548 research outputs found
Model Dependence of Baryon Decay Enhancement by Cosmic Strings
Cosmic strings arising from GUTs can catalyse baryon decay processes with
strong interaction cross sections. We examine the mechanism by which the cross
section is enhanced and find that it depends strongly on the details of the
distribution of gauge fields within the string core. We propose a calculational
scheme for estimating wavefunction amplification factors and also a physical
understanding of the nature of the enhancement process.Comment: 20 pages, LaTeX, DAMTP-R92/2
Ebola Virus Localization in the Macaque Reproductive Tract during Acute Ebola Virus Disease.
Sexual transmission of Ebola virus (EBOV) has been demonstrated more than a year after recovery from the acute phase of Ebola virus disease (EVD). The mechanisms underlying EBOV persistence and sexual transmission are not currently understood. Using the acute macaque model of EVD, we hypothesized EBOV would infect the reproductive tissues and sought to localize the infection in these tissues using immunohistochemistry and transmission electron microscopy. In four female and eight male macaques that succumbed to EVD between 6 and 9 days after EBOV challenge, we demonstrate widespread EBOV infection of the interstitial tissues and endothelium in the ovary, uterus, testis, seminal vesicle, epididymis, and prostate gland, with minimal associated tissue immune response or organ pathology. Given the widespread involvement of EBOV in the reproductive tracts of both male and female macaques, it is reasonable to surmise that our understanding of the mechanisms underlying sexual transmission of EVD and persistence of EBOV in immune-privileged sites would be facilitated by the development of a nonhuman primate model in which the macaques survived past the acute stage into convalescence
Proper incorporation of self-adjoint extension method to Green's function formalism : one-dimensional -function potential case
One-dimensional -function potential is discussed in the framework
of Green's function formalism without invoking perturbation expansion. It is
shown that the energy-dependent Green's function for this case is crucially
dependent on the boundary conditions which are provided by self-adjoint
extension method. The most general Green's function which contains four real
self-adjoint extension parameters is constructed. Also the relation between the
bare coupling constant and self-adjoint extension parameter is derived.Comment: LATEX, 13 page
A pragmatic approach to the problem of the self-adjoint extension of Hamilton operators with the Aharonov-Bohm potential
We consider the problem of self-adjoint extension of Hamilton operators for
charged quantum particles in the pure Aharonov-Bohm potential (infinitely thin
solenoid). We present a pragmatic approach to the problem based on the
orthogonalization of the radial solutions for different quantum numbers. Then
we discuss a model of a scalar particle with a magnetic moment which allows to
explain why the self-adjoint extension contains arbitrary parameters and give a
physical interpretation.Comment: 8 pages, LaTeX, to appear in J. Phys.
Temperature-scaling behavior of the Hall conductivity for Hg-based superconducting thin films
The Hall conductivities of HgBa_{2}CaCu_{2}O_{6+\delta}and
HgBa_{2}Ca_{2}Cu_{3}O_{8+\delta} thin films are investigated for a magnetic
field parallel to the c axis. The mixed-state Hall conductivity for these
compounds is well described by \sigma_{xy}=C_{1}/H+C_{2}+C_{3}H. The prefactor
C_1 shows a temperature dependence of the form C_1 = A(1-t)^n near T_c, where
t=T/T_c is the reduced temperature. Contrary to the previous results, C_2 also
follows a temperature-scaling behavior similar to that of the coefficient C_1.
The observed value of n = 1.8 - 2.3 is comparable to the previously observed
values for YBa_{2}Cu_{3}O_{7-\delta} and La_{2-x}Sr_{x}CuO_{4}.Comment: 5 pages, 4 eps figure
On Aharonov-Casher bound states
In this work bound states for the Aharonov-Casher problem are considered.
