Review of nanofluids for heat transfer applications

Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first repotted about a decade ago,though much controversy and inconsistency have been reported,and insufficient understanding of the formulation and mechanism of nanofluids further limits their applications.This work presents a critical review of research on heat transfer applications of nanofluids with the aim of identifying the limiting factors so as to push forward their further development.     

A new modification of false position method based on homotopy analysis method

A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method （HAM）. Some numerical illustrations are given to show the efficiency of algorithm.     

基于同伦分析方法的一种改进的试位法

应用同伦分析方法,提出了一种求解非线性方程改进的试位法．给出的一些数值例证显示了该运算法则的有效性．     

A mechanistic study on the synthesis of branched functional polyethylene through reactive co-polymer approach

The reactive co-polymer approach is one of the most promising techniques for the synthesis of functional polyolefins. Following this concept, 1-hexene and p-methylstyrene are co-polymerized in the presence of a generic Brookhart-type catalyst. The microstructures of the co-polymers imply the tendency of p-methylstyrene co-monomers to place at the end of the structural branches formed by the chain walking reaction. The molar masses of the co-polymers decrease, not only at higher levels of co-monomer but surprisingly by decreasing reaction temperature. A mechanism consisting of a highly stable η³ metal–benzyl intermediate, which is quantitatively approved by density functional theory calculations, can delicately justify all the aforementioned observations. A series of the produced co-polymers is selectively functionalized by maleic anhydride at the benzylic position of p-methylstyrene, under very mild reaction conditions. Such a reactive intermediate opens the path for the introduction of different types of functionalities in polyolefins. Namely, the grafted co-polymers were further functionalized by a triazole ring, which provides a transient supramolecular network through intermolecular hydrogen bonding.     

Photocatalytic oxidation of primary and secondary benzylic alcohols to carbonyl compounds catalyzed by H3PW12O40/SiO2 under an O2 atmosphere

An efficient, selective and green procedure for the photocatalytic oxidation of primary and secondary benzylic alcohols to the corresponding aldehydes and ketones has been achieved using silica-encapsulated H₃PW₁₂O₄₀ as a recyclable heterogeneous photocatalyst in acetonitrile under oxygen gas as the sole reoxidant of the catalyst.     

Arrangement and nature of intermolecular hydrogen bonding in complex biomolecular systems: modeling the vitamin C---L-alanine interaction

Vitamin C is known as an essential dietary supplement and implicated in diverse biological processes. We present here a theoretical study on the nature of hydrogen bonding of vitamin C in biological systems. For this reason, the complexes of vitamin C (VC) with neutral and zwitterionic L-alanine (as the simplest chiral amino acid) were studied at the MP2/6-311++G(d,p) level of theory. In the gas phase, neutral L-alanine leads to more stable complexes than the zwitterionic forms while the reverse is true in the aqueous phase. The complexes are formed via two hydrogen bond interactions, which result in a ring-like hydrogen-bonded networks. The nature of H-bonds was characterized in terms of natural bond orbital and quantum theory of atoms in molecule analyses (QTAIM). The H-bonds in the studied complexes were electrostatic in nature; however, in the case of shorter and directional H-bonds and ionic interactions, contributions of covalent character were also non-negligible. Natural energy decomposition analysis of hydrogen-bonded complexes reveals that the charge transfer and electrical components are the largest contributors for the interaction energies of complexes. Natural resonance theory analysis suggests higher resonance weight for charge-assisted interactions of vitamin C---alanine (zwitterionic) complexes, where the total interaction energy is considerably higher than that of neutral alanine.     

Optimization of Photooxidative Removal of Phenazopyridine from Water

The photooxidative removal of analgesic pharmaceutical compound phenazopyridine (PhP) from aqueous solutions by UV/H₂O₂ system with a re-circulated photoreactor was investigated. Response surface methodology (RSM) was employed to optimize the effect of operational parameters on the photooxidative removal efficiency. The investigated variables were: the initial PhP and H₂O₂ concentrations, irradiation time, volume of solution and pH. The analysis of variance (ANOVA) of quadratic model demonstrated that the described model was highly significant. The predicted values of the photooxidative removal efficiency were found to be in a fair agreement with experimental values (R² = 0.9832, adjusted R² = 0.9716). The model predicted that the optimal reaction conditions for a maximum removal of PhP (>98%) were: initial PhP concentration less than 23 mg L^–1, initial concentration of H₂O₂ higher than 470 mg L^–1, solution volume less than 500 mL, pH close to 2 and irradiation time longer than 6 min.     

Rapidly Estimating Natural Gas Compressibility Factor

Natural gases containing sour components exhibit different gas compressibility factor(Z) behavior than do sweet gases.Therefore,a new accurate method should be developed to account for these differences.Several methods are available today for calculating the Z-factor from an cquation of state. However,these equations are more complex than the foregoing correlations,involving a large number of parameters,which require more complicated and longer computations.The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas.In this article,two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity.Then,a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases' compressibility factor as a function of reduced pressure and temperature.Finally,a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.     

Binding properties of adenosine deaminase interacted with theophylline

Thermodynamic studies were carried out to evaluate the binding of theophylline on adenosine deaminase (ADA) in 50 mM sodium phosphate buffer pH 7.5, at 300 K, using isothermal titration calorimetry (ITC). A simple method for determination of binding isotherm in the drug--ADA interaction was applied using ITC data. ADA has two binding sites for theophylline, which show positive cooperativity in its sites. The intrinsic association equilibrium constants are 6 and 52 mM(-1) in the first and second binding sites, respectively. Hence, occupation of the first site has produced an appreciable enhancement by 8.7 of the binding affinity of the second site. The molar enthalpies of binding are -12.2 and -14.9 kJ/mol in the first and second binding sites, respectively.     

A combined temperature-dependent electron and single-crystal X-ray diffraction study of the fresnoite compound Rb2VV2O8

High-purity Rb₂V₃O₈ has been grown and temperature-dependent electron and single-crystal X-ray diffraction used to carefully investigate its fresnoite-type reciprocal lattice. In contrast to other recently investigated representatives of the fresnoite family of compounds, Rb₂V₃O₈ is not incommensurately modulated with an incommensurate basal plane primary modulation wave vector given by q∼0.3 〈110〉^*. A careful low-temperature electron diffraction study has, however, revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave vector q₁∼0.16c^*. The reciprocal space positioning of these incommensurate satellite reflections, the overall (3+1)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from single-crystal XRD refinement, are all consistent with their arising from a distinct type of condensed rigid unit modes (RUMs) of distortion of the Rb₂V₃O₈ parent structure.