Finite-element analysis of vibrational modes in piezoelectric ceramic disks.

PubMed

Kunkel, H A; Locke, S; Pikeroen, B

1990-01-01

The natural vibrational modes of axially symmetric piezoelectric ceramic disks have been calculated by the finite-element method. The disks are of the type used as active elements in compressional wave ultrasonic transducers, and are electrically polarized in thickness with full electrodes on the disk's major faces. To optimize disk geometry for ultrasonic transducer application, the dependence of the vibrational modes on the disk diameter-to-thickness ratio for ratios from 0.2 (a tall cylinder) to 10.0 (a thin disk) has been studied. Series and parallel resonance frequencies for each of the modes are determined through an eigenfrequency analysis, and effective electromechanical coupling coefficients are calculated. The modal displacement fields in the disk are calculated to determine the physical nature of each mode. An analysis of the complete spectrum of piezoelectrically active modes as a function of diameter-thickness ratio is presented for the ceramic PZT-5H, including and identification of radial, edge, length expander, thickness shear, and thickness extensional vibrations. From this analysis, optimal diameter-to-thickness ratios for good transducer performance are discussed.

Development of High Interruption Capability Vacuum Circuit Breaker -Technology of Vacuum Arc Control-

NASA Astrophysics Data System (ADS)

Niwa, Yoshimitsu; Kaneko, Eiji

Vacuum circuit breakers (VCB) have been widely used for power distribution systems. Vacuum Interrupters, which are the current interruption unit, have been increased its interruption capability with the development of vacuum arc control technology by magnetic field. There are three major type electrodes: disk shaped electrodes, radial magnetic field electrodes, axial magnetic field (AMF) electrodes. In the disk shaped electrode, the vacuum arc between the electrodes is not controlled. In the AMF electrode, the vacuum arc is diffused and stabilized by an axial magnetic field, which is parallel to the arc current. In the last type of electrodes, the vacuum arc column is rotated by magnetic force generated by the current flowing in the electrodes. The interruption current and the voltage of one break VCB is increased to 100 kA, 144 kV respectively. This paper describes basic configurations and functions of VCB, vacuum arc control technology in vacuum interrupters, recent researches and applications of VCB.

Quantitative Analysis of Homogeneous Electrocatalytic Reactions at IDA Electrodes: The Example of [Ni(PPh2NBn2)2]2+

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

Liu, Fei; Parkinson, B. A.; Divan, Ralu

Interdigitated array (IDA) electrodes have been applied to study the EC’ (electron transfer reaction followed by a catalytic reaction) reactions and a new method of quantitative analysis of IDA results was developed. In this new method, currents on IDA generator and collector electrodes for an EC’ mechanism are derived from the number of redox cycles and the contribution of non-catalytic current. And the fractions of bipotential recycling species and catalytic-active species are calculated, which helps understanding the catalytic reaction mechanism. The homogeneous hydrogen evolution reaction catalyzed by [Ni(PPh2NBn2)2]2+ (where PPh2NBn2 is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) electrocatalyst was examined and analyzed with IDA electrodes.more » Besides, the existence of reaction intermediates in the catalytic cycle is inferred from the electrochemical behavior of a glassy carbon disk electrodes and carbon IDA electrodes. This quantitative analysis of IDA electrode cyclic voltammetry currents can be used as a simple and straightforward method for determining reaction mechanism in other catalytic systems as well.« less

Extended foil capacitor with radially spoked electrodes

DOEpatents

Foster, James C.

1990-01-01

An extended foil capacitor has a conductive disk electrically connected in oncrushing contact to the extended foil. A conductive paste is placed through spaces between radial spokes on the disk to electrically and mechanically connect the extended foil to the disk.

Development of CE-dual opposite carbon-fiber micro-disk electrode detection for peak purity assessment of polyphenols in red wine.

PubMed

Du, Fuying; Fung, Ying Sing

2010-07-01

A new dual opposite carbon-fiber micro-disk electrode detector was fabricated and tested for hyphenation with CE in the polyphenol determination. Under optimized conditions, CE-dual opposite carbon-fiber micro-disk electrode was found able to baseline separate and determine five important polyphenols (trans-resveratrol, (+)-catechin, (-)-epicatechin, quercetin and gallic acid) in red wine within 16 min with low detection limit (0.031-0.21 mg/L) and satisfactory repeatability (2.0-3.3% RSD, n=5). The opposite dual electrode enables simultaneous determination of CE eluents for current ratio measured at +0.8 and +1.0 V versus Ag/AgCl for the peak purity assessment. The capability to identify the presence of co-migrating impurities in given polyphenol peaks was demonstrated in a mixed standard solution with overlapping (+)-catechin and (-)-epicatechin peaks and in commercial red wine with unknown impurities and confirming the reliability for polyphenol quantitation in red wine with matching migration time and current ratio.

A dual electrochemical microsensor for simultaneous imaging of oxygen and pH over the rat kidney surface.

PubMed

Ha, Yejin; Myung, Dongshin; Shim, Jun Ho; Kim, Myung Hwa; Lee, Youngmi

2013-09-21

In this study, a dual microsensing electrochemical probe for measuring oxygen (O2) and pH levels was developed based on a dual recessed Pt disk electrode (each disk diameter, 10 μm) with the use of two Ag/AgCl reference electrodes (one for each disk of the dual electrode). One of the recessed Pt disks of the dual electrode was electrodeposited with a porous Pt layer and then coated with a hydrophobic photocured polymer (partially fluorinated epoxy diacrylate, abbreviated as FED). The Pt-FED covered disk was used as an amperometric O2 sensor and exhibited a linear current increase that was proportional to the PO2 level (partial O2 pressure) with high sensitivity (168.4 ± 33.8 pA mmHg(-1)) and fast response time (t90% = 0.17 ± 0.05 s). The other recessed Pt disk was electrodeposited with an IrO2 layer. The potential between the IrO2 deposited electrode and the Ag/AgCl reference electrode produced a reliable Nernstian response to pH changes (58.3 ± 1.5 mV pH(-1)) with a t90% of 0.43 ± 0.09 s. The sensor displayed high stability in the in vitro organ tissue measurements for at least 2.5 h. By using the developed dual O2/pH microsensor as a probe tip for scanning electrochemical microscopy, the two-dimensional images of the location-dependent PO2 and pH levels were simultaneously acquired and could be used to assess the surface of a rat kidney tissue slice. When compared to the corresponding medullary levels, both PO2 and pH were observed to be higher in the cortex area, while the modest level gradient was observed near the cortex-medulla border. This finding suggests that there is a direct relationship between the tissue O2 supply/consumption and pH, which is mainly determined by metabolite, such as CO2, production.

Electrochemical determination of the onset of bacterial surface adhesion

NASA Astrophysics Data System (ADS)

Jones, Akhenaton-Andrew; Buie, Cullen

2017-11-01

Microbial biofouling causes economic loss through corrosion and drag losses on ship hulls, and in oil and food distribution. Microorganisms interacting with surfaces under these open channel flows contend with high shear rates and active transport to the surface. The metallic surfaces they interact with carry charge at various potentials that are little addressed in literature. In this study we demonstrate that the Levich curve, chronoamperometry, and cyclic voltammetry in a rotating disk electrode are ideal for studying adhesion of microbes to metallic surfaces. We study the adhesion of Escherichia coli, Bacillus subtilis, and 1 μm silica microspheres over a 0.15 - 37.33 dynes .cm-2 or shear rates of 14.73 - 3727.28 s-1 range. Our results agree with literature on red blood cells in rotating disk electrodes, deposition rates from optical systems, and show that we can quantify changes in active electrode area by bacteria adhesion and protein secretion. These methods measure changes in area instead of mass, are more accurate than fluorescence microscopy, and apply to a larger range of problems than on-chip flow devices.

A theoretical consideration of ion size effects on the electric double layer and voltammetry of nanometer-sized disk electrodes.

PubMed

Gao, Yu; Liu, Yuwen; Chen, Shengli

2016-12-12

Considering that an electric-double-layer (EDL) structure may significantly impact on the mass transport and charge transfer kinetics at the interfaces of nanometer-sized electrodes, while EDL structures could be altered by the finite sizes of electrolyte and redox ions, the possible effects of ion sizes on EDL structures and voltammetric responses of nanometer-sized disk (nanodisk) electrodes are investigated. Modified Boltzmann and Nernst-Planck (NP) equations, which include the influence of the finite ion volumes, are combined with the Poisson equation and modified Butler-Volmer equation to gain knowledge on how the finite sizes of ions and the nanometer sizes of electrodes may couple with each other to affect the structures and reactivities of a nanoscale electrochemical interface. Two typical ion radii, 0.38 nm and 0.68 nm, which could represent the sizes of the commonly used aqueous electrolyte ions (e.g., the solvated K + ) and the organic electrolyte ions (e.g., the solvated TEA + ) respectively, are considered. The finite size of ions can result in decreased screening of electrode charges, therefore magnifying EDL effects on the ion transport and the electron transfer at electrochemical interfaces. This finite size effect of ions becomes more pronounced for larger ions and at smaller electrodes as the electrode radii is larger than 10 nm. For electrodes with radii smaller than 10 nm, however, the ion size effect may be less pronounced with decreasing the electrode size. This can be explained in terms of the increased edge effect of disk electrodes at nanometer scales, which could relax the ion crowding at/near the outer Helmholtz plane. The conditions and situations under which the ion sizes may have a significant effect on the voltammetry of electrodes are discussed.

Multifunctional carbon nanoelectrodes fabricated by focused ion beam milling.

PubMed

Thakar, Rahul; Weber, Anna E; Morris, Celeste A; Baker, Lane A

2013-10-21

We report a strategy for fabrication of sub-micron, multifunctional carbon electrodes and application of these electrodes as probes for scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM). The fabrication process utilized chemical vapor deposition of parylene, followed by thermal pyrolysis to form conductive carbon and then further deposition of parylene to form an insulation layer. To achieve well-defined electrode geometries, two methods of electrode exposure were utilized. In the first method, carbon probes were masked in polydimethylsiloxane (PDMS) to obtain a cone-shaped electrode. In the second method, the electrode area was exposed via milling with a focused ion beam (FIB) to reveal a carbon ring electrode, carbon ring/platinum disk electrode, or carbon ring/nanopore electrode. Carbon electrodes were batch fabricated (~35/batch) through the vapor deposition process and were characterized with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and cyclic voltammetry (CV) measurements. Additionally, Raman spectroscopy was utilized to examine the effects of Ga(+) ion implantation, a result of FIB milling. Constant-height, feedback mode SECM was performed with conical carbon electrodes and carbon ring electrodes. We demonstrate the utility of carbon ring/nanopore electrodes with SECM-SICM to simultaneously collect topography, ion current and electrochemical current images. In addition, carbon ring/nanopore electrodes were utilized in substrate generation/tip collection (SG/TC) SECM. In SG/TC SECM, localized delivery of redox molecules affords a higher resolution, than when the redox molecules are present in the bath solution. Multifunctional geometries of carbon electrode probes will find utility in electroanalytical applications, in general, and more specifically with electrochemical microscopy as discussed herein.

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method.

PubMed

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-03-16

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced.

On the Preparation and Testing of Fuel Cell Catalysts Using the Thin Film Rotating Disk Electrode Method

PubMed Central

Inaba, Masanori; Quinson, Jonathan; Bucher, Jan Rudolf; Arenz, Matthias

2018-01-01

We present a step-by-step tutorial to prepare proton exchange membrane fuel cell (PEMFC) catalysts, consisting of Pt nanoparticles (NPs) supported on a high surface area carbon, and to test their performance in thin film rotating disk electrode (TF-RDE) measurements. The TF-RDE methodology is widely used for catalyst screening; nevertheless, the measured performance sometimes considerably differs among research groups. These uncertainties impede the advancement of new catalyst materials and, consequently, several authors discussed possible best practice methods and the importance of benchmarking. The visual tutorial highlights possible pitfalls in the TF-RDE testing of Pt/C catalysts. A synthesis and testing protocol to assess standard Pt/C catalysts is introduced that can be used together with polycrystalline Pt disks as benchmark catalysts. In particular, this study highlights how the properties of the catalyst film on the glassy carbon (GC) electrode influence the measured performance in TF-RDE testing. To obtain thin, homogeneous catalyst films, not only the catalyst preparation, but also the ink deposition and drying procedures are essential. It is demonstrated that an adjustment of the ink's pH might be necessary, and how simple control measurements can be used to check film quality. Once reproducible TF-RDE measurements are obtained, determining the Pt loading on the catalyst support (expressed as Pt wt%) and the electrochemical surface area is necessary to normalize the determined reaction rates to either surface area or Pt mass. For the surface area determination, so-called CO stripping, or the determination of the hydrogen underpotential deposition (Hupd) charge, are standard. For the determination of the Pt loading, a straightforward and cheap procedure using digestion in aqua regia with subsequent conversion of Pt(IV) to Pt(II) and UV-vis measurements is introduced. PMID:29608166

A Simple and Low-Cost Ultramicroelectrode Fabrication and Characterization Method for Undergraduate Students

ERIC Educational Resources Information Center

Sur, Ujjal Kumar; Dhason, A.; Lakshminarayanan, V.

2012-01-01

A laboratory experiment is described in which students fabricate disk-shaped gold and platinum microelectrodes with diameters of 10-50 [mu]m by sealing sodalime glass with metal microwires. The electrodes are characterized by performing cyclic voltammetry in aqueous and acetonitrile solution. Commercial microelectrodes are expensive (cost depends…

Accurate Assessment of the Oxygen Reduction Electrocatalytic Activity of Mn/Polypyrrole Nanocomposites Based on Rotating Disk Electrode Measurements, Complemented with Multitechnique Structural Characterizations

PubMed Central

Sánchez, Carolina Ramírez; Taurino, Antonietta; Bozzini, Benedetto

2016-01-01

This paper reports on the quantitative assessment of the oxygen reduction reaction (ORR) electrocatalytic activity of electrodeposited Mn/polypyrrole (PPy) nanocomposites for alkaline aqueous solutions, based on the Rotating Disk Electrode (RDE) method and accompanied by structural characterizations relevant to the establishment of structure-function relationships. The characterization of Mn/PPy films is addressed to the following: (i) morphology, as assessed by Field-Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscope (AFM); (ii) local electrical conductivity, as measured by Scanning Probe Microscopy (SPM); and (iii) molecular structure, accessed by Raman Spectroscopy; these data provide the background against which the electrocatalytic activity can be rationalised. For comparison, the properties of Mn/PPy are gauged against those of graphite, PPy, and polycrystalline-Pt (poly-Pt). Due to the literature lack of accepted protocols for precise catalytic activity measurement at poly-Pt electrode in alkaline solution using the RDE methodology, we have also worked on the obtainment of an intralaboratory benchmark by evidencing some of the time-consuming parameters which drastically affect the reliability and repeatability of the measurement. PMID:28042491

[Non-invasive estimation of aortic flow by local electrical impedance changes].

PubMed

Okuda, N; Ohashi, N; Yamada, M; Fujinami, T

1986-09-01

Aortic flow velocity was measured by catheter-tip flow transducer in 25 patients who underwent left cardiac catheterization for non-invasive estimates by the impedance method. Disk electrodes were attached to the skin at the levels of the second thoracic vertebra in the posterior median line and the V8 lead position for electrocardiography. Alternating current, 350 micro-amperes, 50 KHz constant, was applied to the outer electrode, and impedance changes were detected via the inner electrode. The e wave, or height of the first derivative dz/dt wave of the electrical impedance was lower in cases of old myocardial infarction and higher in cases of aortic valve regurgitation, as compared with the values of the healthy control group. The time lag between the start of the upward deflection and the peak value of the dz/dt wave coincided with that of the aortic flow curve as measured at the aortic arch and descending aorta. These time lags were about 20 to 30 msec as compared with the ascending aortic flow curve, and were -20 to -30 msec as compared with the abdominal aortic flow curve. There was a close correlation between the maximum flow velocity measured at the aortic arch and the height of the e waves. The regression equation was: Y = 0.21X - 1.53, r = 0.88, p less than 0.01. These data suggest that the first derivative of electrical impedance change as obtained by the disk electrode method reflects aortic flow at the arch and descending aorta.

Porous Teflon ring-solid disk electrode arrangement for differential mass spectrometry measurements in the presence of convective flow generated by a jet impinging electrode in the wall-jet configuration.

PubMed

Treufeld, Imre; Jebaraj, Adriel Jebin Jacob; Xu, Jing; Martins de Godoi, Denis; Scherson, Daniel

2012-06-19

A porous Teflon ring|solid disk electrode is herein described specifically designed for acquiring online mass spectrometric measurements under well-defined forced convection created by liquid emerging from a circular nozzle impinging on the disk under wall-jet conditions. Measurements were performed for the oxidation of hydrazine, N(2)H(4), in a deaerated phosphate buffer electrolyte (pH 7) on Au, a process known to yield dinitrogen as the product. The N(2)(+) ion currents, measured by the mass spectrometer, i(N(2)(+)), as well as the corresponding polarization curves recorded simultaneously displayed very similar s-like shapes when plotted as a function of the potential applied to the Au disk. In fact, the limiting currents observed both electrochemically and spectrometrically were found to be proportional to [N(2)H(4)]. However, the limiting values of i(N(2)(+)) did not increase monotonically with the flow rate, ν(f), reaching instead a maximum and then decreasing to values independent of ν(f). This behavior has been attributed in part to hindrances in the mass transport of gases through the porous materials.

Direct-current arc and alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials

USGS Publications Warehouse

Grimes, D.J.; Marranzino, A.P.

1968-01-01

Two spectrographic methods are used in mobile field laboratories of the U. S. Geological Survey. In the direct-current arc method, the ground sample is mixed with graphite powder, packed into an electrode crater, and burned to completion. Thirty elements are determined. In the spark method, the sample, ground to pass a 150-mesh screen, is digested in hydrofluoric acid followed by evaporation to dryness and dissolution in aqua regia. The solution is fed into the spark gap by means of a rotating-disk electrode arrangement and is excited with an alternating-current spark discharge. Fourteen elements are determined. In both techniques, light is recorded on Spectrum Analysis No. 1, 35-millimeter film, and the spectra are compared visually with those of standard films.

Deterministic multi-step rotation of magnetic single-domain state in Nickel nanodisks using multiferroic magnetoelastic coupling

NASA Astrophysics Data System (ADS)

Sohn, Hyunmin; Liang, Cheng-yen; Nowakowski, Mark E.; Hwang, Yongha; Han, Seungoh; Bokor, Jeffrey; Carman, Gregory P.; Candler, Robert N.

2017-10-01

We demonstrate deterministic multi-step rotation of a magnetic single-domain (SD) state in Nickel nanodisks using the multiferroic magnetoelastic effect. Ferromagnetic Nickel nanodisks are fabricated on a piezoelectric Lead Zirconate Titanate (PZT) substrate, surrounded by patterned electrodes. With the application of a voltage between opposing electrode pairs, we generate anisotropic in-plane strains that reshape the magnetic energy landscape of the Nickel disks, reorienting magnetization toward a new easy axis. By applying a series of voltages sequentially to adjacent electrode pairs, circulating in-plane anisotropic strains are applied to the Nickel disks, deterministically rotating a SD state in the Nickel disks by increments of 45°. The rotation of the SD state is numerically predicted by a fully-coupled micromagnetic/elastodynamic finite element analysis (FEA) model, and the predictions are experimentally verified with magnetic force microscopy (MFM). This experimental result will provide a new pathway to develop energy efficient magnetic manipulation techniques at the nanoscale.

Discrimination of Inner- and Outer-Sphere Electrode Reactions by Cyclic Voltammetry Experiments

ERIC Educational Resources Information Center

Tanimoto, Sachiko; Ichimura, Akio

2013-01-01

A laboratory experiment for undergraduate students who are studying homogeneous and heterogeneous electron-transfer reactions is described. Heterogeneous or electrode reaction kinetics can be examined by using the electrochemical reduction of three Fe[superscript III]/Fe[superscript II] redox couples at platinum and glassy carbon disk electrodes.…

Reaction kinetics and product distributions in photoelectrochemical cells

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

Koval, C.A.

1992-01-01

Hot electron reaction studies at p-InP/CH[sub 3]CN interface revealed essential/desirable features for redox systems used to investigate hot carriers in photoelectrocehmical cells. Reduction of dibromoethylbenzene (DBEB) in presence of metallocene couples is being studied using rotating rink disk electrodes of n-and p-InP disks and Pt rings. At highly doped p-InP electrodes, reduction of DBEB can be very efficient (>30%). A minielectrochemical cell was used to investigate electron transfer at nonilluminated n-WSe[sub 2]/dimethylferrocene[sup +/0] interfaces.

Electrochemical Generation of a Hydrogen Bubble at a Recessed Platinum Nanopore Electrode.

PubMed

Chen, Qianjin; Luo, Long; White, Henry S

2015-04-21

We report the electrochemical generation of a single hydrogen bubble within the cavity of a recessed Pt nanopore electrode. The recessed Pt electrode is a conical pore in glass that contains a micrometer-scale Pt disk (1-10 μm radius) at the nanopore base and a nanometer-scale orifice (10-100 nm radius) that restricts diffusion of electroactive molecules and dissolved gas between the nanopore cavity and bulk solution. The formation of a H2 bubble at the Pt disk electrode in voltammetric experiments results from the reduction of H(+) in a 0.25 M H2SO4 solution; the liquid-to-gas phase transformation is indicated in the voltammetric response by a precipitous decrease in the cathodic current due to rapid bubble nucleation and growth within the nanopore cavity. Finite element simulations of the concentration distribution of dissolved H2 within the nanopore cavity, as a function of the H(+) reduction current, indicate that H2 bubble nucleation at the recessed Pt electrode surface occurs at a critical supersaturation concentration of ∼0.22 M, in agreement with the value previously obtained at (nonrecessed) Pt disk electrodes (∼0.25 M). Because the nanopore orifice limits the diffusion of H2 out of the nanopore cavity, an anodic peak corresponding to the oxidation of gaseous and dissolved H2 trapped in the recessed cavity is readily observed on the reverse voltammetric scan. Integration of the charge associated with the H2 oxidation peak is found to approach that of the H(+) reduction peak at high scan rates, confirming the assignment of the anodic peak to H2 oxidation. Preliminary results for the electrochemical generation of O2 bubbles from water oxidation at a recessed nanopore electrode are consistent with the electrogeneration of H2 bubbles.

The aluminum electrode in AlCl3-alkali-halide melts.

NASA Technical Reports Server (NTRS)

Holleck, G. L.; Giner, J.

1972-01-01

Passivation phenomena have been observed upon cathodic and anodic polarization of the Al electrode in AlCl3-KCl-NaCl melts between 100 and 160 C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents increased with temperature and with decreasing AlCl3 content of the melt. Current voltage curves obtained on a rotating aluminum disk showed a linear relationship between the anodic limiting current and omega to the minus 1/2 power. Upon cathodic polarization, dendrite formation occurs at the Al electrode. The activation overvoltage in AlCl3-KCl-NaCl was determined by galvanostatic current step methods. An apparent exchange current density of 270 mA/sq cm at 130 C and a double layer capacity of 40 plus or minus 10 microfarad/sq cm were measured.

Preparation of PEMFC Electrodes from Milligram-Amounts of Catalyst Powder

DOE PAGES

Yarlagadda, Venkata; McKinney, Samuel E.; Keary, Cristin L.; ...

2017-06-03

Development of electrocatalysts with higher activity and stability is one of the highest priorities in enabling cost-competitive hydrogen-air fuel cells. Although the rotating disk electrode (RDE) technique is widely used to study new catalyst materials, it has been often shown to be an unreliable predictor of catalyst performance in actual fuel cell operation. Fabrication of membrane electrode assemblies (MEA) for evaluation which are more representative of actual fuel cells generally requires relatively large amounts (>1 g) of catalyst material which are often not readily available in early stages of development. In this study, we present two MEA preparation techniques usingmore » as little as 30 mg of catalyst material, providing methods to conduct more meaningful MEA-based tests using research-level catalysts amounts.« less

Development of capillary electrophoresis methods for quantitative determination of taurine in vehicle system and biological media.

PubMed

da Silva, Dayse L P; Rüttinger, Hans H; Mrestani, Yahia; Baum, Walter F; Neubert, Reinhard H H

2006-06-01

CE methods have been developed for the determination of taurine in pharmaceutical formulation (microemulsion) and in biological media such as sweat. The CE system with end-column pulsed amperometric detection has been found to be an interesting method in comparison with UV and fluorescence detection for its simplicity and rapidity. A gold-disk electrode of 100 mm diameter was used as the working electrode. The effects of a field decoupler at the end of the capillary, separation voltage, injection and pressure times were investigated. A detection limit of 4 x 10(-5) mol/L was reached using integrated pulsed amperometric detection, a method successfully applied to taurine analysis of the biological samples such as sweat. For taurine analysis of oil-in-water microemulsion, fluorescence detector was the favored method, the detection limit of which was 4 x 10(-11) mol/L.

Palladium nanoparticles decorated on reduced graphene oxide rotating disk electrodes toward ultrasensitive hydrazine detection: effects of particle size and hydrodynamic diffusion.

PubMed

Krittayavathananon, Atiweena; Srimuk, Pattarachai; Luanwuthi, Santamon; Sawangphruk, Montree

2014-12-16

Although metal nanoparticle/graphene composites have been widely used as the electrode in electrochemical sensors, two effects, consisting of the particle size of the nanoparticles and the hydrodynamic diffusion of analytes to the electrodes, are not yet fully understood. In this work, palladium nanoparticles/reduced graphene oxide (PdNPs/rGO) composites were synthesized using an in situ polyol method. Palladium(II) ions and graphene oxide were reduced together with a reducing agent, ethylene glycol. By varying the concentration of palladium(II) nitrate, PdNPs with different sizes were decorated on the surface of rGO sheets. The as-fabricated PdNPs/rGO rotating disk electrodes (RDEs) were investigated toward hydrazine detection. Overall, a 3.7 ± 1.4 nm diameter PdNPs/rGO RDE exhibits high performance with a rather low limit of detection of about 7 nM at a rotation speed of 6000 rpm and provides a wide linear range of 0.1-1000 μM with R(2) = 0.995 at 2000 rpm. This electrode is highly selective to hydrazine without interference from uric acid, glucose, ammonia, caffeine, methylamine, ethylenediamine, hydroxylamine, n-butylamine, adenosine, cytosine, guanine, thymine, and l-arginine. The PdNPs/rGO RDEs with larger sizes show lower detection performance. Interestingly, the detection performance of the electrodes is sensitive to the hydrodynamic diffusion of hydrazine. The as-fabricated electrode can detect trace hydrazine in wastewater with high stability, demonstrating its practical use as an electrochemical sensor. These findings may lead to an awareness of the effect of the hydrodynamic diffusion of analyte that has been previously ignored, and the 3.7 ± 1.4 nm PdNPs/rGO RDE may be useful toward trace hydrazine detection, especially in wastewater from related chemical industries.

High Rate Oxygen Reduction in Non-aqueous Electrolytes with the Addition of Perfluorinated Additives

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

Wang, Y.; Yang, X.; Zheng, D.

2011-08-04

The discharge rate capability of Li-air batteries is substantially increased by using perfluorinated compounds as oxygen carriers. The solubility of oxygen in a non-aqueous electrolyte can be significantly increased by the introduction of such compounds, which leads to the increase in the diffusion-limited current of oxygen reduction on the gas diffusion electrode in a Li-air battery. The perfluorinated compound is found to be stable within the electrochemical window of the electrolyte. A powder microelectrode and a rotating disk electrode were used to study the gas diffusion-limited current together with a rotating disk electrode. A 5 mA cm{sup -2} discharge ratemore » is demonstrated in a lab Li-O{sub 2} cell.« less

Reaction kinetics and product distributions in photoelectrochemical cells. Technical progress report, March 15, 1992--March 14, 1993

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

Koval, C.A.

1992-12-01

Hot electron reaction studies at p-InP/CH{sub 3}CN interface revealed essential/desirable features for redox systems used to investigate hot carriers in photoelectrocehmical cells. Reduction of dibromoethylbenzene (DBEB) in presence of metallocene couples is being studied using rotating rink disk electrodes of n-and p-InP disks and Pt rings. At highly doped p-InP electrodes, reduction of DBEB can be very efficient (>30%). A minielectrochemical cell was used to investigate electron transfer at nonilluminated n-WSe{sub 2}/dimethylferrocene{sup +/0} interfaces.

Application of a palladium hexacyanoferrate film-modified aluminum electrode to electrocatalytic oxidation of hydrazine.

PubMed

Razmi, Habib; Azadbakht, Azadeh; Sadr, Moayad Hossaini

2005-11-01

A palladium hexacyanoferrate (PdHCF) film as an electrocatalytic material was obtained at an aluminum (Al) electrode by a simple electroless dipping method. The modified Al electrode demonstrated a well-behaved redox couple due to the redox reaction of the PdHCF film. The PdHCF film showed an excellent electrocatalytic activity toward the oxidation of hydrazine. The electrocatalytic oxidation of hydrazine was studied by cyclic voltammetry and rotating disk electrode voltammetry techniques. A calibration graph obtained for the hydrazine consisted of two segments (localized at concentration ranges 0.39-10 and 20-75 mM). The rate constant k and transfer coefficient alpha for the catalytic reaction and the diffusion coefficient of hydrazine in the solution D, were found to be 3.11 x 10(3) M(-1) s(-1), 0.52 and 8.03 x 10(-6) cm2 s(-1) respectively. The modified electrode was used to amperometric determination of hydrazine in photographic developer. The interference of ascorbic acid and thiosulfate were investigated and greatly reduced using a thin film of Nafion on the modified electrode. The modified electrode indicated reproducible behavior and a high level of stability during electrochemical experiments, making it particularly suitable for analytical purposes.

Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

PubMed Central

Lupu, Stelian; Lete, Cecilia; Balaure, Paul Cătălin; Caval, Dan Ion; Mihailciuc, Constantin; Lakard, Boris; Hihn, Jean-Yves; del Campo, Francisco Javier

2013-01-01

Bio-composite coatings consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and tyrosinase (Ty) were successfully electrodeposited on conventional size gold (Au) disk electrodes and microelectrode arrays using sinusoidal voltages. Electrochemical polymerization of the corresponding monomer was carried out in the presence of various Ty amounts in aqueous buffered solutions. The bio-composite coatings prepared using sinusoidal voltages and potentiostatic electrodeposition methods were compared in terms of morphology, electrochemical properties, and biocatalytic activity towards various analytes. The amperometric biosensors were tested in dopamine (DA) and catechol (CT) electroanalysis in aqueous buffered solutions. The analytical performance of the developed biosensors was investigated in terms of linear response range, detection limit, sensitivity, and repeatability. A semi-quantitative multi-analyte procedure for simultaneous determination of DA and CT was developed. The amperometric biosensor prepared using sinusoidal voltages showed much better analytical performance. The Au disk biosensor obtained by 50 mV alternating voltage amplitude displayed a linear response for DA concentrations ranging from 10 to 300 μM, with a detection limit of 4.18 μM. PMID:23698270

Novel method for fast characterization of high-surface-area electrocatalytic materials using carbon fiber microelectrode.

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

Strmcnik, D.; Hodnik, N.; Hocevar, S. B.

2010-02-18

A carbon fiber microelectrode (CFME) was used for characterization of the nanoparticle catalysts as an alternative to the well-established rotating disk electrode (RDE) method. We found that the novel CFME method yielded comparable results to the RDE method when investigating the adsorption/desorption processes as well the specific activity for reactions such as the oxygen reduction reaction. Its major advantage over the RDE method is a fast sample preparation and rapid measurement, reducing significantly the time of a single sample characterization from 2-3 h to a favorable 5-10 min.

Apparatus and method for plasma processing of SRF cavities

NASA Astrophysics Data System (ADS)

Upadhyay, J.; Im, Do; Peshl, J.; Bašović, M.; Popović, S.; Valente-Feliciano, A.-M.; Phillips, L.; Vušković, L.

2016-05-01

An apparatus and a method are described for plasma etching of the inner surface of superconducting radio frequency (SRF) cavities. Accelerator SRF cavities are formed into a variable-diameter cylindrical structure made of bulk niobium, for resonant generation of the particle accelerating field. The etch rate non-uniformity due to depletion of the radicals has been overcome by the simultaneous movement of the gas flow inlet and the inner electrode. An effective shape of the inner electrode to reduce the plasma asymmetry for the coaxial cylindrical rf plasma reactor is determined and implemented in the cavity processing method. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise way to establish segmented plasma columns. The test structure was a pillbox cavity made of steel of similar dimension to the standard SRF cavity. This was adopted to experimentally verify the plasma surface reaction on cylindrical structures with variable diameter using the segmented plasma generation approach. The pill box cavity is filled with niobium ring- and disk-type samples and the etch rate of these samples was measured.

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

DOE PAGES

Mauger, Scott A.; Neyerlin, K. C.; Alia, Shaun M.; ...

2018-03-13

Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalystmore » materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation.« less

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

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

Mauger, Scott A.; Neyerlin, K. C.; Alia, Shaun M.

Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalystmore » materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation.« less

Capacitor electrode stimulates nerve or muscle without oxidation-reduction reactions.

PubMed

Guyton, D L; Hambrecht, F T

1973-07-06

Porous tantalum disks, available as "slugs" from the capacitor industry, have large available surface area and a thin insulating coating of tantalum pentoxide. When implanted, they fill with extracellular fluid and operate as capacitor-stimulating electrodes having high capacitance per unit volume. Capable of stimulating excitable tissute without generating electrochemical by-products, these electrodes should provide a safer interface between neural prosthetic devices and human tissue.

Solid state electro-optic color filter and iris

NASA Technical Reports Server (NTRS)

1974-01-01

The electro-optic properties of lanthanum-modified lead zirconate titanate (PLZT) ferroelectric ceramic material are evaluated when utilized as a variable density and/or spectral filter in conjunction with a television scanning system. Emphasis was placed on the development of techniques and procedures for processing the PLZT disks and for applying efficient electrode structures. A number of samples were processed using different combinations of cleaning, electrode material, and deposition process. Best overall performance resulted from the direct evaporation of gold over chrome electrodes. A ruggedized mounting holder assembly was designed, fabricated, and tested. The assembly provides electrical contacts, high voltage protection, and support for the fragile PLZT disk, and permits mounting and optical alignment of the associated polarizers. Operational measurements of a PLZT sample mounted in the holder assembly were performed in conjunction with a television camera and the associated drive circuits. The data verified achievement of the elimination of the observed white-line effect.

Photoconducting positions monitor and imaging detector

DOEpatents

Shu, Deming; Kuzay, Tuncer M.

2000-01-01

A photoconductive, high energy photon beam detector/monitor for detecting x-rays and gamma radiation, having a thin, disk-shaped diamond substrate with a first and second surface, and electrically conductive coatings, or electrodes, of a predetermined configuration or pattern, disposed on the surfaces of the substrate. A voltage source and a current amplifier is connected to the electrodes to provide a voltage bias to the electrodes and to amplify signals from the detector.

Corrosion Modeling and Testing of Riveted Aluminum Alloy Panel

DTIC Science & Technology

2012-08-28

Curve Measurement • V-I measurement using rotating disk electrode ( RDE ) captures mass transport contribution • Mass transport can be important for...curve measurement needed Rotating Disk Electrode ( RDE ) y = 0.0353x + 0.1796 0 10 20 30 40 50 60 70 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 5 10 15 B ou nd...ar y la ye r t hi ck ne ss , um D iff us io n Li m ite d C ur re nt ( m A /c m 2 ) Rotation Rate, w1/2 (radian s-1)1/2 Cu RDE Tests IL, mA

Experimental investigation on sandwich structure ring-type ultrasonic motor.

PubMed

Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

2015-02-01

This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC. Copyright © 2014 Elsevier B.V. All rights reserved.

Segmentally structured disk triboelectric nanogenerator

DOEpatents

Wang, Zhong Lin; Zhu, Guang; Lin, Long; Wang, Sihong; Chen, Jun

2016-11-01

A generator includes a disc shaped first unit, a disc shaped second unit and an axle. The first unit includes a substrate layer, a double complementary electrode layer and an electrification material layer. The electrode layer includes a first electrode member and a second electrode member. The first electrode member includes evenly spaced apart first electrode legs extending inwardly. The second electrode member is complementary in shape to the first electrode member. The legs of the first electrode member and the second electrode member are interleaved with each other and define a continuous gap therebetween. The electrification material includes a first material that is in a first position on the triboelectric series. The second unit defines elongated openings and corresponding elongated leg portions, and includes a second material that is at a second position on a triboelectric series, different than the first position.

Kinetics of intercalation of lithium into NbSe3 and TiS2 cathodes

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Nagasubramanian, G.; Di Stefano, S.; Bankston, C. P.

1992-01-01

Titanium disulfide and niobium triselenide are two well-studied candidate materials for positive electrodes in rechargeable lithium cells. A comparative study of the kinetics of intercalation of lithium in both the cathodes is made here based on various electrochemical techniques, i.e., linear polarization, potentiodynamic polarization, and ac impedance under different experimental conditions such as prismatic or disk configuration of fresh, partially discharged, or cycled electrode. Further, the diffusion coefficients of lithium ions in these cathodes are estimated under these conditions using conventional techniques, i.e., ac impedance, chronocoulometry, chronoamperometry, and current pulse relaxation. Based on the values of the diffusion coefficients, the applicability of these methods for the determination of diffusion coefficients is discussed.

Rechargeable Al/Cl2 battery with molten AlCl4/-/ electrolyte.

NASA Technical Reports Server (NTRS)

Holleck, G. L.; Giner, J.; Burrows, B.

1972-01-01

A molten salt system based on Al- and Cl2 carbon electrodes, with an AlCl3 alkali chloride eutectic as electrolyte, offers promise as a rechargeable, high energy density battery which can operate at a relatively low temperature. Electrode kinetic studies showed that the electrode reactions at the Al anode were rapid and that the observed passivation phenomena were due to the formation at the electrode surface of a solid salt layer resulting from concentration changes on anodic or cathodic current flow. It was established that carbon electrodes were intrinsically active for chlorine reduction in AlCl3-alkali chloride melts. By means of a rotating vitreous carbon disk electrode, the kinetic parameters were determined.

Gastight Hydrodynamic Electrochemistry: Design for a Hermetically Sealed Rotating Disk Electrode Cell.

PubMed

Jung, Suho; Kortlever, Ruud; Jones, Ryan J R; Lichterman, Michael F; Agapie, Theodor; McCrory, Charles C L; Peters, Jonas C

2017-01-03

Rotating disk electrodes (RDEs) are widely used in electrochemical characterization to analyze the mechanisms of various electrocatalytic reactions. RDE experiments often make use of or require collection and quantification of gaseous products. The combination of rotating parts and gaseous analytes makes the design of RDE cells that allow for headspace analysis challenging due to gas leaks at the interface of the cell body and the rotator. In this manuscript we describe a new, hermetically sealed electrochemical cell that allows for electrode rotation while simultaneously providing a gastight environment. Electrode rotation in this new cell design is controlled by magnetically coupling the working electrode to a rotating magnetic driver. Calibration of the RDE using a tachometer shows that the rotation speed of the electrode is the same as that of the magnetic driver. To validate the performance of this cell for hydrodynamic measurements, limiting currents from the reduction of a potassium ferrocyanide (K 4 [Fe(CN) 6 ]·3H 2 O) were measured and shown to compare favorably with calculated values from the Levich equation and with data obtained using more typical, nongastight RDE cells. Faradaic efficiencies of ∼95% were measured in the gas phase for oxygen evolution in alkaline media at an Inconel 625 alloy electrocatalyst during rotation at 1600 rpm. These data verify that a gastight environment is maintained even during rotation.

Is The Real In Vivo Nitric Oxide Concentration Pico or Nano Molar? Influence of Electrode Size on Unstirred Layers and NO Consumption

PubMed Central

Bohlen, H. Glenn

2012-01-01

Objective There is a debate if the nitric oxide concentration ([NO]) required to influence vascular smooth muscle is below 50 nM or much higher. 30 μm and larger diameter electrodes report [NO] below 50 nM, whereas diameters of < 10–12 μm report hundreds of nM. This study examined how size of electrodes influenced [NO] measurement due to NO consumption and unstirred layer issues. Methods Electrodes were 2 mm disk, 30μm X 2 mm carbon fiber, and single 7μm diameter carbon fiber within open tip microelectrode, and exposed 7 μm carbon fiber of ~15 μm to 2 mm length. Results All electrodes demonstrated linear calibrations with sufficient stirring. As stirring slowed, 30 μm and 2 mm electrodes reported much lower [NO] due to unstirred layers and high NO consumption. The three 7 μm microelectrodes had minor stirring issues. With limited stirring with NO present, 7 μm open tip microelectrodes advanced toward 30 μm and 2 mm electrodes experienced dramatically decreased current within 10–50μm of the larger electrodes due to high NO consumption. None of the 7 μm microelectrodes interacted. Conclusions The data indicate large electrodes underestimate [NO] due to excessive NO consumption under conditions where unstirred layers are unavoidable and true microelectrodes are required for valid measurements. PMID:22925222

Preparation and evaluation of thin-film sodium tungsten bronzes

NASA Technical Reports Server (NTRS)

Kautz, H. E.; Fielder, W. L.; Singer, J.; Fordyce, J. S.

1974-01-01

Thin films of sodium tungsten bronze (NaxWO3) were investigated as reversible sodium ion electrodes for solid electrolytes. The films were made by electron beam evaporation of the three phases, W metal, Na2WO4, and WO3, followed by sintering. The substrates were sodium beta alumina disks and glass slides. X-ray diffraction analyses of the films showed that sintering in dry nitrogen with prior exposure to air lead to mixed phases. Sintering in vacuum with no air exposure produced tetragonal I bronze with a nominal composition of Na0.31WO3, single phase within the limits of X-ray diffraction detectability. The films were uniform and adherent on sodium beta alumina substrates. The ac and dc conductivities of the beta alumina were measured with the sodium tungsten bronze films as electrodes. These experiments indicated that the tetragonal I bronze electrodes were not completely reversible. This may have resulted from sodium ion blocking within the bronze film or at the bronze beta alumina interface. Methods for attempting to make more completely reversible electrodes are suggested.

pH matters: The influence of the catalyst ink on the oxygen reduction activity determined in thin film rotating disk electrode measurements

NASA Astrophysics Data System (ADS)

Inaba, Masanori; Quinson, Jonathan; Arenz, Matthias

2017-06-01

We investigated the influence of the ink properties of proton exchange membrane fuel cell (PEMFC) catalysts on the oxygen reduction reaction (ORR) activity determined in thin film rotating disk electrode (TF-RDE) measurements. It was found that the adaption of a previously reported ink recipe to home-made catalysts does not lead to satisfying results, although reported work could be reproduced using commercial catalyst samples. It is demonstrated that the pH of the catalyst ink, which has not been addressed in previous TF-RDE studies, is an important parameter that needs to be carefully controlled to determine the intrinsic ORR activity of high surface area catalysts.

Oxygen Reduction Reaction Activity of Platinum Thin Films with Different Densities

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

Ergul, Busra; Begum, Mahbuba; Kariuki, Nancy

Platinum thin films with different densities were grown on glassy carbon electrodes by high pressure sputtering deposition and evaluated as oxygen reduction reaction catalysts for polymer electrolyte fuel cells using cyclic voltammetry and rotating disk electrode techniques in aqueous perchloric acid electrolyte. The electrochemically active surface area, ORR mass activity (MA) and specific activity (SA) of the thin film electrodes were obtained. MA and SA were found to be higher for low-density films than for high-density film.

Rotating disk electrode system for elevated pressures and temperatures.

PubMed

Fleige, M J; Wiberg, G K H; Arenz, M

2015-06-01

We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

Rotating disk electrode system for elevated pressures and temperatures

NASA Astrophysics Data System (ADS)

Fleige, M. J.; Wiberg, G. K. H.; Arenz, M.

2015-06-01

We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

Circular chemiresistors for microchemical sensors

DOEpatents

Ho, Clifford K [Albuquerque, NM

2007-03-13

A circular chemiresistor for use in microchemical sensors. A pair of electrodes is fabricated on an electrically insulating substrate. The pattern of electrodes is arranged in a circle-filling geometry, such as a concentric, dual-track spiral design, or a circular interdigitated design. A drop of a chemically sensitive polymer (i.e., chemiresistive ink) is deposited on the insulating substrate on the electrodes, which spreads out into a thin, circular disk contacting the pair of electrodes. This circularly-shaped electrode geometry maximizes the contact area between the pair of electrodes and the polymer deposit, which provides a lower and more stable baseline resistance than with linear-trace designs. The circularly-shaped electrode pattern also serves to minimize batch-to-batch variations in the baseline resistance due to non-uniform distributions of conductive particles in the chemiresistive polymer film.

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

PubMed

Cao, H; Besio, W; Jones, S; Medvedev, A

2009-01-01

Tripolar electrodes have been shown to have less mutual information and higher spatial resolution than disc electrodes. In this work, a four-layer anisotropic concentric spherical head computer model was programmed, then four configurations of time-varying dipole signals were used to generate the scalp surface signals that would be obtained with tripolar and disc electrodes, and four important EEG artifacts were tested: eye blinking, cheek movements, jaw movements, and talking. Finally, a fast fixed-point algorithm was used for signal independent component analysis (ICA). The results show that signals from tripolar electrodes generated better ICA separation results than from disc electrodes for EEG signals with these four types of artifacts.

Sea urchin-likeNiCoO2@C nanocompositesforLi-ionbatteries and supercapacitors

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

Liang, Jin; Xi, Kai; Tan, Guoqiang

The rational construction of battery electrode architecture that offers both high energy and power densities on a gravimetric and volumetric basis is a critical concern but achieving this aim is beset by many fundamental and practical challenges. Here we report a new sea urchin-like NiCoO2@C composite electrode architecture composed of NiCoO2 nanosheets grown on hollow concave carbon disks. Such a unique structural design not only preserves all the advantages of hollow structures but also increases the packing density of the active materials. NiCoO2 nanosheets grown on carbon disks promote a high utilization of active materials in redox reactions by reducingmore » the path length for Li+ ions and for electron transfer. Meanwhile, the hollow concave carbon not only reduces the volume change, but also improves the volumetric energy density of the entire composite electrode. As a result, the nanocomposites exhibit superior electrochemical performance measured in terms of high capacity/capacitance, stable cycling performance and good rate capability in both Li-ion battery and supercapacitor applications. Such nanostructured composite electrode may also have great potential for application in other electrochemical devices.« less

A passive ozone sampler based on a reaction with iodide.

PubMed

Yanagisawa, Y

1994-02-01

A new passive sampler for ozone and its simple analytical system have been developed. Because it is small and sensitive, the sampler can be used for determining personal exposures to ozone and oxidants and for multilocation measurements. The sampler consists of an electrode, a spacer, and several layers of membrane filters and Teflon meshes. The electrode is a carbon paper disk coated with nylon-6 polymer and potassium iodide. The membrane filters are used to remove interferences. A sampling rate of ozone is controlled by the spacer and Teflon meshes. Iodine is liberated by an oxidation reaction of potassium iodide with ozone. The iodine is stabilized by forming a charge transfer complex with nylon-6 and is accumulated in the nylon-6 layer. The amount of iodine, which is proportional to the level of ozone exposure, is quantified by constant current coulometry. The discharge time of a galvanic battery is measured using the electrode as a positive electrode and a zinc plate as a counter electrode. A time-weighted average concentration of ozone is derived from the discharge time after exposing the electrode to ozone. The effects of various environmental conditions on the sampler's performance were investigated. The results indicated that the sampler showed a linear response to ozone exposure up to 1,450 parts per billion for every hour of use (ppb.hour). The minimum detectable exposure was about 400 ppb.hour. The effects of surface wind velocity, temperature, and humidity were small. However, a relative humidity below 20% resulted in an underestimation of the ozone concentration. Because the electrode requires no pretreatment and the analytical method is very simple, this method is suitable for large-scale studies of personal exposures to ozone and oxidants using multilocation measurements.

Electrochemical and in situ spectroscopic studies of materials of relevance to energy storage and electrocatalysis

NASA Astrophysics Data System (ADS)

Mo, Yibo

In situ X-ray absorption (XAS), surface enhanced Raman spectroscopy (SERS) and rotating ring disk electrode techniques have been employed for the characterization of materials of relevance to electrochemical energy storage and electrocatalysis. In particular, analysis of in situ Ir LIII-edge extended X-ray absorption fine structure (EXAFS) of IrO2 films electrodeposited on Au substrates yielded Ir-O bond lengths decreasing in the sequence 2.02, 1.97 and 1.93 A, for Ir3+, Ir4+ and Ir5+ sites, respectively. Although features consistent with the presence of crystalline IrO2 in the highly hydrated films were found from in situ SERS, the lack of intense shells in the FT of the EXAFS function beyond the nearest oxygen neighbors indicates that the films by and large do not display long range order. In similar studies, the Fourier transform of the k3-weighted Ru K-edge EXAFS of electrodeposited RuO2 films recorded in situ were characterized by two shells attributed to Ru-O and Ru-Ru interactions at 1.94(1) and 3.12(2) A, in agreement with results obtained ex situ for Ru4+ in hydrous RuO2, whereas films in the reduced state yielded a single Ru-O interaction shell at 2.02(1) A. Extensions of these in situ XAS to the study of electrocatalysts for the nitrite reduction made it possible to identify and characterize the electronic and structural properties of a nitrosyl iron porphyrin adduct adsorbed on an electrode surface via the analysis of Fe K-edge XAS data. The effects of Se and S ad-atoms on the electrocatalytic activity of Pt electrodes have been examined using RRDE techniques. In acid, within a rather narrow range of coverages, both S- and Se-modified Pt surfaces promote the 2-electron reduction of dioxygen to hydrogen peroxide at ca. 100% faradaic efficiency over a wide potential region. Also developed were methods for immobilizing unsupported dispersed high area Pt particles a glassy carbon (GC) disk of a rotating Pt(ring)/GC(disk) electrode assembly allowing electrochemical measurements to be performed under forced convection with only minimal losses of Pt from the surface.

Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes.

PubMed

Trouillon, Raphaël; Lin, Yuqing; Mellander, Lisa J; Keighron, Jacqueline D; Ewing, Andrew G

2013-07-02

During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.

Techniques for chronic monitoring of brain activity in freely moving sheep using wireless EEG recording.

PubMed

Perentos, N; Nicol, A U; Martins, A Q; Stewart, J E; Taylor, P; Morton, A J

2017-03-01

Large mammals with complex central nervous systems offer new possibilities for translational research into basic brain function. Techniques for monitoring brain activity in large mammals, however, are not as well developed as they are in rodents. We have developed a method for chronic monitoring of electroencephalographic (EEG) activity in unrestrained sheep. We describe the methods for behavioural training prior to implantation, surgical procedures for implantation, a protocol for reliable anaesthesia and recovery, methods for EEG data collection, as well as data pertaining to suitability and longevity of different types of electrodes. Sheep tolerated all procedures well, and surgical complications were minimal. Electrode types used included epidural and subdural screws, intracortical needles and subdural disk electrodes, with the latter producing the best and most reliable results. The implants yielded longitudinal EEG data of consistent quality for periods of at least a year, and in some cases up to 2 years. This is the first detailed methodology to be described for chronic brain function monitoring in freely moving unrestrained sheep. The developed method will be particularly useful in chronic investigations of brain activity during normal behaviour that can include sleep, learning and memory. As well, within the context of disease, the method can be used to monitor brain pathology or the progress of therapeutic trials in transgenic or natural disease models in sheep. Copyright © 2016 Elsevier B.V. All rights reserved.

Implications of Marcus-Hush theory for steady-state heterogeneous electron transfer at an inlaid disk electrode.

PubMed

Feldberg, Stephen W

2010-06-15

For an outer-sphere heterogeneous electron transfer, Ox + e = Red, between an electrode and a redox couple, the Butler-Volmer formalism predicts that the operative heterogeneous rate constant, k(red) (cm s(-1)) for reduction (or k(ox) for oxidation) increases without limit as an exponential function of -alpha (E - E(0)) for reduction (or (1 - alpha)(E - E(0)) for oxidation), where E is the applied electrode potential, alpha (~1/2) is the transfer coefficient and E(0) is the formal potential. The Marcus-Hush formalism, as exposited by Chidsey (Chidsey, C. E. D. Science 1991, 215, 919), predicts that the value of k(red) or k(ox) limits at sufficiently large values of -(E - E(0)) or (E - E(0)). The steady-state currents at an inlaid disk electrode obtained for a redox species in solution were computed using both formalisms with the Oldham-Zoski approximation (Oldham, K. B.; Zoski, C. G. J. Electroanal. Chem. 1988, 256, 11). Significant differences are noted for the two formalisms. When k(0)r(0)/D is sufficiently small (k(0) is the standard rate constant, r(0) is the radius of the disk electrode, and D is the diffusion coefficient of the redox species), the Marcus-Hush formalism effects a limiting current that can be significantly smaller than the mass transport limited current. This is easily explained in terms of the limiting values of k(red) and k(ox) predicted by the Marcus-Hush formalism. The experimental conditions that must be met to effect significant differences in behavior are discussed; experimental conditions that effect virtually identical behavior are also discussed. As a caveat for experimentalists, applications of the Butler-Volmer formalism to systems that are more properly described using the Marcus-Hush formalism are shown to yield incorrect values of k(0) and meaningless values of alpha, which serves only as a fitting parameter.

Fine structure of modal focusing effect in a three dimensional plasma-sheath-lens formed by disk electrodes

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

Stamate, Eugen, E-mail: eust@dtu.dk; Venture Business Laboratory, Nagoya University, C3-1, Chikusa-ku, Nagoya 464-8603; Yamaguchi, Masahito

2015-08-31

Modal and discrete focusing effects associated with three-dimensional plasma-sheath-lenses show promising potential for applications in ion beam extraction, mass spectrometry, plasma diagnostics and for basic studies of plasma sheath. The ion focusing properties can be adjusted by controlling the geometrical structure of the plasma-sheath-lens and plasma parameters. The positive and negative ion kinetics within the plasma-sheath-lens are investigated both experimentally and theoretically and a modal focusing ring is identified on the surface of disk electrodes. The focusing ring is very sensitive to the sheath thickness and can be used to monitor very small changes in plasma parameters. Three dimensional simulationsmore » are found to be in very good agreement with experiments.« less

Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

DOE PAGES

Lambert, Timothy N.; Vigil, Julian A.

2016-08-22

Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnO x/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnO x/PEDOT provided improvements over MnO x-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnO x/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnO x/PEDOTmore » also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnO x/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnO x with PEDOT and due to the increase in Mn 3+ content at the surface of the oxide.« less

Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

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

Lambert, Timothy N.; Vigil, Julian A.

Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnO x/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnO x/PEDOT provided improvements over MnO x-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnO x/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnO x/PEDOTmore » also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnO x/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnO x with PEDOT and due to the increase in Mn 3+ content at the surface of the oxide.« less

A mathematical model for predicting cyclic voltammograms of electronically conductive polypyrrole

NASA Technical Reports Server (NTRS)

Yeu, Taewhan; Nguyen, Trung V.; White, Ralph E.

1988-01-01

Polypyrrole is an attractive polymer for use as a high-energy-density secondary battery because of its potential as an inexpensive, lightweight, and noncorrosive electrode material. A mathematical model to simulate cyclic voltammograms for polypyrrole is presented. The model is for a conductive porous electrode film on a rotating disk electrode (RDE) and is used to predict the spatial and time dependence of concentration, overpotential, and stored charge profiles within a polypyrrole film. The model includes both faradic and capacitance charge components in the total current density expression.

A mathematical model for predicting cyclic voltammograms of electronically conductive polypyrrole

NASA Technical Reports Server (NTRS)

Yeu, Taewhan; Nguyen, Trung V.; White, Ralph E.

1987-01-01

Polypyrrole is an attractive polymer for use as a high-energy-density secondary battery because of its potential as an inexpensive, lightweight, and noncorrosive electrode material. A mathematical model to simulate cyclic voltammograms for polypyrrole is presented. The model is for a conductive porous electrode film on a rotating disk electrode (RDE) and is used to predict the spatial and time dependence of concentration, overpotential, and stored charge profiles within a polypyrrole film. The model includes both faradic and capacitance charge components in the total current density expression.

A spatially resolved retarding field energy analyzer design suitable for uniformity analysis across the surface of a semiconductor wafer

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

Sharma, S., E-mail: shailesh.sharma6@mail.dcu.ie; National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9; Gahan, D., E-mail: david.gahan@impedans.com

2014-04-15

A novel retarding field energy analyzer design capable of measuring the spatial uniformity of the ion energy and ion flux across the surface of a semiconductor wafer is presented. The design consists of 13 individual, compact-sized, analyzers, all of which are multiplexed and controlled by a single acquisition unit. The analyzers were tested to have less than 2% variability from unit to unit due to tight manufacturing tolerances. The main sensor assembly consists of a 300 mm disk to mimic a semiconductor wafer and the plasma sampling orifices of each sensor are flush with disk surface. This device is placedmore » directly on top of the rf biased electrode, at the wafer location, in an industrial capacitively coupled plasma reactor without the need for any modification to the electrode structure. The ion energy distribution, average ion energy, and average ion flux were measured at the 13 locations over the surface of the powered electrode to determine the degree of spatial nonuniformity. The ion energy and ion flux are shown to vary by approximately 20% and 5%, respectively, across the surface of the electrode for the range of conditions investigated in this study.« less

Near-Field Phase-Change Optical Recording of 1.36 Numerical Aperture

NASA Astrophysics Data System (ADS)

Ichimura, Isao; Kishima, Koichiro; Osato, Kiyoshi; Yamamoto, Kenji; Kuroda, Yuji; Saito, Kimihiro

2000-02-01

A bit density of 125 nm was demonstrated through near-field phase-change (PC) optical recording at the wavelength of 657 nm by using a supersphere solid immersion lens (SIL). The lens unit consists of a standard objective and a φ2.5 mm SIL@. Since this lens size still prevents the unit from being mounted on an air-bearing slider, we developed a one-axis positioning actuator and an active capacitance servo for precise gap control to thoroughly investigate near-field recording. An electrode was fabricated on the bottom of the SIL, and a capacitor was formed facing a disk material. This setup realized a stable air gap below 50 nm, and a new method of simulating modulation transfer function (MTF) optimized the PC disk structure at this gap height. Obtained jitter of 8.8% and a clear eye-pattern prove that our system successfully attained the designed numerical-aperture (\\mathit{NA}) of 1.36.

Silicon micromachined accelerometer/seismometer and method of making the same

NASA Technical Reports Server (NTRS)

Martin, Richard D. (Inventor); Pike, W. Thomas (Inventor)

2001-01-01

A silicon-based microaccelerometer for seismic application is provided using a low-resonant frequency (10 Hz), large proof mass (1 gram), and high Q suspension to achieve high sensitivity of less than 1 ng with a bandwidth a 0.05 to 50 Hz. The proof mass is cut away from a planar substrate in the form of a disk using abrasive cutting, which disk closely fits but does not touch a surrounding angular frame. The spring of the microaccelerometer between the angular frame and the proof mass is provided from two continuous, 3 microns thick membranes. The fixed capacitive electrodes are provided on separate, subsequently bonded substrates, and movable capacitive plates are provided on the membranes. By fabricating capacitive plates on the separate substrates, the gap between the fixed and movable capacitive plates in the differential capacitive sensor is closely controlled. The use of continuous membranes for the spring produces a shock resistant, robust sensor.

Note: a novel vacuum ultraviolet light source assembly with aluminum-coated electrodes for enhancing the ionization efficiency of photoionization mass spectrometry.

PubMed

Zhu, Zhixiang; Wang, Jian; Qiu, Keqing; Liu, Chengyuan; Qi, Fei; Pan, Yang

2014-04-01

A novel vacuum ultraviolet (VUV) light source assembly (VUVLSA) for enhancing the ionization efficiency of photoionization mass spectrometer has been described. The VUVLSA composes of a Krypton lamp and a pair of disk electrodes with circular center cavities. The two interior surfaces that face the photoionization region were aluminum-coated. VUV light can be reflected back and forth in the photoionization region between the electrodes, thus the photoionization efficiency can be greatly enhanced. The performances of two different shaped electrodes, the coated double flat electrodes (DFE), and double conical electrodes, were studied. We showed that the signal amplification of coated DFE is around 4 times higher than that of uncoated electrodes without VUV light reflection. The relationship between the pressure of ionization chamber and mass signal enhancement has also been studied.

MULTI-PLATE IONIZATION CHAMBER FOR THE DETECTION OF SLOW NEUTRONS

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

Bubzanowski, A.; Grotowski, K.

1957-01-01

A description is given of an ionization chamber, the electrodes of which are coated with a layer of natural boron of thickness 3 mg/cm/sup 2/. Each electrode of the chamber consists of three disks, placed between plates of the other electrodes. The capacitance between the electrodes does not exceed 15 micromicrofarads. The technology of coating the layer is as follows: the boron is mixed with alcohol and a small amount of Canada balsam and is coated in the form of an emulsion on the plates. The chamber efficiency is approximately 2%. The filler is argon at atmospheric pressure. The durationmore » of the output pulses after forming is approximately 5 microseconds.« less

Pulse-voltammetric glucose detection at gold junction electrodes.

