Danaher Corp announced it would buy air and water-filter maker Pall Corp in a $13.8 billion deal, pipeline operator Williams Cos said it would buy affiliate Williams Partners LP also for about $13.8 billion in stock and Verizon Communications Inc said it would buy AOL Inc in a $4.4 billion deal. Worldwide M&A activity is up 30 percent so far this year compared to the same period in 2014, with $1.4 trillion worth of deals having been struck.