Oscar Pistorius of South Africa runs in the men's 200-meter event at the Paralympic World Cup in May. Some observers have suggested Pistorius receives an unfair advantage from his carbon-fiber "blade" legs. Michael Steele/Getty Images hide caption

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Timothy Ray Brown, shown in May 2011 with his dog Jack in San Francisco, is the only man ever known to have been fully cured from AIDS. Brown is known as the "Berlin patient" because he had a bone marrow transplant in a German hospital five years ago. Eric Risberg/AP hide caption

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United States runner Kam Conley sheds layers to train for the Olympics in England on Monday. Less clothing means more evaporation, keeping athletes cooler. Hussein Malla/AP hide caption

itoggle caption Hussein Malla/AP

Can You Help Me Tie My Shoe? Researchers found that when study participants were asked an unusual request, they were more likely later on to perform a favor. iStockphoto.com hide caption

itoggle caption iStockphoto.com