Mid-caps were firmly in the red on Monday afternoon, with every sector registering losses, as debt talks between Greece and its creditors came to an abrupt finish.As of 14:30, the FTSE 250 was trading 1.18% lower at 17,738.Aveva was trading higher on reports the software developer has hired bankers Lazard to consider its strategic options as speculation over a bid from an American suitor grows. According to The Sunday Times, Aveva began working on takeover options with Lazard in February, though the company is known to have a relationship with the bank dating back to last year.NMC Health gained after acquiring long-term medical care provider ProVita for $160.6m. The acquisition is set to be completed by the third quarter of this year.Tullet Prebon topped the fallers as analysts at RBC Capital downgraded their rating on the stock to 'hold' in a research note issued to investors.Victrex also sank on negative broker comments, following a downgrade to 'hold' from Deutsche Bank, which also cut its price target from 2,350p to 2,200p.Thomas Cook sank after setting up a joint venture with shareholder Fosun in the Chinese travel market. The company also announced that Carl Symon would step down from his role as non-executive director on 30 September. RisersSoco International (SIA) 190.90p +7.25%Supergroup (SGP) 1,192.00p +1.88%UK Commercial Property Trust (UKCM) 90.00p +1.81%Synergy Health (SYR) 1,772.00p +1.78%Zoopla Property Group (WI) (ZPLA) 263.50p +1.35%Enterprise Inns (ETI) 128.20p +0.87%NMC Health (NMC) 787.00p +0.83%Polymetal International (POLY) 543.50p +0.83%Aveva Group (AVV) 1,934.00p +0.83%Jimmy Choo (CHOO) 165.40p +0.79%FallersTullett Prebon (TLPR) 373.20p -7.56%Ashmore Group (ASHM) 302.20p -4.46%Allied Minds (ALM) 566.50p -4.23%Spire Healthcare Group (SPI) 333.20p -3.06%Tullow Oil (TLW) 366.00p -2.92%Crest Nicholson Holdings (CRST) 546.50p -2.84%Indivior (INDV) 229.40p -2.76%Man Group (EMG) 161.00p -2.72%Victrex plc (VCT) 1,940.00p -2.71%Dignity (DTY) 2,053.00p -2.66%