39,574 research outputs found
Opposite spin accumulations on the transverse edges by the confining potential
We show that the spin-orbit interaction induced by the boundary confining
potential causes opposite spin accumulations on the transverse edges in a zonal
two-dimensional electron gas in the presence of external longitudinal electric
field. While the bias is reversed, the spin polarized direction is also
reversed. The intensity of the spin accumulation is proportional to the bias
voltage. In contrast to the bulk extrinsic and intrinsic spin Hall effects, the
spin accumulation by the confining potential is almost unaffected by impurity
and survives even in strong disorder. The result provides a new mechanism to
explain the recent experimental data.Comment: 5 pages, 6 figure
Nonlinear dynamics of self-sustained supersonic reaction waves: Fickett's detonation analogue
The present study investigates the spatio-temporal variability in the
dynamics of self-sustained supersonic reaction waves propagating through an
excitable medium. The model is an extension of Fickett's detonation model with
a state dependent energy addition term. Stable and pulsating supersonic waves
are predicted. With increasing sensitivity of the reaction rate, the reaction
wave transits from steady propagation to stable limit cycles and eventually to
chaos through the classical Feigenbaum route. The physical pulsation mechanism
is explained by the coherence between internal wave motion and energy release.
The results obtained clarify the physical origin of detonation wave instability
in chemical detonations previously observed experimentally.Comment: 4 pages, 3 figure
Optical properties of Si/Si0.87Ge0.13 multiple quantum well wires
Nanometer-scale wires cut into a Si/Si0.87Ge0.13 multiple quantum well structure were fabricated and characterized by using photoluminescence and photoreflectance at temperatures between 4 and 20 K. It was found that, in addition to a low-energy broadband emission at around 0.8 eV and other features normally observable in photoluminescence measurements, fabrication process induced strain relaxation and enhanced electron-hole droplets emission together with a new feature at 1.131 eV at 4 K were observed. The latter was further identified as a transition related to impurities located at the Si/Si0.87Ge0.13 heterointerfaces
Deranged calcium signaling and neurodegeneration in spinocerebellar ataxia type 3
Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is
an autosomal-dominant neurodegenerative disorder caused by a polyglutamine
expansion in ataxin-3 (SCA3, MJD1) protein. In biochemical experiments we demonstrate
that mutant SCA3exp specifically associated with the type 1 inositol 1,4,5-trisphosphate
receptor (InsP3R1), an intracellular calcium (Ca2+) release channel. In electrophysiological
and Ca2+ imaging experiments we show that InsP3R1 are sensitized to activation by InsP3
in the presence of mutant SCA3exp. We found that feeding SCA3-YAC-84Q transgenic
mice with dantrolene, a clinically relevant stabilizer of intracellular Ca2+ signaling,
improved their motor performance and prevented neuronal cells loss in pontine nuclei
and substantia nigra regions. Our results indicate that deranged Ca2+ signaling may play
an important role in SCA3 pathology and that Ca2+ signaling stabilizers such as
dantrolene may be considered as potential therapeutic drugs for treatment of SCA3
patients
A Lagrangian kinetic model for collisionless magnetic reconnection
A new fully kinetic system is proposed for modeling collisionless magnetic
reconnection. The formulation relies on fundamental principles in Lagrangian
dynamics, in which the inertia of the electron mean flow is neglected in the
expression of the Lagrangian, rather then enforcing a zero electron mass in the
equations of motion. This is done upon splitting the electron velocity into its
mean and fluctuating parts, so that the latter naturally produce the
corresponding pressure tensor. The model exhibits a new Coriolis force term,
which emerges from a change of frame in the electron dynamics. Then, if the
electron heat flux is neglected, the strong electron magnetization limit yields
a hybrid model, in which the electron pressure tensor is frozen into the
electron mean velocity.Comment: 15 pages, no figures. To Appear in Plasma Phys. Control. Fusio
How familiarity warps representation in the face space
Recognition of familiar as compared to unfamiliar faces is robust and resistant to marked image distortion or degradation. Here we tested the flexibility of familiar face recognition with a morphing paradigm where the appearance of a personally familiar face was mixed with the appearance of a stranger (Experiment 1) and the appearance of one's own face with the appearance of a familiar face and the appearance of a stranger (Experiment 2). The aim of the two experiments was to assess how categorical boundaries for recognition of identity are affected by familiarity. We found a narrower categorical boundary for the identity of personally familiar faces when they were mixed with unfamiliar identities as compared to the control condition, in which the appearance of two unfamiliar faces was mixed. Our results suggest that familiarity warps the representational geometry of face space, amplifying perceptual distances for small changes in the appearance of familiar faces that are inconsistent with the structural features that define their identities
Correlated Quantum Transport of Density Wave Electrons
Recently observed Aharonov-Bohm quantum interference of period h/2e in charge
density wave rings strongly suggest that correlated density wave electron
transport is a cooperative quantum phenomenon. The picture discussed here
posits that quantum solitons nucleate and transport current above a Coulomb
blockade threshold field. We propose a field-dependent tunneling matrix element
and use the Schrodinger equation, viewed as an emergent classical equation as
in Feynman's treatment of Josephson tunneling, to compute the evolving
macrostate amplitudes, finding excellent quantitative agreement with voltage
oscillations and current-voltage characteristics in NbSe3. A proposed phase
diagram shows the conditions favoring soliton nucleation versus classical
depinning. (Published in Phys. Rev. Lett. 108, 036404 (2012).)Comment: 9 pages, 4 figures, (5 pages & 3 figures for main article), includes
Supplemental Material with 1 figure. Published version: Physical Review
Letters, vol. 108, p. 036404 (2012
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