Smoothed particle hydrodynamics on GPU computing

Smoothed Particle Hydrodynamics (SPH) is a powerful technique used to simulate complex free-surface flows. However one of the main drawbacks of this method is the expensive computational runtime and the large number of particles needed when 3D simulations are performed. High Performance Computing (HPC) therefore becomes essential to accelerate these codes and perform simulations. In this study, parallelization using Graphics Processing Units (GPU) is applied to the SPHysics code (www.sphysics.org) dedicated to free-surface flows with SPH. Simulations involving several million particles on a single GPU exhibit speedups of up to two orders of magnitude over the same calculations using CPU codes, while parallelization using MPI for multi-GPU leads to further acceleration. This cheap technology allows studying real-life engineering problems at reasonable computational runtimes

Epidemics in partially overlapped multiplex networks

Many real networks exhibit a layered structure in which links in each layer reflect the function of nodes on different environments. These multiple types of links are usually represented by a multiplex network in which each layer has a different topology. In real-world networks, however, not all nodes are present on every layer. To generate a more realistic scenario, we use a generalized multiplex network and assume that only a fraction $q$ of the nodes are shared by the layers. We develop a theoretical framework for a branching process to describe the spread of an epidemic on these partially overlapped multiplex networks. This allows us to obtain the fraction of infected individuals as a function of the effective probability that the disease will be transmitted $T$. We also theoretically determine the dependence of the epidemic threshold on the fraction $q > 0$ of shared nodes in a system composed of two layers. We find that in the limit of $q \to 0$ the threshold is dominated by the layer with the smaller isolated threshold. Although a system of two completely isolated networks is nearly indistinguishable from a system of two networks that share just a few nodes, we find that the presence of these few shared nodes causes the epidemic threshold of the isolated network with the lower propagating capacity to change discontinuously and to acquire the threshold of the other network.Comment: 13 pages, 4 figure

Servicio de asesoramiento grupal agropecuario

Outreach activities, along with teaching and research, are part of the educational mission of higher education institutions. All three must be integrated into the policies and strategies of the institutions, interacting and enriching each other through channels of communication and mutual support. The objective of this work was to contribute to the training and development of agricultural producers, considering good agricultural practices. In order to do this, we worked in the districts of Serrezuela, Caminiaga and Sebastian Elcano. We worked to consolidate groups of producers and to promote behavioural changes; to this end, two aspects were exploited: i) the group dynamics, which consists of an active, participatory and reflective methodology through gradual, intentional and continuous work, and ii) the space-workshop, through which the learning of new behaviors related to livestock production was generated. The training, action and management of three groups of producers were consolidated. Producers and young coordinators of the groups created a space where knowledge was exchanged through an informal educational process.La extensión, a la par de la docencia y la investigación, forma parte de la misión educativa de las instituciones de educación superior. Todas deben estar presentes en las políticas y estrategias de las instituciones, interrelacionándose y enriqueciéndose recíprocamente a través de canales de comunicación y de apoyo mutuo. El objetivo de este trabajo fue contribuir a la capacitación y desarrollo de los productores agropecuarios, considerando las buenas prácticas agropecuarias. Para ello, se trabajó en las localidades Serrezuela, Caminiaga y Sebastián Elcano. Se trabajó en consolidar la formación de grupos de productores y promover cambios de conductas; para esto, se utilizaron dos ejes: la dinámica de grupo, que consiste en una metodología activa, participativa y reflexiva a través de un trabajo gradual, intencional y continuo y el espacio-taller, a través del cual se generó el aprendizaje de nuevas conductas referidas a la producción pecuaria. Se consolidó la formación, acción y autogestión de tres grupos de productores. Los productores y los jóvenes profesionales coordinadores de grupo generaron un espacio donde se intercambiaron saberes mediante un proceso educativo no formal

Utilización de pantallas multimedia en escolares de la ciudad de Corrientes

Las pantallas multimedia, desde la televisión a los nuevos medios de comunicación, son un componente importante de la vida de niños y adolescentes. El objetivo del presente estudio fue determinar las pautas de utilización de dispositivos multimedia en niños de 1º grado de dos escuelas primarias de la ciudad de Corrientes. Estudio observacional, descriptivo, transversal. La recolección de los datos se realizó a través de una encuesta a padres de los niños incluidos en el estudio que aceptaron participar voluntariamente. De las 268 encuestas analizadas el 99% de los niños utilizaban dispositivos multimedia: 71% niños televisión, 15% computadoras y tablets, 12% teléfonos celulares, 1%videojuegos y 1% no utilizaban pantallas. El 46% utilizaba pantallas entre 2 y 4 hs diarias. Durante las comidas el 53% de los menores utilizaba dispositivos multimedia mientras que el 80% los utilizaba antes de dormir. El 92% de los niños estudiados eran acompañados por adultos durante la mayor parte del tiempo de utilización de pantallas y el 68% presentaba normas para un correcto uso en el hogar. El uso de pantallas multimedia implica riesgos y beneficios de diversa índole, por lo que es fundamental el rol del médico a la hora de informar a los familiares de la necesidad de limitar el uso de pantallas y advertir sobre los riesgos de un uso excesivo

Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV

We present the first simultaneous measurement of the ratio of branching fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top quark pair production cross section sigma_ttbar in the lepton plus jets channel using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the D0 detector. We extract R and sigma_ttbar by analyzing samples of events with 0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with the standard model prediction.Comment: submitted to Phys.Rev.Letter

Measurement of the Bs0B^{0}_{s} Lifetime Using Semileptonic Decays

We report a measurement of the $B^0_{s}$ lifetime in the semileptonic decay channel $B^0_{s}\to D^-_s \mu^{+}\nu X$ (and its charge conjugate), using approximately 0.4 fb$^{-1}$ of data collected with the D0 detector during 2002 -- 2004. We have reconstructed 5176 $D^-_s \mu^{+}$ signal events, where the $D_s^-$ is identified via the decay $D_s^-\to \phi\pi^-$, followed by $\phi\to K^+ K^-$. Using these events, we have measured the $B^0_s$ lifetime to be $\tau(B^0_{s}) = 1.398 \pm 0.044$ $({stat}) ^{+0.028}_{-0.025}$ $({syst}) {ps}$. This is the most precise measurement of the $B_s^0$ lifetime to date.Comment: To appear in Phys. Rev. Lett., 7 pages, 2 figure

Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States

Using the data accumulated in 2002-2004 with the DO detector in proton-antiproton collisions at the Fermilab Tevatron collider with centre-of-mass energy 1.96 TeV, the branching fractions of the decays B -> \bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0 \mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) = (0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+ \nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) = (0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge conjugated states are always implied.Comment: submitted to Phys. Rev. Let

Search for dark photons from supersymmetric hidden valleys

We search for a new light gauge boson, a dark photon, with the D0 experiment. In the model we consider, supersymmetric partners are pair produced and cascade to lightest neutralinos that can decay into the hidden sector state plus either a photon or a dark photon. The dark photon decays through its mixing with a photon into fermion pairs. We therefore investigate a previously unexplored final state that contains a photon, two spatially close leptons, and large missing transverse energy. We do not observe any evidence for dark photons and set a limit on their production.Comment: submitted to PR