Complex sentence: After gaining his Masters by thesis in 1978, Marshall moved to the University of Western Australia, where he commenced his PhD research, studying patients suffering from diabetes and infertility at the Charles Gairdner Hospital.
Split into simpler sentences: After gaining his Masters in 1978, by thesis, Marshall moved to the University of Western Australia, where he commenced his PhD thesis research. During that time, he studied patients suffering from diabetes and infertility at the Charles Gairdner Hospital.