863 research outputs found

    Chloride channels in stellate cells are essential for uniquely high secretion rates in neuropeptide-stimulated Drosophila diuresis

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    Epithelia frequently segregate transport processes to specific cell types, presumably for improved efficiency and control. The molecular players underlying this functional specialization are of particular interest. In Drosophila, the renal (Malpighian) tubule displays the highest per-cell transport rates known and has two main secretory cell types, principal and stellate. Electrogenic cation transport is known to reside in the principal cells, whereas stellate cells control the anion conductance, but by an as-yet-undefined route. Here, we resolve this issue by showing that a plasma membrane chloride channel, encoded by ClC-a, is exclusively expressed in the stellate cell and is required for Drosophila kinin-mediated induction of diuresis and chloride shunt conductance, evidenced by chloride ion movement through the stellate cells, leading to depolarization of the transepithelial potential. By contrast, ClC-a knockdown had no impact on resting secretion levels. Knockdown of a second CLC gene showing highly abundant expression in adult Malpighian tubules, ClC-c, did not impact depolarization of transepithelial potential after kinin stimulation. Therefore, the diuretic action of kinin in Drosophila can be explained by an increase in ClC-a–mediated chloride conductance, over and above a resting fluid transport level that relies on other (ClC-a–independent) mechanisms or routes. This key segregation of cation and anion transport could explain the extraordinary fluid transport rates displayed by some epithelia

    Dealing with non-termination in DCGs

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    The objective of this paper is to study a practical approach to deal with non-termination in de nite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical e ciency and operational completeness. In order to guarantee the validity of our conclusions, we rst map our study to a common situated framework, where the e ectiveness of each approach will be examined and, later, compared by running experiments.Eje: TeoríaRed de Universidades con Carreras en Informática (RedUNCI

    Stereoselective cyanation of 4-formyl and 4-imino-β-lactams: Application to the synthesis of polyfunctionalized γ-lactams

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    The stereoselective reaction of 4-oxoazetidine-2-carbaldehydes and their corresponding imines with cyanide-based reagents give β-lactam α-aminonitriles, which are chameleonic building blocks for the controlled synthesis of a variety of new compounds including functionalized γ-lactams, succinimide derivatives, and diamino-lactams derivatives in optically pure form. © 2012 Elsevier Ltd. All rights reserved.Peer Reviewe

    Dealing with non-termination in DCGs

    Get PDF
    The objective of this paper is to study a practical approach to deal with non-termination in de nite clause grammars. We focus on two problems, loop and cyclic structure detection and representation, maintaining a tight balance between practical e ciency and operational completeness. In order to guarantee the validity of our conclusions, we rst map our study to a common situated framework, where the e ectiveness of each approach will be examined and, later, compared by running experiments.Eje: TeoríaRed de Universidades con Carreras en Informática (RedUNCI

    Performance assessment of existing models to predict brittle failure modes of steel-to-timber connections loaded parallel-to-grain with dowel-type fasteners

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    For safety reasons, ductile failure in timber connections with dowel-type fasteners is always recommended. It has usually been assumed that it can be achieved by fulfilling minimum spacing requirements between fasteners. However, recent works address the need to account for brittle failure modes (namely splitting, row-shear, and block and plug-shear) in connections loaded parallel-to-the-grain in an explicit manner, in order to evaluate them and achieve the desired ductility. This article describes the brittle failure modes and reviews the existing calculation models proposed by several authors – some of them included in standards. Finally, the performance of these models is assessed against an extensive database of tests gathered from the literature following a comprehensive methodology

    Systematic Evaluation of Applying Space-Filling Curves to Automotive Maneuver Detection

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    Identifying driving maneuvers plays an essential role on-board vehicles to monitor driving and driver states, as well as off-board to train and evaluate machine learning algorithms for automated driving for example. Maneuvers can be characterized by vehicle kinematics or data from its surroundings including other traffic participants. Extracting relevant maneuvers therefore requires analyzing time-series of (i) structured, multi-dimensional kinematic data, and (ii) unstructured, large data samples for video, radar, or LiDAR sensors. However, such data analysis requires scalable and computationally efficient approaches, especially for non-annotated data. In this paper, we are presenting a maneuver detection approach based on two variants of space-filling curves (Z-order and Hilbert) to detect maneuvers when passing roundabouts that do not use GPS data. We systematically evaluate their respective performance by including permutations of selections of kinematic signals at varying frequencies and compare them with two alternative baselines: All manually identified roundabouts, and roundabouts that are marked by geofences. We find that encoding just longitudinal and lateral accelerations sampled at 10Hz using a Hilbert space-filling curve is already successfully identifying roundabout maneuvers, which allows to avoid the use of potentially sensitive signals such as GPS locations to comply with data protection and privacy regulations like GDPR.Comment: 7 pages, 4 figure

    Modelo de competencia docente del profesor de medicina en la UNAM

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    El estudio presenta un modelo de competencia docente del profesor de medicina. Fue generado a partir de un modelo conceptual preexistente: a) dicho modelo se sometió al juicio de expertos quienes seleccionaron las competencias de mayor impacto; b) se construyó un perfil de competencias; c) se generó un instrumento basado en la opinión de los estudiantes y otro de autoevaluación; d) ambos fueron validados por 18 expertos en evaluación; e) se aplicó a 2,281 estudiantes y 107 profesores, obteniendo un comportamiento psicométrico adecuado que permitió establecer un modelo acorde a las tendencias actuales en evaluación del desempeño docente

    Promoting Entrepreneurship amid Youth in Windhoek’s Informal Settlements: A Namibian Case

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    Considering the high unemployment rate among Namibian youth and a lack of job opportunities, the promotion of entrepreneurship has gained wider attention in the country. A number of initiatives have been started such as entrepreneurship trainings and workshops, business idea competitions, etc. All these aim to inspire young people to think of alternative income sources. As part of a two-year funded community outreach research and development (R&D) project, we have investigated participatory approaches to engage marginalized youth into conceptualizing their own context, imparting skills, and deriving new career paths. This article reports and reflects on one of the interventions we have recently concluded with a group of youth in Havana, an informal settlement in the outskirts of Windhoek. We conducted what we entitled “The Havana Entrepreneur”, a series of interactions inspired upon the model of the American reality game show “The Apprentice”. Over a number of weeks two youth groups were given challenges to tackle by means of competing against one another. After completion of each challenge, groups were rated by a number of judges on skills demonstrated such as marketing, presentation, reflection and creativity among others. We observed an increase in, and improvement of skills revealed along tasks’ completion, besides an openly expressed self-realization and discovery of abilities by participants. Moreover, the youth are currently engaged in the continuation of activities beyond the initial entrepreneurial interactions. Thus we suggest replicating “The Havana Entrepreneur”, including the recording on camera of it by the youth themselves as a new mode to instigating a wider entrepreneurial spirit in informal settlements
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