Computer simulation of crystallization kinetics and morphology in fiber-reinforced thermoplastic composites. II. Three-dimensional case

A three-dimensional computer simulation has been used to predict crystallization kinetics and crystalline morphology in composite materials that are based on crystallizable thermoplastics. Reinforcing fibers in three-dimensional simulations show similar behavior to those in two-dimensional simulations; fibers suppress crystallization relative to an unreinforced polymer since they constrain spherulitic growth by an impingement mechanism, and also enhance crystallization by providing added surface nucleation sites. The effects of varying controlling parameters on crystallization kinetics and morphology are qualitatively the same as those observed in the two-dimensional case. The relative bulk and fiber nucleation denisities, in addition to the fiber volume fraction, fiber diameter, and spherulitic growth rate control the crystallization kinetics and crystalline morphology that develop in reinforced thermoplastic composites. It is more difficult to achieve the transcrystalline morphology in slices of three-dimensional composites than it is in two-dimensional composites because nuclei in 3-D systems are not constrained to positions in or near a 2-D plane. © 1993 John Wiley & Sons, Inc.     

龙头山饮用天然锗泉水概况

报告了龙头山饮用天然锗泉水的锗浓度，水质和保健作用等概况。     

Li and K NMR relaxation study of a LiKSO4 single crystal

The ⁷Li and ³⁹K NMR relaxations in a LiKSO₄ single crystal grown by the slow evaporation method were investigated by employing a pulse NMR spectrometer. From the experimental data, the quadrupole coupling constant and asymmetry parameter were determined at the temperatures of 180 and 300 K. The relaxation processes of ⁷Li and ³⁹K were studied for the LiKSO₄ crystal, and the relaxation times for the ⁷Li and ³⁹K nuclei exhibit remarkable changes near T_c2 (=190 K). The activation energies for ⁷Li and ³⁹K were determined in phases I and III. The large change in the activation energy at 190 K indicates that the Li and K ions are significantly affected during this transition. The correlation time of the ⁷Li calculated from the spin-lattice relaxation time and quadrupole parameters was larger than that of the ³⁹K calculated using the same method. The reason for this is that the Li ion undergoes molecular motion as in the LiO₄ groups.     

Statistical Properties of the nonlinear SU（1,1） Coherent States

Using non-Hermitian realizations of SU(1,1) Lie algebra in terms of an f-oscillator,we generalize the notion of nonlinear coherent states to the single-mode and two-mode nonlinear SU(1,1) coherent states.Taking the nonlinearity function f(k)=Lk^1(η^2)[(k 1)Lk^0(η^2)]^-1,their statistical properties are studied.     

Preparation of β-cyclodextrin sulfate-immobilized hydrophilic vinyl-polymer gel as a selective,high recovery and stable adsorbent for high-performance affinity chromatography of heparin-binding substances

Summary β-Cyclodextrin sulfate having heparin-mimicking activity was immobilized on a hydrophilic vinyl-polymer gel, TSKgel AF-Epoxy, TOYOPEARL 650M. A column packed with this material could be used for high-performance affinity chromatographic separation of heparin-binding substances such as growth factors, enzymes, coagulation factors and lipoproteins. The substances retained on the column were recovered more easily than those on a heparin-immobilized column. Furthermore, the β-Cyclodextin sulfate-immobilized gel was superior in stability to the heparin-immobilized gel when exposed to acidic and basic solutions.     

Molecular Control of Bioactivity in Sol-Gel Glasses

Bioactive materials can be divided into: Class A bioactive glasses which exhibit rapid bonding to bone and soft connective tissue and are osteoproductive, and osteoconductive; and Class B bioactive ceramics, which bond slowly only to bone and are only osteoconductive. Bioactive sol-gel glasses composed of SiO2-CaO-P2O5 have Class A behavior in vitro and in vivo and also resorb as they enhance the proliferation of new trabecular bone.     

On the Properties of Accretive-Dissipative Matrices

Let A be a complex n × n matrix, and let A = B + iC, B = B*, C = C* be its Toeplitz decomposition. Then A is said to be (strictly) accretive if B > 0 and (strictly) dissipative if C > 0. We study the properties of matrices that satisfy both these conditions, in other words, of accretive-dissipative matrices. In many respects, these matrices behave as numbers in the first quadrant of the complex plane. Some other properties are natural extensions of the corresponding properties of Hermitian positive-definite matrices.__________Translated from Matematicheskie Zametki, vol. 77, no. 6, 2005, pp. 832–843.Original Russian Text Copyright ©2005 by A. George, Kh. D. Ikramov.     

有机半导体外延生长的扫描隧道显微镜研究

有机半导体薄膜的光、电等性质取决于有机分子的取向以及长程有序性.研究有机半导体的生长机理以及内在驱动力是一个重要环节.文章通过两个典型生长体系,perylene在Ru(0001)表面上的生长和tetracene在Ag(110)表面上生长过程的介绍,给出了形成有机半导体晶化薄膜的可能性以及决定其有序生长的内在驱动力.对于perylene在Ru(0001)表面上的生长,决定其过程的主要驱动力是分子间的相互排斥作用,在单分子层时,由于这种相互作用导致形成Ru(0001)-12×12-8 perylene有序超结构.而对于tetracene/Ag(110)体系,决定生长的驱动力主要表现为相互吸引作用,因此,在小于单分子层时,tetracene呈有序的岛状生长;而当tetracene膜的厚度大于单分子层时,呈逐层生长模式,并形成具有正交晶系结构的晶化薄膜.     

Synthetic studies on the DEF-rings of FR182877 and hexacyclinic acid

A synthesis of model DEF-rings of the polyketide anti tumor natural products FR182877 and hexacyclinic acid has been achieved. The key steps in the synthesis are an intramolecular Pd(0) catalyzed allylic substitution reaction, which was used to generate a 9-membered carbocycle, and a novel transannular iodocyclization reaction which furnished the DF-rings of both natural products.