剔除基因可减少辐射损伤

【路透社纽约2002年9月30日电】 人们对由核电厂和核武器等人造辐射源的有害效应十分关注,但科学家的报告表明,高水平的天然辐射也能使遗传物质DNA产生突变。 这份报告的编写者之一,英国剑桥大学的Peter Forster博士表示,这个研究结果并不意味着生活在高天然辐射水平地区的人们应当为此担忧:目前还没有结论性的证据表明他们患癌症或其他疾病的风险更大。但结果确实表明,应当重新考虑工作人员的辐射限值。 Peter Forster表示,由于印度南部的天然辐射水平是正常值的10倍,可以使遗传DNA突变达到可以测量的水平,因此应当考虑重新设置生育年…     

剔除基因可减少辐射损伤

【美国《核新闻》2002年7月刊报道】2002年5月15日发表在《国家癌症研究所杂志》上的一篇研究报告表明,剔除控制炎症的基因能够显著降低因辐射治疗而导致的长期损伤。该报告还建议患者可以通过服用阻碍这种基因发挥作用的药物来避免辐射治疗的某些并发症。 对胸腔进行辐射治疗是治疗乳腺癌、肺癌、食管癌及其他癌症方法的组成部分。事实上,接受这种治疗的患者几乎都患上了程度不同的肺炎,通常这种疾病都会在几周内好转。这主要是由于辐射给肺造成了损伤,人体免疫系统中的炎性细胞就作出反应,就像人体受创伤之后一样。但是,有些患者的肺炎可…     

sCD40L在小鼠急性辐射损伤中的应用研究

CD40和CD40L的相互作用在机体细胞和体液免疫调节及其应答中起重要作用，注射可溶性CD40L（sCD40L)可促进骨髓移植小鼠粒细胞和血小板数量的恢复。本实验采用外周血细胞计数、白细胞分类计数、免疫荧光标记和流式细胞技术，了sCD40L对小鼠急性辐射损伤的救治作用。结果显示，体内注射sCD40L以最佳剂量100μg处理受照小鼠时可明显延长其存活时间，并促进CD8^ T细胞比例和CD4^ /CD8^ T细胞比值的恢复。说明sCD40L对受照小鼠免疫系统损伤具有一定的修复作用。     

血细胞基因突变作为评估电离辐射损伤的分子标志

综合简述了ｈｐｒｔ基因、Ｔ细胞受体（ＴＣＲ）基因、人白细胞抗原基因Ａ（ＨＬＡ－Ａ）基因和血型糖蛋白Ａ（ＧＰＡ）基因作为辐射生物剂量标志的研究进展，从它们的生物学特性，检测方法和人体实际应用情况以及存在的问题进行讨论。     

抗辐射损伤药物的研究现状

对氨琉基类辐射防护剂、细胞因子、激素、中草药等6类抗辐射损伤药物的特性,抗辐射效果、作用机理以及常见毒副作用进行了综述,并对其研究前景作了展望.     

BCC金属Nb的重离子辐射损伤研究

采用81 MeV碳离子辐照,模拟中子注量为10~(23)/cm~2的堆中子在Nb中产生的辐射损伤,用时间微分扰动角关联和正电子湮没二种方法研究辐射损伤及其高温退火效应。实验发现经注量2.5×10~(16)/cm~2的碳离子辐照后,在BCC金属Nb中产生单空位和双空位二种缺陷。随退火温度升高,双空位分解,单空位的总浓度逐步减小,经过1058K退火后,在Nb中由辐射损伤造成的缺陷消失。     

银辐射损伤的扰动角关联研究

采用时间微分扰动角关联方法研究了由~(109)Ag(α;2n)反应产生的反冲核~(111)In在银中产生的辐射损伤及其退火现象和治愈效应。反冲核在银中产生单空位,实验观察到频率为76.2MHz的恒定的四极相互作用;经673K退火,恒定的四极相互作用消失,作用在探针核上的只是远处缺陷产生的电场梯度分布;经873K退火,辐射损伤全部消失。银中辐射损伤与治愈时间关系测量表明,经360h治愈,探针核仍直接捕获缺陷,但相对成分减小到1/3.5;电场梯度分布宽度随治愈时间增长而减小,150h后,不随治愈时间而变。治愈主要发生在辐照后2—10d。     

大鼠睾丸辐射损伤的组织病理学研究

运用生精上皮周期理论,以定量组织学方法,结合采用电镜组化技术,观察了~(60)Coγ射线全身照射大鼠后睾丸生精上皮、曲细精管界膜和界膜内碱性磷酸酶的改变。探讨了~(60)Coγ射线对生精上皮的损伤特点,曲细精管界膜内碱性磷酸酶的辐射敏感性,以及界膜和界膜内碱性磷酸酶与生精上皮在辐射损伤、修复中的相互关系。结果显示,分化型精原细胞对辐射最敏感;4Gyγ射线全身照射后,大鼠生精上皮仍可恢复,幸存的耐辐射精原干细胞是修复上皮的唯一来源;支持细胞超微结构随照射后生精细胞数量的减少而改变;照射后界膜明显增厚、分层、皱折;界膜内碱性磷酸酶的辐射耐受性较高,受照后12天碱性磷酸酶反应产物明显减少,其恢复早于生精上皮的修复。     

