Prominent alumni in the field of science include Douglas L. Coleman, who discovered leptin; Richard Bader, noted for his work on the atoms in molecules theory; Harold E. Johns, who pioneered the use of cobalt-60 in the treatment of cancer, Karl Clark, who pioneered the separation method to extract bitumen from the oil sands; Peter R. Jennings, computer programmer and developer of Microchess; and Simon Sunatori, an engineer and inventor. Notable faculty members include chemist Ronald Gillespie, who helped shape VSEPR theory, as well as David Sackett and Gordon Guyatt, whose research team was credited for establishing the methodologies used in evidence-based medicine. Notable alumni and faculty members in the field of social sciences include Harold Innis, who helped shape communication theory and the staples thesis, and sociologist Henry Giroux, one of the founding theorists of critical pedagogy. Two medical researchers, and members of McMaster had travelled in space; faculty member Dafydd Williams, and alumna Roberta Bondar, the first Canadian woman in space.