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X D Zou

Publications and source records attributed to X D Zou.

8 recordsLinked to original sources
PubMed2006

Structure model for the tau(mu) phase in Al-Cr-Si alloys deduced from the lambda phase by the strong-reflections approach.

There are very obvious common features in the electron diffraction patterns of the lambda and tau(mu) phases in the Al-Cr-Si system. The positions of the strong reflections and their intensity distributions are similar for the two structures. The relation of the reciprocal lattices of the lambda and tau(mu) phases is studied. By applying the strong-reflections approach, the structure factors of tau(mu) are deduced from the corresponding structure factors of the known lambda phase. Rules for selecting reflections for the strong-reflections approach are described. Similar to that of lambda, the structure of tau(mu) contains six layers stacked along the c axis in each unit cell. There are 752 atoms in each unit cell, 53 of them are unique. The corresponding composition of the tau(mu) model is Al(3.82 - x)CrSi(x). Simulated electron diffraction patterns from the structure model are in good agreement with the experimental ones. The arrangement of interpenetrated icosahedral clusters in the tau(mu) phase is discussed.

Journal Article↗
PubMed2003

Three-dimensional reconstruction of the nu-AlCrFe phase by electron crystallography.

The three-dimensional (3D) structure of the huge quasicrystal approximant nu-AlFeCr (space group P6(3)/m, a = 40.687 and c = 12.546 A) was solved by electron crystallography. High-resolution transmission-electron-microscopy (HREM) images and selected-area electron diffraction patterns from 13 different zone axes were combined to give a 3D potential map. 124 out of 129 unique atoms were found in the 3D map. Procedures for ab initio structure determination by 3D reconstruction are given. It is demonstrated that 3D reconstruction from HREM images is very powerful for solving structures--even very complicated ones. There is no limit in terms of the number of unique atoms in a structure that can be solved by 3D reconstruction.

Journal Article↗
PubMed2001

Solving modulated structures by X-ray and electron crystallography.

X-ray diffraction can be used for accurately determining not only classical, ordinary structures, but also modulated ones. For structures with weak modulations, the modulation induced satellite reflections are often hard to be observed by X-ray diffraction, but they appear clearly in electron diffraction. In these cases, X-ray diffraction will give only average structures whereas electron diffraction will yield information about the modulations. Sr(1.4)Ta(0.6)O(2.9) is a complex modulated compound with weak modulation and small modulated domains. Here we demonstrate the power of combining X-ray and electron crystallography for studying modulated structures on powders. The modulations of Sr(1.4)Ta(0.6)O(2.9) were determined from electron diffraction (SAED) and high resolution electron microscopy (HREM) images. With specially developed image processing techniques, the weak modulations were enhanced, facilitating the interpretation of HREM images in terms of atomic structure.

Journal Article↗
PubMed1990

Serum lipid and apolipoprotein levels in a Tibetan population sample.

Serum lipid and apolipoprotein levels were measured in a Tibetan population sample. In both men and women serum cholesterol levels were markedly lower than in Western populations. In men HDL-cholesterol levels were higher compared to both Oriental and Western populations while in women the values were markedly higher than in other Oriental populations and similar to Western populations. Highly significant positive relationships were found between serum lipid levels and corresponding apolipoprotein levels. In men but not in women serum cholesterol was markedly higher in office workers than in factory workers.

Adult↗
PubMed1987

Application of convergent beam electron diffraction in the structural study of high-temperature superconducting oxides.

Convergent beam electron diffraction (CBED) is a powerful technique for symmetry study of crystal. It has widespread application in physics and material sciences, as demonstrated in a recent superconducting oxide study. Using this technique, we have studied Ba-La-Cu-O superconductors with a transition temperature of about 40 degrees K and Ba-Y-Cu-O superconductors with a critical temperature (Tc) of about 90 degrees K. We have found that in Ba-La-Cu-O superconductors the superconducting phase La2-xBaxCuO4-y has a distorted K2NiF4-type structure and the space group Fmmm. The two other phases in Ba-La-Cu-O superconductors have also been studied. In our Ba-Y-Cu-O superconductors, the Ba2YCu3O7-x compound, which is responsible for 90 degrees K superconductivity, has two different space groups: An orthorhombic space group Pmmm and a tetragonal space group P4mm or P4/mmm.

Crystallography↗