Number theory in the national compulsory examination at the end of the French secondary level: between organizing and operative dimensions

International audienceIn our researches in didactic of number theory, we are especially interested in proving in the secondary-tertiary transition. In this paper, we focus on the "baccalauréat", the national examination that pupils have to take at the end of French secondary level. In reasoning in number theory, we distinguish two complementary dimensions, namely the organising one and the operative one, and this distinction permits to situate the autonomy devolved to learners in number theory problems such as baccalauréat's exercises. We have analysed 38 exercises, from 1999 to 2008, and we present the results obtained giving emblematic examples

Direct observation of the turbulent emf and transport of magnetic field in a liquid sodium experiment

International audienceFor the first time, we have directly measured the transport of a vector magnetic field by isotropic turbulence in a high Reynolds number liquid metal flow. In analogy with direct measurements of the turbulent Reynolds stress (turbulent viscosity) that governs momentum transport, we have measured the turbulent electromotive force (emf) by simultaneously measuring three components of velocity and magnetic fields, and computed the correlations that lead to mean-field current generation. Furthermore, we show that this turbulent emf tends to oppose and cancel out the local current, acting to increase the effective resistivity of the medium, i.e., it acts as an enhanced magnetic diffusivity. This has important implications for turbulent transport in astrophysical objects, particularly in dynamos and accretion disks

Holocene land-use evolution and associated soil erosion in the French Prealps inferred from Lake Paladru sediments and archaeological evidences

International audienceA source-to-sink multi-proxy approach has been performed within Lake Paladru (492 m a.s.l., French Prealps) catchment and a six-meter long sediment sequence retrieved from the central lacustrine basin. The combination of minerogenic signal, specific organic markers of autochthonous and allochthonous supply and archaeological data allows the reconstruction of a continuous record of past human disturbances. Over the last 10000 years, the lacustrine sedimentation was dominated by autochthonous carbonates and the watershed was mostly forest-covered. However, seven phases of higher accumulation rate, soil erosion, algal productivity and landscape disturbances have been identified and dated from 8400-7900, 6000-4800, 4500-3200, 2700-2050 cal BP as well as AD 350-850, AD 1250-1850 and after AD 1970. Before 5200 cal BP, soil erosion is interpreted as resulting from climatic deterioration phases toward cooler and wetter conditions. During the Mid-Late Holocene period, erosion fluxes and landscape disturbances are always associated with prehistorical and historical human activities and amplified by climatic oscillations. Such changes in human land-used led to increasing minerogenic supply and nutrients loading that affected lacustrine trophic levels, especially during the last 1600 years. In addition, organic and molecular markers document previously unknown human settlements around Lake Paladru during the Bronze and the Iron Ages

Modular termination of C programs

In this paper we describe a general method to prove termination of C programs in a scalable and modular way. The program to analyse is reduced to the smallest relevant subset through a termination-specific slicing technique. Then, the program is divided into pieces of code that are analysed separately, thanks to an external engine for termination. The result is implemented in the prototype \stoptool over our previous toolsuite WTC [compsys-termination-sas10] and preliminary results shows the feasibility of the method

Drug launch timing and international reference pricing

This paper analyzes the timing decisions of pharmaceutical firms to launch a new drug in countries involved in international reference pricing. We show three important features of launch timing when all countries reference the prices in all other countries and in all previous periods of time. First, there is no withdrawal of drugs in any country and in any period of time. Second, there is no strict incentive to delay the launch of a drug in any country. Third, whenever the drug is sold in a country, it is also sold in all countries with larger willingness to pay. We then show that the three results do not hold when the countries only reference a subset of all countries. The first two results do not hold when the reference is on the last period prices only

Un modèle de trafic adapté à la volatilité de charge d'un service de vidéo à la demande: Identification, validation et application à la gestion dynamique de ressources.

