1. Division of Gastroenterology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
2. Division of Gastroenterology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139; Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115
3. Tecnologico de Monterrey, Escuela de Ingenieria y Ciencias, Eugenio Garza Sada 2501 sur col. Tecnológico c.p, Monterrey, Nuevo León 64849, México