Sparsity-based localization of spatially coherent distributed sources

International audienceIn this paper, the localization of spatially distributed sources is considered. Based on the problem formulation of the De-convolution Approach for the Mapping of Acoustic Sources (DAMAS), a criterion based on a convex optimization under sparsity constraint is proposed to locate the sources. Also an original method is given to recover the angular distributions and the power of the sources. Simulations executed in the scenario of a mixture of distributed and point sources illustrate the validation of the proposed approach compared to other methods

Synthèse, étude et caractérisation de nouveaux catalyseurs moléculaires pour la réduction du Coú en vue de son utilisation comme source de carbone

Ce travail de thèse s'inscrit dans le contexte général des solutions envisageables pour répondre aux problèmes du réchauffement climatique global et de la diminution des ressources fossiles. Il a été en majeure partie consacré à l'étude et au développement d'électrocatalyseurs moléculaires pour la réduction du dioxyde de carbone. Un tel procédé pourrait permettre de transformer et valoriser le CO2 en l'exploitant comme une matière première carbonée disponible en quantité non limitée, bon marché et peu toxique. Dans une première partie, un métallocavitand, dont la structure est basée sur un calix[4]arène fonctionnalisé par quatre complexes phénanthroline tris-carbonyl de rhénium(I), a été étudié en solution et sur déposé sur surface transparente conductrice. Le but de cette étude était de contrôler par un stimulus électrochimique la fermeture et l'ouverture du bord large du cavitand. La complexité des processus rédox de ces métallo-macrocycles nous a conduits à étudier en détails les propriétés électrochimiques de complexes de rhénium(I) modèles. Ces propriétés avaient précédemment été rapportées dans la littérature mais étaient sujettes à désaccords entre les différents auteurs. Finalement l'ensemble de cette étude nous a conduits à préciser et à mieux comprendre le mécanisme de la catalyse de réduction du CO2 par ce type de complexes. Dans une deuxième partie, qui représente la partie la plus conséquente de cette thèse, la synthèse, la caractérisation physico-chimique et l'étude spectro-électrochimique de complexes bipyridine tris-carbonyle de manganèse, analogues des complexes de rhénium évoqués ci-dessus, ont été entreprises. Le but était de développer un catalyseur innovant pour la réduction électrochimique du dioxyde de carbone, du type complexe métallique, en substituant les métaux rares utilisés actuellement par un métal non-noble et abondant : le manganèse. Les propriétés électrochimiques des nouveaux complexes de Mn synthétisés ont été caractérisées en détail. La simulation des voltammétries cycliques, associée à des études mécanistiques par spectro-électrochimie UV-vis, a permis d'accéder aux données cinétiques et thermodynamiques des différentes réactions chimiques associées aux réactions de transferts d'électron irréversibles. Ces complexes de manganèse se sont révélés être des électrocatalyseurs de la réduction du CO2 au moins aussi efficaces que les complexes analogues de rhénium, décrits jusque-là comme étant les meilleurs systèmes pour cette application. Les complexes de Mn ainsi préparés montrent une excellente sélectivité (rendements faradiques élevés et peu ou pas de H2) et une bonne efficacité pour l'électro-réduction du CO2 en CO en milieu hydro-organique. Les catalyses à l'échelle préparatrice fonctionnent avec des surtensions modérées. Les mécanismes mis en jeu lors de la catalyse ont été étudiés par spectro-électrochimie UV-vis et RPE (en onde continue et pulsée) associées à des caculs théoriques DFT. Un intermédiaire-clé a ainsi pu être mis en évidence et caractérisé. Enfin, l'étude des réactions de décarbonylation photo-induites dans ces complexes est rapportée.This PhD takes place in the general context of possible solutions to global warming and peak oil issues. It mostly deals with the study and development of molecular electrocatalysts for carbon dioxide reduction. This process may open the way to the use and valorization of CO2 as a raw material. In the first part, a metallocavitand, which structure is based on a calix[4]arene modified by four phenanthroline tris-carbonyl rhenium(I) complexes, was studied in solution and deposited on a conductive transparent surface. The aim of this study was to control through an electrochemical stimulus the closing and opening of the wide rim of the cavitand. Complexity of the redox properties of the metallocavitand led us to investigate in detail the electrochemical properties of simpler examples of these rhenium(I) complexes. These properties were previously described in the literature ; however, there was disagreement in the interpretation of the results. Finally this study led us to a more precise and better understanding of the mechanism of the reduction of CO2 by a complex of this kind. In the second part, which is the main part of this PhD, synthesis, physico-chemical characterization and spectro-electrochemical study of bipyridine tris-carbonyl manganese complexes, analogues of the rhenium complexes mentioned above, were undertaken. The aim was to develop an innovative catalyst for the electrochemical reduction of carbon dioxide, based on a metallic complex, by substituting rare and noble metals currently used by a non-noble and abundant metal: manganese. Electrochemical properties of newly synthesized manganese complexes were investigated in detail. Simulations of cyclic voltammetry, associated with mechanism studies by UV-vis spectro-electrochemistry, allowed us to determine kinetic and thermodynamic properties of the different chemical reactions coupled with the irreversible electron transfers. These manganese complexes proved to electrocatalyse the reduction of carbon dioxide at least as efficiently as the analog rhenium complexes which were, until now, the best system for this application. These manganese electrocatalysts exhibit a very good selectivity (high faradic yields and no or very little H2) and a good efficiency for reduction of CO2 to CO in aqueous-organic media. Preparative scale electrolysis operates at low overpotential. Mechanisms of the different catalytic pathways were studied using UV-vis and EPR (continuous wave or pulsed) spectro-electrochemistry associated with DFT calculations. A key-intermediate was evinced and investigated. Finally the study of photo-induced decarbonylation reactions of these complexes is also described.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Guidelines for the diagnosis and management of chylomicron retention disease based on a review of the literature and the experience of two centers

