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Efficient estimation of jump parameters for stochastic differential equations driven by Lévy processes
No full textIn a high-frequency context, we investigate the efficient estimation of scaling and jump activity parameters for a stochastic differential equation driven by a Lévy process with both diffusion component and pure-jump component. We first study efficiency for the prototype Lévy process. With an in-depth analysis of the behavior of the density of the process in small time, we prove that the LAN Property holds for the joint estimation of the diffusion, scaling and jump activity parameters. We next consider a stochastic equation driven both by a Brownian Motion and a locally stable pure-jump Lévy process. Using a quasi-likelihood estimation method, we exhibit an estimator that attains the optimal rate of convergence previously identified. The asymptotic properties of the estimator are derived from sharp approximation results for the stochastic equation and for the locally stable distribution
Étude spectrale et dynamique linéaire des opérateurs de composition pondérés sur le disque et la boule unité
No full textThe work in this thesis concerns the study of weighted composition operators on the unit disc and the unit ball. This subject is at the crossroads of operator theory, complex analysis and linear dynamics. After giving the main results of the theory of holomorphic functions on the unit disc and the unit ball, we obtain necessary and sufficient conditions for these operators to be continuous, invertible and compact, and determine their spectrum, depending on their symbol and weight.Next, we analyse the linear isometries of the space of holomorphic functions on the unit disc. We note that these are certain weighted composition operators, and generalise these results to the annulus. Finally, we determine the linear dynamics of these operators. We restrict ourselves here to multiplication and weightless composition operators. Depending on the nature of the symbol, we are able to determine which of these operators are cyclic or hypercyclicLes travaux de cette thèse portent sur l'étude des opérateurs de composition pondérés sur le disque et la boule unité. Ce sujet est au croisement de la théorie des opérateurs, de l'analyse complexe et de la dynamique linéaire. Après avoir donné les résultats principaux de la théorie des fonctions holomorphes du disque et de la boule unité, nous obtenons des conditions nécessaires et suffisantes pour que ces opérateurs soient continus, inversibles, et compacts, et nous déterminons leur spectre en fonction de leur symbole et de leur poids. Par la suite, nous analysons les isométries linéaires de l'espace des fonctions holomorphes sur le disque unité. Nous remarquons qu'il s'agit de certains opérateurs de composition pondérés, et nous généralisons ces résultats sur l'anneau. Enfin, nous déterminons la dynamique linéaire de ces opérateurs. Nous nous limitons ici aux opérateurs de multiplication, et de composition sans poids. Selon la nature du symbole, nous sommes en mesure de savoir parmi ces opérateurs lesquels sont cycliques ou hypercyclique
Clinical Presentation and Outcomes After Surgery for Mitral Regurgitation: Real-World Insights From the MITRACURE International Registry
No full textInternational audienceBackground: Comprehensive knowledge of the clinical presentation, contemporary management, and outcomes on "allcomer" patients referred for mitral valve surgery (MVS) are critical to evaluate current practice and adherence to guidelines, understand selection biases, and inform key stakeholders on quality improvement. Methods: MITRACURE is a large international retrospective registry of consecutive adult patients who underwent isolated or combined MVS for mitral regurgitation (MR) in France or Canada in 2019 with in-depth clinical and echocardiographic characterization. Patients operated on for isolated mitral stenosis or who had a prior mitral valve intervention were excluded. Data were obtained from detailed chart abstraction and were site reported. Results: In 2019, 3522 patients underwent MVS (48% combined) across 40 centers (88±46 MVSs/center, median 80, interquartile [51–131]). Mean age was 65±12 years, and 35% were women. The most common MR etiology was myxomatous (61%), followed by functional (9%), infective endocarditis (9%), and rheumatic disease (7%). MR quantification was performed in only 43%. Advanced clinical presentation was common: 43% were in New York Heart Association class III/IV, 30% exhibited congestive heart failure, 47% were on diuretics, 22% had atrial fibrillation/flutter, 35% presented with reduced ejection fraction, and 22% had pulmonary hypertension (≥50 mm Hg). Most patients were symptomatic or presented with class I/IIa indication for intervention, and an early intervention was performed only in 3% of patients. The repair rate was 62% overall and 80% in myxomatous disease. In-hospital mortality was 4.5% overall but 2.3% in patients with myxomatous MR (1.8% isolated, 3.1% combined). Conclusions: MITRACURE provides a contemporary, multicenter, "real-world" picture of the clinical presentation, management, and in-hospital outcomes of MVS for MR in two Western countries. Patients were often referred late in the disease process, with few patients undergoing early intervention. The higher mortality and lower repair rates reported may be more reflective of an unselected MR patient population but have room for improvement. Our results underline the need to develop strategies to improve management and outcomes of patients with MR
