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排序方式: 共有149条查询结果,搜索用时 31 毫秒
41.
Barrero AF Quílez Del Moral JF Herrador MM Cortés M Arteaga P Catalan JV Sanchez EM Arteaga JF 《The Journal of organic chemistry》2006,71(15):5811-5814
Regioselective halogenation of the terminal isopropylidene unit of different acyclic polyolefinic polyprenoids (farnesyl acetate, geranylgeranyl acetate, squalene, etc.) using NCS/catalytic polymer-supported selenenyl bromide is described; good to excellent yields are obtained (68-96%). The first applications of this protocol include the concise synthesis of bioactive terpenoids 1-3. 相似文献
42.
43.
Starting from a generalized Gibbs equation and from the Einstein formula for the probability of fluctuations, we obtain the correlation function of heat fluctuations. 相似文献
44.
A new method for separation of several amino acids using mobile phases (MPs) containing mixed micelles as well as 1-butanol and aprotic organic solvents as modifying additives has been developed. The effect of experimental factors (the ratio of MP components, nature of stationary phase) on separation of amino acids is investigated and all conditions for separation are optimized. It was found that separation of three amino acids l-lysine, l-histidine and l-tryptophan on silica gel stationary phase in the interval from micrograms to milligrams is available. The proposed method is simple and allows determining the amino acids in the linear interval of 0.1-1.5mg. 相似文献
45.
Sandra del Moral Clarita Olvera Maria Elena Rodriguez Agustin Lopez Munguia 《BMC biochemistry》2008,9(1):6
Background
Inulosucrase (IslA) from Leuconostoc citreum CW28 belongs to a new subfamily of multidomain fructosyltransferases (FTFs), containing additional domains from glucosyltransferases. It is not known what the function of the additional domains in this subfamily is. 相似文献46.
González-del Moral O Hernán-Gómez A Martín A Mena M Santamaría C 《Dalton transactions (Cambridge, England : 2003)》2008,(1):44-46
The [{TiCp*(micro-O)}3(mu3-CH)] (1) metalloligand, (Cp* = eta5-C5Me5), coordinates in a 1:1 ratio to [AlMe3] or 9-BBN to give [{Me3Al}{(mu3-O)(mu-O)2(TiCp)2(TiCp)3(mu3-CH)}](2) or [{(C8H14)B}(mu-H) {(mu3-O)(mu-O)2(TiCp*)3(mu3-CH)}](4), respectively, partial hydrolysis of 2 leads to the new hydroxo-aluminium derivative [{MeAl} {(mu-OH)(mu3-O)}2{(mu-O)2(TiCp*)3-(mu3-CH)}2](3). 相似文献
47.
The first total synthesis of (-)-achilleol B was achieved using a convergent approach with a longest linear sequence of 14 steps. Three key steps were employed, including an enantioselective Robinson annelation for the construction of the bicyclic moiety. The monocyclic synthon was prepared through a Ti(III)-mediated cylization of a chiral monoepoxide obtained via asymmetric dihydroxylation of geranylacetone. The asymmetric preparation of these subunits also permitted us to achieve the enantioselective synthesis of elegansidiol, achilleol A, and farnesiferol B. 相似文献
48.
In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)-SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or π-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1-2 mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA-SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100 ng L−1 for the determination of the 17 pesticides tested. Recoveries from spiked (at the ng L−1 level) river and underground water samples was quantitative for most of the pesticides tested. 相似文献
49.
Juan C. Espinosa Dr. Sergio Navalón Dr. Ana Primo Dr. Mónica Moral Prof. Javier Fernández Sanz Prof. Mercedes Álvaro Prof. Hermenegildo García 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):11966-11971
Reduced graphene oxide exhibits high activity as Fenton catalyst with HO. radical generation efficiency over 82 % and turnover numbers of 4540 and 15023 for phenol degradation and H2O2 consumption, respectively. These values compare favorably with those achieved with transition metals, showing the potential of carbocatalysts for the Fenton reaction. 相似文献
50.
I. Santamaría-Holek Z.J. Grzywna J.M. Rubi 《The European physical journal. Special topics》2013,222(1):129-141
We analyze the kinetics of diffusion-adsorption processes of one component systems in micropores. In realistic situations, the pores exhibit irregular forms which give rise to inhomogeneous adsorption with preferred sites for the adsorbing particles. By modeling the tortuosity of the pores by means of entropic barriers, we obtain a kinetic equation for the averaged concentration of particles along the pore and on its surface. The analysis performed yields expressions for the adsorption rate, the effective diffusion coeffcient, the adsorption isotherms and the concentration of the adsorbed particles. It is shown that this last quantity strongly depends on the form of the pore. This feature opens the possibility to design micropores with an optimal adsorption rate at selected sites. Our results show that to consider the geometry of the pore in the reaction-diffusion scheme is crucial to reproduce experimental observations of the concentration of adsorbed particles in micropores. 相似文献