Dislocation-based description of the sliding of a free-surface emerging grain boundary

International audienceThe sliding phenomenon of a high-angle tilt boundary containing a disclination dipole emerging at the free-surface of a thin film deposited on a semi-infinite substrate is studied theoretically from a static point of view in the framework of a dislocation-based description. The formation from the surface of a dislocation in the boundary is investigated, and its different equilibrium positions are determined in the stress field of the disclination dipole. It is found that the formation of the dislocation in the stress field of the disclination is only possible for an inclined dipole with respect to the normal of the free-surface. Finally, the effects of the inclination angle and strength of the grain boundary disclination dipole on the stable and metastable equilibrium positions of the dislocation are analyzed

Experimental study of Ni3Al slip traces by atomic force microscopy: an evidence of mobile dislocation exhaustion

Slip markings produced on the surfaces of Ni3(Al, Ta) single crystals, plastically deformed at various temperatures in the flow stress anomaly domain, were examined by atomic force microscopy (AFM). A dominant feature is that for all investigated temperatures, the slip traces are rectilinear and correspond to the primary octahedral glide plane. In addition, their lengths drastically decrease when the temperature is raised. This latter result is interpreted as a strong increase of the exhaustion rate of mobile dislocations with increasing temperatures. The consequences of these results in the understanding of Ni3Al flow stress anomaly are discussed

Geometrical Features of Dislocations Gliding on non-compact Planes in Al-Zn Single Crystal

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Microorganisms in Dry Polar Snow Are Involved in the Exchanges of Reactive Nitrogen Species with the Atmosphere

International audienceThe snowpack is a complex photochemical reactor that emits a wide variety of reactive molecules to the atmosphere. In particular, the photolysis of nitrate ions, NO 3-, produces NO, NO 2 , and HONO, which affects the oxidative capacity of the atmosphere. We report measurements in the European High Arctic where we observed for the first time emissions of NO, NO 2 , and HONO by the seasonal snowpack in winter, in the complete or near-complete absence of sunlight and in the absence of melting. We also detected unusually high concentrations of nitrite ions, NO 2-, in the snow. These results suggest that microbial activity in the snowpack is responsible for the observed emissions. Isotopic analysis of NO 2-and NO 3-in the snow confirm that these ions, at least in part, do not have an atmospheric origin and are most likely produced by the microbial oxidation of NH 4 + coming from clay minerals into NO 2-and NO 3-. These metabolic pathways also produce NO. Subsequent dark abiotic reactions lead to NO 2 and HONO production. The snow cover is therefore not only an active photochemical reactor but also a biogeochemical reactor active in the cycling of nitrogen and it can affect atmospheric composition all year round

The human gut microbiome as source of innovation for health: Which physiological and therapeutic outcomes could we expect?

International audienceFrom the moment of birth, each human being builds a microbe-host symbiosis which is key for the preservation of its health and well-being. This personal symbiotic coexistence is the result of progressive enrichments in microorganism diversity through external supplies. This diversity is nowadays massively overthrown by drastic changes related to clinical practice in birth management, environmental exposure, nutrition and healthcare behaviors. The last two generations have been the frame of massive modifications in life and food habits, with people being more and more sedentary, overfed and permeated with drugs and pollutants. We are now able to measure the impact of these changes on the gut microbiota diversity. Concomitantly, these modifications of lifestyle were associated with a dramatic increase in incidence of immune-mediated diseases including metabolic, allergic and inflammatory diseases and most likely neurodegenerative and psychiatric disorders. Microbiota is becoming a hot topic in the scientific community and in the mainstream media. The number of scientific publications increased by up to a factor three over the last five years, with gastrointestinal and metabolic diseases being the most productive areas. In the intellectual property landscape, the patent families on microbiota have more than doubled in the meantime. In parallel, funding either from National Institutes (e.g. from NIH which funds research mainly in the field of allergies, infections, cancer and cardiovascular diseases, from the White House which launched the national microbiome initiative) or by pharmaceutical companies follow the same trend, showing a boost and a strong support in the research field on microbiota. All major health players are investing in microbiome research as shown by the number of deals signed and by funding during 2015. The Glens round table addressed how. the medicine of tomorrow, considering human beings as a human-microbe symbiotic supraorganism, could leverage microbiome knowledge and tools. The rationale for our working group has been structured around four domains of innovation that could derive from ongoing efforts in deciphering the interactions between human cells and intestinal microbiome as a central component of human health, namely: (1) development of stratification and monitoring tools; (2) identification of new target and drug discovery, as a part of our supra-genome; (4) exploitation of microbiota as a therapeutic target that can be modulated; (4) and finally as a source of live biotherapeutics and adjuvants. These four streams will exemplify how microbiota has changed the way we consider a wide range of chronic and incurable diseases and the consequences of long-lasting dysbiosis. In-depth micro biota analysis is opening one of the broadest fields of investigation for improving human and animal health and will be a source of major therapeutic innovations for tackling today's medical unmet needs. We thus propose a range of recommendations for basic researchers, care givers as welt as for health authorities to gain reliability in microbiome analysis and accelerate discovery processes and their translation into applications for the benefits of the people. Finally, les Ateliers de Glens round table on microbiota benefited from the richness of the French ecosystem. France represents a center of excellence in the microbiota research field, with French institutions as Institut national de la recherche agronomique (INRA [Metagenopolis, Micalis]), Centre national de ta recherche scientifique (CNRS), Unite de recherche sur les maladies infectieuses et tropicales emergentes (URMITE), Institut of Cardiometabolism and Nutrition (ICAN), Institut des maladies metaboliques et cardiovasculaires (I2MC). Institut national de la sante et de la recherche medicate (Inserm), Pasteur Institute and Gustave-Roussy being top-players for the number of publications