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Dynamics of gadolinium oxide clogging in porous media: insights from 4D X-ray microtomography
No full textInternational audienceThe mobility of rare earth element (REE) nanoparticles in subsurface environments is a growing concern due to their increasing use and potential ecological risks [1]. The dynamic monitoring at the micro scale of gadolinium (Gd) nanoparticle transport holds significant potential in biomedical and environmental applications, however, the existing literature is scarce and is mostly focused on the macroscale column studies [2],[3]. In this study, we investigate the pore-scale mechanisms governing the transport and retention behavior of Gadolinium oxide (Gd₂O₃) nanoparticles under single-phase flow conditions within porous media using high-resolution 4D X-ray microtomography. Gd₂O₃ was selected as a representative REE nanoparticle due to its high X-ray attenuation, allowing direct visualization of its spatiotemporal distribution in situ. Experiments were conducted using cylindrical sintered glass columns (4 mm diameter, 40 mm length) with pore throat sizes ranging from 40 to 100 µm, which were pre-saturated with 80% glycerol at an ionic strength of 10mM NaCl (figure 1). The influence of flow velocity on nanoparticle retention was systematically analyzed. Our results reveal distinct retention mechanisms, including straining at pore throats and reduction in permeability due to clogging of the pores. These localized depositions, quantified in terms of Gd₂O₃ concentrations, were shown to alter local flow paths, highlighting the coupling between colloid dynamics and hydrodynamic conditions. This study provides new insights into the fate of REE nanoparticles in the subsurface, which is essential for risk assessment and remediation strategies. These experiments will also guide the future surface complexation modeling of REE and numerical modeling simulations of fluid flow and transport
Transformer l'argent en or. L'enrichissement de surface des monnaies carthaginoises en alliages or-argent (IVe-IIIe siècles av. n. è.) : réflexions préliminaires et premiers résultats expérimentaux
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L’utilisation du jeu <i>Ferme les Portes</i> pour l’apprentissage du calcul mental en CP : un outil pour favoriser l’apprentissage des faits numériques
No full textThis study looks at how the game Ferme les Portes can help first-grade pupils learn and remember basic addition facts from the Pythagorean table. Pupils were divided into three groups: one group without any game, one using Ferme les Portes, and one using different math games. The results, based on written tests and oral interviews, show that regular use of the game helps improve calculation speed, reduces mistakes, and supports the use of better strategies, like using commutativity. These effects are stronger when the game is used as part of a wellplanned teaching sequence, with time to talk and reflect. The study shows that educational games can help pupils, especially those who struggle with math.Cette recherche s’intéresse aux effets de l’utilisation du jeu Ferme les Portes sur l’automatisation des faits numériques issus de la table de Pythagore chez des élèves de CP. Les élèves répartis en trois groupes participent à l’étude : un groupe sans jeu, un groupe utilisant Ferme les Portes, et un groupe travaillant avec des jeux mathématiques variés. À partir d’un protocole combinant tests écrits, entretiens oraux et observations, les résultats montrent que le jeu ritualisé améliore la fluidité de calcul, renforce l’exactitude des réponses et favorise l’acquisition de procédures expertes telles que la commutativité. Ces effets sont plus marqués lorsque le jeu est intégré dans une séquence structurée, avec un étayage didactique et des temps de verbalisation. Ce travail souligne l’intérêt du jeu comme levier pédagogique, notamment pour les élèves les plus en difficulté
Strategic decision-making styles and post-succession performance in french SMES : Impact of managers origin?
