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JWST Observations of Cosmic-Ray-excited H in Barnard 68: Spatial Variations and Constraints on Cosmic-Ray Attenuation
No full textInternational audienceWe present James Webb Space Telescope (JWST) NIRSpec observations of the starless dark cloud Barnard 68 (B68) that reveal the spatially resolved signature of cosmic-ray-excited molecular hydrogen (CRXH) emissions for the first time. Following up on our initial detection of CRXH emissions from B68, we now exploit JWST’s sensitivity and spatial multiplexing to map CRXH rovibrational lines across 16 sight lines through the cloud. By disentangling the CRXH and UV-pumped H components, we isolate the para-H-dominated spectrum attributable to cosmic-ray (CR) excitation. We find that there are significant spatial variations in the ratio of the CRXH line intensity to the line-of-sight H column density; these cannot be accounted for by dust extinction alone and demonstrate a clear attenuation of the CR flux with increasing shielding column. Modeling B68 as a Bonnor–Ebert sphere, we constrain both the unshielded CR ionization rate, ζH2, and how it decreases with shielding column. At a reference depth of N(H) = 3 × 10 cm, we infer ζH2≈1.4×10−16s, a factor of ≈3 higher than the average value derived from H3+absorption studies. These results provide the most direct probe to date of CR penetration into cold, dense gas, offering new constraints on both the microphysics of CR–H interactions and the attenuation of low-energy CRs in molecular clouds. Our findings establish CRXH emission as a powerful new diagnostic of the CR environment in interstellar space
Les MICAS pendant les JOP, ou l’usage extraordinaire d’outils routiniers
No full textInternational audienceIf the administrative antiterrorism legal framework remained unchanged during the Olympics and Paralympics, its application by the Home Office services demonstrates that the scope of behavior administratively qualified as “terrorism” has been extended. The Olympics window illustrates that, in a specific context, authorities can apply this legal framework in a way recalling the state of emergency regime operative in 2015-2017. Moreover, the Olympics of 2024 show the expansion attempts of administrative anti-terrorist policy, and suggest future reforms, particularly in the context of the 2030 Winter Olympics in the French Alps.Si le cadre juridique relatif aux MICAS est resté inchangé pendant les Jeux Olympiques et Paralympiques (JOP), son application par les services du ministère de l’Intérieur témoigne d’une extension considérable du champ des comportements pouvant être qualifiés, sur le plan administratif, de « menace terroriste ». La fenêtre olympique démontre ainsi qu’à la faveur d’un contexte particulier, le cadre juridique issu de la normalisation de l’état d’urgence peut être appliqué dans un cadre rappelant la mise en œuvre de ce dernier entre 2015 et 2017. Surtout, cette fenêtre témoigne des tentatives d’extension de la police administrative antiterroriste, et laisse présager de futures réformes, notamment dans le cadre des JOP d’hiver de 2030
Vos conceptions sur la preuve en mathématiques peuvent-elles évoluer ?
No full textInternational audiencePlusieurs travaux à l’international pointent la nécessité d’approfondir les recherches sur la preuveen formation des enseignants. Mais quelles sont les conceptions des futurs enseignants enformation initiale sur la preuve et son enseignement ? Peut-on caractériser un socle deconnaissances et compétences en mathématiques permettant de fonder des dispositifs deformation d’enseignants ?Notre conférence apporte une contribution à cette réflexion avec, pour volonté, d’enrichir lesconnaissances et les pratiques des futurs enseignants du primaire. Des éléments d’état de l’art surces questions seront apportés et des premiers résultats et exemples illustratifs sur les conceptionsd’étudiants seront présentés en lien avec des expérimentations en cours menées en France et enSuisse. Et vous, quelles sont vos conceptions ? Évolueront-elles au fil de la conférence
Efficacité et équité de l’enseignement de l’algèbre après une formation continue en didactique au collège
No full textInternational audienceHaving observed recurring difficulties in the learning of elementary algebra, teachers decided to collaborate with researchers to develop tools for analysing students’ work and to design a new teaching method based on the analyses carried out. The method was tested and evaluated in terms of effectiveness and fairness, and the positive results convinced the teachers to extend the experiment. Scientifically, this research addresses a double problem: documenting teachers’ appropriation and use of mathematics education knowledge, and questioning the concepts of effectiveness and fairness for a quantitative approach to the effects of teaching.Le constat de difficultés récurrentes d’apprentissage de l’algèbre élémentaire a conduit des professeurs à s’engager auprès de chercheurs dans un dispositif collaboratif en vue de développer des outils d’analyse des productions des élèves, et de concevoir un dispositif d’enseignement nouveau qui réponde aux analyses effectuées. Ce dispositif a été expérimenté et évalué en termes d’efficacité et d’équité ; les résultats positifs ont convaincu les enseignants de prolonger l’expérimentation. Du point de vue scientifique, cette recherche répond à une double problématique : documenter l’appropriation et l’utilisation de savoirs didactiques par des enseignants, interroger les concepts d’efficacité et d’équité pour une approche quantitative des effets de l’enseignement
