131 resultados para 60-459
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足球状全碳烯 C_(60)具有丰富的化学性质,可以做为活泼的自由基捕捉试剂,在质谱常规化学电离源内气相 C_(60)可与 CCl_4,CHCl_3,CH_2Cl_2和 CHBr_3等产生的碎片发生化学反应,生成了[C_(60)CX_2]~+等多种气相衍生物离子.单独引入 CCl_4的离子源内存在着CCl_3~+(m/z117,100%),CCl_2~+(m/z82,22%),CCl~+(m/z47,24%)和 Cl+(m/z35,14%)阳离子、多种阴离子及 CCl_3,CCl_2,Cl 等自
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本文概述了C_(60)系列化合物的NMR谱、磁化率、磁性的某些进展。
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本文综述了各种新发现的C_(60)超导体及其研究进展,包括其超导转变温度制备方法,与氧化物陶瓷超导体的比较及目前存在的问题和今后的展望。
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在1.0~5.0GPa、700~1750℃条件范围内,对固熔体0.6NaAlSi_2O_6-0.4CaMgSi_2O_6进行了研究,探讨了该固熔体在高温高压下的存在行为,研究了由非晶态玻璃向翡翠转化过程中γT作用的相图,得到的透辉石翡翠的晶胞参数为α=0.9439nm,b=0.8573nm,c=0.5233nm,β=107.28°和V=0.41702nm~3。本实验中合成的宝石级翡翠为色泽温润,具有玻璃光泽,半透明的极富观赏性的透辉石翡翠。
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硅膜改性弹性玻璃毛细管柱做为一种新柱型,它具有类似弹性石英柱的柔性和惰性,也具有玻璃柱制作容易、材质易得的优点。硅膜做为固定相载体的色谱特性研究目前报道还很少,非极性硅酮相在其上的交联我们曾做过报
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Based on the second-order random wave solutions of water wave equations in finite water depth, a statistical distribution of the wave-surface elevation is derived by using the characteristic function expansion method. It is found that the distribution, after normalization of the wave-surface elevation, depends only on two parameters. One parameter describes the small mean bias of the surface produced by the second-order wave-wave interactions. Another one is approximately proportional to the skewness of the distribution. Both of these two parameters can be determined by the water depth and the wave-number spectrum of ocean waves. As an illustrative example, we consider a fully developed wind-generated sea and the parameters are calculated for various wind speeds and water depths by using Donelan and Pierson spectrum. It is also found that, for deep water, the dimensionless distribution reduces to the third-order Gram-Charlier series obtained by Longuet-Higgins [J. Fluid Mech. 17 (1963) 459]. The newly proposed distribution is compared with the data of Bitner [Appl. Ocean Res. 2 (1980) 63], Gaussian distribution and the fourth-order Gram-Charlier series, and found our distribution gives a more reasonable fit to the data. (C) 2002 Elsevier Science B.V. All rights reserved.
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Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Two unique and highly compartmentalized bay scallop Argopecten irradians superoxide dismutases: MnSOD and ecCuZnSOD, have been molecularly characterized in our previous study. To complete characterize the SOD family in A. irradians, a novel intracellular copper/zinc SOD from the A. irradians (Ai-icCuZnSOD) was obtained and characterized. The full-length cDNA of Ai-icCuZnSOD was 1047 bp with a 459 bp open reading frame encoding 152 amino acids. The genomic length of the Ai-icCuZnSOD gene was about 4279 bp containing 4 exons and 3 introns. The promoter region containing many putative transcription factor binding sites were analyzed. Furthermore, quantitative reverse transcriptase real-time PCR (qRT-PCR) analysis indicated that the highest expression of the Ai-icCuZnSOD was detected in gill and the expression profiles in hemocytes of bay scallops challenged with bacteria Vibrio anguillarum and lipopolysaccharide (LPS) were different. The result presented an increased expression after injection with LPS whereas no significant changes were observed after V. anguillarum injection. A fusion protein containing Ai-icCuZnSOD was produced in vitro. The rAi-icCuZnSOD is a stable enzyme, retaining more than 80% of its activity between 10 and 60 degrees C and keeping above 88% of its activity at pH values between 5.8 and 9. Ai-icCuZnSOD is more stable under alkaline than acidic conditions. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.
