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Preconditioning donors with corticosteroids improves the early lung graft immunity: lung immunity upon donor preconditioning with corticosteroids
No full textInternational audienceBackground: Preclinical studies have recently revealed the critical role of innate immunity in determining lung transplantation outcomes. Although the International Society for Heart and Lung Transplantation recommends high-dose corticosteroid administration to donors, this practice is inconsistently applied worldwide. Investigating its impact on the donor lung’s innate immune response – an unexplored area - could provide valuable evidence to support adoption of donor preconditioning with corticosteroids, beyond their traditional administration to recipients.Method: We used a cross-circulatory pig platform that consists of a donor lung placed extracorporeally and connected to the circulation of a recipient pig whose leukocytes are fluorescently labeled. Results: Donor preconditioning - compared to recipient’s treatment alone - reduced the presence of CD3pos T-cell in the graft from both the donor and recipient, and enhanced the anti-inflammatory profile of alveolar macrophages, at least during the first 10 hours of donor-recipient interaction. The alveolar macrophages isolated from corticosteroid-preconditioned pig lungs exhibited decreased gene expression of T-cell attracting chemokines during the 10-hour reperfusion period, correlating with the reduced T-cell infiltration. Similarly, human lung macrophages showed lower expression of these T-cell-attracting chemokines and higher anti-inflammatory profiles upon corticosteroid treatment. Conclusion: Our results show that the early immune status of lung grafts is improved by treating donors with corticosteroids through macrophage-targeted mechanisms. This finding provides an immunological rationale for expanding the implementation of donor preconditioning with corticosteroids
Life in the frozen Ocean
No full textInternational audiencePresent seasonally or year-round in polar and subpolar seas, sea ice is one of the most complex and biologically rich ecosystems on Earth. Throughout the history of our planet, sea ice has periodically covered vast proportions of the world's oceans, and it may also serve as a plausible habitat on other ocean worlds. In this review, we provide a comprehensive overview of current knowledge on sea ice as a habitat, both on Earth and in extraterrestrial environments. We focus on bacteria, microalgae, and their associated viruses, describing the key physicochemical characteristics that shape this unique ecosystem. Additionally, we explore hypotheses on how microorganisms colonize sea ice, survive by protecting themselves and altering their environment, and ultimately proliferate and evolve. Finally, we consider the potential role of the sea-ice microbiome in the evolution of life on Earth and its possible existence beyond our planet
Descriptions de quelques structures lithiques archéologiques : marae de Bora Bora, îles de la Société
No full textWhat is the current state of the lithic complexes that are the marae of Bora Bora in comparison with the very brief description of some of them more than a century ago and what new knowledge can we provide? This is the purpose of this work on 5 marae studied with 3 objectives: 1. To describe with precision the lithic assemblage and specify the nature of the stones, standing or not, that constitute them - 2. To establish the origin of the coral stones that make up these structures and to try to determine the time of construction of these complexes – 3. To emphasize the risks that the marae along the coast run in the face of the projected rise in sea level, which made it urgent to describe them accurately before their destruction.Quel est l’état actuel des ensembles lithiques que sont les marae de Bora Bora en comparaison de la description très sommaire de quelques-uns d’entre eux il y a plus d’un siècle et quelles connaissances nouvelles pouvons-nous apporter. Tel est l’objet de ce travail sur 5 marae étudiés avec 3 objectifs : 1. Décrire avec précision les alignements lithiques et préciser la nature des pierres dressées ou non qui les constituent - 2. Etablir l’origine des pierres coralliennes constitutives de ces structures et tenter de déterminer l’époque de construction de ces ensembles – 3. Souligner les risques que les marae en bordure du littoral encourent face à l’élévation prévue du niveau de la mer qui rendait urgente leur description précise avant leur destruction
Advances in Radical Remote γ-Functionalization of α,β-Unsaturated Carbonyl Compounds