A reappraisal of the amorphization kinetics of water ice: Combined experimental and numerical investigations and amorphization cross-sections in the 90–120 K range
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Water Production of Interstellar Comet 3I/ATLAS from SOHO/SWAN Observations after Perihelion
No full textInternational audienceThe Solar Wind Anisotropies all-sky hydrogen Lyman-alpha camera on the Solar and Heliosphere Observatory observed the hydrogen coma of interstellar comet 3I/ATLAS, also called C/2025 N1 (ATLAS), beginning on 2025 November 6, 9 days after perihelion. Water production rates were calculated from each image of 3I/ATLAS using the methodology of J. T. T. Mäkinen and M. R. Combi, and fluorescence rates and g-factors were calculated using the daily solar Lyman-alpha fluxes from the LASP database ( https://lasp.colorado.edu/lisird/data ) corrected for solar rotation and for the comet’s heliocentric velocity. The method has been used for over 90 comet apparitions. A water production rate of 3.17 × 10 29 s −1 was found on November 6 when the comet was at a heliocentric distance of 1.40 au and at a sufficient solar elongation angle. It decreased over time after that, down to 1–2 × 10 28 s −1 around 40 days postperihelion (December 9)
Inhibition of the macrophage demethylase LSD1 reverses Leishmania amazonensis-induced transcriptomic changes and causes a decrease in parasite load
No full textIntracellular pathogens exploit host cell functions to favor their own survival. In recent years, the subversion of epigenetic regulation has emerged as a key microbial strategy to modify host cell gene expression and evade antimicrobial immune responses. Using the protozoan parasite Leishmania as a model system, we have recently demonstrated that infection causes histone H3 hypomethylation, which is associated with the establishment of an antiinflammatory phenotype, suggesting that host cell demethylases may play a role in the intracellular survival of these parasites. In this study, we combined pharmacological inhibition with RNA sequencing and quantitative immune-precipitation analysis to investigate the role of the macrophage lysine demethylase LSD1 (KDM1a) in Leishmania intracellular infection in vitro. Treatment of infected macrophages with validated, LSD1-specific inhibitors resulted in a significant reduction in parasite burden. We confirmed the impact of these inhibitors on LSD1 activity within macrophage nuclear extracts using an in vitro demethylase assay and established their LSD1 target engagement in situ by cellular thermal shift assay. RNA-seq analysis of infected and inhibitor-treated macrophages linked parasite killing to a partial reversion of infection-dependent expression changes, restoring the macrophage anti-microbial response and limiting cholesterol biosynthesis. While we ruled out any impact of Leishmania on LSD1 expression or localization, we uncovered significant alterations in LSD1 complex formation within infected macrophages, involving unique interactions with host cell regulatory proteins such as Rcor-1. Our study sheds important new light on the epigenetic mechanisms of macrophage immuno-metabolic subversion by intracellular Leishmania and identifies LSD1 as a potential candidate for host-directed, anti-leishmanial therapy
Exprimer son identité en ligne : Variations gauche-droite et transnationales dans l'autoreprésentation sur les réseaux sociaux
No full textPolitical orientations are known to be closely linked to positions on identity-related issues, whose salience and framing can vary both within and across countries. To capture patterns of issue-based self-identification and address pressing questions about identity (mis)alignment across EU countries and between Left- and Right-leaning user groups, we study Social Media profile bios from Twitter/X, where individuals present themselves. Our analysis combines Structural Topic Modeling seeded with Manifesto Project data, and Ideology Scaling calibrated with political expert survey data. The proposed approach allows us to study how more than 1.2 million individuals from eight EU countries self-identify with political issues across the Left-Right ideological spectrum.We find that issues such as democracy, national way of life, and decentralization emerge as the most divisive at