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Vers une architecture homogène des Assemblées de la Terre : réflexions à partir du modèle français
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In situ and real-time observations to obtain benchmark data during solidification studies: focus on growth competition
No full textInternational audienceDuring solidification from the melt, the morphology of the solid-liquid interface depends on both material properties and processing parameters. Characterizing the interface is crucial, as it directly influences the final material properties. Directional solidification provides precise control over process parameters, making it a powerful tool for studying the interface dynamics. A comprehensive understanding remains challenging and requires key information that could only be brought by in situ and real time observation of the process. Such experiments provide benchmark data essential for understanding microstructure formation and for developing numerical models. Some of the most striking results from our team on both metallic and organic alloys will be presented.Microstructures formed during solidification are often polycrystalline, composed of multiple grains with different crystallographic orientations with respect to the thermal gradient. Grains with low misorientation can persist into later stages of growth, forming subgrain boundaries—common yet largely unavoidable defects in metal products. The effects of grain and subgrain boundaries in bulk samples will be explored [1]. Observations revealing, for the first time, that cellular structures from one grain can invade a neighboring grain during polycrystalline growth will be reported [2]. This unexpected invasion process causes grains to interpenetrate each other on the fine scale of the array spacing, and hence grain borders to become highly irregular. As an inherent property of polycrystalline alloy solidification, this phenomenon has broad implications for the processing of metallic alloys.[1] F.L. Mota, J. Pereda, K. Ji, et al., Acta Materialia 204, 116500 (2021)[2] Y. Song, F.L. Mota, D. Tourret, et al., Nature Communications 14, 2244 (2023
Influence of two strength training modalities (hypertrophy vs. contrast training) on muscular strength, bone health parameters and quality of life in a group of older adults with low skeletal muscle mass index
No full textInternational audienceThe main aim of the current study was to compare the effects of two strength training modalities (hypertrophy vs. contrast training) on bone health parameters, physical performance and quality of life in a group of subjects aged 60 and above with low skeletal muscle mass index (SMI). 45 older adults voluntarily participated in this study, but only 41 (22 women and 19 men) completed it. The participants were assigned to 3 different groups: control group (CG; n = 15), contrast training group (CTG; n = 13) and hypertrophy training group (HTG; n = 13). The duration of the training protocol was six months. The experimental groups performed two sessions of strength training per week; the duration of each session was forty-five minutes. Several measurements (which included anthropometrics, body composition, bone parameters, maximal strength parameters, physical performance parameters, fracture risk and quality of life) were performed in the three groups before and after the six-month training period. The different measurements of the protocol were carried out under the same conditions with identical materials and investigators for all the participants and for each approach. The current study has demonstrated that the two training modalities show common benefits such as improving maximal strength, physical performance and quality of life parameters but have no significant effects on bone mineral density (BMD) and bone mineral content (BMC). The influence of training was marked more for improving maximal strength and reducing fracture risk for the contrast training group (who performs movements at high speed) compared to the hypertrophy training group (who performs movements at spontaneous speed). In conclusion, this study shows that both resistance training programs are effective in improving maximal strength, physical performance and quality of life in older adults with low SMI. However, this 6-month intervention was not sufficient to significantly increase BMC nor BMD values in this population.</div
La coopération sans coopérative : la gestion des tensions au sein d’une organisation alternative d’inspiration anarchiste
No full textFNEGE 3International audienceThrough the study of self-managed grocery stores inspired by anarchist philosophy, we illustrate how tensions inherent to the alternative cooperative model manifest and are understood by the members of these organizations.To achieve this, we rely on a set of qualitative data. The results of the study highlight two specificities derived from anarchist philosophy—freedom and individual responsibility on the one hand, and autonomist leadership on the other—that enable actors to activate the three modes of tension resolution identified in the literature: acceptance, confrontation, and transcendence (Smith, 2011), in an original way. These results highlight ways to better manage tensions and avoid coalition dynamics that are present in most cooperatives.