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Ectoprocta

(Encyclopedia)CE5 Bugula, a moss animal, representative of the phylum Ectoprocta Ectoprocta ĕkˌtəprŏkˈtə [key], phylum of sessile, colonial aquatic animals (commonly known as moss animals or oryonzoans). ...

meteor shower

(Encyclopedia)meteor shower, increase in the number of meteors observed in a particular part of the sky. The trails of the meteors of a meteor shower all appear to be traceable back to a single point in the sky, kn...

kinetic-molecular theory of gases

(Encyclopedia)kinetic-molecular theory of gases, physical theory that explains the behavior of gases on the basis of the following assumptions: (1) Any gas is composed of a very large number of very tiny particles ...

photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...

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 ...

californium

(Encyclopedia)californium kălˈĭfôrˌnēəm [key] [from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900℃; b...

brittlestar

(Encyclopedia)brittlestar, common name for echinoderms belonging to the class Ophiuroidea. The name is derived from their habit of breaking off arms as a means of defense. New arms are easily regenerated. They are ...

sea cucumber

(Encyclopedia)sea cucumber, any of the flexible, elongated echinoderms belonging to the class Holothuroidea. Although sea cucumbers have the basic echinoderm radial symmetry (see Echinodermata), they do not have ar...

Pestalozzi, Johann Heinrich

(Encyclopedia)Pestalozzi, Johann Heinrich yōˈhän hīnˈrĭkh pĕsˌtälôtˈsē [key], 1746–1827, Swiss educational reformer, b. Zürich. His theories laid the foundation of modern elementary education. He stu...

atomic weight

(Encyclopedia)atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass, which is the mass of any individual isotope. Althoug...