Premier Foods is leading the food sector lower after RBS has downgraded its rating on the maker of Hovis bread from buy to hold and cut its target price by a whopping 84% following the group's profit warning on Friday. The food manufacturer revealed that third quarter results were "significantly below our expectations" and said that full-year trading profits will be below market forecasts. The target price now stands at just 6p, from 38p before.ARM Holdings is the top riser in a buoyant tech sector after RBS reiterated its "buy" status on the designer of chips used in gadgets, a view contradicted by JPMorgan, who have set a 220p target share price for the firm, with an "underweight" recommendation. Also in the world of chips, Nanoco Group, a firm which makes tiny semi-conductors, is higher after saying it has agreed to continue its relationship with the Japanese company Tokyo Electron to develop cheap solar cells. Top performing sectors so far todayTechnology Hardware & Equipment 711.06 +3.70%Oil Equipment, Services & Distribution 20,491.73 +3.41%Life Insurance 3,770.89 +3.33%Forestry & Paper 5,391.06 +3.20%Mining 20,004.90 +3.13%Bottom performing sectors so far todayAlternative Energy 8,914.98 -2.58%Food Producers & Processors 5,274.94 -0.41%Electricity 8,307.14 -0.27%Gas, Water & Multiutilities 4,795.54 -0.27%Electronic & Electrical Equipment 2,450.88 -0.13%