An intercomparison of flow around a 3D wall-mounted cylinder using TELEMAC-3D and OpenFOAM

Hydrodynamic

Dépôts funéraires d’amphisbénidés ou “serpents à deux têtes” sur la plate-forme Uhle, Huacas de Moche, Pérou.

International audienceFourteen animal species have been identified in Mochica tombs (100-800 A.D.). Among them the discovery of amphisbaenids, a group of reptilesknown in South America as “culebras de dos cabezas” (two-headed snakes), stands as a new fact. Rests of Amphisbaena sp., in particular A. occidentalis, the only species actually present in this area, were found in five tombs of the Uhle’s Platform at Huacas de Moche site. This constitutes the first occurrence of these reptiles in Precolumbian archaeological sites from the western slope of the Andean Cordillera. The amphisbaenids were discovered in jars sitting by the side of the dead, indicating that they were intentional deposits and not intrusive vestiges. Amphisbaenids offerings are also known in North-West Argentina, in the Ciénaga culture (2000-1400 BP), and during the periods of Regional Development, Inca and Hispano-Natives (800-250 BP). This kind of offerings thus does not constitute an isolated cultural phenomenon, but should clearly be regarded within a wider temporal and space context. The Mochica iconographic register brings additional details and seems to indicate that these animals could have a link with death and sacrifice, but also with the Milky Way. The discovery of these taxa brings new data for nderstanding their ritual role and symbolic function in Mochica culture tombs.Catorce especies animales fueron identificadas en las tumbas mochicas (100-800 d.C.). Entre ellos, el descubrimiento de anfisbenios, un grupo de reptiles conocidos en América del Sur como «serpientes o culebras de dos cabezas», es un hallazgo nuevo. Restos de Amphisbaena sp., en particular A. occidentalis, la única especie actualmente presente en esta área, fueron encontrados en cinco tumbas de la Plataforma Uhle en el sitio Huacas de Moche. Esto constituye la primera mención de estos reptiles en sitios arqueológicos precolombinos de la vertiente occidental de la Cordillera de los Andes. Los anfisbénidos fueron descubiertos en cántaros colocados al lado de los muertos, lo que indica que eran depósitos intencionales y no vestigios intrusivos. Se conocen también ofrendas de anfisbénidos en el noroeste de Argentina, en la cultura Ciénaga (2000-1400 BP), y durante los períodos de Desarrollo Regional, Inca e Hispano-Indígena (800-250 BP). Este tipo de depósitos no constituye unfenómeno cultural aislado, pero debe considerarse dentro de un contexto temporal y espacial más amplio. El registro iconográfico mochica aporta detalles adicionales y parece indicar que estos animales podrían tener un vínculo con la muerte y el sacrificio, pero también con la Vía Láctea. El descubrimiento de estos taxones ofrece nuevos datos para la comprensión de su papel ritual y de su función simbólica en las tumbas de la cultura Mochica.Quatorze espèces animales ont été identifiées dans les tombes mochicas (100-800 apr. J.-C.). Parmi eux, la découverte d'amphisbénidés, un groupe de reptiles connue en Amérique du Sud comme «culebras de dos cabezas» (serpent à deux-têtes), se présente comme un fait nouveau. Les restes d’Amphisbaena sp., en particulier A. occidentalis, la seule espèce actuellement présente dans cette zone, ont été trouvés dans cinq tombes de la Plate-forme Uhle sur le site de Huacas de Moche. Ceci constitue la première occurrence de ces reptiles dans des sites archéologiques précolombiens du versant ouest de la Cordillère des Andes. Les amphisbénidés ont été découverts dans des jarres,déposées à côté des corps des morts, indiquant ainsi qu’il s'agissait de dépôts intentionnels et non de vestiges intrusifs. Les offrandes d’amphisbénidés sont également connues dans le nord-ouest de l’Argentine, dans la culture Ciénaga (2000-1400 BP), et pendant les périodes de Développement régional, Inca et Hispano-Indigène (800-250 BP). Ce type d’offrandes ne constitue donc pas un phénomène culturel isolé, mais doit clairement être considérée dans un contexte temporel et spatial plus large. Le registre iconographique Mochica apporte des détails supplémentaires et semble indiquer que ces animaux pourraient avoir un lien avec la mort et le sacrifice, mais aussi avec la VoieLactée. La découverte de ces taxons apporte de nouvelles données pour la compréhension de leur rôle rituel et de leur fonction symbolique dans les tombes de la culture Mochica

Distribution de vers de terre et forme d'humus lors du développement d'une pessière subnaturelle

