1. Dr Vuorinen () is at CSIR, Manufacturing and Materials Technology, National Metrology Laboratory, PO Box 395, Pretoria 0001, South Africa, Dr Kalman is with the Bay Zoltan Foundation for Applied Research, H-1116 Budapest, Fehervari ut 130, Hungary, Chemical Research Centre, Institute of Chemistry, Hungarian Academy of Sciences, H-1025 Budapest, Pusztaszeri ut 59-67, Hungary and Dr Focke is in the Institute of Applied Materials, University of Pretoria, Pretoria 0002, South Africa.