二甲基二烯丙基氯化铵的辐射聚合和性质研究

对二甲基二烯丙基氯化铵进行了辐射聚合,得到线型聚合物的交联的水凝胶, 实验测定了线型聚合的转化率与剂量和水凝胶的凝胶的凝胶分数、平衡溶胀与剂量 的关系。结果表明聚二甲基二烯丙基氯化铵水凝胶的凝胶含量与剂量的关系符合 Charlesby-Pinner公式,外推S + S~(1/2) = 2求得凝胶剂量D_g,从而求出G(x) 等值;并首次利用二甲基二烯丙基氯化铵及其聚合物稀水溶液的电导率与浓度的线 性关系,发展了一种对电解质的辐射聚合反应转化率的电导测定法。     

基于临床实例的影响蒙特卡罗程序MCNP计算精度和速度的若干参数模拟研究

蒙特卡罗方法是目前最精确的剂量计算方法,但其较长的模拟时间阻碍了它在临床治疗中的应用。基于蒙特卡罗程序MCNP4c,针对一临床头部病例,探讨了记数方法、电子和光子截断能、光子产生次级电子参数ENUM对计算速度和精度的影响,给出了在保证一定精度前提下的最佳计算模式,以获得计算速度的有效提升。Monte its long simulation and photons, and investigated based Carlo method is regarded as the most accurate method for dose calculation at present, whereas time hinders its clinic application. The effects of the tally method, the cut-off energy of electrons the secondary electron number parameter ENUM on precision and speed of MCNP4c have been on a clinical case to seek for a relatively optimum calculation mode.     

低剂量辐射诱导hepG2细胞克隆存活和细胞周期适应性反应

以低剂量γ射线(0.05 Gy)预照射人肝癌细胞hep G2, 8 h后再用高剂量(3 Gy)照射, 测定了细胞的克隆存活率和细胞周期。 结果表明, 低剂量辐射预处理可诱导hep G2细胞产生克隆存活适应性反应, 并且有助于细胞通过G2/M期阻滞; 低剂量辐射诱导的克隆存活适应性反应与增强的通过细胞周期阻滞的能力之间有一定的相关性。 Human hepatoma cells hep G2 were irradiated with 3 Gy of γ ray 8 hours after primed with 0.05 Gy of γ ray, thereafter,cell survival and cell cycle were determined. The results indicated that both survival adaptive response and the enhanced ability to overcome G2/M arrest could be induced by pre irradiation with low dose of γ ray. It is suggested that there is a certain correlation between the survival adaptive response and the enhanced ability to overcome cell cycle arrest.     

Pitanga (Eugenia uniflora L.) as a source of bioactive compounds for health benefits: A review

The pitangueira (Eugenia uniflora) is a tree native to Brazil but is cultivated in several subtropical countries. A great diversity of nutrients and bioactive compounds have been found in the leaves and fruits of E. uniflora, which supports its use in folk medicine to treat diseases such as stomach and intestinal disorders, fever and general inflammation. Antimicrobial, antiviral, antifungal and antioxidant effects on metabolism have been reported for this plant. This review discusses the phytochemical profile, toxicity and pharmacological action of E. uniflora leaves and fruits and points out that gaps in the literature that need to be investigated further. This review also discusses studies developed with E. uniflora demonstrating its promising therapeutic potential for several diseases with an apparent low toxicity in mammals. The compilation of the main pharmacological and toxicological results, as well as the phytochemical characterization of the varieties and constituents of E. uniflora are general aspects that this review attempts to demonstrate in order to contribute to the new approaches and developments to plant-derived natural product drug discovery. However, further studies are required to establish the nutraceutical effects and uses of E. uniflora as an important and safe supplement for human health.     

FFT-BP神经网络模型对车载γ能谱辐射剂量率的预测分析

为了实现车载γ谱仪巡测系统对辐射剂量率的准确测定，提出基于快速傅里叶变换(FFT)本底扣除法的改进型BP神经网络模型(FFT-BP神经网络模型)。实验采用γ射线能谱分析法，对不同间距处的137Cs放射源进行车载γ能谱测试，将得到的谱数据通过快速傅里叶变换(FFT)扣除本底，获得新的谱线数据。应用FFT-BP神经网络模型对未知剂量的车载γ谱线作辐射剂量率的定量预测，将预测结果同3个函数模型的拟合结果比较，验证FFT-BP神经网络模型的预测效果。结果表明，FFT扣除法能较好的削弱散射本底对γ谱线的影响，能有效的降低谱线本底。通过新谱线获得的特征峰面积和净谱线面积与辐射剂量率的相关系数均为0.99(p<0.05)，相关性显著。模型拟合分析过程中，FFT-BP神经网络模型表现出较强的学习泛化能力，预测较理想，相对误差和累计误差分别低于0.6%和9%，效果明显优于数学模型和γ能谱全能峰法，可显著降低γ能谱分析辐射剂量率的误差，且能有效提升工作效率。因此，FFT-BP神经网络模型适用于γ能谱辐射剂量的预测分析，为车载γ谱仪巡测系统测量辐射剂量提供了一种新型有效的分析方法。     

