845 research outputs found
Surface states in nearly modulated systems
A Landau model is used to study the phase behavior of the surface layer for
magnetic and cholesteric liquid crystal systems that are at or near a Lifshitz
point marking the boundary between modulated and homogeneous bulk phases. The
model incorporates surface and bulk fields and includes a term in the free
energy proportional to the square of the second derivative of the order
parameter in addition to the usual term involving the square of the first
derivative. In the limit of vanishing bulk field, three distinct types of
surface ordering are possible: a wetting layer, a non-wet layer having a small
deviation from bulk order, and a different non-wet layer with a large deviation
from bulk order which decays non-monotonically as distance from the wall
increases. In particular the large deviation non-wet layer is a feature of
systems at the Lifshitz point and also those having only homogeneous bulk
phases.Comment: 6 pages, 7 figures, submitted to Phys. Rev.
Visual monitoring of water deficit stress using infra-red thermography in wheat
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Low-Loss All-Optical Zeno Switch in a Microdisk Cavity Using EIT
We present theoretical results of a low-loss all-optical switch based on
electromagnetically induced transparency and the classical Zeno effect in a
microdisk resonator. We show that a control beam can modify the atomic
absorption of the evanescent field which suppresses the cavity field buildup
and alters the path of a weak signal beam. We predict more than 35 dB of
switching contrast with less than 0.1 dB loss using just 2 micro-Watts of
control-beam power for signal beams with less than single photon intensities
inside the cavity.Comment: Updated with new references, corrected Eq 2a, and added introductory
text. 7 pages, 5 figures, 3 table
Anomalous dimensions and phase transitions in superconductors
The anomalous scaling in the Ginzburg-Landau model for the superconducting
phase transition is studied. It is argued that the negative sign of the
exponent is a consequence of a special singular behavior in momentum space. The
negative sign of comes from the divergence of the critical correlation
function at finite distances. This behavior implies the existence of a Lifshitz
point in the phase diagram. The anomalous scaling of the vector potential is
also discussed. It is shown that the anomalous dimension of the vector
potential has important consequences for the critical dynamics in
superconductors. The frequency-dependent conductivity is shown to obey the
scaling . The prediction is
obtained from existing Monte Carlo data.Comment: RevTex, 20 pages, no figures; small changes; version accepted in PR
The effect of carbohydrate ingestion on the motor skill proficiency of soccer players
This study examined the effects of ingesting a glucose-polymer (GP) solution on the motor skill proficiencies of association football (soccer) players from two teams playing during two matches in a cool environment. Fifteen minutes before each match and at halftime, players from both teams ingested 5 ml/kg of either placebo or a 6.9% GP solution. GP ingestion did not improve tackling, heading, dribbling, or shooting ability. On the contrary, the mean of successful tackles was lower with GP ingestion than with placebo. The success rate for heading, dribbling, and shooting also tended to be lower in the GP than in the placebo condition. In contrast, success in passing and ball control was similar in the two conditions. Improvements in passing and ball control may have been related to a decrease in the intensity of play in the second half of the game. These data indicate that there are no measurable benefits of GP ingestion for the motor skill proficiencies of soccer players during games played in a cool environment.IS
The MSSM invisible Higgs in the light of dark matter and g-2
Giving up the assumption of the gaugino mass unification at the GUT scale,
the latest LEP and Tevatron data still allow the lightest supersymmetric Higgs
to have a large branching fraction into invisible neutralinos. Such a Higgs may
be difficult to discover at the LHC and is practically unreachable at the
Tevatron. We argue that, for some of these models to be compatible with the
relic density, light sleptons with masses not far above the current limits are
needed. There are however models that allow for larger sleptons masses without
being in conflict with the relic density constraint. This is possible because
these neutralinos can annihilate efficiently through a Z-pole. We also find
that many of these models can nicely account, at the 2\sigma level, for the
discrepancy in the latest g-2 measurement. However, requiring consistency with
the g-2 at the 1\sigma level, excludes models that lead to the largest Higgs
branching fraction into LSP's. In all cases one expects that even though the
Higgs might escape detection, one would have a rich SUSY phenomenology even at
the Tevatron, through the production of charginos and neutralinos.Comment: 16 pages and 5 figures. New references added, text and figures
unchange
Diagnosis and treatment of Guillain-Barré syndrome during the Zika virus epidemic in Brazil: A national survey study
The Zika virus (ZIKV) epidemic in Brazil in 2015-2016 was followed by an increase in the incidence of patients with Guillain-Barré syndrome (GBS). With this national survey study, we aimed to gain a better understanding of how neurologists in Brazil are currently diagnosing and treating patients with GBS, and how this increase in incidence has impacted the management of the disease. The questionnaire consisted of 52 questions covering: personal profile of the neurologist, practice of managing GBS during and outside of the ZIKV epidemic, and limitations in managing GBS. All 3264 neurologists that were member of the Brazilian Academy of Neurology at the time of the study were invited to participate. The questionnaire was fully answered by 171 (5%) neurologists. Sixty-one percent of neurologists noticed an increase in patients with GBS during the ZIKV epidemic, and 30% experienced an increase in problems in managing GBS during this time. The most important limitations in the diagnosis and management of GBS included the availability of nerve conduction studies (NCS), beds in the Intensive Care Unit (ICU) and referral to rehabilitation centers. Most neurologists did not use a protocol for treating patients with GBS and the treatment practice varied. Increasing availability of NCS and beds in the ICU and rehabilitation centers, and the implementation of (inter)national guidelines, are critical in supporting Brazilian neurologist in their management of GBS, an
Exact Hypersurface-Homogeneous Solutions in Cosmology and Astrophysics
A framework is introduced which explains the existence and similarities of
most exact solutions of the Einstein equations with a wide range of sources for
the class of hypersurface-homogeneous spacetimes which admit a Hamiltonian
formulation. This class includes the spatially homogeneous cosmological models
and the astrophysically interesting static spherically symmetric models as well
as the stationary cylindrically symmetric models. The framework involves
methods for finding and exploiting hidden symmetries and invariant submanifolds
of the Hamiltonian formulation of the field equations. It unifies, simplifies
and extends most known work on hypersurface-homogeneous exact solutions. It is
shown that the same framework is also relevant to gravitational theories with a
similar structure, like Brans-Dicke or higher-dimensional theories.Comment: 41 pages, REVTEX/LaTeX 2.09 file (don't use LaTeX2e !!!) Accepted for
publication in Phys. Rev.
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