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1.
Martin Proudmore Ji-Feng Ding Richard H. Mobbs Stephen G. Yeates Colin Price Colin Booth 《Journal of polymer science. Part A, Polymer chemistry》1995,33(10):1615-1625
Poly(hexafluoropropylene oxide), poly(HFPO), networks were prepared from functional polymers by end linking via urethane groups. The prepolymers were characterized by NMR spectroscopy and GPC. The networks were characterized by determination of the number of network chains from the shear modulus, and were snown to contain both trifunctional crosslinks and difunctional links. The properties of the networks were investigated by a range of techniques. Compared with fully-fluorinated networks formed via triazine cross-links, investigated previously, the urethane-linked networks were more readily prepared but were poorer elastomers, were less thermally stable, and were less resistant to swelling by common polar solvents. © 1995 John Wiley & Sons, Inc. 相似文献
2.
对烘烤前后南瓜籽中的化学成分进行分析并对比。采用同时蒸馏萃取装置萃取南瓜籽中的挥发性成分,采取超临界CO2萃取技术萃取南瓜籽油脂,并将其分为酸、碱、中性三个部分,用气相色谱-质谱联用方法分析其中化学成分并进行对比。结果表明,南瓜籽挥发性成分中含有多种醛类和酯类化合物,烘烤后产生了大量的烷基吡嗪,其在碱性部分中的相对含量比烘烤前提高14倍多,不饱和醛类化合物含量也有明显提高。南瓜籽油脂中的主要化学成分是油酸、亚油酸及其酯类。还含有生物活性功能成分如植物甾醇、角鲨烯和维生素E等。烘烤后除角鲨烯含量有所降低,维生素E、植物甾醇、亚麻酸等均有提高。 相似文献
3.
Arachin and its molecular species (arachin I and arachin II) were separated and isolated. The number and kind of subunits of arachin, arachin I and arachin II were determined. Studies were carried out under different experimental conditions using slab gel electrophoresis, size-exclusion chromatography and reversed-phase high-performance liquid chromatography. Gel electrophoresis was done under varying concentrations of resolving gel. Tube gel as well as slab gel electrophoresis were used and continuous as well as discontinuous buffer systems were used for both types of electrophoresis. In addition, the subunits were separated by reversed-phase HPLC using a gradient program. Arachin and arachin II were found to have 12 subunits each while arachin I showed six subunits. The subunits of arachin I were allowed to reconstitute by removing SDS. Eight combinations were tried for studying the reconstitution pattern. Molecular weight and weight ratio in each case were also determined. 相似文献
4.
云南菊科中草药中铅含量特征分析 总被引:3,自引:2,他引:1
论述了云南27种菊科中草药及其水提取物中铅含量的特征。菊科植物及水提物中铅含量的频数分布为正偏态,两者的相关系数r=0.09,未呈现显著的线性相关。提取率较高的山紫苑、佩兰、木香铅实际含量低;铅含量高的叶下花、狭叶兔耳风、臭灵丹提取率又较低,减少了人体对Pb的过量摄入。 相似文献
5.
Trace elements were determined in South West African potsherds by instrumental NAA and by PIXE. The elements for which the
relative spread of concentrations were greatest were selected as indicators. From these the methods of the Minimal Spanning
Tree and of Nonlinear Mapping were used to classify about 60 specimens. Groups were tested by concentration, sum of concentration
and normalized concentration indices. Similar groupings were obtained irrespective of which analytical data or mathematical
techniques was used. 相似文献
6.
利用密度泛函理论方法研究了IClO2异构化反应机理. 优化得到了七种异构体, 其中OIClO和IClOO还未见报道, 对各异构体的热力学稳定性进行了比较. 找到了异构化过程的过渡态, 并通过内禀反应坐标(IRC)计算确认了各个异构体之间的相互转化关系. 从量子拓扑学的角度, 对典型异构化反应通道IRC途径上的各点进行了电子密度拓扑分析, 讨论了反应过程中化学键的断裂、生成以及化学键的变化规律, 找到了反应途径上的能量过渡态(ETS)和结构过渡态(STS). 相似文献
7.
Young Duk Kim Bong Keun Lee Eun Jin Jeon Yong Cheol Shin Sung Chul Kim 《Macromolecular Symposia》1995,98(1):665-672
Hydrophilic-hydrophobic IPN materials of poly(acrylic acid)-poly(styrene-co-acrylonitrile) were synthesized and the pervaporation characteristics of the IPN membranes were evaluated for the separation of ethanol/water mixture. Hydrophilic-hydrophobic IPN materials of polyurethane-polystyrene were synthesized and the blood compatibility of the IPN's were measured for the biomedical application. Dicyanate-engineering plastics semi-IPN's were prepared and the morphology and mechanical properties were evaluated for the high temperature composite matrix materials. 相似文献
8.
