Heat always spontaneously flows from a hotter place to a colder one – so says the second law of thermodynamics. But within an extremely sparse gas, the opposite may be possible, with heat flowing from ...

Tear gas tends to be classified as a “chemical irritant,” and the term itself, per the Centers for Disease Control, is often used interchangeably to refer to a variety of substances, including pepper ...

Selected members of the research team (left to right): Xiaosu Ding (Purdue University), Satya S. Patra (Purdue University), Connor Keech (Durag Group), Jinglin Jiang (Purdue University), Brandon E.

A gas becomes a plasma when the atoms it’s made of become so hot that their negatively charged electrons split apart from their positively charged nuclei. Now that the charged particles are separated ...