Nanopowders are agglomerates of ultrafine particles, nanoparticles, or nanoclusters. The danger of ingesting microscopic particles remained. Entanglement is usually created by direct interactions between subatomic particles. The chalk particles entrap some impurities and absorb others. The reacting gases adsorb onto active sites on the iron particles. Electric charge is a characteristic property of many subatomic particles. Synchrotrons were originally designed for use by high-energy physicists studying subatomic particles and cosmic phenomena. Neutrophils are phagocytes, capable of ingesting microorganisms or particles. The fallout had the appearance of small flaky dust particles. Radioactivity is the ability of a substance to emit high energy particles. Lithium is also used as a source for alpha particles, or helium nuclei. This process gives a suspension of polymer particles. QED vacuum is a state with no matter particles (hence the name), and no photons. This prevents it from dissociating or forming clusters with other particles. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles.