1. Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
2. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
3. Engineering Research Accelerator, Carnegie Mellon University, Pittsburgh 15213, USA.
4. Aerodyne Research Inc., Billerica, MA 01821, USA.
5. Bioenergy and Catalysis Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerland.
6. School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.