PubMed

Rassaei, Liza; Marken, Frank

2010-09-01

A novel glucose sensing concept based on the localized change or "modulation" in pH within a symmetric gold-gold junction electrode is proposed. A paired gold-gold junction electrode (average gap size ca. 500 nm) is prepared by simultaneous bipotentiostatic electrodeposition of gold onto two closely spaced platinum disk electrodes. For glucose detection in neutral aqueous solution, the potential of the "pH-modulator" electrode is set to -1.5 V vs saturated calomel reference electrode (SCE) to locally increase the pH, and simultaneously, either cyclic voltammetry or square wave voltammetry experiments are conducted at the sensor electrode. A considerable improvement in the sensor electrode response is observed when a normal pulse voltammetry sequence is applied to the modulator electrode (to generate "hydroxide pulses") and the glucose sensor electrode is operated with fixed bias at +0.5 V vs SCE (to eliminate capacitive charging currents). Preliminary data suggest good linearity for the glucose response in the medically relevant 1-10 mM concentration range (corresponding to 0.18-1.8 g L(-1)). Future electroanalytical applications of multidimensional pulse voltammetry in junction electrodes are discussed.

Rotating disk electrodes to assess river biofilm thickness and elasticity.

PubMed

Boulêtreau, Stéphanie; Charcosset, Jean-Yves; Gamby, Jean; Lyautey, Emilie; Mastrorillo, Sylvain; Azémar, Frédéric; Moulin, Frédéric; Tribollet, Bernard; Garabetian, Frédéric

2011-01-01

The present study examined the relevance of an electrochemical method based on a rotating disk electrode (RDE) to assess river biofilm thickness and elasticity. An in situ colonisation experiment in the River Garonne (France) in August 2009 sought to obtain natural river biofilms exhibiting differentiated architecture. A constricted pipe providing two contrasted flow conditions (about 0.1 and 0.45 m s(-1) in inflow and constricted sections respectively) and containing 24 RDE was immersed in the river for 21 days. Biofilm thickness and elasticity were quantified using an electrochemical assay on 7 and 21 days old RDE-grown biofilms (t(7) and t(21), respectively). Biofilm thickness was affected by colonisation length and flow conditions and ranged from 36 ± 15 μm (mean ± standard deviation, n = 6) in the fast flow section at t(7) to 340 ± 140 μm (n = 3) in the slow flow section at t(21). Comparing the electrochemical signal to stereomicroscopic estimates of biofilms thickness indicated that the method consistently allowed (i) to detect early biofilm colonisation in the river and (ii) to measure biofilm thickness of up to a few hundred μm. Biofilm elasticity, i.e. biofilm squeeze by hydrodynamic constraint, was significantly higher in the slow (1300 ± 480 μm rpm(1/2), n = 8) than in the fast flow sections (790 ± 350 μm rpm(1/2), n = 11). Diatom and bacterial density, and biofilm-covered RDE surface analyses (i) confirmed that microbial accrual resulted in biofilm formation on the RDE surface, and (ii) indicated that thickness and elasticity represent useful integrative parameters of biofilm architecture that could be measured on natural river assemblages using the proposed electrochemical method. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

Wang, Li-Fang; Ou, Chin-Ching; Striebel, Kathryn A.

The goal of this research was to measure Mn dissolution from a thin porous spinel LiMn{sub 2}O{sub 4} electrode by rotating ring-disk collection experiments. The amount of Mn dissolution from the spinel LiMn{sub 2}O{sub 4} electrode under various conditions was detected by potential step chronoamperometry. The concentration of dissolved Mn was found to increase with increasing cycle numbers and elevated temperature. The dissolved Mn was not dependent on disk rotation speed, which indicated that the Mn dissolution from the disk was under reaction control. The in situ monitoring of Mn dissolution from the spinel was carried out under various conditions.more » The ring currents exhibited maxima corresponding to the end-of-charge (EOC) and end-of-discharge (EOD), with the largest peak at EOC. The results suggest that the dissolution of Mn from spinel LiMn{sub 2}O{sub 4} occurs during charge/discharge cycling, especially in a charged state (at >4.1 V) and in a discharged state (at <3.1 V). The largest peak at EOC demonstrated that Mn dissolution took place mainly at the top of charge. At elevated temperatures, the ring cathodic currents were larger due to the increase of Mn dissolution rate.« less

The rhythms of predictive coding? Pre-stimulus phase modulates the influence of shape perception on luminance judgments

PubMed Central

Han, Biao; VanRullen, Rufin

2017-01-01

Predictive coding is an influential model emphasizing interactions between feedforward and feedback signals. Here, we investigated the temporal dynamics of these interactions. Two gray disks with different versions of the same stimulus, one enabling predictive feedback (a 3D-shape) and one impeding it (random-lines), were simultaneously presented on the left and right of fixation. Human subjects judged the luminance of the two disks while EEG was recorded. The choice of 3D-shape or random-lines as the brighter disk was used to assess the influence of feedback signals on sensory processing in each trial (i.e., as a measure of post-stimulus predictive coding efficiency). Independently of the spatial response (left/right), we found that this choice fluctuated along with the pre-stimulus phase of two spontaneous oscillations: a ~5 Hz oscillation in contralateral frontal electrodes and a ~16 Hz oscillation in contralateral occipital electrodes. This pattern of results demonstrates that predictive coding is a rhythmic process, and suggests that it could take advantage of faster oscillations in low-level areas and slower oscillations in high-level areas. PMID:28262824

Annual AFOSR Chemistry Program Review (19th)

DTIC Science & Technology

1974-01-01

Chem., 42, 161 (1973). "A Rotating Ring Disk Electrode Study of the Adsorption of Lead on Gold in 0.5M Potassium Chloride," V. A. Vicente and S...Gold," D. F. Untereker and S. Bruckenstein, in preparation. "A Rotating Ring-Disk Study of the Adsorption of Thallium on Gold in 0.5H Potassium ... polyacrylic acid, and polydiallyl- phthalate. This paper will only cite the work on the photolysis of polydiallylphthalate. (PDAP). 70 The goal of this

Tremella-like graphene-Au composites used for amperometric determination of dopamine.

PubMed

Li, Cong; Zhao, Jingyu; Yan, Xiaoyi; Gu, Yue; Liu, Weilu; Tang, Liu; Zheng, Bo; Li, Yaru; Chen, Ruixue; Zhang, Zhiquan

2015-03-21

Electrochemical detection of dopamine (DA) plays an important role in medical diagnosis. In this paper, tremella-like graphene-Au (t-GN-Au) composites were synthesized by a one-step hydrothermal method for selective detection of DA. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterize as-prepared t-GN-Au composites. The t-GN-Au composites were directly used for the determination of DA via cyclic voltammetry (CV) and the chronoamperometry (CA) technique. CA measurement gave a wide linear range from 0.8 to 2000 μM, and the detection limit of 57 nM (S/N = 3) for DA. The mechanism and the heterogeneous electron transfer kinetics of the DA oxidation were discussed in the light of rotating disk electrode (RDE) experiments. Moreover, the modified electrode was applied to the determination of DA in human urine and serum samples.

Determination of phenolic constituents of biological interest in red wine by capillary electrophoresis with electrochemical detection.

PubMed

Peng, Youyuan; Chu, Qingcui; Liu, Fanghua; Ye, Jiannong

2004-01-28

A simultaneous determination of trans-resveratrol, (-)-epicatechin, and (+)-catechin in red wine by capillary electrophoresis with electrochemical detection (CE-ED) is reported. The effects of the potential of the working electrode, pH and concentration of running buffer, separation voltage, and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 100 mmol/L borate buffer (pH 9.2) within 20 min. A 300 microm diameter carbon disk electrode has a good response at +0.85 V (vs SCE) for all analytes. The response was linear over 3 orders of magnitude with detection limit (S/N = 3) ranging from 2 x 10(-7) to 5 x 10(-7) g/mL for all analytes. This method has been used for the determination of these analytes in red wine without enrichment, and the assay result was satisfactory.

Molecular Diagnostics for the Study of Hypersonic Flows

DTIC Science & Technology

2000-04-01

between the at the F4 high-enthalpy wind tunnel [21]. Figure 5 electrodes. The fast electrons exit the anode disk shows the image acquired 90 ms after...Discharge Figure 5 Typical F4 run, flow at 90 ms , Grounded Electrode convection imaged 5 jis after beam emission. Figure 4 Schematic diagram of the...accounts for the classical phenomena like absorption and Figure 6 Velocity profile at 90 ms for run of refraction. X(2) is the second-order

Compact, Portable Pulsed-Power

DTIC Science & Technology

2006-08-31

adding this fast pulse to a slow, 30kV pulse which is below the threshold for significant corona emission. This scheme is presently being explored with...the smaller stressed electrode area. Further results from these systems were reported at the 2006 Power Modulator Conference in Washington, D.C...BLT and the medium-BLT is similar. The mini BLT electrodes are made of 3 mm thick molybdenum disks with a 3 mm central hole, capped on a hollow OFHC 1

Electrochemical properties of electrodes with different shapes and diffusion kinetic analysis of microbial fuel cells on ocean floor

NASA Astrophysics Data System (ADS)

Fu, Yubin; Liu, Jia; Su, Jia; Zhao, Zhongkai; Liu, Yang; Xu, Qian

2012-03-01

Microbial fuel cell (MFC) on the ocean floor is a kind of novel energy- harvesting device that can be developed to drive small instruments to work continuously. The shape of electrode has a great effect on the performance of the MFC. In this paper, several shapes of electrode and cell structure were designed, and their performance in MFC were compared in pairs: Mesh (cell-1) vs. flat plate (cell-2), branch (cell-3) vs. cylinder (cell-4), and forest (cell-5) vs. disk (cell-6) FC. Our results showed that the maximum power densities were 16.50, 14.20, 19.30, 15.00, 14.64, and 9.95 mWm-2 for cell-1, 2, 3, 4, 5 and 6 respectively. And the corresponding diffusion-limited currents were 7.16, 2.80, 18.86, 10.50, 18.00, and 6.900 mA. The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes. The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former's extended solid/liquid/gas three-phase boundary. These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC, and the differences in the electrode shape lead to the differences in cell performance. These results would be useful for MFC structure design in practical applications.

Apparatus for Screening Multiple Oxygen-Reduction Catalysts

NASA Technical Reports Server (NTRS)

Whitacre, Jay; Narayanan, Sekharipuram

2009-01-01

An apparatus that includes an array of multiple electrodes has been invented as a means of simultaneously testing multiple materials for their utility as oxygen-reduction catalysts in fuel cells. The apparatus ensures comparability of test results by exposing all the catalyst-material specimens to the same electrolytic test solution at the same potential. Heretofore, it has been possible to test only one specimen at a time, using a precise rotating disk electrode that provides a controlled flux of solution to the surface of the specimen.

PLASMA DEVICE

DOEpatents

Baker, W.R.; Brathenahl, A.; Furth, H.P.

1962-04-10

A device for producing a confined high temperature plasma is described. In the device the concave inner surface of an outer annular electrode is disposed concentrically about and facing the convex outer face of an inner annular electrode across which electrodes a high potential is applied to produce an electric field there between. Means is provided to create a magnetic field perpendicular to the electric field and a gas is supplied at reduced pressure in the area therebetween. Upon application of the high potential, the gas between the electrodes is ionized, heated, and under the influence of the electric and magnetic fields there is produced a rotating annular plasma disk. The ionized plasma has high dielectric constant properties. The device is useful as a fast discharge rate capacitor, in controlled thermonuclear research, and other high temperature gas applications. (AEC)

Utility of CT-compatible EEG electrodes in critically ill children.

PubMed

Abend, Nicholas S; Dlugos, Dennis J; Zhu, Xiaowei; Schwartz, Erin S

2015-04-01

Electroencephalographic monitoring is being used with increasing frequency in critically ill children who may require frequent and sometimes urgent brain CT scans. Standard metallic disk EEG electrodes commonly produce substantial imaging artifact, and they must be removed and later reapplied when CT scans are indicated. To determine whether conductive plastic electrodes caused artifact that limited CT interpretation. We describe a retrospective cohort of 13 consecutive critically ill children who underwent 17 CT scans with conductive plastic electrodes during 1 year. CT images were evaluated by a pediatric neuroradiologist for artifact presence, type and severity. All CT scans had excellent quality images without artifact that impaired CT interpretation except for one scan in which improper wire placement resulted in artifact. Conductive plastic electrodes do not cause artifact limiting CT scan interpretation and may be used in critically ill children to permit concurrent electroencephalographic monitoring and CT imaging.

Oxygen reduction reaction on stepped platinum surfaces in alkaline media.

PubMed

Rizo, Ruben; Herrero, Enrique; Feliu, Juan M

2013-10-07

The oxygen reduction reaction (ORR) in 0.1 M NaOH on platinum single crystal electrodes has been studied using hanging meniscus rotating disk electrode configuration. Basal planes and stepped surfaces with (111) and (100) terraces have been employed. The results indicate that the Pt(111) electrode has the highest electrocatalytic activity among all the studied surfaces. The addition of steps on this electrode surface significantly diminishes the reactivity of the surface towards the ORR. In fact, the reactivity of the steps on the surfaces with wide terraces can be considered negligible with respect to that measured for the terrace. On the other hand, Pt(100) and Pt(110) electrodes have much lower activity than the Pt(111) electrode. These results have been compared with those obtained in acid media to understand the effect of the pH and the adsorbed OH on the mechanism. It is proposed that the surface covered by adsorbed OH is active for the reduction of the oxygen molecules.

Screening of redox couples and electrode materials

NASA Technical Reports Server (NTRS)

Giner, J.; Swette, L.; Cahill, K.

1976-01-01

Electrochemical parameters of selected redox couples that might be potentially promising for application in bulk energy storage systems were investigated. This was carried out in two phases: a broad investigation of the basic characteristics and behavior of various redox couples, followed by a more limited investigation of their electrochemical performance in a redox flow reactor configuration. In the first phase of the program, eight redox couples were evaluated under a variety of conditions in terms of their exchange current densities as measured by the rotating disk electrode procedure. The second phase of the program involved the testing of four couples in a redox reactor under flow conditions with a varity of electrode materials and structures.

New Electrochemical Methods for Studying Nanoparticle Electrocatalysis and Neuronal Exocytosis

NASA Astrophysics Data System (ADS)

Cox, Jonathan T.

This dissertation presents the construction and application of micro and nanoscale electrodes for electroanalytical analysis. The studies presented herein encompass two main areas: electrochemical catalysis, and studies of the dynamics of single cell exocytosis. The first portion of this dissertation engages the use of Pt nanoelectrodes to study the stability and electrocatalytic properties of materials. A single nanoparticle electrode (SNPE) was fabricated by immobilizing a single Au nanoparticle on a Pt disk nanoelectrode via an amine-terminated silane cross linker. In this manner we were able to effectively study the electrochemistry and electrocatalytic activity of single Au nanoparticles and found that the electrocatalytic activity is dependent on nanoparticle size. This study can further the understanding of the structure-function relationship in nanoparticle based electrocatalysis. Further work was conducted to probe the stability of Pt nanoelectrodes under conditions of potential cycling. Pt based catalysts are known to deteriorate under such conditions due to losses in electrochemical surface area and Pt dissolution. By using Pt disk nanoelectrodes we were able to study Pt dissolution via steady-state voltammetry. We observed an enhanced dissolution rate and higher charge density on nanoelectrodes than that previously found on macro scale electrodes. The goal of the second portion of this dissertation is to develop new analytical methods to study the dynamics of exocytosis from single cells. The secretion of neurotransmitters plays a key role in neuronal communication, and our studies highlight how bipolar electrochemistry can be employed to enhance detection of neurotransmitters from single cells. First, we developed a theory to quantitatively characterize the voltammetric behavior of bipolar carbon fiber microelectrodes and secondly applied those principles to single cell detection. We showed that by simply adding an additional redox mediator to the back-fill solution of a carbon fiber microelectrode, there is a significant enhancement in detection. Additionally we used solid state nanopores to detect individual phospholipid vesicles in solution. Vesicles are key cellular components that play essential biological roles especially in neurotransmission. This work represents preliminary studies in detection and size determination from vesicles isolated from individual cells.

Functionalized Cobalt Triarylcorrole Covalently Bonded with Graphene Oxide: A Selective Catalyst for the Two- or Four-Electron Reduction of Oxygen.

PubMed

Tang, Jijun; Ou, Zhongping; Guo, Rui; Fang, Yuanyuan; Huang, Dong; Zhang, Jing; Zhang, Jiaoxia; Guo, Song; McFarland, Frederick M; Kadish, Karl M

2017-08-07

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV-vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H 2 SO 4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O 2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.

Sampling for silver nanoparticles in aqueous media using a rotating disk electrode: evidence for selective sampling of silver nanoparticles in the presence of ionic silver.

PubMed

Steinberg, Spencer; Hodge, Vernon; Schumacher, Brian; Sovocool, Wayne

2017-03-01

Amendment of a carbon paste electrode consisting of graphite and Nujol®, with a variety of organic and inorganic materials, allows direct adsorption of silver nanoparticles (AgNPs) from aqueous solution in either open or close circuit modes. The adsorbed AgNPs are detected by stripping voltammetry. Detection limits of less than 1 ppb Ag are achievable with a rotating disk system. More than one silver peak was apparent in many of the stripping voltammograms. The appearance of multiple peaks could be due to different species of silver formed upon stripping or variation in the state of aggregation or size of nanoparticles. With most of these packing materials, dissolved Ag + was also extracted from aqueous solution, but, with a packing material made with Fe(II,III) oxide nanoparticles, only AgNPs were extracted. Therefore, it is the best candidate for determination of metallic AgNPs in aqueous environmental samples without interference from Ag + .

Observation of a spark channel generated in water with shock wave assistance in plate-to-plate electrode configuration

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

Stelmashuk, V., E-mail: vitalij@ipp.cas.cz

2014-01-15

When a high voltage pulse with an amplitude of 30 kV is applied to a pair of disk electrodes at a time when a shock wave is passing between them, an electrical spark is generated. The dynamic changes in the spark morphology are studied here using a high-speed framing camera. The primary result of this work is the provision of experimental evidence of plasma instability that was observed in the channel of the electric spark.

Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

NASA Astrophysics Data System (ADS)

Chong-Lin, Jia; Chang-Chun, Ge; Qing-Zhi, Yan

2016-02-01

Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

Magnetic modulation of inverse spin Hall effect in lateral spin-valves

NASA Astrophysics Data System (ADS)

Andrianov, T.; Vedyaev, A.; Dieny, B.

2018-05-01

We analytically investigated the spin-dependent transport properties in a lateral spin-valve device comprising pinned ferromagnetic electrodes allowing the injection of a spin current in a spin conducting channel where spin orbit scattering takes place. This produces an inverse spin Hall (ISHE) voltage across the thickness of the spin conducting channel. It is shown that by adding an extra soft ferromagnetic electrode with rotatable magnetization along the spin conducting channel, the ISHE generated voltage can be magnetically modulated by changing the magnetization orientation of this additional electrode. The dependence of the ISHE voltage on the direction of magnetization of the ferromagnetic electrode with rotatable magnetization was calculated in various configurations. Our results suggest that such structures could be considered as magnetic field sensors in situations where the total thickness of the sensor is constrained such as in hard disk drive readers.

Fabrication of Carbon-Platinum Interdigitated Array Electrodes and Their Application for Investigating Homogeneous Hydrogen Evolution Catalysis

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

Liu, Fei; Divan, Ralu; Parkinson, Bruce A.

2015-06-29

Carbon interdigitated array (IDA) electrodes have been applied to study the homogeneous hydrogen evolution electrocatalyst [Ni(PPh2NBn2)2]2+ (where PPh2NBn2 is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane). The existence of reaction intermediates in the catalytic cycle is inferred from the electrochemical behavior of a glassy carbon disk electrodes and carbon IDA electrodes. The currents on IDA electrodes for an EC’ (electron transfer reaction followed by a catalytic reaction) mechanism are derived from the number of redox cycles and the contribution of non-catalytic currents. The catalytic reaction rate constant was then extracted from the IDA current equations. Applying the IDA current and kinetic equations to the electrochemical responsemore » of the [Ni(PPh2NBn2)2]2+ catalyst yielded a rate constant of 0.10 s-1 for the hydrogen evolution reaction that agrees with the literature value. The quantitative analysis of IDA cyclic voltammetry can be used as a simple and straightforward method for determining rate constants in other catalytic systems. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE. Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.« less

Electrical characteristic of the titanium mesh electrode for transcutaneous intrabody communication to monitor implantable artificial organs.

PubMed

Okamoto, Eiji; Kikuchi, Sakiko; Mitamura, Yoshinori

2016-09-01

We have developed a tissue-inducing electrode using titanium mesh to obtain mechanically and electrically stable contact with the tissue for a new transcutaneous communication system using the human body as a conductive medium. In this study, we investigated the electrical properties of the titanium mesh electrode by measuring electrode-tissue interface resistance in vivo. The titanium mesh electrode (Hi-Lex Co., Zellez, Hyogo, Japan) consisted of titanium fibers (diameter of 50 μm), and it has an average pore size of 200 μm and 87 % porosity. The titanium mesh electrode has a diameter of 5 mm and thickness of 1.5 mm. Three titanium mesh electrodes were implanted separately into the dorsal region of the rat. We measured the electrode-electrode impedance using an LCR meter for 12 weeks, and we calculated the tissue resistivity and electrode-tissue interface resistance. The electrode-tissue interface resistance of the titanium mesh electrode decreased slightly until the third POD and then continuously increased to 75 Ω. The electrode-tissue interface resistance of the titanium mesh electrode is stable and it has lower electrode-tissue interface resistance than that of a titanium disk electrode. The extracted titanium mesh electrode after 12 weeks implantation was fixed in 10 % buffered formalin solution and stained with hematoxylin-eosin. Light microscopic observation showed that the titanium mesh electrode was filled with connective tissue, inflammatory cells and fibroblasts with some capillaries in the pores of the titanium mesh. The results indicate that the titanium mesh electrode is a promising electrode for the new transcutaneous communication system.

Photocatalytic properties of PbS/graphene oxide/polyaniline electrode for hydrogen generation.

PubMed

Shaban, Mohamed; Rabia, Mohamed; El-Sayed, Asmaa M Abd; Ahmed, Aya; Sayed, Somaya

2017-10-26

In this work, roll-graphene oxide (Ro-GO), polyaniline (PANI) nano/microparticles, and PbS nanoparticles were prepared by modified Hammer, oxidative polymerization, and chemical bath deposition methods, respectively. These nano/microstructures were characterized, optimized, and designed to form PbS/Ro-GO/PANI nano/microcomposite. Also, the ratios of PbS and Ro-GO were optimized, and the optimized composition of the used composite was 0.4 g PANI, 0.125 g Ro-GO, and 0.075 g PbS. The band gap values for PANI, PbS, Ro-GO, and PbS/Ro-GO/PANI rocomposite were 3, 1.13, 2.86, (1.16, 2) eV, respectively. Two photoelectrode assemblies, Au/PbS/Ro-GO/PANI and PbS/Ro-GO/PANI/ITO/glass were used for the photoelectrochemical (PEC) hydrogen generation. In the first assembly 45 nm- Au layer was sputtered on the surface of a disk of PbS/Ro-GO/PANI composite. For the second assembly, a disk of PbS/Ro-GO/PANI composite was glued on ITO glass using Ag-THF paste. The lifetime efficiency values were 64.2 and 43.4% for the first and second electrode for 2 h, respectively. Finally, the incident photon-to-current conversion efficiency (IPCE) and photon-to-current efficiency (ABPE) were calculated under monochromatic illumination conditions. The optimum IPCE efficiency at 390 nm was 9.4% and 16.17%, whereas ABPE % efficiency was 1.01% and 1.75% for Au/PbS/Ro-GO/PANI and PbS/Ro-GO/PANI/ITO/glass, respectively.

Rotating disk electrode study of borohydride oxidation in a molten eutectic electrolyte and advancements in the intermediate temperature borohydride battery

NASA Astrophysics Data System (ADS)

Wang, Andrew; Gyenge, Előd L.

2017-08-01

The electrode kinetics of the NaBH4 oxidation reaction (BOR) in a molten NaOH-KOH eutectic mixture is investigated by rotating disk electrode (RDE) voltammetry on electrochemically oxidized Ni at temperatures between 458 K and 503 K. The BH4- diffusion coefficient in the molten alkali eutectic together with the BOR activation energy, exchange current density, transfer coefficient and number of electrons exchanged, are determined. Electrochemically oxidized Ni shows excellent BOR electrocatalytic activity with a maximum of seven electrons exchanged and a transfer coefficient up to one. X-ray photoelectron spectroscopy (XPS) reveals the formation of NiO as the catalytically active species. The high faradaic efficiency and BOR rate on oxidized Ni anode in the molten electrolyte compared to aqueous alkaline electrolytes is advantageous for power sources. A novel molten electrolyte battery design is investigated using dissolved NaBH4 at the anode and immobilized KIO4 at the cathode. This battery produces a stable open-circuit cell potential of 1.04 V, and a peak power density of 130 mW cm-2 corresponding to a superficial current density of 160 mA cm-2 at 458 K. With further improvements and scale-up borohydride molten electrolyte batteries and fuel cells could be integrated with thermal energy storage systems.

Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction.

PubMed

Parnell, Charlette M; Chhetri, Bijay; Brandt, Andrew; Watanabe, Fumiya; Nima, Zeid A; Mudalige, Thilak K; Biris, Alexandru S; Ghosh, Anindya

2016-08-16

Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material's -0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 10(6) mol(-1)s(-1) was observed for the polydopamine-coated material-over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells.

Impedance analysis of a disk-type SOFC using doped lanthanum gallate under power generation

NASA Astrophysics Data System (ADS)

Kato, Tohru; Nozaki, Ken; Negishi, Akira; Kato, Ken; Monma, Akihiko; Kaga, Yasuo; Nagata, Susumu; Takano, Kiyonami; Inagaki, Toru; Yoshida, Hiroyuki; Hosoi, Kei; Hoshino, Koji; Akbay, Taner; Akikusa, Jun

Impedance measurements were carried out under practical power generation conditions in a disk-type SOFC, which may be utilized as a small-scale power generator. The tested cell was composed of doped lanthanum gallate (La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3- δ) as the electrolyte, Sm 0.5Sr 0.5CoO 3 as the cathode electrode and Ni/Ce 0.8Sm 0.2O 2 cermet as the anode electrode. The cell impedance was measured between 10 mHz and 10 kHz by varying the fuel utilization and gas flow rate and plotted in complex impedance diagrams. The observed impedance shows a large semi-circular pattern on the low frequency side. The semi-circular impedance, having a noticeably low characteristic frequency between 0.13 and 0.4 Hz, comes from the change in gas composition, originally caused by the cell reaction. The change in impedance with the fuel utilization (load current) and the gas flow rate agreed qualitatively well with the theoretical predictions from a simulation. This impedance was dominant under high fuel-utilization power-generation conditions. The impedance, which described the activation polarizations in the electrode reactions, was comparatively small and scarcely changed with the change in fuel utilization (load current) and gas flow rate.

Role of Additives in Minimizing Zinc Electrode Shape Change: The Effect of Lead on the Kinetics of Zn(II) Reduction in Concentrated Alkaline Media.

DTIC Science & Technology

1985-07-01

adherent, and showed excellent physical stability. U -12- 4. RESULTS AND DISCUSSION 4.1 CYCLIC VOLTAMETRY AT A SILVER DISK ELECTRODE Silver screens are...45% KOH containing 5.5% ZnO is shown in Figure 17A. Several sweeps are recorded at scan rates of 10, 20, 50, 100, 200, and 500 mV/s with the highest...voltammetry curves is difficult since the anodic peak depends on the amount of metal deposition in the previous cathodic sweep (16).) The peak currents versus

A label-free impedimetric DNA sensing chip integrated with AC electroosmotic stirring.

PubMed

Wu, Ching-Chou; Yang, Dong-Jie

2013-05-15

AC electroosmosis (ACEO) flow and label-free electrochemical impedance spectroscopy are employed to increase the hybridization rate and specifically detect target DNA (tDNA) concentrations. A low-ionic-strength solution, 6.1μS/cm 1mM Tris (pH 9.3), was used to produce ACEO and proved the feasibility of hybridization. Adequate voltage parameters for the simultaneous ACEO driving and DNA hybridization in the 1mM Tris solution were 1.5 Vpp and 200Hz. Moreover, an electrode set with a 1:4 ring width-to-disk diameter ratio exhibited a larger ACEO velocity above the disk electrode surface to improve collecting efficiency. The ACEO-integrated DNA sensing chips could reach 90% saturation hybridization within 117s. The linear range and detection limit of the sensors was 10aM-10pM and 10aM, respectively. The label-free impedimetric DNA sensing chips with integrated ACEO stirring can perform rapid hybridization and highly-sensitive detections to specifically measure tDNA concentrations. Copyright © 2013 Elsevier B.V. All rights reserved.

Mass transport at rotating disk electrodes: effects of synthetic particles and nerve endings.

PubMed

Chiu, Veronica M; Lukus, Peter A; Doyle, Jamie L; Schenk, James O

2011-11-01

An unstirred layer (USL) exists at the interface of solids with solutions. Thus, the particles in brain tissue preparations possess a USL as well as at the surface of a rotating disk electrode (RDE) used to measure chemical fluxes. Time constraints for observing biological kinetics based on estimated thicknesses of USLs at the membrane surface in real samples of nerve endings were estimated. Liposomes, silica, and Sephadex were used separately to model the tissue preparation particles. Within a solution stirred by the RDE, both diffusion and hydrodynamic boundary layers are formed. It was observed that the number and size of particles decreased the following: the apparent diffusion coefficient excluding Sephadex, boundary layer thicknesses excluding silica, sensitivity excluding diluted liposomes (in agreement with results from other laboratories), limiting current potentially due to an increase in the path distance, and mixing time. They have no effect on the detection limit (6 ± 2 nM). The RDE kinetically resolves transmembrane transport with a timing of approximately 30 ms. Copyright © 2011 Elsevier Inc. All rights reserved.

Anodic concentration loss and impedance characteristics in rotating disk electrode microbial fuel cells.

PubMed

Shen, Liye; Ma, Jingxing; Song, Pengfei; Lu, Zhihao; Yin, Yao; Liu, Yongdi; Cai, Lankun; Zhang, Lehua

2016-10-01

A rotating disk electrode (RDE) was used to investigate the concentration loss and impedance characteristics of anodic biofilms in microbial fuel cells (MFCs). Amperometric time-current analysis revealed that at the rotation rate of 480 rpm, a maximum current density of 168 µA cm(-2) can be achieved, which was 22.2 % higher than when there was no rotation. Linear sweep voltammetry and electrochemical impedance spectroscopy tests showed that when the anodic potential was set to -300 mV vs. Ag/AgCl reference, the power densities could increase by 59.0  %, reaching 1385 mW m(-2), the anodic resistance could reduce by 19  %, and the anodic capacitance could increase by 36 %. These results concur with a more than 85 % decrease of the diffusion layer thickness. Data indicated that concentration loss, diffusion layer thickness, and the mixing velocity play important roles in anodic resistance reduction and power output of MFCs. These findings could be helpful to the design of future industrial-scale MFCs with mixed bacteria biofilms.

Metal molybdate nanorods as non-precious electrocatalysts for the oxygen reduction

NASA Astrophysics Data System (ADS)

Wu, Tian; Zhang, Lieyu

2015-12-01

Development of non-precious electrocatalysts with applicable electrocatalytic activity towards the oxygen reduction reaction (ORR) is important to fulfill broad-based and large-scale applications of metal/air batteries and fuel cells. Herein, nickel and cobalt molybdates with uniform nanorod morphology are synthesized using a facile one-pot hydrothermal method. The ORR activity of the prepared metal molybdate nanorods in alkaline media are investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperomety in rotating disk electrode (RDE) techniques. The present study suggests that the prepared metal molybdate nanorods exhibit applicable electrocatalytic activities towards the ORR in alkaline media, promising the applications as non-precious cathode in fuel cells and metal-air batteries.

The alkaline zinc electrode as a mixed potential system

NASA Technical Reports Server (NTRS)

Fielder, W. L.

1979-01-01

Cathodic and anodic processes for the alkaline zinc electrode in 0.01 molar zincate electrolyte (9 molar hydroxide) were investigated. Cyclic voltammograms and current-voltage curves were obtained by supplying pulses through a potentiostat to a zinc rotating disk electrode. The data are interpreted by treating the system as one with a mixed potential; the processes are termed The zincate and corrosion reactions. The relative proportions of the two processes vary with the supplied potential. For the cathodic region, the cathodic corrosion process predominates at higher potentials while both processes occur simultaneously at a lower potential (i.e., 50 mV). For the anodic region, the anodic zincate process predominates at higher potentials while the anodic corrosion process is dominant at lower potential (i.e., 50 mV) if H2 is present.

Logic operations based on magnetic-vortex-state networks.

PubMed

Jung, Hyunsung; Choi, Youn-Seok; Lee, Ki-Suk; Han, Dong-Soo; Yu, Young-Sang; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

2012-05-22

Logic operations based on coupled magnetic vortices were experimentally demonstrated. We utilized a simple chain structure consisting of three physically separated but dipolar-coupled vortex-state Permalloy disks as well as two electrodes for application of the logical inputs. We directly monitored the vortex gyrations in the middle disk, as the logical output, by time-resolved full-field soft X-ray microscopy measurements. By manipulating the relative polarization configurations of both end disks, two different logic operations are programmable: the XOR operation for the parallel polarization and the OR operation for the antiparallel polarization. This work paves the way for new-type programmable logic gates based on the coupled vortex-gyration dynamics achievable in vortex-state networks. The advantages are as follows: a low-power input signal by means of resonant vortex excitation, low-energy dissipation during signal transportation by selection of low-damping materials, and a simple patterned-array structure.

Chemical fabrication of heterometallic nanogaps for molecular transport junctions.

PubMed

Chen, Xiaodong; Yeganeh, Sina; Qin, Lidong; Li, Shuzhou; Xue, Can; Braunschweig, Adam B; Schatz, George C; Ratner, Mark A; Mirkin, Chad A

2009-12-01

We report a simple and reproducible method for fabricating heterometallic nanogaps, which are made of two different metal nanorods separated by a nanometer-sized gap. The method is based upon on-wire lithography, which is a chemically enabled technique used to synthesize a wide variety of nanowire-based structures (e.g., nanogaps and disk arrays). This method can be used to fabricate pairs of metallic electrodes, which exhibit distinct work functions and are separated by gaps as small as 2 nm. Furthermore, we demonstrate that a symmetric thiol-terminated molecule can be assembled into such heterometallic nanogaps to form molecular transport junctions (MTJs) that exhibit molecular diode behavior. Theoretical calculations demonstrate that the coupling strength between gold and sulfur (Au-S) is 2.5 times stronger than that of Pt-S. In addition, the structures form Raman hot spots in the gap, allowing the spectroscopic characterization of the molecules that make up the MTJs.

Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

PubMed

Pullamsetty, Ashok; Sundara, Ramaprabhu

2016-10-01

Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. Copyright © 2016 Elsevier Inc. All rights reserved.

The Mochi LabJet Experiment for Measurements of Canonical Helicity Injection in a Laboratory Astrophysical Jet

NASA Astrophysics Data System (ADS)

You, Setthivoine; von der Linden, Jens; Sander Lavine, Eric; Carroll, Evan Grant; Card, Alexander; Quinley, Morgan; Azuara-Rosales, Manuel

2018-06-01

The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are ∼1022 m‑3, ∼0.4 T, and 5–25 eV, with velocities of ∼20–80 km s‑1. The combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (∼10 μs, ≳5 Alfvén times) collimated magnetic jets with a ∼10:1 aspect ratio and long-lived (∼100 μs, ≳40 Alfvén times) flow-stabilized, collimated, magnetic jets with a ∼30:1 aspect ratio.

Analyzing the electrooxidation of ethylene glycol and glucose over platinum-modified gold electrocatalysts in alkaline electrolyte using in-situ infrared spectroscopy

NASA Astrophysics Data System (ADS)

Mahoney, Elizabeth G.; Sheng, Wenchao; Cheng, Mei; Lee, Kevin X.; Yan, Yushan; Chen, Jingguang G.

2016-02-01

Platinum modified gold (Pt/Au) catalysts are evaluated for the electrooxidation of ethylene glycol (EG) and glucose (Glc). The Pt/Au catalysts are synthesized on an Au disk and supported Au/C particles through the galvanic displacement of a copper monolayer with Pt. The Pt/Au catalysts are compared to monometallic Pt and Au catalysts for the oxidation of EG and Glc in alkaline electrolyte. The Pt/Au disk has an onset potential for these reactions that is similar to Pt and is lower than Au. The supported catalysts are less active toward the electrooxidation of EG and Glc than the corresponding disk electrodes, but the Pt/Au/C also has an onset potential similar to Pt/C. In-situ FTIR is used to analyze the C-C bond scission in both reactions on the surfaces of Pt, Au, and Pt/Au disks. While the Pt/Au disk is found to have a low onset potential for the oxidation of EG, it does not produce as much CO2 as bulk Pt. On the other hand, the FTIR results show that CO2 is produced for the oxidation of Glc on the Pt/Au disk. These results show promise for the possibility of decreasing the amount of Pt needed for the electrooxidation of polyol molecules.

Correlation Of 2-Chlorobiphenyl Dechlorination By Fe/Pd With Iron Corrosion At Different pH

EPA Science Inventory

The rate of 2-chlorobiphenyl dechlorination by palladized iron (Fe/Pd) decreased with increasing pH until pH > 12.5. Iron corrosion potential (E_c) and current (j_c), obtained from polarization curves of a rotating disk electrode of iron, followed the Tafel e...

Use of a Soluble Anode in Electrodeposition of Thick Bismuth Telluride Layers

NASA Astrophysics Data System (ADS)

Maas, M.; Diliberto, S.; de Vaulx, C.; Azzouz, K.; Boulanger, C.

2014-10-01

Integration of thermoelectric devices within an automotive heat exchanger could enable conversion of lost heat into electrical energy, contributing to improved total output from the engine. For this purpose, synthesis of thick bismuth telluride (Bi2Te3) films is required. Bismuth telluride has been produced by an electrochemical method in nitric acid with a sacrificial bismuth telluride anode as the source of cations. The binary layer grows on the working electrode while the counter-electrode, a Bi2Te3 disk obtained by high frequency melting, is oxidized to BiIII and TeIV. This process leads to auto-regeneration of the solution without modification of its composition. The thickness of films deposited by use of the Bi2Te3 anode was approximately 10 times that without. To demonstrate the utility of a soluble anode in electrochemical deposition, we report characterization of the composition and morphology of the films obtained under different experimental conditions. Perfectly dense and regular Bi2Te3 films (˜400 μm) with low internal stress and uniform composition across the cross-section were prepared. Their thermoelectric properties were assessed.

Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures

NASA Astrophysics Data System (ADS)

Hu, Yang; Jiang, Yiliang; Jensen, Jens Oluf; Cleemann, Lars N.; Li, Qingfeng

2018-01-01

Phosphoric acid is the common electrolyte for high-temperature polymer electrolyte fuel cells (HT-PEMFCs) that have advantages such as enhanced CO tolerance and simplified heat and water management. The currently used rotating disk electrode technique is limited to tests in dilute solutions at low temperatures and hence is not suitable for catalyst evaluation for HT-PEMFCs. In this study, we have designed and constructed a half-cell setup to measure the intrinsic activities of catalysts towards the oxygen reduction reaction (ORR) in conditions close to HT-PEMFC cathodes. By optimization of the hydrophobic characteristics of electrodes and the catalyst layer thickness, ORR activities of typical Pt/C catalysts are successfully measured in concentrated phosphoric acid at temperatures above 100 °C. In terms of mass-specific activities, the catalyst exhibits about two times higher activity in the half-cell electrode than that observed in fuel cells, indicating the feasibility of the technique as well as the potential for further improvement of fuel cell electrode performance.

Molecular lego for the assembly of biosensing layers.

PubMed

Mano, N; Kuhn, A

2005-03-31

We propose a procedure to assemble monolayers of redox mediator, coenzyme, enzyme and stabilizing polyelectrolyte on an electrode surface using essentially electrostatic and complexing interactions. In a first step a monolayer of redox mediator, substituted nitrofluorenones, is adsorbed. In a second step, a layer of calcium cations is immobilized at the interface. It establishes a bridge between the redox mediator and the subsequently adsorbed coenzyme NAD(+). In the next step we use the intrinsic affinity of the NAD(+) monolayer for dehydrogenases to build up a multilayer composed of mediator/Ca(2+)/NAD(+)/dehydrogenase. The so obtained modified electrode can be used as a biosensor. Quartz crystal microbalance measurements allowed us to better understand the different parameters responsible for the adsorption. A more detailed investigation of the system made it possible to finally stabilize the assembly sufficiently by the adsorption of a polyelectrolyte layer in order to perform rotating disk electrode measurements with the whole supramolecular architecture on the electrode surface.

System and Method for High-Speed Data Recording

NASA Technical Reports Server (NTRS)

Taveniku, Mikael B. (Inventor)

2017-01-01

A system and method for high speed data recording includes a control computer and a disk pack unit. The disk pack is provided within a shell that provides handling and protection for the disk packs. The disk pack unit provides cooling of the disks and connection for power and disk signaling. A standard connection is provided between the control computer and the disk pack unit. The disk pack units are self sufficient and able to connect to any computer. Multiple disk packs are connected simultaneously to the system, so that one disk pack can be active while one or more disk packs are inactive. To control for power surges, the power to each disk pack is controlled programmatically for the group of disks in a disk pack.

3,4-Ethylenedioxythiophene functionalized graphene with palladium nanoparticles for enhanced electrocatalytic oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Choe, Ju Eun; Ahmed, Mohammad Shamsuddin; Jeon, Seungwon

2015-05-01

Poly(3,4-ethylenedioxythiophene) functionalized graphene with palladium nanoparticles (denoted as Pd/PEDOT/rGO) has been synthesized for electrochemical oxygen reduction reaction (ORR) in alkaline solution. The structural features of catalyst are characterized by scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The TEM images suggest a well dispersed PdNPs onto PEDOT/rGO film. The ORR activity of Pd/PEDOT/rGO has been investigated via cyclic voltammetry (CV), rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) techniques in 0.1 M KOH aqueous solution. Comparative CV analysis suggests a general approach of intermolecular charge-transfer in between graphene sheet and PdNPs via PEDOT which leads to the better PdNPs dispersion and subsequently superior ORR kinetics. The results from ORR measurements show that Pd/PEDOT/rGO has remarkable electrocatalytic activity and stability compared to Pd/rGO and state-of-the-art Pt/C. The Koutecky-Levich and Tafel analysis suggest that the proposed main path in the ORR mechanism has direct four-electron transfer process with faster transfer kinetic rate on the Pd/PEDOT/rGO.

Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

DOE PAGES

Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; ...

2016-04-11

Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstratemore » that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OH ad/O ad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.« less

Corrosion protection of reusable surgical instruments.

PubMed

Shah, Sadiq; Bernardo, Mildred

2002-01-01

To understand the corrosion properties of surgical scissors, 416 stainless steel disks and custom electrodes were used as simulated surfaces under various conditions. These simulated surfaces were exposed to tap water and 400-ppm synthetic hard water as Ca2CO3 under different conditions. The samples were evaluated by various techniques for corrosion potential and the impact of environmental conditions on the integrity of the passive film. The electrodes were used to monitor the corrosion behavior by potentiodynamic polarization technique in water both in the presence and absence of a cleaning product. The surface topography of the 416 stainless steel disks was characterized by visual observations and scanning electron microscopy (SEM), and the surface chemistry of the passive film on the surface of the scissors was characterized by x-ray photoelectron spectroscopy (XPS). The results suggest that surgical instruments made from 416 stainless steel are not susceptible to uniform corrosion; however, they do undergo localized corrosion. The use of suitable cleaning products can offer protection against localized corrosion during the cleaning step. More importantly, the use of potentiodynamic polarization techniques allowed for a quick and convenient approach to evaluate the corrosion properties of surgical instruments under a variety of simulated-use environmental conditions.

An integrated bienzyme glucose oxidase-fructose dehydrogenase-tetrathiafulvalene-3-mercaptopropionic acid-gold electrode for the simultaneous determination of glucose and fructose.

PubMed

Campuzano, Susana; Loaiza, Oscar A; Pedrero, María; de Villena, F Javier Manuel; Pingarrón, José M

2004-06-01

A bienzyme biosensor for the simultaneous determination of glucose and fructose was developed by coimmobilising glucose oxidase (GOD), fructose dehydrogenase (FDH), and the mediator, tetrathiafulvalene (TTF), by cross-linking with glutaraldehyde atop a 3-mercaptopropionic acid (MPA) self-assembled monolayer (SAM) on a gold disk electrode (AuE). The performance of this bienzyme electrode under batch and flow injection (FI) conditions, as well as an amperometric detection in high-performance liquid chromatography (HPLC), are reported. The order of enzyme immobilisation atop the MPA-SAM affected the biosensor amperometric response in terms of sensitivity, with the immobilisation order GOD, FDH, TTF being selected. Similar analytical characteristics to those obtained with single GOD or FDH SAM-based biosensors for glucose and fructose were achieved with the bienzyme electrode, indicating that no noticeable changes in the biosensor responses to the analytes occurred as a consequence of the coimmobilisation of both enzymes on the same MPA-AuE. The suitability of the bienzyme biosensor for the analysis of real samples under flow injection conditions was tested by determining glucose in two certified serum samples. The simultaneous determination of glucose and fructose in the same sample cannot be performed without a separation step because at the detection potential used (+0.10 V), both sugars show amperometric response. Consequently, HPLC with amperometric detection at the TTF-FDH-GOD-MPA-AuE was accomplished. Glucose and fructose were simultaneously determined in honey, cola softdrink, and commercial apple juice, and the results were compared with those obtained by using other reference methods.

Application of preparative disk gel electrophoresis for antigen purification from inclusion bodies.

PubMed

Okegawa, Yuki; Koshino, Masanori; Okushima, Teruya; Motohashi, Ken

2016-02-01

Specific antibodies are a reliable tool to examine protein expression patterns and to determine the protein localizations within cells. Generally, recombinant proteins are used as antigens for specific antibody production. However, recombinant proteins from mammals and plants are often overexpressed as insoluble inclusion bodies in Escherichia coli. Solubilization of these inclusion bodies is desirable because soluble antigens are more suitable for injection into animals to be immunized. Furthermore, highly purified proteins are also required for specific antibody production. Plastidic acetyl-CoA carboxylase (ACCase: EC 6.4.1.2) from Arabidopsis thaliana, which catalyzes the formation of malonyl-CoA from acetyl-CoA in chloroplasts, formed inclusion bodies when the recombinant protein was overexpressed in E. coli. To obtain the purified protein to use as an antigen, we applied preparative disk gel electrophoresis for protein purification from inclusion bodies. This method is suitable for antigen preparation from inclusion bodies because the purified protein is recovered as a soluble fraction in electrode running buffer containing 0.1% sodium dodecyl sulfate that can be directly injected into immune animals, and it can be used for large-scale antigen preparation (several tens of milligrams). Copyright © 2015 Elsevier Inc. All rights reserved.

Response of the plasma to the size of an anode electrode biased near the plasma potential

DOE PAGES

Barnat, E. V.; Laity, G. R.; Baalrud, S. D.

2014-10-01

As the size of a positively biased electrode increases, the nature of the interface formed between the electrode and the host plasma undergoes a transition from an electron-rich structure (electron sheath) to an intermediate structure containing both ion and electron rich regions (double layer) and ultimately forms an electron-depleted structure (ion sheath). In this study, measurements are performed to further test how the size of an electron-collecting electrode impacts the plasma discharge the electrode is immersed in. This is accomplished using a segmented disk electrode in which individual segments are individually biased to change the effective surface area of themore » anode. Measurements of bulk plasma parameters such as the collected current density, plasma potential, electron density, electron temperature and optical emission are made as both the size and the bias placed on the electrode are varied. Abrupt transitions in the plasma parameters resulting from changing the electrode surface area are identified in both argon and helium discharges and are compared to the interface transitions predicted by global current balance [S. D. Baalrud, N. Hershkowitz, and B. Longmier, Phys. Plasmas 14, 042109 (2007)]. While the size-dependent transitions in argon agree, the size-dependent transitions observed in helium systematically occur at lower electrode sizes than those nominally derived from prediction. Thus, the discrepancy in helium is anticipated to be caused by the finite size of the interface that increases the effective area offered to the plasma for electron loss to the electrode.« less

Electromagnetic studies of redox systems for energy storage

NASA Technical Reports Server (NTRS)

Wu, C. D.; Scherson, D.; Yeager, E.

1981-01-01

Both chromium and iron couples were studied on various electrode surfaces in acidic perchlorate solution by using rotating ring-disk techniques. It was found that chloride which forms inner sphere coordination complexes with the redox species enhances the electrode kinetics dramatically. The effects of lead underpotential deposition and surface alloy formation on the kinetics of the chromium couple on gold were studied using both linear sweep voltammetry and potential step techniques. The lad underpotential deposition was found to slow down the kinetics of the reduction of the Cr species on gold surfaces although increase the hydrogen overvoltage. The effect on the chromium kinetics can be explained in terms of principally a double layer effect. The underpotential deposition lead species with its positive charge results in a decrease in the concentration of the Cr species at the electrode surface. Similar phenomena were also observed with bismuth underpotential deposition on gold for the iron couple.

Novel Spiral-Like Electrode Structure Design for Realization of Two Modes of Energy Harvesting.

PubMed

Chen, Lin; Guo, Hengyu; Xia, Xiaona; Liu, Guanlin; Shi, Haofei; Wang, Mingjun; Xi, Yi; Hu, Chenguo

2015-08-05

A planar spiral-like electrodes (PSE) based triboelectric generator has been designed for harvesting rotary mechanical energy to translate into electricity. The performance of the PSE-triboelectric generator with different cycles of spiral-like electrode strip at different rotating speeds is investigated, which demonstrates the open-circuit voltage and short-circuit current of 470 V and 9.0 μA at rotating speed of 500 r/min with three cycles. In addition, a novel coaxially integrated multilayered PSE-triboelectric generator is built, which can enhance the output of the power effectively. The short-circuit current, the open-circuit voltage, and output power reach to 41.55 μA, 500 V, and 11.73 mW, respectively, at rotating speed of 700 r/min. The output power of the multilayered PSE-triboelectric generator can drive 200 LEDs connected in antiparallel and charge a 110 μF commercial capacitor to 6 V in 23 s. Besides, due to the spiral-like electrode structure, the PSE-generator can work simultaneously in the modes of triboelectricity and electromagnetic induced electricity by sticking a small magnet on the rotating disk. The electromagnetic induced output power reaches to 21 μW at a loading resistance of 2 Ω at a rotating rate of 200 r/min. The spiral-like electrode structure not only broadens the electrode structure design but also adds a new function to the electrode.

Design of interdigital spiral and concentric capacitive sensors for materials evaluation

NASA Astrophysics Data System (ADS)

Chen, Tianming; Bowler, Nicola

2013-01-01

This paper describes the design of two circular coplanar interdigital sensors with i) a spiral interdigital configuration and ii) a concentric interdigital configuration for the nondestructive evaluation of multilayered dielectric structures. A numerical model accounting for sensor geometry, test-piece geometry and real permittivity, and metal electrode thickness has been developed to calculate the capacitance of the sensors when in contact with a planar test-piece comprising up to four layers. Compared with a disk-and-ring coplanar capacitive sensor developed previously, the interdigital configurations are predicted to have higher signal-to-noise ratio and better accuracy in materials characterization. The disk-and-ring configuration, on the other hand, possesses advantages such as deeper penetration depth and better immunity to lift-off variations.

Identification of myoelectric signals of pregnant rat uterus: new method to detect myometrial contraction

PubMed Central

Szűcs, Kálmán F.; Grosz, György; Süle, Miklós; Nagy, Anikó; Tiszai, Zita; Samavati, Reza; Gáspár, Róbert

2017-01-01

Aim To develop an electromyography method for pregnant rat uterus in vivo and to separate myometrial signals from the gastrointestinal tract signals. Methods Pregnant Sprague-Dawley rats (n = 8) were anaesthetized and their stomach, small intestine, and large intestine were removed from the abdomen. A pair of thread electrodes was inserted into the uterus, while a pair of disk electrodes was placed subcutaneously above the myometrium. Additionally, a strain gauge sensor was fixed on the surface of the myometrium and cecum for the parallel detection of mechanical contractions in rats (n = 18) with intact gastrointestinal tract. The filtered electric signals were amplified and recorded by an online computer system and analyzed by fast Fourier transformation. The frequency of the electric activity was characterized by cycle per minute (cpm), the magnitude of the activity was described as power spectrum density maximum (PsDmax). Results The frequency of the pregnant uterine activity was 1-3 cpm, which falls within the same range as that of cecum. Measuring by both electrodes, oxytocin (1 µg/kg) increased and terbutaline (50 µg/kg) decreased the PsDmax by 25%-50% (P < 0.001) and 25%-40% (P < 0.01), respectively. We found a strong positive correlation between the alterations of PsDmax values and the strain gauge sensor-detected mechanical contractions (area under curve). The GI specific compounds (neostigmine, atropine) mainly affected the cecal activity, while myometrium specific drugs (oxytocin, terbutaline) influenced the myometrial signals only. Conclusion Our method proved to be able to detect the myoelectric activity that reflects the mechanical contraction. The overlapping myometrial and cecal signals are not separable, but they can be distinguished based on the much higher activity and different pharmacological reactivity of the pregnant uterus. Thus, the early signs of contractions can be detected and labor may be predicted in a fast and sensitive way. PMID:28409497

Understanding the Reduction Kinetics of Aqueous Vanadium(V) and Transformation Products Using Rotating Ring-Disk Electrodes.

PubMed

Chen, Gongde; Liu, Haizhou

2017-10-17

Vanadium(V) is an emerging contaminant in the most recent Environmental Protection Agency's candidate contaminant list (CCL4). The redox chemistry of vanadium controls its occurrence in the aquatic environment, but the impact of vanadium(V) speciation on the redox properties remains largely unknown. This study utilized the rotating ring-disk electrode technique to examine the reduction kinetics of four pH- and concentration-dependent vanadium(V) species in the presence and the absence of phosphate. Results showed that the reduction of VO 2 + , H x V 4 O 12+x (4+x)- (V 4 ), and HVO 4 2- proceeded via a one-electron transfer, while that of Na x H y V 10 O 28 (6-x-y)- (V 10 ) underwent a two-electron transfer. Koutecky-Levich and Tafel analyses showed that the intrinsic reduction rate constants followed the order of V 10 > VO 2 + > V 4 > HVO 4 2- . Ring-electrode collection efficiency indicated that the reduction product of V 10 was stable, while those of VO 2 + , HVO 4 2- , and V 4 had short half-lives that ranged from milliseconds to seconds. With molar ratios of phosphate to vanadium(V) varying from 0 to 1, phosphate accelerated the reduction kinetics of V 10 and V 4 and enhanced the stability of the reduction products of VO 2 + , V 4 , and HVO 4 2- . This study suggests that phosphate complexation could enhance the reductive removal of vanadium(V) and inhibit the reoxidation of its reduction product in water treatment.

Diamondlike carbon coating as a galvanic corrosion barrier between dental implant abutments and nickel-chromium superstructures.

PubMed

Ozkomur, Ahmet; Erbil, Mehmet; Akova, Tolga

2013-01-01

The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures.

Methods of Stress Calculation in Rotating Disks

NASA Technical Reports Server (NTRS)

Tumarkin, S.

1944-01-01

The paper describes nethods of computing the stresses in disks of a given profile as well as methods of choosing the disk profiles for a given stress distribution for turhines, turbo blowers, and so forth. A new method of in tegrating the differential equations of Stodola leads to a simplification of the computation for disks of hyperbolic profile.

Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

NASA Astrophysics Data System (ADS)

Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

2016-09-01

The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

Development of a reactor with carbon catalysts for modular-scale, low-cost electrochemical generation of H 2O 2

DOE PAGES

Chen, Zhihua; Chen, Shucheng; Siahrostami, Samira; ...

2017-03-01

The development of small-scale, decentralized reactors for H 2O 2 production that can couple to renewable energy sources would be of great benefit, particularly for water purification in the developing world. Herein, we describe our efforts to develop electrochemical reactors for H 2O 2 generation with high Faradaic efficiencies of >90%, requiring cell voltages of only ~1.6 V. The reactor employs a carbon-based catalyst that demonstrates excellent performance for H 2O 2 production under alkaline conditions, as demonstrated by fundamental studies involving rotating-ring disk electrode methods. Finally, the low-cost, membrane-free reactor design represents a step towards a continuous, modular-scale, de-centralizedmore » production of H 2O 2.« less

Porous metal-organic framework Cu3(BTC)2 as catalyst used in air-cathode for high performance of microbial fuel cell.

PubMed

Tian, Pei; Liu, Di; Li, Kexun; Yang, Tingting; Wang, Junjie; Liu, Yi; Zhang, Song

2017-11-01

Metal-organic framework Cu 3 (BTC) 2 , prepared by an easy hydrothermal method, was used as the oxygen-based catalyst in microbial fuel cell (MFC). The maximum power density of Cu 3 (BTC) 2 modified air-cathode MFC was 1772±15mWm -2 , almost 1.8 times higher than the control. BET results disclosed high specific surface area of 2159.7m 2 g -1 and abundant micropores structure. Regular octahedron and porous surface of Cu 3 (BTC) 2 were observed in SEM. XPS testified the existence of divalent copper in the extended 3D frameworks, which importantly acted as the Lewis-acid sites or redox centers in ORR. Additionally, the total resistance decreased by 42% from 17.60 to 10.24Ω compared with bare AC electrode. The rotating disk electrode test results showed a four-electron transfer pathway for Cu 3 (BTC) 2 , which was crucial for electrochemical catalytic activity. All the structural and electrochemical advantages make Cu 3 (BTC) 2 a promising catalyst for ORR in MFC. Copyright © 2017. Published by Elsevier Ltd.

Improvement of amperometric transducer selectivity using nanosized phenylenediamine films

NASA Astrophysics Data System (ADS)

Soldatkina, O. V.; Kucherenko, I. S.; Pyeshkova, V. M.; Alekseev, S. A.; Soldatkin, O. O.; Dzyadevych, S. V.

2017-11-01

In this work, we studied the conditions of deposition of a semipermeable polyphenylenediamine (PPD)-based membrane on amperometric disk platinum electrodes. Restricting an access of interfering substances to the electrode surface, the membrane prevents their impact on the sensor operation. Two methods of membrane deposition by electropolymerization were compared—at varying potential (cyclic voltammetry) and at constant potential. The cyclic voltammetry was shown to be easier in performing and providing better properties of the membrane. The dependence of PPD membrane effectiveness on the number of cyclic voltammograms and phenylenediamine concentration was analyzed. It was shown that the impact of interfering substances (ascorbic acid, dopamine, cysteine, uric acid) on sensor operation could be completely avoided using three cyclic voltammograms in 30 mM phenylenediamine. On the other hand, when working with diluted samples, i.e., at lower concentrations of electroactive substances, it is reasonable to decrease the phenylenediamine concentration to 5 mM, which would result in a higher sensitivity of transducers to hydrogen peroxide due to a thinner PPD layer. The PPD membrane was tested during continuous operation and at 8-day storage and turned out to be efficient in sensor and biosensors.

Attachment of Porphyromonas gingivalis to corroded commercially pure titanium and titanium-aluminum-vanadium alloy.

PubMed

Barão, Valentim A R; Yoon, Cheon Joo; Mathew, Mathew T; Yuan, Judy Chia-Chun; Wu, Christine D; Sukotjo, Cortino

2014-09-01

Titanium dental material can become corroded because of electrochemical interaction in the oral environment. The corrosion process may result in surface modification. It was hypothesized that a titanium surface modified by corrosion may enhance the attachment of periodontal pathogens. This study evaluates the effects of corroded titanium surfaces on the attachment of Porphyromonas gingivalis. Commercially pure titanium (cp-Ti) and titanium-aluminum-vanadium alloy (Ti-6Al-4V) disks were used. Disks were anodically polarized in a standard three-electrode setting in a simulated oral environment with artificial saliva at pH levels of 3.0, 6.5, or 9.0. Non-corroded disks were used as controls. Surface roughness was measured before and after corrosion. Disks were inoculated with P. gingivalis and incubated anaerobically at 37°C. After 6 hours, the disks with attached P. gingivalis were stained with crystal violet, and attachment was expressed based on dye absorption at optical density of 550 nm. All assays were performed independently three times in triplicate. Data were analyzed by two-way analysis of variance, the Tukey honestly significant difference test, t test, and Pearson's correlation test (α = 0.05). Both cp-Ti and Ti-6Al-4V alloy-corroded disks promoted significantly more bacterial attachment (11.02% and 41.78%, respectively; P <0.0001) than did the non-corroded controls. Significantly more (11.8%) P. gingivalis attached to the cp-Ti disks than to the Ti-6Al-4V alloy disks (P <0.05). No significant difference in P. gingivalis attachment was noted among the corroded groups for both cp-Ti and Ti-6Al-4V alloy (P >0.05). There was no significant correlation between surface roughness and P. gingivalis attachment. A higher degree of corrosion on the titanium surface may promote increased bacterial attachment by oral pathogens.

