Article Photos: Man with bionic leg to climb Chicago skyscraper 8/8

  In this Oct. 25, 2012 photo, Zac Vawter, fitted with an experimental "bionic" leg, looks down from the Ledge at the Willis Tower in Chicago. Vawter is training for the world's tallest stair-climbing event where he'll attempt to climb 103 flights to the top of the Willis Tower using the new prosthesis. (AP Photo/Brian Kersey)