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Les déchets et leurs usages (XIXe-XXIe siècle) : ruptures métaboliques, conflictualités sociales et transitions environnementales
No full textCe dossier pluridisciplinaire réunit des contributions qui mettent en perspective l’histoire et le présent des déchets dans nos sociétés contemporaines. En présentant leurs usages multiples et parfois controversés, il souligne que la gestion des déchets revêt une dimension éminemment politique
“Pour une éthique de l'hospitalité. L'accueil du migrant comme exigence”, conférence durant la journée Migration. Actualités françaises, réalités mondiales, Couvent dominicain de la Tourette, 28 mars 2026.
No full textInternational audienc
Pulsed X‐Ray Radiation Responses of Single‐Mode and Multimode Fluorine‐Doped Optical Fibers
No full textInternational audienceIn this study, we compare the pulsed X‐ray radiation responses of standard, radiation‐tolerant optical fibers with those of super‐hard, radiation‐resistant multimode (MM‐SRH) and single‐mode (SM‐SRH) fluorine‐doped optical fibers. Real‐time measurements of radiation‐induced attenuation (RIA) spectra were conducted in the spectral range of 0.6 to 3.0 eV (400–2000 nm), both at room temperature and at liquid nitrogen temperature, to characterize the nature of metastable defects, quickly recombining after the short (a few tens of ns) irradiation pulse. Additionally, we monitored the RIA kinetics at the two telecommunication wavelengths, 1550 and 1310 nm, from the microsecond timescale to several hundreds of seconds. MM‐SRH fibers exhibit superior light transmission efficiency following the X‐ray irradiation pulse, better than the other fiber compositions and the one expected from current literature on transient responses of silica‐based optical fibers. Possible explanation of this radiation hardness could be the very high level F‐doping distribution in this graded‐index optical fiber, demonstrating how the RIA in optical fibers strongly depends on fiber composition and manufacturing parameters
When is an owl not an owl? An analysis of Attic tetradrachms circulating in the southern Levant in the late fifth and fourth centuries BCE
No full textInternational audienceThis article, dedicated to the memory of the late Prof. John H. Kroll, focuses on late fifth century BCE Athenian-style tetradrachms found in the southern Levant, to shed new light on whether they are genuine Athenian issues or local imitations. To address this important yet vexed historical question, we analysed the Pb isotope compositions of 22 coins from ten controlled archaeological excavations in Israel and compared them against the ~ 7,000 galena samples in the Lyon Pb isotope database. Nineteen of the coins are of the "three-quarter profile eye" variety conventionally dated mid to late fifth century BCE. We found that they match Attic or Athenian-controlled silver sources, suggesting they are authentic Athenian issues and not imitations as some of them were originally categorised. We argue that these coins likely entered the Western Asian money supply during Athens' massive naval campaigns in the eastern Aegean in the third and final phase of the Peloponnesian War, and that the series should be refined to end with the city's defeat and loss of silver sources in 404 BCE. The fact that three of the coins are plated supports the contention that they were part of the series minted when Athens was under extreme financial duress. The remaining two coins are of the pi-style series struck in the early 340 s BCE, as proposed by John H. Kroll (personal communication and cf. also Flament, 2023). The Pb isotope data indicate that our examples were not struck from Athenian silver casting doubt on the current theory that they were restruck Attic coins. These overall findings call for a reassessment of monetary sources, coin circulation, and local minting in the fourth century BCE in the southern Levant. This study also highlights the need for independent archaeological dating beyond reliance upon numismatic typology.</div
Numerical modeling of dust particle motion in a corona discharge-based ionic wind cleaning system for solar panels
No full textInternational audienceThis study explores innovative solutions to reduce efficiency losses in solar panels caused by dust accumulation, using corona discharge as a mitigation method. Ions produced by the positive or negative corona discharge transfer momentum to neutral air molecules through collisions, resulting in an airflow (ionic wind) that can help to eliminate dust accumulation. The cleaning system whose operation is numerically modeled consists of a corona blower device that moves along the panel, conveying the dust in a linear direction and providing a non-contact cleaning method. Dust particles are affected by different forces, such as Coulomb force, gravitational force, aerodynamic drag force, and van der Waals adhesion. Poisson's equation, the continuity equation for charged particles and the Navier-Stokes equations are solved to evaluate the Coulomb and drag force. Emphasis is placed on understanding how forces affect particle trajectories, and which forces are most relevant to the operation of the cleaning system
