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Exploration des enjeux de mise en œuvre des intelligences artificielles génératives en santé - Une enquête menée auprès d'experts en France et au Canada
No full textInternational audienceExploration des enjeux de mise en œuvre des intelligences artificielles génératives en santé - Une enquête menée auprès d'experts en France et au Canad
Exploration de l’impact des stimuli mécaniques sur la morphologie du cartilage de croissance et l’adaptation trabéculaire : une approche par éléments finis
No full textInternational audienceBackgroundThis research investigates how trabecular patterns affect growth plate morphology, focusing on shape, trabecular patterns, and ossification bridges. By studying mechanical adaptations, we propose a new methodology to model endochondral growth and bone remodeling, applicable to clinical cases involving growth abnormalities or growth plate diseases.MethodsWe developed a finite element model that integrates bone remodeling with an endochondral ossification law. The osteogenic index was used to impose a strain rate tensor, capturing growth from chondrocyte hypertrophy and proliferation in the growth plate. Then an examination was performed of the mechanical influence of trabecular structures on growth plate development and ossification through qualitative topology comparisons and statistical analysis of shape parameters affecting bone formation. Validation was conducted using medical images and μ-CT scans. The model was calibrated with a benchmark case, adjusting growth plate shape and thickness, and then applied to a hip dysplasia case and tibial growth.FindingsGrowth plate adapts its shape in response to the local mechanical environment and this has implications for growth plate closure. Unlike previous models treating the environment as a continuum, our model assessed localized load transmission via trabecular groups. Morphological changes in the growth plate and nearby bone adaptation help withstand shear stress, increasing bone density in specific regions, the most significant parameters being growth plate thickness and period of oscillations. A response surface and Pearson coefficient analysis show that the thickness and amplitude of the growth plate have the most significant effect on the bone density in the vicinity of the growth plate.ConclusionsThis new model has the potential to advance the management of medical conditions such as slipped capital femoral epiphysis, Sever's disease, and interventions like epiphysiodesis. This research may lead to improved diagnostic tools and therapeutic strategies for treating growth plate-related disorders
Integrated Optimization of Railway Timetables and Rolling Stock Scheduling
No full textInternational audienceThis study presents an efficient approach for integrated railway timetabling and rolling stock planning. The method employs a slot graph and a maximal clique algorithm to generate a conflict-free timetable. When additional slots are required, a column generation procedure suggests alternative paths, improving network coverage. Rolling stock allocation is optimized through the use of fictive nodes and edges, minimizing resource consumption and reducing empty trips. Overall, this integrated framework simplifies timetable generation and resource management, offering a robust solution for complex railway networks
Optimization of railway resource planning process in a multi-level scale
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Elicitation des hyper-paramètres des classifieurs prudents : premières propositions
No full textNational audienceIn the presence of uncertainty, cautious prediction methodsare essential to avoid serious errors when using machinelearning in sensitive domains, e.g., medicine, autonomousvehicles, etc. These methods involve the useof utility or loss functions in the decision and/or evaluationstages. The utility function, which is inherentlysubjective, extends the classical and inherently objectiveaccuracy metric to comparisons of subsets. These functionsare parameterized to express the user’s dispositionfor imprecision. This article presents preliminary workaddressing the underexplored problem of eliciting theseparameters from the user. We show how the user is guidedthrough successive comparisons toward the optimalvalue.En pr´esence d’incertitude, les m´ethodes de pr´edictionprudente sont essentielles pour ´eviter des erreurs graveslors de l’utilisation de l’apprentissage automatique dansdes domaines sensibles, e.g. m´edecine, voiture autonome,etc. Ces m´ethodes impliquent l’utilisation de fonctiond’utilit´e ou de perte dans l’´etape de d´ecision et/ou l’´etaped’´evaluation. La fonction d’utilit´e en question, par essencesubjective, ´etend la m´etrique classique de justesse,par essence objective, aux comparaisons de sousensembles.Ces fonctions sont param´etr´ees pour exprimerla disposition de l’utilisateur `a l’impr´ecision. Cetarticle propose un travail pr´eliminaire qui s’int´eresse auprobl`eme sous explor´e de l’´elicitation de ces param`etresavec l’utilisateur. Nous montrons comment l’utilisateurest guid´e par des comparaisons successives jusqu’`a la valeuroptimale
