单茂钛／MAO体系催化乙烯／丙烯共聚合研究：Ⅰ.乙烯／丙烯共聚物的合成及聚合

采用合成的催化剂五甲基环戊二烯基三烯丙氧基钛「Ｃｐ＾＊Ｔｉ（ＯＡｌｌｙｌ）３」与改性甲基铝氧烷（ｍＭＡＯ）组成新型催化体系进行了乙烯／丙烯共聚合,考察了助催化剂（ｍＭＡＯ）中ＴＭＡ含量、气体配比、聚合温度、助催化剂和主催化剂浓度等因素对共聚合活性及产物分子量的影响,研究了其变化规律。结果表明,Ｃｐ＾Ｔｉ（ＯＡｌｌｙｌ）３／ｍＭＡＯ催化体系中钛的价态分布为Ｔｉ（Ⅳ）时对共聚合更为有利,制得了乙烯／丙烯无规共聚物弹性体。     

单茂钛／MAO体系催化乙烯／丙烯共聚合研究：Ⅲ.乙烯／丙烯共聚物的表征与结构

采用合成的催化剂五甲基环戊二烯基三烯丙氧基钛「Ｃｐ＾＊Ｔｉ（ＯＡｌｌｙｌ）３」与改性甲基铝氧烷（ｍＭＡＯ）组成催化体系棉乙烯／丙烯共聚物,红外分析显示,乙醚可溶和己烷可溶两个级分的化学结构几乎相同ＧＰＣ测试结果表明共聚物分子量高,分子量分布窄。Ｘ－射线衍射分析,大多数样品的图谱为宽的弥散峰,表明它们是无规共的;只有当乙烯含量很高时,样品的谱图才有较为尖锐的结晶峰,结晶度不高。经热分析（ＤＳＣ、ＴＧ）,大多数样品没有出现明显的熔点,只有当乙烯含量很高时才显示出熔点;共聚物的热稳定性较高,ＤＭＡ分析表明,共聚物品中乙烯含量多的,其储能模量（Ｅ′）大一些,共聚物的玻璃温度随着丙烯链节的增多而升高。     

On the Eigenvalues of Half‐Linear Boundary Value Problems

We consider the half‐linear boundary value problem where and the weight function q is assumed to change sign. We prove the existence of two sequences , of eigenvalues and derive asymptotic estimates for as .     

Ab initio investigations in magnetic oxides

It is argued that band theory can be used as a valuable tool to investigate and model properties of several classes of oxide systems. This theoretical framework is presented in the first part of the article with details on the density functional theory (DFT) and its approximations leading to the local spin density functional LSDF as well as on the common methods built around it (mainly the augmented spherial wave ASW method used throughout this work). The major part of the article is devoted to case studies meant to illustrate the wealth and limits of the LSDF in addressing the electronic and magnetic structures of a selected variety of transition metal oxides of technological importance. Such systems are iron monoxide “FeO” (mainly the high pressure form), the archetype of half metallic ferro magnets CrO₂, used in magnetic recording media, the simple and double perovskite derived systems: SrFeO₃ and La₂TIrO₆ (T=Mn, Fe, Co) as well as manganese oxides (CaMnO₃, Ca₄Mn₄O₁₀ and Tl₂Mn₂O₇) for which a giant magnetoresistive GMR behaviour was identified in recent years. The computed ground state magnetic configurations and electronic structure results are discussed and confrontations with experimental data are carried out when available. The chemical bonding properties are analysed, and a new conceptual approach is provided.     

TWO BOUNDED HALF ORTHOTROPIC PLANE MATERIALS WITH CRACKS

ＴＷＯＢＯＵＮＤＥＤＨＡＬＦＯＲＴＨＯＴＲＯＰＩＣＰＬＡＮＥＭＡＴＥＲＩＡＬＳＷＩＴＨＣＲＡＣＫＳＣａｉＨａｉｔａｏ（蔡海涛）（ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｃｈａｎｇｓｈａ４１００８３，Ｃｈｉｎａ）Ａｂｓｔｒ...     

