Microseismic activity and fluid fault interactions: some results from the Corinth Rift Laboratory (CRL), Greece

International audienceThe Gulf of Corinth, in western-central Greece, is one of the fastest continental rifts in theworld. In its western section near the city of Aigion, the previous work has outlined theexistence of a shallow dipping seismogenic zone between 5 and 12 km. This seismic activityhas been monitored with a network of 12 three-component stations for the period 2000–2007. Three, few months long, seismic swarms have been observed. They mobilize a complexstructural fault system that associates both shallow dipping elements and subvertical structureswith very different azimuths, some of which extend to depths greater than that of the shallowdipping zone. The swarm activity associates intensely active, short crises (a few days) withmore quiescent periods. The long-term growth velocity of the seismically activated domainsis compatible with a fluid diffusion process. Its characteristics are discussed in the context ofthe results from the 1000 m deep AIG10 well that intersects the Aigion Fault at 760 m. Thevertical growth directions of the seismically activated volumes outline two different sources forthe fluid and imply non-steady pressure conditions within the seismic domain. The diffusivityalong the cataclastic zone of the faults is in the order of 1 m2s−1, while faults act as hydraulicbarrier in the direction perpendicular to their strike. If the vertical direction is a principalstress component, the high pore pressure values that must be reached to induce slip on theshallowly dipping planes can result only from transitory dynamic conditions. It is argued thatthe shallow dipping active seismic zone is only local and does not correspond to a 100 kmscale decollement zone. We propose to associate the localization process with deep fluid fluxesthat have progressively modified the local stress field and may be the cause for the quiescenceof the West Heliki Fault presently observed

Anisotropic and inhomogeneous Coulomb screening in the Thomas-Fermi approximation: Application to quantum dot-wetting layer system and Auger relaxation

International audienceA model for anisotropic and inhomogeneous Coulomb screening due to 2D and 3D carriers, is proposed in the Thomas–Fermi approximation. Analytical expressions for the screened interaction potentials and scattering matrix elements are obtained. This model is applied to the Auger relaxation of carriers in an InAs/InP quantum dot (QD) – wetting layer (WL) system. The influences of the QD morphology and carriers densities on screening and Auger effects are studied. 2D–2D scattering is found to be the most important process, depending especially on QD morphology. A smearing effect is associated to the wetting layer wavefunction extension along the growth axis. The screened potential is similar to a potential screened by 3D carriers

Semianalytical model for simulation of electronic properties of narrow-gap strained semiconductor quantum nanostructures

International audienceA complete semianalytical model is proposed for the simulation of the electronic, mechanical, and piezoelectric properties of narrow-gap strained semiconductor quantum nanostructures. A transverse isotropic approximation for the strain and an axial approximation for the strained 8x8 Hamiltonian are proposed. It is applied extensively to the case of InAs/InP quantum dots (QDs). Symmetry analysis shows that there does exist a nonvanishing splitting on the electron P states due to the coupling with valence band. This splitting, which was not considered before, is found to be smaller in InAs/GaAs QD than in InAs/InP QD. Analytic expressions for the first and second order piezoelectric polarizations are used to evaluate the perturbation of electronic states

Procédés Limités par le Transfert de Rayonnement en Milieu Hétérogène: Étude des couplages cinétiques et énergétiques dans les photo-bioréacteurs par une approche thermodynamique

L'étude présente des approches théoriques et expérimentales permettant de modéliser les procédés physiquement limités par le transfert de rayonnement dans des milieux potentiellement complexes (semi-transparents, diffusants et participants). Les propriétés optiques et radiatives des particules de formes quelconques sont d'abord calculées, comme paramètres d'entrée pour la résolution de l'équation linéaire de Boltzmann (ou Équation des Transferts Radiatifs) conduisant à la connaissance du champ de radiation. Le couplage thermocinétique est ensuite formulé dans le cas concret des photo-bioréacteurs. Le modèle de connaissance prédictif et réifié obtenu est alors utilisé pour simuler, concevoir, optimiser ou contrôler divers photo-bioréacteurs

From k·p to atomic calculations applied to semiconductor heterostructures

International audienceWe present a brief overview of the main results obtained in our group for the simulation of electronic and optical properties of semiconductor heterostructures. A short introduction is given on InAs quantum dots, grown on InP, GaAs and GaP substrates. It is shown that 1-band k·p calculations can be used in the reciprocal space, in order to get a simulation of perfectly ordered array of quantum dots. A semianalytical modeling is also presented, including an axial approximation of the 8*8 band k·p calculations. Linear and nonlinear contributions to piezoelectricity are discussed. A complete 8*8 band k·p approach is then used to show the properties of InAs/InP quantum dots, with different substrate orientations. Finally, a study of the highly strained InAs/GaP interface is performed with a first principle modeling using ABINIT packages. Band lineups and evolution of gap energies are calculated, and compared to those found by Chuang et al. [1

Modélisation et Ingénierie de la Photosynthèse

National audienceLa modélisation numérique a permis d'améliorer de nombreux procédés biotechnologiques à tous les niveaux (conception, optimisation, commande, supervision). C'est également le cas pour la culture des microalgues, où des efforts intenses sont aujourd'hui déployés pour développer des modèles de divers niveaux de complexité en fonction des objectifs et des dispositifs de production considérés (photobioréacteurs ou raceways), relevant cependant tous de l'ingénierie. Lorsqu'il s'agit de produire de la biomasse, le procédé est conduit de façon à ce que tous les éléments nutritifs soient maintenus à des concentrations optimales pour la croissance. Les deux principaux facteurs restants (éminemment variables dans le temps) agissant sur la croissance sont alors la lumière et la température dont les évolutions résultent du flux d'énergie solaire. Ce chapitre propose une revue des différents modèles physiques et biologiques existant, et présente les défis futur pour améliorer la modélisation de ces systèmes biotechnologiques émergeants