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971.
972.
Shuzhen Hu Yong Guo Jian Xu Shijun Shao 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(5):1043-1046
Some acyl-thiourea derivatives containing isatin group were synthesized and their interactions with anions were investigated using UV–vis spectroscopy and 1H NMR titrations in DMSO and DMSO-d6, respectively. These compounds have a same molecular framework, functionalising with different groups lead to different anion binding strength of these receptors. Receptor 1 showed a higher binding affinity for AcO− than for F−, due to the cooperative multiple hydrogen bond interactions of AcO− with the acyl-thiourea group and N–H group in the indole unit of receptor 1. Displacing the N–H proton in the indole unit with –CH3 group, receptor 2 showed no obviously discriminative responses for F−, AcO− and H2PO4− due to lack of such additional binding. In the case of receptor 3, which was functionalised with strong electron-withdrawing group, it showed selectively chromogenic response for F− based on double deprotonation of the receptor in DMSO, whereas AcO− and H2PO4− induced single deprotonation only. 相似文献
973.
Xiaogang Wang Jianhui Liao Changpeng Liu Wei Xing Tianhong Lu 《Electrochemistry communications》2009,11(1):198-201
The PtRu/C electrocatalyst with high loading (PtRu of 60 wt%) was prepared by synergetic effect of ultrasonic radiation and mechanical stirring. Physicochemical characterizations show that the size of PtRu particles of as-prepared PtRu/C catalyst is only several nanometers (2–4 nm), and the PtRu nanoparticles were homogeneously dispersed on carbon surface. Electrochemistry and single passive direct methanol fuel cell (DMFC) tests indicate that the as-prepared PtRu/C electrocatalyst possessed larger electrochemical active surface (EAS) area and enhanced electrocatalytic activity for methanol oxidation reaction (MOR). The enhancement could be attributed to the synergetic effect of ultrasound radiation and mechanical stirring, which can avoid excess concentration of partial solution and provide a uniform environment for the nucleation and growth of metal particles simultaneously hindering the agglomeration of PtRu particles on carbon surface. 相似文献
974.
Yang Yang Xiao-Zhen Liao Zi-Feng Ma Bao-Feng Wang Li He Yu-Shi He 《Electrochemistry communications》2009,11(6):1277-1280
A facile chemical polymerization method was applied to prepare LiFePO4/C-PPy composite using Fe(III)tosylate as oxidant. The as-prepared LiFePO4/C-PPy sample with PPy content of approximately 4 wt% showed great rate capability with a discharge capacity of 115 mAh/g at 20C. High temperate cycling performance of the LiFePO4/C-PPy sample was compared with bare LiFePO4/C at 5C charge–discharge rate at 55 °C. The LiFePO4/C-PPy cathode showed superior cycling stability with an initial capacity of 155 mAh/g. Ninety percentage of this initial capacity was retained after 300 cycles, compared to 40% of that of bare LiFePO4/C. The LiFePO4/C-PPy electrode showed stable discharge plateau voltage of 3.35–3.25 V vs. Li+/Li during long term cycling. The superior performance of the LiFePO4/C-PPy electrode was due to the enhanced electrical conductivity, negligible iron dissolution and alleviated electrode cracking contributed by PPy coating. 相似文献
975.
Xiaogang Wang Weilin Xu Xiaochun Zhou Tianhong Lu Wei Xing Changpeng Liu Jianhui Liao 《Journal of Solid State Electrochemistry》2009,13(9):1449-1453
A prominent methanol-tolerant characteristic of the PtCeOx/C electrocatalyst was found during oxygen reduction reaction process. The carbon-supported platinum modified with cerium
oxide (PtCeOx/C) as cathode electrocatalyst for direct methanol fuel cells was prepared via a simple and effective route. The synthesized
electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. It was found that the cerium
oxide within PtCeOx/C present in an amorphous form on the carbon support surface and the PtCeOx/C possesses almost similar disordered morphological structure and slightly smaller particle size compared with the unmodified
Pt/C catalyst. 相似文献
976.
977.
A rapid and effective method was developed for the chiral separation of raltitrexed (RD) enantiomers by carboxymethyl-beta-cyclodextrin
(CM-β-CD)-modified micellar electrokinetic chromatography (MEKC). Optimization of conditions including the type and concentration
of the chiral selector, concentration of sodium dodecyl sulfate (SDS), pH and concentration of the background electrolyte
(BGE), capillary temperature, and applied voltage was investigated. The enantiomers of raltitrexed could be separated with
satisfactory resolution and linear response by using 75 mM Tris-phosphate at pH 8.0 containing 30 mM SDS and 8 mM CM-β-CD
as buffer system. Furthermore, the usefulness of this method was demonstrated in a purity test of a real synthetic drug sample.
Figure Chiral separation of raltitrexed by CM-β-CD MEKC was optimized and applied to test the purity of a synthetic drug sample 相似文献
978.
A coefficient inverse problem of the one-dimensional parabolic equation is solved by a high-order compact finite difference method in this paper. The problem of recovering a time-dependent coefficient in a parabolic partial differential equation has attracted considerable attention recently. While many theoretical results regarding the existence and uniqueness of the solution are obtained, the development of efficient and accurate numerical methods is still far from satisfactory. In this paper a fourth-order efficient numerical method is proposed to calculate the function u(x,t) and the unknown coefficient a(t) in a parabolic partial differential equation. Several numerical examples are presented to demonstrate the efficiency and accuracy of the numerical method. 相似文献
979.
This paper discusses the optimum order quantity of the EOQ model that is not only dependent on the inventory policy but also on firm’ credit policy. Here, the conditions of using a discounted cash-flows (DCF) approach and trade credit depending on the quantity ordered are discussed. We consider that if the order quantity is less than at which the delay in payments is permitted, the payment for the item must be made immediately. Otherwise, the fixed trade credit period is permitted. 相似文献
980.
Jun Cheng Jie Cang Shi-Jun Liao 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,60(3):450-478
A train of periodic deep-water waves propagating on a steady shear current with a vertical distribution of vorticity is investigated
by an analytic method, namely the homotopy analysis method (HAM). The magnitude of the vorticity varies exponentially with
the magnitude of the stream function, while remaining constant on a particular streamline. The so-called Dubreil–Jacotin transformation
is used to transfer the original exponentially nonlinear boundary-value problem in an unknown domain into an algebraically
nonlinear boundary-value problem in a known domain. Convergent series solutions are obtained not only for small amplitude
water waves on a weak current but also for large amplitude waves on a strong current. The nonlinear wave-current interaction
is studied in detail. It is found that an aiding shear current tends to enlarge the wave phase speed, sharpen the wave crest,
but shorten the maximum wave height, while an opposing shear current has the opposite effect. Besides, the amplitude of waves
and fluid velocity decay over the depth more quickly on an aiding shear current but more slowly on an opposing shear current
than that of waves on still water. Furthermore, it is found that Stokes criteria of wave breaking is still valid for waves
on a shear current: a train of propagating waves on a shear current breaks as the fiuid velocity at crest equals the wave
phase speed. Especially, it is found that the highest waves on an opposing shear current are even higher and steeper than
that of waves on still water. Mathematically, this analytic method is rather general in principle and can be employed to solve
many types of nonlinear partial differential equations with variable coefficients in science, finance and engineering. 相似文献