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101.
Guoqiang Cai Zhengjian Chen Kehua Tu Liqun Wang Kangjie Zhu 《European Polymer Journal》2009,45(6):1674-3144
A facile strategy was proposed for synthesizing chitosan-O-poly(ε-caprolactone) (CS-O-PCL). Stoichiometric sodium dodecyl sulfate-chitosan complex (SCC) which was soluble in common organic solvents was adopted as an intermediate. Regioselective conjugation of PCL onto SCC could be achieved through condensation reaction between isocyanate-terminated PCL and hydroxyl groups of chitosan. The grafting level of PCL could be modulated by varying PCL/SCC weight ratio. SDS was removed from SCC-O-PCL using trihydroxymethylamine (Tris) as a decomplexation agent. The self-assemble behavior of the amphiphilic copolymers was studied by fluorometry, TEM and laser light scattering. The morphology of the CS-O-PCL nanoparticles was found to be dependent on PCL grafting level. Both spherical micelles and vesicle could be formed by dialysis method. 相似文献
102.
Surfactant-free fabrication of Cu2O nanosheets from Cu colloids and their tunable optical properties
Novel sheetlike Cu2O two-dimensional (2D) nanoarchitectures were successfully synthesized via a copper nanoparticle-mediated process for the first time. Uniform and nearly monodisperse Cu nanocolloids were firstly synthesized by disproportionating reaction of Cu+ at the surfactant-free ambient conditions, and Cu2O nanosheets were subsequently synthesized by choosing ethanol solvent agent to limit the oxidized processes of Cu nanocolloids. The synthesized products were systematically studied by X-ray powder diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis absorption spectra. It was demonstrated that the solvent agent of ethanol played key roles in the formation of the as-synthesized nanosheets. By choosing the different solvent agents to limit the oxidized processes, Cu2O nanospheres and nanocubes can be selectively synthesized accordingly. 相似文献
103.
Yuxin Wang Guangji Wang Pengfei Tu Yan Liang Hao Yang Chaonan Zheng Nan Cui 《Talanta》2009,80(2):572-1747
Metabolite identification for the compounds that undergo multiple and sequential metabolism is still a great challenge. Echinacoside (ECH), a typical phenylethanoid glycoside, contains multiple unstable chemical bonds and high reactive functional groups which are susceptible to multiple pathways of degradation and metabolism, leading great difficulties for its metabolite identification. This study proposed a novel approach for rapidly identifying the complicated and unpredictable metabolites of ECH, based on the powerful liquid chromatography hybrid ion trap and time of flight mass spectrometry (LC/MS-IT-TOF) analysis. Four degradation products were rapidly identified via the “fragmentation-degradation” comparisons. Five phase I and phase II metabolites of the degradation products were rapidly characterized via the crossover mass differences comparisons of their quasi-molecular ions with the potential precursors. Four direct phase I and phase II metabolites of the parent compound were identified by the mass differences analysis of the molecular ions between metabolites and the parent compound. Multiple stages of fragmentation patterns were used to confirm the metabolites characterizations. This study provides a novel approach to characterizing the complicated metabolites, and would be widely applicable for the metabolite identification of natural products. 相似文献
104.
Xiao‐jia Chen Peng‐fei Tu Yong Jiang Yi‐tao Wang Shao‐Ping Li 《Journal of separation science》2009,32(2):275-281
A CZE method was developed for the simultaneous determination of 15 flavonoids, including epimedin B, epimedin A, hexandraside F, epimedin C, icariin, sagittatoside B, sagittatoside A, hexandraside E, 2′′‐O‐rhamnosyl icariside II, baohuoside VII, baohuoside I, caohuoside C, epimedoside C, baohuoside II, and kaempferol‐3‐O‐rhamnoside, in different species of Epimedium, and the effect of stability of internal standard (IS) on quantification was also investigated. As a result, rutin was not available for use as an IS because of its unstable property in sample solution, which suggested that the stability of IS both in standards and sample solution should be considered for the analysis. Using stable daidzein as IS, the analysis was performed within 35 min by using 50 mM borax buffer containing 20% ACN as a modifier (pH 10.0), while separation voltage was 25 kV and temperature was at 30°C. The method was validated to be accurate, simple, and repeatable, and was successfully applied to the analysis of 36 samples from 17 species of Epimedium. 相似文献
105.
