Epitaxial growth of isotactic polypropylene on oriented polyethylene from solution

Oriented polyethylene (PE) films with surfaces bounded by the (100) plane were prepared. On the film surfaces, isotactic polypropylene (iPP) was crystallized epitaxially from solution as quadrits with their sides parallel and perpendicular to the polyethylene chain axis. In the through wide-angle x-ray diffraction pattern (taken with incident x-rays normal to the polyethylene film surface), the 111 iPP reflections was observed on the meridian (Parallel to the polyethylene chain axis). In the edge patterns (taken with x-rays incident on the edge of the polyethylene film), 040 and 060 reflections were observed on the equator. From the diffraction patterns, the following lattice coincidence was observed between polyethylene and isotactic polypropylene: (010)iPP//(100) PE, [101]iPP//[001] PE. The Small-angle x-ray scattering patterns showed that edge-on isotactic polypropylene lamellae 9 nm thick were arranged with their long axes inclined at an angle of 40° from the polyethylene axis. Molecular chains were oriented within the lamellae normal to the surfaces.     

Interference effects in the strong isospin dependence of the polarization asymmetry in 12C(p,p′)12C11+ transitions

The strong isospin-dependence observed in the polarization asymmetry data for the ¹²C(p,p′)¹²C¹ 1⁺ transitions has been successfully interpreted as a result of interference effects between one-step and two-step (pdp′) excitation mechanisms, in addition to the interference between the central and tensor terms in the one-step excitation process.     

Rheo-optical studies on the deformation mechanism of semicrystalline polymers. XIV. Alpha and beta mechanical dispersions of spherulitic high-density polyethylene and the dynamic orientation distribution function of crystallites

The dynamic tensile deformation mechanism of spherulitic high-density polyethylene was investigated by dynamic x-ray diffraction at various temperatures and frequencies in order to assign the α and β mechanical dispersions explicity. The uniaxial orientation distribution function q(ζ_j,0) of the jth crystal plane and its dynamic response Δq′_j(ζ_j,0) in phase with dynamic strain were observed for the (110), (200), (210) and (020) crystal planes. Then the orientation distribution function w(ζ,0,η) of crystallites (crystal grains) and its dynamic response Δw′(ζ,0,η), also in phase with the dynamic strain, were determined by a mathematical transformation procedure proposed by Roe and Krigbaum on the basis of the Legendre addition theorem. The temperature and frequency dependences of w′(ζ,0,η) were analyzed in terms of the model parameters for dynamic spherulite deformation combining affine orientation of crystal lamellae with several types of preferential reorientation of the crystal grains within the orienting lamellae. The following assignments are made: (i) The α mechanical dispersion must be assigned to the dynamic orientation dispersion of crystal grains within the crystal lamellae, involving two types of preferential rotations of the grains about their own crystal b and a axes. The rotation about the b axis is associated with lamellar detwisting, mostly in the equatorial zone of uniaxially deformed spherulites; the rotation about the a axis is associated with intralamellar shearing, mostly in the polar zone of the spherulites. Thus both rotations are intralamellar grain-boundary phenomena. (ii) The β mechanical dispersion must be assigned to the dynamic orientation dispersion of the crystal lamellae behaving as rigid bodies. It is not accompanied by reorientation of the crystal grains, but is associated with orientation dispersion of noncrystalline material between the lamellae. Thus it is an interlamellar grain-boundary phenomena.     

Modification of active carbon and zeolite as ammonia separation materials for a new de-NO<Subscript>x</Subscript> process with ammonia on-site synthesis

Ammonia adsorption and desorption behavior of surface treated active carbon (AC) and ion-exchanged Y zeolite, as ammonia separation and storage materials for a new de-NO_x process with ammonia on-site synthesis, were studied. Surface oxidized AC adsorbed more ammonia than non-treated AC due to ammonium ion formation. These materials were found to increase weak adsorption of ammonia and to be useful for pressure swing adsorption. Transition metal ion exchanged Y-zeolite adsorbed more ammonia (both weak and strong form) than Na Y-zeolite due to ammine complex formation. These materials adsorb and desorb more ammonia than treated AC when used for temperature swing adsorption.     

