Ségrégation interfaciale dans les métaux en cours de déformation à chaud : cas du système nickel - soufre

Equilibrium grain boundary segregation in metals has been widely studied, but not the non-equilibrium one. In this study, we aimed to characterize the segregation during annealing and during hot deformation in the nickel - sulphur system. Two different methods of quantification were used: Auger electron spectroscopy and wavelength dispersive X-ray spectroscopy (WDS). The latter was originally adapted by our research group to the quantification of monolayers on a substrate. The diffusion coefficient of sulphur in nickel was measured at 550°C and 750°C and we obtained respectively 2.9 10-14 cm2.s-1 and 2.6 10-12 cm2.s-1. Measurements on samples annealed at different temperatures led to a free energy of segregation of 102 kJ.mol-1 and a concentration of sulphur in the grain boundary of 63.5 ng.cm-2 when saturated. We also investigated the influence of the temperature (450 and 550°C) and the deformation rate (3.9 10-5 s-1 and 3.8 10-4 s-1) on the interface segregation. During hot compression, we obtained a segregation up to 150 000 times faster compared to simple annealing at the same temperature. Multiplying the deformation rate by ten leads to a similar deformation-dependence of the segregation but a time-dependence 6,5 times as fast. In the investigated ranges of temperature and deformation rate, the segregation rate is nearly independent of the temperature. The segregation kinetics during hot deformation was satisfactorily modelled by taking account of the effect of the deformation-induced vacancies on the solute diffusion coefficient. The phenomenon of accelerated sulphur grain boundary segregation in nickel can then be attributed to the excess vacancies.Dans cette thèse, nous avons cherché à caractériser la ségrégation intergranulaire dans les métaux en cours de recuit et de déformation à chaud, dans le système modèle nickel - soufre. Deux méthodes de quantification ont été utilisées : la spectrométrie d'électrons Auger et l'analyse par dispersion de longueur d'onde des rayons X (WDX). Cette dernière a été adaptée de façon originale par notre équipe pour la quantification de monocouches sur un substrat. Le tracé de cinétiques de ségrégation en cours de recuit à 550 et 750°C a permis la mesure des coefficients de diffusion du soufre dans le nickel, respectivement de 2,9.10-14 cm2.s-1 et 2,6.10-12 cm2.s-1. Par l'étude d'échantillons recuits à différentes températures nous avons obtenu une enthalpie libre de ségrégation de 102 kJ.mol-1 et une concentration en soufre dans le joint de grain à saturation de 63,5 ng.cm-2. Nous avons également étudié l'influence de la température (450 et 550°C) et de la vitesse de déformation (3,9.10-5 s-1 et 3,8.10-4 s-1) sur la ségrégation intergranulaire. En cours de compression, nous obtenons une cinétique jusqu'à 150 000 fois plus rapide que lors d'un recuit d'équilibre. Décupler la vitesse de déformation ne modifie pas l'évolution de la ségrégation en fonction de la déformation mais multiplie la cinétique par 6,5. Enfin, dans les domaines étudiés, la vitesse de ségrégation est quasiment indépendante de la température. Un modèle calculant la concentration en lacunes en cours de déformation pour en déduire la diffusion du soufre permet de reproduire correctement nos mesures de ségrégation. Le phénomène de ségrégation intergranulaire accélérée du soufre dans le nickel en cours de déformation à chaud semble donc attribuable à la présence de lacunes en sursaturation

Etude métallurgique du soudage par friction malaxage sur un acier à haute limite élastique destiné à la construction navale : le 80 HLES

Le soudage par friction malaxage est un procédé de soudage relativement récent (début des années 90). Il est aujourd'hui utilisé couramment sur des alliages légers mais ne l'est que depuis peu sur les aciers. L'objectif de nos travaux est de chercher à caractériser la microstructure métallurgique et l'état de déformation et de contrainte après soudage par friction malaxage sur des échantillons d'aciers à haute limite élastique utilisés dans l'industrie navale. Nous chercherons à comprendre les phénomènes métallurgiques qui interviennent en cours de soudage

Vectorial Release of Hepatitis E Virus in Polarized Human Hepatocytes

International audienceHepatitis E virus (HEV) is a common cause of acute viral hepatitis worldwide. Most HEV infections are asymptomatic, but immunocompromised patients infected with HEV genotype 3 (HEV3), HEV4, or HEV7 may develop chronic infections. The HEV particles in stools are naked (nHEV), while those in the serum and culture supernatants (eHEV) are associated with lipids. Hepatocytes are polarized epithelial cells that have basolateral (oriented toward the blood) and apical (oriented toward the bile) exosomal pathways. We isolated a subclone, F2, from the human hepatocarcinoma cell line HepG2/C3A that grew as a polarized monolayer culture and had better HEV production than HepG2/C3A cells. F2 cells cultured on semipermeable collagen inserts and infected basolaterally with nHEV3 released 94.6% of virus particles apically, those infected with eHEV3 released 96.8% apically, and eHEV1-infected cells released 99.3% apically. Transcytosis was not involved. Density gradient centrifugation and NP-40 treatment showed that HEV particles released both apically and basolaterally were lipid associated. The apically released HEV3 and HEV1 particles were six and nine times more infectious than those released basolaterally, respectively. Confocal microscopy indicated that the open reading frame 2 (ORF2) capsid protein colocalized apically with ORF3 virus protein, the apical marker DPP4, and the recycling endosome GTPase Rab27a. The amounts of soluble glycosylated ORF2 secreted apically and basolaterally were similar. These polarized-hepatocyte data suggest that infectious HEV particles are mainly released into bile, while the small fraction released into blood could spread HEV throughout the host.IMPORTANCE Hepatitis E virus (HEV) in stools is naked, while that in culture supernatants and patients' blood is lipid associated. Its life cycle in hepatocytes, polarized cells with a basolateral side communicating with blood and an apical side connected with bile, is incompletely understood. We have developed a polarized hepatocyte model and used the cells to analyze the supernatants bathing the apical and basolateral sides and HEV subcellular distribution. HEV particles from both sides were lipid associated, and most infectious HEV particles left the cell via its apical side. Similar amounts of the open reading frame 2 (ORF2) soluble capsid protein were secreted from both sides of the hepatocytes. This model mimicking physiological conditions should help clarify the HEV cell cycle in polarized hepatocytes

Fondation recherche endométriose: le catalyseur de la recherche sur l’endométriose en France

International audienceThe Endometriosis Research Foundation (FRE) was created in January 2021 under the aegis of the Foundation for Medical Research with the vision of promoting innovative, multidisciplinary, and collaborative research dedicated to endometriosis. The FRE mission is to accelerate the research on endometriosis. For that purpose, it supports every year innovative Research projects aiming to better understand and treat the pathology and spreads pedagogical contents on the latest scientific advances in the domain.The values of the FRE are innovation mindset and collaboration, independence and integrity. The governance is based on an executive committee that decides on the strategy of the FRE and communicates on its goals and resources. In its scientific mission, it is assisted by an international committee. The FRE wishes to place patients at the heart of the Foundation’s actions and decisions and to promote a participatory research approach. To this end, a Patient and Caregiver Advisory Committee (PCAC) was created in September 2022. The Endometriosis Research Foundation, under the aegis of the MRF, aims to increase its impact in the field of promoting and supporting research, both in terms of funding and in providing expertise to support researchers. Copyrigh

Metastatic colorectal carcinoma with signet-ring cells: Clinical, histological and molecular description from an Association des Gastro-Entérologues Oncologues (AGEO) French multicenter retrospective cohort

International audienc