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Reshetikhin-Turaev construction and Chern-Simons partition function
No full textInternational audienceIn this article, we show that the Chern-Simons partition functions are related to Reshetikhin-Turaev invariants. In this abelian context, it turns out that the Reshetikhin-Turaev construction that yields these invariants relies on a ``twisted" category rather than a modular one. Furthermore, the Chern-Simons duality of the partition functions straightforwardly extend to the corresponding Reshetikhin-Turaev invariants
First observation of the decay and search for pentaquarks in the system
No full textInternational audienceThe decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of with the LHCb detector, corresponding to an integrated luminosity of . The ratio of branching fraction to that of decays is measured as , where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the system. No evidence is found, and upper limits on the production ratio of and pentaquarks relative to the final state are set at the confidence level as and , respectively
Caractérisation des propriétés mécaniques du groupe musculaire des ischio-jambiers chez les sportives : impact du cycle menstruel et adaptations aux dommages musculaires induits par l'exercice
No full textFemale sports participation is rapidly growing, yet women remain underrepresented in sports science and medicine studies compared to men. Nevertheless, an increasing number of studies are examining the influence of sex and, more specifically, the female hormonal environment during the menstrual cycle and oral contraceptive use on the mechanical properties of muscles, which play a significant role in muscle injury processes. However, the effects of 17β-estradiol and progesterone, the primary sex hormones whose concentrations fluctuate throughout the menstrual cycle, remain underexplored in vivo, particularly regarding their potential impact on the severity of exercise-induced muscle damage and subsequent tissue regeneration capacity. In vivo assessment of muscle mechanical properties is facilitated by non-invasive imaging techniques such as shear-wave elastography, which allows for highly localised evaluation of muscle tissue rigidity. This doctoral work aims to characterise differences in the mechanical properties of hamstring muscles between women and men and to assess potential changes in muscle rigidity throughout the menstrual cycle and oral contraceptive use. It also explores the relationship between the menstrual cycle, oral contraceptive use, and the severity of muscle damage induced by isokinetic eccentric exercise. Our main results show that the passive rigidity of the semitendinosus, one of the hamstring muscles, is lower in women than in men. However, the passive rigidity of the hamstrings does not change throughout the menstrual cycle or with oral contraceptive use, whereas the active rigidity of the semitendinosus is lower during the luteal phase of the menstrual cycle, when 17β-estradiol and progesterone concentrations are high. These findings highlight the importance of considering the potential effects of progesterone on muscle tissue, which remain largely under-researched, even in animal studies. Moreover, while our results indicate that the severity of muscle damage induced by isokinetic eccentric exercise is not dependent on the menstrual cycle phase or oral contraceptive use, muscle tissue rigidity during submaximal contractions is affected by damage only during the luteal phase, once again suggesting an effect of progesterone on muscle mechanical properties. Additionally, the recovery of passive mechanical properties of the semitendinosus is slower in groups with increasing 17β-estradiol concentrations, suggesting a potential deleterious effect of this hormone on extracellular matrix remodelling. Finally, our results show delayed recovery of maximal voluntary strength during the luteal phase. Thus, post-injury recovery appears to be slower when muscle damage occurs in the second half of the menstrual cycle.La pratique sportive féminine se développe rapidement, tandis que les femmes sont encore sous-représentées dans les études en sciences et médecine du sport par rapport aux hommes. Néanmoins, de plus en plus d’études s’intéressent à l’influence du sexe et plus spécifiquement de l’environnement hormonal féminin, au cours du cycle menstruel et de l’utilisation d’une contraception orale, sur les propriétés mécaniques musculaires, qui jouent un rôle important dans les processus de blessure musculaire. Pourtant, les effets du 17β-œstradiol et de la progestérone, les principales hormones sexuelles dont les concentrations varient au cours du cycle menstruel, demeurent peu étudiés in vivo, notamment au regard de leur impact potentiel sur la sévérité des dommages musculaires induits par l’exercice et sur les capacités subséquentes de régénération tissulaire. L’évaluation in vivo des propriétés mécaniques musculaires est facilitée par des techniques non-invasive d’imagerie comme l’élastographie ultrasonore par ondes