February 2005 Archives

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Researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, have found that zinc deficiency in humans is associated with an increased risk of developing esophageal squamous cell carcinoma, an often-fatal form of esophageal cancer numbering about 7,000 cases a year. The research basically measures the zinc concentration contained in the tissue by means of X-ray fluorescence analysis using synchrotron radiation at Advanced Photon Source, Argonne, USA. For more details, see the paper, "Zinc concentration in esophageal biopsy specimens measured by X-ray fluorescence and esophageal cancer risk", C.C. Abnet, B. Lai, Y.-L. Qiao, S. Vogt, X.-M. Luo, P.R. Taylor, Z.-W. Dong, S.D. Mark, S.M. Dawsey, J. Nat. Cancer I. 97, 301 (2005). Information about cancer is available at http://www.cancer.gov or NCI's Cancer Information Service at +1-800-422-6237.

An Austrian research group recently succeeded in obtaining highly collimated, spatially coherent X-rays, at a wavelength of about 1 nm and at photon energies extending to 1.3 keV, from high-order harmonic generation in an atomic gas ionized by a 720-nm, 5-fs, 0.2-TW laser pulse. The beam divergence was evaluated as 0.2 mrad for the spectral range above 200 eV from a knife-edge scan, indicating perfect coherence of the atomic dipoles within a macroscopic volume of diameters of 13μm and 4μm at photon energies of 0.3 keV and 1 keV, respectively. The beam seems to be diffraction-limited to within a factor of five. The spectrum of the generated radiation was observed by an energy-dispersive X-ray spectrometer with some filters. The results are really exciting, because they could detect the copper L-edges (~950 eV)! One would notice that the energy of photons produced by laser technologies has been increasing every year - the main idea behind this progress is the creation of time-gradient in the driving pulse, which allows some 25% of the helium atoms to be ionized within half a cycle before the pulse peak. The electrons detached within this time are pushed in the most intense half-cycle back to the atomic core. For more information, see the paper, "Source of coherent kiloelectronvolt X-rays", J. Seres et al., Nature, 433, 596 (2005). C. Streli and P. Wobrauschek (Atominstitut der Osterreichischen Universtitaten, Technische Universitat Wien) were the co-authors of this paper.

The international union of crystallography (IUCr) announced that Professor P. Coppens (Department of Chemistry, State University of New York at Buffalo, USA) has been awarded the seventh Ewald Prize for his contributions to developing the fields of electron density determination and the crystallography of molecular excited states, and for his contributions to the education and inspiration of young crystallographers as an enthusiastic teacher by participating in and organizing many courses and workshops. The Prize consists of a medal, a certificate, and an award of USD 30,000. The former recipients are Michael M. Woolfson (UK, 2002), G.N. Ramachandran (1999), M. G. Rossmann (USA, 1996), N. Kato (Japan, 1993), B.K. Vainshtein (Russia, 1990), J.M. Cowley (USA) and A.F. Moodie (Australia) in 1987.