1. Max Planck Institute for Nuclear Physics (MPIK), P.O. Box 103980, D-69029
Heidelberg, Germany
2. Deutsches Zentrum für Luft und Raumfahrt (DLR), Oberpfaffenhofen,
Germany
3. Department of Technology, Metropolia University of Applied Sciences, P.O. Box
4021, FIN-00180 Helsinki, Finland
4. Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki,
Finland
5. Aerosol Physics
Laboratory,
Department of Physics, Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere, Finland