Dynamic resource management has become an active area of research in the Cloud Computing paradigm. Cost of resources varies significantly depending on configuration for using them. Hence efficient management of resources is of prime interest to both Cloud Providers and Cloud Users. In this report we suggest a probabilistic resource provisioning approach that can be exploited as the input of a dynamic resource management scheme. Using a Video on Demand use case to justify our claims, we propose an analytical model inspired from standard models developed for epidemiology spreading, to represent sudden and intense workload variations. As an essential step we also derive a heuristic identification procedure to calibrate all the model parameters and evaluate the performance of our estimator on synthetic time series. We show how good can our model fit to real workload traces with respect to the stationary case in terms of steady-state probability and autocorrelation structure. We find that the resulting model verifies a Large Deviation Principle that statistically characterizes extreme rare events, such as the ones produced by "buzz effects" that may cause workload overflow in the VoD context. This analysis provides valuable insight on expectable abnormal behaviors of systems. We exploit the information obtained using the Large Deviation Principle for the proposed Video on Demand use-case for defining policies (Service Level Agreements). We believe these policies for elastic resource provisioning and usage may be of some interest to all stakeholders in the emerging context of cloud networking.La gestion dynamique de ressources est un élément clé du paradigme de cloud computing et plus récemment de celui de cloud networking. Dans ce contexte d'infrastructures virtualisées, la réduction des coûts associés à l'utilisation et à la ré-allocation des ressources contraint les opé- rateurs et les utilisateurs de clouds à une gestion rationnelle de celles-ci. Dans ce travail nous proposons une description probabiliste des besoins liée à la volatilité de la charge d'un service de distribution de vidéos à la demande. Cette description peut alors servir de consigne (input) à la provision et à l'allocation dynamique des ressources nécessaires. Notre approche repose sur la construction d'un modèle stochastique inspiré des modèles de Markov standards de propaga- tion épidémiologique, capable de reproduire des variations soudaines et intenses d'activité (buzz). Nous proposons alors une procédure heuristique d'identification du modèle à partir de séries tem- porelles du nombre d'utilisateurs connectés au serveur. Les performances d'estimation de chacun des paramètres du modèle sont évaluées numériquement, et nous vérifions l'adéquation du modèle aux données en comparant les distributions des états stationnaires ainsi que les fonctions d'auto- corrélation des processus. Les propriétés markoviennes de notre modèle garantissent qu'il vérifie un principe de grandes dé- viations permettant de caractériser statistiquement l'ampleur et la durée d'évènements extrêmes et rares tels que ceux produits par les buzzs. C'est cette propriété que nous exploitons pour di- mensionner le volume de ressources (e.g. bande-passante, nombre de serveurs, taille de buffers) à prévoir pour réaliser un bon compromis entre coût de re-déploiement des infrastructures et qualité de service. Cette approche probabiliste de la gestion des ressources ouvre des perspectives sur les politiques de Service Level Agreement adaptées aux clouds et servant au mieux les intérêts des opérateurs de réseaux, de services et de leurs clients

Enseigner la France en géographie aux jeunes écoliers (1788-2008)

For the last two centuries, the ways of teaching geography of France to the young French pupils from 9 to 11 years old have known many transformations. The objectives and the finality have changed. These transformations result from the general changes in pedagogical methods at school, but also from the particular changes of how the French conceive their own territory and national identity.Since the beginning of the 19th century Geography taught in primary schools differs from the geography made for colleges and high schools, which has remained for a long time within the tradition of historical geography from the Ancient time to the modern period. At the end of the 19th century the 3rd French Republic put France and its colonies as the centre and the horizon of the geography studies. Geography at school was a main way to build up a national identity.In the 20th century, and more particularly during the sixties, thanks to the development of new media, space as perceived by young children became wider and more various. New curricula have been opened to new spatial dimensions: Europe and the world. The building of a national identity blends with regional, European and world wide scalar levels. Even if the latest curriculum is more focused on France.L'évolution de la façon dont la géographie de la France est présentée aux petits Français âgés de 9 à 11 ans montre les transformations des méthodes pédagogiques, en particulier celles en usage dans la leçon de géographie ; elle témoigne des transformations des finalités de l'enseignement de la géographie à l'école élémentaire et reflète autant l'évolution de l'espace français que la façon dont les Français pensent leur territoire.La géographie destinée aux élèves des écoles communales se différencie d'emblée des savoirs géographiques enseignés dans l'enseignement secondaire en rompant d'emblée avec la tradition de la géographie historique. La IIIe République fait ensuite de la France et de ses colonies l'horizon de la géographie de l'école primaire et le cadre identitaire des jeunes français. Depuis les années soixante l'espace perçu par les jeunes enfants via les différents médias s'est considérablement élargi et diversifié et les programmes scolaires se sont ouverts sur l'Europe et le monde, associant la construction de l'identité nationale avec d'autres niveaux scalaires de référence : la région, l'Europe, le monde ; même si le dernier programme est plus centré sur la France

Babel, une dynamique de la différence.

Cet article propose une analyse sémiotique du récit de la Tour de Babel, dans le livre de la Genèse. Il s'agit de montrer comment s'articulent dans le récit des enjeux fondamentaux autour de la fusion, de la dispersion et de la différence

Mission de Hadir Qinnasrin 2003, rapport préliminaire

Rapport préliminaire de la campagne 2003 à al-Hadir (région de Qinnasrin)

Constraints on source-forming processes of West Greenland kimberlites inferred from Hf-Nd isotope systematics.

International audienceKimberlites from West Greenland have Hf-Nd isotope as well as major and trace element compositions that are similar to other Group I kimberlites, but that are distinctive in the spectrum of magmas sampled at Earth's surface. The West Greenland kimberlites have εNdi that ranges from +1.6 to +3.1 and εHfi that ranges from −4.3 to +4.9. The samples exhibit ubiquitous negative ΔεHfi (deviation from the ocean island basalt εHf-εNd reference line), ranging from −1.8 to −11.2. The kimberlites are characterized by steep heavy rare earth element patterns, positive Ta-Nb anomalies and negative Hf-Zr anomalies. These chemical signals are consistent with the presence of ancient, subducted oceanic crust in the kimberlite source region. In the model we present, dewatering and possibly partial melting of rutile-bearing oceanic crust during subduction results in characteristic trace element patterns in the residual crust. During aging, the Hf-Nd isotopic composition of this dewatered/partially melted EMORB-type crust evolves to negative ΔεHfi values. Metasomatic fluids derived from this ancient subducted oceanic crust infiltrate and impart their trace element and isotopic signal on proximal peridotitic mantle. Melting of this metasomatized mantle peridotite results in kimberlite magmas