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Ionic Transport (ionic + transport)

Distribution by Scientific Domains

Polymers and Materials Science	50%
Medical Sciences	33%

Selected Abstracts

A pH-Gating Ionic Transport Nanodevice: Asymmetric Chemical Modification of Single Nanochannels

ADVANCED MATERIALS, Issue 22 2010
Xu Hou
Inspired by biological ion channels, the generation of artificial nanochannels has strong implications for the simulation of different processes of ionic transport as well as enhance the functionality of biological ion channels. Here, we show plasma asymmetric chemical modification approach to prepare the pH asymmetric gating nanochannel that can achieve pH control for both different ionic rectification and perfect gating function, simultaneously. [source]

Mesoscopic Morphology of Proton-Conducting Polyelectrolyte Membranes of Nafion® Type: A Self-Consistent Mean Field Simulation

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2006
Dmitry Y. Galperin
Abstract Summary: A SCMF simulation is presented for a coarse-grained model of Nafion®. Based on a number of simplifying assumptions, this study predicts distinct morphological changes in the material upon alteration of temperature and water content. We found that the hydration level corresponding to the microphase segregation depends on the temperature of the system. Spherical clusters constituting the hydrophilic microphase of the membrane at relatively low water content (but above the transition point) grow in size, coalesce and form a network of channels responsible for the ionic transport at higher hydration levels. This hydrophilic phase is shielded from the hydrophobic matrix by the sidechains of Nafion®, their end-groups being turned towards the water clusters. The results obtained are similar to those reported from dissipative particle dynamics studies and support the "cluster-network" model for the low hydration levels and the "sponge" model at higher hydration levels. The simulation approach chosen proved to be effective for the mesoscopic structure analysis of the heterogeneous polymeric material. Schematic representation of the structure of Nafion®-water blends. [source]

Biomedical applications of 7Li NMR

NMR IN BIOMEDICINE, Issue 2 2005
Richard A. Komoroski
Abstract The biomedical applications of 7Li MRS and MRI have been progressing slowly. The interest derives primarily from the clinical use of Li to treat bipolar disorder. One area of concern is the nature of ionic transport and binding, so as to elucidate the mechanism(s) of therapeutic action and toxicity. Another is the development of a non-invasive, in vivo analytical tool to measure brain Li concentration and environment in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review the most recent progress toward these goals. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Electrical properties of the five-component chalkogenides of silver

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
O. L. Kheifets-Kobeleva
Abstract The electrical properties of AgGeSbS3xSe3(1-x) (x = 0.4-0.7) were investigated by means of impedance measurements in the frequency range between 10 Hz and 800 kHz and at temperatures between 78 K and 500 K. In all investigated chalcogenides ionic conductivity (Ag+) was found. The onset of ionic transport was found at 250 K-300 K, depending on the composition. The complex impedance and admittance plots, the electrical properties are given. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Highly conductive, oriented polymer electrolytes for lithium batteries,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002
D. Golodnitsky
Abstract In semicrystalline complexes of poly(ethylene oxide) (PEO) with different salts, such as lithium iodide, lithium trifluoromethanesulfonate (LiTF) and lithium trifluoromethanesulfonimide (LiTFSI), stretching induced longitudinal DC conductivity enhancement was observed, in spite of the formation of more ordered polymer electrolyte (PE) structure. It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. The results of our investigation suggest that ionic transport occurs preferentially along the PEO helical axis, at least in the crystalline phase, and that the rate-determining step of the lithium ion conduction in LiI:P(EO)20, LiTF:P(EO)20 polymer electrolytes below Tm is "interchain" hopping. Understanding ion transport processes is clearly a fertile field for research and development in the synthesis of new rigid polymers with ordered channels and composition appropriate for enhanced ionic conductivity. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Mechanistic hypotheses for nonsynaptic epileptiform activity induction and its transition from the interictal to ictal state,Computational simulation

EPILEPSIA, Issue 11 2008
Antônio-Carlos G. De Almeida
Summary Purpose:, The aim of this work is to study, by means of computational simulations, the induction and sustaining of nonsynaptic epileptiform activity. Methods:, The computational model consists of a network of cellular bodies of neurons and glial cells connected to a three-dimensional (3D) network of juxtaposed extracellular compartments. The extracellular electrodiffusion calculation was used to simulate the extracellular potential. Each cellular body was represented in terms of the transmembrane ionic transports (Na+/K+ pumps, ionic channels, and cotransport mechanisms), the intercellular electrodiffusion through gap-junctions, and the neuronal interaction by electric field and the variation of cellular volume. Results:, The computational model allows simulating the nonsynaptic epileptiform activity and the extracellular potential captured the main feature of the experimental measurements. The simulations of the concomitant ionic fluxes and concentrations can be used to propose the basic mechanisms involved in the induction and sustaining of the activities. Discussion:, The simulations suggest: The bursting induction is mediated by the Cl, Nernst potential overcoming the transmembrane potential in response to the extracellular [K+] increase. The burst onset is characterized by a critical point defined by the instant when the Na+ influx through its permeable ionic channels overcomes the Na+/K+ pump electrogenic current. The burst finalization is defined by another critical point, when the electrogenic current of the Na+/K+ pump overcomes its influx through the channels. [source]