The ion-induced nucleation of six vapors (carbon tetrachloride, chloroform, o-xylene, methanol, ethanol, and water) has been investigated in a thermal diffusion cloud chamber using helium as a carrier gas. High densities of ions were produced in the chamber by use of «-sources and separation of positive and negative charges has been achieved by use of an electric field. Experiments have been conducted such that nucleation occurred in the presence or absence of an electric field in the nucleation zone. When the electric field was present, the so-called sign effect was observed, while no effect occurred in the absence of the electric field.

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Self-thermal initiated gas phase polymerization in styrene vapor is investigated employing the nucleation and growth of liquid monomer droplets (in supersaturated styrene vapor) for detection. The results show rather definitively that styrene does polymerize thermally, in the vapor phase, at temperatures as low as 250 K. The same is true for a-methylstyrene which is also studied (but not so thoroughly). Phenylacetylene retards the gas phase polymerization of styrene. Polymers with degree of polymerization in the range 9 to 24 are involved in this study.The degree of polymerization increases with temperature and bimolecular termination appears to be absent. The total concentration of growing radicals is of the order of 6 X 1

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This paper provides accurate numerical solutions of "stiff", nonlinear, diffusional boundary value problems involving diffusant which can be bound in a thermodynamically reversible manner to "traps" within the diffusion field. The physical system to which this model corresponds could, for example, be a film of conducting polymer within which the diffusant is an electroactive dopant. This diffusant is also distributed in a thermodynamically reversible manner between the external phase and the