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951.
氯化血红素催化新型荧光反应测定葡萄糖的研究 总被引:3,自引:0,他引:3
本文用流动注射分析了研究了过氧化物模拟酶催化过氧新型荧光底物(N,N-二氰甲基邻苯二胺,DCMOPA)的最优条件。结果表明,该系统可用于定量测定氧化氢及催化氯化血红素的浓度。 相似文献
952.
A convergent formal total synthesis of OF 4949 III is described. Arene-ruthenium chemistry was used in the construction of the diaryl ether linkage in high yield, and cycloamidation under high dilution conditions (0.005 M) was achieved using DPPA as coupling reagent. SmI(2) was used to reductively remove the 2-iodoethyl ester protecting group in the presence of DMPU or HMPA. 相似文献
953.
Miaosheng Li 《Tetrahedron letters》2004,45(34):6407-6411
A short enantioselective route to the highly functionalized α,β-unsaturated δ-lactone natural product phomopsolide D and three of its stereoisomers, has been accomplished. All of the carbon atoms of phomopsolide D come from tiglic acid and 2-furyl-1-penta-1′,3′-dienylketone (furan plus hexadienal). This approach derives its asymmetry from the sequential use of two catalytic asymmetric reactions; these being a Sharpless dihydroxylation reaction and a Noyori furylketone reduction. The resulting furfuryl alcohols were stereoselectively transformed into α,β-unsaturated δ-lactones via a short highly diastereoselective oxidation and reduction sequence. 相似文献
954.
E. Sabbioni M. Bonardi G. Tanet Li Da-Kang M. Gallorini B. Weckermann M. Castiglioni 《Journal of Radioanalytical and Nuclear Chemistry》1989,134(1):199-208
No-carrier-added48V at 37 Mbq (mCi) levels was produced at the JRC-Ispra cyclotron by (, n) reactions on a scandium target and used to label environmental and physiological levels of vanadium for metallobiochemical investigations. The radiochemical separation of48V from Sc is very simple and rapid and involves a single chromatographic step after fast dissolution of the bombarded target. The yield of the separation and the radioisotopic purity of the separated48V were nearly 100% A summary of the main results concerning different metabolic investigations on rats including absorption, retention, transfer of48V from mothers to newborns, binding with enzymes as well as uptake by cell culture system is reported.At the time of this study visiting scientists at the4,5Radiochemistry and3Functional Materials Divisions of the JRC-Ispra. 相似文献
955.
Tian-Ling Ren Lin-Tao Zhang Li-Tian Liu Zhi-Jian Li 《Journal of Sol-Gel Science and Technology》2002,24(3):271-274
A novel silicon-based PbTiO3/Pb(Zr,Ti)O3/PbTiO3 (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm2 respectively. The current density is less than 5 × 10–9 A/cm2 below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 109 read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications. 相似文献
956.
The flow-injection system combines on-line ion-exchange preconcentration with atomic absorption spectrometry (a.a.s.) for the determination of traces (μg l?1) of heavy metals in water samples. Miniature columns packed with 60–100 mesh chelating resin (122) with a salicylic acid functional group are used for preconcentration. A multifunctional rotary sampling valve which incorporated two parallel sampling columns allows sampling, exchange, elution and a.a.s. to be achieved sequentially. The increases in sensitivity for nickel, copper, lead and cadmium were 20–28-fold at a sampling rate of 40 h?1 with 5-ml samples. Relative standard deviations were 1.5–4.1%. The recoveries of these four metals added to tap, sea and polluted waters were generally satisfactory, except for cadmium in polluted water. The effects of column diameter and elution flow rates on sensitivity are discussed. Possible interferences are described. 相似文献
957.
Dushmantha Kannangara Hailong Zhang Wei Shen 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):203-215
The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction. 相似文献
958.
The immobilization of biological cells in micro-devices requires high efficiency and easy control while maintaining cell viability. One approach for cell immobilization is to utilize constriction structures such as dams to trap cells in microfluidics. In this paper, we present a comprehensive hydrodynamic analysis of two different types of constriction structures for cell immobilization: dams either in perpendicular or in parallel to the main flow route. Various structural models and experimental conditions were compared for cell docking and alignment, and the pressure and velocity profiles of the flow in the micro-channels and the hydrodynamic force and shear stress on the docked cells were calculated based on fluid dynamic theory and numerical simulation. The effects of the dam structures and cell docking on the flow properties, the transportation efficiency, and the induced stress on the docked cells were analyzed. Improved hydraulic pressure profiles in the auxiliary inlets were discussed for the modulation of the flow characteristics and attenuation of hydrodynamic forces exerted on the cells. Furthermore, a new design combining the advantages of perpendicular and parallel dam structures was proposed for cell-based microfluidics. 相似文献
959.
The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence. 相似文献
960.
The sorption and desorption isotherms of untreated calcareous soil and three treated soils to remove CaCO3, organic matter (OM) and both CaCO3 and OM were determined and analyzed with the Freundlich equation at pH 7.8, moderate concentrations of NpO2
+ (~10-5mol/l), in the presence of 0.01 mol/l CaCl2 and under ambient aerobic conditions. The relative contribution of CaCO3 and OM to the neptunium(V) sorption on calcareous soil and the sorption/desorption hysteresis is discussed. The effects of adding fulvic acid (FA) and carbonate in to the solution on the sorption of neptunium(V) on the soils were also studied. The sorption and desorption characteristics of NpO2
+, Zn2+, Sr2+ and Cs+ on the soils are compared. 相似文献