Mergers and acquisitions are perking up across sectors as confidence in the economy improves. With enterprise price tags relatively low and private equity firms shut out, corporations with access to capital are making strategic acquisitions to bolster their competitive positions. Just last week, Agilent Technologies ( ) agreed to buy Varian ( ) for $1.5 billion. Also in the technology space, International Business Machines ( ) agreed to buy Chicago-based predictive analysis software provider SPSS ( ) for $1.2 billion. In the health care sector, France's Sanofi Aventis ( ) is forking out $4 billion to Merck ( ) to take full-control of its 50-50 animal health joint venture Merial. Sanofi is also buying India-based vaccine maker Shantha Biotechnics for $781 million. In energy, pipeline operator Targa Resources Partners ( ) is acquiring the natural gas liquids business of Targa Resources for $530 million. Wireless services provider Sprint Nextel ( ) is buying Virgin Mobile USA ( ) for $420 million.