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Capturing ultrafast molecular motions and lattice dynamics in spin crossover film using femtosecond diffraction methods
No full textInternational audienceA comprehensive insight into ultrafast dynamics of photo-switchable materials is desired for efficient control of material properties through light excitation. Here, we study a polycrystalline spin crossover thin film as a prototypical example and reveal the sequential photo-switching dynamics, from local molecular rearrangement to global lattice deformation. On the earliest femtosecond timescale, the local molecular structural rearrangement occurs within a constant unit-cell volume through a two-step process, involving initial Fe−ligand bond elongation followed by ligand rotation. The highly-oriented structure of the nanocrystalline films and the experimental geometry enables resolving the full anisotropic lattice structural dynamics in and out of the sample plane separately. While both molecular switching and lattice heating influence lattice volume, they exert varying degrees of impact at disparate time scales following photoexcitation. This study highlights the opportunities provided by Mega-electron-volt electron and X-ray free electron laser to advance the understanding of ultrafast dynamics of photo-switchable materials
What a peaty contribution to global warming! An interdisciplinary study of atmospheric and hydrologic carbon fluxes in a temperate peatland in the Jura Mountains, eastern France
No full textInternational audiencePeatlands, though covering only 3 % of the global land surface, play an active role in the Critical Zone (CZ) by mediating substantial water and carbon exchanges with adjacent aquifers, surface waters, and the atmosphere. These ecosystems provide key services, such as carbon and water storage and local climate regulation, addressing contemporary challenges related to climate change, biodiversity loss, and water resource management. However, peatlands are increasingly threatened by global pressures, including climate change, and local disturbances, such as drainage for agriculture, forestry, and peat extraction. To mitigate these threats, it is essential to understand the hydrological, biogeochemical, and ecological processes governing peatland dynamics across spatiotemporal scales. To explore the factors controlling greenhouse gases sources, production, and transport in peatlands, an interdisciplinary field campaign was conducted at the Frasne peatland (7 ha, 46.826°N, 6.1754°E, 840 m a.s.l.), a long-term observatory since 2008. The site is part of the French CZ research infrastructure (OZCAR) and the long term ecological research site Jurassian Arc, which focuses on the interaction between human and nature. The campaign was supported by the TERRA FORMA project, which develops smart, connected, low-cost, and low-impact environmental sensors to monitor CZ trajectories in the Anthropocene. The fieldwork integrated microbiological analyses of peat material, including membrane lipid profiling to trace microbial metabolisms, combined with detailed hydrogeochemical investigations of peat pore water along lateral flow and depth gradients. Measurements included physicochemical parameters (temperature, electrical conductivity, pH) and major elements, dissolved organic and inorganic carbon (DOC and DIC), CO₂, and CH₄ concentration, as well as their isotopic characterization (δ¹⁸O, δ²H, δ¹³C) . Additionally, greenhouse gases fluxes were quantified at multiple scales, employing methods such as dissolved gas profiling, chamber measurements, eddy covariance, and UAV-based surveys. This multiscale approach aims to tackle critical challenges in peatland research and management, including three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues. three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues
Deciphering the molecular mechanisms of oyster resistance to Pacific Oyster Mortality Syndrome (POMS) disease induced by high temperatures
