6,707 research outputs found
MAGNETOROTATIONAL TURBULENCE IN STRATIFIED SHEARING BOXES WITH PERFECT GAS EQUATION OF STATE AND FINITE THERMAL DIFFUSIVITY
We present a numerical study of turbulence and dynamo action in stratified
shearing boxes with zero mean magnetic flux. We assume that the fluid obeys the
perfect gas law and has finite (constant) thermal diffusivity. The calculations
begin from an isothermal state spanning three scale heights above and below the
mid-plane. After a long transient the layers settle to a stationary state in
which thermal losses out of the boundaries are balanced by dissipative heating.
We identify two regimes. A conductive regime in which the heat is transported
mostly by conduction and the density decreases with height. In the limit of
large thermal diffusivity this regime resembles the more familiar isothermal
case. Another, the convective regime, observed at smaller values of the thermal
diffusivity, in which the layer becomes unstable to overturning motions, the
heat is carried mostly by advection and the density becomes nearly constant
throughout the layer. In this latter constant-density regime we observe
evidence for large-scale dynamo action leading to a substantial increase in
transport efficiency relative to the conductive cases.Comment: 18 pages, 10 figures, ApJ accepte
Exercise and physical performance in older adults with sarcopenic obesity: A systematic review
BackgroundSarcopenic obesity is characterized by low muscle mass and high body fat; prevalence increases with age, particularly after age 65 years. For this systematic literature review we searched scientific databases for studies on exercise interventions for improving physical performance in adults with sarcopenic obesity; also, we identified potential gaps in clinical practice guidelines that need to be addressed.MethodsWe followed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The databases were searched for studies published through November 2021 that measured physical performance in adults with sarcopenic obesity.ResultsMost of the studies applied a strength training protocol in which improvement was noted post-treatment on the Time Chair Rise (TCR), 30-s Chair Stand, and Single Leg Stance (SLS) tests. Discrepancies between the studies were observed when resistance training was combined with or without elastic bands or electromyostimulation, as measured with the Short Physical Performance Battery (SPPB), Physical Performance Test (PPT), Gait Speed, and Timed Up & Go (TUG) test. Post-intervention SPPB, PPT, and gait speed scores showed an increase or maintenance of performance, while TUG test scores were higher according to one study but lower according to another.ConclusionsEngagement in physical exercise, and resistance training in particular, can improve or maintain physical performance in adults with sarcopenic obesity. Study samples should include more men. A future area of focus should be the impact of different types of training (aerobic, power training, combined modalities). Finally, studies with longer intervention periods and follow-up periods are needed to gain a better understanding of the effectiveness of exercise on physical function in adults with sarcopenic obesity
Automatic 3DS Conversion of Historical Aerial Photographs
In this paper we present a method for the generation of 3D stereo (3DS) pairs from sequences of historical aerial photographs. The goal of our work is to provide a stereoscopic display when the existing exposures are in a monocular sequence. Each input image is processed using its neighbours and a synthetic image is rendered, which, together with the original one, form a stereo pair. Promising results on real images taken from a historical photo archive are shown, that corroborate the viability of generating 3DS data from monocular footage
A strong-coupling analysis of two-dimensional O(N) sigma models with on square, triangular and honeycomb lattices
Recently-generated long strong-coupling series for the two-point Green's
functions of asymptotically free lattice models are
analyzed, focusing on the evaluation of dimensionless renormalization-group
invariant ratios of physical quantities and applying resummation techniques to
series in the inverse temperature and in the energy . Square,
triangular, and honeycomb lattices are considered, as a test of universality
and in order to estimate systematic errors. Large- solutions are carefully
studied in order to establish benchmarks for series coefficients and
resummations. Scaling and universality are verified. All invariant ratios
related to the large-distance properties of the two-point functions vary
monotonically with , departing from their large- values only by a few per
mille even down to .Comment: 53 pages (incl. 5 figures), tar/gzip/uuencode, REVTEX + psfi
Work stress and burnout among physicians and nurses in Internal and Emergency Departments
Burnout has been defined as loss of enthusiasm for work, feelings of cynicism, and a low sense of personal accomplishment. Work environment and working conditions exposes the individual to numerous factors of stress. Stress-related diseases are defined as burnout. The increased workload, the repeated reorganizations in the hospital with iterative downsizing suggestions and budget cuts, without any perspective of career progression, with a social culture of bureaucracy and blame, resulting both in subtracting direct care time with patients and in the fear by healthcare professionals from the burden of their responsibility, are the backgrounds on which more and more frequent cases of burnout may develop. We need to establish homogenous standards all over the national territory on workload and about the procedures that have to be implemented for the prevention of burnout in our wards
