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Fixing the Global Nitrogen Problem

Humanity depends on nitrogen to fertilize croplands, but growing global use is damaging the environment and threatening human health. How can we chart a more sustainable path?

By Alan R. Townsend and Robert W. Howarth

"Impossible" Colors: See Hues That Can't Exist

People can be made to see reddish green and yellowish blue—colors forbidden by theories of color perception. These and other hallucinations provide a window into the phenomenon of visual opponency

By Vincent A. Billock and Brian H. Tsou

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