While the miners were dominating the downward trend on the second-tier FTSE 250 index on Tuesday afternoon, there were a handful of outperformers, most notably high-flying plant hire firm Ashtead.Ashtead saw shares jump after saying this morning that full-year results will be "materially ahead of our previous expectations". Underlying profit before tax in the first quarter rose 82% year-on-year while underlying revenues gained 21%. "Given this early stage of the recovery, we see further outperformance from re-rating as well as scope for further positive earnings surprises," said analyst Andrew Nussey from Peel Hunt. Veterinary pharmaceuticals firm Dechra rose after revealing growing sales across all its major brands and profits ahead of market forecasts for the full year to the end of June. Recycled packing company DS Smith was in demand after saying it was trading in line with market expectations and expected substantial year-on-year growth in earnings per share. Also on the rise was Old Speckled Hen brewer Greene King which shrugged off the Olympics and the poor weather to make a robust start to the financial year.FTSE 250 - RisersAshtead Group (AHT) 315.00p +11.50%Heritage Oil (HOIL) 198.60p +4.47%Dixons Retail (DXNS) 18.88p +4.31%Smith (DS) (SMDS) 168.20p +3.83%Greene King (GNK) 584.00p +3.64%SIG (SHI) 102.50p +2.40%Ophir Energy (OPHR) 600.00p +2.39%Synergy Health (SYR) 907.00p +2.31%Hansteen Holdings (HSTN) 77.40p +2.04%SDL (SDL) 650.00p +1.80%FTSE 250 - FallersTalvivaara Mining Company (TALV) 133.10p -4.93%Bumi (BUMI) 288.60p -4.82%Gem Diamonds Ltd. (DI) (GEMD) 158.00p -4.30%Hochschild Mining (HOC) 432.70p -3.84%Fenner (FENR) 347.00p -3.50%Centamin (DI) (CEY) 80.40p -3.42%Ruspetro (RPO) 122.00p -3.17%Hikma Pharmaceuticals (HIK) 715.00p -2.72%Genus (GNS) 1,341.00p -2.47%Domino's Pizza Group (DOM) 532.00p -2.39%BC