Wavelet-based estimators of partial derivatives of a multivariate density function for discrete stationary and ergodic processes
No full textInternational audienceIn this work, we propose a wavelet-based framework for estimating the derivatives of a density function in the setting of discrete, stationary, and ergodic processes. Our primary focus is the derivation of the integrated mean square error (IMSE) over compact subsets of Rd, which provides a quantitative measure of estimation accuracy. In addition, the uniform convergence with rate and the normality are established. To establish the asymptotic behavior of the proposed estimators, we adopt a martingale approach that accommodates the ergodic nature of the underlying processes. Importantly, beyond ergodicity, our analysis does not require additional assumptions on the data. By demonstrating that the wavelet methodology remains robust under these weaker dependence conditions, we extend earlier results originally developed in the context of independent observations
Nonparametric conditional U-statistics on Lie groups with measurement errors
No full textInternational audienceThis study presents a comprehensive framework for conditionalU -statistics of a general order in the context of Lie group-valuedpredictors affected by measurement errors. Such situations arise ina variety of modern statistical problems. Our approach is groundedin an abstract harmonic analysis on Lie groups, a setting rela-tively underexplored in statistical research. In a unified study, weintroduce an innovative deconvolution method for conditional U -statistics and investigate its convergence rate and asymptotic dis-tribution for the first time. Furthermore, we explore the applicationof conditional U -statistics to variables that combine, in a nontrivialway, Euclidean and non-Euclidean elements subject to measure-ment errors, an area largely uncharted in statistical research. Wederive general asymptotic properties, including convergence ratesacross various modes and the asymptotic distribution. All resultsare established under fairly general conditions on the underlyingmodels. Additionally, our results are used to derive the asymp-totic confidence intervals derived from the asymptotic distributionof the estimator. We also discuss applications of the general ap-proximation results and give new insights into the Kendall rankcorrelation coefficient and discrimination problems
Flavobacterium aerium sp. nov., a bacterium isolated from the air of the Icelandic volcanic island Surtsey
No full textInternational audienceA novel bacterium, designated 19SA41, was isolated from the air of the Icelandic volcanic island Surtsey. Cells of strain 19SA41 are Gram-stain-negative, strictly aerobic, non-motile rods and form pale yellow-pigmented colonies. The strain grows at 4–30 °C (optimum, 22 °C), at pH 6–10 (optimum, pH 7.5) and with 0–4% NaCl (optimum, 0.5%). Phylogenetic analyses based on 16S rRNA gene sequences showed that 19SA41 belonged to the genus Flavobacterium and is most similar to Flavobacterium xinjiangense DSM 19743 T , with a sequence similarity of 96.52%. The new strain contained iso-C 15 : 0 (22%) and summed feature 3 (C 16∶1 ω6c/C 16∶1 ω7c) (20%) as the predominant fatty acids. The major respiratory quinone was menaquinone-6 (100%). The polar lipid profile consisted of phosphatidylethanolamine and several uncharacterized amino lipids, glycolipids and lipids. The genome of the new strain was 4.01 Mbp, and its G+C content was 33.2 mol%. Based on characterization and comparative results, using a polyphasic taxonomic approach, we propose that the new isolate represents a novel species of the genus Flavobacterium with the name Flavobacterium aerium sp. nov. The type strain is ISCaR-07695 T (=DSM 116640 T =UBOOC-M-3567 T )
Élaboration de nanoparticules d’oxyde de fer pour l’amélioration des nanocomposites polymères : synthèse, caractérisation et optimisation des performances
