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Gram's stain

(Encyclopedia)Gram's stain, laboratory staining technique that distinguishes between two groups of bacteria by the identification of differences in the structure of their cell walls. The Gram stain, named after its...

gram-calorie

(Encyclopedia)gram-calorie: see calorie.

weight-average molecular weight

(Encyclopedia)weight-average molecular weight: see molecular weight. ...

weight lifting

(Encyclopedia)weight lifting, international sport, also a training technique for athletes in other sports. From the earliest times men have lifted weights as a test of strength. Long popular as a competitive sport ...

atomic clock

(Encyclopedia)atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a...

atomic mass

(Encyclopedia)atomic mass, the mass of a single atom, usually expressed in atomic mass units (amu). Most of the mass of an atom is concentrated in the protons and neutrons contained in the nucleus. Each proton or n...

atomic bomb

(Encyclopedia)atomic bomb or A-bomb, weapon deriving its explosive force from the release of nuclear energy through the fission (splitting) of heavy atomic nuclei. The first atomic bomb was produced at the Los Alam...

atomic number

(Encyclopedia)atomic number, often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a c...