5,636 research outputs found
Structure formation in the presence of relativistic heat conduction: corrections to the Jeans wave number with a stable first order in the gradients formalism
The problem of structure formation in relativistic dissipative fluids was
analyzed in a previous work within Eckart's framework, in which the heat flux
is coupled to the hydrodynamic acceleration, additional to the usual
temperature gradient term. It was shown that in such case, the pathological
behavior of fluctuations leads to the disapperance of the gravitational
instability responsible for structure formation. In the present work the
problem is revisited now using a constitutive equation derived from
relativistic kinetic theory. The new relation, in which the heat flux is not
coupled to the hydrodynamic acceleration, leads to a consistent first order in
the gradients formalism. In this case the gravitational instability remains,
and only relativistic corrections to the Jeans wave number are obtained. In the
calculation here shown the non-relativistc limit is recovered, opposite to what
happens in Eckart's case.Comment: 10 pages, no figure
Stratify or adjust? Dealing with multiple populations when evaluating rare variants
The unrelated individuals sample from Genetic Analysis Workshop 17 consists of a small number of subjects from eight population samples and genetic data composed mostly of rare variants. We compare two simple approaches to collapsing rare variants within genes for their utility in identifying genes that affect phenotype. We also compare results from stratified analyses to those from a pooled analysis that uses ethnicity as a covariate. We found that the two collapsing approaches were similarly effective in identifying genes that contain causative variants in these data. However, including population as a covariate was not an effective substitute for analyzing the subpopulations separately when only one subpopulation contained a rare variant linked to the phenotype
Application of smooth particle hydrodynamics method for modelling blood flow with thrombus formation
Thrombosis plays a crucial role in atherosclerosis or in haemostasis when a blood vessel is injured. This article focuses on using a meshless particle-based Lagrangian numerical technique, the smoothed particles hydrodynamic (SPH) method, to study the flow behaviour of blood and to explore the flow parameters that induce formation of a thrombus in a blood vessel. Due to its simplicity and effectiveness, the SPH method is employed here to simulate the process of thrombogenesis and to study the effect of various blood flow parameters. In the present SPH simulation, blood is modelled by two sets of particles that have the characteristics of plasma and of platelet, respectively. To simulate coagulation of platelets which leads to a thrombus, the so-called adhesion and aggregation mechanisms of the platelets during this process are modelled by an inter-particle force model. The transport of platelets in the flowing blood, platelet adhesion and aggregation processes are coupled with viscous blood flow for various low Reynolds number scenarios. The numerical results are compared with the experimental observations and a good agreement is found between the simulated and experimental results
Linkage analysis merging replicate phenotypes: an application to three quantitative phenotypes in two African samples
We report two approaches for linkage analysis of data consisting of replicate phenotypes. The first approach is specifically designed for the unusual (in human data) replicate structure of the Genetic Analysis Workshop 17 pedigree data. The second approach consists of a standard linkage analysis that, although not specifically tailored to data consisting of replicate genotypes, was envisioned as providing a sounding board against which our novel approach could be assessed. Both approaches are applied to the analysis of three quantitative phenotypes (Q1, Q2, and Q4) in two sets of African families. All analyses were carried out blind to the generating model (i.e., the “answers”). Using both methods, we found numerous significant linkage signals for Q1, although population colocalization was absent for most of these signals. The linkage analysis of Q2 and Q4 failed to reveal any strong linkage signals
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Automated generation of colluding apps for experimental research
Colluding apps bypass the security measures enforced by sandboxed operating systems such as Android. App collusion can be a real threat in cloud environments as well. Research in detecting and protecting against app collusion requires a variety of colluding apps for experimentation. Presently the number of (real or manually crafted) apps available to researchers is very limited. In this paper we propose a system called Application Collusion Engine (ACE) to automatically generate combinations of colluding and non-colluding Android apps to help researchers fairly evaluate different collusion detection and protection methods. Our initial implementation includes a variety of components that enable the system to create more than 5,000 different colluding and non-colluding app sets. ACE can be extended with more functional components to create even more colluding apps. To show the usefulness of our system, we have applied different risk evaluation and collusion detection methods to the created set of colluding apps
Bioactive compounds and antibacterial activities in crystallized honey liquefied with ultrasound
The effect of ultrasound on the crystal size, phenols, flavonoids, Maillard products and antibacterial activity of
crystallized honeys was studied. Three multifloral honeys (M), one monofloral (MO) and one honeydew (HD)
honey were used. Ultrasound was performed at 42 kHz for different times (0, 5, 10 and 15 min). The antibacterial activities were tested against Salmonella typhimurium, Bacillus subtilis, Pseudomonas aeruginosa, Listeria mono cytogenes, Staphylococcus aureus and Escherichia coli. In all honeys, the parameters analyzed had significant dif ferences ((P < 0.05)). After 15 min of ultrasound the HD had increments of 44 mg of gallic acid/100 g of honey in phenols, and some M showed increase in flavonoids (5.64 mg of quercitin /100 g of honey) and improvement in inhibition against Salmonella typhimurium was 13.1%. In some honeys the correlation between phenols or fla vonoids and antibacterial activity were significant ((P < 0.05)). No correlation was found between Maillard products and antibacterial activity. The ultrasound treatment effect on the crystal size, phenols, flavonoid, Maillard products, and antibacterial activity of crystallized honeys were different in each honey.info:eu-repo/semantics/publishedVersio
High-resolution spectro-polarimetry of a flaring sunspot penumbra
We present simultaneous photospheric and chromospheric observations of the
trailing sunspot in NOAA 10904 during a weak flare eruption (GOES magnitude
B7.8), obtained with the Swedish Solar Telescope (SST) in La Palma, Canary
Islands. High-resolution \ion{Ca}{ii} images show a typical two-ribbon
structure that has been hitherto only known for larger flares, and the flare
appears in a confined region that is discernible by a bright border. The
underlying photosphere shows a disturbed penumbral structure with intersecting
branches of penumbral filaments. High-resolution Doppler- and
vector-magnetograms exhibit oppositely directed Evershed flows and magnetic
field vectors in the individual penumbral branches, resulting in several
regions of magnetic azimuth discontinuity and several islands where the
vertical magnetic field is reversed. The discontinuity regions are co-spatial
with the locations of the onset of the flare ribbons. From the results, we
conclude that the confined flare region is detached from the global magnetic
field structure by a separatrix marked by the bright border visible in
\ion{Ca}{ii} . We further conclude that the islands of reversed vertical
field appear because of flux emergence and that the strong magnetic shear
appearing in the regions of magnetic azimuth discontinuity triggers the flare.Comment: 20 pages + 1 online Figure for A&
Tuberculosis Trends in Saudis and Non-Saudis in the Kingdom of Saudi Arabia – A 10 Year Retrospective Study (2000–2009)
Tuberculosis (TB) remains a public health problem in the Kingdom of Saudi Arabia (KSA), which has a very large labour force from high TB endemic countries. Understanding the epidemiological and clinical features of the TB problem, and the TB burden in the immigrant workforce, is necessary for improved planning and implementation of TB services and prevention measures
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