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free radical

(Encyclopedia)free radical, in chemistry, a molecule or atom that contains an unpaired electron but is neither positively nor negatively charged. Free radicals are usually highly reactive and unstable. They are pro...

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...

Binnig, Gerd

(Encyclopedia)Binnig, Gerd gĕrt bĭnˈĭkh [key], 1947–, German physicist, Ph.D. Univ. of Frankfurt, 1978. At the IBM Research Laboratory in Zürich, Binnig and fellow researcher Heinrich Rohrer built the first ...

microscope

(Encyclopedia)CE5 Compound microscope microscope, optical instrument used to increase the apparent size of an object. The electron microscope, which is not limited by the powers of optical lenses and light,...

Elementary Particles (table)

(Encyclopedia)Elementary Particles Leptons Quarks1 Gauge Bosons Some Sample Hadrons For each of these particles, except the photon, gluon, and Z-boson, there is an antiparticle with the same mass and op...

Klug, Sir Aaron

(Encyclopedia)Klug, Sir Aaron klo͞og [key], 1926–2018, British biochemist, b. Lithuania. Raised and educated in South Africa, he moved to England and completed his doctorate at Trinity College, Cambridge, in 195...

anion

(Encyclopedia)anion ănˈīˌən [key], atom or group of atoms carrying a negative charge. The charge results because there are more electrons than protons in the anion. Anions can be formed from nonmetals by reduc...

Claude, Albert

(Encyclopedia)Claude, Albert älbârrˈ klōd [key], 1899–1983, Belgian biologist, b. Longlier, M.D., Univ. of Liège, 1928. He joined the Rockefeller Institute (now Rockefeller Univ.) in 1929 and spent his entir...

exclusion principle

(Encyclopedia)exclusion principle, physical principle enunciated by Wolfgang Pauli in 1925 stating that no two electrons in an atom can occupy the same energy state simultaneously. The energy states, or levels, in ...

rectifier

(Encyclopedia)rectifier, component of an electric circuit used to change alternating current to direct current. Rectifiers are made in various forms, all operating on the principle that current passes through them ...