INAA研究南极菲尔德斯半岛西湖沉积物和植物残体的生物地球化学特征

用仪器中子活化法(INAA)对南极菲尔德斯半岛西湖钻孔沉积物和植物残体进行了多元素测定。发现沉积物和植物残体在不同沉积深度分别有相似的元素分布模式;并且二者的元素分布特别是稀土元素分布模式也具有相似性,反映出二者的物源基本相同。植物残体中不同元素的生物富集系数有差异,反映了植物吸收元素的选择性。植物残体中许多元素呈现出明显的规律性变化,初步推测植物残体的元素组合特征对环境变化的响应可能比沉积物更灵敏。     

~(115)Cd在小青菜中的残留

应用同位素示踪方法研究植物-土壤系统中重金属的污染状况,已有不少报导。有人用自动射线照相法查明Cd在植物体中的迁移是通过蒸腾流作用进行的,也有人用~(115)Cd示踪法查明Cd在植物体各器官和组织中的分布情况。作物吸收Cd与土壤中投Cd量之间是现有一种良好的正相关。John认为投Zn到土壤中能明显降低Cd迁移到植物体中。Girling等用~(109)Cd水培试验也证明了这种趋势。在分析土壤的各种因子对植物吸镉影响时,Forstner等认为土壤有机质能螯合和络合重金属,从而减少了植物对重金属的有效吸收。对农用污泥中镉的研究,也发现土壤有机质能明显地降低植物吸收镉的现象。John等指出,与重粘土等其它因素比较,有机质的这种因素占首位。     

传统铀水冶工艺对稀土元素分布模式的影响及其在核法证中的应用

从生产过程的角度研究了稀土元素分布模式在核法证溯源中的适用性。通过跟踪调查某传统铀水冶厂从铀矿石到重铀酸钠的生产过程,在低本底(<0.512 ng/mL)、低检出限(<0.007 5 ng/mL)的实验条件下,对铀矿石、澄清浸出液、萃余液和重铀酸钠样品进行了前处理后,采用TRU树脂分离稀土元素、电感耦合等离子体质谱(ICP-MS)测定稀土元素的含量,并绘制了稀土元素分布模式图。结果表明,上述4种样品整体上都是轻稀土富集,Eu亏损明显,稀土元素分布总体呈右倾斜深谷状。这说明经历了传统铀水冶工艺的铀材料仍会基本保留铀矿石的稀土特征,稀土元素分布模式有助于查明铀材料的来源和历史。     

砷超富集植物中砷化学形态及其转化的EXAFS研究

通过同步辐射扩展X射线吸收精细结构(SR EXAFS)研究As超富集植物大叶井口边草(Pteris cretica L.)中As的化学形态及其在植物体中的转化。结果表明，在大叶井口边草中As主要与0配位，根部存在与GSH结合的As，但是在叶片中没有发现与GSH结合的As。在As(1lI)和As(V)处理中，植物根系的As分别以As(III)和As(V)为主，但是在叶柄和叶片中As都以As(III)的形态为主。植物根系吸收的As(v)在向上转运的过程中具有向As(III)转化的趋势，其转化过程主要发生在根部。实验证明，As-GSH并不是大叶井口边草中砷解毒的主要机理，超富集植物可能具有与一般耐性植物不同的重金属解毒机制。     

作物吸收稀土元素的研究

在农用稀土产品中含有多种稀土元素,主要有La,Ce,Pr,Nd,它们的氧化物占稀土氧化物总量的99％。应用~(140)La,~(141)Ce,~(147)Nd示踪方法,结合显微放射自显影技术,研究了稀土元素进入植株的过程。结果表明,稀土元素能被植物根系或叶面吸收,沿输导组织输送到器官中。由根系向地上部的输出量是Nd>Ce>Y>La,叶面吸收率和吸收速率均高于根系吸收。叶面吸收速率随时间t呈衰减趋势:Y=a·b~t。在混合稀土情况下,能促进植物对Nd的吸收,抑制对Ce的吸收。     

