Stochastic ordering of medians in exchangeable trivariate normal vectors

In this paper, we establish the stochastic ordering of median from an exchangeable trivariate normal vector based on the strength of the correlation coefficient. Specifically, by considering two exchangeable trivariate normal vectors with different correlation coefficients, we show that the absolute value of the median in the vector with smaller correlation coefficient is stochastically smaller than the absolute value of the median in the vector with larger correlation coefficient. We prove this result by utilizing skew-normal distributions.     

Effects of radiation on mixed convection stagnation-point flow of MHD third-grade nanofluid over a vertical stretching sheet

This paper considers the problem of the two-dimensional mixed convection stagnation-point flow of a magnetohydrodynamic non-Newtonian nanofluid bounded by a vertical stretching sheet. Convective surface boundary and zero surface nanoparticle mass flux conditions are employed. The effects of buoyancy, radiation, Brownian motion, thermophoresis, and viscous dissipation are taken into account. The stretching velocity is assumed to vary linearly with the distance from the stagnation point. The fluid is electrically conducted with uniform magnetic field, and the work done due to deformation is taken into consideration. The three-coupled partial differential boundary layer equations are reduced to ordinary differential equations by using proper similarity transformations. Analytical solution by homotopy analysis method is obtained. Effects of different physical parameters on the dynamics of the problem are analyzed and discussed.

     

Gallic acid grafted to amine‐functionalized magnetic nanoparticles as a proficient catalyst for environmentally friendly synthesis of α‐aminonitriles

An effective approach of one‐pot catalytic Strecker reaction between aromatic aldehydes, aniline or toluidine and trimethylsilyl cyanide in the presence of amine‐functionalized Fe₃O₄@SiO₂ nanoparticles grafted with gallic acid (GA) as a powerful catalyst was developed. The fabricated reusable catalyst demonstrated high efficiency in the synthesis of α‐aminonitriles along with facile work‐up procedure. Fe₃O₄@SiO₂‐NH₂‐GA was characterized by Fourier transform‐infrared spectroscopy, scanning electron microscopy image, vibrating‐sample magnetometer curve, energy‐dispersive X‐ray analysis and thermogravimetric analysis.     

Analysis of Thermal Flow in a Rotating Porous U-Turn Duct Using Lattice Boltzmann Method

The lattice Boltzmann method is carried out to investigate the heat transfer enhancement in a U-turn duct which is partially filled with a porous media. The porous layer is inserted at the core of the duct and is modeled using the Brinkman–Forchheimer assumptions. In order to validate the results, first a channel flow problem without any porous layer is compared with available data. Second, the porous Couette flow and partially porous channel flow are successfully compared with the studies of other researchers. Then, fluid flow in a clear U-turn duct is studied looking carefully at the velocity, curvature and rotation effects. Finally, the effects of porous layer thickness on the rate of heat transfer and pressure drop are investigated. Parametric studies are conducted to evaluate the effects of various parameters (i.e., Reynolds number, Darcy number, rotation number), highlighting their influences on the thermo-hydrodynamics behavior of the flow. The optimum values of porous layer thickness are presented for specific flow parameters.     

Microgels based on isotactic poly(styrene): Synthesis and characterization

Poly(styrene) microgels are known, but the influence of tacticity on particle formation and behavior has not been investigated yet. Isotactic poly(styrene) (iPS) with M_n = 15–120 kg/mol is synthesized by coordinate polymerization and cross‐linked by Friedel–Crafts alkylation in a miniemulsion. Nuclear magnetic resonance (NMR) spectroscopy, light microscopy, cryogenic transmission electron microscopy, and wide‐angle powder diffraction are applied to understand the structure of microgels obtained. Typically, spherical microgels with overall diameter of 40–500 nm are found. Isotacticity of the polymer is retained during microgel formation. Increase of cross‐linker content leads to partial crystallinity inside the microgel. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 175–180     

Organocatalyzed domino reactions: diversity oriented synthesis of pyran-annulated scaffolds using in situ-developed benzylidenemalononitriles

Research on Chemical Intermediates - Molecular diversity for the synthesis of pyran annulated heterocyclic scaffolds has been achieved from the multicomponent reaction of aldehyde, malonitrile and...     

A developed high-performance thin-layer chromatography method for the determination of baicalin in Oroxylum indicum L. and its antioxidant activity

JPC – Journal of Planar Chromatography – Modern TLC - A simple, accurate, precise, and specific high-performance thin-layer chromatography (HPTLC) method for the quantitative...     

Enhanced catalytic performance of copper iodide in 1,2,3-triazole-imidazole hybrid synthesis,and evaluation of their anti-cancer activities along with optical properties besides 1H-tetrazole-imidazole hybrids

New triazole-imidazole and tetrazole-imidazole hybrids were obtained using 2,4,5-triaryl-1-(4-aminophenyl) imidazoles by copper-catalyzedazide-alkyne cycloaddition (CuAAC) and Ugi-azidefour-component(UA-4CRs) process. The synthesis of triazole hybrids was performed in the presence of new copper-incorporated white sandstone nanocatalyst, which was fully characterized by different methods. The construction of newly prepared hybrids was confirmed by spectroscopic techniques. Some of these compounds were evaluated for their anti-cancer properties against MCF-7 cancer cell lines. The absorption and emission parameters of the triazole- and tetrazole-substituted imidazoles were also investigated and compared with each other.     

Applicability of some mass spectrometric criteria for the confirmation of pesticide residues

This study was initiated to demonstrate the impact of tolerance intervals calculated based on experimental data and standard criteria on the capability to detect and identify pesticide residues by GC-MS in plant extract. The tolerance intervals specified by the current guidelines and standards (EU, EPA, ISO, EC) result in a large number of false negative values. The tolerance intervals calculated based on the actually measured ion ratios at 2 different probability levels did not provide a better estimate. Based on experimental findings a 2-phase procedure for confirmation of pesticide residues is recommended. The first screening phase comprises identification of those pesticide residues that are likely to be present avoiding false negatives as far as possible. Relatively large tolerance intervals, +/-30% of absolute ion abundances ratios, have to be used at this point. When 2 or 3 selected ion ratios are within the established tolerance intervals the residue is confirmed. When the ions detected still indicate the possible presence of a residue the result may be reported as tentatively identified. However, when the result would lead to regulatory action, second confirmatory phase has to be undertaken. This can be achieved with the same GC-MS equipment, by injecting matrix-matched standards of the suspected analyte, in order to compensate for matrix influence on ion ratios. Alternatively, methods using different physico-chemical properties of the compound have to be used. The choice of the technique depends on their availability, time and cost.