Crystal structure of mixed sodium-potassium paradodecatungstate 6-hydrate

The crystal structure of K7Na3[H2W12O42]3 . 6H(2)O was determined by X-ray crystallography,and refined to R=0.0864 based on 7024 observed reflections (I>2 sigma(I)). The crystallographic parameters are a=11.755(2), b=13.0493(3), c=16.289(3) Angstrom; alpha=77.13(3)degrees, beta=82.92(3)degrees, gamma=89.65(3)degrees, triclinic, space group, P (1) over bar, V=2416.7(8) Angstrom(3), Z=2, M-r=3330.98, D-cal=4.578Mg/m(3), F(000)=2904; mu (MoK alpha)=29.170mm(-1), T=293K. Two independent polyanions are centered respectively at 1,1,1/2 and 1/2, 1/2, 0, approximately perpendicular to each other with dihedral angle between the equatorial planes of the molecules at 96 degrees. K+ and Na+ respectively occupy the clefts of the two discrete polyanions.

General expression for probabilistic estimation of multiphase structure invariants in the case of a native protein and multiple derivatives. Application to estimates of the three-phase structure invariants

Concise probabilistic formulae with definite crystallographic implications are obtained from the distribution for eight three-phase structure invariants (3PSIs) in the case of a native protein and a heavy-atom derivative [Hauptman (1982). Acta Cryst. A38, 289-294] and from the distribution for 27 3PSIs in the case of a native and two derivatives [Fortier, Weeks & Hauptman (1984). Acta Cryst. A40, 646-651]. The main results of the probabilistic formulae for the four-phase structure invariants are presented and compared with those for the 3PSIs. The analysis directly leads to a general formula of probabilistic estimation for the n-phase structure invariants in the case of a native and m derivatives. The factors affecting the estimated accuracy of the 3PSIs are examined using the diffraction data from a moderate-sized protein. A method to estimate a set of the large-modulus invariants, each corresponding to one of the eight 3PSIs, that has the largest \Delta\ values and relatively large structure-factor moduli between the native and derivative is suggested, which remarkably improves the accuracy, and thus a phasing procedure making full use of all eight 3PSIs is proposed.

Investigation of irradiated PA1010 containing heterogeneous nuclei

This paper deals with radiation effects on PA1010 containing heterogeneous nuclei (Nd2O3). With the help of DSC, WAXD and ESR techniques, the change in the crystallinity and the perfection of the crystal of irradiated PA1010 containing heterogeneous nuclei were studied. Copyright (C) 1996 Elsevier Science Ltd.

Recrystallization of HDPE in HDPE/iPP quenched films

Epitaxial crystallization behavior of HDPE/iPP double layers under quenching and annealing conditions has been studied by means of transmission electron microscopy (TEM). The results obtained from bright field TEM observations indicate that in the as-quenched state the HDPE that is in direct contact with the surface of the oriented iPP substrate recrystallizes in the form of oriented crystallites dispersed on the iPP substrate. The electron diffraction results show that besides the two normally observed epitaxial orientations between HDPE and iPP, there is also a special orientation with [001](HDPE)parallel to[001](iPP). The HDPE which is in contact with the clean surface of a glass slide crystallizes in small lamellae with random orientation. In the boundary region, the epitaxially crystallized HDPE small lamellae stop right on the boundary of the oriented iPP film. If the quenched samples are annealed at 128 degrees C (below T-m of HDPE) for 2 h, the small HDPE crystals grow to thick lamellae in both areas. But only the epitaxial orientation of HDPE with [001](HDPE)parallel to[101](iPP) has been observed.

酞侧基聚芳醚砜的核磁共振研究──PES－C的氢谱归属及碳谱峰的确认

用１３Ｃ－ＮＭＲ谱和二维异核化学位移相关谱（ＨＥＴＣＯＲ）归属了酞侧基聚芳醚砜（ＰＥＳ－Ｃ）的１Ｈ－ＮＭＲ谱峰，并经二维同核化学位移相关谱（ＣＯＳＹ）验证．对原１３Ｃ－ＮＭＲ谱峰归属作了部分修正．二维同核及异核相关谱为ＰＥＳ－Ｃ的碳、氢核磁谱峰归属提供了重要信息．由ＰＥＳ－Ｃ的核磁谱图可见其链结构的规整性

离子交换分子筛对NO吸附的研究

在273K条件下,考察了不同阳离子交换的ZSM-5型和Y型两种分子筛对NO的吸附性能,得出了在273K时的可逆及不可逆吸附量,并对不可逆吸附的NO进行了程序升温脱附(TPD)研究;对样品吸附NO的本质进行了讨论.

β─烷氧羰乙基三氯化锡与2─羟基─1─萘醛缩苯胺类席夫碱配合物的合成与结构

合成并表征了１４种β－烷氧羰乙基三氯化锡与２－羟基－１－萘醛缩苯胺类席夫碱配合物。测定了其中β－丁氧羰乙基三氯化锡与２－羟基－１－萘醛缩对甲苯胺席夫碱配合物的晶体结构。晶体属于三斜晶系，Ｐ１－空间群。晶胞参数：ａ＝１．２４８７（６）ｎｍ，ｂ＝１．３５５１（７）ｎｍ，ｃ＝０．９３８５（３）ｎｍ，α＝９２．８５（３）°，β＝１０４．６８（３）°，γ＝７０．４３（４）°，Ｖ＝１．４４６４（１）ｎｍ３，Ｄｃ＝１．３３ｇ／ｃｍ３，Ｚ＝２，Ｆ（０００）＝５８８。配合物为畸变的八面体构型，配体以酚羟基氧原子与锡原子配位，分子内存在着羰基氧原子与锡原子的配键

ELECTROCHEMICAL REDUCTION PROCESS OF BILIRUBIN IN DIMETHYLFORMAMIDE

The electrochemical reduction behavior of bilirubin (BR) at platinum electrode in DMF was investigated by cyclic voltammetry, in situ electron spin resonance spectroscopy and in situ rapid scanning thin layer spectroelectrochemistry. Experimental results revealed that the reduction of BR firstly undergoes an ECE process: GRAPHICS The generated (BR)(2)(3-). can be re-oxidized to BR and then to purpurin (Pu) by a series of oxidation processes: GRAPHICS However, the re-reduction reactions of Pu are not the reverse processes. The different reduction mechanisms are discussed in detail.

