Changlong Cai

Introduction: Accurate modeling of beta-decay energy spectra is essential for theoretical analysis and performance optimization in radioisotope energy conversion. Conventional parameterization methods may introduce fitting bias, while fixed-bandwidth KDE lacks local adaptability for asymmetric, multi-peak and long-tailed spectral distributions. Methods: This study developed an Artificial Fish Swarm Algorithm-Adaptive Kernel Density Estimation (AFSA-AKDE) framework. After spectral data preprocessing, RMSE was used as the fitness function, the bandwidth was reformulated as an adaptive coefficient-controlled structure, and AFSA was used to optimize key parameters through foraging, swarming and following behaviors. Results: The method was validated using Ni-63, S-35 and C-14 samples with different thicknesses. For a 2 um Ni-63 sample, AFSA-AKDE achieved MAE = 0.0116%, RMSE = 0.0156% and R2 = 0.9998792. For a 0.2 um C-14 sample, it achieved MAE = 0.0158%, RMSE = 0.0243% and R2 = 0.996687. Discussion: Compared with fixed-bandwidth KDE, normal distribution models and recent adaptive KDE variants, AFSA-AKDE provides improved accuracy, stability and local adaptability for reconstructing complex beta-decay energy distributions.

Low-energy N+ implantation mutagenesis allows Staphylococcus aureus to develop resistance to vancomycin. Then the vancomycin-resistant S. aureus strain was examined using drug-resistance phenotypes, and biofilm growth analysis to explore the potential resistance mechanism underlying the vancomycin-resistant S. aureus strain. The results showed that 9 vancomycin-resistant S. aureus strains were constructed by low energy N+ implantation mutagenesis. The biofilm biomass and density as well as the matrix protein content within the biofilms of five representative vancomycin-resistant strains with muti-drug resistance capacity were significantly enhanced over the original strain, and their resistance to vancomycin increased by between two and four times. These vancomycin-resistant strains acquired multiple resistance to different antibiotics. The results indicate that the enhancement of biofilm formation ability and the matrix protein content within the biofilm might be attributed to be the changes in the expression of drug-resistant-related genes in vancomycin-resistant S. aureus strains, which were mediated by low energy N+ implantation, thereby accelerating the formation of drug resistance. These results provide the theoretical basis for examining the mechanism of environmental radiation-mediating the drug-resistant formation in S. aureus.

To achieve low wavefront error and high throughput with vignetting-free target simulators, a concave-convex-concaveoff-axis spherical system is designed in this paper, which effectively eliminates astigmatism and coma of the system by fields of view (FOVs) and aperture offset and provides theoretical basis for the realization of 100% matching between the exit pupil of the field lens and entrance pupil of the three-mirror anastigmat (TMA) system. Only spherical mirror element is used in this target simulator, which not only reduces the difficulty of manufacturing and cost but also greatly reduces the difficulty of assembling and adjusting. It provides an effective scheme for the design of target simulator and has strong engineering application value.

In this paper, the Fe³⁺ doped rutile phase TiO₂ nanotubes arrays (NTAs) were prepared in a low temperature water-assistant crystallization method. It is noteworthy that the Fe³⁺ doping hardly hinders either the crystallization of rutile TiO₂ NTAs or the highly-ordered nanotubular morphologies. Moreover, Fe³⁺ did not form other compound impurities, which indicated that Fe³⁺ substitute Ti⁴⁺ into the lattice of TiO₂. With the introduction of Fe³⁺, the light absorption range of TiO₂ NTAs extends from the ultraviolet band to the visible light range. Photocatalytic testing results indicate that Fe³⁺ doped TiO₂ NTAs can effectively improve the degradation rate of methyl orange aqueous solution in visible light, and the TiO₂ NTAs with 0.2 mol/L Fe³⁺ doping exhibits the highest photocatalytic degradation efficiency.

The activity concentrations of TENORM including ²²⁶Ra, ²³²Th and ⁴⁰K of the ten main brands of glazed tiles produced in China and their radiological hazard parameters such radium equivalent radioactivity, alpha index, external exposure index, absorbed dose rate in air indoors, indoors annual effective dose, and activity concentration index are measured and estimated. The activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K in glazed tile samples are within the international tile reference values for ²²⁶Ra (30–200 Bq·kg⁻¹), ²³²Th (20–200 Bq·kg⁻¹) and ⁴⁰K (160–1410 Bq·kg⁻¹). The estimated mean values of radiological hazard parameters such as radium equivalent radioactivity, alpha index, external exposure index, indoors annual effective dose, and activity concentration index are also found to be below the international recommended limits or referenced values. The mean value of the absorbed dose rate in air indoors is within the country average range of 20–190 nGy·h⁻¹. Moreover, combined with statistical analysis, it is concluded that the activity concentrations of ²²⁶Ra and ²³²Th in glazed tile samples have a strong correlation with the calculated radiological parameters, which has a significant impact on radioactivity in glazed tiles. Finally, it can be concluded that the ten brands of glazed tiles used in decoration of building materials are identified as grade A, which are unlikely to have a significant radiological hazard to the public. Therefore, the production, marketing and use scope of glazed tiles should be not restricted, but the early monitoring and classification should be done.

Lead free piezoelectric crystals of (K_xNa_1−x)NbO₃ (x = 0.11 and 0.17) have been grown by the modified Bridgman method. The structure and chemical composition of the obtained crystals were determined by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The domain structure evolution with increasing temperature for (K_xNa_1−x)NbO₃ (x = 0.11 and 0.17) crystals was observed using polarized light microscopy (PLM), where distinguished changes of the domain structures were found to occur at 400 °C and 412 °C respectively, corresponding to the tetragonal to tetragonal phase transition temperatures. Dielectric measurements performed on (K_0.11Na_0.89)NbO₃ crystals exhibited tetragonal to tetragonal and tetragonal to cubic phase transitions temperatures at 405 °C and 496 °C, respectively.