de cisaillement, qui permet d’évaluer de façon très localisée la rigidité du tissu musculaire. Ces travaux de thèse ont pour objectif de caractériser les différences de propriétés mécaniques des muscles ischio-jambiers entre femmes et hommes et d’évaluer de potentielles modifications de rigidité musculaire au cours du cycle menstruel et de la prise d’une contraception orale. Ils explorent également la relation entre le cycle menstruel, la prise d’une contraception orale et la sévérité des dommages musculaires induits par un exercice excentrique isocinétique. Nos principaux résultats montrent que la rigidité musculaire passive du semi-tendineux, un des muscles ischio-jambiers, est plus faible chez les femmes que chez les hommes. En revanche, la rigidité passive des ischio-jambiers n’évolue pas au cours du cycle menstruel ou avec la prise d’une contraception orale, tandis que la rigidité active du semi-tendineux est plus faible lors de la phase lutéale du cycle menstruel, quand les concentrations en 17β-œstradiol et progestérone sont élevées. Ces résultats soulignent l’importance de considérer les potentiels effets de la progestérone sur le tissu musculaire, qui restent très peu étudiés pour le moment, y compris chez l’animal. Par ailleurs, bien que nos résultats montrent que la sévérité des dommages musculaires induits par un exercice excentrique isocinétique n’est pas dépendante de la phase du cycle menstruel et de la prise d’une contraception orale, la rigidité du tissu musculaire lors de contractions sous-maximales n’est affectée par les dommages que lors de la phase lutéale, suggérant à nouveau un effet de la progestérone sur les propriétés mécaniques musculaires. De plus, la récupération des propriétés mécaniques passives du semi-tendineux est ralentie dans les groupes présentant des concentrations croissantes en 17β-œstradiol, suggérant un potentiel effet délétère de cette hormone sur le remodelage de la matrice extra-cellulaire. Enfin, nos résultats montrent une récupération retardée de la force maximale volontaire lors de la phase lutéale. Ainsi, la récupération post-lésionnelle semble plus lente lorsque les dommages musculaires sont induits dans la seconde partie du cycle menstruel
Quand la neige fond : trajectoire d’adaptation stratégique des ressources d’une station-village alpine
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Symposium Report: US Network Series of the 2000s
No full textInternational audienceThe symposium “US Network Series of the 2000s,” organized by Claire Cornillon (Université de Nîmes), Monica Michlin (Université Paul-Valéry Montpellier 3), Sarah Hatchuel (Université Paul-Valéry Montpellier 3) and David Roche (Université Paul-Valéry Montpellier 3) within the “Network TV” project and the GUEST Program, was held on October 10th and 11th, 2024 at Université Paul-Valéry in Montpellier. It marked the final instalment of the “Network TV” project’s cycle of conferences which previously focused on US network series produced from the 1950s to the 1970s, during the 1980s and during the 1990s respectively. The overall project, which began in 2016 at Université du Havre, is dedicated to developing research on network television, as opposed to cable or platform shows. “Network TV” aims to assess the narrative, social, cultural, aesthetic and political impact of these series and constitutes one of the branches of the broader research group GUEST (Groupe Universitaire d’Étude sur les Séries Télévisées) dedicated to the study of TV series. This year’s symposium was organized by the RiRRa21 (Représenter et Inventer la Réalité, du Romantisme au XXIe siècle) and EMMA (Études Montpelliéraines du Monde Anglophone) research teams of Université Paul-Valéry, with funding from the IUF (Institut Universitaire de France). It featured five panels in which international scholars presented their work on US network series of the 2000s, ranging from in-depth narrative aesthetic readings of individual episodes to historical, sociological and translation studies
Cation Contamination Redistribution throughout the PEMFC MEA: Towards the Establishment of Regeneration Protocols
No full textInternational audienceProton exchange membrane fuel cells (PEMFCs) are a promising technology for automotive applications. The membrane electrode assembly (MEA) remains the most vulnerable element in fuel cells due to its membrane composed of perfluorosulfonic acids. Over the lifetime of the PEMFC, cation contamination occurs from corrosion of fuel cell stack components such as bipolar plates and could be concentrated at particular locations. These cations can migrate from the bipolar plate into the electrode and the membrane. Indeed, due to their affinity toward sulfonic groups, they tend to replace protons affecting membrane conductivity. In addition, some ionic species such as iron cations are commonly known as catalysts for the Fenton reaction responsible for the chemical degradation of the membrane.In this work, we investigate the local effect of ferric contamination and its diffusion through electrochemical tests and post-mortem