Defence firm Chemring was one of the top risers after its Chief Executive put boots on the ground in the form of new directors of finance and human resources.Investec has reiterated its 'buy' rating and 280p target price for Chemring, highlighting Thursday's appointment of new FD Steve Bowers. "We regard Steve highly and the market should welcome a further strengthening of the executive team charged with steering the group after a difficult year," the broker said. Along with Chemring's new Chief Executive Mark Papworth - who was appointed in November - Investec said that this "completes wholesale change of the executive management team".Without any discernible evidence to explain the 10.17% jump in Imagination Technologies, it would be nice to think it was an acknowledgement of Hossein Yassaie's recent Knighthood.The Chief Executive was given the award in her majesty's New Year Honours 2013 in recognition of his services to technology and innovation.With little news on the biggest FTSE 250 fallers either, it looks likely there was profit taking after yesterday's buying fever in the wake of the fiscal cliff deal.A certain amount of sobriety has returned now investors have started thinking about further obstacles ahead for the US economy, such as the $109bn spending cuts and talks over the debt ceiling.For example, Elementis, one of the big risers on Wednesday with a 2.4% gain, gave most of this back today.WH Smith said it will open eight stores at New Doha International Airport when panes begin landing their later this year, however, this hardly seems to be a reason for shares to drop off almost 3%.FTSE 250 - RisersImagination Technologies Group (IMG) 449.50p +10.17%Chemring Group (CHG) 259.40p +8.85%Kenmare Resources (KMR) 34.55p +4.70%Man Group (EMG) 87.95p +4.33%Fenner (FENR) 436.40p +3.98%SDL (SDL) 537.50p +3.86%Ferrexpo (FXPO) 276.40p +2.94%Tullett Prebon (TLPR) 262.60p +2.58%AZ Electronic Materials SA (DI) (AZEM) 360.60p +2.44%Grainger (GRI) 119.70p +2.40%FTSE 250 - FallersHowden Joinery Group (HWDN) 170.00p -3.63%WH Smith (SMWH) 635.50p -2.75%Premier Farnell (PFL) 193.60p -1.97%Ashtead Group (AHT) 436.60p -1.93%Elementis (ELM) 232.70p -1.48%ITE Group (ITE) 240.60p -1.43%Rentokil Initial (RTO) 96.55p -1.43%Bwin.party Digital Entertainment (BPTY) 111.00p -1.42%Capital & Counties Properties (CAPC) 246.90p -1.40%BH Global Ltd. USD Shares (BHGU) 11.35 -1.30%