The existence of the isomer 130lm (9.2 min) has been established by the growth of the gamma-ray spectrum of the 13°1 ground state following neutron irradiation of 129 1, and also by the incorporation of 13°1 into organic combination as a result of the isomeric transition of 12 (1 30 lm) dissolved in n-hexane. The isomer decays to the ground state by a highly converted isomeric transition with a 0.77 probability and to the 0.54-MeV level of 13°Xe by beta emission with 0.23 probability. The cross-section ratio, ".(1 30 1 m ) /".(1 30 1), for production of the isomers from 129 1 by pile neutrons is about 2.0. The fraction of the isomeric transition events which result in organic incorporation of the 13°1 daughter in solutions of 12( 130 lm) in n-hexane, or in solutions of RI (130lm) in ethyl iodide, is about 0.40.

The intra- and inter-subject reproducibility of pulmonary mucociliary clearance was investigated in nine healthy male subjects following deposition of an aerosol of 7.9 microns aerodynamic diameter iron oxide particles labeled with TC-99m. The results have been analyzed for both total bronchial clearance and for clearance from areas representing central (Zone I), mid (Zone II), and peripheral (Zone III) regions of the lung. The observed clearance rates were compared to the predictions of a mathematical model for lung clearance based on Weibel's dicotomous branching system. The results for total bronchial clearance showed an average TB120 (percent cleared in 2 hr) of 57%, while the average TB120 for Zone I, II, and III was 56%, 62%, and 48%, respectively. The mean half-times (times required to clear 50% of the deposited activity) for the total bronchial clearance and for Zones I, II, and III were 1.90 hr, 1.97 hr, and 1.70 hr and 2.62 hr, respectively. Total bronchial and regional clearance was reproducible (P = .05) within subjects, but significant variation was observed among subjects. The predictions of the mathematical model for total bronchial clearance are in good agreement with the experimental results. However, the experimental clearance rate was slower in Zone I, and faster in Zone II and III than is predicted by the model. The implications of these results are discussed.

Dilute aqueous solutions of CH3I127 and I2(I129) [or I~(I129)] have been irradiated with neutrons and analyzed to determine the fractions of the 127( , ) 128 and 129( , ) 3°events which lead to I128 and to I130 in organic combination. The organic yield of each isotope is significant, confirming an earlier report2 that organic combination of (Reactivated iodine atoms can be achieved in aqueous CH3TT2 systems, but showing that such combination does not require the geminate retention previously postulated.2 The yields are independent of the Iconcentration from 10 ~5 to at least 10-3 mole % and increase with CH3I concentration in the range from 1.8 X 10~3 mole % to the saturated solution concentration of 0.18 mole %. Like the ( , ) processes, the I130m -* I130 isomeric transition in aqueous solutions of 0.08 mole % CH3I and 10~3 mole % I2(I130m) or I~(I130m) leads to organically bound I130, the organic yields being about 7%. The entry into organic combination of I atoms originating from I2 or I-, and activated by the ( , ) or IT process, seems to be explained most plausibly in terms of the autoradiation hypothesis. Techniques have been developed for correcting for thermal exchange in the systems used and it has been shown that photochemically produced I atoms do not exchange readily with CH3I in aqueous solution.

Publication costs assisted by the U.S. Energy Research and Development AdministrationThe G values of trapped radicals produced by the y irradiation of polycrystalline n-alkanes at 77 K are independent of carbon number from C6 to C10, are -70% higher than in the glassy branched alkanes, and are -40% higher for the protiated forms than for perdeuterated. In an uncracked single crystal of n-C6H14, the G(R.) and decay kinetics are consistent with a rapid intraspur decay followed by second-order reaction of randomly distributed radicals, as observed in glasses, in contrast to the "stepwise" decays observed in polycrystalline samples. 30-35% of the radicals produced by y irradiation of protiated n-alkanes are removable by exposure to 254-nm light, compared to 18% or less in deuterated n-alkanes. Thermally reversible photoisomerization of the remaining radicals occurs. Both the photoinduced removal of radicals and the photoisomerization occur at 4 K as well as at 77 K. Ultraviolet absorption by carbanions formed by the capture of electrons by radicals in y-irradiated n-C6H14 has been observed, and an upper limit of 0.25 has been set on G(R-)initid. The carbanion concentration reaches a steady state after a dose of -2 x IO2" eV g '. Phase effects on G(R-) in polycrystalline cyclohexane have been examined.

Experiments have been done to determine whether thermal D atoms produced at 77 K in 3-methylpentane-d14 containing ∼1% C–H bonds as an isotopic impurity are able to abstract H by a low activation energy process, as CH3 radicals are known to do. The D atoms have been produced by 254 nm photolysis of DI. The trends in HD/D2 ratio with changing ratio of C–H bonds to [DI] are consistent with the conclusion that the D+C6H13H→ HD+C6H13 abstraction occurs at 77 K with low activation energy requiring either a tunneling mechanism or unusual molecular distortion in the glass.