MINNEAPOLIS, Minn., April 14 -- Photran Corp., a manufacturer of high performance optical and electrically-conductive thin-film-coated products for the flat-panel display industry, is closing its doors and terminating its employees. The action follows a series of setbacks that left the firm without money for ongoing operations.The move followed a decision by Photran's principal secured creditor and primary funding source to refuse to extend additional credit to the company. Over the past year, Photran terminated most of its 100-plus person workforce and pursued aggressive marketing activities in an effort to offset continued weakness in the Asian economy, the primary market for its products.