and suggest that cathodal stimulation can increase negative emotional responses to social exclusion.

Parametric dependence of ion temperature and relative density in the NASA Lewis SUMMA facility. [superconducting magnetic mirror

NASA Technical Reports Server (NTRS)

Snyder, A.; Lauver, M. R.; Patch, R. W.

1976-01-01

Further hot-ion plasma experiments were conducted in the SUMMA superconducting magnetic mirror facility. A steady-state ExB plasma was formed by applying a strong radially inward dc electric field between cylindrical anodes and hollow cathodes located near the magnetic mirror maxima. Extending the use of water cooling to the hollow cathodes, in addition to the anodes, resulted in higher maximum power input to the plasma. Steady-state hydrogen plasmas with ion kinetic temperatures as high as 830 eV were produced. Functional relations were obtained empirically among the plasma current, voltage, magnetic flux density, ion temperature, and relative ion density. The functional relations were deduced by use of a multiple correlation analysis. Data were obtained for midplane magnetic fields from 0.5 to 3.37 tesla and input power up to 45 kW. Also, initial absolute electron density measurements are reported from a 90 deg Thomson scattering laser system.

Direct regeneration of recycled cathode material mixture from scrapped LiFePO4 batteries

NASA Astrophysics Data System (ADS)

Li, Xuelei; Zhang, Jin; Song, Dawei; Song, Jishun; Zhang, Lianqi

2017-03-01

A new green recycling process (named as direct regeneration process) of cathode material mixture from scrapped LiFePO4 batteries is designed for the first time. Through this direct regeneration process, high purity cathode material mixture (LiFePO4 + acetylene black), anode material mixture (graphite + acetylene black) and other by-products (shell, Al foil, Cu foil and electrolyte solvent, etc.) are recycled from scrapped LiFePO4 batteries with high yield. Subsequently, recycled cathode material mixture without acid leaching is further directly regenerated with Li2CO3. Direct regeneration procedure of recycled cathode material mixture from 600 to 800 °C is investigated in detail. Cathode material mixture regenerated at 650 °C display excellent physical, chemical and electrochemical performances, which meet the reuse requirement for middle-end Li-ion batteries. The results indicate the green direct regeneration process with low-cost and high added-value is feasible.

Cathodal transcranial direct-current stimulation over right posterior parietal cortex enhances human temporal discrimination ability.

PubMed

Oyama, Fuyuki; Ishibashi, Keita; Iwanaga, Koichi

2017-12-04

Time perception associated with durations from 1 s to several minutes involves activity in the right posterior parietal cortex (rPPC). It is unclear whether altering the activity of the rPPC affects an individual's timing performance. Here, we investigated the human timing performance under the application of transcranial direct-current stimulation (tDCS) that altered the neural activities of the rPPC. We measured the participants' duration-discrimination threshold by administering a behavioral task during the tDCS application. The tDCS conditions consisted of anodal, cathodal, and sham conditions. The electrodes were placed over the P4 position (10-20 system) and on the left supraorbital forehead. On each task trial, the participant observed two visual stimuli and indicated which was longer. The amount of difference between the two stimulus durations was varied repeatedly throughout the trials according to the participant's responses. The correct answer rate of the trials was calculated for each amount of difference, and the minimum amount with the correct answer rate exceeding 75% was selected as the threshold. The data were analyzed by a linear mixed-effects models procedure. Nineteen volunteers participated in the experiment. We excluded three participants from the analysis: two who reported extreme sleepiness while performing the task and one who could recognize the sham condition correctly with confidence. Our analysis of the 16 participants' data showed that the average value of the thresholds observed under the cathodal condition was lower than that of the sham condition. This suggests that inhibition of the rPPC leads to an improvement in temporal discrimination performance, resulting in improved timing performance. In the present study, we found a new effect that cathodal tDCS over the rPPC enhances temporal discrimination performance. In terms of the existence of anodal/cathodal tDCS effects on human timing performance, the results were consistent with a previous study that investigated temporal reproduction performance during tDCS application. However, the results of the current study further indicated that cathodal tDCS over the rPPC increases accuracy of observed time duration rather than inducing an overestimation as a previous study reported.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization.

PubMed

Zhang, H-S; Komvopoulos, K

2008-07-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp3) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study.

Electrochemical formation of hydroxide for enhancing carbon dioxide and acid gas uptake by a solution

DOEpatents

Rau, Gregory Hudson [Castro Valley, CA

2012-05-15

A system is described for forming metal hydroxide from a metal carbonate utilizing a water electrolysis cell having an acid-producing anode and a hydroxyl-producing cathode immersed in a water solution of sufficient ionic content to allow an electric current to pass between the hydroxyl-producing cathode and the acid-producing anode. A metal carbonate, in particular water-insoluble calcium carbonate or magnesium carbonate, is placed in close proximity to the acid-producing anode. A direct current electrical voltage is provided across the acid-producing anode and the hydroxyl-producing cathode sufficient to generate acid at the acid-producing anode and hydroxyl ions at the hydroxyl-producing cathode. The acid dissolves at least part of the metal carbonate into metal and carbonate ions allowing the metal ions to travel toward the hydroxyl-producing cathode and to combine with the hydroxyl ions to form the metal hydroxide. The carbonate ions travel toward the acid-producing anode and form carbonic acid and/or water and carbon dioxide. Among other uses, the metal hydroxide formed can be employed to absorb acid gases such as carbon dioxide from a gas mixture. The invention can also generate hydrogen and oxidative gases such as oxygen or chlorine.

High-Voltage, High-Power Gaseous Electronics Switch For Electric Grid Power Conversion

NASA Astrophysics Data System (ADS)

Sommerer, Timothy J.

2014-05-01

We are developing a high-voltage, high-power gas switch for use in low-cost power conversion terminals on the electric power grid. Direct-current (dc) power transmission has many advantages over alternating current (ac) transmission, but at present the high cost of ac-dc power interconversion limits the use of dc. The gas switch we are developing conducts current through a magnetized cold cathode plasma in hydrogen or helium to reach practical current densities > 1 A/cm2. Thermal and sputter damage of the cathode by the incident ion flux is a major technical risk, and is being addressed through use of a ``self-healing'' liquid metal cathode (eg, gallium). Plasma conditions and cathode sputtering loss are estimated by analyzing plasma spectral emission. A particle-in-cell plasma model is used to understand various aspects of switch operation, including the conduction phase (where plasma densities can exceed 1013 cm-3), the switch-open phase (where the high-voltage must be held against gas breakdown on the left side of Paschen's curve), and the switching transitions (especially the opening process, which is initiated by forming an ion-matrix sheath adjacent to a control grid). The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000298.

Plasma opening switch

DOEpatents

Savage, Mark E.; Mendel, Jr., Clifford W.

2001-01-01

A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.

Electrochemical device for converting carbon dioxide to a reaction product

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

Masel, Richard I.; Chen, Qingmei; Liu, Zengcai

An electrochemical device converts carbon dioxide to a reaction product. The device includes an anode and a cathode, each comprising a quantity of catalyst. The anode and cathode each has reactant introduced thereto. A polymer electrolyte membrane is interposed between the anode and the cathode. At least a portion of the cathode catalyst is directly exposed to gaseous carbon dioxide during electrolysis. The average current density at the membrane is at least 20 mA/cm.sup.2, measured as the area of the cathode gas diffusion layer that is covered by catalyst, and CO selectivity is at least 50% at a cell potentialmore » of 3.0 V. In some embodiments, the polymer electrolyte membrane comprises a polymer in which a constituent monomer is (p-vinylbenzyl)-R, where R is selected from the group consisting of imidazoliums, pyridiniums and phosphoniums. In some embodiments, the polymer electrolyte membrane is a Helper Membrane comprising a polymer containing an imidazolium ligand, a pyridinium ligand, or a phosphonium ligand.« less

A new structure design and the basic radiation characteristics test of the intense current tube

NASA Astrophysics Data System (ADS)

Li, Zhiyuan; Ai, Xianyun; Fu, Li; Cui, Hui

2018-02-01

As a kind of special G-M counter, the intense current tube (ICT) is characterized by small ratio of cathode to anode radius, high working current or count rate, and can be used as the detection units of ultra-high range radiation instruments. In this paper, a new design of ICT structure is introduced, not only does it have a minimum ratio of cathode to anode but it also has a cathode which directly sticks out from the sensitive gas. Using COMSOL Multiphysics, we simulated the electric field between the anode and cathode and finalized the optimal structure. The results of processes and experiments show that the structure has better properties, with plateau slope reaching up to 7.4% within 100V, and it also has a wider range of dose rate. The linear data between the bottom limit of 0.2mGy/h and the upper limit of 1Gy/h is quite accurate but it becomes less reliable beyond 1Gy/h. By using Paralyzable model, we deduce that the dead time of the said ICT is less than 13.4 µs, and we will further optimize the readout circuit in order to reduce the resolution time of the circuit in the near future.

Investigation of Ruthenium Dissolution in Advanced Membrane Electrode Assemblies for Direct Methanol Based Fuel Cell Stacks

NASA Technical Reports Server (NTRS)

Valdez, Thomas I.; Firdosy, S.; Koel, B. E.; Narayanan, S. R.

2005-01-01

Dissolution of ruthenium was observed in the 80-cell stack. Duration testing was performed in single cell MEAs to determine the pathway of cell degradation. EDAX analysis on each of the single cell MEAs has shown that the Johnson Matthey commercial catalyst is stable in DMFC operation for 250 hours, no ruthenium dissolution was observed. Changes in the hydrophobicity of the cathode backing papers was minimum. Electrode polarization analysis revealed that the MEA performance loss is attributed to changes in the cathode catalyst layer. Ruthenium migration does not seem to occur during cell operation but can occur when methanol is absent from the anode compartment, the cathode compartment has access to air, and the cells in the stack are electrically connected to a load (Shunt Currents). The open-to-air cathode stack design allowed for: a) The MEAs to have continual access to oxygen; and b) The stack to sustain shunt currents. Ruthenium dissolution in a DMFC stack can be prevented by: a) Developing an internally manifolded stacks that seal reactant compartments when not in operation; b) Bringing the cell voltages to zero quickly when not in operation; and c) Limiting the total number of cells to 25 in an effort to limit shunt currents.

Acute and chronic effects of noradrenergic enhancement on transcranial direct current stimulation-induced neuroplasticity in humans.

PubMed

Kuo, Hsiao-I; Paulus, Walter; Batsikadze, Giorgi; Jamil, Asif; Kuo, Min-Fang; Nitsche, Michael A

2017-02-15

Chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) increased and prolonged the long-term potentiation-like plasticity induced by anodal transcranial direct current stimulation (tDCS) for over 24 h. Chronic administration of RBX converted cathodal tDCS-induced long-term depression-like plasticity into facilitation for 120 min. Chronic noradrenergic activity enhancement on plasticity of the human brain might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases. Noradrenaline affects cognition and motor learning processes via its impact on long-term potentiation (LTP) and depression (LTD). We aimed to explore the impact of single dose and chronic administration of the selective noradrenaline reuptake inhibitor (NRI) reboxetine (RBX) on plasticity induced by transcranial direct current stimulation (tDCS) in healthy humans via a double-blinded, placebo-controlled, randomized crossover study. Sixteen healthy volunteers received placebo or single dose RBX (8 mg) before anodal or cathodal tDCS of the primary motor cortex. Afterwards, the same subjects took RBX (8 mg day -1 ) consecutively for 21 days. During this period, two additional interventions were performed (RBX with anodal or cathodal tDCS), to explore the impact of chronic RBX treatment on plasticity. Plasticity was monitored by motor-evoked potential amplitudes elicited by transcranial magnetic stimulation. Chronic administration of RBX increased and prolonged the LTP-like plasticity induced by anodal tDCS for over 24 h. Chronic RBX significantly converted cathodal tDCS-induced LTD-like plasticity into facilitation, as compared to the single dose condition, for 120 min after stimulation. The results show a prominent impact of chronic noradrenergic enhancement on plasticity of the human brain that might partially explain the delayed therapeutic impact of selective NRIs in depression and other neuropsychiatric diseases. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Interference effects of transcranial direct current stimulation over the right frontal cortex and adrenergic system on conditioned fear.

PubMed

Nasehi, Mohammad; Soltanpour, Reyhaneh; Ebrahimi-Ghiri, Mohaddeseh; Zarrabian, Shahram; Zarrindast, Mohammad-Reza

2017-11-01

The effects of pharmacological interventions on fear memory have widely been studied, but there are very few studies about the effects of brain electrical stimulation on fear memory function. Therefore, our aim was to determine whether anodal/cathodal transcranial direct current stimulation (tDCS) over the right frontal cortex would modify propranolol-induced contextual and auditory fear memory deficits, before or after training. The adult NMRI male mice were randomly assigned into three groups: the sham group, the anodal tDCS group, and the cathodal tDCS group. Fear memories were evaluated using a classical fear conditioning apparatus. While the anodal stimulation did not affect fear retrieval, post-training cathodal stimulation improved fear memory retrieval. Regardless of when propranolol (0.1 mg/kg) was administered, it impaired fear memory retrieval. However, when anodal stimulation and propranolol were applied prior to the training, contextual fear memory retrieval was increased and auditory fear memory was reversed. An enhanced contextual retrieval was also observed when propranolol was administered prior to the training and stimulation occurred after the training. Only when the stimulation occurred prior to the training and propranolol was administered after the training was there a selective improvement in contextual fear memory retrieval, leaving the auditory fear memory retrieval impaired. Interestingly, cathodal stimulation improved the effects of propranolol on auditory fear memory only when it occurred prior to the training. The results highlight possible improving effects for anodal/cathodal tDCS on propranolol-induced deficits on fear memories. The timing of the interventions related to the specific phases of memory formation is important in modulating fear behaviors.

Multi-session transcranial direct current stimulation (tDCS) elicits inflammatory and regenerative processes in the rat brain.

PubMed

Rueger, Maria Adele; Keuters, Meike Hedwig; Walberer, Maureen; Braun, Ramona; Klein, Rebecca; Sparing, Roland; Fink, Gereon Rudolf; Graf, Rudolf; Schroeter, Michael

2012-01-01

Transcranial direct current stimulation (tDCS) is increasingly being used in human studies as an adjuvant tool to promote recovery of function after stroke. However, its neurobiological effects are still largely unknown. Electric fields are known to influence the migration of various cell types in vitro, but effects in vivo remain to be shown. Hypothesizing that tDCS might elicit the recruitment of cells to the cortex, we here studied the effects of tDCS in the rat brain in vivo. Adult Wistar rats (n = 16) were randomized to either anodal or cathodal stimulation for either 5 or 10 consecutive days (500 µA, 15 min). Bromodeoxyuridine (BrdU) was given systemically to label dividing cells throughout the experiment. Immunohistochemical analyses ex vivo included stainings for activated microglia and endogenous neural stem cells (NSC). Multi-session tDCS with the chosen parameters did not cause a cortical lesion. An innate immune response with early upregulation of Iba1-positive activated microglia occurred after both cathodal and anodal tDCS. The involvement of adaptive immunity as assessed by ICAM1-immunoreactivity was less pronounced. Most interestingly, only cathodal tDCS increased the number of endogenous NSC in the stimulated cortex. After 10 days of cathodal stimulation, proliferating NSC increased by ∼60%, with a significant effect of both polarity and number of tDCS sessions on the recruitment of NSC. We demonstrate a pro-inflammatory effect of both cathodal and anodal tDCS, and a polarity-specific migratory effect on endogenous NSC in vivo. Our data suggest that tDCS in human stroke patients might also elicit NSC activation and modulate neuroinflammation.

Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

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

Kaur, Manjit, E-mail: manjit@ipr.res.in; Bose, Sayak; Chattopadhyay, P. K.

2015-09-15

Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of themore » dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.« less

Electrically conductive concrete : a laboratory study.

DOT National Transportation Integrated Search

1987-01-01

In the cathodic protection of existing reinforced concrete bridge decks, there is a need for a simple secondary-anode system to facilitate the distribution of direct current over the structure being protected. It is believed that a durable, electrica...

Bi-frontal direct current stimulation affects delay discounting choices.

PubMed

Hecht, David; Walsh, Vincent; Lavidor, Michal

2013-01-01

In delay discounting tasks, participants decide between receiving a certain amount of money now or a larger sum sometime in the future. This study investigated the effects of transcranial direct current stimulation on delay discounting. Participants made delay discounting choices while receiving a bi-frontal stimulation of right-hemisphere anodal/left-hemisphere cathodal, left-hemisphere anodal/right-hemisphere cathodal, and sham stimulation, in three separate sessions. When the difference between the alternatives was 10% or more, participants generally preferred to wait for the larger sum. Nevertheless, there were more choices of smaller "immediate" gains, instead of the larger delayed options, when the left dorsolateral prefrontal cortex (DLPFC) was facilitated and the right DLPFC inhibited, compared to the sham stimulation. These observations indicate the significant role of the prefrontal cortex in delay discounting choices, and demonstrate that increased left frontal activation combined with decreased right frontal activation can alter decision-making by intensifying a tendency to choose immediate gains.

Tagging motor memories with transcranial direct current stimulation allows later artificially-controlled retrieval

PubMed Central

Nozaki, Daichi; Yokoi, Atsushi; Kimura, Takahiro; Hirashima, Masaya; Orban de Xivry, Jean-Jacques

2016-01-01

We demonstrate that human motor memories can be artificially tagged and later retrieved by noninvasive transcranial direct current stimulation (tDCS). Participants learned to adapt reaching movements to two conflicting dynamical environments that were each associated with a different tDCS polarity (anodal or cathodal tDCS) on the sensorimotor cortex. That is, we sought to determine whether divergent background activity levels within the sensorimotor cortex (anodal: higher activity; cathodal: lower activity) give rise to distinct motor memories. After a training session, application of each tDCS polarity automatically resulted in the retrieval of the motor memory corresponding to that polarity. These results reveal that artificial modulation of neural activity in the sensorimotor cortex through tDCS can act as a context for the formation and recollection of motor memories. DOI: http://dx.doi.org/10.7554/eLife.15378.001 PMID:27472899

Electrokinetic remediation of inorganic and organic pollutants in textile effluent contaminated agricultural soil.

PubMed

Annamalai, Sivasankar; Santhanam, Manikandan; Sundaram, Maruthamuthu; Curras, Marta Pazos

2014-12-01

The discharge from the dyeing industries constitutes unfixed dyes, inorganic salts, heavy metal complexes etc., which spoil the surrounding areas of industrial sites. The present article reports the use of direct current electrokinetic technique for the treatment of textile contaminated soil. Impressed direct current voltage of 20 V facilitates the dye/metal ions movement in the naturally available dye contaminated soil towards the opposite electrode by electromigration. IrO2–RuO2–TiO2/Ti was used as anode and Ti used as cathode. UV–Visible spectrum reveals that higher dye intensity was nearer to the anode. Ni, Cr and Pb migration towards the cathode and migration of Cu, SO42− and Cl− towards anode were noticed. Chemical oxygen demand in soil significantly decreased upon employing electrokinetic. This technology may be exploited for faster and eco-friendly removal of dye in soil environment.

Polarity-Dependent Misperception of Subjective Visual Vertical during and after Transcranial Direct Current Stimulation (tDCS).

PubMed

Santos-Pontelli, Taiza E G; Rimoli, Brunna P; Favoretto, Diandra B; Mazin, Suleimy C; Truong, Dennis Q; Leite, Joao P; Pontes-Neto, Octavio M; Babyar, Suzanne R; Reding, Michael; Bikson, Marom; Edwards, Dylan J

2016-01-01

Pathologic tilt of subjective visual vertical (SVV) frequently has adverse functional consequences for patients with stroke and vestibular disorders. Repetitive transcranial magnetic stimulation (rTMS) of the supramarginal gyrus can produce a transitory tilt on SVV in healthy subjects. However, the effect of transcranial direct current stimulation (tDCS) on SVV has never been systematically studied. We investigated whether bilateral tDCS over the temporal-parietal region could result in both online and offline SVV misperception in healthy subjects. In a randomized, sham-controlled, single-blind crossover pilot study, thirteen healthy subjects performed tests of SVV before, during and after the tDCS applied over the temporal-parietal region in three conditions used on different days: right anode/left cathode; right cathode/left anode; and sham. Subjects were blind to the tDCS conditions. Montage-specific current flow patterns were investigated using computational models. SVV was significantly displaced towards the anode during both active stimulation conditions when compared to sham condition. Immediately after both active conditions, there were rebound effects. Longer lasting after-effects towards the anode occurred only in the right cathode/left anode condition. Current flow models predicted the stimulation of temporal-parietal regions under the electrodes and deep clusters in the posterior limb of the internal capsule. The present findings indicate that tDCS over the temporal-parietal region can significantly alter human SVV perception. This tDCS approach may be a potential clinical tool for the treatment of SVV misperception in neurological patients.

77 FR 51722 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-27

... that AD to prevent electrical energy from lightning, hot shorts, or fault current from entering the... that AD to prevent electrical energy from lightning, hot shorts, or fault current from entering the... specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this...

Materials Characteristics and Surface Morphology of a Cesium Iodide Coated Carbon Velvet Cathode (POSTPRINT)

DTIC Science & Technology

2009-03-31

cathodes consist of an array of carbon fibers pyrolytically bonded to a carbon substrate. The fibers then receive a CsI coating using either a...the oil side of the vacuum interface along the cathode shank. Current transformers provide current measurements of the cathode current, again

NEXIS Reservoir Cathode 2000 Hour Life Test

NASA Technical Reports Server (NTRS)

Vaughn, Jason; Schneider, Todd; Polk, Jay; Goebel, Dan; Ohlinger, Wayne; Hill, D. Norm

2004-01-01

The current design of the Nuclear Electric Xenon Ion System (NEXIS) employs a reservoir cathode as both the discharge and neutralizer cathode to meet the 10 yr thruster design life. The main difference between a reservoir cathode and a conventional discharge cathode is the source material (barium-containing compound) is contained within a reservoir instead of in an impregnated insert in the hollow tube. However, reservoir cathodes do not have much life test history associated with them. In order to demonstrate the feasibility of using a reservoir cathode as an integral part of the NEXIS ion thruster, a 2000 hr life test was performed. Several proof-of-concept (POC) reservoir cathodes were built early in the NEXIS program to conduct performance testing as well as life tests. One of the POC cathodes was sent to Marshall Space Flight Center (MSFC) where it was tested for 2000 hrs in a vacuum chamber. The cathode was operated at the NEXIS design point of 25 A discharge current and a xenon flow rate of 5.5 sccm during the 2000 hr test. The cathode performance parameters, including discharge current, discharge voltage, keeper current; keeper voltage, and flow rate were monitored throughout test. Also, the temperature upstream of cathode heater, the temperature downstream of the cathode heater, and the temperature of the orifice plate were monitored throughout the life of the test. The results of the 2000 hr test will be described in this paper. Included in the results will be time history of discharge current, discharge voltage, and flow rate. Also, a time history of the cathode temperature will be provided.

Effect of vacuum arc cathode spot distribution on breaking capacity of the arc-extinguishing chamber

NASA Astrophysics Data System (ADS)

Ding, Can; Yuan, Zhao; He, Junjia

2017-10-01

A DC circuit breaker performs a key function in breaking an intermediate-frequency (IF) current since breaking a pure IF current is equivalent to breaking a very small DC with a reverse IF current. In this study, it is found that cathode spots show a ring-shaped distribution at 2000 Hz. An arc with an uneven distribution of cathode spots has been simulated. The simulation results show that the distribution of cathode spots significantly affect the microparameter distribution of arc plasma. The current distribution on the anode side differs from that on the cathode side under the total radial electric field. Specifically, the anode current distribution is both uneven and concentrated. The applied axial magnetic field, which cannot reduce the concentrated anode current distribution effectively, might increase the concentration of the anode current. Finally, the uneven distribution of cathode spots reduces the breaking capacity of the arc-extinguishing chamber.

Modulation of iTBS after-effects via concurrent directional TDCS: A proof of principle study.

PubMed

Tremblay, Sara; Hannah, Ricci; Rawji, Vishal; Rothwell, John C

Polarising currents can modulate membrane potentials in animals, affecting the after-effect of theta burst stimulation (TBS) on synaptic strength. We examined whether a similar phenomenon could also be observed in human motor cortex (M1) using transcranial direct current stimulation (TDCS) during monophasic intermittent TBS (iTBS). TDCS was applied during posterior-anterior iTBS using three different conditions: posterior-anterior TDCS (anode 3.5 cm posterior to M1, cathode 3.5 cm anterior to M1), anterior-posterior TDCS (cathode 3.5 cm posterior to M1, anode 3.5 cm anterior to M1), and sham TDCS. When the direction of TDCS (posterior-anterior) matched the direction of the electrical field induced by iTBS, we found a 19% non-significant increase in excitability changes in comparison with iTBS combined with sham TDCS. When the TDCS was reversed (anterior-posterior), the excitatory effect of iTBS was abolished. Our findings suggest that excitatory after-effects of iTBS can be modulated by directionally-specific TDCS. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

The effect of current flow direction on motor hot spot allocation by transcranial magnetic stimulation.

PubMed

Stephani, Caspar; Paulus, Walter; Sommer, Martin

2016-01-01

The objective of this study was to investigate the significance of pulse configurations and current direction for corticospinal activation using transcranial magnetic stimulation (TMS). In 11 healthy subjects (8 female), a motor map for the motor evoked potentials (MEPs) recorded from the first dorsal interosseus (FDI), abductor digiti minimi (ADM), extensor carpi radialis, and biceps brachii (BB) muscles of the dominant side was established. Starting from a manually determined hot spot of the FDI representation, we measured MEPs at equal oriented points on an hexagonal grid, with 7 MEPs recorded at each point, using the following pulse configurations: posteriorly directed monophasic (Mo-P), anteriorly directed monophasic (Mo-A), biphasic with the more relevant second cycle oriented posteriorly (Bi-P) as well as a reversed biphasic condition (Bi-A). For each pulse configuration, a hot spot was determined and a center of gravity (CoG) was calculated. We found that the factor current direction had an effect on location of the CoG-adjusted hot spot in the cranio-caudal axis but not in the latero-medial direction with anteriorly directed pulses locating the CoG more anteriorly and vice versa. In addition, the CoG for the FDI was more laterally than the cortical representations for the abductor digiti minimi (ADM) and extensor carpi radialis (ECR) which were registered as well. The results indicate that direction of the current pulse should be taken into account for determination of the motor representation of a muscle by TMS. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Effect of current ripple on cathode erosion in 30 kWe class arcjets

NASA Technical Reports Server (NTRS)

Harris, William J.; O'Hair, Edgar A.; Hatfield, Lynn L.; Kristiansen, M.; Grimes, Montgomery D.

1991-01-01

An investigation was conducted to study the effect of current ripple on cathode erosion in 30 kWe class arcjets to determine the change in the cathode erosion rate for high (11 percent) and low (4 percent) current ripple. The measurements were conducted using a copper-tungsten cathode material to accelerate the cathode erosion process. It is shown that the high ripple erosion rate was initially higher than the low ripple erosion rate, but decreased asymptotically with time to a level less than half that of the low ripple value. Results suggest that high ripple extends the cathode lifetime for long duration operation, and improves arc stability by increasing the cathode attachment area.

Novel nanodisperse composite cathode for rechargeable lithium/polymer batteries

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

Striebel, K.A.; Wen, S.J.; Ghantous, D.I.

1997-05-01

A novel approach to the design of a composite positive electrode for lithium/polymer cells based on a polyethylene oxide (PEO) polymer, manganese (II), and lithium hydroxide has been discovered. A chemical reaction leading to a stable suspension occurs when the precursor salts are added directly to a polymer solution. The electrode film is cast directly and then vacuum-dried with no calcination step. The film is amorphous as-prepared and has been named the nanodisperse composite cathode, or NCC. Film characterization with x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy indicates that the Mn (II) has been oxidized to Mn (IV), whichmore » forms a complex with the PEO. This leads to highly disperse Mn sites within the polymer matrix and highly mobile Li ions within the PEO. Cells have been assembled with NCC films, PEO-LiN(SO{sub 2}CF{sub 3}){sub 2} electrolyte and lithium metal, and cycled at 85 to 105 C at current densities of 0.2 mA/cm{sup 2} between the voltage limits of 3.5 and 2.0 V. Discharge capacities as high as 340 mAh/g-cathode film have been achieved on the first half-cycle. The discharge capacity declines consistently during a formation process to steady values as high as 50 mAh/g-cathode. This cathode capacity is equivalent to an active material capacity of 150 mAh/g in a composite cathode at a loading of 30 weight percent. The synthesis process for the NCC is simple, should be relatively easy to scale up, and should lead to an extremely useful composite cathode for a lithium polymer battery.« less

The effect of a miniature argon flow rate on the spectral characteristics of a direct current atmospheric pressure glow micro-discharge between an argon microjet and a small sized flowing liquid cathode

NASA Astrophysics Data System (ADS)

Jamróz, Piotr; Żyrnicki, Wiesław; Pohl, Paweł

2012-07-01

A stable direct current atmospheric pressure glow microdischarge (dc-μAPGD) was generated between a miniature Ar flow microjet and a small sized flowing liquid cathode. The microdischarge was operated in the open to air atmosphere. High energy species, including OH, NH, NO, N2, H, O and Ar were identified in the emission spectra of this microdischarge. Additionally, atomic lines of metals dissolved in water solutions were easily excited. The near cathode and the near anode zones of the microdischarge were investigated as a function of an Ar flow rate up to 300 sccm. The spectroscopic parameters, i.e., the excitation, the vibrational and the rotational temperatures as well as the electron number density, were determined in the near cathode and the near anode regions of the microdischarge. In the near cathode region, the rotational temperatures obtained for OH (2000-2600 K) and N2 bands (1600-1950 K) were significantly lower than the excitation temperatures of Ar (7400 K-7800 K) and H (11 000-15 500 K) atoms. Vibrational temperatures of N2, OH and NO varied from 3400 to 4000 K, from 2900 to 3400 K and from 2700 to 3000 K, respectively. In the near anode region, rotational temperatures of OH (350-1750 K) and N2 (400-1350 K) and excitation temperatures of Ar (5200-5500 K) and H (3600-12 600 K) atoms were lower than those measured in the near cathode region. The effect of the introduction of a liquid sample on the microdischarge radiation and spectroscopic parameters was also investigated in the near cathode zone. The electron number density was calculated from the Stark broadening of the Hβ line and equals to (0.25-1.1) × 1015 cm- 3 and (0.68-1.2) × 1015 cm- 3 in the near cathode and the near anode zones, respectively. The intensity of the Na I emission line and the signal to background ratio (SBR) of this line were investigated in both zones to evaluate the excitation properties of the developed excitation microsource. The limit of detection for Na was determined at the level of 3 ng mL- 1.

Slow-Frequency Pulsed Transcranial Electrical Stimulation for Modulation of Cortical Plasticity Based on Reciprocity Targeting with Precision Electrical Head Modeling

PubMed Central

Luu, Phan; Essaki Arumugam, Easwara Moorthy; Anderson, Erik; Gunn, Amanda; Rech, Dennis; Turovets, Sergei; Tucker, Don M.

2016-01-01

In pain management as well as other clinical applications of neuromodulation, it is important to consider the timing parameters influencing activity-dependent plasticity, including pulsed versus sustained currents, as well as the spatial action of electrical currents as they polarize the complex convolutions of the cortical mantle. These factors are of course related; studying temporal factors is not possible when the spatial resolution of current delivery to the cortex is so uncertain to make it unclear whether excitability is increased or decreased with anodal vs. cathodal current flow. In the present study we attempted to improve the targeting of specific cortical locations by applying current through flexible source-sink configurations of 256 electrodes in a geodesic array. We constructed a precision electric head model for 12 healthy individuals. Extraction of the individual’s cortical surface allowed computation of the component of the induced current that is normal to the target cortical surface. In an effort to replicate the long-term depression (LTD) induced with pulsed protocols in invasive animal research and transcranial magnetic stimulation studies, we applied 100 ms pulses at 1.9 s intervals either in cortical-surface-anodal or cortical-surface-cathodal directions, with a placebo (sham) control. The results showed significant LTD of the motor evoked potential as a result of the cortical-surface-cathodal pulses in contrast to the placebo control, with a smaller but similar LTD effect for anodal pulses. The cathodal LTD after-effect was sustained over 90 min following current injection. These results support the feasibility of pulsed protocols with low total charge in non-invasive neuromodulation when the precision of targeting is improved with a dense electrode array and accurate head modeling. PMID:27531976

Theoretical and experimental investigation into high current hollow cathode arc attachment

NASA Astrophysics Data System (ADS)

Downey, Ryan T.

This research addresses several concerns of the mechanisms controlling performance and lifetime of high-current single-channel-hollow-cathodes, the central electrode and primary life-limiting component in Magnetoplasmadynamic thrusters. Specifically covered are the trends, and the theorized governing mechanisms, seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), cathode exit plume plasma density and energy, along with plasma property distributions of the internal plasma column (the IPC) of a single-channel-hollow-cathode. Both experiment and computational modeling were employed in the analysis of the cathodes. Employing Tantalum and Tungsten cathodes (of 2, 6 and 10 mm inner diameter), experiments were conducted to measure the temperature profile of operating cathodes, the width of the active zone, the discharge voltage, power, plasma arc resistance and efficiency, with mass flow rates of 50 to 300 sccm of Argon, and discharge currents of 15 to 50 Amps. Langmuir probing was used to obtain measurements for the electron temperature, plasma density and plasma potential at the cathode exit plane (down stream tip). A computational model was developed to predict the distribution of plasma inside the cathode, based upon experimentally determined boundary conditions. It was determined that the peak cathode temperature is a function of both interior cathode density and discharge current, though the location of the peak temperature is controlled gas density but not discharge current. The active zone width was found to be an increasing function of the discharge current, but a decreasing function of the mass flow rate. The width of the active zone was found to not be controlled by the magnitude of the peak cathode wall temperature. The discharge power consumed per unit of mass throughput is seen as a decreasing function of the mass flow rate, showing the increasing efficiency of the cathode. Finally, this new understanding of the mechanisms of the plasma attachment phenomena of a single-channel-hollow-cathode were extrapolated to the multi-channel-hollow-cathode environment, to explain performance characteristics of these devices seen in previous research.

Adult subependymal neural precursors, but not differentiated cells, undergo rapid cathodal migration in the presence of direct current electric fields.

PubMed

Babona-Pilipos, Robart; Droujinine, Ilia A; Popovic, Milos R; Morshead, Cindi M

2011-01-01

The existence of neural stem and progenitor cells (together termed neural precursor cells) in the adult mammalian brain has sparked great interest in utilizing these cells for regenerative medicine strategies. Endogenous neural precursors within the adult forebrain subependyma can be activated following injury, resulting in their proliferation and migration toward lesion sites where they differentiate into neural cells. The administration of growth factors and immunomodulatory agents following injury augments this activation and has been shown to result in behavioural functional recovery following stroke. With the goal of enhancing neural precursor migration to facilitate the repair process we report that externally applied direct current electric fields induce rapid and directed cathodal migration of pure populations of undifferentiated adult subependyma-derived neural precursors. Using time-lapse imaging microscopy in vitro we performed an extensive single-cell kinematic analysis demonstrating that this galvanotactic phenomenon is a feature of undifferentiated precursors, and not differentiated phenotypes. Moreover, we have shown that the migratory response of the neural precursors is a direct effect of the electric field and not due to chemotactic gradients. We also identified that epidermal growth factor receptor (EGFR) signaling plays a role in the galvanotactic response as blocking EGFR significantly attenuates the migratory behaviour. These findings suggest direct current electric fields may be implemented in endogenous repair paradigms to promote migration and tissue repair following neurotrauma.

Characterization of Hollow Cathode Performance and Thermal Behavior

NASA Technical Reports Server (NTRS)

Polk, James E.; Goebel, Dan M.; Watkins, Ron; Jameson, Kristina; Yoneshige, Lance; Przybylowski, JoHanna; Cho, Lauren

2006-01-01

Hollow cathodes are one of the main life-limiting components in ion engines and Hall thrusters. Although state-of-the-art hollow cathodes have demonstrated up to 30,352 hours of operation in ground tests with careful handling, future missions are likely to require longer life, more margin and greater resistance to reactive contaminant gases. Three alternate hollow cathode technologies that exploit different emitter materials or geometries to address some of the limitations of state-of-the-art cathodes are being investigated. Performance measurements of impregnated tungsten-iridium dispenser cathodes at discharge currents of 4 to 15 A demonstrated that they have the same operating range and ion production efficiency as conventional tungsten dispenser cathodes. Temperature measurements indicated that tungsten-iridium cathodes also operate at the same emitter temperatures. They did not exhibit the expected reduction in work function at the current densities tested. Hollow cathodes with lanthanum hexaboride emitters operated over a wide current range, but suffered from lower ion production efficiency at currents below about 12.4 A because of higher insert heating requirements. Differences in operating voltages and ion production rates are explained with a simple model of the effect of cathode parameters on discharge behavior.

Forward and reverse control system for induction motors

DOEpatents

Wright, J.T.

1987-09-15

A control system for controlling the direction of rotation of a rotor of an induction motor includes an array of five triacs with one of the triacs applying a current of fixed phase to the windings of the rotor and four of the triacs being switchable to apply either hot ac current or return ac current to the stator windings so as to reverse the phase of current in the stator relative to that of the rotor and thereby reverse the direction of rotation of the rotor. Switching current phase in the stator is accomplished by operating the gates of pairs of the triacs so as to connect either hot ac current or return ac current to the input winding of the stator. 1 fig.

Integrated main rail, feed rail, and current collector

DOEpatents

Petri, Randy J.; Meek, John; Bachta, Robert P.; Marianowski, Leonard G.

1994-01-01

A separator plate for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced.

Thermal management for high-capacity large format Li-ion batteries

DOEpatents

Wang, Hsin; Kepler, Keith Douglas; Pannala, Sreekanth; Allu, Srikanth

2017-05-30

A lithium ion battery includes a cathode in electrical and thermal connection with a cathode current collector. The cathode current collector has an electrode tab. A separator is provided. An anode is in electrical and thermal connection with an anode current collector. The anode current collector has an electrode tab. At least one of the cathode current collector and the anode current collector comprises a thermal tab for heat transfer with the at least one current collector. The thermal tab is separated from the electrode tab. A method of operating a battery is also disclosed.

Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans.

PubMed

Batsikadze, G; Moliadze, V; Paulus, W; Kuo, M-F; Nitsche, M A

2013-04-01

Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA with an electrode size of 35 cm(2) has been shown to induce shifts of cortical excitability during and after stimulation. These shifts are polarity-specific with cathodal tDCS resulting in a decrease and anodal stimulation in an increase of cortical excitability. In clinical and cognitive studies, stronger stimulation intensities are used frequently, but their physiological effects on cortical excitability have not yet been explored. Therefore, here we aimed to explore the effects of 2 mA tDCS on cortical excitability. We applied 2 mA anodal or cathodal tDCS for 20 min on the left primary motor cortex of 14 healthy subjects. Cathodal tDCS at 1 mA and sham tDCS for 20 min was administered as control session in nine and eight healthy subjects, respectively. Motor cortical excitability was monitored by transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) from the right first dorsal interosseous muscle. Global corticospinal excitability was explored via single TMS pulse-elicited MEP amplitudes, and motor thresholds. Intracortical effects of stimulation were obtained by cortical silent period (CSP), short latency intracortical inhibition (SICI) and facilitation (ICF), and I wave facilitation. The above-mentioned protocols were recorded both before and immediately after tDCS in randomized order. Additionally, single-pulse MEPs, motor thresholds, SICI and ICF were recorded every 30 min up to 2 h after stimulation end, evening of the same day, next morning, next noon and next evening. Anodal as well as cathodal tDCS at 2 mA resulted in a significant increase of MEP amplitudes, whereas 1 mA cathodal tDCS decreased corticospinal excitability. A significant shift of SICI and ICF towards excitability enhancement after both 2 mA cathodal and anodal tDCS was observed. At 1 mA, cathodal tDCS reduced single-pulse TMS-elicited MEP amplitudes and shifted SICI and ICF towards inhibition. No significant changes were observed in the other protocols. Sham tDCS did not induce significant MEP alterations. These results suggest that an enhancement of tDCS intensity does not necessarily increase efficacy of stimulation, but might also shift the direction of excitability alterations. This should be taken into account for applications of the stimulation technique using different intensities and durations in order to achieve stronger or longer lasting after-effects.

Nanoporous Ru as a carbon- and binder-free cathode for Li-O2 batteries.

PubMed

Liao, Kaiming; Zhang, Tao; Wang, Yongqing; Li, Fujun; Jian, Zelang; Yu, Haijun; Zhou, Haoshen

2015-04-24

Porous carbon-free cathodes are critical to achieve a high discharge capacity and efficient cycling for rechargeable Li-O2 battery. Herein, we present a very simple method to directly grow nanoporous Ru (composed of polycrystalline particles of ∼5 nm) on one side of a current collector of Ni foam via a galvanic replacement reaction. The resulting Ru@Ni can be employed as a carbon- and binder-free cathode for Li-O2 batteries and delivers a specific capacity of 3720 mAh gRu (-1) at a current density of 200 mA gRu (-1) . 100 cycles of continuous discharge and charge are obtained at a very narrow terminal voltage window of 2.75∼3.75 V with a limited capacity of 1000 mAh gRu (-1) . The good performance of the nanoporous Ru@Ni cathode can be mainly attributed to the effective suppression of the by-products related to carbon or binder, the good adhesion of the catalyst to the current collector, and the good permeation of O2 and electrolyte into the active sites of the nanoporous Ru with the open pore system. This new type electrode provides a snapshot toward developing high-performance carbon- and binder-free Li-O2 batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of a High Current, Long Life Hollow Cathode

NASA Technical Reports Server (NTRS)

VanNoord, Jonathan L.; Kamhawi, Hani; McEwen, Heather K.

