1,994 research outputs found
Spin Accumulation in Diffusive Conductors with Rashba and Dresselhaus Spin-Orbit Interaction
We calculate the electrically induced spin accumulation in diffusive systems
due to both Rashba (with strength and Dresselhaus (with strength
spin-orbit interaction. Using a diffusion equation approach we find
that magnetoelectric effects disappear and that there is thus no spin
accumulation when both interactions have the same strength, .
In thermodynamically large systems, the finite spin accumulation predicted by
Chaplik, Entin and Magarill, [Physica E {\bf 13}, 744 (2002)] and by Trushin
and Schliemann [Phys. Rev. B {\bf 75}, 155323 (2007)] is recovered an
infinitesimally small distance away from the singular point .
We show however that the singularity is broadened and that the suppression of
spin accumulation becomes physically relevant (i) in finite-sized systems of
size , (ii) in the presence of a cubic Dresselhaus interaction of strength
, or (iii) for finite frequency measurements. We obtain the parametric
range over which the magnetoelectric effect is suppressed in these three
instances as (i) , (ii), and (iii) |\alpha|-|\beta| \lesssiM
\sqrt{\omega/m p_{\rm F}\ell} with the elastic mean free path and
the Fermi momentum. We attribute the absence of spin accumulation
close to to the underlying U (1) symmetry. We illustrate and
confirm our predictions numerically
Extracting current-induced spins: spin boundary conditions at narrow Hall contacts
We consider the possibility to extract spins that are generated by an
electric current in a two-dimensional electron gas with Rashba-Dresselhaus
spin-orbit interaction (R2DEG) in the Hall geometry. To this end, we discuss
boundary conditions for the spin accumulations between a spin-orbit coupled
region and contact without spin-orbit coupling, i.e. a normal two-dimensional
electron gas (2DEG). We demonstrate that in contrast to contacts that extend
along the whole sample, a spin accumulation can diffuse into the normal region
through finite contacts and detected by e.g. ferromagnets. For an
impedance-matched narrow contact the spin accumulation in the 2DEG is equal to
the current induced spin accumulation in the bulk of R2DEG up to a
geometry-dependent numerical factor.Comment: 18 pages, 7 figures, submitted to NJP focus issue on Spintronic
Oxalate-Induced Damage to Renal Tubular Cells
Our own studies and those of others have shown that the incidence of calcium oxalate stones and plaques is markedly increased by nephrotoxins. The possible role of oxalate as a nephrotoxin has not been fully appreciated. However, recent studies in experimental animals and in cultured cells support this possibility. The results of these studies led us to hypothesize that hyperoxaluria promotes stone formation in several ways: by providing a substrate for the formation of the most common form of renal stones, calcium oxalate stones, and by inducing damage to renal epithelial cells. Damaged cells in turn would produce an environment favorable for crystal retention and provide membranous debris that promotes crystal nucleation, aggregation and adherence. The present report summarizes evidence for oxalate nephrotoxicity and discusses the potential importance of oxalate toxicity in the pathogenesis of stone disease
Baryon stopping and strange baryon/antibaryon production at SPS energies
The amount of proton stopping in central Pb+Pb collisions from 20-160 AGeV as
well as hyperon and antihyperon rapidity distributions are calculated within
the UrQMD model in comparison to experimental data at 40, 80 and 160 AGeV taken
recently from the NA49 collaboration. Furthermore, the amount of baryon
stopping at 160 AGeV for Pb+Pb collisions is studied as a function of
centrality in comparison to the NA49 data. We find that the strange baryon
yield is reasonably described for central collisions, however, the rapidity
distributions are somewhat more narrow than the data. Moreover, the
experimental antihyperon rapidity distributions at 40, 80 and 160 AGeV are
underestimated by up to factors of 3 - depending on the annihilation cross
section employed - which might be addressed to missing multi-meson fusion
channels in the UrQMD model.Comment: 18 pages, including 7 eps figures, to be published in Phys. Rev.
