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Temporal and regional X-linked gene reactivation in the mouse germline reveals site-specific retention of epigenetic silencing
No full textInternational audienceRandom X-chromosome inactivation is a hallmark of female mammalian somatic cells. This epigenetic mechanism, mediated by the long noncoding RNA Xist, occurs in the early embryo and is stably maintained throughout life, although inactivation is lost during primordial germ cell (PGC) development. Using a combination of single-cell allele-specific RNA sequencing and low-input chromatin profiling on developing mouse PGCs, we provide a detailed map of X-linked gene reactivation. Despite the absence of Xist expression, PGCs still harbor a fully silent X chromosome at embryonic day 9.5 (E9.5). Subsequently, X-linked genes undergo gradual and distinct regional reactivation. At E12.5, a substantial part of the inactive X chromosome resists reactivation, retaining an epigenetic memory of its silencing. Our findings define the orchestration of reactivation of the inactive X chromosome, a key event in female PGC reprogramming with direct implications for reproduction
Nondestructive testing of railway embankments by measuring multi-modal dispersion of surface waves induced by high-speed trains with linear geophone arrays
No full textInternational audienceTo effectively address engineering challenges and risks, it is crucial to characterize mechanical properties of near-surface environments. The Multichannel Analysis of Surface Waves (MASW) has proven to be a valuable active seismic imaging technique by providing near-surface shear (S)-wave velocities estimations. However, its application to urban areas requires further development. This study leverages well-constrained experimental sites to assess the viability of a passive-MASW technique, utilizing seismic waves induced by high-speed train traffic instead of conventional active sources. We suggest employing short 96-geophone uniform linear arrays to capture surface waves in a broad frequency band (10-200 Hz). Train passages are automatically detected and categorized regarding to the train travel direction. Seismic interferometry and phase-weighted stack techniques are applied to generate virtual shot-gathers that are transformed into high-resolution multi-modal dispersion images. Our results demonstrate a strong coherence between the picked dispersion curves from the passive-MASW approach and those obtained through traditional active MASW with a hammer source. We discuss the validity of higher modes and explore array density limits to ensure reliable results. Our findings highlight that seismic interferometry, coupled with a high phase-weighted stack power, effectively recovers energy at high frequencies, enhancing the characterization of multi-modal surface-wave dispersion associated with thin near-surface layers
Upcycling stale bread into (meso)porous materials: Xerogels and aerogels
No full textInternational audienceThis work explores the upcycling of stale bread into bio-based, low-density porous materials with partial mesoporosity, produced through gelatinization and drying, using either supercritical CO 2 (aerogels) or low-vacuum conditions (xerogels). Cryogels were also fabricated via freeze-drying for comparison purposes. Stale bread particles (Bread) were subjected to proteolytic gluten depletion (Gluten-Depleted Bread, GDB) or particle size reduction (Finely milled Bread, FB) to investigate the effect of protein removal or particle size on porous materials' properties. Porous materials made from wheat starch (WS) and wheat flour (Flour) were also examined for comparison. The solvent exchange induced volume shrinkage (SE-VS), which accounted for over 87% of the total shrinkage, ranged from 62% in GDB to 78% in WS. Bread-based porous materials presented comparable specific surface area (~40 m 2 /g) and water absorption capacity (~400%) to WS materials, but outperformed in resistance to volume shrinkage, resulting in lower density. FB porous materials possessed a higher specific surface area than Bread materials, indicating the benefits of particle size reduction. Furthermore, gluten depletion resulted in GDB-aerogels with the highest specific surface area (~80 m 2 /g), highlighting the benefits of gluten depletion. However, WS materials exhibited significantly greater maximum compressive stress (>2.0 MPa) and compressive modulus (>6 MPa) than stale bread-based porous materials. Importantly, the porous properties of xerogels and aerogels were similar (differences < 10%), indicating the feasibility of using low vacuum drying to produce new porous materials with partial mesoporosity (surface area 60-80 m 2 /g) from stale bread at a lower cost
Can democracy save children’s lives? Addressing the constitutional problem of expertise
