Search results for "Diffusion"
showing 10 items of 1615 documents
Ultra-high repetition all optical picosecond pulsed sources : applications in optical telecommunications
2013
This thesis presents the work carried out on the realization of fibered 40-GHz picosecond optical pulse sources in the telecommunications C-band. In the first part, we present a numerical and experimental study of the generation of 40-GHz pulse trains thanks to the nonlinear compression of an initial beat-signal by multiple Four-Wave Mixing process. Enhanced temporal stability is achieved by generating the sinusoidal beating thanks to a Mach-Zehnder modulator driven at its zero-transmission working point. In order to improve the quality of the generated pulses, we also demonstrate the suppression of stimulated Brillouin back-scattering by inserting several optical isolators into the compres…
Quantum dynamics of the oxygen isotopic exchange : lifetimes of metastable states of the ozone intermediate complex
2021
This thesis aims to describe the ozone dynamics during the isotopic exchange reactions of oxygen of type xO + yO zO (xO yO zO)* xO yO + zO, where x, y and z are the atomic masses of the stable oxygen isotopes (16, 17, 18). Firstly, we analyze several methods of accurate description of the atom interactions and numerical schemes to obtain the observables for the collision. Then, in a full-quantum hyperspherical formalism, we study the actual dynamics of the reactive process O + O2 -> O3* -> O2 + O. The metastable ozone created can then either decompose into oxygen by the inverse reaction, or relax into stable ozone by exchanging energy with the environment, typically N2 or O2 molecules. Thes…
Molecular semiconductor-doped insulator (MSDI) heterojunctions as new transducers for chemical sensors
2011
International audience; This article describes a new principle of transduction involving an heterojunction between a Molecular Semiconductor and a Doped Insulator (MSDI). Herein, we report on an MSDI-based sensor featuring an heterojunction between a lutetium bisphthalocyanine (LuPc), which acts as Molecular Semiconductor (MS) and a thin film of Doped Insulator (DI) made of substituted or fluorinated copper phthalocyanine (CuFPc, where = 0, 8, 16). Previously, we reported the peculiar effect of the heterojunction on the MSDI's electronic behavior, suggesting this device as a new kind of transducer for gas chemosensing. Indeed, of particular significance was the key role of modulator played …
Dynamiques de populations en milieu hétérogène : modèles et estimation de paramètres
2017
Prod 2017-344i SPE équipe EA GESTAD INRA; National audience; Cet exposé traite de (i) la modélisation de dynamiques de populations dans des paysages hétérogènes, (ii) la modélisation des paysages eux-mêmes, (iii) l'estimation des paramètres de ces modèles à partir de données d'abondance ou de données génétiques. Nous nous concentrerons sur deux grandes classes de modèles de dynamique des populations : les modèles individu-centrés basés sur des équations différentielles stochastiques, et les modèles de réaction-diffusion. Après une introduction du lien entre ces approches, 5 illustrations issues des projets sont présentées: - modélisation de paysages hétérogènes fragmentés, via l’outil MULTI…
How does shear zone nucleate? An example from the Suretta nappe (Swiss Eastern Alps)
2016
In order to address the question of the processes involved during shear zone nucleation, we present a petro-structural analysis of millimetre-scale shear zones within the Roffna rhyolite (Suretta nappe, Eastern central Alps). Field and microscopic evidences show that ductile deformation is localized along discrete fractures that represent the initial stage of shear zone nucleation. During incipient brittle deformation, a syn-kinematic metamorphic assemblage of white mica + biotite + epidote + quartz precipitated at ca. 8.5 ± 1 kbar and 480 ± 50 °C that represent the metamorphic peak conditions of the nappe stacking in the continental accretionary wedge during Tertiary Alpine subduction. The…
The role of enzymes in biomineralization processes.
2008
56 pages; International audience
Brain lateralization probed by water diffusion at the atomic to micrometric scale
2019
International audience; Combined neutron scattering and diffusion nuclear magnetic resonance experiments have been used to reveal significant interregional asymmetries (lateralization) in bovine brain hemispheres in terms of myelin arrangement and water dynamics at micron to atomic scales. Thicker myelin sheaths were found in the left hemisphere using neutron diffraction. 4.7 T dMRI and quasi-elastic neutron experiments highlighted significant differences in the properties of water dynamics in the two hemispheres. The results were interpreted in terms of hemisphere-dependent cellular composition (number of neurons, cell distribution, etc.) as well as specificity of neurological functions (s…
Dynamiques spatio-temporelles de la vigne (Vitis vinifera) au cours de l’Holocène en France d’après les enregistrements archéobotaniques (graines et …
2021
International audience; Le vin joue un rôle économique et culturel capital depuis l’âge du Fer en France. Dès cette époque, la viticulture s’implante dans le Midi méditerranéen puis va progressivement se diffuser dans la zone tempérée. L’archéologie a bien montré à quel point le Haut-Empire romain représente une étape clé dans cette diffusion (Poux et al. 2011). Cependant, les différents marqueurs à disposition de l’archéologie culturelle et spatiale (aménagements, structures, mobiliers) sont généralement limités à des fenêtres chrono-géographiques particulières. Changeant en fonction du contexte technique, culturel et environnemental, aucun ne permet véritablement de suivre l’expansion de …
The "very loyal pinot": historical trajectory of a mythic grape variety of Burgundy
2019
Grape varieties began to appear in historical sources at the end of Middle Ages. In Burgundy, early mentions of pinot correspond to an evolution in the way wines were named. From the 14th century onwards, pinot wines have persistently demonstrated to express elements of superior quality. This variety is often offered at expensive prices due to the nature of its rarity, and as a result is commonly reserved explicity for the élites. However, it is suggested that the roles of The Dukes of Burgundy, concerning the promotion of grape varieties, is to be moderated. Therefore, if Philippe le Hardi’s proclamation condemns « the very bad and very disloyal plant called gaamez » then, it is evident th…
Diffusion régionale du silex crétacé des minières de Saint-Gond (Marne, France) au Néolithique récent et final
2018
International audience; La région des Marais de Saint-Gond (Marne) comporte un très grand nombre de sites néolithiques. Elle est surtout connue pour ses nombreuses sépultures collectives en hypogées et en allées couvertes. Des ateliers de taille et des habitats y ont également été détectés. Tous ces sites ont fourni des quantités de silex taillés. L’origine de ces silex et le contexte géologique de la région n’avaient pas encore fait l’objet d’une étude détaillée. Depuis 2012 les prospections ont permis de localiser 17 minières et plusieurs dizaines d’affleurements de bancs de silex. Ces données montrent que le silex est très abondant dans la région et qu’il a été intensément exploité au Né…