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Identification d'un modèle d'endommagement à l'échelle du pli composite grâce à des essais hors-axe d'orthotropie
No full textInternational audienceTheidentification of the mechanical properties of composite materials is usually performed on specimens with well suited ply stackings. The industrialists designing CMCs parts face high production costs, and difficulties in producing tailor-suited specimens without compromising the representativeness of the manufacturing process. The frame of this work is the mechanical characterization and modelling of a Carbon / Crbon Composite (CCC) material, with no possibility of performing tests on different ply stackings. The in-plane shear properties of composite materials are usually measured by performing simple and standardized tests, such as the (±45°)ns ply stacking tensile tests. These methods cannot be put in place for the characterization of the studied CCC because it is not posible to adapt the manufacturing process to produce this kind of specimens. To palliate this issue, an off-axis tensile test fixture, greatly inspired by the works of [2], [3] and [4], has been designed to allow the measurement of the shear properties of the CCC. This fixture allows the rotation of the grips in the testing plane, with a center of rotation on the border of the effective area of the specimen. These boundary conditions allow the edges of the specimen to rotate freely during the test, which guarantees more uniform strain and stress fields despite the off-axis loading. The identification of the virgin shear modulus of a unidirectional (UD) Carbon / Epoxy composite using this fixture has been presented in [1]. The results were considered satisfying, with a 5% difference relative to standard (±45°)ns tests, which shows the fixture is working for the measurement of the elasticity parameters. These works are extended here, with a new experimental campaign in order to validate the f ixture use for the identification of the parameters of a damage model coupled to inelastic strains for UD composites [5]. Out of axis tensile tests (45°) allow, thanks to the presented fixture, to measure the shear G12 and transverse E2 moduli during the same test, using strain measurements in three different directions. Load-unload cycles allow the computation of the damage variables associated to the variations of the moduli, but also the measurement of the inelastic strain during the test. Tests performed on the rotating fixture, with a 45° off-axis configuration, are compared to standard tests on (±45°)ns and (90°)n, completed with tensile tests on (±67.5°)ns to identify the transverse / shear coupling [6]. To put it in a nutshell, a new ouf-of-axis tensile fixture is presented again, and is tested for the identification of the non-linear transverse and shear behavior of UD composites.L’identification des propriétés mécaniques des matériaux composites est généralement réalisées sur des échantillons dont l’empilement est adapté. Les industriels qui conçoivent des pièces à partir de CMCs sont confrontés aux prix élevés de la production, et aux difficultés de fabriquer des éprouvettes surmesure sans compromettre la représentativité du processus de production. Le cadre des travaux ici présentés est la caractérisation mécanique d’un composite Carbone / Carbone, sans la possibilité de réaliser des essais sur différentes séquences d’empilement. Les propriétés en cisaillement des matériaux composites sont classiquement mesurées en utilisant des essais simples et standardisés, comme les essais de traction sur empilements (±45°)ns. Ces méthodes ne peuvent pas être mises en place pour la caractérisation du composite C/C étudié car il est impossible d’adapter le processus de production pour fabriquer des éprouvettes adaptées. Pour pallier ce problème, unmontagepermettantderéaliser desessais detraction hors axe d’orthotropie, grandement inspirés des travaux de [2], [3] et [4], a été conçu pour permettre la mesure des paramètres d’intérêt. Ce montage autorise les rotations dans le plan d’essai des mors, dont les centres est situé aux bords de la zone utile de l’échantillon. Ces conditions aux limites permettent aux bords de l’éprouvette de tourner librement durant l’essai, ce qui permet d’obtenir des champs de contraintes macroscopiques et de déformations plus uniformes, malgré le chargement hors-axe. L’identification du module de cisaillement vierge d’un composite Carbone / Epoxy unidirectionnel en utilisant ce montage a été présentée en [1]. Les résultats ont été jugés satisfaisants, avec une différence de 5% par rapport à des essais normés, ce qui illustre le bon fonctionnement du montage pour l’identification de paramètres d’élasticité. Ces travaux sont étendus ici, avec une nouvelle campagne expérimentale afin de valider l’utilisation du montage pour l’identification des paramètres d’un modèle d’endommagement couplé à des anélasticités pour les composites unidirectionnels [5]. Des essais de traction hors-axe (45°) permettent, grâce au montage présenté, la mesure du module de cisaillement G12 et du module transverse E2 en un seul essai, en utilisant des mesures de déformations dans trois directions. Des cycles de charge / décharge permettent le calcul des variables d’endommagement associées aux évolutions des modules d’intérêt, mais aussi la mesure des déformations anélastiques pendant l’essai
Translational profiles of interfascicular fibers and xylem cells connect sugar transporters to xylem development
