Dept. of Mechanical Engineering, University of Minnesota, 271 Mechanical Engineering, 111 Church Street S.E., Minneapolis, MN, USA

Dept. of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, 3026 Brauer Hall, St. Louis, MO, USA

Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Rd., Billerica, MA, USA

Dept. of Environmental Science, Policy, & Management, University of California, 147 Mulford Hall, Berkeley, CA, USA

Dept. of Civil and Environmental Engineering, University of California, 147 Mulford Hall, Berkeley, CA, USA

Dept. of Environmental Science, Policy, & Management, University of California, 147 Mulford Hall, Berkeley, CA, USA

Aerosol Dynamics Inc., 935 Grayson St., Berkeley, CA, USA

Aerosol Dynamics Inc., 935 Grayson St., Berkeley, CA, USA

Dept. of Physics, University of Kuopio, Kuopio, Finland

Finnish Meteorological Institute, Helsinki, Finland

Dept. of Physics, University of Helsinki, Helsinki, Finland

Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., 45 Manning Rd., Billerica, MA, USA

Dept. of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA

Cooperative Institute for Research in the Environmental Sciences, Boulder, CO, USA

Dept. of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA

Cooperative Institute for Research in the Environmental Sciences, Boulder, CO, USA

now at: Alion Science and Technology, EPA Office of Research and Development, Research Triangle Park, NC, USA

Dept. of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA

Cooperative Institute for Research in the Environmental Sciences, Boulder, CO, USA