Next-to-Leading Order Corrections to Single Top Quark Production and Decay at the Tevatron: 2. tt-channel Process

We present a study of the $t$-channel mode of single top quark production at the upgraded Tevatron $p\bar{p}$ collider, including the next-to-leading order (NLO) QCD corrections to the production and the decay of a single top quark. The narrow width approximation was adopted in order to preserve the spin of the top quark in its production and decay. We discuss the effects of different $O(\alpha_s)$ contributions on the inclusive cross section as well as various kinematic distributions after imposing the relevant cuts to select $t$-channel single top signal events.Comment: 46 pages, 47 figures. One typo in LaTeX source file is correcte

Resolución de advección difusión en multi-GPGPU

En este trabajo se presenta la solución del problema de advección difusión mediante un enfoque multi-GPGPU con GPUs ubicados en diferentes nodos del clúster que interactúan mediante el protocolo MPI. La idea es usar descomposición de dominio de modo que cada GPU resuelve una parte del dominio computacional y MPI es usado para intercambiar datos de borde. Los solvers están basados en los métodos de Gradientes Conjugados Cuadrado (CGS) y Gradientes Biconjugado Estabilizado (Bi-CGSTAB) que son métodos usados para resolver problemas donde la matriz A no es simétrica como es el caso del problema de advección difusión. La no simetría aparece debido a la discretización del término advectivo en el contexto del método de volúmenes finitos sobre mallas estructuradas cartesianas de paso constante. Se analizan varias opciones de discretización del término advectivo como ser diferencias centradas, up wind y esquemas de alto orden. Se presenta un análisis teórico de cada uno de estos esquemas y su performance computacional en multi-GPGPU. Se presenta además las propiedades de convergencia de los métodos presentados y su performance computacional en multi-GPGPU.Publicado en: Mecánica Computacional vol. XXXV, no. 10.Facultad de Ingenierí

Resolución de advección difusión en multi-GPGPU

En este trabajo se presenta la solución del problema de advección difusión mediante un enfoque multi-GPGPU con GPUs ubicados en diferentes nodos del clúster que interactúan mediante el protocolo MPI. La idea es usar descomposición de dominio de modo que cada GPU resuelve una parte del dominio computacional y MPI es usado para intercambiar datos de borde. Los solvers están basados en los métodos de Gradientes Conjugados Cuadrado (CGS) y Gradientes Biconjugado Estabilizado (Bi-CGSTAB) que son métodos usados para resolver problemas donde la matriz A no es simétrica como es el caso del problema de advección difusión. La no simetría aparece debido a la discretización del término advectivo en el contexto del método de volúmenes finitos sobre mallas estructuradas cartesianas de paso constante. Se analizan varias opciones de discretización del término advectivo como ser diferencias centradas, up wind y esquemas de alto orden. Se presenta un análisis teórico de cada uno de estos esquemas y su performance computacional en multi-GPGPU. Se presenta además las propiedades de convergencia de los métodos presentados y su performance computacional en multi-GPGPU.Publicado en: Mecánica Computacional vol. XXXV, no. 10.Facultad de Ingenierí

Author Correction: Longitudinal assessment of tumor development using cancer avatars derived from genetically engineered pluripotent stem cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

The Focusing DIRC - the first RICH detector to correct the chromatic error by timing, and the development of a new TOF detector concept

We have built and successfully tested a novel particle identification detector called Focusing DIRC. The prototype's concept is based on the BaBar DIRC with several important improvements: (a) much faster pixilated photon detectors based on Burle MCP-PMT and Hamamatsu MaPMT, (b) mirror allowing to make the photon detector smaller and less sensitive to background in future applications, (c) electronics allowing to measure the single photon resolution to better than {sigma} {approx} 100-200ps, which allows a correction of the chromatic error. While testing the timing resolution limits of a 64-pixel MCP-PMT with 10 mm MCP holes, we have achieved a timing resolution of {sigma} {approx} 30ps with single photoelectrons. In this paper we further investigate limits of the timing resolution with this particular detector

Functional genomic analyses uncover APOE-mediated regulation of brain and cerebrospinal fluid beta-amyloid levels in Parkinson disease

Alpha-synuclein is the main protein component of Lewy bodies, the pathological hallmark of Parkinson\u27s disease. However, genetic modifiers of cerebrospinal fluid (CSF) alpha-synuclein levels remain unknown. The use of CSF levels of amyloid bet

Obesity and disease activity in juvenile idiopathic arthritis

<p>Abstract</p> <p>Background</p> <p>Children with physical disabilities may have an increased risk for obesity and obesity might be a risk factor for inflammatory arthritis. The aims of this study were: to determine the prevalence of obesity in children and adolescents with juvenile idiopathic arthritis (JIA), and to examine the association between obesity and disease activity in this population.</p> <p>Findings</p> <p>A cross-sectional analysis of all patients with JIA attending a pediatric rheumatology clinic, between October 2009 and September 2010, was performed. A linear regression model was used to explore the association between obesity and disease activity in patients with JIA. A total of 154 subjects were included in the analysis; median age was 10.6 years, 61% were female, and 88% were white. Obesity was found in 18%, 12% were overweight, and 3% were underweight. There was no association between obesity and JADAS-27 (Juvenile Arthritis Disease Activity Score 27), physician's assessment of disease activity, parent's assessment of child's well-being, erythrocyte sedimentation rate, number of active joints, or C-reactive protein (p-value range 0.10 to 0.95).</p> <p>Conclusions</p> <p>Although 18% of patients with JIA were obese, we did not find an association between obesity and disease activity. As obesity confers an additional health risk in children with arthritis, addressing this co-morbidity should be a health priority in patients with JIA. Future studies are necessary to further explore potential associations between obesity, development of JIA, and disease activity.</p