辐照剂量增量对泥石流物质热释光等效剂量的影响

等效剂量的准确测定是进行地质样品热释光年龄测定的关键。采用不同辐照间隔增量测量泥石流物质标样,测得的等效剂量值是不同的,说明辐照剂量增量对泥石流物质样品等效剂量值存在影响。测试选用已知等效剂量为30 Gy的泥石流标样,按不同的辐照剂量增量进行等效剂量测定。2.5Gy/min的β源(90Sr-90Y)辐照剂量增量分别选用1、2、4、6 min时,测得的等效剂量分别为19.3、22.3、26.4、23.0 Gy;8 Gy/min的β源(90Sr-90Y)辐照剂量增量分别选用0.5、1、1.5、2 min时,测得的等效剂量分别为17.6、19.6、25.3、15.6 Gy。研究表明:对于30 Gy的泥石流标样,剂量率为2.5 Gy/s的β源(90Sr-90Y)测定泥石流物质时最适合的辐照剂量增量为4 min。剂量率为8 Gy/s的β源(90Sr-90Y)测定泥石流物质时最适合的辐照剂量增量为1.5 min。     

UVC诱导的枯草芽孢杆菌DNA双链断裂及影响因素探讨

为探讨短波紫外线（Ultraviolet C，UVC）对枯草芽孢杆菌基因组DNA的损伤效应，探讨研究方法和材料对结果的影响，以枯草芽孢杆菌为研究材料，分别对其菌体样品及DNA样品进行不同剂量的UVC辐照，采用8h、16h、24h脉冲场凝胶电泳分离DNA片段。结果发现，16h脉冲场凝胶电泳最能反映DNA的双链断裂程度。对16h电泳图进行数据分析发现，随UVC辐照剂量的增大DNA释放百分比递增；菌体样品在辐照剂量17．8J／cm^2处其DNA双链断裂产额最大，而DNA样品的最大双链断裂产额出现在辐照剂量为72．7J／cm^2处；另外，同辐照剂量下菌体样品的释放百分比和菌体DNA双链断裂产额均高于DNA样品。结果表明，UVC诱导的枯草芽孢杆菌DNA双链断裂程度与辐照剂量及辐照样品密切相关。     

辐照剂量率对明胶自由基和性能的影响

为探讨剂量率对明胶分子辐照分解的影响机理,采用电子自旋共振(ESR)、凝胶渗透色谱(GPC)等检测技术分析明胶经剂量率为60、480Gy/min 60 Co以及剂量率为12 000Gy/min加速器辐照0~32kGy剂量后,自由基特征、明胶性能与剂量率的关系。结果表明,未辐照明胶ESR信号微弱,三种辐照方式处理后的明胶均呈现相似的ESR双峰特征;相同吸收剂量下,明胶自由基信号强度由大到小依次为60Gy/min 60 Co辐照明胶、480Gy/min 60 Co辐照明胶和12 000Gy/min加速器辐照明胶;60 Co辐照后自由基信号强度(y)与剂量(x)的线性关系为y=26.983x2+1 641.8x-205.69;辐照明胶特性黏度、平均相对分子质量、凝胶强度和断裂伸长率由高到低依次为480Gy/min 60 Co辐照明胶、12 000Gy/min加速器辐照明胶和60Gy/min 60 Co辐照明胶。可见,高剂量率辐照可能减少明胶中有效长寿命自由基的含量,从而抑制明胶辐照灭菌中性能的劣变。     

γ射线诱导的肝癌细胞DNA双链断裂

为了揭示辐射生物学效应的机理,用倒转脉冲场凝胶电泳（ＰＩＧＥ）研究了γ射线辐照肝癌ＳＭＭＣ－７７２１细胞诱导的ＤＮＡ双链断裂（ＤＳＢ）及其修复２４、４８ｈ后的产额和片段的分布情况。结果表明：修复０ｈ和２４ｈ的样品,ＤＮＡ片段释放百分比（ＰＲ）随着剂量的增加而增加;诱导的ＤＳＢ片段主要是１Ｍｂｐ－２Ｍｂｐ的大片段;ＤＳＢ产额分别为０．３８ＤＳＢｓ／１００Ｍｂｐ．Ｇｙ和０．０６ＤＳＢｓ／１００Ｍｂｐ．     

