Gregg Allman and Natalie Cole perform at the Tune In to Hep C benefit concert at the Beacon Theatre in New York on July 27, 2011. Both singers have battled chronic hepatitis C. Rob Bennett/AP Images for TuneInToHepC.com hide caption

itoggle caption Rob Bennett/AP Images for TuneInToHepC.com

Care managers tend elderly people in March 2012 in Minamisoma, Japan. The home's residents were evacuated eight days after the Fukushima Dai-ichi nuclear power station was crippled by the March 11, 2011 tsunami. Koji Sasahara/AP hide caption

itoggle caption Koji Sasahara/AP

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/via Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/via Wikimedia Commons

CamelBak-brand water bottles on display at an outdoor supply store in Arcadia, Calif., in 2008. The company removed BPA from the plastic in its bottles. David McNew/Getty Images hide caption

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Researchers studying brains want to know what's happening in an area called the premotor cortex — the place in the brain that gears up for something the body is about to do, like swimming. Above, Michael Phelps dives off the starting blocks in the final heat of the men's 400-meter individual medley during the 2012 U.S. Olympic Swimming Team Trials in Omaha, Neb., on June 25. Jamie Squire/Getty Images hide caption

itoggle caption Jamie Squire/Getty Images

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/via Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/via Wikimedia Commons

An artist's illustration of events on the sun changing the conditions in near-Earth space. NASA hide caption

itoggle caption NASA

Jeff Hudale, who is autistic, demonstrates a face recognition test at the University of Pittsburgh in 2010. Researchers use eye tracking devices to monitor and record what he is looking at. Rebecca Droke/Pittsburgh Post-Gazette hide caption

itoggle caption Rebecca Droke/Pittsburgh Post-Gazette

A working gas well head is fenced in just opposite of a home in Dish, Texas. Dish is about 30 miles north of Fort Worth. David Gilkey/NPR hide caption

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William Reigle has fibrosis, a disease that may be aggravated by nearby fracking. He's one of more than 2 million Pennsylvanians who get their health care from Geisinger Health System. The system wants to use its extensive database of patient records to study the health impact of natural gas production. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR