Shares in defence group Chemring dropped after its CEO David Price resigned with immediate effect. He will be replaced by Mark Papworth, a former Wood Group executive. Speculation in the market is that Price's exit signals that US private equity firm Carlyle's takeover bid could be collapsing. "It would appear odd to appoint a new CEO with the belief the group is going to be taken over within a matter of weeks," said Guy Brown from Oriel Securities.?Wireless technology firm CSR jumped after revenues were up in the third quarter as it said it had successfully completed a deal with Samsung, paving the way for a big investor pay out. ??Morgan Crucible, the British maker of ceramics used in wind-turbine blades, was making gains on speculation that it has become a potential takeover target. The stock is currently trading at its lowest valuation (price-to-earnings) since 2009.Tech group Laird fell after its third-quarter trading update was "light on revenue" and guidance, according to Investec analyst Chris Dyett. Year-to-date sales are up 3% but down 2% organically. Dyett said that "it looks likely that we need to pull back revenues for 2012 estimates by £20-25m".Catalogue and home shopping firm N Brown rose after UBS raised its target price for the stock from 285p to 340p and reiterated its 'buy' rating after last week's first-half results beat the broker's forecasts.FTSE 250 - RisersOphir Energy (OPHR) 585.00p +1.47%Shanks Group (SKS) 80.95p +1.19%Brown (N.) Group (BWNG) 321.30p +1.04%Paragon Group Of Companies (PAG) 242.40p +0.83%UBM (UBM) 675.50p +0.82%Brewin Dolphin Holdings (BRW) 177.90p +0.68%Dunelm Group (DNLM) 679.00p +0.59%Telecom Plus (TEP) 858.00p +0.59%Betfair Group (BET) 740.50p +0.54%Playtech Ltd. (PTEC) 412.80p +0.44%FTSE 250 - FallersChemring Group (CHG) 315.00p -9.04%Kenmare Resources (KMR) 39.00p -8.84%Lonmin (LMI) 482.20p -4.89%Home Retail Group (HOME) 102.80p -4.19%Soco International (SIA) 324.10p -3.97%Centamin (DI) (CEY) 99.95p -3.89%SDL (SDL) 558.00p -3.88%Elementis (ELM) 218.90p -3.78%Homeserve (HSV) 231.10p -3.35%Petropavlovsk (POG) 419.20p -3.34%BC