Conductance

About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.

Anisotropy in conductance of a quasi-one-dimensional metallic surface state measured by a square micro-four-point probe method.

Abstract: We have devised a "square micro-four-point probe method" using an independently driven ultrahigh-vacuum four-tip scanning tunneling microscope, and succeeded for the first time to directly measure anisotropic electrical conductance of a single-atomic layer on a solid surface. A quasi-one-dimensional metal of a single-domain Si(111)4 x 1-In had a surface-state conductance along the metallic atom chains (sigma(axially)) to be 7.2(+/-0.6) x 10(-4) S/square at room temperature, which was larger than that in the perpendicular direction (sigma(radially)) by approximately 60 times. The sigma(axially) was consistently interpreted by a Boltzmann equation with the anisotropic surface-state band dispersion, while the sigma(radially) was dominated by a surface-space-charge-layer conductance.

A large anion-selective channel has seven conductance levels

Abstract: Ion channels have generally been found to have two predominant conductance levels thought to be associated with 'open' and 'closed' states, but intermediate (subconductance) states have also been reported. We have now found that a large conductance, anion-selective channel in pulmonary alveolar epithelial cells can adopt any of six open levels of conductance that are integer multiples of 60-70 pS. The channel is usually either fully open or fully closed. The frequencies of the different conductance levels are inconsistent with the notion that there are six independent channels. We suggest that the channel consists of six conducting pathways in parallel, 'co-channels', with a shared gating mechanism that can synchronously render all of them non-conducting. Other channels with lower maximum conductance may operate in a similar way but multiple conductance levels would not easily be detected because of a less favourable signal-to-noise ratio.

Inositol 1,4,5-trisphosphate-gated channels in cerebellum: presence of multiple conductance states.

Abstract: The mechanism by which inositol 1,4,5-triphosphate (InsP3) induces calcium (Ca) release from the reticulum of canine cerebellum was examined. Reticular membrane vesicles used in these experiments accumulated Ca in the presence of ATP and then released approximately 30% of the accumulated Ca upon addition of micromolar concentrations of InsP3. When these membrane vesicles were incorporated into planar lipid bilayers, InsP3-gated Ca channels were observed. Up to four current amplitudes were observed at a given voltage, yielding conductances of 20, 40, 60, and 80 pS with 50 mM Ca as the current carrier. Thus, the cerebellar InsP3-gated Ca channel exhibits four conductance levels that are multiples of a unit conductance step. Moreover, examination of the single-channel records showed both openings directly to each of the current levels and rapid transitions between current levels. These four conductance steps may reflect the interaction among the four InsP3 receptors thought to comprise the InsP3-gated Ca channel in these tissues. Examination of the InsP3 dependence of channel openings and Ca release from vesicles, however, yielded Hill coefficients of 1-1.3. Thus, we hypothesize that it takes only one molecule of InsP3 to open the channel. The observation that the conductance of the InsP3-gated Ca channel assumes four levels that are multiples of a unit conductance suggests that the number of interacting InsP3 receptors in one complex can vary from one to four and supports the hypothesis that the channel is a tetramer.

Conductance of alkanedithiol single-molecule junctions: a molecular dynamics study.

Abstract: We study formation and conductance of alkanedithiol junctions using density functional based molecular dynamics. The formation involves straightening of the molecule, migration of thiol end-groups, and pulling out Au atoms. Plateaus are found in the low-bias conductance traces which decrease by 1 order of magnitude when gauche defects are present. We further show that the inelastic electron tunneling spectra depend on the junction geometry. In particular, our simulations suggest ways to identify gauche defects.

Enhancing and tuning phonon transport at vibrationally mismatched solid-solid interfaces

Abstract: The thermal conductance of interfaces plays a major role in defining the thermal properties of nanostructured materials in which heat transfer is predominantly phonon mediated. Ongoing research has improved the understanding of factors that govern interfacial phonon transport as well as the ability to predict thermal interface conductance. However, despite this progress, the ability to control interface conductance remains a major challenge. In this manuscript, we present a method to enhance and tune thermal interface conductance at vibrationally mismatched solid-solid interfaces. Enhancement is achieved through the insertion of an interfacial film with mediating vibrational properties, such that the vibrational mismatch at the interface is bridged, and consequently, the total interface conductance is enhanced. This phenomena is explored using nonequilibrium molecular dynamics simulations, where the effects of altering the interfacial film thickness, vibrational spectrum, and the temperature of the system are investigated. A systematic study of these pertinent design parameters explores the ability to enhance and tune phonon transport at both ideal (sharp) and nonideal (compositionally disordered) interfaces. Results show that interface conductance can be broadly enhanced by up to 53% in comparison to the vibrationally mismatched baseline interface. Additionally, we find that compositional disorder at an interface does not imply a deterministic change in interface conductance, but instead, that the influence of compositional disorder depends on the characteristics of the disordered region itself. These results, in contrast to macroscopic thermal transport theory, imply that it is possible to increase thermal conductance associated with interface scattering by adding more material along the direction of heat flux.