London's top stocks have opened slightly lower after the US gave up most of its gains before trading closed last night.Bus and rail operator Arriva has agreed to be taken over by Germany's Deutsche Bahn in a £1.59bn deal that will create a new European transport giant. Under the terms of the deal, Arriva shareholders will also receive a 2009 dividend of 18.8p per share.Revenues were down at WH Smith in the half year to February 28, but efficiency measures helped the newsagent chain post a rise in pre-tax profits. Revenues slipped to £716m from £731m over the same period the previous year, while pre-tax profits edged up to £62m from £61m.Pubs group Punch Taverns reported a slightly better than expected half year profit but warned that market conditions remain challenging. Pre-tax profits dropped to £66m in the 28 weeks ended 6 March compared with £82m last time, but the figure was still better than average expectations of £65m.Mobile phone giant Vodafone has introduced a new service designed to close a security gap in the monitoring procedures of regulated financial firms.Mining giant Anglo American reported a 23% jump in first-quarter iron ore production and a 7% rise in copper output.Housebuilder Persimmon said sales have remained consistent since it last updated the market on March 2, despite uncertainty over the state of the economy and the coming general election.Sports Direct, owner of Sports World stores and Slazenger and Dunlop brands, said based on current trading it is confident of achieving full year underlying EBITDA of at least £160m. It has been a good year so far for Filtrona, the supplier of speciality plastic and fibre products, with first quarter results ahead of the board's expectations. Engineering and project management company AMEC has been signed up by French power generating company EDF Group to assist with the proposed delivery of four new nuclear reactors at Hinkley Point and Sizewell in the UK. Financial details of the contract have not been divulged.A consortium of which Kier Group is a member has been named as the preferred bidder on a £40m fire station project in Gloucestershire.Casino and bingo hall operator Rank said it has made an 'encouraging' start to 2010, with like-for-like sales climbing by 4% in the 16 weeks to April 18.Speciality chemicals supplier Elementis said full year earnings are expected to be ahead of current market expectations as demand picked up in the first three months of the year. It's been only seven weeks since it announced its preliminary results but since then the outlook for the first half of 2010 has improved substantially for engineer IMI.Investment performance at the majority of its funds continued to be strong at BlueBay Asset Management in the first three months of 2010.FTSE 100 - RisersIntertek Group (ITRK) 1,551.00p +3.06%Amec (AMEC) 889.00p +2.36%Autonomy Corporation (AU.) 1,818.00p +2.02%Randgold Resources (RRS) 5,140.00p +1.28%Reed Elsevier (REL) 540.50p +1.12%Bunzl (BNZL) 774.00p +1.11%International Power (IPR) 333.00p +1.06%Carnival (CCL) 2,698.00p +0.94%Compass Group (CPG) 530.00p +0.86%Reckitt Benckiser Group (RB.) 3,582.00p +0.84%FTSE 100 - FallersAviva (AV.) 380.90p -1.24%Liberty International (LII) 513.00p -1.16%Invensys (ISYS) 323.10p -0.98%ARM Holdings (ARM) 248.10p -0.96%ICAP (IAP) 388.00p -0.89%Land Securities Group (LAND) 665.50p -0.89%BAE Systems (BA.) 355.80p -0.84%Hammerson (HMSO) 387.30p -0.82%Prudential (PRU) 560.00p -0.80%Shire Plc (SHP) 1,451.00p -0.75%