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Metrological framework and modulation-frequency optimization for robust near-field electromagnetic characterization via pulsed light fluorescence thermography
No full textInternational audienc
EROS light-curve database
No full textInternational audienceContext. The project called Expérience de Recherche d'Objets Sombres (EROS) carried out photometric surveys of dense stellar fields toward the Magellanic Clouds (LMC and SMC), the Galactic bulge and Galactic spiral arms in the period 1990-2003. The main goal of the experiment was to search for the Galactic dark matter in the form of massive compact objects (machos) through the gravitational microlensing effect. Aims. The historical record of the flux variations in the monitored stars by EROS-2 will be a unique asset for time-domain astronomy and to complement current and future searches of transient sources. Methods. We describe the set of light curves that was obtained with the EROS-2 program from 1996 to 2003, when more than 86 million stars were monitored. The set is publicly released through the Centre de Données de Strasbourg (CDS). This dataset includes 28.7 and 4.0 million light curves in the LMC and SMC, 42.9 million light curves in the Galactic bulge, and 10.4 million light curves toward the Galactic spiral arms and has several hundred measurements for each object. The data from EROS-1 are also being released.Results. The object catalog, light curves, and images are accessible through the CDS portal. This is useful for determining the past behavior of newly discovered variable objects.</div
Surface emission studies of ion-beam bombarded thin melamine coatings on carbon substrates
No full textInternational audienceThe knowledge of nitrogen content evolution in organic targets, as a function of beam fluence and surface roughness, is crucial in several research and applied fields. We investigated the degradation of melamine (C3H6N6) coatings, deposited on very thin carbon layers, under ion-beam bombardment at high-power density (≈150W/m2). Two types of effects due to the ionic collisions are observed: a prompt ejection of nitrogen atoms, occurring at a low particle fluence, and a subsequent, much slower, release of nitrogen, leading to a saturation-like effect. A detailed analysis of several long-lasting measurements with different layers revealed interesting inverse correlations between the yields of nitrogen ejections and the particle flux. Further, the damage cross section of melamine, leading to nitrogen emission during the slow phase, seems strongly connected to the surface roughness of the carbon backing used to host the melamine material
Écrire l’histoire des femmes et de la photographie dans l’espace atlantique
No full textLes femmes ont contribué à façonner l’histoire de la photographie et de ses circulations transatlantiques depuis les débuts du medium. Écrire cette histoire du point de vue des femmes invite à déplacer notre regard et nos cadres de lecture pour mettre en lumière leurs rôles de passeuses à la croisée des scènes culturelles
Guiding eQTL mapping and genomic prediction of gene expression in three pig breeds with tissue-specific epigenetic annotations from early development
No full textInternational audienceGene expression is a dynamic phenotype influenced by tissue-specific regulatory mechanisms, which can modulate expression directly or indirectly through cis or trans factors. Identifying genetic variants in these regulatory regions can improve both expression quantitative trait locus (eQTL) mapping and gene expression prediction. Whole genome sequences offer the possibility for enhanced eQTL mapping accuracy, but detecting causal variants remains challenging. Here, we evaluate the potential added-value of integrating tissue-specific epigenetic annotations, such as chromatin accessibility and methylation status, into within-breed genomic predictions of expression for three pig breeds. Functional annotations from early developmental stages improved eQTL mapping interpretability as shown by the enrichment of trait-relevant QTLs. However, despite the use of functional annotations, predictions across breeds remain challenging due to differences in genetic architectures. Our work contributes to the understanding of gene expression regulation in livestock and highlights the value of functional annotations, despite continued challenges for predictions across breeds
Interface oxyde semiconducteur - électrolyte aqueux pour la conversion de l'énergie solaire
No full textNowadays, responding to the climate emergency and reducing our greenhouse gas emissions also means optimizing the conversion of existing renewable energy sources such as the Sun light, wind, hydropower, etc. into other types of energy (e.g., electrical, chemical, etc.) which, in turn, will then be used in various applications. As such, part of our research activity must be directed towards the study and optimization of abundant materials with a low carbon footprint for an overall positive balance. In this manuscript I present the production of clean hydrogen by solar water splitting using sunlight and semiconductor oxides. The semiconductor-electrolyte oxide interface plays the central role in this redox reaction. For this reason, the physicochemical characterization of this interface using photoelectrochemical characterization techniques and X-ray spectromicroscopy, at macro- and microscopic scales is essential and must be carried out according to a rigorous and perfectly defined methodology. I wrote this manuscript to be the starting point for the research work of anyone who will work on this topic. I detail several techniques and analysis methods at the interface between electrochemistry, solid-state physics and physical chemistry of materials with the hope that they would be useful for this research activity. The most significant results, my current research project, and the prospects for collaboration and research will be detailed at the end of the manuscript.Aujourd’hui, répondre à l’urgence