National Metrology Institute of South Africa,
Private Bag X34, Lynwood Ridge 0040, South Africa
and Phases Research Lab,
Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, U.S.A.
Siemens AG, Medical Solutions, Vacuum Technology Division,
Röntgenstraße 2, D-07407 Rudolstadt, Germany
Metals and Alloys, Universität Bayreuth,
Ludwig-Thoma-Straße 36b, D-95447 Bayreuth, Germany