130 research outputs found

    Lagrangian diffusive reactor for detailed thermochemical computations of plasma flows

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    The simulation of thermochemical nonequilibrium for the atomic and molecular energy level populations in plasma flows requires a comprehensive modeling of all the elementary collisional and radiative processes involved. Coupling detailed chemical mechanisms to flow solvers is computationally expensive and often limits their application to 1D simulations. We develop an efficient Lagrangian diffusive reactor moving along the streamlines of a baseline flow simulation to compute detailed thermochemical effects. In addition to its efficiency, the method allows us to model both continuum and rarefied flows, while including mass and energy diffusion. The Lagrangian solver is assessed for several testcases including strong normal shockwaves, as well as 2D axisymmetric blunt-body hypersonic rarefied flows. In all the testcases performed, the Lagrangian reactor improves drastically the baseline simulations. The computational cost of a Lagrangian recomputation is typically orders of magnitude smaller with respect to a full solution of the problem. The solver has the additional benefit of being immune from statistical noise, which strongly affects the accuracy of DSMC simulations, especially considering minor species in the mixture. The results demonstrate that the method enables applying detailed mechanisms to multidimensional solvers to study thermo-chemical nonequilibrium flows

    Halyomorpha halys in Emilia, prime risposte dal monitoraggio

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    OSSERVAZIONI IN CAMPO CONDOTTE NEL 2013-2014. Dopo la sua comparsa in Italia, accertata nel 2012, è stato attivato nella zona di ritrovamento un programma di monitoraggio teso a studiare l’insetto e il suo comportamento nell’ambiente. La specie desta maggiori preoccupazioni nel settore frutticolo, dove il danno rappresentato dalle tipiche deformazioni può giungere al 100

    Halyomorpha halys in Italy: first results of field monitoring in fruit orchards

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    The invasive pest Brown Marmorated Stink Bug (BMSB) Halyomorpha halys (Heteroptera, Pentatomidae) was detected for the first time in Italy in September 2012 in Modena province (Northern Italy) during an insect collection for educational purposes. A survey performed in 2013 allowed to detect its presence in Emilia Romagna, Lombardy and Piedmont regions. In 2014, in the provinces of Modena, Reggio Emilia and Bologna a periodical active field monitoring was performed using tree beating, sweep-net and visual observations in selected orchards and vineyards, recording numbers of BMSB adults and nymphs, and of other Heteroptera. Besides, fruit injury and crop loss were recorded at harvest. Partial results from field data obtained between April and July 2014 are presented, indicating that BMSB is already becoming an important pest of fruit orchards and that special attention should be deserved to monitor its spread all over the region and the whole Italian country

    SHANK3 Downregulation in the Ventral Tegmental Area Accelerates the Extinction of Contextual Associations Induced by Juvenile Non-familiar Conspecific Interaction

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    Haploinsufficiency of the SHANK3 gene, encoding for a scaffolding protein located in the postsynaptic density of glutamatergic synapse, has been linked to forms of autism spectrum disorders (ASDs). It has been shown that SHANK3 controls the maturation of social reward circuits in the ventral tegmental area (VTA). Whether the impairments in associative learning observed in ASD relate to SHANK3 insufficiency restricted to the reward system is still an open question. Here, we first characterize a social-conditioned place preference (CPP) paradigm based on the direct and free interaction with a juvenile and non-familiar conspecific. In both group- and single-housed C57Bl6/j late adolescence male mice, this CPP protocol promotes the formation of social-induced contextual associations that undergo extinction. Interestingly, the downregulation of Shank3 expression in the VTA altered the habituation to a non-familiar conspecific during conditioning and accelerated the extinction of social-induced conditioned responses. Thus, inspired by the literature on drugs of abuse-induced contextual learning, we propose that acquisition and extinction of CPP might be used as behavioral assays to assess social-induced contextual association and “social-seeking” dysfunctions in animal models of psychiatric disorders

    Continuous representations of speed by striatal medium spiny neurons

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    The striatum is critical for controlling motor output. However, it remains unclear how striatal output neurons encode and facilitate movement. A prominent theory suggests that striatal units encode movements in bursts of activity near specific events, such as the start or end of actions. These bursts are theorized to gate or permit specific motor actions, thereby encoding and facilitating complex sequences of actions. An alternative theory has suggested that striatal neurons encode continuous changes in sensory or motor information with graded changes in firing rate. Supporting this theory, many striatal neurons exhibit such graded changes without bursting near specific actions. Here, we evaluated these two theories in the same recordings of mice (both male and female). We recorded single-unit and multiunit activity from the dorsomedial striatum of mice as they spontaneously explored an arena. We observed both types of encoding, although continuous encoding was more prevalent than bursting near movement initiation or termination. The majority of recorded units did not exhibit positive linear relationships with speed but instead exhibited nonlinear relationships that peaked at a range of locomotor speeds. Bulk calcium recordings of identified direct and indirect pathway neurons revealed similar speed tuning profiles, indicating that the heterogeneity in response profiles was not due to this genetic distinction. We conclude that continuous encoding of speed is a central component of movement encoding in the striatum

    Development of a melting model for meteors

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    Meteor phenomenon is a frequent event happening on planet Earth. Due to the high entry velocities of these objects the surface of the material undergoes extreme heat loads. Since the material is mainly composed by several oxides, eventually, the surface temperature will overcome the melting point. In this study we propose a melting model, in order to understand the material behavior, coupled with a flow solver. A detailed study of the flow around the stagnation streamline is also presented
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