Australia has a distinguished history of Nobel Laureates in Science and Physiology. There have been 10 Australian-born winners of science's highest honour. Living Nobel Laureates include Peter Doherty for his discoveries concerning cell-mediated immune defence, awarded in 1996; Barry Marshall and John Robin Warren for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic-ulcer disease, and Elizabeth Blackburn, who resides in the United States, "for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase". United States-born Brian Schmidt, vice-chancellor of the ANU, was awarded the Nobel Prize for Physics in 2011, "for the discovery of the accelerating expansion of the universe through observations of distant supernovae".