A bottom-up building process of nanostructured La0.75Sr0.25Cr0.5Mn0.5O3-δ electrodes for symmetrical-solid oxide fuel cell: Synthesis, characterization and electrocatalytic testing

NASA Astrophysics Data System (ADS)

Chanquía, Corina M.; Montenegro-Hernández, Alejandra; Troiani, Horacio E.; Caneiro, Alberto

2014-01-01

Pure-phase La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) nanocrystallites have been successfully synthesized by the combustion method, employing glycine as fuel and complexing agent, and ammonium nitrate as combustion trigger. A detailed morphological and structural characterization is performed, by using of X-ray diffraction, N2 physisorption and electron microscopy. The LSCM material consists in interconnected nanocrystallites (∼30 nm) forming a sponge-like structure with meso and macropores, being its specific surface area around 10 m2 g-1. Crystalline structural analyses show that the LSCM nanopowder has trigonal/rhombohedral symmetry in the R-3c space group. By employing the spin coating technique and quick-stuck thermal treatments of the ink-electrolyte, electrodes with different crystallite size (95, 160 and 325 nm) are built onto both sides of the La0.8Sr0.2Ga0.8Mg0.2O3-δ-disk electrolyte. To test the influence of the electrode crystallite size on the electrocatalytic behavior of the symmetrical cells, electrochemical impedance spectroscopy measurements at 800 °C were performed. When the electrode crystallite size becomes smaller, the area specific resistance decreases from 3.6 to 1.31 Ω cm2 under 0.2O2-0.8Ar atmosphere, possibly due to the enlarging of the triple-phase boundary, while this value increases from 7.04 to 13.78 Ω cm2 under 0.17H2-0.03H2O-0.8Ar atmosphere, probably due to thermodynamic instability of the LSCM nanocrystallites.

Micro-Membrane Electrode Assembly Design to Precisely Measure the in Situ Activity of Oxygen Reduction Reaction Electrocatalysts for PEMFC.

PubMed

Long, Zhi; Li, Yankai; Deng, Guangrong; Liu, Changpeng; Ge, Junjie; Ma, Shuhua; Xing, Wei

2017-06-20

An in situ micro-MEA technique, which could precisely measure the performance of ORR electrocatalyst using Nafion as electrolyte, was designed and compared with regular thin-film rotating-disk electrode (TFRDE) (0.1 M HClO 4 ) and normal in situ membrane electrode assembly (MEA) tests. Compared to the traditional TFRDE method, the micro-MEA technique makes the acquisition of catalysts' behavior at low potential values easily achieved without being limited by the solubility of O 2 in water. At the same time, it successfully mimics the structure of regular MEAs and obtains similar results to a regular MEA, thus providing a new technique to simply measure the electrode activity without being bothered by complicated fabrication of regular MEA. In order to further understand the importance of in situ measurement, Fe-N-C as a typical oxygen reduction reaction (ORR) free-Pt catalyst was evaluated by TFRDE and micro-MEA. The results show that the half wave potential of Fe-N-C only shifted negatively by -135 mV in comparison with state-of-the-art Pt/C catalysts from TFRDE tests. However, the active site density, mass transfer of O 2 , and the proton transfer conductivity are found to strongly influence the catalyst activity in the micro-MEA, thereby resulting in a much lower limiting current density than Pt/C (8.7 times lower). Hence, it is suggested that the micro-MEA is better in evaluating the in situ ORR performance, where the catalysts are characterized more thoroughly in terms of intrinsic activity, active site density, proton transfer, and mass transfer properties.

Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode

DOE PAGES

Kocha, Shyam S.; Shinozaki, Kazuma; Zack, Jason W.; ...

2017-05-02

Thin-film-rotating disk electrodes (TF-RDEs) are the half-cell electrochemical system of choice for rapid screening of oxygen reduction reaction (ORR) activity of novel Pt supported on carbon black supports (Pt/C) electrocatalysts. It has been shown that the magnitude of the measured ORR activity and reproducibility are highly dependent on the system cleanliness, evaluation protocols, and operating conditions as well as ink formulation, composition, film drying, and the resultant film thickness and uniformity. Accurate benchmarks of baseline Pt/C catalysts evaluated using standardized protocols and best practices are necessary to expedite ultra-low-platinum group metal (PGM) catalyst development that is crucial for the imminentmore » commercialization of fuel cell vehicles. We report results of evaluation in three independent laboratories of Pt/C electrocatalysts provided by commercial fuel cell catalyst manufacturers (Johnson Matthey, Umicore, Tanaka Kikinzoku Kogyo - TKK). The studies were conducted using identical evaluation protocols/ink formulation/film fabrication albeit employing unique electrochemical cell designs specific to each laboratory. Furthermore, the ORR activities reported in this work provide a baseline and criteria for selection and scale-up of novel high activity ORR electrocatalysts for implementation in proton exchange membrane fuel cells (PEMFCs).« less

A novel iron (Ⅱ) polyphthalocyanine catalyst assembled on graphene with significantly enhanced performance for oxygen reduction reaction in alkaline medium

NASA Astrophysics Data System (ADS)

Lin, Lin; Li, Meng; Jiang, Liqing; Li, Yongfeng; Liu, Dajun; He, Xingquan; Cui, Lili

2014-12-01

To realize the large-scale commercial application of direct methanol fuel cells (DMFCs), the catalysts for oxygen reduction reaction (ORR) are the crucial obstacle. Here, an efficient non-noble-metal catalyst for ORR, denoted FePPc/PSS-Gr, has been obtained by anchoring p-phenyl-bis(3,4-dicyanophenyl) ether iron(Ⅱ) polyphthalocyanine (FePPc) on poly(sodium-p-styrenesulfonate) (PSS) modified graphene (PSS-Gr) through a solvothermally assisted π-π assembling approach. The Ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results reveal the π-π interaction between FePPc and PSS-Gr. The rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) measurements show that the proposed catalyst possesses an excellent catalytic performance towards ORR comparable with the commercial Pt/C catalyst in alkaline medium, such as high onset potential (-0.08 V vs. SCE), half-wave potential (-0.19 V vs. SCE), better tolerance to methanol crossover, excellent stability (81.1%, retention after 10,000 s) and an efficient four-electron pathway. The enhanced electrocatalytic performance could be chiefly attributed to its large electrochemically accessible surface area, fast electron transfer rate of PSS-Gr, in particular, the synergistic effect between the FePPc moieties and the PSS-Gr sheets.

Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction

PubMed Central

2013-01-01

A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too. PMID:24229351

Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode

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

Kocha, Shyam S.; Shinozaki, Kazuma; Zack, Jason W.

Abstract Thin-film-rotating disk electrodes (TF-RDEs) are the half-cell electrochemical system of choice for rapid screening of oxygen reduction reaction (ORR) activity of novel Pt supported on carbon black supports (Pt/C) electrocatalysts. It has been shown that the magnitude of the measured ORR activity and reproducibility are highly dependent on the system cleanliness, evaluation protocols, and operating conditions as well as ink formulation, composition, film drying, and the resultant film thickness and uniformity. Accurate benchmarks of baseline Pt/C catalysts evaluated using standardized protocols and best practices are necessary to expedite ultra-low-platinum group metal (PGM) catalyst development that is crucial for themore » imminent commercialization of fuel cell vehicles. We report results of evaluation in three independent laboratories of Pt/C electrocatalysts provided by commercial fuel cell catalyst manufacturers (Johnson Matthey, Umicore, Tanaka Kikinzoku Kogyo—TKK). The studies were conducted using identical evaluation protocols/ink formulation/film fabrication albeit employing unique electrochemical cell designs specific to each laboratory. The ORR activities reported in this work provide a baseline and criteria for selection and scale-up of novel high activity ORR electrocatalysts for implementation in proton exchange membrane fuel cells (PEMFCs).« less

Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode

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

Kocha, Shyam S.; Shinozaki, Kazuma; Zack, Jason W.

Thin-film-rotating disk electrodes (TF-RDEs) are the half-cell electrochemical system of choice for rapid screening of oxygen reduction reaction (ORR) activity of novel Pt supported on carbon black supports (Pt/C) electrocatalysts. It has been shown that the magnitude of the measured ORR activity and reproducibility are highly dependent on the system cleanliness, evaluation protocols, and operating conditions as well as ink formulation, composition, film drying, and the resultant film thickness and uniformity. Accurate benchmarks of baseline Pt/C catalysts evaluated using standardized protocols and best practices are necessary to expedite ultra-low-platinum group metal (PGM) catalyst development that is crucial for the imminentmore » commercialization of fuel cell vehicles. We report results of evaluation in three independent laboratories of Pt/C electrocatalysts provided by commercial fuel cell catalyst manufacturers (Johnson Matthey, Umicore, Tanaka Kikinzoku Kogyo - TKK). The studies were conducted using identical evaluation protocols/ink formulation/film fabrication albeit employing unique electrochemical cell designs specific to each laboratory. Furthermore, the ORR activities reported in this work provide a baseline and criteria for selection and scale-up of novel high activity ORR electrocatalysts for implementation in proton exchange membrane fuel cells (PEMFCs).« less

Investigation on electrochemical behavior and its catalytic effect on oxygen reduction reaction of 3-Ferrocenyl dihydropyrazole derivative as electron relay

NASA Astrophysics Data System (ADS)

Zeng, Han; Huo, Wen-Shan; Zhao, Shu-Xian; Zhang, Yu-He

2017-11-01

Amino group surface tailored multi-wall carbon nano-tubes were covalently tethered to the gold disk electrode and Laccase molecules were covalently coupled to nano-tubes to prepare Lac-based electrode. Derivative of 3-ferrocenyl dihydropyrazole (FDPFFP) was proposed to be electron mediator for mediated oxygen reduction reaction. Investigation in electro-chemical behavior and catalytic performance to enzymatic reaction of FDPFFP indicated that it displayed quasi-reversible characteristics of electro-chemical reaction with rapid dynamics of electron shuttle and had apparent catalytic effect in oxygen reduction (onset potential for catalysis at 450 mV vs NHE). This enzymatic catalysis was restrained by the step in diffusion of substrate.

Analysis of a disk-type piezoelectric ultrasonic motor using impedance matrices.

PubMed

Kim, Young H; Ha, Sung K

2003-12-01

The dynamic behavior and the performance characteristics of the disk-type traveling wave piezoelectric ultrasonic motors (USM) are analyzed using impedance matrices. The stator is divided into three coupled subsystems: an inner metal disk, a piezoelectric annular actuator with segmented electrodes, and an outer metal disk with teeth. The effects of both shear deformation and rotary inertia are taken into account in deriving an impedance matrix for the piezoelectric actuator. The impedance matrices for each subsystem then are combined into a global impedance matrix using continuity conditions at the interfaces. A comparison is made between the impedance matrix model and the three-dimensional finite element model of the piezoelectric stator, obtaining the resonance and antiresonance frequencies and the effective electromechanical coupling factors versus circumferential mode numbers. Using the calculated resonance frequency and the vibration modes for the stator and a brush model with the Coulomb friction for the stator and rotor contact, stall torque, and no-load speed versus excitation frequencies are calculated at different preloads. Performance characteristics such as speed-torque curve and the output efficiency of the USM also are estimated using the current impedance matrix and the contact model. The present impedance model can be shown to be very effective in the design of the USM.

Effect of Polymer Electrode Morphology on Performance of a Lithium/Polypyrrole Battery. M.S. Thesis

NASA Technical Reports Server (NTRS)

Nicholson, Marjorie Anne

1991-01-01

A variety of conducting polymer batteries were described in the recent literature. In this work, a Li/Polypyrrole secondary battery is described. The effect of controlling the morphology of the polymer on enhancement of counterion diffusion in the polymer phase is explored. A method of preparing conducting polymers was developed which yields high surface area per unit volume of electrode material. A porous membrane is used as a template in which to electrochemically polymerize pyrrole, then the membrane is dissolved, leaving the polymer in a fibrillar form. Conventionally, the polymer is electrochemically polymerized as a dense polymer film on a smooth Pt disk electrode. Previous work has shown that when the polymer is electrochemically polymerized in fribrillar form, charge transport rates are faster and charge capacities are greater than for dense, conventionally grown films containing the same amount of polymer. The purpose is to expand previous work by further investigating the possibilities of the optimization of transport rates in polypyrrole films by controlling the morphology of the films. The utility of fibrillar polypyrrole as a cathode material in a lithium/polymer secondary battery is then assessed. The performance of the fibrillar battery is compared to the performance of an analogous battery which employed a conventionally grown polypyrrole film. The study includes a comparison of cyclic voltammetry, shape of charge/discharge curves, discharge time and voltage, cycle life, coulombic efficiencies, charge capacities, energy densities, and energy efficiencies.

Appearance of cell-adhesion factor in osteoblast proliferation and differentiation of apatite coating titanium by blast coating method.

PubMed

Umeda, Hirotsugu; Mano, Takamitsu; Harada, Koji; Tarannum, Ferdous; Ueyama, Yoshiya

2017-08-01

We have already reported that the apatite coating of titanium by the blast coating (BC) method could show a higher rate of bone contact from the early stages in vivo, when compared to the pure titanium (Ti) and the apatite coating of titanium by the flame spraying (FS) method. However, the detailed mechanism by which BC resulted in satisfactory bone contact is still unknown. In the present study, we investigated the importance of various factors including cell adhesion factor in osteoblast proliferation and differentiation that could affect the osteoconductivity of the BC disks. Cell proliferation assay revealed that Saos-2 could grow fastest on BC disks, and that a spectrophotometric method using a LabAssay TM ALP kit showed that ALP activity was increased in cells on BC disks compared to Ti disks and FS disks. In addition, higher expression of E-cadherin and Fibronectin was observed in cells on BC disks than Ti disks and FS disks by relative qPCR as well as Western blotting. These results suggested that the expression of cell-adhesion factors, proliferation and differentiation of osteoblast might be enhanced on BC disks, which might result higher osteoconductivity.

Construction of a new selective coated disk electrode for Ag (I) based on modified polypyrrole-carbon nanotubes composite with new lariat ether.

PubMed

Abbaspour, A; Tashkhourian, J; Ahmadpour, S; Mirahmadi, E; Sharghi, H; Khalifeh, R; Shahriyari, M R

2014-01-01

A poly (vinyl chloride) (PVC) matrix membrane ion-selective electrode for silver (I) ion is fabricated based on modified polypyrrole - multiwalled carbon nanotubes composite with new lariat ether. This sensor has a Nernstian slope of 59.4±0.5mV/decade over a wide linear concentration range of 1.0×10(-7) to 1.0×10(-1)molL(-1) for silver (I) ion. It has a short response time of about 8.0s and can be used for at least 50days. The detection limit is 9.3×10(-8)molL(-1) for silver (I) ion, and the electrode was applicable in the wide pH range of 1.6 -7.7. The electrode shows good selectivity for silver ion against many cations such as Hg (II), which usually imposes serious interference in the determination of silver ion concentration. The use of multiwalled carbon nanotubes (MWCNTs) in a polymer matrix improves the linear range and sensitivity of the electrode. In addition by coating the solid contact with a layer of the polypyrrole (Ppy) before coating the membrane on it, not only did it reduce the drift in potential, but a shorter response time was also resulted. The proposed electrode was used as an indicator electrode for potentiometric titration of silver ions with chloride anions and in the titration of mixed halides. This electrode was successfully applied for the determination of silver ions in silver sulphadiazine as a burning cream. © 2013.

Rotating Disk Slurry Au Electrodeposition at Unsupported Carbon Vulcan XC-72 and Ce 3+ Impregnation for Ethanol Oxidation in Alkaline Media

DOE PAGES

Betancourt, Luis E.; Guzman-Blas, Rolando; Luo, Si; ...

2016-11-19

A robust electrodeposition method consisting of the rotating disk slurry electrode (RoDSE) technique to obtain Au nanoparticles highly dispersed on a conductive carbonaceous support, i.e., Vulcan XC-72R, for ethanol electrooxidation reaction in alkaline media was developed. Ceria was used as a cocatalyst using a Ce(III)-EDTA impregnation method in order to enhance the catalytic activity and improve the catalyst’s overall stability. Furthermore, the RoDSE method used to obtain highly dispersed Au nanoparticles does not require the use of a reducing agent or stabilizing agent, and the noble-metal loading was controlled by the addition and tuning of the metal precursor concentration. Inductivelymore » coupled plasma and thermogravimetric analysis indicated that the Au loading in the catalyst was 9 %. We determined the particle size and characteristic Au fcc crystal facets by X-ray diffraction. The morphology of the catalyst was also investigated using electron microscopy techniques. In addition, X-ray absorption spectroscopy was used to corroborate the presence and identify the oxidation state of Ce in the system and to observe if there are any electronic interactions within the 8 % Au/CeO x/C system. Cyclic voltammetry of electrodeposited 9 % Au/C and Ce-promoted 8 % Au/C showed a higher catalytic current density for ethanol oxidation when compared with commercially available catalysts (20 % Au/C) of a higher precious metal loading. Additionally, we report a higher stability toward the ethanol electrooxidation process, which was corroborated by 1 mV/s linear sweep voltammetry and chronoamperometric studies.« less

Modern Optimization Methods in Minimum Weight Design of Elastic Annular Rotating Disk with Variable Thickness

NASA Astrophysics Data System (ADS)

Jafari, S.; Hojjati, M. H.

2011-12-01

Rotating disks work mostly at high angular velocity and this results a large centrifugal force and consequently induce large stresses and deformations. Minimizing weight of such disks yields to benefits such as low dead weights and lower costs. This paper aims at finding an optimal disk thickness profile for minimum weight design using the simulated annealing (SA) and particle swarm optimization (PSO) as two modern optimization techniques. In using semi-analytical the radial domain of the disk is divided into some virtual sub-domains as rings where the weight of each rings must be minimized. Inequality constrain equation used in optimization is to make sure that maximum von Mises stress is always less than yielding strength of the material of the disk and rotating disk does not fail. The results show that the minimum weight obtained for all two methods is almost identical. The PSO method gives a profile with slightly less weight (6.9% less than SA) while the implementation of both PSO and SA methods are easy and provide more flexibility compared with classical methods.

Rotation Disk Process to Assess the Influence of Metals and Voltage on the Growth of Biofilm

PubMed Central

Barry, Dana M.; McGrath, Paul B.

2016-01-01

Biofilms consist of not only bacteria but also extracellular polymer substrates (EPS). They are groups of microorganisms that adhere to each other on a surface, especially as a result of exposure to water and bacteria. They can pose health risks to humans as they grow in hospital settings that include medical supplies and devices. In a previous study, the researchers discovered that bacteria/biofilm grew well on wetted external latex, male catheters. These results concerned the investigators and encouraged them to find ways for prohibiting the growth of bacteria/biofilm on the male catheters (which are made of natural rubber). They carried out a new study to assess the influence of metals and voltage for the growth of bacteria on these latex samples. For this purpose, a unique Rotation Disk Reactor was used to accelerate biofilm formation on external male catheter samples. This setup included a dip tank containing water and a rotating wheel with the attached latex samples (some of which had single electrodes while others had paired electrodes with applied voltage). The process allowed the samples to become wetted and also exposed them to microorganisms in the ambient air during each revolution of the wheel. The results (as viewed from SEM images) showed that when compared to the control sample, the presence of metals (brass, stainless steel, and silver) was generally effective in preventing bacterial growth. Also the use of voltage (9.5 volt battery) essentially eliminated the appearance of rod shaped bacteria in some of the samples. It can be concluded that the presence of metals significantly reduced bacterial growth on latex and the application of voltage was able to essentially eliminate bacteria, providing appropriate electrode combinations were used. PMID:28773689

Solid-state proton conductors

NASA Astrophysics Data System (ADS)

Jewulski, J. R.; Osif, T. L.; Remick, R. J.

1990-12-01

The purpose of this program was to survey the field of solid-state proton conductors (SSPC), identify conductors that could be used to develop solid-state fuel cells suitable for use with coal derived fuel gases, and begin the experimental research required for the development of these fuel cells. This document covers the following topics: the history of developments and current status of the SSPC, including a review of proton conducting electrolyte structures, the current status of the medium temperature SSPC development, electrodes for moderate temperature (SSPC) fuel cell, basic material and measurement techniques applicable for SSPC development, modeling, and optimization studies. Correlation and optimization studies are described which include correlation studies on proton conduction and oxide cathode optimization for the SSPC fuel cell. Experiments with the SSPC fuel cells are presented which include the fabrication of the electrolyte disks, apparatus for conducting measurements, the strontium-cerium based electrolyte, the barium-cerium based electrolyte with solid foil electrodes, the barium-cerium based electrolyte with porous electrodes, and conduction mechanisms.

Hydrogen Oxidation-Selective Electrocatalysis by Fine Tuning of Pt Ensemble Sites to Enhance the Durability of Automotive Fuel Cells.

PubMed

Yun, Su-Won; Park, Shin-Ae; Kim, Tae-June; Kim, Jun-Hyuk; Pak, Gi-Woong; Kim, Yong-Tae

2017-02-08

A simple, inexpensive approach is proposed for enhancing the durability of automotive proton exchange membrane fuel cells by selective promotion of the hydrogen oxidation reaction (HOR) and suppression of the oxygen reduction reaction (ORR) at the anode in startup/shutdown events. Dodecanethiol forms a self-assembled monolayer (SAM) on the surface of Pt particles, thus decreasing the number of Pt ensemble sites. Interestingly, by controlling the dodecanethiol concentration during SAM formation, the number of ensemble sites can be precisely optimized such that it is sufficient for the HOR but insufficient for the ORR. Thus, a Pt surface with an SAM of dodecanethiol clearly effects HOR-selective electrocatalysis. Clear HOR selectivity is demonstrated in unit cell tests with the actual membrane electrode assembly, as well as in an electrochemical three-electrode setup with a thin-film rotating disk electrode configuration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of oxocuprate superconductor microelectrodes for sub-{Tc} use

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

Green, S.J.; Rosseinsky, D.R.; Toohey, M.J.

1995-07-01

The technique of partial resin encapsulation is described for the direct fabrication of cryorobust oxocuprate microelectrodes from bulk ceramic samples, here Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}}, Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10{minus}{delta}}. Cyclic voltammetry is used in tests of the electrochemical response at 295 K (ferrocene in acetonitrile/NBu{sub 4}BF{sub 4}), affording approximated disk radii 2.9, 37.0, and 32.5 {micro}m, and at 123 and at 103 K (ferrocene in chloroethane/tetrahydrofuran/LiBF{sub 4}). Some nonideality in the 295 K responses results from electrode porosity and, at the smallest electrodes, defects in the HTSC/resin seal. Acceptable sub-T{sub c} responses show these problems to bemore » irrelevant in the high viscosity of the electrolytes at low temperature. These microelectrodes usefully advance the emerging study of electrochemistry on superconducting electrodes by responding to free-solute electroactives at <{Tc}.« less

The Relationship between the Current Waveform just before the Current Zero and the Interruption Ability in the High-speed VCB

NASA Astrophysics Data System (ADS)

Niwa, Yoshimitsu; Matsuzaki, Jun; Yokokura, Kunio

The high-speed vacuum circuit breaker, which forced the fault current to zero was investigated. The test circuit breaker consisted of a vacuum interrupter and a high frequency current source. The vacuum interrupter, which had the axial magnetic field electrode and the disk shape electrode, was tested. The arcing period of the high-speed vacuum circuit breaker is much shorter than that of conventional circuit breaker. The arc behavior of the test electrodes immediately after the contact separation was observed by a high-speed video camcorder. The relation between the current waveform just before the current zero and the interruption ability by varying the high frequency current source was investigated experimentally. The results demonstrate the interruption ability and the arc behavior of the high-speed vacuum circuit breaker. The high current interruption was made possible by the low current period just before the current zero, although the arcing time is short and the arc is concentrated.

Prototype Rechargeable Lithium Batteries. Phase 1

DTIC Science & Technology

1987-06-01

pentoxide [ V2o5 ], titanium disulfide [TiS ], vanadium V) sulfide [V2S 5 ], and lithium cobalt oxide [Li Co02]) witi high conductivity, ester-Eased...2400 envelope while the cathodes were supported with porous glass disks to maintain good electrical contact with the expanded metal current collectors...cells consisted of an electrode stack mounted between two glass slides held together with stainless steel wire and sealed in a Fisher & Porter 3-ounce

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes

NASA Technical Reports Server (NTRS)

Chin, D. T.; Hsueh, K. L.; Chang, H. H.

1983-01-01

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. A theoretical expression for the rotating ring-disk electrode technique; the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; oxygen reduction mechanism in trifluoromethanesulfonic acid (TFMSA), considered as an alternate electrolyte for the acid fuel cells; and transport properties of the phosphoric acid electrolyte at high concentrations and temperatures are covered.

The continued value of disk diffusion for assessing antimicrobial susceptibility in clinical laboratories: report from the Clinical and Laboratory Standards Institute Methods Development and Standardization Working Group.

PubMed

Humphries, Romney M; Kircher, Susan; Ferrell, Andrea; Krause, Kevin M; Malherbe, Rianna; Hsiung, Andre; Burnham, C A

2018-05-09

Expedited pathways to antimicrobial agent approval by the United States Food and Drug Administration (FDA) have led to increased delays between drug approval and the availability of FDA-cleared antimicrobial susceptibility testing (AST) devices. Antimicrobial disks for use with disk diffusion testing are among the first AST devices available to clinical laboratories. However, many laboratories are reluctant to implement a disk diffusion method for a variety of reasons, including dwindling proficiency with this method, interruptions to laboratory workflow, uncertainty surrounding the quality and reliability of a disk diffusion test, and perceived need to report an MIC to clinicians. This mini-review provides a report from the Clinical and Laboratory Standards Institute Working Group on Methods Development and Standardization on the current standards and clinical utility of disk diffusion testing. Copyright © 2018 American Society for Microbiology.

Investigation of Structure and Reactivity Relationship in M-N-C Type Catalysts using Density Functional Tight Binding

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

Negre, Christian Francisco Andres; Gonzales, Ivana

Catalysts inhibition studies were performed to indisputably confirm the role of various metal, carbon, and nitrogen moieties in the individual steps of oxygen reduction reaction (ORR) on M-N-C catalysts. ORR activity was studied at University of New Mexico by rotating ring disk electrode method in the acidic electrolyte with the addition of Tris (tris(hydroxymethyl)-aminomethane) as inhibiting agent. To understand the interaction of Tris with different defects that exist in Fe-N-C materials and provide the support for the experimental data, we used density functional theory (DFT) and modeled the interaction of protonated Tris (TrisH) with Fe containingcenters (Fe-N 4 and Fe-Nmore » 2C 2), pyridinic nitrogen, graphitic nitrogen, and pyrrolic nitrogen both as in plane and edge defects.« less

Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

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

Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.

The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particlesmore » located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.« less

Electrocatalysis for oxygen electrodes in fuel cells and water electrolyzers for space applications

NASA Technical Reports Server (NTRS)

Prakash, Jai; Tryk, Donald; Yeager, Ernest

1989-01-01

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation. Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium).

Identification of transitional disks in Chamaeleon with Herschel

NASA Astrophysics Data System (ADS)

Ribas, Á.; Merín, B.; Bouy, H.; Alves de Oliveira, C.; Ardila, D. R.; Puga, E.; Kóspál, Á.; Spezzi, L.; Cox, N. L. J.; Prusti, T.; Pilbratt, G. L.; André, Ph.; Matrà, L.; Vavrek, R.

2013-04-01

Context. Transitional disks are circumstellar disks with inner holes that in some cases are produced by planets and/or substellar companions in these systems. For this reason, these disks are extremely important for the study of planetary system formation. Aims: The Herschel Space Observatory provides an unique opportunity for studying the outer regions of protoplanetary disks. In this work we update previous knowledge on the transitional disks in the Chamaeleon I and II regions with data from the Herschel Gould Belt Survey. Methods: We propose a new method for transitional disk classification based on the WISE 12 μm - PACS 70 μm color, together with inspection of the Herschel images. We applied this method to the population of Class II sources in the Chamaeleon region and studied the spectral energy distributions of the transitional disks in the sample. We also built the median spectral energy distribution of Class II objects in these regions for comparison with transitional disks. Results: The proposed method allows a clear separation of the known transitional disks from the Class II sources. We find six transitional disks, all previously known, and identify five objects previously thought to be transitional as possibly non-transitional. We find higher fluxes at the PACS wavelengths in the sample of transitional disks than those of Class II objects. Conclusions: We show the Herschel 70 μm band to be a robust and efficient tool for transitional disk identification. The sensitivity and spatial resolution of Herschel reveals a significant contamination level among the previously identified transitional disk candidates for the two regions, which calls for a revision of previous samples of transitional disks in other regions. The systematic excess found at the PACS bands could be either a result of the mechanism that produces the transitional phase, or an indication of different evolutionary paths for transitional disks and Class II sources. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A is available in electronic form at http://www.aanda.org

Self-assembled monolayers of n-alkanethiols suppress hydrogen evolution and increase the efficiency of rechargeable iron battery electrodes.

PubMed

Malkhandi, Souradip; Yang, Bo; Manohar, Aswin K; Prakash, G K Surya; Narayanan, S R

2013-01-09

Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

Pt-Pd bimetallic nanoparticles on MWCNTs: catalyst for hydrogen peroxide electrosynthesis

NASA Astrophysics Data System (ADS)

Félix-Navarro, R. M.; Beltrán-Gastélum, M.; Salazar-Gastélum, M. I.; Silva-Carrillo, C.; Reynoso-Soto, E. A.; Pérez-Sicairos, S.; Lin, S. W.; Paraguay-Delgado, F.; Alonso-Núñez, G.

2013-08-01

Bimetallic nanoparticles of Pt-Pd were deposited by the microemulsion method on a multiwall carbon nanotube (MWCNTs) to obtain a Pt-Pd/MWCNTs for electrocatalytic reduction of O2 to H2O2. The activity and selectivity of the catalyst was determined qualitatively by the rotating disk electrode method in acidic medium. The catalyst was spray-coated onto a reticulated vitreous carbon substrate and quantitatively was tested in bulk electrolysis for 20 min under potentiostatic conditions (0.5 V vs Ag/AgCl) in a 0.5 M H2SO4 electrolyte using dissolved O2. The bulk electrolysis experiments show that the Pt-Pd/MWCNTs catalyst is more efficient for H2O2 electrogeneration than a MWCNTs catalyst. Nitrobenzene degradation by electrogenerated H2O2 alone and Electro-Fenton process were also tested. Our results show that both processes decompose nitrobenzene, but the Electro-Fenton process does it more efficiently. The prepared nanoparticulated catalyst shows a great potential in environmental applications.

Evaluating Hydrogen Evolution and Oxidation in Alkaline Media to Establish Baselines

DOE PAGES

Alia, Shaun M.; Pivovar, Bryan S.

2018-04-28

This paper fills a significant gap in the literature for alkaline hydrogen evolution (HER) and oxidation (HOR) baseline performance, while reviewing the different variables that influence observed properties. Although high-performing HER-HOR catalysts in acidic electrolytes are too active to measure kinetic in rotating disk electrode (RDE) half-cells, under alkaline conditions RDE kinetics evaluations are relevant and half-cell performances are comparable to hydrogen pump data. This paper focuses on best practices to ensure that half-cell tests don't unnecessarily lower platinum group metal (PGM) performance or improve non-PGM performance. Specific aspects examined include experiments on PGMs minimizing the impact of impurities (electrolyte,more » cell material) and experiments on non-PGMs minimizing the impact from test protocols (counter electrode).« less

Evaluating Hydrogen Evolution and Oxidation in Alkaline Media to Establish Baselines

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

Alia, Shaun M.; Pivovar, Bryan S.

This paper fills a significant gap in the literature for alkaline hydrogen evolution (HER) and oxidation (HOR) baseline performance, while reviewing the different variables that influence observed properties. Although high-performing HER-HOR catalysts in acidic electrolytes are too active to measure kinetic in rotating disk electrode (RDE) half-cells, under alkaline conditions RDE kinetics evaluations are relevant and half-cell performances are comparable to hydrogen pump data. This paper focuses on best practices to ensure that half-cell tests don't unnecessarily lower platinum group metal (PGM) performance or improve non-PGM performance. Specific aspects examined include experiments on PGMs minimizing the impact of impurities (electrolyte,more » cell material) and experiments on non-PGMs minimizing the impact from test protocols (counter electrode).« less

Active Piezoelectric Diaphragms

NASA Technical Reports Server (NTRS)

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M.; Covington, Ed W., III

2002-01-01

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis (perpendicular to the applied electric field), rather than the expected in-plane (XY-axis) direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Comparison of disk diffusion and agar dilution methods for gentamicin susceptibility testing of Neisseria gonorrhoeae.

PubMed

Gianecini, Ricardo; Oviedo, Claudia; Irazu, Lucia; Rodríguez, Marcelo; Galarza, Patricia

2018-03-29

Gentamicin is a promising antibiotic for the treatment of multidrug-resistant gonorrhea. The aim of this study was to analyze the suitability and reliably of disk diffusion to monitor the susceptibility to gentamicin. We studied 237 Neisseria gonorrhoeae isolates obtained in 2013 and 2015. Reference MICs were correlated with inhibition zone diameters (in millimeters) of gentamicin 10 µg disks manufactured by BBL and Oxoid. The Pearson correlation between disk diffusion and agar dilution was r = -.68 (P < 0.001) for BBL disk and r = -.71 (P < 0.001) for Oxoid disk. No very major or major discrepancies were detected. However, a high percentage of minor discrepancies was observed (44.7%, BBL disk) and (21.9%, Oxoid disk). By adjusting the susceptible breakpoint to S ≥ 17 mm, the minor discrepancies rate was reduced to 19.4% (BBL disk) and 10.1% (Oxoid disk). The disk diffusion may be a screening method in clinical laboratories to detect the gentamicin susceptibility of N. gonorrhoeae. Copyright © 2018 Elsevier Inc. All rights reserved.

Method and system for managing power grid data

DOEpatents

Yin, Jian; Akyol, Bora A.; Gorton, Ian

2015-11-10

A system and method of managing time-series data for smart grids is disclosed. Data is collected from a plurality of sensors. An index is modified for a newly created block. A one disk operation per read or write is performed. The one disk operation per read includes accessing and looking up the index to locate the data without movement of an arm of the disk, and obtaining the data. The one disk operation per write includes searching the disk for free space, calculating an offset, modifying the index, and writing the data contiguously into a block of the disk the index points to.

Probabilistic Analysis of Aircraft Gas Turbine Disk Life and Reliability

NASA Technical Reports Server (NTRS)

Melis, Matthew E.; Zaretsky, Erwin V.; August, Richard

1999-01-01

Two series of low cycle fatigue (LCF) test data for two groups of different aircraft gas turbine engine compressor disk geometries were reanalyzed and compared using Weibull statistics. Both groups of disks were manufactured from titanium (Ti-6Al-4V) alloy. A NASA Glenn Research Center developed probabilistic computer code Probable Cause was used to predict disk life and reliability. A material-life factor A was determined for titanium (Ti-6Al-4V) alloy based upon fatigue disk data and successfully applied to predict the life of the disks as a function of speed. A comparison was made with the currently used life prediction method based upon crack growth rate. Applying an endurance limit to the computer code did not significantly affect the predicted lives under engine operating conditions. Failure location prediction correlates with those experimentally observed in the LCF tests. A reasonable correlation was obtained between the predicted disk lives using the Probable Cause code and a modified crack growth method for life prediction. Both methods slightly overpredict life for one disk group and significantly under predict it for the other.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: I. Impact of Impurities, Measurement Protocols and Applied Corrections

DOE PAGES

Shinozaki, Kazuma; Zack, Jason W.; Richards, Ryan M.; ...

2015-07-22

The rotating disk electrode (RDE) technique is being extensively used as a screening tool to estimate the activity of novel PEMFC electrocatalysts synthesized in lab-scale (mg) quantities. Discrepancies in measured activity attributable to glassware and electrolyte impurity levels, as well as conditioning, protocols and corrections are prevalent in the literature. Moreover, the electrochemical response to a broad spectrum of commercially sourced perchloric acid and the effect of acid molarity on impurity levels and solution resistance were also assessed. Our findings reveal that an area specific activity (SA) exceeding 2.0 mA/cm 2 (20 mV/s, 25°C, 100 kPa, 0.1 M HClO 4)more » for polished poly-Pt is an indicator of impurity levels that do not impede the accurate measurement of the ORR activity of Pt based catalysts. After exploring various conditioning protocols to approach maximum utilization of the electrochemical area (ECA) and peak ORR activity without introducing catalyst degradation, an investigation of measurement protocols for ECA and ORR activity was conducted. Down-selected protocols were based on the criteria of reproducibility, duration of experiments, impurity effects and magnitude of pseudo-capacitive background correction. In sum, statistical reproducibility of ORR activity for poly-Pt and Pt supported on high surface area carbon was demonstrated.« less

Limiting diffusion current at rotating disk electrode with dense particle layer.

PubMed

Weroński, P; Nosek, M; Batys, P

2013-09-28

Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

Determination of elastic stresses in gas-turbine disks

NASA Technical Reports Server (NTRS)

Manson, S S

1947-01-01

A method is presented for the calculation of elastic stresses in symmetrical disks typical of those of a high-temperature gas turbine. The method is essentially a finite-difference solution of the equilibrium and compatibility equations for elastic stresses in a symmetrical disk. Account can be taken of point-to-point variations in disk thickness, in temperature, in elastic modulus, in coefficient of thermal expansion, in material density, and in Poisson's ratio. No numerical integration or trial-and-error procedures are involved and the computations can be performed in rapid and routine fashion by nontechnical computers with little engineering supervision. Checks on problems for which exact mathematical solutions are known indicate that the method yields results of high accuracy. Illustrative examples are presented to show the manner of treating solid disks, disks with central holes, and disks constructed either of a single material or two or more welded materials. The effect of shrink fitting is taken into account by a very simple device.

Heat Treatment Devices and Method of Operation Thereof to Produce Dual Microstructure Superalloys Disks

NASA Technical Reports Server (NTRS)

Gayda, John (Inventor); Gabb, Timothy P. (Inventor); Kantzos, Peter T. (Inventor)

2003-01-01

A heat treatment assembly and heat treatment methods are disclosed for producing different microstructures in the bore and rim portions of nickel-based superalloy disks, particu- larly suited for gas turbine applications. The heat treatment assembly is capable of being removed from the furnace and disassembled to allow rapid fan or oil quenching of the disk. For solutioning heat treatments of the disk, temperatures higher than that of this solvus temperature of the disk are used to produce coarse grains in the rim of each disk so as to give maximum creep and dwell crack resistance at the rim service temperature. At the same time, solution temperature lower than the solvus temperature of the disk are provided to produce fine grain in the bore of the disk so as to give maximum strength and low cycle fatigue resistance.

The Use of Spray-Dried Mn₃O₄/C Composites as Electrocatalysts for Li-O₂ Batteries.

PubMed

Yang, Hong-Kai; Chin, Chih-Chun; Chen, Jenn-Shing

2016-11-07

The electrocatalytic activities of Mn₃O₄/C composites are studied in lithium-oxygen (Li-O₂) batteries as cathode catalysts. The Mn₃O₄/C composites are fabricated using ultrasonic spray pyrolysis (USP) with organic surfactants as the carbon sources. The physical and electrochemical performance of the composites is characterized by X-ray diffraction, scanning electron microscopy, particle size analysis, Brunauer-Emmett-Teller (BET) measurements, elemental analysis, galvanostatic charge-discharge methods and rotating ring-disk electrode (RRDE) measurements. The electrochemical tests demonstrate that the Mn₃O₄/C composite that is prepared using Trition X-114 (TX114) surfactant has higher activity as a bi-functional catalyst and delivers better oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance in Li-O₂ batteries because there is a larger surface area and particles are homogeneous with a meso/macro porous structure. The rate constant ( k f ) for the production of superoxide radical (O₂ • - ) and the propylene carbonate (PC)-electrolyte decomposition rate constant ( k ) for M₃O₄/C and Super P electrodes are measured using RRDE experiments and analysis in the 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF₆)/PC electrolyte. The results show that TX114 has higher electrocatalytic activity for the first step of ORR to generate O₂ • - and produces a faster PC-electrolyte decomposition rate.

Optimization of a Three-Component Green Corrosion Inhibitor Mixture for Using in Cooling Water by Experimental Design

NASA Astrophysics Data System (ADS)

Asghari, E.; Ashassi-Sorkhabi, H.; Ahangari, M.; Bagheri, R.

2016-04-01

Factors such as inhibitor concentration, solution hydrodynamics, and temperature influence the performance of corrosion inhibitor mixtures. The simultaneous studying of the impact of different factors is a time- and cost-consuming process. The use of experimental design methods can be useful in minimizing the number of experiments and finding local optimized conditions for factors under the investigation. In the present work, the inhibition performance of a three-component inhibitor mixture against corrosion of St37 steel rotating disk electrode, RDE, was studied. The mixture was composed of citric acid, lanthanum(III) nitrate, and tetrabutylammonium perchlorate. In order to decrease the number of experiments, the L16 Taguchi orthogonal array was used. The "control factors" were the concentration of each component and the rotation rate of RDE and the "response factor" was the inhibition efficiency. The scanning electron microscopy and energy dispersive x-ray spectroscopy techniques verified the formation of islands of adsorbed citrate complexes with lanthanum ions and insoluble lanthanum(III) hydroxide. From the Taguchi analysis results the mixture of 0.50 mM lanthanum(III) nitrate, 0.50 mM citric acid, and 2.0 mM tetrabutylammonium perchlorate under the electrode rotation rate of 1000 rpm was found as optimum conditions.

Enhancement of Electrode Stability Using Platinum-Cobalt Nanocrystals on a Novel Composite SiCTiC Support.

PubMed

Millán, María; Zamora, Héctor; Rodrigo, Manuel A; Lobato, Justo

2017-02-22

PtCo alloy catalysts for high temperature PEMFCs (protonic exchange membrane fuel cells) were synthesized on a novel noncarbonaceous support (SiCTiC) using the impregnation method with NaBH 4 as the reducing agent at different synthesis temperatures to evaluate the effect of this variable on their physicochemical and electrochemical properties. The catalysts were characterized by inductively coupled plasma optical emission spectrometry, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscope-energy dispersive X-ray,and temperature-programmed reduction. In addition, the electrochemical characterization (i.e., cyclic voltammetry, oxygen reduction reaction, and chronoamperometry) was carried out with a rotating disk electrode. For the cyclic voltammetry investigation, 400 cycles were performed in hot phosphoric acid and a half-cell to evaluate the stability of the synthesized catalysts. The catalyst synthesized on SiCTiC exhibited excellent durability compared to the catalyst synthesized on a Vulcan support. In addition, all synthesized catalysts exhibited better catalytic activity than that of the PtCo/C catalysts. The best results were observed for the catalyst synthesized at 80 °C due to its shorter Pt-Pt nearest-neighbor and higher alloy degree. Finally, a preliminary stability test was conducted in an HT-PEMFC, and promising results in terms of stability and performance were observed.

Preparation of Ag-containing diamond-like carbon films on the interior surface of tubes by a combined method of plasma source ion implantation and DC sputtering

NASA Astrophysics Data System (ADS)

Hatada, R.; Flege, S.; Bobrich, A.; Ensinger, W.; Dietz, C.; Baba, K.; Sawase, T.; Watamoto, T.; Matsutani, T.

2014-08-01

Adhesive diamond-like carbon (DLC) films can be prepared by plasma source ion implantation (PSII), which is also suitable for the treatment of the inner surface of a tube. Incorporation of a metal into the DLC film provides a possibility to change the characteristics of the DLC film. One source for the metal is DC sputtering. In this study PSII and DC sputtering were combined to prepare DLC films containing low concentrations of Ag on the interior surfaces of stainless steel tubes. A DLC film was deposited using a C2H4 plasma with the help of an auxiliary electrode inside of the tube. This electrode was then used as a target for the DC sputtering. A mixture of the gases Ar and C2H4 was used to sputter the silver. By changing the gas flow ratios and process time, the resulting Ag content of the films could be varied. Sample characterizations were performed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, atomic force microscopy and Raman spectroscopy. Additionally, a ball-on-disk test was performed to investigate the tribological properties of the films. The antibacterial activity was determined using Staphylococcus aureus bacteria.

Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Powell, Diana; Murray-Clay, Ruth; Schlichting, Hilke

2018-04-01

The surface density of protoplanetary disks is a fundamental parameter that still remains largely unconstrained due to uncertainties in the dust-to-gas ratio and CO abundance. In this talk I will present a novel method for determining the surface density of protoplanetary disks through consideration of disk “dust lines,” which indicate the observed disk radial scale at different observational wavelengths. I will provide an initial proof of concept of our model through an application to the disk TW Hya where we are able to estimate the disk dust-to-gas ratio, CO abundance, and accretion rate in addition to the total disk surface density. We find that our derived surface density profile and dust-to-gas ratio are consistent with the lower limits found through measurements of HD gas. We further apply our model to a large parameter space of theoretical disks and find three observational diagnostics that may be used to test its validity. Using this method we derive disks that may be much more massive than previously thought, often approaching the limit of gravitational stability.

Comparison of central axis and jet ring coolant supply for turbine disk cooling on a SSME-HPOTP model

NASA Technical Reports Server (NTRS)

Kim, Y. W.; Metzger, D. E.

1992-01-01

The test facility, test methods and results are presented for an experimental study modeling the cooling of turbine disks in the blade attachment regions with multiple impinging jets, in a configuration simulating the disk cooling method employed on the Space Shuttle Main Engine oxygen turbopump. The study's objective was to provide a comparison of detailed local convection heat transfer rates obtained for a single center-supply of disk coolant with those obtained with the present flight configuration where disk coolant is supplied through an array of 19 jets located near the disk outer radius. Specially constructed disk models were used in a program designed to evaluate possible benefits and identify any possible detrimental effects involved in employing an alternate disk cooling scheme. The study involved the design, construction and testing of two full scale rotating model disks, one plane and smooth for baseline testing and the second contoured to the present flight configuration, together with the corresponding plane and contoured stator disks. Local heat transfer rates are determined from the color display of encapsulated liquid crystals coated on the disk in conjunction with use of a computer vision system. The test program was composed of a wide variety of disk speeds, flowrates, and geometrical configurations, including testing for the effects of disk boltheads and gas ingestion from the gas path region radially outboard of the disk-cavity.

Region-based multi-step optic disk and cup segmentation from color fundus image

NASA Astrophysics Data System (ADS)

Xiao, Di; Lock, Jane; Manresa, Javier Moreno; Vignarajan, Janardhan; Tay-Kearney, Mei-Ling; Kanagasingam, Yogesan

2013-02-01

Retinal optic cup-disk-ratio (CDR) is a one of important indicators of glaucomatous neuropathy. In this paper, we propose a novel multi-step 4-quadrant thresholding method for optic disk segmentation and a multi-step temporal-nasal segmenting method for optic cup segmentation based on blood vessel inpainted HSL lightness images and green images. The performance of the proposed methods was evaluated on a group of color fundus images and compared with the manual outlining results from two experts. Dice scores of detected disk and cup regions between the auto and manual results were computed and compared. Vertical CDRs were also compared among the three results. The preliminary experiment has demonstrated the robustness of the method for automatic optic disk and cup segmentation and its potential value for clinical application.

Procedures for shape optimization of gas turbine disks

NASA Technical Reports Server (NTRS)

Cheu, Tsu-Chien

1989-01-01

Two procedures, the feasible direction method and sequential linear programming, for shape optimization of gas turbine disks are presented. The objective of these procedures is to obtain optimal designs of turbine disks with geometric and stress constraints. The coordinates of the selected points on the disk contours are used as the design variables. Structural weight, stress and their derivatives with respect to the design variables are calculated by an efficient finite element method for design senitivity analysis. Numerical examples of the optimal designs of a disk subjected to thermo-mechanical loadings are presented to illustrate and compare the effectiveness of these two procedures.

Ag-Cu nanoalloyed film as a high-performance cathode electrocatalytic material for zinc-air battery

NASA Astrophysics Data System (ADS)

Lei, Yimin; Chen, Fuyi; Jin, Yachao; Liu, Zongwen

2015-04-01

A novel Ag50Cu50 film electrocatalyst for oxygen reduction reaction (ORR) was prepared by pulsed laser deposition (PLD) method. The electrocatalyst actually is Ag-Cu alloyed nanoparticles embedded in amorphous Cu film, based on transmission electron microscopy (TEM) characterization. The rotating disk electrode (RDE) measurements provide evidence that the ORR proceed via a four-electron pathway on the electrocatalysts in alkaline solution. And it is much more efficient than pure Ag catalyst. The catalytic layer has maximum power density of 67 mW cm-2 and an acceptable cell voltage at 0.863 V when current densities increased up to 100 mA cm-2 in the Ag50Cu50-based primary zinc-air battery. The resulting rechargeable zinc-air battery exhibits low charge-discharge voltage polarization of 1.1 V at 20 mAcm-2 and high durability over 100 cycles in natural air.

Nanostructured Perovskite LaCo1-xMnxO3 as Bifunctional Catalysts for Rechargeable Metal-Air Batteries

NASA Astrophysics Data System (ADS)

Ge, Xiaoming; Li, Bing; Wuu, Delvin; Sumboja, Afriyanti; An, Tao; Hor, T. S. Andy; Zong, Yun; Liu, Zhaolin

2015-09-01

Bifunctional catalyst that is active for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the most important components of rechargeable metal-air batteries. Nanostructured perovskite bifunctional catalysts comprising La, Co and Mn(LaCo1-xMnxO3, LCMO) are synthesized by hydrothermal methods. The morphology, structure and electrochemical activity of the perovskite bifunctional catalysts are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and rotating disk electrode (RDE) techniques. Nanorod, nanodisc and nanoparticle are typical morphologies of LCMO. The electrocatalytic activity of LCMO is significantly improved by the addition of conductive materials such as carbon nanotube. To demonstrate the practical utilization, LCMO in the composition of LaCo0.8Mn0.2O3(LCMO82) is used as air cathode catalysts for rechargeable zinc-air batteries. The battery prototype can sustain 470 h or 40 discharge-charge cycles equivalent.

A new servo method using servo layer and transverse MR head for submicron track servo on hard computer disks

NASA Astrophysics Data System (ADS)

Tan, Baolin; Mapps, Desmond J.; Pan, Genhua; Robinson, Paul

1996-03-01

A disk with a data, servo and isolation layer has been fabricated with the data layer magnetized along the circumferential direction. The servo layer was recorded with servo pattern magnetized along the radial direction. A continuous servo signal is obtained and the servo does not occupy any data area. In this new method, the servo and data bits can share media surface area on the disk without interference. Track following on 0.7 μm tracks has been demonstrated using the new servo method on longitudinal rigid disks.

Nanosecond plasma-mediated electrosurgery with elongated electrodes

NASA Astrophysics Data System (ADS)

Vankov, Alexander; Palanker, Daniel

2007-06-01

Progress in interventional medicine is associated with the development of more delicate and less invasive surgical procedures, which requires more precise and less traumatic, yet affordable, surgical instruments. Previously we reported on the development of the pulsed electron avalanche knife for dissection of soft tissue in liquid media using the 100 ns plasma-mediated electric discharges applied via a 25 μm disk microelectrode. Cavitation bubbles accompanying explosive vaporization of the liquid medium in front of such a pointed electrode produced a series of craters that did not always merge into a continuous cut. In addition, this approach of surface ablation provided a limited depth of cutting. Application of an elongated electrode capable of cutting with its edge rather than just with its pointed apex faces a problem of nonuniformity of the electric field on a nonspherical electrode. In this article we explore dynamics of the plasma-mediated nanosecond discharges in liquid medium in positive and negative polarities and describe the geometry of an electrode that provides a sufficiently uniform electric field along an extended edge of a surgical probe. A highly enhanced and uniform electric field was obtained on very sharp (2.5 μm) exposed edges of a planar electrode insulated on its flat sides. Uniform ionization and simultaneous vaporization was obtained along the whole edge of such a blade with 100 ns pulses at 4-6 kV. A continuous cutting rate of 1 mm/s in the retina and in soft membranes was achieved at a pulse repetition rate of 100 Hz. The collateral damage zone at the edges of incision did not exceed 80 μm. Negative polarity was found advantageous due to the lower rate of electrode erosion and due to better spatial confinement of the plasma-mediated discharge in liquid.

Gas spark switches with increased operating life for Marx generator of lightning test complex

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

Bykov, Yu. A.; Krastelev, E. G., E-mail: ekrastelev@yandex.ru

A new design of gas spark switches with an increased operating life and stable dynamic characteristics for the Marx generator of the lightning test complex has been developed. The switches are characterized by the following parameters in the mode of operation: voltage up to 80 kV, discharge current up to 50 kA, flowing charge up to 3.5 C/pulse. An increased operating life is achieved by using torus-shaped electrodes with increased working surface area and a trigger electrode in the form of a thick disk with a hole located between them. Low breakdown delay time and high stability of breakdown voltagemore » under dynamic conditions are provided by gas preionization in the spark gap using UV radiation of an additional corona discharge in the axial region.« less

Concentration Effects of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Activity for Three Platinum Catalysts

DOE PAGES

Christ, J. M.; Neyerlin, K. C.; Richards, R.; ...

2014-10-04

A rotating disk electrode (RDE) along with cyclic voltammetry (CV) and linear sweep voltammetry (LSV), were used to investigate the impact of two model compounds representing degradation products of Nafion and 3M perfluorinated sulfonic acid membranes on the electrochemical surface area (ECA) and oxygen reduction reaction (ORR) activity of polycrystalline Pt, nano-structured thin film (NSTF) Pt (3M), and Pt/Vulcan carbon (Pt/Vu) (TKK) electrodes. ORR kinetic currents (measured at 0.9 V and transport corrected) were found to decrease linearly with the log of concentration for both model compounds on all Pt surfaces studied. Ultimately, model compound adsorption effects on ECA weremore » more abstruse due to competitive organic anion adsorption on Pt surfaces superimposing with the hydrogen underpotential deposition (HUPD) region.« less

Development of Li-S Battery With Improved Sulphur Utilization and Cyclic Stability

DTIC Science & Technology

2017-12-04

blade technique and dried overnight at 80 °C in vacuum oven. The dried sample was cut into 12 mm electrode disks. The 2032 coin assembly has been done...capability up to 2C as shown in Fig. 8(c), after running cell at high current and going back to lower 0.1C the cell shows the specific...shows a high rate capability up to 2C. And after running cell at high current and reverse back to lower 0.1

Cadmium poisoning of oxygen reduction on platinum electrode in potassium hydroxide

NASA Technical Reports Server (NTRS)

Miller, R. O.

1972-01-01

Experiment with a rotating disk and ring apparatus showed no poisoning by cadmium in 8.5 M KOH, alone or with Cl(-) or CO3(=). Poisoning does not occur either in 0.1 M KOH supernatant at CdO, but a partially reversible poisoning results from .0001 M CdCl2 and traces of fatty acid are present. Evidence indicates that the catastrophic poisoning affects the four-electron O2 reduction more than it does the one-electron H3O(+) discharge.

New Materials for Smart Structures: a US: Japan Global Initiative

DTIC Science & Technology

2004-03-01

realization of the MPB in the Gallate:Scandate system and in the modified bismuth lanthanum ferrate lead titanate systems. A major puzzle in BiFeO3 which has...magnetization. A new major clue as to the origin of the high switchable polarization is provided by our most recent work on the modified bismuth lanthanum ...ferrate: gallate solid solutions with MPBs. In suitable composition switchability is only possible with limited electrode in a larger disk, and the fully

Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Powell, Diana; Murray-Clay, Ruth; Schlichting, Hilke E.

2017-05-01

We present a novel method for determining the surface density of protoplanetary disks through consideration of disk “dust lines,” which indicate the observed disk radial scale at different observational wavelengths. This method relies on the assumption that the processes of particle growth and drift control the radial scale of the disk at late stages of disk evolution such that the lifetime of the disk is equal to both the drift timescale and growth timescale of the maximum particle size at a given dust line. We provide an initial proof of concept of our model through an application to the disk TW Hya and are able to estimate the disk dust-to-gas ratio, CO abundance, and accretion rate in addition to the total disk surface density. We find that our derived surface density profile and dust-to-gas ratio are consistent with the lower limits found through measurements of HD gas. The CO ice line also depends on surface density through grain adsorption rates and drift and we find that our theoretical CO ice line estimates have clear observational analogues. We further apply our model to a large parameter space of theoretical disks and find three observational diagnostics that may be used to test its validity. First, we predict that the dust lines of disks other than TW Hya will be consistent with the normalized CO surface density profile shape for those disks. Second, surface density profiles that we derive from disk ice lines should match those derived from disk dust lines. Finally, we predict that disk dust and ice lines will scale oppositely, as a function of surface density, across a large sample of disks.

Flexible micro supercapacitors based on laser-scribed graphene/ZnO nanocomposite

NASA Astrophysics Data System (ADS)

Amiri, Morteza Hassanpour; Namdar, Naser; Mashayekhi, Alireza; Ghasemi, Foad; Sanaee, Zeinab; Mohajerzadeh, Shams

2016-08-01

We report on the fabrication of graphene/Zno nanocomposite supercapacitor electrodes. Laser-scribing process was implemented in order to reduce the graphene oxide (GO)/ZnO mixture on a DVD disk. With reduced graphene oxide (rGO)/ZnO composite prepared by a mass ratio of 1:25 of Zn(NO3)2·6H2O to GO constituents, nanoparticles of ZnO with sizes ranging from 20 to 50 nm are obtained. Consequently, 12 times improvement in the specific capacitance was achieved at a current density of 0.1 mA/cm2 compared with pristine rGO electrodes. In addition, flexible microsupercapacitor was fabricated by spin coating of the gel electrolyte, showing high stack capacitance of 9 F/cm3 at a current density of 150 mA/cm2. This microsupercapacitor delivers power density of 70 mW/cm3 and energy density of 1.2 mWh/cm3. Furthermore, the performance of device was investigated at different bending angles. The resulted characteristics demonstrate that LSG/ZnO nanocomposite is a promising electrode material for high-performance supercapacitors.

Influence of Pb 2+ ions in the H 2 oxidation on Pt catalyzed hydrogen diffusion anodes in sulfuric acid: presence of oscillatory phenomena

NASA Astrophysics Data System (ADS)

Expósito, E.; Sánchez-Sánchez, C. M.; Solla-Gullón, J.; Montiel, V.

The influence of Pb 2+ ions in sulfuric acid medium on the behavior of a platinum catalyzed hydrogen diffusion electrode (HDE) in a filter press reactor has been studied. A voltammetric study of the H 2 oxidation reaction on a polyoriented platinum electrode and a platinum rotating disk electrode (RDE) in presence of lead ions in solution has also been carried out. Potential oscillations were found in galvanostatic experiments of H 2 oxidation using a HDE catalyzed with platinum when Pb 2+ ions are present in solution. This oscillatory phenomenon was also observed when hydrogen oxidation was carried out in presence of Pb 2+ ions using a platinum RDE. The oscillatory behavior observed has been attributed to an adsorption-oxidation-desorption process of lead on the platinum surface. Due to the low solubility of Pb 2+ in sulfuric acid, at high values of coverage, lead is oxidised to insoluble lead sulfate that blocks the Pt surface. The coupling of the dissolution of lead sulfate and the Pb electrochemical adsorption-oxidation processes cause the oscillatory phenomenon.

Analysis of focusing error signals by differential astigmatic method under off-center tracking in the land-groove-type optical disk

NASA Astrophysics Data System (ADS)

Shinoda, Masahisa; Nakatani, Hidehiko

2015-04-01

We theoretically calculate the behavior of the focusing error signal in the land-groove-type optical disk when the objective lens traverses on out of the radius of the optical disk. The differential astigmatic method is employed instead of the conventional astigmatic method for generating the focusing error signals. The signal behaviors are compared and analyzed in terms of the gain difference of the slope sensitivity of the focusing error signals from the land and the groove. In our calculation, the format of digital versatile disc-random access memory (DVD-RAM) is adopted as the land-groove-type optical disk model, and advantageous conditions for suppressing the gain difference are investigated. The calculation method and results described in this paper will be reflected in the next generation land-groove-type optical disks.

Determination of 129I in environmental samples by AMS and NAA using an anion exchange resin disk

NASA Astrophysics Data System (ADS)

Suzuki, Takashi; Banba, Shigeru; Kitamura, Toshikatsu; Kabuto, Shoji; Isogai, Keisuke; Amano, Hikaru

2007-06-01

We have developed a new extraction method for the measurement of 129I by accelerator mass spectrometry (AMS) utilizing an anion exchange resin disk. In comparison to traditional methods such as solvent extraction and ion exchange, this method provides for simple and quick sample handling. This extraction method was tested on soil, seaweed and milk samples, but because of disk clogging, the milk samples and some of the seaweed could not be applied successfully. Using this new extraction method to prepare samples for AMS analysis produced isotope ratios of iodine in good agreement with neutron activation analysis (NAA). The disk extraction method which take half an hour is faster than previous techniques, such as solvent extraction or ion exchange which take a few hours. The combination of the disk method and the AMS measurement is a powerful tool for the determination of 129I. Furthermore, these data will be available for the environmental monitoring before and during the operation of a new nuclear fuel reprocessing plant in Japan.

