Structure and Magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix

Our recent studies on Co-clusters embedded in various matrices reveal that the co-deposition technique (simultaneous deposition of two beams : one for the pre-formed clusters and one for the matrix atoms) is a powerful tool to prepare magnetic nanostructures with any couple of materials even though they are miscible. We study, both sharply related, structure and magnetism of the Co/Nb system. Because such a heterogeneous system needs to be described at different scales, we used microscopic and macroscopic techniques but also local selective absorption ones. We conclude that our clusters are 3 nm diameter f.c.c truncated octahedrons with a pure cobalt core and a solid solution between Co and Nb located at the interface which could be responsible for the magnetically inactive monolayers we found. The use of a very diluted Co/Nb film, further lithographed, would allow us to achieve a pattern of microsquid devices in view to study the magnetic dynamics of a single-Co cluster.Comment: 7 TeX pages, 9 Postscript figures, detailed heading adde

Concurrent Proinflammatory and Apoptotic Activity of a Helicobacter pylori Protein (HP986) Points to Its Role in Chronic Persistence

Helicobacter pylori induces cytokine mediated changes in gastroduodenal pathophysiology, wherein, the activated macrophages at the sub-mucosal space play a central role in mounting innate immune response against the antigens. The bacterium gains niche through persistent inflammation and local immune-suppression causing peptic ulcer disease or chronic gastritis; the latter being a significant risk factor for the development of gastric adenocarcinoma. What favors persistence of H. pylori in the gastric niches is not clearly understood. We report detailed characterization of a functionally unknown gene (HP986), which was detected in patient isolates associated with peptic ulcer and gastric carcinoma. Expression and purification of recombinant HP986 (rHP986) revealed a novel, ∼29 kDa protein in biologically active form which associates with significant levels of humoral immune responses in diseased individuals (p<0.001). Also, it induced significant levels of TNF-α and Interleukin-8 in cultured human macrophages concurrent to the translocation of nuclear transcription factor-κB (NF-κB). Further, the rHP986 induced apoptosis of cultured macrophages through a Fas mediated pathway. Dissection of the underlying signaling mechanism revealed that rHP986 induces both TNFR1 and Fas expression to lead to apoptosis. We further demonstrated interaction of HP986 with TNFR1 through computational and experimental approaches. Independent proinflammatory and apoptotic responses triggered by rHP986 as shown in this study point to its role, possibly as a survival strategy to gain niche through inflammation and to counter the activated macrophages to avoid clearance

Analytical Development of the Hard-Sphere Based Radial Distribution Function for EXAFS Analysis of Disordered Compounds

Errors in distances and neighbors numbers are generally found when a symmetric gaussian radial distribution function (RDF) is used for fitting highly disordered compounds. Among methods used to overcome this problem, we introduced in the EXAFS equation the analytical expression of an asymmetric distances distribution based on a hard-sphere model. Such a model leads to an easy-to-handle formula that can been introduced in any fitting software. The fit gives values of Ri , the lowest distance and s, the asymmetry parameter. The effective RDF can thus be drawed b y convoluting both this distribution with the Debye-Waller gaussian broadenin

Étude par EXAFS du thiophosphate lamellaire NiPS

L’intercalation de lithium dans le thiophosphate lamellaire NiPS3 provoque la réduction du nickel au degré d’oxydation zéro. Des mesures EXAFS, réalisées au seuil du nickel sur des poudres de NiPS3 intercalées, mettent en évidence le déplacement des atomes de nickel réduits. Ceux-ci migrent de leurs sites octaédriques de soufre d’origine dans des sites tétraédriques de soufre à l’intérieur du feuillet de façon à occuper deux à deux des sites adjacents

An Innovating Insulation for<tex>rmNb3rmSnrm Nb_3rm Sn</tex>Wind & React Coils: Electrical Tests

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