1. Department of Mathematics Howard University Washington DC 20059 USA
2. The Earth and Planets Laboratory Carnegie Institution for Science Washington DC 20015 USA
3. Materials Modeling and Development Laboratory, National University of Science and Technology 'MISIS' 119049 Moscow Russia
4. Department of Physics, Chemistry and Biology (IFM) Linköping University 58183 Linköping Sweden
5. Center for Advanced Radiation Sources University of Chicago Lemont IL 60437 USA
6. Bayerisches Geoinstitut 95447 Bayreuth Germany