A first-principles study of the diffusion coefficients of alloying elements in dilute α-Ti alloys.

Using first-principles calculations accompanied by the transition state theory and an 8-frequency model, we present a comprehensive investigation of the diffusion coefficients of substitutional alloying elements X in dilute α-Ti alloys, where X denotes Al, V, Nb, Ta, Mo, Zr, and Sn. The alloying elements Mo and Al exhibit a maximum and a minimum diffusion rate in dilute α-Ti alloys, respectively. It is found that the nearest-neighbor solute-vacancy binding energies and activation energies are roughly inversely proportional to the volume changes induced by solute atoms. There are two exceptions to this trend: Al and Mo. Besides the physical effect (i.e., solute size), two other key factors governing solute diffusion in dilute α-Ti are clarified: the chemical bonding characteristics and vibrational features of X-Ti pairs. It verifies that the ultrafast diffusivity of Mo arises from the interactions with Ti atoms by metallic bonds and its low-frequency contributions to lattice vibration, while the more covalent bonding nature and the high-frequency contributions to the lattice vibration of Al lead to its ultraslow diffusivity. In addition, the correlation effects of diffusion coefficients are non-negligible for the large solutes Ta, Nb, and Zr, in which the direct solute-vacancy migration barriers are much smaller than the solvent-vacancy migration barriers.

[Studies of the mixoploid variation in banana micropropagated plants].

A special type of variation--the mixoploid variation, which had a great effect on the variation in the production of banana vitroplants, was reported for the first time. By means of examining chromosome, isozymes (EST, MDH, POX) and endogenous hormones (iPAs, IAA), the varied characters of the mixoploid varianties during the propagation in vitro when cultured as explant were investigated. The rate of the chromosome aberration in cells was characterized by starting at a much higher level and rising more rapidly in the preceding 15 subcultures as compared with the control. The rate of the isozyme variation was higher obviously than that of the control. The plantlets cloned in vitro from the mixoploid variant were also studied. The experiment showed that both the variant rates of chromosome and phenotype rose obviously. The mixoploid variant can cause the rate of variation to rise during the micropropagation.

[Autopsy study of 100 elderly patients].

Clinical and autopsy records of 100 elderly patients were analyzed. The most common cause of death in this series was malignant tumors (39%). The second leading cause of death was diseases of the circulatory system (37%), in which cerebrovascular accident alone accounted for 21%. Cor pulmonale and myocardial infarction were also common causes of death. In addition, infective diseases, especially pneumonia and septicemia were often fatal to elderly patients. The discrepancy between clinical and post-mortem diagnoses in this series was 24.7%. The causes of incorrect and missed diagnoses are discussed. The results suggest that extensive autoptic study still has vital practical significance.

A new caryolane sesquiterpene from Heteropappus altaicus (Willd.) Novopokr.

A new caryolane sesquiterpene, 1ß-methoxycaryol-9-one (1), along with eight known compounds (2-9), was isolated from the whole plant of Heteropappus altaicus. The structures were elucidated on the basis of comprehensive 1D- and 2D-NMR analysis and high-resolution mass spectrometry. The 13C-NMR data of compound 2 are reported for the first time.