While not conclusive, the two cases are "quite promising," says Anthony Fauci, a longtime AIDS researcher who directs the National Institute of Allergy and Infectious Diseases. Alex Wong/Getty Images hide caption

Going, going, gone. You won't find azodicarbonamide in Nature's Own products. And Subway is phasing it out, too. But lots of manufacturers are still using the additive. Meg Vogel/NPR hide caption

Robert Ashley's operas for television redefined the genre. Joanne Savio/Courtesy of the artist hide caption

Americans for Prosperity Foundation Chairman David Koch addresses attendees of the Defending the American Dream Summit in Orlando, Fla., Friday, Aug. 30, 2013. Phelan M. Ebenhack/AP hide caption

President Obama talks with television hosts Jose Diaz-Balart, center, and Enrique Acevedo, left, about the benefits of the Affordable Care Act for Latinos. Pablo Martinez Monsivais/AP hide caption

From 1952 to 1974, the "Joy Boys" — Walker (left) and Willard Scott — provided D.C. radio listeners with a daily dose of comedy. Scott went on to work in TV, where he can still be seen on The Today Show; Walker stuck with radio. Publicity photos from the WRC Graphics Department/TheJoyBoys.Com hide caption

The Z machine is located in Albuquerque, N.M., and is part of the Pulsed Power Program, which started at Sandia National Randy Montoya/Sandia National Laboratory hide caption