No full textInternational audienceIn plant cells, carbohydrates serve multiple essential roles, including central metabolism, storage as soluble or insoluble sugars, and polysaccharide synthesis. They also act as signaling molecules and protective agents during abiotic stress responses. Effective intercellular and intracellular sugar transport is essential for regulating sugar partitioning at the subcellular level and for enabling cell-to-cell and long-distance translocation, both of which contribute to overall carbon allocation at the tissue and plant levels.The vascular system comprising of phloem, (pro)cambium, and xylem, is crucial for sugar transport. At the cellular level, cytosolic sugar availability is regulated through sugar exchanges at the plasma membrane and tonoplast, driven by active and passive sugar transporters. This sophisticated regulation indicates a finely tuned balance of sugar transport and homeostasis within the vascular tissues. However, the role in vascular tissue development of sugar availability in vascular cells remains incompletely understood.To identify novel molecular players linking sugar transport and xylem development, we conducted TRAP-seq analysis in Arabidopsis thaliana stem using cell type-specific promoters (pVND7, pVND6, pLAC17, pNST1, and pSWEET17) to profile the translatome in interfascicular fibers and xylem cell types. We also developed an R Shiny app, Arabidopsis Gene Network Explorer (ARAGNE), which enables user-friendly gene functional analysis (GO and KEGG) and network generation and visualization in Cytoscape. This approach revealed new gene networks associated with different cell types, including several genes coding for sugar transporters differentially expressed between interfascicular fibers and xylem cell types, notably members of the tonoplastic ESL and SWEET transporter families. An in-depth functional characterization of tonoplastic SWEET transporters expressed in these tissues allowed us to demonstrate their critical role in vascular system development. Our findings highlight the importance of precisely regulating intracellular sugar transport to ensure proper plant growth and vascular tissue differentiation
Self-interacting approximation to McKean-Vlasov long-time limit: a Markov chain Monte Carlo method
No full textInternational audienceFor a certain class of McKean-Vlasov processes, we introduce proxy processes that substitute the mean-field interaction with self-interaction, employing a weighted occupation measure. Our study encompasses two key achievements. First, we demonstrate the ergodicity of the self-interacting dynamics, under broad conditions, by applying the reflection coupling method. Second, in scenarios where the drifts are negative intrinsic gradients of convex mean-field potential functionals, we use entropy and functional inequalities to demonstrate that the stationary measures of the self-interacting processes approximate the invariant measures of the corresponding McKean-Vlasov processes. As an application, we show how to learn the optimal weights of a two-layer neural network by training a single neuron
1736. Les négociants de Francfort, l’empereur Charles VI et la liberté du commerce lorrain
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Role of Innate Immune and Inflammatory Signaling in West Nile Virus Tropism and Neuronal and Glial Cell Death
No full textAbstract West Nile virus (WNV) is a mosquito-borne virus that causes severe neurological disease in humans. Despite substantial advances, our knowledge of the mechanisms involved in damaging the human brain is still limited. To address this gap, we developed a physiologically relevant in vitro model using human neuronal/glial cells and aimed to determine WNV tropism, assess whether the virus induces innate immune and inflammatory responses, and elucidate the resulting pathophysiological consequences. We found that WNV productively infected glial cells, whereas neurons exhibited a remarkable and unexpected resistance to infection. Despite the induction of a robust innate immune response mediated by IFN signalling and a rapid control of WNV replication in glial cells, we observed substantial death of astrocytes, oligodendrocytes, and neurons. Analysis of cytokine and chemokine expression further revealed that infection triggered an inflammatory response, potentially contributing to bystander cell death. We also showed that IFN signaling did not contribute to the resistance of neurons and identified IFI6 as an effector of the antiviral response in human glial cells. Together, our results underscore the importance of human neural models for confirming previous findings obtained in less physiologically relevant models and for unravelling novel cellular and molecular mechanisms
Face à la bureaucratie de la violence : les faussaires de la Résistance (1940-1944)
No full textInternational audienc
Endogenous Discounting and Economic Dynamics
No full textWe study a discrete-time optimal growth model with endogenous discounting.The discount factor may depend on both consumption and the capital stock, and intertemporal utility is modeled as a discounted sum of instantaneous utilities, with the sum of discount factors equal to one. We show that this specification preserves the invariance of optimal paths and steady states to affine transformations of the instantaneous utility function, providing a general and flexible framework for analyzing economic dynamics under endogenous time preference.We prove that optimal capital paths are monotonic, and steady states depend on initial conditions. We also show the robustness of poverty traps under endogenous discounting: in several examples, for a set of parameters with positive measure, the optimal path converges to a positive steady state only if the initial capital stock exceeds a critical level and otherwise converges to the origin.</div
Can supply chain integration mitigate the risks inherent in circular economy transition?