低剂量CT扫描技术在肋骨骨折检查中的研究进展

X线自发现以来,在医学领域运用越来越广泛.但是,医疗用X射线是人类最大的人为辐射来源,并认为辐射是造成癌症等疾病发生的重要危险因素.目前,CT扫描对肋骨骨折的诊断已被认为是最佳检查技术,但人体所受辐射剂量会明显增大.通过降低管电流、管电压、增大螺距,以及根据体重指数或噪声水平设定、采用迭代重建技术等多种方法降低CT扫描...     

一个模拟光子照射人体的蒙特卡罗程序

本文分绍了一个用于辐射防护和医疗目的的蒙特卡罗程序。它能计算出受到光子照射时人体20种器官(组织)的吸收剂量和人体有效剂量当量。程序中使用了一种特殊的方法以加快计算结果的收敛。本文所介绍的方法也可用于其他复杂几何系统的剂量计算。     

基于数字微反射镜灰度光刻的成像模型

在深入探讨DMD(Digital Mirror Device)灰度图形传递的特点基础上,把曝光量分布作为分析数字光刻成像的物理量,建立了数字灰度光刻的成像模型.以制作微米量级微透镜为例,通过模拟分析,讨论了数字光刻过程中DMD的工作方式、成像系统参量对抗蚀剂曝光量分布的影响,揭示了数字灰度光刻成像机理,为开展数字光刻实验研究提供了理论根据.     

The use of track registration detectors to reconstruct contemporary and historical airborne radon (RN) and radon progeny concentrations for radon-lung cancer epidemiologic study

Epidemiologic studies that investigate the relationship between radon and lung cancer require accurate estimates for the long-term average concentrations of radon progeny in dwellings. Year-to-year and home-to-home variations of radon in domestic environments pose serious difficulties for reconstructing an individual's long-term radon-related exposure. The use of contemporary radon gas concentrations as a surrogate for radon-related dose introduces additional uncertainty in dose assessment. Studies of glass exposed in radon chambers and in a home show that radon progeny deposited on, and implanted in, glass hold promise for reconstructing past radon concentrations in a variety of atmospheres. We developed an inexpensive track registration detector for the Iowa Radon Lung Cancer Study (IRLCS) that simultaneously measures contemporary airborne radon concentrations, surface deposited alpha activity density, and implanted ²¹⁰Po activity density. The implanted activity is used to reconstruct the cumulative radon and radon progeny exposure from the age of the glass and the ratios of the contemporary deposited activiteis to airborne radon gas activity. We placed over 2500 of these detectors in more than 1000 homes and retrieved 97% of them after a one-year exposure period. A preliminary analysis of the 1280 detectors that have undergone quality assurance review shows that the modules are meeting their accuracy and precision goals (10%). There is good correlation (r²0.5) between the total radon exposure estimated from contemporary radon gas measurements and historical average reconstructed from the implanted ²¹⁰Po surface activity. The linear regression slope of the airborne radon exposure to implanted activity is the same as the room model slope based on typical room parameters. This correlation improves (r²0.7) when the deposited surface activity measurements are added to the linear regression. Thus, track-registration detectors can contribute to accurate radon-related dose assessment in epidemiologic studies. Additional work is planned to incorporate the deposited activities in a more sophisticated reconstruction model.     

Dose-rate effects on the bulk etch-rate of CR-39 track detector exposed to low-let radiations

The effect of gamma-rays and pulsed electrons has been investigated on the bulk etch rate of CR-39 detector at doses up to 100 kGy under various dose-rate between 0.0044 and 35.0 Gy/s. The bulk etch rate increased exponentially with the dose at every examined dose-rates. It was reveled to be strongly depend on the dose-rate: the bulk etch rate was decreased with increasing dose-rate at the same total dose. A primitive model was proposed to explain the dose-rate effect in which oxygen dissolved was assumed to dominate the damage formation process.