National security, unlocked. Each Thursday, host Mary Louise Kelly and a team of NPR correspondents discuss the biggest national security news of the week. With decades of reporting from battlefields ...

In engineering classrooms, the disconnect between rigorous mathematical concepts and their practical applications can hinder ...

EPA offices and laboratories, and outside organizations, have developed approved methods for measuring the concentration of a substance or pollutant. Below are categories of methods. Learn about how ...

All methods of analysis must be validated, and peer reviewed prior to being issued. Each EPA office is responsible for ensuring minimum method validation and peer review criteria have been achieved.