Mid-caps tracked the FTSE 100's gains on Wednesday afternoon despite mixed US data, as strength in the construction and engineering sectors buoyed the market.As of 15:30 BST, the FTSE 250 was trading 0.4% higher at 18,294.Workspace Group led the risers after beating full-year forecasts for profit and net asset value thanks to strong trade in London, rental growth and redevelopments. Chief executive Jamie Hopkins said demand for the company's office space remains strong, with current inquiry levels and lettings up year-on-year.WH Smith was boosted after reporting that total sales in the 13 weeks to May 30 rose, as the performance of the company's shops based in stations and airports offset a disappointing performance in its high street stores."In all, WH Smith continues to deliver. The group's international store numbers are being expanded, with units at Sydney International Airport set to open from August, whilst group wide cost savings are still being squeezed," said Keith Bowman, equity analyst at Hargreaves Lansdown.Morgan Advanced Materials dipped, following a downgrade to 'sell' from 'neutral' from UBS. The Swiss bank said UBS said the engineering sector's margins have "gone sideways" since 2011 and, though a longer-term pickup is likely, it forecasts a decline in 2015.Synergy Health registered losses, despite overcoming currency headwinds with a 7.5% jump in full-year revenue. Chief executive Richard Steeves said the group was well placed to sustain both medium and long-term growth.AO World extended Monday's losses, which came as it posted a £2.9m loss before tax in its full-year results, although the white good retailer continued to gain market share.RisersWorkspace Group (WKP) 978.00p +6.30%Ocado Group (OCDO) 371.50p +4.65%WH Smith (SMWH) 1,592.00p +3.51%Booker Group (BOK) 182.30p +3.34%Melrose Industries (MRO) 276.30p +3.17%Lonmin (LMI) 145.40p +3.05%Domino's Pizza Group (DOM) 839.00p +2.76%Berendsen (BRSN) 1,063.00p +2.71%Brewin Dolphin Holdings (BRW) 328.40p +2.50%Supergroup (SGP) 1,185.00p +2.24%FallersMorgan Advanced Materials (MGAM) 345.20p -2.49%Home Retail Group (HOME) 156.30p -2.37%Grainger (GRI) 210.80p -1.50%Ashmore Group (ASHM) 329.30p -1.38%Unite Group (UTG) 614.00p -1.21%Virgin Money Holdings (UK) (VM.) 436.90p -1.15%Polymetal International (POLY) 562.50p -1.14%Capital & Counties Properties (CAPC) 412.50p -1.01%Shaftesbury (SHB) 873.50p -0.96%Spectris (SXS) 2,300.00p -0.95%