Practical and Secure Recovery of Disk Encryption Key Using Smart Cards

NASA Astrophysics Data System (ADS)

Omote, Kazumasa; Kato, Kazuhiko

In key-recovery methods using smart cards, a user can recover the disk encryption key in cooperation with the system administrator, even if the user has lost the smart card including the disk encryption key. However, the disk encryption key is known to the system administrator in advance in most key-recovery methods. Hence user's disk data may be read by the system administrator. Furthermore, if the disk encryption key is not known to the system administrator in advance, it is difficult to achieve a key authentication. In this paper, we propose a scheme which enables to recover the disk encryption key when the user's smart card is lost. In our scheme, the disk encryption key is not preserved anywhere and then the system administrator cannot know the key before key-recovery phase. Only someone who has a user's smart card and knows the user's password can decrypt that user's disk data. Furthermore, we measured the processing time required for user authentication in an experimental environment using a virtual machine monitor. As a result, we found that this processing time is short enough to be practical.

A hybrid DNA-templated gold nanocluster for enhanced enzymatic reduction of oxygen

DOE PAGES

Chakraborty, Saumen; Babanova, Sofia; Rocha, Reginaldo C.; ...

2015-08-19

We report the synthesis and characterization of a new DNA-templated gold nanocluster (AuNC) of ~1 nm in diameter and possessing ~7 Au atoms. When integrated with bilirubin oxidase (BOD) and single walled carbon nanotubes (SWNTs), the AuNC acts as an enhancer of electron transfer (ET) and lowers the overpotential of electrocatalytic oxygen reduction reaction (ORR) by ~15 mV as compared to the enzyme alone. In addition, the presence of AuNC causes significant enhancements in the electrocatalytic current densities at the electrode. Control experiments show that such enhancement of ORR by the AuNC is specific to nanoclusters and not to plasmonicmore » gold particles. Rotating ring disk electrode (RRDE) measurements confirm 4e– reduction of O 2 to H 2O with minimal production of H 2O 2, suggesting that the presence of AuNC does not perturb the mechanism of ORR catalyzed by the enzyme. This unique role of the AuNC as enhancer of ET at the enzyme-electrode interface makes it a potential candidate for the development of cathodes in enzymatic fuel cells, which often suffer from poor electronic communication between the electrode surface and the enzyme active site. In conclusion, the AuNC displays phosphorescence with large Stokes shift and microsecond lifetime.« less

Wave excitation at Lindblad resonances using the method of multiple scales

NASA Astrophysics Data System (ADS)

Horák, Jiří

2017-12-01

In this note, the method of multiple scales is adopted to the problem of excitation of non–axisymmetric acoustic waves in vertically integrated disk by tidal gravitational fields. We derive a formula describing a waveform of exited wave that is uniformly valid in a whole disk as long as only a single Lindblad resonance is present. Our formalism is subsequently applied to two classical problems: trapped p–mode oscillations in relativistic accretion disks and the excitation of waves in infinite disks.

Detection of ESBL among ampc producing enterobacteriaceae using inhibitor-based method

PubMed Central

Bakthavatchalu, Sasirekha; Shakthivel, Uma; Mishra, Tannu

2013-01-01

Introduction The occurrence of multiple β-lactamases among bacteria only limits the therapeutic options but also poses a challenge. A study using boronic acid (BA), an AmpC enzyme inhibitor, was designed to detect the combined expression of AmpC β-lactamases and extended-spectrum β-lactamases (ESBLs) in bacterial isolates further different phenotypic methods are compared to detect ESBL and AmpC. Methods A total of 259 clinical isolates of Enterobacteriaceae were isolated and screened for ESBL production by (i) CLSI double-disk diffusion method (ii) cefepime- clavulanic acid method (iii) boronic disk potentiation method. AmpC production was detected using cefoxitin alone and in combination with boronic acid and confirmation was done by three dimensional disk methods. Isolates were also subjected to detailed antibiotic susceptibility test. Results Among 259 isolates, 20.46% were coproducers of ESBL and AmpC, 26.45% were ESBL and 5.40% were AmpC. All of the 53 AmpC and ESBL coproducers were accurately detected by boronic acid disk potentiation method. Conclusion The BA disk test using Clinical and Laboratory Standards Institute methodology is simple and very efficient method that accurately detects the isolates that harbor both AmpCs and ESBLs. PMID:23504148

Finite Element Analysis of Flexural Vibrations in Hard Disk Drive Spindle Systems

NASA Astrophysics Data System (ADS)

LIM, SEUNGCHUL

2000-06-01

This paper is concerned with the flexural vibration analysis of the hard disk drive (HDD) spindle system by means of the finite element method. In contrast to previous research, every system component is here analytically modelled taking into account its structural flexibility and also the centrifugal effect particularly on the disk. To prove the effectiveness and accuracy of the formulated models, commercial HDD systems with two and three identical disks are selected as examples. Then their major natural modes are computed with only a small number of element meshes as the shaft rotational speed is varied, and subsequently compared with the existing numerical results obtained using other methods and newly acquired experimental ones. Based on such a series of studies, the proposed method can be concluded as a very promising tool for the design of HDDs and various other high-performance computer disk drives such as floppy disk drives, CD ROM drives, and their variations having spindle mechanisms similar to those of HDDs.

High-pressure liquid chromatography analysis of antibiotic susceptibility disks.

PubMed Central

Hagel, R B; Waysek, E H; Cort, W M

1979-01-01

The analysis of antibiotic susceptibility disks by high-pressure liquid chromatography (HPLC) was investigated. Methods are presented for the potency determination of mecillinam, ampicillin, carbenicillin, and cephalothin alone and in various combinations. Good agreement between HPLC and microbiological data is observed for potency determinations with recoveries of greater than 95%. Relative standard deviations of lower than 2% are recorded for each HPLC method. HPLC methods offer improved accuracy and greater precision when compared to the standard microbiological methods of analysis for susceptibility disks. PMID:507793

Levofloxacin susceptibility testing against Helicobacter pylori: evaluation of a modified disk diffusion method compared to E test.

PubMed

Boyanova, Lyudmila; Ilieva, Juliana; Gergova, Galina; Mitov, Ivan

2016-01-01

We compared levofloxacin (1 μg/disk) disk diffusion method to E test against 212 Helicobacter pylori strains. Using diameter breakpoints for susceptibility (≥15 mm) and resistance (≤9 mm), very major error, major error rate, and categoric agreement were 0.0%, 0.6%, and 93.9%, respectively. The method may be useful in low-resource laboratories. Copyright © 2016 Elsevier Inc. All rights reserved.

Three-dimensional discrete element method simulation of core disking

NASA Astrophysics Data System (ADS)

Wu, Shunchuan; Wu, Haoyan; Kemeny, John

2018-04-01

The phenomenon of core disking is commonly seen in deep drilling of highly stressed regions in the Earth's crust. Given its close relationship with the in situ stress state, the presence and features of core disking can be used to interpret the stresses when traditional in situ stress measuring techniques are not available. The core disking process was simulated in this paper using the three-dimensional discrete element method software PFC3D (particle flow code). In particular, PFC3D is used to examine the evolution of fracture initiation, propagation and coalescence associated with core disking under various stress states. In this paper, four unresolved problems concerning core disking are investigated with a series of numerical simulations. These simulations also provide some verification of existing results by other researchers: (1) Core disking occurs when the maximum principal stress is about 6.5 times the tensile strength. (2) For most stress situations, core disking occurs from the outer surface, except for the thrust faulting stress regime, where the fractures were found to initiate from the inner part. (3) The anisotropy of the two horizontal principal stresses has an effect on the core disking morphology. (4) The thickness of core disk has a positive relationship with radial stress and a negative relationship with axial stresses.

Collective transport for active matter run-and-tumble disk systems on a traveling-wave substrate

DOE PAGES

Sándor, Csand; Libál, Andras; Reichhardt, Charles; ...

2017-01-17

Here, we examine numerically the transport of an assembly of active run-and-tumble disks interacting with a traveling-wave substrate. We show that as a function of substrate strength, wave speed, disk activity, and disk density, a variety of dynamical phases arise that are correlated with the structure and net flux of disks. We find that there is a sharp transition into a state in which the disks are only partially coupled to the substrate and form a phase-separated cluster state. This transition is associated with a drop in the net disk flux, and it can occur as a function of themore » substrate speed, maximum substrate force, disk run time, and disk density. Since variation of the disk activity parameters produces different disk drift rates for a fixed traveling-wave speed on the substrate, the system we consider could be used as an efficient method for active matter species separation. Within the cluster phase, we find that in some regimes the motion of the cluster center of mass is in the opposite direction to that of the traveling wave, while when the maximum substrate force is increased, the cluster drifts in the direction of the traveling wave. This suggests that swarming or clustering motion can serve as a method by which an active system can collectively move against an external drift.« less

Collective transport for active matter run-and-tumble disk systems on a traveling-wave substrate

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

Sándor, Csand; Libál, Andras; Reichhardt, Charles

Here, we examine numerically the transport of an assembly of active run-and-tumble disks interacting with a traveling-wave substrate. We show that as a function of substrate strength, wave speed, disk activity, and disk density, a variety of dynamical phases arise that are correlated with the structure and net flux of disks. We find that there is a sharp transition into a state in which the disks are only partially coupled to the substrate and form a phase-separated cluster state. This transition is associated with a drop in the net disk flux, and it can occur as a function of themore » substrate speed, maximum substrate force, disk run time, and disk density. Since variation of the disk activity parameters produces different disk drift rates for a fixed traveling-wave speed on the substrate, the system we consider could be used as an efficient method for active matter species separation. Within the cluster phase, we find that in some regimes the motion of the cluster center of mass is in the opposite direction to that of the traveling wave, while when the maximum substrate force is increased, the cluster drifts in the direction of the traveling wave. This suggests that swarming or clustering motion can serve as a method by which an active system can collectively move against an external drift.« less

Analysis of the sweeped actuator line method

DOE PAGES

Nathan, Jörn; Masson, Christian; Dufresne, Louis; ...

2015-10-16

The actuator line method made it possible to describe the near wake of a wind turbine more accurately than with the actuator disk method. Whereas the actuator line generates the helicoidal vortex system shed from the tip blades, the actuator disk method sheds a vortex sheet from the edge of the rotor plane. But with the actuator line come also temporal and spatial constraints, such as the need for a much smaller time step than with actuator disk. While the latter one only has to obey the Courant-Friedrichs-Lewy condition, the former one is also restricted by the grid resolution andmore » the rotor tip-speed. Additionally the spatial resolution has to be finer for the actuator line than with the actuator disk, for well resolving the tip vortices. Therefore this work is dedicated to examining a method in between of actuator line and actuator disk, which is able to model the transient behavior, such as the rotating blades, but which also relaxes the temporal constraint. Therefore a larger time-step is used and the blade forces are swept over a certain area. As a result, the main focus of this article is on the aspect of the blade tip vortex generation in comparison with the standard actuator line and actuator disk.« less

Analysis of the sweeped actuator line method

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

Nathan, Jörn; Masson, Christian; Dufresne, Louis

The actuator line method made it possible to describe the near wake of a wind turbine more accurately than with the actuator disk method. Whereas the actuator line generates the helicoidal vortex system shed from the tip blades, the actuator disk method sheds a vortex sheet from the edge of the rotor plane. But with the actuator line come also temporal and spatial constraints, such as the need for a much smaller time step than with actuator disk. While the latter one only has to obey the Courant-Friedrichs-Lewy condition, the former one is also restricted by the grid resolution andmore » the rotor tip-speed. Additionally the spatial resolution has to be finer for the actuator line than with the actuator disk, for well resolving the tip vortices. Therefore this work is dedicated to examining a method in between of actuator line and actuator disk, which is able to model the transient behavior, such as the rotating blades, but which also relaxes the temporal constraint. Therefore a larger time-step is used and the blade forces are swept over a certain area. As a result, the main focus of this article is on the aspect of the blade tip vortex generation in comparison with the standard actuator line and actuator disk.« less

Free Vibration Analysis of a Spinning Flexible DISK-SPINDLE System Supported by Ball Bearing and Flexible Shaft Using the Finite Element Method and Substructure Synthesis

NASA Astrophysics Data System (ADS)

JANG, G. H.; LEE, S. H.; JUNG, M. S.

2002-03-01

Free vibration of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft is analyzed by using Hamilton's principle, FEM and substructure synthesis. The spinning disk is described by using the Kirchhoff plate theory and von Karman non-linear strain. The rotating spindle and stationary shaft are modelled by Rayleigh beam and Euler beam respectively. Using Hamilton's principle and including the rigid body translation and tilting motion, partial differential equations of motion of the spinning flexible disk and spindle are derived consistently to satisfy the geometric compatibility in the internal boundary between substructures. FEM is used to discretize the derived governing equations, and substructure synthesis is introduced to assemble each component of the disk-spindle-bearing-shaft system. The developed method is applied to the spindle system of a computer hard disk drive with three disks, and modal testing is performed to verify the simulation results. The simulation result agrees very well with the experimental one. This research investigates critical design parameters in an HDD spindle system, i.e., the non-linearity of a spinning disk and the flexibility and boundary condition of a stationary shaft, to predict the free vibration characteristics accurately. The proposed method may be effectively applied to predict the vibration characteristics of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft in the various forms of computer storage device, i.e., FDD, CD, HDD and DVD.

Multi-terabyte EIDE disk arrays running Linux RAID5

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

Sanders, D.A.; Cremaldi, L.M.; Eschenburg, V.

2004-11-01

High-energy physics experiments are currently recording large amounts of data and in a few years will be recording prodigious quantities of data. New methods must be developed to handle this data and make analysis at universities possible. Grid Computing is one method; however, the data must be cached at the various Grid nodes. We examine some storage techniques that exploit recent developments in commodity hardware. Disk arrays using RAID level 5 (RAID-5) include both parity and striping. The striping improves access speed. The parity protects data in the event of a single disk failure, but not in the case ofmore » multiple disk failures. We report on tests of dual-processor Linux Software RAID-5 arrays and Hardware RAID-5 arrays using a 12-disk 3ware controller, in conjunction with 250 and 300 GB disks, for use in offline high-energy physics data analysis. The price of IDE disks is now less than $1/GB. These RAID-5 disk arrays can be scaled to sizes affordable to small institutions and used when fast random access at low cost is important.« less

Method of improving fuel cell performance by removing at least one metal oxide contaminant from a fuel cell electrode

DOEpatents

Kim, Yu Seung [Los Alamos, NM; Choi, Jong-Ho [Los Alamos, NM; Zelenay, Piotr [Los Alamos, NM

2009-08-18

A method of removing contaminants from a fuel cell catalyst electrode. The method includes providing a getter electrode and a fuel cell catalyst electrode having at least one contaminant to a bath and applying a voltage sufficient to drive the contaminant from the fuel cell catalyst electrode to the getter electrode. Methods of removing contaminants from a membrane electrode assembly of a fuel cell and of improving performance of a fuel cell are also provided.

Discharge dynamics of pin-to-plate dielectric barrier discharge at atmospheric pressure

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

Sun Liqun; Huang, Xiaojiang; Member of Magnetic Confinement Fusion Research Center, Ministry of Education of the People's Republic of China, Shanghai 201620

2010-11-15

The discharge dynamics of pin-to-plate dielectric barrier discharge was studied in atmospheric helium at 20 kHz. The discharge was predominately ignited in positive half cycle of applied voltage with sinusoidal waveform. The temporal evolution of the discharge was investigated vertically along the discharge gap and radically on the dielectric surface by time resolved imaging. It is found that a discharge column with a diameter of 2 mm was ignited above the pin electrode and expanded toward a plate electrode. On the dielectric surface with space charge accumulation, plasma disk in terms of plasma ring was formed with radius up tomore » 25 mm. The expansion velocity of plasma ring can reach a hypersonic speed of 3.0 km/s. The ionization wave due to electron diffusion is considered to be the mechanism for plasma ring formation and dynamics.« less

Discharge dynamics of pin-to-plate dielectric barrier discharge at atmospheric pressure

NASA Astrophysics Data System (ADS)

Sun, Liqun; Huang, Xiaojiang; Zhang, Jie; Zhang, Jing; Shi, J. J.

2010-11-01

The discharge dynamics of pin-to-plate dielectric barrier discharge was studied in atmospheric helium at 20 kHz. The discharge was predominately ignited in positive half cycle of applied voltage with sinusoidal waveform. The temporal evolution of the discharge was investigated vertically along the discharge gap and radically on the dielectric surface by time resolved imaging. It is found that a discharge column with a diameter of 2 mm was ignited above the pin electrode and expanded toward a plate electrode. On the dielectric surface with space charge accumulation, plasma disk in terms of plasma ring was formed with radius up to 25 mm. The expansion velocity of plasma ring can reach a hypersonic speed of 3.0 km/s. The ionization wave due to electron diffusion is considered to be the mechanism for plasma ring formation and dynamics.

A Voltammetric Electronic Tongue for the Resolution of Ternary Nitrophenol Mixtures

PubMed Central

González-Calabuig, Andreu; Cetó, Xavier

2018-01-01

This work reports the applicability of a voltammetric sensor array able to quantify the content of 2,4-dinitrophenol, 4-nitrophenol, and picric acid in artificial samples using the electronic tongue (ET) principles. The ET is based on cyclic voltammetry signals, obtained from an array of metal disk electrodes and a graphite epoxy composite electrode, compressed using discrete wavelet transform with chemometric tools such as artificial neural networks (ANNs). ANNs were employed to build the quantitative prediction model. In this manner, a set of standards based on a full factorial design, ranging from 0 to 300 mg·L−1, was prepared to build the model; afterward, the model was validated with a completely independent set of standards. The model successfully predicted the concentration of the three considered phenols with a normalized root mean square error of 0.030 and 0.076 for the training and test subsets, respectively, and r ≥ 0.948. PMID:29342848

Examining the accuracy of astrophysical disk simulations with a generalized hydrodynamical test problem [The role of pressure and viscosity in SPH simulations of astrophysical disks

DOE PAGES

Raskin, Cody; Owen, J. Michael

2016-10-24

Here, we discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extensionmore » of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.« less

Adsorption of Cd2+ on carboxyl-terminated superparamagnetic iron oxide nanoparticles.

PubMed

Feng, Zhange; Zhu, Shun; Martins de Godoi, Denis Ricardo; Samia, Anna Cristina S; Scherson, Daniel

2012-04-17

The affinity of Cd(2+) toward carboxyl-terminated species covalently bound to monodisperse superparamagnetic iron oxide nanoparticles, Fe(3)O(4)(np)-COOH, was investigated in situ in aqueous electrolytes using rotating disk electrode techniques. Strong evidence that the presence of dispersed Fe(3)O(4)(np)-COOH does not affect the diffusion limiting currents was obtained using negatively and positively charged redox active species in buffered aqueous media (pH = 7) devoid of Cd(2+). This finding made it possible to determine the concentration of unbound Cd(2+) in solutions containing dispersed Fe(3)O(4)(np)-COOH, 8 and 17 nm in diameter, directly from the Levich equation. The results obtained yielded Cd(2+) adsorption efficiencies of ~20 μg of Cd/mg of Fe(3)O(4)(np)-COOH, which are among the highest reported in the literature employing ex situ methods. Desorption of Cd(2+) from Fe(3)O(4)(np)-COOH, as monitored by the same forced convection method, could be accomplished by lowering the pH, a process found to be highly reversible.

Preparation and characterization of conductive and transparent ruthenium dioxide sol-gel films.

PubMed

Allhusen, John S; Conboy, John C

2013-11-27

RuO2 conductive thin films were synthesized using the sol-gel method and deposited onto transparent insulating substrates. The optical transmission, film thickness, surface morphology and composition, resistivity, and spectroelectrochemical performance have been characterized. The optical transmission values of these films ranged from 70 to 89% in the visible region and from 56 to 88% in the infrared region. Resistivity values of the RuO2 sol-gel films varied from 1.02 × 10(-3) to 1.13 Ω cm and are highly dependent on the initial solution concentration of RuO2 in the sol-gel. The RuO2 sol-gel films were used as electrodes for the electrochemical oxidation and reduction of ferrocenemethanol. The electrochemical behavior of our novel RuO2 sol-gel films was compared to that of a standard platinum disk electrode and showed no appreciable differences in the half-wave potential (E1/2). The mechanical and chemical stability of the coatings was tested by physical abrasion and exposure to highly acidic, oxidizing Piranha solution. Repeated exposure to these extreme conditions did not result in any appreciable decline in electrochemical performance. Finally, the use of the novel RuO2 sol-gel conductive and transparent films was demonstrated in a spectroelectrochemistry experiment in which the oxidation and reduction of ferrocenemethanol was monitored via UV-vis spectroscopy as the applied potential was cycled.

Time-resolved processes in a pulsed electrical discharge in argon bubbles in water

NASA Astrophysics Data System (ADS)

Gershman, S.; Belkind, A.

2010-12-01

A phenomenological picture of a pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging characterization methods. The discharge is generated by applying 1 μ s pulses of 5 to 20 kV between a needle and a disk electrode submerged in water. An Ar gas bubble surrounds the tip of the needle electrode. Imaging, electrical characteristics, and time-resolved optical emission spectroscopic data suggest a fast streamer propagation mechanism and the formation of a plasma channel in the bubble. Comparing the electrical and imaging data for consecutive pulses applied to the bubble at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from the presence of long-lived chemical species, such as ozone and oxygen. Imaging and electrical data show the presence of two discharge events during each applied voltage pulse, a forward discharge near the beginning of the applied pulse depositing charge on the surface of the bubble and a reverse discharge removing the accumulated charge from the water/gas interface when the applied voltage is turned off. The pd value of ~ 300-500 torr cm, the 1 μs long pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique compared to the traditional corona or dielectric barrier discharges.

Quasar Accretion Disk Sizes With Continuum Reverberation Mapping From the Dark Energy Survey

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

Mudd, D.; et al.

We present accretion disk size measurements for 15 luminous quasars atmore » $$0.7 \\leq z \\leq 1.9$$ derived from $griz$ light curves from the Dark Energy Survey. We measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well-described by a single blackbody. In the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. The second method fits the model parameters for the canonical Shakura-Sunyaev thin disk directly rather than solving for the individual time lags between the light curves. Our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3-1 times the Eddington rate. These results are also in reasonable agreement with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results.« less

Electrocatalysts for oxygen electrodes in fuel cells and water electrolyzers for space applications

NASA Technical Reports Server (NTRS)

Prakash, Jai; Tryk, Donald; Yeager, Ernest

1989-01-01

In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation (1,2). Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium). A possible approach to this problem is to immobilize the pyrochlore catalyst within an ionic-conducting solid polymer, which would replace the fluid electrolyte within the porous gas diffusion O2 electrode. For bulk alkaline electrolyte, an anion-exchange polymer is needed with a transference number close to unity for the Oh(-) ion. Preliminary short-term measurements with lead ruthenates using a commercially available partially-fluorinated anion-exchange membrane as an overlayer on the porous gas-fed electrode indicate lower anodic polarization and virtually unchanged cathodic polarization.

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test.

PubMed Central

Doern, G V; Scott, D R; Rashad, A L; Kim, K S

1981-01-01

A total of 556 unique blood culture isolates of nonfastidious aerobic and facultatively anaerobic bacteria were examined by direct and standardized disk susceptibility test methods (4,234 antibiotic-organism comparisons). When discrepancies which could be accounted for by the variability inherent in disk diffusion susceptibility tests were excluded, the direct method demonstrated 96.8% overall agreement with the standardized method. A total of 1.6% minor, 1.5% major, and 0.1% very major discrepancies were noted. PMID:7325634

Disk Susceptibility Studies with Cefazolin and Cephalothin

PubMed Central

Actor, Paul; Guarini, Joseph; Uri, Joseph; Dickson, Judith; Pauls, John F.; Weisbach, Jerry A.

1974-01-01

Cefazolin and cephalothin disk susceptibility and minimal inhibitory concentration determinations were conducted on 591 clinical isolates. Cefazolin demonstrated superior activity, as shown by lower minimal inhibitory concentrations, and a greater percentage of isolates inhibited in the disk susceptibility test. The cephalothin antibiotic class disk by the standard Bauer-Kirby method failed to detect susceptibility to cefazolin in a significant percentage of Escherchia coli, Enterobacter species, and Enterococcus isolates. A separate cefazolin disk with a susceptibility cut-off point of 18 mm is recommended. An alternative to a separate cefazolin disk would be a reinterpretation of the cephalothin susceptibility disk zone diameters so that it would more adequately predict cefazolin activity. PMID:4840450

Nonlinear calculations of the time evolution of black hole accretion disks

NASA Technical Reports Server (NTRS)

Luo, C.

1994-01-01

Based on previous works on black hole accretion disks, I continue to explore the disk dynamics using the finite difference method to solve the highly nonlinear problem of time-dependent alpha disk equations. Here a radially zoned model is used to develop a computational scheme in order to accommodate functional dependence of the viscosity parameter alpha on the disk scale height and/or surface density. This work is based on the author's previous work on the steady disk structure and the linear analysis of disk dynamics to try to apply to x-ray emissions from black candidates (i.e., multiple-state spectra, instabilities, QPO's, etc.).

Generation and maintenance of bisymmetric spiral magnetic fields in disk galaxies in differential rotation

NASA Astrophysics Data System (ADS)

Sawa, Takeyasu; Fujimoto, M.

1993-05-01

The approximate dynamo equation, which yields asymptotic solutions for the large scale bisymmetric spiral (BSS) magnetic fields rotating rigidly over a large area of the galactic disk, is derived. The vertical thickness and the dynamo strength of the gaseous disk which are necessary to generate and sustain the BSS magnetic fields is determined. The globally BSS magnetic fields which propagate over the disk as a wave without being twisted more tightly are reproduced. A poloidal field configuration is theoretically predicted in the halo around the disk, and is observed in the edge-on galaxy NGC4631. Mathematical methods for the galactic dynamo are shown to be equivalent. Those methods give different growth rates between the BSS and the axisymmetric spiral (ASS) magnetic fields in the disk. Magnetohydrodynamical excitation is discussed between the BSS magnetic fields and the two armed spiral density waves.

EXAMINING THE ACCURACY OF ASTROPHYSICAL DISK SIMULATIONS WITH A GENERALIZED HYDRODYNAMICAL TEST PROBLEM

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

Raskin, Cody; Owen, J. Michael, E-mail: raskin1@llnl.gov, E-mail: mikeowen@llnl.gov

2016-11-01

We discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extension ofmore » SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.« less

Electrocatalysis of fuel cell reactions: Investigation of alternate electrolytes

NASA Technical Reports Server (NTRS)

Chin, D. T.; Hsueh, K. L.; Chang, H. H.

1984-01-01

Oxygen reduction and transport properties of the electrolyte in the phosphoric acid fuel cell are studied. The areas covered were: (1) development of a theoretical expression for the rotating ring disk electrode technique; (2) determination of the intermediate reaction rate constants for oxygen reduction on platinum in phosphoric acid electrolyte; (3) determination of oxygen reduction mechanism in trifluoreomethanesulfonic acid (TFMSA) which was considered as an alternate electrolyte for the acid fuel cells; and (4) the measurement of transport properties of the phosphoric acid electrolyte at high concentrations and temperatures.

Ultrasound-assisted Micro-emulsion Synthesis of a Highly Active Nano-particle Catalyst

DTIC Science & Technology

2010-03-01

saturated calomel electrode [SCE]). 15. SUBJECT TERMS Microemulsion synthesis, Nano particles, Catalysts, Ultrasound, Oxygen reduction, Rotating disk...30 40 50 60 ω1/2 (rpm 1/2) i ( m A .c m -2 ) Ultrasound Assisted Microemulsion Microemulsion non- Microemulsion O2 4e Redc by Diff. Figure 17. Levich...2.0 2.4 0 0.02 0.04 0.06 0.08 0.1 0.12 ω-1/2(rpm-1/2) i-1 (m A -1 cm 2 ) non- Microemulsion Microemulsion Ultrasound Assisted Microemulsion O2 4-e Redc

Cation–hydroxide–water coadsorption inhibits the alkaline hydrogen oxidation reaction

DOE PAGES

Chung, Hoon Taek; Martinez, Ulises; Matanovic, Ivana; ...

2016-10-24

Rotating disk electrode voltammograms and infrared reflection absorption spectra indicate that the hydrogen oxidation reaction of platinum in 0.1 M tetramethylammonium hydroxide solution is adversely impacted by time-dependent and potential-driven cation–hydroxide–water coadsorption. Impedance analysis suggests that the hydrogen oxidation reaction inhibition is mainly caused by the hydrogen diffusion barrier of the coadsorbed trilayer rather than intuitive catalyst site blocking by the adsorbed cation species. Finally, these results give useful insights on how to design ionomeric binders for advanced alkaline membrane fuel cells.

Double-disk solid-phase extraction--Simultaneous cleanup and trace enrichment of herbicides and metabolites from environmental samples

USGS Publications Warehouse

Ferrar, Imma; Barceló, Damià; Thurman, E.M.

1999-01-01

Phenylurea and triazine herbicides, including some metabolites, were isolated from water and soil extracts by solid-phase extraction using a layered system of two extraction disks, a method called double-disk solid-phase extraction. The first disk consisted of strong anion exchange (SAX) of 10-μm styrene divinylbenzene (SDB) particles embedded in Teflon, and the second disk was a C18 disk of 10-μm particles also embedded in Teflon. A volume of 500 mL of water or aqueous soil extract is passed through the layered system with the SAX disk first. The purpose of the SAX disk is to remove the humic and fulvic acids from the water or aqueous soil extract by ion exchange through their carboxyl groups. Even during methanol elution of herbicides, the humic substances remain bound to the SAX disk with >85% retention. Elution with methanol results in more than 90% recovery of the herbicides from the layered extraction disks. Removal of the humic and fulvic acids results in greater sensitivity for diode array detection quantitation (0.05 μg/L for herbicides) by substantially reducing the absorbance of the humic peak on the LC chromatogram. The herbicides adsorb to the SAX disk either through hydrogen bonding to the anion-exchange sites or by hydrophobic interaction with the SDB surface of the anion-exchange disk. The method was tested for the analysis of natural water samples from the Mississippi Embayment, a cotton-growing area of the southeastern United States.

Determination of stresses in gas-turbine disks subjected to plastic flow and creep

NASA Technical Reports Server (NTRS)

Millenson, M B; Manson, S S

1948-01-01

A finite-difference method previously presented for computing elastic stresses in rotating disks is extended to include the computation of the disk stresses when plastic flow and creep are considered. A finite-difference method is employed to eliminate numerical integration and to permit nontechnical personnel to make the calculations with a minimum of engineering supervision. Illustrative examples are included to facilitate explanation of the procedure by carrying out the computations on a typical gas-turbine disk through a complete running cycle. The results of the numerical examples presented indicate that plastic flow markedly alters the elastic-stress distribution.

The performance of disk arrays in shared-memory database machines

NASA Technical Reports Server (NTRS)

Katz, Randy H.; Hong, Wei

1993-01-01

In this paper, we examine how disk arrays and shared memory multiprocessors lead to an effective method for constructing database machines for general-purpose complex query processing. We show that disk arrays can lead to cost-effective storage systems if they are configured from suitably small formfactor disk drives. We introduce the storage system metric data temperature as a way to evaluate how well a disk configuration can sustain its workload, and we show that disk arrays can sustain the same data temperature as a more expensive mirrored-disk configuration. We use the metric to evaluate the performance of disk arrays in XPRS, an operational shared-memory multiprocessor database system being developed at the University of California, Berkeley.

Electrochemical formation of a Pt/Zn alloy and its use as a catalyst for oxygen reduction reaction in fuel cells.

PubMed

Sode, Aya; Li, Winton; Yang, Yanguo; Wong, Phillip C; Gyenge, Elod; Mitchell, Keith A R; Bizzotto, Dan

2006-05-04

The characterization of an electrochemically created Pt/Zn alloy by Auger electron spectroscopy is presented indicating the formation of the alloy, the oxidation of the alloy, and the room temperature diffusion of the Zn into the Pt regions. The Pt/Zn alloy is stable up to 1.2 V/RHE and can only be removed with the oxidation of the base Pt metal either electrochemically or in aqua regia. The Pt/Zn alloy was tested for its effectiveness toward oxygen reduction. Kinetics of the oxygen reduction reaction (ORR) were measured using a rotating disk electrode (RDE), and a 30 mV anodic shift in the potential of ORR was found when comparing the Pt/Zn alloy to Pt. The Tafel slope was slightly smaller than that measured for the pure Pt electrode. A simple procedure for electrochemically modifying a Pt-containing gas diffusion electrode (GDE) with Zn was developed. The Zn-treated GDE was pressed with an untreated GDE anode, and the created membrane electrode assembly was tested. Fuel cell testing under two operating conditions (similar anode and cathode inlet pressures, and a larger cathode inlet pressure) indicated that the 30 mV shift observed on the RDE was also evident in the fuel cell tests. The high stability of the Pt/Zn alloy in acidic environments has a potential benefit for fuel cell applications.

Apparatus and method for pressure testing closure disks

DOEpatents

Merten, Jr., Charles W.

1992-01-21

A method and device for testing the burst pressure of closure disks which provides high pressure to both sides of a disk and rapidly releases pressure from one side thereof causing a high rate of change of pressure. A hollow notched plug allows the rapid release of pressure upon rupturing. A tensile load is transmitted by a piston in combination with fluid pressure to the hollow notched plug.

Compact Packaging of Photonic Millimeter-Wave Receiver

NASA Technical Reports Server (NTRS)

Nguyen, Hung; Pouch, John; Miranda, Felix; Levi, Anthony F.

2007-01-01

A carrier structure made from a single silicon substrate is the basis of a compact, lightweight, relatively inexpensive package that holds the main optical/electronic coupling components of a photonic millimeter-wave receiver based on a lithium niobate resonator disk. The design of the package is simple and provides for precise relative placement of optical components, eliminating the need for complex, bulky positioning mechanisms like those commonly used to align optical components to optimize focus and coupling. Although a prototype of the package was fabricated as a discrete unit, the design is amenable to integration of the package into a larger photonic and/or electronic receiver system. The components (see figure) include a lithium niobate optical resonator disk of 5-mm diameter and .200- m thickness, positioned adjacent to a millimeter- wave resonator electrode. Other components include input and output coupling prisms and input and output optical fibers tipped with ball lenses for focusing and collimation, respectively. Laser light is introduced via the input optical fiber and focused into the input coupling prism. The input coupling prism is positioned near (but not in contact with) the resonator disk so that by means of evanescent-wave coupling, the input laser light in the prism gives rise to laser light propagating circumferentially in guided modes in the resonator disk. Similarly, a portion of the circumferentially propagating optical power is extracted from the disk by evanescent-wave coupling from the disk to the output coupling prism, from whence the light passes through the collimating ball lens into the output optical fiber. The lens-tipped optical fibers must be positioned at a specified focal distance from the prisms. The optical fibers and the prisms must be correctly positioned relative to the resonator disk and must be oriented to obtain the angle of incidence (55 in the prototype) required for evanescent-wave coupling of light into and out of the desired guided modes in the resonator disk. To satisfy all these requirements, precise alignment features are formed in the silicon substrate by use of a conventional wet-etching process. These features include a 5-mm-diameter, 50- m-deep cavity that holds the disk; two trapezoidal-cross-section recesses for the prisms; and two grooves that hold the optical fibers at the correct positions and angles relative to the prisms and disk. The fiber grooves contain abrupt tapers, near the prisms, that serve as hard stops for positioning the lenses at the focal distance from the prisms. There are also two grooves for prismadjusting rods. The design provides a little slack in the prism recesses for adjusting the positions of the prisms by means of these rods to optimize the optical coupling.

High discharge rate characteristics of nickel-cadmium batteries for pulse load filtering

NASA Technical Reports Server (NTRS)

Gearing, G. M.; Cimino, M. B.; Fritts, D. H.; Leonard, J. F.; Terzuoli, A. J., Jr.

1985-01-01

Several tests of specially fabricated nickel-cadmium batteries having circular disk type electrodes were considered. These batteries were evaluated as filter elements between a constant current power supply and a five hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 10 to the 7 charge/discharge cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an electrode to battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 Joules per pound respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10 to the 7 cycles, capacity degradation was negligible for one battery and about 20% for the other. Cadmium electrode failure may be the factor limiting lifetime at extremely low depth of discharge cycling. The output was examined and a simple equivalent circuit was proposed.

NiFe layered double hydroxide/reduced graphene oxide nanohybrid as an efficient bifunctional electrocatalyst for oxygen evolution and reduction reactions

NASA Astrophysics Data System (ADS)

Zhan, Tianrong; Zhang, Yumei; Liu, Xiaolin; Lu, SiSi; Hou, Wanguo

2016-11-01

Highly active and low-cost bifunctional electrocatalysts for oxygen evolution and reduction reactions (OER and ORR) hold a heart position for the renewable energy technologies such as metal-air batteries and fuel cells. Here, we reported the synthesis of NiFe layered double hydroxide/reduced graphene oxide (NiFe-LDH/rGO) nanohybrid via the facile solvothermal method followed by chemical reduction. The template role of surfactant and the hybridization of rGO supplied the NiFe-LDH/rGO catalyst with a porous nanostructure and an enhanced conductivity, favoring both mass transport and charge communication of electrocatalytic reactions. The NiFe-LDH/rGO composite not only displayed highly efficient OER activity in alkaline solution with a low onset overpotential of 240 mV, but also only needed an overpotential of 250 mV to reach the 10 mA cm-2 current density. The NiFe-LDH/rGO nanohybrid also offered excellent ORR catalytic activity with onset potential at 0.796 V in alkaline media. The rotating-disk and rotating-ring-disk electrodes both revealed that the ORR on NiFe-LDH/rGO mainly involved a direct four-electron reaction pathways accompanying part of the two-electron process. The excellent bifunctional activity of the NiFe-LDH/rGO nanohybrid could be attributed to the synergistic effects of rGO and NiFe-LDH components due to the strongly coupled interactions.

Apparatus in the form of a disk for the separation of oxygen from other gases and/or for the pumping of oxygen and the method of removing the oxygen

NASA Technical Reports Server (NTRS)

Suitor, Jerry W. (Inventor); Berdahl, C. Martin (Inventor); Marner, Wilbur J. (Inventor)

1989-01-01

An apparatus in the form of a disk for the separation of oxygen from gases, or for the pumping of oxygen, uses a substantially circular disk geometry for the solid electrolyte with radial flow of gas from the outside edge of the disk to the center of the disk. The reduction in available surface area as the gas flows toward the center of the disk reduces the oxygen removal area proportionally to provide for a more uniform removal of oxygen.

Generation of dynamo magnetic fields in protoplanetary and other astrophysical accretion disks

NASA Technical Reports Server (NTRS)

Stepinski, T. F.; Levy, E. H.

1988-01-01

A computational method for treating the generation of dynamo magnetic fields in astrophysical disks is presented. The numerical difficulty of handling the boundary condition at infinity in the cylindrical disk geometry is overcome by embedding the disk in a spherical computational space and matching the solutions to analytically tractable spherical functions in the surrounding space. The lowest lying dynamo normal modes for a 'thick' astrophysical disk are calculated. The generated modes found are all oscillatory and spatially localized. Tha potential implications of the results for the properties of dynamo magnetic fields in real astrophysical disks are discussed.

Correlation between microdilution, Etest, and disk diffusion methods for antifungal susceptibility testing of fluconazole against Candida sp. blood isolates.

PubMed

Menezes, Everardo Albuquerque; Vasconcelos Júnior, Antônio Alexandre de; Ângelo, Maria Rozzelê Ferreira; Cunha, Maria da Conceição dos Santos Oliveira; Cunha, Francisco Afrânio

2013-01-01

Antifungal susceptibility testing assists in finding the appropriate treatment for fungal infections, which are increasingly common. However, such testing is not very widespread. There are several existing methods, and the correlation between such methods was evaluated in this study. The susceptibility to fluconazole of 35 strains of Candida sp. isolated from blood cultures was evaluated by the following methods: microdilution, Etest, and disk diffusion. The correlation between the methods was around 90%. The disk diffusion test exhibited a good correlation and can be used in laboratory routines to detect strains of Candida sp. that are resistant to fluconazole.

Influence of lead ions on the macromorphology of electrodeposited zinc

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

Tsuda, Tetsuaki; Tobias, Charles W.

1981-09-01

The morphology of zinc as it is electrodeposited from acid solutions demonstrates a remarkable imprint of electrolyte flow conditions. The development of macromorphology of zinc deposits has been investigated under galvanostatic conditions on a rotating plantinum disk electrode by use of photomacrography, scanning electron microscopy, electron probe microanalysis and Auger microprobe analysis. Logarithmic spiral markings, which reflect the hydrodynamic flow on a rotating disk, appear in a certain region of current density well below the limiting current density. Morphological observations revealed the major influence of trace lead ions on the amplifications of surface roughness through coalescence and preferred growth ofmore » initial protrusions. Results obtained from ultra-pure electrolyte suggest preferred crystal growth towards well-mixed orientation in the concentration field caused by slight differences in crystallization overpotential. A qualitative model involving a coupling mechanism between the evolving surface roughness and instability phenomena in the boundary layer is advanced to explain the formation of spiral patterns.« less

Dynamo magnetic field modes in thin astrophysical disks - An adiabatic computational approximation

NASA Technical Reports Server (NTRS)

Stepinski, T. F.; Levy, E. H.

1991-01-01

An adiabatic approximation is applied to the calculation of turbulent MHD dynamo magnetic fields in thin disks. The adiabatic method is employed to investigate conditions under which magnetic fields generated by disk dynamos permeate the entire disk or are localized to restricted regions of a disk. Two specific cases of Keplerian disks are considered. In the first, magnetic field diffusion is assumed to be dominated by turbulent mixing leading to a dynamo number independent of distance from the center of the disk. In the second, the dynamo number is allowed to vary with distance from the disk's center. Localization of dynamo magnetic field structures is found to be a general feature of disk dynamos, except in the special case of stationary modes in dynamos with constant dynamo number. The implications for the dynamical behavior of dynamo magnetized accretion disks are discussed and the results of these exploratory calculations are examined in the context of the protosolar nebula and accretion disks around compact objects.

Evaluation of thermal effects on the beam quality of disk laser with unstable resonator

NASA Astrophysics Data System (ADS)

Shayganmanesh, Mahdi; Beirami, Reza

2017-01-01

In this paper thermal effects of the disk active medium and associated effects on the beam quality of laser are investigated. Using Collins integral and iterative method, transverse mode of an unstable resonator including a Yb:YAG active medium in disk geometry is calculated. After that the beam quality of the laser is calculated based on the generalized beam characterization method. Thermal lensing of the disk is calculated based on the OPD (Optical Path Difference) concept. Five factors influencing the OPD including temperature gradient, disk thermal expansion, photo-elastic effect, electronic lens and disk deformation are considered in our calculations. The calculations show that the effect of disk deformation factor on the quality of laser beam in the resonator is strong. However the total effect of all the thermal factors on the internal beam quality is fewer. Also it is shown that thermal effects degrade the output power, beam profile and beam quality of the output laser beam severely. As well the magnitude of each of affecting factors is evaluated distinctly.

Method of electrode fabrication and an electrode for metal chloride battery

DOEpatents

Bloom, I.D.; Nelson, P.A.; Vissers, D.R.

1993-03-16

A method of fabricating an electrode for use in a metal chloride battery and an electrode are provided. The electrode has relatively larger and more uniform pores than those found in typical electrodes. The fabrication method includes the steps of mixing sodium chloride particles selected from a predetermined size range with metal particles selected from a predetermined size range, and then rigidifying the mixture. The electrode exhibits lower resistivity values of approximately 0.5 [Omega]cm[sup 2] than those resistivity values of approximately 1.0-1.5 [Omega]cm[sup 2] exhibited by currently available electrodes.

Method of electrode fabrication and an electrode for metal chloride battery

DOEpatents

Bloom, Ira D.; Nelson, Paul A.; Vissers, Donald R.

1993-01-01

A method of fabricating an electrode for use in a metal chloride battery and an electrode are provided. The electrode has relatively larger and more uniform pores than those found in typical electrodes. The fabrication method includes the steps of mixing sodium chloride particles selected from a predetermined size range with metal particles selected from a predetermined size range, and then rigidifying the mixture. The electrode exhibits lower resistivity values of approximately 0.5 .OMEGA.cm.sup.2 than those resistivity values of approximately 1.0-1.5 .OMEGA.cm.sup.2 exhibited by currently available electrodes.

Analysis of behavior of focusing error signals generated by astigmatic method when a focused spot moves beyond the radius of a land-groove-type optical disk

NASA Astrophysics Data System (ADS)

Shinoda, Masahisa; Nakatani, Hidehiko; Nakai, Kenya; Ohmaki, Masayuki

2015-09-01

We theoretically calculate behaviors of focusing error signals generated by an astigmatic method in a land-groove-type optical disk. The focusing error signal from the land does not coincide with that from the groove. This behavior is enhanced when a focused spot of an optical pickup moves beyond the radius of the optical disk. A gain difference between the slope sensitivities of focusing error signals from the land and the groove is an important factor with respect to stable focusing servo control. In our calculation, the format of digital versatile disc-random access memory (DVD-RAM) is adopted as the land-groove-type optical disk model, and the dependences of the gain difference on various factors are investigated. The gain difference strongly depends on the optical intensity distribution of the laser beam in the optical pickup. The calculation method and results in this paper will be reflected in newly developed land-groove-type optical disks.

Evaluation of Double-Disk Potentiation and Disk Potentiation Tests Using Dipicolinic Acid for Detection of Metallo-β-Lactamase-Producing Pseudomonas spp. and Acinetobacter spp.

PubMed Central

Yong, Dongeun; Lee, Yangsoon; Jeong, Seok Hoon; Lee, Kyungwon

2012-01-01

Accurate detection of metallo-β-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. became very important with the increasing prevalence of carbapenem-nonsusceptible clinical isolates. The performance of phenotypic MBL detection methods may depend on the types of MBL and the characteristics of the isolates. A high false-positive rate is a problem with EDTA-based MBL detection methods. We evaluated the performance of double-disk potentiation tests (DDPTs) and disk potentiation tests (DPTs) with dipicolinic acid (DPA) using 44 isolates of Pseudomonas spp. and Acinetobacter spp. producing IMP-1-like, VIM-2-like, and SIM-1 type MBLs. Also, we characterized P. aeruginosa isolates with positive imipenem (IPM)-DPA DDPT, but negative meropenem (MEM)-DPA DDPT, and determined possibility of improving a DDPT by using MacConkey agar. Among five different DDPT methods, the IPM-DPA 250-μg method showed the highest sensitivity (97.7%) and specificity (100%). Among four DPT tests, the highest sensitivity (100%) was shown by the IPM-EDTA 1,900-μg disk method, but the specificity was very low (11.4%). Five of six P. aeruginosa isolates with false-negative DDPTs with MEM-DPA 250-μg disks carried blaIMP-6, and the high level resistance to MEM (MIC ≥ 512 μg/ml) was reduced by the presence of phenylalanine arginine β-naphtylamide. Improvement of DDPTs was observed when MacConkey agar was used instead of Mueller-Hinton agar. In conclusion, DPA is a better MBL inhibitor than EDTA for detection of Pseudomonas spp. and Acinetobacter spp. with IMP-1-like, VIM-2-like, and SIM-1-type MBLs. In DPA DDPTs, IPM disks perform better than MEM disks when the isolates are highly resistant to MEM due to the overexpression of efflux pumps. PMID:22837321

Solving Reynolds Equation in the Head-Disk Interface of Hard Disk Drives by Using a Meshless Method

NASA Astrophysics Data System (ADS)

Bao-Jun, Shi; Ting-Yi, Yang; Jian, Zhang; Yun-Dong, Du

2010-05-01

With the decrease of the flying height of the magnetic head/slider in hard disk drives (HDDs), Reynolds equation, which is used to describe the pressure distribution of the air bearing film in HDDs, must be modified to account for the rarefaction effect. Meshless local Petrov-Galerkin (MLPG) method has been successfully used in some fields of solid mechanics and fluid mechanics and was proven to be an efficacious method. No meshes are needed in MLPG method either for the interpolation of the trial and test functions, or for the integration of the weak form of the related differential equation. We solve Reynolds equation in the head-disk interface (HDI) of HDDs by using MLPG method. The pressure distribution of the air baring film by using MLPG method is obtained and compared with the exact solution and that obtained by using a least square finite difference (LSFD) method. We also investigate effects of the bearing number on the pressure value and the center of pressure based on this meshless method for different film-thickness ratios.

Method and apparatus for bistable optical information storage for erasable optical disks

DOEpatents

Land, Cecil E.; McKinney, Ira D.

1990-01-01

A method and an optical device for bistable storage of optical information, together with reading and erasure of the optical information, using a photoactivated shift in a field dependent phase transition between a metastable or a bias-stabilized ferroelectric (FE) phase and a stable antiferroelectric (AFE) phase in an lead lanthanum zirconate titanate (PLZT). An optical disk contains the PLZT. Writing and erasing of optical information can be accomplished by a light beam normal to the disk. Reading of optical information can be accomplished by a light beam at an incidence angle of 15 to 60 degrees to the normal of the disk.

Method and apparatus for bistable optical information storage for erasable optical disks

DOEpatents

Land, C.E.; McKinney, I.D.

1988-05-31

A method and an optical device for bistable storage of optical information, together with reading and erasure of the optical information, using a photoactivated shift in a field dependent phase transition between a metastable or a bias-stabilized ferroelectric (FE) phase and a stable antiferroelectric (AFE) phase in a lead lanthanum zirconate titanate (PLZT). An optical disk contains the PLZT. Writing and erasing of optical information can be accomplished by a light beam normal to the disk. Reading of optical information can be accomplished by a light beam at an incidence angle of 15 to 60 degrees to the normal of the disk. 10 figs.

Method of depositing a catalyst on a fuel cell electrode

DOEpatents

Dearnaley, Geoffrey; Arps, James H.

2000-01-01

Fuel cell electrodes comprising a minimal load of catalyst having maximum catalytic activity and a method of forming such fuel cell electrodes. The method comprises vaporizing a catalyst, preferably platinum, in a vacuum to form a catalyst vapor. A catalytically effective amount of the catalyst vapor is deposited onto a carbon catalyst support on the fuel cell electrode. The electrode preferably is carbon cloth. The method reduces the amount of catalyst needed for a high performance fuel cell electrode to about 0.3 mg/cm.sup.2 or less.

Probing the dusty disk around the Herbig Ae star MWC 480

NASA Astrophysics Data System (ADS)

Hamidouche, M.; Looney, L. W.; Shaw, J.

2004-12-01

It is already quite evident that some Herbig AeBe stars are surrounded by circumstellar dusty disk (e.g. Fuente et al 2003, Natta et al. 2004). We present sub-arcsecond resolution observations at λ = 1mm of dust continuum emission from circumstellar structures around the Herbig AeBe star MWC 480. We have detected a disk-like structure around the star. This is the first well resolved Herbig Ae disk at 1.3 mm. We deduced from the best fit Gaussian a FWHM of 100 AU. We deduce a disk mass of ˜ 0.017 M⊙ assuming optically thin emission. We focus the discussion upon the morphology of the disk and use models to infer the physical parameters (e.g. the density profile). In addition, we discuss a new method with which to fit the numerical model to interferometric data of circumstellar structures around Herbig AeBe stars and T Tauri stars. This method allows us to compare complete Fourier dataset to the Model.

[Evaluation of in vitro antimicrobial activity of cefazolin alone and in combination with cefmetazole or flomoxef using agar dilution method and disk diffusion method].

PubMed

Matsuo, K; Uete, T

1992-10-01

Antimicrobial activities of cefazolin (CEZ) against 251 strains of various clinical isolates obtained during 1989 and 1990 were determined using the Mueller-Hinton agar dilution method at an inoculum level 10(6) CFU/ml. The reliability of the disk susceptility test was also studied using Mueller-Hinton agar and various disks at inoculum levels of 10(3-4) CFU/cm2 in estimating approximate values of MICs. In addition, antimicrobial activities of CEZ and cefmetazole (CMZ) or flomoxef (FMOX) in combination were investigated against methicillin-sensitive and -resistant Staphylococcus aureus (MSSA and MRSA) using the checkerboard agar dilution MIC method and the disk diffusion test either with the disks contained CEZ, CMZ, and FMOX alone, or CEZ, and CMZ or FMOX in combination. In this study, the MICs of CEZ against S. aureus were distributed with the 3 peak values at 0.39 microgram/ml, 3.13 micrograms/ml and > 100 micrograms/ml. MICs against MSSA were 0.39 microgram/ml to 0.78 microgram/ml, whereas those against MRSA were greater than 0.78 microgram/ml. MICs against majority of strains of Enterococcus faecalis were 25 micrograms/ml. Over 90% of strains of Escherichia coli and Klebsiella pneumoniae were inhibited at the level of 3.13 micrograms/ml. About 60% of isolates of indole negative Proteus spp. were inhibited at the levels of less than 3.13 micrograms/ml and 100% at 6.25 micrograms/ml, but MICs against indole positive Proteus spp., Serratia spp. and Pseudomonas aeruginosa were over 100 micrograms/ml. The antimicrobial activities of CEZ against these clinical isolates were not significantly different compared to those reported about 15-20 years ago, except for S. aureus. Highly resistant strains of S. aureus to CEZ were more prevalent in this study. The inhibitory zones obtained with the disk test were compared with MICs. The results of CEZ disk susceptibility test with 30 micrograms disk (Showa) or 10 micrograms disk (prepared in this laboratory) were well correlated with MICs (r = -0.837 and -0.814, respectively), showing the reliavility of the disk method in estimating approximate values of MICs. In the 4 category classification system currently used in Japan, break points in MIC values proposed are () MIC < or = 3 micrograms/ml, (++) > 3-15 micrograms/ml, (+) > 15-60 micrograms/ml, (-) > 60 micrograms/ml. The results obtained with 30 micrograms disks showed false positive in 7.7% and false negative in 6.8% of the samples. The disk results with E. faecalis showed a higher ratio of false positive results.(ABSTRACT TRUNCATED AT 400 WORDS)

Synthesis and characterization of high performing Fe-N-C catalyst for oxygen reduction reaction (ORR) in Alkaline Exchange Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

Hossen, Md Mosaddek; Artyushkova, Kateryna; Atanassov, Plamen; Serov, Alexey

2018-01-01

In this article, three different Fe-N-C oxygen reduction reaction (ORR) catalysts derived from different organic molecules i.e. Fe-NMG, Fe-NMP, Fe-MBZ have been synthesized, characterized by physical-chemical methods and studied in the reaction of oxygen reduction (ORR). It is found that Fe-NMG shows higher ORR performance than Fe-NMP and Fe-MBZ, by both rotating ring disk electrode (RRDE) and fuel cell tests. From characterization and surface analysis, it can be explained that the presence of higher amount of surface oxides and pyridinic nitrogen is the main reason for better performance towards ORR in alkaline media. To achieve the highest performance in alkaline exchange membrane fuel cell (AEMFC), the optimization of catalyst layer composition using various concentrations of ionomer (Tokuyama, AS4) was performed. At the optimum cathode layer configuration utilizing Fe-NMG produces the peak power density of 218 mWcm-2, which is one of the highest values presented in the open literature.

Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy

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

Sheng, WC; Zhuang, ZB; Gao, MR

2015-01-08

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearlymore » increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.« less

Connecting the shadows: probing inner disk geometries using shadows in transitional disks

NASA Astrophysics Data System (ADS)

Min, M.; Stolker, T.; Dominik, C.; Benisty, M.

2017-08-01

Aims: Shadows in transitional disks are generally interpreted as signs of a misaligned inner disk. This disk is usually beyond the reach of current day high contrast imaging facilities. However, the location and morphology of the shadow features allow us to reconstruct the inner disk geometry. Methods: We derive analytic equations of the locations of the shadow features as a function of the orientation of the inner and outer disk and the height of the outer disk wall. In contrast to previous claims in the literature, we show that the position angle of the line connecting the shadows cannot be directly related to the position angle of the inner disk. Results: We show how the analytic framework derived here can be applied to transitional disks with shadow features. We use estimates of the outer disk height to put constraints on the inner disk orientation. In contrast with the results from Long et al. (2017, ApJ, 838, 62), we derive that for the disk surrounding HD 100453 the analytic estimates and interferometric observations result in a consistent picture of the orientation of the inner disk. Conclusions: The elegant consistency in our analytic framework between observation and theory strongly support both the interpretation of the shadow features as coming from a misaligned inner disk as well as the diagnostic value of near infrared interferometry for inner disk geometry.

The interactive electrode localization utility: software for automatic sorting and labeling of intracranial subdural electrodes

PubMed Central

Tang, Wei; Peled, Noam; Vallejo, Deborah I.; Borzello, Mia; Dougherty, Darin D.; Eskandar, Emad N.; Widge, Alik S.; Cash, Sydney S.; Stufflebeam, Steven M.

2018-01-01

Purpose Existing methods for sorting, labeling, registering, and across-subject localization of electrodes in intracranial encephalography (iEEG) may involve laborious work requiring manual inspection of radiological images. Methods We describe a new open-source software package, the interactive electrode localization utility which presents a full pipeline for the registration, localization, and labeling of iEEG electrodes from CT and MR images. In addition, we describe a method to automatically sort and label electrodes from subdural grids of known geometry. Results We validated our software against manual inspection methods in twelve subjects undergoing iEEG for medically intractable epilepsy. Our algorithm for sorting and labeling performed correct identification on 96% of the electrodes. Conclusions The sorting and labeling methods we describe offer nearly perfect performance and the software package we have distributed may simplify the process of registering, sorting, labeling, and localizing subdural iEEG grid electrodes by manual inspection. PMID:27915398

Design of a LaB 6 gun using EGN2 and INTMAG

NASA Astrophysics Data System (ADS)

Becker, R.; Herrmannsfeldt, W. B.

1990-12-01

In order to launch a high-density electron beam to be focused in the 5 T superconducting solenoid of the Frankfurt EBIS [R. Becker et al., Nucl. Instr. and Meth. B24 (1987) 838], an electron gun has been designed, with a 0.5 mm diameter LaB 6 cathode (FEI Comp., Beaverton, USA) in a 70 mm diameter electrode geometry. The emitting surface is placed in the axial fringing field of the solenoid, modified by an axial shielding disk and a bucking coil, to provide either immersed flow or Brillouin flow conditions for the focused beam. Since the cathode diameter is small as compared to the electrodes, a new feature of EGN2 [W.B. Herrmannsfeldt, SLAC-331 (1988)] had to be used in order to have a sufficient number of meshes along the emitting surface. By starting a field line in the large geometry, a curved Neumann boundary is found for a subdivided part of the gun, which represents the influence of the larger part. EGN2 writes the coordinates of this field line on a file, which can be used by POLYGON [R. Becker, Nucl. Instr. and Meth. B42 (1989) 162] (a boundary setup program for EGN2) to define a curved Neumann boundary. By this procedure, it becomes possible to get a reliable simulation of the emission properties of a small cathode in large gun electrodes. The magnetostatic field calculations have been performed with INTMAG [R. Becker, Nucl. Instr. and Meth. B42 (1989) 303], which is a new program of the boundary element method type. Due to the integration calculus, the results do not need smoothing or "Maxwellisation" for the use in EGN2, where the off-axis fields are evaluated by radial expansion. INTMAG provides an output file, which is suitably formatted to be read in by EGN2. The gun design is based on space-charge-limited emission, but no Pierce-type electrode has been provided in the vicinity of the cathode; instead a Wehnelt electrode on negative bias with respect to the cathode is used to create the correct Pierce-type equipotential in free space, ending on the cathode edge with the correct angle. This gives an additional adjustment tool, if the axial position of the gun is not perfect and it relaxes the radial tolerance requirements considerably.

Optical Tip Clearance Measurements as a Tool for Rotating Disk Characterization

PubMed Central

García, Iker; Zubia, Joseba; Beloki, Josu; Arrue, Jon; Durana, Gaizka; Aldabaldetreku, Gotzon

2017-01-01

An experimental investigation on the vibrational behavior of a rotating disk by means of three optical fiber sensors is presented. The disk, which is a scale model of the real disk of an aircraft engine, was assembled in a wind tunnel in order to simulate real operation conditions. The pressure difference between the upstream and downstream sides of the disk causes an airflow that might force the disk to vibrate. To characterize this vibration, a set of parameters was determined by measuring the tip clearance of the disk: the amplitude, the frequency and the number of nodal diameters in the disk. All this information allowed the design of an upgraded prototype of the disk, whose performance was also characterized by the same method. An optical system was employed for the measurements, in combination with a strain gauge mounted on the disk surface, which served to confirm the results obtained. The data of the strain gauge coincided closely with those provided by the optical fiber sensors, thus demonstrating the suitability of this innovative technique to evaluate the vibrational behavior of rotating disks. PMID:28098845

Segmented electrode hall thruster with reduced plume

DOEpatents

Fisch, Nathaniel J.; Raitses, Yevgeny

2004-08-17

An apparatus and method for thrusting plasma, utilizing a Hall thruster with segmented electrodes along the channel, which make the acceleration region as localized as possible. Also disclosed are methods of arranging the electrodes so as to minimize erosion and arcing. Also disclosed are methods of arranging the electrodes so as to produce a substantial reduction in plume divergence. The use of electrodes made of emissive material will reduce the radial potential drop within the channel, further decreasing the plume divergence. Also disclosed is a method of arranging and powering these electrodes so as to provide variable mode operation.

