X射线在金-硅界面剂量增强系数与金和硅厚度关系的模拟研究

用蒙特卡罗(Monte Carlo)方法计算不同能量的X射线在金-硅(Au-Si)界面处中产生的剂量增强系数（DEF）与金(Au)和硅(Si)厚度的关系.结果表明：界面一侧Si中的DEF与Au和Si的厚度有关。当Au厚度分别取1μm、2μm、4μm、8μm时,界面处最大剂量增强系数分别为：19.78、24.78、24.78、32.3,界面处的DEF随Au厚度的增加而增大;当Si厚度分别取1μm、2μm、4μm、8μm时,界面处最大剂量增强系数分别为：24.5、25.91、27.84、30.09,界面处的DEF随Si厚度的增加而增大.并且研究了Au为2μm、4μm时界面下不同位置处的DEF随能量的变化关系,界面处的DEF最大,离界面越远剂量增强效应越小.     

Evaluation of the radiation dose to a phantom for various X-ray exposure factors performed using the dose area product in digital radiography

The aim of this study is to measure the dose area product (DAP) in digital radiography by using a DAP meter to determine the X-ray exposure. Pediatric X-ray examinations can be obtained for any radiographic examinations using the selected radiographic examination parameters (kVp and mAs), the DAP information recorded. The best peak signal-to-noise ratio (PSNR) at a fixed tube voltage of 70 kVp was obtained at tube currents of 20 and 32 mA, whereas the best PSNR at a fixed tube current of 25 mA was obtained at a tube voltage of 73 kVp. The fixed tube voltage of 70 kVp and the fixed tube current of 25 mA could help to obtain the best image quality and depict the spatial resolution of an anthropomorphic torso phantom radiographic examination. The normalized data over the DAP were provided to determine the patient dose from radiography.     

Effective scavenging at cryotemperatures: further increasing the dose tolerance of protein crystals

The rate of radiation damage to macromolecular crystals at both room temperature and 100 K has previously been shown to be reduced by the use of certain radical scavengers. Here the effects of sodium nitrate, an electron scavenger, are investigated at 100 K. For sodium nitrate at a concentration of 0.5 M in chicken egg‐white lysozyme crystals, the dose tolerance is increased by a factor of two as judged from the global damage parameters, and no specific structural damage to the disulfide bonds is seen until the dose is greatly in excess (more than a factor of five) of the value at which damage appears in electron density maps derived from a scavenger‐free crystal. In the electron density maps, ordered nitrate ions adjacent to the disulfide bonds are seen to lose an O atom, and appear to protect the disulfide bonds. In addition, results reinforcing previous reports on the effectiveness of ascorbate are presented. The mechanisms of action of both scavengers in the crystalline environment are elucidated.     

湖北省国控点天然γ辐射空气吸收剂量率研究

使用我国新一代X-γ剂量率测量仪对湖北省9个国控点进行了天然γ辐射空气吸收剂量率的测量,建立了剂量率与剂量当量的数学模型,计算了9个国控点地区人均年有效剂量当量。结果表明,9个国控点地区的剂量率在59.336～141.638 nGy/h,天然γ辐射致公众人均年有效剂量当量为0.390～0.931 mSv;9个国控点地区天然γ辐射均属正常天然本底水平。     

Zur Zuverlässigkeit der Bestimmung der Schilddrüsenbelastung durch Radiojod

Die Arbeit beinhaltet Untersuchungen von Parametern, die die Bestimmung der Schilddrüsenbelastung beeinflussen. Unvermeidliche Fehler im Reproduzieren der Meβgeometrie und eine Mittelwertannahme für die Dicke des die Schilddrüse überlagernden Gewebes führen zu Fehlerbreiten bei der Bestimmung des Jod·Depots von ±40% für ¹²⁵J und ±22% für ¹³¹J.

Untersuchungen an einer Gruppe beruflich strahlenexponierter Personen ergaben Gewebedicken über der Schilddrüse von 1 bis 3 cm bei einem Mittelwert von 2,3 cm und im Mittel eine um 15% geringere effective Halbwertszeit für ¹³¹J als von der ICRP für den Standardmenschen angegeben.

Der Einfluβ dieser Abweichung auf die Dosisbestimmung wird diskutiert.     

Tagungsberichte

Like in other European countries, due to the accident at the Chernobyl nuclear power plant in 1986 the radioactive contamination level of the biological chain increased significantly in Hungary. The external and internal dose burden had a low-dose effect on plants ranging within the dose internal of stimulation and thus exhibiting a biopositive influence on the physiological functions.

Nach dent Unfall im Kernkraftwerk Tschernobyl im Jahre 19S6 slieg in Ungarn die radioaktive Kontamination der biologischen Kette erheblich an. Die externe und interne Strahlenbelastung hatte eine niedrigc Dosiswirkung auf Pflanzen, bewegte sich inncrhalb der Dosisspanne der Stimulation und wies somit einen biopositiven Einfluβ auf die physiologischen Funkionen auf.     

外推电离室测电子剂量问题

本文介绍用外推电离室绝对测量电子加速器电子束在物质深部的吸收剂量率。并运用电子束监测法拉第简和在外推电离室空腔内部测温的方法,较好地解决了电子束流强度不稳、空腔局部温升较高等影响测量精度的实际问题。     

PEO/PVAc共混体系辐射交联反应中溶胶分数与辐照剂量间的关系

交联度对由聚合物共混物辐射交联而制备出的材料的性能影响很大,研究共混体系的辐射交联度和交联行为是十分重要的。通常,用溶胶分数与辐照剂量间的关系表征聚合物的交联度和交联行为。文献[2]发现线性聚合物的溶胶分数与辐照剂量间的关系与高分子链结构参数有关。本文试图考察共混体系的辐射交联行为是否也与高分子链结构有关,并将线性聚合物的关系式(1)推广应用到PEO/PVAc共混体系中。目前,有关这方面的研究工作还未曾见文献详细报道。     

Influence of gas flow patterns on NOx removal efficiency

Dose distribution in flue gas irradiation vessel is not uniform due to limited electron penetration range. This phenomena influence overall NO_x removal efficiency is observed in the process. The remarkable increase in the efficiency can be achieved by multistage gas irradiation and gas mixing between stages. The results of modelling for longitudinal beam scanning as applied at EPS Kawêczyn pilot plant are presented in the paper. These are the basis for process vessel upscaling.     

Experiences using IAEA Code of practice for radiation sterilization of tissue allografts: Validation and routine control

Problems of tissue allografts in using International Standard (ISO) 11137 for validation of radiation sterilization dose (RSD) are limited and low numbers of uniform samples per production batch, those are products obtained from one donor. Allograft is a graft transplanted between two different individuals of the same species. The minimum number of uniform samples needed for verification dose (VD) experiment at the selected sterility assurance level (SAL) per production batch according to the IAEA Code is 20, i.e., 10 for bio-burden determination and the remaining 10 for sterilization test. Three methods of the IAEA Code have been used for validation of RSD, i.e., method A1 that is a modification of method 1 of ISO 11137:1995, method B (ISO 13409:1996), and method C (AAMI TIR 27:2001). This paper describes VD experiments using uniform products obtained from one cadaver donor, i.e., cancellous bones, demineralized bone powders and amnion grafts from one life donor. Results of the verification dose experiments show that RSD is 15.4 kGy for cancellous and demineralized bone grafts and 19.2 kGy for amnion grafts according to method A1 and 25 kGy according to methods B and C.