Limin Shao Christopher W. Roske Peter R. Griffiths 《Analytical and bioanalytical chemistry》2010,397(4):1511-1519
Open-path FT-IR spectra were measured while fireworks were emitting smoke and incandescent particles into the infrared beam. These conditions were designed to simulate the appearance of smoke and explosions in a battlefield. Diethyl ether was used to simulate the vapor-phase spectra of G agents such as sarin. The measured interferograms were corrected by a high-pass filter and were rejected when interfering features were of such high frequency that they could not be removed by application of this filter. The concentration of diethyl ether was calculated correctly by partial least squares regression in the absence of fireworks but significant errors were encountered when the spectra of the oxide particles were not included in the calibration set. Target factor analysis allowed the presence of the analyte to be detected even when the incandescent particles were present in the beam. 相似文献
9.
Several benzimidazole derivatives having electron-withdrawing or -donating substituent(s) at the benzene moiety were used as models of the imidazole moiety of purine bases and their nitration with nitrogen dioxide and ozone (so-called Kyodai nitration) were examined. Products were extracted from the reaction mixture with AcOEt and their structures were analyzed. 1-Nitrobenzimidazole derivatives and unexpected 1-nitrobenzotriazole derivatives were identified. Although the yields of 1-nitrobenzimidazole derivatives were quite low, these were all new compounds that could be obtained only by Kyodai nitration. It was speculated that benzotriazoles were formed via 1-nitrobenzimidazoles and subsequent nitration toward benzotriazoles resulted in the formation of 1-nitrobenzotriazoles. 相似文献
10.
Srivastava Alok Swain Kallola K. Chahar Vikas Bhardwaj Sonakshi Ajith Nicy Mete Uttam Garg Uttam Srivastava Tarak 《Journal of Radioanalytical and Nuclear Chemistry》2019,319(1):271-278
Twenty eight stones were characterized for chemical composition and structure. The concentrations of trace elements were determined using INAA while EDXRF was used for determining the calcium contents of the stones. Twenty stones were found to be mainly composed of calcium, six were mixed type and the remaining two were of uric acid type. The concentrations of trace elements namely Zn, Sr, Fe and Cr were lower in uric acid stones as compared to calcium based stones. Diet analysis of 310 patients who were treated for renal stones showed a diet rich in calcium and oxalate and decreased water consumption.
相似文献11.
Transparent films of titania/poly(dimethylsiloxane) (PDMS) hybrids were prepared by the solvent evaporation from the precursor
solution prepared by the co-hydrolysis and co-condensation of titanium tetraisopropoxide and a methoxy-functionalized PDMS.
The hybrid films were flexible and had high homogeneity of the composition. The organic groups of PDMS were decomposed at
400°C in air to form porous films. Though the heated films were rather brittle compared to the as-synthesized films, they
were still transparent and homogeneous. The BET surface areas of the films after the heat treatment at 400°C were over 300
m2/g, while the as-synthesized hybrid films were non porous. According to the BDDT classification, the nitrogen adsorption/desorption
isotherms of the calcined films were Type I, showing that the films were microporous. The titania domains were still amorphous
after the heat treatment at 400°C and transformed to anatase after the heat treatment at 1,000°C. 相似文献
12.
Contents of lanthanoids (Ln's) of rock salts have been measured by neutron activation analysis. Original salt samples were
treated in advance of neutron irradiation so that Ln's were enriched and amounts of interfering nuclides were reduced. The
contents of Ln's were at ppt-sub ppb levels and were comparable with or slightly lower than those of solar salts. The Ln abundance
patterns of the salts were those with relative depletion in the heavy Ln's, thus having negative slopes. It was indicated
that, when salt deposit was formed, Ln's were taken up by anhydrite more preferentially than by halite. 相似文献
13.
