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    • Biological Unit for Vitamin A - Nature

      Nature· 3 days ago

      VITAMIN A is unique in that the unit by which it has been defined has been measured with reference to a precursor, β-carotene, and not to vitamin A itself ...

    • Surveying for Archæologists 1 - Nature

      Nature· 3 days ago

      II. Horizons—Earthly and Heavenly. SO long as we are dealing with measurements of azimuth on the horizon, and altitude above the horizon, we are considering only our position on the earth—on ...

    • Societies and Academies - Nature

      Nature· 3 days ago

      Euglena viridis and some other micro-organisms, when placed in shallow vessels or narrow tubes in the dark, become aggregated into peculiar network-like patterns or more or less well-