2006-01-01

The advent of higher power spacecraft makes it desirable to use higher power electric propulsion thrusters such as ion thrusters or Hall thrusters. Higher power thrusters require cathodes that are capable of producing higher currents. One application of these higher power spacecraft is deep-space missions that require tens of thousands of hours of operation. This paper presents the approach used to design a high current, long life hollow cathode assembly for that application, along with test results from the corresponding hollow cathode. The design approach used for the candidate hollow cathode was to reduce the temperature gradient in the insert, yielding a lower peak temperature and allowing current to be produced more uniformly along the insert. The lower temperatures result in a hollow cathode with increased life. The hollow cathode designed was successfully operated at currents from 10 to 60 A with flow rates of 5 to 19 sccm with a maximum orifice temperature measured of 1100 C. Data including discharge voltage, keeper voltage, discharge current, flow rates, and orifice plate temperatures are presented.

Cathodic current enhancement via manganese and oxygen related reactions in marine biofilms

NASA Astrophysics Data System (ADS)

Strom, Matthew James

Corrosion is a threat that has economic, and environmental impacts worldwide. Many types of corrosive attack are the subject of ongoing research. One of these areas of research is microbiologically influenced corrosion, which is the enhancement and/or initiation of corrosion events caused by microorganisms. It is well known that colonies of microorganisms can enhance cathodic currents through biofilm formation. The aim of the present work was to elucidate the role of manganese in enhancing cathodic currents in the presence of biofilms. Repeated polarizations conducted in Delaware Bay waters, on biofilm coated Cr identified potentially sustainable reduction reactions. The reduction of MnO2 and the enhancement of the oxygen reduction reaction (ORR) were proven to be factors that influence cathodic current enhancement. The removal of ambient oxygen during polarizations resulted in a shutdown of cathodic current enhancement. These field data led to an exploration of the synergistic relationship between MnO2 and the ORR. Laboratory studies of the catalysis of peroxide disproportionation by MnO2 were monitored using a hanging mercury drop electrode. Experiments were run at an ambient sweater pH of 8 and pH 9, which simulated the near-surface conditions typical of cathodes immersed in seawater. Rapid reoxidation at the more basic pH was shown to allow manganese to behave as a persistent catalyst under the typical electrochemical surface conditions of a cathode. As a result a mechanism for ORR enhancement by manganese was proposed as a unique mechanism for cathodic current enhancement in biofilms. A separate field study of Delaware biofilms on stainless steel coupled to a sacrificial Al anode was carried out to identify the ORR enhancement mechanism and sustainable redox reactions at the cathode. Chemical treatments of glutaraldehyde and formaldoxime were applied to cathodes with biofilms to distinguish between enzymatic and MnO2 related ORR enhancement. The results ruled out the enzymatic catalysis of ORR and supported the catalysis by MnO2. Sustainable redox reactions at the cathode were evaluated by monitoring the cathodic current of biofilm coated stainless steel for a year under different polarization intensities. The results showed that sustainable cathodic reactions were present in marine biofilms but their influence on the cathodic current was negligible until a potential was reached where the ORR could take place. Additionally seasonal variability was observed in the enhanced cathodic current in Delaware Bay biofilms. This was attributed to the seasonal variability of manganese in the water column.

A study of cathode erosion in high power arcjets

NASA Astrophysics Data System (ADS)

Harris, William Jackson, III

Cathode erosion continues to be one of the predominant technology concerns for high power arcjets. This study will show that cathode erosion in these devices is significantly affected by several mitigating factors, including propellant composition, propellant flowrate, current level, cathode material, and power supply current ripple. In a series of 50-hour and 100-hour long duration experiments, using a water-cooled 30 kilowatt laboratory arcjet, variations in the steady-state cathode erosion rate were characterized for each of these factors using nitrogen propellant at a fixed arc current of 250 Amperes. A complementary series of measurements was made using hydrogen propellant at an arc current of 100 Amperes. The cold cathode erosion rate was also differentiated from the steady-state cathode erosion rate in a series of multi-start cathode erosion experiments. Results of these measurements are presented, along with an analysis of the significant effects of current ripple on arcjet cathode erosion. As part of this study, over a dozen refractory cathode materials were evaluated to measure their resistance to arcjet cathode erosion. Among the materials tested were W-ThO2(1%, 2%, 4%), poly and mono-crystalline W, W-LaB6, W-La2O3, W-BaO2, W-BaCaAl2O4, W-Y2O3, and ZrB2. Based on these measurements, several critical material properties were identified, such work function, density, porosity, melting point, and evaporation rate. While the majority of the materials failed to outperform traditional W-ThO2, these experimental results are used to develop a parametric model of the arcjet cathode physics. The results of this model, and the results of a finite-element thermal analysis of the arcjet cathode, are presented to better explain the relative performance of the materials tested.

Local Neutral Density and Plasma Parameter Measurements in a Hollow Cathode Plume

NASA Technical Reports Server (NTRS)

Jameson, Kristina K.; Goebel, Dan M.; MiKellides, Joannis; Watkins, Ron M.

2006-01-01

In order to understand the cathode and keeper wear observed during the Extended Life Test (ELT) of the DS1 flight spare NSTAR thruster and provide benchmarking data for a 2D cathode/cathode-plume model, a basic understanding of the plasma and neutral gas parameters in the cathode orifice and keeper region of the cathode plume must be obtained. The JPL cathode facility is instrumented with an array of Langmuir probe diagnostics along with an optical diagnostic to measure line intensity of xenon neutrals. In order to make direct comparisons with the present model, a flat plate anode arrangement was installed for these tests. Neutral density is deduced from the scanning probe data of the plasma parameters and the measured xenon line intensity in the optical regime. The Langmuir probes are scanned both axially, out to 7.0 cm downstream of the keeper, and radially to obtain 2D profile of the plasma parameters. The optical fiber is housed in a collimating stainless steel tube, and is scanned to view across the cathode plume along cuts in front of the keeper with a resolution of 1.5 mm. The radial intensities are unfolded using the Abel inversion technique that produces radial profiles of local neutral density. In this paper, detailed measurements of the plasma parameters and the local neutral densities will be presented in the cathode/keeper plume region for a 1.5 cm diameter NEXIS cathode at 25A of discharge current at several different strengths of applied magnetic field.

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

Dubinov, Alexander E.; Petrik, Alexey G.; Kurkin, Semen A.

We report on the possibility of the beam-plasma instability development in the system with electron beam interacting with the single-component hot electron plasma without ions. As considered system, we analyse the interaction of the low-current relativistic electron beam (REB) with squeezed state in the high-current REB formed in the relativistic magnetically insulated two-section vircator drift space. The numerical analysis is provided by means of 3D electromagnetic simulation in CST Particle Studio. We have conducted an extensive study of characteristic regimes of REB dynamics determined by the beam-plasma instability development in the absence of ions. As a result, the dependencies ofmore » instability increment and wavelength on the REB current value have been obtained. The considered process brings the new mechanism of controlled microwave amplification and generation to the device with a virtual cathode. This mechanism is similar to the action of the beam-plasma amplifiers and oscillators.« less

Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS).

PubMed

Lefaucheur, Jean-Pascal; Antal, Andrea; Ayache, Samar S; Benninger, David H; Brunelin, Jérôme; Cogiamanian, Filippo; Cotelli, Maria; De Ridder, Dirk; Ferrucci, Roberta; Langguth, Berthold; Marangolo, Paola; Mylius, Veit; Nitsche, Michael A; Padberg, Frank; Palm, Ulrich; Poulet, Emmanuel; Priori, Alberto; Rossi, Simone; Schecklmann, Martin; Vanneste, Sven; Ziemann, Ulf; Garcia-Larrea, Luis; Paulus, Walter

2017-01-01

A group of European experts was commissioned by the European Chapter of the International Federation of Clinical Neurophysiology to gather knowledge about the state of the art of the therapeutic use of transcranial direct current stimulation (tDCS) from studies published up until September 2016, regarding pain, Parkinson's disease, other movement disorders, motor stroke, poststroke aphasia, multiple sclerosis, epilepsy, consciousness disorders, Alzheimer's disease, tinnitus, depression, schizophrenia, and craving/addiction. The evidence-based analysis included only studies based on repeated tDCS sessions with sham tDCS control procedure; 25 patients or more having received active treatment was required for Class I, while a lower number of 10-24 patients was accepted for Class II studies. Current evidence does not allow making any recommendation of Level A (definite efficacy) for any indication. Level B recommendation (probable efficacy) is proposed for: (i) anodal tDCS of the left primary motor cortex (M1) (with right orbitofrontal cathode) in fibromyalgia; (ii) anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) (with right orbitofrontal cathode) in major depressive episode without drug resistance; (iii) anodal tDCS of the right DLPFC (with left DLPFC cathode) in addiction/craving. Level C recommendation (possible efficacy) is proposed for anodal tDCS of the left M1 (or contralateral to pain side, with right orbitofrontal cathode) in chronic lower limb neuropathic pain secondary to spinal cord lesion. Conversely, Level B recommendation (probable inefficacy) is conferred on the absence of clinical effects of: (i) anodal tDCS of the left temporal cortex (with right orbitofrontal cathode) in tinnitus; (ii) anodal tDCS of the left DLPFC (with right orbitofrontal cathode) in drug-resistant major depressive episode. It remains to be clarified whether the probable or possible therapeutic effects of tDCS are clinically meaningful and how to optimally perform tDCS in a therapeutic setting. In addition, the easy management and low cost of tDCS devices allow at home use by the patient, but this might raise ethical and legal concerns with regard to potential misuse or overuse. We must be careful to avoid inappropriate applications of this technique by ensuring rigorous training of the professionals and education of the patients. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Polarity-Dependent Misperception of Subjective Visual Vertical during and after Transcranial Direct Current Stimulation (tDCS)

PubMed Central

Santos-Pontelli, Taiza E. G.; Rimoli, Brunna P.; Favoretto, Diandra B.; Mazin, Suleimy C.; Truong, Dennis Q.; Leite, Joao P.; Pontes-Neto, Octavio M.; Babyar, Suzanne R.; Reding, Michael; Bikson, Marom; Edwards, Dylan J.

2016-01-01

Pathologic tilt of subjective visual vertical (SVV) frequently has adverse functional consequences for patients with stroke and vestibular disorders. Repetitive transcranial magnetic stimulation (rTMS) of the supramarginal gyrus can produce a transitory tilt on SVV in healthy subjects. However, the effect of transcranial direct current stimulation (tDCS) on SVV has never been systematically studied. We investigated whether bilateral tDCS over the temporal-parietal region could result in both online and offline SVV misperception in healthy subjects. In a randomized, sham-controlled, single-blind crossover pilot study, thirteen healthy subjects performed tests of SVV before, during and after the tDCS applied over the temporal-parietal region in three conditions used on different days: right anode/left cathode; right cathode/left anode; and sham. Subjects were blind to the tDCS conditions. Montage-specific current flow patterns were investigated using computational models. SVV was significantly displaced towards the anode during both active stimulation conditions when compared to sham condition. Immediately after both active conditions, there were rebound effects. Longer lasting after-effects towards the anode occurred only in the right cathode/left anode condition. Current flow models predicted the stimulation of temporal-parietal regions under the electrodes and deep clusters in the posterior limb of the internal capsule. The present findings indicate that tDCS over the temporal-parietal region can significantly alter human SVV perception. This tDCS approach may be a potential clinical tool for the treatment of SVV misperception in neurological patients. PMID:27031726

Reduced Current Spread by Concentric Electrodes in Transcranial Electrical Stimulation (tES).

PubMed

Bortoletto, M; Rodella, C; Salvador, R; Miranda, P C; Miniussi, C

2016-01-01

We propose the use of a new montage for transcranial direct current stimulation (tDCS), called concentric electrodes tDCS (CE-tDCS), involving two concentric round electrodes that may improve stimulation focality. To test efficacy and focality of CE-tDCS, we modelled the current distribution and tested physiological effects on cortical excitability. Motor evoked potentials (MEPs) from first dorsal interosseous (FDI) and abductor digiti minimi (ADM) were recorded before and after the delivery of anodal, cathodal and sham stimulation on the FDI hotspot for 10 minutes. MEP amplitude of FDI increased after anodal-tDCS and decreased after cathodal-tDCS, supporting the efficacy of CE-tDCS in modulating cortical excitability. Moreover, modelled current distribution and no significant effects of stimulation on MEP amplitude of ADM suggest high focality of CE-tDCS. CE-tDCS may allow a better control of current distribution and may represent a novel tool for applying tDCS and other transcranial current stimulation approaches. Copyright © 2016 Elsevier Inc. All rights reserved.

Methanol-tolerant cathode catalyst composite for direct methanol fuel cells

DOEpatents

Zhu, Yimin; Zelenay, Piotr

2006-09-05

A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of Pt.sub.3Cr/C so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

DOEpatents

Zhu, Yimin; Zelenay, Piotr

2006-03-21

A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

Separator plate for a fuel cell

DOEpatents

Petri, R.J.; Meek, J.; Bachta, R.P.; Marianowski, L.G.

1996-04-02

A separator plate is described for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced. 9 figs.

Separator plate for a fuel cell

DOEpatents

Petri, Randy J.; Meek, John; Bachta, Robert P.; Marianowski, Leonard G.

1996-01-01

A separator plate for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced.

Microwave beamed power technology improvement. [magnetrons and slotted waveguide arrays

NASA Technical Reports Server (NTRS)

Brown, W. C.

1980-01-01

The magnetron directional amplifier was tested for (1) phase shift and power output as a function of gain, anode current, and anode voltage, (2) background noise and harmonics in the output, (3) long life potential of the magnetron cathode, and (4) high operational efficiency. Examples of results were an adequate range of current and voltage over which 20 dB of amplification could be obtained, spectral noise density 155 dB below the carrier, 81.7% overall efficiency, and potential cathode life of 50 years in a design for solar power satellite use. A fabrication method was used to fabricate a 64 slot, 30 in square slotted waveguide array module from 0.020 in thick aluminum sheet. The test results on the array are discussed.

TRANSVERSE IMPEDANCE OF THE SQUID GIANT AXON DURING CURRENT FLOW

PubMed Central

Cole, Kenneth S.; Baker, Richard F.

1941-01-01

The change in the transverse impedance of the squid giant axon caused by direct current flow has been measured at frequencies from 1 kc. per second to 500 kc. per second. The impedance change is equivalent to an increase of membrane conductance at the cathode to a maximum value approximately the same as that obtained during activity and a decrease at the anode to a minimum not far from zero. There is no evidence of appreciable membrane capacity change in either case. It then follows that the membrane has the electrical characteristics of a rectifier. Interpreting the membrane conductance as a measure of ion permeability, this permeability is increased at the cathode and decreased at the anode. PMID:19873233

Experimental Analysis of Pseudospark Sourced Electron Beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Pal, U. N.; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.

2011-12-01

The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

Drift waves control using emissive cathodes in the laboratory

NASA Astrophysics Data System (ADS)

Plihon, N.; Desangles, V.; De Giorgio, E.; Bousselin, G.; Marino, R.; Pustelnik, N.; Poye, A.

2017-12-01

Low frequency plasma fluctuations are known to be the cause of strong transport perpendicular to magnetic guiding field line. These low frequency drift waves have been studied in linear devices in the laboratory over the last two decades. Their excitation or mitigation have been addressed using different drives, such as ring biasing or electromagnetic low frequency fields. Here we present an experimental characterization of the behavior of drift waves when the profile of the background plasma rotation is controlled using hot emissive cathodes. We show that electron emission from the cathodes modify the plasma potential, which in turn controls the rotation profile. Mitigation or enhancement of drift waves (on the amplitude or azimuthal mode number) is observed depending on the plasma rotation profile.

Integrated main rail, feed rail, and current collector

DOEpatents

Petri, R.J.; Meek, J.; Bachta, R.P.; Marianowski, L.G.

1994-11-08

A separator plate is described for a fuel cell comprising an anode current collector, a cathode current collector and a main plate, the main plate disposed between the anode current collector and the cathode current collector. The anode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the anode side of the separator plate and the cathode current collector forms a flattened peripheral wet seal structure and manifold wet seal structure on the cathode side of the separator plate. In this manner, the number of components required to manufacture and assemble a fuel cell stack is reduced. 9 figs.

Stationary semi-solid battery module and method of manufacture

DOEpatents

Slocum, Alexander; Doherty, Tristan; Bazzarella, Ricardo; Cross, III, James C.; Limthongkul, Pimpa; Duduta, Mihai; Disko, Jeffry; Yang, Allen; Wilder, Throop; Carter, William Craig; Chiang, Yet-Ming

2015-12-01

A method of manufacturing an electrochemical cell includes transferring an anode semi-solid suspension to an anode compartment defined at least in part by an anode current collector and an separator spaced apart from the anode collector. The method also includes transferring a cathode semi-solid suspension to a cathode compartment defined at least in part by a cathode current collector and the separator spaced apart from the cathode collector. The transferring of the anode semi-solid suspension to the anode compartment and the cathode semi-solid to the cathode compartment is such that a difference between a minimum distance and a maximum distance between the anode current collector and the separator is maintained within a predetermined tolerance. The method includes sealing the anode compartment and the cathode compartment.

Presynaptic and postsynaptic effects of local cathodal DC polarization within the spinal cord in anaesthetized animal preparations

PubMed Central

Bolzoni, F; Jankowska, E

2015-01-01

The present study aimed to compare presynaptic and postsynaptic actions of direct current polarization in the spinal cord, focusing on DC effects on primary afferents and motoneurons. To reduce the directly affected spinal cord region, a weak polarizing direct current (0.1–0.3 μA) was applied locally in deeply anaesthetized cats and rats; within the hindlimb motor nuclei in the caudal lumbar segments, or in the dorsal horn within the terminal projection area of low threshold skin afferents. Changes in the excitability of primary afferents activated by intraspinal stimuli (20–50 μA) were estimated using increases or decreases in compound action potentials recorded from the dorsal roots or peripheral nerves as their measure. Changes in the postsynaptic actions of the afferents were assessed from intracellularly recorded monosynaptic EPSPs in hindlimb motoneurons and monosynaptic extracellular field potentials (evoked by group Ia afferents in motor nuclei, or by low threshold cutaneous afferents in the dorsal horn). The excitability of motoneurons activated by intraspinal stimuli was assessed using intracellular records or motoneuronal discharges recorded from a ventral root or a muscle nerve. Cathodal polarization was found to affect motoneurons and afferents providing input to them to a different extent. The excitability of both was markedly increased during DC application, although post-polarization facilitation was found to involve presynaptic afferents and some of their postsynaptic actions, but only negligibly motoneurons themselves. Taken together, these results indicate that long-lasting post-polarization facilitation of spinal activity induced by locally applied cathodal current primarily reflects the facilitation of synaptic transmission. PMID:25416625

Pharmacological modulation of cortical excitability shifts induced by transcranial direct current stimulation in humans.

PubMed

Nitsche, M A; Fricke, K; Henschke, U; Schlitterlau, A; Liebetanz, D; Lang, N; Henning, S; Tergau, F; Paulus, W

2003-11-15

Transcranial direct current stimulation (tDCS) of the human motor cortex results in polarity-specific shifts of cortical excitability during and after stimulation. Anodal tDCS enhances and cathodal stimulation reduces excitability. Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation, while cathodal tDCS hyperpolarises cortical neurones. However, not much is known about the ion channels and receptors involved in these effects. Thus, the impact of the sodium channel blocker carbamazepine, the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested. tDCS-protocols inducing excitability alterations (1) only during tDCS and (2) eliciting long-lasting after-effects were applied after drug administration. Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS. Flunarizine resulted in similar changes. Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation, which elicits no after-effects, but prevented the induction of long-lasting after-effects independent of their direction. These results suggest that, like in other animals, cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation, thus modulating the conductance of sodium and calcium channels. Moreover, they suggest that the after-effects may be NMDA receptor dependent. Since NMDA receptors are involved in neuroplastic changes, the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting. The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications.

Pharmacological modulation of cortical excitability shifts induced by transcranial direct current stimulation in humans

PubMed Central

Nitsche, M A; Fricke, K; Henschke, U; Schlitterlau, A; Liebetanz, D; Lang, N; Henning, S; Tergau, F; Paulus, W

2003-01-01

Transcranial direct current stimulation (tDCS) of the human motor cortex results in polarity-specific shifts of cortical excitability during and after stimulation. Anodal tDCS enhances and cathodal stimulation reduces excitability. Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation, while cathodal tDCS hyperpolarises cortical neurones. However, not much is known about the ion channels and receptors involved in these effects. Thus, the impact of the sodium channel blocker carbamazepine, the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested. tDCS-protocols inducing excitability alterations (1) only during tDCS and (2) eliciting long-lasting after-effects were applied after drug administration. Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS. Flunarizine resulted in similar changes. Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation, which elicits no after-effects, but prevented the induction of long-lasting after-effects independent of their direction. These results suggest that, like in other animals, cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation, thus modulating the conductance of sodium and calcium channels. Moreover, they suggest that the after-effects may be NMDA receptor dependent. Since NMDA receptors are involved in neuroplastic changes, the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting. The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS, which may have important future clinical applications. PMID:12949224

Mechanistic Study of Electrolyte Additives to Stabilize High-Voltage Cathode-Electrolyte Interface in Lithium-Ion Batteries.

PubMed

Gao, Han; Maglia, Filippo; Lamp, Peter; Amine, Khalil; Chen, Zonghai

2017-12-27

Current developments of electrolyte additives to stabilize electrode-electrolyte interface in lithium-ion batteries highly rely on a trial-and-error search, which involves repetitive testing and intensive amount of resources. The lack of understandings on the fundamental protection mechanisms of the additives significantly increases the difficulty for the transformational development of new additives. In this study, we investigated two types of individual protection routes to build a robust cathode-electrolyte interphase at high potentials: (i) a direct reduction in the catalytic decomposition of the electrolyte solvent; and (ii) formation of a "corrosion inhibitor film" that prevents severely attack and passivation from protons that generated from the solvent oxidation, even the decomposition of solvent cannot be mitigated. Effect of two exemplary electrolyte additives, lithium difluoro(oxalato)borate (LiDFOB) and 3-hexylthiophene (3HT), on LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC 622) cathode were investigated to validate our hypothesis. It is demonstrated that understandings of both electrolyte additives and solvent are essential and careful balance between the cathode protection mechanism of additives and their side effects is critical to obtain optimum results. More importantly, this study opens up new directions of rational design of functional electrolyte additives for the next-generation high-energy-density lithium-ion chemistries.

Effect of cathode cooling efficiency and oxygen plasma gas pressure on the hafnium cathode wall temperature

NASA Astrophysics Data System (ADS)

Ashtekar, Koustubh; Diehl, Gregory; Hamer, John

2012-10-01

The hafnium cathode is widely used in DC plasma arc cutting (PAC) under an oxygen gas environment to cut iron and iron alloys. The hafnium erosion is always a concern which is controlled by the surface temperature. In this study, the effect of cathode cooling efficiency and oxygen gas pressure on the hafnium surface temperature are quantified. The two layer cathode sheath model is applied on the refractive hafnium surface while oxygen species (O2, O, O+, O++, e-) are considered within the thermal dis-equilibrium regime. The system of non-linear equations comprising of current density balance, heat flux balance at both the cathode surface and the sheath-ionization layer is coupled with the plasma gas composition solver. Using cooling heat flux, gas pressure and current density as inputs; the cathode wall temperature, electron temperature, and sheath voltage drop are calculated. Additionally, contribution of emitted electron current (Je) and ions current (Ji) to the total current flux are estimated. Higher gas pressure usually reduces Ji and increases Je that reduces the surface temperature by thermionic cooling.

Studies of Microdischarge Plasma Thrusters for Nanosatellite Propulsion

DTIC Science & Technology

2009-09-30

sections 0^ based on the Lennard - Jones interaction potentials14 are used to determine the neutral transport properties using vk = nk gkt^kb, where g... potential that exists between the MPT and the vacuum. The expulsion of hot gas and ions into the vacuum generates thrust. So far the MPT has been...cathode and e2 is at a potential between ej and e3. In fig. 3 b, ei is anode and e3 is cathode whereas e2 is floating. The power supply for ei is

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

Beilis, I. I.

Experiments in the last decade showed that for cathode spots in a magnetic field that obliquely intercepts the cathode surface, the current per spot increased with the transverse component of the magnetic field and decreased with the normal component. The present work analyzes the nature of cathode spot splitting in an oblique magnetic field. A physical model for cathode spot current splitting was developed, which considered the relation between the plasma kinetic pressure, self-magnetic pressure, and applied magnetic pressure in a current carrying cathode plasma jet. The current per spot was calculated, and it was found to increase with themore » tangential component of the magnetic field and to decrease with the normal component, which agrees well with the experimental dependence.« less

Electrodeposition of molten silicon

DOEpatents

De Mattei, Robert C.; Elwell, Dennis; Feigelson, Robert S.

1981-01-01

Silicon dioxide is dissolved in a molten electrolytic bath, preferably comprising barium oxide and barium fluoride. A direct current is passed between an anode and a cathode in the bath to reduce the dissolved silicon dioxide to non-alloyed silicon in molten form, which is removed from the bath.

Method for manufacturing high quality carbon nanotubes

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M. (Inventor)

2006-01-01

A non-catalytic process for the production of carbon nanotubes includes supplying an electric current to a carbon anode and a carbon cathode which have been securely positioned in the open atmosphere with a gap between them. The electric current creates an electric arc between the carbon anode and the carbon cathode, which causes carbon to be vaporized from the carbon anode and a carbonaceous residue to be deposited on the carbon cathode. Inert gas is pumped into the gap to flush out oxygen, thereby preventing interference with the vaporization of carbon from the anode and preventing oxidation of the carbonaceous residue being deposited on the cathode. The anode and cathode are cooled while electric current is being supplied thereto. When the supply of electric current is terminated, the carbonaceous residue is removed from the cathode and is purified to yield carbon nanotubes.

Preliminary Results of Field Emission Cathode Tests

NASA Technical Reports Server (NTRS)

Sovey, James S.; Kovaleski, Scott D.

2001-01-01

Preliminary screening tests of field emission cathodes such as chemical vapor deposited (CVD) diamond, textured pyrolytic graphite, and textured copper were conducted at background pressures typical of electric thruster test facilities to assess cathode performance and stability. Very low power electric thrusters which provide tens to hundreds micronewtons of thrust may need field emission neutralizers that have a capability of tens to hundreds of microamperes. From current voltage characteristics, it was found that the CVD diamond and textured metals cathodes clearly satisfied the Fowler-Nordheim emission relation. The CVD diamond and a textured copper cathode had average current densities of 270 and 380 mA/sq cm, respectively, at the beginning-of-life. After a few hours of operation the cathode emission currents degraded by 40 to 75% at background pressures in the 10(exp -5) Pa to 10(exp -4) Pa range. The textured pyrolytic graphite had a modest current density at beginning-of-life of 84 mA/sq cm, but this cathode was the most stable of all. Extended testing of the most promising cathodes is warranted to determine if current degradation is a burn-in effect or whether it is a long-term degradation process. Preliminary experiments with ferroelectric emission cathodes, which are ceramics with spontaneous electric polarization, were conducted. Peak current densities of 30 to 120 mA/sq cm were obtained for pulse durations of about 500 ns in the 10(exp -4) Pa pressure range.

Static gas-liquid interfacial direct current discharge plasmas using ionic liquid cathode

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

Kaneko, T.; CREST/JST, Tokyo 102-0075; Baba, K.

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we have succeeded in creating the static and stable gas (plasmas)-liquid (ionic liquids) interfacial field using a direct current discharge under a low gas pressure condition. It is clarified that the ionic liquid works as a nonmetal liquid electrode, and furthermore, a secondary electron emission coefficient of the ionic liquid is larger than that of conventional metal electrodes. The plasma potential structure of the gas-liquid interfacial region, and resultant interactions between the plasma and the ionic liquid are revealed by changingmore » a polarity of the electrode in the ionic liquid. By utilizing the ionic liquid as a cathode electrode, the positive ions in the plasma region are found to be irradiated to the ionic liquid. This ion irradiation causes physical and chemical reactions at the gas-liquid interfacial region without the vaporization of the ionic liquid.« less

Effect of Anodal and Cathodal Transcranial Direct Current Stimulation on DLPFC on Modulation of Inhibitory Control in ADHD.

PubMed

Soltaninejad, Zahra; Nejati, Vahid; Ekhtiari, Hamed

2015-12-20

The purpose of this study was to improve the inhibitory control functions through transcranial direct current stimulation (tDCS) in adolescents with ADHD symptoms. Twenty high school students with ADHD symptoms participated in this single-blinded, crossover, sham-controlled study. All the participants were tested during the application of Stroop and Go/No-Go tasks that is used to measure inhibitory control, using 1.5 mA of tDCS for 15 min over the left dorsolateral prefrontal cortex (DLPFC). Anodal stimulation on left DLPFC had no effect on interference inhibition during the Stroop task and increased the proportion of correct responses in the "Go stage" of the Go/No-Go test compared with sham condition. Cathodal stimulation on the left DLPFC increased the inhibition accuracy in the inhibition stage during Go/No-Go task in comparison with sham. tDCS over the left DLPFC of adolescents who suffer from ADHD symptoms can improve inhibitory control in prepotent response inhibition. © The Author(s) 2015.

Miniaturized cathodic arc plasma source

DOEpatents

Anders, Andre; MacGill, Robert A.

2003-04-15

A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

Experimental Investigation of Pseudospark generated electron beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.; Pal, U. N.

2012-11-01

The pseudospark (PS) discharge is, however, more recently recognized as a different type of discharge which is capable of generating electron beams with the highest combined current density and brightness of any known type of electron source. PS discharge is a specific type of gas discharge, which operates on the left-hand side of the hollow cathode analogy to the Paschen curve with axially symmetric parallel electrodes and central holes on the electrodes. The PS discharge generated electron beam has tremendous applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been carried out experimentally for different applied voltages. The investigation has been done at different axial and radial location inside the drift tube in argon atmosphere. This paper represents experimentally derived axial and radial variation of the beam current inside the plasma filled drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed. It has been further confirmed the successful propagation of electron beam in confined manner without any assistance of external magnetic field.

Influence of emission threshold of explosive emission cathodes on current waveform in foilless diodes

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

Wu, P.; Liu, G. Z.; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024

The emission threshold of explosive emission cathodes (EECs) is an important factor for beam quality. It can affect the explosive emission delay time, the plasma expansion process on the cathode surface, and even the current amplitude when the current is not fully space-charge-limited. This paper researches the influence of the emission threshold of an annular EEC on the current waveform in a foilless diode when the current is measured by a Rogowski coil. The particle-in-cell simulation which is performed under some tolerable and necessary simplifications shows that the long explosive emission delay time of high-threshold cathodes may leave an apparentmore » peak of displacement current on the rise edge of the current waveform, and this will occur only when the electron emission starts after this peak. The experimental researches, which are performed under a diode voltage of 1 MV and a repetitive frequency of 20 Hz, demonstrate that the graphite cathode has a lower emission threshold and a longer lifetime than the stainless steel cathode according to the variation of the peak of displacement current on the rise edge of the current waveform.« less

A Single-Chamber Microbial Fuel Cell without an Air Cathode

PubMed Central

Nimje, Vanita Roshan; Chen, Chien-Cheng; Chen, Hau-Ren; Chen, Chien-Yen; Tseng, Min-Jen; Cheng, Kai-Chien; Shih, Ruey-Chyuan; Chang, Young-Fo

2012-01-01

Microbial fuel cells (MFCs) represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM) as the carbon source and nitrate (1 mM) as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (Rext) of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm2 was achieved at an Rext of 220 Ω. Cyclic voltammograms (CV) showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE) of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater. PMID:22489190

Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams.

PubMed

Liu, Lie; Li, Limin; Wen, Jianchun; Wan, Hong

2009-02-01

This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a approximately 450 kV, approximately 400 ns pulse. It was found that 300-400 MW, approximately 250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.

Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

DOEpatents

Leung, Ka-Ngo; Gordon, K.C.; Kippenhan, D.O.; Purgalis, P.; Moussa, D.; Williams, M.D.; Wilde, S.B.; West, M.W.

1987-10-16

A large area directly heated lanthanum hexaboride (LaB/sub 6/) cathode system is disclosed. The system comprises a LaB/sub 6/ cathode element generally circular in shape about a central axis. The cathode element has a head with an upper substantially planar emission surface, and a lower downwardly and an intermediate body portion which diminishes in cross-section from the head towards the base of the cathode element. A central rod is connected to the base of the cathode element and extends along the central axis. Plural upstanding spring fingers are urged against an outer peripheral contact surface of the head end to provide a mechanical and electrical connection to the cathode element. 7 figs

Xenon excimer emission from pulsed high-pressure capillary microdischarges

NASA Astrophysics Data System (ADS)

Lee, Byung-Joon; Rahaman, Hasibur; Petzenhauser, Isfried; Frank, Klaus; Giapis, Konstantinos P.

2007-06-01

Intense xenon vacuum ultraviolet (VUV) emission is observed from a high-pressure capillary cathode microdischarge in direct current operation, by superimposing a high-voltage pulse of 50ns duration. Under stagnant gas conditions, the total VUV light intensity increases linearly with pressure from 400 to 1013mbar for a fixed voltage pulse. At fixed pressure, however, the VUV light intensity increases superlinearly with voltage pulse height ranging from 08to2.8kV. Gains in emission intensity are obtained by inducing gas flow through the capillary cathode, presumably because of excimer dimer survival due to gas cooling.

Low-threshold field emission in planar cathodes with nanocarbon materials

NASA Astrophysics Data System (ADS)

Zhigalov, V.; Petukhov, V.; Emelianov, A.; Timoshenkov, V.; Chaplygin, Yu.; Pavlov, A.; Shamanaev, A.

2016-12-01

Nanocarbon materials are of great interest as field emission cathodes due to their low threshold voltage. In this work current-voltage characteristics of nanocarbon electrodes were studied. Low-threshold emission was found in planar samples where field enhancement is negligible (<10). Electron work function values, calculated by Fowler-Nordheim theory, are anomalous low (<1 eV) and come into collision with directly measured work function values in fabricated planar samples (4.1-4.4 eV). Non-applicability of Fowler-Nordheim theory for the nanocarbon materials was confirmed. The reasons of low-threshold emission in nanocarbon materials are discussed.

A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron

PubMed Central

Yuan, Xuesong; Zhu, Weiwei; Zhang, Yu; Xu, Ningsheng; Yan, Yang; Wu, Jianqiang; Shen, Yan; Chen, Jun; She, Juncong; Deng, Shaozhi

2016-01-01

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun. PMID:27609247

A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron.

PubMed

Yuan, Xuesong; Zhu, Weiwei; Zhang, Yu; Xu, Ningsheng; Yan, Yang; Wu, Jianqiang; Shen, Yan; Chen, Jun; She, Juncong; Deng, Shaozhi

2016-09-09

Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun.

Ionic liquid-assisted solvothermal synthesis of hollow Mn2O3 anode and LiMn2O4 cathode materials for Li-ion batteries

NASA Astrophysics Data System (ADS)

He, Xin; Wang, Jun; Jia, Haiping; Kloepsch, Richard; Liu, Haidong; Beltrop, Kolja; Li, Jie

2015-10-01

Mn-based Mn2O3 anode and LiMn2O4 cathode materials are prepared by a solvothermal method combined with post annealing process. Environmentally friendly ionic liquid 1-Butyl-3-methylimidazolium tetrafluoroborate as both structure-directing agent and fluorine source is used to prepare hollow polyhedron MnF2 precursor. Both target materials Mn2O3 anode and LiMn2O4 cathode have the morphology of the MnF2 precursor. The Mn2O3 anode using carboxymethyl cellulose as binder could deliver slight better electrochemical performance than the one using poly (vinyldifluoride) as binder. The former has an initial charge capacity of 800 mAh g-1 at a current density of 101.8 mA g-1, and exhibits no obvious capacity decay for 150 cycles at 101.8 mA g-1. The LiMn2O4 cathode material prepared with molten salt assistant could display much better electrochemical performance than the one prepared without molten salt assistance. In particular, it has an initial discharge capacity of 117.5 mAh g-1 at a current density of 0.5C and good rate capability. In the field of lithium ion batteries, both the Mn2O3 anode and LiMn2O4 cathode materials could exhibit enhanced electrochemical performance due to the well formed morphology based on the ionic liquid-assisted solvothermal method.

ε-MnO2 nanostructures directly grown on Ni foam: a cathode catalyst for rechargeable Li-O2 batteries.

PubMed

Hu, Xiaofei; Han, Xiaopeng; Hu, Yuxiang; Cheng, Fangyi; Chen, Jun

2014-04-07

A sponge-like ε-MnO2 nanostructure was synthesized by direct growth of ε-MnO2 on Ni foam through a facile electrodeposition route. When applied as a self-supporting, binder-free cathode material for rechargeable nonaqueous lithium-oxygen batteries, the ε-MnO2/Ni electrode exhibits considerable high-rate capability (discharge capacity of ∼6300 mA h g(-1) at a current density of 500 mA g(-1)) and enhanced cyclability (exceeding 120 cycles) without controlling the discharge depth. The superior performance is proposed to be associated with the 3D nanoporous structures and abundant oxygen defects as well as the absence of side reactions related to carbon-based conductive additives and binders.

Remote control for anode-cathode adjustment

DOEpatents

Roose, Lars D.

1991-01-01

An apparatus for remotely adjusting the anode-cathode gap in a pulse power machine has an electric motor located within a hollow cathode inside the vacuum chamber of the pulse power machine. Input information for controlling the motor for adjusting the anode-cathode gap is fed into the apparatus using optical waveguides. The motor, controlled by the input information, drives a worm gear that moves a cathode tip. When the motor drives in one rotational direction, the cathode is moved toward the anode and the size of the anode-cathode gap is diminished. When the motor drives in the other direction, the cathode is moved away from the anode and the size of the anode-cathode gap is increased. The motor is powered by batteries housed in the hollow cathode. The batteries may be rechargeable, and they may be recharged by a photovoltaic cell in combination with an optical waveguide that receives recharging energy from outside the hollow cathode. Alternatively, the anode-cathode gap can be remotely adjusted by a manually-turned handle connected to mechanical linkage which is connected to a jack assembly. The jack assembly converts rotational motion of the handle and mechanical linkage to linear motion of the cathode moving toward or away from the anode.

Development and Testing of High Current Hollow Cathodes for High Power Hall Thrusters

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Van Noord, Jonathan

2012-01-01

NASA's Office of the Chief Technologist In-Space Propulsion project is sponsoring the testing and development of high power Hall thrusters for implementation in NASA missions. As part of the project, NASA Glenn Research Center is developing and testing new high current hollow cathode assemblies that can meet and exceed the required discharge current and life-time requirements of high power Hall thrusters. This paper presents test results of three high current hollow cathode configurations. Test results indicated that two novel emitter configurations were able to attain lower peak emitter temperatures compared to state-of-the-art emitter configurations. One hollow cathode configuration attained a cathode orifice plate tip temperature of 1132 degC at a discharge current of 100 A. More specifically, test and analysis results indicated that a novel emitter configuration had minimal temperature gradient along its length. Future work will include cathode wear tests, and internal emitter temperature and plasma properties measurements along with detailed physics based modeling.

New bimetallic EMF cell shows promise in direct energy conversion

NASA Technical Reports Server (NTRS)

Hesson, J. C.; Shimotake, H.

1968-01-01

Concentration cell, based upon a thermally regenerative cell principle, produces electrical energy from any large heat source. This experimental bimetallic EMF cell uses a sodium-bismuth alloy cathode and a pure liquid sodium anode. The cell exhibits reliability, corrosion resistance, and high current density performance.

Investigation of a chemically regenerative redox cathode polymer electrolyte fuel cell using a phosphomolybdovanadate polyoxoanion catholyte

NASA Astrophysics Data System (ADS)

Gunn, Natasha L. O.; Ward, David B.; Menelaou, Constantinos; Herbert, Matthew A.; Davies, Trevor J.

2017-04-01

Chemically regenerative redox cathode (CRRC) polymer electrolyte fuel cells (PEFCs), where the direct reduction of oxygen is replaced by an in-direct mechanism occurring outside of the cell, are attractive to study as they offer a solution to the cost and durability problems faced by conventional PEFCs. This study reports the first detailed characterization of a high performance complete CRRC PEFC system, where catholyte is circulated between the cathode side of the cell and an air-liquid oxidation reactor called the "regenerator". The catholyte is an aqueous solution of phosphomolybdovanadate polyoxoanion and is assessed in terms of its performance within both a small single cell and corresponding regenerator over a range of redox states. Two methods for determining regeneration rate are proposed and explored. Expressing the regeneration rate as a "chemical" current is suggested as a useful means of measuring re-oxidation rate with respect to the cell. The analysis highlights the present limitations to the technology and provides an indication of the maximum power density achievable, which is highly competitive with conventional PEFC systems.

