A tracheoesophageal fistula (TEF) is a congenital or acquired abnormal communication between the trachea and esophagus. There are 5 different variants of congenital TEF described in the literature, with the most common being type C, as in our case. A type C TEF involves esophageal atresia of the proximal esophagus resulting in a blind pouch and a fistula connecting the distal trachea and distal esophagus. The other types are variations of a tracheoesophageal connection and frequent esophageal abnormal anatomy. Repair of the TEF is performed in the first few days of life to facilitate feeding after establishing a normal gastrointestinal pathway, to limit aspiration, and to preserve respiratory function. The surgical correction involves ligation of the fistula and reanastomosis of the esophageal ends. It is not uncommon for the repaired esophagus or trachea to become stenotic at the repair site later in life. 1 If the child becomes symptomatic, an esophagogastroduodenoscopy (EGD) or esophagogram is required to diagnose and determine the severity of the esophageal stenosis. Other possible complications from the TEF or its repair include tracheomalacia, vocal cord paralysis, gastroesophageal reflux, an anastomotic leak, esophageal rupture, reoccurrence of the fistula, and esophageal dysmotility. 2,3 Respiratory complications, however, are the most

Summary: Detailed scanning electron microscopy (SEM) of an operational quantum well laser was performed using the differential voltage contrast (DVC) method. Quantitative measurements of Fermi energies in an operational device at high magnifications were possible due to a new calibration procedure described in this study. Precise tailoring of digitized DVC images of an operational laser taken at high and low magnifications is described. The ability to record and to analyze very detailed quasi-Fermi energy (QFE) profiles across an operational laser or transistor with 30-Angstrom features improved the DVC technique. A layered GaAs/Ga x Al 1-x As/In y Ga 1-y As quantum well light emitter was tested through various operational steps, that is, inverse population, threshold, and full emission. The detailed QFE profile allowed us to analyze collective electron behavior at various steps of operation of the laser.