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Électrolytes sûrs pour les batteries lithium-soufre à haute énergie
No full textLithium-sulfur batteries (LSBs) are regarded as one of the most promising candidates for next-generation energy storage systems. Among all existing positive electrode materials, sulfur boasts one of the highest theoretical specific capacities, reaching 1675 mAh g-1 and it is an environmentally friendly natural resource. Furthermore, at the cell level, the coupling of metallic lithium and sulfur yields a theoretical specific energy of 2600 Wh kg-1, surpassing traditional lithium-ion batteries. Despite their potential, the development of LSBs faces intrinsic challenges, including the insulating nature of sulfur, end-product lithium sulfide issues, the "shuttle effect" caused by soluble intermediates of polysulfide, the lithium dendrite formation, as well as the safety concerns related to the flammability and possible leakage of traditional organic liquid electrolytes, which limits the commercialization of LSBs. In this thesis, polymer quasi solid-state electrolytes (PQSSEs) have gained attention for their potential to act as a physical barrier or chemical barrier against polysulfide migration, suppression of lithium dendrite growth, and their high flame resistance. Furthermore, PQSSEs stand out due to their increased safety and flexibility compared with other types of solid-state electrolytes. This thesis focuses on the fabrication of optimized VACNTs@S cathode configurations and synthesis of four types of potential polymer electrolytes via polymerization or cross linking reaction. Various synthesis strategies, including in-situ and ex-situ approaches, were explored to evaluate their impact on the performance of LSBs. Additionally, gel-state and membrane solid-state electrolytes were compared to assess their compatibility with well-designed nanostructured VACNTs@S cathode configuration.Les batteries lithium-soufre (LSBs) sont considérées comme l'un des candidats les plus prometteurs pour les systèmes de stockage d'énergie de la prochaine génération. Parmi tous les matériaux d'électrode positive existants, le soufre possède l'une des capacités spécifiques théoriques les plus élevées, atteignant 1675 mAh g-1, et il s'agit d'une ressource naturelle respectueuse de l'environnement. En outre, au niveau de la cellule, le couplage du lithium métallique et du soufre permet d'obtenir une énergie spécifique théorique de 2 600 Wh kg-1, ce qui surpasse les batteries lithium-ion traditionnelles. Malgré leur potentiel, le développement des LSBs est confronté à des défis intrinsèques, notamment la nature isolante du soufre, les problèmes liés au sulfure de lithium comme produit final, l'« effet de navette » causé par les intermédiaires solubles du polysulfure, la formation de dendrites de lithium, ainsi que les problèmes de sécurité liés à l'inflammabilité et aux fuites possibles des électrolytes liquides organiques traditionnels, ce qui limite la commercialisation des LSBs. Dans cette thèse, les électrolytes quasi solides polymères (PQSSE) ont attiré l'attention pour leur potentiel à agir comme une barrière physique ou chimique contre la migration du polysulfure, la suppression de la croissance de la dendrite de lithium, et leur haute résistance à la flamme. En outre, les PQSSE se distinguent par leur sécurité et leur flexibilité accrues par rapport à d'autres types d'électrolytes à l'état solide. Cette thèse se concentre sur la fabrication optimisée de cathode VACNTs@S et sur la synthèse de quatre types d'électrolytes polymères potentiels par polymérisation et réticulation. Diverses stratégies de synthèse, y compris les approches in-situ et ex-situ, ont été explorées pour évaluer leur impact sur les performances des LSBs. De plus, les électrolytes à l’état gélifié et les électrolytes solides sous forme de membrane ont été comparés afin d’évaluer leur compatibilité avec la cathode nanostructurée VACNTs@S
Travail et Logement Informels dans les Pays en Cours d'Urbanisation : Trois Essais sur l'Afrique du Sud
No full textThis dissertation explores the general equilibrium effects induced by the presence of informal employment and housing in the context of a country undergoing urbanization, namely South Africa. The first chapter focuses on the role of urban informal jobs in the migration decisions of rural households. It shows that these jobs can serve as a stepping stone to the formal sector, and that their regularization can lead to an increase in firms’ labour market power within that sector. The second chapter examines households’ location choices based on their employment opportunities in the case of Cape Town. It shows that informal housing may represent an attractive option for poor households given its lower cost and proximity to certain employment centers. The third chapter extends this analysis by focusing on the vulnerability of informal housing units to flooding. It shows that better information about the risks involved