作物吸收稀土元素的研究

在农用稀土产品中含有多种稀土元素,主要有La,Ce,Pr,Nd,它们的氧化物占稀土氧化物总量的99％。应用~(140)La,~(141)Ce,~(147)Nd示踪方法,结合显微放射自显影技术,研究了稀土元素进入植株的过程。结果表明,稀土元素能被植物根系或叶面吸收,沿输导组织输送到器官中。由根系向地上部的输出量是Nd>Ce>Y>La,叶面吸收率和吸收速率均高于根系吸收。叶面吸收速率随时间t呈衰减趋势:Y=a·b~t。在混合稀土情况下,能促进植物对Nd的吸收,抑制对Ce的吸收。     

大气沉降核素7Be在黄土高原地被物中的分布初探

7Be具有环境微粒示踪价值,在示踪土壤侵蚀研究中有一定的应用,但是有关地被覆盖物对7Be截留吸收的研究目前还相当少,这直接影响了示踪结果的准确性、示踪模型的建立及应用.本文对不同地被物中的7Be含量进行了分析,结果表明:春季末地表不同地被覆盖物中干枯植物的7Be含量最大,半分解物次之,活植物中含量最少.在整个植物生长期内,植物体7Be累积含量呈增长趋势,尤其在秋季增加更为突出;不同植物中7Be含量差异性很大,变异系数达0.6;从总体上看,不同类型植物中7Be的平均含量分布趋势是草本＞半灌木及小灌木＞种植作物;和其它同类植物种相比,不同作物种中7Be含量的变异系数相对较大,为0.47.     

种植在秦山、大亚湾地区土壤中的农作物对~(90)Sr吸收的研究

选择了秦山、大亚湾核电站周围具有代表性的农业土壤,随灌水向土壤中施入~(90)Sr,施入量分为每克土含~(90)Sr:0.037Bq,0.37Bq,3.7Bq,37Bq,370Bq。在上述土壤上种植了水稻、春麦、油菜、大豆、莴笋、西红柿、菜豆等,收获后将作物分成:籽粒、茎叶、颖壳、根等几部分并测其放射性,结果表明:进入植物体~(90)Sr的数量与土壤中~(90)Sr的含量呈正比。进入植物体的~(90)Sr主要分布在茎叶部,籽粒部含量最少;老叶中~(90)Sr多于幼嫩叶片。种植在大亚湾土壤上的各种作物单位干重~(90)Sr的积累量均高于秦山土壤上的作物。土壤中的~(90)Sr80％以上分布在0～4cm的表层。文中给出了各种作物在两种土壤上对~(90)Sr的浓缩系数。     

种植在秦山、大亚湾地区土壤中的农作物对~(90)Sr吸收的研究

选择了秦山、大亚湾核电站周围具有代表性的农业土壤,随灌水向土壤中施入~(90)Sr,施入量分为每克土含~(90)Sr:0.037Bq,0.37Bq,3.7Bq,37Bq,370Bq。在上述土壤上种植了水稻、春麦、油菜、大豆、莴笋、西红柿、菜豆等,收获后将作物分成:籽粒、茎叶、颖壳、根等几部分并测其放射性,结果表明:进入植物体~(90)Sr的数量与土壤中~(90)Sr的含量呈正比。进入植物体的~(90)Sr主要分布在茎叶部,籽粒部含量最少;老叶中~(90)Sr多于幼嫩叶片。种植在大亚湾土壤上的各种作物单位干重~(90)Sr的积累量均高于秦山土壤上的作物。土壤中的~(90)Sr80％以上分布在0～4cm的表层。文中给出了各种作物在两种土壤上对~(90)Sr的浓缩系数。     

介紹一种吸收土壤中Sr~(90)能力較强的作物——蕎麦

我们在过去的工作中曾指出,不同植物吸收土壤中Sr~(90)的能力有很大的差异。国外也有不少关于利用植物来净化污染土壤的报导,例如海西里(F.Haghiri)等指出,养麦对土壤中Sr~90的吸收能力比其他作物强,但作者没有仔细地研究荞麦在各个生育时期、不同部位     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.