Portland-based software developer Urban Airship said this week that it is expanding its international efforts, and has opened up a new office in London. The firm, whose push messaging software is used by mobile developers, said it has poened a new office in the Covent Garden area of London, and appointed Nigel Arthur as Managing Director of Urban Airship UK. Arthur previously was at ExactTarget, and has served at companies such as Premiere Global Services, Responsys and WebTrends. Urban Airship's services are used by such companies as CBS Interactive, ESPN, Groupon, shopkick, and Walgreens.