Portail HAL du Collège de France
Not a member yet
22122 research outputs found
Sort by
Tibetan Plateau paleogeographic reconstructions during the India-Asia collision: from paleoelevation proxies to geodynamic models
No full textInternational audienceThe past topographic evolution of the Tibetan-Himalayan orogen holds the key to understanding interactions between Earth, Climate and Life processes since deep times. This has been hindered so far by the lack of accurate paleogeographic reconstructions of the orogen through time based on well-dated reliable proxies of past elevations. In the sedimentary archives of the basins formed in the orogen during the collision, recovered fossil content including pollen, fish and mammals yielded first order estimates on elevations based on environmental conditions of nearest living relatives while leaf physiognomies provided more direct constraints. Stable isotope composition from ancient meteoric waters preserved in pedogenic carbonates and biomarkers have been recovered and interpreted in terms of paleoelevations assuming past meteoric lapse rates. Outside of the basins in the high massifs, synkinematic hydrous silicates preserving ancient rainfalls have been used for paleoaltimetry purpose, notably in the Himalayas. Despite these significant efforts, the new paleoelevation datasets have led more to controversy than consensus. Fierce debates currently involve several international groups. Widely different topographic growth scenarios have been proposed with end-members ranging from a high Plateau prior to the onset of the India-Asia collision (“Proto-Tibetan Plateau”), to a much more recent - mostly Miocene - uplift and the preservation of broad low elevation valleys late until the Neogene.As part of the starting TIBETOP project (funded by the french ANR) we propose here a state-of-the-art review of paleoelevation proxies across the Tibetan-Himalayan orogen, ranging from surface records in sedimentary basins to deeper crustal rocks now exhumed in the relief and mountain belts bordering these basins. We present a compilation and reappraisal of the existing regional paleoelevation data including revised provenance, stratigraphy dating, and stable isotope data in basin records as well as structural context, exhumation and fluid-rock deformation interactions at different interfaces of the continental crust. The TIBETOP project thus aims to produce a set of interactive paleogeographic reconstructions through time with associated datasets constraining the Himalayan-Tibetan orogen since the India-Asia collision. These will be improved through the project to include new data and updated paleogeographic reconstructions made available to modelers of climatic, biotic and surface processes to enable testing the above cited fundamental hypotheses on the role of mountain and plateau building on Earth System processes over geologic time
Théories et pratiques du gouvernement impérial du début du VIIIe jusqu’au début du XIe siècle : Empire byzantin, monde islamique, Occident latin - Bibliographie
No full textInternational audienc
Quelques commentaires sur les tablettes d’utukkû lemnûtu retrouvées à Sultantepe
No full textInternational audienc
Review of Animals in the Ancient World: The Levett Bestiary, 2014 Mougins, Musée d’art classique by Cl. Dauphin and Les Animaux dans le Monde Antique: Le Bestiaire Levett, 2016, Mougins, Musée d’art classique by Cl. Dauphin
No full textInternational audienc
Occupational exposure to disinfectants and cleaning products, lung function and COPD
No full textInternational audienceAbstractOccupational exposure to Disinfectants and Cleaning Products (DCPs) is a known risk factor for asthma, but only a few studies investigated their impact on lung function and COPD.We studied associations between lifetime occupational exposure to DCPs, lung function, and COPD based on cross-sectional data from the French population-based CONSTANCES cohort.Analyses were carried on 123,535 participants (mean age: 47 years, 55% women) with data on lung function (z-score of FEV1, FVC, and FEV1/FVC) and job histories at inclusion. COPD was defined by airway obstruction (FEV1/FV
Repeated losses of self-fertility shaped heterozygosity and polyploidy in yeast evolution
No full textInternational audienceEvolutionary transitions in mating strategy have profound consequences for genetic variation and adaptation. In the baker’s yeast Saccharomyces cerevisiae, mating-type switching is a central feature of the life cycle that enables homothallism, i.e., mating between mitotic descendants of the same haploid cell. Yet, heterothallic isolates that have lost this ability are found across diverse niches, indicating that this trait is polymorphic. Here we experimentally characterized loss of mating-type switching in a representative panel of strains. Analysis of 117 telomere-to-telomere genome assemblies revealed multiple independent loss-of-function mutations in the Ho endonuclease gene and structural variants in the silent HML and HMR cassettes, the three loci essential for switching. We estimated that at least 13 independent transitions from homothallism to heterothallism have occurred in the species history. Analysis of the HO genotype of 2,915 strains show that at least 27% are heterothallic. We found that heterothallism is strongly associated with polyploidy and elevated genome-wide heterozygosity, although the strength of these associations varies between populations. Heterothallic isolates are most prevalent in domesticated and clinical clades, consistent with an origin linked to human-associated environments. However, they are also found, though less frequently, in natural niches. Signatures of recombination in HO sequences suggest that outcrossing contributed to the ecological and geographical distribution of the trait. Our findings reveal that mating-type switching has undergone repeated losses in S. cerevisiae evolution, with major consequences for genome architecture and ecological diversification
