a galaxy that emits usually large amounts of energy from a very compact central source, such as seyfert galaxies, radio galaxies, and quasars also called active galactic nucleus
a galaxy emitting unusually high quant-ties of radiation from an active galactic nucleus at its center. some active galaxies emit more energy in radio wavelengths than they do visible light. seyfert galaxies are examples of active galaxies. see more at galactic nucleus.
- Active hydrogen
. hydrogen in the form of single atoms, rather than molecules, which makes it extremely reactive.
- Active hyperemia
active hyperemia active hyperemia n. hyperemia due to increased flow of arterial blood in dilated capillaries. also called arterial hyperemia, fluxionary hyperemia. historical examples the first two produce venous or p-ssive hyperemia, and the third, arterial or active hyperemia. surgery, with special reference to podiatry maximilian stern
- Active ingredient
noun the chemically active part of a chemical compound contemporary examples i take a triptan called treximet, which also includes a dose of the painkiller naproxen, the active ingredient in aleve. presidents can have migraines dana goldstein july 19, 2011 the national inst-tute on drug abuse reports the prevalence of mdma (the active ingredient in […]
- Active language i
active language i tool, mathematics an early interactive mathematics system for the xds 930 at the university of california at berkeley. [“active language i”, r. de vogelaere in interactive systems for experimental applied mathematics, a-p 1968]. (1994-11-08)
- Active layer
(in arctic or subarctic regions) the layer of soil, above the permafrost, that thaws during the summer. historical examples in the formation of the organs of sense the nervous layer shews itself throughout as the active layer. the works of francis maitland balfour, volume iii (of 4) francis maitland balfour