enables poor households to adjust their location choices and housing demand, especially once climate change is taken into account. In conclusion, this dissertation aims to shed light on the economic functions that informality can fulfill in emerging countries, and to demonstrate that it often constitutes a second-best solution in the absence of adequate development policies.Cette thèse explore les mécanismes d’équilibre général induits par la présence d’emploi et de logement informels dans le contexte d’un pays en cours d’urbanisation, l’Afrique du Sud. Le premier chapitre se concentre sur le rôle des emplois urbains informels dans le choix migratoire des ménages ruraux. Il montre que ces emplois peuvent servir de tremplin vers le secteur formel, et que leur régularisation peut conduire à une augmentation du pouvoir de marché des entreprises dans ce secteur. Le deuxième chapitre s’intéresse au choix de localisation des ménages en fonction de leurs opportunités professionnelles dans le cas de la ville du Cap. Il montre que le logement informel peut représenter une option intéressante pour les ménages pauvres, étant donné son moindre coût et sa proximité de certains centres d’emploi. Le troisième chapitre prolonge cette étude et porte sur la vulnérabilité des logements informels aux inondations. Il montre qu’une meilleure information quant aux risques encourus permet aux ménages pauvres de modifier leurs choix de localisation et leur demande de logement, d’autant plus après prise en compte du changement climatique. En conclusion, cette thèse vise à renseigner les fonctions économiques que peut remplir l’informalité dans les pays émergents, et à démontrer qu’elle constitue souvent la meilleure solution de second choix en l’absence de politiques de développement adéquates
Improving the scalability of a high-order atmospheric dynamics solver based on the deal. II library
No full textInternational audienceWe present recent advances on the massively parallel performance of a numerical scheme for atmosphere dynamics applications based on the deal.II library. The implicit-explicit discontinuous finite element scheme is based on a matrix-free approach, meaning that no global sparse matrix is built and only the action of the linear operators on a vector is actually implemented. Following a profiling analysis, we focus on the performance optimization of the numerical method and describe the impact of different preconditioning and solving techniques in this framework. Moreover, we show how the use of the latest version of the deal.II library and of suitable execution flags can improve the parallel performance
GTnum ScienceXGames #CreaJV - Bonnes pratiques pour la mise en place d’ateliers de création de jeu vidéo en classe
No full textProductions des groupes thématiques numériques (Direction du numérique pour l'éducation du Ministère de l'Éducation nationale, de l'Enseignement supérieur et de la Recherche)Le GTnum CreaJV (Groupe thématique numérique 2021 - 2024 "Apprendre avec le jeu numérique" #CreaJV) a mis en œuvre et observé des ateliers de création de jeu vidéo en classe, du primaire au BTS. Le groupe de travail a également mené un travail de veille sur les expériences de création de jeu vidéo menées à travers le monde. Dans ce bulletin de veille, nous proposons une synthèse de ces bonnes pratiques pour aider tous les enseignants qui souhaiteraient mettre en place ces ateliers
Natural product total synthesis, a key step into biological applications
No full textInternational audienc
Genome wide analyses reveal the role of mutator phenotypes in Mycobacterium tuberculosis drug resistance emergence
No full textInternational audienceAntimicrobial combination therapy is widely used to combat Mycobacterium tuberculosis (Mtb), yet resistance rates continue to rise. Mutator strains, with defects in DNA repair genes, drive resistance in other bacterial infections, but their role in Mtb remains unclear. Here, we study the contribution of single nucleotide polymorphisms (SNPs) in DNA Repair, Replication, and Recombination (3 R) genes to Mtb resistance. Through large-scale bioinformatics analysis of 53,589 whole-genomes, we identified 18 novel SNPs in lineages 2 and 4 linked to genotypic drug resistance in 3 R genes, covering 12.5% of clinical isolates with available genome sequences. Notably, a number of the detected SNPs were positively selected during Mtb evolution. Experimental tests showed that mutM, fpgg2, xthA, and nucS mutants had increased the mutation frequency compared to the wild type. Our findings highlight the role of 3 R gene mutations in resistance, emphasizing the need for surveillance to improve early detection and control strategies
Inverse Uncertainty Quantification for Personalized Biomechanical Modeling: Application to Pulmonary Poromechanical Digital Twins