No full textInternational audienceClimate change and rising temperatures are frequently cited as key factors in the emergence of diseases. While the increase in temperature can alter host immunity, influence pathogen virulence, and change the geographic distribution of vectors and their associated pathogens, few studies have investigated the impact of temperature variations on the molecular mechanisms controlling disease permissiveness. The present study addresses this question on a panzootic and polymicrobial disease, the Pacific Oyster Mortality Syndrome (POMS). POMS, initiated by the herpesvirus OsHV-1 μVar, affects juveniles of Magallana gigas, which is the most widely cultured oyster species in the world. In our study, two full-sib families were exposed to the disease under permissive (23 °C) and non-permissive (30 °C) conditions. Using an integrative multi-omics approach, we demonstrate that high temperature has a dual effect on oysters (1) inducing a metabolic reprogramming, creating a sub-optimal metabolic environment for viral infection and thereby limiting POMS development, and (2) enhancing the host's antiviral immune capabilities, both at a baseline level and in response to infection. Overall, these responses triggered at elevated temperature improve oyster survival against POMS. Our study showed that temperature exerts complex effects on host-pathogen interactions; and molecular-level mechanistic approaches are crucial to thoroughly understand and accurately assess how temperature changes can influence epidemiological risk
Pour une approche comparée des systèmes symboliques de communication visuelle : le quipu et l'opèlè
No full textCet article propose une approche comparée des systèmes symboliques de communication visuelle (SSCV) à travers l’étude du quipu inca et de l’opèlè yoruba. En s’appuyant sur une réévaluation critique des définitions classiques de l’écriture (Gelb, Goody, Derrida), il s’agit de distinguer les SSCV des formes scripturales proprement dites. Contrairement à l’écriture, qui permet à un sujet d’exprimer directement son intériorité et son rapport au monde par des marques visibles, les SSCV opèrent selon une logique a-discursive où la visualité, la matière et le geste structurent la signification sans médiation linguistique. L’analyse conjointe du quipu et de l’opèlè met en lumière la complexité cognitive et sémiotique de dispositifs oraux-matériels qui, tout en échappant à la graphie, produisent des effets de mémoire, d’interprétation et de transmission. Ces systèmes invitent à repenser les frontières conceptuelles de l’écriture, de la parole et du visible dans une perspective anthropologique élargieCet article propose une approche comparée des systèmes symboliques de communication visuelle (SSCV) à travers l'étude du quipu inca et de l'opèlè yoruba. En s'appuyant sur une réévaluation critique des définitions classiques de l'écriture (Gelb, Goody, Derrida), il s'agit de distinguer les SSCV des formes scripturales proprement dites. Contrairement à l'écriture, qui permet à un sujet d'exprimer directement son intériorité et son rapport au monde par des marques visibles, les SSCV opèrent selon une logique adiscursive où la visualité, la matière et le geste structurent la signification sans médiation linguistique. L'analyse conjointe du quipu et de l'opèlè met en lumière la complexité cognitive et sémiotique de dispositifs oraux-matériels qui, tout en échappant à la graphie, produisent des effets de mémoire, d'interprétation et de transmission. Ces systèmes invitent à repenser les frontières conceptuelles de l'écriture, de la parole et du visible dans une perspective anthropologique élargie.</div
Petrographic insights into phosphate formation in L and LL ordinary chondrites
No full textInternational audienceThe origin and formation mechanisms of phosphate minerals in L and LL ordinary chondrites remain an open question. Here we report detailed quantitative data on the abundances, grain sizes and compositions of apatite and merrillite in L, LL and L/LL chondrites, covering a total analysed area of ~2730 mm 2 . Our results show that the abundances of phosphate minerals are slightly higher in L than in LL chondrites and reveal distinct petrographic differences between merrillite and apatite. Merrillite abundance is anti-correlated with Fe, Ni metal content and increases with petrologic type, as does grain sizeindicating grain coarsening processessupporting the formation of this mineral during thermal metamorphism. In contrast, apatite shows no clear trend in abundance or grain size with petrologic type. Although chlorine contents are similar between apatites from L and LL chondrites, the small dispersion of Cl concentration and its decrease with petrologic type in LL chondrites indicate that apatites in these chondrites undergo equilibration with increasing thermal metamorphism, a pattern not observed in L chondrites. Although the Cl contents in apatites are fairly homogeneous across the samples, scarce F-rich apatites have been observed in some meteorites, leading to significant variability in Cl#. However, due to low concentrations and analytical challenges, we argue that comparisons between different OC groups should primarily be based on Cl concentrations. Furthermore, apatite and merrillite have different grain size distributions in L chondrites, but similar ones in LL chondrites, where they also occur as close assemblages, suggesting a petrogenetic relationship between apatite and merrillite in LL chondrites, but not in L chondrites. Overall, the present study suggests that phosphates did not have exactly the same history in L and LL chondrites
Earth's Energy Imbalance More Than Doubled in Recent Decades
No full textInternational audienceAbstract Global warming results from anthropogenic greenhouse gas emissions which upset the delicate balance between the incoming sunlight, and the reflected and emitted radiation from Earth. The imbalance leads to energy accumulation in the atmosphere, oceans and land, and melting of the cryosphere, resulting in increasing temperatures, rising sea levels, and more extreme weather around the globe. Despite the fundamental role of the energy imbalance in regulating the climate system, as known to humanity for more than two centuries, our capacity to observe it is rapidly deteriorating as satellites are being decommissioned
A cocktail of two chelators is not better than one ligand in excess to halt the Cu,Zn-(amyloid-β)induced ROS production in the context of Alzheimer's disease
No full textInternational audienceIn this study, we demonstrate that an excess of the non-selective chelator EDTA can effectively extract both copper(II) and zinc(II) from the amyloid-β (Aβ) peptide and halt Cu(Aβ)-catalyzed ROS production in the context of Alzheimer's disease. These findings raise questions about the relevance of a recently reported "cocktail" approach employing two different chelators that target Cu and Zn, respectively
Annotation sémantique de données de télédétection. Description des changements de végétation dans les alpages à partir de séries temporelles Sentinel-2.
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Cloudiness retrieved from All-Sky camera and MSG satellite over Reunion Island and Antananarivo Madagascar
No full textInternational audienceTo gain a deeper understanding of cloud variability over the Southwest Indian Ocean (SWIO) region, various measurement techniques can be used. Cloud data focused on two main sites (Antananarivo, Madagascar, and Reunion Island) were collected over nearly three years (September 2019 to June 2022) using ground-based all-sky camera and Meteosat Second Generation (MSG) satellite imagery. This study primarily examined cloud fraction, although additional analysis based on cloud types is also needed. Two image processing algorithms were used to estimate cloud fraction by analyzing the camera images: one provided by the manufacturer Reuniwatt, and the other, Elifan, initially developed by CNRS. Their performance was compared to assess their relative strengths. Additionally, comparisons with MSG satellite data were carried out to ensure consistency and evaluate the complementarity of ground-based and satellite observations. Despite differences in methodology, the various data sources showed strong agreement. The results indicate that in Antananarivo, during the dry season, a high morning cloud fraction ( ∼ 50 %) is typically observed, which gradually decreases throughout the day. In the wet season (December to April), cloud fraction varies between approximately 30 % and 60 %, with reduced cloudiness observed around midday in October and November. In contrast, in Saint-Denis, Reunion, skies are generally clear in the morning but become increasingly cloudy as the day progresses, reaching up to 80 % cloud fraction during the wet season and around 60 % during the dry season
Les collections de sols exposées dans les musées du Monde
No full textInternational audienceLe sol est au centre de grands enjeux mondiaux ce qui a entraîné la naissance du concept de « sécurité des sols ». La dimension sociale des sols de ce concept est décrite par la connexion des sols (dimension sociale des sols). Dans ce cadre, la connaissance des sols doit être partagée par le plus grand nombre. Les musées sur les sols jouent un rôle important dans ce porter à connaissance car ils s'adressent à un très large public. Ils ciblent en particulier les plus jeunes à travers des animations en lien avec le système éducatif. Ils proposent des visites ludiques et dynamiques en abordant tous les domaines de la science du sol et sa connexion à l'environnement (eau, paysage, alimentation…). Ils offrent une belle vision des sols à travers des expositions de monolithes de sol qui permettent au visiteur de découvrir les sols et de pouvoir aborder leur diversité. La réalisation de l'inventaire des musées sur les sols dans le Monde a abouti à la création à un réseau mondial des musées du sol