Barclays has downgraded banking group Standard Chartered from 'overweight' to 'equalweight', citing its exposure to the emerging markets and growing risks in some geographies. "Although we leave our Standard Chartered earnings estimates unchanged and continue to believe that the shares offer value in the longer term, we see little scope for either earnings upgrades or a re-rating of the shares in the near term," Barclays said.Credit Suisse has cut its recommendation for security solutions firm G4S from 'outperform' to 'neutral' and reduced its target price from 290p to 275p after the stock's recent strong performance."GFS has already re-rated strongly and now trades at 14.3 times 2014E earnings, which is the 91st percentile of its nine-year average and a significant premium to both Securitas and Serco," the bank said.JPMorgan Cazenove has upgraded telecoms group TalkTalk from 'neutral' to 'overweight' and lifted its target price from 225p to 300p, saying that its investment in TV should lead to the emergence of a cash cow with low gearing.Concerns over rising competition from BT Sport have meant that the stock has performed in line with the FTSE 250 over the last 12 months despite TalkTalk having beaten expectations on TV adds and churn reduction. JPMorgan said that these fears have been overdone and the first-half results in November should provide early evidence that BT Sport does not pose a significant risk.BC