Bimodal Mass Distribution Research Articles

Scavenging of a coagulating fine aerosol by a coarse particle mode

Aerosol emissions from coal combustion and waste incineration often have a bimodal mass distribution. The coarse mode consists mainly of entrained ash. The fine (submicron) mode may form by volatilization of a small fraction of mineral matter followed by reoxidation and recondensation. Fine mode particles may grow by coagulation into a size range near 0.1 μm, where they are stable over the process residence time. Alternatively, the fine mode may be scavenged by diffusion to the coarse mode. In this paper, we derive a simple analytical criterion for determining whether diffusion to the coarse mode will suppress growth of the fine mode. The analysis is based on two different analytical methods: (1) the self-preserving analysis, and (2) the monodisperse aerosol model and a (numerical) moment method. The half-life, t12, of the fine mode depends strongly on its initial mass concentration, m0, and on the first moment of the coarse mode size distribution, M1c: t12 ∼ m04/M1c5. There is a fairly sharp separation between the regime where a stable fine mode aerosol develops (t12 ⪢ tresidence) and the regime of almost complete scavenging of the fine mode by the coarse mode (t12 ⪡ tresidence). Through m0, the half-life depends on gas temperature and chemical composition in a complex way.

Features of copolymerization of vinylidene fluoride with tetrafluoroethylene using ammonium persulphate

The authors have investigated the copolymerization of vinylidene fluoride with tetrafluoroethylene using ammonium persulphate in conditions of emulsifier-free copolymerization (in absence and presence of a molecular mass regulator) and also in the conditions of the emulsion process in the presence of such a regulator. It is assumed that on the conditions considered the process occurs both in the micelles of the emulsifier and in the solid polymer particles formed on fall out from solution of the oligomeric radicals or coagulations of the unstable particles protected by surfactant oligomers. On emulsifier-free copolymerization as in the conditions of the emulsion process copolymers form with a bimodal molecular mass distribution. It has been established that the molecular mass regulator prevents passage of the chain transfer reaction to the polymer present in the solid phase by reducing the fraction of the high molecular mass component of the molecular mass distribution.

Einstein imaging observations of clusters with a bimodal mass distribution

Einstein imaging observations of four X-ray clusters of galaxies characterized by a double X-ray surface brightness and thus mass distribution are presented. The clusters A98, A115, A1750 and SC 0627-54 were found to exhibit two enhancements in their X-ray surface brightness distributions in observations made with the Einstein Imaging Proportional Counter. Calculations of the probability that the clusters represent chance superpositions indicate that the double clusters are physically associated. The radial distributions of the components are inconsistent with those of single point sources, and have been used to derive cluster luminosities which are typical of rich clusters. Masses of the subclusters are also found to be typical of bound and virialized clusters with gas contributing 10%. Within the framework of the hierarchical theory of galactic clustering, the double clusters are suggested to represent an intermediate evolutionary stage before the merger of subclusters into a relaxed Coma-type cluster.

The Mass Distribution of Large Atmospheric Particles

This paper describes the results of a study to determine the total mass and the mass distribution of atmospheric aerosols, especially that mass associated with particles greater than 10 μm diameter. This study also determined what fraction of the total aerosol mass a standard high-volume air sampler collects and what fraction and size interval settle out on a dust fall plate. A special aerosol sampling system was designed for this study to obtain representative samples of large airborne particles. A suburban sampling site was selected because no local point sources of aerosols existed nearby. Samples were collected under various conditions of wind velocity and direction to obtain measurements on different types of aerosols. Study measurements show that atmospheric particulate matter has a bimodal mass distribution. Mass associated with large particles mainly ranged from 5 to 100 μm in size, while mass associated with small particles ranged from an estimated 0.03 to 5 μm in size. Combined, these two distri...