List of Famous people who died at 81
Torquil Roderick MacLeod, 17th of Raasay
Gustaaf Otto Frederik Baron Huyssen van Kattendijke
Robert Maynard Hazlerigg
William Lawrence Bragg
Sir William Lawrence Bragg, was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structure. He was joint recipient of the Nobel Prize in Physics in 1915, "For their services in the analysis of crystal structure by means of X-ray"; an important step in the development of X-ray crystallography.
J. Barkley Rosser
John Barkley Rosser Sr. was an American logician, a student of Alonzo Church, and known for his part in the Church–Rosser theorem, in lambda calculus. He also developed what is now called the "Rosser sieve", in number theory. He was later director of the Army Mathematics Research Center at the University of Wisconsin–Madison. Rosser also authored mathematical textbooks.