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Temps forts en néphrologie en 2025 : avancées diagnostiques, thérapeutiques et enjeux émergents
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Utilisation de plomb pur pour illustrer, à température ambiante, la déformation en fluage de superalliages à haute température
No full textDiscovering the tensile creep phenomenon, using superalloys, by practical work is neither easy, nor with sufficient safety, nor cheap and nor fast enough to be done in a single session. The present study, which is based on the creep of lead at ambient temperature, can be taken as the assembly and the test of a workstation to allow students in Master of Metallurgy or in Materials Science, to experimentally explore the creep phenomenon. This can be done, eventually by conceiving the manipulation themselves and using it, or by exploiting a manipulation previously mounted. In both cases, they can discover, with they own experiences, the three classical steps of a creep deformation, eventually until the final rupture, and investigate the dependence of the steady state creep rate on the constant applied stress and on temperature. Using lead and a device made of very simple and cheap components, allows establishing {time strain} curves on which one can clearly distinguish the primary, secondary (steady state) and tertiary creep steps, as well as the final rupture. Broken specimens can be of course available for post-mortem measurement of the permanent elongation, the striction… Furthermore, carrying out tests for several stresses (by varying either the gauge section or the hanged mass) and for several temperatures around the ambient temperature, may offer to students the opportunity to re-build themselves the power or exponential laws and to deduce the values of the multiplying constants, exponent and activation energy.Expérimenter, sur les matériaux particulièrement concernés (les superalliages notamment), le fluage–traction lors de séances de travaux pratiques n’est pas chose aisée, ni sans risques, ni peu coûteuse, ni suffisamment rapide pour tenir en une séance de travaux pratiques. Cette étude, reposant sur le fluage du plomb à température ambiante, peut être considérée comme le montage, et le test en situation, d’un poste de travaux pratiques pour permettre à des étudiants de Master de Métallurgie ou de Science des Matériaux de découvrir expérimentalement le phénomène de fluage. Cela peut se faire, possiblement en mettant eux-mêmes au point une manipulation et en l’utilisant, ou simplement en exploitant une manipulation déjà montée. Dans les deux cas ils peuvent ainsi découvrir par leurs propres expériences les trois étapes classiques d’une déformation par fluage, éventuellement jusqu’à rupture, et d’étudier la dépendance de la vitesse de déformation en fluage secondaire vis-à-vis de la contrainte et de la température. L’utilisation du plomb et d’un montage avec du matériel potentiellement très simple et peu coûteux, permet en effet de d’obtenir des courbes {temps allongement} sur lesquelles peuvent être distingués les phases primaire, secondaire et tertiaire du fluage, ainsi que la rupture, ainsi que des éprouvettes rompues sur lesquelles on peut voir l’allongement permanent, la zone de striction … Plus avant, réaliser des tests pour différentes contraintes en jouant sur la section de la partie utile de l’éprouvette de fluage-traction et/ou sur la masse à pendre, et ce à plusieurs niveaux de température, peut donner aux étudiants l’opportunité de ré-établir eux-mêmes les lois puissance ou exponentielle et d’en préciser les constantes multiplicatives, exposant et énergie d’activation
The way forward for assessing the human health safety of cosmetics in the EU: Proceedings of Workshop 2
No full textInternational audienceAbstractUnder the European Cosmetic Regulation, safety assessments of cosmetics and their ingredients must be conducted without the use of animals. This regulatory requirement poses a number of challenges, as validated alternative methods are only available for some of the toxicological endpoints that are typically considered in standard human health risk assessments. Despite significant progress since the ban in 2013, particularly in the development of New Approach Methodologies (NAMs) for local and acute toxicity, and for mutagenicity/genotoxicity, there remains an urgent need for non-animal test methods to assess systemic toxicity, which often becomes evident after repeated or long-term exposure. Currently, no validated animal-free alternatives are available for assessing sub-acute, sub-chronic and chronic toxicity, carcinogenicity, developmental/reproductive toxicity, or for a major part of toxicokinetics. In response to these challenges, the Methodology Working Group of the Scientific Committee on Consumer Safety organised a dedicated workshop in December 2024 to discuss advances in the application of Next Generation Risk Assessment (NGRA) as a strategic animal-free approach for the safety assessment of cosmetic ingredients. The workshop focused on a number of important key issues for the practical application of NAMs and NGRA, their regulatory acceptance and identification of possible (partial) solutions to overcome existing limitations
1D linear stability analysis based on an adjusted correction factor for dynamic expansion: Application to plates and rods
