海洋样品中^106Ru的分析

一、前言海洋环境中~(106)Ru的污染监测很重要。由于~(106)Ru在海洋环境中的价态和存在形式复杂,使分析很困难。国外理想方法不多。本文的201海水中~(106)Ru的分析流程有别于国外的有:CoS浓集量大3倍;还包含了除CoS的条件和除H_2SO_3的步骤等。海水中~(106)Ru的快速分     

Mismatch-, MutS-, MutL-, and helicase II-dependent unwinding from the single-strand break of an incised heteroduplex

Escherichia coli MutS, MutL, and DNA helicase II are sufficient to initiate mismatch-dependent unwinding of an incised heteroduplex (Yamaguchi, M., Dao, V., and Modrich, P. (1998) J. Biol. Chem., 273, 9197-9201). We have studied unwinding of 6.4-kilobase circular G-T heteroduplexes that contain a single-strand incision, 808 base pairs 5' to the mismatch or 1023 base pairs 3' to the mispair as viewed along the shorter path between the two DNA sites. Unwinding of both substrates in the presence of MutS, MutL, DNA helicase II, and single-stranded DNA binding protein was mismatch-dependent and initiated at the single-strand break. Although unwinding occurred in both directions from the strand break, it was biased toward the shorter path linking the strand break and the mispair. MutS and MutL are thus sufficient to coordinate mismatch recognition to the orientation-dependent activation of helicase II unwinding at a single-strand break located a kilobase from the mispair.     

Purification and characterization of a human bradykinin binding protein from inflammatory cells

Bradykinin (BK) is a potent mediator with a broad spectrum of pharmacological and inflammatory actions which are exerted through cell surface receptors. We report here the affinity chromatographic purification of a novel 14 kDa BK binding protein from human blood neutrophils and also peripheral blood mononuclear cells (PBMC), 80% of which are lymphocytes. Radioreceptor crosslinking experiments using bifunctional crosslinkers and radiolabelled BK identified a 14 kDa protein in these cell types both on the cell surface, in glycerol purified plasma membranes and in detergent solubilized cell extracts. Purification by BK affinity chromatography from a variety of BK responsive human cell types i.e. CCD-16Lu lung fibroblasts, HL60 promyelocytes, U937 myelomonocytes and Jurkat T lymphocytes also demonstrated a 14 kDa protein. Purified material obtained from three different BK affinity columns all demonstrated three major proteins at 190, 50 and 14 kDa when eluted with either excess BK or mild acid. Neutrophil fractions from detergent solubilized cell extracts contained an additional 150 kDa protein when eluted with mild acid. Neutrophil and PBMC crude plasma membrane BK affinity column purifications yielded only a single 14 kDa protein. Radioreceptor dot assays of the purified neutrophil eluates containing the 14 kDa protein revealed specific binding to [125I]-BK with a 160 fold excess signal ratio over the original membrane extract. Our data indicates that we have successfully isolated a 14 kDa novel human BK specific binding protein expressed on the surface of inflammatory cells.     

GPS接收机测量电离层TEC的数据处理方法

介绍了应用ＧＰＳ卫星接收机ＳＮＲ－８Ｃ进行电离层ＴＥＣ观测的数据处理方法，并给出了部分数据处理结果。其中包括应用ＧＰＳ双频信号进行ＴＥＣ计算的原理，应用卫星星历参数计算各时刻电离层质心点的经度及卫星仰角和方位角，以及ＴＥＣ的周日变化，逐日变化及一次卫星通过时ＴＥＣ的时空变化结果，讨论了该方法的误差来源及与ＮＮＳＳ方法，法拉第旋转测量ＴＥＣ的比较。应用ＧＰＳ方法测量ＴＥＣ具有很大的优点，具有高精度及     

高频超声波在氧化皮中传播性能标定

对高频超声小在12Cr2MoWVTiB(G102钢）和12Cr1MoV钢钢管运行所产生氧化皮中的传播速度进行了定量标定，并对标定误差进行了统计计算，结果表明，12Cr1MoV钢氧化皮测厚标定点最大偶然误差值为0．050mm,G102钢为0．030mm，并指明了误差来源。     

