Water plant operator Torrey Jones checks the clarity of a sample of treated water at the Beaver Falls Municipal Authority water treatment plant in Beaver Falls, Pa. Keith Srakocic/AP hide caption

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University of Miami pediatrician Judith L. Schaechter gives an HPV vaccination to a 13-year-old girl last week in Miami. Joe Raedle/Getty Images hide caption

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Seeds from Golden Rain acacias like these in Wales provide the active ingredient for a pill to help people stop smoking. Tom Patterson/Flickr hide caption

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