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Yolande MespliÉ Michel Bergon Jean-Pierre Calmon 《Journal of heterocyclic chemistry》1984,21(4):985-993
The alkaline hydrolysis of propargyl 3-chlorocarbanilates was investigated kinetically using uv spectropotometry. The cyclization to 4-methoylene-2-oxazolisinones proceeds via the numcleophilic attack of the substrate anion concomitantly with that of the hydroxide ion on the triple bond. The nucleophilic attack leads directly to the heterocycle whereas the hydroxide ion attack gives rise to a ketocarbamate which is then cyclized to the oxazolidione. 相似文献
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Antonio Da Costa Christian Mathieu Yolande Barbaux Hilde Poelman Gisele Dalmai-Vennik Lucien Fiermans 《Surface science》1997,370(2-3):339-344
Constant force images of the V2O5(001) surface were recorded in ambient conditions with atomic force microscopy. All images exhibit the 11.5 Å × 3.5 Å. periodicity expected for a bulk terminated surface. However, images reveal differences from the ideal structure. The experimental results are interpreted in terms of preferential adsorption sites for water molecules. Because these sites are thought to influence the catalytic properties of the surface, their characterization is an important step towards understanding how the atomic-scale structure of a surface influences its properties. 相似文献
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F. Rueda J. Mendialdua A. Rodríguez R. Casanova Y. Barbaux L. Gengembre L. Jalowiecki D. Bouqueniaux 《Journal of Electron Spectroscopy and Related Phenomena》1995,70(3):225-231
The surface characterization by X-ray photoelectron spectroscopy (XPS) of a natural mineral found in the Venezuelan Andes is reported. We present XPS studies for the natural mineral (sample ULA2) and for the mineral after it has served as a catalyst (sample ULA1) in a Fischer-Tropsch reaction for three months. The effect of different treatments on these samples is also investigated. Both samples exhibit a differential charge effect which is present once their surfaces have interacted with hydrogen. The quantitative XPS results allow us to advance the composition of these samples. The presence of a negatively charged hydrogen species in our samples is discussed based on our XPS results and supported by work function measurements. 相似文献
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Fernández F Cordero B Durand J Muller G Malbosc F Kihn Y Teuma E Gómez M 《Dalton transactions (Cambridge, England : 2003)》2007,(47):5572-5581
A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case. Some tests, including the correlation effect between solvent and ligand, are carried out to try to identify the true nature of the catalyst. All the results obtained suggest that formation of nanoparticles is required to lead to a catalytically active system. 相似文献
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Distinctively different microstructures were obtained depending on the heating rate to which CdGeAs2 glasses were exposed during the devitrification process. Differential scanning calorimetry showed that under very slow heating rates, the single crystallization peak splits into three superimposed exotherms. Quenching from the temperature at which selected features appear on the DSC trace and using X-ray diffraction and transmission electron microscopy interactively, demonstrated the initial formation of a metastable doped precursor germanium crystalline phase. This crystalline structure continued to grow until it could no longer accommodate the impurities, and the transformation terminated. These regions then acted as heterogeneous nucleation sites for the growth of chalcopyrite structured CdGeAs2 with a spherulitic microstructure. The spherulites grew as stacked plates from the nucleation site. At higher temperatures, the metastable germanium structure converted, growing backwards toward the center of each precursor, into the stable chalcopyrite structure, permitted by appropriate ionic diffusion shifting composition toward stoichiometry. At faster heating rates, less of these germanium precursors formed, creating a visually bimodal grain size distribution in the microstructure, as compared to slower heating rates. Using the simplex algorithm, the mechanism and activation energy of each reaction are reported as well as the deconvoluted enthalpies of each transformation. 相似文献
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Sp. Pantelakis An. Kyrsanidi E. El-Magd J. Dünnwald Y. Barbaux G. Pons 《Theoretical and Applied Fracture Mechanics》1999,31(1):1513
Characterization of the creep resistance of 30 newly developed aluminium alloys is made for structural applications of the next generation Supersonic Civil Transport Aircafts (SCT). These materials refer to the 2xxx, 6xxx and 8xxx aluminium alloy series. Creep behaviour is ranked to the usability and applicability of the alloys according to performance. A procedure is developed for validating the criteria of extrapolating creep data. 相似文献
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Eva Castillejos Dr. Pierre‐Jean Debouttière Dr. Lucian Roiban Abderrahim Solhy Dr. Victor Martinez Dr. Yolande Kihn Dr. Ovidiu Ersen Dr. Karine Philippot Dr. Bruno Chaudret Dr. Philippe Serp Dr. 《Angewandte Chemie (International ed. in English)》2009,48(14):2529-2533
Are you in? Bimetallic PtRu nanoparticles have been selectively confined inside or deposited outside carbon nanotubes (see picture). The confined nanoparticles display significantly higher selectivity and catalytic activity in hydrogenation reactions.
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RNA PROTEIN CROSSLINKS INTRODUCED INTO E. coli RIBOSOMES BY USE OF THE INTRINSIC PROBE 4-THIOURIDINE 总被引:1,自引:0,他引:1
Eliane Hajnsdorf Yolande Lemaigre Dubreuil Roberto Bezerra Alain Favre Alain Expert-BezanÇon 《Photochemistry and photobiology》1987,45(4):445-451
Abstract— 70S Ribosome substituted by the uridine photoactivable analogue 4-thiouridine has been prepared by an in vivo method (substitution level 4.5%). The r-proteins crosslinked to 16S and 23S rRNA before and after 366-nm photoactivation were identified. Proteins S2-S7-S9/11-S18 are found linked to 16S RNA in dark-prepared 30S subunits. Illumination increases uniformly their binding by a factor of 2.5. Similarly, proteins L5-L15-L18-L23-L28-L32 are found crosslinked to 23S RNA in dark-prepared 50S subunits. Photoactivation increases their binding but in addition promotes the covalent linking of proteins L1-L3-L4. 相似文献