A. Virtanen, T. Rönkkö, J. Kannosto, J. M. Mäkelä, J. Keskinen, T. Pakkanen, L. Pirjola, and K. Hämeri Tampere University of Technology, Institute of Physics, Aerosol Physics, P.O. Box 692, 33 101 Tampere, Finland Finnish Meteorological Institute, Air Quality Research, Sahaajankatu 20 E, 00 810 Helsinki, Finland Helsinki Polytechnics, Department of Technology, P.O. Box 4020, 00 099 Helsinki, Fi...