Influence of hydrogen and oxygen content on the mechanical behavior of zirconium between 275 and 325°C and titanium at 20°C

International audienceThe mechanical behaviors of α-Zr and α-Ti with various oxygen and hydrogen contents were investigated by loading/relaxation/unloading tensile tests and tests with strain rate jumps, at 300°C and 20°C, respectively. Solute oxygen and hydrogen atoms were found to have antagonist effects. While the former increases the yield stress and hardening exponent, reduces the activation volume and enhances static and dynamic strain aging phenomena, the latter significantly reduces these effects, as long as the O content is not too high

Optical Excitation of Nuclear Spin Coherence in Tm3+:YAG

A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. For the first time, nuclear spin coherence is optically excited, detected and characterized in such a crystal. The lifetime of the spin coherence -- the potential storage entity -- is measured by means of Raman echo to be about 300 $\mu$s over a wide range of ground state splittings. This flexibility, attractive for broadband operation, and well fitted to existing quantum sources, results from the simple hyperfine structure, contrasting with Pr- and Eu- doped crystals

Optical Excitation of Nuclear Spin Coherence in Tm3+:YAG

A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. For the first time, nuclear spin coherence is optically excited, detected and characterized in such a crystal. The lifetime of the spin coherence -- the potential storage entity -- is measured by means of Raman echo to be about 300 $\mu$s over a wide range of ground state splittings. This flexibility, attractive for broadband operation, and well fitted to existing quantum sources, results from the simple hyperfine structure, contrasting with Pr- and Eu- doped crystals

Integrated non-invasive remote-sensing techniques and field survey for the geoarchaeological study of the Sud Lípez mining district, Bolivia

New investigations have been carried out in the framework of a joint French-Argentine project dealing with the mineral resources and the metal production in the Andean plateau from the 10th to the 18th century. Geoarchaeology of the Sud Lípez, southern Bolivia, is revisited using multisource remote-sensing data including archive data from the 1960s and recent very high resolution (VHR) data simultaneously acquired with field work. The detailed geological mapping of the area is allowed by the field survey complemented by the multispectral and VHR data. The emphasis is on integrating all the geological features such as morphologies, petrology of the volcanics, lithology of the volcano-sedimentary rocks, regional and local faulting, veins, hydrothermally altered rocks, etc. GeoEye-1, which features the most advanced technology ever used in a civilian remote-sensing system, allows the detailed mapping of the archaeological remains that are particularly numerous at San Antonio de Lípez, with shallow pits, shafts connected in depth with adits, and large slag areas. Particularly, the plan of three old miners' villages has been drawn and its accuracy has been evaluated.Fil: Deroin, Jean Paul. Universite de Reims-Champagne Ardenne; FranciaFil: Téreygeol, Florian. Centre National de la Recherche Scientifique; FranciaFil: Cruz, Pablo. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guillot, Ivan. Centre National de la Recherche Scientifique; FranciaFil: Méaudre, Jean Charles. Centre National de la Recherche Scientifique; Franci

Spatialiser la transition énergétique: Vers la production d'"écosystèmes énergétiques territoriaux" en milieu ruralRapport intermédiaireOctobre 2014

