The solid state polymerization of hexamethyleyclotrisiloxane by γ-ray irradiation in air has been studied in the temperature range of -78° to 55°. It was shown that the rate of polymerization depends on the size of the reaction vessels at relatively high temperatures, and that the polymerization reaches a limiting conversion, usually about 30-50%. The conversion-time curves suggest that the reaction is retarded owing to the formation of polymer. The temperature dependence of the polymerization rate was unusual between -78° and 0°C, which seems to be related to a phase transition of monomer crystal. The initial rate of polymerization at 55°C was approximately proportional to the first order of dose rate. Besides, the rate of polymerization at 55°C for the sample prepared by slow-cooling was higher than that prepared by shock-cooling. In order to explain these results, a kinetic scheme was assumed which includes the self-retarding effect of the polymerization. The polymerization has been studied also by a microscopic technique. From the observations with a phase contrast microscope and a polarized microscope, it has been proven that the reaction involves the formation of polymer particles and proceeds heterogeneously, and that there is no particular direction of the propagation.
Using autoradiographic technique with 3H-TdR as a marker for DNA synthesis, the chromosome duplication (DNA synthesis) in root tip cells of the female plant of Humulus lupulus, was investigated. The average duration of the each phase of mitotic cycle was found to be as follows: G1 (pre DNA synthesis stage) 2 hours, S (DNA synthesis stage) 3 hours, G2 (post DNA synthesis stage) 4.3 hours and M (mitosis) 0.7 hours. It was also shown that an asynchronous replication of DNA occurred in chromosomes, and that heterochromatin synthesized the DNA at a different time from euchromatin. It was discussed that the late replication might be something characteristic of the DNA in positive heteropycnotic regions, whether they are in autosomes or in sex chromosomes.