No full textInternational audienceThe development of personalized models is a key step for addressing various problems, especially in biomechanics. These models typically include many constants, introduced in the model material law or loading definition, and their estimation is crucial for the model personalization. However, performing solely the estimation does not yield any information on the estimation accuracy. Additionally, all parameters can typically not be estimated based only on clinical data: some parameters are identified, while others are fixed at generic values. The question of the identifiability of the parameters, along with the robustness of the estimation, notably to measurement errors and to model errors, is therefore crucial and should be quantitatively addressed in parallel to the model development. In this paper, we propose a general inverse uncertainty quantification pipeline based on the creation of synthetic data—for which the parameters ground-truth values are known—generated for different noise and model error levels. Estimation is then performed for many realizations of the noise or model errors, as well as parameter initializations, until convergence of the estimated parameters error distributions. This pipeline was applied to a poromechanical lung model for illustration and validation purposes. It provides quantitative information on the actual identifiability of the parameters, and any derived quantity of interest, in the clinical setting. In particular, it allows us to retrieve a confidence interval for each estimated parameter, which represents valuable information for diagnosis or prognosis use of the estimated values. This work is therefore a step toward improving the reliability of digital twins pipelines
Characterization of the solar wind context during the third Mercury flyby of BepiColombo
No full textInternational audienceContext. The interaction of the solar wind (SW) with the coupled magnetosphere-exosphere-surface of Mercury is complex. Charged particles released by the SW can precipitate along planetary magnetic field lines on specific areas of the surface of the planet. The processes responsible for the particle precipitation strongly depend on the orientation of the interplanetary magnetic field (IMF) upstream of Mercury.Aims. During the third Mercury flyby (MFB3) by BepiColombo, the properties of the SW inferred from BepiColombo observations of a highly compressed magnetosphere corresponded to those of a very dense plasma embedded in a slow SW. The Mercury Electron Analyzer (MEA) measured continuous high-energy electron fluxes in the nightside dawn sector of the compressed magnetosphere. In order to constrain further studies related to the origin of these populations, we aim to firmly confirm the initial inferences and detail the SW properties throughout MFB3.Methods. We took advantage of a close radial alignment between Parker Solar Probe (PSP) and Mercury. We monitored the activity of the Sun using SOHO coronagraphs and we used a potential field source surface model to estimate the location of the magnetic footpoints of PSP and BepiColombo on the photosphere of the Sun. We propagated the plasma parameters and the IMF measured by PSP at BepiColombo, to check if the plasma impacted Mercury.Results. We show that during MFB3, PSP and BepiColombo connected magnetically to the same region at the solar surface. The slow SW perturbation first measured at PSP propagated to Mercury and BepiColombo, as was confirmed by similarly elevated plasma densities measured at PSP and BepiColombo. The IMF orientation stayed southward during the whole MFB3.Conclusions. Our results provide strong constraints for future studies of the magnetospheric structure and dynamics during MFB3, including tail reconnection, electron and ion energization, and subsequent plasma precipitation onto the surface of Mercury
Modélisation économique par les systèmes complexes : de la simulation multi‑agents aux goulets d’étranglement du marché du travail
No full textThe methodologies of complex systems and economic modeling provide a powerful framework for exploring the intricate interdependencies within economic systems. By integrating tools from agent-based modeling, network science into modeling economics, this work reveals new perspectives on today's economic challenges. A physics-inspired perspective highlights the dynamic and interconnected nature of economic behavior, presenting innovative frameworks for analyzing and addressing the complexities of economic systems.Agent-based models (ABMs) offer a bottom-up lens to simulate macroeconomic dynamics, capturing emergent phenomena such as business cycles, inflationary trends, and crises. Extending the Mark-0 ABM, this research integrates an expectation-anchoring mechanism to study the drivers of post-COVID inflation and the effectiveness of policies aimed at mitigation. The analysis reveals that the success of monetary policy relies more on anchoring expectations than on the direct economic effects of interest rate adjustments. Key dynamics, such as the wage-price spiral, emerge as critical mechanisms shaping economic outcomes, while the analysis exposes trade-offs between