Efficient numerical schemes for viscoplastic avalanches. Part 2: the 2D case

This paper deals with the numerical resolution of a shallow water viscoplastic flow model. Viscoplastic materials are characterized by the existence of a yield stress: below a certain critical threshold in the imposed stress, there is no deformation and the material behaves like a rigid solid, but when that yield value is exceeded, the material flows like a fluid. In the context of avalanches, it means that after going down a slope, the material can stop and its free surface has a non-trivial shape, as opposed to the case of water (Newtonian fluid). The model involves variational inequalities associated with the yield threshold: finite volume schemes are used together with duality methods (namely Augmented Lagrangian and Bermúdez–Moreno) to discretize the problem. To be able to accurately simulate the stopping behavior of the avalanche, new schemes need to be designed, involving the classical notion of well-balancing. In the present context, it needs to be extended to take into account the viscoplastic nature of the material as well as general bottoms with wet/dry fronts which are encountered in geophysical geometries. Here we derive such schemes in 2D as the follow up of the companion paper treating the 1D case. Numerical tests include in particular a generalized 2D benchmark for Bingham codes (the Bingham–Couette flow with two non-zero boundary conditions on the velocity) and a simulation of the avalanche path of Taconnaz in Chamonix—Mont-Blanc to show the usability of these schemes on real topographies from digital elevation models (DEM)

Efficient numerical schemes for viscoplastic avalanches. Part 1: The 1D case.

This paper deals with the numerical resolution of a shallow water viscoplastic flow model. Viscoplastic materials are characterized by the existence of a yield stress: below a certain critical threshold in the imposed stress, there is no deformation and the material behaves like a rigid solid, but when that yield value is exceeded, the material flows like a fluid. In the context of avalanches, it means that after going down a slope, the material can stop and its free surface has a non-trivial shape, as opposed to the case of water (Newtonian fluid). The model involves variational inequalities associated with the yield threshold: finite-volume schemes are used together with duality methods (namely Augmented Lagrangian and Bermúdez–Moreno) to discretize the problem. To be able to accurately simulate the stopping behavior of the avalanche, new schemes need to be designed, involving the classical notion of well-balancing. In the present context, it needs to be extended to take into account the viscoplastic nature of the material as well as general bottoms with wet/dry fronts which are encountered in geophysical geometries. We derived such schemes and numerical experiments are presented to show their performances

Méthodes morphologiques et morphostructurales appliquées à l'étude des réseaux hydrographiques du Bordelais

L'analyse de la représentation cartographique du relief doit permettre l'étude de la répartition des accidents structuraux superficiels ou profonds qui ont une influence sur les principaux caractères de la morphologie. La feuille au 1/100000 de Langon étudiée en ce sens a permis aux auteurs d'émettre une serie d'hypothèses sur des motifs structuraux à des niveaux différents. Si le tracé des réseaux hydrographiques définit les grandes lignes des formes tectoniques connues, la répartition des longueurs de vallées précise un schéma structural profond dont les traits essentiels sont l'existence de plis varisques et de cassures armoricaines.Vigneaux M., Prud'homme Rémy. Méthodes morphologiques et morphostructurales appliquées à l'étude des réseaux hydrographiques du Bordelais. In: Revue géographique des Pyrénées et du Sud-Ouest, tome 41, fascicule 1, 1970. Pays de l'Adour. pp. 5-14

Characterization and Marking of Primordial Germ Cells

Primordial germ cells (PGC) are the precursors of oocytes and spermatocytes. They are characterized by being the only ones capable of accurately retaining pluripotent developmental ability after gastrulation. These cells come from the epiblast, they differ from somatic cells by signals from the extra-embryonic ectoderm and visceral endoderm, starting from day 6.0 to 7.5 dpc in murine species. Then migrate through the primitive gut and dorsal mesentery to reach genital ridges around 10.5 dpc. The primordial germ cells have a varied morphology and gene expression therefore have different markers according to the stage where they are. Among the most studied and characterized markers are Fragilis, c-Kit, Stella, DAZ, Vasa, GCNA1, Blimp1 and SSEA-1