No full textInternational audienceThis work investigates the onset and development of plastic strain localization during the dynamic expansion of metallic shells. The multiple necking and fragmentation scenario are here viewed as originating from the development of geometrical perturbations (i.e., surface roughness), whose time evolution plays a critical role for the late free flight of fragments. Based on the extended 1DXLSA (One-Dimensional eXtended Linear Stability Analysis) model of Xavier et al. (2021), and using the 2DXLSA of Xavier et al. (2020) and FEM calculations as references, we propose an adjustment of the stress approximation in the neck section to better capture the onset of multiple necking in cylindrical (plate) and ring (round bar) geometries. A modified Bridgman correction factor is then introduced, which highlights the limitations of the previous 1DXLSA study. A good agreement in terms of time evolution of the perturbations is obtained between Finite element simulations, two-dimensional linear stability approach and the new 1D model
Les élections présidentielles vénézuéliennes de 2024: parachèvement d'une dé-démocratrisation
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Process evaluation of a school-based vaccination intervention to improve HPV vaccine coverage: A mixed-method study embedded in the French PrevHPV cluster randomized controlled trial
No full textInternational audienceBackgroundHuman papillomavirus vaccine coverage (HPV VC) remains suboptimal in many countries. French authorities launched the PrevHPV research program, which included a cluster randomized controlled trial (cRCT) to evaluate the effectiveness of an ‘at-school vaccination’ intervention. Within this trial, we conducted a process evaluation of this intervention, specifically analyzing (i) its implementation, (ii) its mechanisms of impact, and (iii) the contextual factors influencing implementation (facilitators/barriers).MethodWe conducted a mixed-method study embedded in the PrevHPV cRCT (April 2021–April 2022). ‘At-school vaccination’ consisted of vaccination day(s) on school premises where mobile vaccination teams (MVTs) initiated HPV vaccination free of charge for eligible adolescents (i.e., non-vaccinated adolescents aged 11+). Quantitative data were collected through activity reports and self-administered questionnaires of adolescents and school staff. Qualitative data collected through six focus groups with school staff and MVTs were analyzed using thematic analysis.ResultsOf the 31 schools (14,772 adolescents) randomized to implement ‘at-school vaccination’, 12 (39 %) dropped out. Among the participating schools, analysis of implementation showed that 17 % of adolescents returned valid consent forms, of whom 89 % initiated vaccination. MVTs played a central role in implementing vaccination day(s), supported by several school staff (e.g., school nurses, education assistants). Regarding mechanisms of impacts, satisfaction with the vaccination days was high among adolescents and school staff. The intervention generated both positive and negative group effects among adolescents. Contextual factors that facilitated implementation included the preparation of a list of adolescents to be vaccinated and the availability and motivation of school staff. The main barriers related to the management of consent forms and missing health records.ConclusionWe formulated recommendations for implementing at-school vaccination, which may be particularly helpful for the French school HPV vaccination campaigns that were scaled up nationally in 2023. We also discussed potential macro-level improvement strategies, involving modifications to the legislative framework
Exploring the colloidal stability of curcumin nanoparticles formed by nanoprecipitation
No full textInternational audiencePure curcumin nanoparticles were prepared by antisolvent precipitation using acetone as the solvent and water as the antisolvent, offering a simple and food-compatible strategy to enhance curcumin dispersibility in aqueous environments. The colloidal stability of the aqueous dispersions was assessed by static multiple light scattering. Progressive particle size growth led to sedimentation. This study then focused on the stability of nanoprecipitated curcumin prior to sedimentation, in order to unambiguously determine the mechanisms responsible for destabilization. Particle size evolution over time was monitored by dynamic light scattering. The physical state of curcumin was determined by 1 H NMR and XRD analyses, confirming that neither coalescence nor crystallization occurred. Ostwald ripening was successfully confirmed by modeling the particle growth kinetics using the Lifshitz-Slyozov-Wagner (LSW) theory. Nevertheless, it is known that the LSW model remains superficial. That is why an original approach is used in this study to validate the destabilization mechanism. This involves varying the composition of the solvent in order to modify the solubility of curcumin in the continuous phase, a key parameter in the context of Ostwald ripening. Thus, varying the acetone content demonstrated the role of curcumin solubility in governing dispersion stability, confirming that Ostwald ripening occurred, as faster particle growth was observed at higher acetone levels. Moreover, curcumin solubility in the continuous phase derived from the LSW model was consistent with measurements performed by HPLC. These findings demonstrated that amorphous curcumin nanoparticles undergo Ostwald ripening in stabilizer-free aqueous systems, with ripening rates controlled by solvent-induced solubility changes
An updated Lagrangian computational homogenization framework for large deformation of thin composite beams/shells
