Cabot and DuPont have named new executives. At Cabot, Sean D. Keohane has been named president and CEO, succeeding Patrick M. Prevost who is stepping down because of health concerns. Keohane was previously head of Cabot performance materials. At DuPont, Randy L. Stone has been named president of the performance materials business, succeeding Patrick E. Lindner who has joined fluoropolymer specialist W.L. Gore & Associates. Stone was previously global business director of the materials business.