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971.
Małgorzata Baśko Przemyslaw Kubisa 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):3090-3097
Cationic copolymerization of L,L ‐lactide (LA) and ε‐caprolactone (CL) initiated by low molecular weight diols in the presence of acid catalyst gives corresponding copolyesters terminated at both ends with hydroxyl groups in practically quantitative yield. Copolymerization proceeds by Activated Monomer mechanism. LA is consumed preferentially and at the later stages of copolymerization the reaction mixture is enriched with CL. In spite of that, random distribution of both units is observed and end‐groups are mainly ? LA‐OH groups and not ? CL‐OH groups. This is explained by the fact that to reach high conversion of both comonomers the relatively long reaction times are required and at those conditions transesterification reaction becomes significant. Thus the microstructure of copolymers and the nature of the end‐groups is governed by transesterification rather then by the kinetics of comonomers incorporation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3090–3097, 2007 相似文献
972.
Mieczysław Kozłowski Helena Wachowska Jan Yperman 《Central European Journal of Chemistry》2003,1(4):366-386
Products of reductive and non-reductive methylation of two high-sulphur coals (Mequinenza and Illinois No. 6) have been extracted
by dichloromethane. It has been established that the efficiency of the transformation of coal to the products soluble in CH2Cl2 is higher for coals subjected to non-reductive methylation by the Liotta method than for those after reduction in the potassium/liquid
ammonia system. The extracts and the extraction residues were subjected to elemental analysis, IR spectroscopy, and AP-TPR
(Atmospheric Pressure-Temperature Programmed Reduction) measurements. It has been shown that the main species undergoing extraction
by CH2Cl2 are aliphatic compounds or aromatic structures of low degree of condensation. The effect of the extraction on the sulphur
groups in coal has been discussed. 相似文献
973.
A simple model mimicking a molecular fluid, introduced by Labik, Nezbeda and Smith (J. Chem. Phys.80 (1984) 5219] is applied to calculations of density profiles of a molecular fluid in contact with a hard wall. This model provides a useful means of investigating many of the quantitative features of more realistic fluid-wall models. In this work we have computed the spherical harmonic coefficients both of the local densities and of the one-particle background correlation functions and have examined the rate of convergence of these expansions. Moreover, we have used this model to test the accuracy of the zeroth-order RAM perturbational theory for the local densityThis work was supported by CPBP, under the Grant No. 01.08.E 2. 相似文献
974.
Kazimierz Włodarczyk Robert Plebaniak Cezary Obczyński 《Nonlinear Analysis: Theory, Methods & Applications》2007
In this paper, we introduce the concepts of the set-valued dynamical systems of asymptotic contractions of Meir–Keeler type and set-valued dynamical systems of strict contractions in uniform spaces and we present a method which is useful for establishing conditions guaranteeing the existence and uniqueness of endpoints of these contractions and the convergence to these endpoints of all generalized sequences of iterations of these contractions. The result, concerning the investigations of problems of the set-valued asymptotic fixed point theory, include some well-known results of Meir and Keeler, Kirk and Suzuki concerning the asymptotic fixed point theory of single-valued maps in metric spaces. The result, concerning set-valued strict contractions (in which the contractive coefficient is not constant), is different from the result of Yuan concerning the existence of endpoints of Tarafdar–Vyborny generalized contractions (in which the contractive coefficient is constant) in bounded metric spaces and provides some examples of Tarafdar–Yuan topological contractions in compact uniform spaces. Definitions and results presented here are new for set-valued dynamical systems in uniform, locally convex and metric spaces and even for single-valued maps. Examples show a fundamental difference between our results and the well-known ones. 相似文献
975.
Summary A new chelate-forming resin was prepared from common anionexchanger Amberlyst A-26 and thoron. Thoron-loaded resin is stable and resistant to mineral acids. To differentiate the selectivity of thoron-loaded resin trien as competitive reagent was used. In the presence of trien thoron-loaded resin is almost selective for Fe(III) as a counter ion. The application of the resin to the analysis of iron in brass and the preconcentration and determination of iron in natural waters was described. 相似文献
976.
Static Hartree-Fock calculations for a model nucleus are carried out under the assumption of axial symmetry and with constraints on the component of angular momentum perpendicular to the symmetry axis. The resulting energy surfaces exhibit a well defined fission barrier which decreases with increasing angular momentum more rapidly than predicted by liquid drop calculations. 相似文献
977.
M. Borówko A. Patrykiejew S. Sokołowski R. Zagórski O. Pizio 《Czechoslovak Journal of Physics》1998,48(3):371-388
The Monte Carlo simulation method introduced by Smith and Triska [J. Chem. Phys.100 (1994) 3019] is extended to the case of a reacting fluid in contact with a hard wall. The fluid structure for both spherical
and nonspherical reaction products is discussed for simple models of reacting hard spheres near a hard wall and near a wall
interacting via Lennard-Jones (9,3) potential. In the latter case the investigated model assumes that the probability of a
chemical reaction changes with a distance from the surface. It is shown that the applied technique is suitable for the study
of reacting nonuniform fluids.
This work is supported by KBN under the Grant No. 3 T09A 062 10. 相似文献
978.
979.
Thermoelectric power studies of the paramagnetic amorphous alloys NixZr1?x (x = 0.36, 0.40, 0.60, 0.65) are in agreement with predictions of the extended Ziman theory and indicate the multi-stage crystallization of some alloys. 相似文献
980.
In this paper, we study prime ideals and radicals of centred extensions of rings. Obtained results are applied to tensor products
of algebras over commutative rings.
This research was partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil. The
second-named author was also supported by KBN grant 2 P301 035 06. 相似文献