Wenwen Tu Jianping Lei Dr. Huangxian Ju Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(3):779-784
A functional composite of single‐walled carbon nanotubes (SWNTs) with hematin, a water‐insoluble porphyrin, was first prepared in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid. The novel composite in ionic liquid was characterized by scanning electron microscopy, ultraviolet absorption spectroscopy, and electrochemical impedance spectroscopy, and showed a pair of direct redox peaks of the FeIII/FeII couple. The composite–[BMIM][PF6]‐modified glassy carbon electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid (TCA) in neutral media due to the synergic effect among SWNTs, [BMIM][PF6], and porphyrin, which led to a highly sensitive and stable amperometric biosensor for TCA with a linear range from 9.0×10?7 to 1.4×10?4 M . The detection limit was 3.8×10?7 M at a signal‐to‐noise ratio of 3. The TCA biosensor had good analytical performance, such as rapid response, good reproducibility, and acceptable accuracy, and could be successfully used for the detection of residual TCA in polluted water. The functional composite in ionic liquid provides a facile way to not only obtain the direct electrochemistry of water‐insoluble porphyrin, but also construct novel biosensors for monitoring analytes in real environmental samples. 相似文献
106.
The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on
two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated
with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers.
The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated
for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three
isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption
on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate
molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties
of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the
feasibility of using the three isomers as adsorbates to extract pore information.
This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec. 相似文献
107.
Ukrainian Mathematical Journal - In connection with the method of construction of lightlike hypersurfaces along spacelike submanifolds, we present a relation between the second fundamental form of... 相似文献
108.
Guo-Bin Jung Cheng-Hsin Tu Pei-Hung Chi Ay Su Fang-Bor Weng Yur-Tsai Lin Yu-Chun Chiang Chi-Yuan Lee Wei-Mon Yan 《Journal of Solid State Electrochemistry》2009,13(9):1455-1465
An experimental and simulation research had been performed to investigate the performance as well as the flow distribution
in the cathode flow field in the case of direct methanol fuel cells (DMFCs). The gas was well distributed in serpentine flow
field, whereas stagnation of the gas was observed in parallel flow field. These would contribute to the cell performance greatly
due to mass transfer effect when the cells start operating. In addition, the durability test of DMFC was drastically affected
in parallel flow field due to poor ability to drain flooded water produced electrochemically at cathode and crossover from
anode. In addition, pressure drops of different flow fields were also investigated to evaluate their contribution and feasibility
as an economic application for DMFC. DMFC with serpentine flow field featuring higher pressure difference resulted in a larger
parasitic energy demand. However, the optimal flow field designs are needed to balance the performance and pressure loss to
achieve a uniform fluid distribution and simultaneously minimize energy demand for mass transport. Consequently, flow field
with grid pattern appears to be the optimal design for the DMFC cathode. 相似文献
109.
TianLiang Tu 《中国科学A辑(英文版)》2009,52(3):493-506
Let Γ be a closed smooth Jordan curve in the complex plane. In this paper, with the help of a class of fundamental functions
of Hermite interpolation, the author introduces a continuous function interpolation which uniformly approximates to f(z) ε C(Γ) with the same order of approximation as that in Jackson Theorem 1 on real interval [−1, 1]. The accuracy of the order
of approximation is proved. Using the method different from the early works, the author studies simultaneous approximation
to function and its derivatives and the desired results analogues to that in Jackson Theorem 2 on real interval [−1, 1] are
obtained.
相似文献
110.
A variant of balancing domain decomposition method by constraints (BDDC) is proposed for solving a class of indefinite systems of linear equations of the form (K?σ2M)u=f, which arise from solving eigenvalue problems when an inverse shifted method is used and also from the finite element discretization of Helmholtz equations. Here, both K and M are symmetric positive definite. The proposed BDDC method is closely related to the previous dual–primal finite element tearing and interconnecting method (FETI‐DP) for solving this type of problems (Appl. Numer. Math. 2005; 54 :150–166), where a coarse level problem containing certain free‐space solutions of the inherent homogeneous partial differential equation is used in the algorithm to accelerate the convergence. Under the condition that the diameters of the subdomains are small enough, the convergence rate of the proposed algorithm is established, which depends polylogarithmically on the dimension of the individual subdomain problems and which improves with a decrease of the subdomain diameters. These results are supported by numerical experiments of solving a two‐dimensional problem. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献