Diffusion of point defects in crystalline silicon using the kinetic activation-relaxation technique method

We study point-defect diffusion in crystalline silicon using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities based on the activation-relaxation technique (ART nouveau), coupled to the standard Stillinger-Weber potential. We focus more particularly on the evolution of crystalline cells with one to four vacancies and one to four interstitials in order to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics. We show formation energies, activation barriers for the ground state of all eight systems, and migration barriers for those systems that diffuse. Additionally, we characterize diffusion paths and special configurations such as dumbbell complex, di-interstitial (IV-pair+2I) superdiffuser, tetrahedral vacancy complex, and more. This study points to an unsuspected dynamical richness even for this apparently simple system that can only be uncovered by exhaustive and systematic approaches such as the kinetic activation-relaxation technique

The scaling of genetic diversity in a changing and fragmented world

Most species do not live in a constant environment over space or time. Their environment is often heterogeneous with a huge variability in resource availability and exposure to pathogens or predators, which may affect the local densities of the species. Moreover, the habitat might be fragmented, preventing free and isotropic migrations between local sub-populations (demes) of a species, making some demes more isolated than others. For example, during the last ice age populations of many species migrated towards refuge areas from which re-colonization originated when conditions improved. However, populations that could not move fast enough or could not adapt to the new environmental conditions faced extinctions. Populations living in these types of dynamic environments are often referred to as metapopulations and modeled as an array of subdivisions (or demes) that exchange migrants with their neighbors. Several studies have focused on the description of their demography, probability of extinction and expected patterns of diversity at different scales. Importantly, all these evolutionary processes may affect genetic diversity, which can affect the chance of populations to persist. In this chapter we provide an overview on the consequences of fragmentation, long-distance dispersal, range contractions and range shifts on genetic diversity. In addition, we describe new methods to detect and quantify underlying evolutionary processes from sampled genetic data.Laboratoire d’Excellence (LABEX) entitled TULIP: (ANR-10-LABX-41)

Economics of stationary electricity storage with various charge and discharge durations

Electricity storage encompasses a disparate list of technologies such as pumped-storage hydroelectricity, compressed-air energy storage, chemical batteries, and flywheels. These technologies can provide the electricity system with heterogeneous services of energy transfers across months, weeks, days or intra-days, power transfers for an hour, a few minutes or seconds, and can assist operators in load following, frequency control, and uninterrupted power supply. The paper presents a unified economic analysis of these technologies and services. We underline the role of charge and discharge durations as a criterion for economic segmentation of technologies and services. We highlight the complementary value of storage in electricity systems with a high share of low variable cost and low carbon generation (nuclear, hydro, wind power, solar photovoltaic). We also underline the limited substitution value of storage for generation with high variable cost (gas combustion-turbines or gas-oil motor engines), given the cost of state-of-the-art storage technologies and the current relatively low cost of fossil fuels and low carbon pricing

Economics of stationary electricity storage with various charge and discharge durations

Electricity storage encompasses a disparate list of technologies such as pumped-storage hydroelectricity, compressed-air energy storage, chemical batteries, and flywheels. These technologies can provide the electricity system with heterogeneous services of energy transfers across months, weeks, days or intra-days, power transfers for an hour, a few minutes or seconds, and can assist operators in load following, frequency control, and uninterrupted power supply. The paper presents a unified economic analysis of these technologies and services. We underline the role of charge and discharge durations as a criterion for economic segmentation of technologies and services. We highlight the complementary value of storage in electricity systems with a high share of low variable cost and low carbon generation (nuclear, hydro, wind power, solar photovoltaic). We also underline the limited substitution value of storage for generation with high variable cost (gas combustion-turbines or gas-oil motor engines), given the cost of state-of-the-art storage technologies and the current relatively low cost of fossil fuels and low carbon pricing

Eco-evolutionary dynamics in fragmented landscapes

Peer reviewedPostprin

Frontières culturelles et architecture rurale en France (ouest et centre-ouest)