Methods for Specific Electrode Resistance Measurement during Transcranial Direct Current Stimulation

PubMed Central

Khadka, Niranjan; Rahman, Asif; Sarantos, Chris; Truong, Dennis Q.; Bikson, Marom

2014-01-01

Background Transcranial Direct Current Stimulation (tDCS) is investigated to treat a wide range of neuropsychiatric disorders, for rehabilitation, and for enhancing cognitive performance. The monitoring of electrode resistance before and during tDCS is considered important for tolerability and safety, where an unusually high resistance is indicative of undesired electrode or poor skin contact conditions. Conventional resistance measurement methods do not isolate individual electrode resistance but rather measures overall voltage. Moreover, for HD-tDCS devices, cross talk across electrodes makes concurrent resistance monitoring unreliable. Objective We propose a novel method for monitoring of the individual electrode resistance during tDCS, using a super-position of direct current with a test-signal (low-intensity and low-frequency sinusoids with electrode– specific frequencies) and a single sentinel electrode (not used for DC). Methods To validate this methodology, we developed lumped-parameter models of two and multi-electrode tDCS. Approaches with and without a sentinel electrode were solved and underlying assumptions identified. Assumptions were tested and parameterized in healthy participants using forearm stimulation combining tDCS (2 mA) and sinusoidal test-signals (38 μA and 76 μA peak to peak at 1 Hz, 10 Hz, and 100 Hz) and an in vitro test (where varied electrode failure modes were created). DC and AC component voltages across the electrodes were compared and participants were asked to rate subjective pain. Results A sentinel electrode is required to isolate electrode resistance in a two-electrode tDCS system. For multi-electrode resistance tracking, cross talk was aggravated with electrode proximity and current/resistance mismatches, but could be corrected using proposed approaches. Average voltage and average pain scores were not significantly different across test current intensities and frequencies (two-way repeated measures ANOVA) indicating the test signal does not itself confound electrode stability or sensation. DC-resistance to AC-impedance ratio was ~1:08, averaged across frequencies. Conclusion Using the methods developed here, a test signal can predict DC electrode resistance. Since unique test frequencies can be used at each tDCS electrode, specific electrode resistance can be resolved for any number of stimulating channels – a process made still more robust by the use of a sentinel electrode. These findings provide the first method for monitoring individual electrode resistance during tDCS that integrated into devices may minimize irritation at electrodes. PMID:25456981

A calibration-free electrode compensation method

PubMed Central

Rossant, Cyrille; Fontaine, Bertrand; Magnusson, Anna K.

2012-01-01

In a single-electrode current-clamp recording, the measured potential includes both the response of the membrane and that of the measuring electrode. The electrode response is traditionally removed using bridge balance, where the response of an ideal resistor representing the electrode is subtracted from the measurement. Because the electrode is not an ideal resistor, this procedure produces capacitive transients in response to fast or discontinuous currents. More sophisticated methods exist, but they all require a preliminary calibration phase, to estimate the properties of the electrode. If these properties change after calibration, the measurements are corrupted. We propose a compensation method that does not require preliminary calibration. Measurements are compensated offline by fitting a model of the neuron and electrode to the trace and subtracting the predicted electrode response. The error criterion is designed to avoid the distortion of compensated traces by spikes. The technique allows electrode properties to be tracked over time and can be extended to arbitrary models of electrode and neuron. We demonstrate the method using biophysical models and whole cell recordings in cortical and brain-stem neurons. PMID:22896724

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

Park, Jun -Sang; Ray, Atish K.; Dawson, Paul R.

A shrink-fit sample is manufactured with a Ti-8Al-1Mo-1V alloy to introduce a multiaxial residual stress field in the disk of the sample. A set of strain and orientation pole figures are measured at various locations across the disk using synchrotron high-energy X-ray diffraction. Two approaches—the traditional sin 2Ψ method and the bi-scale optimization method—are taken to determine the stresses in the disk based on the measured strain and orientation pole figures, to explore the range of solutions that are possible for the stress field within the disk. While the stress components computed using the sin 2Ψ method and the bi-scalemore » optimization method have similar trends, their magnitudes are significantly different. Lastly, it is suspected that the local texture variation in the material is the cause of this discrepancy.« less

Three-dimensional reconstruction of TMJ MR images: a technical note and case report.

PubMed

Kitai, Noriyuki; Eriksson, Lars; Kreiborg, Sven; Wagner, Aase; Takada, Kenji

2004-01-01

MR images of the temporomandibular joint at occlusion and at various stages of mouth opening were registered and reconstructed three-dimensionally before and after a modified condylotomy in a patient with painful disk displacement. Following the condylotomy, the condyle/disk relationship had become normalized in all three planes of space at closed mouth and during mouth opening. The post-operative distances of the condylar and diskal paths had increased when compared with the preoperative distances. The three-dimensional visualizing method may, besides providing diagnostic advantages, be a valuable tool for qualitative and quantitative documentation of the efficiency of different treatment methods for normalization of the disk/condyle relationship in patients with TMJ disk displacement.

Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

DOEpatents

Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

2013-09-17

Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

Design and implementation of reliability evaluation of SAS hard disk based on RAID card

NASA Astrophysics Data System (ADS)

Ren, Shaohua; Han, Sen

2015-10-01

Because of the huge advantage of RAID technology in storage, it has been widely used. However, the question associated with this technology is that the hard disk based on the RAID card can not be queried by Operating System. Therefore how to read the self-information and log data of hard disk has been a problem, while this data is necessary for reliability test of hard disk. In traditional way, this information can be read just suitable for SATA hard disk, but not for SAS hard disk. In this paper, we provide a method by using LSI RAID card's Application Program Interface, communicating with RAID card and analyzing the feedback data to solve the problem. Then we will get the necessary information to assess the SAS hard disk.

Numerical simulation of h-adaptive immersed boundary method for freely falling disks

NASA Astrophysics Data System (ADS)

Zhang, Pan; Xia, Zhenhua; Cai, Qingdong

2018-05-01

In this work, a freely falling disk with aspect ratio 1/10 is directly simulated by using an adaptive numerical model implemented on a parallel computation framework JASMIN. The adaptive numerical model is a combination of the h-adaptive mesh refinement technique and the implicit immersed boundary method (IBM). Our numerical results agree well with the experimental results in all of the six degrees of freedom of the disk. Furthermore, very similar vortex structures observed in the experiment were also obtained.

High power density yeast catalyzed microbial fuel cells

NASA Astrophysics Data System (ADS)

Ganguli, Rahul

Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density increase was shown to quickly saturate with cell mass attached on the electrode. Based on recent modelling data that suggested that the electrode currents might be limited by the poor electrical conductivity of the anode, the power density versus electrical conductivity of a yeast-immobilized anode was investigated. Introduction of high aspect ratio carbon fiber filaments to the immobilization matrix increased the electrical conductivity of the anode. Although a higher electrical conductivity clearly led to an increase in power densities, it was shown that the principal limitation to power density increase was coming from proton transfer limitations in the immobilized anode. Partial overcoming of the gradients lead a power density of ca. 250 microW cm-2, which is the highest reported for yeast powered MFCs. A yeast-catalyzed microbial fuel cell was investigated as a power source for low power sensors using raw tree sap. It was shown that yeast can efficiently utilize the sucrose present in the raw tree sap to produce electricity when excess salt is added to the medium. Therefore the salinity of a potential energy source is an important consideration when MFCs are being considered for energy harvesting from natural sources.

Recursive grid partitioning on a cortical surface model: an optimized technique for the localization of implanted subdural electrodes.

PubMed

Pieters, Thomas A; Conner, Christopher R; Tandon, Nitin

2013-05-01

Precise localization of subdural electrodes (SDEs) is essential for the interpretation of data from intracranial electrocorticography recordings. Blood and fluid accumulation underneath the craniotomy flap leads to a nonlinear deformation of the brain surface and of the SDE array on postoperative CT scans and adversely impacts the accurate localization of electrodes located underneath the craniotomy. Older methods that localize electrodes based on their identification on a postimplantation CT scan with coregistration to a preimplantation MR image can result in significant problems with accuracy of the electrode localization. The authors report 3 novel methods that rely on the creation of a set of 3D mesh models to depict the pial surface and a smoothed pial envelope. Two of these new methods are designed to localize electrodes, and they are compared with 6 methods currently in use to determine their relative accuracy and reliability. The first method involves manually localizing each electrode using digital photographs obtained at surgery. This is highly accurate, but requires time intensive, operator-dependent input. The second uses 4 electrodes localized manually in conjunction with an automated, recursive partitioning technique to localize the entire electrode array. The authors evaluated the accuracy of previously published methods by applying the methods to their data and comparing them against the photograph-based localization. Finally, the authors further enhanced the usability of these methods by using automatic parcellation techniques to assign anatomical labels to individual electrodes as well as by generating an inflated cortical surface model while still preserving electrode locations relative to the cortical anatomy. The recursive grid partitioning had the least error compared with older methods (672 electrodes, 6.4-mm maximum electrode error, 2.0-mm mean error, p < 10(-18)). The maximum errors derived using prior methods of localization ranged from 8.2 to 11.7 mm for an individual electrode, with mean errors ranging between 2.9 and 4.1 mm depending on the method used. The authors also noted a larger error in all methods that used CT scans alone to localize electrodes compared with those that used both postoperative CT and postoperative MRI. The large mean errors reported with these methods are liable to affect intermodal data comparisons (for example, with functional mapping techniques) and may impact surgical decision making. The authors have presented several aspects of using new techniques to visualize electrodes implanted for localizing epilepsy. The ability to use automated labeling schemas to denote which gyrus a particular electrode overlies is potentially of great utility in planning resections and in corroborating the results of extraoperative stimulation mapping. Dilation of the pial mesh model provides, for the first time, a sense of the cortical surface not sampled by the electrode, and the potential roles this "electrophysiologically hidden" cortex may play in both eloquent function and seizure onset.

Parametric Instability of Static Shafts-Disk System Using Finite Element Method

NASA Astrophysics Data System (ADS)

Wahab, A. M.; Rasid, Z. A.; Abu, A.

2017-10-01

Parametric instability condition is an important consideration in design process as it can cause failure in machine elements. In this study, parametric instability behaviour was studied for a simple shaft and disk system that was subjected to axial load under pinned-pinned boundary condition. The shaft was modelled based on the Nelson’s beam model, which considered translational and rotary inertias, transverse shear deformation and torsional effect. The Floquet’s method was used to estimate the solution for Mathieu equation. Finite element codes were developed using MATLAB to establish the instability chart. The effect of additional disk mass on the stability chart was investigated for pinned-pinned boundary conditions. Numerical results and illustrative examples are given. It is found that the additional disk mass decreases the instability region during static condition. The location of the disk as well has significant effect on the instability region of the shaft.

Synthesis and characterization of Ru-Ti[sub 4]O[sub 7] microelectrode arrays

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

He, L.; Franzen, H.F.; Vitt, J.E.

1994-04-01

A synthesis is described for Ru microelectrode arrays within a conductive Ti[sub 4]O[sub 7] ceramic matrix. Data obtained by X-ray diffractometry and scanning electron microscopy are consistent with the existence of heterogeneous mixtures of Ru particles (ca. 0.8 [mu]m diam) within the Ti[sub 4]O[sub 7] matrices. No mixed metal oxides or other new compounds are detected. Rotated disk electrodes (RDEs) constructed from the Ru-Ti[sub 4]O[sub 7] materials are compared on the basis of their voltammetric response for the oxidations of I[sup [minus

Mapping hard magnetic recording disks by TOF-SIMS

NASA Astrophysics Data System (ADS)

Spool, A.; Forrest, J.

2008-12-01

Mapping of hard magnetic recording disks by TOF-SIMS was performed both to produce significant analytical results for the understanding of the disk surface and the head disk interface in hard disk drives, and as an example of a macroscopic non-rectangular mapping problem for the technique. In this study, maps were obtained by taking discrete samples of the disk surface at set intervals in R and Θ. Because both in manufacturing, and in the disk drive, processes that may affect the disk surface are typically circumferential in nature, changes in the surface are likely to be blurred in the Θ direction. An algorithm was developed to determine the optimum relative sampling ratio in R and Θ. The results confirm what the experience of the analysts suggested, that changes occur more rapidly on disks in the radial direction, and that more sampling in the radial direction is desired. The subsequent use of statistical methods principle component analysis (PCA), maximum auto-correlation factors (MAF), and the algorithm inverse distance weighting (IDW) are explored.

Phase-field model for the two-phase lithiation of silicon

NASA Astrophysics Data System (ADS)

Gao, Fangliang; Hong, Wei

2016-09-01

As an ideal anode material, silicon has the highest lithium-ion capacity in theory, but the broader application is limited by the huge volumetric strain caused by lithium insertion and extraction. To better understand the physical process and to resolve the related reliability issue, enormous efforts have been made. Recent experiments observed sharp reaction fronts in both crystalline and amorphous silicon during the first lithiation half-cycle. Such a concentration profile indicates that the process is likely to be reaction limited. Based on this postulation, a phase-field model is developed and implemented into a finite-element code to simulate the coupled large inelastic deformation and motion of the reaction front in a silicon electrode. In contrast to most existing models, the model treats both volumetric and deviatoric inelastic deformation in silicon as a direct consequence of the lithiation at the reaction front. The amount of deviatoric deformation is determined by using the recently developed kinetic model of stress-induced anisotropic reaction. By considering the role of stress in the lithiation process, this model successfully recovers the self-limiting phenomenon of silicon electrodes, and relates it to the local geometry of electrodes. The model is also used to evaluate the energy-release rate of the surface crack on a spherical electrode, and the result suggests a critical size of silicon nanoparticles to avert fracture. As examples, the morphology evolution of a silicon disk and a Si nanowire during lithiation are also investigated.

Thin disk laser with unstable resonator and reduced output coupler

NASA Astrophysics Data System (ADS)

Gavili, Anwar; Shayganmanesh, Mahdi

2018-05-01

In this paper, feasibility of using unstable resonator with reduced output coupling in a thin disk laser is studied theoretically. Unstable resonator is modeled by wave-optics using Collins integral and iterative method. An Yb:YAG crystal with 250 micron thickness is considered as a quasi-three level active medium and modeled by solving rate equations of energy levels populations. The amplification of laser beam in the active medium is calculated based on the Beer-Lambert law and Rigrod method. Using generalized beam parameters method, laser beam parameters like, width, divergence, M2 factor, output power as well as near and far-field beam profiles are calculated for unstable resonator. It is demonstrated that for thin disk laser (with single disk) in spite of the low thickness of the disk which leads to low gain factor, it is possible to use unstable resonator (with reduced output coupling) and achieve good output power with appropriate beam quality. Also, the behavior of output power and beam quality versus equivalent Fresnel number is investigated and optimized value of output coupling for maximum output power is achieved.

Security of patient data when decommissioning ultrasound systems

PubMed Central

2017-01-01

Background Although ultrasound systems generally archive to Picture Archiving and Communication Systems (PACS), their archiving workflow typically involves storage to an internal hard disk before data are transferred onwards. Deleting records from the local system will delete entries in the database and from the file allocation table or equivalent but, as with a PC, files can be recovered. Great care is taken with disposal of media from a healthcare organisation to prevent data breaches, but ultrasound systems are routinely returned to lease companies, sold on or donated to third parties without such controls. Methods In this project, five methods of hard disk erasure were tested on nine ultrasound systems being decommissioned: the system’s own delete function; full reinstallation of system software; the manufacturer’s own disk wiping service; open source disk wiping software for full and just blank space erasure. Attempts were then made to recover data using open source recovery tools. Results All methods deleted patient data as viewable from the ultrasound system and from browsing the disk from a PC. However, patient identifiable data (PID) could be recovered following the system’s own deletion and the reinstallation methods. No PID could be recovered after using the manufacturer’s wiping service or the open source wiping software. Conclusion The typical method of reinstalling an ultrasound system’s software may not prevent PID from being recovered. When transferring ownership, care should be taken that an ultrasound system’s hard disk has been wiped to a sufficient level, particularly if the scanner is to be returned with approved parts and in a fully working state. PMID:28228821

Method for analysis of psychopharmaceuticals in real industrial wastewater and groundwater with suspended organic particulate matter using solid phase extraction disks extraction and ultra-high performance liquid chromatography/time-of-flight mass spectrometry.

PubMed

Křesinová, Zdena; Linhartová, Lucie; Petrů, Klára; Krejčová, Lucie; Šrédlová, Kamila; Lhotský, Ondřej; Kameník, Zdeněk; Cajthaml, Tomáš

2016-04-01

A rapid and reliable analytical method was developed for the quantitative determination of psychopharmaceuticals, their precursors and by-products in real contaminated samples from a pharmaceutical company in Olomouc (Czech Republic), based on SPE disk extraction and detection by ultra performance liquid chromatography, combined with time-of-flight mass spectrometry. The target compounds were quantified in the real whole-water samples (water including suspended particles), both in the presence of suspended particulate matter (SPM) and high concentrations of other organic pollutants. A total of nine compounds were analyzed which consisted of three commonly used antidepressants (tricyclic antidepressants and antipsychotics), one antitussive agent and five by-products or precursors. At first, the SPE disk method was developed for the extraction of water samples (dissolved analytes, recovery 84-104%) and pressurised liquid extraction technique was verified for solid matrices (sludge samples, recovery 81-95%). In order to evaluate the SPE disk technique for whole water samples containing SPM, non contaminated groundwater samples were also loaded with different amounts (100 and 300mgL(-1)) of real contaminated sludge originating from the same locality. The recoveries from the whole-water samples obtained by SPE disk method ranged between 67 and 119% after the addition of the most contaminated sludge. The final method was applied to several real groundwater (whole-water) samples from the industrial area and high concentrations (up to 10(3)μgL(-1)) of the target compounds were detected. The results of this study document and indicate the feasibility of the SPE disk method for analysis of groundwater. Copyright © 2016 Elsevier B.V. All rights reserved.

Optic disk localization by a robust fusion method

NASA Astrophysics Data System (ADS)

Zhang, Jielin; Yin, Fengshou; Wong, Damon W. K.; Liu, Jiang; Baskaran, Mani; Cheng, Ching-Yu; Wong, Tien Yin

2013-02-01

The optic disk localization plays an important role in developing computer-aided diagnosis (CAD) systems for ocular diseases such as glaucoma, diabetic retinopathy and age-related macula degeneration. In this paper, we propose an intelligent fusion of methods for the localization of the optic disk in retinal fundus images. Three different approaches are developed to detect the location of the optic disk separately. The first method is the maximum vessel crossing method, which finds the region with the most number of blood vessel crossing points. The second one is the multichannel thresholding method, targeting the area with the highest intensity. The final method searches the vertical and horizontal region-of-interest separately on the basis of blood vessel structure and neighborhood entropy profile. Finally, these three methods are combined using an intelligent fusion method to improve the overall accuracy. The proposed algorithm was tested on the STARE database and the ORIGAlight database, each consisting of images with various pathologies. The preliminary result on the STARE database can achieve 81.5%, while a higher result of 99% can be obtained for the ORIGAlight database. The proposed method outperforms each individual approach and state-of-the-art method which utilizes an intensity-based approach. The result demonstrates a high potential for this method to be used in retinal CAD systems.

Electrocatalytic activity of LaNiO3 toward H2O2 reduction reaction: Minimization of oxygen evolution

NASA Astrophysics Data System (ADS)

Amirfakhri, Seyed Javad; Meunier, Jean-Luc; Berk, Dimitrios

2014-12-01

The catalytic activity of LaNiO3 toward H2O2 reduction reaction (HPRR), with a potential application in the cathode side of fuel cells, is studied in alkaline, neutral and acidic solutions by rotating disk electrode. The LaNiO3 particles synthesised by citrate-based sol-gel method have sizes between 30 and 70 nm with an active specific surface area of 1.26 ± 0.05 m2 g-1. LaNiO3 shows high catalytic activity toward HPRR in 0.1 M KOH solution with an exchange current density based on the active surface area (j0A) of (7.4 ± 1) × 10-6 A cm-2 which is noticeably higher than the j0A of N-doped graphene. The analysis of kinetic parameters suggests that the direct reduction of H2O2, H2O2 decomposition, O2 reduction and O2 desorption occur through HPRR on this catalyst. In order to control and minimize oxygen evolution from the electrode surface, the effects of catalyst loading, bulk concentration of H2O2, and using a mixture of LaNiO3 and N-doped graphene are studied. Although the mechanism of HPRR is independent of the aforementioned operating conditions, gas evolution decreases by increasing the catalyst loading, decreasing the bulk concentration of H2O2, and addition of N-doped graphene to LaNiO3.

Nonlinear vibration analysis of bladed disks with dry friction dampers

NASA Astrophysics Data System (ADS)

Ciğeroğlu, Ender; Özgüven, H. Nevzat

2006-08-01

In this work, a new model is proposed for the vibration analysis of turbine blades with dry friction dampers. The aim of the study is to develop a multiblade model that is accurate and yet easy to be analyzed so that it can be used efficiently in the design of friction dampers. The suggested nonlinear model for a bladed disk assembly includes all the blades with blade to blade and/or blade to cover plate dry friction dampers. An important feature of the model is that both macro-slip and micro-slip models are used in representing dry friction dampers. The model is simple to be analyzed as it is the case in macro-slip model, and yet it includes the features of more realistic micro-slip model. The nonlinear multidegree-of-freedom (mdof) model of bladed disk system is analyzed in frequency domain by applying a quasi-linearization technique, which transforms the nonlinear differential equations into a set of nonlinear algebraic equations. The solution method employed reduces the computational effort drastically compared to time solution methods for nonlinear systems, which makes it possible to obtain a more realistic model by the inclusion of all blades around the disk, disk itself and all friction dampers since in general system parameters are not identical throughout the geometry. The validation of the method is demonstrated by comparing the results obtained in this study with those given in literature and also with results obtained by time domain analysis. In the case studies presented the effect of friction damper parameters on vibration characteristics of tuned and mistuned bladed disk systems is studied by using a 20 blade system. It is shown that the method presented can be used to find the optimum friction damper values in a bladed disk assembly.

Electromechanical response of silicone dielectric elastomers

NASA Astrophysics Data System (ADS)

Cârlescu, V.; Prisăcaru, G.; Olaru, D.

2016-08-01

This paper presents an experimental technique to investigate the electromechanical properties of silicone dielectric elastomers actuated with high DC electric fields. A non-contact measurement technique is used to capture and monitor the thickness strain (contraction) of a circular film placed between two metallic disks electrodes. Two active fillers such as silica (10, 15 and 30 wt%) and barium titanate (5 and 15 wt%) were incorporated in order to increase the actuation performance. Thickness strain was measured at HV stimuli up to 4.5 kV and showed a quadratic dependence against applied electric field indicating that the induced strain is triggered by the Maxwell effect and/or electrostriction phenomenon as reported in literature. The actuation process evidences a rapid contraction upon HV activation and a slowly relaxation when the electrodes are short-circuit due to visco-elastic nature of elastomers. A maximum of 1.22 % thickness strain was obtained at low actuating field intensity (1.5 V/pm) comparable with those reported in literature for similar dielectric elastomer materials.

Limitations for current production in Geobacter sulfurreducens biofilms.

PubMed

Bonanni, P Sebastian; Bradley, Dan F; Schrott, Germán D; Busalmen, Juan Pablo

2013-04-01

Devices that exploit electricity produced by electroactive bacteria such as Geobacter sulfurreducens have not yet been demonstrated beyond the laboratory scale. The current densities are far from the maximum that the bacteria can produce because fundamental properties such as the mechanism of extracellular electron transport and factors limiting cell respiration remain unclear. In this work, a strategy for the investigation of electroactive biofilms is presented. Numerical modeling of the response of G. sulfurreducens biofilms cultured on a rotating disk electrode has allowed for the discrimination of different limiting steps in the process of current production within a biofilm. The model outputs reveal that extracellular electron transport limits the respiration rate of the cells furthest from the electrode to the extent that cell division is not possible. The mathematical model also demonstrates that recent findings such as the existence of a redox gradient in actively respiring biofilms can be explained by an electron hopping mechanism but not when considering metallic-like conductivities. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Activity inhibition and its mitigation in high temperature proton exchange membrane fuel cells: The role of phosphoric acid, ammonium trifluoromethanesulfonate, and polyvinylidene difluoride

NASA Astrophysics Data System (ADS)

Holst-Olesen, Kaspar; Nesselberger, Markus; Perchthaler, Markus; Hacker, Viktor; Arenz, Matthias

2014-12-01

In the presented work we systematically study the influence of phosphoric acid, ammonium trifluoromethanesulfonate (ATFMS), and polyvinylidene difluoride (PVDF) on the oxygen reduction reaction (ORR) activity of carbon supported, Pt based catalysts. The influence of phosphoric acid is investigated in a mixed solution of perchloric acid with small amounts of phosphoric acid added. Thin-film rotating disk electrode (TF-RDE) measurements show that such a mixed electrolyte is advantageous as the oxygen reduction reaction (ORR) is inhibited without influencing the oxygen solubility in the electrolyte. In contrast to previous reports it is seen when investigating additives that ATFMS acts as a catalyst poison; whereas the results provide evidence of a better performance in case of the PVDF incorporated catalysts as compared to reference samples without PVDF. The technological relevance of the PVDF improvements and its stability over prolonged time was validated by membrane electrode assembly (MEA) tests.

Activity of Co-N multi walled carbon nanotubes electrocatalysts for oxygen reduction reaction in acid conditions

NASA Astrophysics Data System (ADS)

Osmieri, Luigi; Monteverde Videla, Alessandro H. A.; Specchia, Stefania

2015-03-01

Two catalysts are synthesized by wet impregnation of multi walled carbon nanotubes (MWCNT) with a complex formed between Co(II) ions and the nitrogen-containing molecule 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), followed by one or two identical heat treatments in N2 atmosphere at 800 °C for 3 h. Catalysts are fully characterized by FESEM, EDX, BET, XRD, FTIR, TGA, XPS analyses, and electrochemical techniques. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalysts in acid conditions is assessed by means of a rotating disk electrode (RDE) apparatus and a specific type of cell equipped with a gas diffusion working electrode (GDE). In both testing approaches, the catalyst heat-treated twice (Co-N/MWCNT-2) exhibits higher electroactivity than the catalyst heat-treated once (Co-N/MWCNT-1). Chronoamperometries both in RDE and GDE cell are also performed, showing less electroactivity decay and better current performance for the catalyst heat-treated twice.

Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

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

Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen

2011-12-01

Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphitemore » content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present« less

Influence of calcium on glucose biosensor response and on hydrogen peroxide detection.

PubMed

Labat-Allietta, N; Thévenot, D R

1998-01-01

Of small species capable of reaching a platinum working electrode from biological samples, calcium cations have been found to inhibit significantly glucose biosensor responses. The sensitivities to glucose of sensors immersed in carbonate buffer saline solutions decreased when 0.5 mM calcium chloride was added. The degree of inhibition was proportional to the glucose response in the absence of calcium (0-17% of the normalized current). Likewise, sensor sensitivities to hydrogen peroxide decreased, in the 5-90% range, in the presence of 0.5 mM calcium. Bare Pt-lr wires show a reversible inhibition of hydrogen peroxide sensitivity. This reversible inhibition is directly related to the decrease of hydrogen peroxide oxidation rate at the platinum anode: this has been evidenced, using rotating disk electrodes, by plotting Koutecky-Levich plots. Such inhibition has been found both for free and chelated calcium cations at levels below 1 mM. Several hypotheses for possible reactions between platinum, hydrogen peroxide and calcium are discussed.

230% room-temperature magnetoresistance in CoFeB /MgO/CoFeB magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Djayaprawira, David D.; Tsunekawa, Koji; Nagai, Motonobu; Maehara, Hiroki; Yamagata, Shinji; Watanabe, Naoki; Yuasa, Shinji; Suzuki, Yoshishige; Ando, Koji

2005-02-01

Magnetoresistance (MR) ratio up to 230% at room temperature (294% at 20 K) has been observed in spin-valve-type magnetic tunnel junctions (MTJs) using MgO tunnel barrier layer fabricated on thermally oxidized Si substrates. We found that such a high MR ratio can be obtained when the MgO barrier layer was sandwiched with amorphous CoFeB ferromagnetic electrodes. Microstructure analysis revealed that the MgO layer with (001) fiber texture was realized when the MgO layer was grown on amorphous CoFeB rather than on polycrystalline CoFe. Since there have been no theoretical studies on the MTJs with a crystalline tunnel barrier and amorphous electrodes, the detailed mechanism of the huge tunneling MR effect observed in this study is not clear at the present stage. Nevertheless, the present work is of paramount importance in realizing high-density magnetoresistive random access memory and read head for ultra high-density hard-disk drives into practical use.

Evaluation of Amount of Blood in Dry Blood Spots: Ring-Disk Electrode Conductometry.

PubMed

Kadjo, Akinde F; Stamos, Brian N; Shelor, C Phillip; Berg, Jordan M; Blount, Benjamin C; Dasgupta, Purnendu K

2016-06-21

A fixed area punch in dried blood spot (DBS) analysis is assumed to contain a fixed amount of blood, but the amount actually depends on a number of factors. The presently preferred approach is to normalize the measurement with respect to the sodium level, measured by atomic spectrometry. Instead of sodium levels, we propose electrical conductivity of the extract as an equivalent nondestructive measure. A dip-type small diameter ring-disk electrode (RDE) is ideal for very small volumes. However, the conductance (G) measured by an RDE depends on the depth (D) of the liquid below the probe. There is no established way of computing the specific conductance (σ) of the solution from G. Using a COMSOL Multiphysics model, we were able to obtain excellent agreement between the measured and the model predicted conductance as a function of D. Using simulations over a large range of dimensions, we provide a spreadsheet-based calculator where the RDE dimensions are the input parameters and the procedure determines the 99% of the infinite depth conductance (G99) and the depth D99 at which this is reached. For typical small diameter probes (outer electrode diameter ∼ <2 mm), D99 is small enough for dip-type measurements in extract volumes of ∼100 μL. We demonstrate the use of such probes with DBS extracts. In a small group of 12 volunteers (age 20-66), the specific conductance of 100 μL aqueous extracts of 2 μL of spotted blood showed a variance of 17.9%. For a given subject, methanol extracts of DBS spots nominally containing 8 and 4 μL of blood differed by a factor of 1.8-1.9 in the chromatographically determined values of sulfate and chloride (a minor and major constituent, respectively). The values normalized with respect to the conductance of the extracts differed by ∼1%. For serum associated analytes, normalization of the analyte value by the extract conductance can thus greatly reduce errors from variations in the spotted blood volume/unit area.

Development and simulation study of a new inverse-pinch high Coulomb transfer switch

NASA Technical Reports Server (NTRS)

Choi, Sang H.

1989-01-01

The inverse-pinch plasma switch was studied using a computer simulation code. The code was based on a 2-D, 2-temperature magnetohydrodynamic (MHD) model. The application of this code was limited to the disk-type inverse-pinch plasma switch. The results of the computer analysis appear to be in agreement with the experimental results when the same parameters are used. An inverse-pinch plasma switch for closing has been designed and tested for high-power switching requirements. An azimuthally uniform initiation of breakdown is a key factor in achieving an inverse-pinch current path in the switch. Thus, various types of triggers, such as trigger pins, wire-brush, ring trigger, and hypocycloidal-pinch (HCP) devices have been tested for uniform breakdown. Recently, triggering was achieved by injection of a plasma-ring (plasma puff) that is produced separately with hypocycloidal-pinch electrodes placed under the cathode of the main gap. The current paths at switch closing, initiated by the injection of a plasma-ring from the HCP trigger are azimuthally uniform, and the local current density is significantly reduced, so that damage to the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes is four orders of magnitude less than that of a spark-gap switch for the same switching power. Indeed, a few thousand shots with peak current exceeding a mega-ampere and with hold-off voltage up to 20 kV have been conducted without showing measurable damage to the electrodes and insulators.

Method and apparatus for reducing the drag of flows over surfaces

NASA Technical Reports Server (NTRS)

Keefe, Laurence R. (Inventor)

1998-01-01

An apparatus, and its accompanying method, for reducing the drag of flows over a surface includes arrays of small disks and sensors. The arrays are embedded in the surface and may extend above, or be depressed below, the surface, provided they remain hydraulically smooth either when operating or when inactive. The disks are arranged in arrays of various shapes, and spaced according to the cruising speed of the vehicle on which the arrays are installed. For drag reduction at speeds of the order of 30 meters/second, preferred embodiments include disks that are 0.2 millimeter in diameter and spaced 0.4 millimeter apart. For drag reduction at speeds of the order of 300 meters/second, preferred embodiments include disks that are 0.045 millimeter in diameter and spaced 0.09 millimeter apart. Smaller and larger dimensions for diameter and spacing are also possible. The disks rotate in the plane of the surface, with their rotation axis substantially perpendicular to the surface. The rotating disks produce velocity perturbations parallel to the surface in the overlying boundary layer. The sensors sense the flow at the surface and connect to control circuitry that adjusts the rotation rates and duty cycles of the disks accordingly. Suction and blowing holes can be interspersed among, or made coaxial with, the disks for creating general three-component velocity perturbations in the near-surface region. The surface can be a flat, planar surface or a nonplanar surface, such as a triangular riblet surface. The present apparatus and method have potential applications in the field of aeronautics for improving performance and efficiency of commercial and military aircraft, and in other industries where drag is an obstacle, including gas and oil delivery through long-haul pipelines.

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.

Security of patient data when decommissioning ultrasound systems.

PubMed

Moggridge, James

2017-02-01

Although ultrasound systems generally archive to Picture Archiving and Communication Systems (PACS), their archiving workflow typically involves storage to an internal hard disk before data are transferred onwards. Deleting records from the local system will delete entries in the database and from the file allocation table or equivalent but, as with a PC, files can be recovered. Great care is taken with disposal of media from a healthcare organisation to prevent data breaches, but ultrasound systems are routinely returned to lease companies, sold on or donated to third parties without such controls. In this project, five methods of hard disk erasure were tested on nine ultrasound systems being decommissioned: the system's own delete function; full reinstallation of system software; the manufacturer's own disk wiping service; open source disk wiping software for full and just blank space erasure. Attempts were then made to recover data using open source recovery tools. All methods deleted patient data as viewable from the ultrasound system and from browsing the disk from a PC. However, patient identifiable data (PID) could be recovered following the system's own deletion and the reinstallation methods. No PID could be recovered after using the manufacturer's wiping service or the open source wiping software. The typical method of reinstalling an ultrasound system's software may not prevent PID from being recovered. When transferring ownership, care should be taken that an ultrasound system's hard disk has been wiped to a sufficient level, particularly if the scanner is to be returned with approved parts and in a fully working state.

Determination of residual stress in a microtextured α titanium component using high-energy synchrotron X-rays

DOE PAGES

Park, Jun -Sang; Ray, Atish K.; Dawson, Paul R.; ...

2016-05-02

A shrink-fit sample is manufactured with a Ti-8Al-1Mo-1V alloy to introduce a multiaxial residual stress field in the disk of the sample. A set of strain and orientation pole figures are measured at various locations across the disk using synchrotron high-energy X-ray diffraction. Two approaches—the traditional sin 2Ψ method and the bi-scale optimization method—are taken to determine the stresses in the disk based on the measured strain and orientation pole figures, to explore the range of solutions that are possible for the stress field within the disk. While the stress components computed using the sin 2Ψ method and the bi-scalemore » optimization method have similar trends, their magnitudes are significantly different. Lastly, it is suspected that the local texture variation in the material is the cause of this discrepancy.« less

Performance of the EUCAST Disk Diffusion Method, the CLSI Agar Screen Method, and the Vitek 2 Automated Antimicrobial Susceptibility Testing System for Detection of Clinical Isolates of Enterococci with Low- and Medium-Level VanB-Type Vancomycin Resistance: a Multicenter Study

PubMed Central

Giske, Christian G.; Haldorsen, Bjørg; Matuschek, Erika; Schønning, Kristian; Leegaard, Truls M.; Kahlmeter, Gunnar

2014-01-01

Different antimicrobial susceptibility testing methods to detect low-level vancomycin resistance in enterococci were evaluated in a Scandinavian multicenter study (n = 28). A phenotypically and genotypically well-characterized diverse collection of Enterococcus faecalis (n = 12) and Enterococcus faecium (n = 18) strains with and without nonsusceptibility to vancomycin was examined blindly in Danish (n = 5), Norwegian (n = 13), and Swedish (n = 10) laboratories using the EUCAST disk diffusion method (n = 28) and the CLSI agar screen (n = 18) or the Vitek 2 system (bioMérieux) (n = 5). The EUCAST disk diffusion method (very major error [VME] rate, 7.0%; sensitivity, 0.93; major error [ME] rate, 2.4%; specificity, 0.98) and CLSI agar screen (VME rate, 6.6%; sensitivity, 0.93; ME rate, 5.6%; specificity, 0.94) performed significantly better (P = 0.02) than the Vitek 2 system (VME rate, 13%; sensitivity, 0.87; ME rate, 0%; specificity, 1). The performance of the EUCAST disk diffusion method was challenged by differences in vancomycin inhibition zone sizes as well as the experience of the personnel in interpreting fuzzy zone edges as an indication of vancomycin resistance. Laboratories using Oxoid agar (P < 0.0001) or Merck Mueller-Hinton (MH) agar (P = 0.027) for the disk diffusion assay performed significantly better than did laboratories using BBL MH II medium. Laboratories using Difco brain heart infusion (BHI) agar for the CLSI agar screen performed significantly better (P = 0.017) than did those using Oxoid BHI agar. In conclusion, both the EUCAST disk diffusion and CLSI agar screening methods performed acceptably (sensitivity, 0.93; specificity, 0.94 to 0.98) in the detection of VanB-type vancomycin-resistant enterococci with low-level resistance. Importantly, use of the CLSI agar screen requires careful monitoring of the vancomycin concentration in the plates. Moreover, disk diffusion methodology requires that personnel be trained in interpreting zone edges. PMID:24599985

Electrode assemblies, plasma generating apparatuses, and methods for generating plasma

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

Kong, Peter C.; Grandy, Jon D.; Detering, Brent A.

Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating membermore » to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.« less

Magnetorotational instability in decretion disks of critically rotating stars and the outer structure of Be and Be/X-ray disks

NASA Astrophysics Data System (ADS)

Krtička, J.; Kurfürst, P.; Krtičková, I.

2015-01-01

Context. Evolutionary models of fast-rotating stars show that the stellar rotational velocity may approach the critical speed. Critically rotating stars cannot spin up more, therefore they lose their excess angular momentum through an equatorial outflowing disk. The radial extension of such disks is unknown, partly because we lack information about the radial variations of the viscosity. Aims: We study the magnetorotational instability, which is considered to be the origin of anomalous viscosity in outflowing disks. Methods: We used analytic calculations to study the stability of outflowing disks submerged in the magnetic field. Results: The magnetorotational instability develops close to the star if the plasma parameter is large enough. At large radii the instability disappears in the region where the disk orbital velocity is roughly equal to the sound speed. Conclusions: The magnetorotational instability is a plausible source of anomalous viscosity in outflowing disks. This is also true in the region where the disk radial velocity approaches the sound speed. The disk sonic radius can therefore be roughly considered as an effective outer disk radius, although disk material may escape from the star to the insterstellar medium. The radial profile of the angular momentum-loss rate already flattens there, consequently, the disk mass-loss rate can be calculated with the sonic radius as the effective disk outer radius. We discuss a possible observation determination of the outer disk radius by using Be and Be/X-ray binaries.

Database recovery using redundant disk arrays

NASA Technical Reports Server (NTRS)

Mourad, Antoine N.; Fuchs, W. K.; Saab, Daniel G.

1992-01-01

Redundant disk arrays provide a way for achieving rapid recovery from media failures with a relatively low storage cost for large scale database systems requiring high availability. In this paper a method is proposed for using redundant disk arrays to support rapid-recovery from system crashes and transaction aborts in addition to their role in providing media failure recovery. A twin page scheme is used to store the parity information in the array so that the time for transaction commit processing is not degraded. Using an analytical model, it is shown that the proposed method achieves a significant increase in the throughput of database systems using redundant disk arrays by reducing the number of recovery operations needed to maintain the consistency of the database.

Recovery issues in databases using redundant disk arrays

NASA Technical Reports Server (NTRS)

Mourad, Antoine N.; Fuchs, W. K.; Saab, Daniel G.

1993-01-01

Redundant disk arrays provide a way for achieving rapid recovery from media failures with a relatively low storage cost for large scale database systems requiring high availability. In this paper we propose a method for using redundant disk arrays to support rapid recovery from system crashes and transaction aborts in addition to their role in providing media failure recovery. A twin page scheme is used to store the parity information in the array so that the time for transaction commit processing is not degraded. Using an analytical model, we show that the proposed method achieves a significant increase in the throughput of database systems using redundant disk arrays by reducing the number of recovery operations needed to maintain the consistency of the database.

Performance evaluation of redundant disk array support for transaction recovery

NASA Technical Reports Server (NTRS)

Mourad, Antoine N.; Fuchs, W. Kent; Saab, Daniel G.

1991-01-01

Redundant disk arrays provide a way of achieving rapid recovery from media failures with a relatively low storage cost for large scale data systems requiring high availability. Here, we propose a method for using redundant disk arrays to support rapid recovery from system crashes and transaction aborts in addition to their role in providing media failure recovery. A twin page scheme is used to store the parity information in the array so that the time for transaction commit processing is not degraded. Using an analytical model, we show that the proposed method achieves a significant increase in the throughput of database systems using redundant disk arrays by reducing the number of recovery operations needed to maintain the consistency of the database.

A search for debris disks in the Herschel-ATLAS

NASA Astrophysics Data System (ADS)

Thompson, M. A.; Smith, D. J. B.; Stevens, J. A.; Jarvis, M. J.; Vidal Perez, E.; Marshall, J.; Dunne, L.; Eales, S.; White, G. J.; Leeuw, L.; Sibthorpe, B.; Baes, M.; González-Solares, E.; Scott, D.; Vieiria, J.; Amblard, A.; Auld, R.; Bonfield, D. G.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Dariush, A.; de Zotti, G.; Dye, S.; Eales, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.; Ibar, E.; Ivison, R. J.; Lagache, G.; Lopez-Caniego, M.; Maddox, S.; Negrello, M.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Samui, S.; Serjeant, S.; Temi, P.; Valtchanov, I.; Verma, A.

2010-07-01

Aims: We aim to demonstrate that the Herschel-ATLAS (H-ATLAS) is suitable for a blind and unbiased survey for debris disks by identifying candidate debris disks associated with main sequence stars in the initial science demonstration field of the survey. We show that H-ATLAS reveals a population of far-infrared/sub-mm sources that are associated with stars or star-like objects on the SDSS main-sequence locus. We validate our approach by comparing the properties of the most likely candidate disks to those of the known population. Methods: We use a photometric selection technique to identify main sequence stars in the SDSS DR7 catalogue and a Bayesian Likelihood Ratio method to identify H-ATLAS catalogue sources associated with these main sequence stars. Following this photometric selection we apply distance cuts to identify the most likely candidate debris disks and rule out the presence of contaminating galaxies using UKIDSS LAS K-band images. Results: We identify 78 H-ATLAS sources associated with SDSS point sources on the main-sequence locus, of which two are the most likely debris disk candidates: H-ATLAS J090315.8 and H-ATLAS J090240.2. We show that they are plausible candidates by comparing their properties to the known population of debris disks. Our initial results indicate that bright debris disks are rare, with only 2 candidates identified in a search sample of 851 stars. We also show that H-ATLAS can derive useful upper limits for debris disks associated with Hipparcos stars in the field and outline the future prospects for our debris disk search programme. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The Formation and Evolution of Galactic Disks with APOGEE and the Gaia Survey

NASA Astrophysics Data System (ADS)

Li, Chengdong; Zhao, Gang; Zhai, Meng; Jia, Yunpeng

2018-06-01

We explore the structure and evolutionary history of Galactic disks with Apache Point Observatory Galactic Evolution Experiment data release 13 (DR13 hereafter) and Gaia Tycho-Gaia Astrometric Solution data. We use the [α/M] ratio to allocate stars into particular Galactic components to elucidate the chemical and dynamical properties of the thin and thick disks. The spatial motions of the sample stars are obtained in Galactic Cartesian and cylindrical coordinates. We analyze the abundance trends and metallicity and [α/M] gradients of the thick and thin disks. We confirm the existence of metal-weak thick-disk stars in Galactic disks. A kinematical method is used to select the thin- and thick-disk stars for comparison. We calculate the scale length and scale height of the kinematically and chemically selected thick and thin disks based on the axisymmetric Jeans equation. We conclude that the scale length of the thick disk is approximately equal to that of the thin disk via a kinematical approach. For the chemical selection, this disparity is about 1 kpc. Finally, we get the stellar orbital parameters and try to unveil the formation scenario of the thick disk. We conclude that the gas-rich merger and radial migration are more reasonable formation scenarios for the thick disk.

Performance and durability of carbon black-supported Pd catalyst covered with silica layers in membrane-electrode assemblies of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Fujii, Keitaro; Ito, Mizuki; Sato, Yasushi; Takenaka, Sakae; Kishida, Masahiro

2015-04-01

Pd metal particles supported on a high surface area carbon black (Pd/CB) were covered with silica layers to improve the durability under severe cathode condition of proton exchange membrane fuel cells (PEMFCs). The performance and the durability of the silica-coated Pd/CB (SiO2/Pd/CB) were investigated by rotating disk electrode (RDE) in aqueous HClO4 and single cell test of the membrane-electrode assemblies (MEAs). SiO2/Pd/CB showed excellent durability exceeding Pt/CB during potential cycle in single cell test as well as in RDE measurement while Pd/CB significantly degraded. Furthermore, the MEA using SiO2/Pd/CB as the cathode catalyst showed higher performance than that using Pd/CB even in the initial state. The catalytic activity of SiO2/Pd/CB was higher than that of Pd/CB, and the drop of the cell performances due to the inhibition of electron conduction, proton conduction, and oxygen diffusion by the silica layer was not significant. It has been shown that the silica-coating is a very practical technique that can stabilize metal species originally unstable in the cathode condition of PEMFCs without a decrease in the cell performance.

Medical devices of the head, neck, and spine.

PubMed

Hunter, Tim B; Yoshino, Mark T; Dzioba, Robert B; Light, Rick A; Berger, William G

2004-01-01

There are many medical devices used for head, neck, and spinal diseases and injuries, and new devices are constantly being introduced. Many of the newest devices are variations on a previous theme. Knowing the specific name of a device is not important. It is important to recognize the presence of a device and to have an understanding of its function as well as to be able to recognize the complications associated with its use. The article discusses the most common and important devices of the head, neck, and spine, including cerebrospinal fluid shunts and the Codman Hakim programmable valve; subdural drainage catheters, subdural electrodes, intracranial electrodes, deep brain stimulators, and cerebellar electrodes; coils, balloons, adhesives, particles, and aneurysm clips; radiation therapy catheters, intracranial balloons for drug installation, and carmustine wafers; hearing aids, cochlear implants, and ossicular reconstruction prostheses; orbital prostheses, intraocular silicone oil, and lacrimal duct stents; anterior and posterior cervical plates, posterior cervical spine wiring, odontoid fracture fixation devices, cervical collars and halo vests; thoracic and lumbar spine implants, anterior and posterior instrumentation for the thoracic and lumbar spine, vertebroplasty, and artificial disks; spinal column stimulators, bone stimulators, intrathecal drug delivery pumps, and sacral stimulators; dental and facial implant devices; gastric and tracheal tubes; vagus nerve stimulators; lumboperitoneal shunts; and temperature- and oxygen-sensing probes. Copyright RSNA, 2004

The influence of disk's flexibility on coupling vibration of shaft disk blades systems

NASA Astrophysics Data System (ADS)

Yang, Chia-Hao; Huang, Shyh-Chin

2007-03-01

The coupling vibrations among shaft-torsion, disk-transverse and blade-bending in a shaft-disk-blades unit are investigated. The equations of motion for the shaft-disk-blades unit are first derived from the energy approach in conjunction with the assumed modes method. The effects of disk flexibility, blade's stagger angle and rotational speed upon the natural frequencies and mode shapes are particularly studied. Previous studies have shown that there were four types of coupling modes, the shaft-blade (SB), the shaft-disk-blades (SDBs), the disk-blades (DB) and the blade-blade (BB) in such a unit. The present research focuses on the influence of disk flexibility on the coupling behavior and discovers that disk's flexibility strongly affects the modes bifurcation and the transition of modes. At slightly flexible disk, the BB modes bifurcate into BB and DB modes. As disk goes further flexible, SB modes shift into SDB modes. If it goes furthermore, additional disk-predominating modes are generated and DB modes appear before the SDB mode. Examination of stagger angle β proves that at two extreme cases; at β=0° the shaft and blades coupled but not the disk, and at β=90° the disk and blades coupled but not the shaft. In between, coupling exists among three components. Increasing β may increase or decrease SB modes, depending on which, the disk or shaft's first mode, is more rigid. The natural frequencies of DB modes usually decrease with the increase of β. Rotation effects show that bifurcation, veering and merging phenomena occur due to disk flexibility. Disk flexibility is also observed to induce more critical speeds in the SDBs systems.

Evaluation of available analytical techniques for monitoring the quality of space station potable water

NASA Technical Reports Server (NTRS)

Geer, Richard D.

1989-01-01

To assure the quality of potable water (PW) on the Space Station (SS) a number of chemical and physical tests must be conducted routinely. After reviewing the requirements for potable water, both direct and indirect analytical methods are evaluated that could make the required tests and improvements compatible with the Space Station operation. A variety of suggestions are made to improve the analytical techniques for SS operation. The most important recommendations are: (1) the silver/silver chloride electrode (SB) method of removing I sub 2/I (-) biocide from the water, since it may interfere with analytical procedures for PW and also its end uses; (2) the orbital reactor (OR) method of carrying out chemistry and electrochemistry in microgravity by using a disk shaped reactor on an orbital table to impart artificial G force to the contents, allowing solution mixing and separation of gases and liquids; and (3) a simple ultra low volume highly sensitive electrochemical/conductivity detector for use with a capillary zone electrophoresis apparatus. It is also recommended, since several different conductivity and resistance measurements are made during the analysis of PW, that the bipolar pulse measuring circuit be used in all these applications for maximum compatibility and redundancy of equipment.

On Estimating the Mass of Keplerian Accretion Disks in H2O Maser Galaxies

NASA Astrophysics Data System (ADS)

Kuo, C. Y.; Reid, M. J.; Braatz, J. A.; Gao, F.; Impellizzeri, C. M. V.; Chien, W. T.

2018-06-01

H2O maser disks with Keplerian rotation in active galactic nuclei offer a clean way to determine accurate black hole mass and the Hubble constant. An important assumption made in using a Keplerian H2O maser disk for measuring black hole mass and the Hubble constant is that the disk mass is negligible compared to the black hole mass. A simple and useful model of Huré et al. can be used to test this assumption. In that work, the authors apply a linear disk model to a position–dynamical mass diagram and re-analyze position–velocity data from H2O maser disks associated with active galactic nuclei. They claim that a maser disk with nearly perfect Keplerian rotation could have a disk mass comparable to the black hole mass. This would imply that ignoring the effects of disk self-gravity can lead to large systematic errors in the measurement of black hole mass and the Hubble constant. We examine their methods and find that their large estimated disk masses of Keplerian disks are likely the result of their use of projected instead of three-dimensional position and velocity information. To place better constraints on the disk masses of Keplerian maser systems, we incorporate disk self-gravity into a three-dimensional Bayesian modeling program for maser disks and also evaluate constraints based on the physical conditions for disks that support water maser emission. We find that there is little evidence that disk masses are dynamically important at the ≲1% level compared to the black holes.

Disk Diffusion Testing Using Candida sp. Colonies Taken Directly from CHROMagar Candida Medium May Decrease Time Required To Obtain Results

PubMed Central

Klevay, Michael; Ebinger, Alex; Diekema, Daniel; Messer, Shawn; Hollis, Richard; Pfaller, Michael

2005-01-01

We compared results of disk diffusion antifungal susceptibility testing from Candida sp. strains passaged on CHROMagar and on potato dextrose agar. The overall categorical agreements for fluconazole and voriconazole disk testing were 95% and 98% with 0% and 0.5% very major errors, respectively. Disk diffusion testing by the CLSI (formerly NCCLS) M44-A method can be performed accurately by taking inocula directly from CHROMagar. PMID:16000489

Forced response of mistuned bladed disk assemblies

NASA Technical Reports Server (NTRS)

Watson, Brian C.; Kamat, Manohar P.; Murthy, Durbha V.

1993-01-01

A complete analytic model of mistuned bladed disk assemblies, designed to simulate the dynamical behavior of these systems, is analyzed. The model incorporates a generalized method for describing the mistuning of the assembly through the introduction of specific mistuning modes. The model is used to develop a computational bladed disk assembly model for a series of parametric studies. Results are presented demonstrating that the response amplitudes of bladed disk assemblies depend both on the excitation mode and on the mistune mode.

Method of making electrodes for electrochemical cell. [Li-Al alloy

DOEpatents

Kaun, T.D.; Kilsdonk, D.J.

1981-07-29

A method is described for making an electrode for an electrochemical cell in which particulate electrode-active material is mixed with a liquid organic carrier chemically inert with respect to the electrode-active material, mixing the liquid carrier to form an extrudable slurry. The liquid carrier is present in an amount of from about 10 to about 50% by volume of the slurry, and then the carrier is removed from the slurry leaving the electrode-active material. The method is particularly suited for making a lithium-aluminum alloy negative electrode for a high-temperature cell.

Online monitoring of electrocatalytic reactions of alcohols at platinum and gold electrodes in acidic, neutral and alkaline media by capillary electrophoresis with contactless conductivity detection (EC-CE-C4 D).

PubMed

Ferreira Santos, Mauro Sérgio; Silva Lopes, Fernando; Gutz, Ivano Gebhardt Rolf

2017-11-01

An EC-CE-C 4 D flow system was applied to the investigation of electrocatalytic processes by monitoring carboxylic acids formed during the electro-oxidation at various potentials of primary alcohols (mixture of 1 mmol/L of ethanol, n-propanol, n-butanol and n-pentanol) in acidic, neutral and alkaline media. The electro-oxidation was carried out on gold and platinum disk electrodes (3 mm of diameter) in a thin-layer electrochemical flow cell. Products were sampled 50 μm apart from the electrode directly into the capillary. All the generated carboxylates were determined in near real time (less than 2 min) by CE-C 4 D in counter-flow mode, with Tris/HCl buffer solution (pH 8.6) as BGE. Long sequences of 5-min experiments were run automatically, exploring the applied potential, electrolysis time and solution composition. Electro-oxidation at 1.5 V (versus Ag/AgCl quasi-reference) during 50 s in acidic medium was found appropriate for both Pt and Au electrodes when the determination of alcohols after derivatization is intended. A noteworthy selectivity effect was observed on the Au electrode. The signal corresponding to pentanoate is similar on both electrodes while the signal of ethanoate (acetate) is four times larger on gold than on platinum. The carboxylate signals were lower in alkaline medium (below the determination limit on Pt) than in acidic and neutral media. On gold, the formation of carboxylates was anticipated (0.85 V in alkaline medium versus 1.40 V in neutral medium). The automatic online monitoring of electrochemical processes by EC-CE-C 4 D holds great potential to investigate ionic/ionizable intermediates/products of new electrocatalysts and/or alternative fuels. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An intrinsic algorithm for parallel Poisson disk sampling on arbitrary surfaces.

PubMed

Ying, Xiang; Xin, Shi-Qing; Sun, Qian; He, Ying

2013-09-01

Poisson disk sampling has excellent spatial and spectral properties, and plays an important role in a variety of visual computing. Although many promising algorithms have been proposed for multidimensional sampling in euclidean space, very few studies have been reported with regard to the problem of generating Poisson disks on surfaces due to the complicated nature of the surface. This paper presents an intrinsic algorithm for parallel Poisson disk sampling on arbitrary surfaces. In sharp contrast to the conventional parallel approaches, our method neither partitions the given surface into small patches nor uses any spatial data structure to maintain the voids in the sampling domain. Instead, our approach assigns each sample candidate a random and unique priority that is unbiased with regard to the distribution. Hence, multiple threads can process the candidates simultaneously and resolve conflicts by checking the given priority values. Our algorithm guarantees that the generated Poisson disks are uniformly and randomly distributed without bias. It is worth noting that our method is intrinsic and independent of the embedding space. This intrinsic feature allows us to generate Poisson disk patterns on arbitrary surfaces in IR(n). To our knowledge, this is the first intrinsic, parallel, and accurate algorithm for surface Poisson disk sampling. Furthermore, by manipulating the spatially varying density function, we can obtain adaptive sampling easily.

Optical Strain and Crack-Detection Measurements on a Rotating Disk

NASA Technical Reports Server (NTRS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle; Fralick, Gustave

2013-01-01

The development of techniques for the in-situ measurement and structural health monitoring of the rotating components in gas turbine engines is of major interest to NASA. As part of this on-going effort, several experiments have been undertaken to develop methods for detecting cracks and measuring strain on rotating turbine engine like disks. Previous methods investigated have included the use of blade tip clearance sensors to detect the presence of cracks by monitoring the change in measured blade tip clearance and analyzing the combined disk-rotor system's vibration response. More recently, an experiment utilizing a novel optical Moiré based concept has been conducted on a subscale turbine engine disk to demonstrate a potential strain measurement and crack detection technique. Moiré patterns result from the overlap of two repetitive patterns with slightly different spacing. When this technique is applied to a rotating disk, it has the potential to allow for the detection of very small changes in spacing and radial growth in a rotating disk due to a flaw such as a crack. This investigation was a continuation of previous efforts undertaken in 2011-2012 to validate this optical concept. The initial demonstration attempted on a subscale turbine engine disk was inconclusive due to the minimal radial growth experienced by the disk during operation. For the present experiment a new subscale Aluminum disk was fabricated and improvements were made to the experimental setup to better demonstrate the technique. A circular reference pattern was laser etched onto a subscale engine disk and the disk was operated at speeds up to 12 000 rpm as a means of optically monitoring the Moiré created by the shift in patterns created by the radial growth due the presence of the simulated crack. Testing was first accomplished on a clean defect free disk as a means of acquiring baseline reference data. A notch was then machined in to the disk to simulate a crack and testing was repeated for the purposes of demonstrating the concept. Displacement data was acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the optical data and for validating other sensor based crack detection techniques.

Optical Strain and Crack-Detection Measurements on a Rotating Disk

NASA Technical Reports Server (NTRS)

Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle M.; Fralick, Gustave

2013-01-01

The development of techniques for the in-situ measurement and structural health monitoring of the rotating components in gas turbine engines is of major interest to NASA. As part of this on-going effort, several experiments have been undertaken to develop methods for detecting cracks and measuring strain on rotating turbine engine like disks. Previous methods investigated have included the use of blade tip clearance sensors to detect the presence of cracks by monitoring the change in measured blade tip clearance and analyzing the combined disk-rotor system's vibration response. More recently, an experiment utilizing a novel optical Moiré based concept has been conducted on a subscale turbine engine disk to demonstrate a potential strain measurement and crack detection technique. Moiré patterns result from the overlap of two repetitive patterns with slightly different spacing. When this technique is applied to a rotating disk, it has the potential to allow for the detection of very small changes in spacing and radial growth in a rotating disk due to a flaw such as a crack. This investigation was a continuation of previous efforts undertaken in 2011 to 2012 to validate this optical concept. The initial demonstration attempted on a subscale turbine engine disk was inconclusive due to the minimal radial growth experienced by the disk during operation. For the present experiment a new subscale Aluminum disk was fabricated and improvements were made to the experimental setup to better demonstrate the technique. A circular reference pattern was laser etched onto a subscale engine disk and the disk was operated at speeds up to 12 000 rpm as a means of optically monitoring the Moiré created by the shift in patterns created by the radial growth due the presence of the simulated crack. Testing was first accomplished on a clean defect free disk as a means of acquiring baseline reference data. A notch was then machined in to the disk to simulate a crack and testing was repeated for the purposes of demonstrating the concept. Displacement data was acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the optical data and for validating other sensor based crack detection techniques.

Systems and methods for producing low work function electrodes

DOEpatents

Kippelen, Bernard; Fuentes-Hernandez, Canek; Zhou, Yinhua; Kahn, Antoine; Meyer, Jens; Shim, Jae Won; Marder, Seth R.

2015-07-07

According to an exemplary embodiment of the invention, systems and methods are provided for producing low work function electrodes. According to an exemplary embodiment, a method is provided for reducing a work function of an electrode. The method includes applying, to at least a portion of the electrode, a solution comprising a Lewis basic oligomer or polymer; and based at least in part on applying the solution, forming an ultra-thin layer on a surface of the electrode, wherein the ultra-thin layer reduces the work function associated with the electrode by greater than 0.5 eV. According to another exemplary embodiment of the invention, a device is provided. The device includes a semiconductor; at least one electrode disposed adjacent to the semiconductor and configured to transport electrons in or out of the semiconductor.

Surface electrochemistry of CO on reconstructed gold single crystal surfaces studied by infrared reflection absorption spectroscopy and rotating disk electrode.