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Rounding contrast activation in Ngbúgù: licensing and sub-segmental interactions
No full textInternational audienceThe Ngbúgù language (Banda group, Ubangi family; Central African Republic) exhibits a contextual contrast between rounded and un-rounded vowels; the two contrasts /o/ vs /ɤ/ and /u/ vs /ɯ/ only apply in seven contexts: k_, g_, kʁ_, gʁ_, ʁ_, ʔʁ_ and ŋgʁ_. Given the scarce distribution of this contrast, we suggest it is activated in these contexts, rather than neutralized elsewhere. Relying on the frame-works of Element Theory (Kaye et al. 1985, 1990, Backley 2011), Government Phonology (Kaye 1990, Kaye et al. 1990, Charette 1990, 1991), and Feature Geometry (Clements 1985, Sagey 1986, Clements and Hume 1995) suited for elements (Harris and Lindsey 1995, Ulfs-bjorninn 2021), we provide a representational analysis in which the |U| element is responsible for this activation
La littératie numérique : un apprentissage qui concerne tout le monde
No full textAs society becomes increasingly digital, schools play an essential role in learning digital skills. However, despite institutional intentions, the integration of digital technology into teaching practices remains uneven and sometimes superficial. This dissertation looks at how digital technology is actually used in the classroom and the role that teacher training plays in helping teachers adopt these tools.Based on two theoretical models - TPACK, which combines technological, pedagogical and subjectspecificknowledge, and SAMR, which assesses the level of digital integration - the study is based on a questionnaire survey of primary school teachers. The analysis highlights some general trends: digital uses often remain focused on basic functions, while the training provided sometimes appears to be poorly adapted to the realities on the ground. However, there are several levers that need to be explored in greater depth, particularly in terms of support, differentiation and professional development.This work thus offers an initial contribution to the debate on the conditions for a more coherent andformative integration of digital technology in schools, in the interests of teaching practices andstudent success.Dans un contexte de numérisation croissante de la société, l’école joue un rôle essentiel dans l’apprentissage des compétences numériques. Pourtant, malgré les intentions institutionnelles, l’intégration du numérique dans les pratiques pédagogiques reste inégale et parfois superficielle. Ce mémoire questionne les usages réels du numérique en classe et le rôle que joue la formation des enseignants dans leur appropriation de ces outils.Appuyée sur deux modèles théoriques — le TPACK, qui croise les savoirs technologiques, pédagogiques et disciplinaires, et le SAMR, qui évalue le niveau d’intégration du numérique — cette étude repose sur une enquête par questionnaire menée auprès d’enseignants du premier degré. L’analyse met en évidence des tendances générales : les usages numériques restent souvent centrés sur des fonctions de base, tandis que les formations suivies apparaissent parfois peu adaptées aux réalités de terrain. Toutefois, des leviers existent et mériteraient d’être approfondis, notamment en matière d’accompagnement, de différenciation et de valorisation professionnelle. Ce travail propose ainsi une première contribution à la réflexion sur les conditions d’une intégration plus cohérente et formatrice du numérique à l’école, au service des pratiques pédagogiques et de la réussite des élèves
Ressources minières et circulation des matières premières (Cu, Sn, Pb)
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An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345
No full textInternational audienceA crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI-2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of 1 . 504+ 0 . 047 -0 . 044 R ⊕ and a mass of 3 . 49 ± 0 . 85 M ⊕ ; and TOI-2345 c to have a radius of 2 . 451+ 0 . 045 -0 . 046 R ⊕ and a mass of 7 . 27+ 2 . 27 -2 . 45 M ⊕ . To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatized stellar abundances. TOI-2345 adds to the limited sample of well-characterized planetary systems around thick disc stars. This system challenges theories of formation and populations of planets around thick disc stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley.</div
L’usine du Bocard de Vialas (Lozère). Pourquoi fouiller ? L’exemple du moulin à minerai riche
No full textInternational audienceA research program is currently underway on argentiferous galena mining and processing facilities located in Vialas (Cévennes mountains, France). Ore has been extracted there in “ancient” periods, as materialized by traces of fire-setting discovered in some parts of the mines. But activities took on a whole new dimension in the modern era, following the rediscovery of the deposit in 1781. A washing facility and subsequently a foundry were established in the vicinity of the mines. The production reached its peak during the 1860s with an annual silver production close to two tons. However, the operations started to decline from 1869 due to an ore shortage and the facilities finally closed in 1894.The Bocard factory is the only lead and silver foundry preserved in France, and as such, it has inscribed on the Historical Monuments list on 2014. Concurrently with this designation, a preservation and valorization program has been initiated, along with archaeological excavations and 3-D surveys. Archives, including reports from mining engineering students, publications and administrative documents, provide valuable insights into the constant evolution of the site, from its spatial organization to the technics employed. However, these reports from engineering students are, by definition, the work of students and not experienced engineers, containing numerous errors. Additionally, in these reports as in the rest of the archives, some equipment deemed secondary is either briefly mentioned or not discussed at all. Lastly, archives do not document the final decade of operation, with two factors explaining this absence. Once its decline had begun, this operation could not serve as a model to emulate. The second explanation relates to the dispersal of administrative documents upon the site's closure. Thereby, beyond confronting archives with vestiges, archaeological excavation is crucial to supplement and rectify this documentation and for a better understanding of the evolutions that occurred during the last period. Moreover, the excavation is essential for collecting evidence from different stages of the chaîne opératoire associated with the processing of the argentiferous galena, evidence studied through XRF, X-ray diffraction and scanning electron microscopy