Columbia Encyclopedia

Search results

493 results found

feedback

(Encyclopedia)CE5 Basic feedback control system feedback, arrangement for the automatic self-regulation of an electrical, mechanical, or biological system by returning part of its output as input. A simple exam...

pit viper

(Encyclopedia)pit viper, poisonous snake of the family Crotalidae, primarily a New World family. Like the Old World true vipers (family Viperidae), pit vipers have long, hollow, erectile fangs that are folded back ...

neutron star

(Encyclopedia)neutron star, extremely small, extremely dense star, with as much as double the sun's mass but only a few miles in radius, in the final stage of stellar evolution. Astronomers Baade and Zwicky predict...

parthenogenesis

(Encyclopedia)parthenogenesis pärˌthənōjĕnˈəsĭs [key] [Gr.,=virgin birth], in biology, a form of reproduction in which the ovum develops into a new individual without fertilization. Natural parthenogenesis ...

samarium

(Encyclopedia)samarium səmârˈēəm [key], metallic chemical element; symbol Sm; at. no. 62; at. wt. 150.36; m.p. 1,072℃; b.p. 1,791℃; sp. gr. 7.54 at 20℃; valence +2 or +3. Samarium is a lustrous silver-wh...

red giant

(Encyclopedia)red giant, star that is relatively cool but very luminous because of its great size. All normal stars are expected to pass eventually through a red-giant phase as a consequence of stellar evolution. A...

niobium

(Encyclopedia)niobium nīōˈbēəm [key], metallic chemical element; symbol Nb; at. no. 41; at. wt. 92.90638; m.p. about 2,468℃; b.p. 4,742℃; sp. gr. 8.57 at 20℃; valence +2, +3, +4, or +5. Niobium is a rare...

nonmetal

(Encyclopedia)nonmetal, chemical element possessing certain properties by which it is distinguished from a metal. In general, this distinction is drawn on the basis that a nonmetal tends to accept electrons and for...

neptunium

(Encyclopedia)neptunium nĕpto͞oˈnēəm [key], radioactive chemical element; symbol Np; at. no. 93; mass number of most stable isotope 237; m.p. about 640℃; b.p. 3,902℃ (estimated); sp. gr. 20.25 at 20℃; va...

ceramics

(Encyclopedia)ceramics sərămˈĭks [key], materials made of nonmetallic minerals that have been permanently hardened by firing at a high temperature, or objects made of such materials. Most ceramics resist heat a...

Browse by Subject