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1.
蒙特卡罗方法调整探测器死层厚度和冷指尺寸的研究   总被引:5,自引:1,他引:4  
目的 用蒙特卡罗(MC)方法计算效率和实测效率的比较,调整HPGe探测器死层厚度和冷指尺寸,提高MC方法计算HPGe探测器γ射线探测效率的准确度。方法 在理论分析探测器死层厚度和冷指尺寸对γ射线探测效率影响的基础上,用^137Cs刻度源在不同距离处实际测量HPGe探测器的效率,并将探测器死层厚度和冷指尺寸调节前、后计算效率与实测效率进行比较。结果 探测器死层厚度和冷指尺寸调节前与调节后相比,理论计算与实测效率相对偏差的平均值由5.301%提高到3.937%。结论 相对偏差的明显改善,不仅增强了MC软件的模拟计算功能,也提高了放射性测量结果的准确度。  相似文献   

2.
目的 将蒙卡模拟与解析计算相结合,建立一种无源效率刻度方法。方法 通过蒙卡模拟对所需型号的探测器进行点对点探测效率计算,建立探测效率网格;从探测效率网格中插值,并使用数值积分方法对常用的点源、圆盘、圆柱、烧杯、球形、U型管、马林杯样品的探测效率进行解析。结果 使用上述耦合方法进行无源效率刻度计算,结果表明:0.2~3 MeV能量范围内的刻度结果与使用蒙卡模拟的刻度结果相对偏差大部分在10%以内,最大相对偏差为18.06%,计算时间缩短了至少86%。应用上述耦合方法对ORTEC公司产的某型号HPGe探测器进行点源无源效率刻度,与实验刻度结果吻合很好,相对偏差均在10%以内。结论 该方法可以推广到HPGe、LaBr3、NaI等多种探测器的无源效率刻度实际应用中。  相似文献   

3.
γ能谱测量中符合相加修正的实验研究   总被引:2,自引:0,他引:2  
目的:对环境样品γ能谱测量分析中的符合相加效应进行实验研究,并提出修正方法。方法:选取两个测量位置,拟合相关函数,插值求得待测因子,最终得到修正系数.结果:修正提高了数据准确性,结论:对符合相加进行必要的修正是获得准确测量结果的重要环节。  相似文献   

4.
目的 利用LabSOCS无源效率刻度软件模拟优化马林杯状源盒,探究HPGe探测器测量惰性气体的探测效率,为核电站惰性气体流出物的测量优化提供参考。方法 利用LabSOCS软件建立了马林杯模型,探究各惰性气体γ射线的探测效率随气体成分、气体密度、马林杯尺寸参数、马林杯体积、测量源盒形状的变化关系。结果 气体成分对马林杯中惰性气体的探测效率几乎没有影响,低能γ射线的探测效率受气体密度影响较大,选择合适的马林杯高度和半径能够使HPGe探测器获得更好的测量结果。对于BE5030 HPGe探测器,不同体积的马林杯探测效率最高值均位于半径/高度 = 0.7位置处,并给出不同体积的马林杯高度和半径的最优值。结论 选择合适的马林杯尺寸能够提高核电站流出物中惰性气体的探测效率。  相似文献   

5.
目的:用Sievert剂量计算公式结合实验测量的数据计算60Co产生的射线在等效体模中的散射修正系数。方法:采用四川成都体模和TLD法测量体模的吸收剂量,并用MATLAB应用程序来拟合修正系数,结果:给出了等效体模的散射修正系数,并计算了两种模拟事故情况下的重要器官的剂量,和它们与TLD法测出的剂量值间相对偏差。结论:在两种事故情况下,用理论公式计算的剂量与测量值相关不大,说明拟合出的系数在一定的范围内是适用的。  相似文献   

