HAL-INSU
Not a member yet
203706 research outputs found
Sort by
Identifier les dégradateurs de plastique marin par marquage isotopique de l'ADN
No full textInternational audiencePlastic biodegradation in natural environments is performed by the microbial biofilm living on its surface. This study identifies for the first time plastic degraders in marine environment, by using stable isotope tracers. Polyhydroxybutyrate (PHB) biodegradation was proved by monitoring microbial cell growth (via scanning electron microscopy and flow cytometry) and activities (via continuous oxygen consumption measurements and 3 H-leucine incorporation for protein synthesis) during 90 days. We successfully synthetized 13 C-labeled PHB and conducted DNA-stable isotope probing (DNA-SIP) experiments over different time points, which permitted the first description of key PHB degraders belonging to Marinobacter sp. and Cellvibrionaceae together with Glaciecola sp., Pseudoalteromonas sp., Celeribacter sp. and Alteromonas sp. Overall, SIP labeling combined with metabarcoding proved to be a useful tool for discovering and characterizing active plastic degraders from complex marine communities
Discovery of a Pulsar Wind Nebula Candidate Associated with the Galactic PeVatron 1LHAASO J0343+5254u
No full textInternational audienceThe astronomical origin of the most energetic galactic cosmic rays and gamma rays is still uncertain. X-ray followup of candidate "PeVatrons", systems producing cosmic rays with energies exceeding 1 PeV, can constrain their spatial origin, identify likely counterparts, and test particle emission models. Using 120 ks of XMM-Newton observations, we report the discovery of a candidate pulsar wind nebula, a possible counterpart for the LHAASO PeVatron J0343+5254u. This extended source has a power law X-ray spectrum with spectral index of 1.9 - softer at greater distance from the center - and asymmetric spatial extension out to 2'. We conduct leptonic modeling of the X-ray and gamma ray radiation from this complex system, showing that a fully leptonic model with elevated IR photon fields can explain the multiwavelength emission from this source, similar to other VHE pulsar wind nebulae; excess gamma ray emissivity not explained by a leptonic model may be due to hadronic interactions in nearby molecular cloud regions, which might also produce detectable astroparticle flux
Fermi-detection of -ray Emissions from the Hot Coronae of Radio-quiet Active Galactic Nuclei
No full textInternational audienceRelativistic jets around supermassive black holes (SMBHs) are well-known powerful -ray emitters. In absence of the jets in radio-quiet active galactic nuclei (AGNs), how the SMBHs work in -ray bands is still unknown despite of great observational efforts made in the last 3 decades. Considering the previous efforts, we carefully select an AGN sample composed of 37 nearby Seyfert galaxies with ultra-hard X-rays for the goals of -ray detections by excluding all potential contamination in this band. Adopting a stacking technique, here we report the significant -ray detection (, or ) from the sample using 15-year Fermi-Large Area Telescope (LAT) observation. We find an average -ray luminosity of the sample as at energies from 1-300 GeV. Limited by the well-known pair production from the interaction of -rays with low energy photons, several GeV -rays are found to originate from an extended corona (), whereas the canonical much more compact X-ray corona () is responsible for 1 to several GeV -rays. The finding of the compact region lends to strong supports to the long-time theoretical expectations, but the extended corona is beyond all the existing models. One promising scenario is that the electron-positron pairs produced in the compact X-ray corona would expand as fireball, similar to that in -ray bursts, forming the structure of extended corona
Gonyaulax montresoriae sp. nov. (Dinophyceae) from the Adriatic Sea produces predominantly yessotoxin
No full textInternational audienceYessotoxin is one of the shellfish toxins leading to mussel farm closures in the Adriatic Sea of Italy. Two putative Gonyaulax spinifera strains GSA0501 and GSA0602 are known as yessotoxins producers, but their identities have remained elusive since 2005. To address this gap, we established five Gonyaulax strains by incubating sediments from the Adriatic Sea and subsequently isolating single cells. Both cyst and theca morphology were examined using light and scanning electron microscopy. In addition, LSU and/or SSU rRNA gene sequences were obtained for all strains. Two strains produce cysts resembling Spiniferites mirabilis and one strain was related to S. scabratus. The other two strains are described as Gonyaulax montresoriae sp. nov., characterized by a high cingular displacement and overhang, along with two unequal antapical spines. Cysts of G. montresoriae are pear-shaped, showing a smooth surface and exclusively