À travers l’étude d’épiceries autogérées s’inscrivant dans la philosophie anarchiste, nous montrons comment les tensions inhérentes au modèle alternatif des coopératives se manifestent et sont appréhendées par les membres de ces organisations. Pour y parvenir, nous nous appuyons sur un ensemble de données qualitatives. Nous constatons que deux spécificités émanant de la philosophie anarchiste – la liberté et responsabilité individuelle d’une part et le leadership autonomiste d’autre part – permettent aux acteurs d’actionner de manière originale les trois modes de gestion des tensions identifiées dans la littérature que sont : l’acceptation, la confrontation et la transcendance (Smith, 2011). Ces résultats mettent en lumière des pistes pour mieux gérer les tensions et éviter les logiques de coalitions qui se forment souvent au sein des coopératives
Connecting anomalous elasticity and sub-Arrhenius structural dynamics in a cell-based model
No full text5 pages, 5 figuresInternational audienceUnderstanding the structural dynamics of many-particle glassy systems remains a key challenge in statistical physics. Over the last decade, glassy dynamics has also been reported in biological tissues, but is far from being understood. It was recently shown that vertex models of dense biological tissue exhibit very atypical, sub-Arrhenius dynamics, and here we ask whether such atypical structural dynamics of vertex models are related to unusual elastic properties. It is known that at zero temperature these models have an elasticity controlled by their under-constrained or isostatic nature, but little is known about how their elasticity varies with temperature. To address this question we investigate the 2D Voronoi model and measure the temperature dependence of the intermediate-time plateau shear modulus and the bulk modulus. We find that unlike in conventional glassformers, these moduli increase monotonically with temperature until the system fluidizes. We further show that the structural relaxation time can be quantitatively linked to the plateau shear modulus , i.e.\ modulates the typical energy barrier scale for cell rearrangements. This suggests that the anomalous, structural dynamics of the 2D Voronoi model originates in its unusual elastic properties. Based on our results, we hypothesize that under-constrained systems might more generally give rise to a new class of "ultra-strong" glassformers
Investigating the Atmospheric Microbial Ecosystem Through Theory, Bioenergetics, and Numerical Modeling: A Breath of Fresh Air for Aeromicrobiology
No full textInternational audienceThe atmosphere may constitute the Earth's largest microbial ecosystem, yet it remains the least understood. While microorganisms can persist and may even thrive in the polyextremes of the Earth's atmosphere, it is still unknown whether the atmosphere sustains an active microbial community. Despite growing awareness of the role of the aeromicrobiome in shaping global biogeography, epidemiology, and climate, fundamental questions about its metabolic activity and ecological significance remain unanswered. Here, we outline how theoretical approaches and numerical modeling tools provide powerful avenues to investigate the atmospheric microbial ecosystem, offering unique insights that complement experimental and observational-based studies and can overcome many of the challenges they face. We consider frameworks that integrate (a) theoretical considerations for microbial metabolism across a range of catabolic and anabolic processes, (b) microbial physiology and metabolic states, (c) thermodynamics and bioenergetics, (d) the chemical and physical conditions of the atmosphere and bioaerosols, (e) transport and residence time of microorganisms, and (f) bottom-up and top-down approaches. Theory and modeling-based investigations into the aeromicrobiome can generate and test theory and model-informed hypotheses, formulate mechanistic explanations of biological processes and observations, and inform targeted sampling strategies and experimentation. Together, these approaches bring us closer to determining whether the Earth's atmosphere is a true ecosystem-that is, a metabolically active community of organisms interacting with each other and with the environment. Advances in aeromicrobiology research brought about by theory and modeling can reveal significant insights into global biogeography, biogeochemical cycles, climate processes, and the limits for life. Plain Language SummaryThe atmosphere presents numerous challenges to microorganisms including low temperatures, aridity, UV radiation, and low nutrient availability. Despite research demonstrating that microorganisms can tolerate and even grow under these conditions, we still do not have a clear picture of whether the Earth's atmosphere constitutes an active microbial ecosystem. Here, we outline how theoretical and numerical modeling tools provide new avenues to investigate microorganisms in the atmosphere. We evaluate theoretical bases of microbial metabolism (the set of processes used by microorganisms to obtain energy from nutrients), thermodynamics, and bioenergetics (how microbes transform energy), in context with the chemical, physical, and biological composition of the atmosphere, to outline how theory and modeling-based investigations can generate and refine hypotheses, sampling strategies, and experimentation; evaluate the capacity of the atmosphere to sustain life and support a microbial ecosystem; and assess how biological processes influence the Earth's atmosphere. Advances in aeromicrobiology research brought about by theory and modeling can reveal significant insights into global biogeography, biogeochemical cycles, climate processes, and the limits for life in planetary atmospheres.</div
