Death of an African Student in Moscow

RésuméMort d’un étudiant africain à Moscou : la question raciale et la politique pendant la guerre froideLe 18 décembre 1963, la manifestation organisée sur la place Rouge par des étudiants africains séjournant en Union Soviétique devint un incident international. Déclenchée par la mort mystérieuse d’un étudiant ghanéen, elle se faisait l’écho des inquiétudes des Africains vis-à-vis de leur sécurité en URSS. Ces inquiétudes s’étaient cristallisées au fil des années précédentes, lorsque les premiers contingents d’étudiants africains avaient eu à subir malentendus et harcèlement racistes, parallèlement aux expressions officielles de bonne volonté. Le climat international contribua également à alimenter ces inquiétudes. La presse occidentale, à laquelle les étudiants avaient souvent accès, se saisit avec un zèle tout particulier de ces preuves manifestes de tensions raciales. Les facteurs politiques, sociaux et culturels qui entrèrent en jeu dans la manifestation des étudiants africains et ses retombées offrent une perspective nouvelle sur l’histoire des dernières années Hruščev.AbstractAfrican students in the Soviet Union staged a demonstration in Red Square on December 18, 1963, that became an international incident. Triggered by the mysterious death of a Ghanaian student, the protest aired Africans’ concerns over their security in the USSR. These concerns had crystallized over the previous few years, when the first contingents of African students had experienced racial misunderstanding and harassment alongside official expressions of goodwill. The international climate tended to fuel these concerns as well ; the Western press, to which the students often had access, took up evidence of racial tensions in the Soviet Union with particular zeal. The political, social, and cultural factors that played into the African students’ demonstration and its aftermath offer a new angle on the history of the later Khrushchev years

On Potential Application of Coated Ferritic Stainless Steel Grades K41X and K44X in SOFC/HTE Interconnects

K41X is a ferritic stainless steel grade which was successfully developed in exhaust gas manifold where the temperature could reach 950°C. It contains about 18% wt of chromium and it is stabilized with both titanium and niobium to warranty a good weldability, formability and high temperature corrosion resistance. Moreover, an addition of niobium improves high temperature mechanical properties, in particular the creep resistance. K44X, an enhanced version of K41X with 19%-wt. of Cr plus niobium and molybdenum, was recently developed to be used up to 1000°C. It exhibits better high temperature properties and oxidation resistance. Thanks to their high temperature resistance and their cost competitiveness, these two grades were recently considered as potential candidates to be used as interconnects for Solid Oxide Fuel Cells (SOFC) and High Temperature Electrolysis (HTE), either bare or more certainly coated in order to increase the life duration of the SOFC or HTE systems. This paper will present the high temperature properties of K41X and K44X, in particular oxidation behavior in isothermal and cyclic conditions under operating atmosphere. The positive effect of the addition of a protective coating on these steel grades in terms of oxidation resistance will then be presented. Most of the studied coatings are Mn-Co spinels deposited by sol-gel, atmospheric plasma spray or electroplating, their aim being to limit the chromium evaporation and to fit the severe performance requirements. They lead to low and stable contact resistance, which is a requirement necessary for long-term SOFC/HTE operation: for example a contact resistance of 22 mΩ.cm2 was obtained after 3500 h at 800°C in air with MnCoFe spinel coating. In this respect, K41X was recently chosen to be tested for the 3rd generation stacks of SOFC in the European project “REAL SOFC” or the prototypes in French ANR projects

Linking Hydrothermal Geochemistry to Organismal Physiology: Physiological Versatility in Riftia pachyptila from Sedimented and Basalt-hosted Vents

Much of what is known regarding Riftia pachyptila physiology is based on the wealth of studies of tubeworms living at diffuse flows along the fast-spreading, basalt-hosted East Pacific Rise (EPR). These studies have collectively suggested that Riftia pachyptila and its chemoautotrophic symbionts are physiologically specialized, highly productive associations relying on hydrogen sulfide and oxygen to generate energy for carbon fixation, and the symbiont's nitrate reduction to ammonia for energy and biosynthesis. However, Riftia also flourish in sediment-hosted vents, which are markedly different in geochemistry than basalt-hosted systems. Here we present data from shipboard physiological studies and global quantitative proteomic analyses of Riftia pachyptila trophosome tissue recovered from tubeworms residing in the EPR and the Guaymas basin, a sedimented, hydrothermal vent field. We observed marked differences in symbiont nitrogen metabolism in both the respirometric and proteomic data. The proteomic data further suggest that Riftia associations in Guaymas may utilize different sulfur compounds for energy generation, may have an increased capacity for energy storage, and may play a role in degrading exogenous organic carbon. Together these data reveal that Riftia symbionts are far more physiologically plastic than previously considered, and that -contrary to previous assertions- Riftia do assimilate reduced nitrogen in some habitats. These observations raise new hypotheses regarding adaptations to the geochemical diversity of habitats occupied by Riftia, and the degree to which the environment influences symbiont physiology and evolution