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Zewail, Ahmed Hassan

(Encyclopedia)Zewail, Ahmed Hassan, 1946–2016, Egyptian-American chemist, b. Damanhur, Egypt, Ph.D. Univ. of Pennsylvania, 1974. He became a U.S. citizen in 1982. A professor at the California Institute of Techno...

Bessemer, Sir Henry

(Encyclopedia)Bessemer, Sir Henry bĕsˈəmər [key], English engineer and inventor, b. Charleton, Hertfordshire. He made experiments to obtain stronger material for gun manufacture and discovered the basic princip...

Fourteenth Amendment

(Encyclopedia)Fourteenth Amendment, addition to the U.S. Constitution, adopted 1868. The amendment comprises five sections. Section 2 provides for apportionment of membership in the House of Representatives on th...

ectoderm

(Encyclopedia)ectoderm, layer of cells that covers the surface of an animal embryo after the process of gastrulation has occurred. This outer layer, together with the endoderm, or inner layer, is present in all ear...

endocytosis

(Encyclopedia)endocytosis ĕnˌdōsītōˈsəs [key], in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm...

saturated fat

(Encyclopedia)saturated fat, any solid fat that is an ester of glycerol and a saturated fatty acid. The molecules of a saturated fat have only single bonds between carbon atoms; if double bonds are present in the f...

selection

(Encyclopedia)selection. In Darwinism, the mechanism of natural selection is considered of major importance in the process of evolution. Popular formulations sometimes envisage a struggle for existence in which dir...

transplanting

(Encyclopedia)transplanting, in horticulture, the process of removing a plant from the place where it has been growing and replanting it in another. The major requirement in transplanting (especially of larger plan...

casting

(Encyclopedia)casting or founding, shaping of metal by melting and pouring into a mold. Most castings, especially large ones, are made in sand molds. Sand, mixed with a binder to hold it together, is pressed around...

audiovisual education

(Encyclopedia)audiovisual education, educational instruction by means of materials that use the senses of sight and hearing to stimulate and enrich learning experiences. The successful use of motion pictures and ot...