1. Department of Electrical & Computer Engineering, University of Florida, Gainesville 32611-6200, FL, USA
2. Department of Biomedical Engineering, Whitaker Institute, Johns Hopkins University, Baltimore 21205, MD, USA
3. BioSieve, 1026 Springfield Drive, Campbell 95008, CA, USA
4. National Center for Atmospheric Research, Boulder 80307-3000, CO, USA