用4道脉冲幅度甄别器[φ4×4英寸 NaI(Tl)为探测器]测量环境天然辐射水平

本文主要介绍以φ4×4英寸 NaI(Tl)为探测器的4道脉冲甄别器,用以测量和区分包括宇宙射线在内的不同成分的环境天然辐射水平的方法。4道:Disr、Ch1、Ch2、Ch3的甄别阈范围设定为使其能记录的γ射线的能量范围(主要包括天然辐射成分)依次约为0.58MeV—∞(~(40)K、铀、钍系核素的γ射线,宇宙射线)、2.0—4.2MeV(铀系~(214)Bi 中能量为2.2MeV 的γ射线,钍系~(208)Tl 中能量为2.61MeV 的γ射线,少量低能宇宙射线)、>4.2 MeV(除少量低能宇宙射线外的全部宇宙射线)、>12.5MeV(能量较高的宇宙射线)。用此方法在中国辐射防护研究院低本底放射性实验室和地下铁室进行了测量,评价了地下铁室的屏蔽效果。文中还给出了在广州—太原和北京—大阪航线的飞机上的测量结果。     

低本底反康普顿高纯锗γ谱仪

本文介绍的谱仪采用铅-石蜡-铅为主的复合物质屏蔽。HPGe探测器对~(60)Co的1332keV γ射线的相对效率为25％,能量分辨率好于1.75keV。在阱型反符合屏蔽下,系统对放在HPGe端面的~(137)Cs点状薄膜源的峰康比可达800:1;测量时间1000min,置信度95％时,对~(137)Cs点源探测灵敏度好于5.6mBq;谱议在100—2000keV能区内的积分本底好于8.7±0.1次/min,与无反符合屏蔽时相比,压缩倍数为6.6。     

Changes in colour and antioxidant activities of Hizikia fusiformis cooking drips by gamma irradiation

To utilize the cooking drips produced during the seaweed drying process, the effect of gamma irradiation on microbial contamination, colour, and antioxidant activities of Hizikia fusiformis cooking drips (HCD) was investigated. A two log cycles reduction of total aerobic bacteria and yeast and moulds counts was obtained irradiating HCD at 1 kGy. The Hunter L^∗ value of the HCD ethanol extract was increased by the gamma irradiation treatment, but the a^∗ and b^∗ values decreased upon irradiation depending on the absorbed dose. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging and β-carotene bleaching activities of the HCD extracts increased as a result of gamma irradiation, which was rationalized by the observed increase in polyphenolic compounds content. These results suggest that wasted cooking drips can be used as a functional component by the food and cosmetic industries if the irradiation technology were applied.     

Telling Stories …

Neil Spiller celebrates ‘the messier sides to architectural discourse’, which take in myth-making, collaged semiotics and moreover the untidy art of narrative. Copyright © 2010 John Wiley & Sons, Ltd.     

Gamma irradiation of pharmaceutical compounds, nitroimidazoles, as a new alternative for water treatment

The main objectives of this study were: (1) to investigate the decomposition and mineralization of nitroimidazoles (Metronidazole [MNZ], Dimetridazole [DMZ], and Tinidazole [TNZ]) in waste and drinking water using gamma irradiation; (2) to study the decomposition kinetics of these nitroimidazoles; and (3) to evaluate the efficacy of nitroimidazole removal using radical promoters and scavengers. The results obtained showed that nitroimidazole concentrations decreased with increasing absorbed dose. No differences in irradiation kinetic constant were detected for any nitroimidazole studied (0.0014-0.0017 Gy⁻¹). The decomposition yield was higher under acidic conditions than in neutral and alkaline media. Results obtained showed that, at appropriate concentrations, H₂O₂ accelerates MNZ degradation by generating additional HO; however, when the dosage of H₂O₂ exceeds the optimal concentration, the efficacy of MNZ degradation is reduced. The presence of t-BuOH (HO radical scavenger) and thiourea (HO, H and e_aq⁻ scavenger) reduced the MNZ irradiation rate, indicating that degradation of this pollutant can take place via two pathways: oxidation by HO radicals and reduction by e_aq⁻ and H. MNZ removal rate was slightly lower in subterranean and surface waters than in ultrapure water and was markedly lower in wastewater. Regardless of the water chemical composition, MNZ gamma irradiation can achieve i) a decrease in the concentration of dissolved organic carbon, and ii) a reduction in the toxicity of the system with higher gamma absorbed dose.     

