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electron tube

(Encyclopedia)CE5 Triode electron tube electron tube, device consisting of a sealed enclosure in which electrons flow between electrodes separated either by a vacuum (in a vacuum tube) or by an ionized gas at l...

halogen

(Encyclopedia)halogen hălˈəjĕn [key] [Gr.,=salt-bearing], any of the chemically active elements found in Group 17 of the periodic table; the name applies especially to fluorine (symbol F), chlorine (Cl), bromin...

arch

(Encyclopedia)CE5 Arches arch, the spanning of a wall opening by means of separate units (such as bricks or stone blocks) assembled into an upward curve that maintains its shape and stability through the mutual...

slime mold

(Encyclopedia)slime mold or slime fungus, a heterotrophic organism once regarded as a fungus but later classified with the Protista. In a recent system of classification based on analysis of nucleic acid (genetic m...

bacteriophage

(Encyclopedia)bacteriophage băktērˈēəfājˌ [key], virus that infects bacteria and sometimes destroys them by lysis, or dissolution of the cell. Bacteriophages, or phages, have a head composed of protein, an i...

rabbit

(Encyclopedia)rabbit, name for herbivorous mammals of the family Leporidae, which also includes the hare and the pika. Rabbits and hares have large front teeth, short tails, and large hind legs and feet adapted for...

concrete

(Encyclopedia)concrete, structural masonry material made by mixing broken stone or gravel with sand, cement, and water and allowing the mixture to harden into a solid mass. The cement is the chemically active eleme...

conduction

(Encyclopedia)conduction, transfer of heat or electricity through a substance, resulting from a difference in temperature between different parts of the substance, in the case of heat, or from a difference in elect...

pyramid, structure

(Encyclopedia)pyramid. The true pyramid exists only in Egypt and Sudan, though the term has also been applied to similar structures in other countries. Egyptian pyramids are square in plan and their triangular side...

parrot

(Encyclopedia)parrot, common name for members of the order Psittaciformes, comprising nearly 400 species of colorful birds, pantropical in distribution, including the parakeets. Parrots have large heads and short n...