Castro J Pérez RA Miguel E Sánchez-Brunete C Tadeo JL 《Journal of chromatography. A》2002,947(1):119-127
Rapid analytical methods for the determination of endosulfan isomers and endosulfan-sulfate in air and plant samples were developed. The insecticides were trapped from air using a column containing Florisil and extracted with a low volume of ethyl acetate, assisted by sonication. Pesticide residues were determined by gas chromatography with electron-capture detection using a nonpolar capillary column. Residue identities were confirmed by gas chromatography coupled with mass spectrometry. Recoveries of these compounds from air samples were always higher than 78% with an RSD lower than 11% and the detection limits obtained were at least 0.3 ng/l air. Leaf samples were homogenised with ethyl acetate and extracts cleaned-up on an aluminium oxide column. Pesticides were eluted with a hexane-ethyl acetate (80:20, v/v) mixture. Recoveries obtained from plant samples were higher than 78% with an RSD lower than 14% and detection limits in leaves were 0.02 microg/g for each pesticide. These methods were applied to study the volatilisation of endosulfan from tomato leaves under laboratory conditions. A volatilisation rate near 1% of the initial amount of endosulfan per hour was obtained during the first 24 h at room temperature. 相似文献
14.
15.
A series of binary and ternary rare earth complexes with para-substitued benzoic acids and 1,10-phenanthroline were synthesized. The phosphorescence spectra were measured and the lowest triplet state energies of ligands were determined, the phosphorescence lifetimes were obtained and intramolecular energy transfer mechanism between ligands was studied. The luminescence properties were also measured and were in agreement with the prediction. The energy match and intramolecular energy transfer process in these binary and ternary complexes were discussed in detail. 相似文献
16.
Diurnal variation of blood sugar, C-peptide immunoreactivity (CPR), free insulin and total insulin were measured in 10 insulin requiring diabetics after obtaining adequate control of diabetes with commercial lente insulin treatment. Following these tests, insulin treatment were changed to monocomponent insulin (MC-insulin) from commercial lente insulin treatment in all subjects and the same tests were performed at 7th day of MC-insulin treatment. Diurnal variations of blood sugar in both groups were not changed significantly. Also changes in CPR of both groups were nearly same magnitude and endogenous insulin secretion in these insulin treated diabetics were suggested except a case of juvenile diabetic subject. However personal variation were great in diabetics with high antibody titer, diurnal variations of total extractable insulin in both groups were quite comparable. And mean diurnal changes in free insulin were resemble to that of CPR. All of these data suggested that clinical effects of MC-insulin and commercial insulin treatment on insulin requiring diabetics were comparable except insulin antibody or proinsulinspecific antibody production. 相似文献
17.
采用电感耦合等离子体发射光谱法对茶水中的无机元素进行分析,对其中的Cu、Zn、Mn、P、Fe5种元素进行定量,讨论了等离子体发射光谱法最佳实验条件及影响茶叶中无机元素浸出量的因素。Cu、Zn、Mn、P、Fe的回收率为92.5%~103.5%,测定结果的相对标准偏差为1.34%-4.5%(n=5)。 相似文献
18.
碳苷研究 V: 用Grignard试剂合成取代苯酚中酚羟基的保护及脱保护 总被引:1,自引:0,他引:1
本文报道了一些取代苯酚的合成, 并探讨了用Grignard试剂合成取代苯酚中酚羟基的保护及脱保护的问题. 利用苄基和甲基作为酚羟基的保护基, 对文献报道的切断醚键脱保护方法进行了评价. 找到了两种新体系能在更温和条件下切断醚键的方法, 指出了它们的适用条件. 实验结果符合硬软酸碱理论. 相似文献
19.
以过氧化二苯甲酰为引发剂,使丙烯睛在涤沦(PET)纤维上接枝共聚。接枝纤维在含铜化合物,含硫还原剂溶液中反应,制备PET导电纤维。讨论了影响接枝共聚的各种因素,选择出最佳聚合条件。对该纤维的导电成份和结构以及性能进行了研究。 相似文献
20.
Bacterial proteomes were analyzed by use of electrophoretically mediated microanalysis (EMMA) and field-enhanced stacking. A water-soluble protein fraction was injected onto a capillary. Next, a fluorogenic reagent was injected and allowed to react with the protein mixture, producing fluorescent products that were separated by submicellar capillary electrophoresis and detected by laser-induced fluorescence. By use of a low-ionic strength sample buffer and a brief electrophoretic step, slow moving anionic proteins were stacked at the reagent-sample interface and were preferentially labeled. By reversing the order of sample injection and labeling reagent, fast moving cationic proteins were preferentially labeled. By adjustment of the sample buffer pH, proteins with different isoelectric points were selectively labeled. Electrophoresis fingerprints were generated for the water-soluble protein fraction from six Staphylococcus species. The protein patterns produced were species-specific and were used to construct a phylogenetic tree. 相似文献