Tolerance to Sand Burial, Trampling, and Drought of Two Subarctic Coastal Plant Species (Leymus mollis and Trisetum spicatum)

In order to ensure the sustainable development of the North, increased anthropogenic pressure on subarctic environments must be accompanied by appropriate restoration techniques. Locally adapted restoration guidelines need to rely on sound ecological knowledge of the species used in restoration trials. We evaluate the tolerance (emergence and biomass production) of two coastal species (Leymus mollis and Trisetum spicatum) to sand burial, trampling, and drought, all major constraints to plant colonization in the village of Whapmagoostui-Kuujjuarapik in subarctic Quebec. In three 11-week greenhouse experiments, plants were submitted to three intensities of sand burial (0.0, 0.5, and 1.0 cm per week), trampling events (none, once per week, once per day) and drought (50 mL of water every other day, every week, and every other week). While T. spicatum performance decreased under both moderate and high sand burial intensities, L. mollis tolerated moderate burial intensity. Both species were able to sustain trampling, although the performance of T. spicatum was reduced under high trampling intensity. Finally, neither species could tolerate moderate and high drought intensities, suggesting that watering needs to be included in any restoration initiatives. Since L. mollis performed better than T. spicatum in the sand burial experiment, we recommend the use of this species in future small-scale restoration trials.Dans le but d’assurer le développement durable du Nord, des méthodes de restauration appropriées doivent être développées en réponse aux perturbations de nature anthropique accrues. De telles techniques de restauration régionales doivent cependant reposer sur de solides connaissances de l’écologie des espèces utilisées. Dans cette étude, nous avons évalué la tolérance (émergence et production de la biomasse) de deux espèces côtières (Leymus mollis et Trisetum spicatum) à l’ensablement, au piétinement et à la sécheresse, trois contraintes majeures inhibant la recolonisation végétale dans le village subarctique de Whapmagoostui-Kuujjuarapik, au Québec. Pour ce faire, trois expériences en serre d’une durée de 11 semaines ont été menées dans lesquelles les individus des deux espèces ont été soumis respectivement à trois intensités d’ensablement (0,0, 0,5 et 1,0 cm par semaine), de piétinement (aucun, une fois par semaine, une fois par jour) et de sécheresse (50 mL d’eau à tous les 2, 7 et 14 jours). Alors que la performance de T. spicatum a diminué lorsque soumis aux régimes d’ensablement intermédiaire et élevé, L. mollis a toléré le régime d’ensablement intermédiaire. Dans l’expérience de piétinement, les deux espèces considérées ont relativement bien supporté le piétinement imposé, si ce n’est d’une légère diminution de la performance de T. spicatum lorsque soumis à un fort piétinement. Finalement, ni l’une ni l’autre des espèces ne pouvait tolérer les deux intensités de sécheresse (intermédiaire et élevé), ce qui laisse entendre que les plantes doivent être arrosées dans le cadre d’initiatives de restauration. Puisque L. mollis a donné de meilleurs résultats que T. spicatum en matière d’ensablement, nous privilégions l’utilisation de L. mollis pour les futures initiatives de restauration à petite échelle

Total synthesis of cyclotheonamide C using a tandem backbone-extension-coupling methodology

International audienceNo abstrac

Exhumation tectonics of the ultrahigh-pressure metamorphic rocks in the Qinling orogen in east China: New petrological-structural-radiometric insights from the Shandong Peninsula

International audienceIn eastern China, the Sulu area is recognized as the eastern extension of the Qinling-Dabie Belt, which is famous for its ultrahigh-pressure (UHP) metamorphism. Although numerous petrologic and geochemical works are available, structural data are still rare. This paper provides the first extensive study of bulk geometry and kinematic analysis of the Shandong Peninsula. The study area is divided into three tectonic areas by Cretaceous faults, namely, a southern UHP belt or Sulu area, a northern migmatite area, and an eastern eclogite and migmatite area or Weihai area. Conversely to the deeply entrenched idea that the later area belongs to the North China Belt, and the two others to the South China Block (SCB), we argue that all three areas are parts of the SCB. Structural, petrologic, 40Ar/39Ar, and U/Pb data comply with this new interpretation. In the North Shandong area, mafic granulites enclosed as blocks within gneissic migmatites do not significantly differ from the Sulu and Weihai eclogites which also experienced a granulite facies overprint before migmatization. The circa 210–200 Ma age of the main ductile deformation is related to an extensional event during the Triassic (or Indosinian) orogeny. This date corresponds to the temperature climax, but the time of the pressure peak, i.e., the real age of the UHP metamorphism is discussed

An Interactive Forest

International audienceWe present a prototype of a forest in which a video game player can move and interact physically with the trees. The trees are procedurally built on-the-fly at each redraw. Two animation approaches are combined: a procedural method which handles most of the trees efficiently, and a physically-based method which allows user interaction with the trees. The physically-based method is dynamically applied only where needed. Physical data is computed only where the physical method is applied, and deleted afterwards. Smooth transitions between animation methods are performed. Levels of detail are used for rendering and for procedural animation. Our method allows the display and the animation, including user action, of a 256-tree forest at interactive rates

