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961.
Two analogues of diphenylethene carrying phenanthrene (1-(9-phenanthryl)-1-phenylethene (PPE)) and anthracene (1-(2-anthryl)-1-phenylethene (APE)) units were used in radical polymerization of styrene (St) and methyl methacrylate (MMA) at 80 °C using AIBN as initiator. Because of the nature of the polymerization, the resulting polymers possess the corresponding chromophoric groups. Using the methodology of a DPE system, these labelled polymers were further used for the synthesis of block copolymers. In this way poly(methyl methacrylate)-b-poly(styrene) and poly(methyl methacrylate)-b-poly(acrylonitrile) with molar masses of 60,000-90,000 g/mol were synthesized. Incorporation of the chromophoric groups into both homo- and block copolymers was confirmed by spectral measurements. 相似文献
962.
The dependent relation between temperature and pressure of supercritical CO2+ ethanol binary system under the pressure range from 5 to 10 MPa with the variety of densities and mole fractions of ethanol
that range from 0 to 2% was investigated by the static visual method in a constant volume. The critical temperature and pressure
were experimentally determined simultaneously. The PTρ figures at different ethanol contents were described based on the determined pressure and temperature data, from which pressure
of supercritical CO2 + ethanol binary system was found to increase linearly with the increasing temperature. P-T lines show certain convergent feature in a specific concentration of ethanol and the convergent points shift to the region
of higher temperature and pressure with the increasing ethanol compositions. Furthermore, the effect of density and ethanol
concentration on the critical point of CO2 + ethanol binary system was discussed in details. Critical points increase linearly with the increasing mole fraction of
ethanol in specific density and critical points change at different densities. The critical compressibility factors Zc of supercritical CO2 + ethanol binary systems at different compositions of ethanol were calculated and Z
c
-ρ figure was obtained accordingly. It was found from Z
c
-ρ figure that critical compressibility factors of supercritical CO2 unitary or binary systems decline linearly with the increasing density, by which the critical point can be predicted precisely. 相似文献
963.
Inés Maya Óscar LópezSusana Maza José G. Fernández-BolañosJosé Fuentes 《Tetrahedron letters》2003,44(47):8539-8543
The preparation of a urea-bridged β-cyclodextrin dimer and of a 6-monodeoxy-6-mono[3-(β-d-glucopyranos-2-yl)ureido]-β-cyclodextrin has been developed, using triphosgene as the isocyanation agent in an aqueous two-phase system. Per-O-acetylated β-d-gluco and mannopyranosylamines and 2-amino-2-deoxy-α- and β-d-glucose were also transformed into the corresponding isocyanates and converted in situ into ureas by coupling with aromatic and aliphatic amines. 相似文献
964.
Factor Xa is a serine protease which activates thrombin and plays a key regulatory role in the blood-coagulation cascade. Factor Xa is at the crossroads of the extrinsic and intrinsic pathways of coagulation and, hence, has become an important target for the design of anti-thrombotics (inhibitors). It is not known to be involved in other processes than hemostasis and its binding site is different to that of other serine proteases, thus facilitating selective inhibition. The design of high-affinity selective inhibitors of factor Xa requires knowledge of the structural and dynamical characteristics of its active site. The three-dimensional structure of factor Xa was resolved by X-ray crystallography and refined at 2.2 Å resolution by Padmanabhan and collaborators. In this article we present results from molecular dynamics simulations of the catalytic domain of factor Xa in aqueous solution. The simulations were performed to characterise the mobility and flexibility of the residues delimiting the unoccupied binding site of the enzyme, and to determine hydrogen bonding propensities (with protein and with solvent atoms) of those residues in the active site that could interact with a substrate or a potential inhibitor. The simulation data is aimed at facilitating the design of high-affinity selective inhibitors of factor Xa. 相似文献
965.
Manganese is extracted on-line from solid seafood samples by a simple continuous ultrasound-assisted extraction system (CUES). This system is connected to an on-line manifold, which permits the flow-injection flame atomic absorption spectrometric determination of manganese. Optimisation of the continuous leaching procedure is performed by an experimental design. The proposed method allows the determination of manganese with a relative standard deviation of 0.9% for a sample containing 23.4 μg g−1 manganese (dry mass). The detection limit is 0.4 μg g−1 (dry mass) for 30 mg of sample and the sample throughput is ca. 60 samples per hour. Accurate results are obtained by measuring TORT-1 certified reference material. The procedure is finally applied to mussel, tuna, sardine and clams samples. 相似文献
966.
967.
968.
Subir Ghosh Sanpei Kageyama Rahul Mukerjee 《Annals of the Institute of Statistical Mathematics》1992,44(3):593-603
In this paper the problem of finding the design efficiency is considered when a single observation is unavailable in a connected binary block design. The explicit expression of efficiency is found for the resulting design when the original design is a balanced incomplete block design or a group divisible, singular or semiregular or regular with 1>0, design. The efficiency does not depend on the position of the unavailable observation. For a regular group divisible design with 1>0, the efficiency depends on the position of the unavailable observation. The bounds, both lower and upper, on the efficiency are given in this situation. The efficiencies of designs resulting from a balanced incomplete block design and a group divisible design are in fact high when a single observation is unavailable.The work of the first author is sponsored by the Air Force Office of Scientific Research under Grant AFOSR-90-0092.On leave from Indian Statistical Institute, Calcutta, India. The work of the third author was supported by a grant from the CMDS, Indian Institute of Management, Calcutta. 相似文献
969.
A. Žilinskas 《Journal of Global Optimization》1992,2(2):145-153
A review of statistical models for global optimization is presented. Rationality of the search for a global minimum is formulated axiomatically and the features of the corresponding algorithm are derived from the axioms. Furthermore the results of some applications of the proposed algorithm are presented and the perspectives of the approach are discussed. 相似文献
970.
We consider the following (solitary) game: each node of a directed graph contains a pile of chips. A move consists of selecting a node with at least as many chips as its outdegree, and sending one chip along each outgoing edge to its neighbors. We extend to directed graphs several results on the undirected version obtained earlier by the authors, P. Shor, and G. Tardos, and we discuss some new topics such as periodicity, reachability, and probabilistic aspects.Among the new results specifically concerning digraphs, we relate the length of the shortest period of an infinite game to the length of the longest terminating game, and also to the access time of random walks on the same graph. These questions involve a study of the Laplace operator for directed graphs. We show that for many graphs, in particular for undirected graphs, the problem whether a given position of the chips can be reached from the initial position is polynomial time solvable.Finally, we show how the basic properties of the probabilistic abacus can be derived from our results. 相似文献