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Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude.
Some express the concentrations as ppmv (parts per million by volume) and some express the concentrations as mg/m 3 (milligrams per cubic meter), while others require adjusting or correcting the concentrations to reference conditions of moisture content, oxygen content or carbon dioxide content.
In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...
PPB can stand for: Production possibility boundary , a concept in economics; Parts per billion, describing small values of miscellaneous dimensionless quantities; Portland Police Bureau, in Portland, Oregon, U.S. Partido Progressista Brasileiro, former name of Progressive Party of Brazil; Pleuropulmonary blastoma, a type of lung cancer
The turret is fitted with the 2K23 system, which consists of an autoloader with 22 rounds (the remaining 18 rounds are stored in the hull), a 1V539 ballistic computer, a crosswind sensor, a 2E52-2 stabilising system, a 1D16-3 laser rangefinder, a 1K13-2 gunner's sight/guidance device, a PPB-1 gunner's sight and an OU-5-1 IR searchlight ...