Direct electron injection into an oxide insulator using a cathode buffer layer

PubMed Central

Lee, Eungkyu; Lee, Jinwon; Kim, Ji-Hoon; Lim, Keon-Hee; Seok Byun, Jun; Ko, Jieun; Dong Kim, Young; Park, Yongsup; Kim, Youn Sang

2015-01-01

Injecting charge carriers into the mobile bands of an inorganic oxide insulator (for example, SiO2, HfO2) is a highly complicated task, or even impossible without external energy sources such as photons. This is because oxide insulators exhibit very low electron affinity and high ionization energy levels. Here we show that a ZnO layer acting as a cathode buffer layer permits direct electron injection into the conduction bands of various oxide insulators (for example, SiO2, Ta2O5, HfO2, Al2O3) from a metal cathode. Studies of current–voltage characteristics reveal that the current ohmically passes through the ZnO/oxide-insulator interface. Our findings suggests that the oxide insulators could be used for simply fabricated, transparent and highly stable electronic valves. With this strategy, we demonstrate an electrostatic discharging diode that uses 100-nm SiO2 as an active layer exhibiting an on/off ratio of ∼107, and protects the ZnO thin-film transistors from high electrical stresses. PMID:25864642

Life test of a xenon hollow cathode for a space plasma contractor

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1994-01-01

A plasma contacting device using a hollow cathode for plasma production has been baselined for use on the Space Station. This application will require reliable, continuous operation of the cathode at electron emission currents of between 0.75 and 10 A for two years (17,500 hours). In order to validate life-time capability, a hollow cathode, operated in a diode configuration, has been tested for more than 8600 hours of stable discharge operation as of March 30, 1994. This cathode is operated at a steady-state emission current of 12.0 and a fixed xenon flow rate of 4.5 sccm. Discharge voltage and cathode temperature have remained relatively stable at approximately 12.9 V and 1260 C during the test. The test has experienced 7 shutdowns to date. In all instances, the cathode was reignited at about 42 V and resumed stable operation. This test represents the longest demonstration of stable operation of high current (greater than 1A) xenon hollow cathodes reported to date.

Cathode-constriction and column-constriction in high current vacuum arcs subjected to an axial magnetic field

NASA Astrophysics Data System (ADS)

Zhang, Zaiqin; Ma, Hui; Liu, Zhiyuan; Geng, Yingsan; Wang, Jianhua

2018-04-01

The influence of the applied axial magnetic field on the current density distribution in the arc column and electrodes is intensively studied. However, the previous results only provide a qualitative explanation, which cannot quantitatively explain a recent experimental data on anode current density. The objective of this paper is to quantitatively determine the current constriction subjected to an axial magnetic field in high-current vacuum arcs according to the recent experimental data. A magnetohydrodynamic model is adopted to describe the high current vacuum arcs. The vacuum arc is in a diffuse arc mode with an arc current ranged from 6 kArms to 14 kArms and an axial magnetic field ranged from 20 mT to 110 mT. By a comparison of the recent experimental work of current density distribution on the anode, the modelling results show that there are two types of current constriction. On one hand, the current on the cathode shows a constriction, and this constriction is termed as the cathode-constriction. On the other hand, the current constricts in the arc column region, and this constriction is termed as the column-constriction. The cathode boundary is of vital importance in a quantitative model. An improved cathode constriction boundary is proposed. Under the improved boundary, the simulation results are in good agreement with the recent experimental data on the anode current density distribution. It is demonstrated that the current density distribution at the anode is sensitive to that at the cathode, so that measurements of the anode current density can be used, in combination with the vacuum arc model, to infer the cathode current density distribution.

[Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

PubMed

Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

2002-02-01

A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.

Influence of propellant choice on MPD arcjet cathode surface current density distribution

NASA Astrophysics Data System (ADS)

Sheshadri, T. S.

1989-10-01

The radial current density on an MPD arcjet cathode surface is theoretically investigated for five propellants. It is found that excessive current concentration at the upstream end of the cathode occurs in the case of hydrogen. This undesirable effect is traced to the higher electrical conductivity of hydrogen plasma.

Frontal transcranial direct current stimulation (tDCS) abolishes list-method directed forgetting.

PubMed

Silas, Jonathan; Brandt, Karen R

2016-03-11

It is a point of controversy as to whether directed forgetting effects are a result of active inhibition or a change of context initiated by the instruction to forget. In this study we test the causal role of active inhibition in directed forgetting. By applying cathodal transcranial direct current stimulation (tDCS) over the right prefrontal cortex we suppressed cortical activity commonly associated with inhibitory control. Participants who underwent real brain stimulation before completing the directed forgetting paradigm showed no directed forgetting effects. Conversely, those who underwent sham brain stimulation demonstrated classical directed forgetting effects. We argue that these findings suggest that inhibition is the primary mechanism that results in directed forgetting costs and benefits. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Motion of a virtual cathode in a cylindrical channel with electron beam transport in the “compressed” state

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

Belomyttsev, S. Ya.; Grishkov, A. A.; Tsygankov, R. V.

2014-03-15

This paper studies the motion of a virtual cathode in a two-section drift tube with the formation and breakup of the “compressed” state of an electron beam. Experimental arrangements to intercept part of the injected current during the voltage pulse and to provide virtual cathode motion toward the collector are proposed. The arrangements were implemented on the SINUS-7 high-current electron accelerator. Theoretical and experimental dependences of the virtual cathode velocity on the injected current and cathode voltage are presented. The experimental data on virtual cathode motion agree with its theoretical model based on analytical solutions of equations assisted by computermore » simulation with the PIC code KARAT. The results of the work demonstrate the feasibility of controlling the virtual cathode motion which can be used in collective ion acceleration and microwave generation.« less

Large area directly heated lanthanum hexaboride cathode structure having predetermined emission profile

DOEpatents

Leung, Ka-Ngo; Gordon, Keith C.; Kippenham, Dean O.; Purgalis, Peter; Moussa, David; Williams, Malcom D.; Wilde, Stephen B.; West, Mark W.

1989-01-01

A large area directly heated lanthanum hexaboride (LaB.sub.6) cathode system (10) is disclosed. The system comprises a LaB.sub.6 cathode element (11) generally circular in shape about a central axis. The cathode element (11) has a head (21) with an upper substantially planar emission surface (23), and a lower downwardly and an intermediate body portion (26) which diminishes in cross-section from the head (21) towards the base (22) of the cathode element (11). A central rod (14) is connected to the base (22) of the cathode element (11) and extends along the central axis. Plural upstanding spring fingers (37) are urged against an outer peripheral contact surface (24) of the head end (21) to provide a mechanical and electrical connection to the cathode element (11).

Transcranial Direct Current Stimulation (tDCS) Targeting Left Dorsolateral Prefrontal Cortex Modulates Task-Induced Acute Pain in Healthy Volunteers

PubMed Central

Mariano, Timothy Y.; Wout, Mascha van't; Garnaat, Sarah L.; Rasmussen, Steven A.; Greenberg, Benjamin D.

2016-01-01

Objective Current chronic pain treatments target nociception rather than affective “suffering” and its associated functional and psychiatric comorbidities. Left dorsolateral prefrontal cortex (DLPFC) has been implicated in affective, cognitive, and attentional aspects of pain and is a primary target of neuromodulation for affective disorders. Transcranial direct current stimulation (tDCS) can noninvasively modulate cortical activity. The present study tests if anodal tDCS targeting left DLPFC will increase tolerability of acute painful stimuli versus cathodal tDCS. Methods Forty tDCS-naive healthy volunteers received anodal and cathodal stimulation targeting left DLPFC in two randomized and counterbalanced sessions. During stimulation, each participant performed cold pressor (CP) and breath holding (BH) tasks. We measured pain intensity with the Defense and Veterans Pain Rating Scale (DVPRS) before and after each task. Results Mixed ANOVA revealed no main effect of stimulation polarity for mean CP threshold, tolerance, or endurance, or mean BH time (all p > 0.27). However, DVPRS rise associated with CP was significantly smaller with anodal versus cathodal tDCS (p = 0.024). We further observed a significant tDCS polarity × stimulation order interaction (p = 0.042) on CP threshold suggesting task sensitization. Conclusions Although our results do not suggest that polarity of tDCS targeting left DLPFC differentially modulates tolerability of CP- and BH-related pain distress in healthy volunteers, there was a significant effect on DVPRS pain ratings. This contrasts with our previous findings that tDCS targeting left dorsal anterior cingulate cortex showed a trend towards higher mean CP tolerance with cathodal versus anodal stimulation. The present results may suggest tDCS-related effects on nociception or DLPFC-mediated attention, or preferential modulation of the affective valence of pain as captured by DVPRS. Sham-controlled clinical studies are needed. PMID:26814276

Transcranial Direct Current Stimulation (tDCS) Targeting Left Dorsolateral Prefrontal Cortex Modulates Task-Induced Acute Pain in Healthy Volunteers.

PubMed

Mariano, Timothy Y; Van't Wout, Mascha; Garnaat, Sarah L; Rasmussen, Steven A; Greenberg, Benjamin D

2016-04-01

Current chronic pain treatments target nociception rather than affective "suffering" and its associated functional and psychiatric comorbidities. The left dorsolateral prefrontal cortex (DLPFC) has been implicated in affective, cognitive, and attentional aspects of pain and is a primary target of neuromodulation for affective disorders. Transcranial direct current stimulation (tDCS) can non-invasively modulate cortical activity. The present study tests whether anodal tDCS targeting the left DLPFC will increase tolerability of acute painful stimuli vs cathodal tDCS. Forty tDCS-naive healthy volunteers received anodal and cathodal stimulation targeting the left DLPFC in two randomized and counterbalanced sessions. During stimulation, each participant performed cold pressor (CP) and breath holding (BH) tasks. We measured pain intensity with the Defense and Veterans Pain Rating Scale (DVPRS) before and after each task. Mixed ANOVA revealed no main effect of stimulation polarity for mean CP threshold, tolerance, or endurance, or mean BH time (allP > 0.27). However, DVPRS rise associated with CP was significantly smaller with anodal vs cathodal tDCS (P = 0.024). We further observed a significant tDCS polarity × stimulation order interaction (P = 0.042) on CP threshold, suggesting task sensitization. Although our results do not suggest that polarity of tDCS targeting the left DLPFC differentially modulates the tolerability of CP- and BH-related pain distress in healthy volunteers, there was a significant effect on DVPRS pain ratings. This contrasts with our previous findings that tDCS targeting the left dorsal anterior cingulate cortex showed a trend toward higher mean CP tolerance with cathodal vs anodal stimulation. The present results may suggest tDCS-related effects on nociception or DLPFC-mediated attention, or preferential modulation of the affective valence of pain as captured by the DVPRS. Sham-controlled clinical studies are needed. © 2015 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effects of a common transcranial direct current stimulation (tDCS) protocol on motor evoked potentials found to be highly variable within individuals over 9 testing sessions.

PubMed

Horvath, Jared Cooney; Vogrin, Simon J; Carter, Olivia; Cook, Mark J; Forte, Jason D

2016-09-01

Transcranial direct current stimulation (tDCS) uses a weak electric current to modulate neuronal activity. A neurophysiologic outcome measure to demonstrate reliable tDCS modulation at the group level is transcranial magnetic stimulation engendered motor evoked potentials (MEPs). Here, we conduct a study testing the reliability of individual MEP response patterns following a common tDCS protocol. Fourteen participants (7m/7f) each underwent nine randomized sessions of 1 mA, 10 min tDCS (3 anode; 3 cathode; 3 sham) delivered using an M1/orbito-frontal electrode montage (sessions separated by an average of ~5.5 days). Fifteen MEPs were obtained prior to, immediately following and in 5 min intervals for 30 min following tDCS. TMS was delivered at 130 % resting motor threshold using neuronavigation to ensure consistent coil localization. A number of non-experimental variables were collected during each session. At the individual level, considerable variability was seen among different testing sessions. No participant demonstrated an excitatory response ≥20 % to all three anodal sessions, and no participant demonstrated an inhibitory response ≥20 % to all three cathodal sessions. Intra-class correlation revealed poor anodal and cathodal test-retest reliability [anode: ICC(2,1) = 0.062; cathode: ICC(2,1) = 0.055] and moderate sham test-retest reliability [ICC(2,1) = 0.433]. Results also revealed no significant effect of tDCS at the group level. Using this common protocol, we found the effects of tDCS on MEP amplitudes to be highly variable at the individual level. In addition, no significant effects of tDCS on MEP amplitude were found at the group level. Future studies should consider utilizing a more strict experimental protocol to potentially account for intra-individual response variations.

Transcranial direct current stimulation to primary motor area improves hand dexterity and selective attention in chronic stroke.

PubMed

Au-Yeung, Stephanie S Y; Wang, Juliana; Chen, Ye; Chua, Eldrich

2014-12-01

The aim of this study was to determine whether transcranial direct current stimulation (tDCS) applied to the primary motor hand area modulates hand dexterity and selective attention after stroke. This study was a double-blind, placebo-controlled, randomized crossover trial involving subjects with chronic stroke. Ten stroke survivors with some pinch strength in the paretic hand received three different tDCS interventions assigned in random order in separate sessions-anodal tDCS targeting the primary motor area of the lesioned hemisphere (M1lesioned), cathodal tDCS applied to the contralateral hemisphere (M1nonlesioned), and sham tDCS-each for 20 mins. The primary outcome measures were Purdue pegboard test scores for hand dexterity and response time in the color-word Stroop test for selective attention. Pinch strength of the paretic hand was the secondary outcome. Cathodal tDCS to M1nonlesioned significantly improved affected hand dexterity (by 1.1 points on the Purdue pegboard unimanual test, P = 0.014) and selective attention (0.6 secs faster response time on the level 3 Stroop interference test for response inhibition, P = 0.017), but not pinch strength. The outcomes were not improved with anodal tDCS to M1lesioned or sham tDCS. Twenty minutes of cathodal tDCS to M1nonlesioned can promote both paretic hand dexterity and selective attention in people with chronic stroke.

Porous boron doped diamonds as metal-free catalysts for the oxygen reduction reaction in alkaline solution

NASA Astrophysics Data System (ADS)

Suo, Ni; Huang, Hao; Wu, Aimin; Cao, Guozhong; Hou, Xiaoduo; Zhang, Guifeng

2018-05-01

Porous boron doped diamonds (BDDs) were obtained on foam nickel substrates with a porosity of 80%, 85%, 90% and 95% respectively by hot filament chemical vapor deposition (HFCVD) technology. Scanning electron microscopy (SEM) reveals that uniform and compact BDDs with a cauliflower-like morphology have covered the overall frame of the foam nickel substrates. Raman spectroscopy shows that the BDDs have a poor crystallinity due to heavily doping boron. X-ray photoelectron spectroscopy (XPS) analysis effectively demonstrates that boron atoms can be successfully incorporated into the crystal lattice of diamonds. Electrochemical measurements indicate that the oxygen reduction potential is unaffected by the specific surface area (SSA), and both the onset potential and the limiting diffusion current density are enhanced with increasing SSA. It is also found that the durability and methanol tolerance of the boron doped diamond catalysts are attenuated as the increasing of SSA. The SSA of the catalyst is directly proportional to the oxygen reduction activity and inversely to the durability and methanol resistance. These results provide a reference to the application of porous boron doped diamonds as potential cathodic catalysts for the oxygen reduction reaction in alkaline solution by adjusting the SSA.

Recent advances on Fe- and Mn-based cathode materials for lithium and sodium ion batteries

NASA Astrophysics Data System (ADS)

Zhu, Xiaobo; Lin, Tongen; Manning, Eric; Zhang, Yuancheng; Yu, Mengmeng; Zuo, Bin; Wang, Lianzhou

2018-06-01

The ever-growing market of electrochemical energy storage impels the advances on cost-effective and environmentally friendly battery chemistries. Lithium-ion batteries (LIBs) are currently the most critical energy storage devices for a variety of applications, while sodium-ion batteries (SIBs) are expected to complement LIBs in large-scale applications. In respect to their constituent components, the cathode part is the most significant sector regarding weight fraction and cost. Therefore, the development of cathode materials based on Earth's abundant elements (Fe and Mn) largely determines the prospects of the batteries. Herein, we offer a comprehensive review of the up-to-date advances on Fe- and Mn-based cathode materials for LIBs and SIBs, highlighting some promising candidates, such as Li- and Mn-rich layered oxides, LiNi0.5Mn1.5O4, LiFe1-xMnxPO4, NaxFeyMn1-yO2, Na4MnFe2(PO4)(P2O7), and Prussian blue analogs. Also, challenges and prospects are discussed to direct the possible development of cost-effective and high-performance cathode materials for future rechargeable batteries.

28,000 Hour Xenon Hollow Cathode LifeTest Results

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1997-01-01

The International Space Station Plasma Contactor System requires a hollow cathode assembly (HCA) with a lifetime of at least 18,000 hours. Critical components of the HCA include the hollow cathode and electron emitter. A series of hollow cathode wear tests was performed which included a life test operated at the maximum current of the HCA. This test sought to verify the hollow cathode design and contamination control protocols. The life test accumulated 27,800 hours of operation before failing to ignite. The hollow cathode exhibited relatively small changes in operating parameters over the course of the test. This life test is the longest duration test of a high current xenon hollow cathode reported to date.

Low-Current, Xenon Orificed Hollow Cathode Performance for In-Space Applications

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Patterson, Michael J.; Gallimore, Alec D.

2002-01-01

An experimental investigation of the operating characteristics of 3.2-mm diameter orificed hollow cathodes was conducted to examine low current and low flow rate operation. Cathode power was minimized with an orifice aspect ratio of approximately one and the use of an enclosed keeper. Cathode flow rate requirements were proportional to orifice diameter and the inverse of the orifice length. The minimum power consumption in diode mode was 10-W, and the minimum mass flow rate required for spot-mode emission was approximately 0.08-mg/s. Cathode temperature profiles were obtained using an imaging radiometer and conduction was found to be the dominant heat transfer mechanism from the cathode tube. Orifice plate temperatures were found to be weakly dependent upon the flow rate and strongly dependent upon the current.

Chronic Enhancement of Serotonin Facilitates Excitatory Transcranial Direct Current Stimulation-Induced Neuroplasticity.

PubMed

Kuo, Hsiao-I; Paulus, Walter; Batsikadze, Giorgi; Jamil, Asif; Kuo, Min-Fang; Nitsche, Michael A

2016-04-01

Serotonin affects memory formation via modulating long-term potentiation (LTP) and depression (LTD). Accordingly, acute selective serotonin reuptake inhibitor (SSRI) administration enhanced LTP-like plasticity induced by transcranial direct current stimulation (tDCS) in humans. However, it usually takes some time for SSRI to reduce clinical symptoms such as anxiety, negative mood, and related symptoms of depression and anxiety disorders. This might be related to an at least partially different effect of chronic serotonergic enhancement on plasticity, as compared with single-dose medication. Here we explored the impact of chronic application of the SSRI citalopram (CIT) on plasticity induced by tDCS in healthy humans in a partially double-blinded, placebo (PLC)-controlled, randomized crossover study. Furthermore, we explored the dependency of plasticity induction from the glutamatergic system via N-methyl-D-aspartate receptor antagonism. Twelve healthy subjects received PLC medication, combined with anodal or cathodal tDCS of the primary motor cortex. Afterwards, the same subjects took CIT (20 mg/day) consecutively for 35 days. During this period, four additional interventions were performed (CIT and PLC medication with anodal/cathodal tDCS, CIT and dextromethorphan (150 mg) with anodal/cathodal tDCS). Plasticity was monitored by motor-evoked potential amplitudes elicited by transcranial magnetic stimulation. Chronic application of CIT increased and prolonged the LTP-like plasticity induced by anodal tDCS for over 24 h, and converted cathodal tDCS-induced LTD-like plasticity into facilitation. These effects were abolished by dextromethorphan. Chronic serotonergic enhancement results in a strengthening of LTP-like glutamatergic plasticity, which might partially explain the therapeutic impact of SSRIs in depression and other neuropsychiatric diseases.

Transcranial direct current stimulation (tDCS) for improving capacity in activities and arm function after stroke: a network meta-analysis of randomised controlled trials.

PubMed

Elsner, Bernhard; Kwakkel, Gert; Kugler, Joachim; Mehrholz, Jan

2017-09-13

Transcranial Direct Current Stimulation (tDCS) is an emerging approach for improving capacity in activities of daily living (ADL) and upper limb function after stroke. However, it remains unclear what type of tDCS stimulation is most effective. Our aim was to give an overview of the evidence network regarding the efficacy and safety of tDCS and to estimate the effectiveness of the different stimulation types. We performed a systematic review of randomised trials using network meta-analysis (NMA), searching the following databases until 5 July 2016: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, AMED, Web of Science, and four other databases. We included studies with adult people with stroke. We compared any kind of active tDCS (anodal, cathodal, or dual, that is applying anodal and cathodal tDCS concurrently) regarding improvement of our primary outcome of ADL capacity, versus control, after stroke. CRD42016042055. We included 26 studies with 754 participants. Our NMA showed evidence of an effect of cathodal tDCS in improving our primary outcome, that of ADL capacity (standardized mean difference, SMD = 0.42; 95% CI 0.14 to 0.70). tDCS did not improve our secondary outcome, that of arm function, measured by the Fugl-Meyer upper extremity assessment (FM-UE). There was no difference in safety between tDCS and its control interventions, measured by the number of dropouts and adverse events. Comparing different forms of tDCS shows that cathodal tDCS is the most promising treatment option to improve ADL capacity in people with stroke.

The influence of stabilizers on the production of gold nanoparticles by direct current atmospheric pressure glow microdischarge generated in contact with liquid flowing cathode.

PubMed

Dzimitrowicz, Anna; Jamroz, Piotr; Greda, Krzysztof; Nowak, Piotr; Nyk, Marcin; Pohl, Pawel

Gold nanoparticles (Au NPs) were prepared by direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between a miniature argon flow microjet and a flowing liquid cathode. The applied discharge system was operated in a continuous flow liquid mode. The influence of various stabilizers added to the solution of the liquid cathode, i.e., gelatin (GEL), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA), as well as the concentration of the Au precursor (chloroauric acid, HAuCl 4 ) in the solution on the production growth of Au NPs was investigated. Changes in the intensity of the localized surface plasmon resonance (LSPR) band in UV/Vis absorption spectra of solutions treated by dc-μAPGD and their color were observed. The position and the intensity of the LSPR band indicated that relatively small nanoparticles were formed in solutions containing GEL as a capping agent. In these conditions, the maximum of the absorption LSPR band was at 531, 534, and 535 nm, respectively, for 50, 100, and 200 mg L -1 of Au. Additionally, scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyze the structure and the morphology of obtained Au NPs. The shape of Au NPs was spherical and uniform. Their mean size was ca. 27, 73, and 92 nm, while the polydispersity index was 0.296, 0.348, and 0.456 for Au present in the solution of the flowing liquid cathode at a concentration of 50, 100, and 200 mg L -1 , respectively. The production rate of synthesized Au NPs depended on the precursor concentration with mean values of 2.9, 3.5, and 5.7 mg h -1 , respectively.

The influence of stabilizers on the production of gold nanoparticles by direct current atmospheric pressure glow microdischarge generated in contact with liquid flowing cathode

NASA Astrophysics Data System (ADS)

Dzimitrowicz, Anna; Jamroz, Piotr; Greda, Krzysztof; Nowak, Piotr; Nyk, Marcin; Pohl, Pawel

2015-04-01

Gold nanoparticles (Au NPs) were prepared by direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between a miniature argon flow microjet and a flowing liquid cathode. The applied discharge system was operated in a continuous flow liquid mode. The influence of various stabilizers added to the solution of the liquid cathode, i.e., gelatin (GEL), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA), as well as the concentration of the Au precursor (chloroauric acid, HAuCl4) in the solution on the production growth of Au NPs was investigated. Changes in the intensity of the localized surface plasmon resonance (LSPR) band in UV/Vis absorption spectra of solutions treated by dc-μAPGD and their color were observed. The position and the intensity of the LSPR band indicated that relatively small nanoparticles were formed in solutions containing GEL as a capping agent. In these conditions, the maximum of the absorption LSPR band was at 531, 534, and 535 nm, respectively, for 50, 100, and 200 mg L-1 of Au. Additionally, scanning electron microscopy (SEM) and dynamic light scattering (DLS) were used to analyze the structure and the morphology of obtained Au NPs. The shape of Au NPs was spherical and uniform. Their mean size was ca. 27, 73, and 92 nm, while the polydispersity index was 0.296, 0.348, and 0.456 for Au present in the solution of the flowing liquid cathode at a concentration of 50, 100, and 200 mg L-1, respectively. The production rate of synthesized Au NPs depended on the precursor concentration with mean values of 2.9, 3.5, and 5.7 mg h-1, respectively.

The effects of tDCS upon sustained visual attention are dependent on cognitive load.

PubMed

Roe, James M; Nesheim, Mathias; Mathiesen, Nina C; Moberget, Torgeir; Alnæs, Dag; Sneve, Markus H

2016-01-08

Transcranial Direct Current Stimulation (tDCS) modulates the excitability of neuronal responses and consequently can affect performance on a variety of cognitive tasks. However, the interaction between cognitive load and the effects of tDCS is currently not well-understood. We recorded the performance accuracy of participants on a bilateral multiple object tracking task while undergoing bilateral stimulation assumed to enhance (anodal) and decrease (cathodal) neuronal excitability. Stimulation was applied to the posterior parietal cortex (PPC), a region inferred to be at the centre of an attentional tracking network that shows load-dependent activation. 34 participants underwent three separate stimulation conditions across three days. Each subject received (1) left cathodal / right anodal PPC tDCS, (2) left anodal / right cathodal PPC tDCS, and (3) sham tDCS. The number of targets-to-be-tracked was also manipulated, giving a low (one target per visual field), medium (two targets per visual field) or high (three targets per visual field) tracking load condition. It was found that tracking performance at high attentional loads was significantly reduced in both stimulation conditions relative to sham, and this was apparent in both visual fields, regardless of the direction of polarity upon the brain's hemispheres. We interpret this as an interaction between cognitive load and tDCS, and suggest that tDCS may degrade attentional performance when cognitive networks become overtaxed and unable to compensate as a result. Systematically varying cognitive load may therefore be a fruitful direction to elucidate the effects of tDCS upon cognitive functions. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Thermoelectric Power Generation System for Future Hybrid Vehicles Using Hot Exhaust Gas

NASA Astrophysics Data System (ADS)

Kim, Sun-Kook; Won, Byeong-Cheol; Rhi, Seok-Ho; Kim, Shi-Ho; Yoo, Jeong-Ho; Jang, Ju-Chan

2011-05-01

The present experimental and computational study investigates a new exhaust gas waste heat recovery system for hybrid vehicles, using a thermoelectric module (TEM) and heat pipes to produce electric power. It proposes a new thermoelectric generation (TEG) system, working with heat pipes to produce electricity from a limited hot surface area. The current TEG system is directly connected to the exhaust pipe, and the amount of electricity generated by the TEMs is directly proportional to their heated area. Current exhaust pipes fail to offer a sufficiently large hot surface area for the high-efficiency waste heat recovery required. To overcome this, a new TEG system has been designed to have an enlarged hot surface area by the addition of ten heat pipes, which act as highly efficient heat transfer devices and can transmit the heat to many TEMs. As designed, this new waste heat recovery system produces a maximum 350 W when the hot exhaust gas heats the evaporator surface of the heat pipe to 170°C; this promises great possibilities for application of this technology in future energy-efficient hybrid vehicles.

Cathode performance during two beam operation of the high current high polarization electron gun for eRHIC

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

Rahman, O.; Ben-Zvi, I.; Degen, C.

Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place in Stangenes Industries in Palo Alto, CA, where the cathodes were placed in diagonally opposite locations inside the high voltage shroud. No significant cross talking between the cathodes was found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test,more » including the QE and lifetimes of the photocathodes at various steps of the experiment.« less

Electrical stimulation modulates injury potentials in rats after spinal cord injury

PubMed Central

Zhang, Guanghao; Huo, Xiaolin; Wang, Aihua; Wu, Changzhe; Zhang, Cheng; Bai, Jinzhu

2013-01-01

An injury potential is the direct current potential difference between the site of spinal cord injury and the healthy nerves. Its initial amplitude is a significant indicator of the severity of spinal cord injury, and many cations, such as sodium and calcium, account for the major portion of injury potentials. This injury potential, as well as injury current, can be modulated by direct current field stimulation; however, the appropriate parameters of the electrical field are hard to define. In this paper, injury potential is used as a parameter to adjust the intensity of electrical stimulation. Injury potential could be modulated to slightly above 0 mV (as the anode-centered group) by placing the anodes at the site of the injured spinal cord and the cathodes at the rostral and caudal sections, or around –70 mV, which is resting membrane potential (as the cathode-centered group) by reversing the polarity of electrodes in the anode-centered group. In addition, rats receiving no electrical stimulation were used as the control group. Results showed that the absolute value of the injury potentials acquired after 30 minutes of electrical stimulation was higher than the control group rats and much lower than the initial absolute value, whether the anodes or the cathodes were placed at the site of injury. This phenomenon illustrates that by changing the polarity of the electrical field, electrical stimulation can effectively modulate the injury potentials in rats after spinal cord injury. This is also beneficial for the spontaneous repair of the cell membrane and the reduction of cation influx. PMID:25206563

Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

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

Yang Jie; Shu Ting; Fan Yuwei

2013-01-28

Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm{sup 2}. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on themore » Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/{mu}s) was much larger than that (90 cm/{mu}s) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 {+-} 1.5 cm/{mu}s, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.« less

Precise method of compensating radiation-induced errors in a hot-cathode-ionization gauge with correcting electrode

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

Saeki, Hiroshi, E-mail: saeki@spring8.or.jp; Magome, Tamotsu, E-mail: saeki@spring8.or.jp

2014-10-06

To compensate pressure-measurement errors caused by a synchrotron radiation environment, a precise method using a hot-cathode-ionization-gauge head with correcting electrode, was developed and tested in a simulation experiment with excess electrons in the SPring-8 storage ring. This precise method to improve the measurement accuracy, can correctly reduce the pressure-measurement errors caused by electrons originating from the external environment, and originating from the primary gauge filament influenced by spatial conditions of the installed vacuum-gauge head. As the result of the simulation experiment to confirm the performance reducing the errors caused by the external environment, the pressure-measurement error using this method wasmore » approximately less than several percent in the pressure range from 10{sup −5} Pa to 10{sup −8} Pa. After the experiment, to confirm the performance reducing the error caused by spatial conditions, an additional experiment was carried out using a sleeve and showed that the improved function was available.« less

Diamond/diamond-like carbon coated nanotube structures for efficient electron field emission

NASA Technical Reports Server (NTRS)

Dimitrijevic, Steven (Inventor); Withers, James C. (Inventor); Loutfy, Raouf O. (Inventor)

2005-01-01

The present invention is directed to a nanotube coated with diamond or diamond-like carbon, a field emitter cathode comprising same, and a field emitter comprising the cathode. It is also directed to a method of preventing the evaporation of carbon from a field emitter comprising a cathode comprised of nanotubes by coating the nanotube with diamond or diamond-like carbon. In another aspect, the present invention is directed to a method of preventing the evaporation of carbon from an electron field emitter comprising a cathode comprised of nanotubes, which method comprises coating the nanotubes with diamond or diamond-like carbon.

Superior Cathode Performance of Nitrogen-Doped Graphene Frameworks for Lithium Ion Batteries.

PubMed

Xiong, Dongbin; Li, Xifei; Bai, Zhimin; Shan, Hui; Fan, Linlin; Wu, Chunxia; Li, Dejun; Lu, Shigang

2017-03-29

Development of alternative cathode materials is of highly desirable for sustainable and cost-efficient lithium-ion batteries (LIBs) in energy storage fields. In this study, for the first time, we report tunable nitrogen-doped graphene with active functional groups for cathode utilization of LIBs. When employed as cathode materials, the functionalized graphene frameworks with a nitrogen content of 9.26 at% retain a reversible capacity of 344 mAh g -1 after 200 cycles at a current density of 50 mA g -1 . More surprisingly, when conducted at a high current density of 1 A g -1 , this cathode delivers a high reversible capacity of 146 mAh g -1 after 1000 cycles. Our current research demonstrates the effective significance of nitrogen doping on enhancing cathode performance of functionalized graphene for LIBs.

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

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

Xiong, Ying; Wang, Bing; Yi, Yong

2013-09-15

The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels (∼0.40 Pa L), slower cathode plasma expansion velocity (∼2.30 cm/μs), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacentmore » pulses is significantly improved in double-pulsed emission mode with ∼500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes.« less

Physical model and experimental results of cathode erosion related to power supply ripple

NASA Technical Reports Server (NTRS)

Harris, W. J.; O'Hair, E. A.; Hatfield, L. L.; Kristiansen, M.

1992-01-01

This paper discusses the physical effects of power supply ripple on cathode erosion and cathode arc attachment in a water-cooled, 30 kW nitrogen arcjet. Experimental results are presented for 2 percent thoriated tungsten, which show that the long-term cathode erosion rate is a decreasing function of current ripple over the range 1-13 percent. Above this range, the cathode discharge becomes unstable, and the erosion rate rapidly increases. A qualitative model of this effect is given in terms of a magnetically induced radial motion of the arc column, and an overall increase in the cathode spot radius due to the higher peak current associated with higher ripple. The most important effect of power supply ripple is therefore shown to be its ability to collectively drive the cathode attachment away from the cathode center. This leads to an increase in the cathode attachment area, and a subsequent decrease in the cathode erosion rate.

Direct current H- source for the medicine accelerator (invited)

NASA Astrophysics Data System (ADS)

Belchenko, Yu.; Savkin, V.

2004-05-01

A compact cw hydrogen negative ion source having reliable operation and a simplified maintenance is developed at Budker Institute of Nuclear Physics for a tandem accelerator of boron capture neutron therapy installation. The source uses a Penning discharge with a hydrogen and cesium feed through the hollows in the cathodes. Discharge voltage is about 60-80 V, current 9 A, hydrogen pressure 4-5 Pa, magnetic field 0.05-0.1 T, and cesium seed <1 mg/h. Negative ions are mainly produced on the cesiated anode surface due to conversion of hydrogen atoms. An optimal anode temperature is 250-350 °C. Negative ion beam current is directly proportional to the discharge current and to the emission hole area. A triode system for the beam extraction and acceleration system is used. The flux of accompanying extracted electrons was decreased by filtering in the transverse magnetic field. This electron flux was intercepted to the special electrode, biased at 4 kV potential with respect to the anode. Source stable cw operation for several hour runs was multiply tested. A H- ion beam with current up to 8 mA, beam energy 23 keV was produced regularly. Negative ion current of heavy impurities had a value of about 3% of the total beam current. Beam normalized emittance is about 0.3 π mm mrad and emission current density -0.1 A/cm2. A built-in cathode heater provides the operation quick start.

Investigation of hollow cathode performance for 30-cm thrusters

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1973-01-01

A parametric investigation of 6.35 mm diameter mercury hollow cathodes was carried out in a bell jar. The parameters that were varied were the amount of initial emissive mix, insert position, emission current, cathode temperature, orifice diameter, and mercury flow rate. Flow characteristic curves and performance as a function of time were obtained for the various cathodes. The results of a 3880 hr life test of a main cathode run at 15 amps emission current with no noticeable changes in keeper and collector voltages are also presented.

Temperature management of photo cathodes at MAMI and MESA

NASA Astrophysics Data System (ADS)

Aulenbacher, K.; Friederich, S.; Tyukin, V.

2018-05-01

Production of highly polarized electron current is limited by cathode heating which leads to the destruction of the active layer. For the new electron accelerator MESA a more efficient solution for the cathode cooling problem is required, with the goal to achieve acceptable temperatures at an incident power of about 1 Watt. The current status of temperature management of photo cathodes at MAMI and MESA is presented.

Direct fabrication of gas diffusion cathode by pulse electrodeposition for proton exchange membrane water electrolysis

NASA Astrophysics Data System (ADS)

Park, Hyanjoo; Choe, Seunghoe; Kim, Hoyoung; Kim, Dong-Kwon; Cho, GeonHee; Park, YoonSu; Jang, Jong Hyun; Ha, Don-Hyung; Ahn, Sang Hyun; Kim, Soo-Kil

2018-06-01

Pt catalysts for water electrolysis were prepared on carbon paper by using both direct current and pulse electrodeposition. Controlling the mass transfer of Pt precursor in the electrolyte by varying the deposition potential enables the formation of various Pt particle shapes such as flower-like and polyhedral particles. Further control of the deposition parameters for pulse electrodeposition resulted in changes to the particle size and density. In particular, the upper potential of pulse was found to be the critical parameter controlling the morphology of the particles and their catalytic activity. In addition to the typical electrochemical measurements, Pt samples deposited on carbon paper were used as cathodes for a proton exchange membrane water electrolyser. This single cell test revealed that our Pt particle samples have exceptional mass activity while being cost effective.

Salt taste inhibition by cathodal current.

PubMed

Hettinger, Thomas P; Frank, Marion E

2009-09-28

Effects of cathodal current, which draws cations away from the tongue and drives anions toward the tongue, depend on the ionic content of electrolytes through which the current is passed. To address the role of cations and anions in human salt tastes, cathodal currents of -40 microA to -80 microA were applied to human subjects' tongues through supra-threshold salt solutions. The salts were sodium chloride, sodium bromide, potassium chloride, ammonium chloride, calcium chloride, sodium nitrate, sodium sulfate, sodium saccharin, sodium acetate and sodium benzoate, which taken together encompass salty, bitter, sour and sweet taste qualities. The taste of NaCl, the salty and bitter tastes of the other chloride salts and the taste of NaNO(3) was inhibited, suggesting the current displaced stimulatory cations from salty and bitter receptors. However, bitter tastes of non-halide sodium salts were not inhibited, likely because other bitter receptors respond to anions. A discharge current at cathode-off ubiquitously evoked a metallic taste reminiscent of anodal taste used in clinical electrogustometry. Analogous effects on ambient NaCl responses were recorded from the hamster chorda tympani nerve. Increases in tastes of the saccharin and benzoate anions were not evoked during current flow, suggesting that cathodal current does not carry stimulatory anions to sweet receptors. Cathodal current may selectively inhibit salty and bitter-salty tastes for which proximal stimuli are cations.

Effect of Immersion Time and Cooling Mode on the Electrochemical Behavior of Hot-Dip Galvanized Steel in Sulfuric Acid Medium

NASA Astrophysics Data System (ADS)

Lekbir, Choukri; Dahoun, Nessrine; Guetitech, Asma; Hacid, Abdenour; Ziouche, Aicha; Ouaad, Kamel; Djadoun, Amar

2017-04-01

In this work, we investigated the influence of galvanizing immersion time and cooling modes environments on the electrochemical corrosion behavior of hot-dip galvanized steel, in 1 M sulfuric acid electrolyte at room temperature using potentiodynamic polarization technique. In addition, the evolution of thickness, structure and microstructure of zinc coatings for different immersion times and two cooling modes (air and water) is characterized, respectively, by using of Elcometer scan probe, x-ray diffraction and metallography analysis. The analysis of the behavior of steel and galvanized steel, vis-a-vis corrosion, by means of corrosion characteristic parameters as anodic (β a) and cathodic (β c) Tafel slopes, corrosion potential (E corr), corrosion current density (i corr), corrosion rate (CR) and polarization resistance (R p), reveals that the galvanized steel has anticorrosion properties much better than that of steel. More the immersion time increases, more the zinc coatings thickness increases, and more these properties become better. The comparison between the two cooling modes shows that the coatings of zinc produced by hot-dip galvanization and air-cooled provides a much better protection to steel against corrosion than those cooled by quenching in water which exhibit a brittle corrosive behavior due to the presence of cracks.

Air-cathode microbial fuel cell array: a device for identifying and characterizing electrochemically active microbes.

PubMed

Hou, Huijie; Li, Lei; de Figueiredo, Paul; Han, Arum

2011-01-15

Microbial fuel cells (MFCs) have generated excitement in environmental and bioenergy communities due to their potential for coupling wastewater treatment with energy generation and powering diverse devices. The pursuit of strategies such as improving microbial cultivation practices and optimizing MFC devices has increased power generating capacities of MFCs. However, surprisingly few microbial species with electrochemical activity in MFCs have been identified because current devices do not support parallel analyses or high throughput screening. We have recently demonstrated the feasibility of using advanced microfabrication methods to fabricate an MFC microarray. Here, we extend these studies by demonstrating a microfabricated air-cathode MFC array system. The system contains 24 individual air-cathode MFCs integrated onto a single chip. The device enables the direct and parallel comparison of different microbes loaded onto the array. Environmental samples were used to validate the utility of the air-cathode MFC array system and two previously identified isolates, 7Ca (Shewanella sp.) and 3C (Arthrobacter sp.), were shown to display enhanced electrochemical activities of 2.69 mW/m(2) and 1.86 mW/m(2), respectively. Experiments using a large scale conventional air-cathode MFC validated these findings. The parallel air-cathode MFC array system demonstrated here is expected to promote and accelerate the discovery and characterization of electrochemically active microbes. Copyright © 2010 Elsevier B.V. All rights reserved.

Bounds on geologically current rates of motion of groups of hot spots

NASA Astrophysics Data System (ADS)

Wang, Chengzu; Gordon, Richard G.; Zhang, Tuo

2017-06-01

It is widely believed that groups of hot spots in different regions of the world are in relative motion at rates of 10 to 30 mm a-1 or more. Here we present a new method for analyzing geologically current motion between groups of hot spots beneath different plates. In an inversion of 56 globally distributed, equally weighted trends of hot spot tracks, the dispersion is dominated by differences in trend between different plates rather than differences within plates. Nonetheless the rate of hot spot motion perpendicular to the direction of absolute plate motion, vperp, differs significantly from zero for only 3 of 10 plates and then by merely 0.3 to 1.4 mm a-1. The global mean upper bound on |vperp| is 3.2 ± 2.7 mm a-1. Therefore, hot spots move slowly and can be used to define a global reference frame for plate motions.