No full textUnderstanding the synthesis and growth mechanisms of nanoparticles is crucial for achieving controlled size, shape, and surface chemistry, all of which are essential for their integration into polymer nanocomposites. This work investigates the thermal decomposition synthesis of iron oxide nanoparticles (IONPs), focusing on the role of different precursors (oleate, dodecanoate, octanoate) in tailoring nanoparticle properties. Particular attention is given to robustness challenges, highlighting how precursor selection and synthesis conditions influence nanoparticle morphology and shape control. In parallel, the in situ synthesis of IONPs within a polyisobutylene (PIB) matrix is explored, examining nanoparticle self-assembly, dispersion, and their impact on the mechanical and functional properties of the resulting nanocomposite. The combination of PIB’s hydrophobic nature and the superparamagnetic behavior of IONPs offers potential applications in sensing and actuation. By bridging fundamental insights into nanoparticle growth, shape control, and polymer-nanoparticle interactions, this study advances the development of robust, high-performance polymer nanocomposites.Comprendre les mécanismes de synthèse et de croissance des nanoparticules est crucial pour obtenir un contrôle précis de leur taille, de leur forme et de leur chimie de surface, qui sont essentiels pour leur intégration dans des nanocomposites polymères. Ce travail explore la synthèse par décomposition thermique des nanoparticules d’oxyde de fer (IONPs), en mettant l’accent sur le rôle des différents précurseurs (oléate, dodécanoate, octanoate) dans l’ajustement des propriétés des nanoparticules. Une attention particulière est portée aux défis de robustesse, en soulignant comment la sélection des précurseurs et les conditions de synthèse influencent la morphologie et le contrôle de la forme desnanoparticules. Parallèlement, la synthèse in situ des IONPs au sein d’une matrice de polyisobutylène (PIB) est étudiée, en examinant l’auto-assemblage des nanoparticules, leur dispersion et leur impact sur les propriétés mécaniques et fonctionnelles du nanocomposite résultant. La combinaison de la nature hydrophobe du PIB et du comportement superparamagnétique des IONPs ouvre des perspectives d’applications dans la détection et l’actionnement. En apportant des éclairages fondamentaux sur la croissance des nanoparticules, le contrôle de leur forme et les interactions polymère-nanoparticules, cette étude contribue à l’avancement du développement de nanocomposites polymères robustes et àhaute performance
Capital écologique et production matérielle : L'écologie populaire d'une petite entreprise industrielle
No full textInternational audienceThis article analyzes how drastically disjointed markets and symbolic and economic logics can be articulated in the strategy and operation of a small industrial company – a localized economic and social space focused on economic sustainability, and a militant national space focused on the symbolic positioning of ecological commitment. Based on a field study of a small French industrial firm that manufactures agroecological tools, we defend the thesis of an economic strengthening that takes place in response to, and at the cost of, a progressive marginalization in the ecologist field, due to a deficit of specific cultural capital that we call “ecological capital”. The article first shows how the trajectory of the company and its founder was marked by social and economic co-optation into the agroecological field (1), before coming up against the limits of their accumulation of ecological capital and the weight of market issues for a popular entrepreneurship (2). He then shows how productive and economic materiality is illegitimate in a field that nevertheless discursively values a direct relationship with matter. This results in the long-term dominated position of an organization and an individual for whom it is essential (3).Cet article vise à comprendre comment peuvent s’articuler dans la stratégie et le fonctionnement d’une petite entreprise industrielle des marchés et des logiques symboliques et économiques radicalement disjointes : un espace économique et social localisé et préoccupé de pérennité économique et un espace national militant préoccupé de positionnement symbolique d’engagement écologiste. En nous fondant sur une enquête de terrain dans une petite entreprise industrielle qui fabrique des outils agroécologiques, nous défendons la thèse d’un renforcement économique qui se fait en réponse et au prix d’une marginalisation progressive dans le champ écologiste, du fait d’un déficit de capital culturel spécifique que nous appelons « capital écologique ». L’article montre d’abord la manière dont la trajectoire de l’entreprise et de son fondateur a été marquée par une cooptation sociale et économique dans le champ agroécologique (1), avant de se heurter aux limites de leur accumulation de capital écologique et au poids des enjeux marchands pour un entrepreneuriat populaire (2). Il montre ensuite de quelle manière la matérialité productive et économique est illégitime dans un champ qui pourtant valorise discursivement le rapport direct à la matière. Cela entraine le maintien dans une position socialement dominée d’une organisation et d’un individu pour lesquels il est essentiel (3)