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51.
The effects of organic solvents on the ammoximation of cyclohexanone to cyclohexanone oxime with H2O2and NH3 over TS-1 were studied. To investigate the effects of ammonia and organic solvents on the structure stability of the catalyst, TS-1 samples were pretreated under severe conditions in ammonia solution or ammonia solution plus methanol, toluene or t-butanol, respectively, and then characterized bySEM, XRD, FTIR, etc. The results revealed that t-butanol is the best solvent for the ammoximation reaction; ammonia tends to destroy the active sites, -Ti-O-Si- structure in TS-1, but the presence of organic solvents remarkably limits this damaging effect of ammonia.  相似文献   
52.
Hu  Chuanjiang  Duan  Chunying  Meng  Qingjin  Liu  Yongjiang  Lu  Changsheng  Reng  Xiaoming  Chen  Yijun  Cao  Mi 《Transition Metal Chemistry》2000,25(2):141-144
The mixed-valence molybdovanadate compound Na2(NH4)4[VIVVV 8Mo)O28] · 10H2O [Vanadata(6-)tetradeca--oxotetra-3-oxodi-6-oxoheptaoxo(oxomolybdate) nonatetrammonium disodium, decahydrate] has been synthesized from sodium molybdate(VI) dihydrate and sodium metavanadate dihydrate in aqueous solution by adding NH2OH · HCl. The molecular structure has been determined by X-ray diffraction and is based on the isopolydecavanadate structure. The molybdate atom is crystallographically disordered over 6MO6 octahedral sites. The e.s.r. spectrum clearly indicates that one vanadium atom has the oxidation number +4.  相似文献   
53.
In this work, an integral equation approach to investigate the atactic polystyrene (aPS) melt based on polymer reference interaction site model (PRISM) theory is proposed. The intramolecular structure factors, required as input to PRISM theory, are obtained from the semiflexible chain model. With a novel coarse-graining procedure and the explicit-atom molecular-dynamics (MD) simulations for aPS, the parameters needed for the coarse-grained model are obtained by using an automatic simplex optimization. These parameters can be used to describe the structure and thermodynamic properties of the complex aPS melt and good agreement is obtained between the theory and MD simulations. The proposed integral equation approach provides a basis for describing the structure and properties of PS nanocomposites where the application of molecular simulation is difficult.  相似文献   
54.
EPO检测技术的研究进展   总被引:3,自引:0,他引:3  
王杉  宓捷波  常文保 《化学进展》2003,15(2):117-122
促红细胞生成素(EPO)是一种临床上广泛应用的重要药物,也是近年来兴奋剂检测的热点。本文主要从EPO的产生和应用出发,对EPO的结构、特性及其检测方法进行了介绍及评价,重点探讨了竞技体育中EPO的检测技术,并对检测前景作了展望。  相似文献   
55.
Pt‐nanoparticles were synthesized and introduced into a carbon paste electrode (CPE), and the resulting modified electrode was applied to the anodic stripping voltammetry of copper(II) ions. The synthesized Pt‐nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy and X‐ray photoelectron spectroscopy techniques to confirm the purity and the size of the prepared Pt‐nanoparticles (ca. 20 nm). This incorporated material seems to act as catalysts with preconcentration sites for copper(II) species that enhances the sensitivity of Cu(II) ions to Cu(I) species at a deposition potential of ?0.6 V in an aqueous solution. The experimental conditions, such as, the electrode composition, pH of the solution, pre‐concentration time, were optimized for the determination of Cu(II) ion using as‐prepared electrode. The sensitivity changes on the different binder materials and the presence of surfactants in the test solution. The interference effect of the coexisted metals were also investigated. In the presence of surfactants, especially TritonX‐100, the Cu(II) detection limit was lowered to 3.9×10?9 M. However, the Pt‐nanoparticle modified CPE begins to degrade when the period of deposition exceeds to 10 min. Linear response for copper(II) was found in the concentration range between 3.9×10?8 M and 1.6×10?6 M, with an estimated detection limit of 1.6×10?8 M (1.0 ppb) and relative standard deviation was 4.2% (n=5).  相似文献   
56.