PubMed

Blizanac, Berislav B; Arenz, Matthias; Ross, Philip N; Marković, Nenad M

2004-08-18

The electrooxidation of CO has been studied on reconstructed gold single-crystal surfaces by a combination of electrochemical (EC) and infrared reflection absorption spectroscopy (IRAS) measurements. Emphasis is placed on relating the vibrational properties of the CO adlayer to the voltammetric and other macroscopic electrochemical responses, including rotating disk electrode measurements of the catalytic activity. The IRAS data show that the C-O stretching frequencies are strongly dependent on the surface orientation and can be observed in the range 1940-1990 cm(-1) for the 3-fold bridging, 2005-2070 cm(-1) for the 2-fold bridging, and 2115-2140 for the terminal position. The most complex CO spectra are found for the Au(110)-(1 x 2) surface, i.e., a band near 1965 cm(-1), with the second, weaker band shifted positively by about 45 cm(-1) and, finally, a weak band near 2115 cm(-1). While the C-O stretching frequencies for a CO adlayer adsorbed on Au(111)-(1 x 23) show nu(CO) bands at 2029-2069 cm(-1) and at 1944-1986 cm(-1), on the Au(100)-"hex" surface a single CO band is observed at 2004-2029 cm(-1). In the "argon-purged" solution, the terminal nu(CO) band on Au(110)-(1 x 2) and the 3-fold bridging band on the Au(111)-(1 x 23) disappear entirely. The IRAS/EC data show that the kinetics of CO oxidation are structure sensitive; i.e., the onset of CO oxidation increases in the order Au(110)-(1 x 2) > or = Au(100)-"hex" > Au(111)-(1 x 23). Possible explanations for the structure sensitivity are discussed.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: II. Influence of Ink Formulation, Catalyst Layer Uniformity and Thickness

DOE PAGES

Shinozaki, Kazuma; Zack, Jason W.; Pylypenko, Svitlana; ...

2015-09-17

Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mgPt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mgPt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1more » M HClO 4, 20 mV/s, 100 kPa O 2 and 23±2°C. An enhancement factor of 2.8 in themeasured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (~4.5 μg/cm 2 Pt) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m2/gPt) and Pt/V (65 ± 5 m 2/gPt) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.« less

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: II. Influence of Ink Formulation, Catalyst Layer Uniformity and Thickness

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

Shinozaki, Kazuma; Zack, Jason W.; Pylypenko, Svitlana

Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mgPt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mgPt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1more » M HClO 4, 20 mV/s, 100 kPa O 2 and 23±2°C. An enhancement factor of 2.8 in themeasured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (~4.5 μg/cm 2 Pt) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m2/gPt) and Pt/V (65 ± 5 m 2/gPt) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.« less

A NEW METHOD TO QUANTIFY AND REDUCE THE NET PROJECTION ERROR IN WHOLE-SOLAR-ACTIVE-REGION PARAMETERS MEASURED FROM VECTOR MAGNETOGRAMS

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

Falconer, David A.; Tiwari, Sanjiv K.; Moore, Ronald L.

Projection errors limit the use of vector magnetograms of active regions (ARs) far from the disk center. In this Letter, for ARs observed up to 60° from the disk center, we demonstrate a method for measuring and reducing the projection error in the magnitude of any whole-AR parameter that is derived from a vector magnetogram that has been deprojected to the disk center. The method assumes that the center-to-limb curve of the average of the parameter’s absolute values, measured from the disk passage of a large number of ARs and normalized to each AR’s absolute value of the parameter atmore » central meridian, gives the average fractional projection error at each radial distance from the disk center. To demonstrate the method, we use a large set of large-flux ARs and apply the method to a whole-AR parameter that is among the simplest to measure: whole-AR magnetic flux. We measure 30,845 SDO /Helioseismic and Magnetic Imager vector magnetograms covering the disk passage of 272 large-flux ARs, each having whole-AR flux >10{sup 22} Mx. We obtain the center-to-limb radial-distance run of the average projection error in measured whole-AR flux from a Chebyshev fit to the radial-distance plot of the 30,845 normalized measured values. The average projection error in the measured whole-AR flux of an AR at a given radial distance is removed by multiplying the measured flux by the correction factor given by the fit. The correction is important for both the study of the evolution of ARs and for improving the accuracy of forecasts of an AR’s major flare/coronal mass ejection productivity.« less

Attaching IBM-compatible 3380 disks to Cray X-MP

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

Engert, D.E.; Midlock, J.L.

1989-01-01

A method of attaching IBM-compatible 3380 disks directly to a Cray X-MP via the XIOP with a BMC is described. The IBM 3380 disks appear to the UNICOS operating system as DD-29 disks with UNICOS file systems. IBM 3380 disks provide cheap, reliable large capacity disk storage. Combined with a small number of high-speed Cray disks, the IBM disks provide for the bulk of the storage for small files and infrequently used files. Cray Research designed the BMC and its supporting software in the XIOP to allow IBM tapes and other devices to be attached to the X-MP. No hardwaremore » changes were necessary, and we added less than 2000 lines of code to the XIOP to accomplish this project. This system has been in operation for over eight months. Future enhancements such as the use of a cache controller and attachment to a Y-MP are also described. 1 tab.« less

Experimental dynamic characterizations and modelling of disk vibrations for HDDs.

PubMed

Pang, Chee Khiang; Ong, Eng Hong; Guo, Guoxiao; Qian, Hua

2008-01-01

Currently, the rotational speed of spindle motors in HDDs (Hard-Disk Drives) are increasing to improve high data throughput and decrease rotational latency for ultra-high data transfer rates. However, the disk platters are excited to vibrate at their natural frequencies due to higher air-flow excitation as well as eccentricities and imbalances in the disk-spindle assembly. These factors contribute directly to TMR (Track Mis-Registration) which limits achievable high recording density essential for future mobile HDDs. In this paper, the natural mode shapes of an annular disk mounted on a spindle motor used in current HDDs are characterized using FEM (Finite Element Methods) analysis and verified with SLDV (Scanning Laser Doppler Vibrometer) measurements. The identified vibration frequencies and amplitudes of the disk ODS (Operating Deflection Shapes) at corresponding disk mode shapes are modelled as repeatable disturbance components for servo compensation in HDDs. Our experimental results show that the SLDV measurements are accurate in capturing static disk mode shapes without the need for intricate air-flow aero-elastic models, and the proposed disk ODS vibration model correlates well with experimental measurements from a LDV.

[Expression and distribution of xenoantigen alpha-Gal in intervertebral disk of Chinese banna minipig inbred line].

PubMed

Shou, Jian-guo; Mi, Jian-hong; Ying, Da-jun

2002-09-01

To investigate the expression and distribution of xenoantigen in intervertebral disk of Chinese banna minipig inbred line, and to study the availability of xenograft transplantation of intervertebral disk. Samples of intervertebral disk were collected from six Banna pigs of 8 to 11-month-old. The fixation, embedment and slice were performed. alpha-Gal specific binding lection (BSI-B4) were used as affinity reagents and affinity-immunohistochemistry assays (SABC methods and DAB stain) were conducted to detect the expression and distribution of xenoantigen (alpha-Gal). alpha-Gal was found in chondrocyte cell and chondrocyte-like cell in intervertebral disk which have the positive yellow-stained particulate aggradation. There was no stain in the matrix, elastic fiber and collagen fiber. The distribution of xenoantigen is locally in the tissue of intervertebral disk and its expression is weak. This suggests that the intervertebral disk of Banna pig may be alternative donor for xenotransplantation.

Moving mode shape function approach for spinning disk and asymmetric disc brake squeal

NASA Astrophysics Data System (ADS)

Kang, Jaeyoung

2018-06-01

The solution approach of an asymmetric spinning disk under stationary friction loads requires the mode shape function fixed in the disk in the assumed mode method when the equations of motion is described in the space-fixed frame. This model description will be termed the 'moving mode shape function approach' and it allows us to formulate the stationary contact load problem in both the axisymmetric and asymmetric disk cases. Numerical results show that the eigenvalues of the time-periodic axisymmetric disk system are time-invariant. When the axisymmetry of the disk is broken, the positive real parts of the eigenvalues highly vary with the rotation of the disk in the slow speeds in such application as disc brake squeal. By using the Floquet stability analysis, it is also shown that breaking the axisymmetry of the disc alters the stability boundaries of the system.

Exact general relativistic disks with magnetic fields

NASA Astrophysics Data System (ADS)

Letelier, Patricio S.

1999-11-01

The well-known ``displace, cut, and reflect'' method used to generate cold disks from given solutions of Einstein equations is extended to solutions of Einstein-Maxwell equations. Four exact solutions of the these last equations are used to construct models of hot disks with surface density, azimuthal pressure, and azimuthal current. The solutions are closely related to Kerr, Taub-NUT, Lynden-Bell-Pinault, and to a one-soliton solution. We find that the presence of the magnetic field can change in a nontrivial way the different properties of the disks. In particular, the pure general relativistic instability studied by Bic̆ák, Lynden-Bell, and Katz [Phys. Rev. D 47, 4334 (1993)] can be enhanced or cured by different distributions of currents inside the disk. These currents, outside the disk, generate a variety of axial symmetric magnetic fields. As far as we know these are the first models of hot disks studied in the context of general relativity.

Complex Analysis of Diffusion Transport and Microstructure of an Intervertebral Disk.

PubMed

Byvaltsev, V A; Kolesnikov, S I; Belykh, E G; Stepanov, I A; Kalinin, A A; Bardonova, L A; Sudakov, N P; Klimenkov, I V; Nikiforov, S B; Semenov, A V; Perfil'ev, D V; Bespyatykh, I V; Antipina, S L; Giers, M; Prul, M

2017-12-01

We studied the relationship between diffusion transport and morphological and microstructural organization of extracellular matrix of human intervertebral disk. Specimens of the lumbar intervertebral disks without abnormalities were studied ex vivo by diffusion-weighed magnetic resonance imaging, histological and immunohistochemical methods, and electron microscopy. Distribution of the diffusion coefficient in various compartments of the intervertebral disk was studied. Significant correlations between diffusion coefficient and cell density in the nucleus pulposus, posterior aspects of annulus fibrosus, and endplate at the level of the posterior annulus fibrosus were detected for each disk. In disks with nucleus pulposus diffusion coefficient below 15×10 -4 mm 2 /sec, collagens X and XI were detected apart from aggrecan and collagens I and II. The results supplement the concept on the relationship between the microstructure and cell composition of various compartments of the intervertebral disk and parameters of nutrient transport.

Ionization detector, electrode configuration and single polarity charge detection method

DOEpatents

He, Z.

1998-07-07

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

Ionization detector, electrode configuration and single polarity charge detection method

DOEpatents

He, Zhong

1998-01-01

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

Investigating dust trapping in transition disks with millimeter-wave polarization

NASA Astrophysics Data System (ADS)

Pohl, A.; Kataoka, A.; Pinilla, P.; Dullemond, C. P.; Henning, Th.; Birnstiel, T.

2016-08-01

Context. Spatially resolved polarized (sub-)mm emission has been observed for example in the protoplanetary disk around HL Tau. Magnetically aligned grains are commonly interpreted as the source of polarization. However, self-scattering by large dust grains with a high enough albedo is another polarization mechanism, which is becoming a compelling method independent of the spectral index to constrain the dust grain size in protoplanetary disks. Aims: We study the dust polarization at mm wavelengths in the dust trapping scenario proposed for transition disks, when a giant planet opens a gap in the disk. We investigate the characteristic polarization patterns and their dependence on disk inclination, dust size evolution, planet position, and observing wavelength. Methods: We combine two-dimensional hydrodynamical simulations of planet-disk interactions with self-consistent dust growth models. These size-dependent dust density distributions are used for follow-up three-dimensional radiative transfer calculations to predict the polarization degree at ALMA bands due to scattered thermal emission. Results: Dust self-scattering has been proven to be a viable mechanism for producing polarized mm-wave radiation. We find that the polarization pattern of a disk with a planetary gap after 1 Myr of dust evolution shows a distinctive three-ring structure. Two narrow inner rings are located at the planet gap edges. A third wider ring of polarization is situated in the outer disk beyond 100 au. For increasing observing wavelengths, all three rings change their position slightly, where the innermost and outermost rings move inward. This distance is detectable when comparing the results at ALMA bands 3, 6, and 7. Within the highest polarized intensity regions the polarization vectors are oriented in the azimuthal direction. For an inclined disk there is an interplay between polarization originating from a flux gradient and inclination-induced quadrupole polarization. For intermediate inclined transition disks, the polarization degree is as high as ~2% at λ = 3.1 mm (band 3), which is well above the detection limit of future ALMA observations.

The cell-in-series method: A technique for accelerated electrode degradation in redox flow batteries

DOE PAGES

Pezeshki, Alan M.; Sacci, Robert L.; Veith, Gabriel M.; ...

2015-11-21

Here, we demonstrate a novel method to accelerate electrode degradation in redox flow batteries and apply this method to the all-vanadium chemistry. Electrode performance degradation occurred seven times faster than in a typical cycling experiment, enabling rapid evaluation of materials. This method also enables the steady-state study of electrodes. In this manner, it is possible to delineate whether specific operating conditions induce performance degradation; we found that both aggressively charging and discharging result in performance loss. Post-mortem x-ray photoelectron spectroscopy of the degraded electrodes was used to resolve the effects of state of charge (SoC) and current on the electrodemore » surface chemistry. For the electrode material tested in this work, we found evidence that a loss of oxygen content on the negative electrode cannot explain decreased cell performance. Furthermore, the effects of decreased electrode and membrane performance on capacity fade in a typical cycling battery were decoupled from crossover; electrode and membrane performance decay were responsible for a 22% fade in capacity, while crossover caused a 12% fade.« less

Finite element method modeling to assess Laplacian estimates via novel variable inter-ring distances concentric ring electrodes.

PubMed

Makeyev, Oleksandr; Besio, Walter G

2016-08-01

Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation has been demonstrated in a range of applications. In our recent work we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts using finite element method modeling. Obtained results suggest that increasing inter-ring distances electrode configurations may decrease the estimation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration the estimation error may be decreased more than two-fold while for the quadripolar configuration more than six-fold decrease is expected.

A Method to Constrain the Size of the Protosolar Nebula

NASA Astrophysics Data System (ADS)

Kretke, K. A.; Levison, H. F.; Buie, M. W.; Morbidelli, A.

2012-04-01

Observations indicate that the gaseous circumstellar disks around young stars vary significantly in size, ranging from tens to thousands of AU. Models of planet formation depend critically upon the properties of these primordial disks, yet in general it is impossible to connect an existing planetary system with an observed disk. We present a method by which we can constrain the size of our own protosolar nebula using the properties of the small body reservoirs in the solar system. In standard planet formation theory, after Jupiter and Saturn formed they scattered a significant number of remnant planetesimals into highly eccentric orbits. In this paper, we show that if there had been a massive, extended protoplanetary disk at that time, then the disk would have excited Kozai oscillations in some of the scattered objects, driving them into high-inclination (i >~ 50°), low-eccentricity orbits (q >~ 30 AU). The dissipation of the gaseous disk would strand a subset of objects in these high-inclination orbits; orbits that are stable on Gyr timescales. To date, surveys have not detected any Kuiper-belt objects with orbits consistent with this dynamical mechanism. Using these non-detections by the Deep Ecliptic Survey and the Palomar Distant Solar System Survey we are able to rule out an extended gaseous protoplanetary disk (RD >~ 80 AU) in our solar system at the time of Jupiter's formation. Future deep all sky surveys such as the Large Synoptic Survey Telescope will allow us to further constrain the size of the protoplanetary disk.

Clinical microbiology laboratories do not always detect resistance of Haemophilus influenzae with disk or tablet diffusion methods. Finnish Study Group for Antimicrobial Resistance (FiRe).

PubMed

Manninen, R; Huovinen, P; Nissinen, A

1998-04-01

The performance of disk diffusion testing of Haemophilus influenzae was evaluated in 20 laboratories. Thirteen disk-medium-breakpoint-inoculum modifications were used in Finnish clinical microbiology laboratories. The performance of various methods was evaluated by testing a susceptible control strain and one with non-beta-lactamase-mediated ampicillin resistance 10 times in 16 laboratories. Gaps in millimeters were measured between these two groups of results. The strains were separated by a gap of at least 5 mm in 8/16 laboratories testing ampicillin, in 7/15 laboratories testing cefaclor, in 5/ 16 laboratories testing cefuroxime, and in 15/16 laboratories testing trimethoprim-sulfa. Detection of ampicillin resistance was better with 2.5 microg tablets than with 10 microg disks or 33 microg tablets. For MIC-determinations, 785 isolates and their disk diffusion results were collected. None of the 12 clinical isolates with non-beta-lactamase-mediated ampicillin resistance was detected as resistant in the participating laboratories. The ampicillin and cefaclor results of the isolates were no better even when a laboratory was able to separate the control strains. Cefaclor results were unreliable because of poor disk diffusion-MIC correspondence and incoherent breakpoint references. Interlaboratory variation of the zone diameters caused false intermediate results of cefuroxime-susceptible strains. When ampicillin, cefaclor and cefuroxime were tested, the discrimination of laboratories using disks and tablets was equal, whereas the laboratories using paper disks were better able to detect trimethoprim-sulfa resistance.

Sonic boom generated by a slender body aerodynamically shaded by a disk spike

NASA Astrophysics Data System (ADS)

Potapkin, A. V.; Moskvichev, D. Yu.

2018-03-01

The sonic boom generated by a slender body of revolution aerodynamically shaded by another body is numerically investigated. The aerodynamic shadow is created by a disk placed upstream of the slender body across a supersonic free-stream flow. The disk size and its position upstream of the body are chosen in such a way that the aerodynamically shaded flow is quasi-stationary. A combined method of phantom bodies is used for sonic boom calculations. The method is tested by calculating the sonic boom generated by a blunted body and comparing the results with experimental investigations of the sonic boom generated by spheres of various diameters in ballistic ranges and wind tunnels. The test calculations show that the method of phantom bodies is applicable for calculating far-field parameters of shock waves generated by both slender and blunted bodies. A possibility of reducing the shock wave intensity in the far field by means of the formation of the aerodynamic shadow behind the disk placed upstream of the body is estimated. The calculations are performed for the incoming flow with the Mach number equal to 2. The effect of the disk size on the sonic boom level is calculated.

New Strategies and Methods to Study Interactions between Tobacco Mosaic Virus Coat Protein and Its Inhibitors

PubMed Central

Li, Xiangyang; Chen, Zhuo; Jin, Linhong; Hu, Deyu; Yang, Song

2016-01-01

Studies of the targets of anti-viral compounds are hot topics in the field of pesticide research. Various efficient anti-TMV (Tobacco Mosaic Virus) compounds, such as Ningnanmycin (NNM), Antofine (ATF), Dufulin (DFL) and Bingqingxiao (BQX) are available. However, the mechanisms of the action of these compounds on targets remain unclear. To further study the mechanism of the action of the anti-TMV inhibitors, the TMV coat protein (TMV CP) was expressed and self-assembled into four-layer aggregate disks in vitro, which could be reassembled into infectious virus particles with TMV RNA. The interactions between the anti-TMV compounds and the TMV CP disk were analyzed by size exclusion chromatography, isothermal titration calorimetry and native-polyacrylamide gel electrophoresis methods. The results revealed that assembly of the four-layer aggregate disk was inhibited by NNM; it changed the four-layer aggregate disk into trimers, and affected the regular assembly of TMV CP and TMV RNA. The four-layer aggregate disk of TMV CP was little inhibited by ATF, DFL and BQX. Our results provide original data, as well as new strategies and methods, for research on the mechanism of action of anti-viral drugs. PMID:26927077

Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

DOE PAGES

Pekin, Thomas C.; Gammer, Christoph; Ciston, Jim; ...

2017-01-28

Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. Here in this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with amore » Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. Lastly, we have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.« less

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Kantzos, Pete T.; Palsa, Bonnie; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.

2012-01-01

Mechanical property requirements vary with location in nickel-based superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 C and 704 C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

Methods for thermodynamic evaluation of battery state of health

DOEpatents

Yazami, Rachid; McMenamin, Joseph; Reynier, Yvan; Fultz, Brent T

2013-05-21

Described are systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and battery systems and for characterizing the state of health of electrodes and battery systems. Measurement of physical attributes of electrodes and batteries corresponding to thermodynamically stabilized electrode conditions permit determination of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and battery systems, such as energy, power density, current rate, cycle life and state of health. Also provided are systems and methods for charging a battery according to its state of health.

Methods and systems for thermodynamic evaluation of battery state of health

DOEpatents

Yazami, Rachid; McMenamin, Joseph; Reynier, Yvan; Fultz, Brent T

2014-12-02

Described are systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and battery systems and for characterizing the state of health of electrodes and battery systems. Measurement of physical attributes of electrodes and batteries corresponding to thermodynamically stabilized electrode conditions permit determination of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and battery systems, such as energy, power density, current rate, cycle life and state of health. Also provided are systems and methods for charging a battery according to its state of health.

Fully Printable Organic and Perovskite Solar Cells with Transfer-Printed Flexible Electrodes.

PubMed

Li, Xianqiang; Tang, Xiaohong; Ye, Tao; Wu, Dan; Wang, Hong; Wang, Xizu

2017-06-07

The perovskite solar cells (PSCs) and organic solar cells (OSCs) with high performance were fabricated with transfer-printed top metal electrodes. We have demonstrated that PSCs and OSCs with the top Au electrodes fabricated by using the transfer printing method have comparable or better performance than the devices with the top Au electrodes fabricated by using the conventional thermal evaporation method. The highest PCE of the PSCs and OSCs with the top electrodes fabricated using the transfer printing method achieved 13.72% and 2.35%, respectively. It has been investigated that fewer defects between the organic thin films and Au electrodes exist by using the transfer printing method which improved the device stability. After storing the PSCs and OSCs with the transfer-printed electrodes in a nitrogen environment for 97 and 103 days without encapsulation, the PSCs and OSCs still retained 71% and 91% of their original PCEs, respectively.

Development of a microchip-pulsed electrochemical method for rapid determination of L-DOPA and tyrosine in Mucuna pruriens.

PubMed

Li, Xinchun; Chen, Zuanguang; Yang, Fan; Pan, Jianbin; Li, Yinbao

2013-05-01

L-3,4-dihydroxyphenylalanine (L-DOPA) is a well-recognized therapeutic compound to Parkinson's disease. Tyrosine is a precursor for the biosynthesis of L-DOPA, both of which are widely found in traditional medicinal material, Mucuna pruriens. In this paper, we described a validated novel analytical method based on microchip capillary electrophoresis with pulsed electrochemical detection for the simultaneous measurement of L-DOPA and tyrosine in M. pruriens. This protocol adopted end-channel amperometric detection using platinum disk electrode on a homemade glass/polydimethylsiloxane electrophoresis microchip. The background buffer consisted of 10 mM borate (pH 9.5) and 0.02 mM cetyltrimethylammonium bromide, which can produce an effective resolution for the two analytes. In the optimal condition, sufficient electrophoretic separation and sensitive detection for the target analytes can be realized within 60 s. Both tyrosine and L-DOPA yielded linear response in the concentration range of 5.0-400 μM (R(2) > 0.99), and the LOD were 0.79 and 1.1 μM, respectively. The accuracy and precision of the established method were favorable. The present method shows several merits such as facile apparatus, high speed, low cost and minimal pollution, and provides a means for the pharmacologically active ingredients assay in M. pruriens. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A guide to the use of the pressure disk rotor model as implemented in INS3D-UP

NASA Technical Reports Server (NTRS)

Chaffin, Mark S.

1995-01-01

This is a guide for the use of the pressure disk rotor model that has been placed in the incompressible Navier-Stokes code INS3D-UP. The pressure disk rotor model approximates a helicopter rotor or propeller in a time averaged manner and is intended to simulate the effect of a rotor in forward flight on the fuselage or the effect of a propeller on other aerodynamic components. The model uses a modified actuator disk that allows the pressure jump across the disk to vary with radius and azimuth. The cyclic and collective blade pitch angles needed to achieve a specified thrust coefficient and zero moment about the hub are predicted. The method has been validated with experimentally measured mean induced inflow velocities as well as surface pressures on a generic fuselage. Overset grids, sometimes referred to as Chimera grids, are used to simplify the grid generation process. The pressure disk model is applied to a cylindrical grid which is embedded in the grid or grids used for the rest of the configuration. This document will outline the development of the method, and present input and results for a sample case.

Clues to the Formation of Lenticular Galaxies Using Spectroscopic Bulge-Disk Decomposition

NASA Astrophysics Data System (ADS)

Johnston, E. J.; Aragón-Salamanca, A.; Merrifield, M. R.; Bedregal, A. G.

2014-03-01

Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to look for clues to the processes that triggered their transformation from spirals. To accomplish this feat, we present a new method for spectroscopic bulge-disk decomposition, in which a long-slit spectrum is decomposed into two one-dimensional spectra representing purely the bulge and disk light. We present preliminary results from applying this method to lenticular galaxies in the Virgo and Fornax Clusters, in which we show that the most recent star formation activity in these galaxies occurred within the bulges. We also find that the star formation timescales of the bulges are longer than the disks, and that more massive galaxies take longer to lose their gas during the transformation. These results point towards slow processes, such as ram-pressure stripping or harassment, being the mechanism responsible for the quenching of star formation in spirals, followed by a burst of star formation in the central regions from the gas that has been funnelled inwards through the disk.

Automated detection and labeling of high-density EEG electrodes from structural MR images.

PubMed

Marino, Marco; Liu, Quanying; Brem, Silvia; Wenderoth, Nicole; Mantini, Dante

2016-10-01

Accurate knowledge about the positions of electrodes in electroencephalography (EEG) is very important for precise source localizations. Direct detection of electrodes from magnetic resonance (MR) images is particularly interesting, as it is possible to avoid errors of co-registration between electrode and head coordinate systems. In this study, we propose an automated MR-based method for electrode detection and labeling, particularly tailored to high-density montages. Anatomical MR images were processed to create an electrode-enhanced image in individual space. Image processing included intensity non-uniformity correction, background noise and goggles artifact removal. Next, we defined a search volume around the head where electrode positions were detected. Electrodes were identified as local maxima in the search volume and registered to the Montreal Neurological Institute standard space using an affine transformation. This allowed the matching of the detected points with the specific EEG montage template, as well as their labeling. Matching and labeling were performed by the coherent point drift method. Our method was assessed on 8 MR images collected in subjects wearing a 256-channel EEG net, using the displacement with respect to manually selected electrodes as performance metric. Average displacement achieved by our method was significantly lower compared to alternative techniques, such as the photogrammetry technique. The maximum displacement was for more than 99% of the electrodes lower than 1 cm, which is typically considered an acceptable upper limit for errors in electrode positioning. Our method showed robustness and reliability, even in suboptimal conditions, such as in the case of net rotation, imprecisely gathered wires, electrode detachment from the head, and MR image ghosting. We showed that our method provides objective, repeatable and precise estimates of EEG electrode coordinates. We hope our work will contribute to a more widespread use of high-density EEG as a brain-imaging tool.

Automated detection and labeling of high-density EEG electrodes from structural MR images

NASA Astrophysics Data System (ADS)

Marino, Marco; Liu, Quanying; Brem, Silvia; Wenderoth, Nicole; Mantini, Dante

2016-10-01

Objective. Accurate knowledge about the positions of electrodes in electroencephalography (EEG) is very important for precise source localizations. Direct detection of electrodes from magnetic resonance (MR) images is particularly interesting, as it is possible to avoid errors of co-registration between electrode and head coordinate systems. In this study, we propose an automated MR-based method for electrode detection and labeling, particularly tailored to high-density montages. Approach. Anatomical MR images were processed to create an electrode-enhanced image in individual space. Image processing included intensity non-uniformity correction, background noise and goggles artifact removal. Next, we defined a search volume around the head where electrode positions were detected. Electrodes were identified as local maxima in the search volume and registered to the Montreal Neurological Institute standard space using an affine transformation. This allowed the matching of the detected points with the specific EEG montage template, as well as their labeling. Matching and labeling were performed by the coherent point drift method. Our method was assessed on 8 MR images collected in subjects wearing a 256-channel EEG net, using the displacement with respect to manually selected electrodes as performance metric. Main results. Average displacement achieved by our method was significantly lower compared to alternative techniques, such as the photogrammetry technique. The maximum displacement was for more than 99% of the electrodes lower than 1 cm, which is typically considered an acceptable upper limit for errors in electrode positioning. Our method showed robustness and reliability, even in suboptimal conditions, such as in the case of net rotation, imprecisely gathered wires, electrode detachment from the head, and MR image ghosting. Significance. We showed that our method provides objective, repeatable and precise estimates of EEG electrode coordinates. We hope our work will contribute to a more widespread use of high-density EEG as a brain-imaging tool.

Comparison of real-time PCR with disk diffusion, agar screen and E-test methods for detection of methicillin-resistant Staphylococcus aureus.

PubMed

Shariati, Laleh; Validi, Majid; Tabatabaiefar, Mohammad Amin; Karimi, Ali; Nafisi, Mohammad Reza

2010-12-01

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen. Our main objective was to compare oxacillin disk test, oxacillin E-test, and oxacillin agar screen for detection of methicillin resistance in S. aureus, using real-time PCR for mecA as the "gold standard" comparison assay. 196 S. aureus isolates were identified out of 284 Staphylococcus isolates. These isolates were screened for MRSA with several methods: disk diffusion, agar screen (6.0 μg/ml), oxacillin E-test, and real-time PCR for detection of mecA gene. Of the 196 S. aureus isolates tested, 96 isolates (49%) were mecA-positive and 100 isolates (51%) mecA-negative. All methods tested had a statistically significant agreement with real-time PCR. E-test was 100% sensitive and specific for mecA presence. The sensitivity and specificity of oxacillin agar screen method were 98 and 99%, respectively and sensitivity and specificity of oxacillin disk diffusion method were 95 and 93%, respectively. In the present study, oxacillin E-test is proposed as the best phenotypic method. For economic reasons, the oxacillin agar screen method (6.0 μg/ml), which is suitable for the detection of MRSA, is recommended due to its accuracy and low cost.

METHOD OF JACKETING A FISSIONABLE BODY

DOEpatents

Creutz, E.C.

1960-02-16

A method for jacketing fuel elements is described. A fissionablc body ts fitted into a steel jacket, and a steel rimmed closure disk is inserted into the open end of the jacket. The jacket is then drawn through a die, aind the rim of the disk is welded to the jacket to form an impervious seal.

Voltammetric analysis apparatus and method

DOEpatents

Almon, A.C.

1993-06-08

An apparatus and method is described for electrochemical analysis of elements in solution. An auxiliary electrode, a reference electrode, and five working electrodes are positioned in a container containing a sample solution. The working electrodes are spaced apart evenly from each other and the auxiliary electrode to minimize any inter-electrode interference that may occur during analysis. An electric potential is applied between the auxiliary electrode and each of the working electrodes. Simultaneous measurements taken of the current flow through each of the working electrodes for each given potential in a potential range are used for identifying chemical elements present in the sample solution and their respective concentrations. Multiple working electrodes enable a more positive identification to be made by providing unique data characteristic of chemical elements present in the sample solution.

Comparison between Disk Diffusion and Microdilution Methods for Determining Susceptibility of Clinical Fungal Isolates to Caspofungin▿

PubMed Central

Milici, Maria Eleonora; Maida, Carmelo Massimo; Spreghini, Elisabetta; Ravazzolo, Barbara; Oliveri, Salvatore; Scalise, Giorgio; Barchiesi, Francesco

2007-01-01

We compared the caspofungin (CAS) susceptibility testing results generated by the disk diffusion (DD) assay with the results of the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BD) reference method for 106 yeast isolates. The isolates represented 11 different fungal species, including Candida albicans (n = 50), C. parapsilosis (n = 10), C. glabrata (n = 10), C. tropicalis (n = 10), C. guillermondii (n = 6), C. rugosa (n = 5), C. krusei (n = 5), C. kefyr (n = 2), C. pelliculosa (n = 2), Saccharomyces cerevisiae (n = 3), and Geotrichum candidum (n = 3). The DD assay was performed in supplemented Mueller-Hinton agar with CAS, which was tested at concentrations of 2, 10, and 25 μg per disk. MICs and inhibition zone diameters were evaluated at 24 and 48 h. In general, the results obtained by the DD assay correlated well with those obtained by the BD method. In particular, a significant correlation between methods was observed when CAS was used at concentration of 2 μg/disk at a reading time of either 24 or 48 h. PMID:17728477

Strain-Life Assessment of Grainex Mar-M 247 for NASA's Turbine Seal Test Facility

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Halford, Gary R.; Steinetz, Bruce M.; Rimnac, Clare M.

2004-01-01

NASA s Turbine Seal Test Facility is used to test air-to-air seals for use primarily in advanced jet engine applications. Combinations of high temperature, high speed, and high pressure limit the disk life, due to the concern of crack initiation in the bolt holes of the Grainex Mar-M 247 disk. The primary purpose of this current work is to determine an inspection interval to ensure safe operation. The current work presents high temperature fatigue strain-life data for test specimens cut from an actual Grainex Mar-M 247 disk. Several different strain-life models were compared to the experimental data including the Manson-Hirschberg Method of Universal Slopes, the Halford-Nachtigall Mean Stress Method, and the Modified Morrow Method. The Halford-Nachtigall Method resulted in only an 18 percent difference between predicted and experimental results. Using the experimental data at a 99.95 percent prediction level and the presence of 6 bolt holes it was found that the disk should be inspected after 665 cycles based on a total strain of 0.5 percent at 649 C.

Nanofiber membrane-electrode-assembly and method of fabricating same

DOEpatents

Pintauro, Peter N.; Ballengee, Jason; Brodt, Matthew

2016-02-02

In one aspect of the present invention, a fuel cell membrane-electrode-assembly (MEA) has an anode electrode, a cathode electrode, and a membrane disposed between the anode electrode and the cathode electrode. At least one of the anode electrode, the cathode electrode and the membrane is formed of electrospun nanofibers.

Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks

NASA Astrophysics Data System (ADS)

Kurfürst, P.; Feldmeier, A.; Krtička, J.

2018-06-01

Context. Evolution of massive stars is affected by a significant loss of mass either via (nearly) spherically symmetric stellar winds or by aspherical mass-loss mechanisms, namely the outflowing equatorial disks. However, the scenario that leads to the formation of a disk or rings of gas and dust around massive stars is still under debate. It is also unclear how various forming physical mechanisms of the circumstellar environment affect its shape and density, as well as its kinematic and thermal structure. Aims: We study the hydrodynamic and thermal structure of optically thick, dense parts of outflowing circumstellar disks that may be formed around various types of critically rotating massive stars, for example, Be stars, B[e] supergiant (sgB[e]) stars or Pop III stars. We calculate self-consistent time-dependent models of temperature and density structure in the disk's inner dense region that is strongly affected by irradiation from a rotationally oblate central star and by viscous heating. Methods: Using the method of short characteristics, we specify the optical depth of the disk along the line-of-sight from stellar poles. Within the optically thick dense region with an optical depth of τ > 2/3 we calculate the vertical disk thermal structure using the diffusion approximation while for the optically thin outer layers we assume a local thermodynamic equilibrium with the impinging stellar irradiation. For time-dependent hydrodynamic modeling, we use two of our own types of hydrodynamic codes: two-dimensional operator-split numerical code based on an explicit Eulerian finite volume scheme on a staggered grid, and unsplit code based on the Roe's method, both including full second-order Navier-Stokes shear viscosity. Results: Our models show the geometric distribution and contribution of viscous heating that begins to dominate in the central part of the disk for mass-loss rates higher than Ṁ ≳ 10-10 M⊙ yr-1. In the models of dense viscous disks with Ṁ > 10-8 M⊙ yr-1, the viscosity increases the central temperature up to several tens of thousands of Kelvins, however the temperature rapidly drops with radius and with distance from the disk midplane. The high mass-loss rates and high viscosity lead to instabilities with significant waves or bumps in density and temperature in the very inner disk region. Conclusions: The two-dimensional radial-vertical models of dense outflowing disks including the full Navier-Stokes viscosity terms show very high temperatures that are however limited to only the central disk cores inside the optically thick area, while near the edge of the optically thick region the temperature may be low enough for the existence of neutral hydrogen, for example.

Methods for calculating the electrode position Jacobian for impedance imaging.

PubMed

Boyle, A; Crabb, M G; Jehl, M; Lionheart, W R B; Adler, A

2017-03-01

Electrical impedance tomography (EIT) or electrical resistivity tomography (ERT) current and measure voltages at the boundary of a domain through electrodes. The movement or incorrect placement of electrodes may lead to modelling errors that result in significant reconstructed image artifacts. These errors may be accounted for by allowing for electrode position estimates in the model. Movement may be reconstructed through a first-order approximation, the electrode position Jacobian. A reconstruction that incorporates electrode position estimates and conductivity can significantly reduce image artifacts. Conversely, if electrode position is ignored it can be difficult to distinguish true conductivity changes from reconstruction artifacts which may increase the risk of a flawed interpretation. In this work, we aim to determine the fastest, most accurate approach for estimating the electrode position Jacobian. Four methods of calculating the electrode position Jacobian were evaluated on a homogeneous halfspace. Results show that Fréchet derivative and rank-one update methods are competitive in computational efficiency but achieve different solutions for certain values of contact impedance and mesh density.

Visualizing SPH Cataclysmic Variable Accretion Disk Simulations with Blender

NASA Astrophysics Data System (ADS)

Kent, Brian R.; Wood, Matthew A.

2015-01-01

We present innovative ways to use Blender, a 3D graphics package, to visualize smoothed particle hydrodynamics particle data of cataclysmic variable accretion disks. We focus on the methods of shape key data constructs to increasedata i/o and manipulation speed. The implementation of the methods outlined allow for compositing of the various visualization layers into a final animation. The viewing of the disk in 3D from different angles can allow for a visual analysisof the physical system and orbits. The techniques have a wide ranging set of applications in astronomical visualization,including both observation and theoretical data.

The DiskMass Survey. II. Error Budget

NASA Astrophysics Data System (ADS)

Bershady, Matthew A.; Verheijen, Marc A. W.; Westfall, Kyle B.; Andersen, David R.; Swaters, Rob A.; Martinsson, Thomas

2010-06-01

We present a performance analysis of the DiskMass Survey. The survey uses collisionless tracers in the form of disk stars to measure the surface density of spiral disks, to provide an absolute calibration of the stellar mass-to-light ratio (Υ_{*}), and to yield robust estimates of the dark-matter halo density profile in the inner regions of galaxies. We find that a disk inclination range of 25°-35° is optimal for our measurements, consistent with our survey design to select nearly face-on galaxies. Uncertainties in disk scale heights are significant, but can be estimated from radial scale lengths to 25% now, and more precisely in the future. We detail the spectroscopic analysis used to derive line-of-sight velocity dispersions, precise at low surface-brightness, and accurate in the presence of composite stellar populations. Our methods take full advantage of large-grasp integral-field spectroscopy and an extensive library of observed stars. We show that the baryon-to-total mass fraction ({F}_bar) is not a well-defined observational quantity because it is coupled to the halo mass model. This remains true even when the disk mass is known and spatially extended rotation curves are available. In contrast, the fraction of the rotation speed supplied by the disk at 2.2 scale lengths (disk maximality) is a robust observational indicator of the baryonic disk contribution to the potential. We construct the error budget for the key quantities: dynamical disk mass surface density (Σdyn), disk stellar mass-to-light ratio (Υ^disk_{*}), and disk maximality ({F}_{*,max}^disk≡ V^disk_{*,max}/ V_c). Random and systematic errors in these quantities for individual galaxies will be ~25%, while survey precision for sample quartiles are reduced to 10%, largely devoid of systematic errors outside of distance uncertainties.

Detection of EEG electrodes in brain volumes.

PubMed

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

2010-01-01

This paper presents a method to detect 128 EEG electrodes in image study and to merge with the Nuclear Magnetic Resonance volume for better diagnosis. First we propose three hypotheses to define a specific acquisition protocol in order to recognize the electrodes and to avoid distortions in the image. In the second instance we describe a method for segmenting the electrodes. Finally, registration is performed between volume of the electrodes and NMR.

Comparison of Interaural Electrode Pairing Methods for Bilateral Cochlear Implants

PubMed Central

Dietz, Mathias

2015-01-01

In patients with bilateral cochlear implants (CIs), pairing matched interaural electrodes and stimulating them with the same frequency band is expected to facilitate binaural functions such as binaural fusion, localization, and spatial release from masking. Because clinical procedures typically do not include patient-specific interaural electrode pairing, it remains the case that each electrode is allocated to a generic frequency range, based simply on the electrode number. Two psychoacoustic techniques for determining interaurally paired electrodes have been demonstrated in several studies: interaural pitch comparison and interaural time difference (ITD) sensitivity. However, these two methods are rarely, if ever, compared directly. A third, more objective method is to assess the amplitude of the binaural interaction component (BIC) derived from electrically evoked auditory brainstem responses for different electrode pairings; a method has been demonstrated to be a potential candidate for bilateral CI users. Here, we tested all three measures in the same eight CI users. We found good correspondence between the electrode pair producing the largest BIC and the electrode pair producing the maximum ITD sensitivity. The correspondence between the pairs producing the largest BIC and the pitch-matched electrode pairs was considerably weaker, supporting the previously proposed hypothesis that whilst place pitch might adapt over time to accommodate mismatched inputs, sensitivity to ITDs does not adapt to the same degree. PMID:26631108

A combined compensation method for the output voltage of an insulated core transformer power supply

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

Yang, L.; Yang, J., E-mail: jyang@mail.hust.edu.cn; Liu, K. F.

2014-06-15

An insulated core transformer (ICT) power supply is an ideal high-voltage generator for irradiation accelerators with energy lower than 3 MeV. However, there is a significant problem that the structure of the segmented cores leads to an increase in the leakage flux and voltage differences between rectifier disks. A high level of consistency in the output of the disks helps to achieve a compact structure by improving the utilization of both the rectifier components and the insulation distances, and consequently increase the output voltage of the power supply. The output voltages of the disks which are far away from themore » primary coils need to be improved to reduce their inhomogeneity. In this study, by investigating and comparing the existing compensation methods, a new combined compensation method is proposed, which increases the turns on the secondary coils and employs parallel capacitors to improve the consistency of the disks, while covering the entire operating range of the power supply. This method turns out to be both feasible and effective during the development of an ICT power supply. The non-uniformity of the output voltages of the disks is less than 3.5% from no-load to full-load, and the power supply reaches an output specification of 350 kV/60 mA.« less

The Stability of Galaxy Disks

NASA Astrophysics Data System (ADS)

Westfall, Kyle B.; Andersen, D. R.; Bershady, M. A.; Martinsson, T.; Swaters, R. A.; Verheijen, M. A.

2013-01-01

Using measurements of velocity dispersion and mass surface density for both the gas and stellar components, we calculate the multi-component stability (Q) for 30 galaxy disks observed by the DiskMass Survey. Despite their sub-maximality (Bershady et al. 2011, ApJL, 739, 47), we find all disks to be stable with roughly 85% falling in the range 1

Recyclable organic solar cells on substrates comprising cellulose nanocrystals (CNC)

DOEpatents

Kippelen, Bernard; Fuentes-Hernandez, Canek; Zhou, Yinhua; Moon, Robert; Youngblood, Jeffrey P

2015-12-01

Recyclable organic solar cells are disclosed herein. Systems and methods are further disclosed for producing, improving performance, and for recycling the solar cells. In certain example embodiments, the recyclable organic solar cells disclosed herein include: a first electrode; a second electrode; a photoactive layer disposed between the first electrode and the second electrode; an interlayer comprising a Lewis basic oligomer or polymer disposed between the photoactive layer and at least a portion of the first electrode or the second electrode; and a substrate disposed adjacent to the first electrode or the second electrode. The interlayer reduces the work function associated with the first or second electrode. In certain example embodiments, the substrate comprises cellulose nanocrystals that can be recycled. In certain example embodiments, one or more of the first electrode, the photoactive layer, and the second electrode may be applied by a film transfer lamination method.

System Identification of Mistuned Bladed Disks from Traveling Wave Response Measurements

NASA Technical Reports Server (NTRS)

Feiner, D. M.; Griffin, J. H.; Jones, K. W.; Kenyon, J. A.; Mehmed, O.; Kurkov, A. P.

2003-01-01

A new approach to modal analysis is presented. By applying this technique to bladed disk system identification methods, one can determine the mistuning in a rotor based on its response to a traveling wave excitation. This allows system identification to be performed under rotating conditions, and thus expands the applicability of existing mistuning identification techniques from integrally bladed rotors to conventional bladed disks.

An 80 au cavity in the disk around HD 34282

NASA Astrophysics Data System (ADS)

van der Plas, G.; Ménard, F.; Canovas, H.; Avenhaus, H.; Casassus, S.; Pinte, C.; Caceres, C.; Cieza, L.

2017-11-01

Context. Large cavities in disks are important testing grounds for the mechanisms proposed to drive disk evolution and dispersion, such as dynamical clearing by planets and photoevaporation. Aims: We aim to resolve the large cavity in the disk around HD 34282, whose presence has been predicted by previous studies modeling the spectral energy distribution of the disk. Methods: Using ALMA band 7 observations we studied HD 34282 with a spatial resolution of 0.10″ × 0.17'' at 345 GHz. Results: We resolve the disk around HD 34282 into a ring between 0.24'' and 1.15'' (78 and 374 au adopting a distance of 325 pc). The emission in this ring shows azimuthal asymmetry centered at a radial distance of 0.46'' and a position angle of 135° and an azimuthal FWHM of 51°. We detect CO emission both inside the disk cavity and as far out as 2.7 times the radial extent of the dust emission. Conclusions: Both the large disk cavity and the azimuthal structure in the disk around HD 34282 can be explained by the presence of a 50 Mjup brown dwarf companion at a separation of ≈0.1''.

A novel fabrication method of carbon electrodes using 3D printing and chemical modification process.

PubMed

Tian, Pan; Chen, Chaoyang; Hu, Jie; Qi, Jin; Wang, Qianghua; Chen, Jimmy Ching-Ming; Cavanaugh, John; Peng, Yinghong; Cheng, Mark Ming-Cheng

2017-11-23

Three-dimensional (3D) printing is an emerging technique in the field of biomedical engineering and electronics. This paper presents a novel biofabrication method of implantable carbon electrodes with several advantages including fast prototyping, patient-specific and miniaturization without expensive cleanroom. The method combines stereolithography in additive manufacturing and chemical modification processes to fabricate electrically conductive carbon electrodes. The stereolithography allows the structures to be 3D printed with very fine resolution and desired shapes. The resin is then chemically modified to carbon using pyrolysis to enhance electrochemical performance. The electrochemical characteristics of 3D printing carbon electrodes are assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3D printing carbon electrodes is much higher than the same sized platinum (Pt) electrode. In-vivo electromyography (EMG) recording, 3D printing carbon electrodes exhibit much higher signal-to-noise ratio (40.63 ± 7.73) than Pt electrodes (14.26 ± 6.83). The proposed biofabrication method is envisioned to enable 3D printing in many emerging applications in biomedical engineering and electronics.

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

NASA Astrophysics Data System (ADS)

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

2010-04-01

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

Simulations of polarization from accretion disks

NASA Astrophysics Data System (ADS)

Schultz, J.

2000-12-01

The Monte Carlo Method was used to estimate the level of polarization from axisymmetric accretion disks similar to those in low-mass X-ray binaries and some classes of cataclysmic variables. In low-mass X-ray binaries electron scattering is supposed to be the dominant opacity source in the inner disk, and most of the optical light is produced in the disk. Thompson scattering occuring in the disk corona produces linear polarization. Detailed theoretical models of accretion disks are numerous, but simple mathematical disk models were used, as the accuracy of polarization measurements does not allow distinction of the fine details of disk models. Stokes parameters were used for the radiative transfer. The simulations indicate that the vertical distribution of emissivity has the greatest effect on polarization, and variations of radial emissivity distribution have no detectable effect on polarization. Irregularities in the disk may reduce the degree of polarization. The polarization levels produced by simulations are detectable with modern instruments. Polarization measurements could be used to get rough constraints on the vertical emissivity distribution of an accretion disk, provided that a reasonably accurate disk model can be constructed from photometric or spectrosopic observations in optical and/or X-ray wavelengths. Mainly based on observations taken at the Observatoire de Haute-Provence, France, and on some observations obtained at the European Southern Observatory, Chile (ESO Prog. IDs: 57.C-0492, 59.C-0293, 61.C-0512).

Voltametric analysis apparatus and method

DOEpatents

Almon, Amy C.

1993-01-01

An apparatus and method for electrochemical analysis of elements in solution. An auxiliary electrode 14, a reference electrode 18, and five working electrodes 20, 22, 26, 28, and 30 are positioned in a container 12 containing a sample solution 34. The working electrodes are spaced apart evenly from each other and auxiliary electrode 14 to minimize any inter-electrode interference that may occur during analysis. An electric potential is applied between auxiliary electrode 14 and each of the working electrodes 20, 22, 26, 28, and 30. Simultaneous measurements taken of the current flow through each of the working electrodes for each given potential in a potential range are used for identifying chemical elements present in sample solution 34 and their respective concentrations. Multiple working electrodes enable a more positive identification to be made by providing unique data characteristic of chemical elements present in the sample solution.

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

Pintauro, Peter N.; Ballengee, Jason; Brodt, Matthew

In one aspect of the present invention, a method of fabricating a fuel cell membrane-electrode-assembly (MEA) having an anode electrode, a cathode electrode, and a membrane disposed between the anode electrode and the cathode electrode, includes fabricating each of the anode electrode, the cathode electrode, and the membrane separately by electrospinning; and placing the membrane between the anode electrode and the cathode electrode, and pressing then together to form the fuel cell MEA.

Electronic drop sensing in microfluidic devices: automated operation of a nanoliter viscometer

PubMed Central

Srivastava, Nimisha; Burns, Mark A.

2007-01-01

We describe three droplet sensing techniques: a digital electrode, an analog electrode, and a thermal method. All three techniques use a single layer of metal lines that is easy to microfabricate and an electronic signal can be produced using low DC voltages. While the electrode methods utilize changes in electrical conductivity when the air/liquid interface of the droplet passes over a pair of electrodes, the thermal method is based on convective heat loss from a locally heated region. For the electrode method, the analog technique is able to detect 25 nL droplets while the digital technique is capable of detecting droplets as small as 100 pL. For thermal sensing, temperature profiles in the range of 36 °C and higher were used. Finally, we have used the digital electrode method and an array of electrodes located at preset distances to automate the operation of a previously described microfluidic viscometer. The viscometer is completely controlled by a laptop computer, and the total time for operation including setup, calibration, sample addition and viscosity calculation is approximately 4 minutes. PMID:16738725

Determination of glucose in human urine by cyclic voltammetry method using gold electrode

NASA Astrophysics Data System (ADS)

Riyanto; Supwatul Hakim, Muh.

2018-01-01

This study has been the determination of glucose in human urine by cyclic voltammetry method using gold electrode. The gold electrode was prepared using gold wire with purity 99.99%, size 1.0 mm by length and wide respectively, connected with silver wire using silver conductive paint. The effect of electrolyte, pH and glucose concentration has been determined to produce the optimum method. The research showed the KNO3 is a good electrolyte for determination of glucose in human urine using gold electrode. The effect of glucose concentration have the coefficient correlation is R2 = 0.994. The results of the recovery using addition method showed at range95-105%. As a conclusion isa gold electrode is a good electrode for electrochemical sensors to the determination of glucose in human urine.

PaCER - A fully automated method for electrode trajectory and contact reconstruction in deep brain stimulation.

PubMed

Husch, Andreas; V Petersen, Mikkel; Gemmar, Peter; Goncalves, Jorge; Hertel, Frank

2018-01-01

Deep brain stimulation (DBS) is a neurosurgical intervention where electrodes are permanently implanted into the brain in order to modulate pathologic neural activity. The post-operative reconstruction of the DBS electrodes is important for an efficient stimulation parameter tuning. A major limitation of existing approaches for electrode reconstruction from post-operative imaging that prevents the clinical routine use is that they are manual or semi-automatic, and thus both time-consuming and subjective. Moreover, the existing methods rely on a simplified model of a straight line electrode trajectory, rather than the more realistic curved trajectory. The main contribution of this paper is that for the first time we present a highly accurate and fully automated method for electrode reconstruction that considers curved trajectories. The robustness of our proposed method is demonstrated using a multi-center clinical dataset consisting of N  = 44 electrodes. In all cases the electrode trajectories were successfully identified and reconstructed. In addition, the accuracy is demonstrated quantitatively using a high-accuracy phantom with known ground truth. In the phantom experiment, the method could detect individual electrode contacts with high accuracy and the trajectory reconstruction reached an error level below 100 μm (0.046 ± 0.025 mm). An implementation of the method is made publicly available such that it can directly be used by researchers or clinicians. This constitutes an important step towards future integration of lead reconstruction into standard clinical care.

Method of making electrodes for electrochemical cell

DOEpatents

Kaun, Thomas D.; Kilsdonk, Dennis J.

1983-01-01

A method of making an electrode for an electrochemical cell in which particulate electrode-active material is mixed with a liquid organic carrier chemically inert with respect to the electrode-active material, mixing the liquid carrier to form an extrudable slurry. The liquid carrier is present in an amount of from about 10 to about 50 percent by volume of the slurry, and then the carrier is removed from the slurry leaving the electrode-active material.

Perovskite electrodes and method of making the same

DOEpatents

Seabaugh, Matthew M [Columbus, OH; Swartz, Scott L [Columbus, OH

2009-09-22

The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

Perovskite electrodes and method of making the same

DOEpatents

Seabaugh, Matthew M.; Swartz, Scott L.

2005-09-20

The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

Nondestructive evaluation of epoxy-coated reinforcing bars in concrete using bi-electrode half-cell potential techniques.

DOT National Transportation Integrated Search

2006-01-01

This study evaluated two half-cell mapping methods for nondestructive evaluation of epoxy-coated rebar (ECR) in concrete: the semi-fixed bi-electrode and the moving bi-electrode methods. These methods were expected to provide early detection of corro...

Method of making chalcogen catalysts for polymer electrolyte fuel cells

DOEpatents

Choi, Jong-Ho; Zelenay, Piotr; Wieckowski, Andrzej; Cao, Dianxue

2010-12-14

A method of making an electrode catalyst material using aqueous solutions. The electrode catalyst material includes a support comprising at least one transition metal and at least one chalcogen disposed on a surface of the transition metal. The method includes reducing a metal powder, mixing the metal powder with an aqueous solution containing at least one inorganic compound of the chalcogen to form a mixture, and providing a reducing agent to the mixture to form nanoparticles of the electrode catalyst. The electrode catalyst may be used in a membrane electrode assembly for a fuel cell.

Observability of characteristic binary-induced structures in circumbinary disks

NASA Astrophysics Data System (ADS)

Avramenko, R.; Wolf, S.; Illenseer, T. F.

2017-07-01

Context. A substantial fraction of protoplanetary disks form around stellar binaries. The binary system generates a time-dependent non-axisymmetric gravitational potential, inducing strong tidal forces on the circumbinary disk. This leads to a change in basic physical properties of the circumbinary disk, which should in turn result in unique structures that are potentially observable with the current generation of instruments. Aims: The goal of this study is to identify these characteristic structures, constrain the physical conditions that cause them, and evaluate the feasibility of observing them in circumbinary disks. Methods: To achieve this, first we perform 2D hydrodynamic simulations. The resulting density distributions are post-processed with a 3D radiative transfer code to generate re-emission and scattered light maps. Based on these distributions, we study the influence of various parameters, such as the mass of the stellar components, mass of the disk, and binary separation on observable features in circumbinary disks. Results: We find that the Atacama Large (sub-)Millimetre Array (ALMA) as well as the European Extremely Large Telescope (E-ELT) are capable of tracing asymmetries in the inner region of circumbinary disks, which are affected most by the binary-disk interaction. Observations at submillimetre/millimetre wavelengths allow the detection of the density waves at the inner rim of the disk and inner cavity. With the E-ELT one can partially resolve the innermost parts of the disk in the infrared wavelength range, including the disk's rim, accretion arms, and potentially the expected circumstellar disks around each of the binary components.

A Rigorous Solution for Finite-State Inflow throughout the Flowfield

NASA Astrophysics Data System (ADS)

Fei, Zhongyang

In this research, the Hseih/Duffy model is extended to all three velocity components of inflow across the rotor disk in a mathematically rigorous way so that it can be used to calculate the inflow below the rotor disk plane. This establishes a complete dynamic inflow model for the entire flow field with finite state method. The derivation is for the case of general skewed angle. The cost of the new method is that one needs to compute the co-states of the inflow equations in the upper hemisphere along with the normal states. Numerical comparisons with exact solutions for the z-component of flow in axial and skewed angle flow demonstrate excellent correlation with closed-form solutions. The simulations also illustrate that the model is valid at both the frequency domain and the time domain. Meanwhile, in order to accelerate the convergence, an optimization of even terms is used to minimize the error in the axial component of the induced velocity in the on and on/off disk region. A novel method for calculating associate Legendre function of the second kind is also developed to solve the problem of divergence of Q¯mn (ieta) for large eta with the iterative method. An application of the new model is also conducted to compute inflow in the wake of a rotor with a finite number of blades. The velocities are plotted at different distances from the rotor disk and are compared with the Glauert prediction for axial flow and wake swirl. In the finite-state model, the angular momentum does not jump instantaneously across the disk, but it does transition rapidly across the disk to correct Glauert value.

Method of manufacturing fibrous hemostatic bandages

DOEpatents

Larsen, Gustavo; Spretz, Ruben; Velarde-Ortiz, Raffet

2012-09-04

A method of manufacturing a sturdy and pliable fibrous hemostatic dressing by making fibers that maximally expose surface area per unit weight of active ingredients as a means for aiding in the clot forming process and as a means of minimizing waste of active ingredients. The method uses a rotating object to spin off a liquid biocompatible fiber precursor, which is added at its center. Fibers formed then deposit on a collector located at a distance from the rotating object creating a fiber layer on the collector. An electrical potential difference is maintained between the rotating disk and the collector. Then, a liquid procoagulation species is introduced at the center of the rotating disk such that it spins off the rotating disk and coats the fibers.

Dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks

NASA Astrophysics Data System (ADS)

Wang, Xue-She; Mazzoleni, Michael J.; Mann, Brian P.

2018-03-01

This paper presents the results of an investigation on the dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks. The full equation of motion for both rocking disks is derived from first principles. For unforced behavior, Lamb's method is used to derive the linear natural frequency of both disks, and harmonic balance is used to determine their amplitude-dependent rocking frequencies. A stability analysis then reveals that the equilibria and stability of the two disks are considerably different, as the semi-elliptical disk has a super-critical pitchfork bifurcation that enables it to exhibit bistable rocking behavior. Experimental studies were conducted to verify the trends. For vertically forced behavior, numerical investigations show the disk's responses to forward and reverse frequency sweeps. Three modes of periodicity were observed for the steady state behavior. Experiments were performed to verify the frequency responses and the presence of the three rocking modes. Comparisons between the experiments and numerical investigations show good agreement.

Single camera photogrammetry system for EEG electrode identification and localization.

PubMed

Baysal, Uğur; Sengül, Gökhan

2010-04-01

In this study, photogrammetric coordinate measurement and color-based identification of EEG electrode positions on the human head are simultaneously implemented. A rotating, 2MP digital camera about 20 cm above the subject's head is used and the images are acquired at predefined stop points separated azimuthally at equal angular displacements. In order to realize full automation, the electrodes have been labeled by colored circular markers and an electrode recognition algorithm has been developed. The proposed method has been tested by using a plastic head phantom carrying 25 electrode markers. Electrode locations have been determined while incorporating three different methods: (i) the proposed photogrammetric method, (ii) conventional 3D radiofrequency (RF) digitizer, and (iii) coordinate measurement machine having about 6.5 mum accuracy. It is found that the proposed system automatically identifies electrodes and localizes them with a maximum error of 0.77 mm. It is suggested that this method may be used in EEG source localization applications in the human brain.

Roll-to-roll light directed electrophoretic deposition system and method

DOEpatents

Pascall, Andrew J.; Kuntz, Joshua

2017-06-06

A roll-to-roll light directed electrophoretic deposition system and method advances a roll of a flexible electrode web substrate along a roll-to-roll process path, where a material source is positioned to provide on the flexible electrode web substrate a thin film colloidal dispersion of electrically charged colloidal material dispersed in a fluid. A counter electrode is also positioned to come in contact with the thin film colloidal dispersion opposite the flexible electrode web substrate, where one of the counter electrode and the flexible electrode web substrate is a photoconductive electrode. A voltage source is connected to produce an electric potential between the counter electrode and the flexible electrode web substrate to induce electrophoretic deposition on the flexible electrode web substrate when the photoconductive electrode is rendered conductive, and a patterned light source is arranged to illuminate the photoconductive electrode with a light pattern and render conductive illuminated areas of the photoconductive electrode so that a patterned deposit of the electrically charged colloidal material is formed on the flexible electrode web substrate.

Inner Disk Structure and Transport Mechanisms in the Transitional Disk around T Cha

NASA Astrophysics Data System (ADS)

Brown, Alexander

2017-08-01

To better understand how Earth-like planets form around low-mass stars, we propose to study the UV (HST), X-ray (XMM), and optical (LCOGT) variability of the young star T Cha. This variability is caused by obscuration of the star by clumpy material in the rim of its inner disk. Changing sight lines through the disk allow measurement of the temperature and column density of both molecular and atomic gas and the physical properties of the dust grains in the well-mixed inner disk, as well as determining the gas-to-dust ratio. The gas-to-dust ratio affects planetesimal growth and disk stability but is difficult to measure in local regions of disks. Three 5 orbit visits, separated by 3-7 days, are required for use of analysis techniques comprising both differential pair-method comparison of spectra with differing A_v (particularly important for determining the dust extinction curve, A_lambda, where removal of the foreground extinction requires multiple epochs) and detailed spectral fitting of gas absorption features at each epoch. The inner disk of T Cha is particularly interesting, because T Cha has a transitional disk with a large gap at 0.2-15 AU in the dust disk and allows study of the gas and dust structure in the terrestrial planet formation zone during this important rapid phase of protoplanetary disk evolution. Characterizing the high energy (UV/X-ray) radiation field is also essential for in-depth studies of the disk in other spectral regions. Results from these observations will have wide relevance to the modeling and understanding of protoplanetary disk structure and evolution, and the complex gas and dust physics and chemistry in disk surface layers.

Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

NASA Astrophysics Data System (ADS)

Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

2017-09-01

The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

Determination of wear metals in engine oil by mild acid digestion and energy dispersive X-ray fluorescence spectrometry using solid phase extraction disks.

PubMed

Yang, Zheng; Hou, Xiandeng; Jones, Bradley T

2003-03-10

A simple, particle size-independent spectrometric method has been developed for the multi-element determination of wear metals in used engine oil. A small aliquot (0.5 ml) of an acid-digested oil sample is spotted onto a C-18 solid phase extraction disk to form a uniform thin film. The dried disk is then analyzed directly by energy dispersive X-ray fluorescence spectrometry. This technique provides a homogeneous and reproducible sample surface to the instrument, thus overcoming the typical problems associated with uneven particle size distribution and sedimentation. As a result, the method provides higher precision and accuracy than conventional methods. Furthermore, the disk sample may be stored and re-analyzed or extracted at a later date. The signals arising from the spotted disks, and the calibration curves constructed from them, are stable for at least 2 months. The limits of detection for Fe, Cu, Zn, Pb, and Cr are 5, 1, 4, 2, and 4 microg g(-1), respectively. Recoveries of these elements from spiked oil samples range from 92 to 110%. The analysis of two standard reference materials and a used oil sample produced results comparable to those found by inductively coupled plasma atomic emission spectrometry.

The performance of spinel bulk-like oxygen-deficient CoGa2O4 as an air-cathode catalyst in microbial fuel cell

NASA Astrophysics Data System (ADS)

Liu, Di; Mo, Xiaoping; Li, Kexun; Liu, Yi; Wang, Junjie; Yang, Tingting

2017-08-01

Nano spinel bulk-like CoGa2O4 prepared via a facile hydrothermal method is used as a high efficient electrochemical catalyst in activated carbon (AC) air-cathode microbial fuel cell (MFC). The maximum power density of the modified MFC is 1911 ± 49 mW m-2, 147% higher than the MFC of untreated AC cathode. Transmission electron microscope (TEM) and X-ray diffraction (XRD) exhibit the morphology and crystal structure of CoGa2O4. Rotating disk electrode (RDE) confirms the four-electron pathway at the cathode during the oxygen reduction reaction (ORR). Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) illustrate that the high rate oxygen vacancy exist in the CoGa2O4. The oxygen vacancy of CoGa2O4 plays an important role in catalytic activity. In a word, the prepared nano spinel bulk-like CoGa2O4 provides an alternative to the costly Pt in air-cathode for power output.

Highly active nitrogen-doped nanocarbon electrocatalysts for alkaline direct methanol fuel cell

NASA Astrophysics Data System (ADS)

Kruusenberg, Ivar; Ratso, Sander; Vikkisk, Merilin; Kanninen, Petri; Kallio, Tanja; Kannan, Arunachala M.; Tammeveski, Kaido

2015-05-01

Direct methanol fuel cells are assembled and evaluated using Fumatech FAA3 alkaline anion exchange membrane. Two novel metal-free cathode catalysts are synthesised, investigated and compared with the commercial Pt-based catalyst. In this work nitrogen-doped few-layer graphene/multi-walled carbon nanotube (N-FLG/MWCNT) composite and nitrogen-doped MWCNT (N-MWCNT) catalyst are prepared by pyrolysing the mixture of dicyandiamide (DCDA) and carbon nanomaterials at 800 °C. The resulting cathode catalyst material shows a remarkable electrocatalytic activity for oxygen reduction reaction (ORR) in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. Fuel cell tests are performed by using 1 M methanol as anode and pure oxygen gas cathode feed. The maximum power density obtained with the N-FLG/MWCNT material (0.72 mW cm-2) is similar to that of the Pt/C catalyst (0.72 mW cm-2), whereas the N-MWCNT material shows higher peak power density (0.92 mW cm-2) than the commercial Pt/C catalyst.

Nanostructured F doped IrO2 electro-catalyst powders for PEM based water electrolysis

NASA Astrophysics Data System (ADS)

Kadakia, Karan Sandeep; Jampani, Prashanth H.; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Park, Sung Kyoo; Hong, Dae Ho; Chung, Sung Jae; Kumta, Prashant N.

2014-12-01

Fluorine doped iridium oxide (IrO2:F) powders with varying F content ranging from 0 to 20 wt.% has been synthesized by using a modification of the Adams fusion method. The precursors (IrCl4 and NH4F) are mixed with NaNO3 and heated to elevated temperatures to form high surface area nanomaterials as electro-catalysts for PEM based water electrolysis. The catalysts were then coated on a porous Ti substrate and have been studied for the oxygen evolution reaction in PEM based water electrolysis. The IrO2:F with an optimum composition of IrO2:10 wt.% F shows remarkably superior electrochemical activity and chemical stability compared to pure IrO2. The results have also been supported via kinetic studies by conducting rotating disk electrode (RDE) experiments. The RDE studies confirm that the electro-catalysts follow the two electron transfer reaction for electrolysis with calculated activation energy of ∼25 kJ mol-1. Single full cell tests conducted also validate the superior electrochemical activity of the 10 wt.% F doped IrO2.

Chemometrics-assisted investigation of interactions of Tasmar with human serum albumin at a glassy carbon disk: Application to electrochemical biosensing of electro-inactive serum albumin.

PubMed

Mohammadi, Ghobad; Faramarzi, Elahe; Mahmoudi, Majid; Ghobadi, Sirous; Ghiasvand, Ali Reza; Goicoechea, Hector C; Jalalvand, Ali R

2018-07-15

In this work, voltammetric data recorded by a glassy carbon electrode (GCE) was used to investigate the interactions of tolcapone (Tasmar, TAS) with human serum albumin (HSA) at the electrode surface. The recorded voltammetric data was also combined with spectroscopic data to construct an augmented data matrix which was analysed by multivariate curve resolution-alternating least squares (MCR-ALS) as an efficient chemometric tool to obtain more information about TAS-HSA interactions. The results of MCR-ALS confirmed formation of one complex species (HSA-TAS 2 ) and application of MCR-BANDS to the results of MCR-ALS confirmed the absence of rotational ambiguities and existing unambiguous and reliable results. Binding of TAS to HSA was also modeled by molecular docking and the results showed that the TAS was bound to sub-domain IIA of HSA which were compatible with the ones obtained by recording experimental data. Hard-modeling of combined voltammetric and spectroscopic data by EQUISPEC helped us to compute binding constant of HSA-TAS 2 complex species which was compatible with the binding constant value obtained by direct analysis of experimental data. Finally, a new electroanalytical method was developed based on TAS-HSA interactions for determination of HSA in two ranges of 0-541 nM and 541-1200 nM with a limit of detection of 0.04 nM and a sensitivity of 0.02 μA nM -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

A methodology for investigating new nonprecious metal catalysts for PEM fuel cells.

PubMed

Susac, D; Sode, A; Zhu, L; Wong, P C; Teo, M; Bizzotto, D; Mitchell, K A R; Parsons, R R; Campbell, S A

2006-06-08

This paper reports an approach to investigate metal-chalcogen materials as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. The methodology is illustrated with reference to Co-Se thin films prepared by magnetron sputtering onto a glassy-carbon substrate. Scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) have been used, in parallel with electrochemical activity and stability measurements, to assess how the electrochemical performance relates to chemical composition. It is shown that Co-Se thin films with varying Se are active for oxygen reduction, although the open circuit potential (OCP) is lower than for Pt. A kinetically controlled process is observed in the potential range 0.5-0.7 V (vs reversible hydrogen electrode) for the thin-film catalysts studied. An initial exposure of the thin-film samples to an acid environment served as a pretreatment, which modified surface composition prior to activity measurements with the rotating disk electrode (RDE) method. Based on the SAM characterization before and after electrochemical tests, all surfaces demonstrating activity are dominated by chalcogen. XRD shows that the thin films have nanocrystalline character that is based on a Co(1-x)Se phase. Parallel studies on Co-Se powder supported on XC72R carbon show comparable OCP, Tafel region, and structural phase as for the thin-film model catalysts. A comparison for ORR activity has also been made between this Co-Se powder and a commercial Pt catalyst.

Method for fabrication of electrodes

DOEpatents

Jankowski, Alan F.; Morse, Jeffrey D.; Barksdale, Randy

2004-06-22

Described herein is a method to fabricate porous thin-film electrodes for fuel cells and fuel cell stacks. Furthermore, the method can be used for all fuel cell electrolyte materials which utilize a continuous electrolyte layer. An electrode layer is deposited on a porous host structure by flowing gas (for example, Argon) from the bottomside of the host structure while simultaneously depositing a conductive material onto the topside of the host structure. By controlling the gas flow rate through the pores, along with the process conditions and deposition rate of the thin-film electrode material, a film of a pre-determined thickness can be formed. Once the porous electrode is formed, a continuous electrolyte thin-film is deposited, followed by a second porous electrode to complete the fuel cell structure.

Method for optical pumping of thin laser media at high average power

DOEpatents

Zapata, Luis E [Livermore, CA; Beach, Raymond J [Livermore, CA; Honea, Eric C [Sunol, CA; Payne, Stephen A [Castro Valley, CA

2004-07-13

A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

Discovery of Super-Thin Disks in Nearby Edge-on Spiral Galaxies

NASA Astrophysics Data System (ADS)

Schechtman-Rook, A.; Bershady, M. A.

2014-03-01

We report the identification of a super-thin disk (hz˜ 60 pc) in the edge-on spiral galaxy NGC 891. This component is only apparent after we perform a physically motivated attenuation correction, based on detailed radiation transfer models, to our sub-arcsecond resolution near-infrared imaging. In addition to the super-thin disk, we also find several structural features near the center of NGC 891, including an inner disk truncation at ˜3 kpc. Inner disk truncations may be commonplace among massive spiral galaxies, possibly due to the effects of instabilities, such as bars. Having successfully demonstrated our methods, we are poised to apply them to a small sample of nearby edge-on galaxies, consisting both of massive and low-mass spirals.

Low Cost Electrode Assembly for EEG Recordings in Mice

PubMed Central

Vogler, Emily C.; Flynn, Daniel T.; Busciglio, Federico; Bohannan, Ryan C.; Tran, Alison; Mahavongtrakul, Matthew; Busciglio, Jorge A.

2017-01-01

Wireless electroencephalography (EEG) of small animal subjects typically utilizes miniaturized EEG devices which require a robust recording and electrode assembly that remains in place while also being well-tolerated by the animal so as not to impair the ability of the animal to perform normal living activities or experimental tasks. We developed simple and fast electrode assembly and method of electrode implantation using electrode wires and wire-wrap technology that provides both higher survival and success rates in obtaining recordings from the electrodes than methods using screws as electrodes. The new wire method results in a 51% improvement in the number of electrodes that successfully record EEG signal. Also, the electrode assembly remains affixed and provides EEG signal for at least a month after implantation. Screws often serve as recording electrodes, which require either drilling holes into the skull to insert screws or affixing screws to the surface of the skull with adhesive. Drilling holes large enough to insert screws can be invasive and damaging to brain tissue, using adhesives may interfere with conductance and result in a poor signal, and soldering screws to wire leads results in fragile connections. The methods presented in this article provide a robust implant that is minimally invasive and has a significantly higher success rate of electrode implantation. In addition, the implant remains affixed and produces good recordings for over a month, while using economical, easily obtained materials and skills readily available in most animal research laboratories. PMID:29184480

Low Cost Electrode Assembly for EEG Recordings in Mice.

PubMed

Vogler, Emily C; Flynn, Daniel T; Busciglio, Federico; Bohannan, Ryan C; Tran, Alison; Mahavongtrakul, Matthew; Busciglio, Jorge A

2017-01-01

Wireless electroencephalography (EEG) of small animal subjects typically utilizes miniaturized EEG devices which require a robust recording and electrode assembly that remains in place while also being well-tolerated by the animal so as not to impair the ability of the animal to perform normal living activities or experimental tasks. We developed simple and fast electrode assembly and method of electrode implantation using electrode wires and wire-wrap technology that provides both higher survival and success rates in obtaining recordings from the electrodes than methods using screws as electrodes. The new wire method results in a 51% improvement in the number of electrodes that successfully record EEG signal. Also, the electrode assembly remains affixed and provides EEG signal for at least a month after implantation. Screws often serve as recording electrodes, which require either drilling holes into the skull to insert screws or affixing screws to the surface of the skull with adhesive. Drilling holes large enough to insert screws can be invasive and damaging to brain tissue, using adhesives may interfere with conductance and result in a poor signal, and soldering screws to wire leads results in fragile connections. The methods presented in this article provide a robust implant that is minimally invasive and has a significantly higher success rate of electrode implantation. In addition, the implant remains affixed and produces good recordings for over a month, while using economical, easily obtained materials and skills readily available in most animal research laboratories.

Three-dimensional orientation of iris in an ocular prosthesis using a customized scale.

PubMed

Gupta, Lokendra; Aparna, I N; Dhanasekar, B; Prabhu, Nayana; Malla, Nirjalla; Agarwal, Priyanka

2014-04-01

The success of an ocular prosthesis depends largely on the correct orientation of the iris disk. Various methods have been put forth to achieve this. This article emphasizes one such simplified method, wherein a customized scale has been used to orient the iris disk mediolaterally, superoinferiorly, and anteroposteriorly in an ocular prosthesis. A scleral wax pattern was fabricated. The customized scale was used to measure the dimension and orientation of the natural iris. These measurements were then transferred to the scleral wax pattern with the customized scale. An iris disk was fabricated using black crayon on the scleral wax pattern according to the measurements. The scleral wax pattern, including the iris disk, was then placed in the eye socket to verify its dimension and orientation. A prefabricated iris disk was modified according to the measured dimensions and transferred to the final scleral wax pattern. The transfer of these dimensions to the definitive prosthesis was achieved successfully, ultimately improving the patient's social and psychological well being. © 2013 by the American College of Prosthodontists.

Method for producing edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure

NASA Technical Reports Server (NTRS)

Hunt, Brian D. (Inventor); Leduc, Henry G. (Inventor)

1992-01-01

A method for fabricating an edge geometry superconducting tunnel junction device is discussed. The device is comprised of two niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier sandwiched between the two electrodes. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 C to 500 C for improved quality of the electrode.

Intervertebral disk width in dogs with and without clinical signs of disk associated cervical spondylomyelopathy

PubMed Central

2012-01-01

Background Disk-associated cervical spondylomyelopathy (DA-CSM) is a multifactorial neurological disorder in which progressive caudal cervical spinal cord compression is mainly caused by one or more intervertebral disk protrusions. The Doberman pinscher breed seems predisposed for this condition. The underlying cause and pathophysiology of DA-CSM are currently unknown. Recently, wider intervertebral disks have been put forward as a risk factor for development of clinically relevant DA-CSM. However, little is known about other factors affecting intervertebral disk width. Therefore the aim of this study was to assess the association between intervertebral disk width, measured on magnetic resonance imaging (MRI), and clinical status, age, gender and intervertebral disk location in dogs with and without clinical signs of DA-CSM. Methods Doberman pinschers with clinical signs of DA-CSM (N=17),clinically normal Doberman pinschers (N=20), and clinically normal English Foxhounds (N=17), underwent MRI of the cervical vertebral column. On sagittal T2-weighted images, intervertebral disk width was measured from C2-C3 to C6-C7. Intra –and interobserver agreement were assessed on a subset of 20 of the 54 imaging studies. Results Intervertebral disk width was not significantly different between Doberman pinschers with clinical signs of DA-CSM, clinically normal Doberman pinschers or clinically normal English Foxhounds (p=0.43). Intervertebral disk width was positively associated with increasing age (p=0.029). Each monthly increase in age resulted in an increase of disk width by 0.0057mm. Intervertebral disk width was not significantly affected by gender (p=0.056), but was significantly influenced by intervertebral disk location (p <0.0001). The assessed measurements were associated with a good intra –and interobserver agreement. Conclusions The present study does not provide evidence that wider intervertebral disks are associated with clinical status in dogs with and without DA-CSM. Instead, it seems that cervical intervertebral disk width in dogs is positively associated with increase in age. PMID:22839697

The Nucleation Rate of Single O2 Nanobubbles at Pt Nanoelectrodes.

PubMed

Soto, Álvaro Moreno; German, Sean R; Ren, Hang; van der Meer, Devaraj; Lohse, Detlef; Edwards, Martin A; White, Henry S

2018-06-13

Nanobubble nucleation is a problem that affects efficiency in electrocatalytic reactions since those bubbles can block the surface of the catalytic sites. In this article, we focus on the nucleation rate of O 2 nanobubbles resulting from the electrooxidation of H 2 O 2 at Pt disk nanoelectrodes. Bubbles form almost instantaneously when a critical peak current, i nb p , is applied, but for lower currents, bubble nucleation is a stochastic process in which the nucleation (induction) time, t ind , dramatically decreases as the applied current approaches i nb p , a consequence of the local supersaturation level, ζ, increasing at high currents. Here, by applying different currents below i nb p , nanobubbles take some time to nucleate and block the surface of the Pt electrode at which the reaction occurs, providing a means to measure the stochastic t ind . We study in detail the different conditions in which nanobubbles appear, concluding that the electrode surface needs to be preconditioned to achieve reproducible results. We also measure the activation energy for bubble nucleation, E a , which varies in the range from (6 to 30) kT, and assuming a spherically cap-shaped nanobubble nucleus, we determine the footprint diameter L = 8-15 nm, the contact angle to the electrode surface θ = 135-155°, and the number of O 2 molecules contained in the nucleus (50 to 900 molecules).

A Molten Salt Lithium-Oxygen Battery.

PubMed

Giordani, Vincent; Tozier, Dylan; Tan, Hongjin; Burke, Colin M; Gallant, Betar M; Uddin, Jasim; Greer, Julia R; McCloskey, Bryan D; Chase, Gregory V; Addison, Dan

2016-03-02

Despite the promise of extremely high theoretical capacity (2Li + O2 ↔ Li2O2, 1675 mAh per gram of oxygen), many challenges currently impede development of Li/O2 battery technology. Finding suitable electrode and electrolyte materials remains the most elusive challenge to date. A radical new approach is to replace volatile, unstable and air-intolerant organic electrolytes common to prior research in the field with alkali metal nitrate molten salt electrolytes and operate the battery above the liquidus temperature (>80 °C). Here we demonstrate an intermediate temperature Li/O2 battery using a lithium anode, a molten nitrate-based electrolyte (e.g., LiNO3-KNO3 eutectic) and a porous carbon O2 cathode with high energy efficiency (∼95%) and improved rate capability because the discharge product, lithium peroxide, is stable and moderately soluble in the molten salt electrolyte. The results, supported by essential state-of-the-art electrochemical and analytical techniques such as in situ pressure and gas analyses, scanning electron microscopy, rotating disk electrode voltammetry, demonstrate that Li2O2 electrochemically forms and decomposes upon cycling with discharge/charge overpotentials as low as 50 mV. We show that the cycle life of such batteries is limited only by carbon reactivity and by the uncontrolled precipitation of Li2O2, which eventually becomes electrically disconnected from the O2 electrode.

Comparison Simulations of Gas Giant Planet Formation via Disk Instability

NASA Astrophysics Data System (ADS)

Pickett, Megan K.; Cai, K.; Durisen, R.; Milne, M.

2011-01-01

There has been disagreement about whether cooling in protoplanetary disks can be sufficiently fast to induce the formation of gas giant protoplanets via gravitational instabilities. Simulations by our own group and others indicate that this method of planet formation does not work for disks around young, low-mass stars inside several tens of AU, while simulations by other groups show fragmentation into protoplanetary clumps in this region. To allow direct comparison in hopes of isolating the cause of the differences, we here present a comparison high-resolution three-dimensional hydrodynamics simulation of a protoplanetary disk,using an improved version of one of our own radiative schemes. We find that the disk does not fragment in our code but instead quickly settles into a state with only low amplitude nonaxisymmetric structure, which persists for at least several outer disk rotations. Further, we see no rapid radiative or convective cooling.

Microwave inversion of leaf area and inclination angle distributions from backscattered data

NASA Technical Reports Server (NTRS)

Lang, R. H.; Saleh, H. A.

1985-01-01

The backscattering coefficient from a slab of thin randomly oriented dielectric disks over a flat lossy ground is used to reconstruct the inclination angle and area distributions of the disks. The disks are employed to model a leafy agricultural crop, such as soybeans, in the L-band microwave region of the spectrum. The distorted Born approximation, along with a thin disk approximation, is used to obtain a relationship between the horizontal-like polarized backscattering coefficient and the joint probability density of disk inclination angle and disk radius. Assuming large skin depth reduces the relationship to a linear Fredholm integral equation of the first kind. Due to the ill-posed nature of this equation, a Phillips-Twomey regularization method with a second difference smoothing condition is used to find the inversion. Results are obtained in the presence of 1 and 10 percent noise for both leaf inclination angle and leaf radius densities.

Algorithm to find high density EEG scalp coordinates and analysis of their correspondence to structural and functional regions of the brain

PubMed Central

Giacometti, Paolo; Perdue, Katherine L.; Diamond, Solomon G.

2014-01-01

Background Interpretation and analysis of electroencephalography (EEG) measurements relies on the correspondence of electrode scalp coordinates to structural and functional regions of the brain. New Method An algorithm is introduced for automatic calculation of the International 10–20, 10-10, and 10-5 scalp coordinates of EEG electrodes on a boundary element mesh of a human head. The EEG electrode positions are then used to generate parcellation regions of the cerebral cortex based on proximity to the EEG electrodes. Results The scalp electrode calculation method presented in this study effectively and efficiently identifies EEG locations without prior digitization of coordinates. The average of electrode proximity parcellations of the cortex were tabulated with respect to structural and functional regions of the brain in a population of 20 adult subjects. Comparison with Existing Methods Parcellations based on electrode proximity and EEG sensitivity were compared. The parcellation regions based on sensitivity and proximity were found to have 44.0 ± 11.3% agreement when demarcated by the International 10–20, 32.4 ± 12.6% by the 10-10, and 24.7 ± 16.3% by the 10-5 electrode positioning system. Conclusions The EEG positioning algorithm is a fast and easy method of locating EEG scalp coordinates without the need for digitized electrode positions. The parcellation method presented summarizes the EEG scalp locations with respect to brain regions without computation of a full EEG forward model solution. The reference table of electrode proximity versus cortical regions may be used by experimenters to select electrodes that correspond to anatomical and functional regions of interest. PMID:24769168

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

Pezeshki, Alan M.; Sacci, Robert L.; Veith, Gabriel M.

Here, we demonstrate a novel method to accelerate electrode degradation in redox flow batteries and apply this method to the all-vanadium chemistry. Electrode performance degradation occurred seven times faster than in a typical cycling experiment, enabling rapid evaluation of materials. This method also enables the steady-state study of electrodes. In this manner, it is possible to delineate whether specific operating conditions induce performance degradation; we found that both aggressively charging and discharging result in performance loss. Post-mortem x-ray photoelectron spectroscopy of the degraded electrodes was used to resolve the effects of state of charge (SoC) and current on the electrodemore » surface chemistry. For the electrode material tested in this work, we found evidence that a loss of oxygen content on the negative electrode cannot explain decreased cell performance. Furthermore, the effects of decreased electrode and membrane performance on capacity fade in a typical cycling battery were decoupled from crossover; electrode and membrane performance decay were responsible for a 22% fade in capacity, while crossover caused a 12% fade.« less

Fast Response Polypyrrole Actuators with Auxiliary Electrodes

NASA Astrophysics Data System (ADS)

Zama, Tetsuji; Hara, Susumu; Takashima, Wataru; Kaneto, Keiichi

2005-11-01

Electrochemical polypyrrole (PPy) actuators, prepared electrochemically from a methyl benzoate solution of tetra-n-butylammonium trifluoromethanesulfonate (TBACF3SO3), have been studied to improve the response rate by two methods; 1) a PPy film attached with plural auxiliary electrodes of thin Au coils, 2) a PPy film equipped with a compliant Au electrode on one side of the film. With increasing the number of auxiliary electrodes for the first method, the film responded faster as if it were a shorter film. These results are due to the decrease in the IR voltage drop along the film from the electrodes and also due to the increased current to the whole film via plural electrodes. The PPy film with the Au thin layer (the second method) exhibited up to 8.8%/s strain rate, which was much faster than that (0.5%/s) without the auxiliary electrodes, keeping the maximum strain of 12--13%. The auxiliary electrodes improved not only the response speed of the PPy actuators but also the durability upon cycling electrochemically.

Electrochemical properties of Sn-based nanopowders synthesized by a pulsed wire evaporation method and effect of binder coating

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

Ha, Jong-Keun; Song, Ju-Seok; Cho, Gyu-Bong

Highlights: • Sn-based nanoparticles are fabricated by using the pulsed wire evaporation method. • The electrodes are prepared by mixing the graphene and coating the surface. • Coating the surface of electrode is used with brushing of simple and facile method. • The electrochemical measurements are performed with galvanostatic experiments. • The coating electrode maintains capacity nearly of 501 mAh g{sup −1} up to 100 cycles. - Abstract: Sn-based nanoparticles are prepared with the O{sub 2} concentrations in chamber of Ar atmosphere (by v/v) by using the pulsed wire evaporation (PWE) method. The prepared electrodes are only Sn-based powder electrode,more » its binder coating electrode and Sn-based powder/graphene nanocomposite electrode. Morphology and structure of the synthesized powders and electrodes are investigated with a field emission scanning electron microscope (FE-SEM) and an X-ray diffraction (XRD) analysis. The electrochemical measurements were performed with galvanostatic cycling experiments using a coin type cell of CR2032 (Ø20, T3.2 mm). The binder coating electrode is superior to others and maintains delithiation capacity nearly of 501 mAh g{sup −1} as 58.3% of first delithiation capacity at 0.2 C-rate up to 100 cycles.« less

Evaluation of the constant potential method in simulating electric double-layer capacitors

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Yang, Yang; Olmsted, David L.; Asta, Mark; Laird, Brian B.

2014-11-01

A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of "inner-sphere adsorbed" Li+ ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li+ ions to the electrode surface.

Influence of Intracranial Electrode Density and Spatial Configuration on Interictal Spike Localization: A Case Study.

PubMed

Lie, Octavian V; Papanastassiou, Alexander M; Cavazos, José E; Szabó, Ákos C

2015-10-01

Poor seizure outcomes after epilepsy surgery often reflect an incorrect localization of the epileptic sources by standard intracranial EEG interpretation because of limited electrode coverage of the epileptogenic zone. This study investigates whether, in such conditions, source modeling is able to provide more accurate source localization than the standard clinical method that can be used prospectively to improve surgical resection planning. Suboptimal epileptogenic zone sampling is simulated by subsets of the electrode configuration used to record intracranial EEG in a patient rendered seizure free after surgery. sLORETA and the clinical method solutions are applied to interictal spikes sampled with these electrode subsets and are compared for colocalization with the resection volume and displacement due to electrode downsampling. sLORETA provides often congruent and at times more accurate source localization when compared with the standard clinical method. However, with electrode downsampling, individual sLORETA solution locations can vary considerably and shift consistently toward the remaining electrodes. sLORETA application can improve source localization based on the clinical method but does not reliably compensate for suboptimal electrode placement. Incorporating sLORETA solutions based on intracranial EEG in surgical planning should proceed cautiously in cases where electrode repositioning is planned on clinical grounds.

Production of highly charged heavy ions by 18 GHz superconducting electron cyclotron resonance at Research Center for Nuclear Physics.

PubMed

Yorita, Tetsuhiko; Hatanaka, Kichiji; Fukuda, Mitsuhiro; Kibayashi, Mitsuru; Morinobu, Shunpei; Okamura, Hiroyuki; Tamii, Atsushi

2010-02-01

An 18 GHz superconducting electron cyclotron resonance ion source has been installed as a subject of the azimuthally varying field cyclotron upgrade project (K. Hatanaka et al., in Proceedings of the 17th International Conference on Cyclotrons and Their Applications, Tokyo, Japan, 18-22 October 2004, pp. 115-117), in order to increase beam currents and to extend the variety of ions. The production development of several ions has been performed since 2006 and some of them have already been used for user experiments [T. Yorita et al., Rev. Sci. Instrum. 79, 02A311 (2008)]. Further optimizations for each component such as the material of plasma electrode, material, and shape of bias probe and mirror field have been continued and more intense ion beams have been obtained for O, N, and Ar. For the purpose of obtaining highly charged Xe with several microamperes, the optimization of position and shape of plasma electrode and bias disk has also been done and highly charged Xe(32+) beam has been obtained successfully.

Experimental identification of the active sites in pyrolyzed carbon-supported cobalt-polypyrrole-4-toluenesulfinic acid as electrocatalysts for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Sha, Hao-Dong; Yuan, Xianxia; Li, Lin; Ma, Zhong; Ma, Zi-Feng; Zhang, Lei; Zhang, Jiujun

2014-06-01

A series of carbon supported cobalt-polypyrrole-4-toluenesulfinic acid have been pyrolyzed in an argon atmosphere at 800 °C, then structurally characterized and electrochemically evaluated as oxygen reduction reaction (ORR) catalysts in aqueous 0.5 M sulfuric acid. The structures are cobalt bonded to nitrogen species (Co-Nx) along with metallic cobalt and cobalt oxide. When the cobalt loading in the compound is less than 1.0 wt%, the predominate form is Co-Nx, when the loading is higher than 1.0 wt%, metallic Co and Co oxide particles co-exist with the Co-Nx compound. At a Co loading of ∼1.0 wt%, the catalyst gives the best ORR activity. Both metallic Co and Co oxide are not active for catalyzing ORR, and block the catalytically active Co-Nx species from the surface and reduce the catalytic activity since the diffusion limiting current density on a rotating disk electrode (RDE) increases when the electrode blocking agents are washed away with acid.

Platinum Electrodeposition at Unsupported Electrochemically Reduced Nanographene Oxide for Enhanced Ammonia Oxidation

PubMed Central

2015-01-01

The electrochemical reduction of highly oxidized unsupported graphene oxide nanosheets and its platinum electrodeposition was done by the rotating disk slurry electrode technique. Avoiding the use of a solid electrode, graphene oxide was electrochemically reduced in a slurry solution with a scalable process without the use of a reducing agent. Graphene oxide nanosheets were synthesized from carbon platelet nanofibers to obtain highly hydrophilic layers of less than 250 nm in width. The graphene oxide and electrochemically reduced graphene oxide/Pt (erGOx/Pt) hybrid materials were characterized through different spectroscopy and microscopy techniques. Pt nanoparticles with 100 facets, clusters, and atoms at erGOx were identified by high resolution transmission electron microscopy (HRTEM). Cyclic voltammetry was used to characterize the electrocatalytic activity of the highly dispersed erGOx/Pt hybrid material toward the oxidation of ammonia, which showed a 5-fold current density increase when compared with commercially available Vulcan/Pt 20%. This is in agreement with having Pt (100) facets present in the HRTEM images of the erGOx/Pt material. PMID:24417177

Issues on the production and electrochemical separation of oxygen from carbon dioxide

NASA Technical Reports Server (NTRS)

Kaloupis, P.; Sridhar, K. R.

1991-01-01

There is considerable interest in in-situ propellant manufacturing on the moon and Mars. One of the concepts of oxygen production that is being actively pursued is the processing of atmospheric carbon dioxide on Mars to produce oxygen by means of thermal decomposition and electrochemical separation. The key component of such a production facility is the electrochemical separation cell that filters out the oxygen from the gas mixture of carbon dioxide, carbon monoxide, and oxygen. Efficient design of the separation cell and the selection of electrolyte and electrode materials of superior performance for the cell would translate to significant reduction in the power requirement and the mass of the production facility. The objective is to develop the technology required to produce the cells in-house and test various electrolyte and electrode materials systematically until the optimal combination is found. An effective technique was developed for the fabrication of disk shaped cells. Zirconia and Ceria cells were made in-house. Complete modules of the electrochemical cell and housings were designed, fabricated, and tested.

Ultrasound assisted synthesis, characterization and electrochemical study of a tetradentate oxovanadium diazomethine complex

NASA Astrophysics Data System (ADS)

Merzougui, Moufida; Ouari, Kamel; Weiss, Jean

2016-09-01

The oxovanadium (IV) complex ;VOL; of a tetradentate Schiff base ligand derived from the condensation of diaminoethane and 2-hydroxy-1-naphthaldehyde was efficiently prepared via ultrasound irradiation and the template effect of VO(acac)2. The resulting product was characterized by elemental analysis, infrared, electronic absorption and molar conductance measurement. Single X-ray structure analysis showed that the complex is a monomeric five-coordinate with a distorted square pyramidal geometry. It crystallizes in monoclinic system having unit cell parameters a = 8.3960 (5) Å; b = 12.5533 (8) Å and c = 18.7804 (11) Å; α = γ = 90°; β = 104.843°(2), with P 21/c space group. Cyclic voltammetry of the complex, carried out on a glassy carbon (GC) electrode in DMF, showed reversible cyclic voltammograms response in the potential range 0.15-0.60 V involving a single electron redox wave VV/VIV, the diffusion coefficient is determinedusing GC rotating disk electrode. The Levich plot Ilim = f(ω1/2), was used to calculate the diffusion-convection controlled currents.

Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes

PubMed Central

Makeyev, Oleksandr; Besio, Walter G.

2016-01-01

Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected. PMID:27294933

Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes.

PubMed

Makeyev, Oleksandr; Besio, Walter G

2016-06-10

Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected.

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method

PubMed Central

Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N.

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination. PMID:29301258

Improvement in Electrode Performance of Novel SWCNT Loaded Three-Dimensional Porous RVC Composite Electrodes by Electrochemical Deposition Method.

PubMed

Aldalbahi, Ali; Rahaman, Mostafizur; Almoigli, Mohammed; Meriey, Al Yahya; Alharbi, Khalid N

2018-01-01

The three-dimensional (3D) composite electrodes were prepared by depositing different amounts of acid-functionalized single-walled carbon nanotubes (a-SWCNTs) on porous reticulated vitreous carbon (RVC) through the electrochemical deposition method. The SWCNT was functionalized by the reflux method in nitric acid and was proven by Raman and visible spectra. The optimum time for sonication to disperse the functionalized SWCNT (a-SWCNT) in dimethyl formamide (DMF) well was determined by UV spectra. The average pore size of RVC electrodes was calculated from scanning electron microscopy (SEM) images. Moreover, the surface morphology of composite electrodes was also examined by SEM study. All 3D electrodes were evaluated for their electrochemical properties by cyclic voltammetry. The result showed that the value of specific capacitance of the electrode increases with the increase in the amount of a-SWCNT in geometric volume. However, the value of specific capacitance per gram decreases with the increase in scan rate as well as the amount of a-SWCNT. The stability of the electrodes was also tested. This revealed that all the electrodes were stable; however, lower a-SWCNT-loaded electrodes had excellent cyclic stability. These results suggest that the a-SWCNT-coated RVC electrodes have promise as an effective technology for desalination.

Applications of Graphene-Modified Electrodes in Microbial Fuel Cells

PubMed Central

Yu, Fei; Wang, Chengxian; Ma, Jie

2016-01-01

Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy. PMID:28773929

A FEM-based method to determine the complex material properties of piezoelectric disks.

PubMed

Pérez, N; Carbonari, R C; Andrade, M A B; Buiochi, F; Adamowski, J C

2014-08-01

Numerical simulations allow modeling piezoelectric devices and ultrasonic transducers. However, the accuracy in the results is limited by the precise knowledge of the elastic, dielectric and piezoelectric properties of the piezoelectric material. To introduce the energy losses, these properties can be represented by complex numbers, where the real part of the model essentially determines the resonance frequencies and the imaginary part determines the amplitude of each resonant mode. In this work, a method based on the Finite Element Method (FEM) is modified to obtain the imaginary material properties of piezoelectric disks. The material properties are determined from the electrical impedance curve of the disk, which is measured by an impedance analyzer. The method consists in obtaining the material properties that minimize the error between experimental and numerical impedance curves over a wide range of frequencies. The proposed methodology starts with a sensitivity analysis of each parameter, determining the influence of each parameter over a set of resonant modes. Sensitivity results are used to implement a preliminary algorithm approaching the solution in order to avoid the search to be trapped into a local minimum. The method is applied to determine the material properties of a Pz27 disk sample from Ferroperm. The obtained properties are used to calculate the electrical impedance curve of the disk with a Finite Element algorithm, which is compared with the experimental electrical impedance curve. Additionally, the results were validated by comparing the numerical displacement profile with the displacements measured by a laser Doppler vibrometer. The comparison between the numerical and experimental results shows excellent agreement for both electrical impedance curve and for the displacement profile over the disk surface. The agreement between numerical and experimental displacement profiles shows that, although only the electrical impedance curve is considered in the adjustment procedure, the obtained material properties allow simulating the displacement amplitude accurately. Copyright © 2014 Elsevier B.V. All rights reserved.

Disk diffusion quality control guidelines for NVP-PDF 713: a novel peptide deformylase inhibitor.

PubMed

Anderegg, Tamara R; Jones, Ronald N

2004-01-01

NVP-PDF713 is a peptide deformylase inhibitor that has emerged as a candidate for treating Gram-positive infections and selected Gram-negative species that commonly cause community-acquired respiratory tract infections. This report summarizes the results of a multi-center (seven participants) disk diffusion quality control (QC) investigation for NVP PDF-713 using guidelines of the National Committee for Clinical Laboratory Standards and the standardized disk diffusion method. A total of 420 NVP-PDF 713 zone diameter values were generated for each QC organism. The proposed zone diameter ranges contained 97.6-99.8% of the reported participant results and were: Staphylococcus aureus ATCC 25923 (25-35 mm), Streptococcus pneumoniae ATCC 49619 (30-37 mm), and Haemophilus influenzae ATCC 49247 (24-32 mm). These QC criteria for the disk diffusion method should be applied during the NVP-PDF 713 clinical trials to maximize test accuracy.

An Efficient Monte Carlo Method for Modeling Radiative Transfer in Protoplanetary Disks

NASA Technical Reports Server (NTRS)

Kim, Stacy

2011-01-01

Monte Carlo methods have been shown to be effective and versatile in modeling radiative transfer processes to calculate model temperature profiles for protoplanetary disks. Temperatures profiles are important for connecting physical structure to observation and for understanding the conditions for planet formation and migration. However, certain areas of the disk such as the optically thick disk interior are under-sampled, or are of particular interest such as the snow line (where water vapor condenses into ice) and the area surrounding a protoplanet. To improve the sampling, photon packets can be preferentially scattered and reemitted toward the preferred locations at the cost of weighting packet energies to conserve the average energy flux. Here I report on the weighting schemes developed, how they can be applied to various models, and how they affect simulation mechanics and results. We find that improvements in sampling do not always imply similar improvements in temperature accuracies and calculation speeds.

Automated feature extraction in color retinal images by a model based approach.

PubMed

Li, Huiqi; Chutatape, Opas

2004-02-01

Color retinal photography is an important tool to detect the evidence of various eye diseases. Novel methods to extract the main features in color retinal images have been developed in this paper. Principal component analysis is employed to locate optic disk; A modified active shape model is proposed in the shape detection of optic disk; A fundus coordinate system is established to provide a better description of the features in the retinal images; An approach to detect exudates by the combined region growing and edge detection is proposed. The success rates of disk localization, disk boundary detection, and fovea localization are 99%, 94%, and 100%, respectively. The sensitivity and specificity of exudate detection are 100% and 71%, correspondingly. The success of the proposed algorithms can be attributed to the utilization of the model-based methods. The detection and analysis could be applied to automatic mass screening and diagnosis of the retinal diseases.

Implementing New Methods of Laser Marking of Items in the Nuclear Material Control and Accountability System at SSC RF-IPPE: An Automated Laser Marking System

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

Regoushevsky, V I; Tambovtsev, S D; Dvukhsherstnov, V G

2009-05-18

For over ten years SSC RF-IPPE, together with the US DOE National Laboratories, has been working on implementing automated control and accountability methods for nuclear materials and other items. Initial efforts to use adhesive bar codes or ones printed (painted) onto metal revealed that these methods were inconvenient and lacked durability under operational conditions. For NM disk applications in critical stands, there is the additional requirement that labels not affect the neutron characteristics of the critical assembly. This is particularly true for the many stainless-steel clad disks containing highly enriched uranium (HEU) and plutonium that are used at SSC RF-IPPEmore » for modeling nuclear power reactors. In search of an alternate method for labeling these disks, we tested several technological options, including laser marking and two-dimensional codes. As a result, the method of laser coloring was chosen in combination with Data Matrix ECC200 symbology. To implement laser marking procedures for the HEU disks and meet all the nuclear material (NM) handling standards and rules, IPPE staff, with U.S. technical and financial support, implemented an automated laser marking system; there are also specially developed procedures for NM movements during laser marking. For the laser marking station, a Zenith 10F system by Telesis Technologies (10 watt Ytterbium Fiber Laser and Merlin software) is used. The presentation includes a flowchart for the automated system and a list of specially developed procedures with comments. Among other things, approaches are discussed for human-factor considerations. To date, markings have been applied to numerous steel-clad HEU disks, and the work continues. In the future this method is expected to be applied to other MC&A items.« less

Electrolyte measurement device and measurement procedure

DOEpatents

Cooper, Kevin R.; Scribner, Louie L.

2010-01-26

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

Pulsed Plasma Lubrication Device and Method

NASA Technical Reports Server (NTRS)

Hofer, Richard R. (Inventor); Bickler, Donald B. (Inventor); D'Agostino, Saverio A. (Inventor)

2016-01-01

Disclosed herein is a lubrication device comprising a solid lubricant disposed between and in contact with a first electrode and a second electrode dimensioned and arranged such that application of an electric potential between the first electrode and the second electrode sufficient to produce an electric arc between the first electrode and the second electrode to produce a plasma in an ambient atmosphere at an ambient pressure which vaporizes at least a portion of the solid lubricant to produce a vapor stream comprising the solid lubricant. Methods to lubricate a surface utilizing the lubrication device in-situ are also disclosed.

Evolution of protoplanetary disks from their taxonomy in scattered light: Group I vs. Group II

NASA Astrophysics Data System (ADS)

Garufi, A.; Meeus, G.; Benisty, M.; Quanz, S. P.; Banzatti, A.; Kama, M.; Canovas, H.; Eiroa, C.; Schmid, H. M.; Stolker, T.; Pohl, A.; Rigliaco, E.; Ménard, F.; Meyer, M. R.; van Boekel, R.; Dominik, C.

2017-07-01

Context. High-resolution imaging reveals a large morphological variety of protoplanetary disks. To date, no constraints on their global evolution have been found from this census. An evolutionary classification of disks was proposed based on their IR spectral energy distribution, with the Group I sources showing a prominent cold component ascribed to an earlier stage of evolution than Group II. Aims: Disk evolution can be constrained from the comparison of disks with different properties. A first attempt at disk taxonomy is now possible thanks to the increasing number of high-resolution images of Herbig Ae/Be stars becoming available. Methods: Near-IR images of six Group II disks in scattered light were obtained with VLT/NACO in polarimetric differential imaging, which is the most efficient technique for imaging the light scattered by the disk material close to the stars. We compare the stellar/disk properties of this sample with those of well-studied Group I sources available from the literature. Results: Three Group II disks are detected. The brightness distribution in the disk of HD 163296 indicates the presence of a persistent ring-like structure with a possible connection with the CO snowline. A rather compact (<100 AU) disk is detected around HD 142666 and AK Sco. A taxonomic analysis of 17 Herbig Ae/Be sources reveals that the difference between Group I and Group II is due to the presence or absence of a large disk cavity (≳5 AU). There is no evidence supporting the evolution from Group I to Group II. Conclusions: Group II disks are not evolved versions of the Group I disks. Within the Group II disks, very different geometries exist (both self-shadowed and compact). HD 163296 could be the primordial version of a typical Group I disk. Other Group II disks, like AK Sco and HD 142666, could be smaller counterparts of Group I unable to open cavities as large as those of Group I. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under program number 095.C-0658(A).

Comparison of methods to determine disk and heartwood areas

Treesearch

Michael C. Wiemann; John P. Brown; Neal D. Bennett

2002-01-01

The feasibility of using radius measurements on disks to determine cross-sectional areas of tree stems and the heartwood they contain was examined in sugar maple and red oak butt logs. Areas calculated from quadratic means of four stem radii and four heartwood radii were compared with areas measured with a planimeter. The lineal measurement method was less precise for...

Initial investigation of the corrosion stability of craniofacial implants.

PubMed

Beline, Thamara; Vechiato Filho, Aljomar José; Wee, Alvin G; Sukotjo, Cortino; Dos Santos, Daniela Micheline; Brandão, Thaís Bianca; Barão, Valentim Adelino Ricardo

2018-01-01

Although craniofacial implants have been used for retention of facial prostheses, failures are common. Titanium undergoes corrosion in the oral cavity, but the corrosion of craniofacial implants requires evaluation. The purpose of this in vitro study was to investigate the corrosion stability of commercially pure titanium (CP Ti) exposed to simulated human perspiration at 2 different pH levels (5.5 and 8). Fifteen titanium disks were divided into 3 groups (n=5 per group). The control group was subjected to simulated body fluid (SBF) (control). Disks from the 2 experimental groups were immersed in simulated alkaline perspiration (SA K P) and simulated acidic perspiration (SA C P). Electrochemical tests, including open circuit potential (3600 seconds), electrochemical impedance spectroscopy, and potentiodynamic tests were performed according to the standardized method of 3-cell electrodes. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference tests (α=.05). Simulated human perspiration reduced the corrosion stability of CP Ti (P<.05). The SBF group presented the lowest capacitance values (P<.05). SA K P and SA C P groups showed increased values of capacitance and showed no statistically significant differences (P>.05) from each other. The increase in capacitance suggests that the acceleration of the ionic exchanges between the CP Ti and the electrolyte leads to a lower corrosion resistance. SA K P reduced the oxide layer resistance of CP Ti (P<.05), and an increased corrosion rate was noted in both simulated human perspiration groups. Craniofacial implants can corrode when in contact with simulated human perspiration, whereas alkaline perspiration shows a more deleterious effect. Perspiration induces a more corrosive effect than simulated body fluid. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Electrochemical slurry compositions and methods for preparing the same

DOEpatents

Doherty, Tristan; Limthongkul, Pimpa; Butros, Asli; Duduta, Mihai; Cross, III, James C.

2016-11-01

Embodiments described herein generally relate to semi-solid suspensions, and more particularly to systems and methods for preparing semi-solid suspensions for use as electrodes in electrochemical devices such as, for example batteries. In some embodiments, a method for preparing a semi-solid electrode includes combining a quantity of an active material with a quantity of an electrolyte to form an intermediate material. The intermediate material is then combined with a conductive additive to form an electrode material. The electrode material is mixed to form a suspension having a mixing index of at least about 0.80 and is then formed into a semi-solid electrode.

Electrode structure and methods of making same

DOEpatents

Ruud, James Anthony; Browall, Kenneth Walter; Rehg, Timothy Joseph; Renou, Stephane; Striker, Todd-Michael

2010-04-06

A method of making an electrode structure is provided. The method includes disposing an electrocatalytic material on an electrode, applying heat to the electrocatalytic material to form a volatile oxide of the electrocatalytic material, and applying a voltage to the electrode to reduce the volatile oxide to provide a number of nano-sized electrocatalytic particles on or proximate to a triple phase boundary, where the number of nano-sized electrocatalytic particles is greater on or proximate to the triple phase boundary than in an area that is not on or proximate to the triple phase boundary, and where the triple phase boundary is disposed on the electrode.

Skin-electrode impedance measurement during ECG acquisition: method’s validation

NASA Astrophysics Data System (ADS)

Casal, Leonardo; La Mura, Guillermo

2016-04-01

Skm-electrode impedance measurement can provide valuable information prior. dunng and post electrocardiographic (ECG) or electroencephalographs (EEG) acquisitions. In this work we validate a method for skm-electrode impedance measurement using test circuits with known resistance and capacitor values, at different frequencies for injected excitation current. Finally the method is successfully used for impedance measurement during ECG acquisition on a subject usmg 125 Hz and 6 nA square wave excitation signal at instrumentation amplifier mput. The method can be used for many electrodes configuration.

Evaluation of different methods to detect methicillin resistance in Staphylococcus aureus (MRSA).

PubMed

Alipour, Farzad; Ahmadi, Malahat; Javadi, Shahram

2014-01-01

The studies suggest that dogs living with human are potential risk of becoming MRSA carrier and increased risk of infections caused by MRSA. Phenotypic methods to detect methicillin resistance in Staphylococcus aureus (MRSA) are inadequate. The objective of the present study was to determine methicillin resistance in S. aureus by phenotypic susceptibility test (oxacillin disk diffusion, cefoxitin disk diffusion, oxacillin screen agar) and molecular methods (PCR as a gold standard) and the latex agglutination test for the detection of PBP2a and to evaluate the results of these tests for its sensitivity and specificity. A total of 100 swab samples were taken from muzzle site, in more contact with human, of dogs and MRSA were isolated. Oxacillin (1 μg), cefoxitin (30 μg) disk diffusion and oxacillin screen agar method were used. The isolates were also subjected to latex agglutination test for detection of PBP2a and PCR to detect mecA gene. By PCR 37% of isolates show the presence of mecA. Latex agglutination was found to be the most sensitive (97.29%) and cefoxitin disk diffusion to be the most specific (96.82%) tests for detection of MRSA. Our finding showed that combining oxacillin screen agar or cefoxitin disk diffusion with latex agglutination improves sensitivity and specificity to detect methicillin resistance S. aureus (MRSA) isolates. Copyright © 2014 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

Method of manufacturing lead electrodes for storage cells

DOEpatents

Jonville, P.; Stoehr, H.; Beccu, K.D.

1975-09-23

A method of manufacturing electrodes for lead storage batteries is described. Molten lead or lead alloy is deposited on a felt of glass fibers by spraying in a molten state to fill the space between the fibers of the felt to form an electrically conductive zone defining electrode contacts. A mass of powdered lead-based material is introduced into the felt by filtration for subsequently producing an active electrode mass by at least one electrochemical transformation. The felt is then cut into individual electrodes. (auth)

Investigating FP Tau’s protoplanetary disk structure through modeling

NASA Astrophysics Data System (ADS)

Brinjikji, Marah; Espaillat, Catherine

2017-01-01

This project presents a study aiming to understand the structure of the protoplanetary disk around FP Tau, a very young, very low mass star in the Taurus star-forming region. We have gathered existing optical, Spitzer, Herschel and submillimeter observations to construct the spectral energy distribution (SED) of FP Tau. We have used the D’Alessio et al (2006) physically self-consistent irradiated accretion disk model including dust settling to model the disk of FP Tau. Using this method, the best fit for the SED of FP Tau is a model that includes a gap located 10-20 AU away from the star. This gap is filled with optically thin dust that separates the optically thick dust in the outer disk from the optically thick dust in the inner disk. These characteristics indicate that FP Tau’s protostellar system is best classified as a pre-transitional disk. Near-infrared interferometry in the K-Band from Willson et al 2016 indicates that FP Tau has a small gap located 10-20 AU from the star, which is consistent with the model we produced, lending further support to the pre-transitional disk interpretation. The most likely explanation for the existence of a gap in the disk is a forming planet.

Mechanical properties of human articular disk and its influence on TMJ loading studied with the finite element method.

PubMed

Tanaka, E; Sasaki, A; Tahmina, K; Yamaguchi, K; Mori, Y; Tanne, K

2001-03-01

The present study was designed to investigate the elastic modulus of human temporomandibular joint (TMJ) disk under tension and its influences on TMJ loading. Seven human TMJ disks served as specimens. Continuous tensile stress was applied to each specimen, and the elastic moduli of human TMJ disks were calculated at 2% strain. Furthermore, using a three-dimensional finite element model of the mandible including the TMJ, changes in the TMJ stresses during clenching were evaluated in association of varying elastic moduli of the articular disk determined by the tensile tests. The elastic moduli at 2% strain varied from 27.1 to 65.2 MPa with a mean of 47.1 MPa. A significant correlation was found between the elastic moduli and age (P < 0.01). On the surface of condyle, compressive stress in the anterior area and tensile stress in the posterior area increased when the elastic moduli of the TMJ disk was varied from 25 to 65 MPa. In the TMJ disk, shear stresses in all the areas became larger with greater stiffness. In conclusion, it is shown that the elastic modulus of human TMJ disk is increased with age and that higher stiffness of the disk exerts substantial influences on mechanical loading for the TMJ structures.

Use of interactive multimedia disks in the applied environmental sciences program at the Oregon Institute of Technology

NASA Astrophysics Data System (ADS)

Jones, Charles R.

Although a number of studies have been performed regarding the use of interactive multimedia disks in education, none were found which investigated their effect on either retention or recruitment for universities. The purpose of this case study was to gather information regarding student and teacher perceptions on the use of interactive multimedia disks and their effect on retention and recruitment. The primary source of data for this case study was student and teacher interviews. A purposive sample of students taking courses using the interactive multimedia disks in course at the Oregon Institute of Technology and at two Oregon high schools was chosen for the case study. Major findings of the case study were as follows: (1) Students interviewed in this case study perceived the interactive multimedia disk-based instructional method to be equally as effective as the lecture method. (2) Time flexibility in class scheduling was slightly more beneficial to female students than male students and the lack of instructor-led classroom interaction was more of a problem for female students than male students. (3) There was no difference in the perceptions of the college students and the high school students regarding the benefits and drawbacks of the interactive multimedia disk-based classes. (4) The flexible class scheduling made possible through the use of interactive multimedia disks influences some Oregon Institute of Technology students to stay and complete their degree programs. (5) There is some potential for interactive multimedia disk-based courses to be a recruiting tool. However, there is no evidence that it has been a successful recruiting tool for the Oregon Institute of Technology yet.

Differences in the protein composition of bovine retinal rod outer segment disk and plasma membranes isolated by a ricin-gold-dextran density perturbation method

PubMed Central

1987-01-01

The plasma membrane and disk membranes of bovine retinal rod outer segments (ROS) have been purified by a novel density-gradient perturbation method for analysis of their protein compositions. Purified ROS were treated with neuraminidase to expose galactose residues on plasma membrane-specific glycoproteins and labeled with ricin-gold-dextran particles. After the ROS were lysed in hypotonic buffer, the plasma membrane was dissociated from the disks by either mild trypsin digestion or prolonged exposure to low ionic strength buffer. The dense ricin-gold-dextran-labeled plasma membrane was separated from disks by sucrose gradient centrifugation. Electron microscopy was used to follow this fractionation procedure. The dense red pellet primarily consisted of inverted plasma membrane vesicles containing gold particles; the membrane fraction of density 1.13 g/cc consisted of unlabeled intact disks and vesicles. Ricin-binding studies indicated that the plasma membrane from trypsin-treated ROS was purified between 10-15-fold. The protein composition of plasma membranes and disks was significantly different as analyzed by SDS gels and Western blots labeled with lectins and monoclonal antibodies. ROS plasma membrane exhibited three major proteins of 36 (rhodopsin), 38, and 52 kD, three ricin-binding glycoproteins of 230, 160, and 110 kD, and numerous minor proteins in the range of 14-270 kD. In disk membranes rhodopsin appeared as the only major protein. A 220-kD concanavalin A-binding glycoprotein and peripherin, a rim-specific protein, were also present along with minor proteins of 43 and 57-63 kD. Radioimmune assays indicated that the ROS plasma membrane contained about half as much rhodopsin as disk membranes. PMID:2447095

Li-alloy electrode for Li-alloy/metal sulfide cells

DOEpatents

Kaun, Thomas D.

1996-01-01

A method of making a negative electrode, the electrode made thereby and a secondary electrochemical cell using the electrode. Lithium, silicon and nickel is alloyed in a prescribed proportion forming an electroactive material, to provide an improved electrode and cell.

Fundamental electrode kinetics

NASA Technical Reports Server (NTRS)

Elder, J. P.

1968-01-01

Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

A simple screening test for the detection of metallo-β-lactamase-producing Pseudomonas aeruginosa and Acinetobacter in a tertiary care hospital.

PubMed

Wan Nor Amilah, W A W; Noor Izani, N J; Ng, W K; Ashraful Haq, J

2012-12-01

Clinical utilization of carbapenems remains under threat with the emergence of acquired carbapenemase-producing bacteria, particularly metallo-β-lactamases (MBL). Rapid detection of MBL-producing Gram-negative bacilli is essential to prevent their widespread dissemination. However, no standardized detection method is available for routine laboratory use. The purpose of the study was to evaluate a chelating-agent based double disk synergic test and disk potentiation test for MBL-producing strain detection and to determine the isolation rate of MBL-producing Pseudomonas aeruginosa and Acinetobacter from clinical samples in our tertiary teaching hospital. A total of 22 and 66 imipenem-resistant P. aeruginosa and Acinetobacter isolates respectively were tested with ceftazidime (CAZ) disk by modified double disk synergic test and disk potentiation test using ethylenediaminetetraacetic acid (EDTA) and 2-mercaptopropionic acid (as chelating agents) to detect MBL production. The tests were compared with EDTA-phenanthroline-imipenem (EPI) microdilution MIC test as gold standard. MBL positive strains were detected in 17 (77.3%) P. aeruginosa and 2 (3.5%) Acinetobacter isolates. The disk potentiation test with 2-mercaptopropionic acid (2-MPA) dilution of 1:12 provided the most acceptable sensitivities and specificities (88.2% sensitivity and 100% specificity in P. aeruginosa; 100% sensitivity and specificity in Acinetobacter) compared to other screening methods used in this study. This study provided useful information on the local prevalence of MBL-producing P. aeruginosa and Acinetobacter in our hospital. Disc potentiation test with CAZ/2-MPA disc appears to be reliable and convenient MBL detection method in the routine clinical laboratory.

Sputter-deposited fuel cell membranes and electrodes

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Chun, William (Inventor); Ruiz, Ron P. (Inventor); Valdez, Thomas I. (Inventor)

2001-01-01

A method for preparing a membrane for use in a fuel cell membrane electrode assembly includes the steps of providing an electrolyte membrane, and sputter-depositing a catalyst onto the electrolyte membrane. The sputter-deposited catalyst may be applied to multiple sides of the electrolyte membrane. A method for forming an electrode for use in a fuel cell membrane electrode assembly includes the steps of obtaining a catalyst, obtaining a backing, and sputter-depositing the catalyst onto the backing. The membranes and electrodes are useful for assembling fuel cells that include an anode electrode, a cathode electrode, a fuel supply, and an electrolyte membrane, wherein the electrolyte membrane includes a sputter-deposited catalyst, and the sputter-deposited catalyst is effective for sustaining a voltage across a membrane electrode assembly in the fuel cell.

Electrode holder useful in a corrosion testing device

DOEpatents

Murphy, R.J. Jr.; Jamison, D.E.

1986-08-19

The present invention is directed to an apparatus and method for holding one or more test electrodes of precisely known exposed surface area. The present invention is particularly useful in a device for determining the corrosion properties of the materials from which the test electrodes have been formed. The present invention relates to a device and method for holding the described electrodes wherein the exposed surface area of the electrodes is only infinitesimally decreased. Further, in the present invention the exposed, electrically conductive surface area of the contact devices is small relative to the test electrode surface area. The holder of the present invention conveniently comprises a device for contacting and engaging each test electrode at two point contacts infinitesimally small in relation to the exposed surface area of the electrodes. 4 figs.

Electrode holder useful in a corrosion testing device

DOEpatents

Murphy, Jr., Robert J.; Jamison, Dale E.

1986-01-01

The present invention is directed to an apparatus and method for holding one or more test electrodes of precisely known exposed surface area. The present invention is particularly useful in a device for determining the corrosion properties of the materials from which the test electrodes have been formed. The present invention relates to a device and method for holding the described electrodes wherein the exposed surface area of the electrodes is only infinitesimally decreased. Further, in the present invention the exposed, electrically conductive surface area of the contact devices is small relative to the test electrode surface area. The holder of the present invention conveniently comprises a device for contacting and engaging each test electrode at two point contacts infinitesimally small in relation to the exposed surface area of the electrodes.

Physical properties of dusty protoplanetary disks in Lupus: evidence for viscous evolution?

NASA Astrophysics Data System (ADS)

Tazzari, M.; Testi, L.; Natta, A.; Ansdell, M.; Carpenter, J.; Guidi, G.; Hogerheijde, M.; Manara, C. F.; Miotello, A.; van der Marel, N.; van Dishoeck, E. F.; Williams, J. P.

