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Episciences: Bridging Open Repositories for Diamond OA Publishing Workflows and Enhanced Metadata Interoperability
No full textInternational audienceEpisciences is a comprehensive platform for editing and publishing scientific overlay journals across all disciplines. It adheres to the Diamond Open Access model-free of charge for both authors and readers-and incorporates aspects of the Green Open Access model by hosting content in open repositories. As part of the European open access infrastructure ecosystem, Episciences integrates with databases and indexing services to provide enriched metadata and ensure broad and effective dissemination of publications
Hydrolytic aging-induced embrittlement in short-fiber reinforced polyamide: A micromechanical approach using numerical homogenization
No full textInternational audienceThis work introduces a simulation framework for predicting the durability of 30 wt.% glass fiber reinforced polyamide-66 (PA66-GF30) composites under hydrolytic aging by directly coupling a chemical aging descriptor, the number-average molar mass (Mn), with a local mechanical failure indicator at the matrix level. Unlike prior studies that correlates Mn with global composite properties such as strain-at-break or maximum stress, the proposed approach targets the polyamide matrix, which is primarily affected by hydrolysis, enabling a more physical description of embrittlement. The identification of a local failure indicator was performed using FFT-based numerical homogenization on a representative three-dimensional microstructure, which was reconstructed from high-resolution micro-computed tomography (μCT) data. Accumulated plastic strain (APS) was found as a robust, orientation-independent criterion of failure initiation that correlates linearly with the drop of the Mn. The model predicts a critical Mn of approximately 18kgmol-1 for full embrittlement in PA66, consistent with values of the literature. Failure modeling was validated at the macroscale using FE-based simulations of hydrolyzed injection-molded components loaded in tension mode. This modeling approach is applicable to different hygro-thermal conditions and constitutes one of the first integrated chemo-mechanical simulation methods for fiber-reinforced polyamides. This framework provides a promising route for mechanistic-based lifetime assessment of polymer-based engineering components in hydrolytic environments
Environmental and technical efficiency of French sheep farms in less favored areas: off-season production penalizes environmental performance
No full textInternational audienceGiven the need for farms to reduce their negative environmental impacts while maintaining their productive performance, this study analyzes the technical and environmental efficiency of a sample of sheep farms in France, with a focus on greenhouse gas emissions and nitrogen surplus. To do so, we use a multi-equation stochastic frontier approach that accounts for the physical processes that generate environmental pollution. The results indicate that, on average, the potential technical and environmental efficiency gains for the farms in our sample would be approximately 20% if they could align their practices with best practices observed. The results also show that farms with low environmental efficiency have a high proportion of out-of-season production to meet the sheep industry’s demand, which increases their use of concentrates, nitrogen on forage areas, and energy, thereby worsening their environmental performance. Likewise, econometric estimates show that while off-season production could enhance farms’ productive efficiency, it is detrimental to their environmental efficiency. A set of production practices was identified as suitable for alleviating this issue by improving both the technical and environmental efficiency of the sheep farms in our sample
Insights Into the Mechanisms Controlling the Residual Strength of Bio‐cemented Sands
No full textInternational audienceMicrobially induced carbonate precipitation (MICP) is an emerging technique for enhancing the mechanical properties of granular soils. Although several experimental studies have reported increased shear strength in MICP‐treated soils at both peak and residual states, other findings have shown reductions in residual strength compared to untreated soils. This study uses the discrete element method (DEM) to investigate the mechanisms governing the residual strength of bio‐cemented sands. The results indicate that residual strength may decrease when carbonate precipitates in the form of grain‐bridging patterns. In that case, the introduction of carbonates alters the contact network and may induce metastable configurations, particularly when the bonds are weak or non‐cohesive. These configurations are prone to strain localisation upon shearing, leading to the development of shear bands and a reduction in residual strength. Conversely, higher cohesive strength enhances microstructural stability, offsetting the weakening effects of localisation. The residual strength of bio‐cemented sands is therefore governed by two competing mechanisms, namely bond‐induced stabilisation and instability‐driven localisation
Sooty terns as large-scale bioindicator of mercury contamination in marine ecosystems: A pantropical approach
