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liquid air

(Encyclopedia)liquid air, ordinary air that has been liquefied by compression and cooling to extremely low temperatures (see liquefaction). Its commercial preparation involves purification by washing to remove solu...

aerobics

(Encyclopedia)aerobics ârōˈbiks [key], [Gr.,=with oxygen], system of endurance exercises that promote cardiovascular fitness by producing and sustaining an elevated heart rate for a prolonged period of time, the...

Semenza, Gregg Leonard

(Encyclopedia)Semenza, Gregg Leonard, 1956–, American oncologist and molecular biologist, b. New York City, Ph.D. Univ. of Pennsylvania, 1984. Semenza has spent his entire career at the Johns Hopkins School of Me...

Kaelin, William George, Jr.

(Encyclopedia)Kaelin, William George, Jr., 1957–, American oncologist, b. New York City, M.D. Duke Univ., 1982. He has spent his entire career at the Dana-Farber Cancer Institute, Boston, Mass., and also is a pro...

nitro group

(Encyclopedia)nitro group, in chemistry, functional group that consists of a nitrogen atom joined to two oxygen atoms. Compounds that contain a nitro group, e.g., picric acid and trinitrotoluene (TNT), are called n...

formula weight

(Encyclopedia)formula weight, in chemistry, a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a formula by the number of atoms of that element present in the formula, an...

potassium nitrate

(Encyclopedia)potassium nitrate, chemical compound, KNO3, occurring as colorless, prismatic crystals or as a white powder; it is found pure in nature as the mineral saltpeter, or niter. (The name saltpeter is also ...

chemical reaction

(Encyclopedia)chemical reaction, process by which one or more substances may be transformed into one or more new substances. Energy is released or is absorbed, but no loss in total molecular weight occurs. When, fo...

compound

(Encyclopedia)compound, in chemistry, a substance composed of atoms of two or more elements in chemical combination, occurring in a fixed, definite proportion and arranged in a fixed, definite structure. A compound...

O

(Encyclopedia)O, 15th letter of the alphabet. It is a usual symbol for a mid-back, rounded vowel, rather like the first part of oi. Such a vowel was represented by omicron [Gr.,=little o], its formal and positional...