February 2009 Archives

The use of short pulses of extremely bright synchrotron X-rays has opened up a new world. In Japan, Dr. S. Adachi (KEK, Tsukuba Japan) and his colleagues recently succeeded in recording movies during changes in the molecule structures of myoglobin. The samples used are frozen myoglobin crystals that had CO (carbon monoxide) stored inside before the start of the experiments. Even at 100K, irradiating pulsed laser light gave the trigger for the migration of CO molecules. To see changes in atomic scale, time-resolved X-ray diffraction measurements were performed. The obtained movie tells us that the CO molecules penetrate into a number of cavities in the crystal and even expand their size. The research group has obtained an important result suggesting some self-opening mechanism in the ligand migration channel. For more information, see the paper, "Visualizing breathing motion of internal cavities in concert with ligand migration in myoglobin", A. Tomita et al., Proceedings of National Academy of Science, 106, 2612-2616 (2009) Published online before print February 9, 2009, doi: 10.1073/pnas.0807774106

An international symposium on micro and trace X-ray analysis was held in Osaka, Japan, on February 12-14, with financial aid from the Japan Science and Technology Agency (JST). Professor K. Tsuji (Osaka City Univ.) organized the symposium, which had 102 participants including 12 scientists from outside Japan. In addition to highly sophisticated analytical experiments with brilliant synchrotron radiation, recent progress regarding the instrumentation and applications of laboratory/mobile X-ray sources was extensively discussed. The speakers were as follows; P. Wobrauschek (Atominstitut, TU Wien), K. Janssens (Antwerp Univ.), A. Hokura (Tokyo Univ. of Sci.), K. Nakano (Osaka City Univ.), A. von Bohlen (ISAS Institute for Anal. Sci.), S. Maeo (Osaka Electro-Comm. Univ.), Y. Kataoka (Rigaku), G. Havrilla (Los Alamos National Lab), C. Numako (Tokushima Univ.), K. Hayashi (Tohoku Univ.), T. Sakae (Nihon Univ.), K. Sakurai (National Inst. for Materials Sci.), S. Hayakawa (Hiroshima Univ.), K. Tsuji (Osaka City Univ.), S. B. Dabagov (INFN, Frascati), N. Gao (X-Ray Optical Systems, Inc.), H. Soejima (Shimadzu), K. Taniguchi (Inst. of X-ray Tech. Co., Ltd), J. E. Fernandez (Bologna Univ.), H. Kumagai (Osaka City Univ.), A. Bando (Horiba Ltd.), K. Yamauchi (Osaka Univ.), B. De Samber (Ghent Univ.), Y. Kagoshima (Hyogo Univ.), C. Streli (Atominstitut, TU Wien), P. Pianetta (SLAC, Stanford), S. Shimoyama (Kibi International Univ.), R. Van Grieken (Antwerp Univ.). The proceedings booklet is available from the organizer, Phone/Fax: +81-6-6605-3080, tsuji@a-chem.eng.osaka-cu.ac.jp

In classical metallurgy, there exists a very famous rule known as Hume-Rothery's rule, which describes the conditions necessary for the formation of a solid solution from two independent metals. In order to have a substitutional crystalline solid solution in which the atoms of one element randomly substitute for atoms of another element in a crystal structure, the components must have an atomic size within 15% and electronegativity within 0.4 of each other. According to this rule, a Ce-Al solid solution cannot be obtained. Recently, a research team led by Professor H.K. Mao (Carnegie Institution of Washington) and Professor R. Ahuja (Uppsala University) found during high pressure research on the intermetallic compound of Ce₃Al that a solid solution is formed in a Ce-Al system. The differences in radii and electronegativity of Ce and Al were diminished by applying pressure. Both synchrotron X-ray studies (XRD and X-ray absorption spectroscopy) and ab initio calculations showed the same cause for bringing the two elements closer in radii and electronegativity, resulting in the new alloy phase. Even after the release of pressure, this substitutional alloy remained. During in-situ X-ray absorption measurements at the Ce LIII edge, conspicuous changes in the sharpness of the absorption, correlated to delocalization of 4f electrons, were observed. For more information, see the paper, "Substitutional alloy of Ce and Al", Q-S.Zeng et al., Proceedings of National Academy of Science, 106, 2515-2518 (2009) Published online before print February 2, 2009, doi: 10.1073/pnas.0813328106