1 The National Aeronautics and Space Administration (NASA, retired) Johnson Space Center, Houston, TX 77058, USA. tgoodwin3@comcast.net.
2 Division of Pulmonary, Allergy, and Critical Care Medicine and the Department of Medicine, University of Pennsylvania Perelman School of Medicine, 3450 Hamilton Walk, Edward J. Stemmler Hall, 2nd Floor, Office Suite 227, Philadelphia, PA 19104, USA. melpo@mail.med.upenn.edu.