analyses. A membrane is strategically contaminated by Fe3+ ions, then assembled into MEA using a hot-pressing method. A segmented cell monitors the ferric ion impact on local cell performance and impedance parameters at different operating conditions. After in-situ tests, MEA’s membrane and gas diffusion electrodes (GDE) are separated for analysis. Then, iron species are quantified to visualize the migration of Fe3+ in both in- and through-plane directions.Post-mortem analysis suggests that at high local contamination, a part of cations is leached from the contaminated regions of the membrane after a PEMFC operating (Figure 1). In terms of cation distribution, post-mortem analyses reveal a preferential diffusion of Fe3+ perpendicular to the gas diffusion channels and in the flow direction of H2. On a local scale, performances of contaminated channels are affected especially at low hydration levels Besides the in-plane diffusion the propagation of cations from the membrane to electrodes has been detected, at rates approaching 25% of total contamination. The impact of the Fe3+ migration on radical scavenger diffusion is discussed. Our results provide useful information about cation diffusion in complex systems such as MEAs and gives us some hints on recovery protocols to extend lifetime of fuel cells
Time-dependent receiver extension for full-waveform inversion: An alternative extension method for cycle-skipping mitigation
No full textInternational audienceExtension strategies for full-waveform inversion (FWI) rely on introducing additional degrees of freedom to the FWI problem, which expands the search space. This search space extension helps by relaxing the nonconvexity of the problem and thereby alleviating the cycle-skipping issue. The receiver-based extension strategy introduces the receiver position as the additional degree of freedom to FWI to improve the fit between the observed and calculated data at early iterations. This helps circumvent the cycle-skipping phenomenon. In this study, we make this receiver position time dependent, meaning that the receiver positions vary as a function of the acquisition time. The resulting mathematical problem is a two-nested-loop minimization, where the outer loop is the conventional FWI loop to update the subsurface mechanical parameters and the inner loop aims at finding the optimal time-dependent virtual receiver positions. This inner-loop problem is heavily nonlinear and nonconvex. Finding the global minimum is therefore a challenging task. To do so, we use a computational intelligence technique, particle swarm optimization (PSO). PSO makes it possible to thoroughly explore the search space with few iterations. Numerical experiments using a North Sea exploration 2D synthetic model, starting from crude initial models, illustrate that the method is robust and very easy to tune
CO2 monitoring at Sleipner field using reflection oriented full waveform inversion: Part 1 - baseline reconstruction
No full textInternational audienceIn this study, we illustrate the application of a 3D reflection oriented workflow for full waveform inversion (FWI) to the offset data from the Sleipner field. The data set is having maximum offset of less than 2000 m, and has been pre-processed with a low-cut filter below 6 Hz, imposing strong challenges for the FWI application. To tackle these challenges, a reflection oriented full waveform inversion is applied to the data set, which utilize joint full waveform inversion (JFWI) to constrain the low wavenumber updates at the deepest part of the reconstructed model. It consists of two steps, an impedance model building serving as a prior reflector information followed by a velocity model building. In this case, JFWI workflow is taking advantage of the pseudo-time formulation to honor the zero offset travel time, fast and robust asymptotic preconditioner for impedance model building, and graph space optimal transport misfit function to mitigate cycle skipping. To show the effects of limited offset, conventional FWI is performed. In this case, it is clear that the meaningful updates coming from the diving waves are restricted to the shallow part no deeper than 500 m of depth, while no meaningful perturbation are observed beyond the diving waves penetration. Taking advantage of the meaningful shallow updates, diving wave only inversion is performed prior to the impedance model building, and then followed by the JFWI workflow. The results of the field data application show that JFWI is able to produces meaningful velocity updates both in shallow part and the deeper part. The result is supported by satisfactory fit of the calculated data based on the JFWI model compared to the observed data. In addition, the velocity model fits the low wavenumber trend of the well log data. A subsequent run of conventional FWI is performed starting from JFWI model, in order to improve the resolution of the velocity model. The results is able to introduce higher wavenumber content to the velocity model, producing satisfactory fit with the observed data, and matching the well log data