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1.
We give a Gray code and constant average time generating algorithm for derangements, i.e., permutations with no fixed points. In our Gray code, each derangement is transformed into its successor either via one or two transpositions or a rotation of three elements. We generalize these results to permutations with number of fixed points bounded between two constants. 相似文献
2.
The synthesis of 2-substituted 1,4-diacetoxybutadiene derivatives with a partial control of stereochemistry is described from two potentially precursor enals by a judicious choice of experimental conditions (Ac2O/DMAP in Et3N). These conditions have been successfully applied in the first total synthesis of caulerpenyne. 相似文献
3.
An alternative definition of entropy for non-commutative systems, equivalent to the one by A. Connes, H. Narnhofer, and W. Thirring, is given. It is based on the concepts of conditional entropy, and stationary couplings with classical systems. It allows to prove that any quantum dynamical system with singular spectrum has zero entropy. 相似文献
4.
It has been recently shown that computation with stochastic numbers as regard to addition and multiplication by scalars can be reduced to computation in familiar vector spaces. In this work we show how this can be used for the algebraic solution of linear systems of equations with stochastic right-hand sides. On several examples we compare the algebraic solution with the simulated solution using the CADNA package. 相似文献
5.
A novel approach to H-phosphonates from hypophosphorous acid using a transfer hydrogenation process was developed. This method is atom-economical, environmentally friendly, catalytic, and efficient, leading easily to H-phosphonate monoesters or ammonium salt in moderate to good yields. 相似文献
6.
This work deals with an experimental study of an indirect temperature swing adsorption process for VOC removal from air or for gas purification. A 1 m long and 70 mm diameter column with an internal heat exchanger has been filled with Ambersorb 600 carbonaceous adsorbent. This column is equipped with sensors to measure temperature at several points inside the bed, as well as the inlet and outlet gas concentration, pressure, temperature and mass flow. In a first step, CO2 or ethane/dry nitrogen mixtures were used to simulate a single VOC in air, with different concentrations (350 ppm, 1% and 10%). As a first results very effective gas purification was obtained and an advantage of this process is the high pollutant concentration during the regeneration phase. Experiments were performed with various ethane/CO2 mixtures. The influence of the presence of CO2 on the ethane concentration breakthrough curves and on the ethane concentration during regeneration is reported. The IAS theory was used, as a first approach, to predict the adsorbed pollutants amount. Relatively good prediction is obtained with a maximum error in the order of 10%. An energy balance study is reported as well. 相似文献
7.
Epoxidation of olefins by sodium periodate is effected by the catalysis of RuCl3, (H2O)n associated with bipyridyl. The reaction is stereospecific for both cis and trans alkenes. 相似文献
8.
The fragmentation patterns of 24 substituted phenyltrifluoromethanesulfonates has been determined by exact mass and metastable transition measurements. The influence of the ring substituent(s) on the abundance of the [ArO]+ ions has been investigated at low energies and a new standard parameter for plotting against Hammett's ó constants is proposed. The direct loss of CF3SO3 from the molecular ion of 3,5-(diisopropyl)-phenyl-, 3,5-(dicyclopropyl)phenyl- and 3,5-di(α-methylcyclopropyl)-phenyl-methanesulfonate, and further observations on the fragmentation processes of these compounds are consistent with M.O. calculations on the ‘through bond’ stabilization of the [Ar]+ σ state by meta electron donor substituents. 相似文献
9.
Résumé Les auteurs décrivent une méthode efficate et les conditions (faibles valeurs de pH, milieu dioxane/eau (1∶2), carbodiimide
hydrosoluble) de formation de peptides colorés par réaction de leur groupe carboxylique avec un colorant aminé (par exemple:
1(4-diméthylamino-1 phénylazo)-4-aminobenzène=p,p′-dimapa-aniline), sans polymérisation du peptide non-protégé. Quelques méthodes
chromatographiques, faciles à mettre en oeuvre, pour l'isolement de peptide-p,p′-dimapa-anilides et quelques propriétés de
ces nouveaux composés (peptides-C-colorés) sont présentées.
相似文献
Method for labelling carboxylic groups in peptides. Chromatographic and other properties of peptide-p,p′-dimapa-anilides
Summary The authors describe an effective method and the conditions (low pH values, dioxane/water (1∶2) media, watersoluble carbodiimide) for making coloured carboxylic peptides from amino-dye (i.e.: 1(4-dimethylamino-1 phenylazo)-4-aminobenzene=p,p′-dimapa-aniline), without polymerisation of unprotected peptide. Some easy chromatographic methods for isolation of peptide-p,p′-dimapa-anilides and some properties of these new compounds (C-dyed-peptides) are given.
相似文献
10.
Steric and electronic influences of various substituted pyridines support the hypothesis of the coordination of pyridine in the manganese porphyrin-catalysed epoxidation of olefins with sodium hypochlorite solution. 相似文献