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Influence of the Amazon River plume on the biodiversity and assemblage structure of lanternfishes (Myctophidae)
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Impact of extrusion parameters on polymer and composite electrolyte membranes via melt-based processing
No full textInternational audienceTo address the safety challenges induced by the ever-growing demand of mobile and stationary energy storage systems such as Li-ion batteries, numerous studies have been conducted over several decades on the development of solid polymer or composite electrolytes (SPE/SCE) to replace the flammable and potentially explosive liquid electrolytes currently used in the manufacturing of Gen3 Li-ion batteries1. These studies focusing on many different systems (polymer matrix, lithium salt, additives) are predominantly carried out via liquid casting. However, this process, used today for the manufacturing of Li-ion battery electrodes, requires a huge quantity of toxic solvents, especially at the positive electrode, that must then be removed during evaporation and be treated. This cumbersome step in the manufacturing process accounts for 48% of the total energy consumption of a production plant2. Thus, the twin-screw extrusion (TSE) process has been identified as a promising process of components for "all-solid state" batteries and is already use by BlueSolution company at the industrial scale. SPE is particularly adapted to melt-based processing of highly filled mixtures already widely used in plastics manufacturing allows the elimination of dissolution, evaporation, and drying steps. However, TSE is a complex process with numerous adjustable parameters such as processing temperature, material flow rate, screw profiles and rotational speed. This first set of parameters affect operational parameters such as residence time and the specific energy input into the material during mixing. All these variables can influence the quality of the mixture and his performances.In this work, we will present our study that aims at identifying and understanding the impact of various parameters on the melt-based processing of polymer and composite electrolyte membranes with different formulations. A comparison will be made of the performances of the membranes produced by this method with those manufactured through liquid casting.A system known in the literature3, consisting of polycaprolactone (PCL) polymer matrix, LiTFSI salt and ZrO2 as mechanical reinforcement, were chosen for their low cost and availability in high volume. Various analyses were combined : mechanical properties by tensile test and DMA, morphologies by SEC and LPS, conductivity by EIS and more The experimental processing data collected were also compared with the data obtained by simulation with LUDOVIC© software (SCC)
SVOM GRB 250314A at z 7.3: an exploding star in the era of reionization
No full textInternational audienceMost long Gamma-ray bursts originate from a rare type of massive stellar explosion. Their afterglows, while rapidly fading, can be initially extremely luminous at optical/near-infrared wavelengths, making them detectable at large cosmological distances. Here we report the detection and observations of GRB 250314A by the SVOM satellite and the subsequent follow-up campaign with the near-infrared afterglow discovery and the spectroscopic measurements of its redshift z 7.3 . This burst happened when the Universe was only 5% of its current age. We discuss the signature of these rare events within the context of the SVOM operating model, and the ways to optimize their identification with adapted ground follow-up observation strategies
JWST reveals a supernova following a gamma-ray burst at z 7.3
No full textInternational audienceThe majority of energetic long-duration gamma-ray bursts (GRBs) are thought to arise from the collapse of massive stars, making them powerful tracers of star formation across cosmic time. Evidence for this origin comes from the presence of supernovae in the aftermath of the GRB event, whose properties in turn link back to those of the collapsing star. In principle, with GRBs we can study the properties of individual stars in the distant universe. Here, we present JWST/NIRCAM observations that detect both the host galaxy and likely supernova in the SVOM GRB 250314A with a spectroscopically measured redshift of z 7.3, deep in the era of reionisation. The data are well described by a combination of faint blue host, similar to many z 7 galaxies, with a supernova of similar luminosity to the proto-type GRB supernova, SN 1998bw. Although larger galaxy contributions cannot be robustly excluded, given the evidence from the blue afterglow colours of low dust extinction, supernovae much brighter than SN 1998bw can be. These observations suggest that, despite disparate physical conditions, the star that created GRB 250314A was similar to GRB progenitors in the local universe
Finite actions and asymptotic charges at null infinity for any spin
No full textInternational audienceWe identify boundary terms renormalizing the free on-shell actions for massless fields of arbitrary spin, including electromagnetism and linearized gravity, with boundary conditions allowing for supertranslation-like asymptotic symmetries. Our focus is on null infinity, in any spacetime dimensions. We also comment on the renormalization of the corresponding asymptotic charges
Measurement of transverse and hyperon polarization in Pb collisions at TeV