Operando characterization of cathodic reactions in a liquid-state lithium-oxygen micro-battery by scanning transmission electron microscopy.

PubMed

Liu, Pan; Han, Jiuhui; Guo, Xianwei; Ito, Yoshikazu; Yang, Chuchu; Ning, Shoucong; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei

2018-02-16

Rechargeable non-aqueous lithium-oxygen batteries with a large theoretical capacity are emerging as a high-energy electrochemical device for sustainable energy strategy. Despite many efforts made to understand the fundamental Li-O 2 electrochemistry, the kinetic process of cathodic reactions, associated with the formation and decomposition of a solid Li 2 O 2 phase during charging and discharging, remains debate. Here we report direct visualization of the charge/discharge reactions on a gold cathode in a non-aqueous lithium-oxygen micro-battery using liquid-cell aberration-corrected scanning transmission electron microscopy (STEM) combining with synchronized electrochemical measurements. The real-time and real-space characterization by time-resolved STEM reveals the electrochemical correspondence of discharge/charge overpotentials to the nucleation, growth and decomposition of Li 2 O 2 at a constant current density. The nano-scale operando observations would enrich our knowledge on the underlying reaction mechanisms of lithium-oxygen batteries during round-trip discharging and charging and shed lights on the strategies in improving the performances of lithium-oxygen batteries by tailoring the cathodic reactions.

Short-term anomia training and electrical brain stimulation.

PubMed

Flöel, Agnes; Meinzer, Marcus; Kirstein, Robert; Nijhof, Sarah; Deppe, Michael; Knecht, Stefan; Breitenstein, Caterina

2011-07-01

Language training success in chronic aphasia remains only moderate. Electric brain stimulation may be a viable way to enhance treatment efficacy. In a randomized, double-blind, sham-controlled crossover trial, we assessed if anodal transcranial direct current stimulation compared to cathodal transcranial direct current stimulation and sham stimulation over the right temporo-parietal cortex would improve the success of short-term high-frequency anomia training. Twelve chronic poststroke aphasia patients were studied. Naming outcome was assessed after training and 2 weeks later. All training conditions led to a significant increase in naming ability, which was retained for at least 2 weeks after the end of the training. Application of anodal transcranial direct current stimulation significantly enhanced the overall training effect compared to sham stimulation. Baseline naming ability significantly predicted anodal transcranial direct current stimulation effects. Anodal transcranial direct current stimulation applied over the nonlanguage dominant hemisphere can enhance language training outcome in chronic aphasia. Clinical Trial Registration- URL: www.clinicaltrials.gov/. Unique identifier: NCT00822068.

Boundary-value problem for a counterrotating electrical discharge in an axial magnetic field. [plasma centrifuge for isotope separation

NASA Technical Reports Server (NTRS)

Hong, S. H.; Wilhelm, H. E.

1978-01-01

An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 1,000,000 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.

Computationally optimized ECoG stimulation with local safety constraints.

PubMed

Guler, Seyhmus; Dannhauer, Moritz; Roig-Solvas, Biel; Gkogkidis, Alexis; Macleod, Rob; Ball, Tonio; Ojemann, Jeffrey G; Brooks, Dana H

2018-06-01

Direct stimulation of the cortical surface is used clinically for cortical mapping and modulation of local activity. Future applications of cortical modulation and brain-computer interfaces may also use cortical stimulation methods. One common method to deliver current is through electrocorticography (ECoG) stimulation in which a dense array of electrodes are placed subdurally or epidurally to stimulate the cortex. However, proximity to cortical tissue limits the amount of current that can be delivered safely. It may be desirable to deliver higher current to a specific local region of interest (ROI) while limiting current to other local areas more stringently than is guaranteed by global safety limits. Two commonly used global safety constraints bound the total injected current and individual electrode currents. However, these two sets of constraints may not be sufficient to prevent high current density locally (hot-spots). In this work, we propose an efficient approach that prevents current density hot-spots in the entire brain while optimizing ECoG stimulus patterns for targeted stimulation. Specifically, we maximize the current along a particular desired directional field in the ROI while respecting three safety constraints: one on the total injected current, one on individual electrode currents, and the third on the local current density magnitude in the brain. This third set of constraints creates a computational barrier due to the huge number of constraints needed to bound the current density at every point in the entire brain. We overcome this barrier by adopting an efficient two-step approach. In the first step, the proposed method identifies the safe brain region, which cannot contain any hot-spots solely based on the global bounds on total injected current and individual electrode currents. In the second step, the proposed algorithm iteratively adjusts the stimulus pattern to arrive at a solution that exhibits no hot-spots in the remaining brain. We report on simulations on a realistic finite element (FE) head model with five anatomical ROIs and two desired directional fields. We also report on the effect of ROI depth and desired directional field on the focality of the stimulation. Finally, we provide an analysis of optimization runtime as a function of different safety and modeling parameters. Our results suggest that optimized stimulus patterns tend to differ from those used in clinical practice. Copyright © 2018 Elsevier Inc. All rights reserved.

Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells.

PubMed

Sim, Junyoung; An, Junyeong; Elbeshbishy, Elsayed; Ryu, Hodon; Lee, Hyung-Sool

2015-11-01

Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2O2 conversion efficiency was negligible at 0.3-12%. Current density decreased for passive O2 diffusion to the cathode, but H2O2 conversion efficiency increased by 65%. An MEC equipped with a gas diffusion cathode was operated with acetate medium and domestic wastewater, which presented relatively high H2O2 conversion efficiency from 36% to 47%, although cathode overpotential was fluctuated. Due to different current densities, the maximum H2O2 production rate was 141 mg H2O2/L-h in the MEC fed with acetate medium, but it became low at 6 mg H2O2/L-h in the MEC fed with the wastewater. Our study clearly indicates that improving anodic current density and mitigating membrane fouling would be key parameters for large-scale H2O2-MECs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Pulsed electromagnetic gas acceleration. [magnetohydrodynamics, plasma power sources and plasma propulsion

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1975-01-01

Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.

Virtual cathode emission of an annular cold cathode

NASA Astrophysics Data System (ADS)

Park, S.-d.; Kim, J.-h.; Han, J.; Yoon, M.; Park, S. Y.; Choi, D. W.; Shin, J. W.; So, J. H.

2009-11-01

Recent measurement of voltage V and current I of the electron gun of a relativistic klystron amplifier revealed that the resulting current-voltage relationship appeared to differ from the usual Child-Langmuir law (I∝V3/2) especially during the initial period of voltage increase. This paper attempts to explain this deviation by examining the emission mechanism using particle-in-cell simulation. The emission area in the cathode increased stepwise as the applied voltage increased and within each step the current and voltage followed the Child-Langmuir law. The electron emission began when the voltage reached a threshold, and the perveance increased with the emission area. Furthermore, an apparent virtual cathode was formed which was larger than the cathode tip. This occurs because, above a certain voltage, the emission from the edge and the side of the cathode surface dominates the emission from the front-end surface.

Use of predissociation to enhance the atomic hydrogen ion fraction in ion sources

DOEpatents

Kim, Jinchoon

1979-01-01

A duopigatron ion source is modified by replacing the normal oxide-coated wire filament cathode of the ion source with a hot tungsten oven through which hydrogen gas is fed into the arc chamber. The hydrogen gas is predissociated in the hot oven prior to the arc discharge, and the recombination rate is minimized by hot walls inside of the arc chamber. With the use of the above modifications, the atomic H.sub.1.sup.+ ion fraction output can be increased from the normal 50% to greater than 70% with a corresponding decrease in the H.sub.2.sup.+ and H.sub.3.sup.+ molecular ion fraction outputs from the ion source.

Mutagenic and genotoxic potential of direct electric current in Escherichia coli and Salmonella thyphimurium strains.

PubMed

Gomes, Marina das Neves; Cardoso, Janine Simas; Leitão, Alvaro Costa; Quaresma, Carla Holandino

2016-05-01

Direct electric current has several therapeutic uses such as antibacterial and antiprotozoal action, tissues scarring and regeneration, as well as tumor treatment. This method has shown promising results in vivo and in vitro, with significant efficacy and almost no side effects. Considering lack of studies regarding direct electric current mutagenic and/or genotoxic effects, the present work evaluated both aspects by using five different bacterial experimental assays: survival of repair-deficient mutants, Salmonella-histidine reversion mutagenesis (Ames test), forward mutations to rifampicin resistance, phage reactivation, and lysogenic induction. In these experimental conditions, cells were submitted to an approach that allows evaluation of anodic, cathodic, and electro-ionic effects generated by 2 mA of direct electric current, with doses ranging from 0.36 to 3.60 Coulombs. Our results showed these doses did not induce mutagenic or genotoxic effects. © 2016 Wiley Periodicals, Inc.

Cortical activation changes underlying stimulation-induced behavioural gains in chronic stroke

PubMed Central

Bachtiar, Velicia; O'Shea, Jacinta; Allman, Claire; Bosnell, Rosemary Ann; Kischka, Udo; Matthews, Paul McMahan; Johansen-Berg, Heidi

2012-01-01

Transcranial direct current stimulation, a form of non-invasive brain stimulation, is showing increasing promise as an adjunct therapy in rehabilitation following stroke. However, although significant behavioural improvements have been reported in proof-of-principle studies, the underlying mechanisms are poorly understood. The rationale for transcranial direct current stimulation as therapy for stroke is that therapeutic stimulation paradigms increase activity in ipsilesional motor cortical areas, but this has not previously been directly tested for conventional electrode placements. This study was performed to test directly whether increases in ipsilesional cortical activation with transcranial direct current stimulation are associated with behavioural improvements in chronic stroke patients. Patients at least 6 months post-first stroke participated in a behavioural experiment (n = 13) or a functional magnetic resonance imaging experiment (n = 11), each investigating the effects of three stimulation conditions in separate sessions: anodal stimulation to the ipsilesional hemisphere; cathodal stimulation to the contralesional hemisphere; and sham stimulation. Anodal (facilitatory) stimulation to the ipsilesional hemisphere led to significant improvements (5–10%) in response times with the affected hand in both experiments. This improvement was associated with an increase in movement-related cortical activity in the stimulated primary motor cortex and functionally interconnected regions. Cathodal (inhibitory) stimulation to the contralesional hemisphere led to a functional improvement only when compared with sham stimulation. We show for the first time that the significant behavioural improvements produced by anodal stimulation to the ipsilesional hemisphere are associated with a functionally relevant increase in activity within the ipsilesional primary motor cortex in patients with a wide range of disabilities following stroke. PMID:22155982

Quasistationary magnetic field generation with a laser-driven capacitor-coil assembly.

PubMed

Tikhonchuk, V T; Bailly-Grandvaux, M; Santos, J J; Poyé, A

2017-08-01

Recent experiments are showing possibilities to generate strong magnetic fields on the excess of 500 T with high-energy nanosecond laser pulses in a compact setup of a capacitor connected to a single turn coil. Hot electrons ejected from the capacitor plate (cathode) are collected at the other plate (anode), thus providing the source of a current in the coil. However, the physical processes leading to generation of currents exceeding hundreds of kiloamperes in such a laser-driven diode are not sufficiently understood. Here we present a critical analysis of previous results and propose a self-consistent model for the high current generation in a laser-driven capacitor-coil assembly. It accounts for three major effects controlling the diode current: the space charge neutralization, the plasma magnetization between the capacitor plates, and the Ohmic heating of the external circuit-the coil-shaped connecting wire. The model provides the conditions necessary for transporting strongly super-Alfvenic currents through the diode on the time scale of a few nanoseconds. The model validity is confirmed by a comparison with the available experimental data.

Development program on a cold cathode electron gun

NASA Technical Reports Server (NTRS)

Spindt, C. A.; Holland, C. E.

1985-01-01

During this phase of the cathode development program, SRI improved the multiple electron beam exposure system used to print hole patterns for the cathode arrays, studied anisotropic etch processes, conducted cathode investigations using an emission microscope, reviewed possible alternate materials for cathode fabrication, studied cathode storage techniques, conducted high power operation experiments, and demonstrated high-current-density operation with small arrays of tips.

Development of a high average current polarized electron source with long cathode operational lifetime

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

C. K. Sinclair; P. A. Adderley; B. M. Dunham

Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and havemore » often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2?105???C/cm2 and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.« less

Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

NASA Astrophysics Data System (ADS)

Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

2016-10-01

This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions in a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.

Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

DOE PAGES

Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; ...

2016-08-15

This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions inmore » a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Lastly, simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.« less

The anodic emitter effect and its inversion demonstrated by temperature measurements at doped and undoped tungsten electrodes

NASA Astrophysics Data System (ADS)

Hoebing, T.; Bergner, A.; Hermanns, P.; Mentel, J.; Awakowicz, P.

2016-04-01

The admixture of a small amount of emitter oxides, e.g. \\text{Th}{{\\text{O}}2} , \\text{L}{{\\text{a}}2}{{\\text{O}}3} or \\text{C}{{\\text{e}}2}{{\\text{O}}3} to tungsten generates the so-called emitter effect. It reduces the work function of tungsten cathodes, that are applied in high intensity discharge (HID) lamps. After leaving the electrode bulk and moving to the surface, a monolayer of Th, La, or Ce atoms is formed on the surface, which reduces the effective work function ϕ. Depending on the coverage of the electrode, the effective reduction in ϕ is subjected to the thermal desorption of the monolayer from the hot electrode surface. The thermal desorption of emitter atoms from the cathode is compensated not only by the supply from the interior of the electrode and by surface diffusion of the emitter material to its tip, but also to a large extent by a repatriation of the emitter ions from the plasma by the strong electric field in front of the cathode. Yet, an emitter ion current from the arc discharge to the anode may only be present, if the anode is cold enough to refrain from thermionic emission. Therefore, the ability of emitter oxides to reduce the temperature of tungsten anodes is only given for a moderate temperature so that the thermal desorption is low and an additional ion current is present in front of the anode. A higher electrode temperature leads to their evaporation and to an inversion of the emitter effect, which increases the temperature of the respective anodes in comparison with pure tungsten anodes. Within this article, the emitter effect of doped tungsten anodes and the transition to its inversion is investigated for thoriated, lanthanated, and ceriated tungsten electrodes by measurements of the electrode temperature in dependence on the discharge current. It is shown for a lanthanated and a ceriated anode that the emitter effect is sustained by an ion current at anode temperatures at which the thermal evaporation of emitter material is completed.

Control of plasma properties in a short direct-current glow discharge with active boundaries

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

Adams, S. F.; Demidov, V. I., E-mail: vladimir.demidov@mail.wvu.edu; West Virginia University, Morgantown, West Virginia 26506

2016-02-15

To demonstrate controlling electron/metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (lacking the positive-column region) direct-current glow discharge with a cold cathode. The applied negative voltage can modify the trapping of the low-energy part of the energetic electrons that are emitted from the cathode sheath and that arise from the atomic and molecular processes in the plasma within the device volume. These electrons are responsible for heating the slow, thermal electrons, while production of slowmore » electrons (ions) and metastable atoms is mostly due to the energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons (ions), while decay rate of metastable atoms and production rates of slow electrons (ions) and metastable atoms practically are unchanged. The result is in the variation of electron/metastable density ratio and electron temperature with the variation of the wall negative voltage.« less

Image intensifier gain uniformity improvements in sealed tubes by selective scrubbing

DOEpatents

Thomas, S.W.

1995-04-18

The gain uniformity of sealed microchannel plate image intensifiers (MCPIs) is improved by selectively scrubbing the high gain sections with a controlled bright light source. Using the premise that ions returning to the cathode from the microchannel plate (MCP) damage the cathode and reduce its sensitivity, a HeNe laser beam light source is raster scanned across the cathode of a microchannel plate image intensifier (MCPI) tube. Cathode current is monitored and when it exceeds a preset threshold, the sweep rate is decreased 1000 times, giving 1000 times the exposure to cathode areas with sensitivity greater than the threshold. The threshold is set at the cathode current corresponding to the lowest sensitivity in the active cathode area so that sensitivity of the entire cathode is reduced to this level. This process reduces tube gain by between 10% and 30% in the high gain areas while gain reduction in low gain areas is negligible. 4 figs.

Image intensifier gain uniformity improvements in sealed tubes by selective scrubbing

DOEpatents

Thomas, Stanley W.

1995-01-01

The gain uniformity of sealed microchannel plate image intensifiers (MCPIs) is improved by selectively scrubbing the high gain sections with a controlled bright light source. Using the premise that ions returning to the cathode from the microchannel plate (MCP) damage the cathode and reduce its sensitivity, a HeNe laser beam light source is raster scanned across the cathode of a microchannel plate image intensifier (MCPI) tube. Cathode current is monitored and when it exceeds a preset threshold, the sweep rate is decreased 1000 times, giving 1000 times the exposure to cathode areas with sensitivity greater than the threshold. The threshold is set at the cathode current corresponding to the lowest sensitivity in the active cathode area so that sensitivity of the entire cathode is reduced to this level. This process reduces tube gain by between 10% and 30% in the high gain areas while gain reduction in low gain areas is negligible.

Improving lithium-ion battery performances by adding fly ash from coal combustion on cathode film

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

Dyartanti, Endah Retno; Jumari, Arif, E-mail: arifjumari@yahoo.com; Nur, Adrian

A lithium battery is composed of anode, cathode and a separator. The performance of lithium battery is also influenced by the conductive material of cathode film. In this research, the use of fly ash from coal combustion as conductive enhancer for increasing the performances of lithium battery was investigated. Lithium iron phosphate (LiFePO{sub 4}) was used as the active material of cathode. The dry fly ash passed through 200 mesh screen, LiFePO{sub 4} and acethylene black (AB), polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent were mixed to form slurry. The slurry was then coated, driedmore » and hot pressed to obtain the cathode film. The ratio of fly ash and AB were varied at the values of 1%, 2%, 3%, 4% and 5% while the other components were at constant. The anode film was casted with certain thickness and composition. The performance of battery lithium was examined by Eight Channel Battery Analyzer, the composition of the cathode film was examined by XRD (X-Ray Diffraction), and the structure and morphology of the anode film was analyzed by SEM (Scanning Electron Microscope). The composition, structure and morphology of cathode film was only different when fly ash added was 4% of AB or more. The addition of 2% of AB on cathode film gave the best performance of 81.712 mAh/g on charging and 79.412 mAh/g on discharging.« less

Design, construction and long life endurance testing of cathode assemblies for use in microwave high-power transmitting tubes

NASA Technical Reports Server (NTRS)

Batra, R.; Marino, D.

1986-01-01

The cathode life test program sponsored by NASA Lewis Research Center at Watkins-Johnson Company has been in continuous operation since 1972. Its primary objective has been to evaluate the long life capability of barium dispenser cathodes to produce emission current densities of 2 A sq. cm. or more in an operational environment simulating that of a highpower microwave tube. The life test vehicles were equipped with convergent flow electron guns, drift space tubes with solenoid magnets for electron beam confinement and water-cooled depressed collectors. A variety of cathode types has been tested, including GE Tungstate, Litton Impregnated, Philips Type B and M, Semicon types S and M, and Spectra-Mat Type M. Recent emphasis has been on monitoring the performance of Philips Type M cathodes at 2 A sq. cm. and Sprectra-Mat and Semicon Type M cathodes at 4 A sq. cm. These cathodes have been operated at a constant current of 616 mA and a cathode anode voltage on the order of 10 kV. Cathode temperatures were maintained at 1010 C true as measured from black body holes in the backs of the cathodes. This report presents results of the cathode life test program from July l982 through April l986. The results include hours of operation and performance data in the form of normalized emission current density versus temperature curves (Miram plots).

Investigation of hollow cathode performance for 30-cm thrusters

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1973-01-01

A parametric investigation of 6.35 mm diameter mercury hollow cathodes was carried out in a bell jar. The parameters that were varied were the amount of initial emissive mix, the insert position, the emission current, the cathode temperature, the orifice diameter, and the mercury flow rate. Flow characteristic curves and performance as a function of time were obtained for the various cathodes of interest. Also presented are the results of a 3880 hr life test of a main cathode run at 15 amps emission current with no noticeable changes in keeper and collector voltages.

The hollow cathode in the quasi-steady MPD discharge

NASA Technical Reports Server (NTRS)

Von Jaskowsky, W. F.; Jahn, R. G.; Clark, K. E.; Krishnan, M.

1973-01-01

A large hollow cathode has been operated in a quasi-steady MPD discharge over a range of current from 7 to 30 kA and argon mass flow from 0.04 to 6.0 g/sec. The 1.3-cm-i.d. cathode cavity attains steady emission characteristics in some tens of microseconds without the assistance of auxiliary heating, low work function inserts, or external keeper electrodes. Measured current and potential distributions within the cavity reveal that the current attaches in a zone 1 to 2 cm long with a surface current density greater than 1000 A/sq cm and a local axial electric field less than 10 V/cm. Electron densities within the cavity, estimated from spectroscopic records, are above 10 to the 17th power per cu cm, at least one order of magnitude greater than has been reported for either ion engine hollow cathodes or conventional solid cathodes in similar arc discharges.

Electrochemical power-producing cell. [Li/Se

DOEpatents

Cairns, E.J.; Chilenskas, A.A.; Steunenberg, R.K.; Shimotake, H.

1972-05-30

An electrochemical power-producing cell including a molten lithium metal anode, a molten selenium metal cathode, a paste electrolyte separating the anode from the cathode, an anode current collector, and a single layer of niobium expanded metal formed in corrugated shape as cathode current collector is described. In addition, means are provided for sealing the anode and the cathode from loss of lithium and selenium, respectively, and an insulator is provided between the anode housing and the paste electrolyte disk.

Apparatus Notes.

ERIC Educational Resources Information Center

Eaton, Bruce G., Ed.

1979-01-01

Describes the following: a low-pressure sodium light source; a design of hot cathodes for plasma and electron physics experiments; a demonstration cart for a physics of sound course; Bernoulli force using coffee cups; a spark recording for the linear air track; and a demonstration of the effect of altering the cavity resonance of a violin. (GA)

Effect of Ti-Al cathode composition on plasma generation and plasma transport in direct current vacuum arc

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

Zhirkov, I., E-mail: igozh@ifm.liu.se; Petruhins, A.; Dahlqvist, M.

2014-03-28

DC arc plasma from Ti, Al, and Ti{sub 1-x}Al{sub x} (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the cathode surfaces were used for exploring the correlation between cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10{sup −6} Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathodemore » stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental cathodes, and approximately independent on the cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically reduced when comparing the elemental Ti and Al cathodes with Ti{sub 0.5}Al{sub 0.5}, going from ∼150 and ∼175 eV to ∼100 and ∼75 eV for Ti and Al ions, respectively. This may be explained by a reduction in electron temperature, commonly associated with the high energy tail of the IED. The average Ti and Al ion energies ranged between ∼50 and ∼61 eV, and ∼30 and ∼50 eV, respectively, for different cathode compositions. The attained energy trends were explained by the velocity rule for compound cathodes, which states that the most likely velocities of ions of different mass are equal. Hence, compared to elemental cathodes, the faster Al ions will be decelerated, and the slower Ti ions will be accelerated when originating from compound cathodes. The intensity of the macroparticle generation and thickness of the deposited films were also found to be dependent on the cathode composition. The presented results may be of importance for choice of cathodes for thin film depositions involving compound cathodes.« less

Monitoring transcranial direct current stimulation induced changes in cortical excitability during the serial reaction time task.

PubMed

Ambrus, Géza Gergely; Chaieb, Leila; Stilling, Roman; Rothkegel, Holger; Antal, Andrea; Paulus, Walter

2016-03-11

The measurement of the motor evoked potential (MEP) amplitudes using single pulse transcranial magnetic stimulation (TMS) is a common method to observe changes in motor cortical excitability. The level of cortical excitability has been shown to change during motor learning. Conversely, motor learning can be improved by using anodal transcranial direct current stimulation (tDCS). In the present study, we aimed to monitor cortical excitability changes during an implicit motor learning paradigm, a version of the serial reaction time task (SRTT). Responses from the first dorsal interosseous (FDI) and forearm flexor (FLEX) muscles were recorded before, during and after the performance of the SRTT. Online measurements were combined with anodal, cathodal or sham tDCS for the duration of the SRTT. Negative correlations between the amplitude of online FDI MEPs and SRTT reaction times (RTs) were observed across the learning blocks in the cathodal condition (higher average MEP amplitudes associated with lower RTs) but no significant differences in the anodal and sham conditions. tDCS did not have an impact on SRTT performance, as would be predicted based on previous studies. The offline before-after SRTT MEP amplitudes showed an increase after anodal and a tendency to decrease after cathodal stimulation, but these changes were not significant. The combination of different interventions during tDCS might result in reduced efficacy of the stimulation that in future studies need further attention. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Golgi polarization plays a role in the directional migration of neonatal dermal fibroblasts induced by the direct current electric fields.

PubMed

Kim, Min Sung; Lee, Mi Hee; Kwon, Byeong-Ju; Koo, Min-Ah; Seon, Gyeung Mi; Park, Jong-Chul

2015-05-01

Directional cell migration requires cell polarization. The reorganization of the Golgi apparatus is an important phenomenon in the polarization and migration of many types of cells. Direct current electric fields (dc (EF) induced directional cell migration in a wide variety of cells. Here nHDFs migrated toward cathode under 1 V/cm dc EF, however 1 μM of brefeldin A (BFA) inhibited the dc EF induced directional migration. BFA (1 μM) did not cause the complete Golgi dispersal for 2 h. When the Golgi polarization maintained their direction of polarity, the direction of cell migration also kept toward the same direction of the Golgi polarization even though the dc EF was reversed. In this study, the importance of the Golgi polarization in the directional migration of nHDf under dc EF was identified. Copyright © 2015 Elsevier Inc. All rights reserved.

The effect of the interval-between-sessions on prefrontal transcranial direct current stimulation (tDCS) on cognitive outcomes: a systematic review and meta-analysis.

PubMed

Dedoncker, Josefien; Brunoni, Andre R; Baeken, Chris; Vanderhasselt, Marie-Anne

2016-10-01

Recently, there has been wide interest in the effects of transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) on cognitive functioning. However, many methodological questions remain unanswered. One of them is whether the time interval between active and sham-controlled stimulation sessions, i.e. the interval between sessions (IBS), influences DLPFC tDCS effects on cognitive functioning. Therefore, a systematic review and meta-analysis was performed of experimental studies published in PubMed, Science Direct, and other databases from the first data available to February 2016. Single session sham-controlled within-subject studies reporting the effects of tDCS of the DLPFC on cognitive functioning in healthy controls and neuropsychiatric patients were included. Cognitive tasks were categorized in tasks assessing memory, attention, and executive functioning. Evaluation of 188 trials showed that anodal vs. sham tDCS significantly decreased response times and increased accuracy, and specifically for the executive functioning tasks, in a sample of healthy participants and neuropsychiatric patients (although a slightly different pattern of improvement was found in analyses for both samples separately). The effects of cathodal vs. sham tDCS (45 trials), on the other hand, were not significant. IBS ranged from less than 1 h to up to 1 week (i.e. cathodal tDCS) or 2 weeks (i.e. anodal tDCS). This IBS length had no influence on the estimated effect size when performing a meta-regression of IBS on reaction time and accuracy outcomes in all three cognitive categories, both for anodal and cathodal stimulation. Practical recommendations and limitations of the study are further discussed.

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

Kandlakunta, P; Pham, R; Zhang, T

Purpose: To develop and characterize a high brightness multiple-pixel thermionic emission x-ray (MPTEX) source. Methods: Multiple-pixel x-ray sources allow for designs of novel x-ray imaging techniques, such as fixed gantry CT, digital tomosynthesis, tetrahedron beam computed tomography, etc. We are developing a high-brightness multiple-pixel thermionic emission x-ray (MPTEX) source based on oxide coated cathodes. Oxide cathode is chosen as the electron source due to its high emission current density and low operating temperature. A MPTEX prototype has been developed which may contain up to 41 micro-rectangular oxide cathodes in 4 mm pixel spacing. Electronics hardware was developed for source controlmore » and switching. The cathode emission current was evaluated and x-ray measurements were performed to estimate the focal spot size. Results: The oxide cathodes were able to produce ∼110 mA cathode current in pulse mode which corresponds to an emission current density of 0.55 A/cm{sup 2}. The maximum kVp of the MPTEX prototype currently is limited to 100 kV due to the rating of high voltage feedthrough. Preliminary x-ray measurements estimated the focal spot size as 1.5 × 1.3 mm{sup 2}. Conclusion: A MPTEX source was developed with thermionic oxide coated cathodes and preliminary source characterization was successfully performed. The MPTEX source is able to produce an array of high brightness x-ray beams with a fast switching speed.« less

Low resistance, low-inductance power connectors

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

Coteus, Paul W.; Ferencz, Andrew; Hall, Shawn Anthony

An electrical connector includes an anode assembly for conducting an electrical supply current from a source to a destination, the anode assembly includes an anode formed into a first shape from sheet metal or other sheet-like conducting material. A cathode assembly conducts an electrical return current from the destination to the source, the cathode assembly includes a cathode formed into a second shape from sheet metal or other sheet-like conducting material. An insulator prevents electrical conduction between the anode and the cathode. The first and second shapes are such as to provide a conformity of one to the other, withmore » the insulator therebetween having a predetermined relatively thin thickness. A predetermined low-resistance path for the supply current is provided by the anode, a predetermined low-resistance path for the return current is provided by the cathode, and the proximity of the anode to the cathode along these paths provides a predetermined low self-inductance of the connector, where the proximity is afforded by the conformity of the first and second shapes.« less

Self-pulsing in a low-current hollow cathode discharge: From Townsend to glow discharge

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

Qin, Yu; School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081; Xie, Kan, E-mail: xiekan@bit.edu.cn

We investigate the self-pulsing phenomenon of a low current cavity discharge in a cylindrical hollow cathode in pure argon. The waveforms of pulsed current and voltage are measured, and the time-averaged and time-resolved images of hollow cathode discharge are recorded by using high-speed intensified charge coupled device camera. The results show that the self-pulsing is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. During the self-pulsing, the current rising time relates to the dissipation of space charges, and the decay time relates to the reconstruction of the virtual anode by the accumulation ofmore » positive ions. Whether or not space charges can form and keep the virtual anode is responsible for the discharge mode and hence plays an important role in the self-pulsing phenomenon in low current hollow cathode discharge.« less

Process for testing a xenon gas feed system of a hollow cathode assembly

NASA Technical Reports Server (NTRS)

Patterson, Michael J. (Inventor); Verhey, Timothy R. R. (Inventor); Soulas, George C. (Inventor)

2004-01-01

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Process for Ignition of Gaseous Electrical Discharge Between Electrodes of a Hollow Cathode Assembly

NASA Technical Reports Server (NTRS)

Patterson, Michael J. (Inventor); Verhey, Timothy R. R. (Inventor); Soulas, George C. (Inventor)

2000-01-01

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Novel Architectures for Achieving Direct Electron Transfer in Enzymatic Biofuel Cells

NASA Astrophysics Data System (ADS)

Blaik, Rita A.

Enzymatic biofuel cells are a promising source of alternative energy for small device applications, but still face the challenge of achieving direct electron transfer with high enzyme concentrations in a simple system. In this dissertation, methods of constructing electrodes consisting of enzymes attached to nanoparticle-enhanced substrates that serve as high surface area templates are evaluated. In the first method described, glucose oxidase is covalently attached to gold nanoparticles that are assembled onto genetically engineered M13 bacteriophage. The resulting anodes achieve a high peak current per area and a significant improvement in enzyme surface coverage. In the second system, fructose dehydrogenase, a membrane-bound enzyme that has the natural ability to achieve direct electron transfer, is immobilized into a matrix consisting of binders and carbon nanotubes to extend the lifetime of the anode. For the cathode, bilirubin oxidase is immobilized in a carbon nanotube and sol-gel matrix to achieve direct electron transfer. Finally, a full fuel cell consisting of both an anode and cathode is constructed and evaluated with each system described.

Effiectiveness and safety of transcranial direct current stimulation in fibromyalgia: A systematic review and meta-analysis.

PubMed

Zhu, Chang-E; Yu, Bo; Zhang, Wen; Chen, Wen-Hua; Qi, Qi; Miao, Yun

2017-01-19

To evaluate the effectiveness and safety of transcranial direct current stimulation for fibro-myalgia. Databases, conference records and registered trials were searched for articles published from the date of establishment of the database through to October 2015. Six randomized controlled trials (n=192) of transcranial direct current stimulation for fibromyalgia were included in the current study. Two researchers independently screened the literature, assessed methodological quality using the Cochrane Collaboration's tool, and extracted data. Studies were divided into 3 groups for meta-analysis according to stimulation site and polarity. Significant improvement in pain and general fibromyalgia-related function was seen with anodal transcranial direct current stimulation over the primary motor cortex (p<0.05). However, the pressure pain threshold did not improve (p>0.05). Anodal transcranial direct current stimulation over the left dorsolateral prefrontal cortex did not significantly reduce pain or improve general fibromyalgia-related function compared with sham stimulation (p>0.05). Cathodal transcranial direct current stimulation over the primary motor cortex did not improve the pressure pain threshold compared with sham stimulation (p>0.05). No significant adverse effects were seen. Anodal transcranial direct current stimulation over the primary motor cortex is more likely than sham transcranial direct current stimulation to relieve pain and improve general fibromyalgia-related function.

Numerical simulation and analysis of electromagnetic-wave absorption of a plasma slab created by a direct-current discharge with gridded anode

NASA Astrophysics Data System (ADS)

Yuan, Chengxun; Tian, Ruihuan; Eliseev, S. I.; Bekasov, V. S.; Bogdanov, E. A.; Kudryavtsev, A. A.; Zhou, Zhongxiang

2018-03-01

In this paper, we present investigation of a direct-current discharge with a gridded anode from the point of view of using it as a means of creating plasma coating that could efficiently absorb incident electromagnetic (EM) waves. A single discharge cell consists of two parallel plates, one of which (anode) is gridded. Electrons emitted from the cathode surface are accelerated in the short interelectrode gap and are injected into the post-anode space, where they lose acquired energy on ionization and create plasma. Numerical simulations were used to investigate the discharge structure and obtain spatial distributions of plasma density in the post-anode space. The numerical model of the discharge was based on a simple hybrid approach which takes into account non-local ionization by fast electrons streaming from the cathode sheath. Specially formulated transparency boundary conditions allowed performing simulations in 1D. Simulations were carried out in air at pressures of 10 Torr and higher. Analysis of the discharge structure and discharge formation is presented. It is shown that using cathode materials with lower secondary emission coefficients can allow increasing the thickness of plasma slabs for the same discharge current, which can potentially enhance EM wave absorption. Spatial distributions of electron density obtained during simulations were used to calculate attenuation of an incident EM wave propagating perpendicularly to the plasma slab boundary. It is shown that plasma created by means of a DC discharge with a gridded anode can efficiently absorb EM waves in the low frequency range (6-40 GHz). Increasing gas pressure results in a broader range of wave frequencies (up to 500 GHz) where a considerable attenuation is observed.

Modulating oscillatory brain activity correlates of behavioral inhibition using transcranial direct current stimulation.

PubMed

Jacobson, Liron; Ezra, Adi; Berger, Uri; Lavidor, Michal

2012-05-01

Studies have mainly documented behavioral changes induced by transcranial direct current stimulation (tDCS), but recently cortical modulations of tDCS have also been investigated. Our previous work revealed behavioral inhibition modulation by anodal tDCS over the right inferior frontal gyrus (rIFG); however, the electrophysiological correlates underlying this stimulation montage have yet to be established. The current work aimed to evaluate the distribution of neuronal oscillations changes following anodal tDCS over rIFG coupled with cathodal tDCS over left orbitofrontal cortex (lOFC) using spectral power analysis. Healthy subjects underwent sham and real tDCS (15 min, 1.5 mA, anodal rIFG; cathodal lOFC) stimulation conditions in a single-blind, placebo-controlled cross-over trial. Following tDCS session, resting EEG recordings were collected during 15 min. Analysis showed a significant and selective diminution of the power of theta band. The theta diminution was observed in the rIFG area (represented the anode electrode), and was not found in the lOFC area (represented the cathode electrode). A significant effect was observed only in the theta but not in other bands. These results are the first demonstration of modulating oscillatory activity as measured by EEG with tDCS over rIFG in general, and documenting theta band reduction with this montage in particular. Our results may explain the improvement in behavioral inhibition reported in our previous work, and although this study was conducted with healthy subjects, the findings suggest that tDCS may also modulate electrophysiological changes among ADHD patients, where decreasing theta activity is the target of neuro-feedback methods aimed to improve cognitive control. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Thermionic gas switch

DOEpatents

Hatch, G.L.; Brummond, W.A.; Barrus, D.M.

1984-04-05

The present invention is directed to an improved temperature responsive thermionic gas switch utilizing a hollow cathode and a folded emitter surface area. The folded emitter surface area of the thermionic switch substantially increases the on/off ratio by changing the conduction surface area involved in the two modes thereof. The improved switch of this invention provides an on/off ratio of 450:1 compared to the 10:1 ratio of the prior known thermionic switch, while providing for adjusting the on current. In the improved switch of this invention the conduction area is made small in the off mode, while in the on mode the conduction area is made large. This is achieved by utilizing a folded hollow cathode configuration and utilizing a folded emitter surface area, and by making the dimensions of the folds small enough so that a space charge will develop in the convolutions of the folds and suppress unignited current, thus limiting the current carrying surface in the off mode.

Trak Investigation of Focusing Electrode Geometries for the DARHT Axis-I Diode

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

Kallas, Nicholas Dimitrious

2017-05-15

An investigation was carried out on the effects of different cathode shroud geometries of the DARHT Axis-1 diode using the Trak ray tracing software. Pierce angles of 20, 30, 45, 60, and 67.5 degrees were investigated. For each geometry the current density with respect to radial position will be presented as it evolves in the longitudinal direction. In addition the emittances for each geometry are compared and this information is used to determine the optimal geometry from the selected angles. These results are compared to the baseline geometry currently employed at DARHT of a simple 2.5mm recessed velvet cathode. Ofmore » the selected angles it was found that 45 degrees produced the lowest normalized emittance value, whereas 60 degrees produced the most uniform current density profile at 1cm away from the emission surface. For the purpose of this investigation the effects of the bucking coil and solenoid around the hollow anode of the DARHT Axis I injector are neglected.« less

Effect of hydrogen on cathodic corrosion of titanium aluminide

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

Gao, K.W.; Jin, J.W.; Qiao, L.J.

1996-01-01

Cathodic corrosion of titanium aluminide (TiAl) during hydrogen charging in various acidic aqueous solutions and in molten salt at 160 C was studied. At constant potential, the rate of cathodic corrosion (V) was much higher than during anodic dissolution, and V increased linearly with increasing current. V was 10 times higher in the acid solution than in the salt solution under the same current. Disruption of the surface film by local hydride formation during cathodic polarization was shown to be the key step.

Input-output relationship in galvanotactic response of Dictyostelium cells.

PubMed

Sato, Masayuki J; Ueda, Michihito; Takagi, Hiroaki; Watanabe, Tomonobu M; Yanagida, Toshio; Ueda, Masahiro

2007-04-01

Under a direct current electric field, Dictyostelium cells exhibit migration towards the cathode. To determine the input-output relationship of the cell's galvanotactic response, we developed an experimental instrument in which electric signals applied to the cells are highly reproducible and the motile response are analyzed quantitatively. With no electric field, the cells moved randomly in all directions. Upon applying an electric field, cell migration speeds became about 1.3 times faster than those in the absence of an electric field. Such kinetic effects of electric fields on the migration were observed for cells stimulated between 0.25 and 10 V/cm of the field strength. The directions of cell migrations were biased toward the cathode in a positive manner with field strength, showing galvanotactic response in a dose-dependent manner. Quantitative analysis of the relationship between field strengths and directional movements revealed that the biased movements of the cells depend on the square of electric field strength, which can be described by one simple phenomenological equation. The threshold strength for the galvanotaxis was between 0.25 and 1 V/cm. Galvanotactic efficiency reached to half-maximum at 2.6 V/cm, which corresponds to an approximate 8 mV voltage difference between the cathode and anode direction of 10 microm wide, round cells. Based on these results, possible mechanisms of galvanotaxis in Dictyostelium cells were discussed. This development of experimental system, together with its good microscopic accessibility for intracellular signaling molecules, makes Dictyostelium cells attractive as a model organism for elucidating stochastic processes in the signaling systems responsible for cell motility and its regulations.

Direct current stimulation over the anterior temporal areas boosts semantic processing in primary progressive aphasia.

