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971.
马来酸酐与聚烯烃接枝产物的表征   总被引:21,自引:1,他引:21  
综述了马来酸酐与聚烯烃接枝产物的多种表征手段,重点分析了纯化处理,化学滴定以及红外分析方法的表征原理,应用和改进方法。  相似文献   
972.
An attempt has been made to develop a radiochemical methodology for the decontamination of a trace amount of radioactive cesium from a bulk amount of natural NaCl by liquid-liquid extraction (LLX). Open chain crown ethers, of amide type, namely, N,N,N",N"-tetraphenyl-3,6-dioxaoctanediamide (TDD), N,N,N",N"-tetraphenyl-3,6,9-trioxaundecanediamide and N,N"-dinaphthyl-N,N"-diphenyl-3,6-dioxaoctanediamide (DDD) have been chosen for this purpose. The separation factor between Cs and Na is the highest when 10-4M TDD dissolved in nitrobenzene is used as extractant and 0.4M picric acid at pH 5.0 is used as aqueous phase. About 60% Cs is extracted in this condition in a single run.  相似文献   
973.
An enantioselective total synthesis of hamacanthin B (1) is described. This synthesis is based on the asymmetric synthesis of (S)-2-azido-(indol-3-yl)ethylamine 7, which is coupled with the 3-indolyl-alpha-oxoacetyl chloride 8 and subsequently used in a successful intramolecular Staudinger-aza Wittig cyclization to form the central dihydropyrazinone ring. The stereochemistry of naturally isolated hamacanthin B is revealed as the (S)-configuration.  相似文献   
974.
By the use of differential scanning calorimetry (DSC), a new method to measure the wax content of crude oil has been developed. In this paper, the wax content of a crude oil is proposed and proved to be the Q (total thermal effect of wax precipitation in sample) ratio of the crude oil and its corresponding wax obtained by using standard acetone method, i.e. Qoil/Qwax. For the 14 studied crude oils with the wax content ranging from 1 to 27 wt.%, the wax contents determined by the presented method are in good agreement with those determined by standard acetone method, with an absolute average deviation of only 0.82 wt.%. This method has an advantage over reported DSC methods in which the exact dissolution or precipitation enthalpy of wax is a must. It is also found that the wax contents determined by either of the two methods show good linear relationship with the total thermal effect Qoil, with the correlation coefficients over 0.96. According to the empirical correlations, the wax content of a crude oil can be easily determined by using the DSC total thermal effect Qoil. In addition and more significantly, the new method can be applied to improve the accuracy in determining the amount of precipitated wax in a waxy crude oil at different temperatures.  相似文献   
975.
Wu XJ  Choi MM  Wu XM 《The Analyst》2004,129(11):1143-1149
This paper presents a recycle amplification optical biosensor to monitor phenol in hydrophobic organic solvents. Tyrosinase was first immobilised by entrapping it in a copolymer membrane of poly(vinyl alcohol)-hydroxyethyl carboxymethylcellulose doped with octadecylsilica particles. The biosensor was then constructed by co-mixing small particles of the immobilised tyrosinase with the adduct of L-ascorbic acid-poly(vinyl alcohol) (AsA-PVA) in conjunction with an optical oxygen transducer. The biosensor was characterised by its amplifying response to phenol, stable biocatalytic activity of entrapped-tyrosinase, free of interference from o-quinone polymerisation, and large water buffer capacity in hydrophobic organic solvents. The working range of the biosensor to phenol was 0.08-40 mmol dm(-3) in the flow mode. The response times (95%) of the biosensor were 4-7 min for phenol. The operational lifetime was more than 40 assays and the shelf lifetime of the biosensor was longer than 3 months. The biosensor has been successfully applied to quantify the phenol contents in some commercial ointment samples.  相似文献   
976.
含铈不锈钢的抗菌性能   总被引:6,自引:0,他引:6  
以00Cr18Ni9不锈钢成分为基础,添加0~5%的稀土元素铈(Ce).利用电子探针分析了加铈(Ce)不锈钢中Ce的分布;用化学分析法测定了含铈不锈钢中铈(Ce)和碳(C)的含量;用X射线衍射方法测试了含铈(Ce)不锈钢中铈(Ce)的析出相成分;采用贴膜法测试了含Ce不锈钢对大肠杆菌ATCC 8099、金黄色葡萄球菌ATCC 6538的抗菌性能.结果表明: 含Ce不锈钢具有优异的抗菌性能,与含Cu抗菌不锈钢相比,含Ce不锈钢无需时效热处理就具有优异的抗菌性能.并讨论了含Ce不锈钢的抗菌机制.  相似文献   
977.
978.
Dispersion of MoO3, NiO, ZnO on rutile TiO2 with low specific surface area was studied with Mercury Porosimeter, SEM, XPS and Ammonia Extraction method. The dispersion thresholds of MoO3, NiO, ZnO on three rutile TiO2 carriers were obtained with XPS, and com-pared with those on anatase TiO2 with high specific surf are area. Ammonia Extraction method was used to identify the surface oxide species interarting with support surface in different strength and it was found that the proportions of oxides that can not be extracted by ammonia extraction are different for MoO3, NiO and ZnO which are supported on rutile TiO2.  相似文献   
979.
N-Methylol dimethylphosphonopropionamide (MDPA), known as “Pyrovatex CP” and “Pyrovatex CP New” commercially, has been one of the most commonly used durable flame retardant agents for cotton for many years. In our previous research, we developed a flame retardant finishing system for cotton based on a hydroxy-functional organophosphorus oligomer (HFPO) in combination with a bonding agent such as trimethylolmelamine (TMM) and dimethyloldihydroxyethyleneurea (DMDHEU). In this research, we investigated the bonding of these two flame retardant finishing agents to cotton. We found that the majority of MDPA is bound to cotton by its N-methylol group and that the use of TMM as a co-reactant modestly increases the fixation of MDPA onto cotton. For HFPO, however, the use of a bonding agent is necessary to form a covalent linkage between HFPO and cotton. Both the fixation of HFPO on cotton and its laundering durability are influenced by the effectiveness and concentration of the bonding agent. The commercial product of HFPO contains approximately 33% more phosphorus than that of MDPA and the percent fixation of HFPO on cotton is also moderately higher than that of MDPA. The bonding between MDPA and cotton is significantly more resistant to hydrolysis during multiple launderings than that between HFPO and cotton. The selection of catalyst also plays a significant role in influencing the bonding of the flame retardant agents to cotton.  相似文献   
980.
Under the background of algae removal and growth inhibition by ultrasonic irradiation, the effects of ultrasonic irradiation on removal of Microcystis, the concentration variation of microcystins (MC) produced by Microcystis in Microcystis suspension, and sonochemical degradation of microcystins in water, were studied in the paper. The results showed that ultrasonic irradiation could efficiently inhibit the growth of Microcystis, and ultrasonic irradiation shorter than 5 min would not introduce the increase of microcystins dissolved in Microcystis suspension simultaneity. Also, microcystins dissolved in Microcystis suspension would not increase as ultrasonic power increasing. Further research showed that microcystins were effectively degraded in ultrasonic fields. After 20 min ultrasonic irradiation at 150 kHz and 30 W, the removal rate of microcystins reached 70%.  相似文献   
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