Dr. Alexander Rack, Dipl.-Phys. European Synchrotron Radiation Facility - ESRF Structure of Materials Group - ID19, S-19 CS 40220 F-38043 Grenoble Cedex 9 France ESRF - ID19 sector 19.1, office 19.5.01 telephone: +33 (0)476 88 1781 fax: +33 (0)476 88 2252 e-mail: arack_AT_snafu.de ... theoria cum praxi ...