Arctic sea ice extent through most of April changed very little. Only at the end of the month did extent begin to decline. Because the month started with unusually low extent, however, the average ...

Abstract: This article presents an efficient synthesis method for generating vortex beams based on donut-shaped orbital angular momentum (OAM) metasurfaces. It not only allows one to synthesize the ...

Tiny bone fragments from Alaska suggest birds started breeding and nesting in the Arctic 30 million years earlier than ...