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61.
Enzymatic resolution of bicyclic 1-heteroarylamines using Candida antarctica lipase B 总被引:1,自引:0,他引:1
Skupinska KA McEachern EJ Baird IR Skerlj RT Bridger GJ 《The Journal of organic chemistry》2003,68(9):3546-3551
Candida antarctica lipase B has been used to kinetically resolve a structurally diverse series of bicyclic 1-heteroaryl primary amines by enantioselective acetylation. High yields of either enantiomer could be obtained with excellent enantioselectivity (90-99% ee), while the undesired enantiomer could, in some cases, be recycled by thermal racemization. The absolute stereochemistry of the products was confirmed by an X-ray crystal structure. 相似文献
62.
Pollutants removal in two vertical flow experimental wetlands receiving pre-treated municipal wastewater was investigated. Laboratory investigations using microcosms were also carried out in order to identify key processes regulating pollutants removal. Results obtained from experimental wetlands seem to confirm the ability of a single stage installation, where nitrification and denitrification processes are jointly optimised using a gravel medium, always wet but not saturated with water. Results obtained from microcosm investigations show the prominent role of O2 supply, of microbial activity and of bio-available C from vegetal metabolism in the nitrogen removal. 相似文献
63.
The hydrogen bonds formed between the hydroperoxyl radical and formic, acetic, and trifluoroacetic acids were characterized using geometric, energetic, and electronic parameters through calculations done with the UB3LYP/6-311++G (3df,3pd) and UB3LYP/EPR-III methods. The wave functions were analyzed through the natural bond orbital, natural steric analysis, natural resonance theory, and atoms in molecules methods. The energy decomposition method proposed by Xantheas was used. The vibrational frequencies and the intensity of the O-H stretching bands, as well as the spin densities, were compared with experimental evidence. The results allowed the characterization of the hydrogen bonds formed in the complexation of the acids with the hydroperoxyl radical. Complexation led to significant alterations in the equilibrium geometry of the monomers. Energetic analysis proved that the studied complexes are stable and allowed the understanding of the effect of the electron-donating and electron-withdrawing groups in their stabilization. The alterations in the electronic structure of the monomers after complexation led to an increase in the resonance of the carboxyl group, which can be partially attributed to the hydrogen bond. 相似文献
64.
65.
Layered stable equilibria of a reaction-diffusion equation with nonlinear Neumann boundary condition
Arnaldo Simal do Nascimento Renato José de Moura 《Journal of Mathematical Analysis and Applications》2008,347(1):123-135
In this work we investigate the existence and asymptotic profile of a family of layered stable stationary solutions to the scalar equation ut=ε2Δu+f(u) in a smooth bounded domain Ω⊂R3 under the boundary condition εν∂u=δεg(u). It is assumed that Ω has a cross-section which locally minimizes area and limε→0εlnδε=κ, with 0?κ<∞ and δε>1 when κ=0. The functions f and g are of bistable type and do not necessarily have the same zeros what makes the asymptotic geometric profile of the solutions on the boundary to be different from the one in the interior. 相似文献
66.
Renato Noto Silvestre Buscemi Giuseppe Werber Domenico Spinelli 《Journal of heterocyclic chemistry》1987,24(5):1449-1452
The effect of micelles and mixed solvents on the decarboxylation of some N-alkyl- or N-aryl-substituted 5-amino-1,3,4-oxadiazole-2-carboxylic acids has been studied. The data support the unimolecular decarboxylation mechanism proposed by us. Moreover, they show that mixed solvents and micelles have different effects on reactivity of the amino acids under study. 相似文献
67.
Huanwen Chen Gerardo Gamez Renato Zenobi 《Journal of the American Society for Mass Spectrometry》2009,20(11):1947-1963
Ambient mass spectrometry—mass spectrometric analysis with no or minimal effort for sample preparation—has experienced a very
rapid development during the last 5 years, with many different methods now available for ionization. Here, we review its range
of applications, the hurdles encountered for its quantitative use, and the proposed mechanisms for ion formation. Clearly,
more effort needs to be put into investigation of matrix effects, into defining representative sampling of heterogeneous materials,
and into understanding and controlling the underlying ionization mechanisms. Finally, we propose a concept to reduce the number
of different acronyms describing very similar embodiments of ambient mass spectrometry. 相似文献
68.
A heterodyne interferometric polarimeter for detection of the Jones components and Stokes parameters is demonstrated. The measurement of both sets of quantities for various polarization states is achieved with excellent precision. The details of the corresponding Lissajous picture (ellipse) can be visualized in real time. Finally, the polarization data collected at the output of a highly birefringent fiber have been used for submillimetric beat-Length measurements. 相似文献
69.
In this paper we study the hyperstructures, saidP-hypergroupoids, (H, P*) in whichH is a set andP* is one of the hyperoperations defined as follows: ?(x, y) εH 2,xP*y=xyP orxP*y=Pxy whereP is a subset ofH. In particular we give a general formula for to express the simple hyperproducts ofn elements and then we consider some cases in which (H, P*) is feebly associative. We study, in such cases theβ-relations. 相似文献
70.
Signori AM Santos Kde O Eising R Albuquerque BL Giacomelli FC Domingos JB 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17772-17779
A new and straightforward method for screening highly catalytically active silver nanoparticle-polymer composites derived from branched polyethyleneimine (PEI) is reported. The one-step systematic derivatization of the PEI scaffold with alkyl (butyl or octyl) and ethanolic groups led to a structural diversity correlated to the stabilization of silver nanoparticles and catalysis. Analysis of PEI derivative libraries identified a silver nanoparticle-polymer composite that was able to efficiently catalyze the p-nitrophenol reduction by NaBH(4) in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 0.57 s(-1) m(-2) L. Carried out in the presence of excess NaBH(4), the catalytic reaction was observed to follow pseudo-first-order kinetics and the apparent rate constant was linearly dependent on the total surface area of the silver nanoparticles (Ag-NPs), indicating that catalysis takes place on the surface of the nanoparticles. All reaction kinetics presented induction periods, which were dependent on the concentration of substrates, the total surface of the nanoparticles, and the polymer composition. All data indicated that this induction time is related to the resistance to substrate diffusion through the polymer support. Hydrophobic effects are also assumed to play an important role in the catalysis, through an increase in the local substrate concentration. 相似文献