No full textInternational audienceAbstract α,β-Unsaturated carbonyl compounds are of significant biological and industrial importance, playing a key role in pharmaceutical chemistry, particularly in drug design. γ-Enolizable carbonyl compounds exhibit unique reactivity when undergoing functionalization at the remote γ-position. Despite notable advancements, γ-functionalization of these compounds still confronts considerable unresolved challenges. Radical chemistry has emerged as a powerful tool for constructing carbon–carbon and carbon–heteroatom bonds at the γ-position. In this review, we have summarized and categorized radical γ-functionalization methods developed over the past decades, focusing on substrates such as α,β-unsaturated amides, ketones, esters, and aldehydes
Modeling the Coupled and Decoupled states of Polar Boundary-Layer Mixed-Phase Clouds
No full textInternational audienceAbstract. Representing mixed-phase clouds (MPCs) is a long-standing challenge for climate models, with major consequences regarding the simulation of radiative fluxes at high-latitudes and uncertainties in future cryosphere melting estimates. Low-level boundary-layer MPCs that prevail at high-latitudes can be either coupled or decoupled to the surface, which modulates their dynamical and microphysical properties. This study leverages a recent physically-based parameterization of phase partitioning considering an explicit coupling between microphysics and subgrid-scale dynamics and involving direct interactions between the cloud and turbulent diffusion schemes. This parameterization makes it possible to capture the structure of the decoupled state of polar boundary-layer MPCs – with a supercooled liquid dominated cloud-top sitting on top of precipitating ice crystals – in single column simulations with the LMDZ Atmospheric General Circulation Model. The positive feedback loop involving cloud-top radiative cooling induced by supercooled liquid droplets, subsequent buoyancy production of turbulence as well as the supercooled liquid water production associated with turbulence, is captured by the model. However, the liquid and cloud ice water path remain slightly underestimated which may be due to an underestimation of the net upward water flux from low layers. The paper further shows that accounting for the detrainment of shallow convective plume's air when diagnosing the in-cloud supersaturation makes it possible to capture the overall vertical structure of surface-coupled clouds, with realistic liquid and ice water contents. A parameteric sensitivity analysis further shows the importance of properly calibrating the parameter controling the supercooled liquid water production term by subgrid turbulence
Zero-Shot Transportation Mode Classification in Île-de-France : Generalizing the PromptRide-LLM Pipeline
No full textInternational audienc
Increased rainfall in southern Central America under glacial climate conditions
No full textInternational audienceLate Pleistocene hydroclimate variability in Central America and its associated climate forcings are poorly constrained. The region is influenced by complex ocean-atmosphere-continent interactions, and documented palaeohydrological responses, which vary by site and/or proxy specificity, are far from conclusive. We used δD of n-alkanes from a marine sediment core in the Panama Basin to infer past changes in precipitation over the last 56 kyr. Our results indicate a progressive intensification of precipitation during the last glacial period, culminating in a precipitation maximum during the Last Glacial Maximum (LGM, 23-19 kyr BP), followed by a rapid decline during the Heinrich Event 1 (H1, 18-15 kyr BP) time interval. While the regional pattern of the precipitation anomaly during the LGM is proxy and site dependent, the regional drying during H1 shows a clear north-south signature associated with the southward meridional migration of the Intertropical Convergence Zone 1 (ITCZ). Using iTrace and PMIP4 model simulations, we show that the precipitation changes associated with the ITCZ shift are closely linked to the equatorial SST front induced by changes in the oceanic circulation. We propose that an increase in this latitudinal SST gradient could have locally pushed the ITCZ further north, bringing rainfall to southern Central America during the LGM
Diversification chimique des réservoirs atmosphériques en chimie prébiotique : incorporation d'oxygène et de soufre dans les aérosols photochimiques organiques