En reprenant la classification des maisons rurales françaises d’Albert Demangeon, et en la confrontant à certaines des limites, culturelles et autres, mises en évidence depuis longtemps par les géographes et les ethnologues, il est possible d’avancer plus loin dans la définition des contrastes de tous ordres qui divisaient le monde rural français : 1) la maison rurale à cour ouverte, majoritaire dans les contrées de l’Ouest et du Centre-Ouest, était partie intégrante du système agraire en vigueur dans ces contrées, qui s’opposait à celui du Nord-Nord-Est de la France ; 2) l’étude des lieux et des techniques du battage montre cependant qu’il a existé une zone d’interférence entre les deux systèmes, surtout probablement entre la fin du XVIIIème et le milieu du XIXème siècle ; 3) le passage de la Loire ne se limite pas à un changement dans la charpente et la couverture des maisons : leur organisation peut connaître en réalité des modifications importantes de part et d’autre du fleuve, qui relèvent des modes de vie.Tacking back the Demangeon’s classification of french rural houses, and confronting it with any cultural lines discovered in rural France by geographists and ethnologists, it is possible to go further in the definition of contrasts which divided traditional rural France: 1) the rural house with open court, dominant in the West and Center-West countries, was an integrant part of the agrarian system which prevailed in these countries, quite different from the one of Northern and Northern-East countries; 2) meroever, the study of the treshing places and technics shows that a mixted area had existed, probably since the end of the XVIIIth century from the middle of the XIXth; 3) in the western countries, the Loire crossing represents more than a change in the houses’s framework and roofing: the organization of theses may be quite different on both sides of the river

Effets de facteurs internes (traits d'histoire de vie et sexe) et externes (qualité d'habitat et densité de population) sur la dispersion et mise en évidence de syndromes de dispersion

La dispersion, définie comme un mouvement individuel pouvant induire des flux de gènes, est un processus crucial pour le maintien à long terme des (méta-)populations. L'apport de nouveaux gènes dans une population permet de contrecarrer l'effet négatif de la dérive génétique et ainsi de limiter les risques de consanguinité, pouvant être néfastes pour les individus et engendrer une extinction des populations. Cette thèse a pour objectif principal d'améliorer notre connaissance sur la dispersion et sur le fonctionnement des populations. Dans un premier temps, des relations entre ce comportement, pouvant être différent d'un sexe à l'autre (dispersion biaisée par le sexe) et des traits d'histoire de vie ont été mises en évidence chez les amphibiens et les papillons, permettant dans un deuxième temps de prédire à partir de quelques traits les capacités de dispersion chez les espèces pour lesquelles les données de dispersion restent manquantes. Certains traits d'histoire de vie ont également montré des coévolutions avec la dispersion biaisée par le sexe. En parallèle de ces traits internes, l'influence de la qualité d'habitat, de la densité de population ainsi que du sexe ratio a également été étudié sur la dispersion de la piéride du chou (Pieris brassicae) en milieu expérimental (le Métatron). Tous les résultats de ce travail soulignent la complexité des pressions - internes, environnementales ou populationnellles - agissant sur la dispersion des individus (impact différent en fonction des sexes), et permettent de mieux comprendre les processus responsables de ce comportement nécessaire au maintien à long terme des populations.Dispersal, defined as an individual movement can induce gene flow, is a key process for metapopulations persistence. The addition of new genes in a population can counteract the negative effects of the genetic drift and thus reduce the risk of inbreeding, increasing the extinction rate of populations. The main objective of this thesis was to improve our understanding about the factors inducing dispersal and about the metapopulations functioning. At first, the relationship between this behavior - may be different from one sex to the other (sex-biased dispersal) - and life history traits have been identified in amphibians and butterflies. These relationships were then used to predict dispersal abilities among species for which data about dispersal are still missing. Some life history traits also showed coevolutions with sex-biased dispersal. Adding to these internal factors, the influence of habitat quality, population density and sex ratio were also studied on the dispersal of the cabbage butterfly (Pieris brassicae) in experimental condition (the Metatron). All results of this study highlight the complexity of pressures - internal, environmental or populationnal - acting on the dispersal of individuals (different impact by gender), and improve our understanding about the metapopulations functioning

Regards croisés sur le patrimoine

Ce gros volume, à la présentation soignée, est issu d'un colloque qui s'est tenu en Sorbonne du 7 au 9 octobre 1999. Il répondait à une intention ambitieuse de la part des organisatrices : poser "la question du patrimoine dans le monde de manière croisée dans des contextes différents" (p. 11). Ce sont les soixante communications, effectuées par 68 personnes, qui composent l'ouvrage. L'approche tient en quatre questions essentielles : 1) Les approches de la notion de patrimoine dans les différ..