Accumulation of Self-Reactive Naive and Memory B Cell Reveals Sequential Defects in B Cell Tolerance Checkpoints in Sjogren's Syndrome
This work was funded by grants number 18237 and 20089 from Arthritis Research UK (http://www.arthritisresearchuk.org) to MB and the William Harvey Research Foundation. EC was recipient of short-term travel fellowships from EMBO (ASTF 318-2010) and EFIS-IL
Nonequilibrium models of relativistic heavy-ion collisions
To be published in J. Phys. G - Proceedings of SQM 2004 : We review the results from the various hydrodynamical and transport models on the collective flow observables from AGS to RHIC energies. A critical discussion of the present status of the CERN experiments on hadron collective flow is given. We emphasize the importance of the flow excitation function from 1 to 50 A.GeV: here the hydrodynamic model has predicted the collapse of the v2-flow ~ 10 A.GeV; at 40 A.GeV it has been recently observed by the NA49 collaboration. Since hadronic rescattering models predict much larger flow than observed at this energy we interpret this observation as evidence for a first order phase transition at high baryon density r b. Moreover, the connection of the elliptic flow v2 to jet suppression is examined. It is proven experimentally that the collective flow is not faked by minijet fragmentation. Additionally, detailed transport studies show that the away-side jet suppression can only partially (< 50%) be due to hadronic rescattering. Furthermore, the change in sign of v1, v2 closer to beam rapidity is related to the occurence of a high density first order phase transition in the RHIC data at 62.5, 130 and 200 A.GeV
Parallelization of Kinetic Theory Simulations
Numerical studies of shock waves in large scale systems via kinetic
simulations with millions of particles are too computationally demanding to be
processed in serial. In this work we focus on optimizing the parallel
performance of a kinetic Monte Carlo code for astrophysical simulations such as
core-collapse supernovae. Our goal is to attain a flexible program that scales
well with the architecture of modern supercomputers. This approach requires a
hybrid model of programming that combines a message passing interface (MPI)
with a multithreading model (OpenMP) in C++. We report on our approach to
implement the hybrid design into the kinetic code and show first results which
demonstrate a significant gain in performance when many processors are applied.Comment: 10 pages, 3 figures, conference proceeding
Zettawatt-Exawatt Lasers and Their Applications in Ultrastrong-Field Physics: High Energy Front
Since its birth, the laser has been extraordinarily effective in the study
and applications of laser-matter interaction at the atomic and molecular level
and in the nonlinear optics of the bound electron. In its early life, the laser
was associated with the physics of electron volts and of the chemical bond.
Over the past fifteen years, however, we have seen a surge in our ability to
produce high intensities, five to six orders of magnitude higher than was
possible before. At these intensities, particles, electrons and protons,
acquire kinetic energy in the mega-electron-volt range through interaction with
intense laser fields. This opens a new age for the laser, the age of nonlinear
relativistic optics coupling even with nuclear physics. We suggest a path to
reach an extremely high-intensity level W/cm in the coming
decade, much beyond the current and near future intensity regime W/cm, taking advantage of the megajoule laser facilities. Such a laser at
extreme high intensity could accelerate particles to frontiers of high energy,
tera-electron-volt and peta-electron-volt, and would become a tool of
fundamental physics encompassing particle physics, gravitational physics,
nonlinear field theory, ultrahigh-pressure physics, astrophysics, and
cosmology. We focus our attention on high-energy applications in particular and
the possibility of merged reinforcement of high-energy physics and ultraintense
laser.Comment: 25 pages. 1 figur
Triple coalescence singularity in a dynamical atomic process
We show that the high energy limit for the amplitude of the double electron
capture to the bound state of the Coulomb field of a nucleus with emission of a
single photon is determined by behavior of the wave function in the vicinity of
the singular triple coalescence point.Comment: 3 page
Does the Constitution Provide More Ballot Access Protection for Presidential Elections Than for U.S. House Elections?
Both the U.S. Constitution and The Federalist Papers suggest that voters ought to have more freedom to vote for the candidate of their choice for the U.S. House of Representatives than they do for the President or the U.S. Senate. Yet, strangely, for the last thirty-three years, the U.S. Supreme Court and lower courts have ruled that the Constitution gives voters more freedom to vote for the candidate of their choice in presidential elections than in congressional elections. Also, state legislatures, which have been writing ballot access laws since 1888, have passed laws that make it easier for minor-party and independent candidates to get on the ballot for President than for the U.S. House. As a result, voters in virtually every state invariably have far more choices on their general election ballots for the President than they do for the House. This Article argues that the right of a voter to vote for someone other than a Democrat or a Republican for the House is just as important as a voter’s right to do so for President, and that courts should grant more ballot access protection to minor-party and independent candidates for the House
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