No full textLiving organisms are composed of a variety of chemical elements, including C, H, N, O, P, and S, which define their organic structure at the molecular level. However, the origin of this complex organic composition and the incorporation of the heteroelements N, O, P, and S remains a unexplained so far. To answer this question, it is essential to characterize primitive organic reservoirs in order to shed light on the transition from abiotic to biological organic matter.Among these primordial reservoirs, sources of organic matter, the atmosphere of the early Hadean Earth may have played a major role through photochemistry. Exploration of the solar system over the last few decades has helped to show that atmospheric chemistry could be a source of complex organic matter. The study of Titan and its dense atmosphere by the Cassini mission (2004-2017) revealed the existence of an advanced chemistry leading to the formation of organic aerosols (solid particles) from its main volatiles N2 and CH4. Cassini's observations, coupled with laboratory experiments reproducing Titan's atmospheric chemistry, have highlighted the molecular complexity of these aerosols and their high nitrogen content. Characterizing the structure of these aerosols has also provided constraints on their formation mechanisms, highlighting certain organic complexification reaction pathways that may have been active in the primitive atmosphere. Nevertheless, the photochemistry of the primitive atmosphere cannot be limited to Titan photochemistry. Although the composition of the primitive Hadean atmosphere is not constrained at present, it may have been significantly different from TitanThe primitive atmosphere may have contained a greater diversity of chemical elements, including carbon, hydrogen, nitrogen, oxygen, and sulfur. The latter two elements coudl have been produced in significant quantities into the atmosphere, mainly through volcanic activity and magmatic degassing, which are thought to have been particularly intense during the Hadean era.In this thesis, we sought to approach the results of this chemically diverse Hadean photochemistry by producing and characterizing organic aerosols incorporating all of these chemical elements (C, H, N, O, S). This approach aims to highlight new organic compounds and new reaction pathways to understand the chemistry of the origins.To produce these chemically diverse aerosols, we relied on a complex, well-characterized organic matrix rich in carbon, nitrogen, and hydrogen: Titan aerosol analogues, also known as tholins. We explored conditions favorable to the incorporation of oxygen and sulfur into this matrix. Characterization of the resulting organic aerosols revealed the formation of new oxidized and organosulfur compounds. Among this diversity of new chemical functionalities, we mainly identified thiocyanates (RSCN) and isothiocyanates (RNCS) for sulfur, and urea as well as carboxylic acid derivatives for oxygen. The formation mechanisms of these compounds are dominated by heterogeneous processes occurring on the surface of the grains.Le vivant se compose d'une diversité d'éléments chimiques, les C, H, N, O, P, S, qui définissent sa structure organique à l'échelle moléculaire. Néanmoins l'origine de cette composition organique complexe et de l'incorporation des hétéro-éléments N, O, P, S demeure à ce jour une véritable énigme. Pour y répondre, la caractérisation des réservoirs organiques primitifs est indispensable afin de mettre en lumière la transition de l'organique abiotique à l'organique biologique. Parmi ces réservoirs primordiaux, source de matière organique, l'atmosphère de la Terre primitive hadéenne a pu jouer un rôle prépondérant via la photochimie. L'exploration du système solaire au cours des dernières décennies a contribué à montrer que la chimie atmosphérique pouvait être une source de matière organique complexe. L'étude de Titan et de son atmosphère dense par la mission Cassini (2004-2017) a notamment révélé l'existence d'une chimie avancée conduisant, à partir de ses principaux volatiles N2 et CH4, à la formation d'aérosols (particules solides) organiques. Les observations de Cassini couplées aux expériences de laboratoire reproduisant la chimie atmosphérique de Titan ont mis en évidence la complexité moléculaire de ces aérosols ainsi que leur forte teneur en azote. La caractérisation de la structure de ces aérosols a également apporté des contraintes sur leurs mécanismes de formation, mettant en avant certaines voies réactionnelles de complexification organique potentiellement actives dans l'atmosphère primitive.Néanmoins la photochimie de l'atmosphère primitive ne peut se restreindre à celle de l'atmosphère de Titan. Si la composition de l'atmosphère primitive hadéenne n'est pas contrainte à ce jour, il est très vraisemblable que celle-ci ait significativement différé de celle de Titan.L'atmosphère primitive a notamment pu accueillir une plus grande diversité d'éléments chimiques à savoir le carbone, l'hydrogène, l'azote, mais aussi l'oxygène et le soufre. Ces deux derniers éléments ont pu être émis en quantité significative dans l'atmosphère principalement via l'activité volcanique et le dégazage magmatique supposés particulièrement intenses à l'hadéen.Dans cette thèse nous avons cherché à approcher le fruit de cette photochimie hadéenne chimiquement diversifiée en produisant et caractérisant des aérosols organiques intégrant l'ensemble de ces