L'IRM s'aventure hors des sentiers du monde médical

National audienceL'agroalimentaire et le génie civil constituent deux domaines d'applications très particuliers pour l'imagerie par résonance magnétique (IRM). Essentiellement axées sur les problèmes d'élaboration, de conditionnement et d'évolution de produits et de matériaux en contexte industriel, les études doivent souvent être menées sur des échantillons massifs. Elles mettent en oeuvre des imageurs de grande taille et réclament le développement de méthodologies spécifiques par rapport aux applications médicales. Des systèmes originaux d'instrumentation et de sollicitation in situ des matériaux ont pu être conçus dans ce cadre, nourris par des collaborations étroites entre différents corps de métiers. Deux laboratoires, l'Unité Technologie des équipements agroalimentaires de l'Irstea et le Laboratoire Navier de l'Université Paris-Est, livrent leur témoignage, fruit de plusieurs années d'expertise. Food-processing and civil engineering are very particular application fields for magnetic resonance imaging (MRI). Studies mainly focus on preparation, packaging, and further evolution of products and materials in industry. They are often carried out on massive samples. They involve the use of large MRI facilities, and require the development of specific methodology as compared with routine medical studies. Stimulating close collaborations between various technical specialties, they saw the raise of original experimental setups for in situ measurements and sample solicitations. Two French laboratories, the " Technologie des équipements agroalimentaires " Unity at Irstea and " Laboratoire Navier " at Paris-Est University, report on their long standing expertise

Water transfer and crack regimes in nano-colloidal gels

International audienceDirect observations of the surface and shape of model nano-colloidal gels associated with measurements of the spatial distribution of water content during drying show that air starts to significantly penetrate the sample when the material stops shrinking. We show that whether the material fractures or not during desiccation, as air penetrates the porous body, the water saturation decreases but remains almost homogeneous throughout the sample. This air-invasion is at the origin of another type of fracture due to capillary effects; these results provide a new insight in the liquid dynamics at the nano-scale. PACS number(s): 47.56.+r, 68.03.Fg, 81.40.N

SOFA: A modular yet efficient simulation framework

International audienceSOFA is a new open source framework primarily targeted at medical simulation research and industry. It is based on a scene graph data structure extended to physical models and abstract algorithms. Additionally, multiple models of the same objects can easily be used to optimize different tasks such as force computation, collision handling, and rendering. This results in a highly flexible architecture able to model and animate a wide range of simulated objects. We explain the main concepts of SOFA and detail an example of application to a surgery procedure

Étude RMN de la répartition de nanoparticules lors du séchage d'un milieu poreux

Le séchage d’un milieu poreux initialement saturé par une suspension colloïdale joue un rôle important dans de nombreux processus industriels ou naturels ; par exemple lors du transport de polluants dans les sols ou du colmatage des pores des matériaux de construction. L’expérience sur un cylindre de billes compactées rempli de café permet de mettre en évidence le phénomène. A la fin du séchage, on observe un gradient de couleur en direction de la surface ainsi qu’une région blanche sans aucune particule au fond de l’échantillon. Ceci suggère que les particules ont été transportées vers la surface. Pour mieux comprendre, nous effectuons la même expérience sur un système modèle (séparation d’échelle : billes de verre + nanoparticules monodisperses) avec une technique IRM nouvelle permettant de mesurer à la fois les distributions de liquide et de nanoparticules dans le milieu poreux non saturé. Nous observons la remontée des particules vers la surface libre (phénomène identique au café), alors que l’eau semble distribuée de façon homogène quand la saturation décroît. La vitesse de séchage diminue lorsque la zone de compaction des nanoparticules augmente. Nous proposons un modèle simple prédisant la vitesse de séchage ainsi que la répartition finale des nanoparticules, en bonne accord avec les mesures ; ce qui valide notre compréhension des mécanismes physiques

Precursors predicted by artificial neural networks for mass balance calculations: quantifying hydrothermal alteration in volcanic rocks

This study proposes an artificial neural networks-based method for predicting the unaltered (precursor) chemical compositions of hydrothermally altered volcanic rock. The method aims at predicting precursor’s major components contents (SiO2, FeOT, MgO, CaO, Na2O, and K2O). The prediction is based on ratios of elements generally immobile during alteration processes; i.e. Zr, TiO2, Al2O3, Y, Nb, Th, and Cr, which are provided as inputs to the neural networks. Multi-layer perceptron neural networks were trained on a large dataset of least-altered volcanic rock samples that document a wide range of volcanic rock types, tectonic settings and ages. The precursors thus predicted are then used to perform mass balance calculations. Various statistics were calculated to validate the predictions of precursors’ major components, which indicate that, overall, the predictions are precise and accurate. For example, rank-based correlation coefficients were calculated to compare predicted and analysed values from a least-altered test dataset that had not been used to train the networks. Coefficients over 0.87 were obtained for all components, except for Na2O (0.77), indicating that predictions for alkali might be less performant. Also, predictions are performant for most volcanic rock compositions, except for ultra-K rocks. The proposed method provides an easy and rapid solution to the often difficult task of determining appropriate volcanic precursor compositions to rocks modified by hydrothermal alteration. It is intended for large volcanic rock databases and is most useful, for example, to mineral exploration performed in complex or poorly known volcanic settings. The method is implemented as a simple C++ console progra