gonal processes with perforations at the base, the latter similar to S. lazus. LSU rRNA gene sequence comparison suggests that the G. spinifera strain GSA0501 isolated from the Adriatic Sea in 2005 should also be identified as G. montresoriae. Maximum likelihood and Bayesian inference analyses based on LSU and SSU rRNA gene sequences reveal that G. montresoriae is monophyletic, and close to several toxic strains of presumable Gonyaulax spinifera from the Adriatic Sea and New Zealand, whose taxonomic positions are uncertain. One strain of G. montresoriae was examined for yessotoxin production using LC-MS/MS, and found to produce predominantly yessotoxin at a concentration of 3.0 pg cell-1. Our results highlight the rich diversity and risks associated with Gonyaulax species in the Mediterranean Sea
« Agir autrement » Guide pour co-construire des trajectoires d’adaptation des territoires littoraux, Rapport Projet Trajectoires Fondations de France
No full textCe guide a été réalisé dans le cadre du projet de recherche action TRAJECTOIRES (Temps long et progressivité de l'action publique. Acceptabilité et opérationnalisation des trajectoires d'adaptation des territoires littoraux) financé par la Fondation de France. Ce projet était à la fois pluridisciplinaire (Economie, Géographie, Psychologie environnementale, Science politique, Droit) et de type « recherche action » mené en partenariat étroit avec des partenaires diversifiés (AURCACe document résulte d’une co-construction rassemblant des chercheurs de diverses disciplines, ainsi que des acteurs divers de collectivités territoriales, services déconcentrés de l’Etat, associations. Il s’agit d’offrir un éclairage opérationnel qui rende compte à la fois des connaissances scientifiques et des résultats observés sur divers terrains. La collaboration étroite avec le CNFPT vise à faciliter l’acquisition de nouvelles compétences et plus généralement l’évolution de l’ingénierie territoriale face aux nouveaux enjeux de la gestion des risques côtiers et de la transition des territoires littoraux.</div
ias L Pagano
No full textInternational audienceWe describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of Planck. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at z < 3; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from Rubin of overlapping sky
Parallels and discrepancies between non‐native species introductions and human migration
No full textInternational audienceBiological invasions and human migrations have increased globally due to socio‐economic drivers and environmental factors that have enhanced cultural, economic, and geographic connectivity. Both processes involve the movement, establishment, and spread of species, yet unfold within fundamentally different philosophical, social and biological contexts. Hence, studying biological invasions (invasion science) and human migration (migration studies) presents complex parallels that are potentially fruitful to explore. Here, we examined nuanced parallels and differences between these two phenomena, integrating historical, socio‐political, and ethical perspectives. Our review underscores the need for context‐specific approaches in policymaking and governance to address effectively the challenges and opportunities of human migration and harm from biological invasions. We suggest that approaches to studying the drivers of biological invasions and human migration provide an excellent opportunity for transdisciplinary research; one that acknowledges the complexities and potential insights from both fields of study. Ultimately, integrating natural and social sciences offers a promising avenue for enriching the understanding of invasion biology and migration dynamics while pursuing just, equitable, and sustainable solutions. However, while human migration is a clear driver of biological invasions, drawing on principles from biological invasions to understand past and current human migration risks oversimplification and the potential for harmful generalisations that disregard the intrinsic rights and cultural dynamics of human migrations. By doing so, we provide insights and frameworks to support the development of context‐specific policies that respect human dignity, foster cultural diversity, and address migration challenges in ways that promote global cooperation and justice. This interdisciplinary approach highlights the potential for transdisciplinary research that acknowledges complexities in both fields, ultimately enriching our understanding of invasion biology and migration dynamics while pursuing equitable and sustainable solutions
A primordial origin to cosmic tensions: towards a joint solution to the and tensions with early dark energy and scale-dependent primordial non-Gaussianities