No full textInternational audienceThis comment critically examines Collins, Evans, and Reyes-Galindo’s (CE&RG) concept of ‘virtual diversity’, proposed as a norm to safeguard scientific expertise in policy-making. CE&RG argue that scientists should acquire ‘interactional expertise’ in relevant ‘non-scientific domains’, enabling informed policy advice while preserving scientific integrity. This comment describes CE&RG’s dualist approach, which separates epistemic and political concerns, and discusses its implications. It shows that for virtual diversity to contribute to the quality of and trust in expertise, this approach needs to be radically re-worked to include legitimacy-building processes. Using examples such as South Africa’s AIDS policy and the COVID-19 pandemic, the comment argues that defending expertise requires ensuring the robustness of both scientific and political representations, of, in other terms, addressing expertise as a constitutional problem. Without a broader critical constitutional analysis, CE&RG’s proposal risks reinforcing the crisis of expertise it seeks to remedy
Géostatistique et cartographie du fond pédo-géochimique: Test d'application du filtrage géostatistique sur le jeu de données METOTRASS
No full textInternational audienceThe national method for managing polluted sites and soils, as well as the management guides for excavated soils, refer to pedo-geochemical backgrounds as reference values for soil quality. However, due to the absence of specific sampling for determining these values at local or regional scale, a method of geostatistical mapping by filtering by krigeant analysis, aimeing at separating anomalies from the background, was developed (Sauvaget et al, 2022). First tested at the scale of an urban center district, it is here tested at the scale of a department via the METOTRASS dataset. The results obtained show that the method is applicable directly for zinc (taking into account the relationship with altitude) or more indirectly for arsenic, lead and copper by partitioning the territory. Finally, ungrouping applied to data appears to be essential in the statistical processing of data with heterogeneous spatial distribution, as is often the case for data in urban areas.La méthode nationale de gestion des sites et sols pollués, de même que les guides de gestion des terres excavées se réfèrent aux fonds pédo-géochimiques comme valeurs de référence pour la qualité des sols. Or, du fait de l'absence d'échantillonnage spécifique pour la détermination de ces valeurs à échelle local ou régionale, une méthode de cartographie géostatistique par filtrage par analyse krigeante, visant à séparer les anomalies du fond, a été développée (Sauvaget et al, 2022). D'abord testée à l'échelle d'un quartier de centre urbain, elle est ici expérimentée à l'échelle d'un département via le jeu de données METOTRASS. Les résultats obtenus montrent que la méthode est applicable directement pour le zinc (en tenant compte de la relation avec l'altitude) ou plus indirectement pour l'arsenic, le plomb et le cuivre en partitionnant le territoire. Enfin le dégroupement appliqué aux données apparait comme primordial dans le traitement statistique de données à la répartition spatiale hétérogène comme c'est souvent le cas pour les données en milieu urbain
RayGauss: Volumetric Gaussian-Based Ray Casting for Photorealistic Novel View Synthesis
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A scalable solvent-exchange strategy for the drying of colorless Japanese cedar ( Cryptomeria japonica )
No full textInternational audienceThe thermal insulation properties of wood can be improved by wood modification nanotech- nology, but scaling up drying techniques remains a challenge. This study aims to enhance the industrial feasibility of drying colorless (lignin-free) wood by solvent-exchange strategy. In this work, the delignification of Japanese cedar wood was applied through combined organosolv and sodium chlorite bleaching, and different drying techniques were compared to analyze their effects on porosity and dimensional stability, with water, ethanol, or acetone as solvents. The results show that the dimensional stability of colorless wood is strongly influenced by the liquid’s surface tension in the porous structure. Ethanol-exchanged samples dried at 80 °C showed the best balance between drying efficiency and preservation of wood structure, reducing density to 0.16 g/cm³ and increasing specific surface area to 7.2 m²/g. The results describe how the drying step is optimized for the potential large-scale production of functionalized wood scaffolds or bio-based thermal insulators. The findings contribute to understanding colorless wood drying mechanisms and guide the selection of appropriate techniques for desired end-use properties, advancing wood modification nanotechnology
