The Times's Tempus column assesses Carnival, the FTSE 100 cruise ship operator. Following years of not hedging against fuel costs the company has started to do so after fuel prices in the fourth quarter grew 39%.The firm has done well in North America increasing the amount it makes on each berth by 4% but the performance in Europe, Australia and Asia showed no growth on 2010Price cuts do seem to have boosted volumes recently but with net income down to $217m from $248m in 2010 and a yield forecast of just 3.9% Tempus sees no reason to buy.The Times also assesses Petra Diamonds, which competes against the big daddies of the diamond industry: De Beers and the Russian firm Alrosa. After a recent purchase of the Finsch mine from De Beers Petra is interesting, says Tempus.If the global economy avoids meltdown and the Chinese wedding market behaves as some expect then there could well be a huge demand for diamonds at a time when no one can find anymore to mine. A speculative buy, says Tempus.BSPlease note: Digital Look provides a round-up of news, tips and information that is impacting share prices and the market. Digital Look cannot take any responsibility for information provided by third parties. This is for your general information only as not intended to be relied upon by users in making an investment decision or any other decision. Please obtain a copy of the relevant publication and carry out your own research before considering acting on any of this information.