Regulators have closed a small bank in Arizona, bringing the number of U.S. bank failures to 13 this year. The Federal Deposit Insurance Corp. on Tuesday seized Central Arizona Bank, based in Scottsdale, Ariz. The lender, which operated a single branch, had roughly $31.6 million in assets and $30.8 million in deposits as of March 31. Western State Bank, based in Devils Lake, N.D., agreed to assume all of the failed bank’s deposits and to buy essentially all of its assets. …