Fundamental equations of turbulent two-phase flow

A new set of Reynolds equations for predicting turbulent two-phase flows has been developed by means of Reynolds averaging method on the unsteady laminar equations of two-phase flow. These equations involve average terms of products of turbulent fluctuations in some physical parameters in a large degree. The interaction forces between two phases, the pressures for dispersed phase, extra stresses except for pressure and the expressions for energy interchange between two phases have been discussed.     

超声与微波条件下Ce4+对柴油氧化脱硫的比较研究

分别在超声和微波条件下使用Ce4 把柴油中的硫化物(主要为苯并噻吩类)氧化成砜类化合物后,再用DMF把它萃取除去。超声条件下的氧化脱硫得到95.5%的高脱硫率,达到世界燃料规范Ⅲ柴油质量标准。微波条件下的氧化脱硫得到82.7%的脱硫率。Ce4 氧化媒质可以经电化学方法再生循环利用,DMF也可以循环利用,无三废排放,具有优化的经济效益比,符合绿色化学发展的趋势。     

Environmental application of elemental speciation analysis based on liquid or gas chromatography hyphenated to inductively coupled plasma mass spectrometry—A review

In recent years the number of environmental applications of elemental speciation analysis using inductively coupled plasma mass spectrometry (ICP-MS) as detector has increased significantly. The analytical characteristics, such as extremely low detection limits (LOD) for almost all elements, the wide linear range, the possibility for multi-elemental analysis and the possibility to apply isotope dilution mass spectrometry (IDMS) make ICP-MS an attractive tool for elemental speciation analysis. Two methodological approaches, i.e. the combination of ICP-MS with high performance liquid chromatography (HPLC) and gas chromatography (GC), dominate the field. Besides the investigation of metals and metalloids and their species (e.g. Sn, Hg, As), representing “classic” elements in environmental science, more recently other elements (e.g. P, S, Br, I) amenable to ICP-MS determination were addressed. In addition, the introduction of isotope dilution analysis and the development of isotopically labeled species-specific standards have contributed to the success of ICP-MS in the field. The aim of this review is to summarize these developments and to highlight recent trends in the environmental application of ICP-MS coupled to GC and HPLC.     

Nobiletin: a citrus flavonoid displaying potent physiological activity

Nobiletin [systematic name: 2‐(3,4‐dimethoxyphenyl)‐5,6,7,8‐tetramethoxy‐4H‐chromen‐4‐one; C₂₁H₂₂O₈] is a flavonoid found in citrus peels, and has been reported to show a wide range of physiological properties, including anti‐inflammatory, anticancer and antidementia activities. We have solved the crystal structure of nobiletin, which revealed that the chromene and arene rings of its flavone moiety, as well as the two methoxy groups bound to its arene ring, were coplanar. In contrast, the C atoms of the four methoxy groups bound to the chromene ring are out of the plane, making the molecule conformationally chiral. A comparison of the crystal structures of nobiletin revealed that it could adopt a variety of different conformations through rotation of the covalent bond between the chromene and arene rings, and the orientations of methoxy groups bound to the chromene ring.     

Tuning of the methylimidazolium/imidazole balance in polycations for gene carrier

The chemical structure of methylated poly(1‐vinylimidazole) (PVIm‐Me) has been tuned for gene carrier properties, which are cell viability, the stability of its DNA polyion complexes, and gene expression. The resulting PVIm‐Me with lower methylation degree (6 and 20 mol%) exhibited no significant cytotoxicity, as compared with 40 mol% PVIm‐Me, in spite of the same concentration and chemical structure of positive charges. The DNA complex with 20 mol% PVIm‐Me stably retained the DNA, as compared with 6 or 40 mol% PVIm‐Me, which was examined by competitive exchange with dextran sulfate. As a result, the DNA complex with 20 mol% PVIm‐Me mediated most efficient gene delivery, where the resulting transfection activity was higher than that mediated by a positive control, poly(ethylenimine). These results suggest that the optimization of the balance of the methylimidazolium and the imidazole groups of PVIm‐Me is essential for gene carrier design. Copyright © 2014 John Wiley & Sons, Ltd.     

