Science & Mathematics

The meridional Overturning Circulation (MOC) of the North Atlantic ocean is a key component of the global climate system, through its role in redistributing heat, freshwater end chemical properties between low and high latitude regions. In mid-high latitude regions, the North Atlantic Current (NAC) forms the upper limb of the MOC. It flows northeastward at the subtropical/subpolar boundary, and splits into two main branches in the eastern subpolar gyre: a northern branch that recirculates within the subpolar region and a southern branch that feed the Nordic Seas.A realistic eddy-permitting simulation (ORCA025-G70, 1/4°) is combined with a Lagrangian analysis tool (ARIANE) to investigate the MOC variability (1965-2004) across the A25-Ovide line, which joins Greenland to Portugal. Two vertical overturning cells are identified: a subtropical cell connecting low and high latitudes (12Sv) and a cell internal to the subpolar gyre (4Sv). The decadal MOC variability is associated with synchronized transport changes of the subtropical and subpolar inflow within the NAC. The latter undergoes important horizontal restructuring with opposed transport changes of its northern and southern branches. Those horizontal transport changes are largely induced by the horizontal variability of the subtropical inflow.Changes in oceanic heat transport across A25-Ovide are largely responsible for the observed heat content changes in the eastern subpolar gyre (1965-2004). Heat transport variability at A25-Ovide results from an imbalance between opposed changes in its velocity and temperature components. Both temperature and velocity anomalies are partly reflected in large scale heaves of isopycnals, and potentially relate to the varying proportion of warm subtropical waters and cold subpolar waters advected within the northern NAC branch.A 2000’s mean full-depth circulation computed along the merged AR7W/A25-Ovide line from repeated hydrographic profile and altimetry data indicates a minor contribution of the Labrador Sea to the basin wide mean MOC. However, the strength of the diapycnal overturning at AR7W has almost halved between the 1990’s and the 2000’s, confirming the importance of the region for the low-frequency MOC Variability.

L'amélioration des propriétés des mélanges de polymères immiscibles par l'ajout d'argile fait l'objet d'un intérêt croissant. Les systèmes ternaires étudiés sont constitués de polyéthylène, de polyamide et d'une nanocharge argileuse présentant une bonne affinité avec le polyamide. Deux modes d'élaboration sont confrontés : mélange d'un nanocomposite PA/argile et du polyéthylène d'une part, et mélange simultanément des trois composants d'autre part. L'influence du taux d'argile sur les propriétés morphologiques et rhéologiques de chaque système est étudiée. La morphologie des systèmes ternaires est très dépendante du mode d'élaboration et de la fraction de la phase dispersée. Les propriétés viscoélastiques sont étudiées en relation avec les propriétés morphologiques. Le comportement viscoélastique a été confronté aux prédictions du modèle de Palierne. Les différences dues au mode d'élaboration sont attribuées à la localisation préférentielle de l'argile dans la phase polyamide et/ou à l'interface PE/PA.

L'estimation de la profondeur par l'analyse du flou optique sur les contours d'images peut être vue comme un problème d'estimation de paramètres de modèles de contours et de défocalisation grâce à l'acquisition d'un couple d'images nette et floue. Nous proposons de résoudre ce problème par une méthode génétique appliquée simultanément à l'image nette et à l'image floue. La technique génétique est ensuite utilisée uniquement avec l'image floue en estimant l'ensemble des paramètres de contours et la quantité de flou optique en évitant l'acquisition de l'image nette. Les performances de cette approche sont évaluées avec deux puis une image et comparées à une de nos méthodes précédemment développées.