No full textInternational audienceMercury (Hg) is a toxic contaminant, which poses serious threats to both wildlife and humans worldwide. Although tropical oceans receive half of the world’s atmospheric Hg depositions, its biomonitoring is largely overlooked in these ecosystems. This study provides a comprehensive, pantropical assessment of Hg contamination of marine ecosystems, using the sooty tern (Onychoprion fuscatus) as bioindicator. Total Hg concentrations were measured from feathers collected in 28 colonies across all tropical oceans (2003–2022), from adults (n =564) and chicks (n =407), to evaluate longer- and shorter-term contamination. To investigate the role of bird trophic ecology on Hg contamination, bulk stable isotopes of carbon (δ13C) and nitrogen (δ15N) were also analysed, as respective proxies for feeding habitat and diet. Because baselines of stable isotopes may vary at large spatial scales, compound-specific nitrogen stable isotope analyses of amino-acids were performed on a subset of adults (n =91, 19 colonies), to calculate their trophic position (TP), accounting for both baseline and trophic effects. As expected, Hg concentrations were higher in adults than chicks, because of their shorteraccumulation period. Overall, colonies from the Northern Hemisphere exhibited the highest Hg concentrations, consistently with higher historical anthropogenic emissions of Hg in the North. Models revealed that Hg contamination was driven by environmental contamination (colony location, feeding habitat) rather than diet (TP), which remained similar across the pantropical range. Our findings provide important baseline data for tropical marine ecosystems and underscore the need for enhanced monitoring in regions, where gold-mining and changing oceanographic conditions will likely modify future Hg exposure
Natural variation in Arabidopsis uncouples leaf and flower development and reveals massive transcriptomic heterochrony
No full textInternational audiencePlant development is a sequence of precisely timed and spatially coordinated events that produce organs such as leaves and flowers. In Arabidopsis thaliana, for example, the development of leaves (called bracts in the inflorescence) halts once the first flower forms. Understanding how this transition is regulated is key for decoding how developmental programmes are coordinated during the floral transition. In this study, we investigated a natural phenotypic variation that uncouples bract repression from flower initiation. We discovered that the continued formation of bracts after the floral transition involves complex genetic interactions across at least four loci. Interestingly, none of these loci included known floral identity genes previously linked to bract repression, pointing to novel regulators in the coordination of bract and flower development. Using time-series transcriptomics and curve registration, we found that differences in gene expression levels when bracts persist are mainly driven by a massive desynchronization of gene dynamics. This affects a wide range of biological processes beyond those associated with leaf identity. These findings align with the ‘inverse hourglass’ model, which proposes that transcriptomic divergence at transitional stages contributes to morphological variation. Our results suggest that this model may also explain trait variability within species, highlighting how transcriptome dynamics shape phenotypic robustness during developmental transitions
Hysteresis phenomenon within unsaturated granular assemblies: Capillary forces and matric suction
No full textInternational audienceIn this paper, we present a numerical approach to simulate the condensation and evaporation processes of capillary bridges within granular materials. The formation and dynamics of capillary bridges are captured using the phase-field-based Lattice Boltzmann model (LBM) to solve Allen-Cahn and Navier-Stokes equations, while evaporation and condensation processes accounted by local changes in position of the capillary interfaces. Our model captures the emergence of hysteresis as a result of irreversible geometric transitions-such as bridge coalescence and snap-off-without prescribing any constitutive relation between suction and saturation degrees. This change in capillary regimes arises naturally from the interface dynamics and not solved by the LBM. In particular, we can capture and analyze the discontinuities in capillary forces, when capillary bridges merge or split within small elementary assemblies of three or four spherical particles. Having validated our numerical results for the above elementary assemblies, a poly-dispersed granular assembly composed of 1,000 spherical grains is next addressed. Our simulations capture well-known condensation and evaporation hysteresis phenomenon while offering the possibility to inspect the underlying topology of air/water cluster for the same water saturation along different hydraulic paths
Évaluer l’impact des jeux sérieux pour les transitions: Guide méthodologique
No full textThis guide is a resource for anyone using serious games (SGs) to support sustainability transitions and who wishes to understand their impact. It proposes a comprehensive evaluation approach enabling the analysis of change both in itinere (during implementation) and ex post.Ce guide s’adresse à toute personne mobilisant les jeux sérieux (JS) comme outil d’accompagnement des transitions et qui souhaite en évaluer l’impact. Il propose une démarche d’évaluation réflexive permettant d’analyser le changement in itinere et ex post
Minimum wages in a dual labor market: Evidence from the 2019 minimum-wage hike in Spain
No full textNational audienceThis paper provides an assessment of the 2019 minimum-wage hike in Spain, which increased the minimum wage by 22 % and directly concerned 7 % of dependent employees. We make use of two complementary approaches, one that follows incumbent workers over time and hence does not take account of any possible effects on new hires, and one that tracks employment in wage bins over time and takes account of both separations and new hires. The results are as follows. First, the minimum wage hike significantly increased the wages of directly affected workers, with small positive wage spillovers on workers with initial wages just about the new minimum wage. Second, the increase in wages comes at the expense of a reduction in low-wage employment. While employment increases just above the minimum wage, it is not sufficient to offset the decline in employment below it. Third, the reduction in employment is mainly driven by a reduction in hires of workers on open-ended contracts and to a smaller extent job losses among workers on fixed-term contracts. This illustrates that limiting the study of minimum wage hikes to stayers can dampen the estimated impact on employment