3,892 research outputs found
Discovery Of Bilaterian-Type Through-Guts In Cloudinomorphs From The Terminal Ediacaran Period
Discovery Of Bilaterian-Type Through-Guts In Cloudinomorphs From The Terminal Ediacaran Period
Brachial Artery Constriction during Brachial Artery Reactivity Testing Predicts Major Adverse Clinical Outcomes in Women with Suspected Myocardial Ischemia: Results from the NHLBI-Sponsored Women's Ischemia Syndrome Evaluation (WISE) Study
Background:Limited brachial artery (BA) flow-mediated dilation during brachial artery reactivity testing (BART) has been linked to increased cardiovascular risk. We report on the phenomenon of BA constriction (BAC) following hyperemia.Objectives:To determine whether BAC predicts adverse CV outcomes and/or mortality in the women's ischemic Syndrome Evaluation Study (WISE). Further, as a secondary objective we sought to determine the risk factors associated with BAC.Methods:We performed BART on 377 women with chest pain referred for coronary angiography and followed for a median of 9.5 years. Forearm ischemia was induced with 4 minutes occlusion by a cuff placed distal to the BA and inflated to 40mm Hg > systolic pressure. BAC was defined as >4.8% artery constriction following release of the cuff. The main outcome was major adverse events (MACE) including all-cause mortality, non-fatal MI, non-fatal stroke, or hospitalization for heart failure.Results:BA diameter change ranged from -20.6% to +44.9%, and 41 (11%) women experienced BAC. Obstructive CAD and traditional CAD risk factors were not predictive of BAC. Overall, 39% of women with BAC experienced MACE vs. 22% without BAC (p=0.004). In multivariate Cox proportional hazards regression, BAC was a significant independent predictor of MACE (p=0.018) when adjusting for obstructive CAD and traditional risk factors.Conclusions:BAC predicts almost double the risk for major adverse events compared to patients without BAC. This risk was not accounted for by CAD or traditional risk factors. The novel risk marker of BAC requires further investigation in women. © 2013 Sedlak et al
Climate influences on flood probabilities across Europe
The link between streamflow extremes and climatology has been widely studied
in recent decades. However, a study investigating the effect of large-scale
circulation variations on the distribution of seasonal discharge extremes at
the European level is missing. Here we fit a climate-informed generalized
extreme value (GEV) distribution to about 600 streamflow records in Europe
for each of the standard seasons, i.e., to winter, spring, summer and autumn
maxima, and compare it with the classical GEV distribution with parameters
invariant in time. The study adopts a Bayesian framework and covers the
period 1950 to 2016. Five indices with proven influence on the European
climate are examined independently as covariates, namely the North Atlantic
Oscillation (NAO), the east Atlantic pattern (EA), the east Atlantic–western
Russian pattern (EA/WR), the Scandinavia pattern (SCA) and the
polar–Eurasian pattern (POL).
It is found that for a high percentage of stations the climate-informed
model is preferred to the classical model. Particularly for NAO during
winter, a strong influence on streamflow extremes is detected for large
parts of Europe (preferred to the classical GEV distribution for 46 % of the stations).
Climate-informed fits are characterized by spatial coherence and form
patterns that resemble relations between the climate indices and seasonal
precipitation, suggesting a prominent role of the considered circulation
modes for flood generation. For certain regions, such as northwestern
Scandinavia and the British Isles, yearly variations of the mean seasonal
climate indices result in considerably different extreme value distributions
and thus in highly different flood estimates for individual years that can
also persist for longer time periods.</p
Tight-Binding model for semiconductor nanostructures
An empirical tight-binding (TB) model is applied to the
investigation of electronic states in semiconductor quantum dots. A basis set
of three -orbitals at the anions and one -orbital at the cations is
chosen. Matrix elements up to the second nearest neighbors and the spin-orbit
coupling are included in our TB-model. The parametrization is chosen so that
the effective masses, the spin-orbit-splitting and the gap energy of the bulk
CdSe and ZnSe are reproduced. Within this reduced TB-basis the
valence (p-) bands are excellently reproduced and the conduction (s-) band is
well reproduced close to the -point, i.e. near to the band gap. In
terms of this model much larger systems can be described than within a (more
realistic) -basis. The quantum dot is modelled by using the (bulk)
TB-parameters for the particular material at those sites occupied by atoms of
this material. Within this TB-model we study pyramidal-shaped CdSe quantum dots
embedded in a ZnSe matrix and free spherical CdSe quantum dots (nanocrystals).
Strain-effects are included by using an appropriate model strain field. Within
the TB-model, the strain-effects can be artifically switched off to investigate
the infuence of strain on the bound electronic states and, in particular, their
spatial orientation. The theoretical results for spherical nanocrystals are
compared with data from tunneling spectroscopy and optical experiments.
Furthermore the influence of the spin-orbit coupling is investigated
First-principles investigation of 180-degree domain walls in BaTiO_3
We present a first-principles study of 180-degree ferroelectric domain walls
in tetragonal barium titanate. The theory is based on an effective Hamiltonian
that has previously been determined from first-principles
ultrasoft-pseudopotential calculations. Statistical properties are investigated
using Monte Carlo simulations. We compute the domain-wall energy, free energy,
and thickness, analyze the behavior of the ferroelectric order parameter in the
interior of the domain wall, and study its spatial fluctuations. An abrupt
reversal of the polarization is found, unlike the gradual rotation typical of
the ferromagnetic case.Comment: Revtex (preprint style, 13 pages) + 3 postscript figures. A version
in two-column article style with embedded figures is available at
http://electron.rutgers.edu/~dhv/preprints/index.html#pad_wal
Gyrokinetic simulations of microturbulence in tokamak plasmas presenting an electron internal transport barrier, and development of a global version of the GENE code
The abstract goes here
Duality and Multicritical Point of Two-Dimensional Spin Glasses
Determination of the precise location of the multicritical point and phase
boundary is a target of active current research in the theory of spin glasses.
In this short note we develop a duality argument to predict the location of the
multicritical point and the shape of the phase boundary in models of spin
glasses on the square lattice.Comment: 4 pages, 1 figure; Reference updated, definition of \tilde{V} added;
to be published in J. Phys. Soc. Jp
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