剂量率对辐照牛血清蛋白生化特性和结构的影响

为研究高剂量率对牛血清辐照灭菌中的活性下降的抑制作用,将新生牛血清分别经平均剂量率为60、600 Gy/min钴源和300 k Gy/min电子加速器3种方式辐照30 k Gy后,分析牛血清蛋白的生化特性和结构变化及其与剂量率的关系。结果表明,与未辐照牛血清相比,辐照后蛋白浊度、疏水氨基酸荧光强度、放热峰出峰时间分别从0.742、24.1 u和16.5 min升高至0.802、99.3 u和17.2 min,而蛋白浓度、放热峰温度分别从0.473和76.4℃下降至0.444和74.5℃。电泳分析(SDS-PAGE)显示,600 Gy/min钴源辐照牛血清中相对分子质量为175 k Da和58 k Da的蛋白组分含量明显大于低剂量率辐照牛血清。经扫描电镜(SEM)分析,辐照后牛血清中沉淀部分呈现密集的网络结构,未沉淀部分呈现碎片和球状体混合的形貌结构,低剂量率辐照的样品蛋白球状体形貌不突出。可见高剂量率有抑制辐照灭菌牛血清蛋白分子变性的作用,3种方式中600 Gy/min钴源效果最明显。     

保偏光纤电离辐射效应研究

本文从光纤陀螺中主要部件保偏光纤空间应用的角度出发,利用60Co辐照源模拟空间辐照,对保偏光纤环的电离辐射效应展开研究,基于保偏光纤在不同剂量率条件下的辐照试验,探索保偏光纤随辐照剂量的变化规律。实验结果表明,累积剂量和剂量率为63Gy与0.01Gy/s、32Gy与0.02Gy/s、326Gy与0.0835Gy/s的光纤损耗分别增加1.0dB、0.55dB和5.8dB,也即保偏光纤损耗随总剂量与剂量率增大。理论分析得到的光纤辐照损耗与剂量率的关系与试验数据相吻合。本文结果可为保偏光纤电离辐射效应的地面试验提供参考。     

快中子辐照对枯草芽孢杆菌的灭菌效果研究

利用快中子脉冲堆(Chinese Fast Burst ReactorⅡ,CFBR-Ⅱ)产生的快中子,采用枯草芽孢杆菌黑色变种为材料,考查了中子辐射灭菌效果及剂量、剂量率、辐照温度、照射状态等辐射灭菌影响因素.结果表明,在剂量率为7.4 Gy/min时的D10值为384.6Gy,中子剂量与存活芽孢对数满足y=-0.0026x 10.462的函数关系;在剂量为800Gy时,剂量率与存活芽孢对数满足y=7.7414X-0.0834的函数关系;升高温度有利于中子辐射灭菌;中子辐照不同状态芽孢,其存活率为:菌片＞粉末＞液体.     

30%TBP-煤油-HNO3体系的α辐解行为Ⅱ.溶剂辐解生成羰基化合物的规律

以分光光度法研究了²³⁸Pu 为α源的30%TBP-煤油-HNO₃体系辐解产物羰基化合物的生成规律,考察了还原反萃、酸碱洗涤、钚浓度等工艺条件对羰基化合物分析的影响。研究表明：羰基化合物生成量随着α辐照剂量率以及吸收剂量的增加而增大,在剂量率73.7 Gy/min、吸收剂量5×10⁵ Gy时,羰基化合物浓度达到0.039 mol/L;吸收剂量在10⁵ Gy以上时,α辐照产生的羰基化合物生产量明显高于γ辐照;不同稀释剂对羰基化合物生成量影响不明显。     

电离辐射诱导体外DNA链断裂机理研究进展

概述了电离辐射诱导体外DNA单链断裂（SSB）和双链断裂（DSB）的形成机理。研究结果表明,DNA链断裂产额与DNA浓度和自由基清除剂的清除有力有关。并受DNA超螺旋度的影响。DNAαDSBB除可由直接作用形成外,还可分别由单自由基传递机制和LMDS机制产生;对LET辐射,αDSB主要由LMDS机制产生,而硫醇类化合物对DNA的辐射保护作用则随其电荷态的增加而增加;由于次级自由基反应,体外DNA链断裂具有反向氧效应;非均一动力学的柱模型被广泛地应用于OH等自由基与DNA反应的理论研究。     

ESR测年研究中水成沉积物对不同人工辐照剂量率响应初探

本文以水成沉积物为研究对象,在实验室常用辐照剂量率1×10-1-1×102Gy/min范围内,选择不同的剂量率对同种样品进行辐照,观察不同剂量率辐照下Al心ESR信号的剂量响应曲线特征.实验结果表明,不同人工辐照剂量率对水成沉积物样品的剂量响应特征没有影响,现有的人工辐照技术能够满足我们的实验要求.     

Comparison of DNA double—strand breaks induced by ^16O^8＋ in deproteinized DNA and intact cells

The yield of DNA double-strand breaks(DSBs) is sure to be influenced by the environment around DNA molecule.Inverse pulsed-field gel electrophoresis(PIGE)has been applied to compared the sensitivity of B16 cells and their DNA in DSBs induced by 75MeV/u 16O^8 beam.Results show that the percentages of DNA released from the plug(PR)in both kinds of the samples increase with the dose and approach a similar quasi-threshold of about 81%.A simple new equation was presented to calculated the break level of DNA molecules.Within a certain dose,the relationship between the break level and the dose is linear.THe yield of DSBs in deproteinized DNA was 1.11DSBs/100Mbp/Gy,while that in intact cells was 0.60DSBs/100Mbp/Gy.it is testified that deproteinized DNA is more sensitive to oxygen ions irradiation than intact cells.     

