Two Princeton University professors were honored by the American Mathematical Society (AMS) for their contributions to mathematics. Professor of Mathematics Yakov Sinai received the Leroy P. Steele Prize for Lifetime Achievement for his 50 years of research into dynamical systems, probability, chaos and mechanics. Sinai published papers and books instrumental in the development of physics and nonlinear science, and also supervised more than 50 doctoral students. A second prize, the Leroy P. Steele Prize for Mathematical Exposition, went to Philip Holmes, Princeton's Eugene Higgins Professor of Mechanical and Aerospace Engineering. Holmes shares the prize with Cornell University's John Guckenheimer for their 1983 book "Nonlinear Oscillations, Dynamical Systems and Bifurcations of Vector Fields" (Springer), a now-standard textbook the AMS credited for uniting the theoretical and applied fields of dynamical systems.