One of the country's best-known diet centers is closed after more than 70 years of attracting celebrities, business executives and others suffering chronic illness and obesity to North Carolina. The Rice Diet Program has operated a year-round clinic where people from around the world came to live the low-salt, low-calorie, low-protein regimen since Duke University's hospital spun it off in 2002. The program closed in November with plans to reopen early this year with new investors, but its owner Dr. Robert Rosati was unable to close a sale with any of three potential buyers. His wife Kitty Rosati says the buildings where clients ate their meals and received counseling is for sale. Separately, a businessman is aiming to set up a new venture using rice diet principles.