Une méthode de Galerkin Discontinu pour la résolution des équations de Maxwell en milieu hétérogène

Ce travail consiste à appliquer une méthode dite Galerkin Discontinu à la résolution du système de Maxwell dans un milieu hétérogène. La méthode est basée sur le choix d'une base locale, et des formules de quadrature pour approcher les différentes intégrales. On obtient ainsi une solution approchée discontinue. Afin de vérifier les conditions de transmission d'un domaine à un autre, nous avons utilisé un schéma de Godunov pour calculer les flux numériques. Nous avons ensuite, comparé les solutions obtenues par cette méthode avec celles obtenues par une méthode de Volumes Finis

A Centered Second-Order Finite Volume Scheme for the Heterogeneous Maxwell Equations in Three Dimensions on Arbitrary Unstructured Meshes

We prove a sufficient CFL-like condition for the L^2 stability of the second-order accurate finite volume scheme proposed by Remaki for the time-domain solution of Maxwell equations in heterogenous media, with metallic and absorbing boundary conditions. We yield a very general sufficient condition, valid for any finite volume partition in two and three space dimensions. Numerical tests show the potential of this original finite volume scheme in one, two and three space dimensions for the numerical solution of Maxwell equations in the time domain

Un nouveau schéma de type volumes finis appliqué aux équations de Maxwell en milieu hétérogène

Nous décrivons ici une méthode de volumes finis pour la résolution du système de Maxwell en milieu hétérogène. Nous utilisons une extension du schéma de Godunov pour satisfaire aux conditions de transmission aux interfaces. Nous proposons, pour l'amélioration de la précision spatiale, une nouvelle définition des gradients qui nous semble plus compatible avec la formulation volumes finis

A non-diffusive finite volume scheme for the 3D Maxwell equations on unstructured meshes

International audienc

Une methode de Galerkin Discontinu pour la resolution des equations de Maxwell en milieu heterogene

Theme 4 - Simulation et optimisation de systemes complexes. Projet CAIMANAvailable from INIST (FR), Document Supply Service, under shelf-number : 14802 E, issue : a.1998 n.3501 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Un nouveau schema de type volumes finis applique aux equations de Maxwell en milieu heterogene

Theme 4 - Simulation et optimisation de systemes complexes. Projet CAIMANAvailable from INIST (FR), Document Supply Service, under shelf-number : 14802 E, issue : a.1998 n.3351 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

A novel brain-penetrant oral UGT8 inhibitor decreases in vivo galactosphingolipid biosynthesis in murine Krabbe disease.

Krabbe disease is a rare, inherited neurodegenerative disease due to impaired lysosomal β-galactosylceramidase (GALC) activity and formation of neurotoxic β-galactosylsphingosine ('psychosine'). We investigated substrate reduction therapy with a novel brain-penetrant inhibitor of galactosylceramide biosynthesis, RA 5557, in twitcher mice that lack GALC activity and model Krabbe disease. This thienopyridine derivative selectively inhibits uridine diphosphate-galactose glycosyltransferase 8 (UGT8), the final step in the generation of galactosylceramides which are precursors of sulphatide and, in the pathological lysosome, the immediate source of psychosine. Administration of RA 5557, reduced pathologically elevated psychosine concentrations (72-86%) in the midbrain and cerebral cortex in twitcher mice: the inhibitor decreased galactosylceramides by about 70% in midbrain and cerebral cortex in mutant and wild type animals. Exposure to the inhibitor significantly decreased several characteristic inflammatory response markers without causing apparent toxicity to myelin-producing cells in wild type and mutant mice; transcript abundance of oligodendrocyte markers MBP (myelin basic protein) and murine UGT8 was unchanged. Administration of the inhibitor before conception and during several breeding cycles to mice did not impair fertility and gave rise to healthy offspring. Nevertheless, given the unchanged lifespan, it appears that GALC has critical functions in the nervous system beyond the hydrolysis of galactosylceramide and galactosylsphingosine. Our findings support further therapeutic exploration of orally active UGT8 inhibitors in Krabbe disease and related galactosphingolipid disorders. The potent thienopyridine derivative with effective target engagement here studied appears to have an acceptable safety profile in vivo; judicious dose optimization will be needed to ensure efficacious clinical translation.Sponsored by Sanofi phamaceuticals but with Cambridge NIHR BRC salary support for one author from Cambridge (Cachon-Gonzalez

Antitussive activity of sigma-1 receptor agonists in the guinea-pig

1. Current antitussive medications have limited efficacy and often contain the opiate-like agent dextromethorphan (DEX). The mechanism whereby DEX inhibits cough is ill defined. DEX displays affinity at both NMDA and sigma receptors, suggesting that the antitussive activity may involve central or peripheral activity at either of these receptors. This study examined and compared the antitussive activity of DEX and various putative sigma receptor agonists in the guinea-pig citric-acid cough model. 2. Intraperitoneal (i.p.) administration of DEX (30 mg kg(−1)) and the sigma-1 agonists SKF-10,047 (1–5 mg kg(−1)), Pre-084 (5 mg kg(−1)), and carbetapentane (1–5 mg kg(−1)) inhibited citric-acid-induced cough in guinea-pigs. Intraperitoneal administration of a sigma-1 antagonist, BD 1047 (1–5 mg kg(−1)), reversed the inhibition of cough elicited by SKF-10,047. In addition, two structurally dissimilar sigma agonists SKF-10,047 (1 mg ml(−1)) and Pre-084 (1 mg ml(−1)) inhibited cough when administered by aerosol. 3. Aerosolized BD 1047 (1 mg ml(−1), 30 min) prevented the antitussive action of SKF-10,047 (5 mg kg(−1)) or DEX (30 mg kg(−1)) given by i.p. administration and, likewise, i.p. administration of BD 1047 (5 mg kg(−1)) prevented the antitussive action of SKF-10,047 given by aerosol (1 mg ml(−1)). 4. These results therefore support the argument that antitussive effects of DEX may be mediated via sigma receptors, since both systemic and aerosol administration of sigma-1 receptor agonists inhibit citric-acid-induced cough in guinea-pigs. While significant systemic exposure is possible with aerosol administration, the very low doses administered (estimated <0.3 mg kg(−1)) suggest that there may be a peripheral component to the antitussive effect