GENEVA -- UBS chief executive Oswald Gruebel has resigned over a $2.3 billion rogue trading loss, the bank said Saturday. The move ends days of speculation about whether Gruebel could retain his position following the latest scandal to hit Switzerland's biggest bank.UBS Europe chief Sergio P. Ermotti will take over immediately as interim chief executive until Gruebel's replacement is appointed, the bank said in a statement.Read More... More on Business