Geometric Estimates of the First Eigenvalue of (p,q)-elliptic Quasilinear System Under Integral Curvature Condition

Consider (M,g) as a complete, simply connected Riemannian manifold. The aim of this paper is to provide various geometric estimates in different cases for the first eigenvalue of (p,q)-elliptic quasilinear system in both Dirichlet and Neumann conditions on Riemannian manifold. In some cases we add integral curvature condition and maybe we prove some theorems under other conditions.     

Enhanced spectrofluorimetric determination of aflatoxin B1 in wheat by second-order standard addition method

Determination of aflatoxin B1 (AFB1) in wheat has been accomplished by enhanced spectrofluorimetry in combination with second-order standard addition method (EF-SOSAM). The adopted strategy combined the use of parallel factor analysis (PARAFAC) for extraction of the pure analyte signal and the standard addition method, for a determination in the presence of matrix effect caused by wheat matrix. The method is based on the enhanced fluorescence of AFB1 by beta-cyclodextrin in 10% (w/w) methanol-water solution. After sample treatment and without any extended cleanup steps and derivatization process, four standard additions were performed for each sample. A specific PARAFAC model was built from three-way arrays formed by excitation-emission spectra and 5 measurements (sample plus 4 additions). The scores related to AFB1 were used for a linear regression in the standard addition method. Two naturally contaminated wheat and spiked wheat samples containing AFB1 in the range 0-18 microg kg(-1) were analyzed by EF-SOSAM and compared with HPLC results. EF-SOSAM analysis of spiked wheat samples gave a good correlation with spiked values (R(2)>0.990). The limit of detection of method was 0.9 microg kg(-1) for the determination of AFB1 in wheat samples.     

Chemiluminescence of Aldehydes in Pyrogallol–NaOH System Using Polyaniline/Cu(I) as Catalyst

Journal of Analytical Chemistry - In this research, chemiluminescence (CL) of several aldehydes (such as oxalaldehyde, N-isovaleryl-3-amino-propanal as the bioluminescent earthworm luciferin,...     

H3PMo12O40‐immobilized chitosan/Co3O4: A novel and recyclable nanocomposite for the synthesis of pyrimidinedione derivatives

An efficient three‐component reaction of aromatic aldehydes, 6‐aminouracil/6‐amino‐1,3‐dimethyluracil and 4‐hydroxycoumarin in the presence of a novel heterogeneous catalyst H₃PMo₁₂O₄₀‐immobilized Co₃O₄/chitosan led to a synthesis of a new class of pyrimidinedione derivatives under reflux conditions. The magnetically recoverable nanocomposite of Co₃O₄/chitosan/H₃PMo₁₂O₄₀ was fully characterized by Fourier transform‐infrared spectrophotometry, scanning electron microscopy, X‐ray powder diffraction, energy‐dispersive X‐ray spectroscopy, vibrating‐sample magnetometry and N₂ adsorption–desorption by Brunauer–Emmett–Teller analysis. Results show that Keggin‐type 12‐molybdophosphoric acid immobilized into the network of the cross‐linked chitosan with super‐paramagnetic Co₃O₄ nanoparticles. The present method offers several advantages, such as simple procedure, short reaction times and excellent yields of products. The novelty of the catalyst, high catalytic activity, easy separation from the reaction with an external magnetic field and reusability of the catalyst in six consecutive runs are additional eco‐friendly attributes of this catalytic system.     

Application of novel copper organic material for facile microextraction of sodium valproate from human plasma samples: Experimental design optimization and isotherm study

Well‐designed metal organic materials (MOMs) were synthesized and applied for pre‐concentration and determination of sodium valproate (Na‐VP) from biological samples, bound to the copper complex of 1,4‐phenylenedioxydiacetic acid under mild conditions. The channels of this sorbent provide high efficiency and also selectivity. The MOMs were structurally characterized using Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning electron microscopy and X‐ray diffraction, and they were found to have suitable features for quantification of Na‐VP using HPLC coupled with UV detection at λ = 215 nm. Moreover, the rate of adsorption is improved by ultrasonic power and the experimental data are best fitted according to Freundlich adsorption isotherm. According to the central composite design, the best experimental conditions are 280.0 μl, 3.0 min and 17.0 mg for volume of eluent, sonication time and sorbent mass respectively. Calibration plots show linear responses towards Na‐VP concentrations (0.4–18.0 μg ml^?1), satisfactory limit of detection (0.06 μg ml^?1, S/N = 3) and reasonable enrichment factor (70.58). The coefficient of variation values of both inter‐ and intra‐day analyses were less than 4.0%, indicating a candidate method for the determination of Na‐VP in human plasma with reasonable recovery and efficiency.     

Sparse semidefinite programs with guaranteed near-linear time complexity via dualized clique tree conversion

Mathematical Programming - Clique tree conversion solves large-scale semidefinite programs by splitting an $$n\times n$$ matrix variable into up to n smaller matrix variables, each representing a...     

A Novel ICP Torch with Conical Geometry

Plasma Chemistry and Plasma Processing - This paper presents the development of a novel radio-frequency inductively coupled plasma (RF-ICP) torch. Computer simulations and experiments were employed...     

Bifurcation analysis and nonlinear dynamics of a capacitive energy harvester in the vicinity of the primary and secondary resonances

Nonlinear Dynamics - The objective of the present study is to examine the effect of nonlinearity on the efficiency enhancement of a capacitive energy harvester. The model consists of a cantilever...     

Molecular docking studies,biological evaluation and synthesis of novel 3-mercapto-1,2,4-triazole derivatives

Molecular Diversity - Synthesis of bioactive heterocyclic compounds having effective biological activity is an essential research area for wide-ranging applications. In this study, a conventional...