According to Hagen's work on the exact equivalence between spin-1/2
Aharonov-Bohm and Aharonov-Casher effects, is known that the
term cannot be neglected in the
Hamiltonian if the spin of particle is considered. This term leads to the
existence of a singular potential at the origin. By modeling the problem by
boundary conditions at the origin which arises by the self-adjoint extension of
the Hamiltonian, we derive for the first time an expression for the bound state
energy of the Aharonov-Casher problem. As an application, we consider the
Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the
expression for the harmonic oscillator energies and compare it with the
expression obtained in the case without singularity. At the end, an approach
for determination of the self-adjoint extension parameter is given. In our
approach, the parameter is obtained essentially in terms of physics of the
problem.Comment: 11 pages, matches published versio
A survey for pulsating subdwarf B stars with the Nordic Optical Telescope
A search programme for pulsating subdwarf B stars was conducted with the
Nordic Optical Telescope on La Palma over 59 nights between 1999 and 2009. The
purpose of the programme was to significantly extend the number of rapidly
pulsating sdB stars to better understand the properties of this new group of
variable compact stars. Candidates were selected initially from the HS and HE
surveys, but were supplemented with additional objects from other surveys.
Short sequences of time-series photometry were made on the candidates to
determine the presence of rapid pulsations. In total twenty new pulsators were
found in this survey, most of which have already been published and some
extensively studied. We present four new short period pulsators, bringing the
total of such pulsators up to 49. We also give limits on pulsation amplitudes
for 285 objects with no obvious periodic variations, summarise the results of
the survey, and provide improved physical parameters on the composite pulsators
for which only preliminary estimates were published earlier.Comment: 17 pages, accepted for publication in A&
Genome-Wide Identification, Functional Analysis and Expression Profiling of the Aux/IAA Gene Family in Tomato
Auxin is a central hormone that exerts pleiotropic effects on plant growth including the development of roots, shoots,
flowers and fruit. The perception and signaling of the plant
hormone auxin rely on the cooperative action of several components,among which auxin/indole-3-acetic acid (Aux/IAA)
proteins play a pivotal role. In this study, we identified and comprehensively analyzed the entire Aux/IAA gene family in tomato (Solanum lycopersicum), a reference species for Solanaceae plants, and the model plant for fleshy fruit development. Functional characterization using a dedicated single cell system revealed that tomato Aux/IAA proteins function as active repressors of auxin-dependent gene transcription, with, however, different Aux/IAA members displaying varying levels of repression. Phylogenetic analysis indicated that the Aux/IAA gene family is slightly contracted in tomato compared with Arabidopsis, with a lower representation of non-canonical proteins. Sl-IAA genes display distinctive expression pattern in different tomato organs and tissues, and some of them display differential responses to auxin and ethylene, suggesting that Aux/IAAs may play a role in linking both hormone signaling pathways. The data presented here shed more light on Sl-IAA genes and provides new leads towards the elucidation of their function during plant development and in mediating hormone cross-talk
Supersymmetries of the spin-1/2 particle in the field of magnetic vortex, and anyons
The quantum nonrelativistic spin-1/2 planar systems in the presence of a
perpendicular magnetic field are known to possess the N=2 supersymmetry. We
consider such a system in the field of a magnetic vortex, and find that there
are just two self-adjoint extensions of the Hamiltonian that are compatible
with the standard N=2 supersymmetry. We show that only in these two cases one
of the subsystems coincides with the original spinless Aharonov-Bohm model and
comes accompanied by the super-partner Hamiltonian which allows a singular
behavior of the wave functions. We find a family of additional, nonlocal
integrals of motion and treat them together with local supercharges in the
unifying framework of the tri-supersymmetry. The inclusion of the dynamical
conformal symmetries leads to an infinitely generated superalgebra, that
contains several representations of the superconformal osp(2|2) symmetry. We
present the application of the results in the framework of the two-body model
of identical anyons. The nontrivial contact interaction and the emerging N=2
linear and nonlinear supersymmetries of the anyons are discussed.Comment: 18 pages, 1 figure, published versio
AUXIN RESPONSE FACTOR1 and AUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission in Arabidopsisthaliana
In plants, both endogenous mechanisms and environmental signals regulate developmental transitions such as seed germination, induction of flowering, leaf senescence and shedding of senescent organs. Auxin response factors (ARFs) are transcription factors that mediate responses to the plant hormone auxin. We have examine
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