Viscous dissipation effect on heat transfer characteristics of rectangular microchannels under slip flow regime and H1 boundary conditions

Viscous dissipation effect on heat transfer characteristics of a rectangular microchannel is studied. Flow is governed by the Navier–Stokes equations with the slip flow and temperature jump boundary conditions. Integral transform technique is applied to derive the temperature distribution and Nusselt number. The velocity distribution is taken from literature. The solution method is verified for the case where viscous dissipation is neglected. It is found that, the viscous dissipation is negligible for gas flows in microchannels, since the contribution of this effect on Nu number is about 1%. However, this effect should be taken into account for much more viscous flows, such as liquid flows. Neglecting this effect for a flat microchannel with an aspect ratio of 0.1 for Br=0.04 underestimates the Nu number about 5%.     

Synthesis of chiral acetoxy lactones via the Baeyer-Villiger oxidation of cyclic aromatic acetoxy ketones

The α-acetoxylation of indanones and tetralones by using Mn(OAc)₃ followed by the enzyme catalyzed kinetic resolution of acetoxy ketones furnished both of the enantiomers of α-acetoxy ketones in good chemical and optical yields. The Baeyer-Villiger oxidation of α-acetoxy ketones with m-CPBA, CF₃SO₃H, and CH₂Cl₂, at rt gives the corresponding lactones without racemization. The acetoxy ketone moiety migrates selectively in order to form lactones. The mild hydrolysis of lactones affords phenolic α-hydroxycarboxylic acid derivatives.     

Phenolic compounds from Scorzonera latifolia (Fisch. & Mey.) DC

A new 3-benzylphthalide, scorzoveratrin 4'-O-β-glucoside (1), together with the known 3-benzylphthalides, scorzoveratrin (2) and scorzoveratrozit (3), the caffeoyl derivatives, chlorogenic acid methyl ester (4), 4,5-dicaffeoylquinic acid (5), 4,5-dicaffeoylquinic acid methyl ester (6), 3,5-dicaffeoylquinic acid (7) and caffeic acid (8) were isolated from the subaerial parts of Scorzonera latifolia (Fisch. & Mey.) DC. All secondary metabolites were assigned using physicochemical and spectroscopic data. The known compounds 2-8 were isolated for the first time from this species.     

新型二氧代氮杂茂并[3’,4’-d]N-甲基异噁唑四氯化铁酸盐衍生物的合成及其生物活性

硫酸二甲酯作为N-甲基化试剂,与相应的异噁唑啉反应,并在盐酸中三氯化铁作为阴离子交换试剂,合成了15个未见文献报道的2-甲基-3-(1’,2’-二-O-环亚己基二氧乙基)-5-芳基-3a,6a-二氢-4,6-二氧代氮杂茂并[3’,4’-d]异噁唑四氯化铁酸盐衍生物4a～4o.化合物4a～4o结构结构经1H NMR,IR和元素分析确证,并进行了初步药物活性筛选,大部分化合物显示了不同程度的抗癌和抗炎症性及免疫性疾病活性.体外抗癌活性试验表明,当样品浓度为20μg/mL时,除了4h无活性外,其余化合物对细胞分裂周期磷酸酯酶Cdc25B的抑制率为≥97.55%.此外,体外白细胞共同抗原活性试验表明,当样品浓度为20μg/mL时,所有化合物4a～4o对白细胞共同抗原CD45蛋白酪氨酸磷酸酶A具有良好的抑制活性,其抑制率为68.41%～93.38%.在此基础上,初步讨论了该类化合物的构效关系.     

