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catalyst

(Encyclopedia)catalyst, substance that can cause a change in the rate of a chemical reaction without itself being consumed in the reaction; the changing of the reaction rate by use of a catalyst is called catalysis...

physics

(Encyclopedia)physics, branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this na...

respiration

(Encyclopedia)CE5 Respiratory system respiration, process by which an organism exchanges gases with its environment. The term now refers to the overall process by which oxygen is abstracted from air and is tran...

coronagraph

(Encyclopedia)coronagraph kərōˈnəgrăfˌ [key], device invented by the French astronomer B. Lyot (1931) for the purpose of observing the corona of the sun and solar prominences occurring in the chromosphere. Be...

Alentejo

(Encyclopedia)Alentejo əlāntāˈzho͝o [key], historic province, SE Portugal, now divided into Altro (Upper) Alentejo (4,888 sq mi/12,660 sq km) and Baixo (Lower) Alentejo (5,318 sq mi/13,774 sq km). The capital ...

Davidson, George

(Encyclopedia)Davidson, George, 1825–1911, American geographer and astronomer, b. England. From 1845 to 1895 he was on the staff of the U.S. Coast and Geodetic Survey. He charted (1850–60) the U.S. Pacific coas...

‘Oumuamua

(Encyclopedia)‘Oumuamua ōmo͞oˈəmo͞oˈə [key], officially 1I/2017 U1 (‘Oumuamua), interstellar object, the first to be discovered in the solar system. Highly variable in brightness, it also is highly and u...

Julian Day calendar

(Encyclopedia)Julian Day calendar, system of astronomical dating that allows the difference between two dates to be calculated more easily than conventional civil calendars with their uneven months. It was devised ...

nuclear physics

(Encyclopedia)nuclear physics, study of the components, structure, and behavior of the nucleus of the atom. It is especially concerned with the nature of matter and with nuclear energy. ...

Ritz, Walter

(Encyclopedia)Ritz, Walter, 1878–1909, Swiss physicist. He taught at the universities of Zürich and Göttingen. Ritz's combination principle, confirmed by later research, stated that the frequencies of spectral ...