Paul Ehrenfest 1880 - 1933
Paul Ehrenfest (January 18, 1880 – September 25, 1933) was an Austrian and Dutch theoretical physicist, who made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition and the Ehrenfest theorem.
http://en.wikipedia.org/wiki/Paul_Ehrenfest (2 February 2015)