1. Institute for Environmental Medicine and Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
2. Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology
3. Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
4. Department of Psychiatry and Center for Interdisciplinary Research on Nicotine Addiction, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
5. Pulmonary, Allergy, and Critical Care Division, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania