Marc Day is Group Manager and Principal Scientist at National Renewable Energy Laboratory (NREL), where he manages the High-Performance Algorithms and Complex Fluids Group within the Computational Science Center. Dr. Day has contributed to projects associated with compressible and low Mach number astrophysics, compressible and low Mach number terrestrial combustion, and reacting multiphase flows in subsurface porous media. He also works with uncertainty propagation in large complex applications using techniques based on Markov chain Monte Carlo and implicit sampling, as well as in machine learning with applications in reacting and inert fluid flows. Dr. Day earned a PhD from UCLA. He can be reached at marcus.day@nrel.gov.