1. Institute
of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße
31, D-93040 Regensburg, Germany
2. Institute
of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, D-93040 Regensburg, Germany
3. Department
of Operative Dentistry and Periodontology, University of Regensburg, Franz-Josef-Strauss-Allee 11, D-93053 Regensburg, Germany