共查询到19条相似文献,搜索用时 62 毫秒
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电离辐射致DNA损伤的程度受到很多因素的影响,如剂量、剂量率、射线种类、DNA浓度等。北京师范大学周宏余课题组利用电子顺磁共振谱仪测量了不同电荷态的低能C离子辐照丙氨酸薄膜后产生的自由基浓度,实验结果发现,当离子注量达到10^13cm-2时,随着离子电荷态的增加,产生自由基相对浓度减少。 相似文献
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235U的裂变产物产额是核能应用和核物理研究中的重要基础数据。本工作应用高纯锗γ能谱法绝对测量了0.57、1.0 MeV和1.5 MeV中子诱发235U裂变的各能量点30个质量链的产额数据。样品的裂变率通过双裂变室监测,并利用蒙特卡罗(MCNP)模拟了辐照时样品的中子能谱,结果与国际上相应能量点数据在实验不确定度范围内吻合。本工作得到的产额数据澄清了原有数据最高16%的差异并将数据精度从国际上原有数据精度5%~7%提高到3%~5%。 相似文献
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为研究不同类型和能量的粒子照射细胞核DNA时导致的DNA损伤等辐射生物效应,建立了DNA、染色质原子模型,并开发了纳剂量蒙特卡罗程序NASIC。该程序可模拟包括光子、电子、质子在内的多种粒子在生物介质中的作用过程,既包括物理和化学径迹结构,也包括后续的生物响应过程。使用NASIC程序模拟了~(137)Cs源、Al的K层特征X射线(Al_K)源照射哺乳动物细胞后造成的单链断裂和双链断裂产额。研究结果表明,本文使用的DNA原子模型更加接近真实结构,DNA双链断链产额计算结果与实验值吻合较好。 相似文献
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14.8MeV单能中子所致染色体畸变的剂量-效应关系 总被引:1,自引:0,他引:1
采用14.8 MeV单能中子对3名健康成人外周血进行照射,照射剂量分别为0、0.1、0.3、0.6、1.0、2.0、3.0、4.0Gy,观察淋巴细胞染色体畸变情况,建立本实验室染色体畸变与受照剂量的剂量-效应关系.实验结果表明:双着丝粒体+环状体数、无着丝粒体数、总畸变数、畸变细胞率与中子剂量均存在良好的线性关系,回归方程分别为Ydic+r=0.0291+0.0607(r2=0.986)、Yace=0.0124+0.1411D(r2=0.982)、Ya=0.0434+0.2035(r2=0.989)、Yac=0.0362+0.0475D(r2=0.927). 相似文献
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医用电子直线加速器产生的X射线已广泛的应用于放射治疗过程。由于X射线能量高于某一阈值与周围物质发生(γ,n),(γ,2n)反应而产生光核中子,导致治疗过程中,存在一定程度的中子污染危害。采用Monte-Carlo模拟方法,以点源模型对一台工作在15MeV能量档的Primμs-M型医用电子直线加速器,对照射野在0cm×0cm、3cm×3cm、5cm×5cm、10cm×10cm和20cm×20cm时,使用CR-39固体核径迹探测器和中子气泡探测器(BND)对照射野及照射野外中子剂量分布进行了测量,并对光中子剂量分布进行了模拟。测量和模拟的结果均表明,单一照射野内,光核中子引起的剂量随照射野周长减少呈指数增强趋势。随着照射野面积增大,光核中子总注量逐步增强。采用调强适形放射治疗时,光核中子引起的中子剂量贡献不容忽视。 相似文献
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采用14.8 MeV单能中子对3名健康成人外周血进行照射,照射剂量分别为0.0、0.1、0.3、0.6、1.0、2.0、3.0、4.0 Gy,观察双核CB细胞微核,建立本实验室CB微核法的微核细胞率和微核率与受照剂量的剂量-效应关系。微核细胞率与中子剂量的回归方程为Y=14.8681+43.3973D(r2=0.976),Y=3.3758+73.4099D-7.9360D2(r2=0.986),Y=69.8514D0.6735(r2=0.986);微核率与中子剂量的回归方程为Y=13.9096+55.9122D(r2=0.986),Y=2.6949+85.1997D-7.7442D2(r2=0.991),Y=81.5022D0.7367(r2=0.990)。结果表明,人体外周血CB细胞微核细胞率和微核率与14.8 MeV单能中子照射剂量存在良好的二次多项式和幂函数关系。 相似文献
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在空间辐射环境中,辐射源主要是银河宇宙射线(GCR)和随机发生的太阳粒子辐射(质子事件)。其中以质子含量最为丰富,其次为α粒子和少量其它更重的离子。已有的模型计算结果表明,在飞往火星的路途中,宇航员身体内的每个细胞每几天就会被1个质子击中。 相似文献
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质子作为一种高传能线密度(LET)的辐射,具有能量沉积与局部剂量远大于低LET辐射(如X射线、γ射线和电子束等)的特点,通过物质时有完全不同的径迹结构,能够更有效的诱发DNA发生双链断裂,产生更多的不能修复性损伤,引起细胞的转化和死亡以及癌的发生等较高的相对生物效应(RBE)。在DNA分子水平上研究质子致生物损伤的机理,深入了解其辐射特点及危害程度,并研究相应的防护途径十分重要, 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):523-534
