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Le Lexicon français
No full textCe document est la version française complète d’un lexique réalisé dans le cadre du projet international LEXICON par l’équipe constituée de Thierry Chevalarias et Florence Debertonne-Dassule, professeurs de mathématiques et animateurs à l’IREM de Poitiers, et de Michèle Artigue, Brigitte Grugeon, Julie Horoks et Julia Pilet, chercheuses au LDAR (Laboratoire de Didactique André Revuz). Le projet LEXICON a eu pour objectif d’identifier la terminologie didactico-pédagogique dont disposent des enseignants de mathématiques expérimentés de collège pour décrire ce qui se passe dans une classe de ce niveau d’enseignement. Lancé par David Clarke, professeur à Melbourne University et spécialiste des études comparatives en éducation mathématique, il a impliqué des équipes d’enseignants et chercheurs de 10 pays : Allemagne, Australie, Chili, Chine, Corée du Sud, Finlande, France, Japon, République Tchèque et USA. Les résultats de ce projet ont été publiés dans le livre Teachers Talking about their Classrooms. Learning from the Professional Lexicons of Mathematics Teachers around the World, édité par Carmel Mesiti, Michèle Artigue, Hilary Hollingsworth, Yiming Cao et David Clarke et publié par Routledge en 2021
Vers une normalisation du contentieux disciplinaire des universitaires
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Selection of Chemical Adsorbents and Operating Conditions for the Injection Traps of the Gas Chromatograph on Board the Dragonfly Mass Spectrometer
No full textInternational audienceThe Dragonfly mission is set to explore Titan’s surface in the mid-2030s. This relocatable lander is equipped with the Dragonfly Mass Spectrometer (DraMS) instrument. One of DraMS functioning mode is gas chromatography−mass spectrometry, to identify organic compounds in solid samples. DraMS-GC includes two independent chemical injection traps to focus the molecules released from the sample. Initially, Tenax TA was planned to be the adsorbent in the injection traps because of its heritage in previous space probes. However, Tenax TA has shown some decomposition products that challenge the identification of the molecules indigenous to the sample. In this work, the performance of another adsorbent powder, Carbotrap C, was compared to Tenax TA. Performance was evaluated in DraMS-like desorption conditions by comparing the recovery yield after adsorption and desorption of a set of 53 organic compounds of interest to Titan. Recovery with Carbotrap C was either similar or better than with Tenax TA for 79% of compounds. This recovery yield was further improved by increasing the desorption temperature. DraMS low desorption flow rate appears to be the most limiting parameter for recovery. Desorption from both Tenax TA and Carbotrap C led to partial but comparable racemization for three of the four amino acids that were enantiomerically resolved. Together, these results led to the integration of Carbotrap C in one of the DraMS injection traps
Volcanoes: Composition of Emissions
No full textInternational audienceVolcanic emissions mainly consist of water vapor, carbon dioxide, and sulfur gases, with smaller amounts of halogens and other trace gases. Their composition varies depending on the magma’s source and its storage conditions in the crust. Large explosive eruptions can release gases directly into the stratosphere, affecting atmospheric composition, especially the ozone layer, and altering the global climate for years. In recent decades, most global volcanic impacts have been caused by stratospheric aerosols formed from sulfur gas oxidation, though water vapor and halogens may also contribute to atmospheric changes
Unraveling energy flow mechanisms in semiconductors by ultrafast spectroscopy: Germanium as a case study