Potential application of low dose gamma irradiation to improve the microbiological safety of fresh coriander leaves

A local market survey of fresh, raw coriander leaves, which is a component of many ready-to-eat, Indian dishes showed large variation in their bacterial load (7.0×10⁶–1.36×10⁸ cfu/gm) and mold and fungi (3.0×10³–1.0×10⁴ cfu/gm) and presence of potentially pathogenic bacteria such as faecal coliforms, Listeria and Yersinia. Conventional chlorination treatment affected the structural integrity of leaves leading to enhancement of rotting. Exposure to a low dose of 1 kGy was efficient for bacterial decontamination and elimination of potential pathogens without affecting the keeping quality of coriander leaves upto two weeks storage at 8–10 °C, measured visually in terms of degree of yellowing and rotting. Irradiation at higher doses led to the increased rotting during storage. The total chlorophyll contents as well its components, chlorophyll a and b did not change significantly on irradiation and subsequent storage. Similarly, the total carotenoid levels remained unaffected by exposure to 1 kGy dose, however, a dose dependent enhancement in their extractability was observed in irradiated leaves. No qualitative differences were observed in the GLC profile of volatile oils of control and irradiated (1 kGy) samples. There were no significant quantitative changes in the constituents of the major aroma compounds obtained from these two samples. Effects of irradiation on storage of the seasoning were also assessed.     

NS2扩展突发性业务流：设计与实现

结合Markov调制泊松过程（MMPP）和混合泊松流,为突发性分组业务设计了Gamma调制泊松过程（GMPP）业务流模型。面向开源仿真器NS2的功能扩展,给出了纯泊松流、MMPP流和GMPP流的NS2扩展设计和实现方案,并经仿真实验进行了验证。分析表明GMPP更适用于实际业务流。     

四川盆地深层页岩气水平井优快钻井技术——以泸203井为例

泸203井是中国石油天然气集团有限公司部署在四川盆地南部泸县—长宁页岩气区块的1口重点超深页岩气探井,实际完钻井深达5 600 m,测试日产气量为137.9×10~4 m~3,成为目前国内首口单井测试日产量超百万立方米的页岩气井。为了给深层页岩气井优快钻井提供借鉴和经验,以泸203井为例,在分析储层特征对钻井要求的基础上,归纳总结了保障该井页岩气水平井钻井井身质量、优质储层钻遇率、快速钻进以及降低复杂事故率的优快钻井综合配套技术,并对其应用效果进行了评价。研究结果表明:(1)采用旋转导向工具并配合钻柱扭摆系统钻进,减少了滑动定向钻进进尺,成功地控制了钻具托压现象,大幅度降低了定向辅助时间;(2)实施的4种削减钻具振动措施很好地解决了水平段钻进中螺杆故障问题,进一步提高了钻井速度;(3)采用近钻头伽马测量系统实时追踪储层,控制轨迹在优质产层内钻进,保证了优质页岩储层钻遇率;(4)优配钻井装备及高密度的油基钻井液的应用保证了井下动力钻具的动力和井眼携砂的需求以及钻井液性能的净化,确保了井眼畅通、保持了井壁稳定,起到了提高钻井速度的重要作用。结论认为,泸203井按照地质工程一体化的技术思路,采取先打直导眼再侧钻水平井的方式,优质页岩储层钻遇率达到100%,该井的实施进一步完善了四川盆地新区块超深页岩气水平井配套优快钻井技术。     

Disinfestation of stored wheat grain and flour using gamma rays and microwave heating

Samples of wheat grain and flour (20 gm of each) were infested with 20 larvae or 5 pairs of adult insects of Tribolium confusum, Lasioderma serricorne, Corcyra cephalonica or Rhyzopertha dominica. The infested samples were tested as follows : (1) microwave heating at four temperature levels 40, 45,50 and 55 °C, for exposure times from10 to 50 s; (2) gamma irradiation over the dose range of 0.5-4 KGy; (3) gamma irradiation + microwave heating. Complete kill of all stages tested was achieved at 50 °C with an exposure time of 50 s. A dose of 2 KGy induced 100% mortality of R. dominica after three days, but it took up to 7 days for all T. confusum and L. serricorne adults to die after a 4-KGy exposure. All insects died within 24 h when exposed to the combination of 1KGy + 50 °C for 30 s.Biochemical analyses on the samples of wheat grain and flour subjected to those treatments at which high mortality was obtained generally showed no detectable changes in the quality of protein, fat, fiber, carbohydrates or ash. The germination of wheat grain was lowered after treatment with microwave radiation but was not affected by a dose of 1 KGy gamma radiation.