No full textInternational audienceThe transverse polarization of and hyperons is measured in Pb collisions collected by the LHCb experiment at a nucleon-nucleon center-of-mass energy of TeV. The polarization is averaged over hyperon transverse momentum in the range GeV/, and Feynman- in the ranges (forward region) and (backward region) defined relative to the proton beam direction. The transverse polarization is found to be compatible with zero for both and hyperons. The results are also measured as a function of and with no significant dependence on these variables observed. The results are compared with previous experimental measurements at different center-of-mass energies and collision environments
Neutrino non-radiative decay in matter: constraints and prospects
No full textInternational audienceNeutrinos, being massive, can decay. A heavier neutrino could decay into a lighter one and a massless scalar or pseudoscalar boson, such as the Majoron. Two-body non-radiative decay could occur in dense matter, such as in the inner dense regions of a core-collapse supernova. We first derive novel bounds on neutrino-Majoron couplings using the spectral distortions induced by neutrino non-radiative two-body decay in matter, and two-dimensional likelihood analyses of the 24 events from SN1987A. We then explore the prospects of neutrino-Majoron couplings from a future galactic core-collapse supernova, leaving either a neutron star or a black-hole. To this aim, we use information from detailed one-dimensional supernova simulations. We consider the supernova neutrino signal associated with inverse-beta decay in the upcoming JUNO and Hyper-Kamiokande detectors, with neutrino-argon scattering in DUNE, or with coherent neutrino-nucleus scattering in the DARWIN experiment. In a full 3 framework, based on the spectral distortions induced by neutrino decay in matter, we perform two-dimensional likelihood analyses and provide prospects for the limits on neutrino-Majoron couplings. Our results show that the observation of a future supernova will significantly improve on the current bounds, in particular from SN1987A and neutrinoless double-beta decay. Finally, we explore the impact of neutrino decay in matter on the diffuse supernova neutrino background formed by past supernova explosions. We show for the first time that the effects on black-hole contributions are important and modify the DSNB number of events by several tens of percent in Hyper-Kamiokande
Anomalous frequency scaling of acoustic phonon damping in freestanding nickel cavities fabricated via laser delamination
No full textInternational audienceSingle-shot picosecond (ps) laser-induced delamination allows for the direct generation of suspended membranes from a continuous metallic film, offering a promising platform for the control of ultrafast magnetization dynamics driven by acoustic waves. Using the picosecond-ultrasonics method, we demonstrate that long-lived low-frequency acoustic waves can be optically excited in the delaminated cavities. At the same time, higher-frequency modes above 60 GHz exhibit a surprisingly fast damping, following a scaling law incompatible with the expected attenuation mediated by phonon–phonon scattering. Comparing measurements between delaminated cavities and a benchmark nickel film in contact with the substrate, we link our findings to structural modifications of the nickel crystal induced by the delamination process
GW241011 and GW241110: Exploring Binary Formation and Fundamental Physics with Asymmetric, High-spin Black Hole Coalescences
No full textInternational audienceWe report the observation of gravitational waves from two binary black hole coalescences during the fourth observing run of the LIGO–Virgo–KAGRA detector network, GW241011 and GW241110. The sources of these two signals are characterized by rapid and precisely measured primary spins, nonnegligible spin–orbit misalignment, and unequal mass ratios between their constituent black holes. These properties are characteristic of binaries in which the more massive object was itself formed from a previous binary black hole merger and suggest that the sources of GW241011 and GW241110 may have formed in dense stellar environments in which repeated mergers can take place. As the third-loudest gravitational-wave event published to date, with a median network signal-to-noise ratio of 36.0, GW241011 furthermore yields stringent constraints on the Kerr nature of black holes, the multipolar structure of gravitational-wave generation, and the existence of ultralight bosons within the mass range 10–10 eV
Indirectly LED-pumped Nd:glass: potential for high energy laser facilities
No full textInternational audienceFlashlamp-pumpedNd:glass is used as a power amplifier in many high energy laser facilities. Despite the problems of this old technology, flashlamps are still being considered for the next generation of lasers as diode laser pumping is far from being ready. This work presents an alternative for pumping high energy lasers: LEDs combined with luminescence concentrators. Using a pump head consisting of a green-yellow Ce:LuAG luminescent concentrator pumped by 2240 LEDs, we demonstrate a Nd:glass laser oscillator producing 25 mJ at 1053 nm for an absorbed pump energy of 138 mJ. The small signal gain reaches 1.25 in a single pass despite the short length of the Nd:glass rod (20 mm). These results reveal the potential of indirect LED pumping for Nd:glass amplifiers in high energy lasers.</div