2017-10-01

Context. The formation of planets strongly depends on the total amount as well as on the spatial distribution of solids in protoplanetary disks. Thanks to the improvements in resolution and sensitivity provided by ALMA, measurements of the surface density of mm-sized grains are now possible on large samples of disks. Such measurements provide statistical constraints that can be used to inform our understanding of the initial conditions of planet formation. Aims: We aim to analyze spatially resolved observations of 36 protoplanetary disks in the Lupus star forming complex from our ALMA survey at 890 μm, aiming to determine physical properties such as the dust surface density, the disk mass and size, and to provide a constraint on the temperature profile. Methods: We fit the observations directly in the uv-plane using a two-layer disk model that computes the 890 μm emission by solving the energy balance at each disk radius. Results: For 22 out of 36 protoplanetary disks we derive robust estimates of their physical properties. The sample covers stellar masses between 0.1 and 2 M⊙, and we find no trend in the relationship between the average disk temperatures and the stellar parameters. We find, instead, a correlation between the integrated sub-mm flux (a proxy for the disk mass) and the exponential cut-off radii (a proxy of the disk size) of the Lupus disks. Comparing these results with observations at similar angular resolution of Taurus-Auriga and Ophiuchus disks found in literature and scaling them to the same distance, we observe that the Lupus disks are generally fainter and larger at a high level of statistical significance. Considering the 1-2 Myr age difference between these regions, it is possible to tentatively explain the offset in the disk mass-size relation with viscous spreading, however with the current measurements other mechanisms cannot be ruled out.

Reagentless and calibrationless silicate measurement in oceanic waters.

PubMed

Giraud, William; Lesven, Ludovic; Jońca, Justyna; Barus, Carole; Gourdal, Margaux; Thouron, Danièle; Garçon, Véronique; Comtat, Maurice

2012-08-15

Determination of silicate concentration in seawater without addition of liquid reagents was the key prerequisite for developing an autonomous in situ electrochemical silicate sensor (Lacombe et al., 2007) [11]. The present challenge is to address the issue of calibrationless determination. To achieve such an objective, we chose chronoamperometry performed successively on planar microelectrode (ME) and ultramicroelectrode (UME) among the various possibilities. This analytical method allows estimating simultaneously the diffusion coefficient and the concentration of the studied species. Results obtained with ferrocyanide are in excellent agreement with values of the imposed concentration and diffusion coefficient found in the literature. For the silicate reagentless method, successive chronoamperometric measurements have been performed using a pair of gold disk electrodes for both UME and ME. Our calibrationless method was tested with different concentrations of silicate in artificial seawater from 55 to 140×10(-6) mol L(-1). The average value obtained for the diffusion coefficient of the silicomolybdic complex is 2.2±0.4×10(-6) cm(2) s(-1), consistent with diffusion coefficient values of molecules in liquid media. Good results were observed when comparing known concentration of silicate with experimentally derived ones. Further work is underway to explore silicate determination within the lower range of oceanic silicate concentration, down to 0.1×10(-6) mol L(-1). Copyright © 2012 Elsevier B.V. All rights reserved.

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

Rodigas, Timothy J.; Hinz, Philip M.; Malhotra, Renu, E-mail: rodigas@as.arizona.edu

Planets can affect debris disk structure by creating gaps, sharp edges, warps, and other potentially observable signatures. However, there is currently no simple way for observers to deduce a disk-shepherding planet's properties from the observed features of the disk. Here we present a single equation that relates a shepherding planet's maximum mass to the debris ring's observed width in scattered light, along with a procedure to estimate the planet's eccentricity and minimum semimajor axis. We accomplish this by performing dynamical N-body simulations of model systems containing a star, a single planet, and an exterior disk of parent bodies and dustmore » grains to determine the resulting debris disk properties over a wide range of input parameters. We find that the relationship between planet mass and debris disk width is linear, with increasing planet mass producing broader debris rings. We apply our methods to five imaged debris rings to constrain the putative planet masses and orbits in each system. Observers can use our empirically derived equation as a guide for future direct imaging searches for planets in debris disk systems. In the fortuitous case of an imaged planet orbiting interior to an imaged disk, the planet's maximum mass can be estimated independent of atmospheric models.« less

WIRED for EC: New White Dwarfs with WISE Infrared Excesses and New Classification Schemes from the Edinburgh–Cape Blue Object Survey

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

Dennihy, E.; Clemens, J. C.; Dunlap, B. H.

We present a simple method for identifying candidate white dwarf systems with dusty exoplanetary debris based on a single temperature blackbody model fit to the infrared excess. We apply this technique to a sample of Southern Hemisphere white dwarfs from the recently completed Edinburgh–Cape Blue Object Survey and identify four new promising dusty debris disk candidates. We demonstrate the efficacy of our selection method by recovering three of the four Spitzer confirmed dusty debris disk systems in our sample. Further investigation using archival high-resolution imaging shows that Spitzer data of the unrecovered fourth object is likely contaminated by a line-of-sightmore » object that either led to a misclassification as a dusty disk in the literature or is confounding our method. Finally, in our diagnostic plot, we show that dusty white dwarfs, which also host gaseous debris, lie along a boundary of our dusty debris disk region, providing clues to the origin and evolution of these especially interesting systems.« less

Electrical resistance tomography using steel cased boreholes as electrodes

DOEpatents

Daily, W.D.; Ramirez, A.L.

1999-06-22

An electrical resistance tomography method is described which uses steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constrain the models. 2 figs.

Electrical resistance tomography using steel cased boreholes as electrodes

DOEpatents

Daily, William D.; Ramirez, Abelardo L.

1999-01-01

An electrical resistance tomography method using steel cased boreholes as electrodes. The method enables mapping the electrical resistivity distribution in the subsurface from measurements of electrical potential caused by electrical currents injected into an array of electrodes in the subsurface. By use of current injection and potential measurement electrodes to generate data about the subsurface resistivity distribution, which data is then used in an inverse calculation, a model of the electrical resistivity distribution can be obtained. The inverse model may be constrained by independent data to better define an inverse solution. The method utilizes pairs of electrically conductive (steel) borehole casings as current injection electrodes and as potential measurement electrodes. The greater the number of steel cased boreholes in an array, the greater the amount of data is obtained. The steel cased boreholes may be utilized for either current injection or potential measurement electrodes. The subsurface model produced by this method can be 2 or 3 dimensional in resistivity depending on the detail desired in the calculated resistivity distribution and the amount of data to constain the models.

Online performance evaluation of RAID 5 using CPU utilization

NASA Astrophysics Data System (ADS)

Jin, Hai; Yang, Hua; Zhang, Jiangling

1998-09-01

Redundant arrays of independent disks (RAID) technology is the efficient way to solve the bottleneck problem between CPU processing ability and I/O subsystem. For the system point of view, the most important metric of on line performance is the utilization of CPU. This paper first employs the way to calculate the CPU utilization of system connected with RAID level 5 using statistic average method. From the simulation results of CPU utilization of system connected with RAID level 5 subsystem can we see that using multiple disks as an array to access data in parallel is the efficient way to enhance the on-line performance of disk storage system. USing high-end disk drivers to compose the disk array is the key to enhance the on-line performance of system.

Magnetic printing characteristics using master disk with perpendicular magnetic anisotropy

NASA Astrophysics Data System (ADS)

Fujiwara, Naoto; Nishida, Yoichi; Ishioka, Toshihide; Sugita, Ryuji; Yasunaga, Tadashi

With the increase in recording density and capacity of hard-disk drives (HDD), high speed, high precision and low cost servo writing method has become an issue in HDD industry. The magnetic printing was proposed as the ultimate solution for this issue [1-3]. There are two types of magnetic printing methods, which are 'Bit Printing (BP)' and 'Edge Printing (EP)'. BP method is conducted by applying external field whose direction is vertical to the plane of both master disk (Master) and perpendicular magnetic recording (PMR) media (Slave). On the other hand, EP method is conducted by applying external field toward down track direction of both master and slave. In BP for bit length shorter than 100 nm, the SNR of perpendicular anisotropic master was higher than isotropic master. And the SNR of EP for the bit length shorter than 50 nm was demonstrated.

Application of Enrofloxacin and Orbifloxacin Disks Approved in Japan for Susceptibility Testing of Representative Veterinary Respiratory Pathogens

PubMed Central

HARADA, Kazuki; USUI, Masaru; ASAI, Tetsuo

2014-01-01

ABSTRACT In this study, susceptibilities of Pasteurella multocida, Mannheimia haemolytica and Actinobacillus pleuropneumoniae to enrofloxacin and orbifloxacin were tested using an agar diffusion method with the commercial disks and a broth microdilution method. Good correlation between the 2 methods for enrofloxacin and orbifloxacin was observed for P. multocida (r = −0.743 and −0.818, respectively), M. haemolytica (r = −0.739 and −0.800, respectively) and A. pleuropneumoniae (r = −0.785 and −0.809, respectively). Based on the Clinical and Laboratory Standards Institute interpretive criteria for enrofloxacin, high-level categorical agreement between the 2 methods was found for P. multocida (97.9%), M. haemolytica (93.8%) and A. pleuropneumoniae (92.0%). Our findings indicate that the tested commercial disks can be applied for susceptibility testing of veterinary respiratory pathogens. PMID:25008965

Three-dimensional modeling of radiative disks in binaries

NASA Astrophysics Data System (ADS)

Picogna, G.; Marzari, F.

2013-08-01

Context. Circumstellar disks in binaries are perturbed by the companion gravity causing significant alterations of the disk morphology. Spiral waves due to the companion tidal force also develop in the vertical direction and affect the disk temperature profile. These effects may significantly influence the process of planet formation. Aims: We perform 3D numerical simulations of disks in binaries with different initial dynamical configurations and physical parameters. Our goal is to investigate their evolution and their propensity to grow planets. Methods: We use an improved version of the SPH code VINE modified to better account for momentum and energy conservation via variable smoothing and softening length. The energy equation includes a flux-limited radiative transfer algorithm. The disk cooling is obtained with the use of "boundary particles" populating the outer surfaces of the disk and radiating to infinity. We model a system made of star/disk + star/disk where the secondary star (and relative disk) is less massive than the primary. Results: The numerical simulations performed for different values of binary separation and disk density show that trailing spiral shock waves develop when the stars approach their pericenter. Strong hydraulic jumps occur at the shock front, in particular for small separation binaries, creating breaking waves, and a consistent mass stream between the two disks. Both shock waves and mass transfer cause significant heating of the disk. At apocenter these perturbations are reduced and the disks are cooled down and less eccentric. Conclusions: The disk morphology is substantially affected by the companion perturbations, in particular in the vertical direction. The hydraulic jumps may slow down or even halt the dust coagulation process. The disk is significantly heated up by spiral waves and mass transfer, and the high gas temperature may prevent the ice condensation by moving the "snow line" outward. The disordered motion triggered by the spiral waves may, on the other hand, favor direct formation of large planetesimals from pebbles. The strength of the hydraulic jumps, disk heating, and mass exchange depends on the binary separation, and for larger semi-major axes, the tidal spiral pattern is substantially reduced. The environment then appears less hostile to planet formation.

Searching for Faint Traces of CO(2-1) and HCN(4-3) Gas In Debris Disks

NASA Astrophysics Data System (ADS)

Stafford Lambros, Zachary; Hughes, A. Meredith

2018-01-01

The surprising presence of molecular gas in the debris disks around main sequence stars provides an opportunity to study the dissipation of primordial gas and, potentially, the composition of gas in other solar systems. Molecular gas is not expected to survive beyond the pre-main sequence phase, and it is not yet clear whether the gas is a remnant of the primordial protoplanetary material or whether the gas, like the dust, is second-generation material produced by collisional or photodesorption from planetesimals, exocomets, or the icy mantles of dust grains. Here we present two related efforts to characterize the prevalence and properties of gas in debris disks. First, we place the lowest limits to date on the CO emission from an M star debris disk, using 0.3" resolution observations of CO(2-1) emission from the AU Mic system with the Atacama Large Millimeter/submillimeter Array (ALMA). We place a 3-sigma upper limit on the integrated flux of 0.39 Jy km/s, corresponding to a maximum CO mass of 5e10-6 (Earth Masses) if the gas is in LTE. We also present the results of an ALMA search for HCN(4-3) emission from the prototypical gas-rich debris disk around 49 Ceti at a spatial resolution of 0.3". Despite hosting one of the brightest CO-rich debris disks yet discovered, our observations of 49 Ceti also yield a low upper limit of 0.057 Jy km/s in the HCN line, leaving CO as the only molecule clearly detected in emission from a debris disk. We employ several methods of detecting faint line emission from debris disks, including a model based on Keplerian kinematics as well as a spectral shifting method previously used to detect faint CO emission from the Fomalhaut debris disk, and compare our results.

Determination of diphenylarsinic acid, phenylarsonic acid and inorganic arsenic in drinking water by graphite-furnace atomic-absorption spectrometry after simultaneous separation and preconcentration with solid-phase extraction disks.

PubMed

Hagiwara, Kenta; Inui, Tetsuo; Koike, Yuya; Nakamura, Toshihiro

2013-01-01

A simple method of graphite-furnace atomic-absorption spectrometry (GFAAS) after solid-phase extraction (SPE) was developed for the determination of diphenylarsinic acid (DPAA), phenylarsonic acid (PAA), and inorganic arsenic (iAs) in drinking water. This method involves the simultaneous collection of DPAA, PAA, and iAs using three stacked SPE disks, i.e., an Empore SDB-XD disk (the upper layer), an activated carbon disk (the middle layer), and a Cation-SR disk loaded with Zr and Ca (ZrCa-CED; the lower layer). A 200-mL aqueous sample was adjusted to pH 3 with nitric acid and passed through the SPE disks at a flow rate of 15 mL min(-1), to concentrate DPAA on the SDB-XD disk, PAA on the activated carbon disk, and iAs on the ZrCa-CED. The As compounds were eluted from the disks with 10 mL of ethanol containing 0.5 mol L(-1) ammonia solution for DPAA, 20 mL of 1 mol L(-1) ammonia solution for PAA, and 20 mL of 6 mol L(-1) hydrochloric acid for iAs. The eluates of DPAA, PAA, and iAs were diluted to 20, 25, and 25 mL, respectively, with deionized water, and then analyzed by GFAAS. The detection limits of As (three-times the standard deviation (n = 3) of the blank values) were 0.13 and 0.16 μg L(-1) at enrichment factors of 10 and 8, respectively, using a 200-mL water sample. Spike tests with 2 μg (10 μg L(-1)) of DPAA, PAA, and iAs in 200 mL of tap water and bottled drinking water showed good recoveries (96.1-103.8%).

Freeze Tape Cast Thick Mo Doped Li 4Ti 5O 12 Electrodes for Lithium-Ion Batteries

DOE PAGES

Ghadkolai, Milad Azami; Creager, Stephen; Nanda, Jagjit; ...

2017-08-30

Lithium titanate (Li 4Ti 5O 12) powders with and without molybdenum doping (LTO and MoLTO respectively) were synthesized by a solid-state method and used to fabricate electrodes on Cu foil using a normal tape-cast method and a novel freeze-tape-cast method. Modest molybdenum doping produces a significant electronic conductivity increase (e.g. 1 mS cm -1 for MoLTO vs 10 -7 mS cm -1 for LTO) that is thought to reflect a partial Ti 4+ reduction to Ti 3+ with charge compensation by the Mo 6+ dopant, producing a stable mixed-valent Ti 4+/3+ state. Freeze-tape-cast electrodes were fabricated by a variant ofmore » the normal tape-cast method that includes a rapid freezing step in which the solvent in the Cu-foil-supported slurry is rapidly frozen on a cold finger then subsequently sublimed to create unidirectional columnar macropores in the electrode. The resulting electrodes exhibit high porosity and low tortuosity which enhances electrolyte accessibility throughout the full electrode thickness. Freeze-tape-cast electrodes subjected to galvanostatic charge-discharge testing as cathodes in cells vs. a lithium metal anode exhibit higher specific capacity and lower capacity loss at high discharge rates compared with normal-tape-cast electrodes of the same mass loading, despite the fact that the freeze-tape-cast electrodes are nearly twice as thick as the normal tape cast electrodes.« less

Brief review: Preparation techniques of biomass based activated carbon monolith electrode for supercapacitor applications

NASA Astrophysics Data System (ADS)

Taer, Erman; Taslim, Rika

2018-02-01

The synthesis of activated carbon monolith electrode made from a biomass material using the hydrolytic pressure or the pelletization technique of pre-carbonized materials is one of standard reported methods. Several steps such as pre-carbonization, milling, chemical activation, hydraulic press, carbonization, physical activation, polishing and washing need to be accomplished in the production of electrodes by this method. This is relatively a long process that need to be simplified. In this paper we present the standard method and proceed with the introduction to several alternative methods in the synthesis of activated carbon monolith electrodes. The alternative methods were emphasized on the selection of suitable biomass materials. All of carbon electrodes prepared by different methods will be analyzed for physical and electrochemical properties. The density, degree of crystallinity, surface morphology are examples for physical study and specific capacitance was an electrochemical properties that has been analysed. This alternative method has offered a specific capacitance in the range of 10 to 171 F/g.

Alloys of clathrate allotropes for rechargeable batteries

DOEpatents

Chan, Candace K; Miller, Michael A; Chan, Kwai S

2014-12-09

The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

Development status of EUV sources for use in beta-tools and high-volume chip manufacturing tools

NASA Astrophysics Data System (ADS)

Stamm, U.; Kleinschmidt, J.; Bolshukhin, D.; Brudermann, J.; Hergenhan, G.; Korobotchko, V.; Nikolaus, B.; Schürmann, M. C.; Schriever, G.; Ziener, C.; Borisov, V. M.

2006-03-01

In the paper we give an update about the development status of gas discharge produced plasma (GDPP) EUV sources at XTREME technologies. Already in 2003 first commercial prototypes of xenon GDPP sources of the type XTS 13-35 based on the Z-pinch with 35 W power in 2π sr have been delivered and integrated into micro-exposure tools from Exitech, UK. The micro-exposure tools with these sources have been installed in industry in 2004. The first tool has made more than 100 million pulses without visible degradation of the source collector optics. For the next generation of full-field exposure tools (we call it Beta-tools) we develop GDPP sources with power of > 10 W in intermediate focus. Also these sources use xenon as fuel which has the advantage of not introducing additional contaminations. Here we describe basic performance of these sources as well as aspects of collector integration and debris mitigation and optics lifetime. To achieve source performance data required for high volume chip manufacturing we consider tin as fuel for the source because of its higher conversion efficiency compared to xenon. While we had earlier reported an output power of 400 W in 2π sr from a tin source we could reach meanwhile 800 W in 2π sr from the source in burst operation. Provided a high power collector is available with a realistic collector module efficiency of between 9% and 15 % these data would support 70-120 W power in intermediate focus. However, we do not expect that the required duty cycle and the required electrode lifetimes can be met with this standing electrode design Z-pinch approach. To overcome lifetime and duty cycle limitations we have investigated GDPP sources with tin fuel and rotating disk electrodes. Currently we can generate more than 200 W in 2π sr with these sources at 4 kHz repetition rate. To achieve 180 W power in intermediate focus which is the recent requirement of some exposure tool manufacturers this type of source needs to operate at 21-28 kHz repetition rate which may be not possible by various reasons. In order to make operation at reasonable repetition rates with sufficient power possible we have investigated various new excitation concepts of the rotating disk electrode configurations. With one of the concepts pulse energies above 170 mJ in 2π sr could be demonstrated. This approach promises to support 180 W intermediate focus power at repetition rates in the range between 7 and 10 kHz. It will be developed to the next power level in the following phase of XTREME technologies' high volume manufacturing source development program.

Precise spectroscopic analysis of solar-type stars with moderate and fast rotation

NASA Astrophysics Data System (ADS)

Tsantaki, Maria

In the present work the performance and applicability of the thin mercury film electrode (TMFE) in the dynamic speciation of trace metals was investigated. Two different electroanalytical stripping techniques were used: the classical anodic stripping voltammetry (ASV) and a recent developed technique, scanning stripping chronopotentiometry (SSCP). The ion-exchange and the mass transport features of novel mixed coatings of two sulfonated cation-exchange polymers with dissimilar characteristics, Nafion (NA) and poly(sodium 4-styrenesulfonate) (PSS) were evaluated, prior to its application in the field of trace metal analysis. Suitable NA-PSS polymer coatings could be used in the modification of TMFE, presenting a high sensitivity, reproducibility, mechanical stability and adequate antifouling properties in the ASV determination of trace metal cations in complex media. Also the features of the PSS polyelectrolyte layers for ion-exchange voltammetry (IEV) were evaluated. The goal was to search for the best conditions to obtain stable PSS coated electrodes, which could present high negative charge densities in order to enhance the electrostatic accumulation of cations within the film, thus enlarging the ASV signal. The applicability and performance of the TMFE in the trace metal speciation studies, by SSCP, were for the first time exploited. The optimized TMFE presented a high sensitivity and resolution, being an excellent complement to the conventional mercury electrodes and could be use for 1-day term with no significant variation in the SCP analytical signal and no apparent degradation. The calculated SSCP curves were in excellent agreement with experimental data at the TMFE and the stability constant (K), calculated from the shift in the SSCP half-wave potential, of two labile metal-complex systems were in good agreement with the ones obtained using the conventional Hanging mercury drop electrode (HMDE) and those predicted by theory. Additionally, the experimental lability diagnosis inherent to the SSCP technique was validated and a rigorous quantification of the lability degree was made. Due to the well defined hydrodynamic conditions at the thin mercury film rotating disk electrode (TMF-RDE), during the deposition step, this electrode is quite valuable in the determination of kinetic parameters, like the association rate constants (ka).

Disk stars in the Milky Way detected beyond 25 kpc from its center

NASA Astrophysics Data System (ADS)

López-Corredoira, M.; Allende Prieto, C.; Garzón, F.; Wang, H.; Liu, C.; Deng, L.

2018-05-01

Context. The maximum size of the Galactic stellar disk is not yet known. Some studies have suggested an abrupt drop-off of the stellar density of the disk at Galactocentric distances R ≳ 15 kpc, which means that in practice no disk stars or only very few of them should be found beyond this limit. However, stars in the Milky Way plane are detected at larger distances. In addition to the halo component, star counts have placed the end of the disk beyond 20 kpc, although this has not been spectroscopically confirmed so far. Aims: Here, we aim to spectroscopically confirm the presence of the disk stars up to much larger distances. Methods: With data from the LAMOST and SDSS-APOGEE spectroscopic surveys, we statistically derived the maximum distance at which the metallicity distribution of stars in the Galactic plane is distinct from that of the halo populations. Results: Our analysis reveals the presence of disk stars at R > 26 kpc (99.7% C.L.) and even at R > 31 kpc (95.4% C.L.).

AGN Space Telescope and Optical Reverberation Mapping Project V. Continuum Time Delays and Disk Inclinations

NASA Astrophysics Data System (ADS)

Starkey, David; Agn Storm Team

2015-01-01

Reverberation mapping is a proven method for obtaining black hole mass estimates and constraining the size of the BLR. We analyze multi-wavelength continuum light curves from the 7 month AGN STORM monitoring of NGC 5548 and use reverberation mapping to model the accretion disk time delays. The model fits the light curves at UV to IR wavelengths assuming reprocessing on a flat, steady-state blackbody accretion disk. We calculate the inclination-dependent transfer function and investigate to what extent our model can determine the disk inclination, black hole MMdot and power law index of the disc temperature-radius relation.

Pt-Ni/WC Alloy Nanorods Arrays as ORR Catalyst for PEM Fuel Cells

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

Begum, Mahbuba; Yurukcu, Mesut; Yurtsever, Fatma

Polymer electrolyte membrane fuel cells (PEMFCs) among the other types of fuel cell technology are attractive power sources, especially for electric vehicle applications. While significant progress and plausible prospects of PEMFCs have been achieved, there are still some challenges related to the performance, durability, and cost that need to be overcome to make them economically viable for widespread commercialization. Our strategy is to develop thin films of high-active and stable catalyst coated on vertically aligned nanorod arrays of conductive and stable support. In this work, we fabricated tungsten carbide (WC) nanorods as support and coated them with a platinum-nickel (Pt-Ni)more » alloy shell denoted as Pt-Ni/WC catalysts. The Pt- Ni/WC nanorods were deposited on glassy carbon disks as well as on silicon substrates for evaluation of their electrocatalytic oxygen reduction reaction (ORR) activity and physical properties. Cyclic voltammetry experiments using rotating disk electrode were performed in perchloric acid (0.1 M HClO4) electrolyte at room temperature to characterize the ORR activity and stability of Pt-Ni/WC nanorods catalysts. Scanning electron microscopy and X-ray diffraction techniques were utilized to study the morphology and crystallographic properties, respectively.« less

Novel air electrode for metal-air battery with new carbon material and method of making same

DOEpatents

Ross, P.N. Jr.

1988-06-21

This invention relates to a rechargeable battery or fuel cell. More particularly, this invention relates to a novel air electrode comprising a new carbon electrode support material and a method of making same. 3 figs.

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

Ghadkolai, Milad Azami; Creager, Stephen; Nanda, Jagjit

Lithium titanate (Li 4Ti 5O 12) powders with and without molybdenum doping (LTO and MoLTO respectively) were synthesized by a solid-state method and used to fabricate electrodes on Cu foil using a normal tape-cast method and a novel freeze-tape-cast method. Modest molybdenum doping produces a significant electronic conductivity increase (e.g. 1 mS cm -1 for MoLTO vs 10 -7 mS cm -1 for LTO) that is thought to reflect a partial Ti 4+ reduction to Ti 3+ with charge compensation by the Mo 6+ dopant, producing a stable mixed-valent Ti 4+/3+ state. Freeze-tape-cast electrodes were fabricated by a variant ofmore » the normal tape-cast method that includes a rapid freezing step in which the solvent in the Cu-foil-supported slurry is rapidly frozen on a cold finger then subsequently sublimed to create unidirectional columnar macropores in the electrode. The resulting electrodes exhibit high porosity and low tortuosity which enhances electrolyte accessibility throughout the full electrode thickness. Freeze-tape-cast electrodes subjected to galvanostatic charge-discharge testing as cathodes in cells vs. a lithium metal anode exhibit higher specific capacity and lower capacity loss at high discharge rates compared with normal-tape-cast electrodes of the same mass loading, despite the fact that the freeze-tape-cast electrodes are nearly twice as thick as the normal tape cast electrodes.« less

Li-alloy electrode for Li-alloy/metal sulfide cells

DOEpatents

Kaun, T.D.

1996-07-16

A method of making a negative electrode is described, the electrode made thereby and a secondary electrochemical cell using the electrode. Lithium, silicon and nickel is alloyed in a prescribed proportion forming an electroactive material, to provide an improved electrode and cell. 7 figs.

Lithium aluminum/iron sulfide battery having lithium aluminum and silicon as negative electrode

DOEpatents

Gilbert, Marian; Kaun, Thomas D.

1984-01-01

A method of making a negative electrode, the electrode made thereby and a secondary electrochemical cell using the electrode. Silicon powder is mixed with powdered electroactive material, such as the lithium-aluminum eutectic, to provide an improved electrode and cell.

Method for Predicting the Energy Characteristics of Li-Ion Cells Designed for High Specific Energy

NASA Technical Reports Server (NTRS)

Bennett, William, R.

2012-01-01

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

Novel PVC-membrane electrode for flow injection potentiometric determination of Biperiden in pharmaceutical preparations.

PubMed

Khaled, Elmorsy; El-Sabbagh, Inas A; El-Kholy, N G; Ghahni, E Y Abdel

2011-12-15

The construction and performance characteristics of Biperiden (BP) polyvinyl chloride (PVC) electrodes are described. Different methods for electrode fabrication are tested including; incorporation of BP-ion pairs (BP-IPs), incorporation of ion pairing agents, or soaking the plain electrode in BP-ion pairs suspension solution. Electrode matrices were optimized referring to the effect of modifier content and nature, plasticizer and the method of modification. The proposed electrodes work satisfactorily in the BP concentration range from 10(-5) to 10(-2)mol L(-1), with fast response time (7s) and adequate operational lifetime (28 days). The electrode potential is pH independent within the range 2.0-7.0, with good selectivity towards BP in presence of various interfering species. The developed electrodes have been applied for potentiometric determination of BP in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. FIA offers the advantages of accuracy and automation feasibility with high sampling frequency. The dissolution profile for Akineton tablets (2mg BP/tablet) was studied using the proposed electrode in comparison with the official methods. Copyright © 2011 Elsevier B.V. All rights reserved.

Electrocatalytic performance of fuel cell reactions at low catalyst loading and high mass transport.

PubMed

Zalitis, Christopher M; Kramer, Denis; Kucernak, Anthony R

2013-03-28

An alternative approach to the rotating disk electrode (RDE) for characterising fuel cell electrocatalysts is presented. The approach combines high mass transport with a flat, uniform, and homogeneous catalyst deposition process, well suited for studying intrinsic catalyst properties at realistic operating conditions of a polymer electrolyte fuel cell (PEFC). Uniform catalyst layers were produced with loadings as low as 0.16 μgPt cm(-2) and thicknesses as low as 200 nm. Such ultra thin catalyst layers are considered advantageous to minimize internal resistances and mass transport limitations. Geometric current densities as high as 5.7 A cm(-2)Geo were experimentally achieved at a loading of 10.15 μgPt cm(-2) for the hydrogen oxidation reaction (HOR) at room temperature, which is three orders of magnitude higher than current densities achievable with the RDE. Modelling of the associated diffusion field suggests that such high performance is enabled by fast lateral diffusion within the electrode. The electrodes operate over a wide potential range with insignificant mass transport losses, allowing the study of the ORR at high overpotentials. Electrodes produced a specific current density of 31 ± 9 mA cm(-2)Spec at a potential of 0.65 V vs. RHE for the oxygen reduction reaction (ORR) and 600 ± 60 mA cm(-2)Spec for the peak potential of the HOR. The mass activity of a commercial 60 wt% Pt/C catalyst towards the ORR was found to exceed a range of literature PEFC mass activities across the entire potential range. The HOR also revealed fine structure in the limiting current range and an asymptotic current decay for potentials above 0.36 V. These characteristics are not visible with techniques limited by mass transport in aqueous media such as the RDE.

Electrical separation of protein concentrate from juice of forages. Final report

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

Koegel, R.G.; Straub, R.J.; McFate, K.L.

1993-03-01

Previous research has shown that large quantities of high-quality, low-fiber protein concentrate can be separated from the juice of forage crops such as alfalfa. The value of adding such extracted protein to the diet of undernourished children in Mexico and other developing countries has been well demonstrated. In the past, protein separation has been achieved by either heat coagulation of the protein or by a pH adjustment of the juice. Both techniques have disadvantages including irreversible changes in the protein and high energy or material costs. This used electrostatic fields to manipulate the small charges found in protein molecules. Suchmore » an approach could result in an on-farm or portable protein separation system that does not require the transport of large quantities of forage. Researchers, using a dc power supply with appropriately placed electrodes to separate protein from juices, varied voltage levels to modify field strength and tried various shapes of electrodes and configurations of apparatus. The relative impact of centrifugation, use of various flocculents, and ultrafiltration in attempts to enhance dc voltage-supply test results were explored. One steady-flow system used a plastic vessel with stainless steel walls that served as electrodes. Another steady-flow ac voltage system used a trough through which juice was allowed to flow While two spinning-disk electrodes passed electricity directly through the juice. A four-step process was developed using an, ac power supply. The juice is first treated with an ac current, then held for approximately 60 minutes, after which it is centrifuged at 10,000 g. In the final phase the soluble protein is concentrated 5--10 fold by ultrafiltration using filters with a 10,000 molecular weight cutoff. This process shows potential for meeting project objectives.« less

PdNi- and Pd-coated electrodes prepared by electrodeposition from ionic liquid for nonenzymatic electrochemical determination of ethanol and glucose in alkaline media.

PubMed

Huang, Hsin-Yi; Chen, Po-Yu

2010-12-15

Nonenzymatic electrochemical determination of ethanol and glucose was respectively achieved using PdNi- and Pd-coated electrodes prepared by electrodeposition from the novel metal-free ionic liquid (IL); N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA). BMP-DCA provided an excellent environment and wide cathodic limit for electrodeposition of metals and alloys because many metal chlorides could dissolve in this IL where the reduction potentials of Pd(II) and Ni(II) indeed overlapped, leading to the convenience of potentiostatic codeposition. In aqueous solutions, the reduction potentials of Pd(II) and Ni(II) are considerably separated. The bimetallic PdNi coatings with atomic ratios of ∼ 80/20 showed the highest current for ethanol oxidation reaction (EOR). Ethanol was detected by either cyclic voltammetry (CV) or hydrodynamic amperometry (HA). Using CV, the dependence of EOR peak current on concentration was linear from 4.92 to 962 μM with a detection limit of 2.26 μM (σ=3), and a linearity was observed from 4.92 to 988 μM using HA (detection limit 0.83 μM (σ=3)). The Pd-coated electrodes prepared by electrodeposition from BMP-DCA showed electrocatalytic activity to glucose oxidation and CV, HA, and square-wave voltammetry (SWV) were employed to determine glucose. SWV showed the best sensitivity and linearity was observed from 2.86 μM to 107 μM, and from 2.99 mM to 10.88 mM with detection limits of 0.78 μM and 25.9 μM (σ=3), respectively. For glucose detection, the interference produced from ascorbic acid, uric acid, and acetaminophen was significantly suppressed, compared with a regular Pt disk electrode. Copyright © 2010 Elsevier B.V. All rights reserved.

A Peculiar Class of Debris Disks from Herschel/DUNES: A Steep Fall Off in the Far Infrared

NASA Technical Reports Server (NTRS)

Ertel, S.; Wolf, S.; Marshall, J. P.; Eiroa, C.; Augereau, J. C.; Krivov, A. V.; Lohne, T.; Absil, O.; Ardila, D.; Arevalo, M.;

Multiplexed microimmunoassays on a digital versatile disk.

PubMed

Morais, Sergi; Tortajada-Genaro, Luis A; Arnandis-Chover, Tania; Puchades, Rosa; Maquieira, Angel

2009-07-15

Multiplexed microimmunoassays for five critical compounds were developed using a digital versatile disk (DVD) as an analytical support and detecting technology. To this end, coating conjugates were adsorbed on the polycarbonate face of the disk; a pool of specific antibodies, gold labeled secondary antibodies, and silver amplification were addressed for developing the assays. The detection principle is based on the capture of attenuated analog signals with the disk drive that were proportional to optical density of the immunoreaction product. The multiplexed assay achieved detection limits (IC10) of 0.06, 0.25, 0.37, 0.16, and 0.10 microg/L, sensitivities of (IC50) 0.54, 1.54, 2.62, 2.02, and 5.9 microg/L, and dynamic ranges of 2 orders of magnitude for atrazine, chlorpyrifos, metolachlor, sulfathiazole, and tetracycline, respectively. The features of the methodology were verified by analyzing natural waters and compared with reference chromatographic methods, showing its potential for high-throughput multiplexed screening applications. Analytes of different chemical nature (pesticides and antibiotics) were directly quantified without sample treatment or preconcentration in a total time of 30 min with similar sensitivity and selectivity to the ELISA plate format using the same immunoreagents. The multianalyte capabilities of immunoassaying methods developed with digital disk and drive demonstrated the competitiveness to quantify targets that require different sample treatment and instrumentation by chromatographic methods.

Activity and Durability of Iridium Nanoparticles in the Oxygen Evolution Reaction

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

Alia, Shaun M.; Rasimick, Brian; Ngo, Chilan

Unsupported iridium (Ir) nanoparticles, that serve as standard oxygen evolution reaction (OER) catalysts in acidic electrolyzers, were investigated for electrochemical performance and durability in rotating disk electrode (RDE) half-cells. Fixed potential holds and potential cycling were applied to probe the durability of Ir nanoparticles, and performance losses were found to be driven by particle growth (coarsening) at moderate potential (1.4 to 1.6 V) and Ir dissolution at higher potential (>/=1.8 V). Several different commercially available samples were evaluated and standardized conditions for performance comparison are reported. In conclusion, the electrocatalyst RDE results have also been compared to results obtained formore » performance and durability in electrolysis cells.« less

Activity and Durability of Iridium Nanoparticles in the Oxygen Evolution Reaction

DOE PAGES

Alia, Shaun M.; Rasimick, Brian; Ngo, Chilan; ...

2016-07-15

Unsupported iridium (Ir) nanoparticles, that serve as standard oxygen evolution reaction (OER) catalysts in acidic electrolyzers, were investigated for electrochemical performance and durability in rotating disk electrode (RDE) half-cells. Fixed potential holds and potential cycling were applied to probe the durability of Ir nanoparticles, and performance losses were found to be driven by particle growth (coarsening) at moderate potential (1.4 to 1.6 V) and Ir dissolution at higher potential (>/=1.8 V). Several different commercially available samples were evaluated and standardized conditions for performance comparison are reported. In conclusion, the electrocatalyst RDE results have also been compared to results obtained formore » performance and durability in electrolysis cells.« less

Systems and Methods for Implementing High-Temperature Tolerant Supercapacitors

NASA Technical Reports Server (NTRS)

Bugga, Ratnakumar V. (Inventor); Brandon, Erik J. (Inventor); West, William C. (Inventor)

2016-01-01

Systems and methods in accordance with embodiments of the invention implement high-temperature tolerant supercapacitors. In one embodiment, a high-temperature tolerant super capacitor includes a first electrode that is thermally stable between at least approximately 80C and approximately 300C; a second electrode that is thermally stable between at least approximately 80C and approximately 300C; an ionically conductive separator that is thermally stable between at least approximately 80C and 300C; an electrolyte that is thermally stable between approximately at least 80C and approximately 300C; where the first electrode and second electrode are separated by the separator such that the first electrode and second electrode are not in physical contact; and where each of the first electrode and second electrode is at least partially immersed in the electrolyte solution.

Characterization of microtopography and its influence on vegetation patterns in created wetlands

USGS Publications Warehouse

Moser, K.; Ahn, C.; Noe, G.

2007-01-01

Created wetlands are increasingly used to mitigate wetland loss. Thus, identifying wetland creation methods that enhance ecosystem development might increase the likelihood of mitigation success. Noting that the microtopographic variation found in natural wetland settings may not commonly be found in created wetlands, this study explores relationships between induced microtopography, hydrology, and plant species richness/ diversity in non-tidal freshwater wetlands, comparing results from two created wetland complexes with those from a mature reference wetland complex in northern Virginia. Elevation, steel rod oxidation depth, and species cover were measured along replicate multiscale (0.5 m-, 1 m-, 2 m-, and 4 m-diameter) tangentially conjoined circular transects in each wetland. Microtopography was surveyed using a total station and results used to derive three roughness indices: tortuosity, limiting slope, and limiting elevation difference. Steel rod oxidation depth was used to estimate water table depth, with data collected four times during the growing season for each study site. Plant species cover was estimated visually in 0.2 m2 plots surveyed at peak growth and used to assess species richness, diversity, and wetland prevalence index. Differences in each attribute were examined among disked and non-disked created wetlands and compared to a natural wetland as a reference. Disked and non-disked created wetlands differed in microtopography, both in terms of limiting elevation difference and tortuosity. However, both were within the range of microtopography encompassed by natural wetlands. Disked wetlands supported higher plant diversity and species richness than either natural or non-disked wetlands, as well as greater within-site species assemblage variability than non-disked wetlands. Irrespective of creation method, plant diversity in created wetlands was correlated with tortuosity and limiting elevation difference, similar to correlations observed for natural wetlands. Vegetation was more hydrophytic at disked sites than at non-disked sites, and of equivalent wetland indicator status to natural sites, even though all sites appeared comparable in terms of hydrology. Results suggest that disking may enhance vegetation community development, thus better supporting the goals of wetland mitigation. ?? 2007, The Society of Wetland Scientists.

Influence of fundamental mode fill factor on disk laser output power and laser beam quality

NASA Astrophysics Data System (ADS)

Cheng, Zhiyong; Yang, Zhuo; Shao, Xichun; Li, Wei; Zhu, Mengzhen

2017-11-01

An three-dimensional numerical model based on finite element method and Fox-Li method with angular spectrum diffraction theoy is developed to calculate the output power and power density distribution of Yb:YAG disk laser. We invest the influence of fundamental mode fill factor(the ratio of fundamental mode size and pump spot size) on the output power and laser beam quality. Due to aspherical aberration and soft aperture effect in laser disk, high beam quality can be achieve with relative lower efficiency. The highest output power of fundamental laser mode is influenced by the fundamental mode fill factor. Besides we find that optimal mode fill factor increase with pump spot size.

Simulation of aerodynamic noise and vibration noise in hard disk drives

NASA Astrophysics Data System (ADS)

Zhu, Lei; Shen, Sheng-Nan; Li, Hui; Zhang, Guo-Qing; Cui, Fu-Hao

2018-05-01

Internal flow field characteristics of HDDs are usually influenced by the arm swing during seek operations. This, in turn, can affect aerodynamic noise and airflow-induced noise. In this paper, the dynamic mesh method is used to calculate the flow-induced vibration (FIV) by transient structure analysis and the boundary element method (BEM) is utilized to predict the vibration noise. Two operational states are considered: the arm is fixed and swinging over the disk. Both aerodynamic noise and vibration noise inside drives increase rapidly with increase in disk rotation and arm swing velocities. The largest aerodynamic noise source is always located near the arm and swung with the arm.

Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters

NASA Astrophysics Data System (ADS)

Richert, A. J. W.; Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Broos, P. S.; Povich, M. S.; Bate, M. R.; Garmire, G. P.

2018-04-01

Photometric detections of dust circumstellar disks around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disk longevity, starting with Haisch, Lada & Lada (2001), use star samples from PMS clusters but do not consider datasets with homogeneous photometric sensitivities and/or ages placed on a uniform timescale. Here we conduct the largest study to date of the longevity of inner dust disks using X-ray and 1-8 {μ m} infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disk-free objects, we impose similar stellar mass sensitivity limits for disk-bearing and disk-free YSOs while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disk longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disk fraction of 100% at zero age, the inferred disk half-life changes significantly, from t1/2 ˜ 1.3 - 2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disk fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disk fraction and star-forming environment are also explored.

Near-Infrared Polarimetric Imaging of Disks around Young Intermediate-mass Stars in SEEDS

NASA Astrophysics Data System (ADS)

Fukagawa, Misato; Hashimoto, Jun; Grady, C. A.; Momose, Munetake; Wisniewski, J. P.; Okamoto, Yoshiko; Muto, Takayuki; Kusakabe, Nobuhiko; Bonnefoy, Mickael; Kotani, Takayuki; Maruta, Yayoi; Tamura, Motohide; Seeds/Hiciao/Ao188 Collaboration,

2013-07-01

We present our recent results to directly image circumstellar disks around Herbig Fe/Ae/Be stars in scattered light with Subaru. Observations of such young disks are critically important to understand how disks evolve possibly under the mutual interaction with new-born planets. One of the observational approaches is direct imaging in scattered light, and the progress in this field since PPV can be found in the ability to prove inner regions of disks. This improvement largely owes to the technique of polarization differential imaging (PDI) which provides higher contrast by extracting scattered light from the disk while suppressing unpolarized stellar light. Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) is the project dedicated to exoplanet hunting and study of circumstellar disks by direct imaging. Since its beginning in 2009, thirteen Herbig Fe/Ae/Be stars have been observed primarily in H band (1.6 micron). The PDI method has been employed with adaptive optics, enabling us to look into the inner region as close as 0.2 arcsec (˜30 AU) in radius with the typical angular resolution of 0.06 arcsec (˜8 AU). As a result, the SEEDS imagery has newly uncovered rich structures such as spiral arms, inner holes, and gaps for (pre-)transitional disks while suggested the variably illuminated disks for primordial systems. The highlight is the discovery of two spiral arms each for SAO 206462 and MWC 758. The spiral feature has been uniquely found toward Herbig Fe/Aes so far, which might be due to their warmer disks producing arms loosely wound and more easily detected. The observed morphology can be interpreted by the density-wave model, and those disks are implied to harbor Jupiter-mass companions as the exciting sources of the spiral structures according to these models.

Method and apparatus for simultaneous spectroelectrochemical analysis

DOEpatents

Chatterjee, Sayandev; Bryan, Samuel A; Schroll, Cynthia A; Heineman, William R

2013-11-19

An apparatus and method of simultaneous spectroelectrochemical analysis is disclosed. A transparent surface is provided. An analyte solution on the transparent surface is contacted with a working electrode and at least one other electrode. Light from a light source is focused on either a surface of the working electrode or the analyte solution. The light reflected from either the surface of the working electrode or the analyte solution is detected. The potential of the working electrode is adjusted, and spectroscopic changes of the analyte solution that occur with changes in thermodynamic potentials are monitored.

Electrode structures and surfaces for Li batteries

DOEpatents

Thackeray, Michael M.; Kang, Sun-Ho; Balasubramanian, Mahalingam; Croy, Jason

2017-03-14

This invention relates to methods of preparing positive electrode materials for electrochemical cells and batteries. It relates, in particular, to a method for fabricating lithium-metal-oxide electrode materials for lithium cells and batteries. The method comprises contacting a hydrogen-lithium-manganese-oxide material with one or more metal ions, preferably in an acidic solution, to insert the one or more metal ions into the hydrogen-lithium-manganese-oxide material; heat-treating the resulting product to form a powdered metal oxide composition; and forming an electrode from the powdered metal oxide composition.

Accretion Disks and the Formation of Stellar Systems

NASA Astrophysics Data System (ADS)

Kratter, Kaitlin Michelle

2011-02-01

In this thesis, we examine the role of accretion disks in the formation of stellar systems, focusing on young massive disks which regulate the flow of material from the parent molecular core down to the star. We study the evolution of disks with high infall rates that develop strong gravitational instabilities. We begin in chapter 1 with a review of the observations and theory which underpin models for the earliest phases of star formation and provide a brief review of basic accretion disk physics, and the numerical methods that we employ. In chapter 2 we outline the current models of binary and multiple star formation, and review their successes and shortcomings from a theoretical and observational perspective. In chapter 3 we begin with a relatively simple analytic model for disks around young, high mass stars, showing that instability in these disks may be responsible for the higher multiplicity fraction of massive stars, and perhaps the upper mass to which they grow. We extend these models in chapter 4 to explore the properties of disks and the formation of binary companions across a broad range of stellar masses. In particular, we model the role of global and local mechanisms for angular momentum transport in regulating the relative masses of disks and stars. We follow the evolution of these disks throughout the main accretion phase of the system, and predict the trajectory of disks through parameter space. We follow up on the predictions made in our analytic models with a series of high resolution, global numerical experiments in chapter 5. Here we propose and test a new parameterization for describing rapidly accreting, gravitationally unstable disks. We find that disk properties and system multiplicity can be mapped out well in this parameter space. Finally, in chapter 6, we address whether our studies of unstable disks are relevant to recently detected massive planets on wide orbits around their central stars.

The structure of disks around intermediate-mass young stars from mid-infrared interferometry. Evidence for a population of group II disks with gaps

NASA Astrophysics Data System (ADS)

Menu, J.; van Boekel, R.; Henning, Th.; Leinert, Ch.; Waelkens, C.; Waters, L. B. F. M.

2015-09-01

Context. The disks around Herbig Ae/Be stars are commonly divided into group I and group II based on their far-infrared spectral energy distribution, and the common interpretation for that is flared and flat disks. Our understanding of the evolution of these disks is rapidly changing. Recent observations suggest that many flaring disks have gaps, whereas flat disks are thought to be gapless. Aims: The different groups of objects can be expected to have different structural signatures in high-angular-resolution data, related to gaps, dust settling, and flaring. We aim to use such data to gain new insight into disk structure and evolution. Methods: Over the past 10 years, the MIDI instrument on the Very Large Telescope Interferometer has collected observations of several tens of protoplanetary disks. We modeled the large set of observations with simple geometric models and compared the characteristic sizes among the different objects. A population of radiative-transfer models was synthesized for interpreting the mid-infrared signatures. Results: Objects with similar luminosities show very different disk sizes in the mid-infrared. This may point to an intrinsic diversity or could also hint at different evolutionary stages of the disks. Restricting this to the young objects of intermediate mass, we confirm that most group I disks are in agreement with being transitional (i.e., they have gaps). We find that several group II objects have mid-infrared sizes and colors that overlap with sources classified as group I, transition disks. This suggests that these sources have gaps, which has been demonstrated for a subset of them. This may point to an intermediate population between gapless and transition disks. Conclusions: Flat disks with gaps are most likely descendants of flat disks without gaps. Potentially related to the formation of massive bodies, gaps may therefore even develop in disks in a far stage of grain growth and settling. The evolutionary implications of this new population could be twofold. Either gapped flat disks form a separate population of evolved disks or some of them may evolve further into flaring disks with large gaps. The latter transformation may be governed by the interaction with a massive planet, carving a large gap and dynamically exciting the grain population in the disk. Appendices A and B are available in electronic form at http://www.aanda.org

Direct mapping of local redox current density on a monolith electrode by laser scanning.

PubMed

Lee, Seung-Woo; Lopez, Jeffrey; Saraf, Ravi F

2013-09-15

An optical method of mapping local redox reaction over a monolith electrode using simple laser scanning is described. As the optical signal is linearly proportional to the maximum redox current that is measured concomitantly by voltammetry, the optical signal quantitatively maps the local redox current density distribution. The method is demonstrated on two types of reactions: (1) a reversible reaction where the redox moieties are ionic, and (2) an irreversible reaction on two different types of enzymes immobilized on the electrode where the reaction moieties are nonionic. To demonstrate the scanning capability, the local redox behavior on a "V-shaped" electrode is studied where the local length scale and, hence, the local current density, is nonuniform. The ability to measure the current density distribution by this method will pave the way for multianalyte analysis on a monolith electrode using a standard three-electrode configuration. The method is called Scanning Electrometer for Electrical Double-layer (SEED). Copyright © 2013 Elsevier B.V. All rights reserved.

Young stars in ɛ Chamaleontis and their disks: disk evolution in sparse associations

NASA Astrophysics Data System (ADS)

Fang, M.; van Boekel, R.; Bouwman, J.; Henning, Th.; Lawson, W. A.; Sicilia-Aguilar, A.

2013-01-01

Context. The nearby young stellar association ɛ Cha has an estimated age of 3-5 Myr, making it an ideal laboratory to study the disk dissipation process and provide empirical constraints on the timescale of planet formation. Aims: We wish to complement existing optical and near-infrared data of the ɛ Cha association, which provide the stellar properties of its members, with mid-infrared data that probe the presence, geometry, and mineralogical composition of protoplanetary disks around individual stars. Methods: We combine the available literature data with our Spitzer/IRS spectroscopy and VLT/VISIR imaging data. We use proper motions to refine the membership of ɛ Cha. Masses and ages of individual stars are estimated by fitting model atmospheres to the optical and near-infrared photometry, followed by placement in the Hertzsprung-Russell diagram. The Spitzer/IRS spectra are analyzed using the two-layer temperature distribution spectral decomposition method. Results: Two stars previously identified as members, CXOU J120152.8 and 2MASS J12074597, have proper motions that are very different from those of the other stars. But other observations suggest that the two stars are still young and thus might still be related to ɛ Cha. HD 104237C is the lowest mass member of ɛ Cha with an estimated mass of ~13-15 Jupiter masses. The very low mass stars USNO-B120144.7 and 2MASS J12005517 show globally depleted spectral energy distributions, pointing at strong dust settling. 2MASS J12014343 may have a disk with a very specific inclination, where the central star is effectively screened by the cold outer parts of a flared disk, but the 10 μm radiation of the warm inner disk can still reach us. We find that the disks in sparse stellar associations are dissipated more slowly than those in denser (cluster) environments. We detect C2H2 rovibrational band around 13.7 μm on the IRS spectrum of USNO-B120144.7. We find strong signatures of grain growth and crystallization in all ɛ Cha members with 10 μm features detected in their IRS spectra. We combine the dust properties derived in the ɛ Cha sample with those found using identical or similar methods in the MBM 12, Coronet, η Cha associations, and in the cores-to-disks legacy program. We find that disks around low-mass young stars show a negative radial gradient in the mass-averaged grain size and mass fraction of crystalline silicates. A positive correlation exists between the mass-averaged grain sizes of amorphous silicates and the accretion rates if the latter is above ~10-9 M⊙ yr-1, possibly indicating that those disks are sufficiently turbulent to prevent grains of several microns in size to sink into the disk interior. Based on observations performed at ESO's La Silla-Paranal observatory under programme 076.C-0470.

A suitable deposition method of CdS for high performance CdS-sensitized ZnO electrodes: Sequential chemical bath deposition

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

Chen, Haining; Li, Weiping; Liu, Huicong

2010-07-15

A suitable deposition method of CdS is necessary for the high performance CdS-sensitized ZnO electrodes. In this paper, chemical bath deposition (CBD) and sequential chemical bath deposition (S-CBD) methods were used to deposit CdS on ZnO mesoporous films for ZnO/CdS electrodes. The analysis results of XRD patterns and UV-vis spectroscopy indicated that CBD deposition method leaded to the dissolving of ZnO mesoporous films in deposition solution and thickness reduction of ZnO/CdS electrodes. Absorption in visible region by the ZnO/CdS electrodes with CdS deposition by S-CBD was enhanced as deposition cycles increased due to the stability of ZnO mesoporous films inmore » the S-CBD deposition solutions. The results of photocurrent-voltage (I-V) measurement showed that the performance of ZnO/CdS electrodes with CdS deposition by CBD first increased and then decreased as deposition time increased, and the greatest short-circuit current (J{sub sc}) was obtained at the deposition time of 4 min. The performance of ZnO/CdS electrodes with CdS deposition by S-CBD increased as deposition cycles increased, and both open-circuit voltage (V{sub oc}) and J{sub sc} were greater than those electrodes with CdS deposition by CBD when the deposition cycles of S-CBD were 10 or greater. These results indicated that S-CBD is a more suitable method for high performance ZnO/CdS electrodes. (author)« less

Vibration and flutter of mistuned bladed-disk assemblies

NASA Technical Reports Server (NTRS)

Kaza, K. R. V.; Kielb, R. E.

1984-01-01

An analytical model for investigating vibration and flutter of mistuned bladed disk assemblies is presented. This model accounts for elastic, inertial and aerodynamic coupling between bending and torsional motions of each individual blade, elastic and inertial couplings between the blades and the disk, and aerodynamic coupling among the blades. The disk was modeled as a circular plate with constant thickness and each blade was represented by a twisted, slender, straight, nonuniform, elastic beam with a symmetric cross section. The elastic axis, inertia axis, and the tension axis were taken to be noncoincident and the structural warping of the section was explicitly considered. The blade aerodynamic loading in the subsonic and supersonic flow regimes was obtained from two-dimensional unsteady, cascade theories. All the possible standing wave modes of the disk and traveling wave modes of the blades were included. The equations of motion were derived by using the energy method in conjunction with the assumed mode shapes for the disk and the blades. Continuities of displacement and slope at the blade-disk junction were maintained. The equations were solved to investigate the effects of blade-disk coupling and blade frequency mistuning on vibration and flutter. Results showed that the flexibility of practical disks such as those used for current generation turbofans did not have a significant influence on either the tuned or mistuned flutter characteristics. However, the disk flexibility may have a strong influence on some of the system frequencies and on forced response.

Vibration and flutter of mistuned bladed-disk assemblies

NASA Technical Reports Server (NTRS)

Rao, K.; Kaza, V.; Kielb, R. E.

1984-01-01

An analytical model for investigating vibration and flutter of mistuned bladed disk assemblies is presented. This model accounts for elastic, inertial and aerodynamic coupling between bending and torsional motions of each individual blade, elastic and inertial couplings between the blades and the disk, and aerodynamic coupling among the blades. The disk was modeled as a circular plate with constant thickness and each blade was represented by a twisted, slender, straight, nonuniform, elastic beam with a symmetric cross section. The elastic axis, inertia axis, and the tension axis were taken to be noncoincident and the structural warping of the section was explicitly considered. The blade aerodynamic loading in the subsonic and supersonic flow regimes was obtained from two-dimensional unsteady, cascade theories. All the possible standing wave modes of the disk and traveling wave modes of the blades were included. The equations of motion were derived by using the energy method in conjunction with the assumed mode shapes for the disk and the blades. Continuities of displacement and slope at the blade-disk junction were maintained. The equations were solved to investigate the effects of blade-disk coupling and blade frequency mistuning on vibration and flutter. Results showed that the flexibility of practical disks such as those used for current generation turbufans did not have a significant influence on either the tuned or mistuned flutter characteristics. However, the disk flexibility may have a strong influence on some of the system frequencies and on forced response.

Evolution of dynamo-generated magnetic fields in accretion disks around compact and young stars

NASA Technical Reports Server (NTRS)

Stepinski, Tomasz F.

1994-01-01

Geometrically thin, optically thick, turbulent accretion disks are believed to surround many stars. Some of them are the compact components of close binaries, while the others are throught to be T Tauri stars. These accretion disks must be magnetized objects because the accreted matter, whether it comes from the companion star (binaries) or from a collapsing molecular cloud core (single young stars), carries an embedded magnetic field. In addition, most accretion disks are hot and turbulent, thus meeting the condition for the MHD turbulent dynamo to maintain and amplify any seed field magnetic field. In fact, for a disk's magnetic field to persist long enough in comparison with the disk viscous time it must be contemporaneously regenerated because the characteristic diffusion time of a magnetic field is typically much shorter than a disk's viscous time. This is true for most thin accretion disks. Consequently, studying magentic fields in thin disks is usually synonymous with studying magnetic dynamos, a fact that is not commonly recognized in the literature. Progress in studying the structure of many accretion disks was achieved mainly because most disks can be regarded as two-dimensional flows in which vertical and radial structures are largely decoupled. By analogy, in a thin disk, one may expect that vertical and radial structures of the magnetic field are decoupled because the magnetic field diffuses more rapidly to the vertical boundary of the disk than along the radius. Thus, an asymptotic method, called an adiabatic approximation, can be applied to accretion disk dynamo. We can represent the solution to the dynamo equation in the form B = Q(r)b(r,z), where Q(r) describes the field distribution along the radius, while the field distribution across the disk is included in the vector function b, which parametrically depends on r and is normalized by the condition max (b(z)) = 1. The field distribution across the disk is established rapidly, while the radial distribution Q(r) evolves on a considerably longer timescale. It is this evolution that is the subject of this paper.

Binder-free Si nanoparticle electrode with 3D porous structure prepared by electrophoretic deposition for lithium-ion batteries.

PubMed

Yang, Yang; Chen, Dingqiong; Liu, Bo; Zhao, Jinbao

2015-04-15

A binder-free silicon (Si) based electrode for lithium-ion battery was fabricated in an organic solvent through one-step electrophoretic deposition (EPD). The nanosized Si and acetylene black (AB) particles were bonded tightly together to form a homogeneous co-deposited film with 3D porous structure through the EPD process. The 3D porous structure provides buffer spaces to alleviate the mechanical stress due to silicon volume change during the cycling and improves lithium-ion conductivity by shortening ion diffusion length and better ion conducting pathway. The electrode prepared with 5 s deposition duration shows the best cycling performance among electrodes fabricated by EPD method, and thus, it was selected to be compared with the silicon electrode prepared by the conventional method. Our results demonstrate that the Si nanoparticle electrode prepared through EPD exhibits smaller cycling capacity decay rate and better rate capability than the electrode prepared by the conventional method.

Method for fabricating carbon/lithium-ion electrode for rechargeable lithium cell

NASA Technical Reports Server (NTRS)

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

1995-01-01

The method includes steps for forming a carbon electrode composed of graphitic carbon particles adhered by an ethylene propylene diene monomer binder. An effective binder composition is disclosed for achieving a carbon electrode capable of subsequent intercalation by lithium ions. The method also includes steps for reacting the carbon electrode with lithium ions to incorporate lithium ions into graphitic carbon particles of the electrode. An electrical current is repeatedly applied to the carbon electrode to initially cause a surface reaction between the lithium ions and to the carbon and subsequently cause intercalation of the lithium ions into crystalline layers of the graphitic carbon particles. With repeated application of the electrical current, intercalation is achieved to near a theoretical maximum. Two differing multi-stage intercalation processes are disclosed. In the first, a fixed current is reapplied. In the second, a high current is initially applied, followed by a single subsequent lower current stage. Resulting carbon/lithium-ion electrodes are well suited for use as an anode in a reversible, ambient temperature, lithium cell.

Design and Optimization Method of a Two-Disk Rotor System

NASA Astrophysics Data System (ADS)

Huang, Jingjing; Zheng, Longxi; Mei, Qing

2016-04-01

An integrated analytical method based on multidisciplinary optimization software Isight and general finite element software ANSYS was proposed in this paper. Firstly, a two-disk rotor system was established and the mode, humorous response and transient response at acceleration condition were analyzed with ANSYS. The dynamic characteristics of the two-disk rotor system were achieved. On this basis, the two-disk rotor model was integrated to the multidisciplinary design optimization software Isight. According to the design of experiment (DOE) and the dynamic characteristics, the optimization variables, optimization objectives and constraints were confirmed. After that, the multi-objective design optimization of the transient process was carried out with three different global optimization algorithms including Evolutionary Optimization Algorithm, Multi-Island Genetic Algorithm and Pointer Automatic Optimizer. The optimum position of the two-disk rotor system was obtained at the specified constraints. Meanwhile, the accuracy and calculation numbers of different optimization algorithms were compared. The optimization results indicated that the rotor vibration reached the minimum value and the design efficiency and quality were improved by the multidisciplinary design optimization in the case of meeting the design requirements, which provided the reference to improve the design efficiency and reliability of the aero-engine rotor.