Vieillissement thermomécanique d'un acier inoxydable martensitique à durcissement structural

Les aciers martensitique inoxydables à durcissement structural sont un des matériaux constitutifs des mats réacteurs d'avion. Cette pièce est soumise aussi bien à des contraintes mécaniques qu'à des contraintes thermiques. Cette dernière engendre le vieillissement de ces aciers, du fait de la présence d'une lacune de miscibilité dans le diagramme Fe-Cr. Deux mécanismes sont possibles dans cette lacune de miscibilité, la précipitation d'une phase riche en chrome α' ou une démixtion suivant un mécanisme de décomposition spinodale. Cette thématique est l'objet du projet PREVISIA financé par l'ANR, dont cette thèse fait partie. Des vieillissements ont été effectués sur l'acier 15 5 PH jusqu'à 15 000 h afin d'étudier la cinétique de vieillissement par décomposition spinodale et son effet sur les propriétés mécaniques de l'alliage en traction, résilience et ténacité. Le vieillissement de l'acier engendre ainsi un durcissement et une fragilisation de l'alliage. De plus, des analyses microstructurales ont permis de mettre en lumière les différents stades de vieillissement, qui correspondent aussi bien à la décomposition spinodale qu'à un complément de phase durcissante. La dureté permet aussi bien de suivre le niveau de vieillissement de l'acier que de déterminer les différentes phases de durcissement. L'effet d'une contrainte appliquée tout au long du vieillissement sur la cinétique de vieillissement a été étudié. Une contrainte de type traction semble ainsi augmenter pour des contraintes élevées le durcissement induit par le complément de précipitation de la phase durcissante, mais aussi accélérer le vieillissement sur les temps de vieillissement plus longs. Une analyse multi échelle est ainsi proposée afin d'expliquer ces différents résultats. ABSTRACT : Precipitation hardened martensitic stainless steels are constitutive of aircraft pylons. During there lifetime , these parts are subjected to mechanical loading and work in temperature. This last induces embrittlement of the steels, because of the miscibility gap in the Fe-Cr phase diagram. Two mechanisms are possible to lead to the demixing of the matrix, either precipitation of α', a chromium rich phase, or spinodal decomposition mechanism. This phenomena is the topic of the project PREVISIA, funded by the ANR, this work is part of. Long term agings have been performed on 15 5 PH stainless steel up to 15 000 hours in order to study the aging kinetic and its effect on the mechanical properties in tensile, resilience and toughness. An embrittlement of the alloy is observed. Furthermore, microstructural analyses have been conducted and lead to the definition of different stages of long term aging corresponding to spinodal decomposition and complementary precipitation of hardening phase. Hardness tests is a usefull tool in order to follow the aging and to detect the different stages of aging. The effect of a stress applied during the long term aging has been studied. A tensile stress seems to have an influence on the complementary precipitation of the hardening phase and to increase the rate of hardening. A multi-scale analysise is proposed in order to explain all these results

Adipocytes cause leukemia cell resistance to daunorubicin via oxidative stress response.

Adipocytes promote cancer progression and impair treatment, and have been shown to protect acute lymphoblastic leukemia (ALL) cells from chemotherapies. Here we investigate whether this protection is mediated by changes in oxidative stress. Co-culture experiments showed that adipocytes protect ALL cells from oxidative stress induced by drugs or irradiation. We demonstrated that ALL cells induce intracellular ROS and an oxidative stress response in adipocytes. This adipocyte oxidative stress response leads to the secretion of soluble factors which protect ALL cells from daunorubicin (DNR). Collectively, our investigation shows that ALL cells elicit an oxidative stress response in adipocytes, leading to adipocyte protection of ALL cells against DNR

R-MOM: A Component-Based Framework for Interoperable and Adaptive Asynchronous Middleware Systems

