1. Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
2. Department of Environmental Science, University of Puerto Rico—Rio Piedras, San Juan, Puerto Rico 00925, United States
3. Department of Chemistry, University of Puerto Rico—Rio Piedras, San Juan, Puerto Rico 00925, United States
4. Droplet Measurement Technologies, Longmont, Colorado 80503, United States