Hal - Université Grenoble Alpes
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Fabrication of Centimeter‐Scale MoWS 2 ‐Based High Performing Solar Cells
No full textInternational audienceThe growing demand for efficient, scalable, and lightweight photovoltaic (PV) technologies has intensified interest in WS 2 and MoS 2 ‐based devices. Despite notable advances, achieving simultaneously high performance and long‐term operational stability remains a key barrier to broader adoption. Here, we address this challenge by fabricating p–n heterojunction solar cells through a single‐step chemical vapor deposition process that directly deposits WS 2 , MoS 2 , and their alloy MoWS 2 onto p‐type silicon substrates. The MoWS 2 alloy exhibits a reduced bandgap and enhanced optoelectronic properties, which translate into substantially improved PV output and device robustness. The MoWS 2 ‐based solar cell achieves a power conversion efficiency of 5.8%, outperforming the WS 2 and MoS 2 counterparts, which reach 1.12% and 3.6%, respectively. In addition, MoWS 2 displays markedly enhanced light‐harvesting capability, with an external quantum efficiency of 80%, compared to 30% for WS 2 and 50% for MoS 2 . Stability assessments further demonstrate that MoWS 2 retains its performance over a 30‐day test period, confirming its superior long‐term durability. By establishing the viability of MoWS 2 as a high‐potential photoactive material for lightweight PVs, this work sets the stage for future research and paves the way toward practical implementation of alloy‐engineered 2D semiconductor solar technologies
Shape evolution in neutron-rich Rh isotopes: First measurement of negative-parity isomers in Rh
No full textInternational audienceThe β-delayed γ-ray spectroscopy of neutron-rich 117,119Rh isotopes has been investigated at the Radioactive Isotope Beam Factory of RIKEN. The 1/2− isomers in 117,119Rh have been identified for the first time. The systematics of energy differences between the 9/2+ and 1/2− states have been extended up to N=74, which shows a tendency to first increase with the neutron number N, then reach a maximum at N ≈ 68, and subsequently decrease. Self-consistent triaxial relativistic Hartree-Bogoliubov (TRHB) calculations highlight the crucial role of triaxial deformation, particularly in the positive-parity states, in driving the observed evolution of energy differences. A shape transition from axially symmetric to triaxial and back to axially symmetric deformation is suggested along the Rh isotopic chain. These findings provide new insights into the structure of neutron-rich nuclei in the A ∼ 110 region and motivate further studies of exotic isotopes in this region to explore the interplay between triaxiality and shell evolution
From the Lorentz ether to a scalar theory of gravity and its implications
No full text25 pagesIn the Lorentz-Poincaré version of special relativity (SR), the "relativistic" effects, beginning with the Lorentz contraction, are seen as absolute, as being due to a motion relative to a privileged frame of reference or "ether". We present a scalar theory of gravitation that extends Lorentz-Poincaré SR. We provide motivations for such a theory, including critical remarks about general relativity. That theory starts from an interpretation of gravity as Archimedes' thrust in a fluid "micro-ether", of which Lorentz's inertial ether is seen as the mean rest frame. Newton's theory propagates instantaneously, hence corresponds with the limiting case of an incompressible fluid. When combined with the Lorentz-Poincaré version of SR, the assumption of a heterogeneous gravitational ether leads naturally to assume effects of gravity on clocks and rods, hence to a curved metric. Motion is governed by an extension of Newton's second law to a curved spacetime, that implies a dynamics for a continuous medium. The main observational tests are discussed. The Maxwell equations in the presence of gravity need to postulate an "interaction energy", which might contribute to dark matter. The present state of calculating that energy in a galaxy is shown
Three- to 8-year old children do not favor male power when allocating resources
No full textInternational audienceAbstract From an early age, children perceive power imbalances between genders, but their attitudes toward gendered power remain largely unexplored. We studied this issue using a resource allocation task with 653 French children aged 3–8 (50.15% girls) recruited between 2022 and 2023. Participants were exposed to a dyadic power interaction and had to distribute more resources to either the dominant or the subordinate character. We tested three hypotheses: H1 predicted a male dominance bias; H2 predicted own-gender favoritism; and H3 predicted sensitivity to hierarchical status only. Contrary to H1, no pro-male bias was found. Results supported H3: younger children favored dominant characters, while older children favored subordinates. H2 was partially supported, showing own-gender bias, stronger in girls, without overriding sensitivity to status
Respirer avec K. Méthodes et enjeux cartographiques
No full textNational audienceCe texte se propose de mener une discussion avec et autour d’une cartographie , celle de l’itinéraire de K., un homme, asthmatique et allergique. Nous - deux chercheurs et une architecte cartographe - avons expérimenté avec K. un itinéraire en marchant centré sur sa respiration et son expérience ordinaire de l’air, en nous donnant l’objectif suivant : produire une cartographie qui non seulement exprime l’expérience de l’itinéraire, mais aussi constitue un outil réflexif et critique des espaces publics contemporain
Black holes in a dense infinite medium: a toy-model regularizing the Schwarzschild metric
No full textInternational audienceWe revisit the dynamics of a black hole accreting energy from a surrounding homogeneous and infinite space. We argue for a simple heuristic modification of the Schwarzschild approximation when the density of the medium is not negligible anymore. The resulting behavior is drastically modified: the mass divergence at finite time is cured and the thermodynamical properties are deeply changed. Some potential consequences for quantum gravity and bouncing models are also pointed out. Those conclusions being mostly obtained from a Newtonian approach, they only aim at guiding toward a more rigorous treatment. Still, interestingly, the behavior is far more convincing that the one usually obtained
