7,784 research outputs found
Actions of arithmetic groups on homology spheres and acyclic homology manifolds
We establish lower bounds on the dimensions in which arithmetic groups with
torsion can act on acyclic manifolds and homology spheres. The bounds rely on
the existence of elementary p-groups in the groups concerned. In some cases,
including Sp(2n,Z), the bounds we obtain are sharp: if X is a generalized
Z/3-homology sphere of dimension less than 2n-1 or a Z/3-acyclic Z/3-homology
manifold of dimension less than 2n, and if n \geq 3, then any action of
Sp(2n,Z) by homeomorphisms on X is trivial; if n = 2, then every action of
Sp(2n,Z) on X factors through the abelianization of Sp(4,Z), which is Z/2.Comment: Final version, to appear in Math Zeitschrif
Micrometeorological processes driving snow ablation in an Alpine catchment
Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micrometeorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological model (ARPS) with a fully distributed energy balance model (Alpine3D). Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modelled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances except for very strong wind conditions. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is below a critical value. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover exerts a dominant control on the timing and magnitude of snow ablation for patchy snow covers.<br/
FACTORS AFFECTING FEEDER CATTLE PRICE DIFFERENTIALS
Feeder cattle prices are determined by the interaction of many factors. This study uses 1986 and 1987 Kansas feeder cattle auction data to investigate the impact of a wide variety of physical characteristics, many of which have not been used in previous studies on feeder cattle prices. Unlike previous studies, this analysis explicitly incorporates changes in feeder cattle market fundamentals during the data collection period and also allows price differentials to vary by sex and weight. Weight, weight-squared, lot size, lot size-squared, health, muscling, frame size, condition, fill, breed, presence of horns, and time of sale are significant factors affecting feeder cattle prices on any given day. Several physical traits also exhibit different seasonal price impacts.Demand and Price Analysis, Livestock Production/Industries,
Jet substructure as a new Higgs search channel at the LHC
It is widely considered that, for Higgs boson searches at the Large Hadron
Collider, WH and ZH production where the Higgs boson decays to b anti-b are
poor search channels due to large backgrounds. We show that at high transverse
momenta, employing state-of-the-art jet reconstruction and decomposition
techniques, these processes can be recovered as promising search channels for
the standard model Higgs boson around 120 GeV in mass.Comment: 4 pages, 3 figure
British Neurotoxin Network recommendations for managing cervical dystonia in patients with a poor response to botulinum toxin
Botulinum toxin (BoNT) injections are an effective
treatment for cervical dystonia. Approximately
20% of patients eventually stop BoNT treatment,
mostly because of treatment failure. These
recommendations review the different
therapeutic interventions for optimising the
treatment in secondary poor responder patients.
Immunoresistance has become less common over
the years, but the diagnosis has to be addressed
with a frontalis test or an Extensor Digitorum
Brevis test. In case of immunoresistance to BoNTA,
we discuss the place the different therapeutic
options (BoNT-A holidays, BoNT-B injections,
alternative BoNT-A injections, deep brain
stimulation). When poor responders are not
immunoresistant, they benefit from reviewing (1)
injections technique with electromyography or
ultrasound guidance, (2) muscles selection and
(3) dose of BoNT. In addition, in both scenarios,
a holistic approach including drug treatment,
retraining and psychological support is valuable
in the management of these complex and severe
cervical dystonia
AdS Strings with Torsion: Non-complex Heterotic Compactifications
Combining the effects of fluxes and gaugino condensation in heterotic
supergravity, we use a ten-dimensional approach to find a new class of
four-dimensional supersymmetric AdS compactifications on almost-Hermitian
manifolds of SU(3) structure. Computation of the torsion allows a
classification of the internal geometry, which for a particular combination of
fluxes and condensate, is nearly Kahler. We argue that all moduli are fixed,
and we show that the Kahler potential and superpotential proposed in the
literature yield the correct AdS radius. In the nearly Kahler case, we are able
to solve the H Bianchi using a nonstandard embedding. Finally, we point out
subtleties in deriving the effective superpotential and understanding the
heterotic supergravity in the presence of a gaugino condensate.Comment: 42 pages; v2. added refs, revised discussion of Bianchi for N
Analysis of coupled heat and moisture transfer in masonry structures
Evaluation of effective or macroscopic coefficients of thermal conductivity
under coupled heat and moisture transfer is presented. The paper first gives a
detailed summary on the solution of a simple steady state heat conduction
problem with an emphasis on various types of boundary conditions applied to the
representative volume element -- a periodic unit cell. Since the results
essentially suggest no superiority of any type of boundary conditions, the
paper proceeds with the coupled nonlinear heat and moisture problem subjecting
the selected representative volume element to the prescribed macroscopically
uniform heat flux. This allows for a direct use of the academic or commercially
available codes. Here, the presented results are derived with the help of the
SIFEL (SIimple Finite Elements) system.Comment: 23 pages, 11 figure
Improving Effective Surgical Delivery in Humanitarian Disasters: Lessons from Haiti
Kathryn Chu and colleagues describe the experiences of Médecins sans Frontières after the 2010 Haiti earthquake, and discuss how to improve delivery of surgery in humanitarian disasters
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