Optimisation Stochastique Distribuée pour la Gestion de Centrales Virtuelles Complexes : Valorisation de la Flexibilité d'une Chaîne de Centrales Hydrauliques au Fil de l'Eau pour l'Intégration des Énergies Renouvelables
No full textThe inherent stochasticity of variable renewable energy sources (vRES) challenges their widespread integration, prompt-ing the emergence of the virtual power plant (VPP) paradigm, which reduces vRES variability through their combined operation with flexible, dispatchable units. As vRES penetration continues to grow, VPPs are expected to expand in portfolio size. However, the portfolio dimension represents only one aspect of the complexity of modern VPPs. These systems also involve factors such as hard nonlinear dynamics, multiple sources of uncertainty, and intricate coupling constraints between aggregated units. Together, these challenges contribute to the evolution of VPPs into large-scale, dynamic systems with complex internal dynamics—referred to here as complex VPPs. A major challenge in the devel-opment of complex VPPs is the need for fast, scalable decision-making tools that can maintain both solution quality and accuracy. To address this, this thesis introduces a two-level, scenario-based, fully stochastic decision-making framework designed to optimize VPP participation in the electricity markets across multiple time stages. The framework is then fully decomposed along both the scenario and spatial dimensions, enabling the creation of a scalable distributed algorithm that guarantees performance, even for mixed-integer VPP models. This methodology is validated through a real-world case study from the French aggregator Compagnie Nationale du Rhône, which manages a complex VPP combining run-of-the-river cascaded hydropower plants, wind, and solar assets. The results show that this complex VPP can enhance vRES integration without relying on conventional storage solutions. Furthermore, the proposed distributed methods effectively address system complexities, providing reliable performance guarantees and scalability for complex VPP operations.La nature stochastique des sources d’énergie renouvelable variables (vRES) pose des défis importants pour leur inté-gration à grande échelle dans les systèmes électriques. Cela a conduit au développement du paradigme des centrales électriques virtuelles (VPP), qui atténue l’intermittence et la variabilité des vRES en les agrégeant avec des unités pilota-bles. À mesure que la pénétration des vRES continue de croître, les VPP devraient se développer en taille de portefeuille. Cependant, la dimension du portefeuille ne représente qu’un aspect de la complexité des VPP modernes. Ces systèmes impliquent également des facteurs tels que des dynamiques non linéaires difficiles, plusieurs sources d’incertitude et des contraintes de couplage complexes entre les unités agrégées. Ensemble, ces défis contribuent à l’évolution des VPP en systèmes à grande échelle et dynamiques, avec des dynamiques internes complexes — que l’on désigne ici sous le nom de VPP complexes. Un défi majeur dans le développement des VPP complexes est la nécessité d’outils de prise de décision rapides et évolutifs capables de maintenir à la fois la qualité de la solution et la précision. Pour y répondre, cette thèse introduit un cadre de prise de décision entièrement stochastique à deux niveaux, conçu pour optimiser la participa-tion des VPP aux marchés de l’électricité sur plusieurs étapes temporelles. Le cadre est ensuite entièrement décomposé selon les dimensions des scénarios et spatiale, permettant la création d’un algorithme distribué évolutif garantissant la performance, même pour les modèles VPP à variables entières mixtes. La méthodologie est validée par une étude de cas réelle de l’agrégateur français Compagnie Nationale du Rhône, qui gère un VPP complexe combinant des centrales hydroélectriques à cours d’eau, des actifs éoliens et solaires. Les résultats montrent que ce VPP complexe peut améliorer l’intégration des vRES sans recourir à des solutions de stockage conventionnelles. De plus, les méthodes distribuées proposées répondent efficacement aux complexités du système, offrant des garanties de performance fiables et une évolutivité pour les opérations des VPP
Qu’est-ce que la "deep tech" ? Définitions et enjeux stratégiques
No full textInternational audienceLe terme "deep tech" s’impose aujourd’hui comme une notion incontournable dans l’univers des technologies, de l’innovation et des affaires. Il suscite un engouement croissant de la part des investisseurs et des acteurs de l’innovation, qui y perçoivent une formidable opportunité de transformations profondes et durables. Cet article propose d’explorer les différentes définitions du concept de "deep tech", d’en analyser les spécificités et les implications réelles, ainsi que d’en dégager les principaux enjeux stratégiques
