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Radiation-induced conductivity (RIC) of polyethyleneterepfthalate and polypiromellitimide has been studied experimentally and numerically in a broad time range from some microseconds to seconds at 103 K. It has been established that the charge carrier transport is dispersive with a low value of the dispersion parameter α (0.08–0.12). We have suggested a direct method of determination of the frequency factor of the Rose–Fowler–Vaisberg (RFV) model, which has been parameterized using computer simulations by the trial-and-error method. The main concern is a critical analysis of the existing theories of geminate recombination. It has been shown that the traditional RFV model is well suited to describe the RIC in studied polymers even at 103 K if due corrections to the notion of a free charge carrier and a non-Langevin bimolecular recombination have been made. The problem of a space charge field due to beam electrons stopped in a polymer sample, which is especially important at low temperatures, has been accounted for but not fully explained. [ABSTRACT FROM AUTHOR]

Context Telomerase reverse transcriptase promoter (TERT- p) mutations, which upregulate TERT expression, are strongly associated with tumor aggressiveness and worse prognosis in papillary thyroid carcinomas (PTCs). TERT expression is also observed in a proportion of PTCs without TERT -p mutations, but such tumors show less aggressiveness and better prognosis than TERT- p mutation–positive tumors. Objective TERT has multiple splicing variants whose relationships with the TERT- p status and clinicopathological characteristics remain poorly understood. We examined the relationship between the TERT -p mutational status, the TERT splicing pattern, and clinicopathological features. Methods We investigated the expression of 2 major variants, α deletion (dA) and β deletion (dB), in a series of 207 PTCs operated on between November 2001 and March 2020 in Nagasaki University Hospital and Kuma Hospital. Results The TERT -p mutations were found in 33 cases, and among 174 mutation-negative cases, 24 showed TERT expression. All cases were classified into 3 groups: the TERT -p mutation–negative/expression–negative group (mut−/exp−), the TERT -p mutation–negative/expression–positive group (mut−/exp+), and the TERT -p mutation–positive group (mut+/exp+). The +A+B/dB ratio in mut+/exp+ was significantly higher than that in mut−/exp+ PTCs. Analysis with clinicopathological data revealed that +A+B expression was associated with higher PTC aggressiveness, whereas dB expression counteracted this effect. Functional in vitro study demonstrated that dB strongly inhibited cell growth, migration, and clonogenicity, suggesting its tumor-suppressive role. Conclusion These results provide evidence that the TERT -p mutations alter the expression of different TERT splice variants, which, in turn, associates with different tumor aggressiveness. [ABSTRACT FROM AUTHOR]

Radiation-induced conductivity (RIC) of polystyrene has been studied experimentally and numerically in a broad time range from milliseconds to seconds at 79 K, which seems to have been done for the first time. It has been established that the hole dispersive transport is still operative but unlike the room temperature behavior it features an extremely small frequency factor (4 × 103 s−1) and accordingly low dispersion parameter (0.09). It has been shown that prompt conductivity per unit dose rate does not depend on temperature (290 or 79 K) and is equal to K p = 3.5 × 10 − 15 Ω − 1 m − 1 G y − 1 s (±20%) at 4 × 107 V/m. At 79 K, current–voltage characteristics of both prompt and delayed components are close enough and non-linear. Due to the contribution of the thermalized charge carriers, the RIC even at 79 K can be satisfactorily described by the semi-empirical Rose–Fowler–Vaisberg model based on the quasi-band multiple trapping mechanism just as it happens at room temperature. [ABSTRACT FROM AUTHOR]

We made numerical calculations of the radiation-induced conductivity by computing current densities, carrier concentrations, and internal electric fields in a disordered sample biased by constant applied voltage under a pulsed or step-function irradiation in a large-signal regime. For this purpose, we used the multiple trapping model featuring an exponential trap distribution with the dispersion parameter α. Calculations of radiation-induced conductivity were done with traditional simplifications (1D-analysis, one-carrier polymer, diffusion currents neglected, and non-injecting electrodes). The nonlinear effects accompanying the large-signal radiation-induced conductivity, such as an internal field variation, the bimolecular recombination, and the charge carrier extraction by electrodes, have been consistently accounted for. Numerical analysis agrees satisfactorily with the results of previously published analytical calculations. [ABSTRACT FROM AUTHOR]

Radiation is an environmental factor that elevates the risk of developing thyroid cancer. Actual and possible scenarios of exposures to external and internal radiation are multiple and diverse. This article reviews radiation doses to the thyroid and corresponding cancer risks due to planned, existing, and emergency exposure situations, and medical, public, and occupational categories of exposures. Any exposure scenario may deliver a range of doses to the thyroid, and the risk for cancer is addressed along with modifying factors. The consequences of the Chornobyl and Fukushima nuclear power plant accidents are described, summarizing the information on thyroid cancer epidemiology, treatment, and prognosis, clinicopathological characteristics, and genetic alterations. The Chornobyl thyroid cancers have evolved in time: becoming less aggressive and driver shifting from fusions to point mutations. A comparison of thyroid cancers from the 2 areas reveals numerous differences that cumulatively suggest the low probability of the radiogenic nature of thyroid cancers in Fukushima. In view of continuing usage of different sources of radiation in various settings, the possible ways of reducing thyroid cancer risk from exposures are considered. For external exposures, reasonable measures are generally in line with the As Low As Reasonably Achievable principle, while for internal irradiation from radioactive iodine, thyroid blocking with stable iodine may be recommended in addition to other measures in case of anticipated exposures from a nuclear reactor accident. Finally, the perspectives of studies of radiation effects on the thyroid are discussed from the epidemiological, basic science, and clinical points of view. [ABSTRACT FROM AUTHOR]