Lipophilic arsenic compound(s) in the liver of a tiger shark (Galeocerdo cuvier)

Homogenized aliquots (100 g) of the liver (8.4 kg, 5 m?g As g^?1) of a tiger shark (Galeocerdo cuvier) were extracted with chloroform/methanol, and the extracts purified by countercurrent extraction (hexane/87% ethanol), silica gel column chromatography (chloroform/methanol mixtures as mobile phases), and silica gel thin-layer chromatography (chloroform/methanol/acetic acid). The purified samples (24 mg arsenic g^?1) gave no ³¹P NMR signal, but gave ¹H and ¹³C NMR signals with similarities to those of dipalmitoylphosphatidic acid and salad on and also signals indicative of the presence of methylated arsenic compounds. The sample could contain a diacyl glyceride with a methylated arsenic group.     

甲基化聚胺型硅基强阴离子交换剂用于生物大分子的分离

用聚胺键合法合成了聚胺型碱性硅胶基质，进一步甲基化后制得了强阴离子交换剂，该强阴离子交换剂将硅工礅子交换剂和树脂型离子交换剂的优点有机地结合起来，具有稳定性好，使用ＰＨ值范围宽（ＰＨ１－１２），柱渗透性好和优点，可理想地用于生物大分子和蛋白南，多肽和酸等的分离。型碱性硅胶     

溴氧化铋/石墨烯可见光下光催化氧化脱硫的研究

采用水热法制备了BiOBr/石墨光催化剂, 并利用X 射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、固体荧光（PL）和紫外-可见漫反射光谱（UV-vis DRS）等方法对其进行表征。以二苯并噻吩的环己烷溶液为模拟油品,考察反应温度、石墨烯负载量和氧化剂H₂O₂用量等条件对BiOBr/石墨光催化氧化脱除模拟油中DBT的性能的影响,不同模型化合物的光催化活性为DBT>4, 6-DMDBT>BT,根据实验结果提出了BiOBr/石墨光催化剂氧化DBT的机理。     

Kinetic Studies upon the Influence of Cyclodextrin on the Polymerization of Methacrylamides in Homogenous Aqueous Solution

Summary: N‐methacryloyl‐1‐aminopropane ( 1 ), N‐methacryloyl‐1‐aminobutane ( 2 ), N‐methacryloyl‐1‐aminopentane ( 3 ), and N‐methacryloyl‐1‐aminohexane ( 4 ) are synthesized and treated with an aqueous solution of randomly methylated β‐cyclodextrin (Me‐β‐CD) to form the water‐soluble host‐guest complexes 1a – 4a . In case of the aqueous polymerization of the free monomers 1 – 4 the initial polymerization rate increases with increasing water solubility. The opposite effect is observed in the case of the polymerizations of the Me‐β‐CD‐complexed methacrylamide monomers 1a – 4a . The polymerization rates are increased with increasing alkyl chain length of the complexed monomers 1a – 4a and decreasing water solubility of the free monomers 1 – 4 .

Initial polymerization rate v₀ of CD‐complexed monomers 1a – 4a (○) vs. water solubilities of monomers 1 – 4 (▪).     

Partially Methylated β-Cyclodextrin Analysis: A Systematic Approach to Appropriate RP Column Selection

In order to establish guidelines to help the analyst in the choice of the most suitable octadecyl or octyl bonded phase for the LC analysis of a given partially methylated β-CD sample, analyses of four commercially available dimethyl-β-cyclodextrins (DM-β-CDs) have been carried out on nine octyl (C₈) or octadecyl (C₁₈) silica bonded or polymeric bonded phases which differ significantly in their hydrophilic and hydrophobic properties. Chromatograms show that the nature of the packing materials has considerable influence on the resolution of complex mixtures composed of closely related compounds such as partially methylated β-CDs. Among various kinds of C₈ and C₁₈ bonded phases, silica based and monomeric phases which present both reinforced hydrophobic and polar interactions showed the best performance. Whatever the complexity of the commercial DM-β-CD, the richest chromatographic fingerprints, which best depict the complexity of the mixture, are obtained with Nucleosil 50-5-C₈ column. For the simplest mixtures, Nucleosil 50-5-C₈ column with acetonitrile-water (34:66) as mobile phase is the most suitable chromatographic system and leads to the best resolution between heptakis (2,6-di-O-methyl)-β-CD and hexakis (2,6-di-O-methyl)-mono(2,3,6-tri-O-methyl)-β-CD (14 OCH₃ and 15 OCH₃). This chromatographic system might enable an LC-MS coupling for direct identification of the different components in the mixture as well as control of batch to batch variations.