电子自旋共振波谱技术检测香辛料类辐照食品的研究

本文研究了四种香辛料类食品（花椒、芥末粉、咖喱粉、姜粉）经0—15kGy剂量辐照后电子自旋共振（ESR）波谱特征及信号强度的变化,并探讨了ESR信号强度在220d贮藏期内的变化规律。结果表明,4种香辛料样品辐照前后ESR波谱均有明显区别,ESR波谱信号强度与剂量呈现正相关。在贮藏期内所有样品信号强度均有减弱,除芥末粉外其余样品经过220d后仍能应用ESR法检测判定是否经过辐照处理。这为制定我国辐照食品的ESR检测办法标准提供了依据。     

ESR法检测含纤维素辐照食品的研究进展

本文阐述了电子自旋共振(ESR)波谱技术检测含纤维素辐照食品的原理,介绍了国内外ESR法检测含纤维素辐照食品的研究进展,提出了该方法在应用中可能存在的问题,并对如何能更好地扩大ESR法检测含纤维素辐照食品的应用范围提出了建议。     

辐照聚丙烯的ESR法鉴定

为间接检测鉴定辐照食品,实验采用电子自旋共振波谱法(Electron spin resonance,ESR)检测食品包装材料聚丙烯,优化实验条件,研究辐照聚丙烯ESR波谱特征.结果表明,未经辐照和辐照聚丙烯ESR图谱差异明显;辐照聚丙烯的gt=2.0350±0.0002,g2=2.0089±0.0002,g3=2.00...     

含纤维素辐照食品的ESR法研究

60Co发出的γ射线于0,0.5,1.0,3.0,5.0,10.0kGy剂量范围对干燥的红辣椒粉、花生和提取出的草莓籽进行了辐照处理,用电子自旋共振(Electron spin resonance,ESR)来分析研究信号强度与辐照剂量的关系以及相关性R2.结果表明,三种样品的ESR信号与剂量正相关,其中草莓的ESR信号随剂量增长最慢,红辣椒粉的计算最为精确,花生的次之.含纤维素辐照食品的剂量与ESR信号关系清晰,可作为建立ESR方法检测辐照食品的方法.     

ESR波谱法检测辐照食品方法研究进展

本文介绍了ESR波谱法检测辐照食品的基本原理,综述了国内外ESR波谱法检测辐照食品的研究进展,提出了影响ESR波谱法检测的六点主要因素。最后,对ESR波谱法检测辐照食品的前景提出了设想,并对未来ESR波谱法检测辐照食品研究方向提出了建议。     

电子自旋共振技术鉴别辐照茶叶

研究黄山毛峰和祁门红茶经Co-60γ射线辐照诱导的电子自旋共振(Electron spin resonance,ESR)波谱特征,以及吸收剂量、贮藏时间与茶叶中自由基ESR信号强度的关系,考察利用ESR技术鉴别辐照茶叶的可行性。结果显示,低吸收剂量能显著增加茶叶中ESR信号强度(p0.01);茶叶中自由基的信号强度随吸收剂量呈多项式关系增长,与贮藏时间呈乘幂函数关系下降;在常温贮藏70 d后,信号强度逐渐稳定,但依然显著高于未辐照样品的信号强度(p0.01),据此表明,使用ESR法可以鉴别辐照与非辐照的茶叶。     

辐射引发的亚油酸和亚麻酸自由基产物及α-生育酚的辐射保护效应的ESR研究

用电子自旋共振波谱法,对在含氧条件下经过低温γ辐照的不饱和脂质亚油酸和亚麻酸产生的初级不稳定自由基,及其在程序升温过程中所产生的自由基变化进行了研究。由77K辐照并测定的ESR谱表明其初级不稳定产物为阴离子自由基和脂质长链上不饱和部分的抽氢自由基,在120 K附近所测得的ESR谱显示了脂质过氧自由基的波谱特征,随着温度继续上升,最后演变为戊二烯基自由基和α-碳抽氢自由基。亚油酸和亚麻酸与α-生育酚(摩尔比1:1)二元体系的ESR研究,揭示了α-生育酚对亚油酸和亚麻酸的辐射保护作用是基于氢原子转移机理。     

含脂食品辐解产物2-烷基环丁酮的研究进展

含脂食品被辐照时,食品中的脂肪酸和酰基甘油会分解形成相应的同碳原子数2-烷基环丁酮(2-alkylcyclobutanones,2-ACBs).自发现以来,2-ACBs一直是含脂辐照食品研究的热点.作为含脂食品辐照的标志性化合物,2-ACBs可用来检测含脂辐照食品.2-ACBs的产生及其稳定性受很多因素影响,如辐照剂量、辐照温度与贮藏条件等.同时,2-ACBs的毒理性也一直是含脂辐照食品研究的热点.本文阐述了利用2-ACBs检测含脂辐照食品方法的研究现状;影响2-ACBs的产生和稳定性的因素;以及2-ACBs的毒理性研究进展.     

聚四氟乙烯电子束辐射降解研究

研究了辐照剂量、辐照剂量率和辐照气体环境等因素对聚四氟乙烯(Polytetrafluoroethene,PTFE)薄膜电子束辐射降解效应的影响,并采用傅里叶变换红外(Fourier Transform Infrared Spectroscopy,FTIR)、电子自旋共振(Electron Spin Resonance,ESR)和X射线衍射(X-ray Diffraction,XRD)等方法进行分析。结果表明:电子束能够有效地对聚四氟乙烯进行降解。PTFE样品的辐射降解主要发生在主链C-C键上;在相同的吸收剂量和气体环境下辐照,低剂量率辐照样品降解好于高剂量率样品;而在相同的吸收剂量和剂量率下辐照,在空气中的辐照降解效果好于N2气环境下。     

不同制备方法对牙髓样品ESR信号的影响

研究了不同制备方法对牙髓样品电子自旋共振(Electron spin resonance,ESR)信号的影响。无放射线照射史成年人群的臼齿分别用机械方法和机械方法加化学方法进行处理,制备牙髓样品和牙釉质样品。用^60Coγ射线照射样品至不同剂量,测量其ESR信号。比较分析了单位质量样品对单位照射剂量的ESR信号响应灵敏度,以寻求能够有效降低牙髓样品本底信号对其剂量学信号的影响,提高牙髓样品ESR信号灵敏度的样品制备、处理方法。结果表明,不同方法制备的牙髓样品和牙釉质样品,其ESR信号对^60Coγ射线的响应有十分明显的差异。在牙釉质样品缺乏的情况下,利用牙髓样品的ESR信号通过叠加剂量法对受照人员剂量进行重建是可行的。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

微型X射线管空气比释动能和能谱的测量

为研究微型X射线管的特性,通过电离室测量光管出射口30 cm远处的空气比释动能,使用高纯锗探测器分别测量了Ag过滤和Cu过滤下的X射线能谱。结果表明,空气比释动能随电流的增加有线性增加的趋势,能谱图明显的观察到银的两个特征X射线。完成了微型X射线管空气比释动能和能谱的测量方法以及实验测量的工作,为微型x射线管下辐射质的建立提够了条件基础。     

Gamma-ray attenuation technique for measuring void fraction in horizontal gas-liquid two-phase flow

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas-liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of 241Am with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas-liquid two-phase flow with high accuracy.