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901.
Synthesis and Characterization of Vanadium-Containing ZrSiO4 Solid Solutions from Gels 总被引:1,自引:0,他引:1
Valentín Carla Muñoz Mari Carmen Alarcón Javier 《Journal of Sol-Gel Science and Technology》1999,15(3):221-230
A procedure is reported for the preparation of vanadium-doped zircon pigmenting system with different vanadia loadings which enabled their complete formation and further characterization. Vanadium-zircon solid solutions were prepared by gelling mixtures of ZrO2 and V2O5 colloidal sols and tetraethylorthosilicate and studied over the temperature range up to the formation of zircon. The reaction sequence of gels was evaluated by X-ray powder diffraction (XRD) and ultraviolet-visible (UV-Vis) diffuse reflectance. It was found that the first crystalline phase detected was a vanadium-containing tetragonal ZrO2 solid solution where vanadium was stabilized in the reduced V+4 state. The formation of the V-ZrSiO4 solid solution occurred by the reaction between the monoclinic form of V+4-ZrO2 solid solution and the amorphous silica phase. Energy dispersive X-ray microanalysis (SEM/EDX) data, measurements of lattice parameters and UV-Vis diffuse reflectance of V-ZrSiO4 solid solutions revealed that vanadium was dissolved as V+4 replacing Si+4 in tetrahedral sites in the crystal structure of zircon. The solubility limit of vanadium in ZrSiO4 was about 0.01 mole of vanadium per mole of zircon (0.5 wt% as V2O5). 相似文献
902.
903.
M. Esmeralda Sousa Dias 《Acta Appl Math》2002,70(1-3):209-230
The pseudo-rigid body model is viewed within the context of continuum mechanics and elasticity theory. A Lagrangian reduction, based on variational principles, is developed for both anisotropic and isotropic pseudo-rigid bodies. For isotropic Lagrangians, the reduced equations of motion for the pseudo-rigid body are a system of two (coupled) Lax equations on so(3)×so(3) and a second-order differential equation on the set of diagonal matrices with a positive determinant. Several examples of pseudo-rigid bodies such as stretching bodies, spinning gas cloud and Riemann ellipsoids are presented. 相似文献
904.
J. Dias De Deus 《Physics letters. [Part B]》1988,200(4):575-579
It is shown that, as a consequence of the centrality of the semi-hard amplitude, it is possible to obtain an upper and a lower bound for the ratio nSH/n of the minijet average multiplicity over the inelastic average multiplicity and an upper bound for the ratio C2 SH/C2 of the corresponding normalized second moments of the particle distributions. In minijet events multiplicities are higher and the KNO distributions are narrower. 相似文献
905.
Let jvk, yvk and cvk denote the kth positive zeros of the Bessel functions Jv(x), Yv(x) and of the general cylinder function Cv(x) = cos αJv(x)?sin αYv(x), 0 ? α < π, respectively. In this paper we extend to cvk, k = 2, 3,..., some linear inequalities presently known only for jvk. In the case of the zeros yvk we are able to extend these inequalities also to k = 1. Finally in the case of the first positive zero jv1 we compare the linear enequalities given in [9] with some other known inequalities. 相似文献
906.
Anna Stella Maria Teresa PiccardoRosella Coradeghini Anna RedaelliSilvia Lanteri Carla ArmaninoFederico Valerio 《Analytica chimica acta》2002,461(2):201-213
This article aims to show how a careful pre-treatment of data can be used to demonstrate various features embedded in a given data set obtained from a “mussel watch” survey, namely site- and source-specific characteristics and weather-related changes, and to provide indications so as to allow comparison with analyses performed on another substrate matrix. Polycyclic aromatic hydrocarbons (PAHs) biomonitored in the aquatic environment by means of caged mussels are compared by site and by season. Moreover, their fingerprints were compared to marine sediments and atmospheric airborne PAHs. The characterization of the sampling stations by means of the multivariate technique called principal component analysis (PCA) allows distinguishing the prevalence of pyrogenic or petrogenic types of pollution and between two kinds of combustibles. This was confirmed by jointly analyzing the percent composition of sea (mussel) and air (filter) samples. 相似文献
907.
Carla Vogt Katja Heinig Barbara Langer Jürgen Mattusch Gerhard Werner 《Fresenius' Journal of Analytical Chemistry》1995,352(5):508-514
High-performance liquid chromatography and capillary zone electrophoresis have been used for the separation of homologues and structural isomers of linear alkylbenzenesulfonates with subsequent UV detection. The analytical advantages of these techniques are applied to the analysis of technical products containing high amounts of LAS as well as river water samples with very low LAS concentrations using preconcentration steps.Dedicated to Professor Dr. H. Kriegsmann on the occasion of his 70th birthday 相似文献
908.
909.
Romualdo Caputo Maria Chianese Carla Ferreri Giovanni Palumbo 《Tetrahedron letters》1985,26(16):2011-2012
Di- and trisubstituted steroidal epoxides are shown to be converted smoothly to halohydrins in high yield by triphenylphosphine-halogen complexes, under non-acidic and non-eliminating conditions. 相似文献
910.
Lauro Camargo Dias Jr Joaquim Delphino Da Motta Neto Daniel Rettori Nelson Durn 《Journal of Molecular Structure》2002,580(1-3):85-90
Violacein is the major pigment produced by Chromobacterium violaceum. We now report the results of semiempirical calculations on the electronic spectrum of violacein. We have used the AM1 and Intermediate Neglect of Differential Overlap (INDO) model Hamiltonians. Solvent effects have been included with the SCRF model for spectroscopy as proposed by Zerner and Karelson. Our results suggest that in the gas phase violacein is almost planar while in ethanolic solution the H-bond interactions force an internal rotation due to sterical factors. The calculated UV-visible spectrum with the inclusion of specific solvent interactions in the Hamiltonian is on good agreement with the experimental spectrum. 相似文献