Assimilation des observations satellitaires au-dessus des surfaces continentales

Dans les modèles de prévision numérique du temps, les observations satellitaires sont devenues indispensables pour la production d'une analyse atmosphérique optimale. Or, malgré les performances et la maturité des systèmes d'assimilation actuels, ces observations demeurent fortement sous-exploitées au-dessus des surfaces continentales pour différentes raisons. L'objectif de cette étude est d'améliorer la représentation de la surface (en température et émissivité) afin de mieux assimiler les observations de télédétection dans les modèles. Dans un premier temps, nous avons cherché à vérifier la validité des hypothèses de surface pour le calcul de l'émissivité micro-onde au dessus d'une surface enneigée (région de l'Antarctique). L'effet de plusieurs hypothèses de surface sur les émissivités micro-ondes a été étudié et la qualité des simulations de températures de brillance a été sensiblement améliorée par la prise en compte d'une hypothèse pertinente. Par la suite l'objectif était d'étendre l'assimilation des données infrarouges sensibles aux surfaces continentales qui étaient jusque là rejetées des systèmes d'assimilation. Les recherches récemment effectuées pour l'assimilation des données micro-ondes au-dessus des continents, ont montré qu'un tel objectif est atteignable si la surface est mieux caractérisée. J'ai consacré une bonne partie de ma thèse a évaluer le potentiel d'une estimation de l'émissivité et de la température de surface à partir des données du radiomètre SEVIRI (Spinning Enhanced Visible and Infrared Imager) embarqué sur MSG (METEOSAT SECONDE GENERATION). La forte sensibilité aux nuages et les biais assez marqués de la température de surface analysée dans ALADIN m'ont poussée à préférer l'utilisation de climatologies d'émissivités IR du Land-SAF (EUMET-SAT Land Surface Analysis - Satellite Application Facilities) plutôt que d'estimer directement ces valeurs à partir des observations. J'ai montré qu'en me basant sur cette climatologie, on pouvait restituer des températures de surface à partir du canal IR10.8 de même qualité que celles du Land-SAF et que l'utilisation de cette température de surface comme condition aux limites au modèle de transfert radiatif permet d'obtenir de bien meilleures simulations aux canaux SEVIRI. Enfin, des expériences d'assimilation, au sein de deux modèles à aire limitée, ont été conduites afin d'apprécier, pour la première fois, l'impact de l'assimilation des observations IR sensibles à la surface sur la qualité des analyses et des prévisions. L'impact prépondérant fut observé sur les analyses d'humidité avec une tendance à assécher l'atmosphère en période estivale et à l'humidifier en période hivernale. Ce changement d'humidité a été évalué avec succès près de la surface à l'aide de données GPS indépendantes. L'impact sur les prévisions et sur celles des précipitations en particulier, a été jugé positif principalement sur le sud de l'Europe.In numerical weather prediction models, satellite observations are essential to perform optimal atmospheric analyses. Despite the performance and maturity of current assimilation systems, for different reasons these observations remain highly underutilized over land surfaces. This study aims to improve the description of the surface (temperature and emissivity) to better assimilate remote sensing observations in models. Initially, the validity of surface approximations used to calculate the microwave emissivity over snow surface was evaluated (over the Antarctica region). The impact of several surface approximations for microwave emissivity computation was studied and it was found that the quality of brightness temperature simulations was improved using relevant approximations. Thereafter, the objective was to extend the assimilation of infrared surface-sensitive observations over land which were until now rejected by the assimilation system. Recent researches to assimilate microwave observations over land have shown that this objective can be reached with an adequatly described surface. A large part of my PhD was devoted to the evaluate the potential to retrieve land surface emissivity and land surface temperature from data provided by the SEVIRI radiometer (Spinning Enhanced Visible and Infrared Imager) onboard METEO-SAT SECOND GENERATION. The strong sensitivity to clouds and the large bias found in the land surface temperature computed by the ALADIN meso-scale model encouraged me to use infrared emissivity climatology from the Land-SAF (EUMETSAT Land Surface Analysis - Satellite Application Facilities) rather than direct retrieval from SEVIRI observations. I have shown that, with these climatologies, the land surface temperature could be retrieved at channel IR10.8 with the same quality as the one from the Land-SAF. The use of this temperature as boundary conditions of the radiative transfer model improve the brightness temperature simulations at SEVIRI channels. For the first time, assimilation experiments were conduced within the two limited area models to assess the impact of the assimilation of surface-sensitive infrared observations over the analysis and forecast skills. The predominant impact was observed on the analysis of the moisture with a tendency to dry out the atmosphere in summer and increase moisture in winter. The change in moisture was successfully evaluated near the surface, using independent GPS data. The impact on forecasts, in particular the cumulative precipitation forecasts, was considered to be positive mainly over southern Europe

