NaI闪烁探测器测量感生放射性及其蒙特卡罗模拟

描述了如何使用蒙特卡罗方法评估产生在加速器屏蔽混凝土中的感生放射性. 使用EGS4程序模拟了NaI闪烁探测器测量屏蔽混凝土块表面剂量率时, 对于半径和厚度的响应. 结果发现,在屏蔽混凝土块半径和厚度分别达到40cm和30cm时, 表面剂量率达到饱和. 研究了东京大学SF回旋加速器北墙位置8和位置9的表面剂量率, 并和使用NaI闪烁探测器的测量结果进行了对比, 发现模拟和实验结果符合很好. 并且, 获得了表面剂量和表面感生放射性之间的转换系数, 对于⁶⁰Co转换系数为0.90(Bq·g^－1)·(μSv·h^－1)^－1, 对于¹⁵²Eu转换系数为1.26(Bq·g^－1)·(μSv·h^－1)^－1. 这样, 就可以通过NaI闪烁探测器表面剂量的测量结果简单评估加速器设备屏蔽混凝土中的感生放射性.     

Functional Fluorescence Labeling of Carbohydrates and Its Use for Preparation of Neoglycoconjugates

Abstract

New bifunctional reagents, 2-amino-6-carboxyethylpyridine and 2-amino-6-cyanoethylpyridine, were designed and synthesized in order to provide a novel procedure for preparation of neoglycoconjugates from fluorescence-labeled and purified sugar chains. Labeling of model sugar chains with these reagents was effected by reductive amination using BH₃.Me₂NH to give corresponding 6-carboxyethylpyridylaminated (CEPA-) and 6-cyanoethylpyridylaminated (CNEPA-) derivatives, which were readily purified by reversed phase HPLC. The reagent parts of the labeled products possess the functional groups which then serve as linkers for coupling with matrices such as proteins and polymers. A CEPA-derivative of glucose was directly coupled with the ε-amino group of a Lys derivative to give a neoglycoprotein model. CNEPA-sugars were hydrogenated to give 6-aminopropylpyridylaminated (APPA-) derivatives, which can then be readily used for the preparation of various types of neoglycoconjugates by use of appropriate spacers as exemplified by the coupling of APPA-maltotriose with bovine serum albumin (BSA), biotin, and acrylic acid. The reaction of APPA-maltotriose with succinimidyl 3-(3-nitro-2-pyridyldithio)propionate gave the corresponding amide to be used for a disulfide formation with BSA. Condensation with biotin was effected by use of N-hydroxysuccinimidobiotin. The conjugation of APPA-maltotriose with acrylic acid was carried out by use of 4-acryloyloxyphenyldimethylsulfonium methylsulfate to give the corresponding acrylamide, which can be used for the preparation of sugar-acrylamide copolymers.     

Dynamic nuclear polarization studies of nitroxyl spin probes in agarose gel using Overhauser‐enhanced magnetic resonance imaging

Agarose is a tissue‐equivalent material and its imaging characteristics similar to those of real tissues. Hence, the dynamic nuclear polarization studies of 3‐carboxy‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl (carboxy‐PROXYL) in agarose gel were carried out. The dynamic nuclear polarization parameters such as spin lattice relaxation time, longitudinal relaxivity, leakage factor, saturation parameter and coupling parameter were estimated for 2 mM carboxy‐PROXYL in phosphate‐buffered saline solution and water/agarose mixture (99 : 1). From these results, the spin probe concentration was optimized as 2 mM, and the reduction in enhancement was observed for carboxy‐PROXYL in water/agarose mixture (99 : 1) compared with phosphate‐buffered saline solution. Phantom imaging was also performed with 2 mM concentration of carboxy‐PROXYL in various concentrations of agarose gel at various radio frequency power levels. The results from the dynamic nuclear polarization measurements agree well with the phantom imaging results. These results pave the way for designing model system for human tissues suited to the biological applications of electron spin resonance/Overhauser‐enhanced magnetic resonance imaging.     

Continuous flame oxidation in supercritical water

Abstract

Continuous flames have been observed in Supercritical water oxidation (scWO) of isopropyl alcohol (IPA), using a vertical continuous reactor with sapphire windows and a mixing nozzle. Two types of continuous flame were confirmed: the one was long pale blue colored and the other was red short cone shaped, changing blue to red at around air ratio 2.0. The flame was strongly influenced by IPA concentration, air ratio and design of the mixing nozzle. Results for decomposition of PA are presented for IPA concentrations ranging from 600 up to 28260 ppm as TOC and initial reactor temperatures, were mostly around 490°C, at 25 MPa. Decomposition rate at steady state was over 99.9%. Experimentally measured CO₂ and O₂ concentrations at the flue gas were in good agreement with theoretically calculated values. Even for low air ratio as 1.1, high decomposition rate without CO, NO, NO₂ was achieved.     

Optimal threshold analysis of segmentation methods for identifying target customers

In CRM (Customer Relationship Management), the importance of a segmentation method for identifying good customers has been increasing. For evaluation of different segmentation methods, Accuracy often plays a key role. This indicator, however, cannot distinguish two types of errors. The purpose of this paper is to overcome this pitfall by introducing two different indicators: Recall and Precision. Assuming that a promotion is addressed exclusively to the selected target customers, the financial effectiveness of the underlying segmentation method is expressed as a function of Recall and Precision. An optimization problem is then formulated so as to maximize the financial measure by finding the optimal threshold level in terms of the severeness for estimating the target set. By introducing a functional form which represents correctness and mistakes about the target set, the unique optimal solution is derived explicitly. The proposed approach is validated by using real customer purchase data.     

Rapid time-decay and net force to the obstacles by the Stokes flow in exterior domains

Consider the nonstationary Stokes equations in exterior domains with the compact boundary . We show first that the solution decays like for all as . This decay rate is optimal in the sense that for some as occurs if and only if the net force exerted by the fluid on is zero. Received: 15 June 2000 / Published online: 18 June 2001