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Transition démographique et transmission de savoirs: nouveaux défis pour le management des Ressources Humaines
No full textInternational audienc
Some random media with optimal three-phase boundary lines
No full textInternational audienceMulti components materials show triple phase boundary (TPB) lines at the interface between three components. TPB lines are of primary importance for the performance of electrochemical devices like Solid Oxide Fuel Cells (SOFC). We provide theoretical estimates of the specific length of (TPB) lines LV ijk for a broad range of multi-component random structures. Since analytical results are obtained, random microstructures with optimal LV ijk can be designed. The effects of the composition, through volume fractions, and of the morphology, through the choice of primary grains, are separate, so that "optimal composition" is derived independently on the geometry. Various models designed with the same basic ingredients may show a large range of values for LV ijk , depending on their mode of construction. Much longer LV ijk than experimental measurements in real materials can theoretically be reached, typically over an order of magnitude. This can be used as a guideline to improve the electrochemical behavior of fuel cell components
Integrating the management of radioactive isotopes into a reactive transport code
No full textInternational audienceThe modeling of radioactive decay chains within reactive transport frameworks remains a complex challenge due to the coupling of chemical reactions, physical transport, and decay processes. Traditional approaches often simplify decay by neglecting chemical interactions or approximating decay chains with first-order reactions. This study introduces a modular methodology employing an analytical solution to decay equations, allowing seamless integration into reactive transport codes. This approach overcomes the classical timestep limitations imposed by element half-lives, while maintaining accuracy through controlled management of numerical errors introduced by the operator splitting technique during decay integration. Implemented in the HYTEC code using a Sequential Iterative Approach (SIA), the method was validated on four test cases involving multiple isotopes, including parent-daughter pairs, coupled with sorption and mineral reactions under equilibrium and kinetic conditions. Results demonstrate robust and accurate simulation of isotope transport and decay dynamics. While validation was primarily one-dimensional, the framework provides a strong foundation for extension to multidimensional, multiphase systems. Future work will focus on applying this model to more realistic and complex scenarios, thereby further validating its robustness and expanding its practical relevance for nuclear waste disposal and environmental geochemistry
Editorial du dossier spécial - Sociétés à missions : réalités du déploiement et nouvelles perspectives
No full textNational audienc
Machine Learning for RNA-Targeting Drug Design
No full textTargeting RNA with small molecules offers significant therapeutic potential. Machine learning could substantially accelerate preclinical drug discovery, from hit identification to lead optimization. Yet a fundamental limitation emerges: drug design machine learning models, tailored for proteins, are not readily applicable to RNAs because of fundamental differences between RNAs and proteins in both structural characteristics and interactions with small molecules.RNA-specific approaches have consequently emerged, primarily focusing on binding site identification and virtual screening. In this review, we comprehensively compare machine learning tools for RNA-targeting drug design according to the tasks they address, their methodology and their relevance in RNA-specific contexts. As open challenges will catalyze new method development, we emphasize the need for standardized, drug designspecific evaluation approaches. We provide clear guidelines to establish these standards along with a benchmark assessing the ability of current machine learning models to predict specific drug-RNA interactions
Influence of Heat Treatment Conditions on the Evolution of the Precipitate Population in VDM Alloy 780
No full textInternational audienceIn order to understand and model microstructural evolutions during hot deformation processes, it is necessary to understand the precipitation kinetics and the evolution of the precipitates at temperatures near the solvus. The goal of the present work is to investigate the influence of thermal paths prior to the isothermal heat treatment on the nucleation and growth of precipitates in nickel-based superalloy VDM Alloy 780. Two different heat treatment paths have been suggested for studying the influence of cooling and reheating conditions on the final precipitation distribution, one isothermal holding at subsolvus temperature after an intermediate quenching from supersolvus domain and reheating from room temperature; and another after continuous cooling from supersolvus domain. By comparing the precipitate populations generated after each heat treatment using SEM, EBSD, and ECCI techniques, it can be determined that cooling path affects the precipitate morphology, nucleation density, and overall kinetics of the precipitation process. Precipitation after reheating from room temperature shows rather homogeneous, spherically shaped precipitates while precipitation after continuous cooling is dendritically shaped and heterogeneously spaced in sparse clusters of dense precipitation, along with important amounts of discontinuous precipitation. The differences in morphology between both heat treatments may be explained by a difference in the nucleation rate before holding. Multiple causes for the presence of cluster precipitations have been considered and studied. Clusters seem to form from infimum amounts of residual stored energy that persist after the solubilization heat treatments, generating preferential sites for precipitation accelerating precipitation in certain grains. Discontinuous precipitation is considered to be a consequence of the heterogeneous state of the observed precipitation
