It is with deep regret that we have heard that Ted Janssen passed away on September 29, 2017 at the age of 81.
Ted Janssen was professor of Theoretical Physics at Radboud University Nijmegen. He was a pioneer in the symmetry description of aperiodic crystals. In 1988 he received the Aminoff prize of the Royal Swedish Academy of Science and in 2014 the Ewald prize of the International Union of Crystallography.
An obituary can be found here.