1. Center for Esophageal Diseases and Swallowing, University of North Carolina School of Medicine, Chapel Hill, NC, USA;
2. Division of Gastroenterology and Hepatology, Department of Medicine, Hospital of the University of Pennsylvania,. Philadelphia, PA, USA;
3. Division of Gastroenterology and Hepatology, Department of Medicine, Center for Gastrointestinal Biology and Disease, University of North Carolina School of Medicine, Chapel Hill, NC, USA.