blue postcards advertising Barack Obama's appearance tomorrow at the Siegessaule....Yesterday and today volunteers from Americans Abroad for Obama, as well as college students...have been plying Berliners and tourists with these rather bizarre cards -- the artwork reminiscent of both German Expressionism and Soviet Constructivism in its depiction of a frowning Barack. Is the Obama brow wrinkled in thought? Is the Senator squinting at the future? Or is he hectoring an audience? Take your pick....