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991.
1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) is one of the promising room-temperature ionic liquids. To test the refined force field for [bmim][BF4] proposed in our previously work (J. Phys. Chem. B, 2004, 108, 12978-12989), thermodynamic properties of mixtures of [bmim][BF4](1)+ acetonitrile (2) are presented by using molecular dynamics over the whole concentration range. The calculated densities are in good agreement with the experimental data with deviations less than 2%, indicating the force field is applicable to the mixtures. In addition, the diffusion constants, viscosities, heats of vaporization, cohesive energy densities and excess properties of the mixtures are reported. The microscopic structures are discussed in detail, corresponding to the thermodynamic properties. 相似文献
992.
993.
Fang-Hui?Wu Guang-Chao?ZhaoEmail author Xian-Wen?Wei Zhou-Sheng?Yang 《Mikrochimica acta》2004,144(4):243-247
Acid-treated multi-walled carbon nanotubes (MWNTs) were immobilized on the surface of a glassy carbon electrode to form an MWNT-modified electrode. The electrocatalytic response of the modified electrode towards tryptophan (Trp) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results demonstrated that the modified electrode exhibited a high degree of catalytic activity towards the oxidation of Trp. An oxidation peak was obtained in Trp solution at the MWNT-modified electrode. Compared with a bare electrode, the peak current had obviously increased, and the peak potential had shifted in a negative direction. However, under the same conditions, no response was observed for other amino acids. The oxidation peak currents were proportional linearly to the concentration of Trp, a property which could be utilized to detect Trp. The determination conditions, such as the concentration, the composition and the pH values of the supporting electrolyte, accumulation time, as well as scan rate etc. were optimized. Under the chosen conditions, the DPV peak current is linear to the concentration of Trp in the range of 2.5×10–7 to 1.0×10–4molL–1, and the detection limit is 2.7×10–8molL–1. Moreover, the detection is free of interference from other amino acids. The modified electrode has been successfully applied to determine the concentration of Trp in composite amino acid injections, and it displays excellent repeatability and higher sensitivity. 相似文献
994.
Recently preparative high-performance liquid chromatography (HPLC) has been used more and more frequently to separate drugs and natural substances. However, large-scale HPLC easily tends to reduce the yield and purity of the product. Hydrodynamic and heat factors play an important roles. Generally, in a large-scale HPLC column, the tracer profile inside column will take on a parabolic shape because of the distributor, which will impact the separation performance of the column. With the inlet temperature suitably lower than the wall temperature, this situation could be improved to some extent. In this work, some experiments were conducted using HPLC, with a column 10 cm in diameter to determine the optimal temperature difference between wall and inlet temperatures. The wall temperature was fixed at about 30 degrees C and the inlet temperature varied from 15 to 30 degrees C. The flow-rate of the eluent, methanol, was 300 ml/min. The experimental result was simulated using CFD software FLUENT 4.4.4. The simulated temperature field fitted the experimental one very well and the simulated flow, temperature and tracer distribution inside column could provide good explanation of separation performance under different conditions. In addition, the simulation could at least approximately predict the optimal temperature difference. 相似文献
995.
996.
We demonstrate the self-assembly of three types of parallel gold nanorod clusters using a rod-like DNA origami as the template. 相似文献
997.
[reaction: see text] A novel solid-phase synthesis of 1,2-dialkoxyindoles on SynPhase lanterns is described. A unique C-C bond formation involving a nucleophilic displacement of a solid-bound aryl fluorine by dimethyl malonate afforded the arylnitro methyl ester, which upon treatment with tin(II) chloride dihydrate gave the N-hydroxyindolone. Alkylation of the N-hydroxyindolones afforded the corresponding N-hydroxy-2-alkoxyindoles, which were further alkylated to give the 1,2-dialkoxyindole. A library of 64 (8R(1) x 8R(2)) discrete 1,2-dialkoxyindoles was prepared using a color encoding technique on SynPhase A-series lanterns. 相似文献
998.
Carbon hollow spheres (400-600 nm) and vessels (400 nm x 3000 nm) have been synthesized from sp3-CCl4 at 190 and 230 degrees C, respectively. The HRTEM images and Raman spectra reveal the sp2 nature of the as-obtained products, indicating that the transformation from carbon sp3 to sp2 occurs in the reactions. The possible mechanism has also been proposed. 相似文献
999.
Xi Li Yi Liu Jun Wu Huigang Liang Songsheng Qu 《Journal of Thermal Analysis and Calorimetry》2002,67(3):589-595
The action of three kinds of the selenomorpholine compounds on a strain ofEscherichia coli was studied by microcalorimetry. Differences in their capacities to affect the metabolism of this bacterium were observed.
The extent and duration of the effect on the metabolism as judged from the rate constant (k) of Escherichia coli (in log phase) varied with the different drugs. The kinetics show that selenomorpholine compounds had an effect on the metabolism
process of Escherichia coli. The k of Escherichia coli in the presence of the drugs increased with the increasing concentrations of the drugs (C) at low concentration; but at high concentration, the rate constant decreased with the increasing concentrations of the drugs.
The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is: N-selenomorpholinemethyl
succinimide and its hydrochloride>N-(α-selenomorpholinebenzyl) succinimide.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
1000.