LONDON -- The FTSE 100 (FTSEINDICES:^FTSE) started hesitantly, but as of 7:55 a.m. EST it's up 0.38% to 6,404 points, having earlier broken the 6,400 level to set a new 52-week high of 6,412 -- its highest level since 2008. Positive results from some FTSE 100 companies, together with improving economic sentiment, appear to lie behind the rise.

So which shares are on the up? Here are three constituents of the indexes rising today.

BT (LSE:BT-A) (NYSE:BT)
Shares in BT Group perked up 1.5% to 281 pence on the news that the telecom giant has been successful in its bidding for 4G spectrum. For the sum of 186 million pounds, BT has secured the rights to 2x15 MHz of FDD and 20 MHz of TDD 2.6 GHz spectrum, with the license good for at least 20 years. According to chief executive Ian Livingstone, the bandwidth will be used to complement BT's existing strategy, rather than to build a new national network.

The auctions, which saw rival Vodafone also succeed in its bid, raised a total of 2.34 billion pounds -- a far cry from the 22 billion pounds raised by 3G auctions in 2000.

Rexam (LSE:REX)
Final results from Rexam boosted the share price by 5% to 500 pence this morning. Sales at the consumer packaging company rose by 2% to 4.3 billion pounds, with underlying pre-tax profit up 1% to 418 million pounds and earnings per share up 5% to 35.5 pence. A total dividend of 15.2 pence was announced, up 6% and representing a yield of 3%.

The period saw the disposal of the firm's personal-care division, with 395 million pounds being returned to shareholders.

Spectris (LSE:SXS)
Spectris shares have picked up 1.2% to 2,455 pence, taking the price up more than 40% over the past year to a new 52-week high after the instrumentation and controls developer released full-year results.

At constant exchange rates, sales for the year to December 2012 were up 13% to 1.23 billion pounds, with adjusted pre-tax profit up the same percentage to 217 million pounds and adjusted earnings per share up 11% to 137.5 pence. The company lifted its dividend by 16% to 39 pence per share for a yield of 1.6%.

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Alan does not own any shares mentioned in this article. The Motley Fool has recommended shares in Vodafone. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.