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La théorie des deux mondes, un outil d’analyse d’une pratique enseignante innovante à l’université : le cas de l’enseignement de la physique par l’escalade
No full textInternational audienceCet article vise à analyser les effets d’une collaboration entre deux enseignantes-chercheuses, l’une chercheuse en physique de la matière condensée (EC1), l’autre en didactique de la physique (EC2), réunies autour d’un enseignement original « la physique de l’escalade ». La collaboration se donne pour objectif d’enrichir la capacité d’analyse d’EC1 sur cet enseignement. Pour cela, nous nous plaçons dans le cadre de la didactique professionnelle afin de développer chez EC1 une aptitude à conceptualiser son action et son réel pédagogique. La théorie des deux mondes vient en appui de ce processus de développement et joue le rôle d’interface entre EC1 et EC2. Spécifiquement nous montrons le rôle joué par la mobilisation de la théorie des deux mondes dans le processus de développement conceptuel d’EC1 en pointant quelques élucidations de difficultés ressenties par EC1 et certaines de leurs conséquences prospectives. D’autres élucidations se font jour qui concernent cette fois EC2 et qui forment autant de pistes pour la recherche en didactique et pour la formation des enseignant.e.s du supérieur
Exploring the control of earthworm faeces micro- and macro-scale features on soil organic matter dynamics across species and ecological categories
No full textInternational audienc
Un exemple au nord : vulnérabilité et résilience de la zone métropolitaine de Paris face au risque de crue majeure de la Seine - l’apport de la recherche à l’action publique à travers le projet RGC4 en France
No full textInternational audienc
Development of an expert judgement debiasing method for assessing levee failure probabilities
No full textInternational audienc
La Somme, une haute antiquité toujours d’actualité : à propos du Paléolithique inférieur
No full textInternational audienceJacques Boucher-de-Perthes’ discoveries in the Somme valley undoubtedly opened up a new scientific field, prehistory. Its subject, prehistoric man, previously unknown at the beginning of the 19th century, is still greatly misunderstood by the public, despite many efforts as well as major scientific discoveries and publi-cations carried out on the Samaritan territory since the identification of prehistoric occupations more than a century and a half ago. Prehistoric studies since Jacques Boucher de Perthes in the vicinity of Abbeville and Amiens have continued without interruption, including during the two World Wars. The Somme has thus seen a succession of researchers whose excavations have joined the list of internationally known reference sites, such as Menchecourt, Saint-Acheul or Cagny. From the very beginning, prehistoric studies in the Somme have focused on the oldest evidence of human occupation, whose consecration and recognition were established when Gabriel de Mortillet chose the site of Saint-Acheul and its “large almond-shaped instruments” in 1872 to define the most advanced period of the Stone Age. This presentation will demon-strate that the current studies carried out in the Somme are keeping this long continuity of research and that the recent discoveries have significantly renewed our knowledge of the Lower Paleolithic. These ad-vances are due to two closely related courses of action, namely the re-examination of reference sites with new means of analysis and interpretative frameworks, and the exploration of new deposits, both in the context of programmed andsalvage archaeology. This is how the research dynamic stimulated by all our illustrious and lesser-known predecessors on the first settlements and ways of life of the first prehistoric men is perpetuated in the Somme. It confirms that the Somme’s potential is worthy of its glorious heritage and remains a reference valley for the Lower Paleolithic
Tipping points in continental hydrology : developing a system dynamics approach to represent the interfaces in the critical zone and built a decade-scale hydrologic model.
No full textInternational audienceWe develop a holistic approach of watershed hydrology, focusing on the interfaces between critical zone components and relying on interdisciplinarity. We mainly explore the first Unsolved Problem in Hydrology (UPH): Is the hydrological cycle regionally accelerating/decelerating under climate and environmental change, and are there tipping points? and 5 other UPH (3,4,7,12,19). As feedbacks exist between the critical zone components, forming a complex system, it can lead to the emergence of tipping points and to shifts between hydrological regimes.A hydrological regime shift is indeed observed since 1950 in the Sahel (semi-arid region, Africa). Stream flows continuously increased in this region despite a severe regional drought in the 70s-90s. This suggests that a tipping point could have been surpassed, because of changes in climate and/or human practices. To explore this hypothesis, we develop a new modeling approach, relying on long term observations (1950-present) of hydrology, geomorphology and land used/land cover. We use System Dynamics modeling to capture feedbacks between water, soil structure, vegetation and flow connectivity between hillslope, channel and aquifer.The modeling results accurately represent the observed decade-scale evolution of the hydrological regime at several watershed scale (1-10000 km²). This shows that tipping points exist in semi-arid land hydrology and allows to explore which processes are at play. We identified domains within watersheds where regime shifts occurred at small scale, propagated across scales and led to large-scale shifts. Ultimately, we aim at identifying areas where the risk of an irreversible hydrological regime shift is high under various climatic and socio-economical possible futures.This study illustrates that using system dynamics to represent the critical zone is complementary to classical hydrologic modeling based on hydrodynamics. While the system-based approach represent correctly the decadal trends of the hydrological regime, the hydrodynamics approach did so for floods and drought at minute/year time scales
A new convergence proof for approximations of the Stefan problem
No full textWe consider the Stefan problem, firstly with regular data and secondly with irregular data. In both cases is given a proof for the convergence of an approximation obtained by regularising the problem. These proofs are based on weak formulations and on compactness results in some Sobolev spaces with negative exponents
Influenceurs et Influenceuses santé : les récits et les savoirs du corps sur les réseaux sociaux
No full textInternational audienc
Existence of SRB measures for hyperbolic maps with weak regularity
No full textWe prove that a hyperbolic map whose differential is regular enough has an SRB measure. The precise regularity condition is weaker than Hölder and was mentionned by various authors through the developement of expanding and uniformly hyperbolic dynamics
Methyl Internal Rotation in Fruit Esters: Chain-Length Effect Observed in the Microwave Spectrum of Methyl Hexanoate
No full textInternational audienceThe gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm−1 and 415 cm−1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methyl internal rotation of methyl hexanoate to those of other CH3-O-(C=O)-R molecules leads to the conclusion that though the barrier height is relatively constant at about 420 cm−1, it decreases in molecules with longer R