CHICAGO -- Power industry, meet the natural gas industry. Pipeline companies, meet some of your best customers, the electric generators. Of course, no such formal introductions are necessary. The two important segments of the nation's energy sector are well acquainted and have existed alongside each other on some level for decades. But efforts to foster improved coordination are taking on heightened importance as aging coal plants are retiring and the shale gas boom is increasing the reliance on gas and interstate pipelines and shaking up the already dynamic and complex energy world.