November 2008 Archives

A new website dedicated to job offers at synchrotron radiation sources has been started by a joint initiative of the European Synchrotron Radiation Facility (ESRF) and Institute of Physics (IOP). So far, job seekers have had to regularly scan the websites of many different facilities in the world. The objective of the new website is to cluster as many offers as possible into a single resource. It will also allow those interested to subscribe to weekly mailings of new positions. Visit the following site, http://www.synchrotronjobs.com/

Recent progress in synchrotron X-ray microscopy has opened up extremely attractive applications. A group led by Professor B. M. Weckhuysen (Utrecht University, The Netherlands) recently watched heterogeneous catalysts in action at high temperature. Solid catalysts have been widely used in the chemical industry, and accelerate the production of many important compounds. They are typically composed of nanometre-sized metal or metal oxide particles attached to a solid support with a high surface area. As complex structural and chemical changes take place during catalytic reactions, direct observation of the reacting catalyst is extremely important. The team employed X-ray microscopy at the Advanced Light Source, Berkeley, United States, to study the catalytic Fischer-Tropsch reaction where a solid catalyst of iron oxide particles mounted on silica is used to convert carbon monoxide and hydrogen into liquid hydrocarbons that can be used as fuels. By the use of Fe LII, III and C K absorption edges, scanning transmission X-ray imaging has revealed that during the reaction the iron oxide underwent several transformations; the initial iron oxide (Fe₂O₃) is converted into another oxide (Fe₃O₄), before iron silicates (Fe₂SiO₄) and metallic iron begin to form. Iron carbides (Fe_xC_y) appear in the final stage. For more information, see the paper, "Nanoscale chemical imaging of a working catalyst by scanning transmission X-ray microscopy", E. de Smit et al., Nature 456, 222-225 (2008).

Neuromeranin (NM) is a dark colored pigment synthesized within specific catecholamine-producing neurons in the human brain. It is of uncertain origin and exists as amorphous granules with a heterogeneous structure called NM granules. At the European Synchrotron Radiation Facility (ESRF) in Grenoble, the microchemical environment of NM in whole neurons from formalin-fixed and paraffin-embedded human substantia nigra sections was recently analyzed. It was found that concentrations of NM-associated elements increase in the developing brain, and that iron-rich microdomains colocalized with other elements within the pigment. Furthermore, intracellular speciation of sulfur in NM has revealed the presence of reduced sulfur compounds and various forms of oxidized sulfur compounds which have not previously been reported. For more information, see the paper, "Intracellular Chemical Imaging of the Developmental Phases of Human Neuromelanin Using Synchrotron X-ray Microspectroscopy", S. Bohic et al., Anal. Chem., Article ASAP, DOI: 10.1021/ac801817k

Professor L. Natarajan (University of Mumbai, India) recently published a paper calculating the energies and electric dipole rates of X-rays from the empty K shells of atoms in the range of Z=12 to 56. For more information, see the paper, "Relativistic fluorescence yields for hollow atoms in the range 12<Z<56", L. Natarajan, Phys. Rev. A78, 052505 (2008).