Thomas Lange Vincent was born September 16, 1935 in Portland, Oregon and died Monday, October 26, 2009 at his home in Tucson from pancreatic cancer. He is survived by his wife, brother and sisters, two children and two grandchildren. He was a resident of Tucson since 1960 and was a professor of aerospace and mechanical engineering at the University of Arizona for 41 years, retiring in 2001. He became an emeritus professor and among his last projects with students was the development of an autonomous underwater vehicle deployed in Alaska. Dr. Vincent was an expert in optimal controls and game theory and published over 150 books and articles related to the topic. He was still active in research with his colleagues when he died. When he wasn't working, he loved to hike, ski, and sail and was a passionate conservationist. He was a one-time president of the Tucson Mountain Association and helped play a role in passing a slope ordinance to keep the Tucson mountains a beautiful place to live. Most recently, he was treasurer of the Friends of Buenos Aires National Wildlife Refuge in southern Arizona. He was a kind and humanitarian man and he always touched people's lives in a positive way. He was well loved and will be missed by the many people who knew him, not only in Tucson but around the world.