Cette recherche vise à interroger la « cohérence spatiale » des logiques de substitution énergétique à l’œuvre en France. On part du constat que les innovations dans ce domaine sont le plus souvent appréhendées dans une logique techniciste, se traduisant en terme d’aménagement par une banalisation et une uniformisation du territoire et des paysages. Dans ce contexte la transition énergétique représente un enjeu spatial de premier ordre devant être saisi dans toute sa complexité, par les diverses échelles d’aménagement qu'elle touche : architecturale, urbaine et paysagère. A cet égard, ce débat doit être impérativement relayé par une réflexion critique sur les logiques d'innovation en cours, en vue d'élaborer d'autres concepts et approches, pour qualifier cette transition et l'aborder en termes de projet. Les territoires ruraux de faible densité à dominante agricole et forestière constituent notre terrain d'étude privilégié. On est parti de l’hypothèse que ces territoires représentent un enjeu de projet stratégique, tant par leurs évolutions démographiques et économiques, que par leur potentiel de production énergétique lié à leurs ressources naturelles. Prenant en compte ces caractéristiques, un des objectifs clefs de cette recherche sera d'identifier à l'échelle locale le nouveau substrat énergétique, mettant à profit la puissance des quatre éléments propres aux énergies renouvelables - énergie chimique contenue dans la biomasse ; énergie mécanique de l'eau ou du vent ; énergie thermique de l'eau chaude du sous-sol ou du rayonnement solaire. Autrement dit, il sera question de préfigurer une nouvelle « économie de l'habiter » en milieu rural, liée à la mise en place de ce nouveau substrat technique et énergétique. Dans cette optique deux concepts fédérateurs sont élaborés de manière hypothétique à cette étape de notre travail : - celui d'« écosystème énergétique territorial », permettant de croiser les « échelles énergétiques » et de travailler autant au stade de « l'énergie finale » (les outils et les infrastructures influant sur la dépense d'énergie), qu'au stade de « l'énergie primaire » (les formes sous lesquelles la nature livre l'énergie)- celui de « plan local d'énergie et de paysage », permettant d'identifier les implications à l'échelle architecturale et territoriale, de ce nouveau substrat énergétique, à moyen et à long termes. Méthodologie de recherche : Cette réponse élaborée conjointement avec des enseignants-chercheurs de l’ENSAG et du réseau ERPS vise à poursuivre une méthode de recherche spécifique explorée précédemment fondée sur l'interdisciplinarité : la recherche par le projet. Selon cette méthode, le projet joue un double rôle : heuristique et expérimental. La dimension heuristique, développée dans la première phase de la recherche consiste à faire émerger par le projet, dans le cadre des ateliers de Master, des questions architecturales et territoriales stratégiques par rapport à nos objectifs de recherche. Traitées d'un point de vue scientifique, ces questions permettront de formuler des hypothèses qui seront livrées aux concepteurs et testées dans le second temps de projet, la phase expérimentale. Le matériel produit à l’issue de ces phases de projet sera ensuite analysé par l’équipe afin de dégager des résultats discutés dans le cadre élargi d’un séminaire international. Au travers de ces travaux en atelier, il s’agit de produire des connaissances spécifiques, susceptibles renouveler nos pratiques d'aménagement vers la construction d'une nouvelle alliance homme/territoire basée sur une redéfinition de notre rapport à l'énergie et à ses modes de production. En somme, de la recherche par l’action et pour l’action. Sa mise en application repose sur une dynamique de travail interdisciplinaire combinant activité scientifique, activité pédagogique et activité de mise en œuvre d'un projet expérimental, à partir du territoire de la commune d'Ambert située dans le Parc naturel régional du Livradois-Forez

Thermalizing a telescope in Antarctica: Analysis of ASTEP observations

The installation and operation of a telescope in Antarctica represent particular challenges, in particular the requirement to operate at extremely cold temperatures, to cope with rapid temperature fluctuations and to prevent frosting. Heating of electronic subsystems is a necessity, but solutions must be found to avoid the turbulence induced by temperature fluctua- tions on the optical paths. ASTEP 400 is a 40 cm Newton telescope installed at the Concordia station, Dome C since 2010 for photometric observations of fields of stars and their exoplanets. While the telescope is designed to spread star light on several pixels to maximize photometric stability, we show that it is nonetheless sensitive to the extreme variations of the seeing at the ground level (between about 0.1 and 5 arcsec) and to temperature fluctuations between --30 degrees C and --80 degrees C. We analyze both day-time and night-time observations and obtain the magnitude of the seeing caused by the mirrors, dome and camera. The most important effect arises from the heating of the primary mirror which gives rise to a mirror seeing of 0.23 arcsec K--1 . We propose solutions to mitigate these effects.Comment: Appears in Astronomical Notes / Astronomische Nachrichten, Wiley-VCH Verlag, 2015, pp.1-2

Nanoindentation: A powerful tool to explore the wide chemical space of high entropy alloys

High entropy alloys (HEA) are multi-component alloys, without any minor or major elements (i.e. : all elements are very concentrated) and they form a unique solid solution. It was proven that, especially for the system Co-Cr-Fe-Mn-Ni, they exist for a very wide range of composition [1]. This opens the opportunity of multi-properties optimization, like cost, density and mechanical resistance. However, to take advantage of this opportunity, accelerated mechanical testing tools are required. Please click Additional Files below to see the full abstract

La pacificación del mineral: Cerro Lípez, un enclave minero en la contienda sobre el Nuevo Mundo