LPV system identification with unknown scheduling variable
No full textA Linear Parameter Varying (LPV) system is a system whose parameters depend on an exogenous variable, the so-called scheduling variable. LPV systems are generally controlled using LPV controllers i.e., controller whose parameters also depend on the scheduling variable. In order to be able to use an LPV controller for an LPV system, it is generally assumed that the scheduling variable of the LPV system is either fully known or measurable. Here, we consider the case where the scheduling variable has to be identified based on data collected on the system. We do that in the case of LPV systems that are successively operated at different constant values of the scheduling variable. We show how to identify the maximum likelihood estimate of the unknown constant scheduling variable and we derive the statistical properties of this estimate. Moreover, we also develop an optimal experimental design framework in order to optimally design the experimental conditions of the identification experiment yielding the estimate of the scheduling variable
Euclid preparation. Decomposing components of the extragalactic background light using multi-band intensity mapping cross-correlations
No full textInternational audienceThe extragalactic background light (EBL) fluctuations in the optical/near-IR encode the cumulative integrated galaxy light (IGL), diffuse intra-halo light (IHL), and high- sources from the epoch of reionisation (EoR), but they are difficult to disentangle with auto-spectra alone. We aim to decompose the EBL into its principal constituents using multi-band intensity mapping combined with cosmic shear and galaxy clustering. We develop a joint halo-model framework in which IHL follows a mass- and redshift-dependent luminosity scaling, IGL is set by an evolving Schechter luminosity function, and EoR emission is modelled with Pop II/III stellar emissivities and a binned star-formation efficiency. Using mock surveys in a flat CDM cosmology with ten spectral bands spanning 0.75-5.0 in the NEP deep fields over about 100 with source detections down to AB=20.5 for masking, and six redshift bins to , we fit auto- and cross-power spectra using a MCMC method. The combined SPHERExEuclid analysis recovers all fiducial parameters within 1 and reduces 1 uncertainties on IHL parameters by 10-35% relative to SPHEREx EBL-only, while EoR star-formation efficiency parameters improve by 20-35%. Cross-correlations reveal a stronger coupling of IHL than IGL to the shear field, enhancing component separation; conversely, the EoR contribution shows negligible correlation with cosmic shear and galaxy clustering, aiding its isolation in the EBL. Relative to the SPHEREx EBL-only case, the inferred IHL fraction as a function of halo mass is significantly tightened over , with uncertainties reduced by 5-30%, and the resulting star-formation rate density constraints extend to , with uncertainty reductions of 22-31%
Elementary blocks of Loop Quantum Gravity
No full textInternational audienceWe embark on the vast program of integrating the dynamics of Loop Quantum Gravity (LQG). Adopting the strategy of decomposing spin network states into small blocks of (quantum) geometry which can later be glued back together, we focus on the more modest objective of studying the Hamiltonian dynamics on the {\it candy graph}, that is two nodes linked together by an arbitrary number of edges and also having open edges. This elementary setting allows both for curvature to develop around the bulk loops and both non-trivial boundary data and dynamics on the open edges. We study this system at the classical level and leave the detailed of its quantum regime for future investigation. Working on a single loop with two external legs, we show how the LQG Hamiltonian ansatz reduces to a pair of non-linear differential equations, similar to the cubic Schrödinger equation, on the areas carried by the bulk links. We provide analytical solutions to this evolution equation, identifying oscillatory modes (bounded modes) and divergent modes (similar to bouncing cosmological trajectories). This provides an explicit template for future investigations of LQG dynamics on more sophisticated spin network architecture built as arrays of candy graphs
