Explosives detection using prompt-gamma neutron activation and neural networks

This work describes a study of the application of a neural network to determine the presence of explosives using the neutron capture prompt gamma-ray spectra of the substances as patterns which were simulated via Monte Carlo N-particle transport code, version 4B. After the training of the neural networks, it was possible to determine the presence of the C-4 explosive, even when they were occluded by several materials. The neural network was a powerful tool, able to recognize prompt gamma-ray explosive patterns in spite of the presence of occluding materials. Besides that, the network was able to generalize, identify the presence of explosive in cases in which it had not been trained. In that way, it was revealed as a potential tool for in situ inspection systems.     

航天飞行中潜伏病毒再活化的研究进展

目的综述航天飞行活动中潜伏病毒再活化研究进展.资料来源与选择国内外公开发表的有关论文及研究报告.资料引用国内外发表的文献24篇.资料综合简要概述了航天活动中和地面模拟研究中潜伏病毒的再激活现象并展望其在未来航天研究中的重要性.结论潜伏病毒再活化研究在航天飞行中具重要意义,应在我国载人航天飞行中开展此类研究.     

飞行人员宇宙辐射受照剂量计算机估算系统

目的为了保障机组人员健康和飞行安全,研究开发宇宙辐射剂量计算机估算系统.方法先通过模拟和测量数据,根据给定日期、地理坐标和海拔计算剂量率,然后按照飞行信息计算航程有效剂量.结果用该系统计算的剂量率和航线剂量的数值结果满足国际放射防护委员会60号出版物的精度要求.结论该计算机宇宙辐射剂量估算系统适用于航空公司辐射防护管理.     

A role for computer simulation in solving the riddles of autoreceptor-mediated regulation of GABA release

Summary The autoreceptor-mediated control of GABA release was simulated on a personal computer using commercially available software (STELLA^TM/ITHINK^TM). The experimental data to be matched were taken from previous publications. A basic model was able to fairly accurately reproduce frequency dependencies of GABA release in the presence and absence of uptake inhibition as well as concentration-response curves for changes in release produced by the agonist, (–)-baclofen, or by relatively low concentrations of the antagonists, phaclofen and CGP 35348. Obvious mismatch was observed at high concentrations of a potent antagonist, at a stimulation frequency of 2 Hz. Whereas the experimental data indicate a 3-fold increase in release as compared to controls, simulation predicts a 7-fold increase. By adaptation of the model, simulation data were obtained indicating that this mismatch was not due to (a) the autoreceptor occurring as two subtypes with different affinities for antagonists, (b) the occurrence of an agonist and antagonist state of the autoreceptor, with the latter prevailing at low synaptic concentrations of endogenous GABA, and (c) overruling of uptake inhibition by markedly elevated synaptic GABA concentrations. On the other hand, a simple restriction of the amount of transmitter able to be released per time unit produced much better matching data. A refined model assuming a restricted replacement capacity for exocytotically emptied synaptic vesicles at their docking sites gave similar results. As a consequence, we shall attempt to address this possibility experimentally.Simulation can never prove a case in the positive sense. It can, however, help to exclude ill-matching solutions of a problem and to prioritize among possible ones, which then must be experimentally addressed. We found simulation with this user-friendly software extraordinarily useful, also and not least because it necessitates and stimulates very intense dealing with a subject.Correspondence to: P. C. Waldmeier at the above address     

Zero and first moment area estimation from microdialysis data

Summary The calculation of classical pharmacokinetic parameters from microdialysis data has been described in a previous paper. In this paper I have derived methods for calculating AUMC and AUC from the time-integral type of data that are generated in microdialysis pharmacokinetics experiments. The method derived to estimate AUC is elementary, but is given a theoretical basis using principles of mathematical real analysis, clearly stating the assumptions.The method derived to estimate AUMC is a numerical approximation method based on the linear trapezoidal method. A simulation study was performed to evaluate the precision of the methods and to compare them with corresponding methods for analysis of blood sample data.The estimates from the presently derived methods have a small bias and a small variance. In the simulation study I investigated the influence of model parameters, number of samples, size of statistical error, and the size of the AUC beyond the last sample. Finally, I have given numerical examples from real data to illustrate the use of the method.     

