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  • Aladdin newsletter header

    THE ELECTRONIC ALADDIN NEWSLETTER NO. 14
    September / October 1997


    SRC USERS MEETING THIS WEEK

    The SRC Users Meeting and a Topical Workshop on Correlated Electrons will take place Friday/Saturday this week (Oct. 24/25).

    The final program and additional information, such as housing and directions to SRC, can be found on the SRC Web site at http://www.src.wisc.edu/


    MICRO-BEAM IRRADIATION FOR STUDYING DNA DAMAGE AND REPAIR

    The field of synchrotron radiation keeps expanding into new directions, as demonstrated by this hot new finding at the SRC:

    Despite years of research and a host of clever experiments, it remains an ongoing challenge to identify both the exact mechanisms of radiation damage and self-repair of DNA. J.H. Petrini, in collaboration with M. Lagally, J. MacKay and B. Nelms at the University of Wisconsin, have developed a novel micro-beam system, consisting of "striped" irradiation masks, to irradiate only partial volumes of individual cells. The "stripes" represent a system for masking the cell dishes so that an irradiated cell absorbs energy in only a fraction of its nucleus.

    Initial results have already produced a few firsts: They demonstrate that ultra-soft X-ray-induced DNA damage is relatively static within the nucleus. Further, it is shown that a DNA repair complex, the hMre11/hRad50 protein, localizes to the sites of DNA damage immediately following irradiation. These data illustrate that this methodology constitutes a powerful tool to examine recombinational DNA repair activities. It has the potential to detect associations between DNA repair and cellular signaling pathways.


    FIRST USER ON THE PGM UNDULATOR BEAM LINE

    Al Arko and John Joyce from Los Alamos National Laboratory were the first users to test ride the newly-installed PGM undulator beamline. They studied heavy fermion effects by means of high resolution photoemission spectroscopy. After a few night shifts of intense data taking they summarized their experience as "this is one of the finest UV and soft X-ray beamlines in world". For details see the SRC Web page http://www.src.wisc.edu/

    The PGM beam line is optimized for the 40-130 eV photon energy range. It contains the strong d-to-f resonances that Al Arko and Jon Joyce used to project out f-states. The PGM is also a prime instrument in the 100-130 eV range which is used for the analysis of silicon surfaces via the Si 2p core level.

    11 proposals were submitted for initial beam time on the PGM. They are being reviewed by the Program Advisory Committee and will be assigned beam time shortly.


    FINAL TEST OF THE SCIENTA ANALYZER SUCCESSFUL

    The Scienta photoelectron spectrometer went through its final, on-site testing Oct. 6-10. After rotating an aperture in the lens and calibrating with an array of angular apertures the analyzer could be operated in the two-dimensional multidetection mode, where an array of energies and polar angles is detected simultaneously.

    For details on this and on earlier resolution tests see the SRC Web page http://www.src.wisc.edu/


    NEW CANADIAN SGM BEAM LINE

    A state-of-the-art, spherical grating monochromator beam line funded by the Canadian group at SRC has been connected to Aladdin and is currently being aligned.