Enhancement of the radiation resistance of cerium-containing fluorophosphate glasses through codoping with Sb2O3 and Bi2O3

The growing demand for radiation-resistant optical glasses for space and nuclear radiation applications has attracted significant research interest. However, radiation-resistant fluorophosphate glasses have been poorly studied. In this work, we report on the tailoring and performance of radiation-resistant fluorophosphate glasses that contained cerium through codoping with Sb₂O₃ and Bi₂O₃. The physical properties, optical properties, microstructure, and defects of fluorophosphate glasses were investigated using transmittance measurements, absorption measurements, as well as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results showed that the radiation resistance of all codoped fluorophosphate glasses was better than the undoped cerium-containing fluorophosphate glasses after 10–250 krad(Si) irradiation. Especially in glasses doped with Bi₂O₃, the optical density increment at 385 nm was only 0.1482 after 250 krad(Si) irradiation. The CeO₂ prevented the development of phosphate-related oxygen hole center (POHC) defects, whereas further codoping with Bi₂O₃ suppressed the formation of oxygen hole center (OHC) and POEC defects, reducing the breaking of phosphate chains caused by CeO₂. Bi³⁺ is more likely than Sb³⁺ to change the valence, affecting the transition equilibrium of intrinsic defects and reducing the concentration of defects produced by irradiation. When codoping with Sb₂O₃ and Bi₂O₃, Bi₂O₃ does not enhance radiation resistance owing to the scission effect of Sb₂O₃ on the phosphate chain, which is not conducive to the radiation resistance of glasses. This indicates that the cerium-containing fluorophosphate glasses doped with Bi₂O₃ can effectively suppress the defects caused by irradiation and improve the radiation resistance of the glasses.     

Protective effect of nanosilica on irradiated dates against saw toothed grain beetle,Oryzaephilus surinamensis (Coleoptera: Silvanidae) adults

The insecticidal activity of nanosilica particles (NSPs) [20 ± 4 nm] was determined using the saw-toothed grain beetle, Oryzaephilus surinamensis (L) adults as the experimental insect. When the unsexed adults were exposed to different doses of nanosilica (0.2, 0.4, 0.6, 0.8 and 1.0 mg/Petri dish) for different periods (1, 2 and 3 days), it was found that NSPs had more insecticidal activity against O. surinamensis. Moreover, it was found that as the exposure time and dose increased, the mortality percentages of the adults increased. When the adult fed on irradiated dates which treated with different doses of nanosilica (0.5, 1,2 and 4 mg/1date) the mortality was higher than in nanosilica alone. The LD₅₀ of the bioassay tests showed that the calculated LD₅₀ values of each treatment were 0.468, 1.201 and 0.572 mg/1date. The adult of O. surinamensis (untreated, treated with LD₅₀ of nanosilica and fed on unirradiated or irradiated dates) examined by a scanning electron microscope. The examination showed the same malformations in all treatments which caused abrasion and damage on the outer surface. Nanosilica can be effectively replacing chemical insecticides to protect stored products.     

伽马刀准直体三维立体定向孔的加工方法

伽马刀准直体上三维立体定向孔的聚焦精度是影响治疗效果的关键因素,也是加工的难点。介绍了伽马刀准直体三维立体定向孔的加工方法,设计了工装,并研究了关键精度控制的问题。     

The radiation-shielding properties of ternary SiO2–SnO–SnF2 glasses: Simulation and theoretical study

In this study, the shielding capabilities of five selected glasses with a (100-x) SiO₂-x(SnO + SnF₂) chemical composition (x = 40, 45, 50, 55 and 60 mol%) have been investigated. The mass attenuation coefficient values were simulated using the MCNP5 Monte Carlo code, while the results were confirmed theoretically by the online version of the XCOM program. Based on the obtained mass attenuation coefficient values, effective shielding parameters such as linear attenuation coefficient, half value layer, mean free path, effective atomic number, and electron densities have been calculated. Exposure and energy absorption buildup factors have also been calculated. Glass shielding capabilities against neutrons has been investigated by calculating the fast neutron removal cross section. The results reveal that an increase in the SnO ratio in the glass composition leads to an increase in the attenuation properties: the investigated glasses are superior as shields against gamma radiation.     

Gamma irradiation of pharmaceutical compounds, nitroimidazoles, as a new alternative for water treatment

The main objectives of this study were: (1) to investigate the decomposition and mineralization of nitroimidazoles (Metronidazole [MNZ], Dimetridazole [DMZ], and Tinidazole [TNZ]) in waste and drinking water using gamma irradiation; (2) to study the decomposition kinetics of these nitroimidazoles; and (3) to evaluate the efficacy of nitroimidazole removal using radical promoters and scavengers. The results obtained showed that nitroimidazole concentrations decreased with increasing absorbed dose. No differences in irradiation kinetic constant were detected for any nitroimidazole studied (0.0014-0.0017 Gy⁻¹). The decomposition yield was higher under acidic conditions than in neutral and alkaline media. Results obtained showed that, at appropriate concentrations, H₂O₂ accelerates MNZ degradation by generating additional HO; however, when the dosage of H₂O₂ exceeds the optimal concentration, the efficacy of MNZ degradation is reduced. The presence of t-BuOH (HO radical scavenger) and thiourea (HO, H and e_aq⁻ scavenger) reduced the MNZ irradiation rate, indicating that degradation of this pollutant can take place via two pathways: oxidation by HO radicals and reduction by e_aq⁻ and H. MNZ removal rate was slightly lower in subterranean and surface waters than in ultrapure water and was markedly lower in wastewater. Regardless of the water chemical composition, MNZ gamma irradiation can achieve i) a decrease in the concentration of dissolved organic carbon, and ii) a reduction in the toxicity of the system with higher gamma absorbed dose.     

