HIRFL-CSRm纵向随机冷却——Palmer冷却研究

对拟在HIRFL CSRm上建造的纵向Palmer冷却进行了数值优化计算 ,得出了最佳带宽、最佳增益及最短冷却时间 ,并运用Fokker Planck方程进行了模拟 ,得到了动量散度分布函数在冷却过程中随时间的变化 ,从而为纵向冷却系统的具体设计和优化提供了重要的理论依据 .

CSR实验探测装置前端电子学的研究

随着国家大科学工程兰州重离子加速器冷却储存环（HIRFL－CSR）的建成， HIRFL－CSR实验探测装置也在建设中。它主要由CSR外靶实验装置和CSRe上的配套实验装置组成，具有高通道数，高探测效率，高能量分辨，高时间分辨和高位置分辨等特点；将实现奇异核性质及奇异核反应研究，核物质的同位旋效应研究等物理目标。如此先进的大型实验探测系统对前端电子学提出了高密度、高集成度，低功耗和良好的长期稳定性等多方面的严格要求，传统的插件化的NIM 和CAMAC 电子学对此已无能为力，因此建造与之相配的读出电子学和数据获取系统成为一个重要的课题和任务。基于这个出发点，论文从发展髙性能多路小型化前端电路和基于先进ASIC芯片的前端电子学系统两个方面进行研究，讨论了我们在这两种电路研究方面采用的新思路和新方法。论文在发展髙性能多路小型化前端电路方面，阐述了一种用于时间分析的宽带放大电路的设计与实现。电路采用超低噪声的集成运放，解决了如何降低噪声的问题；同时引入2阶贝塞尔滤波器加反向求和电路，有效抑制直流漂移，使快放具有良好的直流稳定性和增益稳定性。基于先进ASIC芯片的前端电子学系统的研究是论文的重点。它着重解决了近代核与粒子物理实验中越来越突出的多路多道需求和高性能指标要求。论文首先介绍了一种处于国际先进水平的ASIC芯片的内部结构；随后详细论述了系统的硬件设计和软件开发；最后对系统进行了调试和性能分析。实验室调试结果说明系统已能够适应物理实验的要求，并为最终建立一个完整的满足性能要求的前端电子学系统打下了坚实的基础

长白山主要生态系统苔藓植物的多样性研究

长白山地区共有苔藓植物65科179属437种，32个变种和亚种。其中，石生和岩面薄土生种类(saxicolous bryophyte)最丰富，其次为腐木生种类(saprophytic bryophyte)和树生种类(epiphytic bryophyte)，再次为土生种类(soil and humus bryophyte)。沼泽地、水体等生境中的种类(peat, marsh and water bryophyte) 相对较少。地面生苔藓植物的物种丰富度以暗针叶林(dark conifer forest)最高，而多样性以落叶松－沼泽地(Larix olgensis－bogs)和暗针叶林为最高；腐木生苔藓植物的物种丰富度和多样性均以暗针叶林为最高，树附生苔藓植物的物种丰富度和多样性以暗针叶林以及红松阔叶混交林(Pinus koraiensis broad_leaved mixed forest) 与暗针叶林间的过渡林为最高。定性分析表明，海拔高度、林冠层郁闭度和林内湿度、土壤酸度、含水量、林下倒木的丰富程度等可能是影响本地区苔藓植物多样性的重要环境因子。

Capillary electrophoresis of urinary normal and modified nucleosides of cancer patients

This paper gives a capillary electrophoretic method for the separation of 15 urinary normal and modified nucleosides from cancer patients in less than 40 min. A 500 mmx50 mu m uncoated capillary column (437.5 mm to window) was used. The effects of the voltage and the sodium dodecyl sulfate (SDS) concentration in the buffer on the separation were studied. With reproducibilities of migration times better than 1.2% (R.S.D.) and determined concentrations better than 5-25%, depending on the concentrations of nucleosides in the urine, the analytical characteristics of the method were food. Using this developed method, the concentrations of 13 normal and modified nucleosides, extracted on a phenyl boronic acid affinity chromatography column, in 25 urines from patients of 14 kinds of cancer were determined. The levels (nmol/mol creatinine) of modified nucleosides in urines from cancer patients were increased as compared with those in normal urines. (C) 1998 Elsevier Science B.V.

森林景观变化对森林水文功能的影响评估

以大兴安岭毕拉河林业局为研究区,在分析近十年森林景观在类型、质量变化的基础上对森林三项关键性水文功能即:林冠截留、枯枝落叶截留和森林土壤蓄流功能及其变化进行了评估,并基于地理信息系统将由此三项关键性水文功能构成的森林综合调节能力空间直观表达出来。研究结果发现:由于近十年来人类干扰加强等因素导致的森林景观在类型上和质量上的变化使得林区森林水文综合调节能力由1990年的247489457t下降为2000年的230936445t,下降了6.67%。其中以小二沟和诺敏两个林场下降幅度最大,分别为25.27%和22.23%。

城市空气质量健康风险评估研究进展

随着工业化、城市化的发展,城市大气污染对环境和人体健康的潜在影响正日益引起世界各国的普遍关注。尤其是污染物产生的健康效应评估是当前研究的热点。目前空气质量健康影响评估采用的主要方法是风险评估。完整的环境健康风险评估框架包括危害鉴别,剂量—效应关系评价,暴露评价和风险表征四个环节。作者对城市空气质量数值模拟、人口暴露、大气污染物毒理及其健康效应的研究现状分别阐述,从研究尺度,研究方法和健康效应的量化指标角度剖析了目前研究存在的局限性,提出未来研究的趋向及需重点解决的问题。

