Computational analysis of factors influencing thermal conductivity of nanofluids

Numerical investigations are conducted to study the effect of factors such as particle clustering and interfacial layer thickness on thermal conductivity of nanofluids. Based on this, parameters including Kapitza radius and fractal and chemical dimension which have received little attention by previous research are rigorously investigated. The degree of thermal enhancement is analyzed for increasing aggregate size, particle concentration, interfacial thermal resistance, and fractal and chemical dimensions. This analysis is conducted for water-based nanofluids of Alumina (Al₂O₃), CuO, and Titania (TiO₂) nanoparticles where the particle concentrations are varied up to 4 vol%. Results from the numerical work are validated using available experimental data. For the case of aggregate size, particle concentration, and interfacial thermal resistance, the aspect ratio (ratio of radius of gyration of aggregate to radius of primary particle, R _g/a) is varied from 2 to 60. It was found that the enhancement decreases with interfacial layer thickness. Also the rate of decrease is more significant after a given aggregate size. For a given interfacial resistance, the enhancement is mostly sensitive to R _g/a < 20 indicated by the steep gradients of data plots. Predicted and experimental data for thermal conductivity enhancement are in good agreement. On the influence of fractal and chemical dimensions (d _l and d _f) of Alumina–water nanofluid, the R _g/a was varied from 2 to 8, d _l from 1.2 to 1.8, and d _f from 1.75 to 2.5. For a given concentration, the enhancement increased with the reduction of d _l or d _f. It appears a distinctive sensitivity of the enhancement to d _f, in particular, in the range 2–2.25, for all values of R _g/a. However, the sensitivity of d _l was largely depended on the value of R _g/a. The information gathered from this study on the sensitivity of thermal conductivity enhancement to aggregate size, particle concentration, interfacial resistance, and fractal and chemical dimensions will be useful in manufacturing highly thermally conductive nanofluids. Further research on the refine cluster evolution dynamics as a function of particle-scale properties is underway.     

Simultaneous analysis of cocaine,benzoylecgonine, methylecgonine,and ecgonine in plasma using an exchange resin and gas chromatography-mass spectrometry

Summary A gas chromatographic-mass spectrometric method is described for the simultaneous analysis of cocaine and the hydrolytic products benzoylecgonine, methylecgonine and ecgonine from plasma (0.25–2 g/ml). Isopropylecgonine was incorporated as an internal standard. Samples were extracted using a sulfonate cation exchange resin, then derivatized with pentafluoropropionic anhydride and pentafluoropropanol. Analytical separations were on a dimethylsilicone capillary column using a temperature program, and detection was by selected ion monitoring of the electron impact generated fragments m/z 94, 182, 210, and 300.Presented at the poster session of American Association of Pharmaceutical Scientists 1991 Southeast Regional Meeting, Charleston, South Carolina, USA, April 4–5     

New neolignan glycoside and an unusual benzoyl malic acid derivative from Maytenus senegalensis leaves

Further investigation of the methanol leaf extract of Maytenus senegalensis led to the isolation of six compounds, including mayselignoside (1) and an unusual benzoyl malic acid derivative, benzoyl R-(+)-malic acid (2). Two known lignan derivatives (+)-lyoniresinol (3) and ( ? )-isolariciresinol (4), a known neolignan derivative dihydrodehydrodiconiferyl alcohol (5) and the triterpenoid, β-amyrin (6) were also isolated. The structures of these compounds were elucidated by a combination of 1D and 2D NMR and mass spectroscopy. All compounds were tested for cytotoxicity against mouse lymphoma cell line (L5178Y) and for antimicrobial activity against strains of bacteria and fungi. None of the compounds showed promising cytotoxic and/or antimicrobial activities.     

