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Potential Drop (potential + drop)
Selected AbstractsSheath in Front of a Negatively Biased Collector that Emits Electrons and is Immersed in a Two Electron Temperature PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2005T. Gyergyek Abstract An extension of a recently published [Gyergyek T., ,er,ek M. Contrib. Plasma Phys., 45, (2005), 89] one dimensional fluid model of the sheath formation in front of a floating electrode (collector) that emits secondary electrons and is immersed in a two-electron temperature nonmagnetized, collisionless plasma is presented. The electron velocity distribution function is assumed to be a two-temperature maxwellian, while the singly charged positive ions and the emitted electrons are assumed to be monoenergetic. It is assumed that the electrons in the pre-sheath potential drop obey the Boltzmann relation, so that a larger fraction of the hot than of the cool electrons can penetrate to the sheath edge. Our model predicts that the collector can in some cases have 3 and in some cases, when the emission of electrons from the collector is critical, even 5 different floating potentials at the same hot to cool electron temperature and density ratios very far away from the collector. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electronic gel protein transfer and identification using matrix-assisted laser desorption/ionization-mass spectrometryELECTROPHORESIS, Issue 9 2004Jonathan W. Cooper Abstract An electronic protein transfer technique is described for achieving the rapid and efficient recovery of sodium dodecyl sulfate (SDS)-protein complexes from polyacrylamide gels. This process involves the use of small-dimension capillaries in physical contact with a resolved protein band within the polyacrylamide gel, providing a large potential drop and high electric field strength at the capillary/gel interface. Several factors controlling the electronic protein transfer, including the applied electric field strength, the electrophoresis buffer concentration, and the capillary dimension, are studied to further enhance the use of field-amplification for sample stacking of extracted SDS-protein complexes. As a result of sample stacking, the extracted proteins from a 50 ng gel loading are present in a narrow (,80 nL) and highly concentrated (0.46 mg/mL or 3.3×10,5 M for cytochrome c) solution plug. Three model proteins with molecular mass ranging from 14 kDa (cytochrome c) to 116 kDa (,-galactosidase) are stained by Coomassie blue and electrophoretically extracted from gels with protein loadings as low as 50 ng. The capillary format of the electronic protein transfer technique allows direct deposition of extracted proteins onto a matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) target. Various matrices and solvent compositions are evaluated for the analysis of extracted and concentrated SDS-protein complexes using MALDI-MS. The electronic protein transfer technique, when operated under optimized conditions, is demonstrated for the effective (>70% recovery), speedy (less than 5 min), and sensitive MS identification of gel resolved proteins (as low as 50 ng). [source] Localization Events and Microstructural Evolution in Ultra-Fine Grained NiTi Shape Memory Alloys during Thermo-Mechanical Loading,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Andreas Schaefer Subjecting a thin NiTi specimen to uniaxial tension often leads to a localized martensitic transformation: macroscopic transformation bands form and propagate through the specimen, separating it into regions of fully transformed martensite and original austenite. In the present study, the alternating current potential drop (ACPD) technique is used to analyze the change in electrical resistance of ultra-fine grained NiTi wires subjected to a broad range of thermo-mechanical load cases: (i) uniaxial tensile straining at constant temperatures (pseudoelastic deformation); (ii) cooling and heating through the transformation range at constant load (actuator load case); (iii) a combination of mechanical and thermal loading. We monitor the ACPD signals in several zones along the gauge length of specimens, and we demonstrate that a localized type of transformation is a generic feature of pseudoelastic as well as of shape memory deformation. Moreover, the ACPD signals allow to differentiate between temperature-induced martensite (formed during cooling at no or relatively small loads), stress-induced martensite, and reoriented martensite (formed under load at low temperatures). [source] Non-destructive evaluation of fatigue and creep-fatigue damage by means of the induced-current focused potential drop techniqueFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2001Y. Sato Quantitative evaluation of damage accumulation including crack initiation and propagation is one of the major concerns of industrial plant management and plant licence renewal. In order to develop a novel non-destructive testing (NDT) and non-destructive evaluation (NDE) technique for damage evaluation, the induced-current focused potential drop (ICFPD), originally proposed for a defect inspection, was employed. In this study, ICFPD was successfully applied to a non-destructive damage evaluation based on crack measurements. The measurements were taken on fatigued specimens with various degrees of fatigue