No full textInternational audienceSemiconductor materials are the foundation of modern electronics, and their functionality is dictated by the interactions between fundamental excitations occurring on (sub-)picosecond timescales. Using time-resolved Raman spectroscopy and transient reflectivity measurements, we shed light on the ultrafast dynamics in germanium. We observe an increase in the optical phonon temperature in the first few picoseconds, driven by the energy transfer from photoexcited holes, and the subsequent decay into acoustic phonons through anharmonic coupling. Moreover, the temperature, Raman frequency, and linewidth of this phonon mode show strikingly different decay dynamics. This difference was ascribed to the local thermal strain generated by the ultrafast excitation. We also observe Brillouin oscillations, given by a strain pulse traveling through germanium, whose damping is correlated to the optical phonon mode. These findings, supported by density functional theory and molecular dynamics simulations, provide a better understanding of the energy dissipation mechanisms in semiconductors
Enjeux, principes et méthodologie de l’observation in situ des usages pédagogiques inclusifs du numérique (GTnum #EvalNumInclus)
No full textBulletin de veille réalisé dans le cadre du GTnum #EvalNumInclus.Le cadre théorique et la méthode de l’observation en classe des usages pédagogiques inclusifs du numérique dans le cadre du GTnum #EvalNumInclus sont précisés : le cadre théorique s’inscrit dans une approche anthropocentrée et didactique et se démarque d’une vision technocentrée qui conçoit les outils numériques comme précédant la mise en œuvre du pédagogique et déterminant son efficacité ; la méthode consiste à croiser, dans un contexte scolaire donné, les modalités ou schèmes d’usage pédagogique inclusif des outils numériques et l’identification des moteurs ou freins contextuels de l’opérationnalité inclusive de ces outils
The detection of circularly polarized radio bursts from stellar and exoplanetary systems
No full textInternational audienceIn the Solar System, low-frequency radio emission at frequencies ≲200 MHz is produced by acceleration processes in the Sun and in planetary magnetospheres. Such emission has been actively searched for in other stellar systems, as it could potentially enable the study of the interactions between stars and the magnetospheres of their exoplanets. Here we present radio interferometric multiplexed spectroscopy (RIMS), a method designed to measure the variability of the flux density in an arbitrary number of directions from interferometric datasets. Using it, we synthesized ~200,000 dynamic spectra of stars and exoplanetary systems from an ~1.4 years' long, multi-petabytes dataset from the Low-Frequency Array (LOFAR) at 150 MHz. This extra diagnostic shows that ~25% of the 68 targets previously identified in the LOFAR circularly polarized images also show significant variability on timescales of a few hours. The improved instantaneous sensitivity led to the detection of eight more weak bursts from low-mass stars, most of which varied on ~0.5-1-h timescales. We argue that some are fully compatible with radio emission generated by star-planet interactions, although an intrinsic stellar origin is still a possible explanation. Our results demonstrate the potential of the method for studying stellar and star-planet interactions with the Square Kilometre Array
Inhibition of TRAP1 in the C-terminal domain influences mitochondria properties and breast cancer cell metabolism
No full textInternational audienceBreast cancers are characterized by complex energy metabolisms involving the Warburg effect but also mitochondria, although this area is not yet well understood. Tumor cells are particularly flexible by choosing oxidative phosphorylation (OXPHOS) or glycolysis depending on the needs and aggressiveness. Within the mitochondria, a HSP90-chaperone protein, TRAP1, exerts regulatory effects on several vital functions such as OXPHOS, production of reactive oxygen species and apoptosis by interacting with members of the respiratory chain or the mPTP. However, not all of its roles have yet been elucidated. Here, we propose to modulate TRAP1 functions using a mitochondriotropic molecule (containing triphenylphosphonium) targeting its C-terminal domain, 6BrCaQ-C 10 -TPP, in breast tumor cells. Its blocks proliferation with no massive apoptosis, after 24 h of treatment, and induces dissipation of the mitochondrial membrane potential. 6BrCaQ-C 10 -TPP also appears to modulate regulators of epithelial-mesenchymal transition (Snail and ZEB1) without a common response in all cell lines. Furthermore, the chaperone machinery is affected with a decrease of HSF1 and HSP70, but without degradation of HSP90 or TRAP1, while decreasing the levels of SDH-A and/or SDH-B, partner of TRAP1. Finally, short-term treatments (1 and 3 h) with 6BrCaQ-C 10 -TPP modify energy metabolism by promoting glycolysis. In conclusion, modulation of TRAP1 on the C-terminal domain by 6BrCaQ-C 10 -TPP exerts a cell-line dependent antitumor effect by modulating major mitochondrial functions in vitro. The differences between cell types need to be clarified. This study confirms that TRAP1 is a target of interest in breast cancer cells, but some of its functions still need to be elucidated
