119
extraction
multinational expeditions have increased the knowledge of the world
oceans considerably. At present such large-scale expeditions are also prepared through the Scientific Committee of Ocean Research (SCaR), of the
ICSU (International Council of Scientific Unions) and the International
Oceanographic Committee (laC) located at Unesco. The objectives are
(through multi-vessel expeditions) to study predetermined subjects in predetermined ocean regions.
exploitation pattern the relative fishing mortality rate exercised by the fishery on the
different age groups within a population.
exploitation rate (E) the fraction of the total mortality (Z) of a stock that is
caused by fishing (F) : E = FIZ.
exploration of the ocean -7ocean exploration.
exposure monitoring -7monitoring.
external digestion digestion outside the organism. Microorganisms often produce extracellular enzymes and some animals bring digestive enzymes outside themselves on their prey. As a result macromolecules are split to smaller subunits, which can be easily taken up by the organism.
extinction (1) (biol.) the disappearance of certain animal or plant species in the
course of evolution. Such extinctions have certainly something to do with
changing environmental conditions during geological time. Extinctions in
the past were not randomly distributed but largely confined to short periods. On land the extinction of the large reptiles at the end of the Cretaceous
is the best known. -7mass mortality, iridium-rich level, microfossils, and biohorizon; (2)
(phys.) generally the decrease of energy by dissipation in a beam of radiating energy: light, sound, or mechanical energy (waves). Scattering of energy
from the beam is not considered extinction, but it also contributes to the
energy decrease in the direct beam. Extinction oflight is also called absorption. -7optics.
extraction (trace metals) the transfer of substances into another liquid medium.
The technique of extraction can be applied to concentrate small amounts of
trace elements from seawater. Problems which can occur in the determination of trace elements in seawater with atomic absorption spectrophotometry are very low trace metal concentrations (nM) and high salt matrix. The
method is based on the complexation of trace elements with complex formers
viz. ammonium pyrrolydine dithiocarbonate (APDC) and diethylammonium diethyldithiocarbonate (DDDC). These complexes are extracted into an
organic solvent, viz. freon or methyl-isobutylketone (MIBK). After extrac-
extraction
multinational expeditions have increased the knowledge of the world
oceans considerably. At present such large-scale expeditions are also prepared through the Scientific Committee of Ocean Research (SCaR), of the
ICSU (International Council of Scientific Unions) and the International
Oceanographic Committee (laC) located at Unesco. The objectives are
(through multi-vessel expeditions) to study predetermined subjects in predetermined ocean regions.
exploitation pattern the relative fishing mortality rate exercised by the fishery on the
different age groups within a population.
exploitation rate (E) the fraction of the total mortality (Z) of a stock that is
caused by fishing (F) : E = FIZ.
exploration of the ocean -7ocean exploration.
exposure monitoring -7monitoring.
external digestion digestion outside the organism. Microorganisms often produce extracellular enzymes and some animals bring digestive enzymes outside themselves on their prey. As a result macromolecules are split to smaller subunits, which can be easily taken up by the organism.
extinction (1) (biol.) the disappearance of certain animal or plant species in the
course of evolution. Such extinctions have certainly something to do with
changing environmental conditions during geological time. Extinctions in
the past were not randomly distributed but largely confined to short periods. On land the extinction of the large reptiles at the end of the Cretaceous
is the best known. -7mass mortality, iridium-rich level, microfossils, and biohorizon; (2)
(phys.) generally the decrease of energy by dissipation in a beam of radiating energy: light, sound, or mechanical energy (waves). Scattering of energy
from the beam is not considered extinction, but it also contributes to the
energy decrease in the direct beam. Extinction oflight is also called absorption. -7optics.
extraction (trace metals) the transfer of substances into another liquid medium.
The technique of extraction can be applied to concentrate small amounts of
trace elements from seawater. Problems which can occur in the determination of trace elements in seawater with atomic absorption spectrophotometry are very low trace metal concentrations (nM) and high salt matrix. The
method is based on the complexation of trace elements with complex formers
viz. ammonium pyrrolydine dithiocarbonate (APDC) and diethylammonium diethyldithiocarbonate (DDDC). These complexes are extracted into an
organic solvent, viz. freon or methyl-isobutylketone (MIBK). After extrac-