226280 research outputs found
Sort by
A statistical approach to unveil phytoplankton adaptation to ocean fronts
No full textFine-scale oceanic fronts are ubiquitous and ephemeral physical features that separate contrasting water masses, creating significant heterogeneity in the physical seascape and plankton distributions. Because phytoplankton community composition (PCC) is a key driver of marine ecosystem functioning, understanding the extent to which fine-scale fronts influence PCC remains a critical challenge. However, studying PCC across and within fronts is particularly difficult due to data scarcity and high biophysical variability. We developed a tailored statistical model to characterize PCC within oceanic fronts in the Mediterranean Sea. We modeled the frontal community as a finite mixture model with three components: two communities of adjacent water masses and a potential front-adapted community. Each component was further considered as a discrete mixture of an unknown number of multivariate Gaussian sub-components. First, we used an Expectation-Maximization algorithm to estimate the Gaussian parameters and determine the optimal number of sub-components based on in situ datasets of the PCC within a frontal zone and its adjacent water masses. Second, a hierarchical Bayesian approach was applied to estimate the weight of all components within the frontal dataset. Our results show that within the front a new community component, distinct from those in adjacent water masses, accounts for 70% of the frontal community, indicating that a specific phytoplankton community can emerge in fine-scale oceanic fronts. Despite the limited number of frontal observations, our Bayesian modelling approach provides statistical evidence of the front's influence on phytoplankton community composition, effectively overcoming data scarcity and high variability
The H.E.S.S. extragalactic sky survey with the first decade of observations
No full textInternational audienceThe results of the first extragalactic gamma-ray survey by the High Energy Stereoscopic System (H.E.S.S.) are presented. The survey comprises 2720 hours of very high-energy gamma-ray observations of the extragalactic sky, recorded with H.E.S.S. from 2004 up to the end of 2012. These data have been re-analysed using a common consistent set of up-to-date data calibration and analysis tools. From this analysis, a list of 23 detected objects, predominantly blazars, was obtained. This catalogue was assessed in terms of the source class populations that it contains. The level of source parameter bias for the blazar sources, probed by this observational dataset, was evaluated using Monte-Carlo simulations. Spectral results obtained with the H.E.S.S. data were compared with the Fermi-LAT catalogues to present the full gamma-ray picture of the detected objects. Lastly, this unique dataset was used to assess the contribution of BL Lacertae objects and flat-spectrum radio quasars to the extragalactic gamma-ray background light at several hundreds of gigaelectronvolts. These results are accompanied by the release of the high-level data to the astrophysical community
Inferring astrophysics and cosmology with individual compact binary coalescences and their gravitational-wave stochastic background
No full textInternational audienceGravitational waves (GWs) from compact binary coalescences (CBCs) provide a new avenue to probe the cosmic expansion, in particular the Hubble constant . The spectral sirens method is one of the most used techniques for GW cosmology. It consists of obtaining cosmological information from the GW luminosity distance, directly inferred from data, and the redshift that can be implicitly obtained from the source frame mass distribution of the CBC population. With GW detectors, populations of CBCs can be either observed as resolved individual sources or implicitly as a stochastic gravitational-wave background (SGWB) from the unresolved ones. In this manuscript, we study how resolved and unresolved sources of CBCs can be employed in the spectral siren framework to constrain cosmic expansion. The idea stems from the fact that the SGWB can constrain additional population properties of the CBCs thus potentially improving the measurement precision of the cosmic expansion parameters. We show that with a 5-detector network at O5-designed sensitivity, the inclusion of the SGWB will improve our ability to exclude low values of and the dark matter energy fraction , while also improving the determination of a possible CBC peak in redshift. Although low values of and will be better constrained, we obtain that most on the precsion on will be provided by resolved spectral sirens. We also performed a spectral siren analysis for 59 resolved binary black hole sources detected during the third observing run with an inverse false alarm rate higher than 1 per year jointly with the SGWB. We obtain that with current sensitivities, the cosmological and population results are not impacted by the inclusion of the SGWB
Spin-crossover and high magnetic anisotropy in organometallic structures: W3C6O6 and Re3C6O6