Collectionner les écrivains: Une patrimonialisation éditoriale
No full textInternational audienceL’époque dite des « Trente glorieuses » va de pair avec une démocratisation de l’accès à la culture, qui encourage maints éditeurs à lancer des collections à vocation patrimoniale à destination de nouveaux lecteurs potentiels. Les collections de monographies consacrées aux écrivains, modèle éditorial dont les premiers avatars apparaissent au cours du XIXe siècle, prennent véritablement leur essor à cette époque, du fait de l’introduction d’une importante iconographie et de l’établissement d’un modèle économique à succès.Le présent volume regroupe, sous la notion d’extensions, les formules, formats et types d’approches de la chose littéraire que ces collections tracent au sein du monde éditorial à mesure qu’elles s’enrichissent, précisant à l’occasion une idée de littérature encore latente et produisant ainsi un discours sur le champ culturel. En présentant les collections au sein de généalogies anciennes (« Généalogies »), le volume explore ces extensions à partir de la Seconde Guerre mondiale, aboutissement d’un profond rééquilibrage des forces dans le champ éditorial et point de départ du mouvement politique et culturel de démocratisation qui détermine en France la pensée de la culture jusqu’à la fin du XXe siècle. Il envisage la façon dont ces collections positionnent leur corpus au sein d’un champ concurrentiel (« Positions »), les choix esthétiques et théoriques qui les définissent (« Orientations ») et la façon dont leur modèle estrepris par d’autres supports médiatiques (« Intermédiations »).Par cette exploration du modèle en cours de constitution, ainsi que des adaptations et transferts dont il fait l’objet, le présent volume met en lumière, au-delà de la comparaison structurelle entre collections, la circulation d’une forme éditoriale et son impact dans le paysage éditorial du second XXe siècle. L’ouvrage se fonde sur une analyse des catalogues éditoriaux de ces collections aussi bien que sur une lecture suivie de volumes consacrés à différents écrivains, et mobilise nombre de documents inédits à l’appui de ces analyses
Pliocene contrasted climate conditions in space and over time: A unique pollen dataset from the NW Mediterranean Region for comparison with climate models
No full textInternational audienceA set of 62 Pliocene pollen records and reconstructed climate parameters across the Northwestern Mediterranean Region, together with palaeoclimate simulations from the IPSL earth system model, provide a unique opportunity to study the Pliocene, especially the early Piacenzian Cooling (ePC) and the mid-Piacenzian Warm Period (mPWP). Vegetation reconstructed from pollen records documents strong spatial contrasts in the area. It reveals a retreat of the subtropical broad-leaved evergreen forest to the advantage of Mediterranean sclerophyllous ecosystems.This study is a first attempt to compare observation-based data with model simulations in the Northwestern Mediterranean Region. It reveals substantial discrepancies with encouraging results, pointing out the need to expand the work of data -model comparisons to other regions. The mid-Piacenzian warm period appears to be an interesting past analogue for the ongoing anthropogenic global warming, including its regional impacts. We observe that two areas (Northern Catalonia and the Southern Alps-Liguria) were affected by increased precipitation during brief episodes in the mid-Piacenzian, while the Roussillon-Languedoc-Provence area experienced drier conditions. Such a spatial pattern seems comparable with the present-day context. The significance of ecosystems composed of some Cupressaceae (Cupressus-Juniperus-type) is interpreted partially as subtropical forest, and partially as Mediterranean vegetation. This regional study provides valuable data and interpretations to improve the contribution of past records to such evaluations, and inspires future palaeoclimate simulations with finer resolution