Ferrexpo has roared ahead after a strong performance from the Ukrainian iron ore producer in the third quarter. Total pellet production in the year to date increased 15.7% compared with 2009.Yule Catto is among the stocks helping to dampen sentiment. A mixed trading update sparked a negative reaction from investors.Within Polymer Chemicals, monomer prices continued to rise, the group said, but at a lower rate than the first half. The business continued to recover these increases in its end markets. Volumes remained robust in most segments, it added, though the weak volumes in the low margin compound business persisted.FTSE 250 - RisersFerrexpo (FXPO) 396.00p +10.80%Gartmore Group Ltd. (GRT) 116.00p +5.26%Supergroup (SGP) 1,263.00p +5.25%SIG (SHI) 118.60p +4.86%Rentokil Initial (RTO) 94.05p +3.87%Petropavlovsk (POG) 1,055.00p +3.43%Dunelm Group (DNLM) 507.50p +3.38%Salamander Energy (SMDR) 227.80p +3.36%JD Sports Fashion (JD.) 777.00p +3.12%Hochschild Mining (HOC) 555.00p +2.78%FTSE 250 - FallersYell Group (YELL) 11.25p -7.48%Tullett Prebon (TLPR) 372.70p -6.22%Pace (PIC) 189.40p -6.19%Cookson Group (CKSN) 529.50p -5.95%Yule Catto & Co (YULC) 253.30p -5.49%Ultra Electronics Holdings (ULE) 1,639.00p -5.37%Xchanging (XCH) 119.80p -5.07%Laird (LRD) 135.80p -4.84%Helical Bar (HLCL) 293.40p -4.59%Computacenter (CCC) 376.30p -4.54%