Optimizing the Efficiency of Magnetic Hyperthermia: A Theoretical Investigation of Key Parameters
No full textInternational audienceMagnetic hyperthermia involves converting magnetic energy into heat using a ferrofluid-like assembly of magnetic nanoparticles subjected to an oscillating external magnetic field. This heat is exploited for biomedical and catalytic applications. The efficiency of hyperthermia is quantified by the Specific Absorption Rate (SAR), related to the imaginary component of the AC susceptibility. [1]To enhance heat generation, several parameters play a crucial role through the SAR optimization, including the external field amplitude, frequency, magnetic anisotropy, particle-particle interaction, and nanoparticle size. One of our main objectives is to elucidate the role of dipole-dipole interactions in magnetic hyperthermia processes and to determine under which conditions the SAR is enhanced or suppressed. To achieve this, we first employ a semi-analytical method to study weak DDI for low-density nanoparticle assemblies based on perturbative calculations [2]. Secondly, the numerical simulations method [3] makes it possible to study more realistic densities (strong DDI) such that we can use asystematic study to confirm the analytical trend observed and see the limits of the analytical approach.In this study, we investigate the role of dipole-dipole interactions on the SAR of different nanoparticle assemblies using the time-quantified Monte Carlo (TQMC). Our objective is to explore how these dipole-dipole interactions affect the SAR across a range of nanoparticle configurations. Another key parameter is the influence of the easy axis orientations and the concentration on the imaginary component of theAC magnetic susceptibility. By systematically varying the orientation distributions and particle densities, we analyze how these factors contribute to the overall heating efficiency, particularly in conditions relevant to biomedical applications such as magnetic hyperthermia. We also explore the influence of the intrinsic properties of nanoparticles by considering a combination of uniaxial and cubic magnetocrystalline anisotropies, which may arise from the inherent cubic symmetry of iron oxide nanoparticles.Besides direct numerical simulations, we employ semi-analytical approaches grounded on Debye relaxation theory to gain deeper insight into the mechanisms governing the SAR. This theoretical framework provides the basis for examining the role of the external shape of the nanoparticle assembly, which influences collective magnetic behavior and energy dissipation. By integrating this semi-analytical model with the results of TQMC simulations, we aim to identify the key physical parameters and the optimal conditions for maximizing the SAR by taking advantage of both Intrinsic properties and collective effects within structured nanoparticle assemblies
Managing the whistleblowing process or managing the whistleblower? On the implementation of the European directive in France.
No full textInternational audienc
Clinical and cognitive assessment in Friedreich ataxia clinical trials: a review
No full textInternational audienceFriedreich ataxia (FRDA) is the most common type of inherited ataxia. It is a neurodegenerative disorder characterized by progressive gait and limb ataxia, dysarthria, areflexia, and reduced proprioception and vibration sensation. Although a number of clinical trials have been conducted, there is currently no cure for this disease. In this article we review those clinical trials with a focus on the instruments used as endpoints to assess clinical progression, and discuss the potential benefits of integrating additional measures, including assessments from overlooked domains. We also review tools used to evaluate cognitive functions in individuals with FRDA, particularly those employing quantitative, objective, and time-based measures. We argue for the inclusion of cognitive and speech-related assessments in clinical trials, and examine the potential of developments in cognitive neuroscience and technology to address current measurement challenges and support more accurate and comprehensive evaluation of treatment effects. These innovations have the potential to complement existing approaches, enhance trial design, and advance clinical care
Du tertiaire au logement et à l’hébergement, quelles conditions de transformation ?, Rapport de recherche intermédiaire phase 2
No full textAdvancing medical question answering with a knowledge embedding transformer
No full textInternational audienceEfficient medical question answering is essential for better patient care. Despite progress since Eliza (1966), even advanced LLMs (e.g., GPT-4) struggle with medical data. This study presents a system combining knowledge embedding and transformers. It includes a knowledge understanding layer and an answer generation layer. Tested on the MedQA dataset, it achieved 82.92% accuracy, outperforming GPT-4’s 71.07%. The results demonstrate the system’s ability to deliver accurate and ethical answers. This integrated method improves response speed and quality. Future work will enhance precision, support patient interaction, and integrate multimodal data for improved healthcare query processing
Estimating distances to desertification points from dryland ecosystem images
