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Department of Physics
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Department of Biology
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Department of Chemistry
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  • [Show abstract] [Hide abstract]
    ABSTRACT: Des données issues de simulations numériques directes et d'analyses théoriques relatives à un écoulement turbulent homogène en décroissance libre dans un fluide conducteur sujet à un champ magnétique sont utilisées pour évaluer les modèles de turbulence MHD développés par Widlund et al. et Kenjeres et al. Nous considérons, dans la présente étude, le cas où le nombre de Reynolds magnétique est faible. Ce cas correspond à l'approximation quasi stationnaire. Cette dernière est la plus recommandée dans l'étude des écoulements turbulents industriels. Les résultats de nos calculs montrent la capacité significative du modèle de Widlund et al. à reproduire les effets de la force de Lorentz comparé au modèle de Kenjeres et al.
    Comptes Rendus Physique. 07/2014; 15(6):509–516.
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the identification of a novel CC chemokine receptor 5 (CCR5) variant that seems associated with resistance to HIV-1 infection. The V130I mutation of the CCR5 receptor is located in the intracellular loop ICL2 known as DRY box and described in the literature as a nonsynonymous mutation present in nonhuman primates group. Extensive molecular modeling and dynamics simulations were performed to elucidate the mechanism by which the V130I mutation may induce conformational change of the CCR5 folding protein and prevent the interaction with the β-arrestin protein. Our study provides new mechanistic insight into how a specific mutation in the regulatory domain of CCR5 might alter the structural folding of the DRY box and the possible ICL2 loop binding with the β-arrestin protein, as described in our previous computational study. The results from our large-scale simulations complement recent experimental results and clinical features and offer useful insights into the mechanism behind CCR5 protein folding and signal transduction. In order for HIV, the entry of the virus to the cells must fuse with the CCR5 receptor that sits on the surface of T-helper immune cells. The described V130I mutation in the gene encoding the CCR5 protein may results in a defective CCR5-Arrestin binding complex that blocks entry of the virus.
    Journal of biomolecular structure & dynamics 07/2013;
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    ABSTRACT: This paper is devoted to the second-order closure for compressible turbulent flows with special attention paid to modeling the pressure–strain correlation appearing in the Reynolds stress equation. This term appears as the main one responsible for the changes of the turbulence structures that arise from structural compressibility effects. From the analysis and DNS results of Simone et al. and Sarkar, the compressibility effects on the homogeneous turbulence shear flow are parameterized by the gradient Mach number. Several experiment and DNS results suggest that the convective Mach number is appropriate to study the compressibility effects on the mixing layers. The extension of the LRR model recently proposed by Marzougui, Khlifi and Lili for the pressure–strain correlation gives results that are in disagreement with the DNS results of Sarkar for high-speed shear flows. This extension is revised to derive a turbulence model for the pressure–strain correlation in which the compressibility is included in the turbulent Mach number, the gradient Mach number and then the convective Mach number. The behavior of the proposed model is compared to the compressible model of Adumitroiae et al. for the pressure–strain correlation in two turbulent compressible flows: homogeneous shear flow and mixing layers. In compressible homogeneous shear flows, the predicted results are compared with the DNS data of Simone et al. and those of Sarkar. For low compressibility, the two compressible models are similar, but they become substantially different at high compressibilities. The proposed model shows good agreement with all cases of DNS results. Those of Adumitroiae et al. do not reflect any effect of a change in the initial value of the gradient Mach number on the Reynolds stress anisotropy. The models are used to simulate compressible mixing layers. Comparison of our predictions with those of Adumitroiae et al. and with the experimental results of Goebel et al. shows good qualitative agreement.
    Comptes Rendus Mécanique. 07/2013; 341(7):567–580.


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    Tunis, Tunisia
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Journal of sports science & medicine 01/2006;
TJASSST 2013, Hammamet; 11/2013

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