No full textInternational audienceThe Hubble tension between direct measurements of the expansion rate and the prediction of the CDM cosmological model calibrated on the Cosmic Microwave Background (CMB), is a strong motivation to explore alternative cosmological models. A popular class of such models includes an additional component of dark energy relevant in the early Universe, which solves the Hubble tension. These Early Dark Energy (EDE) models however typically worsen the tension between measurements of weak gravitational lensing and the CDM expectation. Here, we show how combining EDE with scale-dependent primordial non-Gaussianities (sPNG) can in principle solve both tensions at once. Such sPNG are related to non-trivial inflationary physics, and observationally affect the non-linear regime of structure formation while leaving the linear regime mostly untouched. Depending on the amplitude of the sPNG, such models can either yield back the CDM expectation for the PS in the non-linear regime, and hence an parameter compatible with CDM, or can even reconcile the value of from weak-lensing measurements with the CMB, while solving the Hubble tension in all cases. In such models, both tensions would then be entirely related to pre-CMB physics of the early Universe
Generation of ultralight axions by a Kerr black hole. I. Why AGNs are favorable sources
No full textInternational audienceThe hypothetical axion particles have received great attention in recent years in both particle physics, where they contribute to solving some difficulties with the Standard Model, and in astrophysics, where they could be a serious candidate for dark matter and solve problems with the ΛCDM model. We expect that the most powerful radiation sources in the Universe—quasars and, more generally, active galactic nuclei (AGNs)—could produce a significant amount of axions. The central engine of these high-energy objects is a Kerr black hole surrounded by a magnetosphere, where structures called “gaps” form close to the black hole horizon and generate intense electric fields such that E→·B→≠0; such a configuration is favorable for the production of axions, especially in the unsteady regime. First investigations of this sort have been performed for pulsars because of their very intense magnetic fields; however, extragalactic sources are far more powerful and more suitable to produce a large flux of axions particles. Moreover, the axions of interest would have a Compton wavelength comparable with the gravitational radius of their black hole. The primary energy supply stems from the rotation of a black hole threaded by a magnetic field, which powers a Poynting flux through the Blandford-Znajek mechanism that drives relativistic jets, which is supplemented by the Goldreich-Julian generation of an electric charge density whose unsteady screening generates a strong oscillating electric field component aligned with the main magnetic field that threads the black hole. Both processes provide a permanent source of energy for the emission of axion particles through two channels: the internal generation of axion power in vibrating gaps which generates forward and backward axion waves, and the slight extraction of the Blandford-Znajek luminosity by the axions themselves inside the gaps. The work is presented in two parts. In this first part, the astrophysical conditions under which the interaction takes place are presented and the efficiency of axion production is estimated, offering some hope for a cosmological solution in the form of a hot axion dark matter component in halos surrounding quasars and AGNs. In the second part (a separate paper), a detailed investigation of the physics of a Kerr black hole magnetosphere with the production of oscillating gaps reveals their capacity to be a powerful source of axions, in particular how axions participate in the Blandford-Znajek process
Hysteresis of the Antarctic Ice Sheet With a Coupled Climate-Ice-Sheet Model
No full textInternational audienceThe stability of the Antarctic ice sheet under different fixed CO 2 levels and orbital configurations is explored using a coupled climate-ice sheet model, starting from either a pre-industrial ice sheet or an ice-free, isostatically rebounded geometry. Simulations reveal a strong hysteresis effect: equilibrium ice volumes differ significantly for equivalent CO 2 levels, depending on the initial ice sheet geometry. Crucially, the albedo-melt feedback is accounted for in our coupled setting, resulting in a nonlinear response of the ice sheet to the CO 2 forcing. Critical CO 2 thresholds trigger either the complete Antarctic ice sheet loss or near-complete regrowth. The orbital configuration influences these CO 2 thresholds. These findings highlight the importance of ice sheetatmosphere interactions, notably the albedo-melt feedback, in projecting future long-term ice sheet behavior. Neglecting these feedbacks could lead to an overestimation of CO 2 thresholds for ice sheet destabilization, with implications for future long-term sea level rise under high emission scenarios.</div