éléments chimiques C, H, N, O, S. Cette démarche vise à mettre en lumière de nouveaux composés organiques et de nouvelles voies réactionnelles pour comprendre la chimie des origines.Pour former ces aérosols chimiquement diversifiés, nous nous sommes appuyés sur une matrice organique complexe, bien caractérisée et riche en carbone, azote et hydrogène : les analogues d'aérosols de Titan, également appelés tholins. Nous avons exploré des conditions propices à l'incorporation d'oxygène et de soufre au sein de cette matrice. La caractérisation des aérosols organiques ainsi produits a révélé la formation de nouveaux composés organiques oxydés et organo-soufrés. Parmi cette diversité de nouvelles fonctions chimiques, on identifie principalement, pour le soufre, des thiocyanates (RSCN) et des isothiocyanates (RNCS), et pour l'oxygène, de l'urée ainsi que des dérivés d'acides carboxyliques. Les mécanismes de formation de ces composés sont dominés par des processus hétérogènes se déroulant à la surface des grains
Efflorescences phytoplanctoniques : hotspots pour l'absorption du CO<sub>2</sub> dans l'océan Austral
No full textThe Southern Ocean is a major sink of atmospheric CO2 but due to harsh access conditions, observations remain scarce. Estimates of the air-sea CO2 fluxes based on observations diverge from those using ocean models, with discrepancies growing increasingly pronounced over the past decade (Hauck et al., 2023, Mayot et al., 2023). My thesis focuses on the processes affecting air-sea CO₂ fluxes in the subpolar region of the Southern Ocean. During a research cruise in January 2022 as part of the European SO-CHIC (“Southern Ocean Carbon and Heat Impact on Climate”) project, a drifting CARIOCA (“Carbon Interface Ocean Atmosphere”) buoy was deployed north of the Weddell Sea (0°E, 54°S). This buoy acquired data for seventeen months, spanning several seasons, across the southern Atlantic and Indian Oceans. By combining this dataset with satellite observations, analysis and reanalysis products, and measurements taken from other in-situ platforms (gliders, floats, ships), I analyzed the processes impacting oceanic CO₂ fugacity (fCO₂). After its deployment, the CARIOCA buoy, drifting east of 0 °E, 54 °S, observed an anomalously low undersaturation of surface ocean fCO2 with respect to the atmosphere, in a surface fresh layer. Using Lagrangian backward trajectories, I determined that the waters sampled by the buoy in January-February 2022 came from the sea ice edge, where there was a phytoplankton bloom in November 2021, likely promoted by anomalously early sea ice retreat. An ocean analysis and satellite observations also indicate the migration of a freshwater mass from the sea ice edge in spring 2021 to the CARIOCA buoy's location, in the subpolar region, in summer 2022. A simple advective model accounting for strong fCO2 undersaturation in the vicinity of the sea ice edge, as measured under similar conditions by BGC-ARGO floats, and air-sea CO2 exchanges along the north-eastward migration of the water mass, suggests that the undersaturation observed by CARIOCA in the subpolar region results from the strong undersaturation at the ice edge. Therefore, my hypothesis is that fresher and stratified waters, possibly enriched in micronutrients such as iron from ice melt, migrated north-eastward, causing an anomalous carbon sink at more northern latitudes than usual. Extending this study across all ocean basins and years we observe an increase in chlorophyll-a, chl-a, concentrations north of the Marginal Ice Zone. I suggest the hypothesis that this might be due to the northward migration of fertilized, stratified waters, from ice melt. Increasing glacial melt from the Antarctic continent and subglacial melt from ice shelves, might also have contributed to this. In June 2022, the CARIOCA buoy measured high fCO2 variability related to temperature and salinity fluctuations. This variability is associated with the presence of mesoscale eddies, and I describe how these eddies may have impacted ocean fCO2 and dissolved inorganic carbon (DIC) fluctuations. A 15 µatm undersaturation of ocean fCO2 was observed in winter 2022: part of this undersaturation can be explained by a negative sea surface temperature anomaly. In spring 2022-summer 2023, while the CARIOCA buoy drifted south-east of Kerguelen and Crozet islands, it observed a smaller undersaturation of surface ocean fCO2 compared to the one observed in summer 2022, associated with moderate chl-a concentrations. By late autumn 2023, oceanic fCO2 values are back in equilibrium with the atmosphere.L'océan Sud, important puits de CO₂ atmosphérique, reste peu observé en raison de son inaccessibilité. Les estimations de flux air-mer de CO2 issues des observations divergent de celles des modèles, avec des écarts croissants au cours de la dernière décennie (Hauck et al., 