NEW ORLEANS, Louisiana (AP) -- Mayor Ray Nagin unveiled a new evacuation strategy for New Orleans on Tuesday that relies more on buses and trains and eliminates the Superdome and Convention Center as shelters. "There will be no shelter of last resort," Nagin declared. The mayor, facing a runoff election May 20, has been widely criticized for failing to get the city's most vulnerable residents out of town as Hurricane Katrina approached. The Superdome and Morial Convention Center became a scene of misery for days after the August 29 hurricane as thousands of evacuees, many of them ill or elderly,...