Concurrent formation of supermassive stars and globular clusters : implications for early self-enrichment

19 pages, 5 figures, accepted to MNRAS (shortened abstract and included feedback from the community)We present a model for the concurrent formation of globular clusters (GCs) and supermassive stars (SMSs, ≳10 3M ⊙) to address the origin of the HeCNONaMgAl abundance anomalies in GCs. GCs form in converging gas flows and accumulate low-angular momentum gas, which accretes on to protostars. This leads to an adiabatic contraction of the cluster and an increase of the stellar collision rate. A SMS can form via runaway collisions if the cluster reaches sufficiently high density before two-body relaxation halts the contraction. This condition is met if the number of stars ≳10 6 and the gas accretion rate ≳10 5M ⊙ Myr -1, reminiscent of GC formation in high gas-density environments, such as - but not restricted to - the early Universe. The strong SMS wind mixes with the inflowing pristine gas, such that the protostars accrete diluted hot-hydrogen burning yields of the SMS. Because of continuous rejuvenation, the amount of processed material liberated by the SMS can be an order of magnitude higher than its maximum mass. This 'conveyor-belt' production of hot-hydrogen burning products provides a solution to the mass budget problem that plagues other scenarios. Additionally, the liberated material is mildly enriched in helium and relatively rich in other hot-hydrogen burning products, in agreement with abundances of GCs today. Finally, we find a super-linear scaling between the amount of processed material and cluster mass, providing an explanation for the observed increase of the fraction of processed material with GC mass. We discuss open questions of this new GC enrichment scenario and propose observational tests.Peer reviewe

Dynamics of Bacterial Communities Mediating the Treatment of an As-Rich Acid Mine Drainage in a Field Pilot

Passive treatment based on iron biological oxidation is a promising strategy for Arsenic (As)-rich acid mine drainage (AMD) remediation. In the present study, we characterized by 16S rRNA metabarcoding the bacterial diversity in a field-pilot bioreactor treating extremely As-rich AMD in situ, over a 6 months monitoring period. Inside the bioreactor, the bacterial communities responsible for iron and arsenic removal formed a biofilm (“biogenic precipitate”) whose composition varied in time and space. These communities evolved from a structure at first similar to the one of the feed water used as an inoculum to a structure quite similar to the natural biofilm developing in situ in the AMD. Over the monitoring period, iron-oxidizing bacteria always largely dominated the biogenic precipitate, with distinct populations (Gallionella, Ferrovum, Leptospirillum, Acidithiobacillus, Ferritrophicum), whose relative proportions extensively varied among time and space. A spatial structuring was observed inside the trays (arranged in series) composing the bioreactor. This spatial dynamic could be linked to the variation of the physico-chemistry of the AMD water between the raw water entering and the treated water exiting the pilot. According to redundancy analysis (RDA), the following parameters exerted a control on the bacterial communities potentially involved in the water treatment process: dissolved oxygen, temperature, pH, dissolved sulfates, arsenic and Fe(II) concentrations and redox potential. Appreciable arsenite oxidation occurring in the bioreactor could be linked to the stable presence of two distinct monophylogenetic groups of Thiomonas related bacteria. The ubiquity and the physiological diversity of the bacteria identified, as well as the presence of bacteria of biotechnological relevance, suggested that this treatment system could be applied to the treatment of other AMD

Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Mieux saisir la résilience chez les enseignants : étude longitudinale d’un processus non linéaire

La profession enseignante comporte un fort risque d’épuisement. Parce que le fait d’être très résilient s’accompagne d’un meilleur bien-être en faire la promotion dans ce corps de métier devient alléchant. Bien que le concept populaire ait fait naître nombre d’études, la majorité d’entre elles cible l’enfant ou l’adolescent. Très peu d’informations sont disponibles via des études longitudinales, et encore moins au niveau des adultes. Le processus de résilience s’avère donc difficile à décrire bien que le fait de surmonter l’adversité à des situations et des moments précis ne garantit pas du succès dans le futur.La résilience possède un caractère fluctuant. Notre étude longitudinale cible cent cinquante enseignants québécois du primaire et du secondaire et s’attarde au processus dans le temps. Des analyses préliminaires via MANOVA montrent que les plus résilients sont aussi ceux qui sont le plus en bienêtre, aux deux temps de mesure. Par contre, alors que les moins résilients ont des niveaux de résilience et de bien-être supérieurs à la deuxième mesure, les plus résilients au temps un voient leur niveaux diminués aussi bien pour la résilience que pour le bien-être. D’autres variables médiatrices, organisationnelles et personnelles, peuvent intervenir. Le soutien et les contraintes entourant la profession peuvent influencer les capacités personnelles de résilience. Les enseignants les plus résilients sont tout autant à risque de brisure de résilience

Etude du devenir d'adultes ayant présenté une maladie coeliaque durant l'enfance

CLERMONT FD-BCIU-Santé (631132104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Mise en place d'un protocole de cytométrie en flux dans le service d'hématologie et de biologie vasculaire du CHU Conception pour l'identification des plasmocytes myélomateux

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF

L’espace temporairement apprivoisé

Central Asia combines two geocultural domains, steppes and oases, emphasizing two lifestyles. Our multidisciplinary researches, based on international cooperation, intend to explore major historical topics on a broad chronological and geographical scale, including the study of the evolution of fragile ecosystems. The study of two desert areas (Kyzyl-Kum in Uzbekistan, Taklamakan in Xinjiang, China) exemplify our approach: to test in Xinjiang the hypothesis of the existence of ancient agricultural settlements, and to examine in Uzbekistan the hunter-gathererfisher societies on the way to neolithisation, to understand their variety and evolution in nowadays totally dry deltas, and to clarify settlement patterns over the long term (from Neolithic to Antiquity). Archaeological sites discovered by our fieldwork give some clues about cultural patterns, subsistence practices, irrigation systems, and social organization from nomadic to sedentary systems. Our results tend to reconstruct modalities of the interactions between man and the environment in an unstable context, and to illuminate constants and variables of change in local, regional, and “international” scales