Las faldas del cerro Lípez (Prov. Sud-Lípez, Dpto. Potosí, Bolivia), conservan los vestigios de asentamientos, rancherías e instalaciones productivas que estuvieron asociadas con la producción minera y metalúrgica en tiempos coloniales, y posiblemente antes. Inagotable fuente de tesoros tapados para la población local, pueblos fantasmas para los pocos turistas que pasan por allí, estos testimonios materiales constituyen una fuente de información excepcional para el estudio tanto del pasado regional como del universo de la producción de metales. En efecto, a pesar de su lejanía y rudeza climática, este enclave minero fue el escenario donde se sucedieron intensos, cuando no violentos, eventos en torno al control tanto de los yacimientos mineros como de los espíritus humanos. Relocalización de pueblos indígenas, extirpación de antiguos cultos, destrucción de asentamientos y acelerados cambios productivos, transformaciones del paisaje, etc. En su conjunto, estos eventos muestran una síntesis de la empresa colonial en esta región del espacio surandino. A la luz de los nuevos datos y en una aproximación multidisciplinar (historia, arqueología, arqueometría, teledetección) trataremos aquí sobre los parajes que conformaron San Antonio del Nuevo Mundo. El caso de estudio abrirá el debate sobre la articulación entre las fuentes históricas y el registro arqueológico, tanto sus encuentros y complementariedades, como sus desencuentros y silencios.The base of the Cerro Lípez (in the province Sud Lípez, Potosi, Bolivia) preserves the remnants of settlements, ranches and other productive installations that were associated with mining and metalurgical production during the colonial era and most likely, the pre-colonial era as well. While these remnants are an endless source of hidden treasures for the local population and interesting ghost towns for the few tourists that wander through, these material testimonies also constitute an exceptional source of information for the study of not only the region’s past, but also the history of metal production. Despite the remote location and rude climate, this mining enclave was the scene of intense, and sometimes violent, events and conflicts for the control of both minerals and human souls; the relocation of indigenous peoples, the extirpation of ancient cults, the destruction of settlements and accelerated changes in production and transformations of the landscape, etc. Taken as a whole, these events show us a synthesis of the colonial venture in this southern Andean region. In light of new data, and by using an interdisciplinary approach (incorporating history, archaeology, archeometry and teledetection), we will examine the places and spaces that shaped San Antonio del Nuevo Mundo. This case study opens a debate about the relationship between historical sources and the archaeological record, addressing both their complementarity and their points of discord and disagreement.Fil: Cruz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nielsen, Axel Emil. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Téreygeol, Florian. Centre National de la Recherche Scientifique; FranciaFil: Deroin, Jean Paul. No especifíca;Fil: Guillot, Ivan. Centre National de la Recherche Scientifique; Franci

Identification of Pre-frailty Sub-Phenotypes in Elderly Using Metabolomics

Aging is a dynamic process depending on intrinsic and extrinsic factors and its evolution is a continuum of transitions, involving multifaceted processes at multiple levels. It is recognized that frailty and sarcopenia are shared by the major age-related diseases thus contributing to elderly morbidity and mortality. Pre-frailty is still not well understood but it has been associated with global imbalance in several physiological systems, including inflammation, and in nutrition. Due to the complex phenotypes and underlying pathophysiology, the need for robust and multidimensional biomarkers is essential to move toward more personalized care. The objective of the present study was to better characterize the complexity of pre-frailty phenotype using untargeted metabolomics, in order to identify specific biomarkers, and study their stability over time. The approach was based on the NU-AGE project (clinicaltrials.gov, NCT01754012) that regrouped 1,250 free-living elderly people (65–79 y.o., men and women), free of major diseases, recruited within five European centers. Half of the volunteers were randomly assigned to an intervention group (1-year Mediterranean type diet). Presence of frailty was assessed by the criteria proposed by Fried et al. (2001). In this study, a sub-cohort consisting in 212 subjects (pre-frail and non-frail) from the Italian and Polish centers were selected for untargeted serum metabolomics at T0 (baseline) and T1 (follow-up). Univariate statistical analyses were performed to identify discriminant metabolites regarding pre-frailty status. Predictive models were then built using linear logistic regression and ROC curve analyses were used to evaluate multivariate models. Metabolomics enabled to discriminate sub-phenotypes of pre-frailty both at the gender level and depending on the pre-frailty progression and reversibility. The best resulting models included four different metabolites for each gender. They showed very good prediction capacity with AUCs of 0.93 (95% CI = 0.87–1) and 0.94 (95% CI = 0.87–1) for men and women, respectively. Additionally, early and/or predictive markers of pre-frailty were identified for both genders and the gender specific models showed also good performance (three metabolites; AUC = 0.82; 95% CI = 0.72–0.93) for men and very good for women (three metabolites; AUC = 0.92; 95% CI = 0.86–0.99). These results open the door, through multivariate strategies, to a possibility of monitoring the disease progression over time at a very early stage

Models of Neptune-Mass Exoplanets: Emergent Fluxes and Albedos

There are now many known exoplanets with Msin(i) within a factor of two of Neptune's, including the transiting planets GJ436b and HAT-P-11b. Planets in this mass-range are different from their more massive cousins in several ways that are relevant to their radiative properties and thermal structures. By analogy with Neptune and Uranus, they are likely to have metal abundances that are an order of magnitude or more greater than those of larger, more massive planets. This increases their opacity, decreases Rayleigh scattering, and changes their equation of state. Furthermore, their smaller radii mean that fluxes from these planets are roughly an order of magnitude lower than those of otherwise identical gas giant planets. Here, we compute a range of plausible radiative equilibrium models of GJ436b and HAT-P-11b. In addition, we explore the dependence of generic Neptune-mass planets on a range of physical properties, including their distance from their host stars, their metallicity, the spectral type of their stars, the redistribution of heat in their atmospheres, and the possible presence of additional optical opacity in their upper atmospheres.Comment: Accepted and Published in ApJ (2010 ApJ,709,149