HAL-CEA
Not a member yet
145450 research outputs found
Sort by
Ex vivo mechanical properties of human thoracolumbar fascia and erector spinae aponeurosis under traction loading and shear wave elastography
No full textInternational audienceThe thoracolumbar fascia (TLF) and the erector spinae aponeurosis (ESA) play an important role in the biomechanics of the spine and could be a source of low back pain. Although the TLF and ESA are key structures in several musculoskeletal dysfunctions and in tissue engineering, there is still a lack of evidence in the literature to prove that they have different mechanical properties and roles when considered as a single tissue. Furthermore, no methods are currently available to study these structures in vivo. The objective of this study was to analyze the ex-vivo tensile properties TLF and ESA, and to test the potential of ultrasound shearwave elastography (SWE) to characterize these tissues. Hundred samples from N = 10 fresh-frozen human donors were studied. Shear wave speed (SWS) was measured in all samples with SWE, and their tensile properties were measured with mechanical testing. Results show that TLF is anisotropic, and more compliant than ESA. SWS was not significantly correlated to tensile moduli.These findings could potentially aid surgeons in their daily practices, assist engineers with in silico simulations, and support physiotherapists in musculoskeletal rehabilitation by enabling them to customize medical interventions for each specific patient and clinical condition. However, further research is necessary to further investigate the behavior in terms of time-dependent response and link between the tissue anisotropy and microstructural organization
Small brains but big challenges: white matter tractography in early life samples
No full textInternational audienceIn the human brain, white matter development is a complex and long-lasting process involving intermingling micro-and macrostructural mechanisms, such as fiber growth, pruning and myelination. Did you know that all these neurodevelopmental changes strongly affect MRI signals, with consequences on tractography performances and reliability? This communication aims to elaborate on these aspects, highlighting the importance of tracking and studying the developing connections with dedicated approaches
Bioschemas data harvesting project report
No full textpreprintThe promise of Bioschemas is that it makes consuming data from multiple resources more straightforward. However, this hypothesis has not been tested by conducting a large scale harvest of deployed markup and making this available for others to reuse. Therefore, the goal of this hackathon project is to harvest a collection of Bioschemas markup from a number of different sites listed on the Bioschemas live deploys page using the Bioschemas Markup Scraper and Extractor (BMUSE). The harvested data will be made available for others and loaded into a triplestore to allow for further exploration
Prevalent North Atlantic Deep Water during the Last Glacial Maximum and Heinrich Stadial 1
No full textInternational audienceDeep ocean circulation modulated glacial–interglacial climates through feedbacks to the carbon cycle and energy distribution. Past work has suggested that contraction of well-ventilated North Atlantic Deep Water during glacial times facilitated carbon storage in the deep ocean and drawdown of atmospheric CO 2 levels. However, the spatial extent and properties of different water masses remain uncertain, in part due to conflicting palaeoceanographic proxy reconstructions. Here we combine five independent proxies to increase confidence and reconstruct Atlantic deep water distributions during the Last Glacial Maximum (around 21 thousand years ago) and the following Heinrich Stadial 1—a time when massive ice rafting in the North Atlantic interfered with deep water formation and caused global climate shifts. We find that North Atlantic Deep Water remained widespread in both periods, although its properties shifted from a cold, well-ventilated mode to a less-ventilated, possibly warmer, mode. This finding implies a remarkable persistence of deep water formation under these cold boundary conditions, sustained by compensation between the two formation modes. Our constraints provide an important benchmark for evaluating Earth system models, which can enhance confidence in future climate projections
Species assemblages of key prey taxa from the Southern Ocean and the Southern Indian Ocean using biogeographic networks
No full textInternational audiencePlankton plays an important role in the functioning of marine ecosystems, for example, through their role as prey. It is therefore important to understand the spatial distribution of assemblages of key taxa. This study aimed to determine the effect of hydrologic and topographic features on two major macrozooplankton groups: euphausiids and amphipods, which are important prey of seabirds and marine mammals. The biogeography of these taxa's species between the Southern Indian Ocean and the North Indian sector of the Southern Ocean will be assessed by network analyses on species abundances. Our results from the REPCCOAI surveys from 2017 to 2019 between Crozet, Kerguelen and St Paul and New Amsterdam revealed a strong biogeographic separation between the subtropical and subantarctic zones. Species assemblages for each major taxon revealed a distinction between off shelf areas and the neritic zone and between high and low productivity areas, underlining the role of the subantarctic islands and their effect on primary production in the biogeography of the southern plankton. In the subtropical Indian Ocean, no significant major distinction was observed with the network analysis, even if some sites seem to show an influence of the Agulhas Return Current.</div
