Conductance

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

Parametric analysis of nightside conductance effects on inner magnetospheric dynamics for the 17 April 2002 storm

Abstract: [1] Numerous simulations were conducted in order to quantify the influence of nightside conductance morphology and intensity on the storm-time ring current and plasmasphere. The study focused on the moderate magnetic storm of 17 April 2002. The simulation results were compared against measurements of the ring current and plasmasphere in order to assess the accuracy as a function of conductance parameter setting. In particular, three data sets were used: Dst*, plasmapause location as extracted from IMAGE EUV snapshots, and IMAGE HENA flux observations for the 39–60 keV energy range. While no single simulation conducted for this study proved itself to be the best overall match to the selected data sets, many things were learned from the simulations. The most important scientific finding is that there is an optimal conductance level for maximal ring current intensity. Too little conductance leads to large shielding potentials that effectively inhibit ring current growth, while too much conductance leads to continual flow-through of the hot ions with no significant hot ion accumulation in the inner magnetosphere. It was found that the poleward shift of the high conductance region of the auroral oval was the most important factor affecting the data-model comparisons. The peak intensity of the auroral oval conductance was also determined to be a significant factor affecting model accuracy. Tilting the dawnside location of the oval equatorward with respect to its duskside latitude had little effect on the results, as did the setting for the uniformly applied baseline conductance. The high-latitude boundary condition for the potential solution was also found to have little influence on the results.

Quantum Hall Conductance of Two-Terminal Graphene Devices

Abstract: Measurement and theory of the two-terminal conductance of monolayer and bilayer graphene in the quantum Hall regime are compared. We examine features of conductance as a function of gate voltage that allow monolayer, bilayer, and gapped samples to be distinguished. In particular, we analyze the distortions of quantum Hall plateaus and the conductance peaks and dips at the charge-neutrality point, which can be used to identify the incompressible densities. These results are compared to recent theory and possible origins of the discrepancy are discussed.

Three-dimensional percolation effect on electrical conductivity in films of metal nanoparticles linked by organic molecules

Abstract: We study experimentally and theoretically the electrical conductivity of films made of gold nanoparticles linked by alkanedithiol molecules. The dependence of the conductivity on the length of the alkanedithiol molecule and on the thickness of the nanoparticle films at room temperature is investigated. We describe theoretically conductance between adjacent metal nanoparticles in terms of single electron tunneling along the linker molecules. Due to variations in the separation gaps between neighboring nanoparticles a film can be approximated by a network of widely varying tunnel conductances and the film conductivity can be described in terms of percolation theory. We demonstrate that the expected exponential decrease of the conductivity with increasing length of linker molecules is weakened by the presence of high conductance percolation pathways and we show that due to three-dimensional current percolation the conductivity of the nanoparticle films becomes film thickness dependent.

Electrophoretic Force on a Protein-Coated DNA Molecule in a Solid-State Nanopore

Abstract: Using solid-state nanopores with optical tweezers, we perform force spectroscopy on DNA molecules that are coated with RecA proteins. We observe that the electrophoretic force is 2−4 times larger for RecA-DNA filaments than for uncoated DNA molecules and that this force increases at lower salt concentrations. The data demonstrate the efficacy of solid-state nanopores for locally probing the forces on DNA-bound proteins. Our results are described quantitatively by a model that treats the electrophoretic and hydrodynamic forces. The conductance steps that occur when RecA-DNA enters the nanopore change from conductance decreases at high salt to conductance increases at low salt, which allows the apparent charge of the RecA-DNA filament to be extracted. The combination of conductance measurements with local force spectroscopy increases the potential for future solid-state nanopore screening devices.

Numerical study of transport properties in continuum percolation

Abstract: The authors present numerical simulations of AC conductance for a random resistor-capacitor network. The conductance obeys a probability density function p(g) varies as g- alpha (0( alpha (1). They use a highly efficient propagation algorithm to calculate the effective conductance of a long strip of a lattice. At low frequencies, they find that for the concentration p of conducting bonds less than the percolation threshold pc, the imaginary part of conductance is proportional to frequency Im(geff) approximately= omega and the real part of conductance shows an anomalous frequency dependence Re(geff) approximately= omega 2- alpha . The results of simulations in such a continuum system are in agreement with the predictions of the effective medium and the Maxwell-Garnett approximation. They also calculate the non-universal DC conductivity exponents in continuum percolation; the results are consistent with earlier theoretical predictions and numerical calculations.