<Emphasis Type="Italic">K</Emphasis>3 surfaces with involution,equivariant analytic torsion,and automorphic forms on the moduli space

In this paper, we introduce an invariant of a K3 surface with ₂-action equipped with a ₂-invariant Kähler metric, which we obtain using the equivariant analytic torsion of the trivial line bundle. This invariant is shown to be independent of the choice of the Kähler metric. It can be viewed as a function on the moduli space of K3 surfaces with involution. The main result of this paper is that this function can be identified with an automorphic form, which characterizes the discriminant locus. In particular, we show that the Ray–Singer analytic torsion of the trivial line bundle on an Enriques surface with Ricci-flat Kähler metric is given by the value of the norm of the Borcherds -function at its period point. Mathematics Subject Classification (1991) 58G26, 14J28, 14J15, 32G20, 32N10, 32N15     

Interaction of voids and nanoductility in silica glass

Multimillion-to-billion-atom molecular dynamics simulations are performed to investigate the interaction of voids in silica glass under hydrostatic tension. Nanometer size cavities nucleate in intervoid ligaments as a result of the expansion of Si-O rings due to a bond-switching mechanism, which involves bond breaking between Si-O and bond formation between that Si and a nonbridging O. With further increase in strain, nanocracks form on void surfaces and ligaments fracture through the growth and coalescence of ligament nanocavities in a manner similar to that observed in ductile metallic alloys.     

Synthesis,X-ray crystal structure and magnetic study of the 1D {[Cu(N,N-diethyl-1,2-ethanediamine)(μ1,5-dca)(dca)]}n complex

A new complex, {[CuL(μ_1,5-dca)(dca)]}_n (1), has been synthesized from the reaction of Cu(NO₃)₂ · 3H₂O, N,N-diethyl-1,2-ethanediamine (L) and sodium dicyanamide (Nadca) in aqueous medium. Single crystal X-ray analysis reveals that the complex has a 1D infinite zigzag chain structure in which copper(II) ions are bridged by single dicyanamide ligands in an end-to-end fashion. The chains propagate parallel to the crystallographic b-axis and they are stacked one upon another along the c-axis. The coordination environment of the copper(II) centers are distorted square-pyramidal. Of the four coordination sites of the basal plane of the square-pyramid, two are occupied by the nitrogen atoms of the diamine and the remaining two sites are occupied by the terminal nitrogen atoms of the bridging dca groups. One terminal nitrogen atom of a monodentate dca group occupies the apical position of the coordinated polyhedra. [CuL(dca)] units are then connected to each other through a μ_1,5-dca bridge to form 1D chains. The variable temperature magnetic susceptibility measurements evidenced weakly antiferromagnetic interactions (J = −0.35 cm⁻¹) in {[CuL(μ_1,5-dca)(dca)]}_n (1).     

Synthesis and properties of polyimides from thianthrene-2,3,7,8-tetracarboxylic dianhydride-5,5,10,10-tetraoxide

Thianthrene - 2,3,7,8 - tetracarboxylic dianhydride - 5,5,10,10 - tetraoxide (TADATO), a dianhydride having two sulfonyls between two phenyl rings, was synthesized and polymerized with several diamines by a two-step method. Tough polyimide membranes were obtained with flexible diamines but not with rigid diamines. Most of TADATO-based polyimides are soluble in polar solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. IR study confirmed that almost complete imidization of TADATO-based poly(amic acid) membranes could be achieved by thermal treatment at 100, 200, and 300°C for each 1 h. In a series of polyimides based on 4,4′-oxydianiline, the polyimide from TADATO showed higher gas permeability coefficient of CO₂ and higher selectivities of CO₂/N₂ and CO₂/CH₄ than those of polyimides from pyromellitic dianhydride and 3,3′,4,4′-biphenyltetracarboxylic dianhydride, and was comparable to that from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36 : 485–494, 1998     

激光二极管抽运的Nd:GdVO4激光器

用高亮度激光二极管作抽运源 ,研究了连续、腔内倍频和被动调 Q Nd:Gd VO4 激光器的输出特性。在抽运功率为 881m W时获得了 119m V的连续绿光输出 ,光 -光转换效率 13.5%。用Cr4 :YAG作可饱和吸收体实现了 Nd:Gd VO4 激光器的被动调 Q运转 ,脉冲宽度为 116～ 2 4 ns,重复频率在 50 0 k Hz～ 1.8MHz范围内可调。     

A novel tetranuclear copper(II) complex with alternating mu 1,1-azido and phenoxo bridges: synthesis,structure, and magnetic properties of [Cu4(mu-salen)2(mu 1,1-N3)2(N3)2

A novel tetranuclear copper(II) complex containing alternating mu(1,1)-azido and monophenoxo bridges has been synthesized and characterized by spectroscopic methods, X-ray single-crystal analysis, and variable-temperature magnetic measurements. The magnetic behavior, investigated in the temperature range 2-300 K, indicates that the interactions between copper ions are antiferromagnetic in nature for both azido and phenoxo bridges. The temperature dependence of the magnetic susceptibility was fitted with J(1) = -12.8 cm(-1), J(2) = -10 cm(-1), g = 2.171, 2.1% paramagnetic component, and negligible temperature-independent paramagnetism (5 x 10(-8)). At variance with the earlier reports of these types of complexes containing a mu(1,1)-azido group, the end-on double-azido-bridged copper(II) center in this complex shows an antiferromagnetic interaction.