A large, chemically enriched, neutral gas reservoir in a galaxy at z = 6.782
No full textInternational audienceThe chemical characterization of galaxies in the first billion years after the Big Bang is one of the central goals of current astrophysics. Optical/near-infrared spectroscopy of long gamma-ray bursts (GRBs) have been heralded as an effective diagnostic to probe the interstellar medium of their host galaxies and their metal and dust content, up to the highest redshift. An opportunity to fulfill this expectation was provided by the recent blast triggered by the Neil Gehrels Swift Observatory of GRB 240218A at redshift z=6.782. We study a high-redshift galaxy selected in a complementary way with respect to flux-limited surveys, not depending on galaxy luminosity and stellar mass. We present the VLT/X-shooter spectrum of its afterglow enabling the detection of neutral-hydrogen, low-ionization, high-ionization and fine-structure absorption lines. We determine the metallicity, kinematics and chemical abundance pattern, providing the first detailed characterization of the neutral gas of a galaxy at z>6.5. From the analysis of fine-structure lines we estimate the distance of the closest gas clouds as pc. We determine a high neutral hydrogen column density, , which is the highest one at z>6 determined so far for a GRB host galaxy, as well as a surprisingly high metal column density, . The observed metallicity of the host galaxy system is [Zn/H]>-0.8. We find evidence of a high amount of dust depletion and of aluminum overabundance, although a number of transitions are saturated. The high hydrogen column density, metal abundances and dust depletion in the neutral gas align with those of the ionized gas of very high-redshift galaxies unveiled by ALMA and JWST, testifying that a rapid build up of metals and dust, and massive neutral hydrogen reservoirs seem to be common features of galaxies in the early Universe
Certification of a new plutonium metal reference material: the CETAMA MP4 standard
No full textInternational audienceThis paper describes the production and certification of a new plutonium (Pu) metal reference material called MP4. The material’s certification was carried out through an interlaboratory comparison (ILC) involving eight expert laboratories. By performing extensive data analysis on the ILC’s results it was possible to establish the certified reference values for several quantities such as the Pu isotopic abundance and the Pu mass fraction. Thanks to its comprehensive set of certified values and its reduced mass compared to MP2, MP4 constitutes a novel and rare standard for Pu fissile material accountancy and nuclear safeguards activities
Offline Atmospheric Transport on a Global Mesh of Hexagons
No full textInternational audienceWe present a new version of the offline transport model from the LMDz atmospheric general circulation model. It paves the globe with hexagons and 12 pentagons of similar surface areas rather than with regular longitude-latitude rectangles. It is available in a complete, nonlinear version and in a linearized configuration for use in variational atmospheric inversions. It runs on graphics processing units like the previous version. The previous advection approach and physical parameterizations have been kept while the code has been restructured for better numerical efficiency. The change of mesh was made necessary by the evolution of the parent LMDz model, but the technical and scientific evaluation of the new version with a roughly constant number of cells shows some interesting advantages. This evaluation is based on an 11-year simulation of sulfur hexafluoride and on a 10-year atmospheric inversion assimilating column-averaged dry air mole fractions of carbon dioxide (CO 2 ) retrieved from measurements of NASA's second Orbiting Carbon Observatory. As it is used in variational inversion and at 90-km resolution with 79 layers in the vertical, we find that the new offline model is twice as fast. Further, it shows improved interhemispheric transport, some small improvements in terms of inferred (posterior) atmospheric concentrations and small differences in terms of inferred surface fluxes compared to the previous version. These assets allowed it to be commissioned in its 90-km configuration for the operational CO 2 inversions of the European Copernicus Atmosphere Monitoring Service.</div
Particle acceleration and multi-messenger radiation from ultra-luminous X-ray sources: A new class of Galactic PeVatrons
No full textInternational audienceSuper-Eddington accretion onto stellar-mass compact objects powers fast outflows in ultra-luminous X-ray sources (ULXs). Such outflows, which can reach mildly relativistic velocities, are often observed forming bubble structures. Wind bubbles are expected to develop strong wind termination shocks, which are sites of great interest for diffusive shock acceleration. We developed a model of diffusive shock acceleration in the wind bubbles powered by ULXs. We find that the maximum energy in these objects can easily reach the PeV range, promoting winds from ULXs as a new class of PeVatrons. We specialized our model in the context of the Galactic source SS 433 and show that high-energy protons in the bubble might explain the highest energy photons (>100 TeV) and their morphology recently observed by LHAASO. In this paper, we discuss the detectability of such a source in neutrinos, and we analyze the possible radio counterpart of ULXs focusing on the case of W50, the nebula surrounding SS 433. Finally, we discuss the possible contribution of Galactic ULXs to the cosmic-ray flux at the knee, concluding that their role could be significant only if one of these sources, currently undetected, were sufficiently close