Optimizing Epoxy Vitrimer Composites With Sustainable Cellulose Nanofibril Reinforcements: Enhancing Thermal Dimensional Stability While Preserving Dynamic Covalent Behavior
No full textInternational audienceVitrimers are networks with dynamic covalent bonds that are promising for recycling composite materials, which often suffer from significant creep. This study explores the integration of cellulose nanofibrils (CNFs), without any functionalization, into an epoxy vitrimer matrix to enhance mechanical performance and dimensional thermal stability, while preserving the dynamic covalent network properties. Using an optimized infiltration method of CNF template, CNF was effectively impregnated within the epoxy vitrimer matrix, as demonstrated by SEM and AFM morphological characterizations. A slight decrease in the composite's glass transition temperature is attributed to a reduced crosslinking density at the CNF‐resin interface. A 10 wt% CNF resulted in a 77% increase in the composite's storage modulus compared to the neat resin. This CNF‐interpenetrated network within the crosslinked vitrimers leads to a significant reduction in the composite's thermal expansion, which is crucial for applications requiring good dimensional thermal stability. Stress relaxation studies indicate a slight increase in the activation energy of topological rearrangement induced by the CNF, while maintaining complete relaxation, thus enabling the reshaping or recycling of composites
Whistles characterisation using artificial intelligence reveals responses of short-beaked common dolphins to a bio-inspired acoustic mitigation device for fishing nets
No full textInternational audienceUnderstanding cetacean whistles is crucial for assessing their social interactions, behaviours, and responses to anthropic activities. Identifying the various types of whistles present in acoustic recordings is often challenging, but necessary for this purpose. To facilitate this process, we have developed a semi-automated deep learning approach called the "Draw Your Own Contours" (DYOC) method. This is available as an open-source software along with its associated dataset. It utilises YOLOv8m and ResNet18 to identify whistle contours. DYOC was applied to 808 minutes of audio recordings of wild, free-ranging short-beaked common dolphins from the Bay of Biscay, France. It enabled the annotation of 8,730 whistle contours, six times faster than manual annotation. These recordings were associated with observations of dolphin behaviour, the presence of fishing nets, and the activation of the DOLPHINFREE acoustic beacon. Analyses revealed that these variables affected the signal-to-noise ratio, the number of inflections, and the frequency and/or duration of recorded whistles. This study provides the first characterisation of whistle features for a population of shortbeaked common dolphins in the Bay of Biscay. The annotation of whistle contours using the DYOC method helped reveal the complex acoustic behaviour of dolphins in response to external variables
Éditorial. L’intelligence artificielle dans les organisations, comment (mieux) travailler avec ? Perceptions, attitudes et comportements des acteurs face au déploiement de l’IA en milieu professionnel
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Search for steady and flaring neutrino emission from cosmic sources using the complete ANTARES dataset
No full textInternational audienceANTARES, a neutrino detector located in the depths of the Mediterranean Sea, operated successfully for over 15 years before being decommissioned in 2022. The telescope offered an ideal vantage view of the Southern Sky and benefited from optimal water properties for enhanced angular resolution. This study makes use of data collected over the entire operational period of ANTARES to search for sources of high-energy cosmic neutrinos, considering both steady and flaring emission scenarios. First, a time-integrated search for high-energy neutrino clustering across the celestial sphere is conducted. The most significant accumulation is found at coordinates with a post-trial p-value equal to 0.38. A dedicated search in the Galactic Plane is also performed for extended sources, yielding no significant excess. Additionally, a list of potential neutrino sources are investigated. The blazar MG3 J225517+2409 is identified as the most significant object, yet the excess remains compatible with background fluctuations. A mild local excess of 2.4 is found for the blazar TXS 0506+056. The full sky is also examined for the presence of flaring neutrino emissions. The most significant excess in this case corresponds to a 4-day flare from the direction , with a post-trial p-value of 0.30. Finally, the directions of sources highlighted in IceCube's time-dependent searches are investigated. Temporal overlaps between ANTARES and IceCube flares are identified for PKS 1502+106 and TXS 0506+056, with an estimated chance probability of about 0.02%, making this observation particularly noteworthy