Optimization of heat transfer coefficient correlation at supercritical pressure using genetic algorithms

The paper presents a new heat transfer correlation of water at supercritical pressure after review on existing heat transfer correlations. The new correlation is optimized by genetic algorithms based on existing test data. Based on current results, we conclude that genetic algorithms are effective to search a global optimized correlation but it is important to carefully select representative and authentic test data to reach an optimized solution and special attention needs to be paid on the deteriorated heat transfer region in the design of supercritical water reactor because it can not be predicted well by any correlations reviewed. Supported by the National Basic Research Program of China (973 Program No. 2007CB209800) and Atomic Energy of Canada Limited.     

A rapid and green approach to chiral α-hydroxy esters: asymmetric transfer hydrogenation (ATH) of α-keto esters in water by use of surfactants

A series of α-hydroxy esters were rapidly prepared (1.5 h) from α-keto esters via asymmetric transfer hydrogenation (ATH) in water by the use of surfactants for the first time. This green method, catalyzed by a water-soluble and recyclable Ru(II) complex, gave moderate to high enantioselectivities (up to 99.7% ee) with DTAB as an additive and HCOONa as the hydrogen source.     

目标流形为Heisenberg群能量极小映射的逆Poincardé不等式

研究目标流形为Heisenberg群能量极小映射的性质,得到关于能量极小映射的逆Poincaré不等式.     

大苞雪莲内酯的分子结构和晶体结构

新疆雪莲(Saussurea involucrata Kar. et Kin)为我国西北地区名贵中草药,可用于治疗风湿性关节炎和妇科疾病,从中分离得到一种新的倍半萜内酯的β葡萄糖苷,命名为大苞雪莲内酯(右图),其结晶为无色透明针状,m.p.219～221℃。     

Chemical treatment of TiO2-based coatings formed by plasma electrolytic oxidation in electrolyte containing nano-HA, calcium salts and phosphates for biomedical applications

TiO₂-based coatings were formed on titanium alloy by plasma electrolytic oxidation (PEO) in an electrolyte containing nano-HA, calcium salts and phosphates. Bioactive surface was formed after chemical treatment (NaOH aqueous solution) of the PEO coating. The surface of the PEO coating was mainly composed of Ti, O, Ca and P showing anatase and rutile; while that of the chemically treated PEO (CT-PEO) coating mainly contains Ti, O, Ca and Na showing anatase, rutile and amorphous phase. And the chemically treated surface exhibits dissolution of P and introduction of Na during the chemical treatment process. The chemical treatment has no effect on the chemical states of Ca and Ti of the PEO coating. In addition, the surface constituents of the CT-PEO coating show a uniform distribution near its surface with increasing depth. When incubated in a simulated body fluid for 7 and 14 days, the PEO coating does not exhibit apatite-forming ability; however, apatite was successfully deposited on the CT-PEO coating after 7 days probably due to the formation of hydroxyl functionalized surface, enhancing the heterogeneous nucleation of apatite. The addition of nano-HA in the electrolyte has effects on the surface character and apatite-forming ability of the PEO coating; however, it has no obvious influence on those of the CT-PEO coatings.     

Two new benzaldehyde derivatives from mangrove endophytic fungus (No. ZZF 32)

Two new benzaldehyde derivatives, 6-ethyl-2-hydroxy-4-methoxy-3-methylbenzaldehyde (1), 6-ethyl-2,4-dihydroxy-3-methylbenzaldehyde (2), together with 2, 4-dihydroxy-3,6-dimethylbenzaldehyde (3) were isolated from mangrove fungus (No. ZZF 32#) from the South China Sea. The structures of compounds 1 and 2 were established by comprehensive analysis of the spectral data, especially 2D NMR spectral results.     

Simultaneous determination of methylephedrine and pseudoephedrine in human urine by CE with electrochemiluminescence detection and its application to pharmacokeinetics

A novel method for the determination of ephedra alkaloids (methylephedrine and pseudoephedrine) was developed by electrophoresis capillary (CE) separation and electrochemiluminesence detection (ECL). The use of ionic liquid (1‐butyl‐3‐methylimidazolium tetrafluoroborate, BMIMBF₄) improved the detection sensitivity markedly. The conditions for CE separation, ECL detection and effect of ionic liquid were investigated in detail. The two ephedra alkaloids with very similar structures were well separated and detected under the optimum conditions. The limits of detection (signal‐to‐noise ratio = 3) in standard solution were 1.8 × 10^–8 mol/L for methylephedrine (ME) and 9.2 × 10^–9 mol/L for pseudoephedrine (PSE). The limits of quantitation (signal‐to‐noise ratio = 10) in human urine samples were 2.6 × 10^?7 mol/L for ME and 3.6 × 10^–7 mol/L for PSE. The recoveries of two alkaloids at three different concentration levels in human urine samples were between 81.7 and 105.0%. The proposed method was successfully applied to the determination of ME and PSE in human urine and the monitoring of pharmacokinetics for PSE. The proposed method has potential in therapeutic drug monitoring and clinical analysis. Copyright © 2009 John Wiley & Sons, Ltd.