The effect of low-dose X-ray irradiation (10 and 20 Gy) of winter wheat seeds of the cultivars Sofiia Kyivska and Shchedrivka Kyivska on plant resistance to phytopathogenic pressure was investigated. Seed infestation by the phytopathogens Fusarium sp., Aspergillus, and Mucor was identified. It is shown that in both cultivars, both irradiation doses suppressed the development of phytopathogens; however, the 20 Gy dose had a more pronounced effect on infection development. Changes in the hydrogen peroxide content during the experimental period were also sensitive to phytopathogenic pressure and to the cultivar-specific adaptive potential of the plants. Changes in the contents of chlorophylls and carotenoids indicate the functional integrity of leaves following exposure of wheat grains to low doses of X-ray radiation and the compensation of the detrimental effects of the Fusarium pathogen on the photosynthetic apparatus of plants.
Two preconditions are crucial for the calculation of depth-dose distributions in existing semi-empirical models. An available detailed information regarding the electron beam spectrum is one precondition. And the dependence of the model's empirical parameters on the energy and incidence angle of the beam on the irradiated object is the other precondition. However, in industrial applications, the electron beam spectrum is typically not controlled during the radiation sterilization process. The present paper addresses and solves the problem of developing a procedure for using existing semi-empirical models to calculate depth-dose distributions if the electron beam spectrum is not controlled. The procedure for determining the empirical parameters of the model is suggested. It is based on the selection of a single irradiation mode from a set of values for electron energies and electron beam incidence angles on the layer that make a significant contribution to the depth-dose distribution. An estimation of the electron energy range in the spectrum is carried out based on an approximation of the spectrum by a triangular distribution with parameters corresponding to standard characteristics of the electron depth-dose distribution. The errors in determining the empirical parameters of the model are evaluated using a set of irradiation modes in the electron energy range from 5 to 10 MeV and electron beam incidence angles on the layer from 0° to 60°. The error of the SEM2U model is determined based on the deviations of the model’s predictions from the results of numerical experiments obtained by simulating depth-dose curves in the layer using the Monte Carlo method. Standard characteristics of the radiation sterilization process are used to estimate errors: values of optimal layer thicknesses, dose uniformity indices, and beam energy utilization coefficients. The method for using semi-empirical models is described for the cases without any control of the electron spectrum. The method consists of processing measurements taken using a dosimetric wedge to obtain the depth-dose curve under normal incidence of the electron beam on the irradiated object (the baseline curve for the models) and selecting a single irradiation mode to determine the empirical parameters of the models. The depth-dose curves in a semi-infinite medium, calculated using the described method, are compared with the results of simulating depth-dose curves using the Monte Carlo method. For these comparisons, an electron beam with a broad Spectrum_8 spectrum is used at various beam incidence angles on the medium. The error of the calculations of depth-dose curves for electron beams with the Spectrum_8 spectrum is evaluated according to the characteristics of the two-sided irradiation process, which is standard in radiation sterilization. The error is estimated based on the deviation of the predictions of the semi-empirical SEM2U model from the results of numerical experiments obtained by simulating depth-dose curves in the layers of optimal thickness using the Monte Carlo method. It is shown that the procedure for determining the empirical parameters of the model, based on the selection of a single irradiation mode, provides sufficient accuracy for the calculations in the SEM2U model for electron beams with a broad spectrum. The possibilities of the proposed method for using semi-empirical models to calculate depth-dose curves when selecting optimal irradiation modes in radiation sterilization in cases without any control of the spectrum are discussed.
A computer model of a murine rodent has been developed for use in dosimetric calculations. The model is based on information from scientific sources regarding anatomical features of animals' body and skeleton, as well as the structure and chemical composition of bones and bone marrow. The Geant4 software library, designed for the simulation of nuclear physics processes, was used in creating the model. The developed model enables realistic simulation of 90Sr internal irradiation processes of murine rodent bone marrow, corresponding to the exposure of animals under natural conditions of the Chornobyl Exclusion Zone ecosystems.
A comprehensive theoretical study of the angular anisotropy and linear polarization of characteristic L-shell X-ray emission from high-Z atoms (tantalum, tungsten, rhenium, iridium, gold, and thallium) produced by photoionization with unpolarized photons is reported. The calculations are performed within the non-dipole approximation employing three alternative descriptions of the atomic potential: (i) point Coulomb field, (ii) screened Coulomb field, and (iii) analytical perturbative treatment. To examine only direct L-shell fluorescence, the incident photon energy is limited to the range extending from the L3 absorption threshold to the K-shell edge, thereby eliminating contributions from K-shell ionization, Coster-Kronig transitions, and inter-shell vacancy transfer processes. The degree of linear polarization for the Lℓ, Lα1, and Lα2 spectral lines is calculated up to 60 keV to determine their variation with excitation energy. The results indicate that vacancy alignment reaches its maximum close to the threshold, where great changes in subshell ionization amplitudes and photoelectron partial-wave components occur. As the photon energy increases, the alignment progressively decreases, leading to reduced anisotropy and polarization, and gradually approaches a slowly varying high-energy limit. The Lℓ transition consistently shows greater anisotropy than the Lα lines, while the polarization values of Lℓ, Lα1, and Lα2 remain transition-specific because of differences in angular momentum coupling and radiative transition matrix elements. A systematic dependence on atomic number is observed throughout the investigated elements, with heavier atoms exhibiting comparatively greater changes in the polarization behaviour. While this trend may reflect the combined influence of relativistic effects, spin-orbit coupling, and electron-correlation effects commonly associated with heavier atomic systems. Although all three theoretical approaches predict similar overall energy-dependent trends, noticeable quantitative differences are obtained in the polarization magnitudes, demonstrating the sensitivity of the results to the adopted potential model and alignment treatment. Comparison with previously published results of Kämpfer et al. and Özdemir et al. confirms the consistency of the present calculations and offers a deeper theoretical understanding of the combined influence of vacancy alignment, multipole mixing, and relativistic dynamics in L-shell X-ray emission.
Brief biography and scientific achievements of Vasyl Ivanovych Slisenko in relation with his 75th anniversary.
