Boundary layer flow of a Jeffrey fluid with convective boundary conditions

The boundary layer stretched flow of a Jeffrey fluid subject to the convective boundary conditions was investigated. The governing dimensionless problems were computed by using the homotopy analysis approach. Convergence of the derived solutions was checked and the influence of embedded parameters was analyzed by plotting graphs. It was noticed that the velocity increases with an increase in the Deborah number. Furthermore, it was found that the temperature is also an increasing function of the Biot number. We further found that for fixed values of other parameters, the local Nusselt number increases by increasing the suction parameter and Deborah number. Numerical values of the skin friction coefficient and local Nusselt numbers were computed and examined. Copyright © 2011 John Wiley & Sons, Ltd.     

Considerations for environmental fate and ecotoxicity testing to support environmental risk assessments for engineered nanoparticles

There is an increasing concern over the safety of engineered nanoparticles (ENPs) to humans and the environment and it is likely that the environmental risks of these particles will have to be tested under regulatory schemes such as REACH. Due to their unique properties and the fact that their detection and characterisation in complex matrices is challenging, existing analytical methods and test approaches for assessing environmental risk may not be appropriate for ENPs. In this article we discuss the challenges associated with the testing of ENPs to generate data on persistence, mobility, bioavailability and ecotoxicity in the environment. It is essential that careful consideration is given to the selection of the test material, the test system (including test vessels and study media) and the test exposure conditions. During a study it is critical that not only the concentration of the ENP is determined but also its characteristics (e.g. size, shape, degree of aggregation and dissolution). A range of analytical techniques is available including microscopy-based approaches (e.g transmission and scanning electron microscopy), dynamic light scattering, and size separation approaches (e.g. field flow fractionation and hydrodynamic chromatography) coupled to detection methods such as inductively coupled plasma MS. All of these have their disadvantages: some are unable to distinguish between ENPs and natural interferences; some techniques require sample preparation approaches that can introduce artefacts; and others are complex and time-consuming. A combination of techniques is therefore needed. Our knowledge in this area is still limited, and co-ordinated research is required to gain a better understanding of the factors and processes affecting ENP fate and effects in the environment as well as to develop more usable, robust and sensitive methods for characterisation and detection of ENPs in environmental systems.     

Extraction optimization,total phenolic,flavonoid contents,HPLC-DAD analysis and diverse pharmacological evaluations of Dysphania ambrosioides (L.) Mosyakin & Clemants

The present study aims to evaluate phytochemical and pharmacological potentials of Dysphania ambrosioides (L.) Mosyakin & Clemants previously known as Chenopodium ambrosioides L. Extraction was carried out using 14 solvents with wide range of polarity to find out the best solvent system for each bioactivity. Total phenolic and flavonoids contents were measured colorimetrically and polyphenolics were quantified via HPLC-DAD analysis. The samples were screened for inhibitory potentials against free radicals, leishmania, cancer cell lines, protein kinase, α-Amylase enzymes and microbial strains. Among all solvents, maximum percentage of extract was recovered from methanol-water fraction of leaves. HPLC analysis exhibited the presence of rutin, myricetin and quercetin. In DPPH assay, methanolic leaf extract exhibited IC₅₀ value of 130.7 ± 0.57 μg/mL. Considerable α-amylase inhibitory, cytotoxic, leishmanicidal and antimicrobial potentials were exhibited by plant samples. D. ambrosioides revealed significant antioxidant, cytotoxic, antimicrobial and anti-diabetic potentials and thus warrant further detailed studies to find novel drugs.     

Room Temperature Ferromagnetism in Ga1-xHoxN (x=0.0 and 0.05) Diluted Magnetic Semiconductor Thin Films

Holmium doped GaN diluted magnetic semiconductor thin films have been prepared by thermal evaporation technique and subsequent ammonia annealing. X-ray diffraction mea-surements reveal all peaks belong to the purely hexagonal wurtzite structure. Surface mor-phology and composition analysis were carried out by scanning electron microscopy and energy dispersive spectroscopy respectively. The room temperature ferromagnetic proper-ties of Ga_1-xHo_xN(x=0.0, 0.05) films were analyzed using vibrating sample magnetometer at room temperature. Magnetic measurements showed that the undoped films (i.e. GaN) exhibited diamagnetic behavior, while the Ho-doped (Ga_0.95Ho_0.05N) film exhibited a ferro-magnetic behavior.     