BaF_2晶体辐射损伤的光谱研究

本文给出了BaF_2晶体被辐照前后的自发光谱、透射光谱和光激发光谱的变化。结果表明,经~(137)Cs和~(60)Co的γ射线辐照后的BaF_2晶体有较强的自发光,在310nm和650nm附近有两个峰。不同晶体的自发光谱不完全相同,同一块晶体的光谱形状不随受照剂量的大小而改变,但光的强度却与受照剂量有关;自发光随时间的衰减具有多种成分。辐照后BaF_2晶体的透射率下降,恢复缓慢,但紫外光照射可以加速透射率的恢复。290nm的光能激发出BaF_2的慢成分光,不同晶体的光激发发射光谱不完全相同,但辐照后无明显变化。     

以斑马鱼为模式生物的辐射效应修饰剂研究

利用斑马鱼作为模式生物,进行一系列的实验研究,尤其在胚胎发育、基因表达、药物筛选和疾病模型方面有其独特的优势。但它被应用于辐射效应修饰剂的研究时间较短,已有的文献显示发展前景良好。本工作就近些年以斑马鱼为模式生物研究的辐射效应修饰剂进行概述,主要涉及如氨磷汀、DF-1、AG1478、Flavopiridol和一些DNA损伤修复蛋白。     

Preface: IAEA specialists' meetings on radiation damage units in graphite and ferritic and austenitic steel

A porous body model, new in its application for predicting temperature distributions in wire-wrapped fuel rod assemblies, has been developed. The model developed for thermal transport in wire-wrapped rod bundles is similar in principle to the one which has long been successfully used for heat transfer in fixed beds of packed solids. Although the model is applicable to bundles in forced and mixed (combined forced and free) convection, attention in this paper is confined to bundles operating in forced (negligible natural) convection only. The results obtained from this analysis were found to predict available data with as good a precision as does the more complex analysis.     

Effect of the composition of radiation on the radiation damage to graphite

A statistical analysis is performed of the results on the determination of the critical neutron fluence in MR, SM-2, and BOR-60 with different irradiation temperature. It is shown that the critical neutron fluence depends not only on the irradiation temperature but also, and to an even greater extent, on the radiation composition factor (ratio of the neutron and γ-ray flux densities). Thus the critical neutron fluence for irradiation at 600°C in MR (radiation composition factor 0.13) is 17·10²¹ cm⁻² and in SM-2 (radiation composition factor 0.1) 11·10²¹ cm⁻² at the same temperature. When the same graphite is irradiated in the region of the outer corner of a working block of RBMK, where the radiation composition factor is 0.55, it is expected that the critical neutron fluence will be 31.7·10²¹ cm⁻². In summary, taking account of the effect of γ-radiation introduces substantial corrections: the experimental results obtained in research reactors are found to be at least a factor of 2 too low. This gives hope of substantiating the substantial increase in the service life of the RBMK graphite masonry. 3 figures, 8 references. Scientific-Research and Design Power-Engineering Institute. State Science Center—Scientific-Research Institute of Nuclear Reactors. Translated from Atomnaya énergiya, Vol. 87, No. 1, pp. 24–28, July, 1999.     

Study by positron annihilation of radiation damage in an aluminium collimator of a 30 MeV electron linac

A positron annihilation lineshape study was made of samples cut from an aluminium commercial alloy collimator of a 30 MeV electron LINAC. The same material was studied after 60% deformation and both measurements were compared with the results of deformed pure aluminium samples. It was concluded that after irradiation, in addition to dislocations other trapping centres also have to be present. The annealing behaviour of the different samples is discussed.     

igh statistics study of radiation damage on silicon microstripdetectors

This paper investigates the performance of silicon microstrip detectors after heavy irradiation. Full-size prototype sensors (53 × 64 mm²) designed for the CMS Tracker have been irradiated with protons and extensively studied in the laboratory and using a beam of minimum ionising particles operated at low temperature as foreseen for the Large Hadron Collider. We present results of large statistics measurements of collected charge, noise, position resolution, and hit finding efficiency for these irradiated detectors     

Effect of electron excitation on radiation damage in fce metals

Defect production, radiation annealing and defect recovery are studied in several fcc metals (Al, Cu, Ni, Ag and Pt) irradiated with low-energy ( 1 MeV) and high-energy ( 100 MeV) ions. Irradiation of the metals with strong electron-lattice interaction (Al, Ni and Pt) by 100 MeV ions causes an anomalous reduction, or even a complete disappearance of stage-I recovery. This experimental result shows that the energy transferred from excited electrons to lattice atoms through the electron-lattice interaction contributes to the annihilation of single interstitials. This effect is also observed in Ni as a large cross section for radiation annealing, and a decrease of the damage efficiency. On the other hand, in Cu and Ag thin foils, we find that lattice defects are produced not only through elastic interactions, but also through a process strongly associated with electron excitation. In the latter process, the defect production cross section is proportional to S_e^1.7 in Cu and S_e^1.5 in Ag. The nearly quadratic dependence of the cross section on S_e suggests that the mutual Coulomb repulsion of ions positively charged by electron excitation causes the defect production.