Grey matter density changes of structures involved in Posttraumatic Stress Disorder (PTSD) after recovery following Eye Movement Desensitization and Reprocessing (EMDR) therapy

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Impact of Antibiotic Gut Exposure on the Temporal Changes in Microbiome Diversity: Impact of moxifloxacin on gut microbiome

International audienceAlthough the global deleterious impact of antibiotics on the intestinal microbiota is well known, temporal changes in microbial diversity during and after an antibiotic treatment are still poorly characterized. We used plasma and fecal samples collected frequently during treatment and up to one month after from 22 healthy volunteers assigned to a 5-day treatment by moxifloxacin (n = 14) or no intervention (n = 8). Moxifloxacin concentrations were measured in both plasma and feces, and bacterial diversity was determined in feces by 16S rRNA gene profiling and quantified using the Shannon index and number of operational taxonomic units (OTUs). Nonlinear mixed effect models were used to relate drug pharmacokinetics and bacterial diversity over time. Moxifloxacin reduced bacterial diversity in a concentration-dependent manner, with a median maximal loss of 27.5% of the Shannon index (minimum [min], 17.5; maximum [max], 27.7) and 47.4% of the number of OTUs (min, 30.4; max, 48.3). As a consequence of both the long fecal half-life of moxifloxacin and the susceptibility of the gut microbiota to moxifloxacin, bacterial diversity indices did not return to their pretreatment levels until days 16 and 21, respectively. Finally, the model characterized the effect of moxifloxacin on bacterial diversity biomarkers and provides a novel framework for analyzing antibiotic effects on the intestinal microbiome

Impact of Antibiotic Gut Exposure on the Temporal Changes in Microbiome Diversity: Impact of moxifloxacin on gut microbiome

International audienceAlthough the global deleterious impact of antibiotics on the intestinal microbiota is well known, temporal changes in microbial diversity during and after an antibiotic treatment are still poorly characterized. We used plasma and fecal samples collected frequently during treatment and up to one month after from 22 healthy volunteers assigned to a 5-day treatment by moxifloxacin (n = 14) or no intervention (n = 8). Moxifloxacin concentrations were measured in both plasma and feces, and bacterial diversity was determined in feces by 16S rRNA gene profiling and quantified using the Shannon index and number of operational taxonomic units (OTUs). Nonlinear mixed effect models were used to relate drug pharmacokinetics and bacterial diversity over time. Moxifloxacin reduced bacterial diversity in a concentration-dependent manner, with a median maximal loss of 27.5% of the Shannon index (minimum [min], 17.5; maximum [max], 27.7) and 47.4% of the number of OTUs (min, 30.4; max, 48.3). As a consequence of both the long fecal half-life of moxifloxacin and the susceptibility of the gut microbiota to moxifloxacin, bacterial diversity indices did not return to their pretreatment levels until days 16 and 21, respectively. Finally, the model characterized the effect of moxifloxacin on bacterial diversity biomarkers and provides a novel framework for analyzing antibiotic effects on the intestinal microbiome

Bilateral Alternating Auditory Stimulations Facilitate Fear Extinction and Retrieval

International audienceDisruption of fear conditioning, its extinction and its retrieval are at the core of posttraumatic stress disorder (PTSD). Such deficits, especially fear extinction delay, disappear after alternating bilateral stimulations (BLS) during eye movement desensitization and reprocessing (EMDR) therapy. An animal model of fear recovery, based on auditory cued fear conditioning and extinction learning, recently showed that BLS facilitate fear extinction and fear extinction retrieval. Our goal was to determine if these previous results found in animals can be reproduced in humans. Twenty-two healthy participants took part in a classical fear conditioning, extinction, and extinction recall paradigm. Behavioral responses (fear expectations) as well as psychophysiological measures (skin conductance responses, SCRs) were recorded. The results showed a significant fear expectation decrease during fear extinction with BLS. Additionally, SCR for fear extinction retrieval were significantly lower with BLS. Our results demonstrate the importance of BLS to reduce negative emotions, and provide a successful model to further explore the neural mechanisms underlying the sole BLS effect in the EMDR