No full textInternational audienceResource-limited ecosystems, such as drylands, can exhibit self-organized spatial patterns. Theory suggests that these patterns can reflect increasing degradation levels as ecosystems approach possible tipping points to degradation. However, we still lack ways of estimating a distance to degradation points that is comparable across sites. Here, we present an approach to do just that from images of ecosystem landscapes’. After validating the approach on simulated landscapes, we applied it to a global dryland dataset, estimated the distance of each of the sites to their degradation point and investigated the drivers of that distance. Crossing this distance with aridity projections makes it possible to pinpoint the most fragile sites among those studied. Our approach paves the way for a risk assessment method for spatially-organized ecosystems
Avis relatif à la détermination de la VMAX dans les EDCH pour le métabolite de pesticide 1,2,4-triazole et les substances actives chlordécone et glyphosate
No full textAnses. (2025). Avis de l’Anses relatif à la détermination de valeurs sanitaires maximales (VMAX), pour le métabolite de pesticide 1,2,4-triazole et les substances actives chlordécone et glyphosate, dans les eaux destinées à la consommation humaine (EDCH). (saisine 2023-SA0041-c). Maisons-Alfort : Anses, 21 p.CONTEXTE ET OBJET DE LA SAISINEPour garantir la qualité des EDCH, la Directive (UE) 2020/2184 [1], transposée en droit français, fixe des valeurs paramétriques pour les concentrations en pesticides et leurs métabolites pertinents (0,1 µg.L-1 par substance individuelle [2] et 0,5 µg.L-1 pour la somme des pesticides et de leurs métabolites pertinents), sans définir les critères ou les modalités d’évaluation de cette pertinence. L’arrêté du 11 janvier 2007 modifié [3] reprend ces valeurs en tant que limites de qualité (LQ) dans les EDCH pour les pesticides et leurs métabolites pertinents.À la demande de la Direction générale de la santé (DGS), l’Anses a proposé en janvier 2019 (Anses, 2019a) une méthodologie permettant l’évaluation de la pertinence des métabolites de pesticides dans les EDCH au vu des connaissances scientifiques disponibles. Elle est destinée à être mise en œuvre dans le cadre d’une expertise collective de l’Anses, en s’appuyant sur les données disponibles (principalement issues des dossiers de demande d’approbation des substances actives et de la littérature scientifique à disposition). Sur la base du résultat d’une telle évaluation, et de tout autre élément qu’elle considérerait approprié, la DGS désigne les métabolites pertinents et fixe les modalités de leur surveillance. En l’absence d’évaluation, un métabolite est considéré comme pertinent par défaut.En situation de dépassement d’une LQ, la réglementation française prévoit un dispositif dérogatoire et gradué de gestion du risque. La LQ de 0,1 µg.L-1 pour les pesticides et les métabolites pertinents ne reposant pas sur des fondements toxicologiques, le dispositif de gestion des risques liés à des dépassements de cette LQ s’appuie notamment depuis 2007 sur l’élaboration de valeurs sanitaires maximales (VMAX) proposées par l’Anses pour des SA de pesticides et des métabolites pertinents. La référence à ces VMAX a vocation à être utilisée pour une période limitée dans le temps d’une durée maximale de six ans pendant laquelle des actions de remédiation (amélioration de la qualité de l’eau de la ressource, mise en place de traitements pour l’EDCH, interconnexions, etc.) doivent être mises en œuvre.La méthode de détermination des VMAX de pesticides a été actualisée dans l’avis du 17 décembre 2019 (Anses, 2019b). La liste des VMAX de pesticides dans l’EDCH établies pour les SA ou les métabolites pertinents de pesticides est disponible sur le site de l’Agence [4].Dans la perspective de gestion sanitaire de situations de non-conformité (dépassement des LQ) vis-à-vis de pesticides et de métabolites de pesticides dans les EDCH relevées dans le cadre du contrôle sanitaire ou de la campagne nationale exploratoire menée par le Laboratoire d’hydrologie de Nancy (LHN) entre 2020 et 2022 (Anses, 2023), la DGS a saisi l’Anses le 15 février 2023 pour déterminer les VMAX pour 13 pesticides et métabolites de pesticides et, pour certains des métabolites, évaluer le classement de la pertinence au préalable. Ainsi, plusieurs livrables échelonnés dans le temps sont prévus en réponse à cette saisine. Les VMAX déjà déterminées dans le cadre de cette saisine ont fait l’objet d’un avis du 25 juillet 2024 (Anses, 2024).Le présent avis concerne la détermination de VMAX pour les substances actives chlordécone et glyphosate ainsi que pour le métabolite 1,2,4-triazole. [1] Directive (UE) 2020/2184 du Parlement européen et du Conseil du 16 décembre 2020 relative à la qualité des eaux destinées à la consommation humaine[2] À l’exception de l’aldrine, dieldrine, heptachlore et heptachlore époxyde pour lesquels la valeur est de 0,03 µg.L-1[3] Arrêté du 11 janvier 2007 relatif aux limites et références de qualité des eaux brutes et des eaux destinées à la consommation humaine mentionnées aux articles R. 1321-2, R. 1321-3, R. 1321-7 et R. 1321-38 du code de la santé publique[4] Consulter la page Internet consacrée aux travaux de l’Anses sur les pesticides dans les EDCH et en particulier le tableau recensant les VMAX établies par l’Anses : https://www.anses.fr/fr/content/detecter-et-surveiller-les-pesticides-dans-leau-du-robine