768 research outputs found
Endovascular Ruptured Abdominal Aortic Aneurysm Repair (EVRAR): A Systematic Review
BackgroundTo review evidence supporting the use of endovascular ruptured aneurysm repair (EVRAR) for treatment of ruptured abdominal aortic aneurysm (RAAA).MethodsA systematic review of the medical literature was performed for relevant studies. We searched a number of electronic databases and hand-searched relevant journals until November 2006 to identify studies for inclusion. We considered studies in which patients with a confirmed ruptured abdominal aortic aneurysm were treated with EVRAR, which reported endpoints of mortality and major complications.ResultsThere was 1 randomised controlled trial (RCT), 33 non-randomised case series (24 retrospective and 9 prospective) reports were identified comparing EVRAR (n=891) with conventional open surgical repair for the treatment of RAAA. Whilst no benefit in the primary outcome of mortality was noted in the only RCT, evidence from non-randomised studies suggest that EVRAR is feasible in selected patients, where it may be associated with a trend towards reductions in blood loss, duration of intensive care treatment, early complications, and mortality.ConclusionsFor the treatment of symptomatic or ruptured abdominal aortic aneurysm, emergency endovascular repair (EVRAR) is feasible in selected patients, with early outcomes comparable to best conventional open surgical repair for the treatment of RAAA
Stability of Circular Orbits in General Relativity: A Phase Space Analysis
Phase space method provides a novel way for deducing qualitative features of
nonlinear differential equations without actually solving them. The method is
applied here for analyzing stability of circular orbits of test particles in
various physically interesting environments. The approach is shown to work in a
revealing way in Schwarzschild spacetime. All relevant conclusions about
circular orbits in the Schwarzschild-de Sitter spacetime are shown to be
remarkably encoded in a single parameter. The analysis in the rotating Kerr
black hole readily exposes information as to how stability depends on the ratio
of source rotation to particle angular momentum. As a wider application, it is
exemplified how the analysis reveals useful information when applied to motion
in a refractive medium, for instance, that of optical black holes.Comment: 20 pages. Accepted for publication in Int. J. theor. Phy
Next-to-leading order QCD corrections to A_TT for prompt photon production
We present a next-to-leading order QCD calculation of the cross section for
isolated large-p_T prompt photon production in collisions of transversely
polarized protons. We devise a simple method of dealing with the phase space
integrals in dimensional regularization in the presence of the cos(2 phi)
azimuthal-angular dependence occurring for transverse polarization. Our results
allow to calculate the double-spin asymmetry A_TT for this process at
next-to-leading order accuracy, which may be used at BNL-RHIC to measure the
transversity parton distributions of the proton.Comment: 19 pages, LaTeX, 2 figures as eps file
Non-perturbative effects and the resummed Higgs transverse momentum distribution at the LHC
We investigate the form of the non-perturbative parameterization in both the
impact parameter (b) space and transverse momentum (p_T) space resummation
formalisms for the transverse momentum distribution of single massive bosons
produced at hadron colliders. We propose to analyse data on Upsilon
hadroproduction as a means of studying the non-perturbative contribution in
processes with two gluons in the initial state. We also discuss the theoretical
errors on the resummed Higgs transverse momentum distribution at the LHC
arising from the non-perturbative contribution.Comment: 22 pages, 10 figure
The Scale of Cosmic Isotropy
The most fundamental premise to the standard model of the universe, the
Cosmological Principle (CP), states that the large-scale properties of the
universe are the same in all directions and at all comoving positions.
