CHICAGO (AP) — Every time Chicago Officer Nick Spencer gives his police dog a command, he's reminded of 9/11 and that part of his job is to prevent another terrorist attack.That's because the bomb-sniffing dog he works with is named after a New York Police Department sergeant who died after racing into the World Trade Center.Spencer is one of hundreds of officers assigned to transportation centers paired with dogs named after firefighters, police officers and others killed in the attacks.Spencer says he's proud to have a dog named after Sgt. Rodney Gillis — a black Labrador retriever named Ggillis, with an extra "g."The Transportation Safety Administration has had an overwhelmingly positive response to the program from 9/11 families. Gillis' widow and mother say the dog's name is an honor.