14,239 research outputs found
Exact spin dynamics of the 1/r^2 supersymmetric t-J model in a magnetic field
The dynamical spin structure factor S^{zz}(Q,omega) in the small momentum
region is derived analytically for the one-dimensional supersymmetric t-J model
with 1/r^2 interaction. Strong spin-charge separation is found in the spin
dynamics. The structure factor S^{zz}(Q,omega) with a given spin polarization
does not depend on the electron density in the small momentum region. In the
thermodynamic limit, only two spinons and one antispinon (magnon) contribute to
S^{zz}(Q,omega). These results are derived via solution of the SU(2,1)
Sutherland model in the strong coupling limit.Comment: 20 pages, 8 figures. Accepted for publication in J.Phys.
From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations
The underlying plasma composition of relativistic extragalactic jets remains
largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to
reproduce many of the observed macroscopic features of these outflows. The
nonthermal synchrotron emission detected by very long baseline interferometric
(VLBI) arrays, however, is a by-product of the kinetic-scale physics occurring
within the jet, physics that is not modeled directly in most RMHD codes. This
paper attempts to discern the radiative differences between distinct plasma
compositions within relativistic jets using small-scale 3D relativistic
particle-in-cell (PIC) simulations. We generate full Stokes imaging of two PIC
jet simulations, one in which the jet is composed of an electron-proton
(-) plasma (i.e., a normal plasma jet), and the other in which
the jet is composed of an electron-positron (-) plasma (i.e., a
pair plasma jet). We examined the differences in the morphology and intensity
of the linear polarization (LP) and circular polarization (CP) emanating from
these two jet simulations. We find that the fractional level of CP emanating
from the - plasma jet is orders of magnitude larger than the
level emanating from an - plasma jet of a similar speed and
magnetic field strength. In addition, we find that the morphology of both the
linearly and circularly polarized synchrotron emission is distinct between the
two jet compositions. We also demonstrate the importance of slow-light
interpolation and we highlight the effect that a finite light-crossing time has
on the resultant polarization when ray-tracing through relativistic plasma.Comment: 21 pages, 13 figures; accepted for publication in A&
Strong Correlation to Weak Correlation Phase Transition in Bilayer Quantum Hall Systems
At small layer separations, the ground state of a nu=1 bilayer quantum Hall
system exhibits spontaneous interlayer phase coherence and has a
charged-excitation gap E_g. The evolution of this state with increasing layer
separation d has been a matter of controversy. In this letter we report on
small system exact diagonalization calculations which suggest that a single
phase transition, likely of first order, separates coherent incompressible (E_g
>0) states with strong interlayer correlations from incoherent compressible
states with weak interlayer correlations. We find a dependence of the phase
boundary on d and interlayer tunneling amplitude that is in very good agreement
with recent experiments.Comment: 4 pages, 4 figures included, version to appear in Phys. Rev. Let
On the Eigenvalue Density of Real and Complex Wishart Correlation Matrices
Wishart correlation matrices are the standard model for the statistical
analysis of time series. The ensemble averaged eigenvalue density is of
considerable practical and theoretical interest. For complex time series and
correlation matrices, the eigenvalue density is known exactly. In the real
case, however, a fundamental mathematical obstacle made it forbidingly
complicated to obtain exact results. We use the supersymmetry method to fully
circumvent this problem. We present an exact formula for the eigenvalue density
in the real case in terms of twofold integrals and finite sums.Comment: 4 pages, 2 figure
Spin-dependent Seebeck coefficients of Ni_{80}Fe_{20} and Co in nanopillar spin valves
We have experimentally determined the spin-dependent Seebeck coefficient of
permalloy (Ni_{80}Fe_{20}) and cobalt (Co) using nanopillar spin valve devices.