DeepCristae, a CNN for the restoration of mitochondria cristae in live microscopy images
No full textInternational audienceMitochondria play an essential role in the life cycle of eukaryotic cells. However, we still don't know how their ultrastructure, like the cristae of the inner membrane, dynamically evolves to regulate these fundamental functions, in response to external conditions or during interaction with other cell components. Although high-resolution fluorescent microscopy coupled with recently developed innovative probes can reveal this structural organization, their long-term, fast and live 3D imaging remains challenging. To address this problem, we have developed a convolutional neural network, called DeepCristae, to restore mitochondria cristae in low spatial resolution microscopy images. Our network is trained from 2D STED images using a novel loss specifically designed for cristae restoration. To efficiently increase the size of the training set, we also developed a random image patch sampling centered on mitochondrial areas. To evaluate DeepCristae, quantitative assessments were carried out using metrics we derived by focusing on the mitochondria and cristae pixels rather than on the whole image as usual. Depending on the conditions of use indicated, DeepCristae works well on broad microscopy modalities (Stimulated Emission Depletion (STED), Live-SR, AiryScan and Lattice Light Sheet Microscopy). It is ultimately applied in the context of mitochondrial network dynamics during interaction with endo/lysosome membranes
Incidence and duration of human papillomavirus infections in young women: insights from a bimonthly follow-up cohort
No full textInternational audienceBackground. We studied the duration of HPV detection and risk of (re-) detection for 25 HPV genotypes in a cohort of 132 women followed every eight weeks for up to two years between 2016 and 2020. Participants were between 18 and 25 years old at inclusion and half of them were vaccinated against HPV. They were recruited near the University and the STI detection centre in Montpellier, France.Methods. We used genotype-specific longitudinal data to characterise the dynamics of HPV-detected episodes. We investigated the contribution of viral and host factors to the variations in the duration of HPV detection, and the time before (re-)detection of the same genotype using multivariate Cox regression models with frailty at the patient level.Findings. We detected at least one HPV episode in 74% of the participants and re-detected the same genotype in 47% of them. Covariates related to socio-economic difficulties were associated with a lower risk of detectability loss (hazard ratio 0.45 with a 95% confidence interval, CI, from 0.21 to 0.97).The number of lifetime sexual partners was strongly associated with an increased risk of new positive detection (hazard ratio 2.40 with a 95%CI from 1.07 to 5.39). In contrast, vaccination was associated with a lower risk of displaying incident infections (hazard ratio of 0.64 with a 95%CI from 0.43 to 0.96).Conclusion.In the short term, vaccination shows clear signs of protection against new HPV detections, including for some genotypes not targeted by the vaccine, such as HPV31 and HPV51.</p
Detection of an orthogonal alignment between parsec scale AGN jets and their host galaxies
No full textInternational audienceThe relationship between galaxies and their supermassive black holes (SMBHs) is an area of active research. One way to investigate this is to compare parsec-scale jets formed by SMBHs with the projected shape of their kiloparsec-scale host galaxies. We analyse Very Long Baseline Interferometry (VLBI) images of Active Galactic Nuclei (AGN) and optical images of their host galaxies. We compare the inner-jet position angle in VLBI-detected radio sources with the optical shapes of galaxies as measured by several large optical surveys. In total 6273 galaxy-AGN pairs were found. We carefully account for the systematics of the cross-matched sources and find that Dark Energy Spectroscopic Instrument Legacy Imaging Surveys data (DESI LS) is significantly less affected by them. Using DESI LS, with which 5853 galaxy-AGN pairs were cross-matched, we find a weak but significant alignment signal (with a p-value 0.01) between the parsec-scale AGN jet and the kpc projected minor axis of the optical host galaxy in sources with measured spectroscopic redshifts. Our results show that the observed source properties are connected over 3 orders of magnitude in scale. This points towards an intimate connection between the SMBH, their host galaxies and their subsequent evolution