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WS segregation in W-doped NaPS sodium solid electrolyte
No full textInternational audienceBatteries are crucial for addressing global warming, but their reliance on depleting lithium resources is concerning. Sodium-based batteries have emerged as promising alternatives for next-generation solid-state batteries. To improve electrolyte performance, particularly ionic conductivity, scientists have explored aliovalent substitution strategies for archetypal materials like Na3PS4 (NPS). An approach introduces W6+ ions at the 2a (0,0,0) Wyckoff site in place of P5+ in NPS, creating WS4²⁻ tetrahedra and Na vacancies in the Na3-xP1-xWxS4 (NPWS) thiophosphates that enhance ionic mobility. However, X-ray diffraction shows segregation of WS2, indicating limited solubility.[1,2] Unit cell parameters change minimally with increasing W content, with maximum reported values of x = 0.1[1] to 0.15[2] without significant unreacted WS2. In some cases, improved ionic conductivity (σion, up to 1.3 × 10⁻² S cm⁻¹) appears to be the result of changes in the NPS phase during heat treatment rather than W6+ incorporation.[2] We explored NPWS (x = 0.15) by using neutron (NPD) and synchrotron X-ray (SXRD) powder thermodiffraction to understand the phases transition during heat treatment
Calibration Impact on the Characterization of Components at Temperature
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Exploitation multiscalaire des ressources numériques 3D pour l'étude de la grotte ornée de Commarque (Dordogne, France) : pour une chaîne opératoire de la connaissance scientifique
No full textInternational audienceDepuis les premières numérisations au scanner laser de la grotte de Cosquer dans les années 1990 jusqu’au développement récent des méthodes d’acquisitions photogrammétriques à haute résolution ou stéréophotométrie, la recherche sur les sites ornés ne peut désormais plus se « penser » sans des process 3D. Par ailleurs, le contexte instable provoqué par le réchauffement climatique mondial implique d’anticiper les situations de crise et de développer des acquisitions 3D permettant non seulement la conservation et l’archive du bien patrimonial, mais aussi de pouvoir exploiter ces données dans le cadre d’une recherche scientifique. C’est dans cette perspective que depuis 2021 l’étude de la grotte ornée de Commarque a pris le parti de prendre la ressource numérique 3D comme l’un de ses pivots méthodologiques. L'étude de la grotte étant complexe du fait de son histoire (site qui a toujours été accessible au cours du temps), il a été nécessaire d’aborder l’art pariétal et les données archéologiques selon une approche multi-scalaire, allant du contexte environnemental aux observations microscopiques sur les parois. En effet, l’approche paysagère est fondamentale pour mieux comprendre le contexte de la fréquentation paléolithique du réseau, son évolution au cours du temps et son insertion dans le contexte de la vallée (vallée des Beunes) en lien avec les sites paléolithiques voisins (e.g. Cap Blanc, Laussel).Par ailleurs, du point de vue de l’art pariétal, le site présente un unicom, à savoir un dispositif orné en bas-relief en contexte de grotte profonde. Seul site de ce type présentant un tel déroulé en bas relief sur près de 50 mètres, il était nécessaire de garder dans la démarche du relevé archéologique, cette dimension de volume. Nous avons alors exploité au mieux les possibilités des modèles 3D pour réaliser directement en relief, les relevés des parois, avec une démarche multicalque prenant en compte l'ensemble des données interdisciplinaires. Cette approche a permis de concevoir des méthodes innovantes qui assurent l'interopérabilité entre les données 2D et 3D, garantissant ainsi une préservation optimale de l'information et la traçabilité des données. Cette démarche établit ainsi une base essentielle au développement d'un SIG 3D. D’autre part, nous avons pu faire dialoguer les multiples échelles de l’approche d’un site orné et ce, de manière collective avec la construction d’une chaîne opératoire permettant la continuité de la connaissance scientifique et basée notamment sur un support de référence, commun à l’ensemble de l’équipe. Cette interopérabilité des données permet un avancement intégré de la connaissance globale et interdisciplinaire du site : approche géomorphologique de la vallée et de l'intérieur de la grotte, étude des processus taphonomiques de dégradation de la paroi, caractérisation et datations des potentiels pigments noirs, relevé pariétaux, analyse technique de la sculpture et gravure. L'élaboration d'une chaîne opératoire claire et adaptée permet ainsi de garantir une continuité de la recherche scientifique acquise pendant le programme de recherche, et permettra sa mise en valeur et son archivage de manière pérenne
In situ U–Pb dating of upper triassic magmatic flows (Spilite) in the External Western Alps (Pelvoux massif): A peripheral CAMP activity?
