Capturing nonclassical shocks in nonlinear elastodynamic with a conservative finite volume scheme

For a model of nonlinear elastodynamics, we construct a finite volume scheme which is able to capture nonclassical shocks (also called undercompressive shocks). Those shocks verify an entropy inequality but are not admissible in the sense of Liu. They verify a kinetic relation which describes the jump, and keeps an information on the equilibrium between a vanishing dispersion and a vanishing diffusion. The scheme pre-sented here is by construction exact when the initial data is an isolated nonclassical shock. In general, it does not introduce any diffusion near shocks, and hence nonclas-sical solutions are correctly approximated. The method is fully conservative and does not use any shock-tracking mesh. This approach is tested and validated on several test cases. In particular, as the nonclassical shocks are not diffused at all, it is possible to obtain large time asymptotics

A Non-dissipative Reconstruction Scheme for the Compressible Euler Equations

We present a finite volume scheme, first on the Burgers equations, then on the Euler equations, based on a conservative reconstruction of shocks inside each cells of the mesh. Its main features are the following points. First, the scheme is exact whenever the initial datum is a pure shock, in the sense that the approximate solution is the exact solution averaged over the cells of the mesh. Second, the scheme has in general a very low numerical diffusion and the shocks have a width of one or two cells. Third, no spurious oscillations in the momentum appear behind slowly moving shocks, which is not the case in most of the scheme developed so far. We also present prospective result on the full Euler equations with energy. The wall heating phenomenon, which is an artificial elevation of the temperature when a shock reflects on a wall, is also drastically diminished

Mechanistic Characterization of Active Site Residues in Nitronate Monooxygenase from Pseudomonas aeruginosa PAO1

Propionate 3-nitronate (P3N) is a natural toxin that irreversibly inhibits the Krebs cycle – a life sustaining metabolic pathway. Nitronate monooxygenase detoxifies P3N using molecular oxygen. Among ∼500 NMO sequences from various organisms, NMO has evolved to contain Y109, Y254, Y299, Y303, K307, and H183 in putative NMOs. In this thesis, the role of these select residues in the binding and oxidation of P3N is studied. Using steady state kinetics and UV-visible absorption spectroscopy, Y109, Y254, Y299, Y303, and K307 were found to have no role in the turnover of P3N. Utilizing steady-state, rapid kinetics, and x-ray crystallography, H183 was determined to be an essential residue in binding P3N into an enzyme-substrate complex competent for the single electron transfer between P3N and the reactive center of the enzyme

Encouraging ‘Returns’, Obstructing Departures and Constructing Causal Links: The New Creed of Euro-African Migration Management

This paper explores whether the policy level constitutes a new element in what Hernández-León coined as “the migration industry” in 2005. The paper unravels the impact of semantic and legal shifts at different scales over the past two decades on the framing of irregular migration. Several key moments have marked Euro-African relations in the field migration. Through the decoding of political exchanges between African and European actors, this article shows the predominant objectives of migration policies. The first aims to encourage "returns" of migrants from Europe to Africa. The second seeks to dissuade potential African candidates from leaving (implied towards Europe), and the third presupposes that the returns of some migrants will make potential migrants renounce the journey. In order to prevent departures and to justify returns, new causal links appear in speeches. There is here an idea of an archetypal model linking returns and deterrents. This binary justification of a presupposed causality between returns and departures is questionable however because evidence shows that returns will not necessarily have the expected deterrent effect. Nevertheless, the migration and development nexus has gradually come to complement the migration and security nexus. At different scales and through semantic and legal shifts, emigration has been framed as a “problem” then as a “crime” in the dominant policy discourse. Through the design and implementation of departure deterrence programmes, actors from NGOs, international organisations, political institutions and the media are strengthening the controversial notion of "illegal emigration" which, gradually, has become a new resource in the field of migration management.DFI

Saloum, du poste frontière au camp de réfugiés : Les exilés de Libye deux ans après

Ce rapport est basé sur une mission d’étude réalisée en Egypte conjointement par La Cimade et l’Institut de recherche pour le développement (IRD) en février 2013. Il tente de dresser un état des lieux de la situation des exilés vivant au camp de Saloum deux ans après sa création