ISTANBUL — Turkish actress Tuba Büyüküstün, who stars in ATV's drama "XX" has been assigned as UNICEF's Goodwill Ambassador for Turkey. The announcement was made at a press conference yesterday by UNICEF's Turkey representative Dr. Ayman Abulaban. As a goodwill ambassador, Büyüküstün will promote the U.N. agency's work not only in Turkey but across the world.