Modeling dimensionally-heterogeneous problems: analysis, approximation and applications

In the present work a general theoretical framework for coupled dimensionally-heterogeneous partial differential equations is developed. This is done by recasting the variational formulation in terms of coupling interface variables. In such a general setting we analyze existence and uniqueness of solutions for both the continuous problem and its finite dimensional approximation. This approach also allows the development of different iterative substructuring solution methodologies involving dimensionally-homogeneous subproblems. Numerical experiments are carried out to test our theoretical result

PSEUDOSPECTRAL LEAST SQUARES METHOD FOR STOKES-DARCY EQUATIONS

We investigate the first order system least squares Legendre and Chebyshev pseudospectral method for coupled Stokes-Darcy equations. A least squares functional is defined by summing up the weighted L-2-norm of residuals of the first order system for coupled Stokes-Darcy equations and that of Beavers-Joseph-Saffman interface conditions. Continuous and discrete homogeneous functionals are shown to be equivalent to a combination of weighted H(div) and H-1-norms for Stokes and Darcy equations. The spectral convergence for the Legendre and Chebyshev methods is derived. Some numerical experiments are demonstrated to validate our analysisopen0

Numerical analysis of the Navier-Stokes/Darcy coupling

We consider a differential system based on the coupling of the Navier-Stokes and Darcy equations for modeling the interaction between surface and porous-media flows. We formulate the problem as an interface equation, we analyze the associated (nonlinear) Steklov-Poincaré operators, and we prove its well-posedness. We propose and analyze iterative methods to solve a conforming finite element approximation of the coupled proble

Note préliminaire sur les effets expérimentaux de l'aflatoxine chez les bovins tropicaux : effets de l'aflatoxine sur la vache laitière et sur le jeune nourri à la mamelle

Cette première expérimentation se situe dans le cadre d'un programme à long terme sur les effets de l'aflatoxine chez les bovins tropicaux. Elle a pour but de rechercher chez la vache en lactation, recevant une dose expérimentale volontairement forte de 1,5 mg d'aflatoxine par jour, les désordres susceptibles d'être produits, chez la mère et chez le jeune. Alors que les adultes semblent résister à l'intoxication, les répercussions sont plus sensibles chez le jeune qui accuse un retard de croissance significatif. Les troubles observés chez les veaux à la mamelle paraissent liés à la présence d'aflatoxine dans le lai

Note sur la présence d'aflatoxine dans les fanes d'arachides

Les fanes d'arachide constituent en pays arachidien et spécialement au Sénégal un aliment appété par les diverses espèces animales. Des recherches effectuées sur ce fourrage au Laboratoire National de l'Elevage et de Recherches Vétérinaires de Dakar, ont révélé la présence d'aflatoxine de toxicité comparable à celle trouvée dans la graine et les tourteaux d'arachid

Challenges for time and frequency domain aeroacoustic solvers

The linearized Euler equations (LEE) model acoustic propagation in the presence of rotational mean flows. They can be solved in time [1–3] or in frequency [4–6] domain, with both approaches having advantages and disadvantages. Here, those pros and cons are detailed, both from a modeling and a numerical/computational perspective. Furthermore, a performance comparison and cross-validation between two frequency and time domain state-of-the-art solvers is performed. The frequency domain solutions are obtained with the hybridizable discontinuous Galerkin (HDG) [7–12] and the embedded discontinuous Galerkin (EDG) [13–15] method, while the time domain solver is an explicit discontinuous-Galerkin based solver [1]. The performance comparison and cross-validation is performed on a problem of industrial interest, namely acoustic propagation from a duct exhaust in the presence of realistic mean flow.Peer ReviewedPostprint (published version

Low TLR7 gene expression in atherosclerotic plaques is associated with major adverse cardio- and cerebrovascular events

AIMS: Processes in the development of atherosclerotic lesions can lead to plaque rupture or erosion, which can in turn elicit myocardial infarction or ischaemic stroke. The aims of this study were to determine whether Toll-like receptor 7 (TLR7) gene expression levels influence patient outcome and to explore the mechanisms linked to TLR7 expression in atherosclerosis. METHODS AND RESULTS: Atherosclerotic plaques were removed by carotid endarterectomy (CEA) and subjected to gene array expression analysis (n = 123). Increased levels of TLR7 transcript in the plaques were associated with better outcome in a follow-up study over a maximum of 8 years. Patients with higher TLR7 transcript levels had a lower risk of experiencing major cardiovascular and cerebrovascular events (MACCE) during the follow-up period after CEA (hazard ratio: 2.38, P = 0.012, 95% CI 1.21–4.67). TLR7 was expressed in all plaques by T cells, macrophages and endothelial cells in capillaries, as shown by immunohistochemistry. In short-term tissue cultures, ex vivo treatment of plaques with the TLR7 ligand imiquimod elicited dose-dependent secretion of IL-10, TNF-α, GM-CSF, and IL-12/IL-23p40. This secretion was blocked with a TLR7 inhibitor. Immunofluorescent tissue analysis after TLR7 stimulation showed IL-10 expression in T cells, macrophages and vascular smooth muscle cells. TLR7 mRNA levels in the plaques were correlated with IL-10 receptor (r = 0.4031, P < 0.0001) and GM-CSF receptor A (r = 0.4354, P < 0.0001) transcripts. CONCLUSION: These findings demonstrate that TLR7 is abundantly expressed in human atherosclerotic plaques. TLR7 ligation elicits the secretion of pro-inflammatory and anti-inflammatory cytokines, and high TLR7 expression in plaques is associated with better patient outcome, suggesting that TLR7 is a potential therapeutic target for prevention of complications of atherosclerosis

Changing Landscapes: The Provincial Text in Russian-Soviet Culture. Introduction

Introduction to the monographic section “Changing Landscapes: the Provincial Text in Russian-Soviet Culture.

Augmented interface systems for the Darcy-Stokes problem

In this paper we study interface equations associated to the Darcy-Stokes problem using the classical Steklov-Poincaré approach and a new one called augmented. We compare these two families of methods and characterize at the discrete level suitable preconditioners with additive and multiplicative structures. Finally, we present some numerical results to assess their behavior in presence of small physical parameters