International audienceSystems of systems (SoS) are composed of subsystems such as Distributed, Information Technology, Real-Time and Embedded systems. Among distributed systems, Message- Oriented Middleware (MOM) is used by SoS in order to share status information from system elements (component, service, etc.). Often several different MOM technologies are used in one SoS, then interoperability between these MOM is a requirement. In this paper, we present R-MOM, a component-based framework for interoperable and adaptive asynchronous middleware systems. R-MOM provides a reflective component architecture where one MOM functionality is embedded into one component which is modifiable at run-time. Loosely-coupling between reflective components permits to get a fined-personalization of MOM functionalities, such as protocol, encoding rule, Quality of Services (QoS) processing, data production/consumption, description, routing and filtering. Interoperability between integrated protocol functionalities is a consequence of architecture design. R-MOM interoperates with different kinds of MOM, from distributed message queues (Java Message Service, Advanced Message Queueing Protocol, 0MQ) to content-based publish/ subscribe systems (OMG's Data Distribution Service). This paper describes the architectural concepts of the R-MOM framework, discusses its implementation, and evaluates its interoperability capability.Les Systèmes de Systèmes (SoS) sont composés de sous-systèmes tels que les systèmes de type distribué, IT, temps-réel et embarqué. Parmi les systèmes distribués, les intergiciels orientés message (MOM) sont utilisés par les SoS dans le but de partager des informations de statut des éléments du systèmes (composant, service, etc...). Souvent, plusieurs technologies MOM sont utilisées dans un même SoS, et interopérabilité entre MOM devient nécessaire. Dans ce papier, nous présentons R-MOM, un canevas basé sur l'approche composant pour les intergiciels interopérables, adaptatifs et asynchrones. R-MOM offre une architecture à composants réflexif, où une fonctionalité d'un MOM est embarquée dans un composant qui est modifiable durant son exécution. Le couplage lâche entre les composants réflexif permet de jouir d'une personnalisation fine sur les fonctionalités MOM visées, comme le protocole, la règle d'encodage, le support des qualités de service, la production et consommation, la description, le routage et le filtrage des données. L'interopérabilité entre les fonctionnalités protocolaire intégrées est une conséquence du choix de conception de l'architecture. R-MOM est interopérable avec différent types de MOM, depuis les queues de message distribué (Java Message Service, Advanced Message Queueing Protocol, 0MQ) jusqu'aux systèmes de publication/souscription basées sur le contenu (Service de Distribution de Données de l'OMG). Ce papier papier décrit les concepts d'architecture du canevas R-MOM, discute son implémentation et évalue sa capacité d'interopérabilité

A framework to experiment optimizations for real-time and embedded software

Typical constraints on embedded systems include code size limits, upper bounds on energy consumption and hard or soft deadlines. To meet these requirements, it may be necessary to improve the software by applying various kinds of transformations like compiler optimizations, specific mapping of code and data in the available memories, code compression, etc. However, a transformation that aims at improving the software with respect to a given criterion might engender side effects on other criteria and these effects must be carefully analyzed. For this purpose, we have developed a common framework that makes it possible to experiment various code transfor-mations and to evaluate their impact of various criteria. This work has been carried out within the French ANR MORE project.Comment: International Conference on Embedded Real Time Software and Systems (ERTS2), Toulouse : France (2010

Influence of Microstructure and Surface Roughness on Oxidation Kinetics at 500–600 °C of Ti–6Al–4V Alloy Fabricated by Additive Manufacturing

Ti--6Al--4V alloy (TA6V) is the most commonly used titanium-based alloy and is usually manufactured by casting, forging or rolling. Additive manufacturing is a new way of processing metal alloys; it is currently used for production purposes. This study focuses on the microstructure and oxidation kinetics of Ti--6Al--4V fabricated by laser beam melting. Some samples were HIP-treated (hot isostatic pressure). Ti--6Al--4V rolled and annealed was used as a reference material. Ti--6Al--4V fabricated by LBM exhibited prior $\beta$ grains elongated in the building direction with fully acicular martensite, $\alpha${\textasciiacutex}. Isothermal oxidations were performed at 500, 550 and 600 {\textdegree}C for durations of 100, 200 and 500 h. The oxidation kinetics followed a parabolic law. The weight gain of as-built LBM samples was twice as high as that of ground LBM samples of Ti--6Al--4V, although both sets had the same oxide layer thickness and depth of oxygen diffusion in the alloy. Ground LBM samples presented an oxidation rate close to that of conventional rolled and annealed Ti--6Al--4V alloys. It was shown the higher weight gain of LBM-produced Ti--6Al--4V samples was mainly due to their higher specific area and to the oxidation of partially melted powder on their surface