damage. The ICFPD can clearly detect and differentiate the damage accumulation processes including crack initiation, small crack growth and subsequent macroscopic crack growth. In order to demonstrate the applicability of damage evaluation assessments based on small crack measurements, ICFPD has also been applied to creep,fatigue loading where damage evaluation of a fusion reactor material is based on small crack measurements by the ICFPD technique and a novel methodology is proposed. [source] Flow characteristics of a cold helium arc-jet plasma along open field linesIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2009Kazuyuki Yoshida Member Abstract We experimentally study plasma parameters including ion acoustic Mach number of expanding cold helium plasma jet with an electron temperature of less than 1 eV flowing along open field lines. It is experimentally found that the ion Mach number increases from 1 to 3, and that the plasma potential decreases by about 1 V. We discuss the experimental results based on a quasi one-dimensional flow model in which the plasma is assumed to be quasi-neutral and in a state of thermodynamic equilibrium. Our model describes the ion acceleration, the axial profiles of the potential drop, and the electron temperature/density. The model also shows that the helium ions are accelerated both by the electric field and by the increasing cross-sectional area of the transonic flow. After the ion acceleration, the ion Mach number decreases and the electron temperature increases. These phenomena are discussed in terms of a shock wave. It is noted that the electron density decreases even in the shock wave. This is discussed in terms of rapid recombination because of the low electron temperature. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Spatially Resolved Potential Distribution in Carbon Nanotube Cross-Junction DevicesADVANCED MATERIALS, Issue 25-26 2009Eduardo J. H. Lee Crossed-nanotube junctions, the basic constituents of carbon nanotube networks, are investigated by scanning photocurrent microscopy. The location of the predominant electrostatic potential drop, at the electrical contacts or at the junction, is found to be highly dependent on the transport regime. Also, whereas Schottky barriers are formed at M-S (metal,semiconductor) nanotube crossings, isotype heterojunctions are formed at S-S ones (figure). [source] Voltage-induced morphological modifications in oocyte membranes containing exogenous K+ channels studied by electrochemical scanning force microscopyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2008Andrea Alessandrini Abstract We report on a novel use of electrochemical scanning force microscopy (SFM) for the investigation of morphological modifications occurring in plasma membranes containing voltage-gated ion channels, on membrane potential variation. Membrane patches of Xenopus laevis oocytes microinjected with exogenous KAT1 cRNA, deposited by a stripping method at the surface of a derivatized gold film in inside-out configuration, have been imaged by SFM in an electrochemical cell. A potentiostat was used to maintain a desired potential drop across the membrane. Performing imaging at potential values corresponding to open (,120 mV) and closed (+20 mV) states for KAT1, morphological differences in localized sample zones were observed. Particularly, cross-shaped features involving a significant membrane portion appear around putative channel locations. The reported approach constitutes the first demonstration of an SPM-based experimental technique suitable to investigate the rearrangements occurring to the plasma membrane containing voltage-gated channels on transmembrane potential variation. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source] Potentiometry on pentacene OFETs: Charge carrier mobilities and injection barriers in bottom and top contact configurationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008R. Scholz Abstract In a combination of experimental techniques including electrical probes, potentiometry, and charge transient spectroscopy (QTS), we develop concepts how to quantify the potential drops at the contacts, the mobility in the channel region, and the density of states of deep traps in pentacene OFETs. For OFETs grown from unpurified pentacene on pre-patterned Au bottom contacts, a comparison between potentiometry and two-dimensional device simulations determines an injection barrier of 0.73 eV at the source contact and a hole mobility of 0.014 cm2 V,1 s,1 in the pentacene channel. Temperature-dependent QTS data reveal a trap level at about 125 meV from the hole transport band, indicating a relatively high density of unintentional dopants and therefore a high background density of majority charge carriers. In OFETs grown from purified pentacene onto a SiO2 gate dielectric and Au top contacts evaporated onto the pentacene channel without breaking the vacuum, potentiometry reveals a nearly perfect alignment of the metal work function with the hole transport level in the organic layer. The much lower density of deep traps in these samples raises the hole mobility to the range 0.1,0.2 cm2 V,1 s,1. A further improvement of the hole mobility and the resulting device performance can be achieved by a chemical treatment of the gate oxide with n-octadecytrichlorosilane (OTS). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||