PubMed

Teichmann, Marc; Lesoil, Constance; Godard, Juliette; Vernet, Marine; Bertrand, Anne; Levy, Richard; Dubois, Bruno; Lemoine, Laurie; Truong, Dennis Q; Bikson, Marom; Kas, Aurélie; Valero-Cabré, Antoni

2016-11-01

Noninvasive brain stimulation in primary progressive aphasia (PPA) is a promising approach. Yet, applied to single cases or insufficiently controlled small-cohort studies, it has not clarified its therapeutic value. We here address the effectiveness of transcranial direct current stimulation (tDCS) on the semantic PPA variant (sv-PPA), applying a rigorous study design to a large, homogeneous sv-PPA cohort. Using a double-blind, sham-controlled counterbalanced cross-over design, we applied three tDCS conditions targeting the temporal poles of 12 sv-PPA patients. Efficiency was assessed by a semantic matching task orthogonally manipulating "living"/"nonliving" categories and verbal/visual modalities. Conforming to predominantly left-lateralized damage in sv-PPA and accounts of interhemispheric inhibition, we applied left hemisphere anodal-excitatory and right hemisphere cathodal-inhibitory tDCS, compared to sham stimulation. Prestimulation data, compared to 15 healthy controls, showed that patients had semantic disorders predominating with living categories in the verbal modality. Stimulation selectively impacted these most impaired domains: Left-excitatory and right-inhibitory tDCS improved semantic accuracy in verbal modality, and right-inhibitory tDCS improved processing speed with living categories and accuracy and processing speed in the combined verbal × living condition. Our findings demonstrate the efficiency of tDCS in sv-PPA by generating highly specific intrasemantic effects. They provide "proof of concept" for future applications of tDCS in therapeutic multiday regimes, potentially driving sustained improvement of semantic processing. Our data also support the hotly debated existence of a left temporal-pole network for verbal semantics selectively modulated through both left-excitatory and right-inhibitory brain stimulation. Ann Neurol 2016;80:693-707. © 2016 American Neurological Association.

Electron current extraction from a permanent magnet waveguide plasma cathode.

PubMed

Weatherford, B R; Foster, J E; Kamhawi, H

2011-09-01

An electron cyclotron resonance plasma produced in a cylindrical waveguide with external permanent magnets was investigated as a possible plasma cathode electron source. The configuration is desirable in that it eliminates the need for a physical antenna inserted into the plasma, the erosion of which limits operating lifetime. Plasma bulk density was found to be overdense in the source. Extraction currents over 4 A were achieved with the device. Measurements of extracted electron currents were similar to calculated currents, which were estimated using Langmuir probe measurements at the plasma cathode orifice and along the length of the external plume. The influence of facility effects and trace ionization in the anode-cathode gap are also discussed. © 2011 American Institute of Physics

Optimizing membrane electrode assembly of direct methanol fuel cells for portable power

NASA Astrophysics Data System (ADS)

Liu, Fuqiang

Direct methanol fuel cells (DMFCs) for portable power applications require high power density, high-energy conversion efficiency and compactness. These requirements translate to fundamental properties of high methanol oxidation and oxygen reduction kinetics, as well as low methanol and water crossover. In this thesis a novel membrane electrode assembly (MEA) for direct methanol fuel cells has been developed, aiming to improve these fundamental properties. Firstly, methanol oxidation kinetics has been enhanced and methanol crossover has been minimized by proper control of ionomer crystallinity and its swelling in the anode catalyst layer through heat-treatment. Heat-treatment has a major impact on anode characteristics. The short-cured anode has low ionomer crystallinity, and thus swells easily when in contact with methanol solution to create a much denser anode structure, giving rise to higher methanol transport resistance than the long-cured anode. Variations in interfacial properties in the anode catalyst layer (CL) during cell conditioning were also characterized, and enhanced kinetics of methanol oxidation and severe limiting current phenomenon were found to be caused by a combination of interfacial property variations and swelling of ionomer over time. Secondly, much effort has been expended to develop a cathode CL suitable for operation under low air stoichiometry. The effects of fabrication procedure, ionomer content, and porosity distribution on the microstructure and cathode performance under low air stoichiometry are investigated using electrochemical and surface morphology characterizations to reveal the correlation between microstructure and electrochemical behavior. At the same time, computational fluid dynamics (CFD) models of DMFC cathodes have been developed to theoretically interpret the experimental results, to investigate two-phase transport, and to elucidate mechanism of cathode mixed potential due to methanol crossover. Thirdly, a MEA with low water crossover has been developed by employing a highly-hydrophobic microporous layer (MPL) to build up hydraulic pressure at the cathode, promoting product water permeation from the cathode to anode to offset water dragged by electro-osmosis. Water crossover through the MEA is further reduced by an anode hydrophobic MPL through facilitating water back diffusion. Under different current densities, the MEA with hydrophobic MPL has consistently low alpha, several times smaller than those with hydrophilic or without MPL. A simulation study of anode water transport by a two-phase model shows that anode MPL wettability strongly determines liquid saturation in the anode, and thus is identified as playing a crucial role in promoting water back diffusion. Finally, direct feed of highly-concentrated methanol using the optimized MEA has been successfully demonstrated by a face-feed anode plate, which minimizes methanol crossover by controlling the fuel delivery rate. Using 10 M methanol, a steady-state power density of ˜67mW/cm2 is reached at 60°C and 175mA/cm2, which is almost identical to that with 2M methanol.

Imaging of nonlocal hot-electron energy dissipation via shot noise.

PubMed

Weng, Qianchun; Komiyama, Susumu; Yang, Le; An, Zhenghua; Chen, Pingping; Biehs, Svend-Age; Kajihara, Yusuke; Lu, Wei

2018-05-18

In modern microelectronic devices, hot electrons accelerate, scatter, and dissipate energy in nanoscale dimensions. Despite recent progress in nanothermometry, direct real-space mapping of hot-electron energy dissipation is challenging because existing techniques are restricted to probing the lattice rather than the electrons. We realize electronic nanothermometry by measuring local current fluctuations, or shot noise, associated with ultrafast hot-electron kinetic processes (~21 terahertz). Exploiting a scanning and contact-free tungsten tip as a local noise probe, we directly visualize hot-electron distributions before their thermal equilibration with the host gallium arsenide/aluminium gallium arsenide crystal lattice. With nanoconstriction devices, we reveal unexpected nonlocal energy dissipation at room temperature, which is reminiscent of ballistic transport of low-temperature quantum conductors. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Electrolytic/fuel cell bundles and systems including a current collector in communication with an electrode thereof

DOEpatents

Hawkes, Grant L.; Herring, James S.; Stoots, Carl M.; O& #x27; Brien, James E.

2013-03-05

Electrolytic/fuel cell bundles and systems including such bundles include an electrically conductive current collector in communication with an anode or a cathode of each of a plurality of cells. A cross-sectional area of the current collector may vary in a direction generally parallel to a general direction of current flow through the current collector. The current collector may include a porous monolithic structure. At least one cell of the plurality of cells may include a current collector that surrounds an outer electrode of the cell and has at least six substantially planar exterior surfaces. The planar surfaces may extend along a length of the cell, and may abut against a substantially planar surface of a current collector of an adjacent cell. Methods for generating electricity and for performing electrolysis include flowing current through a conductive current collector having a varying cross-sectional area.

Effect of Transcranial Direct Current Stimulation on Severely Affected Arm-Hand Motor Function in Patients After an Acute Ischemic Stroke: A Pilot Randomized Control Trial.

PubMed

Rabadi, Meheroz H; Aston, Christopher E

2017-10-01

The aim of this article was to determine whether cathodal transcranial direct current stimulation (c-tDCS) to unaffected primary motor cortex (PMC) plus conventional occupational therapy (OT) improves functional motor recovery of the affected arm hand in patients after an acute ischemic stroke compared with sham transcranial direct current stimulation plus conventional OT. In this prospective, randomized, double-blinded, sham-controlled trial of 16 severe, acute ischemic stroke patients with severe arm-hand weakness were randomly assigned to either experimental (c-tDCS plus OT; n = 8) or control (sham transcranial direct current stimulation plus OT; n = 8) groups. All patients received a standard 3-hr in-patient rehabilitation therapy, plus an additional ten 30-min sessions of tDCS. During each session, 1 mA of cathodal stimulation to the unaffected PMC is performed followed by the patient's scheduled OT. The primary outcome measure was change in Action Research Arm Test (ARAT) total and subscores on discharge. Application of c-tDCS to unaffected PMC resulted in a clinically relevant 10-point improvement in the affected arm-hand function based on ARAT total score compared with a 2-point improvement in the control group. Application of 30-min of c-tDCS to the unaffected PMC showed a 10-point improvement in the ARAT score. This corresponds to a large effect size in improvement of affected arm-hand function in patients with severe, acute ischemic stroke. Although not statistically significant, this suggests that larger studies, enrolling at least 25 patients in each group, and with a longer follow-up are warranted.

Improved Direct Methanol Fuel Cell Stack

DOEpatents

Wilson, Mahlon S.; Ramsey, John C.

2005-03-08

A stack of direct methanol fuel cells exhibiting a circular footprint. A cathode and anode manifold, tie-bolt penetrations and tie-bolts are located within the circular footprint. Each fuel cell uses two graphite-based plates. One plate includes a cathode active area that is defined by serpentine channels connecting the inlet and outlet cathode manifold. The other plate includes an anode active area defined by serpentine channels connecting the inlet and outlet of the anode manifold, where the serpentine channels of the anode are orthogonal to the serpentine channels of the cathode. Located between the two plates is the fuel cell active region.

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

Choudhary, Mangilal, E-mail: mangilal@ipr.res.in; Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085; Mukherjee, S.

The experimental observation of the self–excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a resultmore » of the ion–dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.« less

Performance Testing of Molten Regolith Electrolysis with Transfer of Molten Material for the Production of Oxygen and Metals on the Moon

NASA Technical Reports Server (NTRS)

Sibille, Laurent; Sadoway, Donald; Tripathy, Prabhat; Standish, Evan; Sirk, Aislinn; Melendez, Orlando; Stefanescu, Doru

2010-01-01

Previously, we have demonstrated the production of oxygen by electrolysis of molten regolith simulants at temperatures near 1600 C. Using an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in the production of molten metallic products at the cathode and oxygen gas at the anode. Initial direct measurements of current efficiency have confirmed that the process offer potential advantages of high oxygen production rates in a smaller footprint facility landed on the moon, with a minimum of consumables brought from Earth. We now report the results of a scale-up effort toward the goal of achieving production rates equivalent to 1 metric ton O2/year, a benchmark established for the support of a lunar base. We previously reported on the electrochemical behavior of the molten electrolyte as dependent on anode material, sweep rate and electrolyte composition in batches of 20-200g and at currents of less than 0.5 A. In this paper, we present the results of experiments performed at currents up to 10 Amperes) and in larger volumes of regolith simulant (500 g - 1 kg) for longer durations of electrolysis. The technical development of critical design components is described, including: inert anodes capable of passing continuous currents of several Amperes, container materials selection, direct gas analysis capability to determine the gas components co-evolving with oxygen. To allow a continuous process, a system has been designed and tested to enable the withdrawal of cathodically-reduced molten metals and spent molten oxide electrolyte. The performance of the withdrawal system is presented and critiqued. The design of the electrolytic cell and the configuration of the furnace were supported by modeling the thermal environment of the system in an effort to realize a balance between external heating and internal joule heating. We will discuss the impact these simulations and experimental findings have on the design of a suitable prototype for lunar applications

Testing and Analysis of NEXT Ion Engine Discharge Cathode Assembly Wear

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Foster, John E.; Soulas, George C.; Nakles, Michael

2003-01-01

Experimental and analytical investigations were conducted to predict the wear of the discharge cathode keeper in the NASA Evolutionary Xenon Thruster. The ion current to the keeper was found to be highly dependent upon the beam current, and the average beam current density was nearly identical to that of the NSTAR thruster for comparable beam current density. The ion current distribution was highly peaked toward the keeper orifice. A deterministic wear assessment predicted keeper orifice erosion to the same diameter as the cathode tube after processing 375 kg of xenon. A rough estimate of discharge cathode assembly life limit due to sputtering indicated that the current design exceeds the qualification goal of 405 kg. Probabilistic wear analysis showed that the plasma potential and the sputter yield contributed most to the uncertainty in the wear assessment. It was recommended that fundamental experimental and modeling efforts focus on accurately describing the plasma potential and the sputtering yield.

Effects of an Internally-Mounted Cathode on Hall Thruster Plume Properties

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Johnson, Lee K.; Goebel, Dan M.; Fitzgerald, Dennis J.

2006-01-01

The effects of cathode position on the plume properties of an 8 kW BHT-8000 Busek Hall thruster are discussed. Experiments were conducted at the Jet Propulsion Laboratory (JPL) in a vacuum chamber suitable for the development and qualification of high-power Hall thrusters. Multi-mode Hall thruster operation was demonstrated at operating conditions ranging from 200-500 V discharge voltage, 10-40 A discharge current, and 2-8 kW discharge power. Reductions in plume divergence and increased near-field plume symmetries were found to result from the use of an internally-mounted cathode instead of the traditional externally-mounted configuration. High-current hollow cathodes developed at JPL utilizing lanthanum hexaboride (LaB6) emitters were also demonstrated. Discharge currents up to 100 A were achieved with the cathode operating alone and up to 40 A during operation with the Hall thruster. LaB6 cathodes were investigated because of their potential to reduce overall system cost and risk due to less stringent xenon purity and handling requirements.

Intra-Subject Consistency and Reliability of Response Following 2 mA Transcranial Direct Current Stimulation.

PubMed

Dyke, Katherine; Kim, Soyoung; Jackson, Georgina M; Jackson, Stephen R

Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation technique that has been shown to influence cortical excitability. While polarity specific effects have often been reported, this is not always the case, and variability in both the magnitude and direction of the effects have been observed. We aimed to explore the consistency and reliability of the effects of tDCS by investigating changes in cortical excitability across multiple testing sessions in the same individuals. A within subjects design was used to investigate the effects of anodal and cathodal tDCS applied to the motor cortex. Four experimental sessions were tested for each polarity in addition to two sham sessions. Transcranial magnetic stimulation (TMS) was used to measure cortical excitability (TMS recruitment curves). Changes in excitability were measured by comparing baseline measures and those taken immediately following 20 minutes of 2 mA stimulation or sham stimulation. Anodal tDCS significantly increased cortical excitability at a group level, whereas cathodal tDCS failed to have any significant effects. The sham condition also failed to show any significant changes. Analysis of intra-subject responses to anodal stimulation across four sessions suggest that the amount of change in excitability across sessions was only weakly associated, and was found to have poor reliability across sessions (ICC = 0.276). The effects of cathodal stimulation show even poorer reliability across sessions (ICC = 0.137). In contrast ICC analysis for the two sessions of sham stimulation reflect a moderate level of reliability (ICC = .424). Our findings indicate that although 2 mA anodal tDCS is effective at increasing cortical excitability at group level, the effects are unreliable across repeated testing sessions within individual participants. Our results suggest that 2 mA cathodal tDCS does not significantly alter cortical excitability immediately following stimulation and that there is poor reliability of the effect within the same individual across different testing sessions. Copyright © 2016. Published by Elsevier Inc.

Effects of prefrontal tDCS on executive function: Methodological considerations revealed by meta-analysis.

PubMed

Imburgio, Michael J; Orr, Joseph M

2018-05-01

A meta-analysis of studies using single-session transcranial direct current stimulation (tDCS) to target the dorsolateral prefrontal cortex (DLPFC) was undertaken to examine the effect of stimulation on executive function (EF) in healthy samples. 27 studies were included in analyses, yielding 71 effect sizes. The most relevant measure for each task was determined a priori and used to calculate Hedge's g. Methodological characteristics of each study were examined individually as potential moderators of effect size. Stimulation effects on three domains of EF (inhibition of prepotent responses, mental set shifting, and information updating and monitoring) were analyzed separately. In line with previous work, the current study found no significant effect of anodal unilateral tDCS, cathodal unilateral tDCS, or bilateral tDCS on EF. Further moderator and subgroup analyses were only carried out for anodal unilateral montages due to the small number of studies using other montages. Subgroup analyses revealed a significant effect of anodal unilateral tDCS on updating tasks, but not on inhibition or set-shifting tasks. Cathode location significantly moderated the effect of anodal unilateral tDCS. Extracranial cathodes yielded a significant effect on EF while cranial cathodes yielded no effect. Anode size also significantly moderated effect of anodal unilateral tDCS, with smaller anodes being more effective than larger anodes. In summary, anodal DLPFC stimulation is more effective at improving updating ability than inhibition and set-shifting ability, but anodal stimulation can significantly improve general executive function when extracranial cathodes or small anodes are used. Future meta-analyses may examine how stimulation's effects on specific behavioral tasks, rather than broader domains, might be affected by methodological moderators. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electromigration effect on intermetallic growth and Young's modulus in SAC solder joint

NASA Astrophysics Data System (ADS)

Xu, Luhua; Pang, John H. L.; Ren, Fei; Tu, K. N.

2006-12-01

Solid-state intermetallic compound (IMC) growth behavior plays and important role in solder joint reliability of electronic packaging assemblies. The directional impact of electromigration (EM) on the growth of interfacial IMCs in Ni/SAC/Ni, Cu/SAC/Ni single BGA ball solder joint, and fine pitch ball-grid-array (FPBGA) at the anode and cathode sides is reported in this study. When the solder joint was subjected to a current density of 5,000 A/cm2 at 125°C or 150°C, IMC layer growth on the anode interface was faster than that on the cathode interface, and both were faster than isothermal aging due to the Joule heating effect. The EM affects the IMC growth rate, as well as the composition and mechanical properties. The Young’s modulus and hardness were measured by the nanoindentation continuous stiffness measurement (CSM) from planar IMC surfaces after EM exposure. Different values were observed at the anode and cathode. The energy-dispersive x-ray (EDX) line scan analysis was conducted at the interface from the cathode to anode to study the presence of species; Ni was found in the anode IMC at SAC/Cu in the Ni/SAC/Cu joint, but not detected when the current was reverse. Electron-probe microanalysis (EPMA) measurement on the Ni/SAC/Ni specimen also confirmed the polarized Ni and Cu distributions in cathode and anode IMCs, which were (Ni0.57Cu0.43)3Sn4 and (Cu0.73Ni0.27)6Sn5, respectively. Thus, the Young’s moduli of the IMC are 141 and 175 GPa, respectively.

In-situ synthesis of 3D GA on titanium wire as a binder- free electrode for electro-Fenton removing of EDTA-Ni.

PubMed

Wen, Shulong; Niu, Zhuyu; Zhang, Zhen; Li, Lianghao; Chen, Yuancai

2018-01-05

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. The three-dimensional (3D) macroporous graphene aerogels (GA), which was in-situ assembled by reduced graphene oxide (rGO) sheets on titanium wire as binder-free electrode, was presented as cathode for the degradation of EDTA-Ni in Electro-Fenton process. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Brunauer-Emmett-Teller (BET) results indicated 3D GA formed three dimensional architecture with large and homogenous macropore structure and surface area. Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV) and Rotating Ring-disk Electrode (RRDE) results showed that the 3D GA cathode at pH 3 displayed the highest current density and electrochemical active surface area (ECSA), and better two-electron selectivity for ORR than other pH value, confirming the 3D-GA cathode at pH 3 has the highest electrocatalytic activity and generates more H 2 O 2 . The factors such as pH, applied current density, concentration of Fe 2+ , Na 2 SO 4, and aeration rates of air were also investigated. Under the optimum conditions, 73.5% of EDTA-Ni was degraded after reaction for 2h. Mechanism analysis indicated that the production of OH on the 3D GA cathode played an important role in the removal of EDTA-Ni in the 3D GA-EF process, where the direct regeneration of Fe 2+ on the cathode would greatly reduce the consumption of H 2 O 2 . Therefore, it is of great promise for 3D-GA catalyst to be developed as highly efficient, cost-effective and durable cathode for the removal of EDTA-Ni. Copyright © 2017 Elsevier B.V. All rights reserved.

A phenomenological model for orificed hollow cathodes. Ph.D. Thesis, 1 Dec. 1981 - 1 Dec. 1982; [electrostatic thruster

NASA Technical Reports Server (NTRS)

Siegfried, D. E.

1982-01-01

A quartz hollow tube cathode was used to determine the operating conditions within a mercury orificed hollow cathode. Insert temperature profiles, cathode current distributions, plasma properties profile, and internal pressure-mass flow rate results are summarized and used in a phenomenological model which qualitatively describes electron emission and plasma production processes taking place within the cathode. By defining an idealized ion production region within which most of the plasma processes are concentrated, this model is expressed analytically as a simple set of equations which relate cathode dimensions and specifiable operating conditions, such as mass flow rate and discharge current, to such important parameters as emission surface temperature and internal plasma properties. Key aspects of the model are examined.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes.

PubMed

Kumar, Niraj; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Pal, Udit Narayan; Rahaman, Hasibur; Prakash, Ram

2016-03-01

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

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

Kumar, Niraj; Pal, Udit Narayan; Prakash, Ram

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electronmore » beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.« less

Modelling bio-electrosynthesis in a reverse microbial fuel cell to produce acetate from CO2 and H2O.

PubMed

Kazemi, M; Biria, D; Rismani-Yazdi, H

2015-05-21

Bio-electrosynthesis is one of the significant developments in reverse microbial fuel cell technology which is potentially capable of creating organic compounds by combining CO2 with H2O. Accordingly, the main objective in the current study was to present a model of microbial electrosynthesis for producing organic compounds (acetate) based on direct conduction of electrons in biofilms. The proposed model enjoys a high degree of rigor because it can predict variations in the substrate concentration, electrical potential, current density and the thickness of the biofilm. Additionally, coulombic efficiency was investigated as a function of substrate concentration and cathode potential. For a system containing CO2 as the substrate and Sporomusa ovata as the biofilm forming microorganism, an increase in the substrate concentration at a constant potential can lead to a decrease in coulombic efficiency as well as an increase in current density and biofilm thickness. On the other hand, an increase in the surface cathodic voltage at a constant substrate concentration may result in an increase in the coulombic efficiency and a decrease in the current density. The maximum coulombic efficiency was revealed to be 75% at a substrate concentration of 0.025 mmol cm(-3) and 55% at a surface cathodic voltage of -0.3 V producing a high range of acetate production by creating an optimal state in the concentration and potential intervals. Finally, the validity of the model was verified by comparing the obtained results with related experimental findings.

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

Korolev, Yu. D.; Landl, N. V., E-mail: landl@lnp.hcei.tsc.ru; Geyman, V. G.

Results from studies of a low-current glow discharge with a hollow cathode are presented. A specific feature of the discharge conditions was that a highly emissive tablet containing cesium carbonate was placed in the cathode cavity. In the absence of a tablet, the discharge ignition voltage was typically ≥3.5 kV, while the burning voltage was in the range of 500–600 V. The use of the tablet made it possible to decrease the ignition voltage to 280 V and maintain the discharge burning voltage at a level of about 130 V. A model of the current sustainment in a hollow-cathode dischargemore » is proposed. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only ion bombardment of the cathode, but also the emission current from an external source. The model is used to interpret the observed current−voltage characteristics. The results of calculations agree well with the experimental data. It is shown that, in some discharge modes, the external emission current from the cathode can reach 25% of the total discharge current.« less

Vacuum vapor deposition gun assembly

DOEpatents

Zeren, Joseph D.

1985-01-01

A vapor deposition gun assembly includes a hollow body having a cylindrical outer surface and an end plate for holding an adjustable heat sink, a hot hollow cathode gun, two magnets for steering the plasma from the gun into a crucible on the heat sink, and a shutter for selectively covering and uncovering the crucible.

Compact Rare Earth Emitter Hollow Cathode

NASA Technical Reports Server (NTRS)

Watkins, Ronald; Goebel, Dan; Hofer, Richard

2010-01-01

A compact, high-current, hollow cathode utilizing a lanthanum hexaboride (LaB6) thermionic electron emitter has been developed for use with high-power Hall thrusters and ion thrusters. LaB6 cathodes are being investigated due to their long life, high current capabilities, and less stringent xenon purity and handling requirements compared to conventional barium oxide (BaO) dispenser cathodes. The new cathode features a much smaller diameter than previously developed versions that permit it to be mounted on axis of a Hall thruster ( internally mounted ), as opposed to the conventional side-mount position external to the outer magnetic circuit ("externally mounted"). The cathode has also been reconfigured to be capable of surviving vibrational loads during launch and is designed to solve the significant heater and materials compatibility problems associated with the use of this emitter material. This has been accomplished in a compact design with the capability of high-emission current (10 to 60 A). The compact, high-current design has a keeper diameter that allows the cathode to be mounted on the centerline of a 6- kW Hall thruster, inside the iron core of the inner electromagnetic coil. Although designed for electric propulsion thrusters in spacecraft station- keeping, orbit transfer, and interplanetary applications, the LaB6 cathodes are applicable to the plasma processing industry in applications such as optical coatings and semiconductor processing where reactive gases are used. Where current electrical propulsion thrusters with BaO emitters have limited life and need extremely clean propellant feed systems at a significant cost, these LaB6 cathodes can run on the crudest-grade xenon propellant available without impact. Moreover, in a laboratory environment, LaB6 cathodes reduce testing costs because they do not require extended conditioning periods under hard vacuum. Alternative rare earth emitters, such as cerium hexaboride (CeB6) can be used in this configuration with possibly an even longer emitter life. This cathode is specifically designed to integrate on the centerline of a high-power Hall thruster, thus eliminating the asymmetries in the plasma discharge common to cathodes previously mounted externally to the thruster s magnetic circuit. An alternative configuration for the cathode uses an external propellant feed. This diverts a fraction of the total cathode flow to an external feed, which can improve the cathode coupling efficiency at lower total mass flow rates. This can improve the overall thruster efficiency, thereby decreasing the required propellant loads for different missions. Depending on the particular mission, reductions in propellant loads can lead to mission enabling capabilities by allowing launch vehicle step-down, greater payload capability, or by extending the life of a spacecraft.

Management of menopause-associated vasomotor symptoms: Current treatment options, challenges and future directions

PubMed Central

Pachman, Deirdre R; Jones, Jason M; Loprinzi, Charles L

2010-01-01

Hot flashes are one of the most common and distressing symptoms associated with menopause, occurring in more than 75% of postmenopausal women. They are especially problematic in breast cancer patients since some breast cancer therapies can induce hot flashes. For mild hot flashes, it is proposed that behavioral modifications are the first step in management. Hormonal therapies, including estrogens and progestogens, are the most well known effective agents in relieving hot flashes; however, the safety of these agents is controversial. There is an increasing amount of literature on nonhormonal agents for the treatment of hot flashes. The most promising data regard newer antidepressant agents such as venlafaxine, which reduces hot flashes by about 60%. Gabapentin is another nonhormonal agent that is effective in reducing hot flashes. While many complimentary therapies, including phytoestrogens, black cohosh, and dehydroepiandrosterone, have been explored for the treatment of hot flashes; none can be recommended at this time. Furthermore, there is a lack of strong evidence to support exercise, yoga, or relaxation for the treatment of hot flashes. Paced respirations and hypnosis appear to be promising enough to warrant further investigation. Another promising nonpharmacological therapy, currently under investigation, involves a stellate ganglion block. PMID:21072305

Simultaneous transcranial direct current stimulation (tDCS) and whole-head magnetoencephalography (MEG): assessing the impact of tDCS on slow cortical magnetic fields.

PubMed

Garcia-Cossio, Eliana; Witkowski, Matthias; Robinson, Stephen E; Cohen, Leonardo G; Birbaumer, Niels; Soekadar, Surjo R

2016-10-15

Transcranial direct current stimulation (tDCS) can influence cognitive, affective or motor brain functions. Whereas previous imaging studies demonstrated widespread tDCS effects on brain metabolism, direct impact of tDCS on electric or magnetic source activity in task-related brain areas could not be confirmed due to the difficulty to record such activity simultaneously during tDCS. The aim of this proof-of-principal study was to demonstrate the feasibility of whole-head source localization and reconstruction of neuromagnetic brain activity during tDCS and to confirm the direct effect of tDCS on ongoing neuromagnetic activity in task-related brain areas. Here we show for the first time that tDCS has an immediate impact on slow cortical magnetic fields (SCF, 0-4Hz) of task-related areas that are identical with brain regions previously described in metabolic neuroimaging studies. 14 healthy volunteers performed a choice reaction time (RT) task while whole-head magnetoencephalography (MEG) was recorded. Task-related source-activity of SCFs was calculated using synthetic aperture magnetometry (SAM) in absence of stimulation and while anodal, cathodal or sham tDCS was delivered over the right primary motor cortex (M1). Source reconstruction revealed task-related SCF modulations in brain regions that precisely matched prior metabolic neuroimaging studies. Anodal and cathodal tDCS had a polarity-dependent impact on RT and SCF in primary sensorimotor and medial centro-parietal cortices. Combining tDCS and whole-head MEG is a powerful approach to investigate the direct effects of transcranial electric currents on ongoing neuromagnetic source activity, brain function and behavior. Copyright © 2015 Elsevier Inc. All rights reserved.

Simultaneous transcranial direct current stimulation (tDCS) and whole-head magnetoencephalography (MEG): assessing the impact of tDCS on slow cortical magnetic fields

PubMed Central

Garcia-Cossio, Eliana; Witkowski, Matthias; Robinson, Stephen E.; Cohen, Leonardo G.; Birbaumer, Niels; Soekadar, Surjo R.

2016-01-01

Transcranial direct current stimulation (tDCS) can influence cognitive, affective or motor brain functions. Whereas previous imaging studies demonstrated widespread tDCS effects on brain metabolism, direct impact of tDCS on electric or magnetic source activity in task-related brain areas could not be confirmed due to the difficulty to record such activity simultaneously during tDCS. The aim of this proof-of-principal study was to demonstrate the feasibility of whole-head source localization and reconstruction of neuromagnetic brain activity during tDCS and to confirm the direct effect of tDCS on ongoing neuromagnetic activity in task-related brain areas. Here we show for the first time that tDCS has an immediate impact on slow cortical magnetic fields (SCF, 0–4 Hz) of task-related areas that are identical with brain regions previously described in metabolic neuroimaging studies. 14 healthy volunteers performed a choice reaction time (RT) task while whole-head magnetoencephalography (MEG) was recorded. Task-related source-activity of SCFs was calculated using synthetic aperture magnetometry (SAM) in absence of stimulation and while anodal, cathodal or sham tDCS was delivered over the right primary motor cortex (M1). Source reconstruction revealed task-related SCF modulations in brain regions that precisely matched prior metabolic neuroimaging studies. Anodal and cathodal tDCS had a polarity-dependent impact on RT and SCF in primary sensorimotor and medial centro-parietal cortices. Combining tDCS and whole-head MEG is a powerful approach to investigate the direct effects of transcranial electric currents on ongoing neuromagnetic source activity, brain function and behavior. PMID:26455796

Advanced space propulsion thruster research

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1981-01-01

Experiments showed that stray magnetic fields can adversely affect the capacity of a hollow cathode neutralizer to couple to an ion beam. Magnetic field strength at the neutralizer cathode orifice is a crucial factor influencing the coupling voltage. The effects of electrostatic accelerator grid aperture diameters on the ion current extraction capabilities were examined experimentally to describe the divergence, deflection, and current extraction capabilities of grids with the screen and accelerator apertures displaced relative to one another. Experiments performed in orificed, mercury hollow cathodes support the model of field enhanced thermionic electron mission from cathode inserts. Tests supported the validity of a thermal model of the cathode insert. A theoretical justification of a Saha equation model relating cathode plasma properties is presented. Experiments suggest that ion loss rates to discharge chamber walls can be controlled. A series of new discharge chamber magnetic field configurations were generated in the flexible magnetic field thruster and their effect on performance was examined. A technique used in the thruster to measure ion currents to discharge chamber walls is described. Using these ion currents the fraction of ions produced that are extracted from the discharge chamber and the energy cost of plasma ions are computed.

Methanol sensor operated in a passive mode

DOEpatents

Ren, Xiaoming; Gottesfeld, Shimshon

2002-01-01

A sensor outputs a signal related to a concentration of methanol in an aqueous solution adjacent the sensor. A membrane electrode assembly (MEA) is included with an anode side and a cathode side. An anode current collector supports the anode side of the MEA and has a flow channel therethrough for flowing a stream of the aqueous solution and forms a physical barrier to control access of the methanol to the anode side of the MEA. A cathode current collector supports the cathode side of the MEA and is configured for air access to the cathode side of the MEA. A current sensor is connected to measure the current in a short circuit across the sensor electrodes to provide an output signal functionally related to the concentration of methanol in the aqueous solution.

On stabilization of field emission and increase in the current density of planar nanostructures with DLC films

NASA Astrophysics Data System (ADS)

Yakunin, Alexander N.; Aban'shin, Nikolay P.; Avetisyan, Yuri A.; Akchurin, Georgy G.; Loginov, Alexander P.; Mosiyash, Denis S.; Akchurin, Garif G.

2018-04-01

The paper provides a justification and a comparative analysis of the scaling directions of the developed and investigated planar triode field emission cathode unit with the aim of increasing the maximum field current density up to 0.75 A-cm-2 without sacrificing durability. The design features of the vacuum device with a planar structure provided low-voltage control - at 150 V in the mode of long-term durability and not more than 250 V in the mode of the maximum permissible emission current.

Electrorefiner

DOEpatents

Miller, W.E.; Tomczuk, Z.

1995-08-22

An apparatus is disclosed capable of functioning as a solid cathode and for removing crystalline structure from the upper surface of a liquid cathode, includes a metallic support vertically disposed with respect to an electrically insulating container capable of holding a liquid metal cathode. A piston of electrically insulating material mounted on the drive tube, surrounding the current lead, for vertical and rotational movement with respect thereto including a downwardly extending collar portion surrounding the metallic current lead. At least one portion of the piston remote from the metallic current lead being removed. Mechanism for lowering the piston to the surface of the liquid cathode and raising the piston from the surface along with mechanism for rotating the piston around its longitudinal axis. 5 figs.

Electrorefiner

DOEpatents

Miller, William E.; Tomczuk, Zygmunt

1995-01-01

An apparatus capable of functioning as a solid cathode and for removing crystalline structure from the upper surface of a liquid cathode, includes a metallic support vertically disposed with respect to an electrically insulating container capable of holding a liquid metal cathode. A piston of electrically insulating material mounted on the drive tube, surrounding the current lead, for vertical and rotational movement with respect thereto including a downwardly extending collar portion surrounding the metallic current lead. At least one portion of the piston remote from the metallic current lead being removed. Mechanism for lowering the piston to the surface of the liquid cathode and raising the piston from the surface along with mechanism for rotating the piston around its longitudinal axis.

Pressed boride cathodes

NASA Technical Reports Server (NTRS)

Wolski, W.

1985-01-01

Results of experimental studies of emission cathodes made from lanthanum, yttrium, and gadolinium hexaborides are presented. Maximum thermal emission was obtained from lanthanum hexaboride electrodes. The hexaboride cathodes operated stably under conditions of large current density power draw, at high voltages and poor vacuum. A microtron electron gun with a lanthanum hexaboride cathode is described.

Magnetic-cusp, cathodic-arc source

DOEpatents

Falabella, S.

1995-11-21

A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission. 3 figs.

Effects of Combining a Brief Cognitive Intervention with Transcranial Direct Current Stimulation on Pain Tolerance: A Randomized Controlled Pilot Study.

PubMed

Powers, Abigail; Madan, Alok; Hilbert, Megan; Reeves, Scott T; George, Mark; Nash, Michael R; Borckardt, Jeffrey J

2018-04-01

Cognitive behavioral therapy has been shown to be effective for treating chronic pain, and a growing literature shows the potential analgesic effects of minimally invasive brain stimulation. However, few studies have systematically investigated the potential benefits associated with combining approaches. The goal of this pilot laboratory study was to investigate the combination of a brief cognitive restructuring intervention and transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex in affecting pain tolerance. Randomized, double-blind, placebo-controlled laboratory pilot. Medical University of South Carolina. A total of 79 healthy adult volunteers. Subjects were randomized into one of six groups: 1) anodal tDCS plus a brief cognitive intervention (BCI); 2) anodal tDCS plus pain education; 3) cathodal tDCS plus BCI; 4) cathodal tDCS plus pain education; 5) sham tDCS plus BCI; and 6) sham tDCS plus pain education. Participants underwent thermal pain tolerance testing pre- and postintervention using the Method of Limits. A significant main effect for time (pre-post intervention) was found, as well as for baseline thermal pain tolerance (covariate) in the model. A significant time × group interaction effect was found on thermal pain tolerance. Each of the five groups that received at least one active intervention outperformed the group receiving sham tDCS and pain education only (i.e., control group), with the exception of the anodal tDCS + education-only group. Cathodal tDCS combined with the BCI produced the largest analgesic effect. Combining cathodal tDCS with BCI yielded the largest analgesic effect of all the conditions tested. Future research might find stronger interactive effects of combined tDCS and a cognitive intervention with larger doses of each intervention. Because this controlled laboratory pilot employed an acute pain analogue and the cognitive intervention did not authentically represent cognitive behavioral therapy per se, the implications of the findings on chronic pain management remain unclear.

The improvement of the analytical performance of direct current atmospheric pressure glow discharge generated in contact with the small-sized liquid cathode after the addition of non-ionic surfactants to electrolyte solutions.

PubMed

Gręda, Krzysztof; Jamróz, Piotr; Pohl, Paweł

2013-04-15

A low power direct current atmospheric glow discharge sustained in the open to air atmosphere in contact with a small-sized flowing liquid cathode was used as an excitation source in optical emission spectrometry. The composition of electrolyte solutions served as the liquid cathode was modified by the addition of non-ionic surfactants, namely Triton x-45, Triton x-100, Triton x-405 and Triton x-705. The effect of the concentration of each surfactant was thoroughly studied on the emission characteristic of molecular bands identified in spectra, atomic emission lines of 16 metals studied and the background level. It was found that the presence of both heavy surfactants results in a significant increase in the net intensity of analytical lines of metals and a notable reduction of the intensity of bands of diatomic molecules and the background. In conditions considered to be a compromise for all metals, selected figures of merit for this excitation source combined with the optical emission spectrometry detection were determined. Limits of detection for all metals were within the range of 0.0003-0.05 mg L(-1), the precision was better than 6%, while calibration curves were linear over 2 orders of the magnitude of the concentration or more, e.g., for K, Li, Mg, Na and Rb. The discharge system with the liquid cathode modified by the addition of the surfactant found its application in the determination of Ca, Cu, Fe, K, Mg, Mn, Na and Zn in selected environmental samples, i.e., waters, soils and spruce needles, with the quite good precision and the accuracy comparable to that for measurements with flame atomic absorption spectrometry (FAAS) and flame atomic emission spectrometry (FAES). Copyright © 2013 Elsevier B.V. All rights reserved.

Are you positive? Electric dipole polarity discrimination in the yellow stingray, Urobatis jamaicensis.

PubMed

Siciliano, Avery M; Kajiura, Stephen M; Long, John H; Porter, Marianne E

2013-10-01

It is well established that elasmobranchs can detect dipole electric fields. However, it is unclear whether they can discriminate between the anode and cathode. To investigate this subject, we employed a behavioral assay to determine the discriminatory ability of the yellow stingray, Urobatis jamaicensis. We conditioned stingrays with food rewards to bite either the anode (n=5) or the cathode (n=6) of a direct-current dipole located on the floor of an experimental tank. All individuals successfully performed the task after 18 to 22 days. Stingrays were then tested in experimental sessions when they were rewarded only after they identified the correct pole. Stingrays successfully discriminated between the poles at a rate greater than chance, ranging among individuals from a mean of 66% to 93% correct. During experimental sessions, stingrays conditioned to distinguish the anode performed similarly to those conditioned to distinguish the cathode. We hypothesize that the ability to discriminate anode from cathode is physiologically encoded, but its utility in providing spatial information under natural conditions remains to be demonstrated. The ability to discriminate polarity may eliminate ambiguity in induction-based magnetoreception and facilitate navigation with respect to the geomagnetic field.

Carbon-containing cathodes for enhanced electron emission

DOEpatents

Cao, Renyu; Pan, Lawrence; Vergara, German; Fox, Ciaran

2000-01-01

A cathode has electropositive atoms directly bonded to a carbon-containing substrate. Preferably, the substrate comprises diamond or diamond-like (sp.sup.3) carbon, and the electropositive atoms are Cs. The cathode displays superior efficiency and durability. In one embodiment, the cathode has a negative electron affinity (NEA). The cathode can be used for field emission, thermionic emission, or photoemission. Upon exposure to air or oxygen, the cathode performance can be restored by annealing or other methods. Applications include detectors, electron multipliers, sensors, imaging systems, and displays, particularly flat panel displays.

A Bidirectional Neural Interface IC with Chopper Stabilized BioADC Array and Charge Balanced Stimulator

PubMed Central

Greenwald, Elliot; So, Ernest; Wang, Qihong; Mollazadeh, Mohsen; Maier, Christoph; Etienne-Cummings, Ralph; Cauwenberghs, Gert; Thakor, Nitish

2016-01-01

We present a bidirectional neural interface with a 4-channel biopotential analog-to-digital converter (bioADC) and a 4-channel current-mode stimulator in 180nm CMOS. The bioADC directly transduces microvolt biopotentials into a digital representation without a voltage-amplification stage. Each bioADC channel comprises a continuous-time first-order ΔΣ modulator with a chopper-stabilized OTA input and current feedback, followed by a second-order comb-filter decimator with programmable oversampling ratio. Each stimulator channel contains two independent digital-to-analog converters for anodic and cathodic current generation. A shared calibration circuit matches the amplitude of the anodic and cathodic currents for charge balancing. Powered from a 1.5V supply, the analog and digital circuits in each recording channel draw on average 1.54 μA and 2.13 μA of supply current, respectively. The bioADCs achieve an SNR of 58 dB and a SFDR of >70 dB, for better than 9-b ENOB. Intracranial EEG recordings from an anesthetized rat are shown and compared to simultaneous recordings from a commercial reference system to validate performance in-vivo. Additionally, we demonstrate bidirectional operation by recording cardiac modulation induced through vagus nerve stimulation, and closed-loop control of cardiac rhythm. The micropower operation, direct digital readout, and integration of electrical stimulation circuits make this interface ideally suited for closed-loop neuromodulation applications. PMID:27845676

Catalyst inks and method of application for direct methanol fuel cells

DOEpatents

Zelenay, Piotr; Davey, John; Ren, Xiaoming; Gottesfeld, Shimshon; Thomas, Sharon C.