基于统计特征分类耦合自适应 Gamma校正的图像增强算法

为了避免图像在亮度增强时导致其颜色失真,且在局部易出现过增强等问题,设计了统计特征分类耦合自适应Gamma校正(adaptive Gamma correction,AGC)的图像增强算法,以更好提高图像细节与视觉效果。首先,将输入图像转换为HSV空间,使颜色与亮度分离,使其在增强亮度通道时不改变像素的原始颜色,有效降低颜色失真。然后,考虑不同图像的性质,利用统计信息将图像分类为高、低两种对比度,每种对比度又分为亮、暗两类。其次,基于传统的Gamma校正方法,通过对于不同类型的图像进行动态参数设置,形成一种AGC机制,从而为不同类型图像的构建了不同的增强函数,以完成不同类别图像的增强处理。实验数据表明,与当前流行的增强算法相比,所提算法具备更高的增强效果,呈现出更为自然的亮度与对比度,且保持了更多的颜色信息。     

Periodic autoregressive conditional duration

We propose an autoregressive conditional duration (ACD) model with periodic time-varying parameters and multiplicative error form. We name this model periodic autoregressive conditional duration (PACD). First, we study the stability properties and the moment structures of it. Second, we estimate the model parameters, using (profile and two-stage) Gamma quasi-maximum likelihood estimates (QMLEs), the asymptotic properties of which are examined under general regularity conditions. Our estimation method encompasses the exponential QMLE, as a particular case. The proposed methodology is illustrated with simulated data and two empirical applications on forecasting Bitcoin trading volume and realized volatility. We found that the PACD produces better in-sample and out-of-sample forecasts than the standard ACD.     

Inactivation of Staphylococcus saprophyticus in chicken meat and purge using thermal processing,high pressure processing,gamma radiation,and ultraviolet light (254 nm)

Staphylococcus saprophyticus is a common contaminant in meat and poultry, and causes urinary tract infections after colonization of the gastrointestinal tract, followed by accidental transfer of contaminated feces to the urethra. There is limited information regarding the inactivation kinetics of S. saprophyticus in meat and poultry. When S. saprophyticus was suspended in ground chicken meat (GCM) the thermal processing D₁₀ was 6.26, 0.60 and 0.09 min at 55, 60 and 65 °C, respectively. When S. saprophyticus was inoculated into GCM and subjected to high pressure processing (5 °C, 0–25 min) at 200, 300 or 400 MPa the HPP D₁₀ was 15.5, 9.43, and 3.54 min, respectively. When the S. saprophyticus cocktail was inoculated into GCM and irradiated (5 and −20 °C) the gamma radiation D₁₀ were 0.64 and 0.77 kGy, respectively. When S. saprophyticus was inoculated into chicken purge which was then placed on food contact surfaces including stainless steel, and high density polyethylene and polypropylene and treated with UV-C (0–60 mJ/cm²) the UV-C D₁₀ ranged from 14.9 to 18.5 mJ/cm². These results indicate the inactivation kinetics for S. saprophyticus are consistent with those for other foodborne pathogens and could be controlled in poultry meat and purge without difficulty.     

Gamma radiation as a phytosanitary treatment against larvae and pupae of Bactrocera dorsalis (Diptera: Tephritidae) in guava fruits

A low-dose gamma radiation phytosanitary treatment against the oriental fruit fly, Bactrocera dorsalis Hendel, was developed for guava fruits. The measure for efficacy of the treatment is preventing adult emergence from late third instars that were reared in the fruit of guava, Psidium guajava L. The dose–response tests with 1-, 2-, 3-, 7-d-old larvae in guava were initiated to determine the most tolerant stages, the late-aged third instars. No adult emerged from a total of 100,684 late-aged third instars irradiated at the dose of 97–116 Gy, resulting in an efficacy of 99.9970% at the 95% confidence level. The minimum dose for 100% preventing adult emergence from 2-, 5-, 7-d-old pupae (1800 pupae in each dose) reared in artificial diets was 100, 500, and 1750 Gy, respectively. Quality determinations on ‘Taiwan’ guavas were conducted at 1, 3 and 7 days after gamma radiation at doses of 200, 400, 600, 800, 1,200, 2000 and 6000 Gy. The guavas could tolerate radiation dose up to 600–800 Gy as there were no significant changes in organoleptic characteristics (≤800 Gy), the chemical and nutritional contents (sugar, sucrose, total sugar, titratable acid, vitamin C, and soluble solid) (≤600 Gy). Therefore, a dose of 116 Gy, which give the disinfestations efficacy of 99.9968% for the late-aged larvae in guavas and 100% mortality of 2-d-old pupae, is suggested as the minimum absorbed dose for phytosanitary irradiation treatment of B. dorsalis in fruits.