447 research outputs found

    Numerical Simulations of Gravity-Driven Fingering in Unsaturated Porous Media Using a Non-Equilibrium Model

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    This is a computational study of gravity-driven fingering instabilities in unsaturated porous media. The governing equations and corresponding numerical scheme are based on the work of Nieber et al. [Ch. 23 in Soil Water Repellency, eds. C. J. Ritsema and L. W. Dekker, Elsevier, 2003] in which non-monotonic saturation profiles are obtained by supplementing the Richards equation with a non-equilibrium capillary pressure-saturation relationship, as well as including hysteretic effects. The first part of the study takes an extensive look at the sensitivity of the finger solutions to certain key parameters in the model such as capillary shape parameter, initial saturation, and capillary relaxation coefficient. The second part is a comparison to published experimental results that demonstrates the ability of the model to capture realistic fingering behaviour

    Estudio comparativo sobre las medidas implementadas por los países de Colombia y México frente a la crisis migratoria

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    Trabajo de investigaciónEn la actualidad la migración a nivel mundial se ha incrementado notablemente, por los problemas económicos y políticos que algunos países enfrentan, generando así que la mayoría de sus habitantes decidan salir a buscar mejores oportunidades, en otros países, como en este caso de estudio Colombia y México, por tal motivo se busca realizar un estudio comparativo sobre las diferentes medidas que han implementado estos países, y las medidas proteccionistas, con el fin de conocer el manejo que se ha brindado a esta misma problemática.RESUMEN INTRODUCCIÓN MARCO TEÓRICO CONCLUSIONES 1 ANEXOSEspecializaciónEspecialista en Formulación y Evaluación Social y Económica de Proyecto

    SHP-1 negatively regulates neuronal survival by functioning as a TrkA phosphatase

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    Nerve growth factor (NGF) mediates the survival and differentiation of neurons by stimulating the tyrosine kinase activity of the TrkA/NGF receptor. Here, we identify SHP-1 as a phosphotyrosine phosphatase that negatively regulates TrkA. SHP-1 formed complexes with TrkA at Y490, and dephosphorylated it at Y674/675. Expression of SHP-1 in sympathetic neurons induced apoptosis and TrkA dephosphorylation. Conversely, inhibition of endogenous SHP-1 with a dominant-inhibitory mutant stimulated basal tyrosine phosphorylation of TrkA, thereby promoting NGF-independent survival and causing sustained and elevated TrkA activation in the presence of NGF. Mice lacking SHP-1 had increased numbers of sympathetic neurons during the period of naturally occurring neuronal cell death, and when cultured, these neurons survived better than wild-type neurons in the absence of NGF. These data indicate that SHP-1 can function as a TrkA phosphatase, controlling both the basal and NGF-regulated level of TrkA activity in neurons, and suggest that SHP-1 regulates neuron number during the developmental cell death period by directly regulating TrkA activity

    Secondary Progressive Multiple Sclerosis: A Review of Clinical Characteristics, Definition, Prognostic Tools, and Disease-Modifying Therapies

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    Many challenges exist in the precise diagnosis and clinical management of secondary progressive multiple sclerosis (SPMS) because of the lack of definitive clinical, imaging, immunologic, or pathologic criteria that demarcate the transition from relapsing-remitting MS to SPMS. This review provides an overview of the diagnostic criteria/definition and the heterogeneity associated with different SPMS patient populations; it also emphasizes the importance of available prospective/retrospective tools to identify patients with SPMS earlier in the disease course so that approved disease-modifying therapies and nonpharmacological strategies will translate into better outcomes. Delivery of such interventions necessitates an evolving patient-clinician dialog within the context of a multidisciplinary team
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