Demonstrating this theoretical hypothesis has proven to be a formidable
challenge. The cross-over scale R_{iso} above which the galaxy distribution
becomes statistically isotropic is vaguely defined and poorly (if not at all)
quantified. Here we report on a formalism that allows us to provide an
unambiguous operational definition and an estimate of R_{iso}. We apply the
method to galaxies in the Sloan Digital Sky Survey (SDSS) Data Release 7,
finding that R_{iso}\sim 150h^{-1} Mpc. Besides providing a consistency test of
the Copernican principle, this result is in agreement with predictions based on
numerical simulations of the spatial distribution of galaxies in cold dark
matter dominated cosmological models.Comment: 15 pages, 4 figures, accepted by JCAP. The text matches the published
versio
A longitudinal study of nest occupancy, trail networks and foraging in a polydomous wood ant population
Most ant colonies live in a single nest (monodomy) or a group of nests (polydomy). However, the length of time for which
nests are inhabited varies significantly between different species. Although colonies of some species frequently move nest
sites, in others, colonies inhabit the same nest or group of nests for many years. Similarly, in some species foraging and
resource-sharing trails are highly dynamic, while in other species trails are used for years. Wood ants are a group of keystone
species that inhabit many northern hemisphere woodlands, where they are important predators of invertebrates and indirectly
act as herbivores through the farming of aphids. Wood ant colonies exhibit both monodomy and polydomy, and can inhabit
nests for many years. Trails in wood ant colonies are also thought to be relatively stable. However, information about colony
dynamics is mostly anecdotal as, until now, no longitudinal datasets have been collected. In this study, we collected data
from ten polydomous wood ant colonies annually for 8 years and a subset of four colonies 16 times over 2 years. We found
that most polydomous wood ant nests are abandoned in the first 2 years after being constructed and are more likely to be
abandoned in the latter part of the active season. However, the rate of nest abandonment decreases after 2 years and is lower
in larger nests. We also found that wood ant trails are relatively static within an active season and become more static later
in the season as trails become established.The NERC ACCE DTPhttp://link.springer.com/journal/40am2020Zoology and Entomolog
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
Tau neutrino deep inelastic charged current interactions
The nu_mu -> nu_tau oscillation hypothesis will be tested through nu_tau
production of tau in underground neutrino telescopes as well as long-baseline
experiments. We provide the full QCD framework for the evaluation of tau
neutrino deep inelastic charged current (CC) cross sections, including
next-leading-order (NLO) corrections, charm production, tau threshold, and
target mass effects in the collinear approximation. We investigate the
violation of the Albright-Jarlskog relations for the structure functions F_4,5
which occur only in heavy lepton (tau) scattering. Integrated CC cross sections
are evaluated naively over the full phase space and with the inclusion of DIS
kinematic cuts. Uncertainties in our evaluation based on scale dependence, PDF
errors and the interplay between kinematic and dynamical power corrections are
discussed and/or quantified.Comment: 28 pages, 10 figure
Spinor Field in Bianchi type-I Universe: regular solutions
Self-consistent solutions to the nonlinear spinor field equations in General
Relativity has been studied for the case of Bianchi type-I (B-I) space-time. It
has been shown that, for some special type of nonliearity the model provides
regular solution, but this singularity-free solutions are attained at the cost
of broken dominant energy condition in Hawking-Penrose theorem. It has also
been shown that the introduction of -term in the Lagrangian generates
oscillations of the B-I model, which is not the case in absence of
term. Moreover, for the linear spinor field, the term provides
oscillatory solutions, those are regular everywhere, without violating dominant
energy condition.
Key words: Nonlinear spinor field (NLSF), Bianch type -I model (B-I),
term
PACS 98.80.C CosmologyComment: RevTex, 21 page
New Fits for the Non-Perturbative Parameters in the CSS Resummation Formalism
We update the non-perturbative function of the Collins-Soper- Sterman
resummation formalism in hadron collisions. Two functional forms in impact
parameter space are considered, one with a pure Gaussian form with two
parameters and the other with an additional linear term. The results for the
two parameter fit are found to be g1=0.24+0.08-0.07 GeV^2, g2=0.34+0.07-0.08
GeV^2. The results for the three parameter fit are g1=0.15+004-0.03 GeV^2,
g2=0.48+0.07-0.05 GeV^2, and g3=-0.58+0.26-0.20 GeV^-1. We discuss the
potential for the full Tevatron Run I Z boson data for further testing of the
universality of the non-perturbative function.Comment: 22 pages, 12 figures, LaTe
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