Familial hypocholesterolemia, namely abetalipoproteinemia, hypobetalipoproteinemia and chylomicron retention disease (CRD), are rare genetic diseases that cause malnutrition, failure to thrive, growth failure and vitamin E deficiency, as well as other complications. Recently, the gene implicated in CRD was identified. The diagnosis is often delayed because symptoms are nonspecific. Treatment and follow-up remain poorly defined

The Relation Between Temperature, Ozone, and Mortality in Nine French Cities During the Heat Wave of 2003

BACKGROUND: During August 2003, record high temperatures were observed across Europe, and France was the country most affected. During this period, elevated ozone concentrations were measured all over the country. Questions were raised concerning the contribution of O(3) to the health impact of the summer 2003 heat wave. METHODS: We used a time-series design to analyze short-term effects of temperature and O(3) pollution on mortality. Counts of deaths were regressed on temperatures and O(3) levels, controlling for possible confounders: long-term trends, season, influenza outbreaks, day of the week, and bank holiday effects. For comparison with previous results of the nine cities, we calculated pooled excess risk using a random effect approach and an empirical Bayes approach. FINDINGS: For the nine cities, the excess risk of death is significant (1.01%; 95% confidence interval, 0.58–1.44) for an increase of 10 μg/m(3) in O(3) level. For the 3–17 August 2003 period, the excess risk of deaths linked to O(3) and temperatures together ranged from 10.6% in Le Havre to 174.7% in Paris. When we compared the relative contributions of O(3) and temperature to this joint excess risk, the contribution of O(3) varied according to the city, ranging from 2.5% in Bordeaux to 85.3% in Toulouse. INTERPRETATION: We observed heterogeneity among the nine cities not only for the joint effect of O(3) and temperatures, but also for the relative contribution of each factor. These results confirmed that in urban areas O(3) levels have a non-negligible impact in terms of public health

Interdiffusion and Chemical Reaction at Interfaces by TEM/EELS

International audienceThis chapter shows how research on interdiffusion and chemical reactions in thin films and their interface with semiconductor substrates can be conducted using the transmission electron microscopy (TEM) based method and their coupling with electron energy‐loss spectroscopy (EELS). Analytical TEMs commonly installed nowadays in most materials science laboratories are mainly considered in this study. The discussion is illustrated in the context of the developments of new gate oxides (commonly called higher dielectric constant (HK) materials) for the replacement of SiO2 in metal oxide semiconductor field‐effect transistors (MOSFETs). Literature data from HfO2, which is already integrated in MOSFET production since end of 2007 and of rare earth‐based oxides (REO), is particularly discussed together with results obtained at CEMES

Synthese de bis-porphyrines obliques : transfert d'energie intramoleculaire

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Microscopie électronique en transmission avancée pour l’étude des oxydes fonctionnels

National audienc

Sur l'élaboration des composites SiC/Al par le procédé au K₂ZrF₆ bases physico-chimiques et incidence sur la résistance des fibres

Amélioration de la mouillabilité des fibres de SiC par les alliages d'aluminium grace à un traitement de surface par une solution aqueuse saturée de K2ZrF6 à température proche de l'ébullition. Analyse des phénomènes responsables des cette amélioration et de leur influence sur la résistance à la rupture des fibresNon disponibl

Contamination and the quantitative exploitation of EELS low-loss experiments

International audienceQuantitative exploitation of the low-loss domain of electron energy loss spectra is based on an accurate determination of the corresponding signal intensity profile. This signal can be erroneous and contains artefacts as a result of sample contamination in the microscope, for example. The consequences of contamination on the signal intensity of the low-loss spectra are discussed. In the case of a carbonaceous contamination, a simple additional spurious signal can be considered, as has been demonstrated in the case of a Si single crystal, a highly oriented pyrolytic graphite (HOPG) and a strontium titanate single crystal (SrTiO3). The linear variation of the rate of contamination with time allows the implementation of a simple method based on the subtraction of the spurious signal in order to correct for the contamination effect. The relative errors induced by the carbonaceous contamination on the determination of the optical properties of SrTiO3 are estimated