639 research outputs found
Complete genome sequence of a newly identified porcine astrovirus genotype 3 strain US-MO123
Astrovirus (AstV) infections are among the most common causes of gastroenteritis and are also associated with extraintestinal manifestations in humans and many animals. Herein, for the first time, the complete genome sequence of newly identified porcine astrovirus genotype 3 (PAstV3) strain US-MO123 was determined. Sequence comparison and phylogenetic analysis showed that PAstV3 has the closest relationship with mink AstV and the human AstV strains VA1, VA2, and SG, indicating the same ancestral origin and zoonotic potential of the virus
A porcine reproductive and respiratory syndrome virus candidate vaccine based on the synthetic attenuated virus engineering approach is attenuated and effective in protecting against homologous virus challenge
Landau Theory of the Phase Transitions in Half Doped Manganites: Interplay of Magnetic, Charge and Structural Orders
The order parameters of the magnetic, charge and structural orders at
half-doped manganites are identified. A corresponding Landau theory of the
phase transitions is formulated. Many structural and thermodynamical behaviors
are accounted for and clarified within the framework. In particular, the theory
provides a unified picture for the scenario of the phase transitions and their
nature with respect to the variation of the tolerance factor of the manganites.
It also accounts for the origin of the incommensurate nature of the orbital
order and its subsequently accompanying antiferromagnetic order.Comment: 4 pages, 3 eps figures, Revtex, Phys. Rev. B61, 200
Specific heat and magnetic measurements in Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 samples
We studied the magnetization as a function of temperature and magnetic field
in the compounds Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3. It allowed
us to identify the ferromagnetic, antiferromagnetic and charge ordering phases
in each case. The intrinsic magnetic moments of Nd3+ and Ho3+ ions experienced
a short range order at low temperatures. We also did specific heat measurements
with applied magnetic fields between 0 and 9 T and temperatures between 2 and
300 K in all three samples. Close to the charge ordering and ferromagnetic
transition temperatures the specific heat curves showed peaks superposed to the
characteristic response of the lattice oscillations. Below 10 K the specific
heat measurements evidenced a Schottky-like anomaly for all samples. However,
we could not successfully fit the curves to either a two level nor a
distribution of two-level Schottky anomaly. Our results indicated that the peak
temperature of the Schottky anomaly was higher in the compounds with narrower
conduction band.Comment: submitted to PR
Unusual magnetic relaxation behavior in La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3
We have carried out a systematic magnetic relaxation study, measured after
applying and switching off a 5 T magnetic field to polycrystalline samples of
La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3. The long time logarithmic relaxation rate
(LTLRR), decreased from 10 K to 150 K and increased from 150 K to 195 K in
La0.5Ca0.5MnO3. This change in behavior was found to be related to the complete
suppression of the antiferromagnetic phase above 150 K and in the presence of a
5 T magnetic field. At 195 K, the magnetization first decreased, and after a
few minutes increased slowly as a function of time. Moreover, between 200 K and
245 K, the magnetization increased throughout the measured time span. The
change in the slope of the curves, from negative to positive at about 200 K was
found to be related to the suppression of antiferromagnetic fluctuations in
small magnetic fields. A similar temperature dependence of the LTLRR was found
for the Nd0.5Sr0.5MnO3 sample. However, the temperature where the LTLRR reached
the minimum in Nd0.5Sr0.5MnO3 was lower than that of La0.5Ca0.5MnO3. This
result agrees with the stronger ferromagnetic interactions that exist in
Nd0.5Sr0.5MnO3 in comparison to La0.5Ca0.5MnO3. The above measurements
suggested that the general temperature dependence of the LTLRR and the
underlying physics were mainly independent of the particular charge ordering
system considered. All relaxation curves could be fitted using a logarithmic
law at long times. This slow relaxation was attributed to the coexistence of
ferromagnetic and antiferromagnetic interactions between Mn ions, which
produced a distribution of energy barriers.Comment: Accepted to PRB as a regular article, 10 figures, Scheduled Issue: 01
June 200
Quantum Interference in Superconducting Wire Networks and Josephson Junction Arrays: Analytical Approach based on Multiple-Loop Aharonov-Bohm Feynman Path-Integrals
We investigate analytically and numerically the mean-field
superconducting-normal phase boundaries of two-dimensional superconducting wire
networks and Josephson junction arrays immersed in a transverse magnetic field.
The geometries we consider include square, honeycomb, triangular, and kagome'
lattices. Our approach is based on an analytical study of multiple-loop
Aharonov-Bohm effects: the quantum interference between different electron
closed paths where each one of them encloses a net magnetic flux. Specifically,
we compute exactly the sums of magnetic phase factors, i.e., the lattice path
integrals, on all closed lattice paths of different lengths. A very large
number, e.g., up to for the square lattice, exact lattice path
integrals are obtained. Analytic results of these lattice path integrals then
enable us to obtain the resistive transition temperature as a continuous
function of the field. In particular, we can analyze measurable effects on the
superconducting transition temperature, , as a function of the magnetic
filed , originating from electron trajectories over loops of various
lengths. In addition to systematically deriving previously observed features,
and understanding the physical origin of the dips in as a result of
multiple-loop quantum interference effects, we also find novel results. In
particular, we explicitly derive the self-similarity in the phase diagram of
square networks. Our approach allows us to analyze the complex structure
present in the phase boundaries from the viewpoint of quantum interference
effects due to the electron motion on the underlying lattices.Comment: 18 PRB-type pages, plus 8 large figure
Cyclotron damping and Faraday rotation of gravitational waves
We study the propagation of gravitational waves in a collisionless plasma
with an external magnetic field parallel to the direction of propagation. Due
to resonant interaction with the plasma particles the gravitational wave
experiences cyclotron damping or growth, the latter case being possible if the
distribution function for any of the particle species deviates from
thermodynamical equilibrium. Furthermore, we examine how the damping and
dispersion depends on temperature and on the ratio between the cyclotron- and
gravitational wave frequency. The presence of the magnetic field leads to
different dispersion relations for different polarizations, which in turn imply
Faraday rotation of gravitational waves.Comment: 15 pages, 3 figures. Accepted for publication in Phys. Rev.
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
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