In this review X-ray Absorption Near Edge Structure (XANES) is compared with EXAFS from the theoretical view point. In the XANES region, the full multiple scattering becomes important, but in the EXAFS region it is not important except the special case. The information about the geometric and the electronic structures obtained from the XANES is illustrated in some recent results.
An in-situ observation method has been developed to observe growth or dissolution processes of crystals at <1800 K, with as high visibility as in air, and under precisely controlled conditions. The method has been applied to silicate systems. Out of varieties of interesting phenomena, observations on metastable nucleation, which often takes place in complex component systems, are selected for this article. It is shown in a variety of silicate systems that a thermodynamically less stable phase can nucleate and grow steadily prior to the nucleation of the stable phase. This metastable nucleation is interpreted in terms of competition between the difference of interfacial energy between a crystal and a solution, which is evaluated by the number of unsaturated dangling bonds at the crystal surface, and chemical potential of the solution, which is evaluated from the solubility curve determined by this method.
A method has been proposed to determine the stability of 4H- and 12R- structures in titaniun sulfide. The differences in the free energies of the two structures were estimated by measuring their sulfur activites at various compositions. These data showed that the 12R structure is metastable at 900C.
The crystal structures of six microbial ribonucleases have been determined. Among these enzymes, homology in both the three-dimensional structure and amino acid sequence is present in the C-terminal half of the polypeptide chain, which is folded as a three-stranded, anti-parallel β-sheet containing the catalytic residues. This fact is consistent with the idea of a diverging family of enzymes.