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Vegetation is very sensitive to climate change. Carbon isotopes in paleosol have been widely used to contruct the propotion of plants using C3 and C4 photosynthetic pathways. δ13C of Loess organic matter were analyzed on the loess- paleosols samples from Jingchuan sections and Luochuan S4—S5 sequence. This paper presents a long carbon isotope time series, covering the last 600kyr. δ13C record of Loess organic matter in Jingchuan is correlated with marine oxygen isotope records. Basing on former research work, this paper discusses temperature, rainfall and P CO2 effect on δ13Corg value. In the interglacial periods, carbon isotope is more sensitive than other proxies and indicates several climate fluctuations. The main conclusions are as follows: 1. Obtained δ13C composition from paleosols and loess sediments in Jingchuan range of -20.0‰ to -24.6‰, the maximum biomass of C4 is 35%, indicating a C3 and C4 mixed steppe with C3 dominated. C4 plant is not always expansion during paleosols periods. The minimum values of Jingchuan section appeared in S4 soil, and the vegetation was almost pure C3 plant at that time. δ13Corg value in S5-2 is also lower than loess in S5, reaching the minimum valus of S5 soil. 2. PCO2 variation has little impact on δ13Corg value in interglacial periods for the last 600kyr. The correlation between δ13Corg value curve and magnetic susceptibility curve as proxy of summer monsoon in general, means summer monsoon drive C4 plant expansion during glacial and interglacial. 3. The lowerδ13Corg values in S4 and S5-2 appear at Jingchuan and Luochuan, suggest origin from woodland or C3 grassland. Whatever vegetation it is, indicate strengthened East Asian summer monsoon and increase of precipitation. C4 plant percentage is lower in S5-1 and S1 which have stronger summer monsoon, than S0 and S2. And it also indicates increase of precipitation.δ13Corg values has not always non-linearity correlation with summer monsoon. 4. The maximum entroy spectral analysis of δ13C values of the last 600kyr indicates there is 21 kyr cycles in Loess sequence. It means that summer monsoon in the Chinese Loess Plateau also has the precession cycles like its origin low latitude.
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云南会泽铅锌矿田是我国著名的超大型特富铅锌矿田之一,由相距3公里的矿山厂和麒麟厂两个独立的矿床组成,Zn+Pb金属量超过五百万吨,矿石品位在25%至35%之间。为确定矿床成矿流体和成矿金属来源,本文系统研究了矿床的Ph、S、C、O、H和Sr同位素组成特征。矿石硫化物的铅N位素组成均一,^206Pb/^204Pb,^207Pb/^204Pb和。^206Pb/^204Pb的变化范围分别为18.251~18.530,15.663~15.855和38.487~39.433,与围岩碳酸盐岩中浸染状黄铁矿一致,与碳酸盐地层相近,在^208Pb/^204Pb-^206Pb/^204Pb图上显示明显的线性关系,表明铅N位素组成相近的碳酸盐围岩地层提供了成矿物质。矿石硫化物的δ^14S变化范围为10.9‰~17.4‰,多数集中于13‰~17‰,表明还原硫主要来自地层中海相硫酸盐的还原,还原方式为热化学还原,下伏页岩、碎屑岩和泥质岩中的有机质在硫酸盐还原过程中发挥了重要作用。三种不同产状的脉石矿物方解石的碳氧同位素组成均一且没有明显差别,δ^13C变化范围为-2.1‰~-3.5‰, δ^18O为16.8‰~18.6‰。脉石矿物方解石中流体包裹体水的δDFI为-50‰~-60‰,取温度为200℃计算包裹体水的δ^18OH2O值为7.0‰~8.8‰。碳、氧和氢、氧同位素研究结果表明,成矿流体为来自下部上升的变质流体,由于下伏页岩、碎屑岩和泥质岩中有机质的参与,成矿流体具有低的δ^13C和δ^13DFI值,在上升过程中与围岩发生了同位素交换。矿石中黄铁矿、闪锌矿和方解石的初始锶同位素组成(^87Sr/^86Sr).值的变化范围为0.714~0.717,赋矿围岩中未蚀变白云岩的初始锶同位素组成(^87Sr/^86Sr).值为0.7083~0.7093,明显低于蚀变白云岩(0.7106),表明成矿流体具有高的(^87Sr/^86Sr),比值。相对围岩碳酸盐岩而言,下伏地层中的页岩、碎屑岩和泥质岩往往具有高得多的^87Sr/^86Sr,因此,流经或者起源于这些地层的流体具有高的锶同位素比值.