Ar3H＋中多体势能拆分的从头计算分析

使用从头算的方法计算了Ar3H＋的稳定构型及红外振动基频，并与Ar2H＋的稳定结构及红外振动频率作了对比，讨论了二者之间的联系与差别.对Ar3H＋一个特殊构型下的势能线作了扫描，在此势能线下将Ar3H＋的四体势能拆解为两体，半三体及三体势能的加和，初步探讨了高阶势能分解为低阶势能的最佳途径.     

Structure, ordering, and bonding of half antiperovskites: PbNi3/2S and BiPd3/2S

In a model study the crystal structures of shandite (Pb₂Ni₃S₂), parkerite (Bi₂Ni₃S₂) and their Pd homologues are investigated in terms of ordered half antiperovskites AM_3/2S (A = Pb, Bi; M = Ni, Pd). This addresses fundamental questions on the structural relations, ordering and chemical bonding. From crystal structure investigations a new cubic parkerite variant is presented for Bi₂Pd₃S₂ that fits in an ordering model equivalently to shandite and parkerite. Type–antitype relations to ordered oxygen deficit perovskites are presented. With the relation to the superconductor Ni₃MgC a model is deduced that provides the complete crystal structure and symmetry in terms of the Ni and Pd ordering in antiperovskite superstructures. Therein a systematic ab initio investigation on the relative stability of shandite and parkerite structures is carried out for the first time. From the DFT modelling results the preferences of the ordering variants and the distinct differences in the atomic coordination spheres are discussed. The bonding in the systems is investigated by site projected density of states and covalent bond energy calculations.     

Homology representations arising from the half cube, II

In a previous work, we defined a family of subcomplexes of the n-dimensional half cube by removing the interiors of all half cube shaped faces of dimension at least k, and we proved that the reduced homology of such a subcomplex is concentrated in degree k−1. This homology module supports a natural action of the Coxeter group W(Dn) of type D. In this paper, we explicitly determine the characters (over C) of these homology representations, which turn out to be multiplicity free. Regarded as representations of the symmetric group Sn by restriction, the homology representations turn out to be direct sums of certain representations induced from parabolic subgroups. The latter representations of Sn agree (over C) with the representations of Sn on the (k−2)-nd homology of the complement of the k-equal real hyperplane arrangement.     

示波极谱同时测定胱氨酸和赖氨酸方法的研究

本文提出在pH为10的Na_2B_4O_7·10H_2O-CH_3CHO-NaOH体系中,于示波极谱仪上,峰电位分别为-0.70V和-1.45V处,可同时测定胱氨酸和赖氨酸,其浓度分别在0.5～100μg/ml和0.5～80μg/ml范围内与峰电流成线性关系,大部分共存氨基酸对测定无大的影响,最大相对标准偏差分别为1.8%和10.0%,接近于氨基酸专用分析仪的测定水平。     

Ab initio investigation of the magnetic states of Ca2MnO4 and Ca2MnO3.5

An analysis of the electronic and magnetic properties of Ca₂MnO₄ and Ca₂MnO_3.5 is carried out within local spin density functional theory using the augmented spherical wave method. From energy differences between the hypothetic magnetic configurations both systems are found to be insulating antiferromagnets in the ground state with a 1 eV gap. However we identify an intermediate half metallic ferromagnetic state with the Hund’s rule expected moments for Mn^IV (3 μ_B) and Mn^III (4 μ_B, high spin HS configuration), respectively. The latter result of moment magnitude finds support in recent experimental evidence of Mn^III bismuth oxide as a ferromagnet in its ground state. This is characterized by a small density of states (DOS) magnitude of itinerant states in spin (↑) channel pointing to a metallic-like behavior as it is experimentally evidenced. For both Ca₂MnO₄ and Ca₂MnO_3.5 the chemical bonding characteristics are resolved for the two spin channels. Relationship to colossal magnetoresistive compounds is proposed.