Absolute cross sections (CSs) for the interaction of low energy electrons with condensed macromolecules are essential parameters to accurately model ionizing radiation induced reactions. To determine CSs for various conformational DNA damage induced by 2-20 eV electrons, we investigated the influence of the attenuation length (AL) and penetration factor (f) using a mathematical model. Solid films of super-coiled plasmid DNA with thicknesses of 10, 15 and 20 nm were irradiated with 4.6, 5.6, 9.6 and 14.6 eV electrons. DNA conformational changes were quantified by gel electrophoresis, and the respective yields were extrapolated from exposureresponse curves. The absolute CS, AL and f values were generated by applying the model developed by Rezaee et al. The values of AL were found to lie between 11 and 16 nm with the maximum at 14.6 eV. The absolute CSs for the loss of the supercoiled (LS) configuration and production of crosslinks (CL), single strand breaks (SSB) and double strand breaks (DSB) induced by 4.6, 5.6, 9.6 and 14.6 eV electrons are obtained. The CSs for SSB are smaller, but similar to those for LS, indicating that SSB are the main conformational damage. The CSs for DSB and CL are about one order of magnitude smaller than those of LS and SSB. The value of f is found to be independent of electron energy, which allows extending the absolute CSs for these types of damage within the range 2-20 eV, from previous measurements of effective CSs. When comparison is possible, the absolute CSs are found to be in good agreement with those obtained from previous similar studies with double-stranded DNA. The high values of the absolute CSs of 4.6 and 9.6 eV provide quantitative evidence for the high efficiency of low energy electrons to induce DNA damage via the formation of transient anions.
Aiming at the optimization of two important parameters (white noise amplitude coefficient and set average number) in the set empirical mode decomposition (EEMD), an adaptive EEMD parameter optimization method is proposed. First of all, this paper extracts the corresponding amplitude of the high-frequency component of the signal through the energy value of the first eigenmode function, uses the relative mean square error to determine the corresponding amplitude of the low-frequency component of the signal, and establishes the optimal amplitude evaluation criteria based on the corresponding amplitude of the two; At the same time, in order to improve the calculation efficiency and reduce the influence of white noise, the energy value of the first modal component is used to determine the optimal average number of sets; Then, the effectiveness of the method in this paper is verified by simulation experiments; Finally, this method is applied to the extraction of bearing inner ring fault vibration signal. The results show that compared with the traditional EEMD method, this method can adaptively determine the noise amplitude and the set average number, and can more effectively identify the periodic fault components of the vibration signal.
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