The devices were specifically designed to completely separate heat related
effects from charge related effects. A pure heat current through the nanopillar
spin valve, a stack of two ferromagnetic layers (F) separated by a non-magnetic
layer (N), leads to a thermovoltage proportional to the spin-dependent Seebeck
coefficient S_{S}=S_{\uparrow}-S_{\downarrow} of the ferromagnet, where
S_{\uparrow} and S_{\downarrow} are the Seebeck coefficient for spin-up and
spin-down electrons. By using a three-dimensional finite-element model (3D-FEM)
based on spin-dependent thermoelectric theory, whose input material parameters
were measured in separate devices, we were able to accurately determine a
spin-dependent Seebeck coefficient of -1.8 microvolt/Kelvin and -4.5
microvolt/Kelvin for cobalt and permalloy, respectively corresponding to a
Seebeck coefficient polarization P_{S}=S_{S}/S_{F} of 0.08 and 0.25, where
S_{F} is the Seebeck coefficient of the ferromagnet. The results are in
agreement with earlier theoretical work in Co/Cu multilayers and spin-dependent
Seebeck and spin-dependent Peltier measurements in Ni_{80}Fe_{20}/Cu spin valve
structures
Dependence of the intrinsic spin Hall effect on spin-orbit interaction character
We report on a comparative numerical study of the spin Hall conductivity in
two-dimensions for three different spin-orbit interaction models; the standard
k-linear Rashba model, the k-cubic Rashba model that describes two-dimensional
hole systems, and a modified k-linear Rashba model in which the spin-orbit
coupling strength is energy dependent. Numerical finite-size Kubo formula
results indicate that the spin Hall conductivity of the k-linear Rashba model
vanishes for frequency much smaller than the scattering rate
, with order one relative fluctuations surviving out to large system
sizes. For the k-cubic Rashba model case, the spin Hall conductivity does not
depend noticeably on and is finite in the {\em dc} limit, in
agreement with experiment. For the modified k-linear Rashba model the spin Hall
conductivity is noticeably dependent but approaches a finite
value in the {\em dc} limit. We discuss these results in the light of a
spectral decomposition of the spin Hall conductivity and associated sum rules,
and in relation to a proposed separation of the spin Hall conductivity into
skew-scattering, intrinsic, and interband vertex correction contributions.Comment: 10 pages, 4 figure
Inter-band magnetoplasmons in mono- and bi-layer graphene
Collective excitations spectrum of Dirac electrons in mono and bilayer
graphene in the presence of a uniform magnetic field is investigated.
Analytical results for inter-Landau band plasmon spectrum within the
self-consistent-field approach are obtained. SdH type oscillations that are a
monotonic function of the magnetic field are observed in the plasmon spectrum
of both mono- and bi-layer graphene systems. The results presented are also
compared with those obtained in conventional 2DEG. The chiral nature of the
quasiparticles in mono and bilayer graphene system results in the observation
of and Berry's phase in the SdH- type oscillations in the plasmon
spectrum.Comment: 9 pages, 2 figure
Human papillomavirus E2 regulates SRSF3 (SRp20) to promote capsid protein expression in infected differentiated keratinocytes
The human papillomavirus (HPV) life cycle is tightly linked to differentiation of the infected epithelial cell suggesting a sophisticated interplay between host cell metabolism and virus replication. Previously we demonstrated in differentiated keratinocytes in vitro and in vivo that HPV16 infection caused increased levels of the cellular SR splicing factors (SRSFs) SRSF1 (ASF/SF2), SRSF2 (SC35) and SRSF3 (SRp20). Moreover, the viral E2 transcription and replication factor that is expressed at high levels in differentiating keratinocytes could bind and control activity of the SRSF1 gene promoter. Here we reveal that E2 proteins of HPV16 and HPV31 control expression of SRSFs 1, 2 and 3 in a differentiation-dependent manner. E2 has the greatest trans-activation effect on expression of SRSF3. siRNA depletion experiments in two different models of the HPV16 life cycle (W12E and NIKS16) and one model of the HPV31 life cycle (CIN612-9E) revealed that only SRSF3 contributed significantly to regulation of late events in the virus life cycle. Increased levels of SRSF3 are required for L1 mRNA and capsid protein expression. Capsid protein expression was regulated specifically by SRSF3 and appeared independent of other SRSFs. Taken together these data suggest a significant role of the HPV E2 protein in regulating late events in the HPV life cycle through transcriptional regulation of SRSF3 expression.
IMPORTANCE Human papillomavirus replication is accomplished in concert with differentiation of the infected epithelium. Virus capsid protein expression is confined to the upper epithelial layers so as to avoid immune detection. In this study we demonstrate that the viral E2 transcription factor activates the promoter of the cellular SRSF3 RNA processing factor. SRSF3 is required for expression of the E4Ì‚L1 mRNA and so controls expression of the HPV L1 capsid protein. Thus we reveal a new dimension of virus-host interaction crucial for production of infectious virus. SRSF proteins are known drug targets. Therefore, this study provides an excellent basis for developing strategies to regulate capsid protein production in the infected epithelium and production of new virions
PCV128 RELATIONSHIPS BETWEEN PHYSICAL INACTIVITY AND HEALTH CARE EXPENDITURE AND RESOURCE USE IN PATIENTS WITH PRIMARY HYPERTENSION
Metamaterial 'Gecko Toe': Optically-Controlled Adhesion to Any Surface
On the mesoscopic scale, electromagnetic forces are of fundamental importance
to an enormously diverse range of systems, from optical tweezers to the
adhesion of gecko toes. Here we show that a strong light-driven force may be
generated when a plasmonic metamaterial is illuminated in close proximity to a
dielectric or metal surface. This near-field force can exceed radiation
pressure and Casimir forces to provide an optically controlled adhesion
mechanism mimicking the gecko toe: at illumination intensities of just a few
tens of nW/um^2 it is sufficient to overcome the Earth's gravitational pull.Comment: 5 pages, 4 figure
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