In this Oct. 25, 2012 photo, biomedical engineer Annie Simon, left, and research prosthetist Elizabeth Halsne fit an experimental "bionic" prosthetic leg on Zac Vawter at the Rehabilitation Institute ... more 
In this Oct. 25, 2012 photo, biomedical engineer Annie Simon, left, and research prosthetist Elizabeth Halsne fit an experimental "bionic" prosthetic leg on Zac Vawter at the Rehabilitation Institute of Chicago. After losing his right leg in a motorcycle accident, the 31-year-old software engineer signed up to become a research subject, helping test a trailblazing prosthetic leg that's controlled by his thoughts. He will put this leg to the ultimate test Sunday, Nov. 4 when he attempts to climb 103 flights of stairs to the top of Chicago's Willis Tower, one of the world’s tallest skyscrapers. (AP Photo/Brian Kersey) less 
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Associated Press | Photo By Brian Kersey
Wed, Oct 31, 2012 3:21 AM EDT