Engineering firm Weir group was the biggest faller among FTSE 100 constituents after wiping more the £250m from its market value. The bad news looks set to continue throughout Friday as miners bear the brunt of the current economic turmoil. Worrying economic data from China added to the woes, with Kazakhymys, Vedanta Resources, Eurasian Natural Resources, and Rio Tinto all heading south. Yesterday, HSBC released its Purchasing Managers' Index for Chinese manufacturing yesterday which showed a slide to 49.4; a reading of 50 or below indicating contraction.Vodafone was on the up after announcing plans to open a new chain of stores across Ghana. The firm hopes the move will enhance customer experience and help it to stay ahead of the game. Evolution Securities has upgraded supermarket giant Tesco from "sell" to "neutral", on the back of a £500m price repositioning which begins next week.The company released a statement on Thursday, titled 'Tesco's Big Price Drop', in which it announced "immediate help for families all over the country in these tough economic times by cutting the price of thousands of essential items." FTSE 100 - RisersVodafone Group (VOD) 161.15p +1.26%Tesco (TSCO) 359.85p +1.01%Unilever (ULVR) 1,952.00p +0.77%Admiral Group (ADM) 1,238.00p +0.65%Centrica (CNA) 284.20p +0.57%Imperial Tobacco Group (IMT) 2,027.00p +0.50%SABMiller (SAB) 2,052.50p +0.27%Serco Group (SRP) 491.20p +0.06%FTSE 100 - FallersWeir Group (WEIR) 1,530.00p -7.22%Kazakhmys (KAZ) 787.50p -6.97%Xstrata (XTA) 793.00p -6.65%Vedanta Resources (VED) 1,045.00p -6.45%Eurasian Natural Resources Corp. (ENRC) 537.50p -5.62%Antofagasta (ANTO) 926.50p -4.73%Petrofac Ltd. (PFC) 1,198.00p -4.69%Rio Tinto (RIO) 2,882.50p -4.65%ARM Holdings (ARM) 549.50p -4.43%Prudential (PRU) 530.50p -4.41%NR