782 research outputs found
On the Conductance Sum Rule for the Hierarchical Edge States of the Fractional Quantum Hall Effect
The conductance sum rule for the hierarchical edge channel currents of a
Fractional Quantum Hall Effect state is derived analytically within the
Haldane-Halperin hierarchy scheme. We provide also an intuitive interpretation
for the hierarchical drift velocities of the edge excitations.Comment: 11 pages, no figure, Revtex 3.0, IC/93/329, ASITP-93-5
Resources and student achievement – evidence from a Swedish policy reform
This paper utilizes a policy change to estimate the effect of teacher density on student performance. We find that an increase in teacher density has a positive effect on student achievement. The baseline estimate – obtained by using the grade point average as the outcome variable – implies that resource increases corresponding to the class-size reduction in the STAR-experiment (i.e., a reduction of 7 students) improves performance by 2.6 percentile ranks (or 0.08 standard deviations). When we use test score data for men, potentially a more objective measure of student performance, the effect of resources appears to be twice the size of the baseline estimate.Student performance; teacher/student ratio; policy reform; differences-in-differences
Phase Behavior of Columnar DNA Assemblies
The pair interaction between two stiff parallel linear DNA molecules depends
not only on the distance between their axes but on their azimuthal orientation.
The positional and orientational order in columnar B-DNA assemblies in solution
is investigated, based on the DNA-DNA electrostatic pair potential that takes
into account DNA helical symmetry and the amount and distribution of adsorbed
counterions. A phase diagram obtained by lattice sum calculations predicts a
variety of positionally and azimuthally ordered phases and bundling transitions
strongly depending on the counterion adsorption patterns.Comment: 4 pages, 3 figures, submitted to PR
A twist in chiral interaction between biological helices
Using an exact solution for the pair interaction potential, we show that
long, rigid, chiral molecules with helical surface charge patterns have a
preferential interaxial angle ~((RH)^1/2)/L, where L is the length of the
molecules, R is the closest distance between their axes, and H is the helical
pitch. Estimates based on this formula suggest a solution for the puzzle of
small interaxial angles in a-helix bundles and in cholesteric phases of DNA.Comment: 7 pages, 2 figures, PDF file onl
ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions
We investigate ac Josephson effect in the resonant tunneling through
mesoscopic superconducting junctions. In the presence of microwave irradiation,
we show that the trajectory of multiple Andreev reflections can be closed by
emitting or absorbing photons. Consequently, photon-assisted Andreev states are
formed and play the role of carrying supercurrent. On the Shapiro steps, dc
component appears when the resonant level is near a series of positions with
spacing of half of the microwave frequency. Analytical result is derived in the
limit of infinite superconducting gap, based on which new features of ac
Josephson effect are revealed.Comment: 11 pages, 3 figure
Intense duskside lower band chorus waves observed by Van Allen Probes: Generation and potential acceleration effect on radiation belt electrons
Abstract Local acceleration driven by whistler mode chorus waves largely accounts for the enhancement of radiation belt relativistic electron fluxes, whose favored region is usually considered to be the plasmatrough with magnetic local time approximately from midnight through dawn to noon. On 2 October 2013, the Van Allen Probes recorded a rarely reported event of intense duskside lower band chorus waves (with power spectral density up to 10-3nT 2/Hz) in the low-latitude region outside of L=5. Such chorus waves are found to be generated by the substorm-injected anisotropic suprathermal electrons and have a potentially strong acceleration effect on the radiation belt energetic electrons. This event study demonstrates the possibility of broader spatial regions with effective electron acceleration by chorus waves than previously expected. For such intense duskside chorus waves, the occurrence probability, the preferential excitation conditions, the time duration, and the accurate contribution to the long-term evolution of radiation belt electron fluxes may need further investigations in future
Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract
Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes, and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons
Weakly Nonlinear AC Response: Theory and Application
We report a microscopic and general theoretical formalism for electrical
response which is appropriate for both DC and AC weakly nonlinear quantum
transport. The formalism emphasizes the electron-electron interaction and
maintains current conservation and gauge invariance. It makes a formal
connection between linear response and scattering matrix theory at the weakly
nonlinear level. We derive the dynamic conductance and predict the
nonlinear-nonequilibrium charge distribution. The definition of a nonlinear
capacitance leads to a remarkable scaling relation which can be measured to
give microscopic information about a conductor
Comparative Plasma Lipidome between Human and Cynomolgus Monkey: Are Plasma Polar Lipids Good Biomarkers for Diabetic Monkeys?
10.1371/journal.pone.0019731PLoS ONE65
Scattering Matrix Theory For Nonlinear Transport
We report a scattering matrix theory for dynamic and nonlinear transport in
coherent mesoscopic conductors. In general this theory allows predictions of
low frequency linear dynamic conductance, as well as weakly nonlinear DC
conductance. It satisfies the conditions of gauge invariance and electric
current conservation, and can be put into a form suitable for numerical
computation. Using this theory we examine the third order weakly nonlinear DC
conductance of a tunneling diode
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