Ray Jayawardhana begins his tenure today as the 10th president of the California Institute of Technology. His selection as Caltechs president, and as the Sonja and William Davidow Presidential Chair and professor of astronomy, was announced Jan. 6. Jayawardhana succeeds Thomas Rosenbaum, who had served as Caltechs president since 2014. Founded in 1891, Caltech manages []