The indications of a Clark-type electrochemical sensor with a polyethylene foil used as a membrane are noticeably changed if vapours of chlorine derivatives of methane (CCl4, CHCl3, CH2Cl2) are present in the atmosphere examined and the sensor has been calibrated in an atmosphere from which those vapours were absent. The sensitivity of the sensor increases and tends to deviate from linearity. The increase is more profound, when the number of chlorine atoms within a molecule of the vapour increases, the partial pressure of the vapour increases and the temperature of the atmosphere examined decreases. If the vapours affect the membrane for a long time, the response time decreases. If the membrane is freshly subjected to the influence of the vapours, a longer period of time is needed to reach a stable indication corresponding to the partial pressure of oxygen actually observed.  相似文献   
57.
N-甲基吡咯烷酮、α-吡咯烷酮合成物系气相色谱分析邱立勤,米镇涛,张香文(天津大学天津石油化工技术开发中心天津300072)1前言N-甲基吡咯烷酮(NMP)具有高极性、高化学稳定性及热稳定性,是重要的工业溶剂,可广泛应用于有机化合物萃取、润滑油精制、...  相似文献   
58.
Molecular reorientation in the presence of internal rotation is investigated and an analytical expression for the spin—rotational rate of a nucleus attached to the internal rotor is obtained in terms of the internal angular-momentum correlation time. A model of a symmetric-top molecule undergoing anisotropic rotational diffusion is extended to include a modified extended diffusion of internal rotation. The result is applied to liquid toluene and the internal angular-momentum correlation time is evaluated from the 13C nuclear spin—rotational relaxation rate of the methyl carbon. A comparison with the previous result on the dipole—dipole relaxation data is made and the consistency of the present theory is discussed.  相似文献   
59.
In this study, we investigated the effects of PAHs and dioxin on mRNA and plasma protein expression using genomic and proteomic analysis for automobile emission inspectors and waste incineration workers. About 54 workers from automobile emission inspection offices, 31 workers from waste incinerating company and 84 unexposed healthy subjects were enrolled in this study. Urine and air samples were collected and analyzed by HPLC and GC/MS. Comet assays were carried out to evaluate any DNA damage in mononuclear and polynuclear cells. A significant difference in Olive tail moments in mononuclear cells was observed between exposed and control subjects (P < 0.0001). To examine the differences of the gene expression profile in automobile emission inspectors and waste incineration workers, radioactive complementary DNA microarrays were used to evaluate changes in the expression of 1,152 total genes. The gene expression profiles showed that 11 genes were up-regulated and 4 genes were down-regulated in waste incinerating workers as compared with controls. Plasma proteins were analyzed by 2-dimentional electrophoresis with pH 3-10 NL IPG Dry strip. The protein expression profiles showed that 8 proteins were up- regulated and 1 protein, haptoglobin, was down- regulated in automobile emission inspectors and waste incineration workers. Serum paraoxonase/ arylesterase was found only in the plasma of waste incineration workers. The expression of genes and proteins involved in oxidative stress were up-regulated in both automobile emission inspectors and waste incineration workers. Several proteins, such as transthyrethin, sarcolectin and haptoglobin, that were highly up- or down-regulated, could serve as biological monitoring markers for future study.  相似文献   
60.
Low molecular, water‐soluble chitosan (LMWSC) with a free amine group was prepared by the novel salts‐removal method described in this study. A weight‐average molecular weight and degree of deacetylation (DDA) of LMWSC were determined by viscometry and Kina titration, resulting in 18,579 Da and 93% DDA, respectively. In the Fourier transform infrared spectroscopic, 1H NMR, and 13C NMR spectra the absorption band by the carboxyl group derived from lactic acid and the impurities formed in the enzymatic process disappeared or were significantly lower than that of the control chitosan. Also, from the 1H NMR and 13C NMR spectra the empirical value for the area ratio of the proton and carbon corresponds nearly to its theoretical values. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum identified the difference in the two adjacent peaks as 161. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3796–3803, 2002  相似文献   
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