Impax, the investment manager focused on environmental sector, saw its assets under management rise by 40% in the six months to March 31 as markets improved.'Evidence of improving macroeconomic conditions, particularly in the United States and in the Asia-Pacific region, has resulted in continued recovery in equity markets in recent months and strengthening investor confidence,' it said.Private equity group BlueGem Capital has made a recommended offer to buy luxury department store operator Liberty for about £32m. The offer is equivalent to 141.8p a share. Liberty plans to pay a 44.2p special dividend to shareholders if the offer is declared unconditional.Shares in security and surveillance company Petards fell sharply after it said it was implementing a capital reorganisation due to the share price being below the nominal value of existing ordinary shares.Sub-prime lender Cattles warned that it will be reporting a significant loss for the year ended 31 December 2009 and a negative value for shareholders' funds.