6.
目的 针对溴化镧闪烁体探测器,开展了GE)函数的计算方法研究,最终实现了空气吸收剂量率的测量。方法 首先,基于蒙特卡罗模拟计算方法,模拟计算出溴化镧探测器的γ能谱,给出不同能量的响应函数;然后,利用最小二乘法计算得到了GE)函数;最后,利用标准点源实验,将溴化镧探测器利用GE)函数转换测量得到的空气吸收剂量率与理论计算值进行了比较。结果 实验验证结果表明,基于GE)函数得到的空气吸收剂量率与理论计算值的相对偏差控制在 ±6%以内,验证了GE)函数的准确性。结论 基于γ谱-剂量转换方法,就地γ谱仪可应用于辐射剂量的测量。  相似文献   

7.
目的验证高纯锗探测器在测量气溶胶中放射性核素γ能谱的优异性能。方法先通过软件模拟出天然放射性气溶胶清晰地能谱,再使用高纯锗探测器与溴化镧探测器进行实际测量,模拟计算与实验对比验证。结果模拟能谱图与探测器能谱图全能峰高度之间的比例十分吻合,各个能峰的分辨率也大致相同,溴化镧探测器的探测效率和能力分辨率都不如高纯锗探测器。结论高纯锗探测器具有优异的分辨率跟探测效率,能够满足气溶胶测量上的需求。  相似文献   

8.
目的将蒙特卡罗效率传递因子应用到溴化镧探测器的无源效率刻度中。方法本文将蒙特卡罗效率传递因子应用到溴化镧探测器的全能峰无源效率刻度中,并基于溴化镧探测器的点源效率实验计算出该探头在121.8~1332.5 keV能量范围内的效率传递因子。在此基础上,将基于蒙特卡罗效率传递因子的效率计算值与实验值进行了比较。结果实验结果表明:在121.8~1332.5 keV能量范围内,全能峰效率计算值与效率测量值的偏差在±5%以内。结论蒙特卡罗效率传递方法进一步提高了辐射探测器无源效率刻度方法的适用性。  相似文献   

9.
目的实验室HPGe1谱仪测量样品的几何尺寸优化设计,针对一定质量的样品,给出探测效率最高时样品的尺寸。方法基于无源效率刻度方法,计算出不同几何尺寸下的实验室HPGey谱仪对圆柱形聚乙烯盒封装的1500g土壤样品的探测效率,作探测效率与样品盒直径的关系曲线,求出探测效率最大时的直径范围。另外采集野外未受人为干扰的表层土壤分装在不同尺寸的聚乙烯盒内进行测量验证。结果计算结果与实验测量值相吻合,表明计算的效率曲线可靠,对曲线进行多项式拟合后得出了最大效率处的几何尺寸。结论基于无源效率刻度方法可以较方便可靠地对实验室HPGeY谱仪测量样品的几何尺寸进行优化设计。  相似文献   

10.
目的测定一台HPGeγ谱仪效率的源自吸收修正函数。方法混合标准源由241Am、109Cd、152EU、137Cs、54Mn和60Co 6种核素组成,其介质密度分别为0.3、0.6、0.8、1.0、1.3、1.6、1.8和2.0/g/cm3。测量不同能量不同密度下γ射线的探测效率并进行S拟合。结果给出了源自吸收效率修正解析函数。结论利用给出的源自吸收修正函数可以计算59.5keV~1408keV的能量范围和0.3g/cm3~2.0g/cm3密度范围内任一源密度及γ能量的全能峰探测效率。  相似文献   

11.
目的探讨活体测量与离体测量两种方法用于监测人体放射性核素内污染的效果。方法利用NaI全身计数器(活体测量)和HPGeγ能谱仪(离体测量)分别对10名待测对象进行了监测试验,将两种方法所获得的监测数据进行对照比较。结果从两种监测方法所获取的γ计数能谱图显示,10名受试对象体内均未发现内污染。结论全身计数器和尿样γ能谱测量都可以作为监测放射性核素内污染的有效方法和手段,但各有优劣,两种方法并不互相排斥,必要时应该互相补充。  相似文献   

