The struggling U.S. Postal Service is expected today to announce plans to close about 250 mail processing centers around the country, including 10 in Ohio. The $3 billion in cuts would slow first-class mail service, ending next-day deliveries of stamped letters. A list of processing centers targeted for closure includes facilities in most parts of the state. A union spokesman says under the plan, processing offices in Columbus and Cleveland would be the only ones left in Ohio.