Dr. Albert M. Kligman, a dermatologist who invented the widely used medication Retin-A but whose experiments involving prisoners raised ethical questions that dogged his career, died Feb. 9 in Philadelphia. He was 93. The cause was a heart attack, said the University of Pennsylvania,where Kligman was a professor emeritus and had been a member of the faculty for more than 50 years. “Dr. Albert Kligman will always remain very much alive in the memories of those who loved, respected and tre...