Joe Keller, one of the greatest applied mathematicians of our time, died on 7 September 2016. He was Professor Emeritus of Mathematics and of Mechanical Engineer at Stanford University and was a longtime member of the Geophysical Fluid Dynamics summer program at the Woods Hole Oceanographic Institute. His brother Herb Keller, also a brilliant applied mathematician, died in 2008.
As described in a Stanford news release and elsewhere, Keller's was a physical applied mathematician whose work spanned a wide range of topics (including many related to dynamical systems) and ranged from the industrial to the playful, with stops everywhere in between. He is probably best known for his mathematical theory of diffraction, which describes wave propagation, scattering, and diffraction (and their interaction with obstacles). Keller is the "K" in EBK quantization. On the playful side, Keller won two Ig Nobel prizes (I believe he is the only two-time winner of the prize): in 1999 for dripping teapots and in 2012 for ponytail dynamics.
Keller won myriad prestigious honors, including the Wolf Prize in Mathematics (1997), the National Medal of Science (1988), the von Karman Prize (1979), and many others. He gave SIAM's von Neumann Lecture in 1983 and the American Mathematical Society's Gibbs Lecture in 1977.
Keller will be missed greatly by the applied mathematics community.