Where have all the swallows gone?

Extinction: the permanent loss of a species. It is deeply troubling—and scientists and birdwatchers are ringing the alarm about a bird species that only a few decades ago was widespread and very common.

21 hours ago 4.9 / 5 (9) 3

Designing exascale computers

"Imagine a heart surgeon operating to repair a blocked coronary artery. Someday soon, the surgeon might run a detailed computer simulation of blood flowing through the patient's arteries, showing how millions ...

21 hours ago 5 / 5 (13) 2