Grasslands cover around 30% of the Earth’s terrestrial surface and provide important ecosystem services. On the other hand, grasslands are among the most endangered ecosystems, threatened by land-use change, mainly through agricultural intensification or abandonment, and ongoing climatic changes, such as warming and drought. The principal aim of this book is to give an overview of current knowledge and future challenges for ecological studies on grasslands and to provide new perspectives for the management and conservation of grassland ecosystems. The first chapter presents some current threats to grasslands by reviewing the influence of land-use and climate change on the integrity of grassland ecosystems through changes in plant species composition and biodiversity (Chapter 1). While aboveground patterns and processes in grasslands are relatively well-known, the importance of belowground components in shaping grassland ecosystems is not well-understood. This is despite recognition that most of the grassland biomass and biodiversity is belowground, and that soil communities provide key ecosystem functions. Chapter 2 readdresses the importance of soil organisms by synthetizing their effects on grassland production and diversity, illustrated by a simplified soil food web with antagonist and mutualistic pathways. Soil microbial communities are particularly important for grassland functioning and need to be taken into account in management practices. As such, Chapter 3 highlights the importance of the seasonal variability of soil microbial communities and gives perspectives for bettering the management of disturbed grasslands. In addition to temporal variation, spatial variability should also be considered in grassland management. Chapter 4 presents a conceptual toolkit that accounts for spatial and temporal variability to facilitate restoration planning and management. Grazing is one of the most common practices in grassland management, with positive or negative effects on biodiversity and ecosystem functioning, depending on intensity and frequency. Chapter 5 investigates how grazing components (i.e. defoliation, trampling, animal excretions) affect spatial heterogeneity and as such, affect the functioning of grassland ecosystems and the services they provide. Grazing can be also used as a tool to restore degraded ecosystems and Chapter 6 shows how grazing, as well as other management practices, affect plant diversity and biomass production in a unique long-term restoration experiment in China. In a historic perspective, over the past two centuries, grasslands have been transformed globally by conversion to intense agricultural use, while extensively low-intensity grazed grasslands are disappearing. The ongoing effects of climate change are an additional threat to these endangered ecosystems as shown in Chapter 7. Climate change impacts are especially important in high elevation ecosystems, which are disproportionally affected, and Chapter 8 and 9 explore the influences of land-use and climate change on mountain and alpine grasslands. Both of these chapters focus explicitly on changes in plant functional group composition, which are key drivers of ecosystem properties and functioning. In this light, Chapter 10 gives an overview of the role of the largely understudied functional group of bryophytes by showing how this group contributes to the biodiversity of grasslands and constitutes a key group in the functioning of grassland ecosystems.

Notre mémoire porte sur l’impact de l’attention dans les apprentissages. Nous nous sommes interrogées sur l'aménagement de l'enseignement afin de prendre en compte les variations de l’attention des élèves. Par ailleurs, l'attention, souvent confondue avec la concentration, est un processus complexe à définir, mais aussi à observer. Ainsi, notre mémoire présente plusieurs définitions de l’attention données dans la littérature scientifique, afin de comprendre les contours de ce processus. L’attention est essentielle aux apprentissages scolaires des élèves. Effectivement, nous évoquons sa place comme pilier des apprentissages. Également, nous abordons le lien entre l’attention et la mémorisation. Pour autant, l’attention fluctue selon de nombreux facteurs, ainsi, nous avons passé en revue les conclusions des études réalisées par les chronobiologistes. Notre mémoire aborde, aussi, l’impact des distracteurs et des écrans sur les capacités attentionnelles des élèves. Le programme ATOLE de Lachaux est également abordé afin de comprendre la façon dont nous pouvons entrainer notre attention. Pour finir, nous avons recueilli des données auprès des élèves comme des enseignants. Nos résultats mettent en évidence l'importance de l'organisation temporelle et spatiale, mais surtout la posture et les gestes de l'enseignant, dans le maintien de l’attention des élèves.

This chapter describes CGAL at the time the ECG book was written. Constant and persistent improvement to the source code and the didactic manuals, review of packages by the Editorial board and exhaustive testing, through the years led to a state of excellent quality internationally recognized as an unrivalled tool in its field. At the time these lines are written, CGAL already has a foothold in many domains related to computational geometry and could be found in many academic and research institutes as well as commercial entities. Release 3.1 was downloaded more than 14.500 times, and the public discussion list counts more than 950 subscribed users.

