Optical modeling of nickel-base alloys oxidized in pressurized water reactor

International audienceThe knowledge of the aging process involved in the primary water of pressurized water reactor entails investigating a mixed growth mechanism in the corrosion of nickel-base alloys. A mixed growth induces an anionic inner oxide and a cationic diffusion parallel to a dissolution-precipitation process forms the outer zone. The in situ monitoring of the oxidation kinetics requires the modeling of the oxide layer stratification with the full knowledge of the optical constants related to each component. Here, we report the dielectric constants of the alloys 600 and 690 measured by spectroscopic ellipsometry and fitted to a Drude-Lorentz model. A robust optical stratification model was determined using focused ion beam cross-section of thin foils examined by transmission electron microscopy. Dielectric constants of the inner oxide layer depleted in chromium were assimilated to those of the nickel thin film. The optical constants of both the spinels and extern layer were determined

TWO NEW COMBINATIONS IN PEYRITSCHIA (POACEAE: POOIDEAE: AVENINAE)

Volume: 22Start Page: 895End Page: 90

A REVISION OF TRISETUM AND GRAPHEPHORUM (POACEAE: POOIDEAE: AVENINAE) IN NORTH AMERICA NORTH OF M\uc9XICO

Volume: 21Start Page: 1419End Page: 145

Atomic force microscopy investigation of a -C:H films prepared by plasma enhanced chemical vapor deposition for inertial confinement fusion experiments

International audienc

International conference ICAWA 2016 : extended book of abstract : the AWA project : ecosystem approach to the management of fisheries and the marine environment in West African waters

Currently only thirteen percent (13 %) of domestic wastewater produced daily in Dakar is being treated. Industrial and agricultural activities and domestic waste are the source of significant pollution of the marine and coastal environment in Senegal. Our work focuses on assessing the overall toxicity of sediments, the microbiological and chemical quality of water, and the quantification of microplastics around the Cape Verde Peninsula. Physicochemical measurements are carried out in situ and the sampling points correspond to effluent outlets, compared to two reference stations that are assumed to have little or no contamination. A total of 15 sites were collected: Cambéréne, Yoff Tonghor, Ngor, Almadie-Vivier, Ouakam, Magdalen Islands, Soumbédioune, Dakar Dantec, Hann1, Hann2, Port of Dakar, Lac rose, Guédiawaye, Mamelles and UCAD. High sediment toxicity [100% ADL (Larval Development Anomalies)] was demonstrated at sixty percent (60%) of the sites. Twenty percent (20%) of sites have intermediate toxicity ranging from 30% to 60% ADL). Sites with the lowest toxicity (up to 30% ADL) accounted for only 20% and no ADL values were reported as nil. Mercury levels in sediments are very low, with a notable variation between sites in the north and those in the south of the peninsula. Coliforms (Escherichia coli) and enterococci are present in large quantities at most sites (64%). The presence of Salmonella is noted only in Cambéréne. The results of mass spectrometry analyzes also show overall high concentrations of heavy metals (Al, Cd, Cr, Co, Cu, Hg, Ni and Zn) with the exception of Fe and Mn, which are below the criteria for "Protection of acute and chronic aquatic life". Microplastic analysis revealed high mean values: 25,864 mpts / km2 (42 g / km2) for microplastics (300 µm and 5 mm) and 37,441 MPTS / km2 (97.33 g / km2) for macroplastics > 5 mm and < 200 mm). All the results obtained show, according to the pollutants, the importance of the sediment granulometry, the nature of the pollution, the size of the effluents, the anthropic contributions, the atmospheric falls like that of the behaviors of the populations. Our results are discussed with a view to environmental monitoring at the local, regional or national level. They will also allow this approach to be extended to other contaminants (hydrocarbons, metals, pesticides, megaplastics) as well as bio-trials in the various compartments of the marine and coastal environment (sediments, waters, fauna and flora ). An in-depth statistical analysis will also allow optimization of ecotoxicological monitoring, sampling and analysis strategies

Study of the spatial variability of marine pollution around the peninsula of Cape Verde [résumé]

ICAWA : International Conference AWA, Dakar, SEN, 13-/12/2016 - 15/12/2016Marine pollution, the scourge of modern times, is due to the runoff of domestic and industrial waters as well as to various anthropogenic activities, i.e. products and objects deliberately or accidentally discharged into the sea. The samples taken from 11 sites on the Cap-Vert peninsula in Senegal, indicate the presence of certain polluting substances in varying amounts. The objective of this work is to study the correlations between the physical, microbiological and chemical parameters in order to highlight the similarities between the sites and, if possible, to determine the most relevant parameter(s) to characterize the pollution. PCA results have shown that some sites appear to be less chemically polluted than others that are more polluted with eutrophication and chemicals (e.g., copper, mercury). From a physical point of view, for example, we observe that the characteristics of sediments (large silt, clays, fine silt) are related to certain chemical parameters.The AFC performed between the overall toxicity of the sediments and the microbiological quality of the water shows that the site of Ouakam has a medium toxicity and a good microbiological quality while that of Cambérène and the Vivier are characterized respectively by bad and good quality but also by low toxicity at both sites. The two sites of Hann (Hann1 and Hann2), Soumbédioune, Ngor, Yoff Tonghor and Dakar Le Dantec are characterized by high toxicity and poor microbiological quality. Those in the Madeleine Islands and the Port of Dakar are characterized by high toxicity and bad microbiological quality. Moreover, as expected Soumbédioune appears as the most polluted sites in terms of microbiological load. The interest of the multivariate approach (ACP and AFC) is then discussed in this type of analysis