[Departement_IRSTEA]GT [TR1_IRSTEA]32 - GECOTER / ECOFRICHInternational audienceThis paper analyses earthworm communities distribution in relation to humus structure and vegetation dynamics in the sylvigenetic cycle of a subnatural mountain spruce forest. Observations come from the Extern North Alps. The earthworms reaction to vegetation changes was studied using two scales of investigation-the eco-unit scale and the tree scale. The sylvigenetic cycle was represented by a 200-m- long transect including the four main developmental phases of the forest (innovation phase, aggradation phase, biostatic phase and degradation phase). Fifteen plots were investigated on the transect. In each plot, a humus profile was described. Earthworms were collected by spraying formaldehyde on each plot. The opération was reapeated three times . The results showed, on one hand, a strong heterogeneity of earthworms distribution within the developmental phases of the forest (eco-unit scale). On the other hand, on the plots, it is observable that earthworms distribution and the age of trees are connected (tree scale). Therefore, earthworms reaction to vegetation dynamics appears strongly at the scale of the trees, whereas worms distribution seems to be more dependant of the abiotic conditions at the eco-unit scale.Les relations entre lombricidés, forme d'humus et peuplement forestier sont étudiées sur un transect de 200 m représentatif des quatre principales phases du cycle sylvigénétique d'une pessière subnaturelle des Alpes du Nord. Les relations lombriciens-pessière sont considérées à deux échelles d'observation : l'éco-unité et l'arbre. Sur 15 sites échantillonnés les profils d'humus sont décrits et les lombriciens collectés après arrosages par une solution de formaldéhyde sur des surfaces de 1m2.Les résultats montrent une forte hétérogénéité dans la distribution des lombriciens à l'échelle des éco-unités. A l'inverse à l'échelle de l'arbre on observe une forte corrélation entre l'age des arbres et la distribution des peuplements de lombriciens. Ainsi les relations entre peuplements lombriciens et peuplement forestier sont fortes à l'échelle de l'arbre. Par contre à l'échelle de l'éco-unité les relations lombriciens-forêt dépendent en grande partie des facteurs abiotiques

Statistical analysis of fractionation resistance by functional category and expression

Abstract Background The current literature establishes the importance of gene functional category and expression in promoting or suppressing duplicate gene loss after whole genome doubling in plants, a process known as fractionation. Inspired by studies that have reported gene expression to be the dominating factor in preventing duplicate gene loss, we analyzed the relative effect of functional category and expression. Methods We use multivariate methods to study data sets on gene retention, function and expression in rosids and asterids to estimate effects and assess their interaction. Results Our results suggest that the effect on duplicate gene retention fractionation by functional category and expression are independent and have no statistical interaction. Conclusion In plants, functional category is the more dominant factor in explaining duplicate gene loss

A two-fluid model for immersed granular avalanches with dilatancy effects

International audienceWhen a deposited layer of granular material fully immersed in a liquid is suddenly inclined above a certain critical angle, it starts to flow down the slope. The initial dynamics of these underwater avalanches strongly depends on the initial volume fraction. If the granular bed is initially loose, i.e. looser than the critical state, the avalanche is triggered almost instantaneously and exhibits a strong acceleration, whereas for an initially dense granular bed, i.e. denser than the critical state, the avalanche's mobility remains low for some time before it starts flowing normally. This behaviour can be explained by a combination of geometrical granular dilatancy and pore pressure feedback on the granular media. In this contribution, a continuum formulation is presented and implemented in a three-dimensional continuum numerical model. The originality of the present model is to incorporate dilatancy as an elasto-plastic normal stress or pressure and not as a modification of the friction coefficient. This allows an explanation of the two different behaviours of initially loose and dense underwater avalanches. It also highlights the contribution from each depth-resolved variable in the strongly coupled transition to a flowing avalanche. The model compares favourably with existing experiments for the initiation of underwater granular avalanches. Results reveal the interplay between shear-induced changes of the granular stress and fluid pressure in the dynamics of avalanches. The characteristic time of the triggering phase is nearly independent of the local rheological parameters, whereas the initial drop in pore pressure and the surface velocity at steady state still strongly depend on them. Finally, the multidimensional capabilities of the model are illustrated for the two-dimensional Hele-Shaw configuration and some of the observed differences between one-dimensional simulations and experiments are clarified.Abstrac

Numerical investigation of mode failures in submerged granular columns

In submerged sandy slopes, soil is frequently eroded as a combination of two main mechanisms: breaching, which refers to the retrogressive failure of a steep slope forming a turbidity current, and instantaneous sliding wedges, known as shear failure, that also contribute to shape the morphology of the soil deposit. Although there are several modes of failures, in this paper we investigate breaching and shear failures of granular columns using the two-fluid approach. The numerical model is first applied to simulate small-scale granular column collapses (Rondon et al. , Phys. Fluids , vol. 23, 2011, 073301) with different initial volume fractions to study the role of the initial conditions in the main flow dynamics. For loosely packed granular columns, the porous medium initially contracts and the resulting positive pore pressure leads to a rapid collapse. Whereas in initially dense-packing columns, the porous medium dilates and negative pore pressure is generated stabilizing the granular column, which results in a slow collapse. The proposed numerical approach shows good agreement with the experimental data in terms of morphology and excess of pore pressure. Numerical results are extended to a large-scale application (Weij, doctoral dissertation, 2020, Delft University of Technology; Alhaddad et al. , J. Mar. Sci. Eng. , vol. 11, 2023, 560) known as the breaching process. This phenomenon may occur naturally at coasts or on dykes and levees in rivers but it can also be triggered by humans during dredging operations. The results indicate that the two-phase flow model correctly predicts the dilative behaviour and the subsequent turbidity currents associated with the breaching process

SedFoam-2.0: a 3-D two-phase flow numerical model for sediment transport

International audienc