Complex sentence: Stephen L. Hauser is the Robert A. Fishman Distinguished Professor and Chair of the Department of Neurology at the University of California, San Francisco (UCSF), where his work has focused on immune mechanisms and multiple sclerosis (MS).
Split into simpler sentences: Stephen L. Hauser is a professor and Chair of the Department of Neurology at the University of California, San Francisco (UCSF). His work specializes on immune mechanisms and multiple sclerosis (MS).