CT模拟定位在食管癌放射治疗的临床应用

目的　探讨CT模拟定位在食管癌放射治疗的临床应用价值。方法　对 49例食管癌应用CT模拟定位技术进行定位扫描 ,将扫描数据传输至放射治疗计划系统计算机工作站 ,比较以食管腔为中心和以实体肿瘤为中心设置照射野的 90 %等剂量线分布情况。结果　以CT图像所示的非对称性肿瘤占 85 .7% ,以实体肿瘤为中心设置照射野的 90 %等剂量线分布能 10 0 %包全肿瘤病灶。结论　CT扫描能更多显示有治疗意义的征象 ,基于CT模拟定位的放射治疗计划使食管癌放疗照射野的设置更加精确合理     

Unit root tests in three‐regime SETAR models

Summary This paper proposes a simple testing procedure to distinguish a unit root process from a globally stationary three‐regime self‐exciting threshold autoregressive process. Following the threshold cointegration literature we assume that the process follows the random walk in the corridor regime, and therefore we propose that the null of a unit root be tested by the Wald statistic for the joint significance of autoregressive parameters in both lower and upper regimes. We establish that when threshold parameters are known, the suggested Wald test has a well‐defined asymptotic null distribution free of nuisance parameters. In the general case where threshold parameters are unknown a priori, we consider the three most commonly used summary statistics based on their average, exponential average and supremum. Assuming that the grid set for thresholds can be selected such that the corridor regime be of finite width both under the null and under the alternative, we can establish both stochastic equicontinuity and uniform convergence of the aforementioned summary statistics. Monte Carlo evidence indicates that the proposed tests are more powerful than the Dickey–Fuller test that ignores the threshold nature under the alternative. We illustrate the usefulness of our proposed tests by examining stationarity of real exchange rates for the G7 countries.     

153Sm-EDTMP吸收剂量的MonteCarlo和MIRD算法比较

目的以153Sm-乙二胺四甲撑膦酸(153Sm-EDTMP)治疗鼻咽癌多发性骨转移为例,分别用蒙特卡罗法(Monte Carlo,MC)和MIRD方法计算153Sm-EDTMP治疗后病灶和骨髓等靶器官的吸收剂量,探讨其临床应用之不同.方法基于病人时序性SPECT/CT扫描和累积尿液的放射性测定,利用优化的MC EGS4程序和MIRD方法分别计算病灶和其他靶器官的吸收剂量.结果MC EGS4法计算结果提示病灶内剂量分布不均匀.患者注射153Sm-EDTMP 33.6×37 MBq,左髂骨转移病灶最高吸收剂量约为5.6 Gy,病灶边缘的吸收剂量为2.0 Gy,以病灶区最高剂量点为参考点,则椎体、皮质、骨髓、脊髓和盆腔组织仅相当于最高剂量的37%、12%、13%、21%和2%;MIRD方法的计算数据仅能粗略提示全身红骨髓吸收剂量,为2.39 Gy.结论MC EGS4方法能准确计算病灶、骨髓和其他靶器官的内照射吸收剂量,故可以真正指导核素临床治疗;而MIRD仅能大致评估153Sm-EDTMP的骨髓毒性.     

统计模拟分光光度法同时测定肺保三效片中4组分含量

前文［１，２］报道了统计模拟分光光度法用于复方制剂２组分、３组分的含量测定。本文进一步对复方制剂４组分进行分析测定。肺保三效片含对乙酰氨基酚、苯妥英、茶碱、咖啡因、盐酸麻黄碱、氯苯那敏、颠茄流浸膏等，法定方法［３］只对前２种组分进行了定量测定，本文用...     

苯乙烯在顺1,4-聚丁二烯上的接枝共聚反应动力学的Monte Carlo模拟

用ＭｏｎｔｅＣａｒｌｏ模拟方法对苯乙烯在顺１，４－聚丁二烯上的接枝反应动力学进行了研究。模拟结果表明，对于不同的橡胶浓度，接枝的和均聚的聚苯乙烯的数均聚合度、接枝效率与苯乙烯在顺１，４－聚丁二烯上的接枝共聚反应的动力学的解析解十分吻合，证明本方法能够有效地应用于自由基型接枝共聚合反应体系。