Topic
Conductance
About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: Variation of the low threshold calcium conductance, gCa(LVA), shows that the ability to generate low-threshold spike bursts critically depends on the density of this conductance.
Abstract: 1. We have developed compartmental models of guinea-pig medial vestibular nuclei neurons (MVNns). The structure and the parameters of the model cells were chosen to reproduce the responses of type A and type B MVNns as described in electrophysiological recordings. 2. Dynamics of membrane potentials were modeled in 46 and 61 branched electrical compartments for Type A and Type B MVNns, respectively. Each compartment was allowed to contain up to nine active ionic conductances: a fast inactivating sodium conductance, gNa, a persistent sodium conductance, gNap, a low-voltage activated calcium conductance, gCa(LVA), a high-voltage activated calcium conductance, gCa(HVA), a fast-voltage activated potassium conductance, gK(fast), a slowly relaxing voltage activated potassium conductance, gK(slow), a fast transient potassium channel, gK(A), a slowly relaxing mixed sodium-potassium conductance activating at hyperpolarized membrane potentials, gH, and a calcium-activated potassium conductance gK(AHP). The kinetics of these conductances were derived from voltage-clamp studies in a variety of preparations. Kinetic parameters as well as distribution and density of ion channels were adjusted to yield the reported electrophysiological behavior of medial vestibular neurons. 3. Dynamics of intracellular free [Ca2]i were modeled by inclusion of a Ca(2+)-pump and a Na(+)-Ca2+ exchanger for extrusion of calcium. Diffusion of calcium between submembraneous sites and the center of an electrical compartment was modeled by 25 and 6 shell-like chemical compartments for the cell body and the proximal dendrites, respectively. These compartments also contained binding sites for calcium. 4. The dynamics of active conductances were the same in both models except for gK(fast). This was necessary to achieve the different shape of spikes and of spike afterhyperpolarization in type A and type B MVNns. An intermediate depolarizing component of the spike afterhyperpolarization of type B neurons in part depended on their dendritic cable structure. 5. Variation of the low threshold calcium conductance, gCa(LVA), shows that the ability to generate low-threshold spike bursts critically depends on the density of this conductance. Sodium plateaus were generated when increasing the density of gNap. 6. The type B model cell generated rhythmic bursts of spiking activity under simulation of two distinct experimental conditions.(ABSTRACT TRUNCATED AT 400 WORDS)
87 citations
TL;DR: This work explains the sensitivity of the porphyrin conductance with the metal center via a detailed and quantitative portrait of the interface electronic structure and provides a new framework for understanding transport quantitatively in complex junctions involving molecules with localized d states of relevance to light harvesting and energy conversion.
Abstract: Using scanning tunneling microscope break-junction experiments and a new first-principles approach to conductance calculations, we report and explain low-bias charge transport behavior of four types of metal–porphyrin–gold molecular junctions. A nonequilibrium Green’s function approach based on self-energy corrected density functional theory and optimally tuned range-separated hybrid functionals is developed and used to understand experimental trends quantitatively. Importantly, due to the localized d states of the porphyrin molecules, hybrid functionals are essential for explaining measurements; standard semilocal functionals yield qualitatively incorrect results. Comparing directly with experiments, we show that the conductance can change by nearly a factor of 2 when different metal cations are used, counter to trends expected from gas-phase ionization energies which are relatively unchanged with the metal center. Our work explains the sensitivity of the porphyrin conductance with the metal center via a...
87 citations
TL;DR: The thermopower has little correlation with the conductance, but it decreases with the transition voltage, which is consistent with a theory based on Landauer's formula and shows that the thermopOWER provides valuable information about the relative alignment between the molecular energy levels and the electrodes' Fermi energy level.
Abstract: We have measured the thermopower as well as other important charge transport quantities, including conductance, current–voltage characteristics, and transition voltage of single molecules. The thermopower has little correlation with the conductance, but it decreases with the transition voltage, which is consistent with a theory based on Landauer’s formula. Since the transition voltage reflects the molecular energy level alignment, our finding also shows that the thermopower provides valuable information about the relative alignment between the molecular energy levels and the electrodes’ Fermi energy level.
86 citations
TL;DR: It is shown that by gating the pyridine-capped molecules it is possible to make the NDR disappear and dramatically modify the I-V characteristics and the length dependence, which suggests that these molecules could be ideal molecular wires for sub-10 nm circuitry.
Abstract: We study the electronic and transport properties of two novel molecular wires made of atomic chains of carbon atoms (polyynes) capped with either benzene-thiols or pyridines. While both molecules are structurally similar, the electrical conductance of benzene-thiol-capped chains attached to gold electrodes is found to be much higher than that of pyridine-capped chains. We predict that the conductance is almost independent of molecular length, which suggests that these molecules could be ideal molecular wires for sub-10 nm circuitry. Both systems exhibit negative differential resistance (NDR) but its origin and characteristics depend on the type of molecule. We find a novel type of NDR mechanism produced by the movement of the lowest unoccupied molecular orbital (LUMO) resonance with bias. We also show that by gating the pyridine-capped molecules it is possible to make the NDR disappear and dramatically modify the I-V characteristics and the length dependence.
86 citations
TL;DR: In this paper, the relationship between the surface potential and the gate voltage, which determines the gap-state density, has been deduced according to the incremental method, already proposed by Suzuki et al., and a new method is based on the temperature dependence of the derivative of the field-effect conductance with respect to gate voltage.
Abstract: The field-effect conductance has been used in two distinct ways to determine the gap-state density in polycrystalline silicon. The relationship between the surface potential and the gate voltage, which determines the gap-state density, has been deduced according to the incremental method, already proposed by Suzuki et al., and a new method. The new method is based on the temperature dependence of the derivative of the field-effect conductance with respect to the gate voltage. The results from the two methods are in good agreement and show a rapidly increasing gap-state density in the upper half of the gap. The temperature analysis of the field-effect conductance indicates that the position of the Fermi level is temperature dependent. The contribution to this dependence from the statistical shift has been determined.
86 citations