Stocks are expected to slip slightly when trading starts on Thursday morning, pulling back after gains made the day before as investors continue to digest comments made by Federal Reserve Chairman Ben Bernanke in his semi-annual testimony to Congress.City sources predict the FTSE 100 will open down around 11 points from yesterday's close of 6,571.Markets rallied in afternoon trade yesterday after Bernanke said that the Fed's $85bn-a-month asset purchase programme is "by no means on a pre-set course". He reiterated that the central bank still expects to begin tapering quantitative easing later this year (with a view to end the programme in mid-2014) but said nothing was predetermined and the plan may change if the economic outlook turned for the worse.He also highlighted some of the downside risks which could affect the economic outlook, such as the recent increases in mortgage rates and the possibility of a weaker-than-expected global economy."Given all the anticipation leading up to yesterday's testimony by the Fed Chairman it would seem that markets are no wiser now than they were beforehand with respect to the Feds intentions," said Senior Market Analyst Michael Hewson from CMC Markets. Stocks to watchPetrofac has agreed to increase its interest in Petrofac Emirates, its Abu Dhabi based joint venture with Mubdala Petroleum, to 75%. It comes after Mubadala Petroleum sold its shares in the joint venture to Nama Project Services, an affiliate of Nama Development Enterprises (Nama), a service provider to the energy industry in the United Arab Emirates (UAE). Nala will now hold the remaining 25% stake.Anglo American, one of the world's largest mining groups, reported mixed production results in the second quarter as increases to copper, platinum, diamond and phosphates output were offset by declines in iron ore, coal, nickel and niobium.Reinforced polymer technology firm Fenner said it has continued to make progress and reiterated results for the full year are expected to be in line with company expectations. BC