Prediction of CL-20 chemical degradation pathways, theoretical and experimental evidence for dependence on competing modes of reaction

Highest occupied and lowest unoccupied molecular orbital energies, formation energies, bond lengths and FTIR spectra all suggest competing CL-20 degradation mechanisms. This second of two studies investigates recalcitrant, toxic, aromatic CL-20 intermediates that absorb from 370 to 430 nm. Our earlier study (Struct. Chem., 15, 2004) revealed that these intermediates were formed at high OH(-) concentrations via the chemically preferred pathway of breaking the C-C bond between the two cyclopentanes, thereby eliminating nitro groups, forming conjugated pi bonds, and resulting in a pyrazine three-ring aromatic intermediate. In attempting to find and make dominant a more benign CL-20 transformation pathway, this current research validates hydroxylation results from both studies and examines CL-20 transformations via photo-induced free radical reactions. This article discusses CL-20 competing modes of degradation revealed through: computational calculation; UV/VIS and SF spectroscopy following alkaline hydrolysis; and photochemical irradiation to degrade CL-20 and its byproducts at their respective wavelengths of maximum absorption.     

Dye fixation and decolourization of vinyl sulphone reactive dyes by using dicyanidiamide fixer in the presence of ferric chloride

A synthetic polymer was synthesized and used for the improvement of dyeing properties as well as decolorization of textile waste water. Two dyes were selected having anthraquinone based Remazol Blue R and azo based Remazol Red RB. It was observed that the synthetic polymer can be used as fixer for the fixation of dye by crosslinking between dye and fibre, which not only improves the dyeing properties but also helpful to coagulate the colour after dyeing. By single point method the concentrations of synthetic polymer were calculated in residual after dyeing. It was examined that the residual synthetic polymer is helpful in colour removal efficiency by coagulation of polymer with dye to form heavy molecules which settle down and decolorization occurred. Colour removal efficiency was found dependents on pH, concentration of synthetic polymer and inorganic coagulant.     

Synthesis and reactivity of dimethoxy-functionalised Tröger’s base analogues

Tröger’s base analogues were prepared bearing methoxy groups in the 1,7-, 2,8-, 3,9- or 4,10-positions. These compounds were converted to their dihydroxy analogues in excellent yields upon treatment with boron tribromide and the 4,10-dihydroxy analogue could be prepared by directly from 4-hydroxyaniline. The synthetic utility of the dihydroxy-functionalised compounds as building blocks was demonstrated by the synthesis of a dialkoxy and a diester Tröger’s base analogue.     

Study on conductivity and dielectric behavior of chemically synthesized polypyrrol dodecylbenzene sulfonic acid blended with poly(methyl methacrylate)

Polypyrrole (PPy) doped with dodecylbenzene sulfonic acid was synthesized and was blended with compatible polymer PMMA in chloroform. Flexible and free-standing films with compositions PPy: PMMA = 10: 90, 20: 80, 30: 70, and 50: 50 were obtained. The percentage of crystallinity and particle size of synthesized polymers were estimated from X-rays diffraction studies. Scanning Electron Micrographs showed that phase separation was observed and compatibility of the mixture decreased with increase of PMMA content. The dielectric measurements were performed in the frequency range 0.1 kHz–1 MHz in temperature range 303–473 K. The frequency dependent conductivity (σ_ac) obeyed a power law of frequency with an exponent s < 1. Electric modulus formalism exhibits a peak in frequency. The peak of conductivity relaxation shifted towards higher frequencies and the magnitude of relaxation decreased with the increase of PMMA content in the composites.     

In Situ Synthesis of Cu3P/P-Doped g-C3N4 Tight 2D/2D Heterojunction Boosting Photocatalytic H2 Evolution†

Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C₃N₄ because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu₃P nanosheet/P-doped g-C₃N₄ (PCN) nanosheet heterojunction photocatalyst (PCN/Cu₃P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C₃N₄ composite for photocatalytic H₂ evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C₃N₄ could be well reserved in the phosphorization process, while CuS and g-C₃N₄ in-situ transformed into Cu₃P and PCN, respectively, leading to the formation of PCN/Cu₃P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu₃P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H₂ evolution reaches 5.12 μmol·h^–1, nearly 24 times and 368 times higher than that of pristine PCN and g-C₃N₄, respectively. This work represents an excellent example in elaborately constructing g-C₃N₄-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system.