An air pressure wave which moves ahead of the main blast wave for some distance as a result of a nuclear (or atomic) explosion of appropriate yield and low burst height over a heat-absorbing (or dusty) surface The pressure at the precursor front increases more gradually than in a true (or ideal) shock wave, so that the behavior in the precursor region is said to be nonideal See Blast wave, Shock front, Shock wave
In photochemistry, a compound antecedent to a pollutant For example, volatile organic com- pounds (VOCs) and nitric oxides of nitrogen react in sunlight to form ozone or other photochemical oxidants As such, VOCs and oxides of nitrogen are precursors
the reactants used in industrial semiconductor manufacture to make the desired product; for instance, ArH3 is often the precursor for the Arsenic in GaAs devices
a substance from which another substance is formed (especially by a metabolic reaction)
A precursor of something is a similar thing that happened or existed before it, often something which led to the existence or development of that thing. He said that the deal should not be seen as a precursor to a merger. something that happened or existed before something else and influenced its development precursor of/to (praecursor, from praecurrere )
Any directly emitted pollutant that, when released into the atmosphere, forms or causes to be formed or contributes to the formation of a secondary pollutant for which an ambient air quality standard has been adopted, or whose presence in the atmosphere will contribute to the violation of one or more ambient air quality standards
For carbon fibers, the rayon, PAN or pitch fibers from which carbon fibers are made
A chemical compound which is released into the atmosphere, undergoes a chemical change, and leads to a new (secondary) pollutant VOCs are precursors to ozone
Any chemical reactant which takes part at any stage in the production by whatever method of a toxic chemical