Editor's Note: Any reference to TheStreet Ratings and its underlying recommendation does not reflect the opinion of TheStreet, Inc. or any of its contributors including Jim Cramer or Stephanie Link. All three major indices are trading up today with the Dow Jones Industrial Average ( ^DJI) trading up 58 points (0.4%) at 15,069 as of Tuesday, Aug. 20, 2013, 1:04 PM ET. The NYSE advances/declines ratio sits at 2,347 issues advancing vs. 659 declining with 81 unchanged. The Basic Materials sector currently sits up 1.0% versus the S&P 500, which is up 0.6%. On the negative front, top decliners within the sector include Teck Resources ( TCK), down 1.9%, ArcelorMittal ( MT), down 1.7%, Statoil ASA ( STO), down 1.1% and Petroleo Brasileiro SA Petrobras ( PBR), down 0.5%. Top gainers within the sector include Marathon Oil ( MRO), up 2.5%, Cabot Oil & Gas Corporation ( COG), up 2.5%, Barrick Gold Corporation ( ABX), up 2.5%, Continental Resources ( CLR), up 2.2% and Newmont Mining Corporation ( NEM), up 2.5%. TheStreet would like to highlight 3 stocks pushing the sector lower today: 3. PetroChina ( PTR) is one of the companies pushing the Basic Materials sector lower today. As of noon trading, PetroChina is down $1.78 (-1.6%) to $112.66 on average volume. Thus far, 82,324 shares of PetroChina exchanged hands as compared to its average daily volume of 168,600 shares. The stock has ranged in price between $111.14-$112.88 after having opened the day at $111.79 as compared to the previous trading day's close of $114.44. PetroChina Company Limited produces and sells oil and gas in the People's Republic of China. The company operates in four segments: Exploration and Production, Refining and Chemicals, Marketing, and Natural Gas and Pipeline. PetroChina has a market cap of $213.1 billion and is part of the energy industry. Shares are down 20.4% year to date as of the close of trading on Monday. Currently there are 3 analysts that rate PetroChina a buy, 1 analyst rates it a sell, and none rate it a hold. TheStreet Ratings rates PetroChina as a buy. The company's strengths can be seen in multiple areas, such as its revenue growth and attractive valuation levels. We feel these strengths outweigh the fact that the company has had somewhat disappointing return on equity. Get the full PetroChina Ratings Report now. STOCKS TO BUY: TheStreet Quant Ratings has identified a handful of stocks that can potentially TRIPLE in the next 12-months. Learn more.