Study on the Ordered Phases with Long Period in the Gold-Zinc Alloy System : II. Structure Analysis of Au_3Zn[R_1], Au_3Zn[R_2] and Au_<3+>Zn

Crystal structures of the ordered phases, Au_3Zn[R_1], Au_3Zn[R_2] and Au_Zn are investigated by X-ray diffraction using single crystals. The structure models proposed by Wilkens and Schubert for Au_3Zn[R_2] and Au_Zn are confirmed substantially, but partly corrected. The structure analysis of a new phase Au_3Zn[R_1] is given, and the stacking faults present in this phase is investigated. It is suggested that the complicated atom shifts similar to those in Au_3Zn[R_1] and Au_3Zn[R_2] take place also in Au_Zn. It is proposed that such complicated atom shifts seem to be a phenomenon not peculiar to the ordered phases in the Au-Zn alloy system but common to the ordered phases with long periods, such as Au_3Cd, Ag_3Mg, Cu_3Pd, CuAu II

Equilibrium Concentration of Vacancies in Titanium Monoxide under High Pressure

A simple statistical thermodynamical calculation is made to estimate an equilibrium concentration of vacancies under high pressure in titanium monoxide which contains an abnormally large number of vacancies in both titanium and oxygen lattice sites. Work necessary to create a vacancy, interaction energies between vacancies and entropy of mixing are taken into account in deriving Gibbs free energy of a titanium monoxide crystal. The contribution to the free energy from thermal vibration is also considered. The result of calculation shows that the concentration of vacancies, that is 14.5% at 1 bar, decreases to 10-14% under the pressure as high as 100 kbar, the amount of decrease being dependent on the parameters chosen. Discussion is given in terms of this theoretical prediction on the results of recent high pressure experiments made on titanium monoxides

Structural Transitions of Amorphous Alloys under High Pressure

An attempt is made in this paper to cover the results of the recent experimental investigations on the effects of high pressure on the crystallization of amorphous Fe-17at.% B, Nb-19at.% Si and Pd-20at.% Si alloys. Pressure is shown to raise appreciably the onset temperature of crystallization and change the structural sequence of crystalline phases forming in the alloys. The phases preferentially forming are the DO_e-type Fe_3B, Al5-type Nb_3Si and bct Si-rich phase. The structural characteristics of these transformations are discussed in the light of the knowledge of atomic structure of the amorphous alloys

Pressure-Induced Change in the Long-Period Stacking Sequence of the Close-Packed Layers in Mg_3In(Physics)

Samples of the alloy Mg_3In were annealed at 200-250℃ in the Bridgman-anvil-type press under pressures between 20 and 100 kbar. After being quenched to ambient pressure and temperature, the crystal structure was studied by X-ray diffraction. The number of close-packed layers in one repeating unit of the alloy structure is twelve with the stacking sequence (31)_3 when annealed under the atmospheric pressure, but at 20, 35 and 55 kbar it increases to eighteen with the sequence (3111)_3, and at 75 and 100 kbar a 24-layered structure with the sequence (311111)_3 has been found to form. The pressure-induced change in the layer-stacking sequence in Mg_3In is similar to the change with the decrease in the electron-atom ratio previously observed for the ternary alloys Mg_3(In_, Cd_x)

Growth of Cu-1.1at.% Sn and Cu-1.7at.% In Alloy Single Crystals

Attempts have been made to grow large single crystals of Cu-1.1at.% Sn and Cu-1.7at.% In alloys from the melt by the Bridgman method. Microscopic observation of the chemically etched surfaces and sections of the alloy ingots has shown that they contain a few large grains, if the growing condition is properly chosen, but otherwise they consist of columnar grains. The growth direction of the columnar grains determined by the X-ray Laue method exhibits a slight preference of the and directions for the Cu-Sn alloy and the and directions for the Cu-In alloy. A concentration profile in the grain investigated by EPMA has shown an appreciable fluctuation in as-grown crystals and an annealing in vacuum at 900℃ for 100 hr has resulted in a homogenization. The alloy crystals thus heat-treated provide the specimens suitable to LEED studies

A preliminary design study of the tension leg platform

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1981.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.Includes bibliographical references.by Hiroshi Iwasaki.M.S

Role of the Schizosaccharomyces pombe F-box DNA helicase in processing recombination intermediates.

In an effort to identify novel genes involved in recombination repair, we isolated fission yeast Schizosaccharomyces pombe mutants sensitive to methyl methanesulfonate (MMS) and a synthetic lethal with rad2. A gene that complements such mutations was isolated from the S. pombe genomic library, and subsequent analysis identified it as the fbh1 gene encoding the F-box DNA helicase, which is conserved in mammals but not conserved in Saccharomyces cerevisiae. An fbh1 deletion mutant is moderately sensitive to UV, MMS, and ¿ rays. The rhp51 (RAD51 ortholog) mutation is epistatic to fbh1. fbh1 is essential for viability in stationary-phase cells and in the absence of either Srs2 or Rqh1 DNA helicase. In each case, lethality is suppressed by deletion of the recombination gene rhp57. These results suggested that fbh1 acts downstream of rhp51 and rhp57. Following UV irradiation or entry into the stationary phase, nuclear chromosomal domains of the fbh1¿ mutant shrank, and accumulation of some recombination intermediates was suggested by pulsed-field gel electrophoresis. Focus formation of Fbh1 protein was induced by treatment that damages DNA. Thus, the F-box DNA helicase appears to process toxic recombination intermediates, the formation of which is dependent on the function of Rhp51