2004-02-24

Inks are formulated for forming anode and cathode catalyst layers and applied to anode and cathode sides of a membrane for a direct methanol fuel cell. The inks comprise a Pt catalyst for the cathode and a Pt--Ru catalyst for the anode, purified water in an amount 4 to 20 times that of the catalyst by weight, and a perfluorosulfonic acid ionomer in an amount effective to provide an ionomer content in the anode and cathode surfaces of 20% to 80% by volume. The inks are prepared in a two-step process while cooling and agitating the solutions. The final solution is placed in a cooler and continuously agitated while spraying the solution over the anode or cathode surface of the membrane as determined by the catalyst content.

Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

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

Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Jiang, Weiman; Wang, Yishan

2015-08-24

A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

Method and apparatus for spatially uniform electropolishing and electrolytic etching

DOEpatents

Mayer, Steven T.; Contolini, Robert J.; Bernhardt, Anthony F.

1992-01-01

In an electropolishing or electrolytic etching apparatus the anode is separated from the cathode to prevent bubble transport to the anode and to produce a uniform current distribution at the anode by means of a solid nonconducting anode-cathode barrier. The anode extends into the top of the barrier and the cathode is outside the barrier. A virtual cathode hole formed in the bottom of the barrier below the level of the cathode permits current flow while preventing bubble transport. The anode is rotatable and oriented horizontally facing down. An extended anode is formed by mounting the workpiece in a holder which extends the electropolishing or etching area beyond the edge of the workpiece to reduce edge effects at the workpiece. A reference electrode controls cell voltage. Endpoint detection and current shut-off stop polishing. Spatially uniform polishing or etching can be rapidly performed.

Method and apparatus for spatially uniform electropolishing and electrolytic etching

DOEpatents

Mayer, S.T.; Contolini, R.J.; Bernhardt, A.F.

1992-03-17

In an electropolishing or electrolytic etching apparatus the anode is separated from the cathode to prevent bubble transport to the anode and to produce a uniform current distribution at the anode by means of a solid nonconducting anode-cathode barrier. The anode extends into the top of the barrier and the cathode is outside the barrier. A virtual cathode hole formed in the bottom of the barrier below the level of the cathode permits current flow while preventing bubble transport. The anode is rotatable and oriented horizontally facing down. An extended anode is formed by mounting the workpiece in a holder which extends the electropolishing or etching area beyond the edge of the workpiece to reduce edge effects at the workpiece. A reference electrode controls cell voltage. Endpoint detection and current shut-off stop polishing. Spatially uniform polishing or etching can be rapidly performed. 6 figs.

Verification of high efficient broad beam cold cathode ion source

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

Abdel Reheem, A. M., E-mail: amreheem2009@yahoo.com; Radiation Physics Department, National Center for Radiation Research and Technology; Ahmed, M. M.

2016-08-15

An improved form of cold cathode ion source has been designed and constructed. It consists of stainless steel hollow cylinder anode and stainless steel cathode disc, which are separated by a Teflon flange. The electrical discharge and output characteristics have been measured at different pressures using argon, nitrogen, and oxygen gases. The ion exit aperture shape and optimum distance between ion collector plate and cathode disc are studied. The stable discharge current and maximum output ion beam current have been obtained using grid exit aperture. It was found that the optimum distance between ion collector plate and ion exit aperturemore » is equal to 6.25 cm. The cold cathode ion source is used to deposit aluminum coating layer on AZ31 magnesium alloy using argon ion beam current which equals 600 μA. Scanning electron microscope and X-ray diffraction techniques used for characterizing samples before and after aluminum deposition.« less

Thin films of aluminum nitride and aluminum gallium nitride for cold cathode applications

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

Sowers, A.T.; Christman, J.A.; Bremser, M.D.

1997-10-01

Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited on n-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by a SiO{sub 2} layer and etched to form arrays of either 1, 3, or 5 {mu}m holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 {mu}m holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10{endash}100 nA and required grid voltages rangingmore » from 20{endash}110 V. The grid currents were typically 1 to 10{sup 4} times the collector currents. {copyright} {ital 1997 American Institute of Physics.}« less

Recent Studies on Methanol Crossover in Liquid-Feed Direct Methanol Fuel Cells

NASA Technical Reports Server (NTRS)

Valdez, T. I.; Narayanan, S. R.

2000-01-01

In this work, the effects of methanol crossover and airflow rates on the cathode potential of an operating direct methanol fuel cell are explored. Techniques for quantifying methanol crossover in a fuel cell and for separating the electrical performance of each electrode in a fuel cell are discussed. The effect of methanol concentration on cathode potential has been determined to be significant. The cathode is found to be mass transfer limited when operating on low flow rate air and high concentrations of methanol. Improvements in cathode structure and operation at low methanol concentration have been shown to result in improved cell performance.

Optical Plasma Control During ARC Carbon Nanotube Growth

NASA Technical Reports Server (NTRS)

Hinkov, I.; Farhat, S.; DeLaChapelle, M. Lamy; Fan, S. S.; Han, H. X.; Li, G. H.; Scott, C. D.

2001-01-01

To improve nanotube production, we developed a novel optical control technique, based on the shape of the visible plasma zone created between the anode and the cathode in the direct current (DC) arc process. For a given inert gas, we adjust the anode to cathode distance (ACD) in order to obtain strong visible vortices around the cathode. This enhance anode vaporization, which improve nanotubes formation. In light of our experimental results, we focus our discussion on the relationship between plasma parameters and nanotube growth. Plasma temperature control during arc process is achieved using argon, helium, and their mixtures as a buffer gases. The variation of the gas mixture from pure argon to pure helium changes plasma temperature. As a consequence, the microscopic characteristics of nanotubes as diameter distribution is changed moving from smaller values for argon to higher diameters for helium. We also observe a dependence of the macroscopic characteristics of the final products as Brunauer-Emmett-Teller (BET) surface area.

Computational modeling of the effect of external electron injection into a direct-current microdischarge

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

Panneer Chelvam, Prem Kumar; Raja, Laxminarayan L.

2015-12-28

Electron emission from the electrode surface plays an important role in determining the structure of a direct-current microdischarge. Here we have developed a computational model of a direct-current microdischarge to study the effect of external electron injection from the cathode surface into the discharge to manipulate its properties. The model provides a self-consistent, multi-species, multi-temperature fluid representation of the plasma. A microdischarge with a metal-insulator-metal configuration is chosen for this study. The effect of external electron injection on the structure and properties of the microdischarge is described. The transient behavior of the microdischarge during the electron injection is examined. Themore » nonlinearities in the dynamics of the plasma result in a large increase of conduction current after active electron injection. For the conditions simulated a switching time of ∼100 ns from a low-current to high-current discharge state is realized.« less

La0.8Sr0.2Fe0.8Cu0.2O3-δ as “cobalt-free” cathode for La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte

NASA Astrophysics Data System (ADS)

Zurlo, Francesca; Di Bartolomeo, Elisabetta; D'Epifanio, Alessandra; Felice, Valeria; Natali Sora, Isabella; Tortora, Luca; Licoccia, Silvia

2014-12-01

A "cobalt-free" cathode material with stoichiometric composition La0.8Sr0.2Fe0.8Cu0.2O3-δ (LSFCu) was specifically developed for use with La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte in intermediate temperature solid oxide fuel cell (IT-SOFC) systems. The chemical stability of LSFCu in contact with LSGM electrolyte was investigated by structural and morphological analysis. The electrochemical properties of LSFCu dense pellets were investigated in the temperature range 600-750 °C by electrochemical impedance spectroscopy (EIS). LSFCu|LSGM|LSFCu symmetrical cells were prepared and area specific resistance (ASR) values, directly depending on the rate limiting step of the oxygen reduction reaction, were evaluated. Fuel cells were prepared using LSFCu as cathode material on a LSGM pellet and electrochemical tests were performed in the 700-800 °C temperature range and compared to similar fuel cells prepared by using commercial La0.6Sr0.4Fe0.8Co0.2O3-δ (LSFCo) as a cathode. The maximum current density and power density recorded for LSFCu and LSFCo were similar. This fact demonstrates that Cu can be used as Co substitute in perovskite cathode materials.

Electron reversal ionizer for detection of trace species using a spherical cathode

NASA Technical Reports Server (NTRS)

Boumsellek, Said (Inventor); Chutjian, Ara (Inventor)

1994-01-01

A reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region employs an indirectly heated cathode having a concave emitting surface of width of W less than 2r, where r is the radius of curvature and preferably a ratio of width to radius approximately equal to one for optimum high current for a given cathode width.

Aluminum reduction cell electrode

DOEpatents

Payne, J.R.

1983-09-20

The invention is directed to an anode-cathode structure for an electrolytic cell for the reduction of alumina wherein the structure is comprised of a carbon anode assembly which straddles a wedge-shaped refractory hard metal cathode assembly having steeply sloped cathodic surfaces, each cathodic surface being paired in essentially parallel planar relationship with an anode surface. The anode-cathode structure not only takes into account the structural weakness of refractory hard metal materials but also permits the changing of the RHM assembly during operation of the cell. Further, the anode-cathode structure enhances the removal of anode gas from the interpolar gap between the anode and cathode surfaces. 10 figs.

Aluminum reduction cell electrode

DOEpatents

Payne, John R.

1983-09-20

The invention is directed to an anode-cathode structure for an electrolytic cell for the reduction of alumina wherein the structure is comprised of a carbon anode assembly which straddles a wedge-shaped refractory hard metal cathode assembly having steeply sloped cathodic surfaces, each cathodic surface being paired in essentially parallel planar relationship with an anode surface. The anode-cathode structure not only takes into account the structural weakness of refractory hard metal materials but also permits the changing of the RHM assembly during operation of the cell. Further, the anode-cathode structure enhances the removal of anode gas from the interpolar gap between the anode and cathode surfaces.

Cathodal Transcranial Direct Current Stimulation (tDCS) to the Right Cerebellar Hemisphere Affects Motor Adaptation During Gait.

PubMed

Fernandez, Lara; Albein-Urios, Natalia; Kirkovski, Melissa; McGinley, Jennifer L; Murphy, Anna T; Hyde, Christian; Stokes, Mark A; Rinehart, Nicole J; Enticott, Peter G

2017-02-01

The cerebellum appears to play a key role in the development of internal rules that allow fast, predictive adjustments to novel stimuli. This is crucial for adaptive motor processes, such as those involved in walking, where cerebellar dysfunction has been found to increase variability in gait parameters. Motor adaptation is a process that results in a progressive reduction in errors as movements are adjusted to meet demands, and within the cerebellum, this seems to be localised primarily within the right hemisphere. To examine the role of the right cerebellar hemisphere in adaptive gait, cathodal transcranial direct current stimulation (tDCS) was administered to the right cerebellar hemisphere of 14 healthy adults in a randomised, double-blind, crossover study. Adaptation to a series of distinct spatial and temporal templates was assessed across tDCS condition via a pressure-sensitive gait mat (ProtoKinetics Zeno walkway), on which participants walked with an induced 'limp' at a non-preferred pace. Variability was assessed across key spatial-temporal gait parameters. It was hypothesised that cathodal tDCS to the right cerebellar hemisphere would disrupt adaptation to the templates, reflected in a failure to reduce variability following stimulation. In partial support, adaptation was disrupted following tDCS on one of the four spatial-temporal templates used. However, there was no evidence for general effects on either the spatial or temporal domain. This suggests, under specific conditions, a coupling of spatial and temporal processing in the right cerebellar hemisphere and highlights the potential importance of task complexity in cerebellar function.

Cathodal transcranial direct current stimulation (tDCS) applied to the left premotor cortex (PMC) stabilizes a newly learned motor sequence.

PubMed

Focke, Jan; Kemmet, Sylvia; Krause, Vanessa; Keitel, Ariane; Pollok, Bettina

2017-01-01

While the primary motor cortex (M1) is involved in the acquisition the premotor cortex (PMC) has been related to over-night consolidation of a newly learned motor skill. The present study aims at investigating the possible contribution of the left PMC for the stabilization of a motor sequence immediately after acquisition as determined by susceptibility to interference. Thirty six healthy volunteers received anodal, cathodal and sham transcranial direct current stimulation (tDCS) to the left PMC either immediately prior to or during training on a serial reaction time task (SRTT) with the right hand. TDCS was applied for 10min, respectively. Reaction times were measured prior to training (t1), at the end of training (t2), and after presentation of an interfering random pattern (t3). Beyond interference from learning, the random pattern served as control condition in order to estimate general effects of tDCS on reaction times. TDCS applied during SRTT training did not result in any significant effects neither on acquisition nor on susceptibility to interference. In contrast to this, tDCS prior to SRTT training yielded an unspecific facilitation of reaction times at t2 independent of tDCS polarity. At t3, reduced susceptibility to interference was found following cathodal stimulation. The results suggest the involvement of the PMC in early consolidation and reveal a piece of evidence for the hypothesis that behavioral tDCS effects vary with the activation state of the stimulated area. Copyright © 2016. Published by Elsevier B.V.

Transcranial Direct Current Stimulation of the Left Dorsolateral Prefrontal Cortex Shifts Preference of Moral Judgments

PubMed Central

Kuehne, Maria; Heimrath, Kai; Heinze, Hans-Jochen; Zaehle, Tino

2015-01-01

Attitude to morality, reflecting cultural norms and values, is considered unique to human social behavior. Resulting moral behavior in a social environment is controlled by a widespread neural network including the dorsolateral prefrontal cortex (DLPFC), which plays an important role in decision making. In the present study we investigate the influence of neurophysiological modulation of DLPFC reactivity by means of transcranial direct current stimulation (tDCS) on moral reasoning. For that purpose we administered anodal, cathodal, and sham stimulation of the left DLPFC while subjects judged the appropriateness of hard moral personal dilemmas. In contrast to sham and cathodal stimulation, anodal stimulation induced a shift in judgment of personal moral dilemmas towards more non-utilitarian actions. Our results demonstrate that alterations of left DLPFC activity can change moral judgments and, in consequence, provide a causal link between left DLPFC activity and moral reasoning. Most important, the observed shift towards non-utilitarian actions suggests that moral decision making is not a permanent individual trait but can be manipulated; consequently individuals with boundless, uncontrollable, and maladaptive moral behavior, such as found in psychopathy, might benefit from neuromodulation-based approaches. PMID:25985442

Differential sensory cortical involvement in auditory and visual sensorimotor temporal recalibration: Evidence from transcranial direct current stimulation (tDCS).

PubMed

Aytemür, Ali; Almeida, Nathalia; Lee, Kwang-Hyuk

2017-02-01

Adaptation to delayed sensory feedback following an action produces a subjective time compression between the action and the feedback (temporal recalibration effect, TRE). TRE is important for sensory delay compensation to maintain a relationship between causally related events. It is unclear whether TRE is a sensory modality-specific phenomenon. In 3 experiments employing a sensorimotor synchronization task, we investigated this question using cathodal transcranial direct-current stimulation (tDCS). We found that cathodal tDCS over the visual cortex, and to a lesser extent over the auditory cortex, produced decreased visual TRE. However, both auditory and visual cortex tDCS did not produce any measurable effects on auditory TRE. Our study revealed different nature of TRE in auditory and visual domains. Visual-motor TRE, which is more variable than auditory TRE, is a sensory modality-specific phenomenon, modulated by the auditory cortex. The robustness of auditory-motor TRE, unaffected by tDCS, suggests the dominance of the auditory system in temporal processing, by providing a frame of reference in the realignment of sensorimotor timing signals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Shaping memory accuracy by left prefrontal transcranial direct current stimulation.

PubMed

Zwissler, Bastian; Sperber, Christoph; Aigeldinger, Sina; Schindler, Sebastian; Kissler, Johanna; Plewnia, Christian

2014-03-12

Human memory is dynamic and flexible but is also susceptible to distortions arising from adaptive as well as pathological processes. Both accurate and false memory formation require executive control that is critically mediated by the left prefrontal cortex (PFC). Transcranial direct current stimulation (tDCS) enables noninvasive modulation of cortical activity and associated behavior. The present study reports that tDCS applied to the left dorsolateral PFC (dlPFC) shaped accuracy of episodic memory via polaritiy-specific modulation of false recognition. When applied during encoding of pictures, anodal tDCS increased whereas cathodal stimulation reduced the number of false alarms to lure pictures in subsequent recognition memory testing. These data suggest that the enhancement of excitability in the dlPFC by anodal tDCS can be associated with blurred detail memory. In contrast, activity-reducing cathodal tDCS apparently acted as a noise filter inhibiting the development of imprecise memory traces and reducing the false memory rate. Consistently, the largest effect was found in the most active condition (i.e., for stimuli cued to be remembered). This first evidence for a polarity-specific, activity-dependent effect of tDCS on false memory opens new vistas for the understanding and potential treatment of disturbed memory control.

Transcranial direct current stimulation (tDCS) of the inferior frontal cortex affects the "social scaling" of extrapersonal space depending on perspective-taking ability.

PubMed

Fini, Chiara; Bardi, Lara; Epifanio, Alessandra; Committeri, Giorgia; Moors, Agnes; Brass, Marcel

2017-03-01

When we have to judge the distance between another person and an object (social condition), we judge this distance as being smaller compared to judging the distance between two objects (nonsocial condition). It has been suggested that this compression is mediated by the attribution of a motor potential to the reference frame (other person vs. object). In order to explore the neural basis of this effect, we investigated whether the modulation of activity in the inferior frontal cortex (IFC) of the left hemisphere (recruited during visuospatial processes with a social component) changes the way we categorize space in a social compared with a nonsocial condition. We applied transcranial direct current stimulation to the left IFC, with different polarities (anodal, cathodal, and sham) while subjects performed an extrapersonal space categorization task. Interestingly, anodal stimulation of IFC induced an higher compression of space in the social compared to nonsocial condition. By contrast, cathodal stimulation induced the opposite effect. Furthermore, we found that this effect is modulated by interindividual differences in cognitive perspective taking. Our data support the idea that IFC is recruited during the social categorization of space.

Electrochemical modification of properties of ZnO films

NASA Astrophysics Data System (ADS)

Abe, Koji; Okubo, Takamasa; Ishikawa, Hirohito

2017-12-01

The properties of Al-doped ZnO films and Li- and Al-doped ZnO films were modified by electrochemical treatment. A constant current was applied between a ZnO film and a Pt electrode in an electrolyte solution. The sheet resistance of the ZnO film increased and decreased depending on the direction of current flow during the electrochemical treatment. When the ZnO film was used as a cathode (forward biased condition), the sheet resistance of the ZnO film decreased with increasing treatment time. The optical bandgap of the H2-annealed ZnO film also depended on the direction of current flow and increased under the forward biased condition. The electrochemical treatment caused the Burstein-Moss effect.

High Current Density, Long Life Cathodes for High Power RF Sources

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

Ives, Robert Lawrence; Collins, George; Falce, Lou

2014-01-22

This program was tasked with improving the quality and expanding applications for Controlled Porosity Reservoir (CPR) cathodes. Calabazas Creek Research, Inc. (CCR) initially developed CPR cathodes on a DOE-funded SBIR program to improve cathodes for magnetron injection guns. Subsequent funding was received from the Defense Advanced Research Projects Agency. The program developed design requirements for implementation of the technology into high current density cathodes for high frequency applications. During Phase I of this program, CCR was awarded the prestigious 2011 R&D100 award for this technology. Subsequently, the technology was presented at numerous technical conferences. A patent was issued for themore » technology in 2009. These cathodes are now marketed by Semicon Associates, Inc. in Lexington, KY. They are the world’s largest producer of cathodes for vacuum electron devices. During this program, CCR teamed with Semicon Associates, Inc. and Ron Witherspoon, Inc. to improve the fabrication processes and expand applications for the cathodes. Specific fabrications issues included the quality of the wire winding that provides the basic structure and the sintering to bond the wires into a robust, cohesive structure. The program also developed improved techniques for integrating the resulting material into cathodes for electron guns.« less

Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells

EPA Science Inventory

Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2...

Effect of Lanthanum-Strontium Cathode Current-Collecting Layer on the Performance of Anode Supported Type Planar Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Park, Sun-Young; Ji, Ho-Il; Kim, Hae-Ryoung; Yoon, Kyung Joong; Son, Ji-Won; Lee, Hae-Weon; Lee, Jong-Ho

2013-07-01

We applied screen-printed (La,Sr)CoO3 as a current-collecting layer of planar type unit-cell for lower temperature operation of SOFCs. In this study the effects of the cathode current-collecting layer on the performance of unit cell and symmetric half cell were investigated via AC and DC polarization experiments. According to our investigation, appropriately controlled current collecting layer was very effective to enhance the unit cell performance by reducing not only the ohmic resistance but also the polarization losses of SOFC cathode.

Investigation on emission characteristics of metal-ceramic cathode applied to industrial X-ray diode.

PubMed

Xun, Ma; Jianqiang, Yuan; Hongwei, Liu; Hongtao, Li; Lingyun, Wang; Ping, Jiang

2016-06-01

The industrial x-ray diode with high impedance configuration is usually adopted to generate repetitive x-ray, but its performance would be worsened due to lower electric field on the cathode of diode when a voltage of several hundreds of kV is applied. To improve its performance, a novel metal-ceramic cathode is proposed in this paper. Key factors (width, relative permittivity of ceramic, and so on) affecting electric field distribution on triple points are analyzed by electrostatic field calculation program, so as to optimize the design of this novel cathode. Experiments are done to study the characteristics including emission current of cathode, diode voltage duration, diode mean dynamic impedance, and diode impedance drop velocity within diode power duration. The results show that metal-ceramic cathode could improve diode performance by enhancing emission current and stabling impedance; the impedance drop velocity of diode with spoke-shaped metal-ceramic cathode was reduced to -5 Ω ns(-1) within diode power duration, comparing to -15 Ω ns(-1) with metal foil cathode.

Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources.

PubMed

Odorici, F; Malferrari, L; Montanari, A; Rizzoli, R; Mascali, D; Castro, G; Celona, L; Gammino, S; Neri, L

2016-02-01

Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to "screen" the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used, as explained by plasma diffusion models.

What is the optimal anodal electrode position for inducing corticomotor excitability changes in transcranial direct current stimulation?

PubMed

Lee, Minji; Kim, Yun-Hee; Im, Chang-Hwan; Kim, Jung-Hoon; Park, Chang-hyun; Chang, Won Hyuk; Lee, Ahee

2015-01-01

Transcranial direct current stimulation (tDCS) non-invasively modulates brain function by inducing neuronal excitability. The conventional hot spot for inducing the highest current density in the hand motor area may not be the optimal site for effective stimulation. In this study, we investigated the influence of the center position of the anodal electrode on changes in motor cortical excitability. We considered three tDCS conditions in 16 healthy subjects: (i) real stimulation with the anodal electrode located at the conventional hand motor hot spot determined by motor evoked potentials (MEPs); (ii) real stimulation with the anodal electrode located at the point with the highest current density in the hand motor area as determined by electric current simulation; and (iii) sham stimulation. Motor cortical excitability as measured by MEP amplitude increased after both real stimulation conditions, but not after sham stimulation. Stimulation using the simulation-derived anodal electrode position, which was found to be posterior to the MEP hot spot for all subjects, induced higher motor cortical excitability. Individual positioning of the anodal electrode, based on the consideration of anatomical differences between subjects, appears to be important for maximizing the effects of tDCS. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes.

PubMed

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-06-23

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H(+) to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H(+), and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m(2)). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

PubMed Central

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-01-01

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H+ to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H+, and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m2). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter. PMID:27333815

Experimental Investigation of a Hall-Current Accelerator. M.S. Thesis

NASA Technical Reports Server (NTRS)

Plank, G. M.

1983-01-01

The Hall-current accelerator is being investigated for use in the 1000-2000 sec. range of specific impulse. Three models of this thruster were tested. The first two models had three permanent magnets to supply the magnetic field and the third model had six magnets to supply the field. The third model thus had approximately twice the magnetic field of the first two. The first and second models differ only in the shape of the magnetic field. All other factors remained the same for the three models except for the anode-cathode distance, which was changed to allow for the three thrusters to have the same magnetic field integral between the anode and the cathode. These Hall thrusters were tested to determine the plasma properties, the beam characteristics, and the thruster characteristics. The thruster operated in three modes: (1) main cathode only, (2) main cathode with neutralizer cathode, and (3) neutralizer cathode only. The plasma properties were measured along an axial line, 1 mm inside the cathode radius, at a distance of 0.2 to 6.2 cm from the anode. Results show that the current used to heat the cathode produced nonuniformities in the magnetic field, hence also in the plasma properties. In a Hall thruster this general design appears to provide the most thrust when operated at a magnetic field less than the maximum value studied.

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

NASA Astrophysics Data System (ADS)

Lee, Seung Ho; Ban, Ju Yeon; Oh, Chung-Hun; Park, Hun-Kuk; Choi, Samjin

2016-06-01

We present the fabrication of an ultra-low cost, disposable, solvent-free air cathode all-paper microbial fuel cell (MFC) that does not utilize any chemical treatments. The anode and cathode were fabricated by depositing graphite particles by drawing them on paper with a pencil (four strokes). Hydrophobic parchment paper was used as a proton exchange membrane (PEM) to allow only H+ to pass. Air cathode MFC technology, where O2 was used as an electron acceptor, was implemented on the paper platform. The bioelectric current was generated by an electrochemical process involving the redox couple of microbial-activated extracellular electron transferred electrons, PEM-passed H+, and O2 in the cathode. A fully micro-integrated pencil-traced MFC showed a fast start-time, producing current within 10 s after injection of bacterial cells. A single miniaturized all-paper air cathode MFC generated a maximum potential of 300 mV and a maximum current of 11 μA during 100 min after a single injection of Shewanella oneidensis. The micro-fabricated solvent-free air cathode all-paper MFC generated a power of 2,270 nW (5.68 mW/m2). The proposed solvent-free air cathode paper-based MFC device could be used for environmentally-friendly energy storage as well as in single-use medical power supplies that use organic matter.

Air breathing direct methanol fuel cell

DOEpatents

Ren, Xiaoming; Gottesfeld, Shimshon

2002-01-01

An air breathing direct methanol fuel cell is provided with a membrane electrode assembly, a conductive anode assembly that is permeable to air and directly open to atmospheric air, and a conductive cathode assembly that is permeable to methanol and directly contacting a liquid methanol source. Water loss from the cell is minimized by making the conductive cathode assembly hydrophobic and the conductive anode assembly hydrophilic.

Freestanding and flexible graphene papers as bioelectrochemical cathode for selective and efficient CO2 conversion.

PubMed

Aryal, Nabin; Halder, Arnab; Zhang, Minwei; Whelan, Patrick R; Tremblay, Pier-Luc; Chi, Qijin; Zhang, Tian

2017-08-22

During microbial electrosynthesis (MES) driven CO 2 reduction, cathode plays a vital role by donating electrons to microbe. Here, we exploited the advantage of reduced graphene oxide (RGO) paper as novel cathode material to enhance electron transfer between the cathode and microbe, which in turn facilitated CO 2 reduction. The acetate production rate of Sporomusa ovata-driven MES reactors was 168.5 ± 22.4 mmol m -2 d -1 with RGO paper cathodes poised at -690 mV versus standard hydrogen electrode. This rate was approximately 8 fold faster than for carbon paper electrodes of the same dimension. The current density with RGO paper cathodes of 2580 ± 540 mA m -2 was increased 7 fold compared to carbon paper cathodes. This also corresponded to a better cathodic current response on their cyclic voltammetric curves. The coulombic efficiency for the electrons conversion into acetate was 90.7 ± 9.3% with RGO paper cathodes and 83.8 ± 4.2% with carbon paper cathodes, respectively. Furthermore, more intensive cell attachment was observed on RGO paper electrodes than on carbon paper electrodes with confocal laser scanning microscopy and scanning electron microscopy. These results highlight the potential of RGO paper as a promising cathode for MES from CO 2 .

Multi-cathode metal vapor arc ion source

DOEpatents

Brown, Ian G.; MacGill, Robert A.

1988-01-01

An ion generating apparatus utilizing a vacuum chamber, a cathode and an anode in the chamber. A source of electrical power produces an arc or discharge between the cathode and anode. The arc is sufficient to vaporize a portion of the cathode to form a plasma. The plasma is directed to an extractor which separates the electrons from the plasma, and accelerates the ions to produce an ion beam. One embodiment of the appaatus utilizes a multi-cathode arrangement for interaction with the anode.

Airway epithelial wounds in rhesus monkey generate ionic currents that guide cell migration to promote healing

PubMed Central

Sun, Yao-Hui; Reid, Brian; Fontaine, Justin H.; Miller, Lisa A.; Hyde, Dallas M.; Mogilner, Alex

2011-01-01

Damage to the respiratory epithelium is one of the most critical steps to many life-threatening diseases, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease. The mechanisms underlying repair of the damaged epithelium have not yet been fully elucidated. Here we provide experimental evidence suggesting a novel mechanism for wound repair: endogenous electric currents. It is known that the airway epithelium maintains a voltage difference referred to as the transepithelial potential. Using a noninvasive vibrating probe, we demonstrate that wounds in the epithelium of trachea from rhesus monkeys generate significant outward electric currents. A small slit wound produced an outward current (1.59 μA/cm2), which could be enhanced (nearly doubled) by the ion transport stimulator aminophylline. In addition, inhibiting cystic fibrosis transmembrane conductance regulator (CFTR) with CFTR(Inh)-172 significantly reduced wound currents (0.17 μA/cm2), implicating an important role of ion transporters in wound induced electric potentials. Time-lapse video microscopy showed that applied electric fields (EFs) induced robust directional migration of primary tracheobronchial epithelial cells from rhesus monkeys, towards the cathode, with a threshold of <23 mV/mm. Reversal of the field polarity induced cell migration towards the new cathode. We further demonstrate that application of an EF promoted wound healing in a monolayer wound healing assay. Our results suggest that endogenous electric currents at sites of tracheal epithelial injury may direct cell migration, which could benefit restitution of damaged airway mucosa. Manipulation of ion transport may lead to novel therapeutic approaches to repair damaged respiratory epithelium. PMID:21719726

A direct ascorbate fuel cell with an anion exchange membrane

NASA Astrophysics Data System (ADS)

Muneeb, Omar; Do, Emily; Tran, Timothy; Boyd, Desiree; Huynh, Michelle; Ghosn, Gregory; Haan, John L.

2017-05-01

Ascorbic Acid (Vitamin C) is investigated as a renewable alternative fuel for alkaline direct liquid fuel cells (DLFCs). The environmentally- and biologically-friendly compound, L-ascorbic acid (AA) has been modeled and studied experimentally under acidic fuel cell conditions. In this work, we demonstrate that ascorbic acid is a more efficient fuel in alkaline media than in acidic media. An operating direct ascorbate fuel cell is constructed with the combination of L-ascorbic acid and KOH as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, metal or carbon black anode materials and metal cathode catalyst. Operation of the fuel cell at 60 °C using 1 M AA and 1 M KOH as the anode fuel and electrolyte, respectively, and oxygen gas at the cathode, produces a maximum power density of 73 mW cm-2, maximum current density of 497 mA cm-2 and an open circuit voltage of 0.90 V. This performance is significantly greater than that of an ascorbic acid fuel cell with a cation exchange membrane, and it is competitive with alkaline DLFCs fueled by alcohols.

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

Majzoobi, A.; Joshi, R. P., E-mail: ravi.joshi@ttu.edu; Neuber, A. A.

Particle-in-cell simulations are performed to analyze the efficiency, output power and leakage currents in a 12-Cavity, 12-Cathode rising-sun magnetron with diffraction output (MDO). The central goal is to conduct a parameter study of a rising-sun magnetron that comprehensively incorporates performance enhancing features such as transparent cathodes, axial extraction, the use of endcaps, and cathode extensions. Our optimum results demonstrate peak output power of about 2.1 GW, with efficiencies of ∼70% and low leakage currents at a magnetic field of 0.45 Tesla, a 400 kV bias with a single endcap, for a range of cathode extensions between 3 and 6 centimeters.

Field Emission Cold Cathode Devices Based on Eutectic Systems

DTIC Science & Technology

1981-07-01

8217RADC-TR-811-170 ’,Final Technical Report July 1981 FIELD EMISSION COLD CATHODE DEVICES BASED ON EUTECTIC SYSTEMS Fulmer Research Institute Ltd...and identify by block numrber) Field Emission Eutectic Systems Cold Cathode Rod Eutectics Electron Emitter Array Directionally Solidified Eutectics...Identify by block number) A survey has been made of the performance as field emission cold cathodes of selected refractory materials fabricated as

Measurement of the Arithmetic Mean Velocity of a Pulsating Flow of High Velocity by the Hot-Wire Method

DTIC Science & Technology

1946-04-01

electric Ympulse’fs iransaitteh and ati$ lified by the-amplifier stages. A variationyof the potential between * grid’and,:cathod.e of the. chrrent...ethods:in Engineering. McGraw-hill Book Co. Inc., 1940, p. 327, "&.: ,. , . 7: -. .’,.:+.- .(: .- ..I‘ 5. Shea, ’Transmission Networks and rave Filters

Prediction of field emitter cathode lifetime based on measurement of I- V curves

NASA Astrophysics Data System (ADS)

Bormashov, V. S.; Nikolski, K. N.; Baturin, A. S.; Sheshin, E. P.

2003-06-01

A technique is presented, which allows the prediction of field emitter cathode lifetime without long-term direct measurements of cathode parameters stability. This technique is based on periodic measurements of cathode I- V characteristics. Moreover, it allows performing a post-experiment optimization for the appropriate choice of the feedback system to provide a stable operation during a long time. The proposed technique was applied to study the emission properties of reticulated vitreous carbon (RVC) and thermo-enlarged graphite (TEG). For the given cathodes, the characteristic time of the cathode destruction was estimated.

Emission characteristics of dispenser cathodes with a fine-grained tungsten top layer

NASA Astrophysics Data System (ADS)

Kimura, S.; Higuchi, T.; Ouchi, Y.; Uda, E.; Nakamura, O.; Sudo, T.; Koyama, K.

1997-02-01

In order to improve the emission stability of the Ir-coated dispenser cathode under ion bombardment, a fine-grained tungsten top layer was applied on the substrate porous tungsten plug before Ir coating. The emission characteristics were studied after being assembled in a CRT gun. Cathode current was measured under pulse operation in a range of 0.1-9% duty. Remarkable anti-ion bombardment characteristics were observed over the range of 1-6% duty. The improved cathode showed 1.5 times higher emission current than that of a conventional Ir-coated dispenser cathode at 4% duty. AES analysis showed that the recovering rates of surface Ba and O atoms after ion bombardment were 2.5 times higher. From these results it is confirmed that the Ir coated cathode with a fine-grained tungsten top layer is provided with a good tolerance against the ion bombardment.

Plasma characteristics in the discharge region of a 20 A emission current hollow cathode

NASA Astrophysics Data System (ADS)

Mingming, SUN; Tianping, ZHANG; Xiaodong, WEN; Weilong, GUO; Jiayao, SONG

2018-02-01

Numerical calculation and fluid simulation methods were used to obtain the plasma characteristics in the discharge region of the LIPS-300 ion thruster’s 20 A emission current hollow cathode and to verify the structural design of the emitter. The results of the two methods indicated that the highest plasma density and electron temperature, which improved significantly in the orifice region, were located in the discharge region of the hollow cathode. The magnitude of plasma density was about 1021 m-3 in the emitter and orifice regions, as obtained by numerical calculations, but decreased exponentially in the plume region with the distance from the orifice exit. Meanwhile, compared to the emitter region, the electron temperature and current improved by about 36% in the orifice region. The hollow cathode performance test results were in good agreement with the numerical calculation results, which proved that that the structural design of the emitter and the orifice met the requirements of a 20 A emission current. The numerical calculation method can be used to estimate plasma characteristics in the preliminary design stage of hollow cathodes.

Cathode Characterization with Steel and Copper Collector Bars in an Electrolytic Cell

NASA Astrophysics Data System (ADS)

Das, Subrat; Morsi, Yos; Brooks, Geoffrey

2013-12-01

This article presents finite-element method simulation results of current distribution in an aluminum electrolytic cell. The model uses one quarter of the cell as a computational domain assuming longitudinal (along the length of the cell) and transverse axes of symmetries. The purpose of this work is to closely examine the impact of steel and copper collector bars on the cell current distribution. The findings indicated that an inclined steel collector bar (φ = 1°) can save up to 10-12 mV from the cathode lining in comparison to a horizontal 100 mm × 150-mm steel collector bar. It is predicted that a copper collector bar has a much higher potential of saving cathode voltage drop (CVD) and has a greater impact on the overall current distribution in the cell. A copper collector bar with 72% of cathode length and size of 100 mm × 150 mm is predicted to have more than 150 mV savings in cathode lining. In addition, a significant improvement in current distribution over the entire cathode surface is achieved when compared with a similar size of steel collector bar. There is a reduction of more than 70% in peak current density value due to the higher conductivity of copper. Comparisons between steel and copper collector bars with different sizes are discussed in terms CVD and current density distribution. The most important aspect of the findings is to recognize the influence of copper collector bars on the current distribution in molten metal. Lorentz fields are evaluated at different sizes of steel and copper collector bars. The simulation predicts that there is 50% decrease in Lorentz force due to the improvement in current distribution in the molten metal.

Contributions of Hot and Cool Self-Regulation to Preschool Disruptive Behavior and Academic Achievement

PubMed Central

Willoughby, Michael; Kupersmidt, Janis; Voegler-Lee, Mare; Bryant, Donna

2017-01-01

The construct of self-regulation can be meaningfully distinguished into hot and cool components. The current study investigated self-regulation in a sample of 926 children aged 3–5 years old. Children’s performance on self-regulatory tasks was best described by two latent factors representing hot and cool regulation. When considered alone, hot and cool regulation were both significantly correlated with disruptive behavior and academic achievement. When considered together, cool regulation was uniquely associated with academic achievement, while hot regulation was uniquely associated with inattentive-overactive behaviors. Results are discussed with respect to treatment studies that directly target improvement in children’s self-regulation. PMID:21347919

Experimental Studies of the Effects of Anode Composition and Process Parameters on Anode Slime Adhesion and Cathode Copper Purity by Performing Copper Electrorefining in a Pilot-Scale Cell

NASA Astrophysics Data System (ADS)

Zeng, Weizhi; Wang, Shijie; Free, Michael L.

2016-10-01

Copper electrorefining tests were conducted in a pilot-scale cell under commercial tankhouse environment to study the effects of anode compositions, current density, cathode blank width, and flow rate on anode slime behavior and cathode copper purity. Three different types of anodes (high, mid, and low impurity levels) were used in the tests and were analyzed under SEM/EDS. The harvested copper cathodes were weighed and analyzed for impurities concentrations using DC Arc. The adhered slimes and released slimes were collected, weighed, and analyzed for compositions using ICP. It was shown that the lead-to-arsenic ratio in the anodes affects the sintering and coalescence of slime particles. High current density condition can improve anode slime adhesion and cathode purity by intensifying slime particles' coalescence and dissolving part of the particles. Wide cathode blanks can raise the anodic current densities significantly and result in massive release of large slime particle aggregates, which are not likely to contaminate the cathode copper. Low flow rate can cause anode passivation and increase local temperatures in front of the anode, which leads to very intense sintering and coalescence of slime particles. The results and analyses of the tests present potential solutions for industrial copper electrorefining process.

Development of plasma cathode electron guns

NASA Astrophysics Data System (ADS)

Oks, Efim M.; Schanin, Peter M.

1999-05-01

The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

Magnetically insulated coaxial vacuum diode with partial space-charge-limited explosive emission from edge-type cathode

NASA Astrophysics Data System (ADS)

Belomyttsev, S. Ya.; Rostov, V. V.; Romanchenko, I. V.; Shunailov, S. A.; Kolomiets, M. D.; Mesyats, G. A.; Sharypov, K. A.; Shpak, V. G.; Ulmaskulov, M. R.; Yalandin, M. I.

2016-01-01

The vacuum current associated with any type of electron emission for arbitrary configuration of the diode depends on the combination of the applied electric field and vacuum space charge (VSC) field created by the current. Such fundamental statement should give very close links between the diode current and the normalized cathode field θ which has been introduced by Forbes in 2008 for planar diodes as a reduction in the cathode surface field: θ = field-with/field-without VSC. This article reports the universal approximation of the type of cos(πθ/2) that is the ratio of the actual current and the fully space-charge-limited current. Also, the theoretical treatment and the experimental method of determination of the dynamic emissive characteristics of the macroscopic explosive emission from edge-type cathodes in the coaxial diode are developed. The experimental results obtained with a picosecond time reference between the cathode voltage and the onset of the high-current electron beam exhibit a good coincidence with the theoretical predictions. The presented methods enable the analysis of a real-time-resolved dynamics associated with the dense, magnetized electron beam formation, acceleration and drift motion, including kinematic effects and the phase-stable excitation of high-power microwave oscillators.

Magnetically insulated coaxial vacuum diode with partial space-charge-limited explosive emission from edge-type cathode

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

Belomyttsev, S. Ya.; Rostov, V. V.; Romanchenko, I. V.

