Word: ultraviolet
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...ultraviolet spectrometer constructed at the Harvard College Observatory has given Harvard astronomers over 4,000 pictures of the sun, revealing new information about its distribution of elements and temperature...
...pictures are the first ever taken of the sun in ultraviolet light from a satellite...
...cells are stimulated to produce more melanin-and a suntan. The black races (Negro, Bushman-Hottentot and Australoid), with a more abundant supply of melanin, are in effect, perpetually tanned. Members of the white race are transparent-skinned in winter, when they must make the most of the limited ultraviolet avail able to synthesize vitamin D, but they take a tan in summer, when they might suffer from an excess. There are other bits of confirmatory evidence: the only relatively dark-skinned people in high latitudes are the Eskimos, who get all the vitamin D they need from fish-liver...
...carries some in his hand throughout life. Babies of all races are lighter than adults, presumably reflecting nature's provision for early vitamin D needs. And people of all races have pale, unpigmented palms and soles. Since these parts have extra keratin and are not exposed to ultraviolet, they need no melanin protection against excess vitamin D synthesis...
...Exceptions: the liver oils of some fish, notably cod and halibut; egg yolks (small quantities) and milk (minute amounts). Milk and many other foods are now "vitamin D enriched" by ultraviolet irradiation...