Energy spectra of neutrons scattered inelastically from natural samples of Ta, W, Au, Hg, TI, Pb and Bi have been studied at an incident energy of 14MeV, using time-of-flight technique. Angular distributions were also measured for Ta and Bi. The energy spectra from 2MeV to 4MeV were found to be qualitatively consistent with the prediction from statistical theory taking account of effects of nuclear pairing and shell structure. The Fermi gas level density parameter and the nuclear temperature were obtained by considering the contribution of the (n,2n) reaction. The variation of level density parameter plotted against mass number was found to agree with the trend predicted theoretically by Newton. Angular distributions proved to be symmetric about 90° and the spin cut-off parameter was estimated to be about 5.8 for Ta and 4.3 for Bi. Cross sections for the (n,n′2n) and (n,2n) reactions were obtained. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(5):301-309
Continuous spectra of neutrons inelastically scattered from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge and As have been measured at an incident energy of 14 MeV with good statistics. Time-of-flight technique was used. In the analyses there were used three sets of inverse-reaction cross section σi: (1) calculated with Perey-Buck potential, (2) with Bjorklund-Fernbach potential and (3) cross section assumed to be constant. The inverse-reaction cross section does not affect appreciably the values of nuclear temperature or nuclear level density parameter for these nuclei except Ti, V and Cr. The nuclear temperature was found to be nearly constant in the mass number region of 48–75. The level density parameter as a function of mass number follows the general trend suggested by Newton. Newton's coefficient is found to be 0.092, in agreement with values obtained in other experiments. The total inelastic scattering cross sections are derived. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(6):417-422
In order to make a benchmark validation of the nuclear data for Zr, the leakage neutron spectrum from a Zr sphere of a 61-cm diameter was measured between 0.1 and 16MeV using a time-of-flight technique with a 14MeV neutron source facility, OKTAVIAN. The result was compared with the calculation using the Monte Carlo code MCNP-4A. To investigate the spectrum dependence on the individual neutron reactions, test calculations were carried out with the MCNP-4A code using the JENDL-3.2-based libraries, in which partial cross section values were reduced from the original values. From the comparison between the measured and the calculated spectra, it was found that each of the results could predict well the experiment in general. However, in detail, both ENDF/B-VI and EFF-2.4 gave considerable overestimation above 1 MeV. The JENDL-3.2 predicts the spectrum almost satisfactorily except below 0.8 MeV and around 10 MeV. The discrepancy found in JENDL-3.2 calculation is considered due to the cross section values of the (n, 2n) reaction and its secondary energy distributions (SED). The modified JENDL-3.2 library with the reduced (n, 2n) reaction values and the lower SED below 1 MeV reproduced the experiment with better agreement over the whole energy range. 相似文献