the EU level. Other issues, such as environmentalism, equality, and freedom & human rights, among others, strongly differentiate how Left- and Right-leaning individuals communicate their identity online at the EU level.Interestingly, we also find that user groups on the Left side of the political spectrum express their identities more similarly across European countries than those on the Right. This pattern is particularly evident for identity-issues related to national way of life, suggesting that the growing international coordination among conservative parties is not (yet) accompanied by an alignment of Right-leaning users' communicated identity across the targeted EU countries. Finally, we show that our Left-Right identity similarity metrics are inversely related to country-specific perceptions of political conflict, as measured by the PEW survey. Our findings provide a major contribution to comparative political identity studies, enabling a qualitative and quantitative characterization of the EU identity puzzle and offering empirically grounded insights for better understanding identity-related mobilization on Social Media, both within and across countries
Analyse didactique de la pertinence d’un dispositif de formation visant à développer une démarche réflexive chez les professeurs des écoles stagiaires
No full textInternational audienceThe main aim of this research article is to demonstrate the relevance and appropriateness of a classroom visit by a trainee primary school teacher in France. The visit is structured around three phases: observation by a trainer of the implementation of a situation by a trainee primary school teacher, post-observation interview, production of a post-interview reflective piece of writing. The methodology is based, on the one hand, on the analysis of the interview that follows the classroom observation and, on the other, on the study of the professional writing drafted by the trainee. Throughout the analysis of the system, the aim is to detect changes in the trainee teacher's posture, and thus to highlight the trainee's ability to adopt a reflective posture in terms of how he or she brings his or her pupils to experience a mathematical situation.Cet article de recherche a pour principale finalité de montrer la pertinence et la cohérence d’un dispositif spécifique de visite en classe d’un enseignant stagiaire au primaire. Ce dispositif s’articule en trois temps : observation par un formateur de la mise en œuvre d’une situation mathématique par un professeur des écoles stagiaire, entretien post-observation, production d’un écrit réflexif post-entretien. La méthodologie repose d’une part sur l’analyse de l’entretien qui fait suite à l’observation de classe, d’autre part sur l’étude de l’écrit professionnel rédigé par le stagiaire. Il s’agit tout au long de l’analyse du dispositif de déceler les changements d’attitude de l’enseignant stagiaire et ainsi de mettre en lumière sa capacité à adopter une démarche réflexive quant à sa manière de faire vivre une situation mathématique à ses élèves
Experimental insights into early cement development in carbonate aquifers: from diffusion to surface-controlled calcite growth
No full textInternational audienceDespite their geological significance, the thermochemical processes leading to the formation of early carbonate cements remain elusive. To bridge this knowledge gap, we carried out here laboratory-simulated diagenesis on aragonite ooids. They were placed in autoclaves, filled with distilled water, and subjected to varying temperatures and durations. Our results focus on the transformation from aragonite to calcite with temperaturedependent kinetics. At the grain scale, considered as a thermodynamic system on its own, two distinct stages of microstructural evolution were observed. In the first stage, diffusion processes predominate: the ooids experience progressive dissolution while a fringe of calcite cement forms around their periphery. In a second stage, radial diffusion stops and transformations are dominated by surface-controlled processes, characterized by calcite crystal growth within the ooids. The end-result is generally referred to as "neomorphism" in natural analogues. The transition from the diffusion-dominated to the surface-controlled stage is temperature-dependent and does not occur below 150°C. This behaviour can be explained by the progressive growth of the calcite fringe, which isolates the ooid from the surrounding pore water, while internal aragonite dissolution continues within the grain. These experiments show that early calcite cements, similar to those observed in meteoric phreatic environments, can grow without any external CaCO 3 input. They also show that neomorphism in ooids requires the closure of the ooid system, a condition that can occur at any stage of diagenesis. Finally, our experiments support the presence of a diffusive boundary layer, offering a process-based refinement of the traditional 'thin film' concept