汞的环境生物地球化学研究进展

汞是毒性极高的全球性环境污染物。即使在极低剂量下,汞对人类和野生动植物都有相当大的毒性,并导致生态系统功能退化和人类健康风险,有关汞及其化合物的环境生物地球化学研究是目前国际上的热点之一。基于近三十年来的相关研究报道,作者阐述了生态环境中汞的分布特征及化学行为、汞的来源及循环、当前汞的暴露及人类健康风险等方面的最新研究动态。同时,指出生态环境中及环境界面间汞的活化、迁移、转化机制研究、人类活动与汞释放间的关系研究以及生态环境中汞的甲基化作用、生物放大作用等过程和交互作用研究等是今后汞的环境生物地球化学领域内的研究重点。

富锌排铅咀嚼片安全性毒理学评价

对富锌排铅咀嚼片(RZLR)进行了急性毒性试验、Ames试验、骨髓微核试验、精子畸形试验和30d喂养试验。结果表明,小鼠急性毒性LD50(BW)>21500mg/kg,属无毒级;Ames试验、小鼠骨髓微核试验、精子畸形试验和30d喂养试验结果均为阴性;30d喂养试验也未显示明显毒性。本研究证实RZLR是一种安全、无毒副作用的保健食品。

湘西多金属矿区汞铅污染土壤的环境质量

以湘西典型多金属矿区为现场,研究了矿区土壤中汞、铅等重金属污染状况及成因.结果表明,湘西矿区是汞、铅污染严重的区域,与中国土壤元素背景值相比,汞矿区土壤中汞、铅含量分别增加1315倍和3.1倍,铅锌矿区土壤中汞、铅含量分别增加14.8倍和16.1倍.运用Muller地积指数进行风险评价,证实湘西矿区是汞、铅等重金属的复合污染区,汞矿区汞污染以极重污染为主,铅污染以中度和轻污染为主;铅锌矿区铅污染以中度和中-重污染为主,汞污染以中-重污染为主.矿区土壤中的重金属污染物来源和分布受原生地球化学条件的控制,而人为采矿活动对矿区土壤中汞、铅的污染格局产生重要影响.

The mechanical properties of magnesium matrix composites reinforced with 10 wt.% W14Al86 alloy particles

The Mg-based metal matrix composite reinforced by 10 wt.% W14Al86 alloy particles has been prepared by mechanical alloying and press-forming process. X-ray diffraction studies confirm the formation of the composite. Microstructure characterization of the samples reveals the uniform distribution of fine W14Al86 alloy. Mechanical properties characterization revealed that the reinforcement of W14Al86 alloy lead to a significant increase in hardness and tensile strength of Mg and AZ91.

Adsorption of heavy rare earth(III) with extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid

In the present paper, the adsorption of thulium(Ill) from chloride medium on an extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid (CL302, HL) has been studied. The results show that 1.5 h is enough for the adsorption equilibrium. The distribution coefficients are determined as a function of the acidity of the aqueous phase and the data are analyzed both graphically and numerically. The plots of log D versus pH give a straight line with a slope of about 3, indicating that 3 protons are released in the adsorption reaction of thulium(III). The content of Cyanex302 in the resin is determined to be 48.21%. The total amount of Tm3+ adsorbed up to resin saturation is determined to be 82.46 mg Tm3+/g resin. Therefore, the sorption reactions of Tm3+ from chloride medium with CL302 can be described as: Tm3+ + 3HL((r)) <----> TmL3(r) + 3H(+) The Freundlich's isothermal adsorption equation is also determined as: log Q = 0.73 log C + 3.05 The amounts (Q) of Tm3+ adsorbed with the resin have been studied at different temperatures (15-40degreesC) at fixed concentrations of Tm3+, amounts of extraction resin, ion strength and acidities in the aqueous phase.

A rapid solid-phase synthesis to soluble oligothiophene molecular wires

A novel method for the preparation of oligothiophene molecular wires is described via a bi-directional solid-phase synthesis. Using an alternating sequence of bromination and Stille coupling reactions, oligomers were obtained up to the heptamer in excellent yield and purity.

Studies on the adduct reaction of disubstituted benzenes with ion system of acetone in gas phase

Ion - molecule reactions of disubstituted benzene with ion system of acetone and deuterium - labelled acetone under chemical ionization conditions were examined and the fragmentation reactions of the adduct ions formed by the ion - molecule reactions were studied using collision - induced dissociation (CID) technique. It was found that the electron - releasing groups favored the adduct reactions, whereas the electron - withdrawing groups did not. The position and properties of substituted groups affected the relative abundance of the adduct ions. The fragmentation reaction of the adduct ion formed by ortho - phenylenediamine with acetyl ion was similar to the reductive alkylation reaction of amine in condensed phase.

气相中双取代苯在丙酮离子体系中的加合反应研究

研究了11组双取代苯在丙酮离子体系中的离子-分子反应特性及加合离子的碎裂反应特性,发现推电子基有利于加合反应的发生而吸电子基不利于加合反应的发生.双取代异构体的加合产物相对强度可以反映出它们取代基的位置及其性质的差异.邻苯二胺与乙酰基离子形成的加合离子在碎裂反应过程中可以发生与液相中胺的还原烷基化反应相类似的碎裂反应.