含高渗透率分布式光伏的配电网故障停电损失评估

随着分布式光伏渗透率的逐步提高,配网的负荷特性发生了重大改变,传统的配网故障停电损失评估方法不再适用。提出了一种含高渗透率分布式光伏的配电网停电损失评估方法,基于典型的配网拓扑,分析了含分布式光伏的配电网负荷特性,综合运用来自营、配、调等业务领域的多源数据,构建了基于配变台区的用电负荷模型光伏发电负荷模型,并对故障停电期间的发电损失及用电损失进行了评估。实际案例的分析结果验证了该算法的有效性。     

孔隙水压力与恒定时间对砂岩变形的实验研究

探讨三峡库水位在145-175 m之间涨落及蓄水时水压对岩(石)体的变形特性影响。以实验为基础,进行了不同轴向应力(1σ=55.54,34.18和12.82 MPa)条件下,周期孔隙水压力(Pmin=2 MPa,Pmax=6 MPa)与上、下限恒定时间(ΔT=120和240 s)作用下砂岩的变形特性实验。通过分析1ε-T与p-T关系曲线和p-1ε滞回曲线,可知:1ε-T砂岩曲线呈连续正弦波形演化,当孔隙水压力加载时,应变减小;上限恒定时,应变持续减小到谷值;卸载时,应变逐渐增大;下限恒定时,应变持续增大到峰值。砂岩p-1ε滞回曲线的2个阶段变化,一是微孔隙压密阶段,未形成明显的滞回曲线;二是孔隙水压力耦合阶段,形成了稳定的滞回曲线,表现形式由疏变密,并且稳定的滞回曲线呈逆时针演化。还对比了不同轴向应力和不同恒定时间条件下,每个p-1ε滞回曲线的四区段(加载段、卸载段、上限恒定段和下限恒定段)的Δε-n关系曲线。     

直接酸浸与焙烧酸浸钒萃取行为的研究

对某石煤矿采用直接酸浸和焙烧酸浸处理,并考察不同浸出过程中氟化物加入的影响。结果表明,该石煤适宜采用含氟化物作用的直接酸浸-萃取工艺,钒浸出率可达92.39%,预处理钒损失率为1.12%,每吨V2O5的CaO耗量为6.38t,钒萃取过程正常且三级萃取率达到98.05%。不同浸出工艺及是否加入氟化物对钒萃取过程有较大的影响:无氟化物加入的直接酸浸使石煤原矿中的有机物引入酸浸液,形成界面膜而导致乳化现象产生;空白焙烧可消除有机物的影响,但由于酸浸溶液中的杂质元素含量显著增加而可能导致乳化现象;氟在溶液中以[AlF5]2-和[SiF6]2-形式存在,可阻止含硅胶体和细微颗粒以及界面膜的生成,有利于萃取正常进行,但当溶液中杂质元素含量过高时,仍可能产生乳化。     

色氨酸抑制体外模型中晚期糖基化终末产物形成机理

食源性晚期糖基化终末产物(advanced glycation end products,AGEs)与多种慢性疾病密切相关,尤其是糖尿病和肾脏疾病.为减少AGEs对机体的健康风险,降低食品中AGEs含量,本研究从13种氨基酸中筛选出具有良好AGEs抑制效果的色氨酸(tryptophan,Trp),利用牛血清白蛋白(bo...     

Physical gelation of cellulose acetate propionate solutions mediated by metal carbonyl complexes

The weak physical gelation of cellulose acetate propionate-butyl butyrate solutions as a result of the in-situ decomposition of iron pentacarbonyl complexes was explored. Viscometry and infrared spectroscopy were used to monitor the iron pentacarbonyl decomposition reaction progress and its effect on viscosity. Changes in viscosity in of the cellulosic fluids in general and gelation in particular were found to be dependent upon the environment in which the Fe(CO)₅ decompositions occurred. Systems under inert atmospheres exhibited a marked increase in viscosity, while systems under oxidative atmospheres exhibited a general decrease in viscosity. We propose a hypothesis that explains the dependence of the viscosity of these cellulosic fluids as a function of the environmental conditions during the precursor decomposition. Under nitrogen atmospheres, zero-valent nanoparticles with highly reactive surfaces are synthesized, which form weak, transient bonds with the cellulosic polymer. The iron particles, under these circumstances, serve as weak bridges between adjacent polymer chains. Conversely, the primary particles synthesized under an oxidative atmosphere are metal oxides, which are less attractive to the polymer chain and, therefore, do not yield such bridges. This work demonstrates the capability to apply a simple method to control the viscosity of cellulose ester fluids.