WHEN the late Dr. R. J. Lythgoe, of University College, London, about 1935, took up research on visual purple--the photosensitive substance of the retinal rods-our knowledge in this field had ...

New research has revealed the distribution of dark matter in never before seen detail, down to a scale of 30,000 light-years. The observed distribution fluctuations provide better constraints on ...

Purple nonsulfur bacteria are strongly photoheterotrophs, even if they are capable of photoautotrophy, and are equipped for living in dark environments. Purple sulfur bacteria can be found in ...