inflation control and unemployment. The findings also highlight that, without strong fiscal measures, economic recovery could stagnate or even regress into a deeper recession.To improve the robustness and interpretability of ABMs, a novel statistical physics-inspired approach is introduced for systematically exploring high-dimensional parameter spaces. By leveraging the “sloppiness” framework, the study identifies a small set of key parameter combinations—stiff directions—that significantly influence model behavior, while de-emphasizing less impactful ones. This insight leads to the development of an efficient algorithm that captures the full range of possible model dynamics with minimal computational effort. Applied to the Mark-0 model, the method recovers the complete spectrum of unemployment dynamics, providing a structured approach to assess parameter sensitivities and enhance the utility of ABMs.The second part of the research shifts focus to labor markets, treating them as complex adaptive systems. Interpreting the labor market as a network of interconnected occupations uncovers structural imbalances, with transitions and occupational sizes following power-law distributions. This hierarchical structure reveals that certain occupations act as hubs of mobility, while others remain isolated. To quantify these dynamics, new metrics—accessibility and transferability—are developed, offering a nuanced understanding of worker mobility. These metrics identify critical roles within the labor market, such as “condenser” occupations, which serve as bottlenecks due to high accessibility but low transferability, hindering inter-occupational mobility. A steady-state analysis reveals long-term inefficiencies, as observed worker distributions diverge significantly from equilibrium states. The incorporation of skill similarity data further enriches the analysis, showing that high-transferability occupations facilitate inter-community transitions, while high-accessibility roles act as gateways into new sectors. These insights have practical applications, from addressing skill mismatches to designing targeted training programs and enhancing labor market fluidity amid technological and economic shifts.This research offers tools and methodologies rooted in statistical physics and network theory to unravel economic complexities, identify key drivers, and address structural inefficiencies, providing a foundation for innovative policy interventions in interconnected economic systems.En mêlant modélisation multi-agents, science des réseaux et approches des systèmes complexes, ce travail apporte de nouvelles perspectives face aux défis économiques. Les modèles multi-agents (ABM) offrent un cadre d’analyse novateur pour simuler des dynamiques macroéconomiques, s’intéressant aux phénomènes émergents tels que les cycles économiques, l’inflation et les crises. En étendant le modèle Mark-0, cette thèse introduit un mécanisme d’ancrage des anticipations pour analyser l’inflation post-COVID et l’efficacité des politiques économiques qui suivirent. Les résultats montrent que le succès de la politique monétaire repose davantage sur la gestion des anticipations que sur ses effets économiques directs, la spirale prix-salaires apparaissant comme un moteur clé. Les arbitrages nécessaires entre le contrôle de l’inflation et le chômage soulignent l’importance des mesures budgétaires pour assurer la stabilité économique. Afin d’améliorer la robustesse des ABM, une approche inspirée de la physique statistique est introduite pour explorer des espaces de paramètres de haute dimension. En exploitant le cadre de la sloppiness, l’étude identifie un petit ensemble de paramètres rigides qui gouvernent le comportement du modèle, tout en minimisant l’importance des paramètres moins influents, améliorant ainsi son interprétabilité et son efficacité.La deuxième partie se concentre sur les marchés du travail en tant que systèmes complexes adaptatifs. En représentant les professions comme des nœuds dans un réseau de mobilité professionnelle, l’analyse met en évidence des déséquilibres structurels où certaines professions jouent le rôle de hubs centraux tandis que d’autres restent isolées. De nouveaux indicateurs—l’accessibilité et la transférabilité—quantifient la mobilité des travailleurs et identifient les professions condensatrices comme des goulets d’étranglement avec une forte accessibilité mais une faible transférabilité. L’intégration des données de compétences révèle que les professions à forte transférabilité facilitent la mobilité entre clusters d’emplois, tandis que celles à forte accessibilité servent de points d’entrée dans de nouveaux secteurs. Ces résultats offrent des perspectives nouvelles pour améliorer les politiques publiques dans ce domaine. Plus particulièrement, cela permettrait de réduire les inadéquations travail-compétences, d’optimiser les programmes de reconversion et d’améliorer la fluidité du marché du travail face aux transformations économiques et technologiques