climatique et réduire nos émissions à effet de serre consiste aussi à optimiser la conversion des sources d’énergie renouvelables existantes comme la lumière du Soleil, le vent, la force hydraulique, etc. dans d’autres types d’énergie (e.g. électrique, chimique etc.) qui, à leur tour, seront ensuite utilisés dans le cadre des diverses applications. A ce titre, une partie de l’activité de nos recherches doit être orientée vers l’étude et l’optimisation de matériaux abondants, ayant une faible empreinte carbone pour un bilan global positif. Dans ce manuscrit je présente la production d’hydrogène « propre » par photoélectrolyse de l’eau, utilisant la lumière solaire et des oxydes semiconducteurs. L’interface oxyde semiconducteur-électrolyte joue le rôle central dans cette réaction d’oxydoréduction. Pour cette raison, la caractérisation physico-chimique de cette interface employant des techniques de caractérisation photoélectrochimiques et de spectromicroscopie de rayons X, à des échelles macro- et micro- scopiques est primordiale et doit être réalisée suivant une méthodologie rigoureuse et parfaitement définie. J’ai rédigé ce manuscrit pour qu’il soit le point de départ pour le travail de recherche de toute personne qui travaillera sur cette thématique. Je détaille plusieurs techniques et méthodes d’analyse à la frontière entre l’électrochimie, la physique du solide et la physico-chimie des matériaux dans la perspective qu’ils soient utiles pour aborder cette activité de recherche. Les résultats les plus marquants, mon projet de recherche actuel ainsi que les perspectives de collaboration et de recherche seront détaillés à la fin du manuscrit
Brutus: A semi-exhaustive program for indexing powder diffraction patterns by using consumer grade GPU
No full textThe ab-initio determination of unit cell parameters from powder diffraction data, known as indexing, is a prerequisite for the structural characterization of new crystalline materials. While exhaustive search algorithms, termed "brute-force" methods, theoretically offer a deterministic solution to the indexing problem by testing all mathematical possibilities, they are computationally intractable for low-symmetry systems due to the factorial explosion of trial hkl sets. In this manuscript, I introduce Brutus, a novel browser-based indexing software that overcomes these hardware limitations by using the WebGPU API. By using parallelization of linear system solving with consumer-grade Graphics Processing Unit (GPU), Brutus enables the evaluation of billions of trial unit cells in a matter of minutes. This paper details the mathematical formalism, the combinatorial search strategy, and the specific memory management techniques required to prevent GPU timeouts, demonstrating that deterministic indexing is a practical routine for the crystallographic community.</div
Did the 2019 Notre-Dame Cathedral Fire impact the lead contamination of sediment in the Seine River in Paris, France?
No full textInternational audienceThe fire that affected Notre-Dame Cathedral in Paris in 2019 has reignited concerns about metal contamination including lead (Pb) in the city. The current research investigated the potential contribution of this event to the contamination of sediment transiting the Seine River. To this end, sediment deposits were collected in Paris just after floods in 2016 (i.e. before the fire), as well as in 2020 and 2021 (i.e. after the fire). They were analysed for fallout radionuclides, organic matter, metal concentrations and Pb isotopic ratios. Results showed that the material deposited by the flood exhibited contrasted characteristics and contamination levels depending on the flood. The major flood event that took place in June 2016 mainly consisted of surface recent material from the upper reaches of the river. This likely explains the large homogeneity of sediment across Paris and the relatively low metal contamination. Then, the occurrence of a lower magnitude flood event in 2020 led to the deposition of a large majority of older subsurface material, likely resuspended from the channel or eroded from the banks. This material showed higher contamination levels than in 2016. Pb levels were particularly significantly higher around Notre-Dame Cathedral. Some samples displayed Pb isotopic signatures that may coincide with those of dust from the Notre-Dame Fire ( 206 Pb/ 207 Pb: 1.1669-1.1685). Finally, in 2021, another winter flood depositing a majority of subsurface material occurred. Overall, the metal contamination levels measured in the material deposited in 2021 were lower than in 2020, except for the sample collected near the Eiffel Tower. These results demonstrate the negligible impact of the Notre-Dame fire on the Pb contamination. In the future, sediment should continue to be monitored to avoid any potential mistrust from the general public, as three bathing sites have been reopened to the public in summer 2025
GaAs solar cell transfer onto copper substrates via thermocompression bonding for photovoltaic thermoelectric hybridization
No full textInternational audienceAbstract For photovoltaic–thermoelectric energy-conversion systems, thermal management is crucial, in particular at the hybrid interfaces in integrated systems, for achieving the best performances. One of the challenges of this integrated PV–TE system is to ensure compatibility in terms of surface area and power generation between PV and TE modules. This work presents the transfer of a 0.5 × 0.5 cm 2 GaAs solar cell onto a copper substrate using Au–Au thermocompression bonding, with a WTi barrier layer to prevent Cu diffusion. Structural integrity and limited interdiffusion were confirmed by scanning electron microscopy. The GaAs substrate was removed via selective etching, and issues with etch selectivity were addressed. Comparison of copper substrates showed that electrodeposited copper offers advantages for scalable bonding. These findings offer a promising approach for efficient thermal management and improving efficiency of integrated photovoltaic–thermoelectric systems