Improvements for imaging ceramics sintering in situ in ESEM

International audienceSintering of green samples of alumina produced by ice-templating was followed in situ in an environmental scanning electron microscope (ESEM) up to temperatures as high as 1375 degrees C. These alumina samples with well-defined architectures are of great interest in the field of materials science due to their high specific strength (especially in compression), low density and adaptable porosity. For the present study, they also have the advantage to exhibit an important topography, inducing interesting contrast when imaged in an ESEM. Improvements of the imaging conditions in the ESEM were essential to really follow the sintering process involving formation of necks between grains or shift of the centre of grains. This paper describes the improvements made and the results observed on the sintering process of alumina green samples processed by ice-templating

The AVuPUR project (Assessing the Vulnerabiliy of Peri-Urbans Rivers): experimental set up, modelling strategy and first results

International audienceLe projet AVuPUR a pour objectif de progresser sur la compréhension et la modélisation des flux d'eau dans les bassins versants péri-urbains. Il s'agit plus particulièrement de fournir des outils permettant de quantifier l'impact d'objets anthropiques tels que zones urbaines, routes, fossés sur les régimes hydrologiques des cours d'eau dans ces bassins. Cet article présente la stratégie expérimentale et de collecte de données mise en ½uvre dans le projet et les pistes proposées pour l'amélioration des outils de modélisation existants et le développement d'outils novateurs. Enfin, nous présentons comment ces outils seront utilisés pour simuler et quantifier l'impact des modifications d'occupation des sols et/ou du climat sur les régimes hydrologiques des bassins étudiés. / The aim of the AVuPUR project is to enhance our understanding and modelling capacity of water fluxes within suburban watersheds. In particular, the objective is to deliver tools allowing to quantify the impact of anthropogenic elements such as urban areas, roads, ditches on the hydrological regime of suburban rivers. This paper presents the observation and data collection strategy set up by the project, and the directions for improving existing modelling tools or proposing innovative ones. Finally, we present how these tools will be used to simulate and quantify the impact of land use and climate changes on the hydrological regimes of the studied catchments

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel NaV1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on NaV1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Transmission electron microscopy observations of composite polymer colloid nucleated by functionalized silica

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STUDY OF COPPER-ALUMINA BONDING

L'adhésion entre un métal et une céramique peut être obtenue en comprimant à haute température les deux antagonistes sous faible pression (< 10 MPa) en atmosphère neutre. La liaison obtenue est testée mécaniquement par un essai de cisaillement de l'interface en fonction du temps et de l'oxydation du cuivre. L'interface et les ruptures sont observées et analysées à la microsonde de Castaing et en microscopie électronique en transmission.Bonding between a metal and a ceramic can be obtained by hot pressing of the two materials under low pressure (< 10 MPa) in protective atmosphere. In the present study this method was used to bond copper with alumina. The interface was assessed mechanically using a shear test as a function of time and copper oxidation. The bonding zone and the failures have been observed and analysed by electron probe microanalysis and transmission electron microscopy

VITREOUS STATE DECOMPOSITION STUDY IN SOME AQUEOUS POLYALCOHOLS SOLUTIONS

Le but de ce travail est de présenter une étude expérimentale des conditions de stabilité de l'état vitreux obtenu après trempe à 77 K avec des solutions de glycérol et de 1,2-propanediol. Cette étude a été réalisée à l'aide de mesures de frottement intérieur et d'observations par diffusion aux petits angles et de diffraction des rayons X. En pratiquant des maintiens isothermes, il a été possible de mettre en évidence deux types de décomposition de cet état vitreux : - une décomposition impliquant la formation de cristaux de glace avec trois domaines de température dans lesquels on a pu distinguer un processus de nucléation, un processus de nucléation et de croissance avec transformation de la glace cubique en glace hexagonale, un processus de coalescence des cristaux de glace hexagonale. - une décomposition de l'état vitreux initial en deux phases vitreuses l'une ayant une concentration en eau plus élevée que l'autre.The aim of this work is to present an experimental study of the stability of vitreous state obtained after quenching at 77 K in the case of both aqueous glycerol and 1,2-propanediol solutions. This study has been performed by means of internal friction measurements and X ray observations, i.e., X ray diffraction and small angle X ray scattering. By means of annealing treatments, it has been possible to point out two mechanisms for the decomposition of vitreous state : - first, involving ice crystallization with three temperature domains corresponding to (i) nucleation (ii) nucleation and growth (where cubic to hexagonal ice transformation occurs) (iii) Ostwald ripening mechanisms are evidenced. - second, involving a vitreous state being decomposed into two vitreous phases having a different water concentration

Sructural morphology of poly(styrene)-poly(butyl acrylate) polymer-polymer composites studied by dynamic mechanical measurements

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INTERNAL FRICTION AT MEDIUM TEMPERATURES IN HIGH PURITY ALUMINIUM

Afin de déterminer le mécanisme qui est à l'origine des relaxations P1 et P'1 nous avons comparé les résultats expérimentaux de frottement intérieur et de microscopie électronique d'un Al 99. 9999 %, obtenus autour de 0.5Tf, avec les prévisions théoriques des différents modèles proposés dans la littérature.In order to determine which mechanism is at the origin of the P1 and P'1 relaxations, the internal friction and electron microscopy experimental results of 99.9999 % Al around 0.5Tm have been compared to the theoretical forecasts of different proposed models