Field-theory results for three-dimensional transitions with complex symmetries
We discuss several examples of three-dimensional critical phenomena that can
be described by Landau-Ginzburg-Wilson theories. We present an
overview of field-theoretical results obtained from the analysis of high-order
perturbative series in the frameworks of the and of the
fixed-dimension d=3 expansions. In particular, we discuss the stability of the
O(N)-symmetric fixed point in a generic N-component theory, the critical
behaviors of randomly dilute Ising-like systems and frustrated spin systems
with noncollinear order, the multicritical behavior arising from the
competition of two distinct types of ordering with symmetry O() and
O() respectively.Comment: 9 pages, Talk at the Conference TH2002, Paris, July 200
Clustering of galaxies around GRB sight-lines
There is evidence of an overdensity of strong intervening MgII absorption
line systems distributed along the lines of sight towards GRB afterglows
relative to quasar sight-lines. If this excess is real, one should also expect
an overdensity of field galaxies around GRB sight-lines, as strong MgII tends
to trace these sources. In this work, we test this expectation by calculating
the two point angular correlation function of galaxies within
120 ( at ) of GRB afterglows. We compare the Gamma-ray burst Optical and
Near-infrared Detector (GROND) GRB afterglow sample -- one of the largest and
most homogeneous samples of GRB fields -- with galaxies and AGN found in the
COSMOS-30 photometric catalog. We find no significant signal of anomalous
clustering of galaxies at an estimated median redshift of around GRB
sight-lines, down to . This result is contrary to the
expectations from the MgII excess derived from GRB afterglow spectroscopy,
although many confirmed galaxy counterparts to MgII absorbers may be too faint
to detect in our sample -- especially those at . We note that the addition
of higher sensitivity Spitzer IRAC or HST WFC3 data for even a subset of our
sample would increase this survey's depth by several orders of magnitude,
simultaneously increasing statistics and enabling the investigation of a much
larger redshift space.}Comment: 10 pages, 6 figures. A&A accepte
Progress and potential in organoid research
Tissue and organ biology are very challenging to study in mammals, and progress can be hindered, particularly in humans, by sample accessibility and ethical concerns. However, advances in stem cell culture have made it possible to derive in vitro 3D tissues called organoids, which capture some of the key multicellular, anatomical and even functional hallmarks of real organs at the micrometre to millimetre scale. Recent studies have demonstrated that organoids can be used to model organ development and disease and have a wide range of applications in basic research, drug discovery and regenerative medicine. Researchers are now beginning to take inspiration from other fields, such as bioengineering, to generate organoids that are more physiologically relevant and more amenable to real-life applications
Heavy-flavour production in Pb-Pb collisions at the LHC, measured with the ALICE detector
We present the first results from the ALICE experiment on the nuclear
modification factors for heavy-flavour hadron production in Pb-Pb collisions at
sqrt{s_NN}=2.76 TeV. Using proton-proton and lead-lead collision samples at
sqrt{s}=7 TeV and sqrt{s_NN}=2.76 TeV, respectively, nuclear modification
factors R_AA(pt) were measured for D mesons at central rapidity (via displaced
decay vertex reconstruction), and for electrons and muons, at central and
forward rapidity, respectively.Comment: 8 pages, 5 figures, plenary talk at Quark Matter 2011, Annecy, Franc
The Role of Obesity, Body Composition, and Nutrition in COVID-19 Pandemia: A Narrative Review
The coronavirus disease 2019 (COVID-19) pandemic has spread worldwide, infecting nearly 500 million people, with more than 6 million deaths recorded globally. Obesity leads people to be more vulnerable, developing worse outcomes that can require hospitalization in intensive care units (ICU). This review focused on the available findings that investigated the link between COVID-19, body composition, and nutritional status. Most studies showed that not only body fat quantity but also its distribution seems to play a crucial role in COVID-19 severity. Compared to the body mass index (BMI), visceral adipose tissue and intrathoracic fat are better predictors of COVID-19 severity and indicate the need for hospitalization in ICU and invasive mechanical ventilation. High volumes of epicardial adipose tissue and its thickness can cause an infection located in the myocardial tissue, thereby enhancing severe COVID-related myocardial damage with impairments in coronary flow reserve and thromboembolism. Other important components such as sarcopenia and intermuscular fat augment the vulnerability in contracting COVID-19 and increase mortality, inflammation, and muscle damage. Malnutrition is prevalent in this population, but a lack of knowledge remains regarding the beneficial effects aimed at optimizing nutritional status to limit catabolism and preserve muscle mass. Finally, with the increase in patients recovering from COVID-19, evaluation and treatment in those with Long COVID syndrome may become highly relevant
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