Investigation into the foundations of the track-event theory of cell survival and the radiation action model based on nanodosimetry

This work aims at elaborating the basic assumptions behind the “track-event theory” (TET) and its derivate “radiation action model based on nanodosimetry” (RAMN) by clearly distinguishing between effects of tracks at the cellular level and the induction of lesions in subcellular targets. It is demonstrated that the model assumptions of Poisson distribution and statistical independence of the frequency of single and clustered DNA lesions are dispensable for multi-event distributions because they follow from the Poisson distribution of the number of tracks affecting the considered target volume. It is also shown that making these assumptions for the single-event distributions of the number of lethal and sublethal lesions within a cell would lead to an essentially exponential dose dependence of survival for practically relevant values of the absorbed dose. Furthermore, it is elucidated that the model equation used for consideration of repair within the TET is based on the assumption that DNA lesions induced by different tracks are repaired independently. Consequently, the model equation is presumably inconsistent with the model assumptions and requires an additional model parameter. Furthermore, the methodology for deriving model parameters from nanodosimetric properties of particle track structure is critically assessed. Based on data from proton track simulations it is shown that the assumption of statistically independent targets leads to the prediction of negligible frequency of clustered DNA damage. An approach is outlined how track structure could be considered in determining the model parameters, and the implications for TET and RAMN are discussed.

Research into Influence from Different Ranges of PAR Radiation on Efficiency and Biochemical Composition of Green Salad Foliage Biomass

Results of the first photobiological studies of optimisation of LED phyto irradiators spectrum and irradiance level, when growing salad­greengrocers plants in greenhouses and plant factories in photoculture conditions, are presented in the article. The results are given as a series of producing capacity curves for salad and basil plants when irradiating by quasi­monochromatic spectrum for three PAR ranges: blue, green and red. In the experiment, levels of photosynthetic photon irradiance (70 ? 230) µmol/s·m2 and of irradiance (13 ? 60) W/m2 were varied within a wide range. “Rough” spectra of optical radiation action estimated over producing capacity of plants with different irradiance levels are given, and questions of additivity of different spectral radiation influence in forming vegetable biomass are considered. Evaluations of efficiency of various PAR intervals for synthesis of biochemical combinations determining nutrition facts of the studied cultures are performed.