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91.
Eloisa Cordoncillo Purification Escribano F. Javier Guaita Clotilde Philippe Bruno Viana Clement Sanchez 《Journal of Sol-Gel Science and Technology》2002,24(2):155-165
Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. Sm3+, Eu3+, Dy3+, Er3+ and Tm3+ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature have been investigated. Even if luminescence efficiency is governed by non-radiative relaxation linked to hydroxyl groups, in these matrices, rare earth fluorescence is always observed but lifetimes and quantum yields are dependent on the elaboration procedure. Eu3+ is used as a probe of the local surrounding around the dopant and the emission and decay profiles measurements in rare earth doped and undoped matrices are presented. 相似文献
92.
An evaluation of two-particle resonances in the complex energy plane is presented. The representation used in the method consists of bound and antibound single-particle states, Gamow resonances and scattering waves on the complex energy plane. Within this representation the structure of halo nuclei is studied. 相似文献
93.
94.
Conditions which must be fulfilled by clusters of nucleons to qualify as elementary modes of excitation are analysed in terms of simple criteria involving experimental binding energies. It is found that the most complex possible mode is the α-like cluster. 相似文献
95.
96.
Guindon Y Ogilvie WW Bordeleau J Cui WL Durkin K Gorys V Juteau H Lemieux R Liotta D Simoneau B Yoakim C 《Journal of the American Chemical Society》2003,125(2):428-436
Johnson-type acetals derived from dimethyl tartrate give, after opening with Me(2)BBr and cuprate displacement, secondary alcohols with high diastereoselectivity (>30:1). The mechanism proposed for the induction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of the Lewis acid as a source of nucleophile and the stereospecific transformation of the resulting bromo acetal through an invertive and temperature-dependent process. The acetals are prepared by reaction of the desired aldehyde with dimethyl tartrate. Removal of the auxiliary is accomplished through SmI(2) reduction or by an addition-elimination protocol using methoxide. 相似文献
97.
Relationship between structure and CO oxidation activity of ceria-supported gold catalysts 总被引:1,自引:0,他引:1
Venezia AM Pantaleo G Longo A Di Carlo G Casaletto MP Liotta FL Deganello G 《The journal of physical chemistry. B》2005,109(7):2821-2827
Gold catalysts supported on cerium oxide were prepared by solvated metal atom dispersion (SMAD), by deposition-precipitation (DP), and by coprecipitation (CP) methods and were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalytic activity was tested in the CO oxidation reaction. The structural and surface analyses evidenced the presence of a modified ceria phase in the case of the DP sample and the presence of pure ceria and gold metal crystallites in the case of the SMAD and CP samples. The DP sample, after a mild treatment in air at 393 K, exhibited only ionic gold, and it was very active below 273 K. By comparing the activities of the different catalysts, it is suggested that the presence of small gold particles, as obtained by the SMAD technique, is not the main requisite for the achievement of the highest CO conversion. The strong interaction between ionic gold and ceria, by enhancing the ceria surface oxygen reducibility, may determine the particularly high activity. 相似文献
98.
99.
Anthony V. Galanti Franic Liotta Brian T. Keen Daniel A. Scole 《Journal of polymer science. Part A, Polymer chemistry》1982,20(1):233-239
Members of a series of N,N′-alkylene bisitaconamic acids were synthesized from the reaction between itaconic anhydride and a homologous group of aliphatic diamines with the general formula H2N (CH2)n NH2, where n = 4–12. Cyclodehydration of the acids in toluene gave the isomeric imides: bisitaconimide, biscitraconimide, and citra-itaconimide. The isomeric imides were isolated, purified, and characterized for each diaminoalkane studied. 相似文献
100.
Lakdawala AS Morgan DM Liotta DC Lynn DG Snyder JP 《Journal of the American Chemical Society》2002,124(51):15150-15151
A previous experimentally defined model for the fibril formed from the core residues of the beta-amyloid (Abeta) peptides of Alzheimer's disease, 10YEVHHQKLVFFAEDVGSNKGAIIGLM, Abeta(10-35) using spectroscopic and scattering analyses reports on the average structure, benefiting immensely from the homogeneous assembly of Abeta(10-35). However, the energetic constraints that contribute to fibril dynamics and stability remain poorly understood. Here we perform molecular dynamics simulations to extend the structural assignment by providing evidence for a dynamic average ensemble with transient backbone H-bonds and internal solvation contributing to the inherent stability of amyloid fibrils. 相似文献