2016-01-14

The vacuum current associated with any type of electron emission for arbitrary configuration of the diode depends on the combination of the applied electric field and vacuum space charge (VSC) field created by the current. Such fundamental statement should give very close links between the diode current and the normalized cathode field θ which has been introduced by Forbes in 2008 for planar diodes as a reduction in the cathode surface field: θ = field-with/field-without VSC. This article reports the universal approximation of the type of cos(πθ/2) that is the ratio of the actual current and the fully space-charge-limited current. Also, themore » theoretical treatment and the experimental method of determination of the dynamic emissive characteristics of the macroscopic explosive emission from edge-type cathodes in the coaxial diode are developed. The experimental results obtained with a picosecond time reference between the cathode voltage and the onset of the high-current electron beam exhibit a good coincidence with the theoretical predictions. The presented methods enable the analysis of a real-time-resolved dynamics associated with the dense, magnetized electron beam formation, acceleration and drift motion, including kinematic effects and the phase-stable excitation of high-power microwave oscillators.« less

Ozone formation in pulsed SDBD in a wide pressure range

NASA Astrophysics Data System (ADS)

Starikovskiy, Andrey; Nudnova, Maryia; mipt Team

2011-10-01

Ozone concentration in surface anode-directed DBD for wide pressure range (150 - 1300 torr) was experimentally measured. Voltage and pressure effect were investigated. Reduced electric field was measured for anode-directed and cathode-directed SDBD. E/n values in cathode-directed SDBD is higher than in cathode-directed on 50 percent at atmospheric pressure. E/n value increase leads to decrease the rate of oxygen dissociation and Ozone formation at lower pressures. Radiating region thickness of sliding discharge was measured. Typical thickness of radiating zone is 0.4-1.0 mm within pressure range 220-740 torr. It was shown that high-voltage pulsed nanosecond discharge due to high E/n value produces less Ozone with compare to other discharges. Kinetic model was proposed to describe Ozone formation in the pulsed nanosecond SDBD.

High temperature molten salt storage

NASA Astrophysics Data System (ADS)

Ives, J.; Newcomb, J. C.; Pard, A. G.

1985-10-01

The design of a high-temperature molten salt thermal energy storage (TES) concept, including some materials testing, was developed by Rockwell International's Rocketdyne Division (RD), under contract to SERI, and is described in this document. The main features of the concept are a conical hot tank with a liner and internal insulation that allows unrestricted relative thermal expansion and the use of cathodic protection (impressed voltage) to inhibit corrosion. The RD design uses two tanks and ternary eutectic lithium-sodium-potassium carbonates for sensible heat storage. The tanks were sized for 6 h of storage at a discharge rate of 300 MW, giving 1800 MWh total usable thermal storage capacity. The molten carbonate storage medium is cycled between 425 and 900C. From the design study, no definitive statement can be made as to the cost-effectiveness of cathodic protection. Several anode design issues need to be resolved before cathodic protection can significantly reduce corrosion where the liner comes in contact with molten salts. However, where the tank is exposed to salt vapor, the large corrosion allowance required for the liner without cathodic protection results in a much thicker liner wall and shorter liner life than originally perceived, which affects system costs significantly.

Anode power deposition in applied-field MPD thrusters

NASA Technical Reports Server (NTRS)

Myers, Roger M.; Soulas, George C.

1992-01-01

Anode power deposition is the principle performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power deposition resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters.

Cathode for aluminum producing electrolytic cell

DOEpatents

Brown, Craig W.

2004-04-13

A method of producing aluminum in an electrolytic cell comprising the steps of providing an anode in a cell, preferably a non-reactive anode, and also providing a cathode in the cell, the cathode comprised of a base material having low electrical conductivity reactive with molten aluminum to provide a highly electrically conductive layer on the base material. Electric current is passed from the anode to the cathode and alumina is reduced and aluminum is deposited at the cathode. The cathode base material is selected from boron carbide, and zirconium oxide.

Effects of Neutral Density on Energetic Ions Produced Near High-Current Hollow Cathodes

NASA Technical Reports Server (NTRS)

Kameyama, Ikuya

1997-01-01

Energy distributions of ion current from high-current, xenon hollow cathodes, which are essential information to understand erosion phenomena observed in high-power ion thrusters, were obtained using an electrostatic energy analyzer (ESA). The effects of ambient pressure and external flow rate introduced immediately downstream of hollow cathode on ion currents with energies greater than that associated with the cathode-to-anode potential difference were investigated. The results were analyzed to determine the changes in the magnitudes of ion currents to the ESA at various energies. Either increasing the ambient pressure or adding external flow induces an increase in the distribution of ion currents with moderate energies (epsilon less than 25 to 35 eV) and a decrease in the distribution for high energies (epsilon greater than 25 to 35 eV). The magnitude of the current distribution increase in the moderate energy range is greater for a cathode equipped with a toroidal keeper than for one without a keeper, but the distribution in the high energy range does not seem to be affected by a keeper. An MHD model, which has been proposed to describe energetic-ion production mechanism in hollow cathode at high discharge currents, was developed to describe these effects. The results show, however, that this model involves no mechanism by which a significant increase of ion current could occur at any energy. It was found, on the other hand, that the potential-hill model of energetic ion production, which assumes existence of a local maximum of plasma potential, could explain combined increases in the currents of ions with moderate energies and decreases in high energy ions due to increased neutral atom density using a charge-exchange mechanism. The existing, simplified version of the potential-hill model, however, shows poor quantitative agreement with measured ion-current-energy-distribution changes induced by neutral density changes.

Reactant gas composition for fuel cell potential control

DOEpatents

Bushnell, Calvin L.; Davis, Christopher L.

1991-01-01

A fuel cell (10) system in which a nitrogen (N.sub.2) gas is used on the anode section (11) and a nitrogen/oxygen (N.sub.2 /O.sub.2) gaseous mix is used on the cathode section (12) to maintain the cathode at an acceptable voltage potential during adverse conditions occurring particularly during off-power conditions, for example, during power plant shutdown, start-up and hot holds. During power plant shutdown, the cathode section is purged with a gaseous mixture of, for example, one-half percent (0.5%) oxygen (O.sub.2) and ninety-nine and a half percent (99.5%) nitrogen (N.sub.2) supplied from an ejector (21) bleeding in air (24/28) into a high pressure stream (27) of nitrogen (N.sub.2) as the primary or majority gas. Thereafter the fuel gas in the fuel processor (31) and the anode section (11) is purged with nitrogen gas to prevent nickel (Ni) carbonyl from forming from the shift catalyst. A switched dummy electrical load (30) is used to bring the cathode potential down rapidly during the start of the purges. The 0.5%/99.5% O.sub.2 /N.sub.2 mixture maintains the cathode potential between 0.3 and 0.7 volts, and this is sufficient to maintain the cathode potential at 0.3 volts for the case of H.sub.2 diffusing to the cathode through a 2 mil thick electrolyte filled matrix and below 0.8 volts for no diffusion at open circuit conditions. The same high pressure gas source (20) is used via a "T" juncture ("T") to purge the anode section and its associated fuel processor (31).

Understanding anode and cathode behaviour in high-pressure discharge lamps

NASA Astrophysics Data System (ADS)

Flesch, P.; Neiger, M.

2005-09-01

High-intensity discharge (HID) lamps have widespread and modern areas of application including general lighting, video/movie projection (e.g. UHP lamp), street/industrial lighting, and automotive headlight lamps (D2/xenon lamp). Even though HID lamps have been known for several decades now, the important plasma-electrode interactions are still not well understood. Because HID lamps are usually operated on ac (electrodes switch alternately from anode to cathode phase), time-dependent simulations including realistic and verified anode and cathode models are essential. Therefore, a recently published investigation of external laser heating of an electrode during anode and cathode phase in an operating HID lamp [28] provided the basis for our present paper. These measurements revealed impressive influences of the external laser heating on electrode fall voltage and electrode temperature. Fortunately, the effects are very different during anode and cathode phase. Thus, by comparing the experimental findings with results from our numerical simulations we can learn much about the principles of electrode behaviour and explain in detail the differences between anode and cathode phase. Furthermore, we can verify our model (which includes plasma column, hot plasma spots in front of the electrodes, constriction zones and near-electrode non-local thermal equilibrium-plasma as well as anode and cathode) that accounts for all relevant physical processes concerning plasma, electrodes and interactions between them. Moreover, we investigate the influence of two different notions concerning ionization and recombination in the near electrode plasma on the numerical results. This improves our physical understanding of near-electrode plasma likewise and further increases the confidence in the model under consideration. These results are important for the understanding and the further development of HID lamps which, due to their small dimensions, are often experimentally inaccessible. Thus, modelling becomes more and more important.

Systematic evaluation of the impact of stimulation intensity on neuroplastic after-effects induced by transcranial direct current stimulation.

PubMed

Jamil, Asif; Batsikadze, Giorgi; Kuo, Hsiao-I; Labruna, Ludovica; Hasan, Alkomiet; Paulus, Walter; Nitsche, Michael A

2017-02-15

Applications of transcranial direct current stimulation to modulate human neuroplasticity have increased in research and clinical settings. However, the need for longer-lasting effects, combined with marked inter-individual variability, necessitates a deeper understanding of the relationship between stimulation parameters and physiological effects. We systematically investigated the full DC intensity range (0.5-2.0 mA) for both anodal and cathodal tDCS in a sham-controlled repeated measures design, monitoring changes in motor-cortical excitability via transcranial magnetic stimulation up to 2 h after stimulation. For both tDCS polarities, the excitability after-effects did not linearly correlate with increasing DC intensity; effects of lower intensities (0.5, 1.0 mA) showed equal, if not greater effects in motor-cortical excitability. Further, while intra-individual responses showed good reliability, inter-individual sensitivity to TMS accounted for a modest percentage of the variance in the early after-effects of 1.0 mA anodal tDCS, which may be of practical relevance for future optimizations. Contemporary non-invasive neuromodulatory techniques, such as transcranial direct current stimulation (tDCS), have shown promising potential in both restituting impairments in cortical physiology in clinical settings, as well as modulating cognitive abilities in the healthy population. However, neuroplastic after-effects of tDCS are highly dependent on stimulation parameters, relatively short lasting, and not expectedly uniform between individuals. The present study systematically investigates the full range of current intensity between 0.5 and 2.0 mA on left primary motor cortex (M1) plasticity, as well as the impact of individual-level covariates on explaining inter-individual variability. Thirty-eight healthy subjects were divided into groups of anodal and cathodal tDCS. Five DC intensities (sham, 0.5, 1.0, 1.5 and 2.0 mA) were investigated in separate sessions. Using transcranial magnetic stimulation (TMS), 25 motor-evoked potentials (MEPs) were recorded before, and 10 time points up to 2 h following 15 min of tDCS. Repeated-measures ANOVAs indicated a main effect of intensity for both anodal and cathodal tDCS. With anodal tDCS, all active intensities resulted in equivalent facilitatory effects relative to sham while for cathodal tDCS, only 1.0 mA resulted in sustained excitability diminution. An additional experiment conducted to assess intra-individual variability revealed generally good reliability of 1.0 mA anodal tDCS (ICC(2,1) = 0.74 over the first 30 min). A post hoc analysis to discern sources of inter-individual variability confirmed a previous finding in which individual TMS SI 1mV (stimulus intensity for 1 mV MEP amplitude) sensitivity correlated negatively with 1.0 mA anodal tDCS effects on excitability. Our study thus provides further insights on the extent of non-linear intensity-dependent neuroplastic after-effects of anodal and cathodal tDCS. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

An experimental investigation of cathode erosion in high current magnetoplasmadynamic arc discharges

NASA Astrophysics Data System (ADS)

Codron, Douglas A.

Since the early to mid 1960's, laboratory studies have demonstrated the unique ability of magnetoplasmadynamic (MPD) thrusters to deliver an exceptionally high level of specific impulse and thrust at large power processing densities. These intrinsic advantages are why MPD thrusters have been identified as a prime candidate for future long duration space missions, including piloted Mars, Mars cargo, lunar cargo, and other missions beyond low Earth orbit (LEO). The large total impulse requirements inherent of the long duration space missions demand the thruster to operate for a significant fraction of the mission burn time while requiring the cathodes to operate at 50 to 10,000 kW for 2,000 to 10,000 hours. The high current levels lead to high operational temperatures and a corresponding steady depletion of the cathode material by evaporation. This mechanism has been identified as the life-limiting component of MPD thrusters. In this research, utilizing subscale geometries, time dependent cathode axial temperature profiles under varying current levels (20 to 60 A) and argon gas mass flow rates (450 to 640 sccm) for both pure and thoriated solid tungsten cathodes were measured by means of both optical pyrometry and charged-coupled (CCD) camera imaging. Thoriated tungsten cathode axial temperature profiles were compared against those of pure tungsten to demonstrate the large temperature reducing effect lowered work function imparts by encouraging increased thermionic electron emission from the cathode surface. Also, Langmuir probing was employed to measure the electron temperature, electron density, and plasma potential near the "active zone" (the surface area of the cathode responsible for approximately 70% of the emitted current) in order to characterize the plasma environment and verify future model predictions. The time changing surface microstructure and elemental composition of the thoriated tungsten cathodes were analyzed using a scanning electron microscope (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS). Such studies have provided a qualitative understanding of the typical pathways in which thorium diffuses and how it is normally redistributed along the cathode surface. Lastly, the erosion rates of both pure and thoriated tungsten cathodes were measured after various run times by use of an analytical scale. These measurements have revealed the ability of thoriated tungsten cathodes to run as long as that of pure tungsten but with significantly less material erosion.

Virtual cathode formations in nested-well configurations

NASA Astrophysics Data System (ADS)

Stephens, K. F.; Ordonez, C. A.; Peterkin, R. E.

1999-12-01

Complete transmission of an electron beam through a cavity is not possible if the current exceeds the space-charge limited current. The formation of a virtual cathode reflects some of the beam electrons and reduces the current transmitted through the cavity. Transients in the injected current have been shown to lower the transmitted current below the value predicted by the electrostatic Child-Langmuir law. The present work considers the propagation of an electron beam through a nested-well configuration. Electrostatic particle-in-cell simulations are used to demonstrate that ions can be trapped in the electric potential depression of an electron beam. Furthermore, the trapped ions can prevent the formation of a virtual cathode for beam currents exceeding the space-charge limit.

Electricity production coupled to ammonium in a microbial fuel cell.

PubMed

He, Zhen; Kan, Jinjun; Wang, Yanbing; Huang, Yuelong; Mansfeld, Florian; Nealson, Kenneth H

2009-05-01

The production of electricity from ammonium was examined using a rotating-cathode microbial fuel cell (MFC). The addition of ammonium chloride, ammonium sulfate, or ammonium phosphate (monobasic) resulted in electricity generation, while adding sodium chloride, nitrate, or nitrite did not cause any increase in current production. The peak current increased with increasing amount of ammonium addition up to 62.3 mM of ammonium chloride, suggesting that ammonium was involved in electricity generation either directly as the anodic fuel or indirectly as substrates for nitrifiers to produce organic compounds for heterotrophs. Adding nitrate or nitrite with ammonium increased current production compared to solely ammonium addition. Using 16S rRNA-linked molecular analyses, we found ammonium-oxidizing bacteria and denitrifying bacteria on both the anode and cathode electrodes, whereas no anammox bacteria were detected. The dominant ammonium-oxidizing bacteria were closely related to Nitrosomonas europaea. The present MFC achieved an ammonium removal efficiency of 49.2 +/- 5.9 or 69.7 +/- 3.6%, depending on hydraulic retention time, but exhibited a very low Coulombic efficiency.

Propagation characteristics of dust-acoustic waves in presence of a floating cylindrical object in the DC discharge plasma

NASA Astrophysics Data System (ADS)

Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

2016-08-01

The experimental observation of the self-excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion-dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.

Cathode Research and the Threshold Cathode Test Facility

DTIC Science & Technology

2002-09-01

SYSTEM (LEFT) AND PULSED POWER TANK (RIGHT ) AS ASSEMBLED AT THE AIR FORCE RESEARCH LABORATORY , DIRECTED ENERGY DIRECTORATE AT KIRTLAND AFB, NM...Final Report APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. AIR FORCE RESEARCH LABORATORY Directed Energy Directorate 3550 Aberdeen Ave SE... Research Laboratory ( AFRL ), Directed Energy Directorate at Kirtland AFB, NM. In addition, simulations were performed that shed new light on the

Electrotaxis of cardiac progenitor cells, cardiac fibroblasts, and induced pluripotent stem cell-derived cardiac progenitor cells requires serum and is directed via PI3'K pathways.

PubMed

Frederich, Bert J; Timofeyev, Valeriy; Thai, Phung N; Haddad, Michael J; Poe, Adam J; Lau, Victor C; Moshref, Maryam; Knowlton, Anne A; Sirish, Padmini; Chiamvimonvat, Nipavan

2017-11-01

The limited regenerative capacity of cardiac tissue has long been an obstacle to treating damaged myocardium. Cell-based therapy offers an enormous potential to the current treatment paradigms. However, the efficacy of regenerative therapies remains limited by inefficient delivery and engraftment. Electrotaxis (electrically guided cell movement) has been clinically used to improve recovery in a number of tissues but has not been investigated for treating myocardial damage. The purpose of this study was to test the electrotactic behaviors of several types of cardiac cells. Cardiac progenitor cells (CPCs), cardiac fibroblasts (CFs), and human induced pluripotent stem cell-derived cardiac progenitor cells (hiPSC-CPCs) were used. CPCs and CFs electrotax toward the anode of a direct current electric field, whereas hiPSC-CPCs electrotax toward the cathode. The voltage-dependent electrotaxis of CPCs and CFs requires the presence of serum in the media. Addition of soluble vascular cell adhesion molecule to serum-free media restores directed migration. We provide evidence that CPC and CF electrotaxis is mediated through phosphatidylinositide 3-kinase signaling. In addition, very late antigen-4, an integrin and growth factor receptor, is required for electrotaxis and localizes to the anodal edge of CPCs in response to direct current electric field. The hiPSC-derived CPCs do not express very late antigen-4, migrate toward the cathode in a voltage-dependent manner, and, similar to CPCs and CFs, require media serum and phosphatidylinositide 3-kinase activity for electrotaxis. The electrotactic behaviors of these therapeutic cardiac cells may be used to improve cell-based therapy for recovering function in damaged myocardium. Published by Elsevier Inc.

PtCu substrates subjected to AC and DC electric fields in a solution of benzene sulfonic acid-phenol as novel batteries and their use in glucose biofuel cells

NASA Astrophysics Data System (ADS)

Ammam, Malika; Fransaer, Jan

2013-11-01

We describe how bi-metal PtCu connected wires, immersed in a solution of benzene sulfonic acid (BSA)-phenol (P) or 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)-phenol (P), then subjected to simultaneous alternating current (AC) and direct current (DC) electric fields generate power. We discovered that PtCu substrate covered by the deposit containing (BSA-PP-Pt-Cu), abbreviated as PtCu(BSA-PP-Pt-Cu) electrode, plays the role of a substantial anode and cathode. The latter was related to the formation of micro-batteries in the deposited film (BSA-PP-Pt-Cu) that are able to take or deliver electrons from the deposited Pt and Cu, respectively. PP-BSA plays probably the role of bridge for proton conduction in the formed micro-batteries. The power density of the fuel cell (FC)-based PtCu(BSA-PP-Pt-Cu) anode and PtCu(BSA-PP-Pt-Cu) cathode in phosphate buffer solution pH 7.4 at room temperature reaches ˜10.8 μW mm-2. Addition of enzymes, glucose oxidase at the anode and laccase at the cathode and, replacement of BSA by ABTS at the cathode in the deposited films increases the power density to 13.3 μW mm-2. This new procedure might be of great relevance for construction of a new generation of FCs operating at mild conditions or boost the power outputs of BFCs and make them suitable for diverse applications.

Microwave decoration of Pt nanoparticles on entangled 3D carbon nanotube architectures as PEM fuel cell cathode.

PubMed

Sherrell, Peter C; Zhang, Weimin; Zhao, Jie; Wallace, Gordon G; Chen, Jun; Minett, Andrew I

2012-07-01

Proton-exchange membrane fuel cells (PEMFCs) are expected to provide a complementary power supply to fossil fuels in the near future. The current reliance of fuel cells on platinum catalysts is undesirable. However, even the best-performing non-noble metal catalysts are not as efficient. To drive commercial viability of fuel cells forward in the short term, increased utilization of Pt catalysts is paramount. We have demonstrated improved power and energy densities in a single PEMFC using a designed cathode with a Pt loading of 0.1 mg cm(-2) on a mesoporous conductive entangled carbon nanotube (CNT)-based architecture. This electrode allows for rapid transfer of both fuel and waste to and from the electrode, respectively. Pt particles are bound tightly, directly to CNT sidewalls by a microwave-reduction technique, which provided increased charge transport at this interface. The Pt entangled CNT cathode, in combination with an E-TEK 0.2 mg cm(-2) anode, has a maximum power and energy density of 940 mW cm(-2) and 2700 mA cm(-2), respectively, and a power and energy density of 4.01 W mg(Pt)(-1) and 6.35 A mg(Pt)(-1) at 0.65 V. These power densities correspond to a specific mass activity of 0.81 g Pt per kW for the combined mass of both anode and cathode electrodes, approaching the current US Department of Energy efficiency target. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Noninvasive transcranial direct current stimulation (tDCS) for the treatment of orofacial pain.

PubMed

Fricova, Jitka; Englerova, Katerina; Rokyta, Richard

2016-10-01

tDCS is a promising method for the treatment of chronic pain. Electrode placement locations must be chosen in accordance with the density and the time course of the current in order to prevent pathological changes in the underlying tissue. In order to reduce current spatial variability, more electrodes of the same polarity are placed in a circle around the second electrode of the opposite polarity. The applied current produced the greatest changes directly beneath the electrodes: the cathode reduces the excitability of cortical neurons, while the anode has the opposite effect. Based on inclusion criteria, 10 patients with chronic orofacial pain, secondary trigeminal neuralgia after oral surgery, were enrolled and underwent both anode and cathode stimulation. Before the first session we measured pain intensity on a numeric pain rating scale and tactile and thermal stimulation were used to assess somatosensory status. tDCS was applied for five consecutive days. At the end of tDCS application, somatosensory status was assessed again. From our results we can conclude that the application of tDCS improves the perception of some types of pain. When we increase our sample size, we would expect confirmation not only on our positive results, but also some additional findings for explaining the pathophysiology of orofacial pain. These pathophysiological findings and explanations are very important for the application of tDCS in the treatment of orofacial pain and also for other types of neuropathic pain.

Physical and technological principles of designing layer-gradient multicomponent surfaces by combining the methods of ion-diffusion saturation and magnetron- and vacuum-arc deposition

NASA Astrophysics Data System (ADS)

Savostikov, V. M.; Potekaev, A. I.; Tabachenko, A. N.

2011-12-01

Using a technological system proposed by the authors, a combined process is developed for formation of stratified-gradient surface layers and multicomponent coatings. It is implemented under the conditions of a combined serial-parallel operation of a hot-cathode gas plasma generator and a duomagnetron with two targets and two electric-arc evaporators. The extended functional potential is ensured by using advanced multi-element and multi-phase cathode targets made of borides, carbides, silicides, and sulfides of metals produced by the SHS-process followed by their immediate compaction. The variations in composition, structure, and physicomechanical properties in the cross-section of the stratified-gradient surface layers and coating is provided by a predetermined alternating replacement of the sputtered cathode targets of the plasma sources, the plasma flow intensity ratios, and variation in the particle energy incident on the substrate, which is determined by the accelerating voltage on the substrate.

Experimental research of different plasma cathodes for generation of high-current electron beams

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

Shafir, G.; Kreif, M.; Gleizer, J. Z.

2015-11-21

The results of experimental studies of different types of cathodes—carbon-epoxy rods, carbon-epoxy capillary, edged graphite, and metal-dielectric—under the application of high-voltage pulses with an amplitude of several hundreds of kV and pulse duration of several nanoseconds are presented. The best diode performance was achieved with the edged graphite and carbon-epoxy-based cathodes characterized by uniform and fast (<1 ns) formation of explosive emission plasma spots and quasi-constant diode impedance. This result was achieved for both annular cathodes in a strong magnetic field and planar cathodes of a similar diameter (∼2 cm) with no external magnetic field. The cathodes based on carbon-epoxy rods andmore » carbon-epoxy capillaries operating with an average current density up to 1 kA/cm{sup 2} showed insignificant erosion along 10{sup 6} pulses of the generator and the generated electron beam current showed excellent reproducibility in terms of the amplitude and waveform.« less

Plasma Emission Characteristics from a High Current Hollow Cathode in an Ion Thruster Discharge Chamber

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

2002-01-01

The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 5A) has been documented in the literature. In order to further elucidate these findings, an investigation of a high current cathode operating in an ion thruster discharge chamber has been undertaken. Using Langmuir probes, a low energy charged particle analyzer and emission spectroscopy, the behavior of the near-cathode plasma and the emitted ion energy distribution was characterized. The presence of energetic ions was confirmed. It was observed that these ions had energies in excess of the discharge voltage and thus cannot be simply explained by ions falling out of plasma through a potential difference of this order. Additionally, evidence provided by Langmuir probes suggests the existence of a double layer essentially separating the hollow cathode plasma column from the main discharge. The radial potential difference associated with this double layer was measured to be of order the ionization potential.

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

Matsubara, Y.; Tahara, H.; Nogawa, S.

A new type of electron source for ion sources, which serves as a cathode has been developed. In this cathode, a high-density microwave plasma is produced under the electron-cyclotron-resonance (ECR) condition, and a high electron current of several amperes can be extracted from it. The structure of this microwave plasma (MP) cathode is very simple and compact. A rod antenna connected to a coaxial line for introducing the microwave power (2.45 GHz) and a rare-earth metal permanent magnet for producing the ECR condition are major components. Since there is no filament in this MP cathode, it has a longer lifetimemore » than the equivalent thermionic filament electron emitter. It offers a great advantage to the operation with reactive as well as inert gases. This MP cathode has been adapted in Kaufman-type ion source and have successfully obtained an argon ion-beam current of 110 mA and an oxygen ion-beam current of 43 mA in 25 mm diameter.« less

Cathodic and anodic biofilms in Single Chamber Microbial Fuel Cells.

PubMed

Cristiani, P; Carvalho, M L; Guerrini, E; Daghio, M; Santoro, C; Li, B

2013-08-01

The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluation on direct interspecies electron transfer in anaerobic sludge digestion of microbial electrolysis cell.

PubMed

Zhao, Zisheng; Zhang, Yaobin; Quan, Xie; Zhao, Huimin

2016-01-01

Increase of methanogenesis in methane-producing microbial electrolysis cells (MECs) is frequently believed as a result of cathodic reduction of CO2. Recent studies indicated that this electromethanogenesis only accounted for a little part of methane production during anaerobic sludge digestion. Instead, direct interspecies electron transfer (DIET) possibly plays an important role in methane production. In this study, anaerobic digestion of sludge were investigated in a single-chamber MEC reactor, a carbon-felt supplemented reactor and a common anaerobic reactor to evaluate the effects of DIET on the sludge digestion. The results showed that adding carbon felt into the reactor increased 12.9% of methane production and 17.2% of sludge reduction. Imposing a voltage on the carbon felt further improved the digestion. Current calculation showed that the cathodic reduction only contributed to 27.5% of increased methane production. Microbial analysis indicated that DIET played an important role in the anaerobic sludge digestion in the MEC. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lymphocyte Electrotaxis in vitro and in vivo

PubMed Central

Lin, Francis; Baldessari, Fabio; Gyenge, Christina Crenguta; Sato, Tohru; Chambers, Robert D.; Santiago, Juan G.; Butcher, Eugene C.

2008-01-01

Electric fields are generated in vivo in a variety of physiologic and pathologic settings, including penetrating injury to epithelial barriers. An applied electric field with strength within the physiologic range can induce directional cell migration (i.e. electrotaxis) of epithelial cells, endothelial cells, fibroblasts, and neutrophils suggesting a potential role in cell positioning during wound healing. In the present study, we investigated the ability of lymphocytes to respond to applied direct current (DC) electric fields. Using a modified transwell assay and a simple microfluidic device, we show that human peripheral blood lymphocytes migrate toward the cathode in physiologically relevant DC electric fields. Additionally, electrical stimulation activates intracellular kinase signaling pathways shared with chemotactic stimuli. Finally, video microscopic tracing of GFP-tagged immunocytes in the skin of mouse ears reveals that motile cutaneous T cells actively migrate toward the cathode of an applied DC electric field. Lymphocyte positioning within tissues can thus be manipulated by externally applied electric fields, and may be influenced by endogenous electrical potential gradients as well. PMID:18684937

Lymphocyte electrotaxis in vitro and in vivo.

PubMed

Lin, Francis; Baldessari, Fabio; Gyenge, Christina Crenguta; Sato, Tohru; Chambers, Robert D; Santiago, Juan G; Butcher, Eugene C

2008-08-15

Electric fields are generated in vivo in a variety of physiologic and pathologic settings, including penetrating injury to epithelial barriers. An applied electric field with strength within the physiologic range can induce directional cell migration (i.e., electrotaxis) of epithelial cells, endothelial cells, fibroblasts, and neutrophils suggesting a potential role in cell positioning during wound healing. In the present study, we investigated the ability of lymphocytes to respond to applied direct current (DC) electric fields. Using a modified Transwell assay and a simple microfluidic device, we show that human PBLs migrate toward the cathode in physiologically relevant DC electric fields. Additionally, electrical stimulation activates intracellular kinase signaling pathways shared with chemotactic stimuli. Finally, video microscopic tracing of GFP-tagged immunocytes in the skin of mouse ears reveals that motile cutaneous T cells actively migrate toward the cathode of an applied DC electric field. Lymphocyte positioning within tissues can thus be manipulated by externally applied electric fields, and may be influenced by endogenous electrical potential gradients as well.

Can Transcranial Direct Current Stimulation Improve Cognitive Functioning in Adults with Schizophrenia?

PubMed

Schretlen, David J; van Steenburgh, Joseph J; Varvaris, Mark; Vannorsdall, Tracy D; Andrejczuk, Megan A; Gordon, Barry

Cognitive impairment is nearly ubiquitous in schizophrenia. First-degree relatives of persons with schizophrenia often show similar but milder deficits. Current methods for the treatment of schizophrenia are often ineffective in cognitive remediation. Since transcranial direct current stimulation (tDCS) can enhance cognitive functioning in healthy adults, it might provide a viable option to enhance cognition in schizophrenia. We sought to explore whether tDCS can be tolerated by persons with schizophrenia and potentially improve their cognitive functioning. We examined the effects of anodal versus cathodal tDCS on working memory and other cognitive tasks in five outpatients with schizophrenia and six first-degree relatives of persons with schizophrenia. Each participant completed tasks thought to be mediated by the prefrontal cortex during two 30-minute sessions of tDCS to the left and right dorsolateral prefrontal cortex (DLPFC). Anodal stimulation over the left DLPFC improved performance relative to cathodal stimulation on measures of working memory and aspects of verbal fluency relevant to word retrieval. The patient group showed differential changes in novel design production without alteration of overall productivity, suggesting that tDCS might be capable of altering self-monitoring and executive control. All participants tolerated tDCS well. None withdrew from the study or experienced any adverse reaction. We conclude that adults with schizophrenia can tolerate tDCS while engaging in cognitive tasks and that tDCS can alter their performance.

Plasma ARC Welding of High-Performance-Ship Materials

DTIC Science & Technology

1979-05-01

19 REFERENCES .................. ............................ 85 iiii -. -’ - -" -. I LIST OF FIGURES Page I - Comparison of PAW and GTAW ...tungsten-arc- welding ( GTAW ) process. Both processes employ an inert-gas-shielded non- consumable tungsten electrode, as shown in Figure 1. In genernl, both...piece acts as the cathode (ground or negative). However, both PAW and GTAW can be and have been, used with direct-current reverse polarity and with

Time-resolved ion energy and charge state distributions in pulsed cathodic arc plasmas of Nb‑Al cathodes in high vacuum

NASA Astrophysics Data System (ADS)

Zöhrer, Siegfried; Anders, André; Franz, Robert

2018-05-01

Cathodic arcs have been utilized in various applications including the deposition of thin films and coatings, ion implantation, and high current switching. Despite substantial progress in recent decades, the physical mechanisms responsible for the observed plasma properties are still a matter of dispute, particularly for multi-element cathodes, which can play an essential role in applications. The analysis of plasma properties is complicated by the generally occurring neutral background of metal atoms, which perturbs initial ion properties. By using a time-resolved method in combination with pulsed arcs and a comprehensive Nb‑Al cathode model system, we investigate the influence of cathode composition on the plasma, while making the influence of neutrals visible for the observed time frame. The results visualize ion detections of 600 μs plasma pulses, extracted 0.27 m from the cathode, resolved in mass-per-charge, energy-per-charge and time. Ion properties are found to be strongly dependent on the cathode material in a way that cannot be deduced by simple linear extrapolation. Subsequently, current hypotheses in cathodic arc physics applying to multi-element cathodes, like the so-called ‘velocity rule’ or the ‘cohesive energy rule’, are tested for early and late stages of the pulse. Apart from their fundamental character, the findings could be useful in optimizing or designing plasma properties for applications, by actively utilizing effects on ion distributions caused by composite cathode materials and charge exchange with neutrals.

Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

NASA Astrophysics Data System (ADS)

Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

2016-09-01

The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

Detrapping of tungsten nanoparticles in a direct-current argon glow discharge

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

Couëdel, L., E-mail: lenaic.couedel@univ-amu.fr; Kumar, K. Kishor; Arnas, C.

2014-12-15

Nanoparticles are grown from the sputtering of a tungsten cathode in a direct current argon glow discharge. Laser light scattering of a vertical laser sheet going through the plasma reveals that the dust particle cloud is compressed and pushed towards the anode during the discharge. Scanning electron microscopy images of substrates exposed to the plasma for given durations show that dust particles are continuously falling down on the anode during the discharge. These observations are explained by the fact that the electrostatic force at the negative glow-anode sheath boundary cannot balance the ion drag, gravity, and thermophoresis forces for particlesmore » of more than a few tens of nanometres in diameter.« less

Study on Properties of CoNi Films with mn Doping Prepared by Magnetic Fields Induced Codeposition Technology

NASA Astrophysics Data System (ADS)

Gang, Liang; Yu, Yundan; Ge, Hongliang; Wei, Guoying; Jiang, Li; Sun, Lixia

Magnetic field parallel to electric field was induced during plating process to prepare CoNiMn alloy films on copper substrate. Electrochemistry mechanism and properties of CoNiMn alloy films were investigated in this paper. Micro magnetohydrodynamic convection phenomenon caused by vertical component of current density and parallel magnetic field due to deformation of current distribution contributed directly to the improvement of cathode current and deposition rate. Cathode current of the CoNiMn plating system increased about 30% with 1T magnetic field induced. It was found that CoNiMn films electrodeposited with magnetic fields basically belonged to a kind of progressive nucleation mode. Higher magnetic intensity intended to obtain CoNiMn films with good crystal structures and highly preferred orientations. With the increase of magnetic intensities, surface morphology of CoNiMn alloy films changed from typically nodular to needle-like structures. Compared with coatings electrodeposited without magnetic field, CoNiMn alloy films prepared with magnetic fields possessed better magnetic properties. Coercivity, remanence and saturation magnetization of samples increased sharply when 1T magnetic field was induced during plating process.

Extended test of a xenon hollow cathode for a space plasma contactor

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1994-01-01

Implementation of a hollow cathode plasma contactor for charge control on the Space Station has required validation of long-life hollow cathodes. A test series of hollow cathodes and hollow cathode plasma contactors was initiated as part of the plasma contactor development program. An on-going wear-test of a hollow cathode has demonstrated cathode operation in excess of 4700 hours with small changes in operating parameters. The discharge experienced 4 shutdowns during the test, all of which were due to test facility failures or expellant replenishment. In all cases, the cathode was reignited at approximately 42 volts and resumed typical operation. This test represents the longest demonstrated stable operation of a high current (greater than 1A) xenon hollow cathode reported to date.

Continuing life test of a xenon hollow cathode for a space plasma contactor

NASA Technical Reports Server (NTRS)

Sarver-Verhey, Timothy R.

1994-01-01

Implementation of a hollow cathode plasma contactor for charge control on the Space Station has required validation of long-life hollow cathodes. A test series of hollow cathodes and hollow cathode plasma contactors was initiated as part of the plasma contactor development program. An on-going wear-test of a hollow cathode has demonstrated cathode operation in excess of 10,000 hours with small changes in operating parameters. The discharge has experienced 10 shutdowns during the test, all of which were due to test facility failures or expellant replenishment. In all cases, the cathode was re-ignited at approximately 42 volts and resumed typical operation. This test represents the longest demonstrated stable operation of a high current (greater than 1 A) xenon hollow cathode reported to date.

A Particle and Energy Balance Model of the Orificed Hollow Cathode

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.

2002-01-01

A particle and energy balance model of orificed hollow cathodes was developed to assist in cathode design. The model presented here is an ensemble of original work by the author and previous work by others. The processes in the orifice region are considered to be one of the primary drivers in determining cathode performance, since the current density was greatest in this volume (up to 1.6 x 10(exp 8) A/m2). The orifice model contains comparatively few free parameters, and its results are used to bound the free parameters for the insert model. Next, the insert region model is presented. The sensitivity of the results to the free parameters is assessed, and variation of the free parameters in the orifice dominates the calculated power consumption and plasma properties. The model predictions are compared to data from a low-current orificed hollow cathode. The predicted power consumption exceeds the experimental results. Estimates of the plasma properties in the insert region overlap Langmuir probe data, and the predicted orifice plasma suggests the presence of one or more double layers. Finally, the model is used to examine the operation of higher current cathodes.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

DOE PAGES

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; ...

2018-03-30

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Direction of R&D and Current Status of Understanding of Advanced Gear Steels

DTIC Science & Technology

1986-02-01

our laboratory. A-Z 9-4 CBS600 was developed by Timken as a carburizing grade bearing steel for service above 150C. The philosophy used in designing...melted (VIM-VAR) steels . The effect of long time aging at 230C on the Charpy energy for CBS600 is currently underway at AMMRC. M50 NIL General Electric, in...contact fatigue life and hot hardness as high as for P50 (the high hot hardness bearing steel widely used in aircraft gas turbine engines in the USA) the

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

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

Follett, R. K.; Shaw, J. G.; Myatt, J. F.

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

NASA Astrophysics Data System (ADS)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; Palastro, J. P.; Short, R. W.; Froula, D. H.

2018-03-01

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ˜0.7 % laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. This allows for higher ablation pressures in future implosion designs by using higher laser intensities.

High negative charge of a dust particle in a hot cathode discharge.

PubMed

Arnas, C; Mikikian, M; Doveil, F

1999-12-01

Dust particle levitation experiments in a plasma produced by a hot filament discharge, operating at low argon pressure, are presented. The basic characteristics of a dust grain trapped in a plate sheath edge in these experimental conditions are reported. Taking into account the sheath potential profiles measured with a differential emissive probe diagnostic, the forces applied to an isolated dust grain can be determined. Two different experimental methods yield approximately the same value for the dust charge. The observed high negative charge is mainly due to the contribution of the primary electrons emitted by the filaments as predicted by a simple model.

Studies on plasma profiles and its effect on dust charging in hydrogen plasma

NASA Astrophysics Data System (ADS)

Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhay, M.

2010-02-01

Plasma profiles and its influence on dust charging are studied in hydrogen plasma. The plasma is produced in a high vacuum device by a hot cathode discharge method and is confined by a cusped magnetic field cage. A cylindrical Espion advanced Langmuir probe having 0.15 mm diameter and 10.0 mm length is used to study the plasma parameters for various discharge conditions. Optimum operational discharge parameters in terms of charging of the dust grains are studied. The charge on the surface of the dust particle is calculated from the capacitance model and the current by the dust grains is measured by the combination of a Faraday cup and an electrometer. Unlike our previous experiments in which dust grains were produced in-situ, here a dust dropper is used to drop the dust particles into the plasma.

AIR QUALITY MODELING OF HAZARDOUS POLLUTANTS: CURRENT STATUS AND FUTURE DIRECTIONS

EPA Science Inventory

The paper presents a review of current air toxics modeling applications and discusses possible advanced approaches. Many applications require the ability to predict hot spots from industrial sources or large roadways that are needed for community health and Environmental Justice...

THE ROLE OF ELECTRICAL SIGNALS IN MURINE CORNEAL WOUND RE-EPITHELIALISATION

PubMed Central

Kucerova, R.; Walczysko, P.; Reid, B.; Ou, J.; Leiper, L. J.; Rajnicek, A. M.; McCaig, C. D.; Zhao, M.; Collinson, J. M.

