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981.
Pérez-Balderas F Ortega-Muñoz M Morales-Sanfrutos J Hernández-Mateo F Calvo-Flores FG Calvo-Asín JA Isac-García J Santoyo-González F 《Organic letters》2003,5(11):1951-1954
[reaction: see text] The construction of multivalent neoglycoconjugates is efficiently achieved by the regiospecific catalytic cycloaddition of alkynes and azides using the organic-soluble copper complexes (Ph(3)P)(3).CuBr and (EtO)(3)P.CuI. The simultaneous use of microwave irradiation shortened notably the reaction times. 相似文献
982.
Roig-Salom JL Doménech-Carbó MT de la Cruz-Cañizares J Bolívar-Galiano F Pelufo-Carbonell MJ Peraza-Zurita Y 《Analytical and bioanalytical chemistry》2003,375(8):1176-1181
A study by SEM/EDX and spectrophotometry in the visible region attempting to assess the stability of new resin-bound mortars used for casting replicas of marble historic fountains is presented in this paper. Different accelerating tests such as thermal ageing, UV light ageing, ageing in an SO(2) pollutant chamber, freezing cycles ageing, salt crystallisation ageing, natural ageing and biological attack have been applied to a series of test specimens prepared with polyester-, epoxy- and gel-coat-bound mortars. Examination of morphology, measurement of chemical composition and chromatic coordinates before and after ageing treatments establish the higher stability and resistance properties of these resin-bound mortars by comparison to those from the natural marbles. 相似文献
983.
Xiao Y Kharitonov AB Patolsky F Weizmann Y Willner I 《Chemical communications (Cambridge, England)》2003,(13):1540-1541
The intercalation of doxorubicin into double-stranded DNA stimulates the electocatalyzed oxidation of aniline to polyaniline and its winding on the DNA template. 相似文献
984.
García-López J Peralta-Pérez E Forcén-Acebal A García-Granda S López-Ortiz F 《Chemical communications (Cambridge, England)》2003,(7):856-857
The first examples of the PN-directed dilithiation of (N-methoxycarbonyl)phosphazenes in the C(alpha) and C(ortho) to the phosphorus, and the use of these dianions in the formation of tri- and tetra-substituted olefins through stereospecific thermolysis of a new type of isolable bicyclic 1,2-oxaphosphetanes are described. 相似文献
985.
Gómez FJ Chen RJ Wang D Waymouth RM Dai H 《Chemical communications (Cambridge, England)》2003,(2):190-191
Norbornene polymerization has been initiated selectively on the surface of single-walled carbon nanotubes (SWNTs) via a specifically adsorbed pyrene-linked ROMP initiator, resulting in a homogeneous non-covalent poly(norbornene) coating. 相似文献
986.
This paper presents a new method - which does not rely on the cut-elimination theorem - for characterizing the provably total functions of certain intuitionistic subsystems of arithmetic. The new method hinges on a realizability argument within an infinitary language. We illustrate the method for the intuitionistic counterpart of Buss's theory S, and we briefly sketch it for the other levels of bounded arithmetic and for the theory IΣ1. 相似文献
987.
Zubia A Cossío FP Morao I Rieumont M Lopez X 《Journal of the American Chemical Society》2004,126(16):5243-5252
One reference tertiary amine and three families of structurally related trialkylamines and dendrimers have been synthesized, characterized, and studied by molecular dynamics simulations. The catalytic activity of these amines in the nitroaldol (Henry) reaction between 2-nitroethanol and benzaldehyde has been measured by FT-IR spectroscopy. It is found that, in this kind of molecule with only one catalytic center at the core, the efficiency of the catalytic process decreases with the size and/or the degree of ramification of the dendrimer. According to these results, there is a linear departure from the behavior predicted by the hard sphere collision theory (HSCT) as the size of the dendrimer increases. Therefore, the behavior of structurally related dendrimers can be quantified in terms of their molecular weight and reagent accessible surfaces. 相似文献
988.
Antonio Membiela Fernando Lázaro M. D. Luque Castro Miguel Valcárcel 《Fresenius' Journal of Analytical Chemistry》1990,338(6):749-751
Summary A fast, simple and convenient method for the individual and total determination of bile acids based on the enzymatic oxidation of the analytes and the fluorimetric measurement of a reaction product (the reduced form of the coenzyme, NADH) is proposed. The method allows the determination of the analytes (taurocholic, chenocholic, glycocholic and chenodesoxycholic acid) over the range of 0.3–10.0 g ml–1, with an r.s.d. smaller than 3.0% in each case. It was applied to the determination of total bile acids in human serum. The simplicity of the method makes it useful for screening clinical samples in order to avoid implementing chromatographic processes on samples with analyte overall contents clearly below pathological limits. 相似文献
989.
Fernando Bernardi Joseph J.W. McDouall Michael A. Robb 《Journal of computational chemistry》1987,8(4):296-306
The theory of an implementation of the diabatic surface model within the Heitler–London valence bond approach is described. It is shown that the HL –VB wave function can be obtained from a Van-Vleck transformation of an MC –SCF wave function which has been built from atom-localized orbitals. This wave function is built from a superposition of two diabatic components, reactantlike and productlike. The transition structure is then obtained as the minimum of the seam of intersection of the diabatic surfaces and the algorithm for performing this constrained optimization is described. Several areas of application are also discussed. 相似文献
990.
The selectiity in the catalytic reduction of aromatic nitro compounds containing O-benzyl, N-benzyl or chlorine with hydrazine and Raney nickel was studied. 相似文献