No full textInternational audienceOrganometallic monolayers of the form TM3C6O6 where TM is any possible transition metal are a very promising material class. Some members of this family with 3d transition metals had been synthesized on noble metal surfaces and we extend here the study to two metals, Tungsten (W) and Rhenium (Re), of the 5d series by the use of ab-initio calculations. One of the key findings is the discovery of spin-crossover behavior in both monolayers. Especially interesting is the spin-crossover behavior of Re3C6O6 which exhibits a transition from intermediate- spin (semiconducting) to high-spin (metallic) states, leading to a significant change in the bandgap, affecting its electrical behavior. In W3C6O6, a small gap in the electronic band structure has been observed. Furthermore, a remarkable high magnetic anisotropy energy has been found in these organometallics with 5d transition metals. Besides the ab-initio energy differences, also the parameters of a Heisenberg model with local anisotropy energies have been determined. The presence of high magnetic anisotropy energies in these organometallics makes them beneficial for potential technological applications, particularly in magnetic storage, spintronics, and other magnetic-based technologies. The high magnetic anisotropy also holds promise for quantum computing, where stable and robust magnetic qubits are essential for information storage and manipulation. Additionally, these materials with high magnetic anisotropy energies are of great interest in fundamental research as they can provide valuable insights into the underlying magnetic interactions and electronic structure of the compounds. In summary, our study highlights the fascinating properties of TM3C6O6 organometallics, with implications for future technologies, quantum computing, and fundamental research in the field of magnetic materials. Furthermore, the discovery of spin-crossover behavior of these materials opens up exciting possibilities for their use in future technologies and epitaxy on different substrates
Euclid preparation LXX. Forecasting detection limits for intracluster light in the Euclid Wide Survey
No full textInternational audienceThe intracluster light (ICL) permeating galaxy clusters is a tracer of the cluster's assembly history, and potentially a tracer of their dark matter structure. In this work we explore the capability of the Euclid Wide Survey to detect ICL using H-band mock images. We simulate clusters across a range of redshifts (0.3-1.8) and halo masses (- M), using an observationally motivated model of the ICL. We identify a 50-200 kpc circular annulus around the brightest cluster galaxy (BCG) in which the signal-to-noise ratio (S/N) of the ICL is maximised and use the S/N within this aperture as our figure of merit for ICL detection. We compare three state-of-the-art methods for ICL detection, and find that a method that performs simple aperture photometry after high-surface brightness source masking is able to detect ICL with minimal bias for clusters more massive than M. The S/N of the ICL detection is primarily limited by the redshift of the cluster, driven by cosmological dimming, rather than the mass of the cluster. Assuming the ICL in each cluster contains 15% of the stellar light, we forecast that Euclid will be able to measure the presence of ICL in up to clusters of >10^{14.2} M between and 1.5 with a S/N>3. Half of these clusters will reside below and the majority of those below will be detected with a S/N >20. A few thousand clusters at M. Euclid will detect the ICL at more than 500 kpc distance from the BCG, up to , in several hundred of these massive clusters over its large survey volume
Diagnosing plague in 17th century camelids from Romania: unmasking role of camelids in plague dissemination along historical Silk Routes
No full textInternational audienceSix camels (R01-R06) exhumed from a 17th century Silk Route site in Agighiol, Romania, along with negative controls, were blindly investigated via dental pulp paleometagenomics and paleoproteomics for traces of Yersinia pseudotuberculosis complex including the plague agent Yersinia pestis. Sample R04 yielded a 32 bp read specific for the Y. pseudotuberculosis complex valine-tRNA ligase gene; sample R05 yielded a 30 bp and a 33 bp reads specific for the Y. pseudotuberculosis complex. Further, samples R04 and R05 yielded a 16S rRNA guanine transferase specific for Y. pestis and one other Y. pseudotuberculosis complex peptide. Taken together, these validated data diagnosed plague in these ancient camels which likely participated in plague dissemination along ancient Silk Routes during the large Medieval and Modern Times pandemic in Europe.Six chameaux (R01-R06) exhumés d'un site de la Route de la Soie du XVIIe siècle à Agighiol, en Roumanie, ainsi que des témoins négatifs, ont été étudiés en aveugle par paléométagénome et paléoprotéomique de la pulpe dentaire à la recherche de traces du complexe Yersinia pseudotuberculosis, dont l'agent de la peste Yersinia pestis. L'échantillon R04 a fourni une lecture de 32 pb spécifique du gène de la valine-ARNt ligase du complexe Y. pseudotuberculosis ; l'échantillon R05 a fourni des lectures de 30 pb et 33 pb spécifiques du complexe Y. pseudotuberculosis. De plus, les échantillons R04 et R05 ont fourni une 16S ARNr guanine transférase spécifique de Y. pestis et un autre peptide du complexe Y. pseudotuberculosis. Prises ensemble, ces données validées ont permis de diagnostiquer la peste chez ces chameaux anciens, qui ont probablement participé à sa dissémination le long des anciennes Routes de la Soie lors de la grande pandémie médiévale et moderne en Europe
Le Minier : histoire et archéologie des entreprises argentifères médiévales, Rapport d’activité 2024 du PCR
