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A multiscale investigation of uranium(VI) interaction with a freshwater diatom species
No full textInternational audienceDiatoms are essential bio-indicators for assessing the impact of heavy metals and hazardous materials on aquatic ecosystems. This study seeks to advance our understanding of the interaction between uranium (U) and the freshwater diatom species Achnanthidium saprophilum, employing macroscopic, microscopic, and spectroscopic approaches. Bio-association experiments with hexavalent U (U(VI)) were conducted during various diatom growth phases and revealed time- and concentration-dependent U retention by the diatoms. U bio-association was observed by scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX), indicating co-localization of U with phosphorus (P). Time-resolved laser-induced fluorescence spectroscopy on U(VI)-associated diatoms suggested the formation of two adsorbed U(VI) species, whose proportions depend on the diatom growth phase. Fourier-transform infrared spectroscopy confirmed the interaction of U(VI) dominated by carboxyl groups on diatoms, while the contribution of silanol groups from the diatom frustule appeared insignificant. U bio-association experiments revealed also U incorporation into diatom cells, confirmed by transmission electron microscopy coupled with EDX. Co-localization of U with P within the vacuole was evident, suggesting co-precipitation of various metals, including U, in form of phosphates. The results of this study highlight not only the adsorption but also the internalization of U by diatoms, which influences the fate of U in aquatic ecosystems and affects its mobility and bioavailability. These findings are highly relevant for the further development of radioecological models
PARALLEL-IN-TIME PRECONDITIONING FOR TIME-DEPENDENT VARIATIONAL MEAN FIELD GAMES
No full textWe study the numerical approximation of a time-dependent variational mean field game system with local couplings and either periodic or Neumann boundary conditions. Following a variational approach, we employ a finite difference discretization and solve the resulting finite-dimensional optimization problem using the Chambolle-Pock primal-dual algorithm. As this involves computing proximal operators and solving ill-conditioned linear systems at each iteration, we propose a general class of parallel-in-time preconditioners based on diagonalization techniques using discrete Fourier transforms. These enable efficient, scalable iterative solvers with robustness across a wide range of viscosities. We further develop fast solvers for the resulting ill-conditioned systems arising at each time step, using exact recursive schemes for structured grids while allowing for other geometries. Numerical experiments confirm the improved performance and parallel scalability of our approach
Accompagner l’autonomisation des salariées du Care : quelle(s) réception(s) du développement personnel à l’occasion de formations professionnelles continues ?
No full textInternational audienc
Atomic scale structure and dynamical properties of (TeO 2 ) 1− x –(Na 2 O) x glasses through first-principles modeling and XRD measurements
No full textInternational audienceWe resort to first-principles molecular dynamics, in synergy with experiments, to study structural evolution and Na+ cation diffusion inside (TeO2)1−x–(Na2O)x (x = 0.10–0.40) glasses. Experimental and modeling results show a fair quantitative agreement in terms of total X-ray structure factors and pair distribution functions, thereby setting the ground for a comprehensive analysis of the glassy matrix evolution. We find that the structure of (TeO2)1−x–(Na2O)x glasses deviates drastically from that of pure TeO2 glass. Specifically, increasing the Na2O concentration leads to a reduction of the coordination number of Te atoms, reflecting the occurrence of a structural depolymerization upon introduction of the Na2O modifier oxide. The depolymerization phenomenon is ascribed to the transformation of Te–O–Te bridges into terminal Te–O non bridging oxygen atoms (NBO). Consequently, the concentration of NBO increases in these systems as the concentration of the modifier increases, accompanied by a concomitant reduction in the coordination number of Na atoms. The structure factors results show a prominent peak at ∼1.4 Å that becomes more and more pronounced as the Na2O concentration increases. The occurrence of this first sharp diffraction peak is attributed to the growth of Na-rich channels inside the amorphous network, acting as preferential routes for alkali-ion conduction inside the relatively stable Te–O matrix. These channels enhance the ion mobility
High concentration down-shifting tetrazines for UV protection of OSCs in hemicellulose polymers; syntheses, properties and solar cell performance
No full textInternational audienc
Numérique et émancipation des salariés au travail : analyse des cas d’intégration des ERP
No full textInternational audienceCet article examine l’émancipation des salariés dans le cadre de l’intégration des ERP (Enterprise Resource Planning). S’appuyant sur le cadre théorique proposé par Alvesson et Willmott (1992, 2012), l’émancipation est définie comme la libération des contraintes imposées par les structures organisationnelles et technologiques. L’étude se concentre spécifiquement sur ces outils numériques, principalement destinés à la gestion et à l’amélioration de l’efficacité décisionnelle, en les analysant au sein du contexte particulier de Madagascar. La méthodologie adoptée repose sur une étude de cas multiples à visée exploratoire menée auprès de grandes entreprises et firmes multinationales opérant dans ce pays. Les résultats mettent en évidence les facteurs clés qui facilitent ou entravent l’émancipation des salariés lors de l’intégration des ERP, en soulignant l’influence prépondérante de la culture locale malgache sur ces dynamiques. Enfin, l’article présente les principales contributions de la recherche, ses limites ainsi que des pistes prometteuses pour des travaux futurs
Les manuels de bonnes manières, à quoi ça sert ?
No full textInternational audienceCompilation de conseils donnés dans des manuels de bonnes manières à l'usage des femmes. Une manière réjouissante de dénoncer les diktats imposés par une société de la fin du 19e siècle, soucieuse de formater la féminité
Retour au lac d'Issarlès : un premier bilan d'étape
No full textInternational audienceLe lac d'Issarlès, joyau touristique du volcanisme se situe dans le très haut bassin de la Loire, dans l'ancienne province du Vivarais. C'est le lac d'origine volcanique le plus profond de Franc
Prior Lending Relationships and the Effectiveness of Commitments in Sustainability-Linked Loans
No full textUsing a global sample of sustainability-linked loans, we examine how prior relationshipsbetween borrowers and lead arranging banks—acting as sustainability agents—influence thestructure of key performance indicators (KPIs) of these loans. We find that existingrelationships are associated with fewer yet broader KPIs spanning multiple ESG dimensions.Moreover, when such relationships are present, greater KPI intensity leads to improved postissuanceESG performance, particularly in the environmental domain. Our results are robust toa variety of checks, including instrumental variable and propensity score matching techniques,highlighting the significance of relationship lending in shaping effective sustainabilityincentives
Construire l’identité de la professeure ou du professeur-stagiaire : quel ressenti de la part de la tutrice ou du tuteur de terrain
No full textInternational audienceCet article vient proposer le bilan d’une enquête effectuée auprès de tutrices et tuteurs de terrain en établissement public local d’enseignement (EPLE) accueillant des enseignantes et des enseignants du second degré en devenir dans le cadre de leur formation initiale à l’Inspé. L’expérimentation a eu lieu dans l’académie de Limoges. Elle vient mettre en évidence le ressenti de nos collègues-expert.e.s en situation de tutorat, partant de l’hypothèse que leur mission pourrait les conduire vers un sentiment de solitude et d’isolement. Elle s’inscrit dans la construction de l’identité professionnelle des enseignantes et des enseignants. Nous avons contacté 214 collègues toutes disciplines scolaires confondues par mail afin qu’ils répondent à une enquête via un questionnaire Google Form. Il ressort de l’analyse des pourcentages obtenus un sentiment plutôt positif de bien-être dans la mission assorti d’une grande responsabilité envers les stagiaires