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Conductance
About: Conductance is a research topic. Over the lifetime, 8088 publications have been published within this topic receiving 235961 citations.
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TL;DR: The results indicate that the long initial delay in NA action occurs prior to or during generation of InsP3, and suggests that this interaction may be important in regulating oscillatory responses of [Ca2+] during hormonal stimulation of guinea‐pig hepatocytes.
Abstract: 1. Guinea-pig hepatocytes respond to noradrenaline (NA, 5-10 microM) with a large membrane conductance increase to K+ and Cl-. The response has a long initial delay (range 2-30 s). Following the delay, the K+ conductance (studied in Cl(-)-free solutions) rises quickly to a peak in 1-2 s and is maintained in the continued presence of NA, though often with superimposed oscillations of conductance. The roles of intracellular Ca2+ and D-myo-inositol 1,4,5-trisphosphate (InsP3) in this complex response have been investigated by rapid photolytic release of intracellular Ca2+ (from Nitr5-Ca2+ buffers) or InsP3 from 'caged' InsP3. 2. A rapid increase of intracellular [Ca2+] produced an immediate membrane conductance increase which rose approximately exponentially to a new steady level, consistent with a direct activation of Ca2(+)-dependent ion channels. 3. Following a pulse of InsP3, conductance rose after a brief delay (range 70-1500 ms) which was shortest at high [InsP3] or if the initial cytosolic [Ca2+] had been raised above normal levels. The maximum conductance produced by InsP3 was similar in each cell to the peak recorded with NA and could be evoked by InsP3 concentrations of 0.5-1 microM. 4. The rates of rise of conductance increased with InsP3 concentration in the range 0.25-12.5 microM (range 10-90%, rise times 90-1000 ms), indicating that InsP3-evoked Ca2(+)-efflux from stores increases with InsP3 concentration in this range. 5. Photochemically released InsP3 and Ca2+ activate at physiological concentrations the same membrane conductances as NA. The results indicate that the long initial delay in NA action occurs prior to or during generation of InsP3. The mechanism of the delay and the subsequent apparently all-or-none conductance increase during NA action are discussed in terms of the high co-operativity in InsP3 and Ca2+ actions and an additional positive feedback step. 6. Evidence was found of a negative interaction between [Ca2+] and InsP3-evoked Ca2+ release. The time course of the recovery of InsP3-evoked Ca2+ release following a rise of cytosolic [Ca2+] suggests that this interaction may be important in regulating oscillatory responses of [Ca2+] during hormonal stimulation of guinea-pig hepatocytes.
80 citations
TL;DR: In this article, the authors theoretically study the temperature and tunnel coupling dependence of the tunneling conductance in a one-dimensional semiconductor nanowire proximitized by a nearby superconductor.
Abstract: A one-dimensional semiconductor nanowire proximitized by a nearby superconductor may become a topological superconductor hosting localized Majorana zero modes at the two wire ends in the presence of spin-orbit coupling and Zeeman spin splitting (arising from an external magnetic field). The hallmark of the presence of such Majorana zero modes is the appearance of a zero-temperature quantized zero-bias conductance peak in the tunneling spectroscopy of the Majorana nanowire. We theoretically study the temperature and the tunnel coupling dependence of the tunneling conductance in such nanowires to understand possible intrinsic deviations from the predicted conductance quantization. We find that the full temperature and the tunneling transmission dependence of the tunnel conductance does not obey any simple scaling relation, and estimating the zero-temperature conductance from finite-temperature and finite-tunnel-broadening tunneling data is difficult in general. A scaling relation, however, does hold at the extreme weak-tunneling low-temperature limit where the conductance depends only on the dimensionless ratio of the temperature and tunnel broadening. We also consider the tunneling contributions from nontopological Andreev bound states which may produce almost-zero-bias conductance peaks, which are not easy to distinguish from the Majorana-induced zero-bias peaks, finding that the nontopological almost-zero-modes associated with Andreev bound states manifest similar temperature and transmission dependence as the topological Majorana modes. We comment on the Zeeman splitting dependence of the zero-bias conductance peak for finite temperature and tunnel coupling.
80 citations
TL;DR: Differences between conductance steps for noble and transition metals are interpreted as being due to the d orbitals that, in transition metals, provide new channels to the electron conductance.
Abstract: Conductance steps for atomic point contacts of Au, Ni, and Pt have been measured. Jump-to-contact and jump-to-tunnel processes have been identified and their conductances measured. Differences between conductance steps for noble and transition metals are interpreted as being due to the d orbitals that, in transition metals, provide new channels to the electron conductance. This interpretation is supported by a theoretical analysis, which shows good agreement with the experimental data. @S0163-1829~96!03323-1#
79 citations
TL;DR: In this paper, the authors studied the conductance of disordered graphene superlattices with short-range structural correlations and showed that the quasiparticle that approaches the barrier interface almost perpendicularly transmits through the system.
Abstract: We study the conductance of disordered graphene superlattices with short-range structural correlations. The system consists of electron- and hole-doped graphenes of various thicknesses, which fluctuate randomly around their mean value. The effect of the randomness on the probability of transmission through the system of various sizes is studied. We show that in a disordered superlattice the quasiparticle that approaches the barrier interface almost perpendicularly transmits through the system. The conductivity of the finite-size system is computed and shown that the conductance vanishes when the sample size becomes very large, whereas for some specific structures the conductance tends to a nonzero value in the thermodynamic limit.
79 citations
TL;DR: In this article, the authors studied the electron transport through a graphene nanoribbon-superconductor junction and obtained the expressions of the current, conductance, normal tunneling coefficient and Andreev reflection coefficient.
Abstract: We study the electron transport through a graphene nanoribbon–superconductor junction. Both zigzag and armchair edge graphene nanoribbons are considered, and the effects of the magnetic field and disorder on the transport property are investigated. By using the tight-binding model and the non-equilibrium Green's function method, the expressions of the current, conductance, normal tunneling coefficient and Andreev reflection coefficient are obtained. For a clean system and at zero magnetic field, the linear conductance increases approximately in a linear fashion with the on-site energy. In the presence of a magnetic field and a moderate disorder, the linear conductance exhibits plateau structures for both armchair and zigzag edges. The plateau values increase with the width of the graphene ribbon. With a wide sample width, a saturated plateau value of |ν|e2/h emerges at the filling factor ν. For a small filling factor, the conductance can reach the saturated value at a small width, but for a high filling factor it requires to have a quite wide sample width to reach the saturated value. In particular, the Andreev reflection coefficient is always at 0.5 after reaching the saturated value, independent of any system parameters. In addition, we also consider the finite bias case, in which the Andreev reflection coefficient and normal tunneling coefficient are studied.
79 citations