Deformation of NaCoF3 perovskite and post-perovskite up to 30 GPa and 1013 K: implications for plastic deformation and transformation mechanism

Texture, plastic deformation, and phase transformation mechanisms in perovskite and post-perovskite are of general interest for our understanding of the Earth's mantle. Here, the perovskite analogue NaCoF3 is deformed in a resistive-heated diamond anvil cell (DAC) up to 30 GPa and 1013 K. The in situ state of the sample, including crystal structure, stress, and texture, is monitored using X-ray diffraction. A phase transformation from a perovskite to a post-perovskite structure is observed between 20.1 and 26.1 GPa. Normalized stress drops by a factor of 3 during transformation as a result of transient weakening during the transformation. The perovskite phase initially develops a texture with a maximum at 100 and a strong 010 minimum in the inverse pole figure of the compression direction. Additionally, a secondary weaker 001 maximum is observed later during compression. Texture simulations indicate that the initial deformation of perovskite requires slip along (100) planes with significant contributions of {110} twins. Following the phase transition to post-perovskite, we observe a 010 maximum, which later evolves with compression. The transformation follows orientation relationships previously suggested where the c axis is preserved between phases and hh0 vectors in reciprocal space of post-perovskite are parallel to [010] in perovskite, which indicates a martensitic-like transition mechanism. A comparison between past experiments on bridgmanite and current results indicates that NaCoF3 is a good analogue to understand the development of microstructures within the Earth's mantle

Species Review of Amphibian Extinction Risks in Madagascar: Conclusions from the Global Amphibian Assessment

We assessed the extinction risks of Malagasy amphibians by evaluating their distribution, occurrence in protected areas, population trends, habitat quality, and prevalence in commercial trade. We estimated and mapped the distribution of each of the 220 described Malagasy species and applied, for the first time, the IUCN Red List categories and criteria to all species described at the time of the assessment. Nine species were categorized as critically endangered, 21 as endangered, and 25 as vulnerable. The most threatened species occur on the High Plateau and/or have been subjected to overcollection for the pet trade, but restricted extent of occurrence and ongoing habitat destruction were identified as the most important factors influencing extinction threats. The two areas with the majority of threatened species were the northern Tsaratanana-Marojejy-Masoala highlands and the southeastern Anosy Mountains. The current system of protected areas includes 82% of the threatened amphibian species. Of the critically endangered species, 6 did not occur in any protected area. For conservation of these species we recommend the creation of a reserve for the species of the Mantella aurantiaca group, the inclusion of two Scaphiophryne species in the Convention on the International Trade in Endangered Species Appendix II, and the suspension of commercial collecting for Mantella cowani . Field surveys during the last 15 years reveal no pervasive extinction of Malagasy amphibians resulting from disease or other agents, as has been reported in some other areas of the world.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75394/1/j.1523-1739.2005.00249.x.pd

Nirvana by Numbers: a Study on the Study

Assumption University, Bangkok, Thailan

Cellular materials made of stacked tubes: influence of the manufacturing process on the dynamic behavior of the constitutive material. part I: microstructure

International audienceCellular materials are very promising as lightweight aeronautical frames thanks to their superior specific mechanical properties such as impact resistance. However, because of the processing routes and heat treatments used in the production process, the material within the cell walls may behave differently from the bulk, and therefore the in situ mechanical properties are often unknown. The present work aims at investigating the link that exists between the processing of cellular architectures and the mechanical properties of their constitutive material. The cellular material studied is an Inconel® 600 tube stacking brazed together using a nickel-phosphorus alloy. The experimental works have been conducted in order to analyse the microstructures of Inconel® 600 tube stacking resulting from brazing and annealing heat treatment. In order to discuss the influence of the manufacturing process of tube stackings on the mechanical properties of their constitutive material, it has been proposed to perform uni-axial tensile tests on tubular specimens. Different material configurations (with or without heat treatments, with or without nickel-phosphorus coating) have been thus characterised and compared, involving both tensile tests from quasi-static to dynamic loads and electron back-scattered diffraction analyses (EBSD) performed on post-mortem specimens

Syndrome phalloïdien : mise au point

National audienceAmatoxin-containing mushroom poisoning occurs after consumption of certain mushroom species, of the genera Amanita, Lepiota and Galerina. Amanita phalloides is the most implicated species, responsible for over more than 90% of mushroom-related deaths. The α-amanitin is responsible for most of the observed effects. Symptoms are characterized by severe delayed gastrointestinal disorders (more than six hours after ingestion). The liver being the main target organ, outcome is marked by an often severe hepatitis which can evolve towards terminal liver failure, justifying orthotopic liver transplantation. Acute renal failure is common. Diagnosis of amatoxin-containing mushroom poisoning is based primarily on clinical data; it can be biologically confirmed using detection of amatoxins, especially from urine samples. In the absence of an antidote, early hospital management is essential. It is based on supportive care (early compensation of hydroelectrolytic losses), gastrointestinal digestive decontamination, elimination enhancement, amatoxin uptake inhibitors and antioxidant therapy. Combined therapy associating silibinin and N-acetylcysteine is recommended. Prognosis of this severe poisoning has greatly benefited from improved resuscitation techniques. Mortality is currently less than 10%. In the event of a suspected or confirmed case, referral to a Poison Control Center is warranted in order to establish the diagnosis and guide the medical management of patients in an early and appropriate way.Le syndrome phalloïdien est le toxidrome mycotoxique survenant après l’ingestion de certaines espèces macromycètes, des genres Amanita, Lepiota et Galerina. Amanita phalloides l’espèce la plus souvent en cause, responsable 90 % décès dus à consommation champignons. L’α-amanitine plupart effets observés. La présentation clinique caractérisée par un tableau digestif sévère survenue tardive (plus six heures l’ingestion). foie étant principal organe cible, l’évolution marquée une hépatite aiguë pouvant évoluer vers l’insuffisance hépatique terminale justifiant recours transplantation orthotopique. Une insuffisance rénale observée. diagnostic repose avant tout sur les données clinique