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排序方式: 共有152条查询结果,搜索用时 18 毫秒
1.
M. Angel Mateos Rocío Gálvez F. Javier Manuel de Villena José M. Pingarrón 《Mikrochimica acta》1995,120(1-4):339-349
An electroanalytical study of the herbicide propazine's reduction process in micellar solutions and oil-in-water emulsions is reported. The anionic surfactant sodium pentanesulphonate was chosen as the most suitable. The differential pulse polarograms of micellar solutions had two reduction peaks below pH 2.0, whereas only one peak was obtained above pH 2.O. Ethyl acetate was chosen as the organic solvent to form propazine emulsions. Unlike in micellar solutions, the DPP polarograms of propazine emulsions showed only one peak even at pH < 2.0, suggesting that propazine hydrolysis was hindered in the emulsified medium. The limiting current is diffusion-controlled and the electrode process is irreversible. Propazine can be determined by differential pulse polarography over the 1.0 × 10–1 – 1.0 × 10–1moll–1 and 1.0 × 10–15 – 4.0 × 10–1 moll–1 concentration ranges and the limit of detection was 2.8 × 10–1 moll–1. Of the potential interferents simazine, methoprotryne and terbutryn (alls-triazines), thiram (a dithiocarbamate), dinoseb (nitrophenolic), and heptachlor (chlorinated cyclo-diene herbicide), only the first two were significant (10% error for equimolar concentrations). The method was applied to the determination of propazine in spiked drinking water. At a concentration level of 2.0 × 10–1 moll–1 a recovery of 94 ± 6% was obtained, after tenfold concentration on Sep-Pak. 相似文献
2.
ABSTRACTA class of semilinear parabolic reaction diffusion equations with multiple time delays is considered. These time delays and corresponding weights are to be optimized such that the associated solution of the delay equation is the best approximation of a desired state function. The differentiability of the mapping is proved that associates the solution of the delay equation to the vector of weights and delays. Based on an adjoint calculus, first-order necessary optimality conditions are derived. Numerical test examples show the applicability of the concept of optimizing time delays. 相似文献
3.
Ivanna Rivera Juan Carlos Mateos Alain Marty Georgina Sandoval Sophie Duquesne 《Tetrahedron letters》2013
Besides the well-known papain, lipolytic activity is another interesting enzymatic activity present in latex from Carica papaya. This lipolytic activity is strongly attached to the latex solid phase, resulting in a naturally immobilized biocatalyst. In this work we describe the kinetic resolution of (R,S)-2-bromophenylacetic acid octyl ester by Carica papaya crude latex and two partially purified latex fractions. Several parameters, such as substrate concentration and solvent effects were studied. The best results were obtained using decane as solvent with 50 mM of substrate and 50 mg/mL enzyme/reaction medium; under these conditions, a high enantioselectivity (E >200) was obtained with crude latex. A twofold increase of the initial rate maintaining E >200 was obtained using purified fractions without protease and without esterase. Lipase from Carica papaya latex is the most enantioselective wild-type enzyme ever described for the studied reaction. 相似文献
4.
5.
Javier Mateos Francesco Rigodanza Alberto Vega‐Pealoza Andrea Sartorel Mirco Natali Tommaso Bortolato Giorgio Pelosi Xavier Company Marcella Bonchio Luca Dell'Amico 《Angewandte Chemie (International ed. in English)》2020,59(3):1302-1312
Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale. They absorb across the UV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited‐state redox potentials, PC*/PC.? (up to 1.65 V) and PC.+/PC* (up to ?1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis. 相似文献
6.
We study the numerical approximation of elliptic control problems with finitely many pointwise state constraints and control
bounds. Results for the continuous problem are collected and a complete study of the discrete problems is carried out, including,
existence of solutions, optimality conditions, convergence to solutions of the continuous problem and error estimates. A numerical
example is provided. 相似文献
7.
V.I. Afonso D. Bazeia M.A. Gonzalez Len L. Losano J. Mateos Guilarte 《Nuclear Physics B》2009,810(3):427-459
This work deals with the construction of networks of topological defects in models described by a single complex scalar field. We take advantage of the deformation procedure recently used to describe kinklike defects in order to build networks of topological defects, which appear from complex field models with potentials that engender a finite number of isolated minima, both in the case where the minima present discrete symmetry, and in the non-symmetric case. We show that the presence of symmetry guide us to the construction of regular networks, while the non-symmetric case gives rise to irregular networks which spread throughout the complex field space. We also discuss bifurcation, a phenomenon that appear in the non-symmetric case, but is washed out by the deformation procedure used in the present work. 相似文献
8.
B. Kotliński D. Androić G. Backenstoss D. Bosnar H. Breuer H. Döbbeling T. Dooling M. Furić P.A.M. Gram N.K. Gregory A. Hoffart C.H.Q. Ingram A. Klein K. Koch J. Köhler M. Kroedel G. Kyle A. Lehmann A.O. Mateos K. Michaelian T. Petković M. Planinić R.P. Redwine D. Rowntree U. Sennhauser N. Šimičević R. Trezeciak H. Ullrich H.J. Weyer M. Wildi K.E. Wilson 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):435-445
The pion absorption reaction (π+,3
p
) on Ar was studied at pion energies of 70, 118, 162 and 239 MeV, and on N and Xe at 239 MeV. The 3p cross section with a 50 MeV cut on the missing energy is presented. The existence of an initial state interaction (ISI) component
to the reaction was investigated. The portion of the 3p cross section assigned to the ISI process is less than one half and at lower energies significantly so.
Received: 11 December 1997 相似文献
9.
研究了三种掺Yb钒酸盐混晶Yb0.005:Y0.298Gd0.697VO4, Yb0.007:Y0.407Gd0.586VO4和Yb0.009:Y0.575Gd0.416VO4的室温偏振吸收谱和发射谱. 结果表明,最强的吸收和发射相应于π偏振,位
关键词:
掺Yb钒酸盐混晶
吸收谱和发射谱
激光振荡
偏振态 相似文献
10.