(Encyclopedia) episomeepisomeĕpˈĭsōm [key], unit of genetic material composed of a series of genes that sometimes has an independent existence in a host cell and at other times is integrated into a…
(Encyclopedia) Green, Thomas Hill, 1836–82, English idealist philosopher. Educated at Oxford, he was associated with the university all his life. He was professor of moral philosophy there from 1878…
(Encyclopedia) half-life, measure of the average lifetime of a radioactive substance (see radioactivity) or an unstable subatomic particle. One half-life is the time required for one half of any…
(Encyclopedia) Andronicus I (Andronicus Comnenus)Andronicus Iăndrənīˈkəs kŏmnēˈnəs [key], 1120?–1185, Byzantine emperor (1183–85), nephew of John II. He acceded to the throne by strangling his cousin…
(Encyclopedia) mutation, in biology, a sudden, random change in a gene, or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any…
(Encyclopedia) magic, in religion and superstition, the practice of manipulating and controlling the course of nature by preternatural means. Magic is based upon the belief that the universe is…
(Encyclopedia) induction, in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a…
(Encyclopedia) James, William, 1842–1910, American philosopher, b. New York City, M.D. Harvard, 1869; son of the Swedenborgian theologian Henry James and brother of the novelist Henry James. In 1872…
(Encyclopedia) ultraviolet radiation, invisible electromagnetic radiation between visible violet light and X rays; it ranges in wavelength from about 400 to 4 nanometers and in frequency from about…
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