The University of California, Merced may have wooed the first lady to its commencement, but professors at its sister campus in San Diego argue the system's newest school should shut its doors to save money. In a terse letter to the University Office of the President released this week, 23 UCSD department chairs suggested shutting campuses in Merced, Riverside or Santa Cruz. The professors said the campuses were a drain on what they called the 10-campus system's flagship institutions.