Fabrication of electrochemical sensor based on molecularly imprinted polymer and nanoparticles for determination trace amounts of morphine

Ionics - A simple and rapid electrochemical method developed for the detection of trace amounts of morphine (MO) at the surface of modified pencil graphite electrode (PGE) with multiwall carbon...     

The influence of Hall current in a circular duct

In this paper, we consider the unsteady flow of an incompressible second grade fluid in a circular duct with a given volume flow rate variation. The effects of Hall current are taken into account. The governing equations are solved analytically using Laplace transform method. The velocity profiles are constructed for the four cases: (a) constant accelerated flow (b) sudden started flow (c) the flow rate has a trapezoidal variation with time (d) starting from rest the volume flow rate oscillates sinusoidally. The present analysis is more general than any previous investigation.     

1H NMR and kinetics studies of the reaction of 4-methyl, 4-bromo and 3-trifluoromethyl benzyltriflones with aromatic nitro-compounds

Rate measurements are reported for the reactions in methanol of carbanions derived from benzyltriflones, 2a–c, with 4-nitrobenzofurazan derivatives, 4a and 4b, to give anionic σ-adducts. ¹H NMR studies in DMSO-d₆ of the reaction of benzyltriflones, 2, and 4-nitrobenzofurazan, 4a, in the presence of triethylamine are consistent with products formed by the elimination of trifluoromethyl sulfinic acid from σ-adducts initially formed by carbanion attack at the 5-position of 4a. Evidence for the high steric requirements of the benzyltriflone anions come from the low value of β; the slope of the linear plot of values of log k₅ versus pK_a.     

Unsteady flow with heat and mass transfer of a third grade fluid over a stretching surface in the presence of chemical reaction

This paper describes the unsteady flow with heat and mass transfer characteristics in a third grade fluid bounded by a stretching sheet. The resulting problems are solved by means of homotopy analysis method (HAM). Convergence of derived series solutions is explicitly discussed. Graphical results for various interesting parameters are presented and analyzed.     

Spherical Wave Diffraction by a Slit in an Impedance Screen

An exact solution is developed for the problem of diffraction of an E-polarized and an H-polarized spherical waves by a slit in an impedance screen. This consideration is important in the sense that point sources are regarded as better substitutes for real sources than line sources/plane waves. The two independent problems are solved using the Fourier transform, the Wiener-Hopf technique and asymptotic approximations.     

Determination of citric acid in fermentation media by pyrolysis mass spectrometry

Rapid and sensitive determination of citric acid in fermentation media by pyrolysis mass spectrometry (Py–MS) is proposed. Owing to high specificity of this method, distinguishing the citric acid from the matrix and by-products formed in the Krebs cycle is possible. Selected ion monitoring (SIM) mode is used for quantitative measurements, in which mass to charge (m/z) values of 175 of citric acid and 138 of 3-nitroaniline as internal standard are chosen. Limit of detection (LOD) for this method has been found to be 1 ng ml⁻¹ and the linear working range was 10 ng ml⁻¹–100 mg ml⁻¹. Relative standard deviation (R.S.D.) of the method for five replicates was 0.84%. Results of Py–MS are compared with those obtained by UV–vis spectrophotometric method. Also, factor analysis is used for evaluating the influence of pH, molasses concentration, time and shaker intensity on the production of citric acid by Aspergillus niger.     

New and efficient one-pot synthesis of functionalized γ-spirolactones mediated by vinyltriphenylphosphonium salts

The addition of dimethyl acetylenedicarboxylate to isatin derivatives in the presence of triphenylphosphine leading to new highly functionalized γ-spirolactones is reported.