It may be that the theory, expressed simply, gives rise to huge numbers of particle types. (discovermagazine.com)
Using that information, they were able to discriminate various particle types and distinctive features of optical arrangements. (sciencedaily.com)
A majority of sub-micrometer particles (< 1 µm in diameter, PM1) originated from diesel engine emissions whereas another sub-micrometer particle type originated from the combustion products of explosives (e.g. nitrate and ammonium). (en.ilmatieteenlaitos.fi)