12.
目的 研究合肥市TSP和PM2.5颗粒物中天然放射性核素7Be和210Pb浓度的年度变化情况及其与颗粒物质量的关系。方法 通过大流量气溶胶采样器和PM2.5粒径切割器采集合肥市一年中各月份同时段的TSP和PM2.5样品,使用超低本底高纯锗谱仪对样品中放射性核素7Be和210Pb的活度进行测量。结果 研究结果表明:TSP样品中7Be和210Pb的活度浓度年均值分别为(5.34 ±1.48) mBq/m3和(1.66 ±0.84) mBq/m3,PM2.5样品中7Be和210Pb的活度浓度年均值分别为(4.32 ±1.23) mBq/m3和(1.35 ±0.68) mBq/m3;PM2.5与TSP中7Be的活度浓度月均值比值范围为0.59~0.99,PM2.5与TSP中210Pb的活度浓度月均值比值范围为0.61~0.94;TSP和PM2.57Be和210Pb的活度浓度的年度变化趋势均与颗粒物质量的年度变化趋势基本一致,呈现冬春季节高,而夏秋季节相对较低,但是TSP和PM2.57Be和210Pb的比活度均与颗粒物质量均无明显的相关性。结论 合肥市TSP和PM2.5颗粒物中7Be和210Pb的活度浓度主要取决于颗粒物质量,并且大气颗粒物中7Be和210Pb主要分布于PM2.5中,因此,在评估大气中放射性颗粒物对人体造成的危害时应主要考虑PM2.5中的放射性核素的贡献。  相似文献   

13.
Epidemiological studies of calcium and osteoporosis have been hampered by the lack of a suitable tool for assessing calcium intake. This report describes a new frequency and amount questionnaire for measuring present and past calcium intake in the elderly. The validity of the questionnaire was tested against two commonly used standards of dietary assessment, five-day duplicate diets and seven-day weighed dietary inventories. The resulting correlation coefficients were, respectively, r = 0.76 and r = 0.69, while that for repeatability was r = 0.84. Furthermore, the questionnaire categorized subjects into thirds of the distribution of intake with almost no gross misclassification. It is suggested that the present findings may be extended to the majority of normal, healthy elderly subjects, implying wide application for the questionnaire in the assessment of calcium intake in the elderly.  相似文献   

14.
This paper examines media coverage of 'breast cancer genetics', and explores its implications for public understanding. We present a content analysis of coverage in British newspapers and look at a variety of popular forms, including women's magazines, television soap opera and radio drama. Genetic/inherited risk receives a great deal of coverage across a wide range of media formats and outlets. Much of this attention has focused on individuals from 'high risk families' and dilemmas around prophylactic mastectomies. Through examining media coverage, combined with interviews with media personnel and their sources, we show why this story proved so attractive to the media and highlight the different production values which influence coverage. Finally, we introduce preliminary findings from focus group discussions to demonstrate how such 'human interest' framing has engaged audience attention and influenced public understandings. The paper concludes by highlighting the implications for analysing, predicting, and engaging with, media representations of science.  相似文献   

15.
Antibiotics represent one of the most important drug groups used in the management of bacterial infections in humans and animals. Due to the increasing problem of antibiotic resistance, assurance of the antibacterial effectiveness of these substances has moved into the focus of public health. The reduction in antibiotic residues in wastewater and the environment may play a decisive role in the development of increasing rates of antibiotic resistance. The present study examines the wastewater of 31 patient rooms of various German clinics for possible residues of antibiotics, as well as the wastewater of five private households as a reference.To the best of our knowledge, this study shows for the first time that in hospitals with high antibiotic consumption rates, residues of these drugs can be regularly detected in toilets, sink siphons and shower drains at concentrations ranging from 0.02?μg·L?1 to a maximum of 79?mg·L?1. After complete flushing of the wastewater siphons, antibiotics are no longer detectable, but after temporal stagnation, the concentration of the active substances in the water phases of respective siphons increases again, suggesting that antibiotics persist through the washing process in biofilms. This study demonstrates that clinical wastewater systems offer further possibilities for the optimization of antibiotic resistance surveillance.  相似文献   