No full textInternational audienceMagmatic activity during the Triassic-Jurassic transition coincided with the breakup of Pangea, marking a pivotal period in Western European tectonic evolution. However, this activity remains poorly documented in the External Western Alps. Dating the emplacement and alteration of Triassic magmatic rocks such as the spilites in the Alps has long been challenging due to the complex alteration history and the scarcity of suitable mineral phases. This study employs in situ U-Pb dating of carbonate to constrain the timing of hydrothermal alteration of spilites from the Pelvoux massif (France), offering a new temporal framework for these processes. Dolomite and calcite filling vesicles and veins in the spilites yield ages of 201 ± 15 Ma and 202 ± 47 Ma, respectively, consistent with the stratigraphic emplacement interval of these lavas during the Upper Triassic. Notably, the U-Pb system in dolomite has preserved hydrothermal conditions related to magmatic emplacement, without resetting during two subsequent geological events at temperatures approaching 300°C, emphasizing its reliability as a chronometer in this context. The obtained ages overlap with the temporal framework of the Central Atlantic Magmatic Province (CAMP) and geochemical signatures of the spilites correspond to medium/high-Ti transitional to alkaline basalts, comparable to continental basalts such as those of the CAMP. This suggests a shared tectono-magmatic context with mantle-derived magmatism. Furthermore, the spatial proximity of the studied spilites to lower crustal CAMP-related magmatism in the Internal Alps supports a potential genetic relationship, with magma ascent likely facilitated by inherited tectonic structures during the Upper Triassic extension and the opening of the Alpine Tethys. Hydrothermal alteration, marked by spilitization and carbonate precipitation, occurred under low- to moderate-temperature conditions (70–360°C), possibly driven by marine or continental-derived fluids. By providing the first absolute geochronological constraints on spilites in the External Western Alps, this study expands the recognized extent of CAMP. It underscores the utility of carbonates as reliable archives for unraveling hydrothermal and magmatic histories
Explorations spéléologiques en France : la flambée des années 1780
No full textInternational audienceIn the 1780s, the limestone regions of France experienced an unprecedented wave of speleological exploration. Whereas in previous decades, academics went underground to verify earlier descriptions and, if need be, to do justice to ancestral legends, a new generation set itself the goal of discovering new extensions and overcoming hitherto insurmountable obstacles. These explorations therefore require the development of new techniques. They are also based on a network of acquaintances between explorers within the provincial scholarly world.Dans les années 1780, les régions calcaires de France connaissent une vogue inédite d’explorations spéléologiques. Alors que dans les décennies précédentes, les savants académiciens allaient sous terre pour vérifier les descriptions antérieures et, le cas échéant, faire justice de légendes ancestrales, une nouvelle génération va au contraire se donner comme objectif de découvrir de nouveaux prolongements et de franchir des obstacles jusque-là insurmontables. Ces explorations supposent donc la mise au point de techniques nouvelles. Elles reposent aussi sur un réseau d’interconnaissances entre explorateurs au sein du monde savant provincial
The untapped potential of food webs in systematic conservation planning: Using food webs in conservation
No full textInternational conservation policy includes the dual aims of protecting biodiversity and nature's contributions to people (NCP). Achieving these goals requires protecting not only species and habitats, but also the networks of biotic interactions that sustain them. Food webs, which represent predator-prey interactions between species, are increasingly recognised as a link between ecosystem structure, function, and resilience, which are concepts that are frequently cited in conservation policy. Yet, conservation planning and policy typically focus on individual species and habitats and overlook the interactions that support their persistence. We review the literature at the intersection of food web ecology and conservation, and highlight how food webs can inform three conservation goals: preventing species extinctions, maintaining ecosystem functions and NCP, and fostering ecosystem resilience. Food web data and metrics, such as interaction diversity, trophic diversity, connectance, or modularity, can be used to prioritise species that are key to ecosystem structure and functioning, and to guide spatial prioritisation to protect functionally diverse and resilient communities. Given the growing availability of food web data, incorporating food webs in conservation planning can lead to more effective and resilient conservation outcomes that sustain biodiversity and ecosystem functions in the long term