Digging deeper: deep joint species distribution modeling reveals environmental drivers of Earthworm Communities
No full textInternational audienceEarthworms are key drivers of soil function, influencing organic matter turnover, nutrient cycling, and soil structure. Understanding the environmental controls on their distribution is essential for predicting the impacts of land use and climate change on soil ecosystems. While local studies have identified abiotic drivers of earthworm communities, broad-scale spatial patterns remain underexplored. We developed a multi-species, multi-task deep learning model to jointly predict the distribution of 77 earthworm species across metropolitan France, using historical (1960–1970) and contemporary (1990–2020) records. The model integrates climate, soil, and land cover variables to estimate habitat suitability. We applied SHapley Additive exPlanations (SHAP) to identify key environmental drivers and used species clustering to reveal ecological response groups. The joint model achieved high predictive performance (TSS >0.7) and improved predictions for rare species compared to traditional species distribution models. Shared feature extraction across species allowed for more robust identification of common and contrasting environmental responses. Precipitation variability, temperature seasonality, and land cover emerged as dominant predictors of earthworm distribution but differed in ranking across species and functional groups. Species clustering into response groups to climatic, land use and soil revealed distinct ecological strategies including a gradient of sensitivity to precipitation seasonality, differential habitat preferences in terms of vegetation cover and wetness and trade-offs between soil acidity and organic matter quality. Our study advances both the methodological and ecological understanding of soil biodiversity. We demonstrate the utility of interpretable deep learning approaches for large-scale soil fauna modeling and provide new insights into earthworm habitat specialization. These findings highlight land cover and seasonal climate variability as efficient proxies for soil biodiversity, providing actionable indicators for global monitoring initiatives and helping to identify habitat requirements of earthworm species to guide emerging earthworm conservation strategies in the face of global environmental change
Microstructure optimization by combinatorial approach applied to Duplex Medium Manganese steels
No full textInternational audienceThis study introduces a novel combinatorial approach for optimizing the microstructure of duplex medium-manganese (Mn) steels by coupling a controlled thermal gradient with in situ high-energy X-ray diffraction (HEXRD) during intercritical annealing. A temperature gradient (680–720 °C) across a single sample enables real-time monitoring of phase transformations over a broad thermal range in one experiment. Compared to isothermal trials, this method offers high-resolution insight into austenite formation kinetics and phase stability, enabling accurate identification of the optimal temperature window for maximizing retained austenite. The results reveal a narrow optimal range (∼700–710 °C) where retained austenite fractions exceed 30 %, surpassing values from traditional methods. Post-mortem Electron Backscatter Diffraction (EBSD) analysis showed the spatial distribution of stabilized austenite, highlighting the complementary roles of in situ and ex situ characterization. This work demonstrates the potential of gradient-based combinatorial metallurgy to accelerate process optimization and support the design of high-performance third-generation advanced high-strength steels
Les conditions de vie et de travail en doctorat à l’Université Grenoble Alpes: 2e partie. Compte-rendu de l’enquête par questionnaire et entretiens
No full textCette étude, commandée par l'Université Grenoble Alpes, explore de manière approfondie la précarité des doctorant·es en adoptant une approche multidimensionnelle qui va au-delà des simples aspects financiers. Elle combine une enquête quantitative auprès de près de 1000 doctorant·es (soit un tiers de la population) et une enquête qualitative basée sur 45 entretiens.Les résultats montrent un paysage contrasté. Environ 75 % des doctorant·es sont dans une situation peu ou pas précaire selon l'indicateur EPICES, utilisé pour évaluer la précarité dans la population générale. Cependant, le quart restant cumule des difficultés : réelles contraintes budgétaires pour les besoins élémentaires, isolement social et absence de complémentaire santé. L'analyse identifie des facteurs qui augmentent significativement l'exposition à la précarité. Les doctorant·es originaires de pays hors Union Européenne, celles et ceux qui sont inscrit·es en sciences humaines et sociales (SHS), et celles et ceux engagé·es au-delà de la quatrième année de thèse apparaissent comme les populations les plus vulnérables.L'enquête qualitative permet de d’approfondir ce portrait statistique et de comprendre les expériences vécues. Elle révèle une population fortement motivée par la recherche et l'idée de contribuer au service public, ce qui conduit parfois à l’acceptation de conditions matérielles difficiles. Les entretiens mettent aussi en lumière des défis spécifiques : le stress lié à l'incertitude de la recherche et à la compétition pour les postes académiques, les difficultés financières en fin de contrat doctoral (notamment en SHS où les thèses sont plus longues), et des situations d'isolement ou d'asymétrie de pouvoir avec l’encadrement de thèse qui peuvent conduire à des abus.En conclusion, cette recherche démontre que si la majorité des doctorant·es de l'UGA évoluent dans des conditions acceptables, une minorité significative affronte une précarité multidimensionnelle et cumulative. L’étude plaide pour des politiques d'accompagnement ciblées, tenant compte des profils les plus à risque, et rappelle que la qualité des conditions de vie et de travail des doctorant·es est essentielle à la mission de production et de diffusion des savoirs de l'université