The Role of Serology for COVID-19 Control:Population, Kinetics and Test Performance Do Matter

SCOPUS: le.jinfo:eu-repo/semantics/publishe

Guide des stations forestières d'Ardenne

editorial reviewedÀ l’heure où les forestiers s’interrogent sur la sylviculture à mener face aux changements climatiques, le Guide des stations d’Ardenne apporte un éclairage sur les potentialités et sensibilités sylvicoles de 17 grands types de stations ardennaises, depuis la tourbière jusqu’au versant chaud au sol superficiel, et y associe des conseils de sylviculture et des suggestions de choix d’essences. Développé à Gembloux Agro-Bio Tech dans le cadre du Plan quinquennal de recherches et vulgarisation forestières et disponible à partir de l’été 2024, le Guide des stations forestières d’Ardenne est un nouvel outil à destination des gestionnaires forestiers, dans le prolongement du Fichier écologique des essences. Il se base sur l’identification de types de station, en utilisant des critères simples, pour proposer des conseils de gestion adaptés qui intègrent les enjeux de durabilité et les contraintes climatiques. Synthèse d’une solide expertise de terrain et du travail de plusieurs chercheurs, ce guide a pour objectif de faciliter la compréhension du territoire et des possibles qu’il offre au 21e siècle, en présentant l’information de manière compréhensible, centralisée et facilement utilisable sur le terrain. Il s’accompagne d’une version cartographique et de cartes thématiques dérivées. Premier tome d’une série, les prochains volumes couvriront la Fagne-Famenne-Calestienne, le Condroz-Thiérache et la Lorraine belge.Développé à Gembloux Agro-Bio Tech dans le cadre du Plan quinquennal de recherches et vulgarisation forestière

Variability among commercial batches of normal pooled plasma in lupus anticoagulant testing

Lupus anticoagulant (LA) testing requires normal pooled plasma (NPP) in performing mixing studies and can be used for normalized ratios of clotting times (CTs). The aims were to demonstrate whether significant differences in clotting times between two batches of a same commercial NPP (CRYOcheck™) directly affect NPP-based cut-off values. Diluted Russell Viper venom time (DRVVT) and activated partial thromboplastin time (aPTT) were used for LA testing. Screening, mixing and confirm tests were performed with Stago® instruments and reagents. Two batches of commercial NPP (A1291 and A1301 from CRYOcheck™; frozen) were compared in the determination of cut-off values. Cut-off values were defined as 99th percentile values of 60 healthy donors and compared with Mann-Whitney U test. Cut-off values obtained with the two NPP batches were significantly different for DRVVT (screen normalized ratio: 1.09 vs. 1.24, screen mix: 41.9 s vs. 38.9 s; index of circulating anticoagulant: 5.0 vs. 8.4; all had p-value <.001). On the contrary, no significant differences were observed for aPTT (screen normalized ratio: 1.32 vs. 1.34; p-value = .4068, screen mix: 37.8 s vs. 38.1 s; p-value = .1153) except for index of circulating anticoagulant: 9.6 versus 10.4 (p-value <.05). This study demonstrates that differences between two commercial NPP batches produced by a same manufacturer influenced LA cut-off values used for mixing studies and normalized ratios. Adequate cut-off setting, taking into account NPP CTs, is important to provide accurate conclusion about the presence or absence of a LA and avoid potential clinical impact