2011-01-01

Ion flow from intact tissue into epithelial wound sites results in lateral electric currents that may represent a major driver of wound healing cell migration. Use of applied electric fields to promote wound healing is the basis of Medicare-approved electric stimulation therapy. This study investigated the roles for electric fields in wound re-epithelialisation, using the Pax6+/− mouse model of the human ocular surface abnormality aniridic keratopathy (in which wound healing and corneal epithelial cell migration are disrupted). Both wild-type and Pax6+/− corneal epithelial cells showed increased migration speeds in response to applied electric fields in vitro. However, only Pax6+/+ cells demonstrated directional galvanotaxis towards the cathode, with activation of pSrc signalling, polarised to the leading edges of cells. In vivo, the epithelial wound site normally represents a cathode, but 43% of Pax6+/− corneas exhibited reversed endogenous wound-induced currents (the wound was an anode). These corneas healed at the same rate as wild-type. Surprisingly, epithelial migration did not correlate with direction or magnitude of endogenous currents for wild-type or mutant corneas. Furthermore, during healing in vivo, no polarisation of pSrc was observed. We found little evidence that Src-dependent mechanisms of cell migration, observed in response to applied EFs in vitro, normally exist in vivo. It is concluded that endogenous electric fields do not drive long-term directionality of sustained healing migration in this mouse corneal epithelial model. Ion flow from wounds may nevertheless represent an important component of wound signalling initiation. PMID:20945376

Specific features of a single-pulse sliding discharge in neon near the threshold for spark breakdown

NASA Astrophysics Data System (ADS)

Trusov, K. K.

2017-08-01

Experimental data on the spatial structure of a single-pulse sliding discharge in neon at voltages below, equal to, and above the threshold for spark breakdown are discussed. The experiments were carried at gas pressures of 30 and 100 kPa and different polarities of the discharge voltage. Photographs of the plasma structure in two discharge chambers with different dimensions of the discharge zone and different thicknesses of an alumina dielectric plate on the surface of which the discharge develops are inspected. Common features of the prebreakdown discharge and its specific features depending on the voltage polarity and gas pressure are analyzed. It is shown that, at voltages below the threshold for spark breakdown, a low-current glow discharge with cathode and anode spots develops in the electrode gap. Above the breakdown threshold, regardless of the voltage polarity, spark channels directed from the cathode to the anode develop against the background of a low-current discharge.

Influence of laser pulse duration on the electrochemical performance of laser structured LiFePO4 composite electrodes

NASA Astrophysics Data System (ADS)

Mangang, M.; Seifert, H. J.; Pfleging, W.

2016-02-01

Lithium iron phosphate is a promising cathode material for lithium-ion batteries, despite its low electrical conductivity and lithium-ion diffusion kinetic. To overcome the reduced rate performance, three dimensional (3D) architectures were generated in composite cathode layers. By using ultrashort laser radiation with pulse durations in the femtosecond regime the ablation depth per pulse is three times higher compared to nanosecond laser pulses. Due to the 3D structuring, the surface area of the active material which is in direct contact with liquid electrolyte, i.e. the active surface, is increased. As a result the capacity retention and the cycle stability were significantly improved, especially for high charging/discharging currents. Furthermore, a 3D structure leads to higher currents during cyclic voltammetry. Thus, the lithium-ion diffusion kinetic in the cell was improved. In addition, using ultrashort laser pulses results in a high aspect ratio and further improvement of the cell kinetic was achieved.

Efficiency of lithium pacemaker batteries as a function of discharge rate and iodine:P2VP cathode composition

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

Helgeson, W.D.; Fester, K.E.

1980-01-01

Electrochemical discharge data for Li/I/sub 2/-P2VP pacemaker batteries at various discharge currents show the efficiency of the battery to be a function of discharge current. Depending on the iodine:P2VP cathode composition, the optimum current drain occurs between discharge currents of 100 to 200 /mu/a. As current drain is reduced to pacemaker application drains, 15-25 /mu/a, the efficiency of the Li/I/sub 2/-P2VP battery decreases. The loss in efficiency at pacemaker rates is attributed primarily to self-discharge. The efficiency of Li/I/sub 2/-P2VP batteries is improved by increasing the percent of iodine in the cathode. I/sub 2/:P2VP weight ratios of 10:1, 15:1 andmore » 20:1 have been discharged at various currents and the data indicate that there is significant improvement in efficiency at pacemaker rate in going from 10:1 to 20:1 cathode weight ratio. 2 refs.« less

Direct Electrolysis of Molten Lunar Regolith for the Production of Oxygen and Metals on the Moon

NASA Technical Reports Server (NTRS)

Sirk, Aislinn H. C.; Sadoway, Donald R.; Sibille, Laurent

2010-01-01

When considering the construction of a lunar base, the high cost ($ 100,000 a kilogram) of transporting materials to the surface of the moon is a significant barrier. Therefore in-situ resource utilization will be a key component of any lunar mission. Oxygen gas is a key resource, abundant on earth and absent on the moon. If oxygen could be produced on the moon, this provides a dual benefit. Not only does it no longer need to be transported to the surface for breathing purposes; it can also be used as a fuel oxidizer to support transportation of crew and other materials more cheaply between the surface of the moon, and lower earth orbit (approximately $20,000/kg). To this end a stable, robust (lightly manned) system is required to produce oxygen from lunar resources. Herein, we investigate the feasibility of producing oxygen, which makes up almost half of the weight of the moon by direct electrolysis of the molten lunar regolith thus achieving the generation of usable oxygen gas while producing primarily iron and silicon at the cathode from the tightly bound oxides. The silicate mixture (with compositions and mechanical properties corresponding to that of lunar regolith) is melted at temperatures near 1600 C. With an inert anode and suitable cathode, direct electrolysis (no supporting electrolyte) of the molten silicate is carried out, resulting in production of molten metallic products at the cathode and oxygen gas at the anode. The effect of anode material, sweep rate, and electrolyte composition on the electrochemical behavior was investigated and implications for scale-up are considered. The activity and stability of the candidate anode materials as well as the effect of the electrolyte composition were determined. Additionally, ex-situ capture and analysis of the anode gas to calculate the current efficiency under different voltages, currents and melt chemistries was carried out.

Free-standing and flexible organic cathode based on aromatic carbonyl compound/carbon nanotube composite for lithium and sodium organic batteries.

PubMed

Yuan, Chenpei; Wu, Qiong; Shao, Qi; Li, Qiang; Gao, Bo; Duan, Qian; Wang, Heng-Guo

2018-05-01

Free-standing and flexible organic cathode based on aromatic carbonyl compound/carbon nanotubes (CNTs) has been successfully synthesized by a simple vacuum filtration strategy. The obtained flexible and free-standing film could be directly used as the binder-, additive- and current collector-free cathode for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Benefitting from the synergistic effect provided by the aromatic carbonyl compound and CNTs, the flexible organic cathode shows excellent lithium and sodium storage properties, including high reversible capacity (∼150 mAh g -1 at 50 mA g -1 for LIBs and 57.8 mAh g -1 at 25 mA g -1 for SIBs), excellent cycling stability (over 500 cycles for LIBs and 300 cycles for SIBs) and good rate capability (48 mAh g -1 even at 2000 mA g -1 for LIBs and 48 mAh g -1 even at 1000 mA g -1 for SIBs). In view of the simple preparation process and excellent performance, the proposed strategy might open new avenues for the design of high-performance flexible organic electrode for the application in energy storage and conversion. Copyright © 2018 Elsevier Inc. All rights reserved.

Verifying the Rechargeability of Li-CO2 Batteries on Working Cathodes of Ni Nanoparticles Highly Dispersed on N-Doped Graphene.

PubMed

Zhang, Zhang; Wang, Xin-Gai; Zhang, Xu; Xie, Zhaojun; Chen, Ya-Nan; Ma, Lipo; Peng, Zhangquan; Zhou, Zhen

2018-02-01

Li-CO 2 batteries could skillfully combine the reduction of "greenhouse effect" with energy storage systems. However, Li-CO 2 batteries still suffer from unsatisfactory electrochemical performances and their rechargeability is challenged. Here, it is reported that a composite of Ni nanoparticles highly dispersed on N-doped graphene (Ni-NG) with 3D porous structure, exhibits a superior discharge capacity of 17 625 mA h g -1 , as the air cathode for Li-CO 2 batteries. The batteries with these highly efficient cathodes could sustain 100 cycles at a cutoff capacity of 1000 mA h g -1 with low overpotentials at the current density of 100 mA g -1 . Particularly, the Ni-NG cathodes allow to observe the appearance/disappearance of agglomerated Li 2 CO 3 particles and carbon thin films directly upon discharge/charge processes. In addition, the recycle of CO 2 is detected through in situ differential electrochemical mass spectrometry. This is a critical step to verify the electrochemical rechargeability of Li-CO 2 batteries. Also, first-principles computations further prove that Ni nanoparticles are active sites for the reaction of Li and CO 2 , which could guide to design more advantageous catalysts for rechargeable Li-CO 2 batteries.

Whether Modulating the Activity of the Temporalparietal Junction Alters Distribution Decisions within Different Contexts: Evidence from a tDCS Study

PubMed Central

Luo, Jun; Chen, Shu; Huang, Daqiang; Ye, Hang; Zheng, Haoli

2017-01-01

Distributive justice concerns how individuals and societies distribute income in a just or equal manner. We aimed to test the roles of social preference in behavioral distributive justice. We thus provide evidence of a causal link between the neural and behavioral results through the application of bilateral transcranial direct current stimulation (tDCS) over the temporoparietal junction (TPJ) of our participants. The participants were found to make fairer distributions within the known position after receiving right anodal/left cathodal tDCS and receiving right cathodal/left anodal tDCS over the TPJ than the participants who received the sham stimulation. Simultaneously, we elicited the participants’ advantage inequity aversion and found that the participants who received right anodal/left cathodal tDCS and who received right cathodal/left anodal tDCS over the TPJ were more averse to advantage inequity. Additionally, the participants’ distributive proportions to the lowest income stratum within the known position were strongly related to their social preference of advantage inequity aversion. Therefore, the present study demonstrated that the modulation of the excitability of the TPJ using tDCS altered the distributive decisions of the participants within the known position, and this effect might be attributable to a change in the individuals’ social preferences. PMID:28270785

Observation of Dust Stream Formation Produced by Low Current, High Voltage Cathode Spots

NASA Technical Reports Server (NTRS)

Foster, John E.

2004-01-01

Macro-particle acceleration driven by low current, high voltage cathode spots has been investigated. The phenomenon was observed to occur when nanometer and micrometer-sized particles in the presence of a discharge plasma were exposed to a high voltage pulse. The negative voltage pulse initiates the formation of multiple, high voltage, low current cathode spots which provides the mechanism of actual acceleration of the charged dust particles. Dust streams generated by this process were detected using laser scattering techniques. The particle impact craters observed at the surface of downstream witness badges were documented using SEM and light microscopy.

Bio-electrochemical synthesis of commodity chemicals by autotrophic acetogens utilizing CO2 for environmental remediation.

PubMed

Jabeen, Gugan; Farooq, Robina

2016-09-01

Bio-electrochemical synthesis (BES) is a technique in which electro-autotrophic bacteria such as Clostridium ljungdahlii utilize electric currents as an electron source from the cathode to reduce CO2 to extracellular, multicarbon, exquisite products through autotrophic conversion. The BES of volatile fatty acids and alcohols directly from CO2 is a sustainable alternative for non-renewable, petroleum-based polymer production. This conversion of CO2 implies reduction of greenhouse gas emissions. The synthesis of heptanoic acid, heptanol, hexanoic acid and hexanol, for the first time, by Clostridium ljungdahlii was a remarkable achievement of BES. In our study, these microorganisms were cultivated on the cathode of a bio-electrochemical cell at -400 mV by a DC power supply at 37 degree Centrigrade, pH 6.8, and was studied for both batch and continuous systems. Pre-enrichment of bio-cathode enhanced the electroactivity of cells and resulted in maximizing extracellular products in less time. The main aim of the research was to investigate the impact of low-cost substrate CO2, and the longer cathode recovery range was due to bacterial reduction of CO2 to multicarbon chemical commodities with electrons driven from the cathode. Reactor design was simplified for cost-effectiveness and to enhance energy efficiencies. The Columbic recovery of ethanoic acid, ethanol, ethyl butyrate, hexanoic acid, heptanoic acid and hexanol being in excess of 80 percent proved that BES was a remarkable technology.

Self-Passivating Lithium/Solid Electrolyte/Iodine Cells

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar; Whitcare, Jay; Narayanan, Sekharipuram; West, William

2006-01-01

Robust lithium/solid electrolyte/iodine electrochemical cells that offer significant advantages over commercial lithium/ iodine cells have been developed. At room temperature, these cells can be discharged at current densities 10 to 30 times those of commercial lithium/iodine cells. Moreover, from room temperature up to 80 C, the maximum discharge-current densities of these cells exceed those of all other solid-electrolyte-based cells. A cell of this type includes a metallic lithium anode in contact with a commercial flexible solid electrolyte film that, in turn, is in contact with an iodine/ graphite cathode. The solid electrolyte (the chemical composition of which has not been reported) offers the high ionic conductivity needed for high cell performance. However, the solid electrolyte exhibits an undesirable chemical reactivity to lithium that, if not mitigated, would render the solid electrolyte unsuitable for use in a lithium cell. In this cell, such mitigation is affected by the formation of a thin passivating layer of lithium iodide at the anode/electrolyte interface. Test cells of this type were fabricated from iodine/graphite cathode pellets, free-standing solid-electrolyte films, and lithium-foil anodes. The cathode mixtures were made by grinding together blends of nominally 10 weight percent graphite and 90 weight percent iodine. The cathode mixtures were then pressed into pellets at 36 kpsi (248 MPa) and inserted into coin-shaped stainless-steel cell cases that were coated with graphite paste to minimize corrosion. The solid-electrolyte film material was stamped to form circular pieces to fit in the coin cell cases, inserted in the cases, and pressed against the cathode pellets with polyethylene gaskets. Lithium-foil anodes were placed directly onto the electrolyte films. The layers described thus far were pressed and held together by stainless- steel shims, wave springs, and coin cell caps. The assembled cells were then crimped to form hermetic seals. It was found that the solid electrolyte films became discolored within seconds after they were placed in contact with the cathodes - a result of facile diffusion of iodine through the solid electrolyte material (see figure).

Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources

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

Odorici, F., E-mail: fabrizio.odorici@bo.infn.it; Malferrari, L.; Montanari, A.

Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to “screen” the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used,more » as explained by plasma diffusion models.« less

Long lifetime hollow cathodes for 30-cm mercury ion thrusters

NASA Technical Reports Server (NTRS)

Mirtich, M. J.; Kerslake, W. R.

1976-01-01

An experimental investigation of hollow cathodes for 30-cm Hg bombardment thrusters was carried out. Both main and neutralizer cathode configurations were tested with both rolled foil inserts coated with low work function material and impregnated porous tungsten inserts. Temperature measurements of an impregnated insert at various positions in the cathode were made. These, along with the cathode thermal profile are presented. A theory for rolled foil and impregnated insert operation and lifetime in hollow cathodes is developed. Several endurance tests, as long as 18000 hours at emission currents of up to 12 amps were attained with no degradation in performance.

Cathodes for molten-salt batteries

NASA Technical Reports Server (NTRS)

Argade, Shyam D.

1993-01-01

Viewgraphs of the discussion on cathodes for molten-salt batteries are presented. For the cathode reactions in molten-salt cells, chlorine-based and sulfur-based cathodes reactants have relatively high exchange current densities. Sulfur-based cathodes, metal sulfides, and disulfides have been extensively investigated. Primary thermal batteries of the Li-alloy/FeS2 variety have been available for a number of years. Chlorine based rechargable cathodes were investigated for the pulse power application. A brief introduction is followed by the experimental aspects of research, and the results obtained. Performance projections to the battery system level are discussed and the presentation is summarized with conclusions.

Surface Alloying of SUS 321 Chromium-Nickel Steel by an Electron-Plasma Process

NASA Astrophysics Data System (ADS)

Ivanov, Yu. F.; Teresov, A. D.; Petrikova, E. A.; Krysina, O. V.; Ivanova, O. V.; Shugurov, V. V.; Moskvin, P. V.

2017-07-01

The mechanisms of forming nanostructured, nanophase layers are revealed and analyzed in austenitic steel subjected to surface alloying using an electron-plasma process. Nanostructured, nanophase layers up to 30 μm in thickness were formed by melting of the film/substrate system with an electron beam generated by a SOLO facility (Institute of High Current Electronics, SB RAS), Tomsk), which ensured crystallization and subsequent quenching at the cooling rates within the range 105-108 K/s. The surface was modified with structural stainless steel specimens (SUS 321 steel). The film/substrate system (film thickness 0.5 μm) was formed by a plasma-assisted vacuum-arc process by evaporating a cathode made from a sintered pseudoalloy of the following composition: Zr - 6 at.% Ti - 6 at.% Cu. The film deposition was performed in a QUINTA facility equipped with a PINK hot-cathode plasma source and DI-100 arc evaporators with accelerated cooling of the process cathode, which allowed reducing the size and fraction of the droplet phase in the deposited film. It is found that melting of the film/substrate system (Zr-Ti-Cu)/(SUS 321 steel) using a high-intensity pulsed electron beam followed by the high-rate crystallization is accompanied by the formation of α-iron cellular crystallization structure and precipitation of Cr2Zr, Cr3C2 and TiC particles on the cell boundaries, which as a whole allowed increasing microhardness by a factor of 1.3, Young's modulus - by a factor of 1.2, wear resistance - by a factor of 2.7, while achieving a three-fold reduction in the friction coefficient.

A novel carbon black graphite hybrid air-cathode for efficient hydrogen peroxide production in bioelectrochemical systems

NASA Astrophysics Data System (ADS)

Li, Nan; An, Jingkun; Zhou, Lean; Li, Tian; Li, Junhui; Feng, Cuijuan; Wang, Xin

2016-02-01

Carbon black and graphite hybrid air-cathode is proved to be effective for H2O2 production in bioelectrochemical systems. The optimal mass ratio of carbon black to graphite is 1:5 with the highest H2O2 yield of 11.9 mg L-1 h-1 cm-2 (12.3 mA cm-2). Continuous flow is found to improve the current efficiency due to the avoidance of H2O2 accumulation. In the biological system, the highest H2O2 yield reaches 3.29 mg L-1h-1 (0.079 kg m-3day-1) with a current efficiency of 72%, which is higher than the abiotic system at the same current density. H2O2 produced in this system is mainly from the oxygen diffused through this air-cathode (>66%), especially when a more negative cathode potential is applied (94% at -1.0 V). This hybrid air-cathode has advantages of high H2O2 yield, high current density and no need of aeration, which make the synthesis of H2O2 more efficient and economical.

Effects of the second X-point on hot VDE in HL-2M

NASA Astrophysics Data System (ADS)

Xue, L.; Duan, X. R.; Zheng, G. Y.; Liu, Y. Q.; Dokuka, V. N.; Lukash, V. E.; Khayrutdinov, R. R.

2017-05-01

Study of the hot-plasma vertical displacement event (VDE) in advanced divertor configurations is of significant importance for ITER and for future fusion reactors. The newly designed, medium-sized copper-conductor machine HL-2M has the capability of generating the second X-point for various advanced divertor configurations. In this paper, effects of the second X-point on the hot VDE in HL-2M are numerically investigated by utilizing the non-linear time-dependent DINA code. The simulation results show that the existence of the second X-point at certain special locations appears to have a better stability in the vertical direction, compared to the standard configuration with the same main plasma parameters. Meanwhile, the peak halo current during the current quench tends to increase as the second X-point changes in the horizontal direction. The same quantity decreases as the second X-point changes in the vertical direction away from the dominant X-point. From the view point of minimizing the halo current, the tripod is better than the standard configuration, followed by the snowflake-plus and the exact snowflake (SF) configuration. The SF-minus is the worst scenario. On the other hand, the tripod configuration, as well as the SF minus configurations, results in relatively higher peak electromagnetic force acting on the vacuum vessel, when compared to other aforementioned configurations.

The Effect of Cerebellar Transcranial Direct Current Stimulation on A Throwing Task Depends on Individual Level of Task Performance.

PubMed

Mizuguchi, Nobuaki; Katayama, Takashi; Kanosue, Kazuyuki

2018-02-10

The effect of cerebellar transcranial direct current stimulation (tDCS) on motor performance remains controversial. Some studies suggest that the effect of tDCS depends upon task-difficulty and individual level of task performance. Here, we investigated whether the effect of cerebellar tDCS on the motor performance depends upon the individual's level of performance. Twenty-four naïve participants practiced dart throwing while receiving a 2-mA cerebellar tDCS for 20 min under three stimulus conditions (anodal-, cathodal-, and sham-tDCS) on separate days with a double-blind, counter-balanced cross-over design. Task performance was assessed by measuring the distance between the center of the bull's eye and the dart's position. Although task performance tended to improve throughout the practice under all stimulus conditions, improvement within a given day was not significant as compared to the first no-stimulus block. In addition, improvement did not differ among stimulation conditions. However, the magnitude of improvement was associated with an individual's level of task performance only under cathodal tDCS condition (p < 0.05). This resulted in a significant performance improvement only for the sub-group of participants with lower performance levels as compared to that with sham-tDCS (p < 0.05). These findings suggest that the facilitation effect of cerebellar cathodal tDCS on motor skill learning of complex whole-body movements depends on the level of an individual's task performance. Thus, cerebellar tDCS would facilitate learning of a complex motor skill task only in a subset of individuals. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Modulation of risk-taking in marijuana users by transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC).

PubMed

Boggio, Paulo S; Zaghi, Soroush; Villani, Ana Beatriz; Fecteau, Shirley; Pascual-Leone, Alvaro; Fregni, Felipe

2010-12-01

Cognitive deficits that are reported in heavy marijuana users (attention, memory, affect perception, decision-making) appear to be completely reversible after a prolonged abstinence period of about 28 days. However, it remains unclear whether the reversibility of these cognitive deficits indicates that (1) chronic marijuana use is not associated with long-lasting changes in cortical networks or (2) that such changes occur but the brain adapts to and compensates for the drug-induced changes. Therefore, we examined whether chronic marijuana smokers would demonstrate a differential pattern of response in comparison to healthy volunteers on a decision-making paradigm (Risk Task) while undergoing sham or active transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC). Twenty-five chronic marijuana users who were abstinent for at least 24h were randomly assigned to receive left anodal/right cathodal tDCS of DLPFC (n=8), right anodal/left cathodal tDCS of DLPFC (n=9), or sham stimulation (n=8); results on Risk Task during sham/active tDCS were compared to healthy volunteers from a previously published dataset. Chronic marijuana users demonstrated more conservative (i.e. less risky) decision-making during sham stimulation. While right anodal stimulation of the DLPFC enhanced conservative decision-making in healthy volunteers, both right anodal and left anodal DLPFC stimulation increased the propensity for risk-taking in marijuana users. These findings reveal alterations in the decision-making neural networks among chronic marijuana users. Finally, we also assessed the effects of tDCS on marijuana craving and observed that right anodal/left cathodal tDCS of DLPFC is significantly associated with a diminished craving for marijuana. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

The effect of left frontal transcranial direct-current stimulation on propranolol-induced fear memory acquisition and consolidation deficits.

PubMed

Nasehi, Mohammad; Khani-Abyaneh, Mozhgan; Ebrahimi-Ghiri, Mohaddeseh; Zarrindast, Mohammad-Reza

2017-07-28

Accumulating evidence supports the efficacy of transcranial direct current stimulation (tDCS) in modulating numerous cognitive functions. Despite the fact that tDCS has been used for the enhancement of memory and cognition, very few animal studies have addressed its impact on the modulation of fear memory. This study was designed to determine whether pre/post-training frontal tDCS application would alter fear memory acquisition and/or consolidation deficits induced by propranolol in NMRI mice. Results indicated that administration of β1-adrenoceptor blocker propranolol (0.1mg/kg) impaired fear memory retrieval. Pre/post-training application of anodal tDCS when propranolol was administered prior to training reversed contextual memory retrieval whereas only the anodal application prior to training could induce the same result in the auditory test. Meanwhile, anodal stimulation had no effect on fear memories by itself. Moreover, regardless of when cathode was applied and propranolol administered, their combination restored contextual memory retrieval, while only cathodal stimulation prior to training facilitated the contextual memory retrieval. Also, auditory memory retrieval was restored when cathodal stimulation and propranolol occurred prior to training but it was abolished when stimulation occurred after training and propranolol was administered prior to training. Collectively, our findings show that tDCS applied on the left frontal cortex of mice affects fear memory performance. This alteration seems to be task-dependent and varies depending on the nature and timing of the stimulation. In certain conditions, tDCS reverses the effect of propranolol. These results provide initial evidence to support the timely use of tDCS for the modulation of fear-related memories. Copyright © 2017 Elsevier B.V. All rights reserved.

The effects of combined repetitive transcranial magnetic stimulation and transcranial direct current stimulation on motor function in patients with stroke.

PubMed

Kwon, Tae Gun; Park, Eunhee; Kang, Chung; Chang, Won Hyuk; Kim, Yun-Hee

2016-11-22

Both transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), when provided to stroke patients in combination with motor training, enhance therapeutic efficacy and motor function. However, the majority of previous studies have only examined a single treatment modality. The authors investigated the modulating influence of combination dual-mode brain stimulation upon bihemispheric stimulation with motor training in stroke patients. Twenty stroke patients with hemiparesis underwent five randomly arranged sessions of diverse combinations of rTMS and tDCS. We applied cathodal or anodal tDCS over the contralesional primary motor cortex (cM1) and 10 Hz rTMS over the ipsilesional primary motor cortex (iM1) in a simultaneous or preconditioning method including sham stimulation. Immediately after dual-mode stimulation, sequential hand motor training was performed for 5 minutes. The total pulses of rTMS and the duration of tDCS and motor training were the same for all sessions. Cortical excitability and sequential motor performance were evaluated before and after each session. Motor function and corticomotor excitability following simultaneous stimulation via cathodal tDCS over the cM1 combined with 10 Hz rTMS over the iM1 were significantly increased after the intervention, with significantly greater motor improvement than seen with other treatment conditions (P < 0.05). For the combination of bihemispheric rTMS and tDCS, simultaneous stimulation of cathodal tDCS and 10 Hz rTMS results in better motor performance in stroke patients than other combination methods. This result seemed to be related to effective modulation of interhemispheric imbalance of cortical excitability by dual-mode stimulation.

Repetitive Transcranial Direct Current Stimulation Induced Excitability Changes of Primary Visual Cortex and Visual Learning Effects-A Pilot Study.

PubMed

Sczesny-Kaiser, Matthias; Beckhaus, Katharina; Dinse, Hubert R; Schwenkreis, Peter; Tegenthoff, Martin; Höffken, Oliver

2016-01-01

Studies on noninvasive motor cortex stimulation and motor learning demonstrated cortical excitability as a marker for a learning effect. Transcranial direct current stimulation (tDCS) is a non-invasive tool to modulate cortical excitability. It is as yet unknown how tDCS-induced excitability changes and perceptual learning in visual cortex correlate. Our study aimed to examine the influence of tDCS on visual perceptual learning in healthy humans. Additionally, we measured excitability in primary visual cortex (V1). We hypothesized that anodal tDCS would improve and cathodal tDCS would have minor or no effects on visual learning. Anodal, cathodal or sham tDCS were applied over V1 in a randomized, double-blinded design over four consecutive days (n = 30). During 20 min of tDCS, subjects had to learn a visual orientation-discrimination task (ODT). Excitability parameters were measured by analyzing paired-stimulation behavior of visual-evoked potentials (ps-VEP) and by measuring phosphene thresholds (PTs) before and after the stimulation period of 4 days. Compared with sham-tDCS, anodal tDCS led to an improvement of visual discrimination learning (p < 0.003). We found reduced PTs and increased ps-VEP ratios indicating increased cortical excitability after anodal tDCS (PT: p = 0.002, ps-VEP: p = 0.003). Correlation analysis within the anodal tDCS group revealed no significant correlation between PTs and learning effect. For cathodal tDCS, no significant effects on learning or on excitability could be seen. Our results showed that anodal tDCS over V1 resulted in improved visual perceptual learning and increased cortical excitability. tDCS is a promising tool to alter V1 excitability and, hence, perceptual visual learning.

Transcranial direct current stimulation improves isometric time to exhaustion of the knee extensors.

PubMed

Angius, L; Pageaux, B; Hopker, J; Marcora, S M; Mauger, A R

2016-12-17

Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electrode above the shoulder (SHOULDER). tDCS was delivered for 10min at 2.0mA, after which participants performed an isometric time to exhaustion (TTE) test of the right knee extensors. Peripheral and central neuromuscular parameters were assessed at baseline, after tDCS application and after TTE. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle exercise-induced muscle pain (PAIN) were monitored during the TTE. TTE was longer and RPE lower in the SHOULDER condition (P<0.05). Central and peripheral parameters, and HR and PAIN did not present any differences between conditions after tDCS stimulation (P>0.05). In all conditions maximal voluntary contraction (MVC) significantly decreased after the TTE (P<0.05) while motor-evoked potential area (MEP) increased after TTE (P<0.05). These findings demonstrate that SHOULDER montage is more effective than HEAD montage to improve endurance performance, likely through avoiding the negative effects of the cathode on excitability. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Effects of direct current electric-field using ITO plate on breast cancer cell migration.

PubMed

Kim, Min Sung; Lee, Mi Hee; Kwon, Byeong-Ju; Seo, Hyok Jin; Koo, Min-Ah; You, Kyung Eun; Kim, Dohyun; Park, Jong-Chul

2014-01-01

Cell migration is an essential activity of the cells in various biological phenomena. The evidence that electrotaxis plays important roles in many physiological phenomena is accumulating. In electrotaxis, cells move with a directional tendency toward the anode or cathode under direct-current electric fields. Indium tin oxide, commonly referred to as ITO has high luminous transmittance, high infrared reflectance, good electrical conductivity, excellent substrate adherence, hardness and chemical inertness and hence, have been widely and intensively studied for many years. Because of these properties of ITO films, the electrotaxis using ITO plate was evaluated. Under the 0 V/cm condition, MDA-MB-231 migrated randomly in all directions. When 1 V/cm of dc EF was applied, cells moved toward anode. The y forward migration index was -0.046 ± 0.357 under the 0 V/cm and was 0.273 ± 0.231 under direct-current electric field of 1 V/cm. However, the migration speed of breast cancer cell was not affected by direct-current electric field using ITO plate. In this study, we designed a new electrotaxis system using an ITO coated glass and observed the migration of MDA-MB-231 on direct current electric-field of the ITO glass.

Axial distribution of plasma fluctuations, plasma parameters, deposition rate and grain size during copper deposition

NASA Astrophysics Data System (ADS)

Gopikishan, S.; Banerjee, I.; Pathak, Anand; Mahapatra, S. K.

2017-08-01

Floating potential fluctuations, plasma parameters and deposition rate have been investigated as a function of axial distance during deposition of copper in direct current (DC) magnetron sputtering system. Fluctuations were analyzed using phase space, power spectra and amplitude bifurcation plots. It has been observed that the fluctuations are modified from chaotic to ordered state with increase in the axial distance from cathode. Plasma parameters such as electron density (ne), electron temperature (Te) and deposition rate (Dr) were measured and correlated with plasma fluctuations. It was found that more the deposition rate, greater the grain size, higher the electron density, higher the electron temperature and more chaotic the oscillations near the cathode. This observation could be helpful to the thin film technology industry to optimize the required film.

Switchable Schottky diode characteristics induced by electroforming process in Mn-doped ZnO thin films

NASA Astrophysics Data System (ADS)

Nam, Yoonseung; Hwang, Inrok; Oh, Sungtaek; Lee, Sangik; Lee, Keundong; Hong, Sahwan; Kim, Jinsoo; Choi, Taekjib; Ho Park, Bae

2013-04-01

We investigated the asymmetric current-voltage (I-V) characteristics and accompanying unipolar resistive switching of pure ZnO and Mn(1%)-doped ZnO (Mn:ZnO) films sandwiched between Pt electrodes. After electroforming, a high resistance state of the Mn:ZnO capacitor revealed switchable diode characteristics whose forward direction was determined by the polarity of the electroforming voltage. Linear fitting of the I-V curves highlighted that the rectifying behavior was influenced by a Schottky barrier at the Pt/Mn:ZnO interface. Our results suggest that formation of conducting filaments from the cathode during the electroforming process resulted in a collapse of the Schottky barrier (near the cathode), and rectifying behaviors dominated by a remnant Schottky barrier near the anode.

Advances in electrometer vacuum tube design

NASA Technical Reports Server (NTRS)

1970-01-01

Single-ended, miniature-cathode tube with a relatively low grid current level is constructed. Adequate cathode temperature at relatively low heater power drain is provided by designing the supporting spacers to provide a square cathode hole. Method of assembling the mount and bonding the elements is discussed.

Energetic ion production in high current hollow cathodes

NASA Astrophysics Data System (ADS)

Foster, John; Kovach, Yao; Arthur, Neil; Viges, Eric; Davis, Chris

2015-09-01

High power Hall and gridded ion thrusters are being considered as a propulsion option supporting human operations (cargo or tug) to Mars. These engines utilize hollow cathodes for plasma production and beam neutralization. It has now been well documented that these cathodes produce energetic ions when operated at high current densities. Such ions are observed with peak energies approaching 100 eV. Because these ions can drive erosion of the cathode assembly, they represent a credible failure mode. An understanding of energetic ion production and approaches to mitigation is therefore desired. Presented here are data documenting the presence of energetic ions for both a barium oxide and a lanthanum hexaboride cathode as measured using a retarding potential analyzer. Also presented are energetic ion mitigation approaches, which are designed to eliminate the ion energy transfer mechanism. NASA SBIR Contract NNX15CP62P.

The effects of hydrogen embrittlement by cathodic protection on the CTOD of buried natural gas pipeline

NASA Astrophysics Data System (ADS)

Kim, Cheol-man; Kim, Woo-sik; Kho, Young-tai

2002-04-01

For the corrosion protection of natural gas transmission pipelines, two methods are used, cathodic protection and a coating technique. In the case of cathodic protection, defects are embrittled by hydrogen occurring at crack tips or surfaces of materials. It is, however, very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed CTOD testing under various test conditions, such as potential and current density. The CTOD of the base steel and weld metal showed a strong dependence on the test conditions. The CTOD decreased with increasing cathodic potential and current density. The morphology of the fracture surface showed quasi-cleavage. Cathodic overprotection results in hydrogen embrittlement at the crack tip.

On-site chemical pre-lithiation of S cathode at room temperature on a 3D nano-structured current collector

NASA Astrophysics Data System (ADS)

Wu, Yunwen; Momma, Toshiyuki; Ahn, Seongki; Yokoshima, Tokihiko; Nara, Hiroki; Osaka, Tetsuya

2017-10-01

This work reports a new chemical pre-lithiation method to fabricate lithium sulfide (Li2S) cathode. This pre-lithiation process is taken place simply by dropping the organolithium reagent lithium naphthalenide (Li+Naph-) on the prepared sulfur cathode. It is the first time realizing the room temperature chemical pre-lithaition reaction attributed by the 3D nanostructured carbon nanotube (CNT) current collector. It is confirmed that the Li2S cathode fabricated at room temperature showing higher capacity and lower hysteresis than the Li2S cathode fabricated at high temperature pre-lithiation. The pre-lithiated Li2S cathode at room temperature shows stable cycling performance with a 600 mAh g-1 capacity after 100 cycles at 0.1 C-rate and high capacity of 500 mAh g-1 at 2 C-rate. This simple on-site pre-lithiation method at room temperature is demonstrated to be applicable for the in-situ pre-lithiation in a Li metal free battery.

Plasmatic ion source

NASA Astrophysics Data System (ADS)

Semenov, A. P.

1986-02-01

A plasmatic ion source was built in which the hollow cathode above the two discharge chamber cathodes is readily replaced upon depletion after 250 to 300 h. The emission outlet hole is restored to original size by replacement of the cathode insert, while gas is continuously admitted by means of a spring mechanism. The source operates in the Penning discharge mode, with argon as the working gas. The hollow cathode is 36 mm long and has an inside diameter of 4 mm. The other two cathodes serve as pole shoes of a toroidal ferrite magnet which produces a longitudinal magnet field of 0.1 T induction in the discharge chamber. All three cathodes are made of magnetic steel and are insulated from cylindrical copper anode by teflon spacers. Heat is dissipated by oil, which carries it away to a water cooled housing compartment. The source generates an ion emission current of 20 mA with a discharge current of 200 mA at a pull voltage of 20kV.

Photoemission experiments of a large area scandate dispenser cathode

NASA Astrophysics Data System (ADS)

Zhang, Huang; Liu, Xing-guang; Chen, Yi; Chen, De-biao; Jiang, Xiao-guo; Yang, An-min; Xia, Lian-sheng; Zhang, Kai-zhi; Shi, Jin-shui; Zhang, Lin-wen

2010-09-01

A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 °C (below or near the thermionic emission threshold) while the vacuum was better than 4×10 -7 Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4×10 -4. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

REGULATOR FOR CALUTRON ION SOURCE

DOEpatents

Miller, B.F.

1958-09-01

Improvements are described in electric discharge devices and circuits for a calutron and, more specifically, presents an arc discharge regulator circuit for the ion source of the calatron. In general, the source comprises a filament which bombards a cathode with electrons, a griid control electrode between the filament and the cathode, and an anode electrode. The control electrode has a DC potential which is varied in response to changes in the anode current flow by means of a saturable reactor installed in its power supply energizing line having the anode current flowing through its control winding. In this manner the bombardment current to the cathode may be decreased when the anode current increases beyond a predetermined level.

Evaluation of a pulsed quasi-steady MPD thruster and associated subsystems

NASA Technical Reports Server (NTRS)

Lien, H.; Garrison, R. L.; Libby, D. R.

1972-01-01

The performance of quasi-steady magnetoplasmadynamic (MPD) thrusters at high power levels is discussed. An axisymmetric configuration is used for the MPD thruster, with various cathode and anode sizes, over a wide range of experimental conditions. Thrust is determined from impulse measurements with current waveforms, while instantaneous measurements are made for all other variables. It is demonstrated that the thrust produced has a predominately self-magnetic origin and is directly proportional to the square of the current. The complete set of impulse measurement data is presented.

Solid oxide fuel cell having monolithic core

DOEpatents

Ackerman, J.P.; Young, J.E.

1983-10-12

A solid oxide fuel cell is described for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween. The electrolyte walls are arranged and backfolded between adjacent interconnect walls operable to define a plurality of core passageways alternately arranged where the inside faces thereof have only the anode material or only the cathode material exposed. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageway; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte and interconnect materials is of the order of 0.002 to 0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002 to 0.05 cm thick.

Reconnaissance electrical surveys in the Coso Range, California

NASA Astrophysics Data System (ADS)

Jackson, Dallas B.; O'Donnell, James E.

1980-05-01

Telluric current, audiomagnetotelluric (AMT), and direct current (dc) methods were used to study the electrical structure of the Coso Range and Coso geothermal area. Telluric current mapping outlined major resistivity lows associated with conductive valley fill of the Rose Valley basin, the Coso Basin, and the northern extension of the Coso Basin east of Coso Hot Springs. A secondary resistivity low with a north-south trend runs through the Coso Hot Springs-Devil's Kitchen geothermal area. The secondary low in the geothermal area, best defined by the 7.5-Hz AMT map and dc soundings, is caused by a shallow conductive zone (5-30 ohm m) interpreted to be hydrothermally altered Sierra Nevada basement rocks containing saline water of a hot water geothermal system. This zone of lowest apparent resistivities over the basement rocks lies within a closed contour of a heat flow anomaly where all values are greater than 10 heat flow units.

Spinel compounds as multivalent battery cathodes: A systematic evaluation based on ab initio calculations

DOE PAGES

Liu, Miao; Rong, Ziqin; Malik, Rahul; ...

2014-12-16

In this study, batteries that shuttle multivalent ions such as Mg 2+ and Ca 2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multivalent cations is considered a major challenge for enabling such multivalent battery technology. In this paper, we use recent advances in high-throughput first-principles calculations to systematically evaluate the performance of compounds with the spinel structure as multivalent intercalation cathode materials, spanning a matrix of five different intercalating ions and seven transition metal redox active cations. We estimate the insertion voltage, capacity,more » thermodynamic stability of charged and discharged states, as well as the intercalating ion mobility and use these properties to evaluate promising directions. Our calculations indicate that the Mn 2O 4 spinel phase based on Mg and Ca are feasible cathode materials. In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; the voltages of Ca spinels are ~0.2 V higher than those of Mg compounds (versus their corresponding metals), and the voltages of Mg compounds are ~1.4 V higher than Zn compounds; consequently, Ca and Mg spinels exhibit the highest energy densities amongst all the multivalent cation species. The activation barrier for the Al³⁺ ion migration in the Mn₂O₄ spinel is very high (~1400 meV for Al 3+ in the dilute limit); thus, the use of an Al based Mn spinel intercalation cathode is unlikely. Amongst the choice of transition metals, Mn-based spinel structures rank highest when balancing all the considered properties.« less

Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry

PubMed Central

Kumarasinghe, Chathurangi S.; Premaratne, Malin; Gunapala, Sarath D.; Agrawal, Govind P.

2016-01-01

We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors. PMID:26887286

Design of all-optical, hot-electron current-direction-switching device based on geometrical asymmetry.

PubMed

Kumarasinghe, Chathurangi S; Premaratne, Malin; Gunapala, Sarath D; Agrawal, Govind P

2016-02-18

We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors.

Solid oxide fuel cell having monolithic core

DOEpatents

Ackerman, John P.; Young, John E.

1984-01-01

A solid oxide fuel cell for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween, and each interconnect wall consists of thin layers of the cathode and anode materials sandwiching a thin layer of interconnect material therebetween. The electrolyte walls are arranged and backfolded between adjacent interconnect walls operable to define a plurality of core passageways alternately arranged where the inside faces thereof have only the anode material or only the cathode material exposed. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageway; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte and interconnect materials is of the order of 0.002-0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002-0.05 cm thick.