Channeling-effect measurements for structural analysis of lattice defects in single crystals are reviewed. Angle dependence of the yields of close collisions such as Rutherford backscattering, X-ray emission and nuclear reaction is shown to be powerful to determine the lattice site of impurity atoms and self-interstitial atoms constituting point-like defects. Energy dependence of the yields of dechanneling is also shown to provide quantitative information on the structure of extended and distortion-type defects such as stacking faults, twins, Guinier-Preston zones and dislocations.
This article briefly deals with the interaction modes between the indole ring of tryptophan and the aromatic rings of pyridine, flavin and thiamin coenzymes on the basis of the crystal structures of these model compounds or complexes. The obtained insights would be important in order to elucidate the physiological functions of tryptophan derivatives in living cell. It appears to be a characteristic of tryptophan derivatives that the electron-donating indole ring associates with the biologically important aromatic rings through the prominent π-π stacking, partly charge-transfer, interaction.
Various alternatives of glass waste forms have so far been researched for immobilization of high level radioactive waste. Out of these, two ceramic forms, SYNROC and Supercalcine are the most feasible ones and have the following characteristics; the constituent materials are synthetic minerals and high level radioactive waste elements occupy the cation sites of the crystal structures of the minerals. The two ceramic forms were reviewed with emphasis on compositions, crystalline phases, preparation and physical and chemical stability.