Kinetic study of electrochemically induced Michael reactions of o‐benzoquinones with 2‐acetylcyclohexanone and 2‐acetylcyclopentanone

The reaction of electrochemically generated o‐benzoquinones ( 2a‐f ) as Michael acceptors with 2‐acetylcyclohexanone (ACH) and 2‐acetylcyclopentanone (ACP), as nucleophiles has been studied in various pHs using cyclic voltammetry. The results indicate that the participation of o‐benzoquinones ( 2a‐f ) in the Michael reaction with acetylcyclohexanone (ACH) to form the corresponding catechol derivatives ( 4a‐f ). Based on an EC mechanism, the homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. Copyright © 2007 John Wiley & Sons, Ltd.     

Reversed‐phase vortex‐assisted liquid–liquid microextraction: A new sample preparation method for the determination of amygdalin in oil and kernel samples

A novel, simple, and rapid reversed‐phase vortex‐assisted liquid–liquid microextraction coupled with high‐performance liquid chromatography has been introduced for the extraction, clean‐up, and preconcentration of amygdalin in oil and kernel samples. In this technique, deionized water was used as the extracting solvent. Unlike the reversed‐phase dispersive liquid–liquid microextraction, dispersive solvent was eliminated in the proposed method. Various parameters that affected the extraction efficiency, such as extracting solvent volume and its pH, vortex, and centrifuging times were evaluated and optimized. The calibration curve shows good linearity (r² = 0.9955) and precision (RSD < 5.2%) in the range of 0.07–20 μg/mL. The limit of detection and limit of quantitation were 0.02 and 0.07 μg/mL, respectively. The recoveries were in the range of 96.0–102.0% with relative standard deviation values ranging from 4.0 to 5.1%. Unlike the conventional extraction methods for plant extracts, no evaporative and re‐solubilizing operations were needed in the proposed technique.     

Evaluation of a tube equipped with different inserts: competition between improvements in heat transfer versus increase in pressure drop

Journal of Thermal Analysis and Calorimetry - This study evaluated the efficacy of different inserts incorporation into the simple tube on the rate of improvement in heat transfer as well as the...     

Synthesis,crystallographic and spectroscopic studies,evaluation as antimicrobial and cytotoxic agents of a novel mixed-ligand nickel(II) complex

A new mononuclear mixed-ligand complex of Ni(II) has been synthesized and structurally characterized by single-crystal X-ray diffraction as [Ni(4-Cl-pydc)(apym)(H₂O)₂], where 4-Cl-pydc and apym are 4-chloropyridine-26-dicarboxylate and 2-aminopyrimidine, respectively. Spectroscopic studies such as FT-IR, UV-vis, ¹H-NMR, and thermal analysis (TGA/DTA) were carried out. The fluorescence properties were studied in solvents with different dipole moments. Antimicrobial activities of 4-chloropyridine-26-dicarboxylic acid (1), 2-aminopyrimidine (2), complex (3), and nickel(II) nitrate hexahydrate (4) were investigated by disk diffusion and broth microdilution methods against three Gram-positive bacteria, Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis and three Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa, S. marcescens; also antifungal effect was evaluated on Aspergillus niger and Saccharomyces cerevisiae in vitro. The highest antibacterial activity of complex was observed nearly equal to gentamicin as a standard drug toward S. epidermids with IZD of 18 mm. The in vitro antiproliferative activity of 1–4 on H1299 (a human non-small cell lung carcinoma), HepG2 (a human liver hepatocellular carcinoma), and β-TC3 (a mouse beta pancreatic) cell lines was evaluated by MTT (3-(45-dimethylthiazol-2-yl)-25-diphenyl-2H-tetrazolium bromide) assay and, effect of complex on depolarization of mitochondrial membrane (MMP) of all three cell lines was measured by rhodamine 123. The highest cytotoxic effect of complex was exhibited toward H1299 cell line with IC₅₀ value equal to 10 μM.     

Utilization of a robust syringe-to-syringe displacement-assisted dispersive liquid-phase microextraction to the preconcentration and determination of palladium in environmental samples with the aid of experimental design

Journal of the Iranian Chemical Society - We introduce a syringe-to-syringe displacement-assisted dispersive liquid-phase microextraction to the separation and preconcentration of trace Pd(II)...     

Use of artificial neural network in forecasting optimal distance of enclosures containing PCM-introduced for improving the performance of the evacuated tube solar collectors

Journal of Thermal Analysis and Calorimetry - In this study, the usefulness of using regression-based methods in estimating the optimal fins distance in a PCM finned enclosure of the evacuated tube...     

Hydrodynamic analysis of a heat exchanger with crosscut twisted tapes and filled with thermal oil-based SWCNT nanofluid: applying ANN for prediction of objective parameters

Journal of Thermal Analysis and Calorimetry - Present study investigates hydrodynamic analysis of heat exchanger with crosscut twisted tapes and filled with thermal oil-based SWCNT nanofluid (NF)....     

L-lysine-Pd Complex Supported on Fe3O4 MNPs: a novel recoverable magnetic nanocatalyst for Suzuki C-C Cross-Coupling reaction

In this work, L-lysine-Pd Complex, immobilized onto the surface of Fe₃O₄ MNPs, was successfully prepared via simple and inexpensive procedure. The prepared nanocatalyst was considered as a robust and clean nano-reactor catalyst for the Suzuki and Heck C-C Cross-Coupling reactions in water as the green condition. This eco-friendly heterogeneous catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray Diffractometer (XRD), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP), X-ray mapping, BET, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. The use of a green medium, easy separation and workup, excellent reusability of the nanocatalyst and short reaction time are some outstanding advantages of this method.     

FVM method based on K − ε model to simulate the turbulent convection of nanofluid through the heat exchanger porous media

Journal of Thermal Analysis and Calorimetry - The current study investigates the effect of the magnetic field on nanoparticle distribution and heat transfer rate. The natural convection of...