No full textFNEGE 3, ABS 3International audienceThe Italian furniture industry increasingly adopts circular economy (CE) practices to address sustainability challenges. However, CE implementation introduces specific risks related to supply chain fragmentation, traceability issues and consumer resistance to sustainable materials. In this context, supply chain integration (SCI) emerges as a critical capability for managing complexity and uncertainty, yet its role in CE-related risk mitigation remains underexplored. While prior studies have examined CE and supply chain risk management (SCRM) separately, few have investigated how integration across supply chain actors enables firms to manage the specific risks of circular transitions. This study employs a multiple case study approach to address this gap, analysing five Italian furniture firms with varying CE maturity levels. Findings show that CE practices, such as the reuse of materials, the refurbishment of end-of-life products and digitalisation, are widespread, yet uneven in their impact. Companies with more advanced SCI systems, including shared data platforms and co-sourcing agreements, are better positioned to mitigate operational and reputational risks. In contrast, firms with limited integration face obstacles in scaling CE due to inefficiencies and low coordination. The study highlights SCI not only as a strategic enabler for circular adoption under uncertainty, but also as relevant for mitigating the risks associated with CE implementation. The findings underscore the need for supportive policy frameworks that foster supply chain integration as a means to reduce risks related to circular transitions and promote their broader adoption
Defining the concept of Massive Collective Intelligence Devices (MCID) : insights from the field
No full textInternational audienceThis article examines the role of Artificial Intelligence (AI) in Collective Intelligence (CI). More precisely, it focuses on large-scale deliberative tools that facilitate participatory decision-making in both democratic and corporate contexts. The research highlights the interplay between humans and AI, emphasizing that these tools, while promising, often result in centralized decision-making, contradicting the ideal of distributed CI found in the reference literature. The empirical study is based on qualitative methods and underscores gaps in empirical evidence of the newly emerging field of collective intelligence in the AI era. After highlighting a few results regarding the characteristics of these tools, the paper calls for more explicit terminology to describe them better and analyze them. The paper aims to propose the term "Massive Collective Intelligence Devices (MCID)." Thus, this article proposes a new concept based on an empirical study and a critical literature review
Exploratory study of accounting rules and practices for crypto-assets: an international evidence
No full textInternational audienceGiven the ongoing evolution, growth potential and diversity of crypto-assets as so as their unique and risky nature, there are intensive debates on the accounting treatment by holders and issuers of crypto-assets at the international level. The purpose of this research is to deepen knowledge about accounting rules and practices adopted in Europe, US and Asia. In the first stage, we make a literature review and a critical analysis of existing accounting rules and guidance in an international perspective. In the second stage, we collect the data from the annual financial reports of 30 publicly listed companies for the 2021, 2022 and 2023 periods. These companies come from following countries: US, Canada, France, UK, Germany, Thailand, China, Japan and Autralia. The study aims to inform standard setters, financial statement preparers and users of the implications of financial accounting rules and practices, to draw up challenges for auditing and taxation purposes as so as to impact future authoritative guidance