Glow Characterization in Low-Pressure Radio-Frequency $\hbox{CH}_{2} \hbox{F}_{2}$ and $\hbox{C}_{2}\hbox{H}_{2}\hbox{F}_{4}$  Plasma Deposition Systems
The glow characteristics and deposited film structures of fluorocarbon monomers in radio-frequency glow discharges are investigated using CH<sub>2</sub>F<sub>2</sub> and C<sub>2</sub>H<sub>2</sub>F<sub>4</sub>, which were compared to hydrocarbon monomer such as CH<sub>4</sub>. The glow was characterized and investigated by optical photography, optical emission spectroscopy, and Fourier transform infrared spectrometry. The glow differences were attributed to the nature of the luminous gas phase in respect to polymer-forming species.
Plasma Polymerization Behavior of Fluorocarbon Monomers in Low‐Pressure AF and RF Discharges
The plasma polymerization behavior of fluorocarbon monomers was investigated using C 3 F 6, C 3 F 6 O, C 4 F 10 and C 2 F 4 H 2 , which were compared to hydrocarbons such as methane and butane. The plots of the normalized thickness growth rates of plasma polymers, GR/FM, versus the energy input composite parameters, W/FM, revealed the energy-deficient and monomer-deficient domains for each monomer, along with the critical energy input, (W/ FM) c , representing the transition between the two domains. The luminous gas phase in fluorocarbon discharges does not contain much polymer-forming species and thus, the monomer-deficient domain shifted to a much lower W/FM and GR/FM values than in the case of hydrocarbon systems. For hydrocarbon systems, deposition rates were greater in RF than in AF discharges, which is opposite to the situation observed for the fluorocarbon systems. These differences were attributed to the locations of the dissociation glows and to the nature of the luminous gas phase in respect to polymer-forming species.
One hundred percent tumor induction in mouse skin after repeated beta irradiation in a limited dose range.
Repeated beta irradiation of the backs of mice three times a week with radiation doses of 250 to 1180 cGy per exposure induced 100% incidence of tumors. The incidence of skin tumors appeared to be determined by the total number of repeated exposures in this dose range. An abrupt delay in tumor emergence was observed when the radiation dose was reduced from 250 to 150 cGy per exposure, indicating the existence of a critical threshold. Mouse skin resembles human skin rather than rat skin in its response to radiation.