2023, Mayot et al., 2023). Ma thèse porte sur les processus impactant les flux air-mer de CO2 dans la région subpolaire de l'océan Sud. Lors d'une campagne en mer réalisée en janvier 2022 dans le cadre du projet européen SO-CHIC (« Southern Ocean Carbon and Heat Impact on Climate »), une bouée dérivante CARIOCA (« Carbon Interface Ocean Atmosphere ») a été déployée au nord de la mer de Weddell (0 °E, 54 °S). Elle a acquis des mesures pendant dix-sept mois, s'étalant sur plusieurs saisons, dans les océans Atlantique et Indien sud. En combinant cet ensemble de mesures avec des observations satellitaires, des produits d'analyse et de réanalyse, et des mesures réalisées sur d'autres vecteurs in-situ (gliders, flotteurs, navires), j'ai analysé les processus influençant la fugacité du CO2 océanique, fCO2.Après son déploiement, la bouée CARIOCA, dérivant à l'est de 0 °E, 54 °S, a détecté une forte sous-saturation en fCO₂ dans une couche de surface à faible salinité. A l'aide de trajectoires lagrangiennes, j'ai montré que les eaux échantillonnées par la bouée en janvier-février 2022 provenaient du bord de glace, où une efflorescence phytoplanctonique a eu lieu en novembre 2021, probablement favorisée par un retrait anormalement précoce de la glace de mer. Une analyse océanique et des observations satellitaires indiquent également la migration à la surface de l'océan d'une masse d'eau dessalée, du bord de glace, au printemps 2021, vers la région subpolaire, au nord-est de la mer de Weddell, en été 2022. Un modèle advectif simple tenant compte d'une forte sous-saturation en fCO2 au voisinage de la glace, telle que mesurée dans des conditions similaires par des flotteurs BGC-ARGO, et des échanges air-mer de CO2 le long de la migration vers le nord-est de la masse d'eau, suggère que la sous-saturation observée par CARIOCA dans la région subpolaire résulte de la forte sous-saturation en bord de glace. Mon hypothèse est donc que des eaux dessalées et stratifiées, possiblement enrichies en micronutriments tels que le fer, issues de la fonte de la glace, ont migré vers le nord-est, provoquant un puits de carbone anormalement élevé à des latitudes plus au nord que d'habitude. En étendant cette étude à tous les bassins océaniques et sur plusieurs années, on observe une augmentation des concentrations de chlorophylle-a, chl-a, au nord de la zone marginale de glace. Je suggère l'hypothèse que ceci pourrait être dû à une migration vers le nord d'eaux fertilisées et stratifiées issues de la fonte des glaces. La fonte croissante de la calotte glaciaire Antarctique et des glaciers, pourraient aussi avoir contribué à cela. En juin 2022, la bouée CARIOCA a mesuré une forte variabilité de fCO2 en lien avec des variabilités de température et salinité. Cette variabilité est associée à la présence de tourbillons de méso échelle. Je documente comment ces tourbillons peuvent avoir eu un impact sur les fluctuations du fCO2 océanique et du carbone inorganique dissous (DIC). Une sous-saturation de 15 µatm du fCO2 océanique a été observée en hiver 2022 : une partie de cette sous-saturation peut s'expliquer par une anomalie négative de la température de surface de la mer. Au printemps 2022-été 2023, alors que la bouée CARIOCA dérivait au sud-est des îles Kerguelen et Crozet, elle a observé une sous-saturation du fCO2 de l'océan de surface moindre que celle observée en été 2022, associée à des concentrations modérées de chl-a. En fin d'automne 2023, les valeurs de fCO2 océanique sont de retour à l'équilibre avec l'atmosphère
Capturing dense shelf water cascading with a high-resolution ocean reanalysis
No full textInternational audienceAbstract. Dense shelf water cascading (DSWC) is an oceanographic process that occurs when dense shelf water overflows over the shelf edge downslope toward the deep sea. Monitored in the northwestern Mediterranean by moorings since 1993 in the Lacaze-Duthiers Canyon and since 2005 in the Cap de Creus Canyon, numerical modeling with reanalysis extends this timeline further into the past. This study investigates a regional reanalysis (1987–2021) validated against mooring observations at 750–1000 m depth. The reanalysis successfully reproduces observed intense DSWC (IDSWC) events from 1999, 2000, 2005, 2006, 2012, 2013, and 2018 while identifying one previously unreported event in 1987 and detecting no IDSWC between 1988 and 1998. The reanalysis effectively matches 84 % of observed IDSWC days within the same week and 56 % on the exact date. Instead of assimilating IDSWC events from mooring observations to resolve the cascading process, the model relies solely on the seawater density on the shelf and revealed the seawater properties along the canyon that caused IDSWC. This work highlights the importance of high-resolution reanalyses in investigating the impacts of mesoscale processes on larger scales in the deep ocean