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Anomalous metallicity and electronic phase separation in theCsC60polymerized fulleride
No full textInternational audienceCs and 13 C-NMR have been used to study the electronic properties of the polymerized phase of CsC 60 at ambient and under hydrostatic pressure. The salient result of this study is the finding of fluctuations in the local field at 133 Cs site, which are independent of the applied pressure and due to thermally activated changes in the local electronic environment of 133 Cs nuclei. We establish that the phase separation between magnetic and nonmagnetic domains observed in the low-temperature state at ambient pressure is the result of a slowing down of these fluctuations likely related to polaronic-charge excitations on the polymers
One dimensional organic superconductors : Beyond the Fermi liquid description
No full textInternational audienceOrganic Superconductivity has been discovered for the first time in 1979 in the one dimensional organic conductor (TMTSF)zPFe. The extensive studies carried on over the last 20 years have revealed the existence of a vast and prototype family of isostructural compounds (TM)zX, exhibiting signatures of non-Fermi behavior at high temperature and a variety of ground states at low temperature
Nouvelle approche de la prédétermination des pluies extrêmes
No full text[Departement_IRSTEA]EEE [TR1_IRSTEA]23 - ALTEAURISK / BORISNational audienceA stochastic model for generating hourly hyetographs use temporal observed rainfall information to reproduce them statistically. Its use on long periods of simulation allows to study rainfalls on all the frequency scale. The modelisation gives a more than exponential behaviour to the cumulative frequency curve of the maximum rainfalls. With the modelisation of observed processes like storms persistence, we give more importance to the extreme events than a simple fitting of the observed cumulative frequency curves. Moreover, this approach based on the analysis of a large number of storms seems more robust beyond the sampling.Un modèle stochastique de génération de hyétogrammes horaires utilise l'information contenue dans les chroniques de pluies observées pour les reproduire statistiquement. Son utilisation sur de très longues périodes de simulation permet d'étudier les distributions de fréquences des pluies du courant à l'exceptionnel. La modélisation conduit alors à un comportement à l'infini super-exponentiel des distributions de fréquence des pluies. Par la prise en compte de phénomènes observés, la modélisation des pluies donne plus de sérieux aux événements extrêmes qu'un simple ajustement des distributions observées. De plus, cette approche basée sur l'analyse d'un grand nombre d'averses semble plus stable face à l'échantillonnage
Ground Reinforcement in Seismic Aeras
No full textThe yield design theory presents a rational tool for the evaluation of the seismic bearing capacity of shallow foundations. It has been successfully implemented and tested against case histories for foundation on unreinforced soil. This theoretical framework is extended to an innovative foundation design concept in seismic areas. This concept based on the reinforcement of the in-situ soil with stiff, closely spaced inclusions, is economic, easy to implement and significantly improves the seismic bearing capacity of the foundation. In addition, but not the least, this concept introduces a capacity design philosophy in foundation engineering. Numerical studies and centrifuge model tests have demonstrated the validity of the concept and of the theoretical tools
Structural Transition in the Quasi-Two-Dimensional Organic Superconductor k-(ET)2Cu[N(CN)2]Br Studied by 13C MAS NMR
No full textInternational audienc
Innovative concepts in foundation engineering
No full textFollowing the 1985 Michoacan Guerrero earthquake, a significant amount of work has been devoted to the evaluation of the foundation bearing capacity under earthquake loading. After a review of the previous studies which have been initiated in France, this paper presents a new, innovative, design concept to improve the seismic bearing capacity of a shallow foundation under difficult soil conditions. Aside from improving the bearing capacity, it introduces the capacity design philosophy in foundation engineering
NMR in the (BEDT)zX Organic Superconductors
No full textInternational audienceWe review recent NMR studies of a layered organic superconductor of the (BEDT)zX family. First the normal state properties are discussed. The central issue is the importance of the interplay between antiferromagnetism and superconductivity in these materials demonstrated by the observation of a pseudogap developing prior to the superconducting transition. The use of high pressure to tune the amplitude of AF fluctuations enables us to draw a general phase diagram of the family. In the second part the NMR experiments in the superconducting state are presented. One of the fundamental questions addressed by these experiments is the symmetry of the order parameter related to the pairing mechanism. The most spectacular NMR measurements are those performed in the lock-in state, which give access to the density of superconducting excitations at low energy. These experiments suggest that the pairing state may be unconventional featuring an anisotropic superconducting gap, possibly with nodes