The first estimation of the ionization fraction in dense and translucent molecular gas across Orion B
No full textInternational audienceContext. The ionization fraction (fe=ne/nH) represents a fundamental parameter of the gas in the interstellar medium. However, estimating fe relies on a deep knowledge of the underlying chemistry of molecular gas as well as observations of atomic recombination lines and electron-sensitive molecular emission, such as deuterated isotopologs of HCO+and N2H+, which are only detectable in the dense cores. Until now, it has been challenging to constrain the ionization fraction in the interstellar gas over a large areas because of the observational limitations on these tracers and chemistry models.Aims. Recent models have provided a set of molecular lines whose ratios (intensities and column densities) can be used to trace fe in different environments of molecular clouds. Here, we use a set of various molecular lines typically detected in the 3−4 mm range to constrain the ionization fraction across the Orion B giant molecular cloud. In this work, we derived the ionization fraction for dense and translucent gas, and we investigated its variation with the density of the gas, n, and the strength of the far-ultraviolet radiation field, G0, with their ratio G0/n.Methods. We present our results for the ionization fraction across one square degree in Orion B derived using analytical models as well as observational intensity and column density ratios of CN(1−0)/N2H+(1−0), 13CO(1−0)/HCO+(1−0), and C18O(1−0)/HCO+(1−0) in the dense and shielded medium (Av ≥ 10 mag). We also used ratios of C2H(1−0)/HNC(1−0), C2H(1−0)/HCN(1−0), and C2H(1−0)/CN(1−0) in the translucent gas (2 mag ≤ Av ≤ 6 mag).Results. We find that the ionization fraction is within the range of 10−5.5−10−4 for the translucent medium and 10−8−10−6 for the dense medium. Our results show that the inferred fe values are sensitive to the value of G0, especially in the dense, highly UV-illuminated gas. We also find that the ionization fraction in dense and translucent gas decreases with an increasing volume density (fe ∝ n−0.227 for dense gas and fe ∝ n−0.3 in translucent gas). It increases with G0, which is a consequence of how sensitive the emission of selected molecular lines (e.g., CN and HCO+) is to the UV radiation field. In the case of the translucent medium, we did not find any significant difference in the ionization fraction computed from different line ratios. The range of fe values found in translucent gas implies that the electron excitation of HCN and HNC becomes significant in this regime.Conclusions. In dense and shielded gas, we recommend using CN(1−0)/N2H+(1−0) to derive an upper limit on the ionization fraction fe, along with C18O(1−0)/HCO+(1−0) to set constraints on the lower limit. In a translucent medium, C2H(1−0)/HNC(1−0) serves as a good tracer of fe. The moderately high fe values found in translucent gas are consistent with the C+/CI/CO transition regime, while the values we find in the dense gas are sufficient to couple the gas with the magnetic field
From bulk toward micro-structured TiO 2 ceramics for all-dielectric metamaterials at terahertz frequencies: what process?
No full textInternational audienceAbstract In this study, we aimed to develop high permittivity ceramics ideal for the fabrication of all-dielectric metamaterials (ADM) operational in the terahertz frequency. ceramic pellets have been fabricated from a commercial powder. A comparative analysis was conducted between spark plasma sintering (SPS) and conventional sintering process. Characterizations were then carried out in the range of 0.2–1.4 THz using THz time-domain spectroscopy. We observed that the samples fabricated by the SPS and post-annealing treatment exhibit a high permittivity associated with minimal loss ( 100 and 0.015). These characteristics make these samples optimal candidates for achieving a negative or near-zero effective index in all-dielectric metamaterials. In addition, four micro-structuring processes were investigated to produce ADM operating in the terahertz range from the ceramics: (i) micro-molding, (ii) direct etching by inductively coupled plasma, (iii) saw cutting and (iv) femtosecond laser etching
Study of charm mixing and CP violation with decays
No full textInternational audienceA study of charm mixing and CP violation in decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6. The ratio of promptly produced to decay rates is measured as a function of decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the mixing parameters and allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including and , which are nonzero in the presence of CP violation. It is found that , , and . These results are consistent with previous measurements and the hypothesis of \CP conservation