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Electrical Behaviour (electrical + behaviour)

Distribution by Scientific Domains

Physics and Astronomy	33%

Selected Abstracts

Electrical behaviour of interleukin-1 beta (IL-1,) and prostaglandin-E2 (PGE2) on colonic myenteric neurones

NEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2002
A. Kelles
Abstract,Intracellular recordings were used to examine the effects on electrical and synaptic behaviour of interleukin (IL)-1, and prostaglandin E2(PGE2) on myenteric neurones of the guinea-pig colon. Application of IL-1, and PGE2resulted in a concentration-dependent slow depolarization with enhanced spike discharge in, respectively, 45% (21/47) and 83% (33/41) of the impaled colonic neurones. Administration of IL-1, in three neurones (6%) elicited a hyperpolarization. Responses remained during tetrodotoxin application, indicative of a direct effect of both substances on the impaled neurones. The effects of IL-1, remained in the presence of indomethacine, a prostaglandin synthase inhibitor. Responses were seen in both nitric oxide synthase- and choline acetyl transferase-immunoreactive neurones. IL-1, evoked a 26% reduction of the fast excitatory postsynaptic potential. These results indicate that the application of IL-1, and PGE2evoke direct excitatory actions on a subset of myenteric neurones. For IL-1,, direct inhibition and presynaptic inhibition of the fast excitatory postsynaptic potential has also been found. In the distal colon, responses to IL-1, are not mediated through PGE2pathways. [source]

Coupling electrical and mechanical effects in discrete element simulations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2008
M. Renouf
Abstract When investigating the electrical characteristics of granular assemblies under dynamical solicitations (powder, steel bead assemblies, etc.), it is difficult to distinguish between effects that are purely electrical and those that are strongly dependent on mechanical effects. Although numerous experimental works have permitted better understanding of the static electrical behaviour of such media, it is difficult to determine the effects control the multi-physical behaviour of the medium, especially under dynamical solicitations. In the present paper, numerical investigations of the electrical characteristics of granular material are proposed. Moreover, it presents the formulation of a new model, embedded in the general scheme of discrete element methods, that couples electrical and mechanical effects and takes into account the oxidation phenomenon. Numerical simulations on the basis of experimental works are performed to validate the model, and the results of dynamical simulations are discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Open-circuit voltage increase dynamics in high and low deposition rate polymorphous silicon solar cells

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010
E. V. Johnson
Abstract The dynamics of the open-circuit voltage (VOC) of polymorphous silicon (pm-Si:H) solar cells deposited at high and low rates (8 and 1.5,Å/s, HR and LR) and containing lightly or heavily doped p-layers (LD or HD) are compared through in situ, variable intensity measurements during light-soaking (LS). The VOC's of the LR cells show an increase with LS, regardless of doping level, whereas the HR cells show decreasing VOC's. This result is in contrast to the changes predicted by the dark diode characteristics, which predict increasing VOC for all the devices. The device measurements are compared to the analogous measurements on co-deposited coplanar p,i layer stacks to determine whether the VOC dynamics can be linked to changes in the p-layer doping efficiency during LS. The changes to the macroscopic electrical behaviour of the cell under varying light conditions are modelled using a simple, three parameter function, and are compared to results from a detailed, numerical modelling tool, AFORS-HET. [source]

Ce and Yb doped InP layers grown for radiation detection

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2007
J. Zavadil
Abstract InP single crystals were grown by liquid phase epitaxy on semi-insulating InP:Fe substrate with cerium (Ce) and ytterbium (Yb) additions to the growth melt. Grown layers were characterised by Hall measurements and low temperature photoluminescence spectroscopy. Both types of layers exhibit the change of electrical conductivity from n to p type. Ce and Yb have been found to be incorporated into the InP lattice since a sharp luminescence lines arising from inner shell transitions of Yb3+ and Ce3+ were detected at 1002 and 3534 nm, respectively. A metastable conductivity state of InP:Ce layers has been found at temperatures below 35 K, a phenomenon previously reported for InP:Yb layers. Similar electrical behaviour of InP (Ce, Yb) layers leads us to conclude that Ce acts as dominant acceptor impurity responsible for n,p conductivity change. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Integration of K+ and Cl, currents regulate steady-state and dynamic membrane potentials in cultured rat microglia

THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
Evan W. Newell
The role of ion channels and membrane potential (Vm) in non-excitable cells has recently come under increased scrutiny. Microglia, the brain's resident immune cells, express voltage-gated Kv1.3 channels, a Kir2.1-like inward rectifier, a swelling-activated Cl, current and several other channels. We previously showed that Kv1.3 and Cl, currents are needed for microglial cell proliferation and that Kv1.3 is important for the respiratory burst. Although their mechanisms of action are unknown, one general role for these channels is to maintain a negative Vm. An impediment to measuring Vm in non-excitable cells is that many have a very high electrical resistance, which makes them extremely susceptible to leak-induced depolarization. Using non-invasive Vm -sensitive dyes, we show for the first time that the membrane resistance of microglial cells is several gigaohms; much higher than the seal resistance during patch-clamp recordings. Surprisingly, we observed that small current injections can evoke large Vm oscillations in some microglial cells, and that injection of sinusoidal currents of varying frequency exposes a strong intrinsic electrical resonance in the 5- to 20-Hz frequency range in all microglial cells tested. Using a dynamic current clamp that we developed to actively compensate for the damage done by the patch-clamp electrode, we found that the Vm oscillations and resonance were more prevalent and larger. Both types of electrical behaviour required Kv1.3 channels, as they were eliminated by the Kv1.3 blocker, agitoxin-2. To further determine how the ion currents integrate in these cells, voltage-clamp recordings from microglial cells displaying these behaviours were used to analyse the biophysical properties of the Kv1.3, Kir and Cl, currents. A mathematical model that incorporated only these three currents reproduced the observed Vm oscillations and electrical resonance. Thus, the electrical behaviour of this ,non-excitable' cell type is much more complex than previously suspected, and might reflect a more common oversight in high resistance cells. [source]

Synaptic facilitation and enhanced neuronal excitability in the submucosal plexus during experimental colitis in guinea-pig

THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
Alan E. Lomax
Intestinal secretion is regulated by submucosal neurones of the enteric nervous system. Inflammation of the intestines leads to aberrant secretory activity; therefore we hypothesized that the synaptic and electrical behaviours of submucosal neurones are altered during colitis. To test this hypothesis, we used intracellular microelectrode recording to compare the excitability and synaptic properties of submucosal neurones from normal and trinitrobenzene sulphonic acid (TNBS)-inflamed guinea-pig colons. Inflammation differentially affected the electrophysiological characteristics of the two functional classes of submucosal neurones. AH neurones from inflamed colons were more excitable, had shorter action potential durations and reduced afterhyperpolarizations. Stimulus-evoked fast and slow excitatory postsynaptic potentials (EPSPs) in S neurones were larger during colitis, and the incidence of spontaneous fast EPSPs was increased. In control preparations, fast EPSPs were almost completely blocked by the nicotinic receptor antagonist hexamethonium, whereas fast EPSPs in inflamed S neurones were only partially inhibited by hexamethonium. In inflamed tissues, components of the fast EPSP in S neurones were sensitive to blockade of P2X and 5-HT3 receptors while these antagonists had little effect in control preparations. Control and inflamed S neurones were equally sensitive to brief application of acetylcholine, ATP and 5-HT, suggesting that synaptic facilitation was due to a presynaptic mechanism. Immunoreactivity for 5-HT in the submucosal plexus was unchanged by inflammation; this indicates that altered synaptic transmission was not due to anatomical remodelling of submucosal nerve terminals. This is the first demonstration of alterations in synaptic pharmacology in the enteric nervous system during inflammation. [source]