The board of directors for Towson, MD-based St. Joseph Medical Center has appointed an outside executive to run the Towson hospital during a federal investigation of its financial dealings with an affiliated doctors group. Beth O'Brien, senior vice president for operations at the Denver-based Catholic Health Initiative, which owns St. Joseph and 71 other hospitals, was named to the post. Three unnamed hospital executives have stepped down from their jobs to avoid a conflict of interest during the inquiry.