Cars that run on natural gas are touted as efficient and environmentally friendly, but getting enough gas onboard to make them practical is a hurdle. A new study led by researchers at Rice University promises to help.  Rather than shoehorn bulky high-pressure tanks like those used in buses and trucks into light vehicles, the Department of Energy (DOE) encourages scientists to look at new materials that can store compressed natural gas (CNG) at low pressure and at room temper