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welding

(Encyclopedia)welding, process for joining separate pieces of metal in a continuous metallic bond. Cold-pressure welding is accomplished by the application of high pressure at room temperature; forge welding (forgi...

tree frog

(Encyclopedia)tree frog, name for any of the small tree- or shrub-inhabiting frogs of the family Hylidae, characterized by an adhesive disk on the tip of each of the clawlike toes. This family has about 300 species...

trichina

(Encyclopedia)trichina trĭkīˈnə [key], common name for species of roundworm of the phylum Nematoda. The species Trichinella spiralis is an important parasite, occurring in rats, pigs, and man, and is responsibl...

tempering

(Encyclopedia)tempering, process involving slow and moderate heating to increase the hardness and toughness of metals that have undergone previous heat treatment. Metals are usually hardened (see hardening) by bein...

Sheffield plate

(Encyclopedia)Sheffield plate, metalware of copper, silver-plated by fusion, originated at Sheffield, England. This process of plating was discovered c.1742 by a Sheffield cutler, Thomas Boulsover, who found while ...

dark matter

(Encyclopedia)dark matter, material that is believed to make up nearly 27% of the mass of the universe but is not readily visible because it neither emits nor reflects electromagnetic radiation, such as light or ra...

adaptation

(Encyclopedia)adaptation, in biology, has several meanings. It can mean the adjustment of living matter to environmental conditions and to other living things either in an organism's lifetime (physiological adaptat...

states of matter

(Encyclopedia)states of matter, forms of matter differing in several properties because of differences in the motions and forces of the molecules (or atoms, ions, or elementary particles) of which they are composed...

dissociation

(Encyclopedia)dissociation, in chemistry, separation of a substance into atoms or ions. Thermal dissociation occurs at high temperatures. For example, hydrogen molecules (H2) dissociate into atoms (H) at very high ...

compression

(Encyclopedia)compression, external stress applied to an object or substance, tending to cause a decrease in volume (see pressure). Gases can be compressed easily, solids and liquids to a very small degree if at al...