After a strong start on Wall Street - which saw the three benchmark indices gain at least 1.1% each - the Footsie ended in positive territory, despite dipping into the red in the afternoon. However, gains were only modest as volatile trade continued.Security services provider G4S was the high riser of the day, after seeing its organic revenue growth accelerate in most regions and business sectors. Group turnover rose 5% on a constant exchange rates basis to £3.76bn in the first six months of 2011, while pre-tax profits climbed 5% to £149m.Wood Group, the oil and gas services firm, was wanted after saying it is seeing "good momentum" across its business, with the order book remaining strong and the bid pipeline healthy. First half EBITA rose 25% to $192m, while profit from continuing operations before tax and exceptional items rose 49% to $102.4m. Total revenues were up by 17% to $2.83bn.A big mover on the FTSE 250 was engineering group Charter International which surged over 20% after it confirmed speculation that it has received a second offer following a previous one from rival Melrose.Heading the other way were the miners, led by silver and gold producer Fresnillo, whose share price took a hit on the back of falling prices of the precious metals. Meanwhile, South America-focused copper miner Antofagasta was lower despite posting a sharp rise in profits for the six months to 30 June. Fellow FTSE 100 miners Randgold Resources and Vedanta Resources also fell. Shares in sector peer Peninsular Gold fell back after the Malaysian miner said revenues and profits for the year to 30 June may be lower than the market expects due to delays caused by heavy rains and low gold grades at its Raub mine. Spectris, the instrumentation and controls company, saw pre-tax profits rise 74% in the first half of 2011 to £77.7m, on the back of revenues that rose 25% to £507.2m. The firm also hiked its dividend by 15% to 8.2p per share. Persimmon, the house builder, saw underlying profits surge in the first half of 2011, strengthening its share price.Publisher and events organiser Daily Mail and General Trust (DMGT) was in demand after announcing that it is to sell its US events management firm George Little Management (GLM). Legacy software firm Micro Focus registered strong gains, recovering after taking a tumble on Monday following the announcement that bid talks had terminated.BCFTSE 100 - RisersG4S (GFS) 264.40p +8.54%John Wood Group (WG.) 542.50p +4.63%ARM Holdings (ARM) 514.00p +4.47%Glencore International (GLEN) 367.45p +3.51%Essar Energy (ESSR) 255.50p +3.07%Lloyds Banking Group (LLOY) 28.30p +2.69%Aggreko (AGK) 1,755.00p +2.27%ITV (ITV) 55.70p +2.11%SABMiller (SAB) 2,087.00p +2.08%Serco Group (SRP) 532.00p +1.92%FTSE 100 - FallersFresnillo (FRES) 1,892.00p -7.21%Randgold Resources Ltd. (RRS) 6,640.00p -3.35%International Consolidated Airlines Group SA (IAG) 164.00p -2.09%Legal & General Group (LGEN) 95.45p -1.65%Vedanta Resources (VED) 1,225.00p -1.37%3i Group (III) 200.70p -1.33%GKN (GKN) 177.00p -1.23%Petrofac Ltd. (PFC) 1,199.00p -0.99%Capital Shopping Centres Group (CSCG) 315.00p -0.79%Compass Group (CPG) 533.50p -0.74%