Contexte : le nombre de personnes âgées de plus de 65 ans en France est en constante augmentation, et représentait plus de 20 % de la population en 2020. Les études réalisées au sein de cette population ont montré des besoins en soins importants. Objectifs : décrire l’état de santé bucco-dentaire des séniors résidants en EHPAD en Nouvelle-Aquitaine en 2022 et 2023, et analyser la relation entre certaines variables socio-démographiques et bucco-dentaires. Méthodes : les données exploitées lors de cette étude transversale ont été recueillies lors de dépistages bucco-dentaires en EHPAD néo-aquitains réalisés par les étudiants en troisième cycle court de l’UFR d’Odontologie de Bordeaux, sur les années scolaires 2022 et 2023. Les données socio-démographiques et médicales ont été recueillies auprès du personnel des EHPAD, alors que les données bucco-dentaires étaient recueillies par questionnaire et examen clinique. Résultats. En 2022, sur 1160 résidents répartis au sein de 46 EHPAD : l’âge moyen était de 86,4 ans (+/-8,71) et le CAOD moyen était de 20,5 (+/-7,31). En 2023, sur 1164 résidents répartis au sein de 37 EHPAD : l’âge moyen était de 87,0 ans (+/-8,3) et le CAOD moyen était de 20,1 (+/-7,45). Plus de 80 % des résidents avaient des besoins en soins sur les années 2022 et 2023, dont environ 60 % nécessitaient un détartrage et plus de 50 % des soins prothétiques. Environ 12 % présentaient des douleurs bucco-dentaires. Conclusion : notre étude montre un réel besoin en soins au sein de cette population : il est important de réfléchir à des moyens de prévention et de prise en charge bucco-dentaire.

Abstract. We describe the setup and first results of an inverse modelling system for atmospheric N2O, based on a four-dimensional variational (4DVAR) technique and the atmospheric transport zoom model TM5. We focus in this study on the European domain, utilizing a comprehensive set of quasi-continuous measurements over Europe, complemented by N2O measurements from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA/ESRL) cooperative global air sampling network. Despite ongoing measurement comparisons among networks parallel measurements at a limited number of stations show that significant offsets exist among the different laboratories. Since the spatial gradients of N2O mixing ratios are of the same order of magnitude as these biases, the direct use of these biased datasets would lead to significant errors in the derived emissions. Therefore, in order to also use measurements with unknown offsets, a new bias correction scheme has been implemented within the TM5-4DVAR inverse modelling system, thus allowing the simultaneous assimilation of observations from different networks. The N2O bias corrections determined in the TM5-4DVAR system agree within ~0.1 ppb (dry-air mole fraction) with the bias derived from the measurements at monitoring stations where parallel NOAA discrete air samples are available. The N2O emissions derived for the northwest European and east European countries for 2006 show good agreement with the bottom-up emission inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Moreover, the inverse model can significantly narrow the uncertainty range reported in N2O emission inventories for these countries, while the lack of measurements does not allow to reduce the uncertainties of emission estimates in southern Europe. Several sensitivity experiments were performed to test the robustness of the results. It is shown that also inversions without detailed a priori spatio-temporal emission distributions are capable to reproduce major regional emission patterns within the footprint of the existing atmospheric network, demonstrating the strong constraints of the atmospheric observations on the derived emissions.

L’enseignement de la langue ourdoue en Angleterre a considérablement évolué, façonné par des approches pédagogiques novatrices visant à renforcer l’appréciation culturelle et la maîtrise linguistique des élèves. Cette communication explore la mise en œuvre du cadre “Enseigner comme une STAR” à l’Eden Girls’ Leadership Academy de Manchester, en tant qu’étude de cas. Ce cadre intègre des méthodes interactives telles que la répétition chorale, les célébrations culturelles, la poésie, la musique et le cinéma pour impliquer activement les élèves dans l’apprentissage de la langue. Au cœur de cette approche se trouve l’enseignement de l’ourdou en tant que langue étrangère, incorporant des méthodologies diverses, des stratégies de développement curriculaire et l’intégration de la technologie pour soutenir les résultats des élèves. Des plateformes numériques comme Language Nut et Lingo Tech offrent des expériences d’apprentissage personnalisées, tandis qu’un contenu riche sur le plan culturel favorise le multilinguisme et la compétence interculturelle. Les enseignements tirés de ce modèle contribuent à des discussions plus larges sur les stratégies d’enseignement des langues, en mettant en lumière l’importance de l’immersion culturelle, des méthodologies pédagogiques innovantes et de la technologie dans l’amélioration de l’acquisition des langues et de la sensibilisation culturelle chez les apprenants dans des contextes éducatifs diversifiés.

Table ronde dans le cadre de la journée de lancement du projet ciblé THEMIS : toucher les publics.

