276 research outputs found

    A Central Partition of Molecular Conformational Space. IV. Extracting information from the graph of cells

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    In previous works [physics/0204035, physics/0404052, physics/0509126] a procedure was described for dividing the 3×N3 \times N-dimensional conformational space of a molecular system into a number of discrete cells, this partition allowed the building of a combinatorial structure from data sampled in molecular dynamics trajectories: the graph of cells, that encodes the set of cells in conformational space that are visited by the system in its thermal wandering. Here we outline a set of procedures for extracting useful information from this structure: 1st) interesting regions in the volume occupied by the system in conformational space can be bounded by a polyhedral cone whose faces are determined empirically from a set of relations between the coordinates of the molecule, 2nd) it is also shown that this cone can be decomposed into a hierarchical set of smaller cones, 3rd) the set of cells in a cone can be encoded by a simple combinatorial sequence.Comment: added an intrduction and reference

    Stressed web environments as strategic games: risk profiles and Weltanschauung

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    We consider the behaviour of a set of services in a stressed web environment where performance patterns may be di cult to pre- dict. In stressed environments the performances of some providers may degrade while the performances of others, with elastic resources, may improve. The allocation of web-based providers to users (brokering) is modelled by a strategic non-cooperative angel-daemon game with risk pro les. A risk pro le speci es a bound on the number of unreliable ser- vice providers within an environment without identifying the names of these providers. Risk pro les o er a means of analysing the behaviour of broker agents which allocate service providers to users. A Nash equilib- rium is a xed point of such a game in which no user can locally improve their choice of provider { thus, a Nash equilibrium is a viable solution to the provider/user allocation problem. Angel daemon games provide a means of reasoning about stressed environments and o er the possibility of designing brokers using risk pro les and Nash equilibria.Postprint (author’s final draft

    A Central Partition of Molecular Conformational Space.III. Combinatorial Determination of the Volume Spanned by a Molecular System

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    In the first work of this series [physics/0204035] it was shown that the conformational space of a molecule could be described to a fair degree of accuracy by means of a central hyperplane arrangement. The hyperplanes divide the espace into a hierarchical set of cells that can be encoded by the face lattice poset of the arrangement. The model however, lacked explicit rotational symmetry which made impossible to distinguish rotated structures in conformational space. This problem was solved in a second work [physics/0404052] by sorting the elementary 3D components of the molecular system into a set of morphological classes that can be properly oriented in a standard 3D reference frame. This also made possible to find a solution to the problem that is being adressed in the present work: for a molecular system immersed in a heat bath we want to enumerate the subset of cells in conformational space that are visited by the molecule in its thermal wandering. If each visited cell is a vertex on a graph with edges to the adjacent cells, here it is explained how such graph can be built

    Effectiveness of rotavirus vaccination in prevention of hospital admissions for rotavirus gastroenteritis among young children in Belgium : case-control study

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    Objective : To evaluate the effectiveness of rotavirus vaccination among young children in Belgium. Design : Prospective case-control study. Setting : Random sample of 39 Belgian hospitals, February 2008 to June 2010. Participants : 215 children admitted to hospital with rotavirus gastroenteritis confirmed by polymerase chain reaction and 276 age and hospital matched controls. All children were of an eligible age to have received rotavirus vaccination (that is, born after 1 October 2006 and aged >= 14 weeks). Main outcome measure : Vaccination status of children admitted to hospital with rotavirus gastroenteritis and matched controls. Results : 99 children (48%) admitted with rotavirus gastroenteritis and 244 (91%) controls had received at least one dose of any rotavirus vaccine (P= 12 months. The G2P[4] genotype accounted for 52% of cases confirmed by polymerase chain reaction with eligible matched controls. Vaccine effectiveness was 85% (64% to 94%) against G2P[4] and 95% (78% to 99%) against G1P[8]. In 25% of cases confirmed by polymerase chain reaction with eligible matched controls, there was reported co-infection with adenovirus, astrovirus and/or norovirus. Vaccine effectiveness against co-infected cases was 86% (52% to 96%). Effectiveness of at least one dose of any rotavirus vaccine (intention to vaccinate analysis) was 91% (82% to 95%). Conclusions : Rotavirus vaccination is effective for the prevention of admission to hospital for rotavirus gastroenteritis among young children in Belgium, despite the high prevalence of G2P[4] and viral co-infection

    An angel-daemon approach to assess the uncertainty in the power of a collectivity to act

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    The final publication is available at link.springer.comWe propose the use of the angel-daemon framework to assess the Coleman's power of a collectivity to act under uncertainty in weighted voting games. In this framework uncertainty profiles describe the potential changes in the weights of a weighted game and fixes the spread of the weights' change. For each uncertainty profile a strategic angel-daemon game can be considered. This game has two selfish players, the angel and the daemon, the angel selects its action as to maximize the effect on the measure under consideration while daemon acts oppositely. Players angel and daemon give a balance between the best and the worst. The angel-daemon games associated to the Coleman's power are zero-sum games and therefore the expected utilities of all the Nash equilibria are the same. In this way we can asses the Coleman's power under uncertainty. Besides introducing the framework for this particular setting we analyse basic properties and make some computational complexity considerations. We provide several examples based in the evolution of the voting rules of the EU Council of Ministers.Peer ReviewedPostprint (author's final draft

    Tutorizando el aprendizaje proactivo de nuevas tecnologías: Taller de programación Android

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    Mediante el Programa Google EMEA’s AndroidEDU, la UPC ha impartido un novedoso taller de programación para Android. Durante diez semanas se tratan diferentes temas sobre este sistema y una veintena de alumnos trabajan ejercicios en grupos reducidos. Los grupos colaboran para investigar y solucionar las dificultades técnicas que surgen. Posteriormente, cada grupo realiza y defiende un proyecto propio. El interés en Android ha permitido fomentar el aprendizaje proactivo, con muy buenos resultados. Como profesores esta experiencia nos ha permitido afrontar nuevos retos docentes, obligándonos a replantear nuestro rol, a crear material docente adecuado a los nuevos medios de difusión social (foro FIB, YouTube, etc.), y a suplir la falta de experiencia en el tema con una interesante colaboración profesoralumno.Within the AndroidEDU Google EMEA Program, the UPC has organized a innovative programming workshop for Android. For ten weeks, twenty students (who are organized in small groups) deal with different topics about Android. Those groups work together to investigate and resolve technical difficulties that may arise. By the end of the course, each group works on and fends for its own project. The growing interest in Android has allowed us to apply proactive learning techniques with very good results. As teachers, this experience has allowed us to meet new challenges, since it has forced us to rethink our role, to create educational material accordant with the new communication media (forum FIB, YouTube, etc.), and to supply the lack of expertise with an interesting collaboration between teachers and students.Trabajo parcialmente financiado por la mención de la Generalitat de Catalunya a ALBCOM como grupo de investigación consolidado (ref. 2009 SGR 1137) y por los proyectos del Ministerio de Ciencia y Tecnología: TIN2007-66523 (FORMALISM) para M. Blesa, J. Gabarró y M. Serna, y TIN2010-17254 (FRADA) para A. Duch. H. Hernández está financiado por el Comissionat per a Universitats i Recerca del DIUE de la Generalitat de Catalunya y por el European Social Fund
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