排序方式: 共有38条查询结果,搜索用时 46 毫秒
1.
3-Hydroxybutyramides are obtained in high optical yield from ethyl (±)-3-hydroxybutyrate and aliphatic amines when the reaction is catalyzed by Candida antartica lipase. The chemical reduction of these 3-hydroxybutyramides yields the corresponding 1,3 -aminoalcohols. 相似文献
2.
This article introduces a concept of transience and recurrence for a Quantum Markov Semigroup and explores its main properties
via the associated potential. We show that an irreducible semigroup is either recurrent or transient and characterize transient
semigroups by means of the existence of non trivial superharmonic operators.
Received: 27 January 2003 / Revised version: 19 February 2003 /
Published online: 12 May 2003
This research has been partially supported by the ``Cátedra Presidencial en Análisis Cualitativo de Sistemas Dinámicos Cuánticos',
DIPUC, FONDECYT project 1030552, MIUR program ``Probabilità Quantistica e Applicazioni', 2003-2004 and MECESUP PUC 0103.
Mathematics Subject Classification (2000): 60J45, 81S25, 60J99, 37A50, 47A40
Key words or phrases: Quantum Markov semigroups – Potential theory – Markov processes 相似文献
3.
In this paper we study the possibility of analyzing a low-intensity light signal modulated by a square wave by measuring the Laplace or the squared cosine transform of the time interval probability. The error in the determination of the period of the signal is studied and compared with that obtained from the correlation function g(2) (τ). We conclude that measurement of the squared cosine transform is a more advantageous method than measurement of g(2) (τ) for low intensity light beams, the advantage increasing as the intensity of the light beam decreases. This technique can, for instance, be applied to the fields of laser Doppler velocimetry and optical communications. 相似文献
4.
M. A. Rebolledo 《光谱学快报》2013,46(8):537-541
The application of fluorescence correlation spectroscopy to the measurement of diffusion coefficients of atoms is proposed. After a theoretical analysis of the problem the experimental viability of this technique is studied in the particular case of Tl. Finally applications to other experiments such as ground state level-crossing are proposed. 相似文献
5.
We study here the free group generated by isomorphism classes of supersingular elliptic curves in positive characteristic. We compare this -module to the homology of the modular curve X0(p). We give an interpretation of Gross formula for special values of L-functions of modular forms in this context. As an application, we obtain a formula for the sum of the squares of the optimal embeddings numbers of quadratic orders in a definite quaternion algebra. 相似文献
6.
Michael Hrušák Diego Rojas‐Rebolledo Jindřich Zapletal 《Mathematical Logic Quarterly》2014,60(1-2):31-39
We study the possible values of the cofinality invariant for various Borel ideals on the natural numbers. We introduce the notions of a fragmented and gradually fragmented ideal and prove a dichotomy for fragmented ideals. We show that every gradually fragmented ideal has cofinality consistently strictly smaller than the cardinal invariant and produce a model where there are uncountably many pairwise distinct cofinalities of gradually fragmented ideals. 相似文献
7.
A family of pincer-like receptors (2-5) has been synthesized and tested for the NMR enantiodiscrimination (CSA) of chiral carboxylic acids. Starting from a previous design (1), different structural variables have been mapped on the receptor frame. The splitting of the signals of the acids upon the addition of the CSAs largely depends on these structural variables. Thus, we concluded that the C2 symmetrical pyridine-2,6-biscarboxamide moiety is a key structural feature for the efficiency of the CSA. Structural studies by NMR and molecular modeling showed that this moiety promotes the U-shape-folded pincer-like conformation by intramolecular H-bonds. On the other hand, we also observed that the cyclohexane-1,2-diamine derivative 5 is a more versatile CSA than its cyclopentane analogue 1, as 5 shows a better performance for more structurally different acids. However, the original cyclopentane derivative (1) remained the best for the arylpropionic acids. Finally, combination of NMR and modeling studies allowed us to propose a reasonable model for the interaction and, accordingly, for the observed NMR enantiodiscrimination. 相似文献
8.
Tartaj P Gonzalez-Carreño T Rebolledo AF Bomatí-Miguel O Serna CJ 《Journal of colloid and interface science》2007,309(1):68-71
A simple and rapid synthetic strategy for fabricating carboxy-functionalized iron oxide colloidal particles displaying reversible magnetic behavior is reported. The method is based on the pyrolysis of aerosols generated from ethanol/water solutions containing iron inorganic salts and mono- or polysaccharides. Essential to the success of the method are the use of hybrid (organo-inorganic) aerosols and the temperature of pyrolysis. The resulting material could be used in advanced biotechnological applications such as the magnetically assisted chemical separation of biocompounds. 相似文献
9.
A straightforward chemoenzymatic synthesis of optically active trans-N,N-dialkylcyclopentane-1,2-diamines has been efficiently developed starting out from their analogous (+/-)-trans-2-(N,N-dialkylamino)cyclopentanols. The route involves the one-pot stereospecific transformation of the racemic amino alcohols into racemic diamines and a subsequent kinetic resolution by means of lipase-B from Candida antarctica-catalyzed acylation reactions. The careful selection of both the alkyl substituents present in the diamine and the derivatization strategy applied to the enzymatic reaction enabled the easy preparation of other synthetically valuable optically active trans-cyclopentane-1,2-diamines derivatives. 相似文献
10.
In this work we intend the analysis of light with a very low intensity be means of the measurement of Laplace or Fourier transform of the probability of the time-intervals between two successive photons. The method is applied to the particular case of light of lorentzian spectrum and the error with which the spectral width would be obtained is studied (with a theoretical model and simulating through a computer). This error is confronted with that which might be attained if the spectral width were determined from the intensity correlation function. Results are discussed. 相似文献