No full textCe Programme Collectif de Recherche est une enquête interdisciplinaire portant sur les entreprises argentifères médiévales de la vallée du Minier (département de l’Aveyron, commune du Viala-du-Tarn). Entre le XIIe et le XVe siècle, au moins, cette vallée fit l’objet d’exploitations discontinues de gisements polymétalliques (cuivre, plomb, zinc, argent) – essentiellement pour produire du plomb et de l’argent. Pour explorer leurs dynamiques et leurs vestiges, le PCR regroupe depuis 2020 des chercheurs de disciplines et d’horizons complémentaires : archéologues, historiens, historiens de l’art, géologues et géochimistes.Les travaux de la campagne 2024 se sont inscrits dans une phase d’achèvement des fouilles et de traitement des données. Au cours de l’année, les dépouillements d’archives ont d’abord mis au jour une brève reprise d’activité au Minier, dans les années 1570-1572. Les sept nouveaux documents ont donc été édités et commentés. Ils nous permettent d’intégrer la vallée du Minier aux réseaux d’affaire qui se déployaient alors en Europe.En parallèle, les prélèvements issus des carottages effectués à la tarière en 2023 ont été analysés à la fluorescence X et au MEB. Nous avons privilégié les prélèvements situés au cœur des anomalies géochimiques, de beaux résultats ont donc déjà été obtenus, confirmant l’existence d’ateliers de traitement du minerai. Lors de la campagne de terrain, nous avons pu achever les prospections géochimiques en couvrant l’espace autour de Doulsac et de la Roubière. Les résultats obtenus sont allés au-delà de nos prévisions en termes d’ampleur spatiale et, peut-être, chronologique avec la supposition d’exploitations antérieures au XIIIe siècle.Les fouilles archéologiques conduites dans la mine de Cantamerle et sur les ateliers des Voltes ont rempli leurs objectifs. Dans la mine, nous avons fouillé autant que possible la salle centrale, élargissant et affinant notre compréhension de la stratigraphie. Aux Voltes, nous avons également été en mesure de terminer la fouille des ateliers qui avaient été ouverts en 2022, et par ailleurs de faire une découverte inattendue, un puits servant à la sortie des matériaux et à leur traitement dans ces ateliers.S’agissant enfin de l’enregistrement des maisons, la campagne de cette année s’est focalisée sur l’achèvement de la maison 1, à l’entrée sud du Minier. Enfin, la campagne estivale a été l’occasion d’expérimenter la capture et l’analyse au MEB de résidus de minerais qui restaient piégés dans les cupules des enclumes et les stries des meules à minerais. Les résultats sont positifs et nous inciteront probablement à systématiser l’approche.En fin d’année, les rapports isotopiques d’un échantillonnage de matériaux (minerais, scories, déchets) mis au jour dans les fouilles ont été reçus. Le référentiel chimique que nous souhaitons établir est donc bien avancé et sera complété les années suivantes. Enfin, la fouille des Voltes étant achevée, nous préparons dès maintenant un projet de valorisation des lieux. La contribution finale de ce rapport présente donc les enjeux et propose un premier cahier des charges
Les échanges économiques entre Marseille et l’Algérie (XIXe-XXe siècle)
No full textSi les échanges entre la cité phocéenne et l’Algérie ont débuté bien avant la colonisation, c’est à partir de la conquête de 1830 qu’ils prennent une nouvelle dimension, à la charnière des économies portuaires, agricoles et industrielles. Au début du XXe siècle, les rivages algériens nourrissent une grande partie des importations et exportations marseillaises. Ces trafics mettent en jeu des produits variés, allant des céréales aux métaux, en passant par les vins, les primeurs, les phosphates et les bestiaux. Ils déterminent également des transformations d’infrastructures portuaires, des reconfigurations d’arrière-pays agricoles et des évolutions dans les techniques de manutention de part et d’autre de la Méditerranée. À cet égard, le marché algérien constitue un laboratoire d’innovations pour le conditionnement de gros volumes de marchandises, à l’instar du transport de vin en vrac sur des navires pinardiers dans les années 1930 ou de l’emploi de containers après-guerre pour sécuriser et normaliser les trafics de primeurs. Loin de disparaître après l’indépendance algérienne, ces échanges économiques se reconfigurent selon une logique post-coloniale autour d’un produit phare : les hydrocarbures sahariens
Extended-interval dosing of rituximab/ocrelizumab is associated with a reduced decrease in IgG levels in multiple sclerosis.
No full textInternational audienceThe potential benefits of extended-interval dosing (EID) of rituximab (RTX) or ocrelizumab (OCR) in mitigating the reduction of immunoglobulin levels and decreasing the risk of infection in persons with relapsing-remitting multiple sclerosis (pwRRMS) remain largely unknown. We retrospectively analyzed two structured data collections including pwRRMS who were prescribed RTX/OCR using different interval dosing regimens, a 6-month standard-interval dosing (SD) or EID. The SD and EID cohorts included 88 and 271 pwRRMS, respectively, with a mean (SD) treatment duration of 3.5 (1.3) and 4.4 (1.5) years, and a mean (SD) interval between infusions of 6.4 (1.7) and 19.2 (11.9) months. After RTX/OCR initiation, the two cohorts did not differ in time to first relapse (p = 0.83), time to first sustained accumulation of disability (p = 0.98) and incidence of MRI activity (p = 0.91). The time to first severe infectious event (SIE) was shorter in the SD cohort (p = 0.005). The effect of treatment duration on reduction of serum IgG level was lower in the EID cohort (Estimate = 0.15 g/L per year of follow-up, 95 % CI -0.06, -0.23, p = 0.001). In the entire patient group, higher serum IgG levels at the last infusion were associated with a lower risk of SIE between two visits (HR = 0.77 per g/L of serum IgG; 95 % CI: 0.66-0.91; p = 0.006). This study suggests that EID of RTX/OCR may reduce the risk of serum IgG decline in pwRRMS without a loss of efficacy and may mitigate the risk of severe infections. These results must be confirmed by future randomized studies
