A new method for finding the center of gravity of polygons

A direct and easy general method is described for finding the center of gravity of all types of convex and concave polygons such as quadrilaterals, pentagons, hexagons and n-sided polygons.     

ZnBr2 catalyzed domino Knoevenagel-hetero-Diels–Alder reaction: An efficient route to polycyclic thiopyranoindol annulated [3,4-c]quinolone derivatives

Various novel polycyclic thiopyranoindol annulated [3,4-c]quinolone derivatives were synthesized via domino Knoevenagel-hetero-Diels–Alder reactions of indoline-2-thions and novel N-acrylated anthranilaldehydes in refluxing ethanol as a solvent in the presence of 20 mol% ZnBr₂ as a Lewis acid catalyst. All reactions proceed with high yields with excellent regio- and stereoselectivity.     

Synthesis and in vitro antibacterial evaluation of 6-substituted 4-amino-pyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

Pyrazolo[3,4-d]pyrimidines are one of the most important classes of fused heterocyclic compounds which exhibit a broad range of biological and medicinal properties. They are known as anticancer, antifungal, antibacterial, antiviral and anti-inflammatory agents. In this study, some new 6-substituted 4-amino-pyrazolo[3,4-d]pyrimidine derivatives were prepared via reaction of 5-amino-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile with various nitriles in the presence of sodium ethoxide as catalyst. The inhibitory properties of synthesized compounds were studied according to CLSI guidelines against some pathogenic bacteria including four gram-positive strains (Streptococcus pyogenes, Staphylococcus aureus, Bacillus cereus and Bacillus subtilis subsp. spizizenii) and three gram-negative strains (Pseudomonas aeruginosa, Shigella flexneri and Salmonella enterica subsp. enterica). The antibacterial effects of all derivatives were compared with those of antibiotics belonging to different classes. The values were reported as inhibition zone diameter (IZD), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The effect of substituents on the biological activity of derivatives was discussed as well. The inhibitory effect of compound 6a, was shown to be the most, with MIC values in the range of 32–4096 μg/mL. Since most of the synthesized compounds were effective against Streptococcus pyogenes and Pseudomonas aeruginosa, they can be considered as inhibitors of these two bacteria.     

Highly sensitive and selective amperometric sensors for nanomolar detection of iodate and periodate based on glassy carbon electrode modified with iridium oxide nanoparticles

Iridium oxide nanoparticles are grown on a glassy carbon electrode by electrodepositing method. The electrochemical behavior and electrocatalytic activity of modified electrode towards reduction of iodate and periodate are studied. The reductions of both ions occur at the unusual positive peak potential of 0.7 V vs. reference electrode. The modified electrode is employed successfully for iodate and periodates detection using cyclic voltammetry, hydrodynamic amperometry and flow injection analysis (FIA). In the performed experiments, flow injection amperometric determination of iodate and periodate yielded calibration curves with the following characteristics: linear dynamic range up to 100 and 80 μM, sensitivity of 140.9 and 150.6 nA μM⁻¹ and detection limits of 5 and 36 nM, respectively. The repeatability of the modified electrode for 21 injections of 1.5 μM of iodate solution is 1.5%. The interference effects of NO₂⁻, NO₃⁻, ClO₃⁻, BrO₃⁻, ClO₄⁻, SO₄²⁻, Cu²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Cd²⁺, Ca²⁺, Na⁺, K⁺, NH₄⁺ and K⁺, CH₃COO⁻ and glucose were negligible at the concentration ratio of more than 1000. The obtained attractive analytical performance together with high selectivity and simplicity of the proposed method provide an effective and e novel modified electrode to develop an iodate and periodate sensor. Sensitivity, selectivity, the liner concentration range and the detection limit of the developed sensor are all much better than all known similar sensors in the literature for iodate and periodate determination.     

Vapor-Phase Alkylation of Phenol with Tert-butyl Alcohol Catalyzed by H3PO4/MCM-41

 The catalytic performance of Al-MCM-41 containing 5?5 wt% H3PO4 was studied for the vapor phase alkylation of phenol with tert-butyl alcohol (TBA) from 383 to 493 K. 4-Tert-butyl phenol was produced as the main product with moderate selectivity. The product distribution depends on the reaction temperature, number of acid sites, and the Br鰊sted to Lewis sites ratios. A lower molar ratio of reactants (TBA/phenol = 2) and a higher space velocity facilitated the production of 4-tert-butyl phenol. The influence of various parameters such as temperature, reactant feed molar ratio, feed rate, and time on stream were investigated for conversion yield and product selectivity.     

The Wiedemannben Franz law in a normal metalben superconductor junction

In this paper the influence of superconducting correlations on the thermal and charge conductances in a normal metal-superconductor (NS) junction in the clean limit is studied theoretically. First we solve the quasiclassical Eilenberger equations, and using the obtained density of states we can acquire the thermal and electrical conductances for the NS junction. Then we compare the conductance in a normal region of an NS junction with that in a single layer of normal metal (N). Moreover, we study the Wiedemann-Franz (WF) law for these two cases (N and NS). From our calculations we conclude that the behaviour of the NS junction does not conform to the WF law for all temperatures. The effect of the thickness of normal metal on the thermal conductivity is also theoretically investigated in the paper.     

Mixed finite difference and Galerkin methods for solving Burgers equations using interpolating scaling functions

The current paper proposes a technique for the numerical solution of Burgers equations. The method is based on finite difference formula combined with the Galerkin method, which uses the interpolating scaling functions. Several test problems are given, and the numerical results are reported to show the accuracy and efficiency of the new algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

A spatio-temporal dynamic regression model for extreme wind speeds

This paper presents a hierarchical regression type model for analyzing the dependency of sample extremes on time, space and a covariate effect. The model is based on the assumption that the observations follow independently a generalized extreme value distribution given location, scale and shape parameters. Then a multivariate spatial process is considered to accommodate the association and spatial correlation in the distribution parameters. The mean of the process incorporates the underlying dynamics which is elaborated on the lower stage of hierarchy. Finally, three spatio-temporal dynamic linear models drive independently this mean function to take the variations in the parameters separately into account. In a Bayesian setting, the model structure leads to parallel implementation of the Markov chain Monte Carlo algorithm in a sense that it is less time consuming. Our methodology is applied to the monthly maxima of wind speed with temperature as a covariate for which the relationship is expressed in terms of a penalized spline regression model. The comparison of the proposed model with several simpler ones suggests considerable improvements in wind speed analysis.