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排序方式: 共有136条查询结果,搜索用时 296 毫秒
1.
Priscila Castelani 《Tetrahedron letters》2004,45(23):4473-4475
Butyl aryl tellurides reacted with dilithium dimethyl cyanocuprate and with dilithium methyl(2-thienyl)cyanocuprate to give the corresponding dilithium aryl cyanocuprates, which were captured with enones leading to 4-aryl ketones in good yields. 相似文献
2.
First, by using linear and trilinear estimates in Bourgain type analytic and Gevrey spaces, the local well‐posedness of the Cauchy problem for the modified Kawahara equation on the line is established for analytic initial data that can be extended as holomorphic functions in a strip around the x‐axis. Next we use this local result and a Gevrey approximate conservation law to prove that global solutions exist. Furthermore, we obtain explicit lower bounds for the radius of spatial analyticity given by , where can be taken arbitrarily small and c is a positive constant. 相似文献
3.
Maíra Fasciotti Gustavo B. Sanvido Vanessa G. Santos Priscila M. Lalli Michael McCullagh Gilberto F. de Sá Romeu J. Daroda Martin G. Peter Marcos N. Eberlin 《Journal of mass spectrometry : JMS》2012,47(12):1643-1647
The use of CO2 as a massive and polarizable drift gas is shown to greatly improve peak‐to‐peak resolution (Rp‐p), as compared with N2, for the separation of disaccharides in a Synapt G2 traveling wave ion mobility cell. Near or baseline Rp‐p was achieved for three pairs of sodiated molecules of disaccharide isomers, that is, cellobiose and sucrose (Rp‐p = 0.76), maltose and sucrose (Rp‐p = 1.04), and maltose and lactose (Rp‐p = 0.74). Ion mobility mass spectrometry using CO2 as the drift gas offers therefore an attractive alternative for fast and efficient separation of isomeric disaccharides. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
4.
Marcolan M Martins PA Pedrosa VA Rodrigues MR de Oliveira HP Codognoto L 《Journal of fluorescence》2011,21(2):733-738
A simple, rapid and effective analytical method based on fluorescence spectroscopy for the determination of coumarin in pharmaceutical
formulations without pre-treatment or pre-concentration step was development. Coumarin had maximum excitation and emission
at 310 nm and 390 nm, respectively. Optimum conditions for the detection of coumarin were investigated. Under optimized conditions,
we observed a linear behavior for the sign of coumarin in the concentration range of 2.5 × 10−6 to 1.0 × 10−4 mol L−1, with linearity of 0.998 and sensitivity of 2.9 × 1010 u.a/mol L−1. The proposed method was validated in terms of accuracy, precision and specificity of coumarin using the standard addition
and external calibration. It was noted that the results support (P < 0.05), indicating that the matrices were not an interference in the determination of coumarin by fluorescence spectroscopy.
The results were favorable compared with those obtained by reference chromatographic methods. 相似文献
5.
Jasquer A. Sehnem Priscila Milani Vanessa Nascimento Leandro H. Andrade Luciano Dorneles Antonio L. Braga 《Tetrahedron: Asymmetry》2010,21(8):997-1003
N-Trifluoracyl β-chalcogeno amides and N-perfluoracyl β-thio amide ligands were prepared by a simple and efficient reaction sequence. These new ligands were evaluated in palladium-catalyzed alkylation of rac-(E)-1,3-diphenyl-2-propenyl acetate in the presence of dimethyl malonate and an enantioselectivity of up to 99% was obtained. After catalysis, the fluorous ligand can be easily recovered by liquid–liquid extraction and reused without loss in the activity. 相似文献
6.
Luiz Augusto N. Barroso Márcia H.C. Fampa Rafael Kelman Mario V.F. Pereira Priscila Lino 《Annals of Operations Research》2002,117(1-4):247-270
The objective of this work is to investigate market power issues in bid-based hydrothermal scheduling. Initially, market power was simulated with a single stage Cournot–Nash equilibrium model. In this static model the equilibrium was calculated analytically. It was shown that the total production of N strategic agents is smaller than the least-cost solution by a factor of (N/(N+1)). Market power analysis for multiple stages was then carried through a stochastic dynamic programming scheme, where the decision in each stage and state is the Cournot–Nash equilibrium of a multi-agent game. Case studies with data taken from the Brazilian system are presented. 相似文献
7.
The water solubility of 1,3,5,7-tetra azatricyclo[3.3.1.13,7]decane, hexamethylenetetramine (HMT) or urotropine was determined at temperatures between 275.15 K and 313.15 K. Van’t Hoff graphs of ln msat versus 1/T gave three different straight lines, suggesting the existence of three different forms of the substance in the temperature region studied.
Previous work reported both increasing and decreasing solubility with temperature. This work found the solubility does not have a simple behavior. 相似文献
8.
Priscila García-Fernndez M. Santos D. García-Puente P. F. Gonzlez-Díaz 《Optics Communications》1982,40(6):451-454
By using the Laplace transform method we obtain exact analytical solutions for the time development of the photon density matrix in anti-Stokes luminescence. The cases of cooperative and sequential mechanism are separately considered. 相似文献
9.
The crystalline structure of Ca10?xSrx(AsO4)6(OH)2 has been studied, and the lattice parameters determined. It has been found that the unit cell expands with x. Geometric parameters of the unit cell, which are defined in relation to the hindered rotation of the OH group around the c axis, have been also obtained. From the ir data, the torsional potential function has been calculated in first and second approximations. A method for computing that function in any order approximation is given. A semiempirical curve is found, relating the stretching and torsional motions for both the OH and OD groups. 相似文献
10.
The aim of this work is to study the effect of the preparation conditions of Ru/CeO2 catalyst (calcination temperature and/or reduction) over the performance in the partial hydrogenation of benzene reaction in the presence of TiCl3. The catalysts were prepared through chlorinated precursors by incipient wetness impregnation method. The reaction occurred in three-phase reactional medium in presence of water at 373 K and 5.0 MPa. Temperature programmed reduction (TPR) profiles of calcinated catalysts indicate the presence of oxidated ruthenium. X-ray photoelectron spectroscopy (XPS) analysis confirms this supposition, showing that the ruthenium appears in the form of RuO2 for the sample calcinated at 673 K, while for the reduced solid at 773 K, the Ru appears in the metallic state. However, the calcination step followed or not by reduction, strongly hinders the catalytic performance. In its turn, the direct reduction leads to a more active Ru/CeO2 catalysts, as well as higher cyclohexene yields throughout all the reaction. 相似文献