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gum, colloidal plant substance

(Encyclopedia)gum, term commonly applied to any of a wide variety of colloidal substances somewhat similar in appearance and general characteristics, exuded by or extracted from plants. In this classification, howe...

aquarium

(Encyclopedia)aquarium, name for any supervised exhibit of aquatic animals and plants. Aquariums are known to have been constructed in ancient Rome, Egypt, and Asia. Goldfish have been bred in China for several hun...

photochemistry

(Encyclopedia)photochemistry, study of chemical processes that are accompanied by or catalyzed by the emission or absorption of visible light or ultraviolet radiation. A molecule in its ground (unexcited) state can...

cerium

(Encyclopedia)cerium sērˈēəm [key] [from the asteroid Ceres], metallic chemical element; symbol Ce; at. no. 58; at. wt. 140.116; m.p. 799℃; b.p. 3,426℃; sp. gr. 6.77 at 25℃; valence +3 or +4. Cerium is a ...

supernova

(Encyclopedia)supernova, a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. Supernovas are the principal distr...

lungs

(Encyclopedia)lungs, elastic organs used for breathing in vertebrate animals, excluding most fish, which use gills, and a few amphibian species that respire through the skin. The word is sometimes applied to the re...

lanthanum

(Encyclopedia)lanthanum lănˈthənəm [key] [Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.90547; m.p. about 920℃; b.p. about 3,460℃; sp. gr. 6.19 at 25℃; valence +3. Lan...

Kuiper, Gerard Peter

(Encyclopedia)Kuiper, Gerard Peter or Gerrit Pieter gĕrˈĭt pēˈtər kīˈpər [key], 1905–73, American astronomer, b. the Netherlands. Kuiper is considered to be the father of modern planetary science for his...

oils

(Encyclopedia)oils, term commonly used to indicate a variety of greasy, fluid substances that are, in general, viscous liquids at ordinary temperatures, less dense than water, insoluble in water but soluble in alco...

histidine

(Encyclopedia)CE5 histidine hĭsˈtĭdēn [key], organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. Histidine is the direct pr...