Spectral element discretization of the vorticity, velocity and pressure formulation of the Stokes problem

We consider the Stokes problem provided with non standard boundary conditions which involve the normal component of the velocity and the tangential components of the vorticity. We write a variational formulation of this problem with three independent unknowns: the vorticity, the velocity and the pressure. Next we propose a discretization by spectral element methods which relies on this formulation. A detailed numerical analysis leads to optimal error estimates for the three unknowns and numerical experiments confirm the interest of the discretization

Le foncier urbain entre opportunité et maîtrise. Cas de Sétif (Algérie).

International audienceL'action foncière est l'un des facteurs clés de la production urbaine. Les grandes orientations des actes d'aménagement et d'urbanisation futurs dépendront de la façon de gérer et de maîtriser l'assiette foncière. Dans ce domaine l'Algérie accuse un certain déficit et le cadastre, malgré son importance capitale dans la maîtrise foncière, n'a jamais été une priorité. L'analyse de la ville de Sétif en est une illustration

Deoxynivalenol (DON) naturally contaminated feed impairs the immune response induced by porcine reproductive and respiratory syndrome virus (PRRSV) live attenuated vaccine

Cereal commodities are frequently contaminated with mycotoxins produced by the secondary metabolism of fungal infection. Among these contaminants, deoxynivalenol (DON), also known as vomitoxin, is the most prevalent type B trichothecene mycotoxin worldwide. Pigs are very sensitive to the toxic effects of DON and are frequently exposed to naturally contaminated feed. Recently, DON naturally contaminated feed has been shown to decrease porcine reproductive and respiratory syndrome virus (PRRSV) specific antibody responses following experimental infection. The objective of this study was to determine the impact of DON naturally contaminated feed on the immune response generated following vaccination with PRRSV live attenuated vaccine. Eighteen pigs were randomly divided into three experimental groups of 6 animals based on DON content of the diets (0, 2.5 and 3.5 mg DON/kg). They were fed these rations one week prior to the vaccination and for all the duration of the immune response evaluation. All pigs were vaccinated intra-muscularly with one dose of Ingelvac® PRRSV modified live vaccine (MLV). Blood samples were collected at day −1, 6, 13, 20, 27 and 35 post vaccination (pv) and tested for PRRSV RNA by RT-qPCR and for virus specific antibodies by ELISA. Results showed that ingestion of DON-contaminated diets significantly decreased PRRSV viremia. All pigs fed control diet were viremic while only 1 (17%) and 3 (50%) out of 6 pigs were viremic in the groups receiving 3.5 and 2.5 mg of DON/kg, respectively. Subsequently, all pigs fed control diet developed PRRSV specific antibodies while only viremic pigs that were fed contaminated diets have developed PRRSV specific antibodies. These results suggest that feeding pigs with DON-contaminated diet could inhibit vaccination efficiency of PRRSV MLV by severely impairing viral replication

Reconstruction of the interface between two layered media using far field measurements

International audienceWe consider an inverse transmission scattering problem. This problem consists in determining an interface between two-layered media by far-field measurements. We prove that the interface is uniquely determined by the measurements of the far field pattern associated to incoming plane waves at a fixed frequency. For the reconstruction of the interface we solve a non linear integral equation using a truncated Newton-CG algorithm

Spectral discretization of Darcy's equations with pressure dependent porosity

International audienceWe consider the flow of a viscous incompressible fluid in a rigid homogeneous porous medium provided with boundary conditions on the pressure around a circular well. When the boundary pressure presents high variations, the permeability of the medium depends on the pressure, so that the model is nonlinear. We propose a spectral discretization of the resulting system of equations which takes into account the axisymmetry of the domain and of the flow. We prove optimal error estimates and present some numerical experiments which confirm the interest of the discretization

Spectral element discretization of the vorticity, velocity and pressure formulation of the Navier-Stokes problem

The two-dimensional Navier–Stokes equations, when provided with non standard boundary conditions which involve the normal component of the velocity and the vorticity, admit a variational formulation with three independent unknowns, the vorticity, the velocity and the pressure. We propose a discretization of this problem by spectral element methods. A detailed numerical analysis leads to optimal error estimates for the three unknowns and numerical experiments confirm the interest of the discretization

Spectral discretization of the Stokes problem with mixed boundary conditions

The variational formulation of the Stokes problem with three independent unknowns, the vorticity, the velocity and the pressure, was born to handle non standard boundary conditions which involve the normal component of the velocity and the tangential components of the vorticity. We propose an extension of this formulation to the case of mixed boundary conditions in a three-dimensional domain. Next we consider a spectral discretization of this problem. A detailed numerical analysis leads to error estimates for the three unknowns and numerical experiments conrm the interest of the discretization

In vivo effect of deoxynivalenol (DON) naturally contaminated feed on porcine reproductive and respiratory syndrome virus (PRRSV) infection

Deoxynivalenol (DON), also known as vomitoxin, is the most prevalent type B trichothecene mycotoxin worldwide. Pigs show a great sensitivity to DON, and because of the high proportion of grains in their diets, they are frequently exposed to this mycotoxin. The objective of this study was to determine the impact of DON naturally contaminated feed on porcine reproductive and respiratory syndrome virus (PRRSV) infection, the most important porcine viral pathogen in swine. Experimental infections were performed with 30 animals. Piglets were randomly divided into three groups of 10 animals based on DON content of diets (0, 2.5 and 3.5 mg/kg DON). All experimental groups were further divided into subgroups of 6 pigs and were inoculated with PRRSV. The remaining pigs (control) were sham-inoculated with PBS. Pigs were daily monitored for temperature, weight and clinical signs for 21 days. Blood samples were collected and tested for PRRSV RNA and for virus specific antibodies. Results of PRRSV infection showed that ingestion of diet highly contaminated with DON greatly increases the effect of PRRSV infection on weight gain, lung lesions and mortality, without increasing significantly viral replication, for which the tendency is rather directed toward a decrease of replication. These results suggest that PRRSV infection could exacerbate anorectic effect of DON, when ingested in large doses. Results also demonstrate a DON negative effect on PRRSV-specific humoral responses. This study demonstrate that high concentrations of DON naturally contaminated feed decreased the immune response against PRRSV and influenced the course of PRRSV infection in pigs