ESTIMATION OF THE ONE-PHASE STRUCTURE SEMINVARIANTS IN THE SINGLE ISOMORPHOUS REPLACEMENT CASE - AN APPLICATION OF HAUPTMANS DISTRIBUTION

A method for estimating the one-phase structure seminvariants (OPSSs) having values of 0 or pi has been proposed on the basis of the probabilistic theory of the three-phase structure invariants for a pair of isomorphous structures [Hauptman (1982). Acta Cryst. A38, 289-294]. The test calculations using error-free diffraction data of protein cytochrome c(550) and its PtCl42- derivative show that reliable estimates of a number of the OPSSs can be obtained. The reliability of the estimation increases with the increase of the differences between diffraction intensities of the native protein and its heavy-atom derivative. A means to estimate the parameters of the distribution from the diffraction ratio is suggested.

酞侧基聚芳醚砜和聚芳醚酮共混物的高温流变行为

用锥板粘度计测试了酞侧基聚芳醚砜（ＰＥＳ－Ｃ）和酞侧基聚芳醚酮（ＰＥＫ－Ｃ）及其共混物的熔体流变行为．试样的流动活化能分别为１４５、１３３和１１２ＫＪ／ｍｏｌ．共混物的熔体粘度显著低于ＰＥＳ－Ｃ和ＰＥＫ－Ｃ粘度的对数加和值．并证明试样的熔体流动性和加工稳定性都已达到注射成型工艺的要求．

MgCl_2·EB／TiCl_4高效载体催化剂的乙烯／1－丁烯共聚反应研究

以ＭｇＣｌ＿３．ＥＢ／ＴｉＣｌ＿４高效载体催化剂，在工业条件下进行了乙烯／１－丁烯共聚合。探讨了１－丁烯的存在及浓度对催化剂效率及聚合动力学的影响。用ＦＴ－ＩＲ和１３ＣＮＭＲ测定了共聚物的组成和序列分布。

氯化镱与α-脯氨酸配合物的合成及结构研究

在水溶液中合成了氯化镱与α-脯氨酸(Pro)的配合物,研究了配合物的红外光谱。X射线衍射测定结果表明,其结构式为{[Yb(Pro)_2(H_2O)]Cl_3}_n,属单斜晶系,空间群P_(21),晶胞参数为:a=0.8268(1)nm,b=1.0980(3)nm,c=1.1965(4)nm,β=106.97(2)°,V=1.04120(5)nm~3,Z=2。每两个镱原子之间通过一个脯氨酸的羧基桥相连而形成一维链式聚合物,另一脯氨酸羧基以单齿形式与镱原子配位。镱的配位数为8,配位多面体为三角十二面体。

SYNTHESIS AND CRYSTAL-STRUCTURE OF (C9H7GDCL2.3THF)THF

The indenylpdolinium dichloride tristetrahydrofuranate (C9H7GdCl2.3THF)THF was prepared and its crystal structure (monoclinic space group P2(1)) determined by X-ray diffraction. In C9H7GdCl2.3THF, Gd, O(1), O(2), O(3) and the centroid of the five-membered indenyl ring form a plane, and Cl(1) and Cl(2) are located at two opposite sides of the plane to give a pseudo-octahedron. The coordination number of Gd is eight.

SYNTHESIS, THERMAL-STABILITY AND X-RAY CRYSTAL-STRUCTURE OF THE BIS(CYCLOPENTADIENYL)YTTERBIUM NAPHTHOXIDE DERIVATIVE (C5H5)2YB(OC10H7)(THF)

Cp3Yb (Cp = C5H5) reacts with a-naphthol (HNP) in THF to form Cp2Yb(NP)(THF) (1), which crystallizes in the space group P2(1)/n with unit cell dimensions a = 8.084(2), b = 15.996(6), c = 15.973(7) angstrom, beta = 98.95(3), V = 2040.3 angstrom and D(calc.) = 1.69 g cm-3 for Z = 4. Least-squares refinement based on 2242 observed reflections converged to a final R value of 0.081. The average Yb-C(Cp) distance is 2.60(2) angstrom and Yb-O(THF) and Yb-O(NP) distances are 2.30(1) and 2.06(1) angstrom, respectively. The title compound loses the coordinated THF molecule readily by heating under vacuum to give dimeric [Cp2Yb(NP)]2 (2), which undergoes disproportionation to give Cp3Yb and Yb(NP)3 on heating above 230-degrees-C.

XPS STUDY OF RADIATION CROSS-LINKED COPOLYMER OF TETRAFLUOROETHYLENE WITH HEXAFLUOROPROPYLENE

In this work the radiation-induced structural changes in F-46 were studied by XPS. In carbon-1s spectra of a highly crosslinked F-46 sheet, the slight increase observed in relative area under the peak due to CF3 was explained by the radiation-induced scission of polymer chains. The peak at 287.6 eV appearing in the spectra caused by ionizing radiation was attributed to carbon structures without primary fluorine substituents, in both branching and unsaturated structures, while that at 289.3 eV was assigned to = CF groups in mid-chain double bonds.