Cinétique intra-hôte des variants du SARS-CoV2

International audienceSince early 2021, SARS-CoV-2 variants of concern (VOCs) have been causing epidemic rebounds in many countries. Their properties are well characterised at the epidemiological level but the potential underlying within-host determinants remain poorly understood. We analyse a longitudinal cohort of 6,944 individuals with 14,304 cycle threshold (Ct) values of RT-qPCR VOC screening tests performed in the general population and hospitals in France between February 6 and August 21, 2021. To convert Ct values into numbers of virus copies, we performed an additional analysis using droplet digital PCR (ddPCR). We find that the number of viral genome copies reaches a higher peak value and has a slower decay rate in infections caused by Alpha variant compared to that caused by historical lineages. Following the evidence that viral genome copies in upper respiratory tract swabs are informative on contagiousness, we show that the kinetics of the Alpha variant translate into significantly higher transmission potentials, especially in older populations. Finally, comparing infections caused by the Alpha and Delta variants, we find no significant difference in the peak viral copy number. These results highlight that some of the differences between variants may be detected in virus load variations.Depuis le début de l'année 2021, les variants préoccupants du SRAS-CoV-2 (VOC) provoquent des rebonds épidémiques dans de nombreux pays. Leurs propriétés sont bien caractérisées au niveau épidémiologique, mais les déterminants potentiels au niveau intra-hôte restent mal compris. Nous analysons une cohorte longitudinale de 6 944 individus avec 14 304 valeurs de cycle threshold (Ct) de tests de dépistage des COV par RT-qPCR réalisés dans la population générale et les hôpitaux en France entre le 6 février et le 21 août 2021. Pour convertir les valeurs Ct en nombre de copies virales, nous avons effectué une analyse supplémentaire en utilisant la PCR digitale. Nous constatons que le nombre de copies du génome viral atteint un pic plus élevé et présente un taux de décroissance plus lent dans les infections causées par le variant Alpha par rapport à celles causées par les lignées historiques. En se basant sur certaines observations montrant que le nombre copies virales dans les écouvillons des voies respiratoires supérieures sont informatives sur la contagiosité, nous montrons que la cinétique du variant Alpha se traduit par des potentiels de transmission significativement plus élevés, en particulier dans les populations plus âgées. Enfin, en comparant les infections causées par les variants Alpha et Delta, nous ne trouvons pas de différence significative dans le nombre maximal de copies virales. Ces résultats soulignent que certaines des différences entre les variants peuvent être détectées dans les variations de la charge virale

Early control of viral load by favipiravir promotes survival to Ebola virus challenge and prevents cytokine storm in non-human primates

Acknowledgments: Experiments were carried out in the Jean Merieux–Inserm BSL4 Laboratory. We would like to thank the members of the in vivo team, S. Barron, L. Barrot, A. Duthey, F. Jacquot, M. Langry, and A. Vallve, for conducting the animal experiments. We are also grateful to A. Bocquin, S. Godard, S. Mely, E. Moissonnier, S. Mundweiler, D. Pannetier, and D. Thomas from the in vitro team, who helped to prepare the samples during the experiments and performed virus titrations. We finally thank Jean Armengaud from the Commissariat à l’Energie Atomique (CEA) for performing the mass spectrometry experiments.International audienceEbola virus has been responsible for two major epidemics over the last several years and there has been a strong effort to find potential treatments that can improve the disease outcome. Antiviral favipiravir was thus tested on non-human primates infected with Ebola virus. Half of the treated animals survived the Ebola virus challenge, whereas the infection was fully lethal for the untreated ones. Moreover, the treated animals that did not survive died later than the controls. We evaluated the hematological, virological, biochemical, and immunological parameters of the animals and performed proteomic analysis at various timepoints of the disease. The viral load strongly correlated with dysregulation of the biological functions involved in pathogenesis, notably the inflammatory response, hemostatic functions, and response to stress. Thus, the management of viral replication in Ebola virus disease is of crucial importance in preventing the immunopathogenic disorders and septic-like shock syndrome generally observed in Ebola virus-infected patients

Chapitre 2. Remobiliser le corps à l’école : regards croisés

International audienceL’école est immobilité, cours d’éducation physique ou pas. La sédentarité juvénile croît et les projets pour « faire bouger » les élèves achoppent. Conjuguer mouvement humain et apprentissage serait-il impossible ? Pour diffuser des pistes de solutions, le Réseau des écoles publiques alternatives du Québec (RÉPAQ), associé à des écoles européennes « différentes » (Viaud, 2005) et à des chercheurs du Québec et de France a lancé un « Festival Bouger » vidéo. En trois minutes, des écoles partagent leurs astuces populaires pour faire apprendre et bouger les jeunes. Ces pratiques ingénieuses pourraient inspirer d’autres écoles vers une sortie de leur quasi-immobilité physique. Des chercheurs d’horizons différents ont analysé ces vidéos publiques. Dans une démarche inductive et qualitative, ils posent des repères théoriques et critiques pour mieux lire ces pratiques. Quatre perspectives de recherches émergent : apprentissage par le vécu moteur, éducation relative à l’environnement, apprentissage par corps grâce au mouvement dansé, pédagogie

An Open-Label, Analgesic Efficacy and Safety of Pituitary Radiosurgery for Patients With Opioid-Refractory Pain: Study Protocol for a Randomized Controlled Trial

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