Professor Julie Langford is the scientist responsible for creating and maintaining Arcadia, and is a main character in the level of the same name, an arboretum that supplies oxygen to Rapture.
Professor Julie Langford went to Berkley collage, and worked for the United States Government before coming to Rapture. She also presumably worked on Agent Orange for WWII.
A greedy woman who comes to see the park as more of a commodity, rather than a leisurely paradise. Eventually her greed gets the better of her, and she and Andrew Ryan decide to sell the oxygen from her trees to the citizens of Rapture. She is killed by Ryan just as you reach her lab.