In Vitro Inhibition Effect of Some Dihydroxy Coumarin Compounds on Purified Human Serum Paraoxonase 1 (PON1)

Human serum paraoxonase 1 (PON1; EC 3.1.8.1) is a high-density lipoprotein associated, calcium-dependent enzyme that hydrolyses aromatic esters, organophosphates and lactones and can protect the low-density lipoprotein against oxidation. In this study, in vitro inhibition effect of some dihydroxy coumarin compounds namely 6,7-dihydroxy-3-(2-methylphenyl)-2H-chromen-2-one (A), 6,7-dihydroxy-3-(3-methylphenyl)-2H-chromen-2-one (B) and 6,7-dihydroxy-3-(4-methylphenyl)-2H-chromen-2-one (C) on purified PON1 were investigated by using paraoxon as a substrate. PON1 was purified using two-step procedures, namely ammonium sulphate precipitation and Sepharose-4B-l-tyrosine-1-naphthylamine hydrophobic interaction chromatography. The purified enzyme had a specific activity of 11.76?U/mg. The dihydroxy coumarin derivatives of A and B compounds inhibited PON1 enzyme activity in a noncompetitive inhibition manner with K _i of 0.0080?±?0.256 and 0.0003?±?0.018?mM values, respectively. C compound exerted an uncompetitive inhibition of PON1 enzyme activity with K _i of 0.0010?±?0.173?mM. Moreover, dihydroxy coumarin derivatives of A, B and C compounds were effective inhibitors on purified human serum PON1 activity with IC₅₀ of 0.012, 0.022 and 0.003?mM values, respectively. IC₅₀ value of unsubstituted 6,7 dihydroxy coumarin was found as 0.178?mM. The present study has demonstrated that PON1 activity is very highly sensitive to studied coumarin derivatives.     

On an inverse scattering problem for a class of Dirac operators with spectral parameter in the boundary condition

In this work, we consider the inverse scattering problem for a class of one dimensional Dirac operators on the semi-infinite interval with the boundary condition depending polynomially on a spectral parameter. The scattering data of the given problem is defined and its properties are examined. The main equation is derived, its solvability is proved and it is shown that the potential is uniquely recovered in terms of the scattering data. A generalization of the Marchenko method is given for a class of Dirac operator.     

Adsorption of Cu(II) ions from aqueous solution by hazelnut husk activated carbon prepared with potassium acetate

Hazelnut husk (HH), an agricultural waste, was converted to carbonaceous material by chemical activation using potassium acetate. The produced activated carbon (KAHHAC) was characterized by FTIR, SEM, N₂ adsorption–desorption experiments, CHN elemental analysis, and determination of moisture, ash, and point of zero charge. KAHHAC was used for the batch adsorption of Cu(II) ions from aqueous solutions. Optimum pH and contact time were found to be 5.0 and 240 minutes, respectively. The adsorption equilibrium data were described well by the Langmuir equation providing 105.3?mg?g^?1 Cu(II) adsorption capacity. The pseudo-second-order model successfully described the kinetic of Cu(II) adsorption by KAHHAC. The adsorbed Cu(II) onto KAHHAC was completely desorbed by 0.5?M nitric acid. In conclusion, HH activated carbon (AC) produced by the potassium acetate activation method is a very useful and efficient sorbent material for the removal of Cu(II) from aqueous solution.     

Cyclopentene-fused [C60]-fullerenes: synthesis and electrochemical properties

New cyclopentene-fused [C60]-fullerene derivatives containing terpene moieties have been synthesized by [3?+?2]-addition to fullerene C₆₀. All obtained products were fully characterized by ¹H- and ¹³C-NMR, IR, and MS. The electrochemical properties have been studied by cyclic voltammograms (CV), combined with absorption spectra, which are consistent with those obtained from density functional theory (DFT) calculations. It was found that all fulleropyrrolidines showed very similar absorption spectra, orbital energies, in which electron densities in both the LUMO and HOMO are mainly located on the fullerene cage, suggesting that C₆₀ act as the acceptor. All the compounds exhibited good thermal stability. All determined characteristics of fullerene conjugates were compared to [6,6]-phenyl-C61-butyric acid methyl ester ([60]PCBM), a popular fullerene-containing compound.

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