4,787 research outputs found

    Francesca Gherardi (1955-2013)

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    Recombination frequencies of mutations located in wc-1 and wc-2.

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    Recombination frequencies of mutations located in wc-1 and wc-2

    Onset and Evolution of the Oblique, Resonant Electron Firehose Instability in the Expanding Solar Wind Plasma

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    A double adiabatically expanding solar wind would quickly develop large parallel to perpendicular temperature anisotropies in electrons and ions that are not observed. One reason is that firehose instabilities would be triggered, leading to an ongoing driving/saturation evolution mechanism. We verify this assumption here for the first time for the electron distribution function and the electron firehose instability (EFI), using fully kinetic simulations with the Expanding Box Model. This allows the self-consistent study of onset and evolution of the oblique, resonant EFI in an expanding solar wind. We characterize how the competition between EFI and adiabatic expansion plays out in high- A nd low-beta cases, in high- A nd low-speed solar wind streams. We observe that, even when competing against expansion, the EFI results in perpendicular heating and parallel cooling. These two concurrent processes effectively limit the expansion-induced increase in temperature anisotropy and parallel electron beta. We show that the EFI goes through cycles of stabilization and destabilization: When higher wave number EFI modes saturate, lower wave number modes are destabilized by the effects of the expansion. We show how resonant wave/particle interaction modifies the electron velocity distribution function after the onset of the EFI. The simulations are performed with the fully kinetic, semi-implicit expanding box code EB-iPic3D

    Specificity of Neuronal Responses in Primary Visual Cortex Is Modulated by Interhemispheric CorticoCortical Input

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    Within the visual cortex, it has been proposed that interhemispheric interactions serve to re-establish the continuity of the visual field across its vertical meridian (VM) by mechanisms similar to those used by intrinsic connections within a hemisphere. However, other specific functions of transcallosal projections have also been proposed, including contributing to disparity tuning and depth perception. Here, we consider whether interhemispheric connections modulate specific response properties, orientation and direction selectivity, of neurons in areas 17 and 18 of the ferret by combining reversible thermal deactivation in one hemisphere with optical imaging of intrinsic signals and single-cell electrophysiology in the other hemisphere. We found interhemispheric influences on both the strength and specificity of the responses to stimulus orientation and direction of motion, predominantly at the VM. However, neurons and domains preferring cardinal contours, in particular vertical contours, seem to receive stronger interhemispheric input than others. This finding is compatible with interhemispheric connections being involved in horizontal disparity tuning. In conclusion, our results support the view that interhemispheric interactions mainly perform integrative functions similar to those of connections intrinsic to one hemisphere

    Lagrangian filtered density function for LES-based stochastic modelling of turbulent dispersed flows

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    The Eulerian-Lagrangian approach based on Large-Eddy Simulation (LES) is one of the most promising and viable numerical tools to study turbulent dispersed flows when the computational cost of Direct Numerical Simulation (DNS) becomes too expensive. The applicability of this approach is however limited if the effects of the Sub-Grid Scales (SGS) of the flow on particle dynamics are neglected. In this paper, we propose to take these effects into account by means of a Lagrangian stochastic SGS model for the equations of particle motion. The model extends to particle-laden flows the velocity-filtered density function method originally developed for reactive flows. The underlying filtered density function is simulated through a Lagrangian Monte Carlo procedure that solves for a set of Stochastic Differential Equations (SDEs) along individual particle trajectories. The resulting model is tested for the reference case of turbulent channel flow, using a hybrid algorithm in which the fluid velocity field is provided by LES and then used to advance the SDEs in time. The model consistency is assessed in the limit of particles with zero inertia, when "duplicate fields" are available from both the Eulerian LES and the Lagrangian tracking. Tests with inertial particles were performed to examine the capability of the model to capture particle preferential concentration and near-wall segregation. Upon comparison with DNS-based statistics, our results show improved accuracy and considerably reduced errors with respect to the case in which no SGS model is used in the equations of particle motion

    Improving plastic management by means of people awareness

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    In past decades the usage of plastic has seen a tremendous increment. This raise is mainly caused by industrial development and by the spread of this material in every aspect of people life, from food package to aerospace application. For sure plastic has a key role in society and it is not possible to erase, nevertheless its overuse has a serious impact on the environment as well know. In particular, just a few percentage of the total amount of plastic is recycled, the rest has to be landfilled or burnt causing serious pollution side effect. This poor circularity in plastic value chain is mainly caused by difficulties in sorting processes and expensiveness of recycling. By the way a great part of plastic applications could be avoided without implying a reduction in life quality for the people. In addition, a better education in plastic objects shopping and plastic waste management could decrease the difficulties in sorting and recycling. One of the crucial reason why these applications and incorrect behaviour are still present is that the information on alternatives are not present or very hard to be found. In the present paper a novel platform to enhance a more plastic-free life is presented. First a detailed description of the problem is stated, then the process to achieve the proposed solution is described. Finally the platform prototype is analysed in details among its functionalities

    Use of microfluidic capillary electrophoresis for the determination of multi-component protein adsorption isotherms: Application to high-throughput analysis for hydrophobic interaction chromatography

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    Chromatography is a widely used separation process for purification of biopharmaceuticals that is able to obtain high purities and concentrations. The phenomena that occur during separation, mass transfer and adsorption are quite complex. To better understand these phenomena and their mechanisms, multi-component adsorption isotherms must be investigated. High-throughput methodologies are a very powerful tool to determine adsorption isotherms and they waste very small amounts of sample and chemicals, but the quantification of component concentrations is a real bottleneck in multi-component isotherm determination. The behavior of bovine serum albumin, Corynebacterium diphtheriae CRM197 protein and lysozyme, selected as model proteins in binary mixtures with hydrophobic resin, is investigated here. In this work we propose a new method for determining multi-component adsorption isotherms using high-throughput experiments with filter plates, by exploiting microfluidic capillary electrophoresis. The precision and accuracy of the microfluidic capillary electrophoresis platform were evaluated in order to assess the procedure; they were both found to be high and the procedure is thus reliable in determining adsorption isotherms for binary mixtures. Multi-component adsorption isotherms were determined with a totally high-throughput procedure that turned out to be a very fast and powerful tool. The same procedure can be applied to every kind of high-throughput screening
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