Study on DNA Damage Induced by Neon Beam Irradiation in Saccharomyces Cerevisiae

Yeast strain Saccharomyces cerevisiae was irradiated with different doses of 85 MeV/u 20Ne10+ to investigate DNA damage induced by heavy ion beam in eukaryotic microorganism. The survival rate, DNA double strand breaks (DSBs) and DNA polymorphic were tested after irradiation. The results showed that there were substantial differences in DNA between the control and irradiated samples. At the dose of 40 Gy, the yeast cell survival rate approached 50%, DNA double-strand breaks were barely detectable, and significant DNA polymorphism was observed. The alcohol dehydrogenase II gene was amplified and sequenced. It was observed that base changes in the mutant were mainly transversions of T→G and T→C. It can be concluded that heavy ion beam irradiation can lead to change in single gene and may be an effective way to induce mutation.     

Assessment of mouse BMMNC DNA damage with a two-tailed comet assay after X-ray and carbon ion total body irradiation

The two-tailed comet assay(2T-comet assay) is a method for simultaneously evaluating DNA single-strand breaks(SSBs) and double-strand breaks(DSBs). In the present study, the endonuclease DNase I and hydrogen peroxide were used to induce DSBs and SSBs in bone marrow mononuclear cells(BMMNCs) from mice, and the damaged DNAs were assessed with a 2T-comet assay. The results demonstrated that this method can detect and discriminate between BMMNC DNA SSBs and DSBs simultaneously. Using this method, we studied DNA damage in BMMNCs from female BALB/c mice after total body irradiation with X-rays and carbon ions. The results indicated that these two types of radiation induced serious DNA damage in BMMNCs in a dose-dependent manner.The DNA damage induced by carbon ions was more severe than that induced by X-rays at the same dose, and a high dose of carbon ion radiation was more likely to cause death in mice. The DSBs and SSBs induced by X-rays were the highest on the 3rd day post-IR. For carbon ion radiation,DSBs were the most serious on the 3rd day, while SSBs were more obvious on the 3rd day and 13th day post-IR.The ratio of DSBs/SSBs was clearly related to the different types of radiation.     

On the use of MWCVD diamond as thermoluminescent gamma dosimeter

The thermoluminescence (TL) characterization of microwave plasma assisted chemical vapor deposition diamond (MWCVD) films of 6 and 12 μm thickness grown on (1 0 0) silicon substrates was performed. The films exhibited a single well-resolved TL peak around 580 K at doses lower than 40 Gy. As the irradiation dose increased the TL peak broaden and shifted towards the low temperature side of the glow curve. The diamond samples exposed to 0.67 Gy/min ⁶⁰Co gamma radiation displayed a linear dose behavior up to 100 Gy being non-linear for higher doses. The 12 μm film showed lower TL efficiency as compared to the 6 μm specimen. The discrepancy was attributed to the non-uniform distribution of nucleated sp³ diamond and sp² bonded carbon on the substrate as revealed by SEM micrograph and Raman spectroscopy of the samples. The integrated TL glow curve of the samples exhibited low room temperature thermal fading and 3% reproducibility. The results show that MWCVD diamond films possess promising properties for radiation dosimetry applications.     

Relationship between cellular radio-sensitivity and naked DNA damage in mammalian cells exposed to heavy ions

The relationship between deoxyribonucleic acid (DNA) damage and the cell death induced by ~(12)C ions irradiation was examined in four kinds of cells, Melanoma B16, cervical squamous carcinoma HeLa, Chinese hamster V79 and hepatoma SMMC-7721. Cell survival was determined by a colonogenic assay, and the sensitivity was described by D_(50)(the dose of radiation necessary to reduce the survival to 50%). For all cell lines, D_(50) ranged from 0.74 Gy to 3.85 Gy, among them B16 was the most radiosensitive to ~(12)C ions, and V79 and HeLa cells had almost the same radio-sensitivity, SMMC-7721 was the last. The induction of deproteinized DNA double-strand breaks induced by ~(12)C ions were measured by pulsed-field gel electrophoresis (PFGE), and the initial yield of the deproteinized DNA dsbs per unit dose was expressed as the DNA double break level (L). A linear dose-response curve was seen for initial DNA dsbs for all cell lines (slopes range from 0.40-0.98 (DSBs/100Mbp/Gy)). V79 was the steepest, B16 was the last.There was an inverse relationship between the initial DNA dsb and D_(50) if the B16 cell line was not considered, but there was no relativity even excludes the B16 cell line. The present results indicate that there is no relationship between cellular sensitivity and initial DNA dsb, even exclude the effects of chromatin structure.