Le Présage is the first restaurant concept in Europe whose cooking system is powered by solar thermal energy. Having confirmed the feasibility of the concept with its "guinguette solaire", the company now wants to optimise the cooking system and integrate it into an innovative building with high environmental quality. The cooking system comprises three elements: a Scheffler reflector that collects and concentrates sunlight; a secondary reflector that reflects the concentrated flux upwards; and a cast-iron plate that acts as a solar absorber on the underside and as a cooking plate on the top. The Scheffler reflector is a parabolic dish that is flexible, enabling it to concentrate solar radiation at a fixed point throughout the year, without requiring the reflector to rotate around this point. As a result, the focal point can be positioned inside a building in which a kitchen can be installed. The aim of this doctoral research project is to understand and evaluate the performance of this promising concentrating solar cooker concept. In the first chapter of this thesis, the overall performance of the solar cooker is evaluated in order to obtain an initial estimate that can serve as a benchmark for comparison with future improvements. First, the different ways of modelling and evaluating solar cooker performance are explored. The specific characteristic time constant, the opto-thermal ratio and the corrected standard power are selected from other performance indicators and expressed using an energy balance based on a lumped-element model. Next, the test bench developed, similar to the cooker used by the Le Présage restaurant, is described. Experiments were carried out using a protocol similar to that used by ASABE, and regression analyses of temperature, efficiency and normalised power are detailed. The opto-thermal ratio of the cooker varies from 0.06 m2 · K · W−1 to 0.22 m2 · K · W−1 , while the corrected standard power reaches up to 416 W. In the second chapter, the Scheffler reflector is studied in more detail. The objectives are to evaluate its energy performance and to obtain information about the shape of the heat flux it delivers. Theoretical and numerical studies in the literature have produced highly variable results, and experimental data is currently lacking. A second test bench and another experimental protocol were therefore developed. Using infrared thermography and inverse techniques, detailed maps of heat flux densities on a vertical absorber were obtained from measurements carried out on different days between March and July. The average energy efficiency is estimated at 68 %. The heat flux distributions provided are then successfully fitted to a two-dimensional Gaussian model. The model parameters are used to calculate, among other things, the mean major and minor diameters of the ellipse containing 99.7 % of the heat flux, i.e. 47 cm and 37 cm respectively. The surface concentration ratio and the heat flux concentration ratio are evaluated at 36 and 24 respectively. The issue of repeatability of measurements and seasonal/daily variations is also addressed. Overall, this work provides a detailed data set on the performance of the solar cooker studied using two innovative methodologies. These results provide fundamental information for identifying improvements to the system, for modelling the reflector and for optimising secondary optical systems and the absorber.

Procedures developed to allow generation of radio nuclide inventory data depend on fluxes and cross sections calculated by assembly spectrum codes. Their accuracy depends on the assembly spectrum code capacity to generate correct prediction data; otherwise corrections have to be made to eliminate the residual calculation/experiment discrepancies. In this work we present the effect of taking into account the temperature and boron history on predicted isotopic compositions (uranium and plutonium) of a 40 GWd/t UO 2 fuel.

We present evidence that the detection of surface magnetism without the application of an external magnetic field is possible by studying the x-ray emission of highly charged ions interacting at grazing incidence with the sample. Measuring the 3 keV n = 2 → 1 transition in the interaction of Ar 17+ with a nickel sample at various temperatures gives access to the n = 2 ion population. The latter evolves from a half-filled to a full shell during the ferro-paramagnetic phase transition of the sample, with the ferromagnetic phase reflecting the filling blocking due to Pauli principle. This finding puts an end to a longstanding controversy arising from contradictory studies of ion-surface interaction using Auger spectroscopy.

Even if it is less controversial today than it used to be that intonation is part of the grammar of languages, it is still a challenge and a major issue to define what the primitives of intonational analysis are and how they contribute to the meaning of the utterance. My research defends the idea of the ‘linguistic normality’ of intonation and intonational meaning by attempting to identify its specificity. I defend the double articulation of intonational patterns into meaning-carrying units (pitch accents and boundary tones), which can themselves be broken down into meaningless units (tones). I argue that the meaning of intonation reflects the intimately dialogical and interactional dimension of language in several respects: 1) it indicates which parts of the utterance refer to the knowledge shared by the interlocutors or to the specific issue at stake in the utterance; 2) it indicates how the speaker assumes or attributes to the interlocutor the knowledge and beliefs brought into play by the situation evoked by the utterance; 3) it suggests the form that the following utterance could or should take, its source and its potential relations with the utterance in progress.