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排序方式: 共有377条查询结果,搜索用时 109 毫秒
1.
2.
Flavio Previale 《Archive for Mathematical Logic》1994,33(3):213-241
The paper contains an axiomatic treatment of the intuitionistic theory of hereditarily finite sets, based on an induction axiom-schema and a finite set of single axioms. The main feature of the principle of induction used (due to Givant and Tarski) is that it incorporates Foundation. On the analogy of what is done in Arithmetic, in the axiomatic system selected the transitive closure of the membership relation is taken as a primitive notion, so as to permit an immediate adaptation of the theory to cases of restricted induction (in particular primitive recursive induction). At the end of the paper several different forms of induction, which play an important role in the development of the theory, are compared. An alternative axiomatization of the theory, which is of intrinsic interest, is also discussed. 相似文献
3.
This paper describes the formation of a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) under different concentrations on a gold sensor disk, monitoring in situ and in real time using surface plasmon resonance spectroscopy (SPR). The film thickness and dielectric constant were determined for a fully formed monolayer using one-color approach SPR. The kinetic studies of the film formation in ethanol solution indicated that the self-assembled monolayer is formed in a two-step adsorption process. In this sense, this unpublished route was applied on the basis of a model where many molecules are adsorbed at an initial step and then can be desorbed and/or rearranged to form a perfect monolayer. 相似文献
4.
Polo F Antonello S Formaggio F Toniolo C Maran F 《Journal of the American Chemical Society》2005,127(2):492-493
The rate constant of intramolecular electron transfer through oligopeptides based on the alpha-aminoisobutyric acid residue was determined as a function of the peptide length and found to depend weakly on the donor-acceptor separation. By measuring the electron-transfer activation energy and estimating the energy gap between donor and bridge, we were able to discard the electron hopping mechanism. 相似文献
5.
Summary The halogen bridges of the dimeric, cyclometallated trimesityl-arsine and -phosphine complexes of palladium(II) and platinum(II), where M=Pd or Pt and E=P or As have been replaced with pyrazolate groups to give the corresponding and less symmetric pyrazolato-bridged complexes, where M=Pd or Pt, E=P or As, Pz=pyrazolato anion, and M=Pd, E=As, Pz=3,5-dimethylpyrazolato anion. In the case of the palladium complexes,1H. n.m.r. clearly indicates the presence of only one isomer which is most likely to have thetrans configuration while the platinum complexes are mixtures of bothcis andtrans forms.Part VI, ref. 3c 相似文献
6.
Dissociative electron transfers (ET) are reactions in which the ET is associated with the cleavage of a sigma bond. Although a rather satisfactory amount of information is currently available on the intermolecular and heterogeneous dissociative ET reactions, less is known for the corresponding intramolecular processes, despite the relevance of these reactions in both chemistry and biochemistry. This tutorial review focuses on the most recent developments in this area, with particular emphasis on the reactions occurring in well-defined Donor-Spacer-Acceptor molecular systems. The goal is to provide the reader with the essential background to understand and possibly predict the feasibility and rates of these reactions, as well as to stimulate the application of the intramolecular dissociative ET concepts and related issues to still unexplored molecular systems. 相似文献
7.
Zanin Gisella M. Neitzel Ivo De Moraes Flavio F. 《Applied biochemistry and biotechnology》1993,(1):477-489
The axial dispersion of a liquid fluidized bed of controlled pore silica (CPS) particles has been determined by the pulse
tracer method. The CPS used was the same as for enzyme immobilization, having an average diameter of 0.436 mm and mean pore
size of 37.5 nm. The fluidization liquid is α-amylase liquefied manioc starch, 30% w/v, 45°C pH=4.5. Nominal bed porosities
tested were 0.7 and 0.8. The results show that the axial dispersion coefficient increases with greater superficial liquid
velocities. Various available correlations tested disagree with each other to a large extent and are unable to represent collected
experimental data. 相似文献
8.
Cleide M. F. Soares Heizir F. de Castro Juliana E. Itako Flavio F. De Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》2005,123(1-3):845-859
Candida rugosa lipase was entrapped in silica sol-gel particles prepared by hydrolysis of methyltrimethoxysilane and assayed by p-nitrophenyl palmitate hydrolysis, as a function of pH and temperature, giving pH optima of 7.8 (free enzyme) and 5.0–8.0
(immobilized enzyme). The optimum temperature for the immobilized enzyme (50–55°C) was 19°C higher than for the free enzyme.
Thermal, operational, and storage stability were determined with n-butanol and bytyric acid, giving at 45°C a half-life 2.7 times greater for the immobilized enzyme; storage time was 21 d
at room temperature. For ester synthesis, the optimum temperature was 47°C, and high esterification conversions were obtained
under repeated batch cycles (half-life of 138 h). 相似文献
9.
Francesca Benedini Giorgio Bertolini Francesco Ferrario Angelo Motti Alberto Sala Flavio Somenzi 《Journal of heterocyclic chemistry》1995,32(1):103-107
The preparation and the physico-chemical characterization of 2H-pyrido[2,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazine-2,4(3H)-diones, 2H-pyrido[4,3-e]-1,3-oxazin-4(3H)-ones, 2H-thieno[2,3-e]-1,3-oxazin-4(3H)-ones and 2H-thieno[3,4-e]-1,3-oxazine-2,4(3H)-diones are reported. 相似文献
10.
Luigia Serpico Mauro De Nisco Flavio Cermola Michele Manfra Silvana Pedatella 《Molecules (Basel, Switzerland)》2021,26(9)
A simple and efficient route for the synthesis of new glycoconjugates has been developed. The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joined to a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontrol detected in the Mitsunobu key reaction led to the most attractive product showing a natural d-configuration. Thus, we were able to obtain the target molecules from the commercially available d-ribose via a shorter and convenient sequence of reactions. 相似文献