A viscosity iterative technique for split variational inclusion and fixed point problems between a Hilbert space and a Banach space

The main purpose of this paper is to introduce a viscosity-type iterative algorithm for approximating a common solution of a split variational inclusion problem and a fixed point problem. Using our algorithm, we state and prove a strong convergence theorem for approximating a common solution of a split variational inclusion problem and a fixed point problem for a multivalued quasi-nonexpansive mapping between a Hilbert space and a Banach space. Furthermore, we applied our results to study a split convex minimization problem. Also, a numerical example of our result is given. Our results extend and improve the results of Byrne et al. (J. Nonlinear Convex Anal. 13, 759–775, 2012), Moudafi (J. Optim. Theory Appl. 150, 275–283, 2011), Takahashi and Yao (Fixed Point Theory Appl. 2015, 87, 2015), and a host of other important results in this direction.     

Phenoxyhydroxypropylhydroxyethylcellulose—new amphiphilic cellulose derivative

A new amphiphilic cellulose derivative phenoxyhydroxypropylhydroxyethylcellulose of substitution degree up to 0.67 was synthesized by reaction of water-soluble hydroxyethylcellulose with 2,3-epoxypropylphenylether in the presence of sodium hydroxide as a catalyst. The chemical composition of the derivative was confirmed by means of UV, IR- and ¹³C-NMR-spectroscopy. The derivatives with substitution degree up to 0.12 are soluble in water and water–alcohol mixtures. With increasing substitution degree, the polymers lose their water solubility, but still dissolve in water–alcohol mixtures. All products are soluble in aprotic solvents. The effect of the reaction conditions, such as temperature and molar ratios of reaction components, on both the reaction rate and degree of substitution was investigated.     

Comparative Analysis of Indoor Levels of Suspended Particulates and Nitrogen Dioxide a Few Hours later after an Asthmatic Attack

Suspended particulates （TSP） and nitrogen dioxide （NO2） are known respiratory irritants linked to asthma aggravation. This pilot study was designed to investigate the role of these pollutants on the frequency of asthmatic attack on two of the inhabitants of a household. The surveillance of TSP and NO2 in this household commenced a few hours later, after one of the occupants suffered an attack. The TSP load determination was done using a High Volume Gravimetric sampler and a light scattering method via a Haz-Dust 10 μm particulate monitor. Palmes Diffusion tubes for NO2 and a portable Crowcon Gasman toxic gas detector were utilized for NO2 screening. In the first day of monitoring in the living room, the in situ particulate sampler （Haz-Dust） recorded a mean TSP level of 26,000 μg·m^-3. A confirmatory test with the eight hour average Gravimetric sampler gave 25,833 μg·m^-3. With the use of the Gasman toxic gas detector for NO2, the NO2 concentration for the first few hours of sampling was lower than 188 μg·m^-3, the detection limit of this instrument. However, the exact NO2 concentrations for the 7 day monitoring after the attack were 27.50 μg·m^-3 （kitchen） and 12.03 μg·m^-3 （living room） as recorded by the Palmes diffusion tubes.     

Testing gauge theories in electron-electron scattering

The magnitudes of the correction terms to Møller scattering in the Weinberg-Salam Model and Georgi-Glashow model are compared. The possible consequences of the variations of the free parametersM E ⁺/M _W ,E/M _φ andE/M _Z with these correction terms are carefully discussed.     

改进的石墨烯基材料用作菜籽油转酯化反应制生物柴油的有效催化剂（英文）

本文研究了不同石墨烯基材料用作转酯化反应制备生物柴油催化剂的性能.将磺酸基或磷酸盐基嫁接到热还原的氧化石墨烯表面,制备了固体酸石墨烯基样品.并采用扫描电镜、X射线衍射、热重分析、X射线光电子能谱、N_2吸附-脱附法、电位滴定法、元素分析以及红外光谱法对所制样品进行了全面表征.将所制样品用于130℃带压力的条件下菜籽油与甲醇转酯化反应中,并将其催化活性与商用的多相酸催化剂Amberlyst-15的进行了比较.结果表明,所有改进的样品在转酯化反应中均表现出催化活性,但各样品上生物柴油产率差别较大.其中以苯二氮磺酸基功能化的热还原氧化石墨烯样品上脂肪酸甲酯产率最高,反应6 h后达70%,也明显高于商用催化剂Amberlyst-15.该样品也表现出良好的重复使用性能.