No full textInternational audienceThe main purposes of the present paper are to present the mathematical and algorithmic aspects of the ANM/FEM numerical model and to show how it is applied to analyze elastic and thermo-elastic nonlinear solid mechanical problems. ANM is a robust continuation method based on a perturbation technique for solving nonlinear problems dependent on a loading parameter. Historically, this technique has been successfully applied to problems in various fields of solid and fluid mechanics. This paper shows how ANM is used to solve nonlinear elastic and nonlinear thermo-elastic problems involving elastic behavior and geometrical nonlinearities. The implementation of ANM for FEM in the FreeFEM++ language is then presented. The FEM software development platform, called FreeFEM++, is structured to work with variational formulations and, therefore, is well adapted to implement ANM for instability problems in solid mechanics. In order to illustrate the great efficiency of FreeFEM++, scripts will be presented for computing the different steps of ANM continuation for solid elastic structures, considering simple geometries subjected to conservative loading. For the purpose of validation, the problem of a cantilever subjected to an applied force is presented. Next, the new numerical model is applied to study wrinkles appearing in a planar film/substrate system that is subjected to compressive surface forces at the lateral faces of the film. Finally, the model is applied to a spherical film/substrate system subjected to thermo-elastic shrinkage. In both cases, the ANM/FEM prediction method, together with a Newton–Riks correction (if needed), identifies the equilibrium paths efficiently, especially after the post-buckling regime
A safari across France: soil fauna insights from a nationwide soil quality monitoring program
No full textInternational audienceSoil biodiversity is fundamental to ecosystem functioning but remains underrepresented in conservation policies and large-scale monitoring. Here, we present RMQS-Biodiversity, a nationwide soil biodiversity survey integrated into the French Soil Quality Monitoring Network (RMQS), and illustrate its potential for soil ecology research. In this pioneer study, we examine three major ecological aspects: (i) how systematic grid-based sampling captures micro-food web patterns using nematode communities, (ii) the spatial turnover of detritivore communities (Collembola, Isopoda, Diplopoda) in response to environmental and geographic gradients, and (iii) the influence of macroecological drivers on predator (Carabidae) morphological traits. Across 69 sites, we identified a few widespread species coexisting with numerous rare taxa, underscoring the value of large-scale surveys for detecting cryptic biodiversity. Nematode indicators revealed high variability in food web structure across land uses, with increased facultative phytophagous nematodes in forests. Isopods and diplopods were strongly structured by dispersal constraints, while springtails exhibited weaker environmental responses, likely due to their higher dispersal capacity. Additionally, sexual size dimorphism in Carabidae varied by habitat, with female-biased dimorphism in closed habitats but no dimorphism in open environments, highlighting habitat stability's role in shaping morphological traits. This study demonstrates the value of multi-taxon, multi-trophic biodiversity assessments in long-term soil monitoring. RMQS-Biodiversity provides a robust framework for soil biodiversity monitoring and conservation, refining bioindicators of soil quality and informing policies such as the EU Soil Monitoring Law
Sol-gel auto-combustion synthesized ZnMn<sub>2</sub>O<sub>4</sub> for efficient photocatalytic Congo red degradation: structural, kinetics, computational, and ecotoxicity analyses
No full textInternational audienceZnMn2O4 was obtained via the sol-gel auto-combustion method to investigate the photocatalytic degradation of Congo Red (CR) under solar irradiation. Various characterization techniques were employed to determine its structural, morphological, optical, and electrochemical properties. XRD confirmed the tetragonal phase (I41/amd) with a crystallite size of 20.17 nm. The material exhibited a specific surface area of 37.32 m 2 /g. A direct bandgap energy of 1.97 eV was determined. Electrochemical analysis revealed a flat band potential of -0.121 V/SCE, indicating p-type behavior. Adsorption kinetics followed a pseudo-second order model, with the Langmuir isotherm providing the best fit, and a monolayer adsorption capacity of 12.155 mg/g. Photocatalytic experiments demonstrated 87.50% CR removal within 3 h under sunlight at a catalyst dosage of 0.8 g/L. The degradation followed pseudo-first order kinetics, with an apparent rate constant (Kapp) of 0.01074 min -1 and a half-life (t1/2) of 64.53 min. Photocatalytic efficiency was influenced by photocatalyst dosage, dye concentration, pH, and scavengers. Incorporating TiO2 improved degradation performance, achieving complete CR removal within 3 h. Recyclability tests confirmed structural stability, with no significant peak 2 shifts or phase transformations after multiple cycles. DFT calculations classified CR as a soft molecule based on its electronic properties. Monte Carlo simulations demonstrated exceptionally strong interactions in the CR/ZnMn2O4 system, with an adsorption energy of -16147.31 kcal/mol. Molecular dynamics simulations further verified CR's superior adsorption affinity for ZnMn2O4 compared to RhB. Notably, ecotoxicity evaluations revealed that the photocatalytic degradation byproducts showed substantially lower acute toxicity than the parent CR compound