16.
深圳公立医院管理体制改革实行政事分开、管办分开,在理事会架构下按法定机构模式组建市医管中心,落实公立医院运营管理自主权.作者从当前公立医院管理体制的弊端入手,介绍了深圳市进行公立医院管理体制改革的基本思路及改革方案设计的主要举措,深入剖析了的改革方案的特点,并对改革效果进行了预测.  相似文献   

17.
Red cell membranes, prepared from red blood cells of rats exposed to 4, 10, or 20 ppm nitrogen dioxide (NO2) for 1 to 10 days, were examined for evidence of changes in membrane components. Appreciable changes were not found in contents of phospholipid and cholesterol during exposure to 10 ppm NO2. By contrast, protein content altered with the time of exposure. Moreover, changes in protein composition were observed by employing sodium dodecyl sulfate — polyacrylamide gel electrophoresis. Twenty-four-hour exposure to NO2 at the concentration above 10 ppm resulted in a marked increase in the percentage of lysophosphatidylethanolamine (LysoPE) to the total phospholipids. The prolonged exposure to 10 ppm NO2 gave rise to a further increase in LysoPE, whereas the percentage of phosphatidylethanolamine (PE) showed a gradual decrease. A 1-day exposure to 4.0 ppm NO2 also caused an increase in sialic acid content and decreases in those of PE and hexose. In addition to contents of these components the percentage of LysoPE increased 5 days after exposure and the elevated values were maintained up to the end of exposure period. These results demonstrate that red blood cells in circulation exhibit different membrane properties in terms of lipid and carbohydrate composition during 10 days of exposure to 4.0 ppm NO2.  相似文献   

18.
Unemployment is considered to be a public health concern sincedeterioration in the health of the unemployed is often anticipated.However, for some groups, such as miners, unemployment mightimprove health due to a cessation of potentially harmful occupationalexposures. This study evaluates the health of 79 miners in oneSwedish iron-ore mine, and 226 age-matched controls from thegeneral population, during one year after the closure of themine. The participants received a questionnaire regarding medicalhistory and subjective symptoms at the beginning of the studyperiod, and after one year. Statistically significant negativeeffects on self-reported health attributable to unemploymentwere not found, although neuropsychiatric symptoms were morecommon among the unemployed miners. The miners reported a statisticallysignificant improvement in grip force (p=0.031). They had asignificantly higher prevalence of symptoms associated withmining related exposures when compared with the population controls;pain in the upper extremities [relative risk (RR)=2.27, 95%confidence interval (Cl)=1.44–3.59), back pain (RR=1.84;Cl=1.237–2.75), vasospastic disease of the fingers (RR=2.05;Cl=1.18–3.57) and obstructive respiratory symptoms (attacksof dyspnea and wheezing: RR=3.67; Cl=1.167–11.6).  相似文献   

19.

Context

Tularemia is a zoonosis affecting humans and hares in France. We describe the results of surveillance in both species, in 2007 and 2008.

Methods

Human tularemia cases are mandatorily notifiable in France since 2003. In hares, surveillance relies on volunteer hunter associations in all districts of the country. Data from mandatory reports and volunteer surveillance in 2007/2008 were analyzed and compared with previous results.

Results

In 2007/2008, 144 cases were reported in humans and 117 cases in hares. This was a 100% increase compared to previous years. Human cases differed from those of previous years only by the frequency of contact with breeding animals. Human cases without any documented risk exposure were also more frequent.

Conclusion

An increase of tularemia cases occurred in 2007/2008 in both species. Complementary studies are needed to identify the species reservoir in France to understand the causes of this peak of cases.  相似文献   

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